THE LAST DEGLACIATION IN THE DENMARK STRAIT, NORTH ATLANTIC: INDCIATIONS OF A LARGE MARINE RESERVOIR EFFECT
HALD, MORTEN . Univeristy of Tromso.
Hagen, Sveinung . Statoil, Norway.
Andrews, John T.. Univ. Colorado, INSTAAR.
Jennings, Anne E.. Univ. Colorado, INSTAAR.
Postnert, G„ran . Univ. Uppsala, Sweden.
Sediment core JM96-1228/1 from the continental slope (1079 m depth) off N. Denmark Strait, has been studied in order to reconstruct the paleoceanography during the last deglaciation for this important gateway in the northern North Atlantic. Proxy records include benthic and planktic foraminiferal ? 13C and ? 18O; foraminiferal census data and ice rafted debris (IRD). A total of 26 AMS 14C dates have been obtained, 15 from planktic foraminifera (Neogloboquadrina pachyderma sinistral), 11 from benthic foraminifera (mixed assemblages) and one on a bivalve shell (Yoldiella intermedia). In addition, the Vedde Ash layer has been identified in the core.
The magnetic susceptibility and rates of sediment accumulation in JM96-1228 are similar to those from an adjacent site, JM96-1229, indicating that the paleoceanographic record will not be unique to the site. By comparing the 14C dates to the Vedde Ash (10,300 14C years) and to an age model produced by correlation of the proxy data (SST-indicators and onset of the regional 15-13 14C ka meltwater spike) to the Greenland Ice Core record, the planktic 14C dates appear to be too old by 1000-1500 years and the benthic dates even older.
The old dates may partly be explained by reworking of old carbonate due to e.g. downslope or overbank deposition by bottom currents. However, the over all robust correlation of this proxy record to the Greenland ice cores and well-dated marine records in the Nordic seas, suggests that the old dates may reflect increased reservoir ages during the last deglaciation. The large amount of meltwater associated with the early deglaciation probably drained like a constant flow within the East Greenland Current through the Denmark Strait. This water may have increased the marine reservoir effect since the bicarbonate, that living organisms use to construct their tests, would be contaminated with old CO2 from the meltwater.
Previous | Abstract Index | Next
Copyright © 2001 INSTAAR, Univ. of Colorado