| dc.description.abstract | The Mid-Pleistocene Transition (MPT), one of the largest climate shifts in the late Quaternary, was characterized by widespread, gradual global cooling accompanied by expansion of Northern Hemisphere ice sheets and a shift towards higher amplitude glacial - interglacial cycles. This study utilizes a benthic foraminiferal fossil record recovered from IODP Expedition 323: Site U1344 (3200mbsl, 59° 3.0'N, 179' 12.2'W) on the northern slope of the Bering Sea to understand changes in the deep waters of the Bering Sea that occurred over the last ~1.9Ma. The benthic foraminiferal fossil record at this site is characterized by low oxygen tolerant and deep infaunal groups, which are characteristic of high surface productivity. Although glacial – interglacial changes are not resolved in this record, large shifts in the benthic foraminiferal assemblage – including changes in abundance and diversity – are evident through the MPT. The largest change in the benthic foraminifera assemblage occurs around 0.9Ma and correlates with fluctuations in other proxy records such as diatoms, biogenic opal, and sedimentation from nearby slope Site U1343 (1950mbsl, 55° 33.39'N, 176° 12.2'W) which suggest the expansion of sea ice over both sites. Two species make up the majority of the benthic foraminiferal record at Site U1344: Elphidium batialis and Valvulineria sadonica; their relative abundances are anti-correlated. Cluster and principal coordinate analyses suggest that these two species represent opposite ends of the environmental gradient at Site U1344. Their records, along with other common species present at Site U1344, imply that the assemblage variations are primarily dependent upon the type of organic matter reaching the sea floor. | en |
