Biomarker determination as a provenance tool for detrital carbonate events (Heinrich events?): Fingerprinting Quaternary glacial sources into Baffin Bay

摘要

Sedimentary deposits associated with Heinrich events are anomalously rich in detrital carbonate. Off Hudson Strait the dominant carbonate is calcite whereas at distal sites in the North Atlantic dolomite is dominant (more diagnostic?). A significant source for dolomite is its outcrop at the northern end of Baffin Bay where major ice streams from the Laurentide, Innuitian and Greenland ice sheets converged. The provenance of samples containing detrital carbonate, mainly dolomite, from a core in Baffin Bay has been confirmed using organic geochemistry to distinguish between alternative sources, based upon the thermal maturity of organic matter in carbonates of the source region. The core contained five distinct carbonate units dating between similar to 14 and 51 cal ka BP and indicates significant ice stream instability associated with iceberg calving and significant volumes of meltwater. The exact temporal relationship to Heinrich events is not yet clear. A long mid-Wisconsin interval (similar to 38 to 22 cal ka BP) devoid of detrital carbonate suggests a major reduction in ice extent at high northern latitudes. The core samples yield thermally sensitive biomarker ratios comparable to those from Laurentian carbonates in the Canadian Arctic islands but unlike those from North Greenland, identifying the former region as their provenance. However, a Late Holocene sample from off Newfoundland shows a stronger affinity with Greenland. (c) 2007 Elsevier B.V. All rights reserved.