Marine diatom assemblage variation across Pleistocene glacial-interglacial transitions from Integrated Ocean Drilling Program Site C9001, Northwest Pacific

In 2006, D/V-Chikyu cruise CK06-06 drilled Hole C9001C at Site C9001 in the Northwest Pacific Ocean, 80 km east of the Shimokita Peninsula, Japan. An existing chronostratigraphic framework provides a continuous glacial-interglacial (G-I) climate record from which a diatom record of paleoenvironmental changes was developed across several G-I cycles. Species counts, diatom temperature values, and calculated sea-surface temperatures (SST) were produced for each sample and calibrated to prior diatom studies in this region. These features were used to characterize and compare interglacial maxima of Marine Isotope Stages (MIS) 1, 5e, 9 and 11 and transitions from the preceding glacial maxima. MIS 9 was the longest and warmest of the four interglacials examined, with a peak calculated temperature of 20.2 °C. Maximum temperature for MIS 1 of 14.9 °C is only 1 °C cooler than peak SSTs calculated for MIS 11 and 5e; however, the temperature trend for MIS 1 continues on a linear trajectory toward warmer modern temperatures to the top of the section. A lead/lag relationship between SST and the benthic oxygen isotope record of ice volume was observed at the onset and reversals of major G-I cycles.