4 High latitude paleoceanographic discoveries from Scientific Ocean Drilling (IODP, ODP, DSDP)

Scientific Ocean Drilling has retrieved thousands of meters of sediment cores from the high latitude oceans.  This session provides the opportunity to present the results of work to understand Cenozoic climate and oceanographic changes.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Room 27

Nature and Provenance of Pleistocene Ice-Rafted Carbonate Beds in IODP Sites U1603 and U1603, NW Greenland Margin: Implications for Glacial Processes in Baffin Bay

Paper number: 4-5
Program: Technical Sessions
Time: 9:25 AM – 9:45 AM

Authors

Abstract

IODP Expedition 400 drilled multiple sites along the northwest margin of Greenland to investigate the Cenozoic evolution of the Greenland Ice Sheet. Pleistocene slope deposits at Sites U1603 and U1604 contain dozens of conspicuous beds of yellow- to reddish-brown detrital carbonate mud with outsized clasts of dolostone, limestone, and other lithologies. Similar deposits recovered in piston cores near the Canadian Arctic Archipelago have been interpreted as the products of ice-rafting from the region of Lancaster Sound, where ice streams were underlain by carbonate bedrock. To investigate the origin, timing, and significance of these beds, their sedimentology, stratigraphic distribution, and sand-gravel (>150 µm) fractions were characterized in Sites U1603 and U1604. Analysis of their stratigraphic distribution shows that although several prominent beds correlate between the sites, many are not laterally extensive. Outsized clasts, separated by wet sieving, were examined in thin section via standard point counting for composition, rounding, and sphericity using visual estimation diagrams. They are typically angular to subrounded with low sphericity, consistent with glacial transport. Compositions are dominated by quartz and sedimentary rocks, notably limestone and dolostone, along with orthogneiss and various lithic fragments. At both sites, the proportion of sedimentary clasts decreases upward from ~60-90% to ~30-80%. At the same time, the proportion of carbonate clasts within the sedimentary fraction increases from ~30-80% to ~40-100%. These trends may reflect prolonged erosion of bedrock by ice streams and temporal variability in ice stream source regions. Similarities with detrital carbonate beds from western Baffin Bay suggest a shared provenance, likely Paleozoic carbonate units exposed in Lancaster Sound. Orthogneisses likely originate from Archean and Paleoproterozoic basement rocks of Baffin Island, though Greenland sources are possible, and mafic clasts may also be derived from Labrador-Baffin Seaway rift volcanics or Precambrian volcanic units. Owing to their relatively distal positions from potential source regions, Sites U1603 and U1604 may contain a more episodic record of ice rafting compared to proximal sites. Whereas major iceberg discharge events may have produced regionally extensive deposits that reached Sites U1603 and U1604, smaller-scale events produced isolated sediment dumps from individual icebergs that terminate laterally. These results contribute to understanding potential spatiotemporal variation in Laurentide and Greenland ice sheet extents, outlets, and erosion patterns through the Pleistocene. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411187

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