HR: 0800h
AN: PP21B-1384    [Abstracts]
TI: Penultimate Glaciation Succeeded by Huge Meltwater Pulse in the Northwind Ridge Area, Western Arctic Ocean
AU: Bischof, J F
EM: jbischof@odu.edu
AU: * Darby, D A
EM: ddarby@odu.edu
AB: Piston core 92 PC 6 from the Northwind Ridge extends our understanding of the glacial history of the western Arctic Ocean back to the late stages of the penultimate glaciation, providing an over 100 cm long record of a full glacial - interglacial cycle. The most interesting aspect is a massive glacial meltwater event at the end of stage 6. The second to last ice age ended with a massive pulse of iceberg calving, indicated by massive amounts of IRD (ice rafted debris) with cm-size stones. The IRD composition points to an origin from the Northwest Territories, Arctic Canada, just like the end of the last glaciation. This event is followed by a quiet period with little IRD. Thereafter follows a massive peak of IRD with almost the same quantities as before, but this time the grains are very well sorted and have an upper size limit of about 2 mm. We attribute this peak to the combined action of glacial meltwaters, sorting the grains, and sea ice rafting to their place of deposition. Supporting this conclusion of a sea ice-rafting event instead of a glacial iceberg event is the abundance of detrital Fe mineral grains of fine sand-size from the Laptev Sea at about the same time. These Fe grains could only be transported by sea ice. Also, there is a spike in Fe grains from the Mackenzie River during the end of the Stage 6 meltwater (IRD) event and coarse IRD typical of glacial icebergs calving from this river have never been found in any Arctic sediments. This evidence of sorted IRD and Fe grains from unglaciated areas at the termination of glacial stages does not preclude that massive amounts of icebergs also calved from ice streams adjacent to Banks Island and also from the Queen Elizabeth Island (Canada) area prior to the meltwater events.
DE: 3600 MINERALOGY AND PETROLOGY (replaces
DE: 4267 Paleoceanography
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 1827 Glaciology (1863)
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting