INTEGRATED STRATIGRAPHIC ANALYSIS AND PETROLEUM SOURCE-ROCK POTENTIAL OF AN UNDERFILLED LAKE BASIN IN THE PUNA PLATEAU (NORTHWEST ARGENTINA)

Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogs. To address this gap, we present stratigraphic, sedimentological, and organic geochemical analyses of radiocarbon-dated sediment cores from the Pozuelos Basin (lat 22°S, lon 66°W). This low-accommodation basin sits on the arid, high-altitude Puna Plateau of northwest Argentina. Our results indicate that the major controls on depositional architecture and basin paleogeography over the past ~ 43 cal kyr are tectonics and climate. Accommodation space was derived from piggyback basin-forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American Summer Monsoon, and perennial-lake deposits likely correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna. Strata from the Pozuelos Basin are interpreted as accumulations of a highly variable, underfilled lake system represented by lake-plain/littoral, profundal, palustrine, saline lake, and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich (Type II kerogen) highstand deposits underlying thicker, organic-poor regressive deposits. Our results shed new light on lake expansion-contraction dynamics in the Pozuelos Basin in particular, and provide a deeper understanding of the petroleum system potential of convergent orogen hinterland lacustrine basins in general.