CGRG Bibliography of Canadian Geomorphology
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Author : Coleman, G.C.; Diefenbach, G.; Roth, W.; Andrews, J.T. ; and Eberl, D.D.
Date : 2006.
Title : The Holocene mineralogy of marine sediments from the Iceland, East Greenland, and eastern Canadian margins from quantitative XRD analysis: changes in supply and processes.
Publication : 36th International Arctic Workshop. March 16-19, 2006. Institute of Arctic and Alpine Research, University of Colorado at Boulder, Colorado, U.S.A.
Issue :
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Abstract
Two great streams of Polar Water bring cold, fresh water, sea ice, and icebergs along the eastern seaboards of Canada and Greenland. A branch of the East Greenland Current also steers "drift ice" from the Greenland margin across to NW and N Iceland. In severe ice years the drift ice moves clockwise around Iceland and can encircle the island. Variations in the extent of sea ice and icebergs (=drift ice) during the Holocene are an important proxy for freshwater variations and potentially might lead to an understanding (i.e. prediction) of variations in the thermohaline circulation. We processed sediments at ~100-yr/sample resolution from cores 1) MD99-2237, off Orphan Knoll, Labrador Sea, 2) MD99-2317, off east Greenland, 3) MD99-2264 off NW Iceland, and several cores off N Iceland. In order to get a sense of "source" variations we have also processed seafloor surface sediments from the Arctic Ocean, the Labrador, East Greenland, and Iceland shelves, plus surface samples from sites within the Nordic Seas. Sediments < 2mm (i.e. sand, silt and clay) are processes with a known weight% of ZnO; they are milled, and then run on an X-ray diffraction instrument between 5 and 65 2-theta at 0.02°steps and a 2 sec scan. The resulting XRD intensities are then processed in "Rockjock", a 50 MD Excel program (Eberl, 2003), and weight% estimates of both non-clay and clay mineral species are obtained. "Indicator" mineral species of drift ice vary from region to region, with dolomite being an indicator in the Labrador Sea and Baffin Bay, and quartz filling the same role off Iceland. The quartz weight% data from cores off NW and N Iceland show similar variations with the most noticeable feature being a rapid increase in quartz weight% over the last 4000 cal yrs BP, i.e. during the Neoglacial. Suprisingly, the sites off Labrador show no clear mid-Holocene/Neoglacial transition. A "regime shift" algorithm is being used to test for regional coherence in shifts in the non-clay and clay mineral species for the suite of cores being investigated, although it is probable that the non-clay fraction might be more diagnostic of the source mineralogy
Bibliography of Canadian Geomorphology