Data Report: Quaternary-Pliocene Diatom Biostratigraphy of ODP Sites 1165 and 1166, Cooperation Sea and Prydz Bay

The biostratigraphic distribution and qualitative relative abundance of Quaternary-Pliocene diatoms from Ocean Drilling Program Leg 188, Sites 1165 (64.380°S, 67.219°E) and 1166 (67.696°S, 74.787°E) offshore from East Antarctica, are documented in this report. The upper ~50 meters below seafloor (mbsf) of Hole 1165B consists of brown diatombearing silty clay spanning the upper Pleistocene to lower Pliocene. The diatom stratigraphy indicates a disconformity at ~17.1 mbsf of 0.5- to 0.6-m.y. duration. The integration of biostratigraphic and magnetostratigraphic data identified other disconformities at ~6.0, 14.4, 15.6, and 16.0 mbsf, but the duration of these hiatuses cannot be resolved through diatom biostratigraphy. In Hole 1166A, a narrow interval of diatomaceous Quaternary sediment is identified in the upper 2.92 mbsf and dated biostratigraphically at <0.38 Ma. The remaining Quaternary- Pliocene section is dominated by diamicton, except at ~114 mbsf, where two thin diatomaceous beds are present. The lower bed is ~65 cm thick, 2.5-2. 7 to 2.7-3. 2 Ma in age, and possibly isconformably overlain by the upper bed, which is ~15 cm thick and 1.8-2. 0 to 2.1-2. 5 Ma in age. The Pliocene assemblages in Hole 1166A contain components of both Southern Ocean and Antarctic continental shelf (Ross Sea) diatom floras.