Morphology and stratal geometry of the Antarctic continental shelf : insights from models

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1995Author
ten Brink, Uri S.
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Schneider, Christopher
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Johnson, Aaron H.
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https://hdl.handle.net/1912/1602As published
https://doi.org/10.1029/AR068p0001DOI
10.1029/AR068p0001Abstract
Reconstruction of past ice-sheet fluctuations from the stratigraphy of glaciated
continental shelves requires understanding of the relationships among the stratal geometry,
glacial and marine sedimentary processes, and ice dynamics. We investigate the formation of
the morphology and the broad stratal geometry of topsets on the Antarctic continental shelf
with numerical models. Our models assume that the stratal geometry and morphology are
principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the seaward edge of the grounded ice. The location of the grounding line varies
with time almost randomly across the shelf. With these simple assumptions, the models can
successfully mimic salient features of the morphology and the stratal geometry. The models
suggest that the current shelf has gradually evolved to its present geometry by many glacial
advances and retreats of the grounding line to different locations across the shelf. The
locations of the grounding line do not appear to be linearly correlated with either fluctuations
in the δ180 record (which presumably represents changes in the global ice volume) or with the
global sea-level curve, suggesting that either a more complex relationship exists or local
effects dominate. The models suggest that erosion of preglacial sediments is confined to the
inner shelf, and erosion decreases and deposition increases toward the shelf edge. Some of the
deposited glacial sediments must be derived from continental erosion. The sediments probably
undergo extensive transport and reworking obliterating much of the evidence for their original
depositional environment. The flexural rigidity and the tectonic subsidence of the underlying
lithosphere modify the bathyrnetry of the shelf, but probably have little effect on the stratal
geometry. Our models provide several guidelines for the interpretation of unconformities, the
nature of preserved topset deposits, and the significance of progradation versus aggradation of
shelf sediments.
Description
This paper is not subject to U.S. copyright. The definitive version was published in Geology and Seismic Stratigraphy of the Antarctic Margin, edited by Peter F. Barker and Alan K. Cooper, :1-24. Washington, DC: American Geophysical Union, 1995. ISBN: 0875908845. doi:10.1029/AR068p0001