NORTH-ATLANTIC ICE-SHEET FLUCTUATIONS 10,000-70,000 YR AGO AS INFERRED FROM DEPOSITS ON THE REYKJANES RIDGE, SOUTHEAST OF GREENLAND

Marine records from the Reykjanes Ridge indicate ice sheet variations and abrupt climate changes. One of these records, ice-rafted detritus (IRD), serves as a proxy for iceberg discharges that probably indicate s ice sheet fluctuations, The IRD records suggest that iceberg dischar ge 68,000-10,000 yr B.P. happened more frequently than the 7000- to 10 ,000-yr spacing of the Heinrich events. An IRD peak 67,000 to 63,000 y r B.P. further suggests that the Middle Weichselian glaciation started about 12,000 yr earlier in the North Atlantic than in the Norwegian S ea. Several later IRD events, in contrast, correlate with Norwegian Se a IRD-rich layers and imply coeval ice sheet advances in the North Atl antic and the Norwegian Sea. Coccoliths in a core from the Reykjanes R idge show distinct peaks in species that record occasional inflow of w arm surface water during the last glaciation, as previously reported f rom the eastern Labrador Sea, High abundances of coccoliths, together with a decrease of Neogloboquadrina pachyderma sin. and relatively low delta(18)O values, imply enhanced advection of the North Atlantic Cur rent 69,000-67,000 yr B.P., 56,000-54,000 yr B.P., 35,000-33,000 yr B. P., and 26,000-23,000 yr B.P. This advection provided a regional moist ure source far extension of ice sheets onto the shelf, In contrast, mo st of the IRD events are characterized by cold polar surface water mas ses indicating rapid variations in ocean surface conditions. (C) 1998 University of Washington.