Author's personal copySedimentary Geology 296 (2013) 9…20 Contents lists available at ScienceDirect Sedimentary Geology jo u rn a l h o m ep ag e: w w w .el se vie r.c o m/ lo ca te/ se dg e o Provenance of Pliocene and recent sedimentary deposits in western Amazônia, Brazil: Consequences for the paleodrainage of the Solimões-Amazonas River Adriana Maria Coimbra Horbe , Marcelo Batista Motta , Carolina Michelin de Almeida , Elton Luiz Dantas , Lucieth Cruz Vieira Departamento de Geociências, Universidade Federal do Amazonas, Av. General Rodrigo Otávio Jordão Ramos, 3000, Coroado, 69077-000 Manaus, AM, Brazil Serviço Geológico do Brasil, CPRM—Manaus, Programa de Pós-Graduação em Geociências, Universidade Federal do Amazonas, Av. André Araújo, 2160, Coroado, 69060-000 Brazil Instituto de Geociências, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Brasília, 70910-900 Brasília, Brazil a 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: Içá Formation Iquitos Arch Zircon grain typology Heavy detrital minerals U…Pb geochronology a b s t r a c t Integrated data on paleocurrents, the morphology of detrital minerals and zircon grains, chemical compositions and U…Pb geochronology, reveal that the ow of the modern Solimões-Amazonas River has changed from west to east since the Plio…Pleistocene. This nding is supported by several lines of evidence, including paleocurrent directions and detrital mineral assemblages in the Içá Formation and in recent sediments. The Içá Formation, which was most likely deposited during the Pliocene, has NE and SE paleocurrents, a high proportion of stable detrital mineral assemblages and U…Pb zircon ages that we interpreted as being derived from the Amazonian craton (e.g., the Rondonian-San Ignácio and Sunsas-Grenvillian geochronologic provinces) and neighboring provinces, including 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 overlying recent deposits have different provenances and are characterized by a more variable detrital assemblage with zircon grains that are enriched in trace elements and depleted in Si and have Mesoproterozoic ages. In our interpretation, the erosion of the Iquitos Arch after deposition of the Içá Formation allowed the westward expansion of the Solimões-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 Amazônia since the Miocene. The marine connection with the Caribbean sea closed, the courses of the Magdalena and Orinoco rivers changed, Andean foreland basins formed due to exural subsidence and the Amazonas established a connection to the Atlantic, increasing the mass accumulation 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 SolimõesAmazonas River must be considered. Hoorn et al. (1995); Dobson et al. (2001) and Wesselingh and Salo (2006) stated that the architecture of the modern Solimões-Amazonas River formed since the Corresponding author. E-mail addresses:
[email protected] (A.M.C. Horbe),
[email protected] (M.B. Motta),
[email protected] (C.M. de Almeida),
[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 late Miocene. Campbell et al. (2001) interpreted that the Andean contribution to the Atlantic occurred in the end of the Pliocene (2.5 Ma), while Bezzerra (2003) and Rossetti et al. (2005) interpreted it as occurring in the late Pleistocene…Holocene. The aim of this paper is to study detrital minerals from the Içá Formation and associated recent deposits along the Solimões 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 Solimões-Amazonas River and their connection to the Atlantic Ocean. These two units are part of the large sedimentary Solimões-Amazonas basin and therefore might clarify the geological evolution and timing of the development of the present course of the Solimões-Amazonas River systems. In addition, we will discuss the in uence of the Iquitos Arch and Andes rocks in the sedimentation and landscape evolution of western Amazônia. To answer these questions, we selected the six most signi cant outcrops in the cliffs, islands and bars along the Solimões River between the cities of Tefé and Manaus (Fig. 1). According to Maia et al. (1977) and Melo and Villas Boas (1993), the cliffs along the river correspond to the Içá Formation, whereas the islands and bars are composed of recent riverbed sediments. 1995.. Latrubesse et al. 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 Solimões-Amazonas Rivers (Latrubesse and Franzinelli. 2006. 1A.. 2007). Geological setting The western portion of the Amazonas River in Brazil is called the Solimões River and drains the Andean cordillera. 1977. The Içá Formation has been correlated to the Madre de Dios Formation in Peru (Campbell et al. 1993) or Late Pleistocene…Holocene (Rossetti et al. Hoorn. 2007) in a uvio-lacustrine to transitional marine environment. Leguizamón Vega. Latrubesse et al. Latrubesse et al.g. 1A) and was deposited during the late Miocene (11…10 Ma. and the lower part is composed of gray-greenish clay layers that contain plant fossil. S stratigraphic section of the Içá Formation.. 1B). 2005b) in the west side in a SRTM image. 2006) and the limit of the Solimões-Amazon hydrographic basin in red. has not been well studied and cannot be dated by biostratigraphy because of the lack of fossils.. The Solimões Formation occurs in a large region in the west of the Içá Formation and in a few outcrops in the study area (1B).. . (A) Location map showing the main Paleozoic sedimentary basins: Amazonas in the east side. The two youngest sedimentary units of the Solimões Paleozoic basin are the Solimões Formation (called the Pebas Formation in Peru and Colombia) and the Içá Formation (Fig. The Andes and the Amazonian craton are considered to be the source area for the rocks that make up this formation (Hoorn et al.. The limits of the Içá Formation in black (CPRM. 1) above an erosive unconformity (Maia et al. which overlies the eastern part of the Solimões Formation (Fig. 1977. 2005.. fairly inaccessible region. Caputo and Silva. Moreover.C. Several studies have investigated the sedimentary environment and palynology of the Solimões Formation (e. / Sedimentary Geology 296 (2013) 9–20 Fig. 1991. 2005) in age.. Its upper part is composed of thin to thick sandstone layers interspersed with massive white-reddish clay layers that are centimeters to meters thick. Solimões in the center and the Peru and Bolivia foreland Amazon basin (NAFB and SAFB after Roddaz et al.. Leguizamón Vega (2005) described sedimentary rocks related to the Solimões Formation along the Solimões River (Fig. and the Central Brazil and Guyana shields (Amazonian craton) (Fig. 2002). sh teeth and scales. 1995. In contrast. the sedimentary rocks of the Solimões Paleozoic basin. 2007). 2006. B). the exact extents of the Içá and Solimões Formations are controversial because they are present in a large. 2005a) (Fig. However. the Içá Formation. (B) Geology and location of the samples in the study area.. 1994.Author's personal copy 10 A. 2006).. 1. 2005a. These studies indicate that the Solimões Formation occupied a large lowland area adjacent to the Andean foreland basins (Roddaz et al. Melo and Villas Boas. (C) Simpli ed chronostratigraphic diagram of the studied units in the Solimões Paleozoic basin. Cozzuol. Leguizamón Vega. Horbe et al. evidence of bioturbation and root marks. 2005). SD samples from recent deposits. It is characterized predominantly by whitish to reddish yellow sandstone that is intercalated with grayish-reddish silty-clay lenses and is thought to be Plio…Pleistocene (Maia et al..M. Wesselingh and Salo. 1C). Hoorn et al. 2. Quaternary deposits overlie both the Solimões and Içá Formations along the Solimões-Amazonas River. kyanite.125…0. andalusite. massive rhythmites. amphibole (crossite and tirodite). Schematic sections of the Içá Formation and proportion of detrital grain minerals in the 0.062…0. and classi ed using the methodology of Pupin (1980). topaz. peds and some wood fossils (Fig. pelites and conglomerate with trough cross-bedding.Author's personal copy A. and some rock fragments such as gneiss. The proportion of zircon decreases from west to east along the river in the study area. 4). 1). Fig.2.M. Ninety. garnet (almandine.250 mm and 0. cross-laminations. The recent sediments that are present along the Solimões River in the study area.062 mm and 0.1. 4. 4. and the paleocurrent data indicate ow to the NE and SE (Fig. 2. Geological characteristics of the sedimentary units The Içá Formation corresponds to a hilly surface with cliffs up to 30 m high and extends along the Solimões River for at least 400 km between the Tefé and Purus Rivers (Fig. / Sedimentary Geology 296 (2013) 9–20 3. 61 samples came from six sections of the Içá Formation on the right bank of the Solimões River. and sandstone are present in the coarse fraction of all sections. which form kilometer-long islands and bars. Materials and methods Eighty samples were collected for detrital heavy mineral analysis.ve individual detrital zircon grains from the Içá Formation and the recent sediments were analyzed by electron microprobe (JEOL JSM 6400) at the University of Western Australia. are neto medium-grained to locally coarse-grained sands. U…Pb dating of 307 in situ zircon grains from sections 1 and 4 of the Içá Formation and the recent sediments was carried out with a Thermo Finnigan Neptune multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) at the University of Brasília. including mica (biotite and anandite).C. zircon. These sediments were most likely deposited in point-bar and oodplain environments. and olivine (Table 1. Fig.125 mm fractions. Results 4. Longitudinal sections along the Solimões River show low-angle and tabular crossstrati cation with W…E direction ux. The detrital mineral composition in the Içá Formation can be divided into two different groups.125…0. anatase. there is a clear distinction between the units. brookite. spessartine and knorringite). such as quartz and feldspar. Zircon grain morphologies were examined under a scanning electron microscope (SEM-LED 1450 VP) at the Museu Emilio Goeldi and Universidade Federal do Pará. sillimanite. Central Amazônia (Fig. quartzite. 2). Brazil. The minerals were separated from fractions of 0. epidote (mukhinite). according to the methods of Bühn et al. This formation comprises whitish 11 sandstones. while the upper part is dominated by mica. titanite. (2009). are angular to subrounded. tabular cross-strati cation. monazite. Fig. The light detrital grains in both units. The lower part of this unit has a higher andalusite content. X-ray diffraction (XRD) analysis was used to supplement the mineral identi cation. tourmaline (dravite and uvite). . the recent deposits have a higher proportion of pyroxene and amphibole than the Içá Formation (Table 1.125 mm using an elutriator and heavy liquids and then mounted on glass slides in Canada balsam. Horbe et al. root marks. In contrast.250…0. An average of 200 transparent grains per slide was identi ed and counted using a petrographic microscope and the ribbon counting procedures of Mange and Maurer (1992). and 19 came from recent sediments on islands and sandbars between Tefé and Manacapuru. 5). sigmoidal strati cation. 2). pyroxene (ferrosilite and enstatite). 1). ripple cross-laminations. staurolite. 3). rutile. However. Fig. zircon and kyanite with less tourmaline and garnet (Table 1. ripple marks. Brazil. Detrital mineral assemblage We identi ed the same range of mineral grains in both sedimentary units. 125…0. However.C.125…0. the proportion of ZTR minerals relative to the more stable (KSAnd: kyanite + sillimanite + andalusite) and unstable (EpPAmp: epidote + pyroxene + amphibole) mineral assemblages varies. However. the forms are controlled mainly by the volatiles Table 1 Detrital mineral grains' (Fig. 6B) and an increasing proportion of EpPAmp toward the recent sediments. Içá Formation Mineral Mica Andalusite Sillimanite Zircon Kyanite Staurolite Pyroxene Tourmaline Garnet Amphibole Monazite Rutile Epidote Anatase Brookite Titanite Topaz Olivine Recent deposits Lower part Upper part 0. mica and andalusite discriminates the lower part of the Içá Formation from the upper part (Fig.250…0.M. 4. 4) average content in % identi ed in the Içá Formation (n = 61) and recent deposits (n = 19) (Tr = trace amount.250…0. Paleocurrent direction data of the Içá Formation.3. Detrital zircon grain morphology and chemical composition Based on the study of zircon grain morphology.062 mm 0. Pupin (1980) proposed 64 possible forms that are related to crystallization temperature (550 to 900 ± 50 °C). the Içá Formation has a higher proportion of ZTR and KSAnd relative to EpPAmp (Fig. Horbe et al.125…0. 7).125 mm 0. the proportion of ZTR minerals.062 mm 1…8 14…59 1…26 3…24 2…23 1…22 1…19 1…15 1…12 1…9 1…6 1…8 1…3 1 Tr Tr Tr Tr 1…8 30…48 1…30 2…30 1…22 1…28 1…23 1…16 1…9 1…19 1…4 1…12 1…6 1…3 Tr Tr Tr Tr 8…38 1…4 4…33 2…46 2…33 1…21 1…15 1…6 1…3 1…17 1…5 1…8 1…5 1…2 … … Tr … 7…71 1…2 1…34 4…46 1…26 1…13 1…18 1…9 1…2 1…16 1…6 1…11 1…2 1 … … Tr … 0. … = not found).125 mm 0. The zircon…tourmaline…rutile ternary diagram (ZTR. Fig.250…0.125 mm 0. 3.062 mm 1…2 2…10 1…14 4…19 4…37 1…36 2…45 1…5 1…11 3…28 … 1…7 2…20 Tr … … … … 2 1…2 1…9 2…45 1…28 1…29 10…56 1…13 1…9 2…40 … 2…14 2…7 … … … … … . These data suggest that the two units have different source areas (provenance). / Sedimentary Geology 296 (2013) 9–20 Fig. 6A) does not show signi cant differences in the contents of the Içá Formation and the recent deposits.Author's personal copy 12 A. Author's personal copy A. While temperature is responsible for the development of prismatic faces (100) relative to faces (110). However.. Among the 14 identi ed types in the recent deposits. monzogranites and granodiorites. 4. Type S18. appear to be sourced from aluminous leucogranites. 8).C. types S3. increasing Na O + K O content favors faces (101) and (301).M. / Sedimentary Geology 296 (2013) 9–20 13 Fig. the main sources are reworked continental crust. types S8 and S24. Based on the Pupin classi cation. the chemical composition based on the ratio of Zr + Hf + Y + REE + Nb + Ta + W + . In addition to the different zircon grain types. which occur only in the lower portion of the Içá Formation. which are major crustal magma derivatives. content of the magma. S12 and S13 may be related to tholeiitic and calc-alkaline granite magma sources. 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 Içá Formation (Table 2. the zircon morphology suggests that types D. could be correlated with more alkaline granitic magma source rocks (Pupin. the Al O /Na O + K O ratio controls the growth of pyramidal faces. Horbe et al. Fig. In all cases. and its chemical composition. particularly H O. 1980). The upper part is characterized mainly by a higher content of the S18 type relative to the lower part (Table 2). S17 and S22 appear to be exclusive to this unit. However. i. Macroscopic characteristics of detrital mineral grains found in the Içá Formation and in the recent deposits. which is more common in the uppermost portion of the Içá Formation. Thus. and type S3 in the recent sediments. a high Al O content promotes the development of faces (211) and (112).e. Ternary diagrams: (A) zircon…tourmaline…rutile (ZTR) and (B) ZTR…EpPAmp (epidote (Ep) + pyroxene (P) + amphibole (Amp))…KSAnd (kyanite (K) + sillimanite (S) + andalusite (And)).M.C.125…0.125 mm fraction. Fig.062 mm fraction. 5. . Proportion of detrital mineral grains in the recent sediments in the 0.062 mm and 0. 6.125…0. gray dots 0.125 mm fractions.Author's personal copy 14 A. Black dots 0. Horbe et al.250…0. / Sedimentary Geology 296 (2013) 9–20 Fig.250…0. However.0 Ga (Fig. U–Pb geochronology The Içá Formation yields a U…Pb age spectrum (see Supplementary data le) that is dominated by two main populations according to the stratigraphic location in the unit.2 Ga. 10C).6 Ga (Fig. / Sedimentary Geology 296 (2013) 9–20 15 Fig. but the proportions of zircons with ages from 0. Pb + Th + U (i. Supplementary data le). Santos et al. cations in the octahedral position) to Si (cations in four-fold coordination) can be used to discriminate between the sedimentary units. Discussion 5. Mineral provenance The complex geologic evolution of western Amazônia. Geraldes et al.9 and 1. respectively. 10A.. B). Fuck et al. although most of the zircon grains found in the recent deposits are chemically similar to those in the Içá Formation. are in the upper part. 2000.6 to 1. and primarily the Rondonian-San Ignácio and Sunsas-Grenvillian provinces (Tassinari and Macambira. 9C). 5. 2004.. 4. The upper part also contains almost 7% of the detrital zircons that are older than 2. . However.M.. 10.3 Ga are different (Fig.1. 9A. mica and andalusite along the Içá Formation sections. The zircon grains in the lower Içá 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.6 Ga. This suggests that a different source area from that of the Içá Formation contributed to the deposition of the recent sediments.4. Distribution of zircon…tourmaline…rutile (ZTR). the juxtaposition of several geological provinces and the insuf cient geochronological data make it dif cult to determine the precise source area of the Içá Formation sediments. are located in the lower part of the Içá Formation. the detrital zircon U…Pb age spectrum.Author's personal copy A. Ruiz et al. which is dominated by Mesoproterozoic zircon ages from 1. the type S12 and S13 zircon grains have higher Zr + Hf + Y + REE + Nb + Ta + W + Pb + Th + U and lower Si contents (Fig. 1999..2 to 0.e.6 to 0.C. 2001. while 47% and 20% of these zircons. 7. B). and 33% of zircons with ages between 0. Horbe et al..7 Ga and 1. indicates that the provinces of the southwest Amazonian craton. The recent deposits have a U…Pb age spectrum that is similar to that of the Içá Formation. 49% of the detrital zircons with ages between 0. when the sedimentation rates increased further (Figueiredo et al. bypassing the Purus Arch in a westward expansion of the hydrological system that allowed the Içá Formation to be deposited with sediment derived from the NW…SW. the absence of geochronological data from the primary rock makes it dif cult to identify this source.. (2009). 11). the Içá Formation was deposited from 6.. 8) contents in % identi ed in the Içá Formation (n = 61) and recent deposits (n = 19) (Tr = trace amount. and U…Pb geochronology. 1989. Implications for the Plio–Pleistocene drainage of the Amazon Based on the paleocurrents. the Amazonas River had captured the Solimões River by the Pliocene. 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. Considering the hypothesis above and the progressively increasing deposition rate over the last 10 Ma (Dobson et al. Zircon types Içá Formation Recent deposits Part D S2 S3 S7 S8 S11 S12 S13 S17 S18 S19 S22 S24 J4 J5 I G1 P4 Lower Upper 41 1 … 3 3 5 7 15 … 1 6 … 3 3 5 … 1 … 37 … … 4 … 6 6 12 … 12 4 … … 7 4 … 2 1 26 … 8 Tr … 8 13 8 4 … 10 12 … 3 4 1 … … 2008). In our hypothesis. which bypasses the Iquitos Arch and carries sediment from the west. 2006. 10). (2001.e.4 Ma. zircon chemistry and age. 6. ii. The present architecture of the Solimões-Amazonas River. Figs. support the change of sediment source. Figueiredo et al. This hypothesis is supported by the mineral assemblages that are found in these mobile belts. and the Amazonas fan was dominated by sediment from the center of the Amazônia. however. Roddaz et al. which suggests different source areas during deposition of these units.4 Ma when the sedimentation rates increased. This western source may have contributed to the upper part of the Içá Formation (i. Restrepo-Pace et al. 2013) (Fig. 11). we postulate that the present-day Solimões-Amazonas River architecture. 2010) the Solimões basin was isolated from the Amazonas basin by the Purus Arch. Figueiredo et al.5 to 6. Conclusions The provenance techniques employed in this study. 2009). was established by 2. although the zircon grains in both parts of the formation have similar U…Pb age signatures (Fig.8 to 2. and most likely in the Plio…Pleistocene. S17 and S22 zircon grain types. this is indicated by the nearly 7% of the Archean detrital zircon ages that are in the grains in these sediments. … = not found). detrital mineral and zircon grain morphology. 7) between the upper and lower parts of the Içá Formation indicate different sources. 10). detrital mineral compositions and zircon grain U…Pb ages...M. Cardona et al. the source of the Archean grains in the study area is unknown. The Iquitos Arch only began to be eroded after deposition of the Içá Formation. The Solimões Formation was deposited in the western portion of the basin..4 Ma and had its main sources in the NW and SW Mesoproterozoic Amazonian provinces with subordinate younger sources (Fig. as proposed by Figueiredo et al. which are typical of high grade granulite and amphibolite facies metamorphism and include pyroxene. From 6. 10C).8 to 2. this requires a different source of sediments from those found in the Içá Formation. the Brazilian…Pampean mobile belts and the Famatinian continental arch) and the basement of the Andes cordillera that is represented by several metamorphic inliers in Colombia. including the Amazônia Central and Maroni-Itacaiúnas provinces (Fig. 2008. The Içá Formation was deposited during this time.. iii... including paleocurrent data. The S3. in our paleogeographic model. 2001.. Fuck et al. 9). This nding is consistent with the NE and SE paleocurrents measured in this formation. The underlying Solimões basin units and the older provinces that are present in the Amazonian craton are also sources of sediments for the Içá Formation and the recent sediments.g.7 Ga and greater than 1. 2005b) was a physical barrier until the end of deposition of the Içá Formation and blocked the input of sediments from the west. were the main sources of the sediments in the Içá Formation (Fig. we have the following scenario in the region: i. / Sedimentary Geology 296 (2013) 9–20 Table 2 Detrital zircon grains' type (Fig. which are typical of the recent deposits and the zircon grains with higher trace element and lower Si contents (Fig. 10).6 and 0.4 Ma. By 2. 1997.. 11). Litherland et al. Thus. 2009 and Figueiredo et al. The differences in the chemical composition of the zircon grains (Fig.. might be more recent than the Pliocene … the probable age of the Içá Formation … because the Solimões Formation is late Miocene in age (Cozzuol. after .8 Ma when the deposition rate was low in the Amazonas fan (Figueiredo et al.Author's personal copy 16 A. 2007). which bypassed the Purus Arch and the Amazonas River captured the Solimões River as a result of rising sea levels. However. chemical compositions. However. Decou et al. 11. the recent deposits have a westerly paleocurrent direction that reveals a change in the uvial system of the Solimões-Amazonas basin.3 Ga compared with the Içá Formation (Fig.. This interpretation that the Solimões-Amazonas River developed its present architecture only after the Pliocene. 9. 2010) in the Amazonas fan. During 10. 2010. occurred the westward expansion of the hydrological system.2.. 2009.C.. The Içá Formation. 2006). indicates that the Iquitos Arch (Fig. revealed that the main sources of the Içá Formation were the Mesoproterozoic provinces from the Amazonian craton and the neighboring younger provinces to the northwest and southwest. with uvial sediment ux to the northwest (Putumayo and Japurá Rivers?) and the southwest (Juruá and Purus River?) and Andean sediments started to arrive to the Amazon fan.. Casquet et al. 9) and in the mica and andalusite contents (Fig. 5. has a high proportion of stable detrital minerals. The NE…SE 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 the weathering of these geochronological provinces in the Içá Formation. sillimanite and kyanite..g. with its westerly ow direction. 2009. Peru and Bolivia (e. morphology and chemical signatures and proportionality of provenance ages of the zircon grains that are opposite of those of the recent sediments. which was most likely deposited during the Pliocene. The U…Pb zircon data that range from Neoproterozoic to Silurian times indicate another potential subordinate source area in the provinces adjacent to the Amazonian craton (e.. Latrubesse et al. Horbe et al. Our proposal for the deposition of the Içá Formation and for the age of the Solimões-Amazonas Rivers agrees with the interpretation of the Madre de Dios Formation in Peru by Campbell et al. which allowed westerly ow of sediments from the Andes to contribute to the recent sediments in a second westward expansion of the hydrological system. Horbe et al. / Sedimentary Geology 296 (2013) 9–20 17 Fig.M. 8. 620003/2006- . bypassing the Iquitos Arch. Zircon grain forms in accordance to Pupin (1980) classi cation.C. Acknowledgments This research was supported by CNPq (Conselho Nacional de Desenvolvimento Cientí co e Tecnológico.Author's personal copy A. a westerly sediment ow and the present Solimões-Amazonas River con guration had been established. This is important in better establishing the landscape development of western Amazônia since the Miocene. grant no. Programa Geologia do Brasil. / Sedimentary Geology 296 (2013) 9–20 Fig.. Motta thanks CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for awarding him a scholarship. Campbell. 2006. Brazil) for assistance with the SEM analyses and to J. Caputo. Compartimentação morfotectônica do inter úvio Solimões-Negro. doi. Romero-Pittman. A. recent deposits.. M. upper part) and recent deposits (C). Horbe et al.org/10. Cardona. U…Pb zircon geochronology and Nd isotopic signatures of the pre-mesozoic metamorphic basement of the eastern Peruvian Andes: growth and provenance of a Late Neoproterozoic to carboniferous accretionary orogen on the Northwest margin of Gondwana. C. K. 169…193.J..D dissertation) Universidade Federal do Pará. G.1016/j.M. Armstrong. A. 295091).2013..Author's personal copy 18 A.D..A. upper part) and C. The Pan-Amazonian Ucayali Peneplain. J. R. 2003. C. P.).M. lower part. 9. Supplementary data Supplementary data to this article can be found online at http://dx. See Supplementary data le for full data set. References Bezzerra. Galindo. (Eds... Origem e Evolução das Bacias Sedimentares. T.P.R. We are also grateful to H. 1991. Anais da Academia Brasileira de Ciências 81. C. Brazil. Zr + Hf + Y + ETR + Nb + Ta + W + Pb + Th + U versus Si concentration in the zircon grains from the Içá Formation (A. Companhia de Pesquisas e Recursos Minerais... Pankhurst. CPRM. Mapa geológico do Estado do Amazonas. Dantas.. Campbell Jr..C. Milani.000. A.. diversity. 2009. M. Rio de Janeiro em CDROM. Journal of South American Earth Sciences 21.W. Silva.A. Upper Cenozoic chronostratigraphy on the southwestern Amazon basin. Journal of South American Earth Sciences 29. P.E. Petrobras. Casquet.B. Geology 29. Chew. M.. Palaeogeography Palaeoclimatology Palaeoecology 239. Frailey...E. Rapela. U.sedgeo.. D.. E.. 2006. C. V. Brazil) and to C. Ministério de Minas e Energia.L.. Sedimentação e tectônica da Bacia do Solimões. 128…142.E. Lamarão (Universidade Federal do Pará .. M.. B. 595…598. M. Ruiz. Matteini.L.000.. (Ph. Pimentel... and the birth of the modern Amazon River system. O. Journal of Geology 117. Nutman. Romero-Pittman. 285…305.J. Costi (Museu Goeldi „ Belém. Torres..Belém. Heizler. Fig. 166…219. M. In: Raja Gabaglia. Sistema de informações Geográ cas „ SIG. . D.M. Muhling (University of Western Australia) for the microprobe analyses. Belém. The Arequipa Massif of Peru: new SHRIMP and isotope constraints on a Paleoproterozoic inlier in the Grenvillian orogen. Fanning.. and geography. B. Valencia. Cozzuol. 10.G.07. The Acre vertebrate fauna: age. 2009. L. Appendix A. pp. 99…114. C.. R. U…Pb geochronology data of detrital zircon grains from the Içá Formation (A. B. lower part. E..W. Cordani. K. Bühn. High spatial resolution analysis of Pb and U isotopes for geochronology by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). 185…203. Sanchez. Prothero. 2001... late Neogene sedimentation in Amazonia.V.007. L. 8) and CLIM-AZON (grant no. Escala 1:1.. B. 2010. 2006. Viers.. Hoorn. P. M. E. 87…108..V. 619…622.. Quaternary Research 63. The Proterozoic of eastern Bolivia and its relationship to the Andean mobile belt.. P. 157…174.M. Restrepo-Pace. 1977.. Roddaz.. Soares. Costa. Departamento de Geociências. M.A... H... London Chapman & Hall (147 pp.M... Babinski. E. H. Mange. Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Foz do Amazonas Basin. J. Klinck.. Geraldes. Late Miocene onset of the Amazon River and the Amazon deep-sea fan: evidence from the Foz do Amazonas basin. R. Sarmiento. G... Dobson.. F.P. 2001. Dickens. de Toledo.F..M. Silva. 210…211. Geomorphology 44. NW Amazonia).. M. J.. 57…78. 4. Maurer. G.P. 2009. 237…240.C.. Schmus. C. 78…89.M.F. 108…126. 241…257. 2005. 91…128.M. P. Hoorn. Palaeogeography Palaeoclimatology Palaeoecology 112. van der Vem. Brazil. Brusset. (2009) and Decou et al. Cazzuol.. Palaeogeography Palaeoclimatology Palaeoecology 165.A.. An environmental reconstruction of the paleo-Amazon River system (Middle-late Miocene. Journal of South American Earth Sciences 45..A. Sediment provenances and drainage evolution of the Neogene Amazonian foreland basin.N. Pit eld. Holanda.I.N. W. Brusset. S.. Hawkins. E... 1993. G.A. Earth-Science Reviews 44. pp. The Holocene alluvial plain of the middle Amazon River. 1994. Geology 23. The estimate position of Iquitos and Purus Arch is shown in red dotted lines (Roddaz et al... Bell. Geology 37. 2008. Zircon and granite petrology.. D. 1980.. / Sedimentary Geology 296 (2013) 9–20 19 Fig. Geology 38 e213..C. P. C.F. 207…220. J. Power. Fletcher... 2005b. Dunkl.. A. K.CPRM-DNPM.F. E. Cosca. B. Precambrian Research 43. A. 1998.. 2005a.P. Moura.. C.. Universidade Federal do Amazonas. Boletim de Resumos Expandidos. M... Hoorn. R.Author's personal copy A. Góes. M.. C. O'Connor. 2005. Maia.. H.M.K. Cardona et al. Reconstituição paleoambiental dos depósitos miocenos na região Centro oriental da Bacia do Solimões. G. 1989. D. Projeto Carvão no Alto Solimões.... Simpósio de Geologia da Amazônia.A. Schobbenhaus. The red arrows and the gray arrow indicate respectively the position of the main primary sources and the sediment ow direction of the Içá Formation and of the recent deposits. Figueiredo. Roddaz. Latrubesse. Relatório Final. C. 1997. R. Leguizamón Vega. Late Eocene to Early Miocene Andean uplift inferred from detrital zircon ssion track and U…Pb dating of Cenozoic forearc sediments (15…18°S).A.. Heavy Mineral in Colour. Guerrero. 187…238. C. Earth and Planetary Science Letters 150.. Sociedade Brasileira de Geologia „ Núcleo Norte.. M. R. 2013.. J. Geochronology and Nd isotopic data of Grenville-age rocks in the Colombian Andes: new constraints for Late Proterozoic… Early Paleozoic paleocontinental reconstructions of the Americas.... Brazil. S. M. Van der Hammen. E. P. Frei. Brazil. .M.A.. B. Earth and Planetary Science Letters 239.N. Journal of South American Earth Sciences 23. Annells.B.J.C.B. D. Terrigenous sediment on Ceara Rise: a Cenozoic record of South American orogeny and erosion.F. 2005a). 2002. Hooghiemstra. A. New geological framework for western Amazonia (Brazil) and implications for biogeography and evolution. Precambrian Research 111. and a literature overview. M.L.. Neves. W. 1995. Condie. 6…23. Herail... Latrubesse.M. Tectonophysics 399.. 2007... Rossetti. I. Absy. H. P. Hermoza. (2013). Rodinia descendants in South America. 11.. Darrozes.C. D.J. von Eynatten.E. Andean tectonics as a cause for changing drainage patterns in Miocene northern South America.. B. Mitchell. J. W. Gehrels. M.F.R. 2001. A. E. M. Godoy. Fuck et al.G. Late Miocene continental sedimentation in southwestern Amazonia and its regional signi cance: biotic and geological evidence. Ruiz. Rea.. Proterozoic geologic evolution of the SW part of the Amazonian craton in Mato Grosso state. Hoorn. 2010. Melo. Caracterização e distribuição da Formação Içá na porção noroeste do Estado do Amazonas..). P. Soares. J. Fuck. Forebulge dynamics and environmental control in western Amazonia: the case study of the Arch of Iquitos (Peru). S. S. Manaus. H.. Costa. Teixeira. Contributions to Mineralogy and Petrology 73....L. Franzinelli...A.F. Figueiredo. Villas Boas. Precambrian Research 160. Darbyshire. Decou. 215…229.S. (2008). Webb.. Wörner. Baby. Unpublished Master's Thesis. Litherland..S.. G. Pupin. Yamaguti. M. P. J... van der Vem.W.... T. Baby. 427…441. 147…183.F. Neogene and Quaternary development of the neotropical rain forest: the forest refugia hypothesis... P. Horbe et al. G.. 1992. Geological map of the Amazônia region showing the geochronological provinces of the Amazon craton and surrounding regions after Tassinari and Macambira (1999).A. 61…80. D.K. J. .B.G. Schmus.A.. M. Scripta Geologica 133. Wesselingh. F. Schmitt. I.S. Geraldes.Author's personal copy 20 A. W..V. Hartmann.R. J. Santos. Gaudette. H. 453…488. Geochronological provinces of the Amazonian craton... Anais da Academia Brasileira de Ciências 76.. Groves.. 174…182.J.P. M. / Sedimentary Geology 296 (2013) 9–20 Ruiz.M. Salo.I. Macambira. 807…824. 2000.E..S. 439…459. The 1590…1520 Ma Cachoeirinha magmatic arc and its tectonic implications for the Mesoproterozoic SW Amazonian craton crustal evolution. Gondwana Research 3. 1999. J.. 2004. Horbe et al. A.C.C. J.B. D. Tassinari. .. A new understanding of the provinces of the Amazon craton based on inte- gration of eld mapping and U…Pb and Sm…Nd geochronology.J. C.... Matos.S... W. Fletcher.O.C. Teixeira. A Miocene perspective on the evolution of the Amazonian biota. 2006.R.. N. Mcnaughton.A. Episodes 22. L. R.