source to sink · 2018. 3. 27. · 12h00 - 12h15 de putter thierry cenozoic sedimentation history...

Programme

A WORKSHOP of the SGF

SOURCE TO SINK:A LONG TERM PERSPECTIVEOF SEDIMENT BUDGETSAND SOURCES CHARACTERIZATION

University of RENNES ICampus of Beaulieu - Amphi. «Louis Antoine»

30 November02 December

2016G

UID

E Book of abstracts

SOURCE TO SINK: A long term perspective of sediment budgets and sources characterization

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30 November / 02 December 2016 - University of RENNES I

INFORMATIONS

Organizers and Sponsors 07Other Sponsors 08Organizing committee 09Scientific committee

Practical informations

Road access 10Access to the campus 11Plan of the campus 12

PLANNING and programme

Invited speakers 15 Programme 17Programme by day: Wednesday 19 Thursday 21 Friday 23

List of Posters 25

ABSTRACTS 27

INDEX of authors 103

CONTENTS

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INFO

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ORGANIZERS and SPONSORS

SGF Société Géologique de France geological company of France www.geosoc.fr

ASF Association des sédimentologistes français Association of the French sedimentologists www.sedimentologie.fr

Université de Rennes 1 university of Rennes 1 www.insu.cnrs.fr

Géosciences Rennes www.univ-rennes1.fr

GET Géosciences Environnement Toulouse www.get.obs-mip.fr

Ifremer Institut français de recherche pour l’exploitation de la mer French Research Institute for Exploitation of the Sea www.ifremer.fr

IUEM Institut Universitaire Européen des Sciences de la Mer European Institute for Marine Studies www-iuem.univ-brest.fr

de Rennesdes Sciences de l’UniversObservatoire

Terre, Écosystèmes et Sociétés

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Other SPONSORS

TOTAL Company www.total.com

Actions Marges program www.insu.cnrs.fr

Labex Mer www.labexmer.eu/fr

Région Bretagne www.bretagne.fr

Rennes Métropôle www.rennes-metropole.fr

Observatoire des Sciences de l’Univers de Rennes Observatory of Sciences of the Universe www.osur.univ-rennes1.fr

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COMMITTEES

Organizing committee

Persons in charge: Cécile ROBIN University of Rennes 1 François GUILLOCHEAU University of Rennes 1

Delphine ROUBY GET Toulouse Massimo DALL’ASTA TOTAL Marina RABINEAU LDO Brest Samuel TOUCANNE Ifremer

Scientific committee

Olivier Dauteuil Géosciences Rennes Pascal Leroy LDO Brest Daniel Aslanian Ifremer Jérome Gaillardet IPGP Paris Yanni Gunnell Lyon 2 Jean-Jacques Jarrige SGF

N137N12

N24

D97

D96

D463

D163D837

D125

D677

D634

E03

E50

SNCFStation

Campus ofBeaulieu

Bd d’ArmoriqueAv de Roches

Bd de Vitré

Bd VolneyBd de M

etz

Av Aristide Briant Av François Château

Av des Préales

Bd des Aliés

R de Châteaugiron

R de Vern

Bd Oscar Leroux

Bd Georges Clemenceau

R de l’Alma

Av H

enri

Frév

ille

R de Lorient Bd de la Liberté

Bd d

e Ve

rdun

Bd d

e Ch

ézy

Av Charles Tillon

R de Fougère

Direction Saint-Malo

Direction Saint-Brieuc

Direction Lorient

Autoroute des Estuaires A84Direction Fougères

Direction Paris

Direction AngersDirection Nantes

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Practical INFORMATIONS

Road access

Rue MartenotRue de Paris

Rue d’Isly

Rue de l’Alma

Rue de Paris

Rue de Paris

Bd de Sévigné

Av. Aristide BriandQuai DujardinQuai ChateaubriandQuai Duguay Trouin

Quai Emile Zola

Bd de la LibertéAv. Jean Janvier

Av. Jean Janvier Bd Solferino

Bd Magenta

Av. du Sergent Maginot

Av. François Château

Av. du Général LeclercBd de Vitré

Bd de Vitré

Bd Villebois Mareuil

Bd de Metz

Bd de Strasbourg

Rue G

ambetta

Bd de la Duchesse Anne

Placede la Mairie

Les HallesMartenot

Placede

la République

GareSNCF

Placedu Parlement

PlaceHoche

EsplanadeCharles De Gaulle

Campusde Beaulieu

Bus C4Bus stop “Tournebride”Stop at

Bus C6 40ex Bus stop “Tournebride”

Métro

200 m

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BusStop at

31Bus stop “Beaulieu chimie”

(École de chimie)

University of RENNES 1Campus of Beaulieu

"Beaulieu Chimie"

"Tournebride"

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Access to the campus

50 m

Bât. 2

Bus 31Bus stop “Beaulieu chimie”

École de chimie

Center town

Center town

Bât. 15 - Géosciences Rennes Bus C4Bus stop “Tournebride”

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Amphi. “Louis Antoine”

Carpark

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Plan of the campus

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PLA

NN

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prog

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Invited SPEAKERS

Jean BRAUN GFZ Postdam

A QUANTITATIVE MODEL FOR CHEMICAL WEATHERING OFCONTINENTAL INTERIORS AND ITS IMPLICATIONFOR THE GEOCHEMICAL EVOLUTION OF THE WORLD’S OCEANS

Sébastien CASTELLTORT University of Geneve

PROPAGATION OF ENVIRONMENTAL SIGNALS FROM SOURCE-TO-SINK AND THE ORIGIN OF STRATIGRAPHIC PATTERNS:EXAMPLES FROM THE SOUTH-PYRENEAN FORELAND BASIN

Peter CLIFFT Woods Hole Oceanographic Institution and University of Aberdeen

SOURCE TO SINK PROCESSES IN THE INDUS DRAINAGE,WESTERN HIMALAYA: CLIMATIC VERSUS SEALEVEL FORCING

Jacob COVAULT University of Texas in Austin

DEEP-TIME SOURCE-TO-SINK SEDIMENT DISPERSAL:NEW GEOCHRONOLOGIC CONSTRAINS FROM THE CENOZOICNORTH AMERICA-GULF OF MEXICO SEDIMENT-ROUTING SYSTEM

Jérome GAILLARDET IPGP Paris

WHAT MODERN RIVER SEDIMENTS TELL US ABOUTWEATHERING REGIMES AND WEATHERING RATES ?

Eduardo GARZANTI University of Milan

THE ORANGE SAND HIGHWAY FROM LESOTHO TO ANGOLA:A SOURCE-TO-SINK STUDY IN PROGRESS

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Invited SPEAKERS

Yanni GUNNEL University of Lyon2

SOURCE-DRIVEN, OR SINK-DRIVEN ?THE ORIGIN AND DIAGNOSTIC VALUE OF EROSION SURFACES IN MOUNTAIN RANGES

Matthias HINDERER University of Darmstadt

A SEDIMENT BUDGET APPROACH TO LARGE-SCALE SOURCESINK STUDIES

Niels HOEVIUS GFZ Postdam

EXTERNAL FORCING, SEDIMENT PRODUCTION AND THE PROPAGATION OF SIGNALS THROUGH THE SEDIMENT ROUTING SYSTEM.

Eric HUTTON University of Colorado

OVERVIEW OF THE CSDMS INITIATIVE, EXAMPLES FROMCOUPLED LANDSCAPE EVOLUTION MODEL WITH A MARINE MODEL

Tor O. SOMME STATOIL Stavanger

APPLICATION OF SOURCE-TO-SINK PRINCIPLES INHYDROCARBON EXPLORATION

Alex WHITAKER Imperial College of London

SEDIMENT ROUTING SYSTEM ANALYSIS FROM SOURCE TO SINK USING GRAIN SIZE FINING AND MASS BALANCE APPROACHES

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PROGRAMME

09h0009h15

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10h0010h15

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12h0012h15

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13h0013h15

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18h0018h15

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HOVIUS Niels COVAULT Jacob

MOUYEN MaximeCRAVE Alain

Posters / coffee break

SOMME Tor

WHITAKER Alex FORD MarySIMON Brendan

Posters / coffee break

GUERIT Laure ASTI RiccardoBARRIER Laurie ROUBY Delphine

Welcomegreetings and coffee

GAILLARDET Jérôme

GARZANTI Eduardo

BONNET NicolasDE PUTTER Thierry

BARBARAND Jocelyn GUNNEL YanniGUILLOCHEAU Francois

BABY GuillaumeSALAH SalemWYNS Robert

BRAUN Jean HINDERER MatthiasRUBINO Jean-LoupRABINEAU Marina

PELLEN Romain

HUTTON EricVAN DER BECK Peter LEROUX Estelle

RAT Juliette

DiscussionCASTELLTORT Sébastien

CLIFT Peter

Posters / coffee break Posters / coffee break

ROBERTS GarethFRANCE-LANORD Christian

coffee break

ANDO SergioBONNET Stephane WAN Shiming

RINTERKNECHT Vincent BERNHARDT AnneBONNEAU Lucile LASSEUR Eric

JAPSEN PeterBESSIN Paul

Posters / DiscussionPosters / Icebreaker

Friday02 december

Thursday01 december

Wednesday30 November

lunch lunch lunch

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PROGRAMME by day

Wednesday 30 November

09h00 - 10h15 Welcome / greetings and coffee

10h15 - 11h00 GAILLARDET Jérôme What modern river sediments tell us about weathering regimes and weathering rates ?

11h00 - 11h45 GARZANTI Eduardo The Orange sand highway from Lesotho to Angola: a source-to-sink study in progress

11h45 - 12h00 BONNET Nicolas Weathering and denudation of the western continental et al. margin of peninsular India: The 40Ar/39Ar dating of lateritic K-rich manganese oxides

12h00 - 12h15 DE PUTTER Thierry Cenozoic sedimentation history of the Congo Basin et al. revisited

12h15 - 12h30 BARBARAND Jocelyn Relationships between the offshore and the onshore et al. parts of the central portugal atlantic margin deduced from low temperature thermochronology data

12h30 - 12h45 WYNS Robert The perched paleosurfaces of the pyrenees -cantabrian et al. belt

12h45 - 13h45 lunch

13h45 - 14h30 BRAUN Jean “A quantitative model for chemical weathering of conti nental interiors and its implication for the geochemical evolution of the world’s oceans”

14h30 - 15h15 HUTTON Eric Overview of the CSDMS initiative, examples from coupled landscape evolution model with a marine model

15h15 - 16h00 CASTELLTORT Propagation of environmental signals from Sébastien source-to-sink and the origin of stratigraphic patterns: examples from the South-Pyrenean foreland basin

16h00 - 16h30 Posters / coffee break

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PROGRAMME by day:Wednesday 30 November

16h30 - 16h45 ROBERTS Gareth Sedimentary flux from inversion of drainage networks: et al. examples from west africa and north america

16h45 - 17h00 BONNET Stephane et Modulation of erosion rates of uplifting landscapes by MOUSSIROU Bérangé long-term climate change: experimental investigation and implications for source to sink (sts) studies

17h00 - 17h15 RINTERKNECHT GLACIVAR: reconstructing glacial oscillations in the Var Vincent et al. catchment basin (Southern French Alps)

17h15 - 17h30 BONNEAU Lucile Millennial-scale climate imprint on sediment sources et al. and transfers, The Var sedimentary system (western Mediterranean Sea)

17h30 - 17h45 BESSIN Paul Quantification of vertical movement of low elevation et al. topography from a new compilation of sea-level curves and scattered marine deposits (Armorican Massif, Western France)

17h45 - 18h45 Posters / Icebreaker

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PROGRAMME by day

Thursday 01 december

09h00 - 09h45 HOVIUS Niels External forcing, sediment production and the propagation of signals through the sediment routing system. 09h45 - 10h00 MOUYEN Maxime Assessing modern rates of river sediment discharge to et al. the ocean using satellite gravimetry

10h00 - 10h15 CRAVE Alain Suspended sediment flux in the Amazon River: et al. latest assessment and uncertainties.

10h15 - 10h45 Posters / coffee break

10h45 - 11h30 WHITAKER Alex Sediment routing system analysis from source to sink using grain size fining and mass balance approaches

11h30 - 11h45 GUERIT Laure Deciphering the grain-size trends through time: et al. case study of the quaternary urumqi alluvial fan in the chinese tian shan piedmont\n

11h45 - 12h00 BARRIER Laurie Sediment budgets in catchment–alluvial fan systems et al. of the northern Tian Shan (China): Implications for mass-balance estimates, denudation and sedimentation rates in orogenic systems

12h00 - 12h45 GUNNEL Yanni Source-driven, or sink-driven? The origin and diagnostic value of erosion surfaces in mountain ranges

12h45 - 13h45 lunch

13h45 - 14h30 HINDERER Matthias A sediment budget approach to large-scale source-sink studies

14h30 - 14h45 VAN DER BECK Tectonics, climate, relief and erosion: disentangling Peter et al. driving forces within a complex system

14h45 - 15h00 RAT Juliette Evolution du contenu détritique au cours d’un cycle et al. orogénique

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PROGRAMME by day

Thursday 01 december

15h00 - 15h45 CLIFT Peter Source to Sink processes in the Indus Drainage, Wetern Himalaya: Climatic versus Sealevel Forcing

15h45 - 16h15 Posters / coffee break 16h15 - 16h30 FRANCE-LANORD Neogene and Quaternary erosion of the Himalaya Christian et al. recorded in the Bengal Fan: IODP Expedition 354

16h30 - 16h45 ANDO Sergio Combined heavy mineral and biomarker analysis in silt: et al. a novel approach for provenance studies (indus fan, iodp expedition 355)

16h45 - 17h00 WAN Shiming Distinct controls on terrigenous flux from the Yellow et al. River and the Japanese Islands to the northern Okinawa Trough since 34 ka

17h00 - 17h15 BERNHARDT Immediate propagation of deglacial environmental Anne et al. change to deep-marine turbidite systems along the Chile convergent margin

17h15 - 17h30 LASSEUR Eric Sediment routing in the syn orogenic series of the et al. Aquitaine basin.

17h30 - 17h45 JAPSEN Peter Establishing a chronology of burial, uplift and et al. denudation of the South American Equatorial Atlantic Margin

17h45 - 18h45 Posters / Discussion

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PROGRAMME by day

Friday 02 December

09h00 - 09h45 COVAULT Jacob Deep-time source-to-sink sediment dispersal: New geochronologic constrains from the Cenozoic North America-Gulf of Mexico sediment-routing system

09h45 - 10h30 SOMME Tor Application of source-to-sink principles in hydrocarbon exploration

10h30 - 11h00 Posters / coffee break 11h00 - 11h15 FORD Mary Sediment routing systems in migrating rifts. Insights et al. from the Corinth rift

11h15 - 11h30 SIMON Brendan A «Source to Sink» approach of the Lake Albert Rift et al. (Uganda, East African Rift System): relationships between sedimentary basin and upstream landforms

11h30 - 11h45 ASTI Riccardo Source-to-sink evolution of a supradetachment basin et al. unraveled by detrital apatite fission track analysis: the gediz graben (menderes massif, western turkey)

11h45 - 12h00 ROUBY Delphine Meso-Cenozoic Source-to-Sink of the African margin of et al. the Equatorial Atlantic

12h00 - 12h15 GUILLOCHEAU Source to sink study of the Congo system since 40 Myr : Francois et al. a measurement of the ratio betwen mechanical and chemical erosion.

12h15 - 12h30 BABY Guillaume Mass transfer between the south african plateau and et al. the adjacent atlantic margin (namibia - south africa) since the gondwana break-up

12h30 - 12h45 SALAH Salem A regional north- south cross section through the et al. ghadames basin and its impications to hc potential in the ghadames basin and the northern areas around jabal nafusah, libya

12h45 - 13h45 lunch

13h45 - 14h00 RUBINO Jean-Loup The Miocene Peri-Alpine foreland Basin: a long lived et al. buffer zone for the Gulf of Lion Sediment Supply

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PROGRAMME by dayFriday 02 December

14h00 - 14h15 RABINEAU Marina Sedimentary markers : a tool for the quantification of et al. subsidence and isostatic movments: exemples from the occidental mediterranean sea

14h15 - 14h30 PELLEN Romain The Minorca Basin: a buffer zone between the Valencia et al. and Liguro-Provençal Basins (NW Mediterranean Sea)

14h30 - 14h45 LEROUX Estelle Quantification of terrigenous sediment fluxes in the et al. Provence Basin using seismic data:relation with climate and tectonics for the last 6 Ma

14h45 - 16h00 Discussion

16h00 - 16h30 coffee break

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List of POSTERS

BONNEAU Lucile Testing the sensitivity of the var river hyperpycnal activity to et al. environmental changes over 50 kyr

BOUCHEZ Julien The dynamics of alkali elements at the earth surface overet al. geological time scales

CHARBONNIER Q. Rubidium isotope fractionation: a possible fingerprint ofet al. biological activity in detrital sediment?

DELAUNAY Antoine Offshore and onshore evidence for a polyphased uplift history et al. and upper miocene doming of Madagascar

DELLINGER Mathieu Lithium isotopes as a proxy for silicate weathering and total et al. denudation in large rivers \n

GAYER Eric Cosmogenic nuclides, river geochemistry, and lanformset al. reconstruction methods comparison to study the coopling between chemical weathering, mechanical erosion and transport in a steep reunion island basins.\N

GUÉRIT Laure Experimental drainage basins as markers of large scaleet al. horizontal deformation

HAWIE N. Integrated source to sink investigation of the sableet al. sub-basin offshore nova scotia using forward stratigraphic modeling

HONEGGER Louis Climatic signal in continental and marine sections of the early et al. eocene pyrenean foreland basin, a corrlation insight through a multi-proxy approach

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List of POSTERS

LAURENT Dimitri 3D stratigraphic modelling of the congo turbidite system since et al. 200 ka: \Ntowards a hierarchization of factors controlling sedimentation

LAUTERBACH Mélanie Late cretaceous onset of the amazonian retroarcet al. foreland basin (madre de dios basin, Peru)

LODHIA Bhavik Harish Sedimentary flux to passive margins from inversion ofet al. drainage patterns: examples from Africa

MOURLOT Yannick Tracing the sources of the central atlantic ocean sedimentary et al. rocks during the oae 2

PONTE Jean Pierre The zambezi sedimentary system: a source to sink approachet al.

ROBIN Cécile A source to sink measurement method in anorogenic settingset al.

ROUSSEAU Tristan Tracing clay provenance offshore to the south americanet al. equatorial margin during the last 150ky with nd and sr isotopes

RUBI Romain From alluvial fan to distal turbiditic systems:et al. preliminary results on deep-water bypass processes based on gilbert-type fan delta outcrops of the corinth rift (Greece).

ZHANG Xu A si-li approach to understanding weathering process in world et al. large rivers

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ABS

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COMBINED HEAVY MINERAL AND BIOMARKER ANALYSIS IN SILT:A NOVEL APPROACH FOR PROVENANCE STUDIES

(INDUS FAN, IODP EXPEDITION 355)

ANDO Sergio 1, BRATENKOV Sophia 2, HAHN Annette 3, GEORGE Simon 2, CLIFT Peter 4 & GARZANTI Eduardo 1

1: Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy ([email protected] )2: Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia 3: MARUM, University of Bremen, Bremen, Germany4: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, USA

A high-resolution mineralogical study of Indus Fan turbiditic sediments cored during IODP Expedition 355 (Arabian Sea Monsoon) in the Laxmi Basin was carried out to investigate and quantify the different compositional signatures encoded in the sand, silt, and clay frac-tions. The turbidite deposits recovered at IODP Sites U1456 and U1457 in sedimentological Unit II were chosen as the best candidate for such a study. The integrated dataset presented here was obtained by coupling traditional and innovative bulk-sediment to single-grain ana-lytical techniques, including bulk petrography, heavy-mineral and biomarker analyses on the same samples. Reliable quantitative results even in the medium to fine silt classes, which re-present the dominant sediment sizes encountered in the recovered cores, were obtained by point-counting under the microscope, assisted by Micro-Raman spectroscopy (Andò et al., 2011; 2014).

Preliminary data from the studied turbidites document rich and diverse heavy mine-ral assemblages in both the sand and silty-sand fractions. Heavy-mineral concentrations, as well as the number of mineral species, reach a maximum in sand and tend to decrease with grain size, becoming minimal in the clay fraction. Conversely, the biomarker analysis is gene-rally focused on the finer sediment fractions and clay, where better preservation of biomarker compounds are obtained. The two approaches are thus complementary. Because biomarkers tend to be depleted in sand and heavy minerals in clay, the medium silt fraction represents the most suitable size window for the joint application of these two techniques. Comparing hea-vy-mineral assemblages with biomarkers allows us to evaluate both continental and marine inputs in turbidites and the hemipelagic deposits of the Indus Fan. This new methodological approach plays a key role in the identification of the effects of climate change on marine depo-sitional environments and helps us to differentiate among the diverse Himalayan versus Indian Peninsular sources of detritus. Considered together, the organic and inorganic compositional fingerprints of sediments opens up a new frontier for future studies of the largely unexplored deep-marine sedimentary record.

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Cited references

S. Andò, P. Vignola, E. Garzanti, 2011. Raman counting: a new method to determine provenance of silt. Rend. Fis. Acc. Lincei, 22: 327-347.

S. Andò, E. Garzanti, 2014. Raman spectroscopy in heavy-mineral studies. Geological Society, London, Special Publications, 386 (1), 395-412.

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SOURCE-TO-SINK EVOLUTION OF A SUPRADETACHMENT BASINUNRAVELED BY DETRITAL APATITE FISSION TRACK ANALYSIS:

THE GEDIZ GRABEN (MENDERES MASSIF, WESTERN TURKEY)

ASTI Riccardo 1, MALUSÀ Marco Giovanni 2 & FACCENNA Claudio 3

1: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex, France ([email protected])2: University of Milano-Bicocca, Department of Earth and Environmental Sciences, Milan, Italy ([email protected]) 3: Università degli Studi Roma Tre, Department of Sciences, Rome, Italy ([email protected])

The Menderes Massif (Western Turkey) is a Tertiary continental metamorphic core complex exhumed in the upper Oligocene – Miocene time, during the deposition of a series of E-W trending basins. Several studies addressed the exhumation history of the massif, but the de-positional history of these basins is still poorly defined. Moreover, the full potential of supra-detachment basins in recording major tectonic events is often unexploited. In this work, we use the Gediz Graben supradetachment basin as a case study to illustrate the benefits of a comprehensive approach to detrital fission track dating that combines analysis of modern river sediments, analysis of fossil sedimentary successions, and mineral fertility determinations. This approach allowed us i) to reconstruct the modern short-term erosion pattern, ii) to constrain the long-term exhumation history of the margins of the basin highlighting relevant along-strike variations and deciphering the spatial relevance of the main exhumation events, iii) to identify major exhumation event recorded in the sedimentary sequence of the basin and iv) to constrain the maximum age for the onset of sedimentation in the basin and for the main sedimentary units. Here we illustrate how to reconcile our detrital apatite fission track dataset with field evidences in order to build a coherent 4D model for the evolution of this suprade-tachment basin, which is eventually discussed within the framework of the Cenozoic evolution of the Menderes Massif.

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MASS TRANSFER BETWEEN THE SOUTH AFRICAN PLATEAU ANDTHE ADJACENT ATLANTIC MARGIN (NAMIBIA - SOUTH AFRICA)

SINCE THE GONDWANA BREAK-UP

BABY G. 1, GUILLOCHEAU F. 1, MORIN J. 1 ROBIN C. 1, DALL’ASTA M. 2

1: Géosciences Rennes, UMR6118, OSUR, Université Rennes 1-CNRS, 35042 Rennes, France. (@) [email protected]: TOTAL R&D, Av. Larribau, 64000 Pau, France.

The South African Plateau (SAP) forms a large - scale topographic anomaly (×1000 km) which rises from sea level to up to 3000 m elevation. Tomographic models suggest that the high elevated southern African topography is the expression of a surface upwelling caused by flows in the underlying mantle. However, documenting the surface uplift due to mantle flows is a major challenge in geology. Here we link onshore landforms (planation surfaces, incised valleys) of the SAP to offshore sediment accumulation along the Atlantic margin (from 18°S to 38°S), using numerous seismic reflexion profiles, well data and outcrops. We attempt to relate source and sink analysis in order to solve some first order issues relative to the timing of the exhumation and the growth of the Southern African Plateau.

Offshore, we calculate the solid sediment volumes history of the margin for the last 131 Ma (i.e. late Hauterivian – today) based on Guillocheau et al. [1] approach. Volumes and accu-mulation rates were higher during the Upper Cretaceous (335 ×103 km3 at 51.5 ×103 km3/Ma from 100 to 93.5 Ma, 790 ×103 km3 at 63 ×103 km3/Ma from 93.5 to 81 Ma, and 395 ×103 km3 at 26.3 ×103 km3/Ma from 81 to 66 Ma). Volumes and accumulation rates were lower for the Lower Cretaceous (73 ×103 km3 at 4 ×103 km3/Ma from 131 to 113 Ma, and 16 ×103 km3 at 12.2 ×103 km3/Ma from 113 to 100 Ma) and the Cenozoic (67 ×103 km3 at 1.6 ×103 km3/Ma from 66 to 30 Ma, and 92 ×103 km3 at 6.5 ×103 km3/Ma from 30 to 11 Ma, and 35 ×103 km3 at 32 ×103 km3/Ma).

Onshore, four generations of landforms were recognised and dated by geometrical re-lationships with volcanism and sediments. The successive growth of these landforms are rela-ted to uplifts (Guillocheau et al. [2]).

• > 80 Ma: two generations of planation surfaces (at least). The oldest one forms the highest reliefs of the study area, which are preserved as remnant plateaus (Etchplains). Its age is not known. The younger, form a large - scale pediplain that could be related to the increase of the sedimentary flux occurring during the Upper Cretaceous (i.e. 100 to 81 Ma), driven by a regional uplift.

• 80 - 75 to 70 - 65 Ma: large scale pediplain called the Bushmanland Surface. It can be related to a strike flexure of the margin (i.e. seaward tilting) recognised offshore from 23°S to 36°S. Most of the present-day relief was probably created by that time. This is supported by the decrease of the sedimentary flux which suggests a reorganisation of the interior drainage pattern.

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• 35 - 25 to 15 - 12 Ma: degradation by river incision of the Bushmanland Surface in response to a continental scale uplift (?) and/or change of the climate conditions.

These results suggest that the Southern African plateau (SAP) results from a two phases uplift history: (1) a widespread tilting of the margin during late Cretaceous, (2) continental scale deformations during the Oligocene. Most of the relief is inherited from the Upper Cretaceous

References:

[1] Guillocheau et al. (2012) Basin Res., 24(1), 3-30[2] Guillocheau et al. (2016) accepted Gondwana Res.

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RELATIONSHIPS BETWEEN THE OFFSHORE AND THE ONSHORE PARTS OF THE CENTRAL PORTUGAL ATLANTIC MARGIN DEDUCED FROM

LOW TEMPERATURE THERMOCHRONOLOGY DATA

BARBARAND Jocelyn 1, MARQUES Fernando 2, HILDENBRAND Anthony 1 &PINNA Rosella 1

1: GEOPS, Univ Paris Sud, CNRS, Université Paris-Saclay, Rue du Belvédère, Bât. 504, Orsay, F-91405, France (jocelyn.barbarand @u-psud.fr, [email protected], [email protected])

2: Universida de Lisboa, Dep. Geologia, Fac. Ciências, Edifício C6, Piso 21749-016 Lisboa, Portugal ([email protected])

The Iberia-Newfoundland conjugate margins constitute one of the best-known examples of a magma-poor continental margin that has been largely studied to decipher the oceanic-continental crustal transition and to define processes at the origin of rifting (Boillot et al. 1989, Péron-Pinvidic and Manatschal 2009). The onshore part of the Iberian margin has, however, received little attention regarding vertical movements and their relationships with the ongoing sedimentation in the newly formed sedimentation area.

The age of continental breakup has been interpreted to occur either during Barre-mian (based on magnetic anomalies, Whitmarsh et Miles, 1995) or during late Aptian - early Albian (based on stratigraphic and structural interpretation, Tucholke and Sibuet 2007). The lithosphere has also been drastically stretched from Tithonian to Barremian and extension migrated towards the ocean between Barremian and Albian (Péron-Pinvidic and Manatschal 2009). The Aptian period also corresponds to the rotation of Iberia. The Lusitanian Basin and the Peniche Basin are part of the proximal domain of the margin, in the Southern Iberia Abys-sal Plain segment, and are characterized by a classical half-graben structure. Grabens depths reach more than 5 km and they are filled with syn- to post-rift sediments ranging in age from the Triassic to the Neogene (Alvès et al., 2006). Sedimentary infill of these basins is variable and includes (1) Late Triassic evaporates and lastest Triassic to Hettangian evaporates, (2) marine deposition at various depths between Sinemurian and Late Oxfordian, (3) shallow marine to fluvial siliciclastic sediments from Late Oxfordian to Berriasian, (4) the set up of carbonate plat-form from Valanginian to Early Barremian and (5) mainly siliciclastic rocks from Late Barremian to Cenozoic with the noteworthy exception of the deep marine carbonate platform develop-ment during Late Cenomanian (Stapel et al., 1996; Rasmussen et al., 1998; Dinis et al., 2008). Four regional unconformities are recognized, recording inversion at several times during the Mesozoic: Upper Oxfordian, Upper Berriasian, mid Barremian and Upper Aptian.

In this study, 17 samples from the onshore basement, mainly from the Central Iberian Zone, and one Triassic sandstone have been studied by apatite fission-track (FT) thermochro-nology. This method is well suited to detect and quantify erosion and inversion as it records

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the thermal history of upper crustal rocks. The new FT ages here obtained range between 75±4 and 191±8 Ma and are younger than formation age. Confined track lengths are rather reduced and are from 12.0±0.1 to 13.4±0.1 µm indicating of relatively slow temperature decrease or complex thermal histories. Assuming that the ages do not decrease close to the main struc-tures in the studied area, we interpret these data as an indicator for erosion controlled by the uplift of the margin. Data inversion using QTQt highlights several episodes of erosion recorded from different parts of the studied areas, from Early Jurassic to Early Cretaceous. This indicates that the onshore section of the margin was active during the opening of the Atlantic Ocean and records little activity associated with the Africa-Europe convergence during the Cenozoic.

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SEDIMENT BUDGETS IN CATCHMENT–ALLUVIAL FAN SYSTEMSOF THE NORTHERN TIAN SHAN (CHINA):

IMPLICATIONS FOR MASS-BALANCE ESTIMATES, DENUDATION ANDSEDIMENTATION RATES IN OROGENIC SYSTEMS

BARRIER Laurie 1, GUERIT Laure 2, JOLIVET Marc 3, DOMINGUEZ Stéphane 4,MÉTIVIER François 1 & FU Bihong 5

1: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, Paris, France ([email protected])

2: Géosciences Environnement Toulouse, UMR 5563 – OMP, Toulouse, France.3: Géosciences Rennes, UMR CNRS 6118, Université de Rennes 1, Rennes, France.4: Géosciences Montpellier, UMR 5243 CNRS, Université Montpellier 2, Montpellier, France5: State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese

Academy of Sciences, Beijing, China

Mass balances are often used to calculate sediment fluxes in sedimentary basins and denuda-tion rates in adjacent topographies on intermediate to long timescales (from a few tens of thousand to a million years). In this study, we focus on simple Quaternary catchment–allu-vial fan systems in the northern Tian Shan Range and its foreland basin to discuss some ideas about sediment production, storage, release, and bypass in relatively short (100 km long) sedi-ment routing systems. Based on a geometrical reconstruction of the fans, we estimated the volumes of sediments exported out of the range and deposited in its alluvial piedmont du-ring the Middle-Late Pleistocene and the Holocene. This work shows that the two areas clearly present evidence of a temporary but significant storage of sediments during the Pleistocene. These sediments were then excavated and delivered farther into the foreland basin during the Holocene. The difference between the volumes of materials released from the range and pied-mont areas and the volume stored in the contemporaneous fans downstream indicates that the latter did not trap the whole sediment load transported by the rivers. The alluvial fans were bypassed by 27 to 78% of this load toward the downstream alluvial plain. It implies a major volumetric partitioning of the deposits between the fans and the alluvial plain, with a sedimen-tation rate about twenty times higher in the fans than in the plain. However, this volumetric partitioning might only occur during periods with a very specific hydrological regime such as the Holocene deglaciation. Eventually, the peculiar sediment storage and release pattern within the range and piedmont areas during the Pleistocene and Holocene complicates the calculation of mean paleodenudation rates using either sediment budgets or in situ produced cosmogenic nuclides.

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IMMEDIATE PROPAGATION OF DEGLACIAL ENVIRONMENTAL CHANGE TO DEEP-MARINE TURBIDITE SYSTEMS ALONG

THE CHILE CONVERGENT MARGIN

BERNHARDT Anne 1, 2, SCHWANGHART Wolfgang 2, HEBBELN Dierk 3,STUUT Jan-Berend 3, 4, STRECKER Manfred R. 2

1: Institute of Geological Sciences, Freie Universität Berlin, Germany ([email protected])2: Institute of Earth and Environmental Science, Potsdam University, Germany ([email protected]) ([email protected]) ([email protected])3: MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany ([email protected]) 4: NIOZ – Royal Netherlands Institute for Sea Research, Department of Ocean Systems, and Utrecht University,

Texel, The Netherlands ([email protected])

Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes. Sedimentary records provide the archives for inferring these processes but their inter-pretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable topographic gradients and related connectivity of terrestrial and marine landscapes. This setting allowed us to study event-related depositional processes from the Last Glacial Maximum to present in different climatic and geomorphic settings. The turbidite record was quantified in terms of turbidite thickness and frequency. The three studied sites show a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise significantly lag the decline in turbidite deposition by 3-6.5 kyrs. However, comparison to paleoclimate proxies shows that this spatio-temporal sedimentary pattern mirrors the deglacial humidity decrease and concomitant warming with little to no lag times. Our results suggest that the deglacial humidity decrease resulted in a decrease of flu-vial sediment supply, which propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chilean systems, connectivity between the Andean erosional zone and the fluvial transfer zone probably decreased abruptly by the deglaciation of piedmont lakes, resulting in a significant and rapid decrease of sedi-ment supply to the ocean. Additionally, reduced moisture supply may have also contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata can act as reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss.

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QUANTICATION OF VERTICAL MOVEMENTOF LOW ELEVATION TOPOGRAPHY FROM A NEW COMPILATION

OF SEA-LEVEL CURVES AND SCATTERED MARINE DEPOSITS(ARMORICAN MASSIF, WESTERN FRANCE)

BESSIN Paul 1, GUILLOCHEAU François 2, ROBIN Cécile 2, BRAUN Jean 3, BAUER Hugues 4 & SCHROËTTER Jean-Michel 5

1: LPG Le Mans, UMR 6112, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans, France ([email protected]) 2: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France3: ISTerre, UMR 5275, Université Grenoble Alpes, CNRS, CS40700 38058 Grenoble cedex 09, France4: BRGM, Centre scientifique et technique, 3 avenue Claude-Guillemin, BP 360009, 45060 Orléans cedex 02,

France5: BRGM, Direction régionale Bretagne, Rennes Atalante Beaulieu, 2 rue de Jouanet, 35700 Rennes

A wide range of methods were developed to quantify vertical motions at plate boundaries and to track their spatial distribution, their wavelength and the associated deformation mecha-nism. However, they cannot be used for intraplate domains due to too low amplitudes of verti-cal movements or too old motions (e.g. thermochronology, cosmogenic isotope studies). Here we propose a new method for quantifying low amplitude vertical movements experienced by intraplate areas by combining dating of marine sediments and correcting their elevation from their depositional bathymetry and global sea level height from a global sea level curve. For accurate quantifications, we re-assess the reliability of published global sea level curves and constructed a composite curve combining their most reliable intervals : i) from ca. 100 to 35 Ma («greenhouse» period), curve which reflects ocean basin volume changes and ii) from ca. 40 to 0 Ma («icehouse» period) curves which reflect ocean water volume changes, which iii) _t for these respective periods with a curve which account for both driving factors. We investi-gate the poorly constrained Paleogene to Neogene vertical motions and deformation history of the Armorican Massif, a western European Variscan basement (France) characterized by a low relief, low elevation topography and twice buried then exhumed from Jurassic to Paleo-cene times. Numerous well dated Cenozoic marine sedimentary remnants are scattered upon this massif and are thus key archives to apply our new method for quantifying low amplitude vertical movements. Vertical movements of low amplitude ranging from 54.5 m of subsidence to 85.0 m of uplift are identified. Their spatial distribution argues for deformations of medium wavelength (x 100 km) which can be related to the deformation history of the northwestern European lithosphere with : i) a phase of no deformation from 38 to 34 Ma, recognized at the northwestern European scale, ii) a 30 to 3.6 Ma low-subsiding phase, possibly due to the loca-tion of the massif upon a syncline of a buckled lithosphere and iii) a 2.6 to 0 Ma uplift either related to the intensification of the Africa-Apulia convergence or enhanced climate effects on this long-term uplift.

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MILLENNIAL-SCALE CLIMATE IMPRINT ON SEDIMENT SOURCESAND TRANSFERS, THE VAR SEDIMENTARY SYSTEM

(WESTERN MEDITERRANEAN SEA)

BONNEAU Lucile 1, 2, 3, TOUCANNE Samuel 2, BAYON Germain 2, JORRY Stéphan 2,EMMANUEL Laurent 1, SILVA JACINTO Ricardo 2

1: Laboratoire Biominéralisations et Environnements Sédimentaires, ISTeP-UMR 7193, Université Pierre et Marie Curie, 75252 Paris, France

2: Laboratoire Environnements Sédimentaires, IFREMER, 29280 Plouzané, France 3: University of Heidelberg, Institute of Geosciences, 69120 Heidelberg, Germany ([email protected])

The Var sedimentary system (NW Mediterranean Sea) is an ideal target to investigate climate perturbations on the marine sedimentation. The absence of a continental shelf off Var river results in direct connection between the river mouth and the deep basin during both high and low stands of the relative sea level. Moreover, hyperpycnal flow initiated during Var floods are the main sediment transfer processes in the Var turbidite system, making changes in sedi-ment supply within headwater source regions possible to discern in the stratigraphic record of the distal sedimentary basin. Based on high-resolution stratigraphic of four cores collected on deep-sea turbidi-tic levee (Var Sedimentary Ridge) we reconstructed Late-Pleistocene-to-Holocene temporal changes of unconfined turbidity current activities. Additionally, major element composition, Neodymium isotopes ratios (εNd) and concentration of REE are used to track and quantify the sediment sources (Southern French Alps). Data reveal that at glacial-interglacial scale changes in sediment sources are associated with concomitant variations in the turbidite activity on the Var Sedimentary Ridge showing that sediment transfers were mainly driven by paleoenviron-mental conditions in the upper basin and in particular by the presence of glaciers. High contri-bution of glaciated area during Last Gacial Maximum is associated with high turbidite activity, both rapidly decrease thereafter, i.e. during major alpine glacier retreat (~17.5 ka), and reach minimum values during the Holocene. During MIS3 and MIS4 (30-75 ka), the turbidite activity seems to be directly connected with Dangaard-Oeschger climate cycles according to a cold & dry/high turbidite activity – warm & wet/low turbidite activity pattern. We conclude that this pattern is driven by changes in hyperpycnal activity of the Var River which ultimately depends on the sediment concentration during floods. In contrast to large/buffered systems, we found that the sediment export from the Var River to the Mediterranean Sea directly responded to cli-mate-induced perturbations within the watershed over millennial scale. Such a pattern might also rule the interglacial-glacial sediment flux cycle in other small mountainous basins.

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TESTING THE SENSITIVITY OF THE VAR RIVER HYPERPYCNAL ACTIVITY TO ENVIRONMENTAL CHANGES OVER 50 KYR

BONNEAU Lucile 1, 2, 3, SILVA JACINTO Ricardo 2, TOUCANNE Samuel 2,JORRY Stéphan 2, EMMANUEL Laurent 1

1: Laboratoire Biominéralisations et Environnements Sédimentaires, ISTeP-UMR 7193, Université Pierre et Marie Curie, 75252 Paris, France

2: Laboratoire Environnements Sédimentaires, IFREMER, 29280 Plouzané, France 3: University of Heidelberg, Institute of Geosciences, 69120 Heidelberg, Germany ([email protected])

Hyperpycnal flows are generated off river mouths during high sediment concentra-ted floods. Although the majority of world’s rivers are able to generate such currents at various frequencies, their potential use as direct land-to-deep-sea sediment transport processes is still underestimated. By focusing on the turbidite layers deposition pattern on the Var Sedimentary Ridge (Ligurian Sea), Bonneau et al. (2014, the Journal of Geology) pointed out the striking link between turbidite frequency and rapid climatic changes including the Dangaard-Oeschger cycles and the last Glacial Termination. They concluded that the turbidite frequency on the Var Sedimentary Ridge could actually reflect the magnitude/frequency of hypepycnal currents spilling over the ridge in relation with variations in the sediment concentration of the Var River floods. Cold/dry climate and presence of glacier seem to be more suitable for the generation of hyperpycnal currents than warm/wet climate and absence of glaciers.

In order to test this hypothesis, the numerical model HydroTrend (Syvitski et al., 1998, Computers & Geosciences) is used to simulate the Var River floods over the last 50 ka. Results show that the sediment concentration during Var river floods is sensitive to (1) the size of gla-ciers in the drainage area (glacier-derived sediment input) and (2) the precipitation rate. Im-portantly the simulation points out that even though high magnitude floods are less frequent during dry intervals, the concentration of sediment carried during these floods is much higher, resulting in higher hyperpycnal activity. Based on daily sediment concentration we produced a simulated 50ky-long hyperpycnal activity record that reproduce the observed (sedimento-logical based) turbidite activity thus confirming that turbidite activity on the Ridge is tied to the hyperpycnal activity of the Var River. Our findings show that hyperpycnal flows can be a driver to transmit climate-driven high-frequency changes in river sediment concentration to sedimentary record.

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WEATHERING AND DENUDATION OFTHE WESTERN CONTINENTAL MARGIN OF PENINSULAR INDIA:THE 40Ar/39Ar DATING OF LATERITIC K-RICH MANGANESE OXIDES

BONNET J. Nicolas 1*, BEAUVAIS Anicet 2, ARNAUD Nicolas 3, CHARDON Dominique 4 and DUPONT-NIVET Guillaume 1, 5 (*[email protected])

1: Université de Rennes 1, Géosciences Rennes, UMR CNRS 6118, 35042 Rennes Cedex, France2: Aix Marseille Univ, CNRS, IRD, Collège de France, CEREGE, Aix en Provence, France3: Université de Montpellier 2, Géosciences Montpellier, UMR CNRS 5243, 34095 Montpellier4: Université de Toulouse, UPS (OMP), IRD, CNRS, GET, 14 avenue Edouard Belin, 31400 Toulouse5: Universität Potsdam, Institute of Earth and Environmental Science, 14476 Potsdam, Germany

The Cenozoic weathering of peninsular India has been advocated as a major driver of global cooling, however, its timing remains virtually unconstrained such that proposed links between tropical weathering of the Deccan Traps, regional monsoonal intensity and global climate re-mains speculative. To solve this conundrum we present here a revised weathering chronology based on the identification of lateritic paleosurfaces and their dating using 40Ar/39Ar on su-pergene K-rich manganese oxides. We focus on the Indian western passive margin where the Western Ghats Escarpment (WGE) – a ~1000 m high topographic barrier resulting from the continental break up of Greater India – exposes exceptionally preserved weathering profiles from the western coastal lowlands to the eastern highland plateaus above the WGE. Four main lateritic paleosurfaces have been identified: Three in the highland; a high landsurface (Al-Fe mostly bauxite) at elevation 1200-1000 m asl, an intermediate landsurface covered by a Fe-duricrust at 1000-900 m asl and a lower pediment landsurface at 850-600 m asl; and one in the coastal lowland underneath a pediment landsurface at 150-50 m asl. The 40Ar/39Ar ages document three major weathering periods over the Cenozoic. The oldest weathering period (W1) is recorded between 53 Ma to 45 Ma both in the highland and the lowland. This correlates to the Global Eocene climatic Optimum, and allows defining a bauxitic paleolandsurface across the escarpment. Intense bauxitic weathering between ~ 45 and 47 Ma in the lowland indicate that the WGE was stabilized before ~ 47 Ma on its margin and also implies low denudation rate at the foot of the WGE (<5 m Ma-1) since that time. The second weathering period between 37 Ma to 19 Ma (W2) occurred in two distinctive stages (W2a and W2b). From 37 to 26 (W2a), weathering is only recorded in the highland and affect intermediate surfaces. The intensity of chemical weathering decreased sensibly between 32 and 29 Ma – potentially linked to the Early Oligocene cooling – and resulted in the formation of the lower pediment surface. From ~26 Ma to 19 Ma (W2b), only the western coastal lowland weathered while the highland sur-faces are mostly dissected. This change and the highland/lowland weathering mitigation after ~26 Ma documents a change in climatic patterns over peninsular India that signs the onset of modern-like monsoon regime. These results are being interpolated to the Deccan Traps basalts to quantify their weathering and ultimately estimate of the contribution to CO2 fluxes of these three weathering periods and their potential link to Asian Monsoons and global cooling.

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THE DYNAMICS OF ALKALI ELEMENTS AT THE EARTH SURFACEOVER GEOLOGICAL TIME SCALES

BOUCHEZ Julien 1, GAILLARDET Jérôme 1 & DELLINGER Mathieu 2

1: Institut de Physique du Globe de Paris, Sorbonne-Paris-Cite ´ University and CNRS, Paris, France ([email protected], [email protected])2: Durham University, Department of Earth Sciences, South Road, Durham DH1 3LE, United Kingdom ([email protected])

After erosion has delivered weathered detrital material to a sedimentary basin, the terrigenous sediment interacts with the surrounding waters and is thereby chemically mo-dified [1]. The resulting sedimentary material is later involved in orogenesis as consolidated «meta-sediments», which at present times form most of the continental material subject to erosion [2]. This «recycling» of eroded and weathered material through continental erosion and sedimentation cycles has important implications for (a) the erosive properties of continental surfaces and (b) the ability for chemical weathering to be an efficient sink of CO2. It is therefore timely to better constrain the dynamics of chemical elements during the formation and des-truction of metasedimentary formations, as potential tracers of long-term the recycling rate of sedimentary material. Large rivers drain significant portions of the continental crust, thus the particles they transport integrate weathering, erosion, and recycling processes at spatial scales that are re-levant for studying global biogeochemical cycles across deep time scales. We report the che-mical composition of large river sediment as a function of grain size, and across a set of rivers draining various proportions of igneous vs. metasedimentary rocks (Amazon and Mackenzie systems). Rivers mostly draining shales (fine-grained metasedimentary rocks) transport sedi-ments that are enriched in the alkali elements Li, K, Rb and especially Cs, and depleted in the most soluble alkali element, Na, compared to other rivers with a significant contribution of igneous rocks in their drainage basins, or compared to the Upper Continental Crust [3]. For a given river, this enrichment / depletion pattern of alkali elements is observed also across the grain size range: fine-grained sediments such as suspended particles are enriched in Li, K, Rb and especially Cs, and depleted in Na, compared to coarse-grained sediments such as bed load. Through simple mass balance modeling accounting for the effects of weathering, hy-drodynamic sorting, and sediment-seawater interaction, we explore the following hypotheses to explain these observations: (i) Present-day weathering processes enrich a fine fraction of the eroded material in Li, K, Rb, and Cs, and the complementary depleted component is not visible in the transported material in the rivers; (ii) Ancient weathering processes have enriched meta-sedimentary material in Li, K, Rb, and Cs, and the complementary depleted component is not involved in the formation of meta-sediments subjected to present-day erosion; (iii) the

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chemical interaction of sediments and water (especially seawater) during diagenesis and pos-sibly metamorphism has led to the enrichment of meta-sediment in Li, K, Rb, and Cs.

[1] Michalopoulos P. and Aller R.C. (1995). Rapid clay mineral formation in Amazon delta sediments: reverse weathering and oceanic elemental cycles. Science 270:614.

[2] Dellinger M., Gaillardet J., Bouchez J., Calmels D., Galy V., Hilton R.G., Louvat P., and France-Lanord C. (2014). Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion. Earth Planet. Sci. Lett. 401:359-372.

[3] Bouchez J., Gaillardet J., France-Lanord C., Maurice L. and Dutra-Maia P. (2014). Grain size control of river suspended sediment geochemistry: Clues from Amazon River depth profile. Geochem. Geophys. Geosyst. 12(3):Q03008.

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RUBIDIUM ISOTOPE FRACTIONATION:A POSSIBLE FINGERPRINT OF BIOLOGICAL ACTIVITY IN

DETRITAL SEDIMENT?

CHARBONNIER Q. 1, BOUCHEZ J. 1, GAILLARDET J. 1, MOYNIER F. 1, PRINGLE E. 1,DELLINGER M. 2

1: Institut de Physique du Globe de Paris, Sorbonne-Paris-Cite University and CNRS, Paris, France2: Durham University, Department of Earth Sciences, South Road, Durham DH1 3LE, United Kingdom

The chemistry of river sediments results from the combination of the chemical composition of eroded rocks with the effect of modern weathering processes. Detrital archives can, therefore, be used to retrieve the history of erosion and weathering of the Earth surface. The measure-ment of isotopic variations in the detrital sediments has been used to reconstruct shifts in rock sources (e.g. strontium or neodymium isotopes; [1]), or the weathering intensity (e.g. lithium isotopes; Dellinger et al. (this conference)) However, proxies for the past intensity of biological activity of the continental surface are still lacking. Here, we explore the stable isotope ratio of rubidium (Rb, ratio 87Rb/85Rb) in river sediment as a potential tracer of biological activity. The alkali trace element Rb is a micro-nutrient that is dominantly transported in the solid load by rivers. To date, no published study has reached a suitable procedure for the separation of Rb (required for isotope measurements) from environmental samples. We, therefore, developed a new protocol of separation of Rb leading to accurate and reproducible measurements of the Rb isotope ratio. Then, we measured the isotopic composition of sediments transported by the 3 of the largest river systems on Earth: the Amazon, Mackenzie, and Ganges-Brahmaputra rivers. Significant differences in Rb isotope composition of the sediments between these river systems are observed, which cannot be explained by a simple mixing between different source rocks (as for Sr isotopes). In bed sediments, lithium (Li, another alkali element) and Rb isotope ratios share the same trend across the set of rivers. Since the chemistry of bed sediments is mostly influenced by source material, this observation suggests that Rb and Li follow the same pathways during the erosion/transport/sedimentation cycle. In suspended sediments, which are also affected by modern weathering processes contrary to bed sediments, these two iso-tope systems are not correlated. As Li is not a nutrient (unlike Rb), we suggest that this diffe-rence is due to the present-day cycling of Rb through the biosphere. In order to further explore this hypothesis, the next step of this work is to obtain the Rb isotope composition of river water and biological material. These results have important implications for tracing biological activity in both modern and ancient sediment archives.

[1] Clift P.D., Wan S., Blusztajn J. (2014): Reconstructing chemical weathering, physical erosion and monsoon intensity since 25 Ma in the northern South China Sea: A review of competing proxies. Earth-Sci. Rev. 130:86–102.

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SUSPENDED SEDIMENT FLUX IN THE AMAZON RIVER:LATEST ASSESSMENT AND UNCERTAINTIES.

CRAVE Alain 1, ARMIJOS Elisa 2, 3, FILIZOLA Naziano 4, GUYOT Jean-Loup 3 , FRAIZY Pascal 3, VAUCHEL Philippe 3, MARTINEZ Jean-Michel 3, ESPINOZA Raul 3, SANTINI William 3, DOS SANTOS Andre 4, 5, COCHONNEAU Gérard 3, FONSECA P. 2 &DE OLIVEIRA Eurides 6,

1: Géoscience Rennes, CNRS UMR 6118, Rennes, France.([email protected])2: Programa de Pós-graduação CLIAMB, Instituto Nacional de Pesquisas da Amazônia (INPA), Universidade do

Estado do Amazonas (UEA), Manaus, Brasil.([email protected])3: Géoscience Environnement Toulouse (GET-CNRS, IRD, 34100 Université de Toulouse), Toulouse, France ([email protected], [email protected], [email protected], , [email protected], [email protected], [email protected])4: Universidade Federal do Amazonas (UFAM), Manaus, Brasil.( [email protected])5: Serviço Geológico do Brasil (CPRM), Manaus, Brasil ([email protected])6: Agência Nacional da Agua (ANA), Brasília, Brasil([email protected])

The Amazon River makes an important contribution to the global sediment flux. However, Amazon is poorly constrained with current estimation of sediment flux varying by a factor of two (600 to 1300 Mt year-1) at the most downstream Óbidos gauging station located at 870 km before the mouth. The difference in the estimates is the difficulty in performing measurements with the traditional methods due to the large scale of the cross section and also high cost for monitoring in long-term. In the context of the HyBam observatory network several methodo-logies have been deployed to reduce uncertainties in the estimation. One of those is to per-form distinct calculation of sediment yield taking into account the two fractions sediments size (silt and sand) that characterize suspended sediment in the downstream part of the Amazon River. Indeed, silt and sand yields don’t show the same annual dynamic during the hydrological year and don’t show the same dependency with the discharge. Following this methodology, the suspended sediment yield of the lower Amazon River (Obidos station) is 1100 Mt year1 ±25%, of which 60% is silty and 40% is sandy sediment yield. However, the sediment yield reaching the Atlantic is still unknown due to logistic challenge for water discharge and sedi-ment concentration monitoring in the most downstream part of the Amazon River.

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OFFSHORE AND ONSHORE EVIDENCE FORA POLYPHASED UPLIFT HISTORY AND UPPER MIOCENE DOMING

OF MADAGASCAR

DELAUNAY Antoine 1@, ROBIN Cécile 1, GUILLOCHEAU François 1, DALL’ASTA Massimo 2, CALVES Gérôme 3

1: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France (@) [email protected]: TOTAL CSTJF, 64000 Pau3: Géosciences Environnement Toulouse, UMR 5563 – OMP, 34100 Toulouse, France

Madagascar is an Archean to Neoproterozoic continental crust surrounded by transform, oblique and divergent margins: the oblique Morondava Basin to the west, pounded by the Davie Fracture Zone, and to the north, the divergent Mahajanga (Majunga) Basin connected to the Somali Oceanic Basin. This 1600 km long island is a high axial plateau with elevations ran-ging from 1200 to 1800m. The top of the plateau corresponds to weathered planation surfaces (etchplains), bounded by more or less high scarps.

We here present geological arguments for the age and the timing of the Madagascar Plateau. This analysis is based on a double, coupled analysis of the onshore geomorphology (stepped planation surfaces) and the offshore margin stratigraphy (seismic stratigraphy and wells).

The geomorphological analysis is based on a characterization, a mapping and dating of step-ped planation surfaces (mantled to stripped etchplains, pediments to pediplains). The dating is based on their geometrical relationships with dated magmatic rocks. The difference of ele-vation between two planation surfaces (corresponding to local base level) providing a proxy of the uplift. The sequence stratigraphic and seismic analysis is based on a biostratigraphic reevaluation of 4 industrial wells (foraminifers and nannofossils on cuttings), several hundreds of kilometers of industrial and oceanographic research seismic surveys. Uplift periods are cha-racterized by (1) seaward tilting of the margins overlain by planar reflectors, (2) forced regres-sion wedges, (3) upstream erosions of older sediments recorded by fauna/flora reworking and (4) major paleogeographic changes within the Morondava basin.

(1) During Middle Cretaceous (99 to 85 Ma), Madagascar undergoes a major volcanic event with the onset of the Madagascar Trap, contemporaneous to Madagascar-India separation. The major mid Cretaceous erosion surface is described onshore as the result of a pre to syn-trap Uplift.

(2) During Paleocene to Lower Miocene times (66 to 20 Ma), Madagascar is a quite flat low elevation domain with remnants of an oldest pre-Madagascar Trap (90 Ma) surface. This

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low relief is highly weathered with growth of numerous lateritic profiles and surrounded by large carbonate platforms with no siliciclastic sand influx.

(3) The Late Miocene is the paroxysm of uplift with (1) a tilting of the margin (Morondova), (2) an increase of the siliciclastic sand flux since middle Miocene and (3) a major stepping of dated planation surfaces.

(4) The end result of this uplift is a convex up shape pattern for the end Cretaceous surface weathered during Eocene times, creating the present-day dome morphology (with a cen-tral plateau) of Madagascar.

(5) The amplitude of this uplift can be estimated based on the present-day elevation of Late Eocene lagoonal sediments located 100 km north-east of Toliara and now at an elevation of 900m. If the absolute sea level was around 50 m (Miller et al., 2005) above present-day sea level during Late Eocene times, this means a surface uplift of around 850 m.

(6) The mechanism of this uplift has to explain a very long wavelength deformation (x1000 km) necessary due to mantle dynamics. The relationships with the other East African domes (Ethiopia, East Africa, South Africa) are discussed.

This study was funded by TOTAL and IFREMER in the frame of the research project PAMELA (PassiveMargin Exploration Laboratories).

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LITHIUM ISOTOPES AS A PROXY FOR SILICATE WEATHERINGAND TOTAL DENUDATION IN LARGE RIVERS

DELLINGER Mathieu 1, 2, BOUCHEZ Julien 2, GAILLARDET Jérôme 2, LOUVAT Pascale 2 & CALMELS Damien 3

1: Durham University, Geography department – DH1 3LE, Durham, UK ([email protected])2: Institut de Physique du Globe de Paris, Sorbonne-Paris-Cite, University and CNRS, Paris, France ([email protected], [email protected], [email protected])3: Université Paris Sud, Departement des sciences de la Terre, Orsay, France ([email protected])

Over long time scales, silicate weathering and physical erosion are major processes regulating the amount of atmospheric CO2 and therefore controlling the evolution of climate, sedimen-tary cycle and Earth’s habitability. Despite this recognition, it is still poorly known how the de-nudation of the continents has changed in the past. Indeed, tracing ancient weathering and erosion processes using conventional geochemical tracers in detrital sediments (e.g. chemical index of alteration CIA) can be challenging because these proxies are also influenced by sedi-ment provenance, grain size effects or diagenesis. The emerging Li isotope proxy has a great potential for tracing silicate weathering and erosion because Li is a soluble, non bio-essential element predominantly hosted in silicate rocks and its isotopes are fractionated during water-rock interactions. In this contribution, we investigate the Li isotope composition in the dis-solved and solid materials transported by the largest rivers on Earth (Amazon, Congo, Ganges, Mackenzie) in order to quantify the relationship between weathering, erosion and Li isotope in the present-day.We show that, in the dissolved load, (i) the Li isotope composition is a function of both the weathering intensity and the locus of weathering (hillslopes versus floodplain weathering) and that (ii) the riverine dissolved Li flux is directly correlated to the denudation. In the river sedi-ments, the Li isotope composition and concentration are controlled by a combination of grain size, provenance and weathering intensity. We find that the sediments transported by these large rivers are mostly sourced from the recycling of sedimentary rocks and contain only a small proportion of clay minerals formed during the present-day weathering cycle. Once cor-rected from grain size and provenance variability, the sediment Li isotope composition define a negative relationship with the weathering intensity. Altogether, we define a new set of relationships between Li isotopes, provenance and denudation that can be used as a framework to interpret the Li isotope record of sedimentary archives (detrital and carbonate) in terms of paleo-weathering and erosion regime and rates. These results have important implications for the understanding of erosion and weathering processes both in the present-day and in the past.

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CENOZOIC SEDIMENTATION HISTORY OF THE CONGO BASIN REVISITED

DE PUTTER Thierry 1, BAYON Germain1, 2, MEES Florias 1, RUFFET Gilles 3 & SMITH Thierry 4

1: Musée Royal de l’Afrique Centrale, Earth Sciences Dept, Tervuren, Belgique ([email protected]; [email protected]; [email protected]; )

2: Ifremer, Plouzané, France 3: Université de Rennes I, Géosciences Rennes, Rennes, France ([email protected])4: Institut Royal des Sciences Naturelles de Belgique, Terre et Histoire de la Vie, Bruxelles, Belgique ([email protected])

The Congo Basin in Central Africa is one of the major river basins of the world. Its history over the last 75 Myr should record global and major regional events, including the Paleocene-Eo-cene Thermal Maximum at ~55 Ma and the Miocene aperture of the Western branch of the East African Rift System along its eastern border at ~25 Ma. Available data for associated off-shore deposits show that the Congo River delta experienced a starvation period during the Mid- to Late Cretaceous and Paleogene, with endorheic lacustrine to desert environments in the upstream basin, followed by a period marked by high rates of drainage and sediment supply in the Neogene.Here we complement this sedimentation history with a multi-proxy analysis of an on-shore Paleogene section along the west coast of Central Africa (Landana, Cabinda Enclave, Angola) and with new age determination results for paleosurface-related manganese oxide deposits from the southern margin of the Congo Basin in the DR Congo.Newly obtained 39Ar-40Ar ages for cryptomelane from Katanga (Kasekelesa) and Kasaï (Mt Mwatshimwa) reveal an old (Cretaceous?) surface that developed before ~76 Ma and they sug-gest the existence of at least two younger Eocene denudation episodes, during the Lutetian (~45 Ma) and the Priabonian (~35 Ma). They furthermore confirm the identification of a series of Mio-Pliocene denudation surfaces that were previously recognized by the same methods for the Kisenge area, Katanga (De Putter et al., 2015). It is likely that the newly obtained Cretaceous age records the subcontinental ‘African Surface’ that had previously not been identified for Central Africa.The Landana section presents a condensed (~45 m) Paleogene-Neogene sequence. The Paleo-gene deposits (~25 m), dated by the rich fossil assemblage they contain (Solé et al., in prep.), record a shallow marine carbonate environment with minor to moderate fine-grained terri-genous detrital input. Sediment provenance, as documented by εNd, does not change signi-ficantly in the course of the Paleogene, whereas weathering, as documented by εHf and δ30Si, increases slightly from the Danian to the Lutetian (Bayon et al., 2016). This time interval cor-responds roughly to the assumed period of deposition of the Kalahari Group of the western part of the Congo Basin, where it occurs as a ~150 m thick sand accumulation. The top of the Lutetian beds of the Landana section is a major discontinuity, marked by strong silicification, which would correspond to the Lutetian denudation surface in Katanga.Sedimentation recorded by the Landana section changes drastically after this hiatus with Lu-

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tetian onset, becoming dominated by coarse-grained siliciclastic sediments. A major change in sediment source is confirmed by εNd, whereas isotopic proxies of weathering (εHf, δ30Si) document a major decrease in weathering intensity. The sharp increase in sediment discharge is attributed to uplift along the southern and eastern margins of the Congo Basin, preceding the opening of the East African Rift in the Oligocene.A combination of sedimentological, geochemical and geochronological proxies provides new constraints for a Paleogene time interval that is only poorly documented for the Congo Ba-sin. During this period, sediments, including those of the Kalahari Group, were deposited on a denudation surface tentatively identified as the Cretaceous African Surface. The uplift that occurred before opening of the East African Rift resulted in increased terrigenous off-shore sedimentation after the Lutetian.

De Putter et al., 2015. Ore Geol. Rev. 71, 350-362Bayon et al., 2016. Goldschmidt Conf. 2016, abstract book, 181This abstract is a contribution to the Brain.be PalEurAfrica project: http://www.paleurafrica.be/

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A REGIONAL NORTH-SOUTH CROSS SECTION THROUGHTHE GHADAMES BASIN AND ITS IMPLICATIONS TO HC POTENTIAL

IN THE GHADAMES BASIN AND THE NORTHERN AREASAROUND JABAL NAFUSAH, LIBYA

EMHANNA S. 1, EL-EKHFIFI S. 2, and MUSBAH B. 3

1: Ajdabya University, Ajdabya Libya, [email protected]: National Oil Corporation-Benghazi, Libya, [email protected]: National Oil Corporation, Libya,

The Ghadames Basin is a highly productive petroleum province with a long exploration history in Algeria, Libya & Tunisia (from the late 1950’s to present day). Ongoing exploration success in all three countries suggests that it will continue to provide attractive exploration targets in the future.

A Regional N-S cross section through the Ghadames Basin has been constructed to docu-ment and improve understanding of the geologic framework and petroleum systems of the Ghadames Basin. It extends from the Mediterranean Sea in the north through the Jifarah Basin, Jabal Nafusah, Ghadames Basin, and Alatshan High to northern part of the Murzuq Basin in the south, covers approximately 700 kilometers and provides a regional view of the structural and stratigraphic framework of the Ghadames Basin.

The information shown on the cross section is based on geophysical data from thirty five wells, most of which penetrate the Paleozoic sedi¬mentary rocks of the basin and two of which bottom in crystalline basement rocks. The correlation of stratigraphic intervals between the wells was based on a diversity of wirelinelogs and lithologic logs. The most commonly used logs were the GR (gamma-ray), SP (spontaneous potential), ILD (resistivity) and DT (sonic) logs.

This cross section was generated by using LandMark StratWork software. Wells included in the section were chosen on basis of location, presence of all the section, depth of penetration and data availability. The wells in the bloc ks and major oil and gas fields were included .

The scope of this project was in the distribution of the key formations and looking for new potential areas especially in the north (Jifarah Basin). In terms of the hydrocarbon potential in the areas around Jabal Nafusah the areas east, west and north of the Tigi discovery are drawn attention for hydrocarbon exploration where all the petroleum system elements are presented;

• Reservoir rock: - Tahara, Acacus, Mamuniyat, Ouled Chebbi and Ras Hamia formations.• Source rock: - Tanezzuft Formation.• Trap: - Structural – Unconformity Trap.• Seal: -Mrar, Bir Al Jaja Formation, Abu Shaybah as well as intraformational seals

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References

Echikh, K., 1998. Geology and hydrocarbon occurrences in the Ghadames Basin, Algeria, Tunisia, Libya, in D.S.

Hallett, D., 2002. Petroleum Geology of Libya. Elsevier, Amsterdam. 503p.Rusk, D. C., 2001. Libya: Petroleum potential of the underexplored basin centers - A twenty-

first-century challenge, in M.W.

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SEDIMENT ROUTING SYSTEMS IN MIGRATING RIFTS. INSIGHTSFROM THE CORINTH RIFT

FORD Mary 1, GAWTHORPE Robert 2 & HEMELSDAEL Romain 1

1: CRPG, University of Lorraine, 54501 Vandoeuvre les Nancy, France. [email protected], [email protected] 2: Department of Earth Sciences, University of Bergen, Norway. [email protected]

The Corinth rift is one of the fastest opening rifts in the world with geodetic NS extension rates of 11-16 mm/a. It initiated in the Late Pliocene (4 Ma) as part of the western Aegean extension system. The older parts of the rift are now relatively inactive and have been uplifted and exposed in a 25-30 km swathe of the northern Peloponnesus. Excellent exposures of the syn-rift succession in the northern Pelopponesus provide the opportunity to investigate the evolution of the syn-rift sedimentary succession, in particular the response of sediment routing systems, facies distributions and depocentre connectivity to rift migration and acceleration over a period of 4 to 5 M yrs. A N-S extension direction is recorded since the beginning of rifting. Extension was accommodated on a dominantly north-dipping, closely spaced system of faults. Present-day extension and seismic activity is focused below the Gulf of Corinth itself, indicating very clearly that the locus of deformation has migrated northward. Rift migration was also associated with acceleration in extension rate. Sediment routing and volumes sup-plied into the rift were strongly influenced by inherited orogenic relief and associated drainage network. A strong antecedent drainage supplied high volumes of coarse sediment from the onset of rifting. The rift displays a clear lateral asymmetry in the volume of sediment supplied to depocentres, with high supply of coarse sediment in the west and low supply of relatively fine sediment in the east. This pattern persists throughout rifting with sediment routing ar-teries responding in different ways to rift migration, uplift of the southern rift shoulder and acceleration through four phases of rift evolution.

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57


NEOGENE AND QUATERNARY EROSIONOF THE HIMALAYA RECORDED IN THE BENGAL FAN:

IODP EXPEDITION 354

FRANCE-LANORD Christian 1, GALY Albert 1, HUYGHE Pascale 2, MEYNADIER Laure 3, SPIESS Volkard 4, KLAUS Adam 5, and SCIENTISTS OF EXPEDITION 354

1: CRPG-CNRS-Univ. Lorraine, Vandoeuvre les Nancy, France mailto: [email protected]: ISTERRE, CNRS-Univ. Grenoble Alpes, France3: IPG, Paris, France4: University of Bremen, Bremen, Germany5: Texas A & M University, College Station, TX, United States

The development of the Himalayan orogeny during Paleogene and Neogene induced major change in continental distribution, topography and climate that impacted the global climate as well as the biogeochemical cycles. The development of the highest mountain range coupled to the intense monsoonal precipitation regime generated the most intense erosional flux of the planet that enhanced both organic carbon burial and silicate weathering. The largest part of the sediment flux was exported to the Bengal fan, accumulating a long-term archive of this erosion. These sediments archived the nature of eroded formations in the Himalaya and allow scaling the impact of Himalayan erosion on the carbon cycle.

IODP Expedition 354 in the Bay of Bengal drilled in February-March 2015 a seven site, 320 km-long transect across the Bengal Fan at 8°N, approximately 1500 km south of the Ganga-Brah-maputra delta. Sediments originate from Himalayan rivers, documenting terrestrial changes of the monsoon evolution and Himalayan erosion and weathering, and are transported through a delta and shelf canyon, supplying turbidity currents loaded with a full spectrum of grain sizes. Mostly following transport channels, sediments deposit on and between levees, while depocenters are laterally shifting over hundreds of km on millennial time scales. Expedition 354 documented these deposits in space and time by identifying, coring and dating nume-rous stratigraphic marker horizons across the transect, allowing a detailed reconstruction of channel-levee migration, abandonment, reoccupation and overall uniform growth in the late Pleistocene. High resolution records of these growth patterns were acquired in several levee, interlevee and hemipelagic successions. Three deep penetration and additional four shallow holes provided a spatial overview of the primarily turbiditic depositional system. which docu-ments the interplay between the monsoon and Himalayan tectonic.

Analyses of detrital sediments reveal close mineralogical, geochemical, and isotopic simili-tudes with those of modern river sediments derived from the Himalaya. Major and trace ele-ment geochemistry show relatively stable compositions throughout the Neogene. They reveal a very weak regime of chemical weathering, lower than present, and with no significant varia-

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tion through time. This clearly differs from the distal fan record (Leg 116 at 1°S) where from ~7 to 1 Ma, weathered and smectite rich sediments are predominant. It implies that the distal fan record does not reflect an evolution of the source erosion. Rather, it is controlled by a change in sediment transport and sorting within the fan. Low weathering of the sediments at 8°N indi-cates that erosion is driven by physical processes and transport rapid enough to prevent evo-lution of particles. In the modern Himalaya, low weathering is achieved primarily by landslides and rapid transfer through the floodplain, i.e. limited recycling of sediment deposited in the floodplain. Both processes are favoured by the seasonality and the intensity of the monsoon. Isotopic compositions of silicates and carbonate document the geological formations exposed to erosion. They imply that exposure to erosion of the different Himalayan formations has evolved as a result of the evolution of the thrusting structures.

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COSMOGENIC NUCLIDES, RIVER GEOCHEMISTRY, AND LANFORMS RECONSTRUCTION METHODS COMPARISON TO STUDY THE COOPLING

BETWEEN CHEMICAL WEATHERING, MECHANICAL EROSION AND TRANSPORT IN A STEEP REUNION ISLAND BASINS.

GAYER Eric 1, LOUVAT Pascale 1, BOUCHEZ Julien 1, MICHON Laurent 1, 2, GAILLARDET Jerome 1, SY Adrien 1, HAVAS Robin 1.

1: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, Paris, France ([email protected])

2: Université de la Réunion, La Réunion, France

Understanding the mechanisms that modify landscapes is essential for identifying feed-backs between climate, tectonic and topography. Because measurements of erosion rates are critical for quantifying landform evolution, the coupling of different techniques has often been used. However, different methods often estimate erosion rates over different time scales, and are sensitive to different erosion processes.

In this study we estimate erosion rates of highly eroding drainage areas of Reunion Island. We compare and combine the results of three methods: i) from cosmogenic 3He concentra-tions, ii) from river geochemistry and iii) from landforms reconstruction. Our aim is to derive, from this new approach, the message provided by each method in terms of chemical weathe-ring, mechanical erosion and erosion processes.

Helium concentrations and isotopic ratios were measured in olivine-rich sands from ri-vers and landslides products. Digital elevation model and K-Ar geochronological data were used to reconstruct basins initial topographies and to calculate the volumes of material ero-ded over the past ~65Ka. Finally, dissolved and suspended loads and river sediments were analyzed for their major and trace elements contents, and a geochemical mass balance was built in order to quantify both chemical and mechanical erosion rates. Results show a good agreement between long-term erosion rates derived from topography reconstructions and so called short-term erosion rates from the geochemical mass balance. The cosmogenic method underestimates erosion rates, but comparison with the geochemical mass balance helps to show that episodic landslides dominates erosion of the basins. Finally, a new approach of the geochemical mass balance with a systematic study along the range of river sediment grain size shows an anti-correlation between weathering and grain size allowing to depict weathering vs genesis and transport of sediments.

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DECIPHERING THE GRAIN-SIZE TRENDS THROUGH TIME:CASE STUDY OF THE QUATERNARY URUMQI ALLUVIAL FAN

IN THE CHINESE TIAN SHAN PIEDMONT

GUERIT Laure 1, BARRIER Laurie 2, GAYER Eric 2, NARTEAU Clément 2, LIU Youcun 3,LAJEUNESSE Eric 2, MEUNIER Patrick 4, VAN DER WOERD Jérôme 5, MURRAY Andrew 6, METIVIER François 2

1: Géosciences Environnement Toulouse, UMR 5563 – OMP, 34100 Toulouse, France ([email protected])2: Institut de Physique du Globe de Paris, 75005 Paris, France ([email protected], [email protected], [email protected],

[email protected], [email protected])3: Key Laboratory of Water Environment and Resource, Tianjin Normal University, Tianjin 300387, China

([email protected])4: École Normale Supérieure de Paris, 75000 Paris, France ([email protected])5: Institut de Physique du Globe de Strasbourg, UMR 7516 CNRS, Université de Strasbourg, 67084 Strasbourg,

France ([email protected])6: The Nordic Laboratory for Luminescence Dating, Earth Sciences, Roskilde, Denmark ([email protected])

Understanding the controls on the size of the sediments observed in sedimentary basins is a key challenge in sedimentology, as it influences strongly the physical processes of transport and deposition, and thus the characteristics of a basin. In addition, the size of the sediments should be related to the conditions prevailing in the area where they have been produced, and we should theoretically be able to read the tectonic and climatic conditions that prevailed at the time of deposition from the granulometric evolution of the sediments coming from a given area. If large changes in the granulometry of the sediments are often associated to climatic or tectonic pertubations, the influence of autogenic processes, and in particular of autogenic incisions of alluvial deposits, should also be considered.

To bring insight into this question, we sampled the grain size along a well-exposed, vertical section of an alluvial fan mainly made up of gravels, and located in the semi-arid piedmont of the Tian Shan in China. In fact, alluvial fans are well designed to explore such questions, as they are located at the outlet of drainage basins, and constitute therefore the first record of the sediments exported out of the relief. Datations based on cosmogenic and OSL analyses provide a good temporal framework, and allow the comparison with the documented climatic events that have affected the area.

We show that the granulometric evolution of the Urumqi alluvial fan in the Chinese Tian Shanfollows the first-order evolution expected from the fan progradation, and from the regional climatic variations. However, we observe a large and short-live increase in the grain size about ~5000 years, that can not be explained by such controls. We propose here that it can be linked to the rapid incision of the river at the period, which could have enhanced the transport capa-city and thus, enabled the river to carry large grains further into the sedimentary system.

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EXPERIMENTAL DRAINAGE BASINS AS MARKERS OF LARGE-SCALEHORIZONTAL DEFORMATION

GUERIT Laure 1, *, DOMINGUEZ Stéphane 2, MALAVIEILLE Jacques 2,CASTELLTORT Sébastien 1

1: Université de Genève, 1205 Geneva, Switzerland ([email protected])2: Université de Montpellier, Géosciences Montpellier UMR5243, F-34095 Montpellier, France ([email protected], [email protected])*now at: Géosciences Environnement Toulouse, 31400 Toulouse, France ([email protected])

The morphology of a fluvial landscape is a balance between its own dynamics and external forcings, and it can be used to reveal tectonic pattern or climate evolution. In particular, rivers have long been recognized as markers of localized horizontal deformation in strike-slip context and used to estimate fault slip velocity. However, deformation is not always partitioned on major faults only and in oblique context, it can be distributed over larger areas, as it is the case in the Southern Alps of New Zealand.

To better document and understand the regional dynamics of such systems, reliable markers of the horizontal tectonic motion over geological time scales are needed. River networks are able to record a large amount of distributed strain and they can thus be used to reconstruct the mode and rate of distribution away from major active structures.

To explore the controls on river resilience to deformation, we developed a sandbox experiment equipped with a rainfall system to model the evolution of a drainage network over a doubly-vergent orogenic wedge growing in a context of oblique convergence. During the experiment, drainage basins are clearly rotated clockwise. Image analysis of the time-space evolution of the landscape shows how the velocity field decreases toward the fault both in amplitude and in obliquity, and we propose that this pattern is responsible for the rotation of the main trunk valleys. This rotation has strong consequences in terms of sedimentary records, as it implies that river outlets can move though time by a non-negligible amount. In addition, it should thus be possible to invert the morphology of a river network to estimate the large-scale, horizontal deformation. However, the rivers do not record the whole imposed rotation rate, suggesting that the channel dynamics compete with the passive deformation.

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SOURCE TO SINK STUDY OF THE CONGO SYSTEM SINCE 40 MYR :A MEASUREMENT OF THE RATIO BETWEN MECHANICAL

AND CHEMICAL EROSION.

GUILLOCHEAU François 1, GALMIER Valentin 1, ROBIN Cécile 1

1: Géosciences Rennes, UMR 6118 Université Rennes 1-CNRS, OSUR, 35042 Rennes cedex

The erosional processes are of two types; mechanical and chemical. If the first one are ex-tensively studied, the chemical ones are less known whether it is for the coupling between geo-morphological processes and chemical alteration or two the knowledge of the ratio between mechanical and chemical erosion. In 1995 Gaillardet and coauthors proposed based on global geochemical mass budget of the modern Congo River, a ratio between physical and chemical weathering of 1.5.

To test this ratio, we here performed a source to sink study of the Congo System (catchment and depositional system up to the abyssal plain) since 40 Myr, time interval during which the Congo catchment did not experience major climate changes.

The continental denudation was measured by subtracting the present-day topography from the so-called African Surface, etchplain (weathering surface) shaped between 70 and 40 Ma. This etchplain is today preserved as remnant planation surfaces from the eastern limb of the East-African Dome to the high plateaus of Cameroon and Angola. The deposited volumes were measured from seismic line and petroleum wells. Dated time-lines were drawn based on the principles of the seismic stratigraphy. The measured volumes from the coastal to the abys-sal plains were compacted for a better comparison with the eroded volumes.

From 40 Ma to today, 799 000 km3 of rocks were denudated over the Congo River catch-ment and 488 000 km3 of (compacted) sediments were deposited along the delta and the deep-sea-fan. The ratio between eroded and deposited volumes is around 1,64 (1,3 – 2,1 in-cluding uncertainties).

In the absence of any type of buffer effect with temporary sediments storage along the Congo Basin, we interpret this difference of volume between erosion and sedimentation as the amount of chemical erosion. The value is quite similar to this measured by Gaillardet et al. (1995).

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INTEGRATED SOURCE TO SINK INVESTIGATION OFTHE SABLE SUB-BASIN OFFSHORE NOVA SCOTIA USING FORWARD

STRATIGRAPHIC MODELING

HAWIE N. 1, SANGSTER C. 2, MARFISI E.1, SAINT ANGE F.1, PE-PIPER G.2, PIPER D.J.W3, MACDONALD A.W.A. 4

1: Beicip-Franlab, France2: Saint Mary’s University, Canada3: Geological Survey of Canada, Canada4: Nova Scotia Department of Energy (NSDOE), Canada

Sediment routing systems represent the integrated behavior of “source to sink” geomor-phologic processes comprising sediment erosion, transport and deposition from catchment areas towards the shelf, slope and basin floor. The use of geomorphological, geological and geophysical multi-scale constraints in Forward Stratigraphic Models has shed light on the va-rious interactions between the local, regional and global scale driving mechanisms (e.g. tecto-nic versus thermal subsidence rates, accommodation, climate evolution, drainage systems ac-tivation, eustatic variations amongst others) that influence sediment transport and deposition along evolving landscapes.

Through this communication we explore the benefits of integrated G&G and deterministic Forward Stratigraphic Modeling workflows in the exploration of the Scotian sub-basin com-plex salt province. Aptian-Albian sedimentary facies and geometries are modelled using a 4x4 km grid size stratigraphic model with 500 kyrs time steps and sensitivity to several environ-mental parameters assessed consequently. The resulting sedimentary facies modelled along the Sable sub-basin point to continental and shallow marine fluvio-deltaic/ estuarine settings that change into inner to middle neritic environments towards the shelf. Shelf incisions drive sediments deeper along the slope and into the basin through hyperpicnal turbidite systems. Three main sediment sources (i.e., the MegumaTerrane, the Carboniferous Maritimes Basin and Grenville Province, and Western Newfoundland) contribute actively to the shelf and basin infill through major river systems (e.g., Sable River, Banquereau River). Modeling results reveal an active influence of complex salt kinematics on the diversion of sedimentary pathways around salt domes and canopies along the slope and deeper basin. Reservoir sediments appear to be trapped following several mechanisms (1) listric faulting along the shelf due to salt withdrawal downslope, (2) mini basin development around the slope and basinal sectors and (3) sediment draping in the deepest basinal setting.

The application of such multi-disciplinary workflows in complex geological settings allow a de-risking of the proposed geological model of the Sable sub-basin, permitting an improved lithology and facies prediction along source to sink depositional profiles.

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CLIMATIC SIGNAL IN CONTINENTAL AND MARINE SECTIONSOF THE EARLY EOCENE PYRENEAN FORELAND BASIN,

A CORRELATION INSIGHT THROUGH A MULTI-PROXY APPROACH

HONEGGER Louis 1, CASTELLTORT Sébastien 1, CLARK Julian 2, ADATTE Thierry 3, PUIGDEFABREGAS Cai 4, DYKSTRA Mason 2, FILDANI Andrea 2, SPANGENBERG Jorge 5

1: Département des Sciences de la Terre, Université de Genève, Rue des Maraichers 13, 1205 Genève, Suisse2: Statoil Research Center, 6300 Bridge Point Parkway, Building 2, Suite 500, Austin, Texas, 78730 USA3: Institut des Sciences de la Terre, Géopolis, Université de Lausanne, 1015 Lausanne, Suisse4: Universitat de Barcelona, Departament de Geodinàmica i Geofísica, C/ Martí i Franquès, s/n, 08028 Barce-

lona, Spain5: IDYST, Géopolis, Université de Lausanne, 1015 Lausanne, Suisse

Geochemical signal in the sedimentary record has proven to be, amongst other markers, a cornerstone in the perspective of unravelling Earth’s past climatic history.

In order to better apprehend the evolution of ancient deposits, we measure a climatic signal in a continental section of the early Eocene Pyrenean Tremp-Graus basin and correlate it with its marine time-equivalent slope deposits in the Ainsa basin.Assumptions about the mechanisms driving the deposition in the two environments are put forward and allow us to draw a high resolution correlation and timing model between two sections: the Isabena section encompassing the Castissent formation, a major fluvial excursion and the Pueyo section including the turbiditic systems of Fosado, Arro and Gerbe

We identify the controling factors of the marine as well as in the continental depositionnal system and attempt to untangle climatic, eustatic and tectonic drivers from each other with the aim of reconstructing a source-to-sink history of the basins.

To address this problem, we use stable isotopes on bulk rock carbonates to trace sea level variations and combine this method with elemental analysis, allowing us to corroborate and interpret independently the data set.

This correlation model also based on fieldwork and previous mapping, permit us to test some fundamental sequence stratigraphy models and debate about the factors controlling stratigra-phic patterns in the fluvial successions that are still debated today (Sømme, 2009)

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ESTABLISHING A CHRONOLOGY OF BURIAL, UPLIFT AND DENUDATION OF THE SOUTH AMERICAN EQUATORIAL ATLANTIC MARGIN

JAPSEN Peter 1, BONOW Johan M. 2, GREEN Paul F. 3, DALL’ASTA Massimo 4, ROIGJean-Yves 5, THEVENIAUT Hervé 5

1: Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, Denmark ([email protected]) 2: Geovisiona AB, Järfälla, Sweden3: Geotrack International, Melbourne, Australia4: Total Research and Development, Pau, France 5: BRGM, Orleans, France

We have initiated a study aimed at understanding the regional history of burial, uplift and denudation of the South American Equatorial Atlantic Margin (SAEAM Uplift) to provide a framework for investigating the hydrocarbon prospectivity of the offshore region. The study combines apatite fission-track analysis (AFTA) and vitrinite reflectance data from samples of outcrops and drillcores, sonic velocity data from drill holes and stratigraphic landscape analysis (mapping of palaeoplains) – all constrained by the available geological information (Green et al. 2013). The study will thus continue the successful approach undertaken in previous uplift studies by combining the thermal history from AFTA data with the denudation history from stratigraphic landscape analysis to provide magnitudes and timing of vertical movements (e.g. Japsen et al. 2012). In this way the study can provide a framework for anticipating possible effects from uplift on the petroleum system along the margin.

At a first glance, the regional geology provides important insights into the denudational his-tory of the Guiana Shield. To the south, along the Amazon Basin, tilted and truncated Paleozoic strata rest on Precambrian basement above a major unconformity, whereas to the north, along the Atlantic margin of Suriname and French Guiana, tilted and truncated Cretaceous siliciclas-tic strata rest on basement. Given the similarity between the Paleozoic successions in the Ama-zon Basin and West Africa (Ford & Golonka 2003), we infer that the Paleozoic succession was continuous across Gondwana prior to denudational events that stripped these strata from the Atlantic margin. Subsequently, the margin subsided in the Cretaceous allowing sediments to accumulate.

Triassic–Jurassic events of uplift and exhumation thus contributed to the present-day shape of the Guiana Shield. According to Sapin et al. (2016), uplift around the K-T boundary is likely to be responsible for the cut off of the sedimentary input from the mainland to the Atlantic during the Paleocene–Miocene build-up of the carbonate platform whereas late Neogene uplift led to the establishment of the present-day Amazon River in Plio–Pleistocene times. We will present new AFTA data from outcrop samples, and we anticipate that these results will provide new details to the burial and exhumation history of the Guiana Shield.

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Ford, D. & Golonka, J. 2003: Phanerozoic paleogeography, paleoenvironment and lithofacies maps of the circum-Atlantic margins. Marine and Petroleum Geology 20, 249-285.

Green, P.F., Lidmar-Bergström, K., Japsen, P., Bonow, J.M. & Chalmers, J.A. 2013: Stratigraphic landscape analysis, thermochronology and the episodic development of elevated passive continental margins. Geological Survey of Denmark and Greenland Bulletin 2013/30, 150 pp.

Japsen, P., Bonow, J.M., Green, P.F., Cobbold, P.R., Chiossi, D., Lilletveit, R., Magnavita, L.P. & Pedreira, A.J. 2012: Episodic burial and exhumation history of NE Brazil after opening of the South Atlantic. GSA Bulletin 124, 800-816.

Sapin, F., Davaux, M., Dall’Asta, M., Lahmi, M., Baudot, G. & Ringenbach, J.-C. 2016: Post-rift subsidence of the French Guiana hyper-oblique margin: from rift-inherited subsidence to Amazon deposition effect. Geological Society, London, Special Publications 431, 20 pp.

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SEDIMENT ROUTING IN SYN OROGENIC SERIESOF THE AQUITAINE BASIN.

LASSEUR Eric 1, LOGET Nicolas 2, RUEDA Thibault 1, MIGUET Johann 2, ORTEGA Carole 1,3, BARBARAND Jocelyn 4 & GAUTHERON Cécile 4

1: Bureau de Recherches Géologiques et Minières, 45060 Orleans cedex 2. ([email protected] )2: Institut des Sciences de la Terre de Paris, UMR 7193 – UPMC, Campus Jussieu, 75005 Paris, France ([email protected] ) 3 : Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France4: Geosciences Paris Sud, UMR 8148 – UPS, 91405 Orsay cedex ([email protected], [email protected]).

The Tertiary evolution of the Aquitaine basin (northern Pyrenean foreland) is closely linked to the Pyrenean orogeny and its northern retrowedge. During the Middle Eocene maximum of Iberia- Eurasia collision (Ypresian- Bartonian) strong denudation of the mountain belt takes place, partly compensated by the subsidence of the foreland. In the Aquitaine basin this period is registered by the progressive transition from dominantly marine underfilled sedimentation to continental overfilled sedimentation. In the proximal part of this system, this overfilling leads to a massive, kilometer thick, conglomeratic sedimentation while deltaic sedimentation progressively fills the basin from east to west. This study focuses on the proximal part of this system in order to characterize (1) the dyna-mics of the piedmont sedimentation and its relation to tectonics, climate and denudation of the orogen, and (2) the transfer of sediments from the piedmont towards more distal areas , through the definition of types of sedimentary systems and identification of zones of trap-ping and bypass . Field study of the syn-orogenic Palassou conglomerates and molasses de Carcassonne from Mouthoumet massif to Lavelanet has been coupled with interpretation of subsurface (well logs and seismic profiles) in order to characterize the geometries and contents of these deposits. The Ypresien – Late Bartonian system is organized along two main megasequences: - A continued progradation during Ypresian from deltaic to proximal braided stream and sheet flood deposits. Clasts are mainly composed of meso-cenozoic cover. This prograding trend accompanies the onset of thrusting in the foreland. The following retrograding trend takes place during Lutetian with the sedimentation of lacustrine and floodplain deposits with intercalated coarse sheet flood deposits. - The second megasequence displays a major progradation with proximal braided stream to alluvial fan deposits which traduces uplift and incision of the piedmont. This se-quence register the first input of material derived from the axial zone.

These two sequences display significantly different geometries revealing strong different controls by tectonics and sediment supply and evolving sediment routing. While the first -un-derfilled- sequence is strongly controlled by the deformation of the foreland, the second one is

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more widespread with limited control of the deformation and progressive sealing of the struc-tures. Thermochronology as well as refined datations and correlations will complete this early results and help linking the dynamics of the Pyrenean orogeny and among all the relative influence of tectonics and climate with the input of sediment and their transfer toward sink areas. The characterization of the transfer of sediments during the syn-orogenic period will be stu-died in the framework of the S2S project (a Total- BRGM collaboration). The current results have been collected during research programs RGF (BRGM) and Gaia (TIGF/BRGM/AEAG).

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3D STRATIGRAPHIC MODELLINGOF THE CONGO TURBIDITE SYSTEM SINCE 200 Ka:

TOWARDS A HIERARCHIZATION OF FACTORSCONTROLLING SEDIMENTATION

LAURENT Dimitri 1, PICOT Marie 2, MARSSET Tania 1, DROZ Laurence 2, RABINEAU Marina 2, GRANJEON Didier 3

1: Ifremer, REM-GM-LES, BP 70 29290 Plouzané, France ([email protected], [email protected])2: IUEM, UMR6538, 1 Place N. Copernic, 29280 Plouzané, France ([email protected], [email protected], [email protected])3: IFP - Energies Nouvelles, Rueil-Malmaison, France ([email protected])

If the geometry and internal functioning of turbidite systems are relatively well-constrained, the respective role of autogenic (topographic compensation, dynamics of turbidity currents…) and allogenic factors (tectonic, sea-level variations, climate) governing their architectural evo-lution is still under debate.

The architecture of the Late Quaternary Congo Fan is characterized by successive sedimen-tary prograding/retrograding cycles reflecting a periodic control of sedimentation (Picot et al., 2016). A strong link with climatic forcing has been proposed, evidenced by changes in fluvial sediment supply consistent with both monsoon intensity variations and glacial/interglacial transitions at the origin of vegetation cover evolution in the Congo catchment area (Picot, 2015).

In the light of these results, the aim of this study is to simulate and investigate the relative im-pact of internal and external forcing factors controlling, both in time and space, the formation and evolution of depocenters since 200 ka. This work represents the first attempt to model in three dimensions the stratigraphic organization of the Congo turbidite system using Dionisos (IFP-EN), a diffusion process-based software. It allows the simulation of sediment transport and the 3D geometry reproduction of sedimentary units, from deltaic to deep-sea environment, based on physical processes such as creation of accommodation space (sea level, subsidence, compaction...), sediment supply and sediment transport.

Preliminary results confirm that the perennial topographic compensation acts as a key para-meter but also reveal that a periodic variation of fluvial sediment discharge is necessary to recreate prograding/retrograding cycles and upfan avulsion events. The ongoing work will decipher the nature and timing of allocyclic factors responsible for water and sediment fluxes changes. In particular, three potential controls will be discussed: (i) seasonal evolution of the water discharge assuming annual dry and wet epochs in the Congo River, (ii) cycles of the West African monsoon in relation with precession of the equinoxes and finally (iii) climate oscilla-tions during glacial and interglacial periods.

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The stratigraphic modelling allows us to propose an evolutionary “source to sink” model of the Congo deep-sea fan development, emphasizing the close interconnection through time between drainage basin changes and sedimentary transfers in deep-water basins

Keywords: Congo, sedimentary basin, Quaternary, turbidite systems, sedimentary cycles, geophy-sical data, stratigraphic modelling, Dionisos software.

Picot, M., (2015). Cycles sédimentaires dans le système turbiditique du Congo : nature et origine (Ph.D. Disserta-tion, Université de Bretagne Occidentale).

Picot, M. et al., (2016). Controls on turbidite sedimentation: Insights from a quantitative approach of subma-rine channel and lobe architecture (Late Quaternary Congo Fan). Marine and Petroleum Geology, 72, 423-446.

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QUANTIFICATION OF TERRIGENOUS SEDIMENT FLUXESIN THE PROVENCE BASIN USING SEISMIC DATA:

RELATION WITH CLIMATE AND TECTONICS FOR THE LAST 6 Ma

LEROUX Estelle 1, RABINEAU Marina 2, ASLANIAN Daniel 1, GORINI Christian 3, MOLLIEX Stéphane 2, BACHE François 4, ROBIN Cécile 5, DROZ Laurence 2, MOULIN Maryline 1, POORT Jeffrey 3, RUBINO Jean-Loup 6 & SUC Jean-Pierre 7

1: IFREMER, REM/GM/LGS, BP 70, 29280 Plouzané, France ([email protected], [email protected], [email protected])

2: CNRS, UMR6538, Domaines Océaniques, IUEM, 29280 Plouzané, France ([email protected], [email protected], [email protected])

3: Sorbonne Universités, UPMC, Univ. Paris 06, UMR 7193, Institut des Sciences de la Terre de Paris (iSTeP), F-75005, Paris, France ([email protected], [email protected])

4: Santos Ltd, GPO Box 2975, Melbourne VIC 3001, Australia ([email protected])5: Université Rennes 1, Campus de Beaulieu, 35 042 Rennes Cedex ([email protected])6: CSTJF, Centre Scientifique et Technique Jean Feger, TOTAL, Avenue Laribau, 64018 Pau, France ([email protected])7: CNRS, UMR 7193, Institut des Sciences de la Terre de Paris (iSTeP), F-75005, Paris, France ([email protected])

The correlation of stratigraphic markers between the shelf, the slope and the deep basin have enabled us to provide a complete and quantitative view of sediments fluxes for the last 6 Ma on the entire Gulf of Lions margin. Messinian units and Pliocene and Pleistocene chronostra-tigraphic markers have been correlated from the shelf to the deep basin and the total sedi-ment thickness from the basement (20 Ma) to the present-day seafloor has also been mapped. After Time/Depth conversion and decompaction of each stratigraphic interval, sedimentary volumes were calculated. Sediment flux evolution shows that a dramatic terrigenous peak oc-curred during the Messinian Salinity Crisis. The Pliocene-Pleistocene average flux appears to have been three times higher than that of the Miocene, which seems in agreement with pu-blished measurements from the World’s ocean. This study also highlights the Mid-Pleistocene Revolution around 0.9 Ma, which resulted in an almost doubling of sedimentary detrital fluxes in the Provencal Basin. These results are discussed in relation with world-wide climate and al-pine tectonics.

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SEDIMENTARY FLUX TO PASSIVE MARGINSFROM INVERSION OF DRAINAGE PATTERNS:

EXAMPLES FROM AFRICA

LODHIA Bhavik Harish 1, ROBERTS Gareth 1, FRASER Al 1 & JARVIS Jerry 2

1: Imperial College London, Department of Earth Science & Engineering, South Kensington Campus, London SW7 2AZ , UK ([email protected], [email protected])

2: Tullow Oil plc., 9 Chiswick Park 566 Chiswick High Road, London W4 5XT, UK

We show that inversion of an inventory of 14801 rivers provides information about Cenozoic uplift and sedimentary flux to northwest Africa’s passive margin. First, we measured solid sedi-mentary flux using 53000 km2 of 2D seismic reflection data and eight wells. Check-shot data were used to convert time to depth and to determine best-fitting compaction parameters. Detailed biostratigraphic records provide excellent age constraint. Six horizons were mapped (seabed, 5.6 Ma, 23.8 Ma, 58.40 Ma, 89.4 Ma and basement). Isopachs were constructed to de-termine solid sedimentary fluxes: ~2x103 km3 /Ma at 58.4-23.8 Ma, ~4x103 km3 /Ma at 23.8-5.6 Ma, and ~28x103 km3 /Ma at 5.6-0 Ma. Compaction parameter errors were propagated into our history of sedimentary flux. Stratigraphy mapped across the margin using a dense two-dimensional grid of seismic data shows that this anomalous subsidence affected an area larger than 500 by 500 km. 500-800 m of Neogene water-loaded subsidence, which we suggest was caused by dynamic drawdown, is recorded in the center of the basin. Measured ocean-age depth residuals and calculated subsidence histories suggest that dynamic uplift of the Cape Verde swell and dynamic drawdown in the east generated a gradient in dynamic support du-ring the last 25 Ma. Secondly, we inverted our drainage inventory to explore the relationship between uplift and erosion onshore and our measured flux. The stream power erosional model was calibrated using independent observations of marine terrace elevations and ages. We in-tegrate incision rates along best-fitting theoretical river profiles to predict sedimentary flux at mouths of the rivers draining northwest Africa (e.g. Senegal). Calculated Neogene uplift and erosion is staged. Our predicted history of sedimentary flux increases in three stages towards the present-day, which agrees with our offshore measurements. Finally, using our inverse ap-proach we systematically tested different erosional scenarios. We find that sedimentary flux to Africa’s passive margins is controlled up the history of uplift and erosional processes play a moderating role. Predicted fluxes are indistinguishable if precipitation rate varies with a period less than ~ 1 Ma or drainage area varies by less than 50%. We tentatively suggest the history of Cenozoic epeirogeny determined the rate of sediment delivery to northwest Africa’s passive margin.

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LATE CRETACEOUS ONSETOF THE AMAZONIAN RETROARC FORELAND BASIN

(MADRE DE DIOS BASIN, PERU)

LOUTERBACH Mélanie 1, RODDAZ Martin 2, ANTOINE Pierre-Olivier 3,MARIVAUX Laurent 3, ADNET Sylvain 3, BAILLEUL Julien 4, DANTAS Elton 5,VENTURA SANTOS Roberto 5, CHEMALE JUNIOR Farid, CALDERON Ysabel 6 andBABY Patrice 2

1: REPSOL Exploración S.A., Calle Mendez Alavaro 44, 28045 Madrid, Spain ([email protected]) 2: Géosciences-Environnement Toulouse, Université de Toulouse; UPS (SVT-OMP); CNRS; IRD; 14 Avenue

Édouard Belin, F-31400 Toulouse, France ([email protected], [email protected]) 3: Institut des Sciences de l’Évolution de Montpellier (ISE-M, UMR 5554, CNRS/UM/IRD/EPHE), c.c. 64, Université

de Montpellier, Place Eugène Bataillon, F-34095 Montpellier Cedex 05, France ([email protected], [email protected], [email protected]) 4: Bassins-Réservoirs-Ressources, Institut Polytechnique Lasalle Beauvais, Département Géosciences, 19 rue

Pierre Waguet, F-60026 Beauvais Cedex, France ([email protected]) 5: Laboratório de Geocronologia, Instituto de Geociências, Universidade de Brasília, Brasília, DF 70910-000,

Brazil6: PERUPETRO S.A., Luis Aldana 320 - San Borja, Lima, Peru ([email protected])

Biostratigraphy, sedimentology and provenance analyses suggest that by the Maastrichtian–Paleocene a retroarc foreland basin system was active in Southern Peru. A 270 m-thick sec-tion shows changes in depositional environments from shallow marine (Early Maastrichtian) to continental (Late Maastrichtian) then back to estuarine (Late Paleocene) conditions. An erosional surface separates Late Maastrichtian from Early Maastrichtian deposits. Above this surface, the Late Maastrichtian unit exhibits well-developed paleosols and syn-sedimentary normal faults. This sedimentary evolution is accompanied by a decrease of sedimentation rates as well as by changes in provenance. Early Maastrichtian deposits have a cratonic provenance as shown by their low εNd(0) values (-15-16) and Precambrian-herited zircon grains. Late Maas-trichtian deposits have a mixed Andean-cratonic origin with εNd(0) values of ~12, and they yield the first Permo-Triassic zircon grain. Late Paleocene deposits have an Andean volcanic arc dominant source as attested by higher εNd(0) values (-6 to -10), and Paleozoic and Late Cretaceous zircon grains. The changes in depositional environment, sedimentation rates and the shift in sediment provenance are consistent with the presence of an eastward migrating forebulge. In agreement with recent published studies, our data suggest that a significant pro-to-Andean Cordillera, extending from 41°s to 10°N, existed by the Cretaceous-Paleogene.

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TRACING THE SOURCES OFTHE CENTRAL ATLANTIC OCEAN SEDIMENTARY ROCKS

DURING THE OAE 2

MOURLOT Yannick 1, 2, DERA Guillaume 1, RODDAZ Martin 1, NAUTON-FOURTEU Martin 1, CHABOUREAU Anne-Claire 4, KIM Jung-Hyun 3, RAISSON François 2 & CALVES Gérôme 1

1: Université Toulouse 3, GET-OMP, 14 avenue Edouard Belin, F-31400, Toulouse, France ([email protected], [email protected], [email protected], [email protected], [email protected])2: Total E&P, CSTJF Avenue Larribau, F-64018, Pau Cedex, France ([email protected])3: Hanyang University, 22 Wangsimni-ro, Seongdong-gu, Seoul, South Korea ([email protected])4: CVA Engineering 9/11, allée de l’Arche, Tour Egée, 92671 Courbevoie, La Défense, France ([email protected])

Oceanic anoxic events (OAEs) are oceanic disturbances corresponding to general drops in oceanic oxygen concentration that occurred during greenhouse periods (Schlanger and Jen-kyns, 1976). Among them, the OAE2 recorded at the Cenomanian-Turonian boundary was of foremost significance, as it led to deposition of major organic-rich sediment on both epicon-tinental and deep oceanic basins at worldwide scale (Kuhnt et al., 1990). Associated with a prominent positive δ13C excursion, this disturbance was especially important in the Central Atlantic Ocean (Jenkyns et al., 1994).

Several complementary mechanisms are invoked to explain the OAE2: (a) warming-in-duced rise in the net primary productivity linked to upwelling intensification or higher conti-nental nutrient input (Schlanger and Jenkyns, 1976); (b) sluggish or stagnant ocean circulation resulting in seawater stratification and anoxic bottom conditions favoring organic matter pre-servation (Schlanger and Jenkyns, 1976); (c) major volcanic events fertilizing the oceans (ashes and/or CO2 degasing, Sinton and Duncan, 1997). Recently, numerical simulations have shown that the paleogeographic changes associated with the Pangean breakup had strong impacts on ocean dynamics and oxygenation (Donnadieu et al., 2016). In details, this study suggests that, after the OAE2, the Central Atlantic deep waters became more ventilated through incur-sions of southern currents preventing the formation of OAEs.

Many studies have been performed on deposits associated with OAE2, especially to des-cribe and characterize their organic content (Arthur et al., 1979), define the redox conditions of the water column or specify the water mass circulation (Schlanger and Jenkyns, 1976). Neody-mium isotopes on fish teeth or seawater oxides have been used to identify changes in ocean dynamics during the Late Cretaceous and during OAE2 (Jiménez Berrocoso et al., 2010). Howe-ver, there is no study dealing with the provenance of the terrigenous sedimentary rocks asso-

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ciated with the OAE2 whereas it is well known that the neodymium isotopic composition of seawater is controlled by the nature of the continental sources (e.g. Jeandel and Oelkers, 2015).

This study is part of a project that attempts to understand what are the processes control-ling the export of organic matter and organic-rich sediments from continental source to sedi-mentation place in the abyssal plain. For this, we integrate several methods: (a) a basin synthe-sis from well data and 2D-seismic surveys to define the paleogeographic framework and the paleo-bathymetry during the deposition of organic-rich sediments; (b) characterize and quan-tify the trapped organic matter in sediments from the continental shelf areas to those of the abyssal plain by analysis of total organic carbon (TOC), δ13C and RockEval pyrolysis data (HI, OI); (c) determine the provenance of terrigenous sedimentary rocks deposited in the Central Atlantic Ocean during the Late Cretaceous using major and trace elements geochemistry and Sr-Nd isotopic compositions.

This study is based on analysis of 40 samples from Deep Sea Drilling Project wells cores (sites 41-367, 41-368, 41-369, 41-370, 14-137, 50-415A) and 20 samples from industry wells located along the West African margin and the Equatorial Margin.

At the time of writing this abstract, some results are still under acquisition. Nevertheless the composition of major and trace elements, 87Sr/86Sr, and εNd(0) of deep water Cretaceous sediments allow a first identification of West African sedimentary sources as well as their evo-lution through time.

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MODULATION OF EROSION RATES OF UPLIFTING LANDSCAPES BY LONG-TERM CLIMATE CHANGE:

EXPERIMENTAL INVESTIGATION AND IMPLICATIONS FORSOURCE TO SINK (STS) STUDIES

MOUSSIROU Bérangé 1 & BONNET Stéphane 1

1: Géosciences Environnement Toulouse, UMR 5563 – OMP, 34100 Toulouse, France ([email protected])

The erosion of continental landscapes produces the elementary detrital sedimentary si-gnal that is trapped in sedimentary basins, after some potential distortions during transport before final deposition. We focus here on the production of this input signal, and we speci-fically investigate how a change in climate influences the erosional dynamics of a landscape and produces a detrital signal that could be ultimately observed in sedimentary sinks. For this purpose we developed an experimental approach where we surveyed the erosion by runoff of water of laboratory-scale landscapes that evolved under the combination of uplift and rainfall forcings (e.g. Bonnet and Crave, 2006). The experimental facility used is a modified of a device initially developed in the Geosciences Rennes laboratory and now set up in the Geosciences Environnement Toulouse laboratory. Following early experiments of Bonnet and Crave (2003), we specifically investigated here the impact of the duration of a decrease of precipitations on the erosion of a landscape that was initially in a steady-state (erosion = uplift).

As predicted theoretically and as already observed in numerical and experimental model-ling studies, a sudden decrease of precipitation rate over a steady-state landscape forced by a continuous rock uplift induces a decrease of its erosion rate, resulting in its surface uplift. Then, as the topography is uplifted both its slope and its erosion rate increase, to a new steady-state value. A fall in precipitation rate then corresponds to a fall in erosion rate and sediment flux lea-ving the landscape, that we will hereafter referred to as a negative peak. It is worth noting that the recovery of new steady-state conditions is done after a time-period that defines a response time of the landscape to the climatic perturbation. From a first set of experiments dedicated to the knowing of this response time, we observe that it is constant, whatever the rate of the uplift forcing or the amplitude of the precipitation change. Then, in a second set of experiments, ins-tead of considering an instantaneous decrease of the precipitation rate, we rather considered the effects of gradual (linear) decrease. When the time-scale of the precipitation decrease is longer that the response-time of the landscape, we observe that the resulting negative peak in erosion rate is humped and delayed with regard to the onset of the precipitation change. Then, our study demonstrates that the shape of the negative peak of erosion rate of a landscape that results from a decrease in precipitations depends to the first order on the ratio of the duration of the precipitation decrease to the response time of the landscape. We show that the erosion rate signal is humped with increasing duration of climatic variations and ultimately that long-

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term climatic variations do not have any impact on the erosion rate of landscapes and on the sediment flux transiting into the STS system. As already noticed by some authors, our study highlights the response time of the landscapes as a very critical unknown for STS studies.

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ASSESSING MODERN RATES OF RIVER SEDIMENT DISCHARGETO THE OCEAN USING SATELLITE GRAVIMETRY

MOUYEN Maxime 1, LONGUEVERGNE Laurent 1, STEER Philippe 1, CRAVE Alain 1 & ROBIN Cécile 1

1: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France ([email protected], [email protected], [email protected], [email protected],[email protected])

The estimates of the worldwide sediment river discharge to the oceans suffer large uncer-tainties, mostly because sediment discharge measurements are scarce in space and time. Yet, knowing this sediment budget is critical in Earth and environmental Sciences, since it is un-der the direct influence of surface processes (such as erosion, transport and sedimentation) and, in particular, controlled by climate, tectonics and human activities (dam, deforestation). Since 2002, the GRACE Satellite provides global gravity time series that have proven useful for quantifying mass transport, including continental water redistribution at the Earth surface (ice sheets and glaciers melting, groundwater storage variations). Because, sediment accumulation in the oceanic sinks leads to a mass increase, we propose to use GRACE data to assess these mass variations, and in turn the sediment discharge to the ocean. However, the order of magni-tude of mass variations due to sediments is only one tenth of the magnitude of continental wa-ter. As a result, unraveling the sedimentological contribution to GRACE signal is a challenge. To tackle it, we pair the analysis of regularized GRACE solutions at high spatial resolution correc-ted from all known contributions (hydrology, ocean, atmosphere) to a particle tracking model that predict the location of the sediment sinks for 13 rivers with the highest sediments loads in the world. This particle tracking model combines global reanalysis of oceanic currents with available data on the grain size and the seasonality of the sediments load at the river mouth and is run over the same time range as GRACE data. We find encouraging correlation between GRACE spatial pattern of mass accumulation and the modeled pattern of sedimentation zones for some rivers, although some discrepancies between modeled and observed mass accumu-lation values are observed. The reasons for these misfits are a combination of inaccuracies both in GRACE solutions and in the particle tracking model: 1) GRACE has a limited spatial resolution and uncertainties, with residual contributions from off-target effects that are poorly estimated; 2) The particle model is highly dependent on the oceanic currents’ velocity field, which also suffers from uncertainties and has limited spatial and temporal resolution as well; 3) We use literature-based estimations of the seasonality of river sediment loads and associated grain sizes, both of which are notoriously uncertain data. We presently aim at refining our sediment particle tracking model in order to get better confidence in the spatial distribution of the sedi-ments. This way, we expect to assess the annual riverine sediment discharge within the uncer-tainty of GRACE, independently from uncertain in situ rivers’ sediment loads data.

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THE MINORCA BASIN:A BUFFER ZONE BETWEEN THE VALENCIA

AND LIGURO-PROVENÇAL BASINS(NW MEDITERRANEAN SEA)

PELLEN Romain 1, 2, *, ASLANIAN Daniel 1, RABINEAU Marina 2, LEROUX Estelle 3,GORINI Christian 3, SILENZARIO Carmine 4, BLANPIED Christian 5, RUBINO Jean-Loup 5

1: IFREMER, REM/GM/LGS, BP 70, 29280 Plouzané, France ([email protected], [email protected])2: CNRS, UMR6538, Domaines Océaniques, IUEM, 29280 Plouzané, France ([email protected])3: Sorbonne Universités, UPMC, Univ. Paris 06, UMR 7193, Institut des Sciences de la Terre de Paris (iSTeP),

F-75005, Paris, France ([email protected], [email protected])4: Schlumberger House, Gatwick Airport, West Sussex, England5: TOTAL, TG/ISS,CSTJF, Avenue Laribau, 64018 Pau, France ([email protected], jean-loup.rubino@

total.com)

Detailed analysis of seismic profiles and boreholes in the Valencia Basin (VB) highlight a dif-ferentiated basin, the Minorca Basin (MB), lying between the old Mesozoic Valencia Basin sensu strico (VBss) and the young Oligocene Liguro-Provençal Basin (LPB). The relationship between these basins is shown through the correlation of four Miocene-to-present-day mega-sequences. The Central and North Balearic Fracture Zones (CFZ and NBFZ) that bor-der the MB represent two morphological and geodynamical thresholds that created an ac-commodation in steps between the three domains. Little to no horizontal Neogene move-ments are found for the Ibiza and Majorca Islands. In contrast, the counterclockwise move-ment of the Corso-Sardinian blocks induced a counterclockwise movement of the Minorca block towards the SE along the CFZ and NBFZ, during the exhumation of lower continental crust in the LPB. This new understanding implies pure Neogene vertical subsidence in the VBss and places the AlKaPeCa northeastward of present-day Alboran Area.

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THE ZAMBEZI SEDIMENTARY SYSTEM:A SOURCE TO SINK APPROACH

PONTE Jean Pierre 1, ROBIN Cecile 1, GUILLOCHEAU François 1, DALL’ASTA Massimo 2, DROZ Laurence 3, RABINEAU Marina 3 et MOULIN Maryline 4

1: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France ([email protected], cecile.robin@univ-rennes 1.fr, franç[email protected])

2: TOTAL CSTJF, 64000 Pau, France ([email protected])3: Laboratoire Domaines Océaniques, UMR 6538, LDO 29280 Plouzané ([email protected], [email protected])4: IFREMER, 29280 Plouzané ([email protected])

The Mozambique margin is an oblique to transform margin which houses one of the largest African turbiditic system (1800 km long and 400km wide) (Droz and Mougenot., AAPG Bull., 1987). The turbiditic system is related to the Zambezi delta which recorded more than 12km of sediments deposits with little destabilizations. In the onshore area, the water catch-ment and the drainage system have been changed through geological times by rivers captures (Thomas and Shaw., J.Afr.Earth Sci., 1988).

Since a few years several studies were realised along the central African margins which led to numerous interpretations, especially on timing of events liked to the lack of a strong age model. The aim of this study is to carry out a source to sink approach along the Mozambique margin and to discuss its evolution since Early Cretaceous times. Within the framework of the Pamela project, a new set of acquisition cruise and data analysis was realised. A biostratigraphy revaluation of wells along the Mozambique shelf combined to a resampling and new datation of Zambezi 3 well provided new ages constraints that we correlated to existing and new Pa-mela seismic reflexion data.

Using this new data set we propose to: 1) realise a new age model of the Mozambican margin since early Cretaceous times, 2) analyse the infill evolution from the Zambezi delta to the deep turbiditic system using isopach maps to recognize its different steps of growth.

1) Late Jurassic (?) - early Late Cretaceous: from Neocomian to Aptian times, the high of the clinoforms is getting higher, with the first occurrence of contouritic ridges during Cenoma-nian times.

2) Late Cretaceous - Early Paleocene: a major drop of relative sea-level occurred as a conse-quence of the South African Plateau uplift. The occurrence of two depocenters suggests sili-ciclastic supplies from the Bushveld and from the North Mozambique domain.

3) Early Paleocene - Eocene: growth of carbonate platforms and large contouritic ridges.

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4) Oligocene - Present-day: birth of the modern Zambezi Delta, with quite low siliciclastic supply during Oligocene times, increasing during Miocene times linked to the East African system. As previously expected (Droz and Mougenot) some sediments are coming from a feeder located east of the Davie Ridge.

This study was financed by TOTAL and Ifremer in the scientific project PAMELA (Passive Margin Exploration Laboratories) framework.

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SEDIMENTARY MARKERS :A TOOL FOR THE QUANTIFICATION OF SUBSIDENCE

AND ISOSTATIC MOVMENTS:EXEMPLES FROM THE OCCIDENTAL MEDITERRANEAN SEA

RABINEAU M. 1, LEROUX E. 1, 2, 3, PELLEN R. 1, 2, ASLANIAN D. 2, MOLLIEX S. 1, 2,GORINI C. 4, MOULIN M. 2, BACHE F. 3, DROZ L. 1, DOS REIS T. 5, RUBINO JL. 6,GUILLOCHEAU F. 7

1: CNRS, UMR6538, Domaines Océaniques, IUEM, 29280 Plouzané, France2: IFREMER, DRO/GM, LGG, BP 70, 29280 Plouzané, France3: Istep, UPMC, 4 place Jussieu, 75252 Paris cedex 054: Santos Ltd · Opportunity Capture, Australia5: Departamento de Oceanografia Geologica/UERJ-Brazil, Rua Sa˜o Francisco Xavier, 524, 48 Andar, Mara-

cana, Rio de Janeiro RJ CEP, 20.550-900, Brazil6: CSTJF, Centre Scientifique et Technique Jean Feger, TOTAL, Avenue Laribau, 64018 Pau, France7: Géosciences Rennes, UMR 6118, Campus de Beaulieu, 35042 Rennes Cedex, France

Passive margins are characterised by an important tectonic and thermal subsidence, which favours a good preservation of sedimentary sequences. This sedimentation in turn en-hances the subsidence because of loading effects. We present here a direct method based on sedimentary markers seen on seismic data, to evaluate total subsidence rates from the coast to the outer shelf and to the deep basin in the Gulf of Lion, from the beginning of massive salt deposition up to present day (the last circa 6 Ma) with minimal theoretical assumptions.

The subsidence is organised in three compartments that are related to the very deep structure of the margin during the opening of the Liguro-provencal basin (Leroux et al., 2015). We also quantifed for the first time the Messinian salinity crisis isostatic rebound of the outer shelf (Rabineau et al., 2014).

These very high total subsidence rates enable high sedimentation rates along the margin with sediments provided by the Rhône river flowing from the Alps, which in turn enable the detailed record of climate evolution during the Neogene that make the Gulf of Lion a unique archive (Rabineau et al., 2015). These results have been extended in 3D (Leroux et al., 2015) but also onland during Stéphane Molliex postdoc and towards the Valencia basin were similar measurements were undertaken (Pellen et al., 2016 ; Pellen et al., in progres).

Leroux, E., Aslanian, D., Rabineau, M., M. Moulin, D. Granjeon, C. Gorini, L. Droz, Sedimentary markers: a window to deep geodynamic processes. Terra Nova 27, 122-129 (2015).Pellen, R., Aslanian, D., Rabineau, M., Leroux, E., Gorini, C., Silenzario, C., Blanpied, C., Rubino, J-L., 2016.

The Minorca Basin: a buffer zone between Valencia and Provençal Basins, Terra Nova. doi: 10.1111/ter.12215

Rabineau, M., Leroux, E., Aslanian, D., Bache, F., Gorini, C., Moulin, M., Molliex, S., Droz, L., Dos Reis, T., Rubino, J-L., Olivet, J-L., 2014. Quantifying Subsidence and Isostasy using paleobathymetric

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markers : example from the Gulf of Lion, EPSL, vol. 288, p. 353- 366. http://dx.doi.org/10.1016/j.epsl.2013.11.059

Rabineau, M., S. Cloetingh, J. Kuroda, D. Aslanian, A Droxler, C. Gorini, D. Garcia-Castellanos, A. Moscariello, Y. Hello, E. Burov, F. Sierro, F. Lirer, F. Roure, P.A. Pezard, L. Matenco, Y. Mart, A. Camerlenghi, A. Tripati and the GOLD and DREAM Working Groups, 2015. Probing connections

between deep earth and surface processes in a land-locked ocean basin transformed into a giant saline basin: the Mediterranean GOLD project, Marine and Petroleum Geology, Volume: 66 Pages: 6-17 Part: 1.

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SPATIAL AND TEMPORAL EVOLUTION OF DETRITAL CONTENTDURING AN OROGENIC CYCLE

RAT Juliette ¹, MOUTHEREAU Frédéric ¹, BRICHAU Stéphanie ¹, BERNET Matthias ²,BALVAY Mélanie ², ANDO Sergio ³ & GARZANTI Eduardo ³

1: Géosciences Environnement Toulouse, UMR 5563 – OMP, 34100 Toulouse, France ([email protected] ; [email protected])

2: Institut des Sciences de laTerre, UMR 5275 - ISTerre 38058 Grenoble, France. 3: Laboratorio di Petrografia del Sedimentario, Università di Milano-Biccoca, Milano, Italy.

Detrital sediment assemblages preserved in basins provide constraints on the nature of source rocks, dynamics of sediment transport, and potentially on tectonics and climate changes. U-Pb dating method on detrital zircon is ideally suited for provenance studies due to the ability of U-Pb age data to resist several orogenic cycles. With the aim to track sediment source evolution over a complete magma-poor orogenic cycle, the U-Pb dating approach is inappropriate. What is the characteristic time and processes of long-term detrital signal preservation from rift evo-lution to syn- and post-collision events?

The Iberian plate recorded a first period of extension in the Late Jurassic, followed during the Early Cretaceous (Aptian-Albian) by a major thinning event documented by thick syn-rift ba-sins and plate-scale heating/cooling of the Iberia crust, as argued by published fission track ages. Paleogeographic reconstructions that are based on stratigraphic and lithofacies analyses in northern Iberia (Iberian Range, Pyrenees and Basque-Cantabrians Range), describe a large domain of continental/fluvial and shallow-marine siliciclastic deposition. The related detrital content was then recycled during the subsequent Pyrenean orogenic phase in the Ebro fore-land basin, and eventually transfer to the Mediterranean realm during post-orogenic re-exca-vation of the Ebro basin.

In this study, we will complete the available time-temperature paths from low-temperature thermochronological dataset in the mesozoic syn-rift basins by performing new thermo-chronological analyses of well-dated syn-collision and post-collision stratigraphic sections of the Ebro basin. This study is combined with new detrital petrological data to identify relative control of source petrography, hydraulic sorting, alteration and diagenesis processes on the si-gnal preservation during sediment transfer from source to sink. All these observations will then be incorporated in a geodynamic reconstruction of Iberia, and compared with age predictions from a model coupling surface processes and thermal evolution.This study is part of the OROGEN research project, co-financed by BRGM, TOTAL & CNRS.

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Fig. 1: Location of the sample sites (red dots) and extension of the glaciers during the LGM (light blue shading).

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GLACIVAR:RECONSTRUCTING GLACIAL OSCILLATIONS

IN THE VAR CATCHMENT BASIN(SOUTHERN FRENCH ALPS)

RINTERKNECHT Vincent 1, TOUCANNE Samuel 2, JORRY Stephan 2 & BRISSET Elodie 3

1: Laboratoire de Géographie Physique, CNRS, UMR 8591([email protected])2: IFREMER, Unité de Recherche Géosciences Marines ([email protected]; [email protected])3: IMBE, CNRS, UMR 7263, IRD 237 ([email protected])

GLACIVAR is the glaciological component of a multidisciplinary project tracing, identifying and quantifying sediments from their source (Var catchment basin) to their sink (Var deepwater tur-bidite system, Ligurian Sea). The goal of GLACIVAR is to build, for the first time, a direct chrono-logy of the retreat of the glaciers in the Mercantour by mean of cosmogenic Be-10. We collec-ted samples from boulders embedded in the top of moraines deposited by former glaciers that once occupied part of the three main valleys in the Var catchment basin. A total of 18 samples from the Var valley were collected on four different moraines. A total of 31 samples from the Ti-née valley were collected on eight different moraines and a total of 23 samples were collected on five moraines from the Vésubie valley. The moraines correspond to the stabilisation of the glaciers in specific climatic conditions of precipitation and temperature. Indeed, the moraine deposited at the foot of the Tinée valley was deposited in colder and wetter conditions compa-red to the moraine deposited at the head of the valley. Dating these moraines will allow us to identify when the maximum ice extent was reached in these valleys (Würm/MIS2? Riss/MIS6?), as well as to identify when the valleys were last glaciated (Little Ice Age, Younger Dryas?). In ad-dition, the reconstructions of the former glacier geometry at each time interval (moraine age) will allow us to define the climato-glaciological conditions prevailing at the time. In turn, these forcings will be discussed in relation to the geochemical data obtained in sediment cores from the Var submarine system, which demonstrate that the turbiditic activity was mainly driven by paleoenvironmental conditions in the upper basin and in particular by the presence of glaciers during the last ice age.

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SEDIMENTARY FLUX FROM INVERSION OF DRAINAGE NETWORKS: EXAMPLES FROM WEST AFRICA AND NORTH AMERICA

ROBERTS Gareth 1, LODHIA Bhavik 1 & WHITE Nicky 2,

1: Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, UK ([email protected], [email protected])

2: Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge, CB3 0EZ ([email protected])

Inverse modelling of substantial inventories of river profiles indicates that continental scale drainage patterns contain coherent signals of regional uplift. This approach calculates uplift rate histories by minimizing misfit between observed and theoretical river profiles. Our results suggest that shapes of river profiles are controlled by headward advection of erosional waves. Calculated uplift and erosion histories are insensitive to short term (less than few Ma) changes in climate and large changes in upstream drainage area (e.g. discharge). They also appear to be insensitive to changes in substrate (e.g. lithology). We examine the wavelet power spectra of river profiles to explore why drainage patterns appear to have a coordinated response to re-gional signals. Results suggest that at wavelengths longer than tens of kilometres river profiles tend to exhibit red noise (i.e. power proportional to k-2, where k is wavenumber). Spectral power decreases dramatically at shorter wavelengths, which are dominated by pink noise. These ob-servations indicate that long wavelength processes (e.g. regional uplift) control the shapes of many river profiles. These spectra suggest that different geomorphological processes control rivers shapes at different wavelengths. The second part of this presentation shows how calcu-lated uplift and erosion histories onshore can be used to predict sedimentary flux to passive margins. Using our inverse approach it is straightforward to track incision rates, which can be integrated for sedimentary flux. We inverted an inventory of 14801 African rivers and predict flux to the Mauritania margin, northwest Africa. Calculated Neogene uplift and erosion of nor-thwest Africa was staged and grew towards to present-day. To test our prediction we measured solid sedimentary flux using 53000 line-km of seismic data and eight commercial wells. Check-shot data were used to convert isopachs from time to depth and to determine best-fitting com-paction parameters. Detailed biostratigraphy provides excellent age constraints. This dataset indicates that solid fluxes were ~2x103 km3 /Ma at 58.4-23.8 Ma, ~4x103 km3 /Ma at 23.8-5.6 Ma, and ~28x103 km3 /Ma at 5.6-0 Ma. Staged increases in sedimentary flux corroborate our predic-tions. We compare flux predicted from a subset of 4161 North American rivers (e.g. Mississippi, Rio Grande) to independent measurements from the Gulf of Mexico. Results suggest that drai-nage networks contain useful information about histories of regional uplift and sedimentary efflux to passive margins.

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A SOURCE TO SINK MEASUREMENT METHODIN ANOROGENIC SETTINGS.

ROBIN Cécile 1, GUILLOCHEAU François 1, BRAUN Jean 1, ROUBY Delphine 3, SIMON Brendan 1, BESSIN Paul 1 et BABY Guillaume 1

1: Géosciences Rennes, UMR 6118 Université Rennes 1-CNRS, OSUR, 35042 Rennes cedex2: GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany3: GET, UMR 5563, Observatoire Midi-Pyrénées 14 avenue Edouard Belin 31400 Toulouse

We developed a double method for measuring both deposited sediment volumes (sink) based on basins stratigraphy and eroded rock volumes in upstream catchments (source) based on geomorphology. This method was drafted in Africa - characterized by large plateaus and plains surrounded by passive margins and interior basins (sags and rifts) - in the frame of the TopoA-frica project funded by the French Research Agency ANR.

Measurement of deposited sediment volumes: This measurement is based on subsurface data (seismic lines and wells) in passive margin or rifts/sags.

• Biostratigraphic dating of reference wells and definition of a regional sequence stratigraphic framework based on key seismic lines,• Isochore maps from the regional propagation of key time-lines,• Depth conversion of the isochore to isopach maps,• Compaction of the sediments (knowledge of the lithology and the porosity),• Measurement of the compacted volumes and quantification of the uncertainties based on the software Volume Estimator developed by J. Braun.

Measurement of the eroded volumes: This study is based on the mapping of the characteristic landforms of the anorogenic reliefs: the planation surfaces.

• Analysis and relative chronology of the different stepped planation surfaces: etchplains and pediments/pediplains, and their associated incised valleys,• Dating of the planation surfaces based on the dating (when they exist) of (1) the thin sediment covers, (2) the contemporaneous magmatism and/or (3) the weathering profiles (magnetostratigraphy, geochronology, chemostratigraphy..),• Mapping of the relevant planation surfaces,• Reconstruction of the successive topographies by restoring the initial shape of the eroded planation surfaces by younger landforms,• Measurement of the eroded volumes.

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MESO-CENOZOIC SOURCE-TO-SINK OF THE AFRICAN MARGINOF THE EQUATORIAL ATLANTIC

ROUBY D. 1, CHARDON D. 1, YE J. 1, GUILLOCHEAU F. 2, ROBIN C. 2, HUYGHE D. 1, LOPAREV A. 1, DALL’ASTA M. 3, GRIMAUD J.L. 4

1: GET (CNRS/IRD/UPS), Observatoire Midi Pyrénées, Toulouse, France2: Géosciences Rennes (CNRS), Université de Rennes, Rennes, France3: Total Exploration-Recherche, Pau, France4: St Anthony Falls Laboratory, Minneapolis, USA

The objective of the Transform Source to Sink Project (TS2P) is to link the dynamics of the erosion of the West African Craton to the offshore sedimentary basins of the African mar-gin of the Equatorial Atlantic at geological time scales. This margin, alternating transform and oblique segments from Guinea to Nigeria, shows a strong structural variability in the margin width, continental geology and relief, drainage networks and subsidence/accumulation pat-terns. We analyzed this system combining onshore geology and geomorphology as well as offshore sub-surface data.

For the Cenozoic, mapping and regional correlation of dated lateritic paleo-landscape remnants allows us to reconstruct two physiographic configurations of West Africa. These geo-metries show that the present-day drainage organization stabilized by at least 29 Myrs ago (probably by 34 Myr) revealing the antiquity of the Senegambia, Niger and Volta catchments toward the Atlantic as well as of the marginal upwarp currently forming a continental divide. The drainage rearrangement that lead to this drainage organization was primarily enhanced by the topographic growth of the Hoggar swell and was associated with a major stratigraphic tur-nover along the Equatorial margin. Elevation differences between paleo-landscape remnants give access to the spatial and temporal distribution of denudation for 3 time-increments since 45 Myrs. From this, we estimate the volumes of sediments and associated lithologies exported by the West African Craton toward different segments of the margin, taking into account the type of eroded bedrock and the successive drainage reorganizations.

For the Mesozoic, we produced paleogeographic maps at the scale of West Africa span-ning the continental domain and offshore basins since 200 Ma. Mapping spatial and temporal distribution of domains either in erosion (sources) or in accumulation (sinks) document the impact of the successive rifting of Central and Equatorial Atlantic on the physiography of the area. We use low temperature thermochronology dating along three transects perpendicular to the margin (Guinea, Ivory Coast and Benin) to determine periods of maximum denudation.

We compare these data to accumulation histories in passive margin basins and discuss their stratigraphic expression according to the type of margin segment they are preserved in.

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TRACING CLAY PROVENANCE OFFSHORETO THE SOUTH AMERICAN EQUATORIAL MARGIN

DURING THE LAST 150KY WITH ND AND SR ISOTOPES

ROUSSEAU Tristan C.C. 1, RODDAZ Martin 2, CALVES Gérôme 2, and BAYON Germain 2

1: Instituto de Ciências do Mar LABOMAR- Universidade Federal do Ceará- Av. da Abolição, 3207 – Meireles CEP 60165-081 – Fortaleza – CES.A (Brazil) ., Calle Mendez Alavaro 44, 28045 Madrid, Spain

([email protected]) 2 : Géosciences-Environnement Toulouse, Université de Toulouse; UPS (SVT-OMP); CNRS; IRD; 14 Avenue

Édouard Belin, F-31400 Toulouse, France ([email protected], [email protected]) 3 : Institut Français de Recherche pour l’Exploitation de la MER – IFREMER Institut Français de Recherche pour

l’Exploitation de la MER – IFREMER Technopôle Brest Iroise - BP 7029280 Plouzané - France ([email protected])

The South American equatorial margin receives the sediments contribution of the Ori-noco and the Amazon, two of the worlds´ largest rivers. Geochemical tracers of provenance are of great potential to understand modern and past sediments dynamics in response to climate and oceanic circulation forcing. In order to constrain present-day river signatures we measu-red major elements concentrations and Nd-Sr isotopic composition of suspended sediments from the Amazon, the Orinoco and the Maroni rivers sampled in the framework of the Hybam observatory. These three end members which drain different geological provinces, exhibited very distinct geochemical signatures, with respective εNd(0) of -10.7, -14.1 and -23.7. We will discuss the provenance variations of the fine lithogenic fractions from three offshore marine sediment cores: one from the Amazon lobe (Lobestory cruise) one from the Demerara rise (IG-KSF 19) and one from the Ceara Rise (ODP Site 925) from the modern period to approximately 150ky. We performed leachings and centrifugations to avoid signal contamination by autigenic particles.

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FROM ALLUVIAL FAN TO DISTAL TURBIDITIC SYSTEMS:PRELIMINARY RESULTS ON DEEP-WATER BYPASS PROCESSES BASED ON GILBERT-TYPE FAN DELTA OUTCROPS OF THE CORINTH RIFT (GREECE).

RUBI Romain1, 3, ROHAIS Sébastien 2, BOURQUIN Sylvie 1, MORETTI Isabelle 3,DESAUBLIAUX Guy 3

1: Géosciences Rennes, UMR 6118 du CNRS, OSUR, Université de Rennes 1, 35042 Rennes Cedex France ([email protected], [email protected] )2: IFP Energies Nouvelles, 1,4, Avenue du Bois Préau, 92852 Rueil-Malmaison cedex France ([email protected] )3: ENGIE, 1 Place Samuel de Champlain, 92930 Paris La Défense Cedex, France ([email protected],

[email protected] )

Source-to-sink (S2S) can be seen as the integration with other earth science disciplines; from geomorphology, sedimentary geology to basin geodynamic analysis. A major limitation to go further is the access to the entire basin geometry (proximal to distal setting, “closed” box, deep crustal and lithospheric geometries) as well as age constrains.

We present the preliminary results of a sedimentological and sequence stratigraphy analysis of outcropping Gilbert-type deltas from the Corinth rift (Plio-Pleistocene). Drone ac-quisition has also been carried out to propagate the correlations in 3D along steep cliffs. The study case provides an unique opportunity to describe the sedimentary facies and correla-ted them though space and time from the proximal to the most distal setting, in a very well constrained basin geometry and timing. In this communication, we will mainly focus on deep-water sediment bypass in terms of flow processes and associated stratigraphic expression, as it is a key issue to address sedimentary budget analysis in a S2S perspective.

A new bottomset typology has been established including 4 end-members: (1) Gravely bottomset, (2) Major erosion – by pass, (3) Fine-grained starved bottomset, and (4) Deep Water Massive Sand (DWMS) bottomset. The relationship between the bottomset end-members and their associated turbiditic system has also been characterized. (1) During Gravely bottomset deposition, unconfined to low relief channel-levee complex occurs at the very end of the bot-tomset. (2) The major erosion in bottomset occurs when the foresets present a maximal pro-gradation rate, the bottomset is eroded and bypassed. Coarse- to fine-grained sediments are exported in the turbiditic system to form large channel-levee complex. (3) During Fine-grained starved bottomset deposition, limited amount of sediment feed the turbiditic system from the delta. Indeed, the major part of the sediments is stored in topset and foreset areas. (4) Deep water massive sand bottomset forms coarse-grained slope apron geometry on the delta toe. Coarse-grained material is massively stored in the bottomset, and only fine-grained sediments are exported to the turbiditic system to form lobe complex. Superimposed onto this dynamic, evidences of contouritic events have also been identified.

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THE MIOCENE PERI-ALPINE FORELAND BASIN:A LONG LIVED BUFFER ZONE FOR THE GULF

OF LION SEDIMENT SUPPLY

RUBINO Jean-Loup 1, PARIZE Olivier 2, BESSON David 3, GORINI Christian 4, LEROUX Estelle 4, RABINEAU Marina 5, ASLANIAN Daniel 6.

1: Total CSTJF, Avenue Larribau, Pau, 64018 cedex, France - [email protected]: Areva, Tour Areva, 1 Place J Millier, 92400, Courbevoie, France - [email protected]: DREAL Centre-Val de Loire, 5 Av Buffon, 45064 Orléans, France - [email protected]: UPMC-ISTEP 4 Place Jussieu, 75005, Paris - [email protected]: UBO Technopole Brest Iroise, R. Dumont d’Urville, 29280, Plouzané, France - [email protected]: IFREMER, Pointe du Diable, 29280, Plouzané, France - [email protected]

Source to sink studies are quite “simple” as soon as continental areas are adjacent to pas-sive margin allowing a direct sediment export. At the opposite when another type of basin occurs between the margin and the drainage area, such as a foreland basin for example, the appraisal and prognosis of sediment nature and budget balance are much more complicated. It is particularly true when marine deposits are developed during the early stage of the fore-land basin infill and even later. In this particular case, the passive margin is either starved or received little amount of clastic deposits coming from local drainage areas; most of the time, the margin is the setting of hemipelagic sedimentation plus the results of distal shaly plumes. In fact, it becomes simpler and we come back to basic scenario, only when the foreland basin is full filled or at least when the deltaic system reaches the passive margin, and even in that case, flexural subsidence can still contribute to accumulate sediments within continental prism again modifying sediment budget delivered to the margin.

The Gulf of Lion (GDL) provides a unique and well documented example of such complex case, in the sense that clastic sediments coming from the Alps and the Massif Central only ar-rived onto the Mediterranean margin during Middle Tortonian, when the Rhône river draining Peri-Alpine foreland basin reaches Camargue Plain, to more or less occupy the same position that the present day delta and also when Rhone Deep Sea Fan starts to be active. Prior to this age, i.e. from Aquitanian to Early Tortonian, the margin sedimentation only consists of shelf to slope marls and bioclastic carbonates as shown by the 13 deep wells crossing the series. It means that clastic sediments are trapped into the proximal part of the foreland basin from Switzerland to Valence and are accumulated as Molasse deposits in proximal highly subsiding areas. Therefore almost no sands are delivered into Mediterranean Sea, if we except the local drainage areas deriving from the Languedoc which are not tributary of the Rhone catchment basin. The second exception comes from the occurrence of well define lowstand prisms occur-ring along Languedoc shelf, mainly in the North, Rubino et al. (2015), locally preserved from Messinian Erosion. They are most likely sandy even if they are still undrilled. They are well da-ted by the Calmar well. These prisms were prognosed from onshore studies because during

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3th order lowstand of the sequences at least from Burdigalian to Lower Tortonian, the entire foreland basin is exposed and incised valleys networks have been traced all along the basin up to the Camargue, Besson et al. (2003-2005); this meaning, that sediments must be export into the GDL.

Comparison of palaeogeographical maps of the most regressive intervals of the 3th or-der sequences from Aquitanian to Lower Messinian is able to help to predict when clastics may reach the GDL, but this only allows a qualitative approach, simply because we are still not in capacity to make any well constrain quantification. First because, in the foreland basin, the outcrop boundaries do not necessarily reflect the initial basin boundaries, second because seismic surveys are old vintages of poor quality and seismic grids are not dense enough to compute volumetrics at the basin scale. Finally offshore, in large areas, Messinian erosion re-moves a significant part of the pre-messinian series, Bache (2008) complicating direct mass balance evaluation. Conversely quantifications are much more easy during Late Messinian and Plio-Quaternary where spatial constrains are better define and quantification more reliable (Bache, 2008; Leroux, 2012).

Bache, F., 2008 – Evolution oligo-miocène des marges du micro-océan liguro-provençal, Thèse de docto-rat, Université de Bretagne Occidentale.

Besson D., Parize O., Rubino J.L., Clauzon G., Dalrymple R.W., James N. & Reynaud J.Y., 2003 – Les sys-tèmes de vallées incisées (IVS) du Miocène en relation avec l’évolution du bassin d‘avant-pays alpin du SE de la France – 9ème Congr. Fr. Sédim., Livre des Résumés, Publ. A.S.F., Paris, 38, p. 54-55.

Besson D., Parize O., Rubino J.L., Aguilar J.P., Aubry M.P., Beaudoin B., Berggren W. A., Clauzon G., Cru-meyrolle P., Dexcoté Y., Fiet N., Iaccarino S., Jiménez-Moreno G., Laporte-Galaa C., Michaux J., von Salis K., Suc J.P., Reynaud J.Y., Wernli R., 2005 – Un réseau fluviatile d’âge Burdigalien terminal dans le sud-est de la France : remplissage, extension, âge, implications. C. R. Geoscience 337, p. 1045-1054.

Leroux E., 2012 – Quantification des flux sédimentaires et de la subsidence du bassin Provençal, Thèse UBO, Brest, 455p. 2 vols, texte & Annexes

Rubino JL, Parize O ; Besson D., Gorini C .,Leroux E., Rabineau M., Aslanian D. 2015, – Stratigraphical links between Miocene Alpine Foreland Basin and Gulf of Lion Passive Margin during lowstands, EGU Vienna abstract & poster

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A «SOURCE TO SINK» APPROACH OF THE LAKE ALBERT RIFT(UGANDA, EAST AFRICAN RIFT SYSTEM):

RELATIONSHIPS BETWEEN SEDIMENTARY BASINAND UPSTREAM LANDFORMS

SIMON Brendan 1, GUILLOCHEAU François 1, ROBIN Cécile 1, DAUTEUIL Olivier1, DALL’ASTA Massimo 2

1: Géosciences Rennes – UMR 6118. Université de Rennes 1, Campus de Beaulieu, 263 av. du Général Leclerc, 35042 Rennes Cedex ([email protected])

2: TOTAL E&P, CSTJF, Avenue Larribau, 64000 Pau, France.

This study is based on a coupled basin infilling study and a landforms analysis of the Lake Albert Rift located at the northern part of the western branch of the East African Rift.

The basin infilling study is based on both subsurface data and outcrops analysis. The objective was to (1) actualize age model, (2) to reconstruct the 3D architecture of the rift using sequence stratigraphy correlations and seismic data interpretation, (3) to characterize the de-formation and its changes through times and (4) to quantify the accommodation for several time intervals. The infilling essentially consists of isopach fault-bounded units composed of lacustrine deposits wherein were characterized two major unconformities dated at 6.2 Ma (Up-permost Miocene) and 2.7 Ma (Pliocene-Pleistocene boundary), coeval with major subsidence and climatic changes.

The landforms analysis is based on the characterization and relative dating of Ugandan landforms which consist of stepped planation surfaces and incised valleys.

We here proposed a seven-steps reconstruction of the deformation-erosion-sedimenta-tion relationships of the Lake Albert Basin and its catchments:

- 55-45 Ma: formation of laterites corresponding to the African Surface during the very humid period of the Lower-Middle Eocene;- 45-22: stripping of the African Surface in response of the beginning of the East-African Dome uplift and formation of a pediplain which associated base level is the Atlantic Ocean;- 17-2.5 Ma: Initiation of the Lake Albert Basin around 17 Ma and creation of local base levels (Lake Albert, Edward and George) on which three pediplains tend to adapt;- 18—16 Ma to 6.2 Ma: «Flexural» stage (subsidence rate: 150-200 m/Ma; sedimentation rate 1.3 km3/Ma between 17 and 12 Ma and 0.6 km3/Ma from 12 to 6 Ma) – depocenters location (southern part of Lake Albert Basin) poorly controlled by fault;- 6.2 Ma to 2.5 Ma: Rift stage 1 (subsidence rate: > 500m/Ma up to 600-800 m/Ma; sedimentation rate: 2.4 km3/Ma) – Rifting climax;

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- 2.5-0.4 Ma: uplift of the Ruwenzori Mountains and shifting from an alluvial system to a network of bedrock river incision – Rift Stage 2 (subsidence rate: 450 to 250 m/Ma; sedi-mentation rate: 1.5 km3/Ma);- 0.4-0 Ma: long wavelength downwarping of the Tanzanian Craton, initiation of the Lake Victoria trough, drainage network inversion and uplift of the present-day Ugandan es-carpment (normal faulting motion of the border faults) with formation of perched valleys associated to the Lower Pleistocene (2.5-0.4 Ma) rivers network.

The sediment budget is successful with, between 17 and 2.5 Ma, an excess of 16 % of upstream eroded material compared to the sediment volume deposited that can be explai-ned by the chemical erosion prevailing at this period in Central Africa. The significant (60%) opposite difference between 2.7 and 0 Ma may be the consequence of a high sediment supply resulting from the erosion of the uplifted Ruwenzori Mountains.

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TECTONICS, CLIMATE, RELIEF AND EROSION:DISENTANGLING DRIVING FORCES WITHIN A COMPLEX SYSTEM

VAN DER BEEK Peter 1, BANDOU Dimitri 1, HERMAN Frédéric 2, VALLA Pierre 2,SERRA Hugo 1

1: 1Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes, Grenoble, France ([email protected], [email protected], [email protected]) 2: Institute of Earth Surface Dynamics, Université de Lausanne, Lausanne, Switzerland ([email protected], [email protected])

Tectonics, climate and erosion interact through a number of couplings and feedbacks; the relief of the Earth’s surface is both an indicator of state and a central element in this complex coupled system. Topography and relief are generated by tectonics and drive erosion. The spa-tial distribution of erosion is influenced by climate, in particular the amount, phase and spatio-temporal distribution of precipitation. Feedbacks between erosion, relief and both tectonics and climate have also been identified. The question of what fundamentally drives erosion rates in this coupled system has been around for at least three decades, but has still not been satis-factorily answered.

We present an analysis of recently constituted global databases of relief1 and denudation rates on different timescales2,3 . These are correlated to various potential climatic and tectonic control parameters. Our results suggest a strong primary control of tectonics on erosion rates, with climate playing a secondary role. This finding is perhaps unsurprising for long-term exhu-mation rates, as these should be fundamentally driven by tectonic influx of material. However, short-term (cosmogenic) erosion rates similarly correlate strongly with tectonic strain rates. Various measures of relief appear surprisingly decoupled from erosion rates; we explore dif-ferent potential explanations for this decoupling. Both physical models and initial analysis of global datasets of sediment flux suggest that relief has a first-order control on erosion rates. However, this control breaks down at high rock-uplift/erosion rates when landsliding becomes the dominant erosional process. It is also modulated by lithology and rock fracturing in ways that are insufficiently understood.

Erosion rates in most (but not all) studied settings appear inversely correlated to the stu-died time interval. If this correlation does not represent an artefact related to measurement interval, it can be interpreted as implying transient climatic control on erosion rates. Relief si-milarly appears to be influenced by climate change, in particular through the strong imprint of glacial processes on relief. Late-Cainozoic climate change may be responsible for both in-creased overall erosion rate and relief in glaciated mountain belts.

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DISTINCT CONTROLS ON TERRIGENOUS FLUX FROMTHE YELLOW RIVER AND THE JAPANESE ISLANDS

TO THE NORTHERN OKINAWA TROUGH SINCE 34 KA

WAN Shiming 1, ZHAO Debo 1, TOUCANNE Samuel 2, CLIFT Peter D. 3, TADA Ryuji 4 & RÉVILLON Sidonie 5

1: Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China ([email protected]; [email protected])

2: IFREMER, Unité de Recherche Géosciences Marines, BP70, 29280 Plouzané, France ([email protected]) 3: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA

([email protected])4: Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan ([email protected])5: SEDISOR/UMR6538 “Domaines Oceaniques”, IUEM, Place Nicolas Copernic, 29280, Plouzane, France ([email protected])

High resolution multiproxy records, including terrigenous grain-size and Sr-Nd-Pb iso-topes of the <2μm silicate fraction of sediments from IODP Site U1429 in the northern Okinawa Trough, provide unambiguous evidence for distinct control mechanism on terrigenous flux from the Yellow (Huanghe) River and the southern Japanese Islands to the northern Okinawa Trough since 34 ka. Provenance proxies indicate that the sediments were mainly derived from the Yellow River and Kyushu. Our study for the first time quantifies the sediment flux from the Yellow River and Japan to the Okinawa Trough since the last glacial. During the last 34 cal. kyr B.P., terrigenous flux from the Yellow River to the study site was strongly influenced by sea level fluctuation, whereas input of materials from Japan was controlled by the East Asian summer monsoon rainfall changes. This in turn was ultimately related to the orbitally-modu-lated summer insolation. During the last glacial and early deglacial (34–15 cal. kyr B.P.), the low sea level fall led to the paleo-Yellow River mouth being positioned significantly closer to the northern Okinawa Trough, thus favoring enhanced fluvial discharge from the paleo-Yellow River to the study area. During the late deglacial and Holocene (~15 cal. kyr B.P. to present), the longer distance from the Yellow River mouth to the study area caused by rising sea-level and coupled with the blocking effect of the Yellow Sea Warm Current, resulted in a nearly six-fold decrease of sediments flux from the Yellow River to the northern Okinawa Trough. In contrast, the enhanced East Asian summer monsoon rainfall since the last deglacial stimulated stronger weathering and erosion on the southern Japanese islands, so that more sediment was delive-red to the nearby northern Okinawa Trough after 15 ka.

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THE PERCHED PALEOSURFACES OF THE PYRENEES -CANTABRIAN BELT

WYNS Robert 1, UZEL, Jessica 2

A Source to Sink Total & BRGM collaboration1: BRGM & ISTO, UMR 7327, BP 36009, 45060 Orléans cedex 2 ([email protected])2: Géosciences Rennes, UMR 6118 – OSUR, 35042 Rennes cedex France

Perched paleosurfaces of the Central and Eastern Pyrenees have been first described by geomorphologists for a long time (Birot, 1937; Lagasquie, 1982; Calvet, 1996) and more re-cently by geologists (Bosch et al., 2015; Monod et al., 2015; Bosch, in progress). These studies are of peculiar interest since they provide robust constraints for the timing and mechanisms of relief creation in a collision belt.

Pyrenean paleosurfaces have been recognized over large areas in the Axial Zone between the Aure valley to the West and the Cerdagne and Capcir grabens to the East. The actual eleva-tion of theses surfaces varies between 1000 and 2500 m above sea level. In Cerdagne, the gra-ben filling has been dated of Vallesian age (Middle to Late Miocene). Based on this constraint, the entire Pyrenean perched paleosurfaces have been considered of Miocene age. Since the palynofacies of the Vallesian sediments is interpreted as a near-sea level deposit, the present elevation of the paleosurfaces should have been acquired after the Vallesian assuming that all paleosurfaces have nearly a Miocene age. In the vicinity of Cerdagne and Capcir grabens, the central Pyrenees paleosurface appears connected to the uppermost terraced paleosurface, suggesting an age prior to the Vallesian times.

A common feature of the Pyrenean paleosurfaces is the preservation of thick lateritic weathering profiles. In the Eastern Pyrenees, the paleosurfaces display a terraced pattern with three or more levels, the highest being likely the oldest. In the Central Pyrenees (from the Aston Massif to the East to the Neouvielle Massif to the West), The single paleosurface is apparently offset along numerous faults. Field work will be conducted in order to collect structural data allowing a detailed tectonic evolution to be reconstructed.

In the Louron valley (close to the Aure valley), the central Pyrenean paleosurface is appa-rently downthrown along N160 trending faults facing the valley that define a graben-like fea-ture with an overall NS trend. Field work will be conducted to check the structural relationships of such possible features with the reverse faults and thrusts linked to the Pyrenean compres-sion. Preliminary investigations show that fault planes here bear shallow dipping slickenslides indicating a probable transtensional mechanism. A second set of normal faults trending N100 to N130, parallel to the belt, seems to offset the central Pyrenean paleosurface. These faults are observed in the Massif of Aston (SW of Ax les Thermes) where a detailed tectonic analysis will be conducted.

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Paleosurfaces will be followed from the Aure valley (central Pyrenees) to the East in order to decipher their origin and evolution: are they terraced surfaces or a single surface offset along recent faults having a general N160 and N100-130 orientation? Special attention will be payed to the occurrence of the preserved lateritic weathering profiles that allows recons-tructing the lateral correlation of the paleosurface remnants. Finally, we plan to map these paleosurface remnants from the central Pyrenees to the Cantabric belt with a special attention to possible faults that might offset some portions. An attempt to date the weathering profiles using syn-weathering minerals (adulaires) will be conducted in the meantime. These data will collectively help better understanding the significance of paleosurfaces in collision belts.

This work is part of the project “Source to Sink”, we thank Total and BRGM.

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A SI-LI APPROACH TO UNDERSTANDING WEATHERING PROCESSIN WORLD LARGE RIVERS

ZHANG Xu 1, PRINGLE Emily 1, DELLINGER Mathieu 2, BOUCHEZ Julien 1, GAILLARDET Jerome 1 & MOYNIER Frederic 1

1: Institut de Physique du Globe de Paris, CNRS and Sorbonne Paris Cité, 1 rue Jussieu, 75238 Paris, France (corresponding author : [email protected]) 2: Durham University, Stockton Road, Durham, DH1 3LE, United Kingdom

This study reports Li and Si isotope measurements in large river sediments as a proxy for weathering processes. Lithium isotopes were reported in Dellinger et al., 2014. Both Li and Si in river sediments inherit their isotope composition from the parent rock and to the inten-sity of the modern weathering processes occurring in soils and watersheds. They are liberated during chemical weathering and potentially taken up by secondary minerals in soils or during river transport. Their reincorporation in secondary solids fractionate their isotopes with res-pect to bedrock. In both cases, the light isotope should be enriched in secondary minerals.

We measured the Si isotope composition (δ30Si) of large river sediments (Amazon and Mackenzie, (Dellinger et al., 2014)) as a function of grain size to answer the following questions. How do Si isotopes behave (specifically compared to Li isotopes) in larger river sediments as a function of grain size? Does the biological activity affect Si isotopes of larger river sediment over geological time scales (i.e. through recycling)? Can the contribution of sandstone to river sediment exported by inferred from Si isotopes?

The result shows that Si isotopes vary in a similar way as Li isotopes in large river as they are fractionated with grain size: lighter Si is enriched in fine-grained sediments and heavier Si is enriched in coarse-grained sediments (using Al/Si as a proxy for grain size). Ad-ditionally, a similarity between the two isotope systems is that in bed sediment δ30Si remains relatively stable whilst in suspended sediments δ30Si decreases. The enrichment of the light Si isotopes in fine-grained sediments could be due to (1) biological activity that leads to the enrichment of light isotopes in organic material and in fine inorganic material derived from topsoil erosion; (2) the higher clay content of fine-grained suspended sediments (clay being enriched in light Si isotopes during modern-day weathering); (3) the higher content of «recy-cled» material in fine-grained sediments, which should carry a light Si isotope signature from previous weathering episodes. These different hypotheses are being explored at the moment.

Dellinger, M., Gaillardet, J., Bouchez, J., Calmels, D., Galy, V., Hilton, R.G., Louvat, P., France-Lanord, C., 2014. Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion. Earth and Planetary Science Letters 401, 359-372.

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INDEX of authors

ADATTE Thierry 64ADNET Sylvain 73ANDO’ Sergio 29, 85ANTOINE Pierre-Olivier 73 ARMIJOS Elisa 46ARNAUD Nicolas 42ASLANIAN Daniel 71, 80, 83, 93ASTI Riccardo 31

BABY Guillaume 33, 89BABY Patrice 73BACHE François 71, 83BAILLEUL Julien 73BALVAY Mélanie 85BANDOU Dimitri 97BARBARAND Jocelyn 35, 67BARRIER Laurie 37, 60BAUER Hugues 39BAYON Germain 40, 51, 91BEAUVAIS Anicet 42BERNET Matthias 85 BERNHARDT Anne 38BESSIN Paul 39, 89BESSON David 93BLANPIED Christian 80BONNEAU Lucile 40, 41BONNET J. Nicolas 42 BONNET Stéphane 77BONOW Johan M. 65BOUCHEZ Julien 43, 45, 49, 59, 101BOURQUIN Sylvie 92BRATENKOV Sophia 29BRAUN Jean 39, 89BRICHAU Stéphanie 85BRISSET Elodie 87

CALDERON Ysabel 73CALMELS Damien 49CALVES Gérôme 47, 75, 91CASTELLTORT Sébastien 61, 64CHABOUREAU Anne-Claire 75CHARBONNIER Q. 45

CHARDON Dominique 42, 90CHEMALE JUNIOR Farid 73CLARK Julian 64CLIFT Peter D. 29, 98COCHONNEAU Gérard 46CRAVE Alain 46, 79

DALL’ASTA Massimo 33, 47, 65, 81, 90, 95DANTAS Elton 73DAUTEUIL Olivier 95DELAUNAY Antoine 47 DELLINGER Mathieu 43, 45, 49, 101DE OLIVEIRA Eurides 46DE PUTTER Thierry 51 DERA Guillaume 75DESAUBLIAUX Guy 92DOMINGUEZ Stéphane 37, 61DOS REIS T. 83DOS SANTOS Andre 46DROZ Laurence 69, 71, 81, 83DUPONT-NIVET Guillaume 42DYKSTRA Mason 64

EL-EKHFIFI S. 53EMHANNA S. 53 EMMANUEL Laurent 40, 41ESPINOZA Raul 46

FACCENNA Claudio 31FILDANI Andrea 64FILIZOLA Naziano 46FONSECA P. 46FORD Mary 55 FRAIZY Pascal 46FRANCE-LANORD Christian 57FRASER Al 72FU Bihong 37

GAILLARDET Jérôme 43, 45, 49, 59, 101GALMIER Valentin 62GALY Albert 57GARZANTI Eduardo 29, 85

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INDEX of authors

MACDONALD A. W. A. 63MALAVIEILLE Jacques 61MALUSÀ Marco Giovanni 31MARFISI E. 63MARIVAUX Laurent 73MARQUES Fernando 35MARSSET Tania 69MARTINEZ Jean-Michel 46MEES Florias 51 MÉTIVIER François 37, 60MEUNIER Patrick 60MEYNADIER Laure 57MICHON Laurent 59MIGUET Johann 67MOLLIEX Stéphane 71, 83MORETTI Isabelle 92MORIN J. 33MOULIN Maryline 71, 81, 83MOURLOT Yannick 75MOUSSIROU Bérangé 77MOUTHEREAU Frédéric 85MOUYEN Maxime 79 MOYNIER Frederic 45, 101MURRAY Andrew 60MUSBAH B. 53

NARTEAU Clément 60NAUTON-FOURTEU Martin 75

ORTEGA Carole 67

PARIZE Olivier 93PELLEN Romain 80, 83PE-PIPER G. PICOT Marie 69PINNA Rosella 35PIPER D. J. W. 63PONTE Jean Pierre 81POORT Jeffrey 71PRINGLE Emily 45, 101PUIGDEFABREGAS Cai 64

GAUTHERON Cécile 67GAWTHORPE Robert 55GAYER Eric 59, 60GEORGE Simon 29GORINI Christian 71, 80, 83, 93GRANJEON Didier 69GREEN Paul F. 65GRIMAUD J.L. 90GUERIT Laure 37, 60, 61GUILLOCHEAU François 33, 39, 47, 62, 81, 83, 89, 90, 95GUYOT Jean-Loup 46

HAHN Annette 29HAVAS Robin 59HAWIE N. 63HEBBELN Dierk 38HEMELSDAEL Romain 55HERMAN Frédéric 97HILDENBRAND Anthony 35HONEGGER Louis 64HUYGHE D. 90HUYGHE Pascale 57

JAPSEN Peter 65JARVIS Jerry 72 JOLIVET Marc 37JORRY Stéphan 40, 41, 87

KIM Jung-Hyun 75KLAUS Adam 57

LAJEUNESSE Eric 60LASSEUR Eric 67LAURENT Dimitri 69LEROUX Estelle 71, 80, 83, 93LIU Youcun 60LODHIA Bhavik Harish 72, 88LOGET Nicolas 67LONGUEVERGNE Laurent 79LOPAREV A. 90LOUTERBACH Mélanie 73LOUVAT Pascale 49, 59

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INDEX of authors

VALLA Pierre 97VAN DER BEEK Peter 97VAN DER WOERD Jérôme 60VAUCHEL Philippe 46VENTURA SANTOS Roberto 73

WAN Shiming 98 WHITE Nicky 88WYNS Robert 99

YE J. 90

ZHANG Xu 101 ZHAO Debo 98

RABINEAU Marina 69, 71, 80 81, 83, 93RAISSON François 75RAT Juliette 85RÉVILLON Sidonie 98RINTERKNECHT Vincent 87ROBERTS Gareth 72, 88ROBIN Cécile 33, 39, 47, 62, 71, 79, 81, 89, 90, 95RODDAZ Martin 73, 75, 91ROHAIS Sébastien 92ROIG Jean-Yves 65ROUBY Delphine 89, 90 ROUSSEAU Tristan C.C. 91 RUBI Romain 92 RUBINO Jean-Loup 71, 80, 83, 93RUEDA Thibault 67RUFFET Gilles 51

SAINT ANGE F. 63SANGSTER C. 63SANTINI William 46SCHROËTTER Jean-Michel 39SCHWANGHART Wolfgang 38SERRA Hugo 97SILENZARIO Carmine 80SILVA JACINTO Ricardo 40, 41SIMON Brendan 89, 95 SMITH Thierry 51SPANGENBERG Jorge 64SPIESS Volkard 57STEER Philippe 79STRECKER Manfred R. 38STUUT Jan-Berend 38SUC Jean-Pierre 71SY Adrien 59

TADA Ryuji 98THEVENIAUT Hervé 65TOUCANNE Samuel 40, 41, 87, 98

UZEL, Jessica 99

de Rennesdes Sciences de l’UniversObservatoire

Terre, Écosystèmes et Sociétés

DESIGN

Graphique

CONTACTS:[email protected]@univ-rennes1.fr

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source to sink · 2018. 3. 27. · 12h00 - 12h15 de putter thierry cenozoic sedimentation history...

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