HR: 09:30h
AN: C51C-07    [Abstracts]
TI: River Response to Deglaciation: a Case-Study of Clyde Fjordhead, Baffin Island, Arctic Canada
AU: * Overeem, I
EM: overeem@colorado.edu
AF: INSTAAR, 1560 30th street University of Colorado, Boulder, CO 80303, United States
AU: Briner, J P
EM: jbriner@buffalo.edu
AF: Geology Department, University at Buffalo, Buffallo, NY 14260, United States
AU: Kettner, A J
EM: kettner@colorado.edu
AF: INSTAAR, 1560 30th street University of Colorado, Boulder, CO 80303, United States
AU: Syvitski, J P
EM: syvitski@colorado.edu
AF: INSTAAR, 1560 30th street University of Colorado, Boulder, CO 80303, United States
AB: River deposits form archives of past dynamics of a number of environmental controls; drainage basin characteristics, climate and sea-level changes. This paper explores long-term river sedimentation based on Late Quaternary deposition in Clyde Inlet on Baffin Island as constrained by 11 cosmogenic and 9 AMS 14C datings. Clyde River drains part of the remaining land ice of Barnes Ice Cap, making it a rare case of a basin in the most advanced stages of deglaciation. A major ice stream of the Laurentide Ice Sheet occupied Clyde Inlet at the Last Glacial Maximum and carved through the U-shaped valley creating a distinct sediment sink. At Early Holocene the system entered deglacial stage; tidewater glaciers retreated rapidly (>100 km in 1000 yrs) through the fjord from 10,4 ka onwards. Grounded ice lobes started retreating from Clyde fjordhead by 9,4 ka coinciding with warm climatic conditions. Then ice contact fans (ICF's) were deposited consisting of flat-topped fan deltas covered with boulder channels and bars. Elevations of their surfaces nowadays vary between 62-77 m above sea level, which is considered to be near contemporaneous sea level. Marine muds have been draped directly onto the ICF complexes and define the minimum marine limit at > 58 m asl. Subsequently, coarse-grained glacio-fluvial valley trains (GVFT's) and deltas were deposited during forced regression. 14C dated bivalves show that relative sea level dropped ~20 m/ka between 9-7 ka. Surfaces of the GVFT's dip downward caused by dominant sea-level fall, despite high sediment supply. At the latest Holocene (3,5 ka) the last remaining lobes of the Laurentide Ice Sheet retreated from the middle parts of Clyde River basin to form the present Barnes Ice Cap. At this phase, strong river incision, despite an order of magnitude slower base-level fall (~1,6 m/ka over the last 3,5 ka), marks reduced sediment supply. Clyde River Basin may not have entered a post-glacial stage by definition, nevertheless the strongly reduced sediment flux is apparent. We speculate that the glacial regime of the retreating proto Barnes Ice Cap switched from a dominantly sediment-producing regime to a non-erosive, cold-based regime. The reconstructed timing of river deposition and incision was compared with climate–driven numerical modeling predictions of water and sediment flux for Clyde River over the Holocene and further supports the dominance of glacial regime and isostatic rebound on river sedimentation.
DE: 0466 Modeling
DE: 1825 Geomorphology: fluvial (1625)
DE: 5419 Hydrology and fluvial processes
DE: 9315 Arctic region (0718, 4207)
SC: Cryosphere [C]
MN: 2007 Fall Meeting