INCITAP   20787
INSTITUTO DE CIENCIAS DE LA TIERRA Y AMBIENTALES DE LA PAMPA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Late Quaternary paleoenvironmental evolution of the proximal area of the Atuel-Diamante distributive fluvial system
Autor/es:
HESSE, P.; WILLIAMS, R.; MEHL, A. E; LORENZO, F. R.; TRIPALDI, A.; ZÁRATE, M. A.
Lugar:
Dublin
Reunión:
Congreso; INQUA 2019; 2019
Institución organizadora:
INQUA
Resumen:
Distributive fluvial systems (DFS) have been described worldwide under diverse climatic and tectonic setting. Studying the deposits of present DFS contributes to understanding Quaternary landscape evolution, doing paleoclimatic inferences, and improving facies models for interpreting sedimentary records. The eastern Andean piedmont, southern South America, shows several DFS, like the recently defined Atuel-Diamante DFS (Fig. 1). The Atuel and Diamante rivers carry seasonal meltwater from the Andes Cordillera and flow to the east. They are deeply entrenched in the San Rafael tectonic block where, at its eastern piedmont, they generate the DFS. This system has been barely studied in terms of its geomorphological, paleohydrological and landscape evolution. A doctoral thesis recently finished and associated investigations in progress have started to expose and interpret its morphology and late Quaternary history. In this presentation we characterize the deposits of the proximal area of the Atuel-Diamante DFS, with the aim of interpreting the late Quaternary paleoenvironmental evolution and to infer paleoclimatic variability. Methodology included geomorphologic mapping by remote sensing, field survey, stratigraphic section analysis of pedosedimentary facies, accompanied by AMS and luminescence chronology. We studied 5 localities along a SW-NE transect (Fig. 1a) where information was obtained at exposed deposits, pits and by augering. Present climate is temperate semiarid, influenced by the Andes rain shadow and the South Atlantic and South Pacific anticyclones. The fluvial drainage is, at present, a misfit system due to the current interglacial and, in the last 150 years, the presence of agricultural irrigation networks and hydroelectric power dams on the Atuel and Diamante rivers. The proximal area, besides the gravel-sand Atuel and Diamante streams, shows many abandoned meandering channels and associated floodplains, with deposits dominated by silty fine sand and silt, together with minor gravelly sand-silt, forming fining-upward successions. Stabilized dune fields restrict, to the north and south, the studied DFS, where the aeolian medium to fine sand was also described and sampled to decipher the aeolian-fluvial relationship. Previously obtained chronology shows, in the Atuel River, a late Pleistocene-early Holocene record in an upper most, 8 m thick, fluvial terrace, suggesting important fluvial aggradation during the last glacial-terminations and a significant change in the system with extensive incision at early-mid Holocene. OSL ages in progress will provide detail about the mid-late Holocene evolution of the Atuel-Diamante DFS, and all together it will provide data for paleoclimatic inferences.