The palaeontology of Bering sea foraminifera from the late quaternary

• Main Author: Aturamu, Adeyinka Oluyemi
• Other Authors: Williams, Mark, Zalasiewicz, Jan
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Department of Geology 2015
• Subjects: Bering Sea; Bowers
• Online Access: http://hdl.handle.net/2381/33161

The taxonomy of benthic foraminifera recovered from 160 core samples over depth 20.59 m and representing the past ~597 Kyr (sedimentary deposit of the Tarantian and Ionian stages) at Bowers Ridge, Bering Sea IODP site U1342, includes some 52 species from 41 genera and 22 families: these species are given formal taxonomic treatment with detailed illustration. A further 16 species are discussed in open nomenclature. Foraminifer assemblages are dominated by species of Takayanagia delicata, Uvigerina bifurcata, Islandiella norcrossi and Alabaminella weddellensis accounting for more than 58 % of all specimens recovered. In addition to their taxonomic identification, this study interrogates the relationship between benthic foraminifera and interpreted changes in oxygen concentration and productivity during a series of late Quaternary glacial– interglacial cycles at site U1342. In particular, the species Bolivina spissa (Cushman) – thought to record changes in seabed oxygen level, shows no correlation between test pore density and interpreted bottom water oxygen level (BW-O2), suggesting that oxygen is not the sole driver influencing the distribution and morphology of this species. Further assessment of the total foraminiferal assemblages at site U1342 - using the sedimentological context and the proportion of deep infaunal species as a proxy for low oxygen conditions at the seabed, and shallow infaunal species as a proxy for a welloxygenated seabed, identify eight broadly defined temporally successive benthic foraminiferal intervals through the sampled core. Three of these intervals, between depths 0 - ~5.40, ~ 6.50 - 9.00 and ~16.90 - 18.67 m-CCSF, signal a well-oxygenated sea bed, whilst the other five intervals suggest increased phytodetritus flux to the seabed, coupled with variations in seabed oxygen level. In general, there is no clear connexion between these intervals and the glacial-interglacial oscillation at the site during the past ~597 ka, suggesting that ecological influences on foraminiferal distribution at Bowers are complex.