Paper No. 136-2
Presentation Time: 1:55 PM
DRAINAGE EVOLUTION IN THE AMAZON FORELAND BASIN DURING UPLIFT OF THE ANDES
HORTON, Brian1, BAKER, Paul A.2, GOMEZ, Sebastian3, PARRA, Mauricio4, JACKSON, Lily5, BANKS, Claudia L.1, GUTIERREZ, E. Gabriela1, VALLEJO, Cristian6, SILVA, Cleverson G.7, WAHNFRIED, Inigo8, KIEFER, Gustavo9, SAWAKUCHI, André O.4 and FRITZ, Sherilyn10, (1)Jackson School of Geosciences, University of Texas, Austin, TX 78712, (2)Division of Earth and Climate Sciences, Duke University, Durham, NC 27708-0228, (3)Institute of Geosciences, University of São Paulo, São Paulo, Butanata 05508-080, Brazil, (4)Institute of Geosciences, University of São Paulo, São Paulo, Brazil, (5)Center for Economic Geology Research, School of Energy Resources, University of Wyoming, Laramie, WY 82071, (6)Departamento de Geología, Escuela Politécnica Nacional, Ladrón de Guevara E11-253, Quito, 170517, Ecuador, (7)Institute of Geosciences, Fluminense Federal University, Niterói, Brazil, (8)Geosciences Department, Amazonas Federal University, Manaus, Brazil, (9)Brazil Potash, Manaus, Brazil, (10)Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588
Detrital zircon results from modern rivers and ancient fluvial deposits help define the paleodrainage history of the Amazon River and South American foreland during uplift of the Andes. The continental-scale Amazon, Orinoco, and Magdalena fluvial drainage systems have impacted erosion, sediment dispersal, biodiversity, and climatic-tectonic interactions in the Andean fold-thrust belt and foreland basin. South America is well suited for provenance studies employing detrital zircon U-Pb geochronology because of age-diagnostic sources, including the Andean magmatic arc, retroarc fold-thrust belt, and Amazonian cratonic basement provinces.
New results from ~100 samples of fluvial basin fill and modern rivers in the Amazon headwaters of Ecuador and Peru demonstrate the spatial and temporal changes in detrital input from different source areas. U-Pb ages of modern river samples show both first-cycle igneous and metamorphic detritus as well as recycled sedimentary detritus from the magmatic arc, fold-thrust belt, and cratonic basement. Within foreland basin fill, U-Pb age distributions demonstrate a drainage reversal from cratonic to Andean sources during the Late Cretaceous-earliest Cenozoic initiation of Andean uplift. Thereafter, Cenozoic exhumation of the Andean orogenic belt resulted in greater input from the growing fold-thrust belt relative to the magmatic arc.
New U-Pb results from ~20 subsurface samples near Manaus, Brazil (~2200 km east of the Andes) show complex changes in source contributions that reflect abrupt alternations between local and regional derivation. These major drainage reorganization events may be related to Andean uplift, intracratonic uplift of basement arches, regional-scale marine incursions, or episodic generation of dynamic topography.
![[Visit Client Website]](/img/gsa/banner.jpg)