Drastic change in the late Pliocene subarctic Pacific diatom community associated with the onset of the Northern Hemisphere Glaciation

DIATOM RECORDS | Pacific

“…During the interval between 2.8 and 2.4 Ma, diatom assemblages fluctuated, with cold peaks dated at 2.75, 2.6, and 2.45 Ma indicating the drastic north-to-south shift of the Front. During the interval of 2.7-2.4 Ma, the diatom assemblages dominated by Coscinodiscus marginatus Ehrenberg and N. kamtschatica rapidly and drastically shifted to one rich in Neodenticula complex, N. koizuii þ N. seminae, due to changes in paleoceanographic conditions in the subarctic region (Shimada et al, 2009 (Koizumi, 1986;Shiono and Koizumi, 2001). Diatom accumulation rates declined sharply due to the increase of terrigenous components, resulting from rapid cooling and the global fall of sea level after about 2.7 Ma in the northeast Pacific Ocean (Barron, 1998;Maruyama, 2000).…”

Allochthonous Diatoms in DSDP Site 436 on the Abyssal Floor off Northeast Japan

“…Hemisphere glaciation at about 2.7 Ma occurs within the context of progressive Cenozoic cooling (Koizumi, 1985;Barron, 1998;Shimada et al, 2009), and also of a gradual increase in the mean global ice volume during from 3.6 to 2.4 Ma (Ravelo et al, 2004). Age (Ma) T. zabelinae This extinct fossil species occurs stratigraphically sporadic and abundant, and lived fairly commonly in intra-bay sediments such as near-shore shallow marine environments.…”

Surface ocean cooling in the subarctic North Pacific during the late Pliocene suggests an atmospheric reorganization prior to extensive Northern Hemisphere glaciation

“…They proposed that enhanced seasonality of SST in the subarctic Pacific Ocean triggered the initiation of NHG by providing water vapor to northern North America. Shimada et al (2009) showed a drastic change in diatom assemblage in ODP Sites 883 and 887 in the subarctic North Pacific at 2.7 Ma, being attributed to severe cooling and/or a change in nutrient regime at the onset of NHG.…”