15. HIGH-RESOLUTION PLEISTOCENE DIATOM BIOSTRATIGRAPHY AND PALEOCEANOGRAPHY OF SITE 919 FROM THE IRMINGER BASIN1

Naln Ko2 and Benjamin P. Flower3

ABSTRACT

Ocean Drilling Program Site 919 from the Irminger Basin provides one of the first opportunities to study high-resolution Pleistocene high-latitude North Atlantic diatom biostratigraphy and paleoceanography. Three Pleistocene diatom datum events are identified and tied directly to the stable oxygen isotope record of Site 919. These datum events are the (1) last occurrence of Thalassiosira nidulus at 0.310 Ma, (2) last occurrence of Proboscia curvirostris at 0.335 Ma, and (3) last occurrence of Neodenticula seminae at 0.817-0.895 Ma. Based on these datums, a Pleistocene diatom zonation for the high-latitude North Atlantic and the Nordic Seas is proposed using high-latitude cold species. The last occurrences of Thalassiosira nidulus and Proboscia curvirostris appear to be isochronous in the middle- to high-latitude North Pacific and the North Atlantic Oceans.

The diatom abundance and preservation record of Site 919 is used to infer polar front fluctuations during the last 1 m.y. Results indicate that during glacial Stages 2, 6, 10, 12, and 16 the polar front migrated eastward, covering Site 919 with sea-ice. Milder climate is indicated during glacial Stages 4, 8, 14, 18, and 20, as the polar front is interpreted to lie to the west of Site 919.

1Saunders, A.D., Larsen, H.C., and Wise, S.W., Jr. (Eds.), 1998. Proc. ODP, Sci. Results,152: College Station, TX (Ocean Drilling Program).
2Department of Geology, University of Bergen, Allgt. 41, N-5007 Bergen, Norway. nalan.koc@geol.uib.no
3Earth Sciences Board, University of California, Santa Cruz, CA 95064, U.S.A.