Analysis of Arctic Beaufort Sea Cores using XRD Methods: Can Dolomite tell us Anything?
Advisor: Dr. Jillian Maloney
Monday, May 10, 2021
watch Athena’s talk
A proposed deglacial history for the Beaufort margin continental slope in the western arctic has defined multiple ice-rafting and meltwater discharge events recorded in the region’s stratigraphy. At the time of the late Wisconsin glaciation, the Laurentide Ice Sheet (LIS) extended from the Brooks Range up to the Canadian Arctic Archipelago. As the LIS retreated, discharge was routed by three major ice streams: the Mackenzie, Amundsen Gulf, and M’Clure Straight. Magnetic anomalies in sediment cores retrieved from the area in 2013 aboard the USCGC Healy correlate to Ice-rafted debris (IRD) layers that were deposited during the LIS retreat. Recent studies from the Arctic Ocean suggest that the presence of dolomite in marine sediment is an indicator of IRD deposits and could possibly identify the ice stream source. The purpose of this study was to use x-ray diffraction (XRD) to test the hypothesis that the presence of dolomite in a sample correlates to IRD and could differentiate between a Mackenzie River or Amundsen Gulf source. We also attempted to eliminate the common assumptions with XRD sample prep of sample amount and grain orientation, by normalizing the data in a variety of ways (normalizing to the largest dolomite peak in the core, to the 4.26 Å quartz peak, and also calculating the area of each dolomite peak). A total of 15 samples from two sediment cores (JPC25 and JPC 15/27) were analyzed based on the interpretations of Klotsko et al. (2019). Our results suggest that 1. the presence of dolomite in sediment along the continental slope does not correlate solely to IRD and cannot be used to confidently identify a source area and 2. normalized data plotted alongside dolomite relative peak intensities show the same trends. The second result suggests that using relative peak intensities is a sufficient way to view and interpret the data.