Mid-Late Pleistocene OSL chronology in western Amazonia and implications for the transcontinental Amazon pathway

摘要: Abstract The origin of the transcontinental Amazon drainage system remains unrevealed. Sedimentary deposits formed from Neogene in Amazonas and Solimoes Basins constitute natural archives for reconstructing this event space time. However, paleoenvironmental chronological analyses focusing on these deposits, or even their basic mapping, are still scarce to allow such investigation. In context, primary interests fluvial strata related lithostratigraphic Ica Formation, mapped over a widespread area western Amazonian lowlands. Although long regarded as Plio-Pleistocene age, unit has not yet been dated its overall depositional setting largely undescribed. main goal present work is contribute improving facies analysis chronology approaching an southwestern Amazonia another northern Amazonia, which located more than 1000 km apart. Despite great distance, sedimentological characteristics two areas analogous. Hence, revealed paleoenvironments including active channel, abandoned point bar, crevasse splay floodplain, altogether compatible with meandering systems. Similarly, optically stimulated luminescence (OSL) dating thirty three ages ranging 65.4 ± 16.9 219.6 ± 25.1 ky (in addition outliners 54.0 ± 7.6, 337.3 ± 36.9 346.6 ± 48.6 ky), nine 97.1 ± 9.9 254.8 ± 23.8 ky respectively. These data lead establish that Formation vast Brazilian have Mid-Late Pleistocene rather previously inferred age. It follows if exist region they remain be must restricted narrow belt well isolated occurrences underlying characterized herein. combination published provenance studies supports Andean sediment sources only Pleistocene. proposed before time, River was eastern being separated basins due presence Purus Arch. Erosion and/or subsidence geological feature would promoted connection systems, ultimately expressive record pathway into Atlantic Ocean