Hydrological variability in southeastern Patagonia and explosive volcanic activity in the southern Andean Cordillera during Oxygen Isotope Stage 3 and the Holocene inferred from lake sediments of Laguna Potrok Aike, Argentina

摘要

Seismic reflection studies in the maar lake Laguna Potrok Aike (51 degrees 58' S, 70 degrees 23' W) revealed an erosional unconformity associated with a sub-aquatic lake-level terrace at a water depth of 30m. Radiocarbon-dated, multi-proxy sediment studies of a piston core from this location indicate that the sediment below this discontinuity has an age of 45kyr BP (Oxygen Isotope Stage 3), and was deposited during an interval of high lake level. In comparison to the Holocene section, geochemical indicators of this older part of the record either point towards a different sediment source or to a different transport mechanism for Oxygen Isotope Stage 3 sediments. Holocene sedimentation started again before 6790cal. yr BP, providing a sediment record of hydrological variability until the present. Geochemical and isotopic data indicate a fluctuating lake level until 5310cal. yr BP. During the late Holocene the lake level shows a receding tendency. Nevertheless, the lake level did not drop below the 30m terrace to create another unconformity. The geochemical characterization of volcanic ashes reveals evidence for previously unknown explosive activity of the Reclus and Mt. Burney volcanoes during Oxygen Isotope Stage 3. (c) 2007 Elsevier B.V. All rights reserved.