18. MID- TO LATE QUATERNARY STABLE ISOTOPIC STRATIGRAPHY AND PALEOCEANOGRAPHY AT SITE 919 IN THE IRMINGER BASIN1

Benjamin P. Flower2

ABSTRACT

Stable isotopic records based on the planktonic foraminifer Neogloboquadrina pachyderma (sinistrally coiling) from Holes 919A and 919B from the western Irminger Basin (6240N, 3728W) provide records of surface water environments of the mid- to late Quaternary in the Irminger Sea. The 147-m sequence clearly shows oxygen isotope Stages 1 through 20 (possibly to 25). Assignment of oxygen isotope stages is supported by calcareous nannofossil biostratigraphy, magnetic polarity stratigraphy, and strontium isotope stratigraphy. Sedimentation rates average ~17.9 cm/k.y. for the 960–420 ka interval and ~13.4 cm/ k.y. for the 420–0 ka interval. Significantly, interglacial delta18O in Stages 21 through 15 is 0.5‰ to 0.8‰ lower than in succeeding interglacials, suggesting warmer sea surface temperatures and/or lower salinity in this interval. The magnitude and rapidity of these low-delta18O events suggest large variations in salinity of the Irminger Sea during the 860–600 ka interval, perhaps reflecting greater meltwater flux derived from the Greenland Ice Sheet.

1Saunders, A.D., Larsen, H.C., and Wise, S.W., Jr. (Eds.), 1998. Proc. ODP, Sci. Results,152: College Station, TX (Ocean Drilling Program).
2Institute of Marine Sciences and Earth Sciences Board, University of California, Santa Cruz, Santa Cruz, CA 95064, U.S.A. flower@earthsci.ucsc.edu