Date of this Version
Purkey, Marcella K., 2013. Marine Diatom Assemblage Variation Across Pleistocene Glacial-Interglacial Transitions and Neogene Diatom Biostratigraphy of Site C9001, NW Pacific Ocean (MS Thesis). University of Nebraska-Lincoln, NE.
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 (GI) climate record from which a diatom record of paleoenvironmental changes was developed across several GI cycles. Species counts, diatom temperature values, calculated sea-surface temperatures (SST) and factor analysis 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 warmest with a peak temperature of 20.2°C. Peak temperatures in MIS 1 are calculated at 14.9°C and are 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 temperatures. A lead/lag relationship between SST and the benthic oxygen isotope record of ice volume was observed at the onset and reversals of major GI cycles. The highest four factors derived from factor analysis of the diatom assemblages explain 88.7% of the total variance and are attributed to diatom preference for specific watermasses. Factor 1 is dominated by Melosira albicans, which does not show a consistent environmental preference through every interval. Factor 2 is dominated by a north-temperate species, and Factors 3 and 4 are both dominated by species indicating sea-ice influence.
Integrated Ocean Drilling Program (IODP) Expedition 337 returned to Site C9001, drilled a new hole in 2012, and extended the total depth at Site C9001 to 2466 meters below sea floor (mbsf). Diatom biostratigraphic analysis presented here confirmed an Early Miocene age at 1246.5 mbsf. These new diatom results, combined with palynological analysis suggest a Late Oligocene-Early Miocene age at the base of the hole. These ages are younger than those predicted by seismic correlations prior to drilling.
Adviser: David M. Harwood