MARINE SEDIMENT PROVENANCE EVIDENCE FOR THE EXTENT OF THE LAURENTIDE ICE SHEET DURING THE LAST GLACIAL CYCLE (Invited Presentation)

Data from ice rafted detritus (IRD) in marine sediment cores from the southern Labrador Sea and western IRD belt provide evidence for the extent of marine-contacting ice margins of the North American ice sheets because of the fortuitous pattern of geological boundaries along the eastern margin of North America. These data are complementary to ice volume estimates from benthic d18O as well as to terrestrial mapping/dating of past ice margin locations. I will review the evidence for armadas of icebergs from Hudson Strait during Heinrich events, especially H1, H2, H4 and H5. Heinrich event H3 has a less prominent IRD imprint in the IRD belt (as defined by Ruddiman, 1977, GSAB), and sparse data exist for H6. However, H3 is a significant event in the Labrador Sea, and there is a strong meltwater signal in the planktonic foraminifera throughout the IRD belt. I will also review the record of continuous down core measurements of ice rafted hornblende provenance, that provides evidence that the southeastern Laurentide ice sheet reached latitudes required to tap Grenvillian (ca. 1.0-1.2 Ga) and Appalachian (ca 0.3-0.4 Ga) geological terrains immediately after H3 and retreated from that around H1. So, from the perspective of IRD the Last Glacial Maximum began at ~35 ka (after H3) and ended at 16.8 ka (~H1). Although the approach is course in scale, the deposition of IRD with Grenville and Appalachian sources must require that the southeastern Laurentide Ice Sheet had advanced to the coastline at least as far as ~50N. Because glaciers tend to erode evidence from former glaciations, this approach could be especially helpful in studies of older glaciations.