PLEISTOCENE ICEBERG PRODUCTION FROM EAST GREENLAND: SYNCHRONOUS BETWEEN SOURCE AREAS, BUT DISTINCT FROM GLOBAL ICE VOLUME

ODP Site 919 is located off SE Greenland, on the lower continental rise of the western Irminger Basin. Site 919 presently lies under the influence of the southward-flowing East Greenland Current, which transports icebergs calved along East Greenland towards the North Atlantic. A record of the input of ice-rafted debris (IRD) to this site during the past 1 m.y. has been developed in order to 1) identify the sources of the IRD, and 2) define the timing of local ice-rafting within global glacial-interglacial cycles.

IRD compositions indicate that the major source regions for IRD found off SE Greenland consistently have been the Precambrian igneous and meta-igneous crystalline basement (predominantly gneiss and granite) of southeast Greenland and the Tertiary flood basalts located further north along the East Greenland coast. The mass accumulation rates (MARs) of provenance-distinctive IRD grain types show similar variations through time, suggesting that these source areas experienced similar iceberg release histories during the Pleistocene. In contrast, no distinct relationship can be drawn between peaks in the IRD MAR record and oxygen-isotope defined glacial-interglacial cycles, suggesting that the history of IRD input off SE Greenland since 1 Ma was dominated by local and regional controls, rather than global ice volume. Comparisons with limited onshore data and with marine microfossil data suggest that the important local and regional controls included availability of easily eroded surficial material, thermal regime of the glacial terminus, sea-ice distribution, and ocean surface current and temperature patterns.