IODP Site U1385 ('Shackleton site'): A reference section for marine-terrestrial correlations

Advances in our understanding of the Earth's climate system will rely on our ability to link high-resolution sedimentary archives from the oceans, ice-cores and terrestrial sequences. Few places exist in the world where sufficiently detailed and unambiguous marine-terrestrial correlations are possible. One such region is the southwest Iberian Margin where it has been demonstrated that the surface oxygen isotopic record could be correlated precisely to temperature variations (i.e., δ¹⁸O) in Greenland ice cores. By comparison, the benthic δ¹⁸O signal in the same cores resembles the temperature record from Antarctica. Moreover, the narrow continental shelf and proximity of the Tagus River results in the rapid delivery of terrestrial material, including pollen, to the deep-sea environment, thereby permitting direct correlation to European terrestrial sequences. For these reasons, IODP Expedition 339 sought to extend the Iberian Margin sediment record by drilling with the DV JOIDES Resolution. Five holes were cored at Site U1385 using the advanced piston corer (APC) system to a maximum depth of ~155.9 mbsf. A total of 67 cores were recovered representing 621.8 m of sediment with a nominal recovery of 103.2% (>100% due to post-recovery core expansion). Cores from all holes were analyzed by core scanning X-ray fluorescence (XRF) for semi-quantitative element data at 1-cm spatial resolution. These data permit accurate hole-to-hole correlation and construction of a verifiably complete spliced stratigraphic section, containing no notable gaps or disturbed intervals to 166.5 mcd. Correlation of variations in Natural Gamma Radiation (NGR) to the oxygen isotope stack and biomagnetostratigraphy suggest Site U1385 contains a continuous record from the Holocene to 1.42 Ma (Marine Isotope Stage 46) with average sedimentation rates of ~ 10 cm kyr^-1. A preliminary astronomically-tuned chronology was established by tuning sediment color variations to orbital precession. The Site U1385 record will serve as a marine reference section of Pleistocene climate variability, and will significantly improve the precision with which marine climate records can be correlated to polar ice cores and European terrestrial sequences.