This document summarizes a study presented at the 2014 GSA Annual Meeting that analyzed sediment cores from the Hugo Island Anvers Trough region along the western Antarctic Peninsula. The cores recorded evidence of deglaciation following the Last Glacial Maximum. Varved sediments in the cores correlate to other records that captured a unique deglacial interface, providing clues about the timing and rate of ice retreat. Analysis of core lithology, water content, and grain size supported the "calving bay reentrant" model of a fjord-like setting formed as ice retreated. The sediment sequences contained varved intervals deposited under conditions when the site existed as an ice-walled fjord. This study supplements understanding of the rapid

1. Start Author Index Meeting Information
2014 GSA Annual Meeting in Vancouver, British Columbia (19–22
October 2014)
Paper No. 126-3
Authors will be present from: 9:00 to 11:00 AM, and 5:00 to 6:30 PM
SEDIMENT RECORD DEMONSTRATES DYNAMICS OF DEGLACIATION IN THE HUGO
ISLAND ANVERS TROUGH: A TEST OF CALVING BAY REENTRANT MODEL
WEISMAN, Isabelle E., Hamilton College, 198 College Hill Road, Clinton, NY 13323, iweisman@hamilton.edu, SHEVENELL, Amelia, College of Marine
Science, University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701, DOMACK, Eugene, College of Marine Science, University of South
Florida, 140 7th Avenue South, St Petersburg, FL 33701, and LEVENTER, Amy, Geology, Colgate University, 13 Oak Drive, Hamilton, NY 13346
The transition between the Last Glacial Maximum (LGM) and the Holocene is recorded by varved sediments deposited in a period of exceptionally high primary
production in fjord-like settings along the western Antarctic Peninsula. Data from jumbo gravity cores retrieved from five sites along a North-South transect of
the Hugo Island Anvers Trough record the deglaciation event in the early Holocene. Specifically, core lithology, water content and grain size data from cores
collected by the R.V. Laurence M. Gould in 12-11 and 13-11 appear to correlate with other records, of note the 1998 Ocean Drilling Project Site 1098 and 1099
in Palmer Deep (PD), as they too capture the unique deglacial interface. Despite a series of projects in the region, poor core recovery interrupted the continuity
of the time series. Thus, the Hugo Island Anvers Trough cores are crucial because they add to our estimation in the timing and rate of ice retreat along the
western Antarctic Peninsula following a seemingly widespread, consistent response to ocean forcings at the end of the LGM.
Both the Palmer Deep and Hugo Island Anvers Trough sediment sequences contain almost identical varved intervals that were deposited under specific
environmental conditions, when the site existed as a “calving bay reentrant”—an ice-walled fjord that formed as ice retreated in the deep, but remained
grounded on the shallower shelf on the banks. Site 1098 contains ~176 couplets of diatom ooze siliciclastic-rich diatom mud spanning ~45m, suggesting that
the calving bay environment was more of a permanent feature in PD. The same facies exists on a much smaller scale along the axis of the trough, spanning as
little as half a meter with ~15 couplets in JGC-6 and ~14 couplets in JGC-4 suggesting the rapid recession of the calving bay model. The resulting calving bay
reentrant facies that correlates along the Hugo Island Anvers Trough is also observed through spikes in water content and grain size. Increases in water
content, ~30%, reflect the laminated diatom ooze and mud unique to the calving bay facies. Similarly, a grain size analysis of KC-6 and JGC-6 illustrates a
distinct transition from silt and clay to a sandy clay rich mud at the reentrant facies. This study supplements our understanding of the calving bay reentrant
model, and the nature of deglaciation at the end of the last glacial.
Session No. 126--Booth# 158
T177. Antarctic Fjords, Interaction of Biotic, Oceanographic, and Cryospheric Systems under Changing Climate (Posters)
Monday, 20 October 2014: 9:00 AM-6:30 PM
Vancouver Convention Centre-West Exhibition Hall C
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.318
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