Cenozoic weathering of fluvial terraces and emergence of biogeographic boundaries in Central Amazonia

Author(s):Show less -

Gautheron, Cecile ; Sawakuchi, Andre O. ; dos Santos Albuquerque, Marcio F. ; Cabriolu, Cristiana ; Parra, Mauricio ; Ribas, Camilla C. ; Pupim, Fabiano N. ; Schwartz, Stephane ; Kern, Andrea K. ; Gomez, Sebastian ; de Almeida, Renato P. ; Horbe, Adriana M. C. ; Haurine, Frederic ; Miska, Serge ; Nouet, Julius ; Findling, Nathaniel ; Riffel, Silvana Bressan ; Pinna-Jamme, Rosella

• Document type: Journal article
• Source: GLOBAL AND PLANETARY CHANGE; v. 212, p. 18-pg., 2022-04-19.

Abstract

The study of paleofluvial dynamics is crucial to understand the role of rivers as biogeographic boundaries in Amazonia during the Cenozoic. In central Amazonia, Mesozoic and Cenozoic fluvial deposits -Alter do Chao, Iranduba and Novo Remanso Formations-host supergene iron oxides and record changes in the distribution of flooded and non-flooded (upland) environments. Geochronological data on these deposits are still scarce to constrain past landscape changes. Therefore, in this study we investigate iron oxides precipitated within weathering profiles developed on ancient fluvial terraces to access the interplay between flooded and non-flooded environments in central Amazonia. We aimed to trace the history of abandonment of alluvial plains and the subsequent weathering of lowland sediment deposits during the Cenozoic. We identified at least two main periods of iron oxide precipitation: (1) one starting before similar to 42 Ma and ending at similar to 18 Ma; and (2) a well-defined humid and weathering prone phase between-8 and 1 Ma. Dominant goethite precipitation marks a major climatic shift towards more humid conditions from similar to 3 Ma. The increase in water discharge of the Negro and Solimoes rivers possibly promoted fluvial incision and conversion of floodplains into long-lasting upland terrains as indicated by the development of lateritic weathering profiles. This major phase of upland expansion corroborates upland birds phylogenetic data, which indicate the emergence of a major biogeographic barrier in central Amazonia during late Pliocene/Pleistocene. (AU)

• FAPESP's process: 14/23334-4 - Coupling Optically Stimulated Luminescence (OSL) and Terrestrial Cosmogenic Nuclides (TCN) analysis to reconstruct changes in the Amazonian fluvial system in the Late Cenozoic (<5 Ma)
• Grantee: Fabiano do Nascimento Pupim
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/23899-2 - Trans-Amazon Drilling Project: origin and evolution of the forests, climate, and hydrology of the South American tropics
• Grantee: André Oliveira Sawakuchi
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 13/03265-5 - Surface processes during active orogenesis: uplift and erosion of the Sierra Nevada de Santa Marta (Colombia) at multiple time scales
• Grantee: Mauricio Parra Amézquita
• Support Opportunities: Research Grants - Young Investigators Grants