QUANTITATIVE RESULTS OF IRD, MICROFOSSIL, AND ISOTOPIC ANALYSES OF PLEISTOCENE SEDIMENTS FROM HOLE 919A IN THE WESTERN IRMINGER BASIN, EAST GREENLAND MARGIN

Hole 919A in the western Irminger Basin yielded a continuous section (100% core recovery) of Pleistocene sediments, which had high rates of deposition (6-35 cm/k.y.) and suitable materials for isotopic analyses. These conditions make 919A ideal for high resolution paleoclimatic and paleoceanographic study of the southeast Greenland margin. Oxygen and carbon isotope data on Neogloboquadrina pachyderma from 919A provide isotope stratigraphy and paleoenvironmental records of Irminger Basin surface waters. Correlation with deep Pacific records indicates that the 919A isotope records are controlled primarily by global influences. A census of the lithic, biogenic, and volcanic components of the >150 micrometer size fraction from each sample provide further proxy data for evaluating fluctuating glacial-interglacial climates on the east Greenland margin. Samples were taken every 20 cm from 0 to 94 meters composite depth (mcd; 0 to 610 ka). Sample resolution is 1.3 k.y. 500 grains were identified and counted in each sample. Results of the preliminary analysis of the counted dataset indicate: 1) Major source areas for IRD included central East Greenland redbeds, based on the abundance of hematite stained quartz, 2) IRD deposition had a 100 k.y. cyclic and saw-toothed pattern, suggesting repeated episodes of gradual ice build-up followed by rapid drawdown, and 3) warm water microfossil assemblages often occurred concurrently with rapid transitions from high to low % IRD.