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C 300 145 ma was again a sustained topographic high

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c. 300-145 Ma),was again a sustained topographic high throughout the Cre-taceous and most of the Cenozoic (c. 145-10 Ma), and be-came buried by Andean-derived sediments with the onset ofthe modern transcontinental Amazon River.Using the terms as defined above, we can better unders-tand the geological setting of Northern South America (Fig.1). The Amazon basin is not a rift valley, or even a singlegeological depression. Rather, the Amazon drainage basinis composed of four larger, and several smaller, structuralbasins, each encompassing one or more geologically distinctsedimentary basins, and all separated from one another bystructural arches. The main axis of the Amazon River drainsa series of sedimentary basins that formed over a protractedinterval during much of the Phanerozoic (541-0 Ma). Most ofthese sedimentary basins formed in association with tectonicrifting of the South American and Africa plates during theLower Cretaceous (145-100 Ma), and all these sedimentarybasins were affected by uplift of the northern Andes duringthe Paleogene and Neogene. Broadly speaking, patterns ofsediment dispersal and accumulation, and drainage reorga-nization in NSA reflect landscape evolution associated withprotracted subduction of the Farallon, Nazca, and CocosPlates (Horton, 2017). The underlying geological mecha-nisms can be traced to tectonic uplifts of the Northern An-des that occurred in several distinct orogenic phases, calledthe Incaic (48-34 Ma), Quechua 1 (17-15 Ma), Quechua 2(9-8 Ma), and Quechua 3 (7-5 Ma) Phases (Gregory-Wodzi-cki, 2000; Pfiffner, Gonzalez, 2013; Bermúdezet al., 2015;Chiarabbaet al., 2016; Horton, 2017).The Western Amazon region encompasses several sub--Andean sedimentary basins (e.g. Acre, Marañon), while theSolimões, Amazonas, and Marajó sedimentary basins areintracratonic basins. Andean-derived fluvial sediments arerecorded in the sub-Andean foreland from at least the earlyPaleocene or Eocene (Hurtadoet al., 2018). The WesternAmazon also separated from the Llanos basin to the north bythe Vaupés Arch, and from the Upper Madeira basin in thesouth by the Fitzcarrald Arch. The Solimões and Amazonasbasins are bounded to the north and south by portions of theAmazon Craton, represented as Guiana Shield to the northand Central Brazilian (or Guaporé Shield) to the south.Recent studies emphasize the complex and diachronous(time-varying) uplift and deformation history of the northernAndes among its several parallel cordilleras and along itslatitudinal extent (Garzioneet al., 2017). While orogenesis(mountain building) is the underlying process that leads tomassive erosion and sedimentation in the adjacent basins,later sediment redistribution and landscape changes mighthave been at least partly controlled by mantle-convectionprocesses affecting the South American plate (Shephardetal., 2010), flat slab subduction (Eakinet al., 2014), and pro-gressive eastward sediment-load driven flexure of the lithos-phere (Sacek 2014).

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Term
Spring
Professor
VAIELLOI
Tags
Test, Amazon River, Drainage basin

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