MEASURING THE CLIMATE PULSE OF THE LATE EARLY EOCENE AND MIDDLE EOCENE HOTHOUSE WORLD (51-42 MA): NEW RESULTS FROM ODP LEG 189 HOLE 1171D, SOUTH TASMAN RISEDETAILS

A high-resolution grain size record coupled with spectral analysis of down hole data developed for the interval between 690 and 410 mbsf (51 - 42 Ma) from Ocean Drilling Program (ODP) Site 1171 show that pervasive cyclicity occurs at both the million-year timescale, which correlates well with sequence boundaries, and at the 10⁴ to 10⁵ year timescale, for sedimentary cycles that occur within the sequences. Site 1171 contains an exceptional archive of Early to Middle Eocene strata that include excellent recovery (91.4%) and a high-resolution chronostratigraphic framework using bio- and magneto-stratigraphy. Site 1171 was drilled on the southern side of the South Tasman Rise (STR), which during the Early to Middle Eocene, the STR was located near the coast of Antarctica. This makes it the most southerly site with excellent core recovery and good preservation of foraminifers for this time. Previous work developed a sequence stratigraphic framework based on an integrated approach using lithofacies and biofacies to reconstruct paleo water depths. Sequence boundaries correlate well with both low-amplitude variance in obliquity (nodes) and ~2.4 Myr eccentricity minimum occurred. Taken together ice sheet growth in Antarctica occurred during extended periods (~200 kyr) of low variance in summer insolation at 65°S owing to 2.4 Myr eccentricity minima and in most cases also to 1.2 Myr obliquity cycle. At shorter timescales, the lithologic patterns appear to be closely linked with the precessional and eccentricity Milankovitch cycles, with obliquity cycles being subdominant. This suggests paleoclimatic and paleoceanographic changes on the STR and the adjacent Antarctic coast were controlled by changes at the lower-latitudes.