horbe et al 2013 - provenance of pliocene and recent sedimentary deposits in western amazônia,...

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Provenance of Pliocene and recent sedimentary deposits in western

Amaznia, Brazil: Consequences for the paleodrainage of the

Solimes-Amazonas River

Adriana Maria Coimbra Horbe , Marcelo Batista Motta , Carolina Michelin de Almeida ,Elton Luiz Dantas , Lucieth Cruz Vieira

Departamento de Geocincias, Universidade Federal do Amazonas, Av. General Rodrigo Otvio Jordo Ramos, 3000, Coroado, 69077-000 Manaus, AM, Brazil

Servio Geolgico do Brasil, CPRMManaus, Programa de Ps-Graduao em Geocincias, Universidade Federal do Amazonas, Av. Andr Arajo, 2160, Coroado, 69060-000 Brazil

Instituto de Geocincias, Universidade de Braslia, Campus Universitrio Darcy Ribeiro, Braslia, 70910-900 Braslia, Brazil

a b s t r a c ta r t i c l e i n f o

Article history:

Received 10 August 2012

Received in revised form 30 July 2013

Accepted 31 July 2013

Available online 6 August 2013

Editor: J. Knight

Keywords:

I Formation

Iquitos Arch

Zircon grain typology

Heavy detrital minerals

UPb geochronology

Integrated data on paleocurrents, the morphology of detrital minerals and zircon grains, chemical compositions

andUPb geochronology, reveal that the owof themodern Solimes-Amazonas River has changed fromwest to

east since the PlioPleistocene. This nding is supported by several lines of evidence, including paleocurrent di-

rections and detritalmineral assemblages in the I Formation and in recent sediments. The I Formation,which

was most likely deposited during the Pliocene, has NE and SE paleocurrents, a high proportion of stable detrital

mineral assemblages and UPb zircon ages thatwe interpreted as being derived from theAmazonian craton (e.g.,

the Rondonian-San Igncio and Sunsas-Grenvillian geochronologic provinces) and neighboring provinces, in-

cluding the Neoproterozoic to Cambrian Brazilian Pampean mobile belts. A small proportion is derived from

the Cambrian to Silurian Famatinian continental arch. Another source is the Precambrian and Paleozoic basement

from the Andes cordillera, which includes several metamorphic inliers in Colombia, Peru and Bolivia. The overly-

ing recent deposits havedifferent provenances and are characterized by amore variable detrital assemblagewith

zircon grains that are enriched in trace elements and depleted in Si and haveMesoproterozoic ages. In our inter-

pretation, the erosion of the Iquitos Arch after deposition of the I Formation allowed thewestward expansion of

the Solimes-Amazonas system in the Plio-Pleistocene.

2013 Elsevier B.V. All rights reserved.

1. Introduction

The uplift and subsequent orogenic deformation of the Andes has

caused important paleogeographic changes in western Amaznia since

the Miocene. The marine connection with the Caribbean sea closed,

the courses of the Magdalena and Orinoco rivers changed, Andean fore-

land basins formed due to exural subsidence and the Amazonas

established a connection to the Atlantic, increasing the mass accumula-

tion rates of terrigenous sediments in the Amazonas fan (e.g., Hoorn

et al., 1995; Hooghiemstra and Van der Hammen, 1998; Dobson et al.,

2001; Roddaz et al., 2005b; Wesselingh and Salo, 2006; Latrubesse

et al., 2007; Figueiredo et al., 2009). Because the effects of these changes

are not clear, different proxies for the geodynamics of the Solimes-

Amazonas River must be considered. Hoorn et al. (1995); Dobson

et al. (2001) and Wesselingh and Salo (2006) stated that the archi-

tecture of the modern Solimes-Amazonas River formed since the

lateMiocene. Campbell et al. (2001) interpreted that theAndean contri-

bution to the Atlantic occurred in the end of the Pliocene (2.5 Ma),

while Bezzerra (2003) and Rossetti et al. (2005) interpreted it as occur-

ring in the late PleistoceneHolocene.

The aim of this paper is to study detrital minerals from the I For-

mation and associated recent deposits along the Solimes River, both

of which represent the youngest sedimentation event recognized in

the Amazonia region, to establish their sediment sources (provenance)

and to investigate the formation of the modern Solimes-Amazonas

River and their connection to the Atlantic Ocean. These two units are

part of the large sedimentary Solimes-Amazonas basin and therefore

might clarify the geological evolution and timing of the development

of the present course of the Solimes-Amazonas River systems. In addi-

tion,wewill discuss the in uence of the Iquitos Arch andAndes rocks in

the sedimentation and landscape evolution of western Amaznia. To

answer these questions, we selected the six most signi cant outcrops

in the cliffs, islands and bars along the Solimes River between the cities

of Tef and Manaus (Fig. 1). According to Maia et al. (1977) and Melo

and Villas Boas (1993), the cliffs along the river correspond to the I

Formation, whereas the islands and bars are composed of recent river-

bed sediments.

Sedimentary Geology 296 (2013) 920

Corresponding author.

E-mail addresses: [email protected] (A.M.C. Horbe), [email protected]

(M.B. Motta), [email protected] (C.M. deAlmeida), [email protected] (E.L. Dantas),

[email protected] (L.C. Vieira).

0037-0738/$ see front matter 2013 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.sedgeo.2013.07.007

Contents lists available at ScienceDirect

Sedimentary Geology

jou rna l homepage: www.el sev ie r .com/ loca te/ sedgeo


2. Geological setting

The western portion of the Amazonas River in Brazil is called the

Solimes River and drains the Andean cordillera, the sedimentary rocks

of the Solimes Paleozoic basin, and the Central Brazil and Guyana shields

(Amazonian craton) (Fig. 1A, B). The two youngest sedimentary units of

the Solimes Paleozoic basin are the Solimes Formation (called the

Pebas Formation in Peru and Colombia) and the I Formation (Fig. 1C).

Several studies have investigated the sedimentary environment and

palynology of the Solimes Formation (e.g., Caputo and Silva, 1991;

Hoorn, 1994; Hoorn et al., 1995; Leguizamn Vega, 2005; Wesselingh

and Salo, 2006; Latrubesse et al., 2007). These studies indicate that the

Solimes Formation occupied a large lowland area adjacent to the Ande-

an foreland basins (Roddaz et al., 2005a) (Fig. 1A) and was deposited

during the late Miocene (1110 Ma; Cozzuol, 2006; Latrubesse et al.,

2007) in a uvio-lacustrine to transitional marine environment. Its

upper part is composed of thin to thick sandstone layers interspersed

with massive white-reddish clay layers that are centimeters to meters

thick, and the lower part is composed of gray-greenish clay layers that

contain plant fossil, sh teeth and scales, evidence of bioturbation and

root marks. The Andes and the Amazonian craton are considered to be

the source area for the rocks that make up this formation (Hoorn

et al., 1995; Latrubesse et al., 2007).

In contrast, the I Formation, which overlies the eastern part of the

Solimes Formation (Fig. 1) above an erosive unconformity (Maia et al.,

1977; Leguizamn Vega, 2005), has not been well studied and cannot

be dated by biostratigraphy because of the lack of fossils. It is character-

ized predominantly by whitish to reddish yellow sandstone that is

intercalated with grayish-reddish silty-clay lenses and is thought to be

PlioPleistocene (Maia et al., 1977; Melo and Villas Boas, 1993) or Late

PleistoceneHolocene (Rossetti et al., 2005) in age. The I Formation

has been correlated to the Madre de Dios Formation in Peru

(Campbell et al., 2006). However, the exact extents of the I and

Solimes Formations are controversial because they are present in a

large, fairly inaccessible region. Moreover, Leguizamn Vega (2005)

described sedimentary rocks related to the Solimes Formation along

the Solimes River (Fig. 1B). Quaternary deposits overlie both the

Solimes and I Formations along the Solimes-Amazonas River.

They formed by the erosion of the Andes and Amazon craton cover

the lowland regions that formed an extensive Quaternary uvial plain

tens of kilometers in length during avulsion of the Solimes-Amazonas

Rivers (Latrubesse and Franzinelli, 2002).

Fig. 1. (A) Location map showing the main Paleozoic sedimentary basins: Amazonas in the east side, Solimes in the center and the Peru and Bolivia foreland Amazon basin (NAFB and

SAFB after Roddaz et al., 2005a, 2005b) in the west side in a SRTM image. The limits of the I Formation in black (CPRM, 2006) and the limit of the Solimes-Amazon hydrographic

basin in red; (B) Geology and location of the samples in the study area, S stratigraphic section of the I Formation, SD samples from recent deposits. The Solimes Formation occurs in

a large region in thewest of the I Formation and in a few outcrops in the study area (1B); (C) Simpli ed chronostratigraphic diagram of the studied units in the Solimes Paleozoic basin.

10 A.M.C. Horbe et al. / Sedimentary Geology 296 (2013) 920


3. Materials and methods

Eighty sampleswere collected for detrital heavymineral analysis; 61

samples came from six sections of the I Formation on the right bankof

the Solimes River, and 19 came from recent sediments on islands and

sandbars between Tef and Manacapuru, Central Amaznia (Fig. 1).

The minerals were separated from fractions of 0.1250.250 mm and

0.0620.125 mm using an elutriator and heavy liquids and then

mounted on glass slides in Canada balsam. An average of 200 transpar-

ent grains per slide was identi ed and counted using a petrographic mi-

croscope and the ribbon counting procedures of Mange and Maurer

(1992). X-ray diffraction (XRD) analysis was used to supplement the

mineral identi cation. Zircon grain morphologies were examined

under a scanning electron microscope (SEM-LED 1450 VP) at the

Museu Emilio Goeldi and Universidade Federal do Par, Brazil, and clas-

si ed using the methodology of Pupin (1980). Ninety- ve individual

detrital zircon grains from the I Formation and the recent sediments

were analyzed by electronmicroprobe (JEOL JSM 6400) at the Universi-

ty of Western Australia. UPb dating of 307 in situ zircon grains from

sections 1 and 4 of the I Formation and the recent sediments was car-

ried out with a Thermo Finnigan Neptune multi-collector inductively

coupled plasma mass spectrometer (LA-MC-ICP-MS) at the University

of Braslia, Brazil, according to the methods of Bhn et al. (2009).

4. Results

4.1. Geological characteristics of the sedimentary units

The I Formation corresponds to a hilly surface with cliffs up to 30 m

high and extends along the Solimes River for at least 400 km between

the Tef and Purus Rivers (Fig. 1). This formation comprises whitish

sandstones, massive rhythmites, pelites and conglomerate with trough

cross-bedding, cross-laminations, ripple marks, ripple cross-laminations,

sigmoidal strati cation, tabular cross-strati cation, root marks, peds and

some wood fossils (Fig. 2). These sediments were most likely deposited

in point-bar and oodplain environments, and the paleocurrentdata indi-

cate ow to the NE and SE (Fig. 3).

The recent sediments that are present along the Solimes River in

the study area, which form kilometer-long islands and bars, are ne-

to medium-grained to locally coarse-grained sands. Longitudinal sec-

tions along the Solimes River show low-angle and tabular cross-

strati cation with WE direction ux.

4.2. Detrital mineral assemblage

We identi ed the same range of mineral grains in both sedimentary

units, including mica (biotite and anandite), andalusite, sillimanite, zir-

con, kyanite, staurolite, pyroxene (ferrosilite and enstatite), tourmaline

(dravite and uvite), garnet (almandine, spessartine and knorringite),

amphibole (crossite and tirodite), monazite, rutile, epidote (mukhinite),

anatase, brookite, titanite, topaz, and olivine (Table 1; Fig. 4). However,

there is a clear distinction between the units. The detrital mineral com-

position in the I Formation can be divided into two different groups.

The lower part of this unit has a higher andalusite content, while the

upper part is dominated bymica, zircon and kyanitewith less tourmaline

and garnet (Table 1; Fig. 2). The proportion of zircon decreases fromwest

to east along the river in the study area.

In contrast, the recentdeposits have a higher proportion of pyroxene

and amphibole than the I Formation (Table 1; Fig. 5). The light detrital

grains in both units, such as quartz and feldspar, are angular to sub-

rounded, and some rock fragments such as gneiss, quartzite, and sand-

stone are present in the coarse fraction of all sections.

Fig. 2. Schematic sections of the I Formation and proportion of detrital grain minerals in the 0.1250.062 mm and 0.2500.125 mm fractions.

11A.M.C. Horbe et al. / Sedimentary Geology 296 (2013) 920

MarcelRealce


The zircontourmalinerutile ternary diagram (ZTR; Fig. 6A) does

not show signi cant differences in the contents of the I Formation

and the recent deposits. However, the proportion of ZTR minerals rela-

tive to the more stable (KSAnd: kyanite + sillimanite + andalusite)

and unstable (EpPAmp: epidote + pyroxene + amphibole) mineral

assemblages varies; the I Formation has a higher proportion of ZTR

and KSAnd relative to EpPAmp (Fig. 6B) and an increasing proportion

of EpPAmp toward the recent sediments. However, the proportion of

ZTR minerals, mica and andalusite discriminates the lower part of the

I Formation from the upper part (Fig. 7). These data suggest that the

two units have different source areas (provenance).

4.3. Detrital zircon grain morphology and chemical composition

Based on the study of zircon grain morphology, Pupin (1980) pro-

posed 64 possible forms that are related to crystallization temperature

(550 to 900 50 C); the forms are controlled mainly by the volatiles

Fig. 3. Paleocurrent direction data of the I Formation.

Table 1

Detrital mineral grains' (Fig. 4) average content in % identi ed in the I Formation (n = 61) and recent deposits (n = 19) (Tr = trace amount; = not found).

I Formation Recent deposits

Mineral Lower part Upper part 0.2500.125 mm 0.1250.062 mm

0.2500.125 mm 0.1250.062 mm 0.2500.125 mm 0.1250.062 mm

Mica 18 18 838 771 12 2

Andalusite 1459 3048 14 12 210 12

Sillimanite 126 130 433 134 114 19

Zircon 324 230 246 446 419 245

Kyanite 223 122 233 126 437 128

Staurolite 122 128 121 113 136 129

Pyroxene 119 123 115 118 245 1056

Tourmaline 115 116 16 19 15 113

Garnet 112 19 13 12 111 19

Amphibole 19 119 117 116 328 240

Monazite 16 14 15 16

Rutile 18 112 18 111 17 214

Epidote 13 16 15 12 220 27

Anatase 1 13 12 1 Tr

Brookite Tr Tr

Titanite Tr Tr

Topaz Tr Tr Tr Tr

Olivine Tr Tr



content of the magma, particularly H O, and its chemical composition.

While temperature is responsible for the development of prismatic

faces (100) relative to faces (110), the Al O /Na O + K O ratio controls

the growth of pyramidal faces; i.e., a high Al O content promotes

the development of faces (211) and (112). However, increasing

Na O + K O content favors faces (101) and (301). Based on the Pupin

classi cation, we identi ed 20 types of zircon shapes in the selected

grains by considering well-preserved faces associated with round and

sub-round crystals in the I Formation (Table 2; Fig. 8). The upper

part is characterized mainly by a higher content of the S18 type relative

to the lower part (Table 2). Among the 14 identi ed types in the recent

deposits, types S3, S17 and S22 appear to be exclusive to this unit.

Thus, the zircon morphology suggests that types D, S12 and S13

may be related to tholeiitic and calc-alkaline granite magma sources.

However, types S8 and S24, which occur only in the lower portion of

the I Formation, and type S3 in the recent sediments, appear to be

sourced from aluminous leucogranites, monzogranites and granodi-

orites, which are major crustal magma derivatives. Type S18, which

is more common in the uppermost portion of the I Formation,

could be correlated with more alkaline granitic magma source

rocks (Pupin, 1980). In all cases, the main sources are reworked con-

tinental crust.

In addition to the different zircon grain types, the chemical composi-

tion based on the ratio of Zr + Hf + Y + REE + Nb + Ta + W +

Fig. 4.Macroscopic characteristics of detrital mineral grains found in the I Formation and in the recent deposits.



Fig. 5. Proportion of detrital mineral grains in the recent sediments in the 0.1250.062 mm and 0.2500.125 mm fractions.

Fig. 6. Ternary diagrams: (A) zircontourmalinerutile (ZTR) and (B) ZTREpPAmp (epidote (Ep) + pyroxene (P) + amphibole (Amp))KSAnd (kyanite (K) + sillimanite (S) + andalusite

(And)). Black dots 0.1250.062 mm fraction, gray dots 0.2500.125 mm fraction.



Pb + Th + U (i.e., cations in the octahedral position) to Si (cations in

four-fold coordination) can be used to discriminate between the sedi-

mentary units. The zircon grains in the lower I Formation have higher

Si and lower Zr + Hf + Y + REE + Nb + Ta + W + Pb + Th + U

contents than those in the upper part of the formation (Fig. 9A, B). How-

ever, althoughmost of the zircon grains found in the recent deposits are

chemically similar to those in the I Formation, the type S12 and S13

zircon grains have higher Zr + Hf + Y + REE + Nb + Ta + W +

Pb + Th + U and lower Si contents (Fig. 9C). This suggests that a differ-

ent source area from that of the I Formation contributed to the depo-

sition of the recent sediments.

4.4. UPb geochronology

The I Formation yields a UPb age spectrum (see Supplementary

data le) that is dominated by two main populations according to the

stratigraphic location in the unit; 49% of the detrital zircons with ages

between 0.9 and 1.2 Ga, and 33% of zircons with ages between 0.2 to

0.6 Ga, are located in the lower part of the I Formation, while 47%

and 20% of these zircons, respectively, are in the upper part. The upper

part also contains almost 7% of the detrital zircons that are older than

2.6 Ga (Fig. 10A, B). The recent deposits have a UPb age spectrum

that is similar to that of the I Formation, but the proportions of zircons

with ages from 0.6 to 0.7 Ga and 1.3 Ga are different (Fig. 10C).

5. Discussion

5.1. Mineral provenance

The complex geologic evolution of western Amaznia, the juxtaposi-

tion of several geological provinces and the insuf cient geochronological

data make it dif cult to determine the precise source area of the I For-

mation sediments. However, the detrital zircon UPb age spectrum,

which is dominated by Mesoproterozoic zircon ages from 1.6 to 1.0 Ga

(Fig. 10, Supplementary data le), indicates that the provinces of the

southwest Amazonian craton, and primarily the Rondonian-San Igncio

and Sunsas-Grenvillian provinces (Tassinari and Macambira, 1999;

Santos et al., 2000; Geraldes et al., 2001; Ruiz et al., 2004; Fuck et al.,

Fig. 7. Distribution of zircontourmalinerutile (ZTR), mica and andalusite along the I Formation sections.



2008), were the main sources of the sediments in the I Formation

(Fig. 11). This hypothesis is supported by the mineral assemblages that

are found in these mobile belts, which are typical of high grade granulite

and amphibolite faciesmetamorphism and include pyroxene, sillimanite

and kyanite.

The UPb zircon data that range from Neoproterozoic to Silurian

times indicate another potential subordinate source area in the prov-

inces adjacent to the Amazonian craton (e.g., the BrazilianPampean

mobile belts and the Famatinian continental arch) and the basement

of the Andes cordillera that is represented by several metamorphic

inliers in Colombia, Peru and Bolivia (e.g., Litherland et al., 1989;

Restrepo-Pace et al., 1997; Fuck et al., 2008; Cardona et al., 2009;

Casquet et al., 2010; Decou et al., 2013) (Fig. 11). The NESE sediment

paleocurrent directions and the high content of stable detrital minerals

with metamorphic and calc-alkaline chemical signatures also suggest

the input of sediments produced by theweathering of these geochrono-

logical provinces in the I Formation. The underlying Solimes basin

units and the older provinces that are present in the Amazonian craton

are also sources of sediments for the I Formation and the recent sed-

iments; this is indicated by the nearly 7% of the Archean detrital zircon

ages that are in the grains in these sediments. However, the source of

the Archean grains in the study area is unknown. The differences in

the chemical composition of the zircon grains (Fig. 9) and in the mica

and andalusite contents (Fig. 7) between the upper and lower parts of

the I Formation indicate different sources, although the zircon grains

in both parts of the formation have similar UPb age signatures

(Fig. 10).

However, the recent deposits have awesterly paleocurrent direction

that reveals a change in the uvial system of the Solimes-Amazonas

basin; this requires a different source of sediments from those found

in the I Formation. The new source is located to the west and brought

sediments with a higher content of unstable minerals (EpPAmp) and

lower proportions of zircons with ages between 0.6 and 0.7 Ga and

greater than 1.3 Ga compared with the I Formation (Fig. 10C). The

S3, S17 and S22 zircon grain types, which are typical of the recent de-

posits and the zircon grains with higher trace element and lower Si con-

tents (Fig. 9), support the change of sediment source. This western

source may have contributed to the upper part of the I Formation

(i.e., zircon chemistry and age; Figs. 9, 10); however, the absenceof geo-

chronological data from the primary rock makes it dif cult to identify

this source.

5.2. Implications for the PlioPleistocene drainage of the Amazon

Based on the paleocurrents, detrital mineral compositions and zircon

grain UPb ages, we postulate that the present-day Solimes-Amazonas

River architecture, with itswesterly owdirection,mightbemore recent

than the Pliocene the probable age of the I Formation because the

Solimes Formation is late Miocene in age (Cozzuol, 2006; Latrubesse

et al., 2007). This interpretation that the Solimes-Amazonas River de-

veloped its present architecture only after the Pliocene, and most likely

in the PlioPleistocene, indicates that the Iquitos Arch (Fig. 11, Roddaz

et al., 2005b) was a physical barrier until the end of deposition of the

I Formation and blocked the input of sediments from the west. This

nding is consistent with the NE and SE paleocurrents measured in this

formation.

Considering the hypothesis above and the progressively increasing

deposition rate over the last 10 Ma (Dobson et al., 2001; Figueiredo et

al., 2009; Figueiredo et al., 2010) in the Amazonas fan, we have the fol-

lowing scenario in the region:

i. During 10.5 to 6.8Ma when the deposition ratewas low in theAma-

zonas fan (Figueiredo et al., 2009 and Figueiredo et al., 2010) the

Solimes basin was isolated from the Amazonas basin by the Purus

Arch. The Solimes Formation was deposited in the western portion

of the basin, and the Amazonas fan was dominated by sediment

from the center of the Amaznia, including the Amaznia Central

and Maroni-Itacainas provinces (Fig. 10), as proposed by

Figueiredo et al. (2009).

ii. From6.8 to 2.4 Mawhen the sedimentation rates increased, occurred

the westward expansion of the hydrological system, which bypassed

the Purus Arch and the Amazonas River captured the Solimes River

as a result of rising sea levels. The I Formationwas deposited during

this time, with uvial sediment ux to the northwest (Putumayo and

Japur Rivers?) and the southwest (Juru and Purus River?) and

Andean sediments started to arrive to the Amazon fan.

iii. The present architecture of the Solimes-Amazonas River, which

bypasses the Iquitos Arch and carries sediment from the west,

was established by 2.4 Ma, when the sedimentation rates in-

creased further (Figueiredo et al., 2009).

Thus, in our paleogeographic model, the I Formation was deposit-

ed from 6.8 to 2.4 Ma and had its main sources in the NW and SW

Mesoproterozoic Amazonian provinces with subordinate younger

sources (Fig. 11). The Iquitos Arch only began to be eroded after de-

position of the I Formation, which allowed westerly ow of sedi-

ments from the Andes to contribute to the recent sediments in a

second westward expansion of the hydrological system.

Our proposal for the deposition of the I Formation and for the age

of the Solimes-Amazonas Rivers agrees with the interpretation of the

Madre de Dios Formation in Peru by Campbell et al. (2001, 2006).

6. Conclusions

The provenance techniques employed in this study, including

paleocurrent data, detrital mineral and zircon grainmorphology, chem-

ical compositions, and UPb geochronology, revealed that the main

sources of the I Formation were the Mesoproterozoic provinces

from the Amazonian craton and the neighboring younger provinces to

the northwest and southwest. The I Formation, whichwasmost likely

deposited during the Pliocene, has a high proportion of stable detrital

minerals, morphology and chemical signatures and proportionality of

provenance ages of the zircon grains that are opposite of those of the re-

cent sediments, which suggests different source areas during deposition

of these units.

In our hypothesis, the Amazonas River had captured the Solimes

River by the Pliocene, bypassing the Purus Arch in a westward expan-

sion of the hydrological system that allowed the I Formation to be de-

posited with sediment derived from the NWSW. By 2.4 Ma, after

Table 2

Detrital zircon grains' type (Fig. 8) contents in % identi ed in the I Formation (n = 61)

and recent deposits (n = 19) (Tr = trace amount; = not found).

Zircon types I Formation Recent deposits

Part

Lower Upper

D 41 37 26

S2 1

S3 8

S7 3 4 Tr

S8 3

S11 5 6 8

S12 7 6 13

S13 15 12 8

S17 4

S18 1 12

S19 6 4 10

S22 12

S24 3

J4 3 7 3

J5 5 4 4

I 1

G1 1 2

P4 1


MarcelRealce


bypassing the Iquitos Arch, a westerly sediment ow and the present

Solimes-Amazonas River con guration had been established. This is

important in better establishing the landscape development of western

Amaznia since the Miocene.

Acknowledgments

This research was supported by CNPq (Conselho Nacional de

Desenvolvimento Cient co e Tecnolgico, grant no. 620003/2006-

Fig. 8. Zircon grain forms in accordance to Pupin (1980) classi cation.



8) and CLIM-AZON (grant no. 295091). M. B. Motta thanks CAPES

(Coordenao de Aperfeioamento de Pessoal de Nvel Superior)

for awarding him a scholarship. We are also grateful to H. T. Costi

(Museu Goeldi Belm, Brazil) and to C. Lamaro (Universidade

Federal do Par - Belm, Brazil) for assistance with the SEM analyses

and to J. Muhling (University of Western Australia) for the micro-

probe analyses.

Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.

doi.org/10.1016/j.sedgeo.2013.07.007.

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Fig. 9. Zr + Hf + Y + ETR + Nb + Ta + W + Pb + Th + U versus Si concentration in

the zircon grains from the I Formation (A. lower part, B. upper part) and recent deposits

(C).

Fig. 10.UPbgeochronology data of detrital zircongrains from the I Formation (A. lower

part, B. upper part) and C. recent deposits. See Supplementary data le for full data set.



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Fig. 11. Geological map of the Amaznia region showing the geochronological provinces of the Amazon craton and surrounding regions after Tassinari andMacambira (1999), Fuck et al.

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