the passage of sediment from mountain source to ocean...
TRANSCRIPT
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The passage of sediment from mountain source to ocean sink:
Results from the MARGINS S2S Waipaoa Sedimentary System, Hikurangi Margin
Alan Orpin & Source-to-Sink WSS Team
Photo: James Syvitski
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Source-to-sink: a God’s-eye view
Canyon’s bypass slope
Intraslope sources
Closely-coupled catchment and
deep ocean sink e.g. Sepik, Var
Weak tectonic Dominant glacio-eustatic
Strong tectonic Weaker glacio-eustatic
Weakly-coupled catchment and deep ocean sink, shelf capture e.g. Amazon
Peak discharge
10x
Peak discharge 100-1000x
Submarine fans
Slope gradient and length
(Figure modified after Sømme et al., 2009)
Slopeward transfer driven by prograding clinoforms
4
Anthony the Anthropocene
Waipaoa, Waiapu
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Waipaoa River mouth. Photo: James Syvitski
“… develop a quantitative understanding of margin dispersal systems and associated stratigraphy, so that we can predict their response to perturbations, such as climatic and tectonic variability, relative sea-level change, and land-use practices”. (Excerpt from MARGINS Source to Sink
Executive Summary)
► Emphasis on quantification of processes and linkages ► Terrestrial and marine
► Limited to the last-glacial cycle, but emphasis on
Holocene and Anthropocene records
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(Image courtesy Josh Mountjoy)
Taupo Volcanic Zone
NE rain
Poverty Bay study area
Southern Ocean swell
Why the Waipaoa?
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Waipaoa because… 1. Dramatic landscape responses to drivers
2003
1958 1939 (Aerial photos C/- Landcare Research)
2008
(Photo Phaedra Upton, GNS Science)
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Dramatic changes in catchment behaviour: millennial scale
Berryman et al. (2010) ► Up to 50% of the post-glacial
downcutting achieved between 10-8 ka ► Rapid upstream migration (~2 km/ka) of
several major knickpoints Upton et al. (2013) ► LGM conditions more erosive compared
to Holocene
(Figure modified after Berryman et al., 2010)
Waihuka tributary of upper Waipaoa
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Strong climate and environmental signals: event scale (10-2 to 102 y)
Lake Tutira catchment Post-cyclone Bola, 1988 (photos courtesy of Noel Trustrum)
1988 (Cyclone Bola)
1985
1977
1960
1973
1938
LTF9 –frozen box core (after Page et al., 1994)
► Gomez et al. (2011, 2013) - global climate teleconnections.
► Orpin et al. (2010) - intra-lake deposits and non-climate triggers.
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Event strata (10-3 y timescales)
Low density, fine-grained upper surface
Low density mottled, weakly bioturbated?
Laminae, hummocky cross-stratification
0 cm
5 cm
10 cm 40
30
20
10
0
Dep
th c
m
(X-radiograph courtesy Rose & Kuehl, 2010)
Bola-style event (Lila Rose Pierce & Steve Kuehl, PhD thesis)
Cyclone Bola event, shelf core
July 2010 storm, shelf core
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Oceanographic tripods
36 m
55 m
48 m
Figure after Richard Hale et al. (submitted, Special Issue of CSR) Oceanographic data courtesy of UW
1 in 8 yr flood
Depositional events ~10 cm deposit
Erosion?
Coherence of event drivers: an annual view
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(Image courtesy Josh Mountjoy)
MD063003 MD063002
MD063008 MD063009
TAN0810-9
TAN0810-5 TAN0810-2
TAN0810-3
Cores show loss of terrestrial event fidelity in deepest ocean, BUT a turbidite record
► Cascadia Margin template (see Goldfinger et al., 2007)
► Cores cross-correlated
► Demanding of sophisticated
age-models
► Synchronicity of events
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► 73 synchrononous turbidites
► 5-fold reduction in slope
sedimentation since LGM
► Hyperpycnites and debris flows rare
► Earthquakes most plausible trigger
► Poverty re-entrants return times c.
150-400 yrs
► Subduction interface earthquakes c.
800 yrs
Characterising Hikurangi Margin turbidites since the LGM
Pouderoux et al. (2012a, b)
After Hugo Pouderoux et al. (2012a, b) - Marine Geology and Natural Hazards and Earth System Science.
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(Figures modified after Gomez et al., 2007; 2013; and in prep)
Cores allow inter-basin millennial-scale correlation through system
Shelf Lower floodplain
Upper floodplain
► Cycle of perturbations and landscape recovery
► Importance of landscape pre-conditioning
► Instantaneous and century-length scales for
“events”
► Human activity has had most profound impact on
late Holocene sedimentation
Catastrophic floods
>M7 earthquakes
Landscape recovery post-Taupo
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Closure of shelf sediment budgets (pre-human)
Post-glacial basin geometry
Holocene accumulation
rates
(Figures after Gerber et al., 2010)
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Last-century budgets and deposition on Poverty shelf
► Supply climate driven (floods) ► Big sediment signals ► At 102 yr timescales, perhaps only 25-50%
stratigraphically complete (Sommerfield, 2006)
Century-scale Century-scale
“Goldilocks Zone Sausage” of strata preservation
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Mid-slope basin
Trough
Basin capture and transfer across the Poverty margin
Mid-shelf basin
Lower-slope basin
Near complete shelf capture (pre-human)
Capture & loss
MSC seismic profile
Active uplift
Active uplift
Imbricate thrust faults
Deformation front
avalanche debris Quaternary
shelf fill
Quaternary basin fill
3 km
2 km
1 km
Holocene riverine supply
Small %
Holocene budget: Gerber et al., 2010; Alexander et al., 2010; Orpin et al., 2006. Slope structure: Pedley et al., 2010.
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Waipaoa 66%, 15%?
Waiapu 77%
Inflection point around 100 km shelf width
Off-shelf sedimentation dominates <20 km
Have anthropogenic impacts overwhelmed margin morphology as the dominant control on off-shelf sediment transfer?
Influence of shelf width and supply on off-shelf dispersal: have we tipped the scales?
91% Var
(Figures modified after Walsh & Nittrouer, 2003)
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(Figure from Paquet et al., 2009)
Tectonic-sediment interactions over 150 ka timescales, upper Hikurangi Margin
Depocentre location controlled by:
► Eustacy <20-30 kyr timescales
► Tectonic deformation >100 kyr timescales
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From mountain source to ocean sink: Waipaoa Sedimentary System
Supply Move + store capture + move capture + move
► Interconnectedness of source and sink, lithological coherence ► Ephemeral preservation of events, both marine and terrestrial
► Inter-basin fidelity at 101+ y timescales
► Utility of budgets: rates, tectonic-sediment interactions, and unknowns
► Marine paleoearthquake record
Figure from “Mountain source to ocean sink”, Special Issue of Marine Geology vol. 270, 2010