Transcontinental retroarc sediment routing controlled by subduction geometry and climate change (Central and Southern Andes, Argentina)

Central Argentina from the Pampean flat-slab segment to northern Patagonia (27°–41°S) represents a classic example of broken retroarc basin with strong tectonic and climatic control on fluvial sediment transport. Combined previous research focused coastal sediments, this actualistic provenance study uses framework petrography heavy-mineral data trace multistep dispersal volcaniclastic detritus first eastwards across central for up ca. 1,500 km next northwards another 760 along Atlantic coast. Although generated in Andes is largely derived mesosilicic volcanic rocks cordillera, its compositional signatures reflect different tectono-stratigraphic levels orogen uplifted strike response varying subduction geometry as well character crystallization condition arc magmas through time space. River sand, thus, changes feldspatho-litho-quartzose or litho-feldspatho-quartzose north, where sedimentary more common, mostly quartzo-feldspatho-lithic centre feldspatho-lithic south, dominant. The transparent-heavy-mineral suite markedly amphibole ? clinopyroxene > orthopyroxene ? ? south. In presently dry climate, discharge drastically reduced point that even Desaguadero trunk river has become endorheic orogenic dumped basin, reworked by winds temporarily accumulated dune fields. During Quaternary, instead, much larger amounts water were released melting Cordilleran ice sheet during pluvial events. sediment-laden waters Colorado rivers then rushed tract greatest topographic structural elevation, fostering alluvial fans inland flowing valleys than today towards Ocean. Sand gravel supply coast was high enough not only promote rapid progradation large deltaic lobes but also feed cell littoral transport extending far north Río de la Plata estuary.