Description: Integrated Ocean Drilling Program Expedition 320/321, "Pacific Equatorial Age Transect" (Sites U1331–U1338), was designed to recover a continuous Cenozoic record of the equatorial Pacific by coring above the paleoposition of the Equator at successive crustal ages on the Pacific plate. These sediments record the evolution of the equatorial climate system throughout the Cenozoic. As we gained more information about the past movement of plates and when in Earth's history "critical" climate events took place, it became possible to drill an age transect ("flow-line") along the position of the paleoequator in the Pacific, targeting important time slices where the sedimentary archive allows us to reconstruct past climatic and tectonic conditions. The Pacific Equatorial Age Transect (PEAT) program cored eight sites from the sediment surface to basement, with basalt aged between 53 and 18 Ma, covering the time period following maximum Cenozoic warmth, through initial major glaciations, to today. The PEAT program allows the reconstruction of extreme changes of the calcium carbonate compensation depth (CCD) across major geological boundaries during the last 53 m.y. A very shallow CCD during most of the Paleogene makes it difficult to obtain well-preserved carbonate sediments during these stratigraphic intervals, but Expedition 320 recovered a unique sedimentary biogenic sediment archive for time periods just after the Paleocene/Eocene boundary event, the Eocene cooling, the Eocene–Oligocene transition, the "one cold pole" Oligocene, the Oligocene–Miocene transition, and the middle Miocene cooling. Expedition 321, the second part of the PEAT program, recovered sediments from the time period roughly from 25 Ma forward, including sediments crossing the Oligocene/Miocene boundary and two major Neogene equatorial Pacific sediment sections. Together with older Deep Sea Drilling Project and Ocean Drilling Program drilling in the equatorial Pacific, we can delineate the position of the paleoequator and variations in sediment thickness from ~150°W to 110°W longitude.

Description: During expedition PS104 with RV Polarstern in February and March 2017 the MARUM MeBo 70 seabed drilling system was deployed at nine sites on the continental shelf of the Amundsen Sea Embayment, West Antarctica. A total of 57 meters of sediment core were recovered from 11 boreholes located in Pine Island Bay, Pine Island Trough, Bear Ridge and Cosgrove-Abbot Trough with recovery rates ranging from 7 to 76%. The main scientific objective of the drilling was to reconstruct the Late Mesozoic to Quaternary environmental history in this part of the Antarctic continental margin, with a special focus on the past dynamics of the marine based West Antarctic Ice Sheet (WAIS) from its inception to the last glacial cycle. Another main goal of the expedition was to test the suitability of the MeBo drill system for operating on the Antarctic continental shelf and recovering pre-glacial and glacially influenced sedimentary sequences. Here we will present the first results of sedimentological investigations carried out on the drill cores. These comprise (i) visual lithological descriptions, (ii) CT-scanning records of core stratigraphy, sedimentary structures, and possible artefacts induced by the drilling process, (iii) measurements of physical properties performed with a multi-sensor core logger, and (iv) characterisation of the geochemical composition of the drilled sedimentary strata using X-ray fluorescence (XRF) scanner data. Preliminary biostratigraphic investigations conducted on board ship indicated that the recovered sedimentary strata were deposited during various time slices spanning from the Late Cretaceous–Palaeocene to the Late Quaternary. We will provide an update of these initial chronological findings. Keywords: Drill cores, shelf sediments, West Antarctic Ice Sheet.