Japan Agency for Marine-Earth Science and Technology, Japan

Integrated Ocean Drilling Program Expeditions 303 and 306 are based on two separate proposals (572-Full3 and 543-Full2/543-ADD) entitled "Ice sheet-ocean atmosphere interactions on millennial timescales during the late Neogene-Quaternary using a paleointensity-assisted chronology (PAC) for the North Atlantic" and "Installation of a CORK in Hole 642E to document and monitor bottom water temperature variations through time," now 2 and 4 years old, respectively. This prospectus updates information presented in the proposals based on site survey data and other operational refinements. The objective of Proposal 572-Full3 is to place late Neogene-Quaternary climate proxies in the North Atlantic into a paleointensity-assisted chronology (PAC), a chronology based on a combination of geomagnetic paleointensity, stable isotope, and detrital layer stratigraphies. Proposed primary sites are located off Orphan Knoll (Newfoundland), on the Eirik Drift (southeast Greenland), on the southern Gardar Drift, and in the central Atlantic "ice-rafted debris (IRD) belt." Mean sedimentation rates are estimated to be in the range of 5-50 cm/k.y. at these sites. The advanced piston corer (APC), utilizing the drillover technique, may be expected to reach penetration depths of approximately 300 meters below seafloor, resulting in recovery of late Neogene to Quaternary climate records. Coring operations will likely be restricted to APC because of the inadequacy of extended core barrel (XCB) cores for high-resolution stratigraphy. The objective of Proposal 543-Full2 is to place a CORK at Ocean Drilling Program Site 642 (Voring Plateau) to document and monitor bottom water temperature variations through time. A 150 m casing string with reentry cone will be drilled into the surface sediment followed by installation of a thermister string and CORK.