ICDP Lake Drilling at Laguna Potrok Aike, Argentina: a Progress Report of the PASADO Project

Within the framework of the ICDP-funded Potrok Aike maar lake sediment archive drilling project (PASADO), an international team of scientists carried out interdisciplinary research at the mid-Pleistocene (770 ka) maar lake of Laguna Potrok Aike in southern Patagonia (Province of Santa Cruz, Argentina). Previous studies on short cores revealed that this lake is very sensitive to variations in southern hemispheric wind and pressure systems. It holds a unique and continuous lacustrine record of climatic and ecological variability of global significance, potentially for the last 770ka. Three months of drilling activities that finished last November 2008 were carried out by DOSECC from the drilling platform R/V "Kerry Kelts". More than 500 m of lacustrine sediments were recovered. This sedimentary archive will provide (1) new insights into the processes of regional back arc volcanism within the Pali Aike Volcanic Field itself as well as the more distant explosive volcanism of the Andean mountain chains; and, (2) high-resolution (decadal) quantitative climate and environmental reconstructions supported by multiple dating and stratigraphic correlations. Marine - ice core - terrestrial linkages will be emphasized as well as the incorporation of results from global climate modeling simulations for the last ca. 100 ka. Two drilled sites in the central deep basin of Laguna Potrok Aike were selected based on four seismic surveys carried out between 2003 and 2005. Sediments were recovered at both drilled sites down to a subbottom depth of slightly more than 100 m using the GLAD800 drill rig with the hydraulic piston corer tool at water depths varying between 95 and 100 m. The total core recovery is 94%. On- site core logging with the multi sensor core logger documents an excellent correlation between the four recovered holes drilled at Site 1 as well as with the three holes obtained from Site 2 which is located ca. 700 m south of Site 1. Additionally, a variety of sedimentological, physical and geochemical analyses were carried out on the core catcher samples during fieldwork. Preliminary interpretation of all the available data before core opening indicates that the record may go back in time as far as oxygen isotope stage 5a.