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 (62°40´N, 37°28´W) 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