GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 142-6
Presentation Time: 2:50 PM


BRACHFELD, Stefanie A.1, CIRONE, Ashley1, WILLIAMS, Trevor2, LICHT, Kathy3 and HEMMING, Sidney R.4, (1)Department of Earth & Environmental Studies, Montclair State University, Montclair, NJ 07043, (2)International Ocean Discovery Program, Texas A&M University, College Station, TX 77845, (3)Department of Earth Sciences, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, SL 118, Indianapolis, IN 46202, (4)Department of Earth and Environmental Sciences, and Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964,

This project seeks to develop “fingerprints” of the glacially eroded sediment transported by Antarctic ice streams. The ability to trace marine ice rafted debris back to the drainage basin from which it was eroded will provide a means of examining past patterns of ice discharge into the ocean. We examined the geochemical and mineralogical signatures of three Antarctic ice streams that drain ice into the Ronne-Filchner Ice Shelf within the Weddell Sea Embayment. Tills were collected from lateral moraines adjacent to the Foundation, Academy, and Recovery ice streams. The < 63 μm fraction was analyzed for major and trace element geochemistry. K-mean Cluster Analysis reveals three major groups, with the majority of Foundation and Academy Ice Stream samples grouping together, which is expected given the close proximity of these two ice streams. Cluster two consists of two Nunataks located on the eastern margin on the Foundation Ice Stream. Till from the southern margin of the Recovery Ice Stream forms the third cluster. Principal Component Analysis of the trace element data indicates that two components explain 90.7% of the variance. The elements Ba, Zr, Rb, Sr, V, and Mn are responsible for the highest loadings, and all are enriched in the three ice streams relative to average compositions reported for shales. The southern margin of the Recovery Ice Stream is additionally enriched in transition metals. We also examined the major and trace element composition of iron-oxide grains extracted from the coarse-silt and sand fraction. Foundation Ice Stream is distinguished by titanomagnetite with high V substitution. Recovery Ice Stream is the only ice stream that contains Mn-bearing minerals, including psilomelane and hausmannite. These results suggest that the both the fine and coarse-fraction of marine sediment deposited in the Weddell Sea and South Atlantic Ocean possess geochemical and mineralogical characteristics that will allow the tracing of their provenance.