Provinciality of ice rafting in the North Atlantic: application of 40Ar/ 39Ar dating of individual ice rafted hornblende grains

Abstract

The history of the Northern Hemisphere ice sheets is an important aspect of the paleoclimate system. The layered record of ice rafted detritus (IRD) and other climate indicators preserved in deep-sea sediment cores provides the potential to unravel the sequences of events surrounding important intervals during the last glacial cycle. The work presented here is a first step in the goal to characterize the composition of glacially derived detritus in proximal locations near the Laurentide, Greenland and Scandinavian ice sheets. The intent of this paper is to highlight the potential for using provenance studies of IRD in marine sediments, in particular 40Ar/ 39Ar ages of hornblende grains in this case, to trace the history of ice sheets in the past. Published work on land and at the glacial marine margins has mapped the margins of important ice sheets, including the locations where glacial ice extended to the shelf-slope break. At these shelf-slope break locations, large glacial marine fans, termed trough mouth fans (TMF), are known to occur in about 25 locations around the North Atlantic/Nordic/Arctic Oceans. By characterizing the sediment sources in these TMFs, the major IRD components for deposition in deep-sea sediment cores are documented. Although there is substantial overlap in the geological histories of the continental sources around the North Atlantic, there are also some systematic variations that will allow distinction of different sources. Realization of the full potential awaits characterizing the sources with multiple tracers as well as sedimentological studies, and documenting the geographic pattern of dispersal in marine sediments within small time windows.