LITHOSTRATIGRAPHY OF JUMBO PISTON CORES FROM THE WOOLSEY MOUND, THE NORTHERN GULF OF MEXICO

This study determined major lithostratigraphic units and associated climate changes captured in jumbo piston cores collected from four sites at MC118 within the Seafloor Observatory of the Gulf of Mexico Hydrates Research Consortium. Four cores, which averaged 14 m in length, were photographed and described. Descriptions and photographs of the cores were integrated to determine major stratigraphic units. Carbon-14 dates, from a previously studied 5-m-long core from MC118, were obtained for age approximation of the upper units contained in both studies.

Seven correlative units were established and will be described from the top down. Unit 1 contains highly bioturbated, homogeneous sandy mud, suggesting a slow rate of deposition and a significant pelagic source. Unit 2 consists of bioturbated mottled mud, consistent with a faster deposition rate. Units below Unit 2 contain distinct strata layers with minimal bioturbation. Unit 3 alternates between homogenous mud and indistinct color strata. Unit 4 contains distinct light-colored layers with a clear boundary at the top and bottom of each light layer. Unit 5 is also stratified, but the colors within strata gradually change from light to dark, with distinct boundaries between. Unit 6 contains indistinct color strata without clear boundaries. Units 4 and 5 also contain frequent, thin, silt laminae. Stratal layers in Units 3-6 indicate fast deposition by dilute turbidity currents. This succession of lithofacies is consistent with climate history in the Gulf of Mexico from the Wisconsinan lowstands to the rapid deglaciation and the present-day high-stand of sea level.