Late Pleistocene-Holocene retreat of the West Antarctic ice-sheet system in the Ross Sea; Part 2, Sedimentologic and stratigraphic signature

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doi: 10.1130/0016-7606(1999)111<1517:LPHROT>2.3.CO;2
Authors:Domack, Eugene W.; Jacobson, Erik A.; Shipp, Stephanie; Anderson, John B.
Author Affiliations:Primary:
Hamilton College, Geology Department, Clinton, NY, United States
Other:
Rice University, Houston, TX, United States
Volume Title:Geological Society of America Bulletin
Source:Geological Society of America Bulletin, 111(10), p.1517-1536. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7606
Publication Date:1999
Note:In English. For reference to Part 1 see Shipp, S., et al., Geol. Soc. Am. Bull., Vol. 111, p. 1486-1516, 1999. 62 refs.; illus., incl. sects., 2 tables, sketch maps
Summary:Sedimentologic, geotechnical, geochemical, and accelerator mass spectrometer (AMS) radiocarbon data from two marine geologic cruises in the Ross Sea have allowed us to constrain facies relationships and temporal changes in the West Antarctic Ice Sheet. The selection of core sites was facilitated by the use of multibeam bottom imagery and a good quality (CHIRP) subbottom reflection system. A complex but consistent succession of facies documents a number of environments from subglacial to open marine. Massive, mud-rich diamictons have low water contents, contain (in places) a calcareous microfossil assemblage, show minimal textural variation, and contain low and uniform total organic carbon values. This reflects a subglacial setting. This unit passes upward into a stratified, thin, granulated facies consisting of pelletized, sandy, muddy gravel that is loosely compacted and contains a variable water content and concentrated horizons of pebble-sized clasts. This facies reflects the lift-off zone or thin water film between the basal debris and sea floor. Overlying this unit are silty clays that contain a well-sorted, very fine-grained sand component. There are no coarse grains within this unit. This facies is, in part, laminated and reflects deposition beneath an ice shelf, near and away from the grounding-line zone. The ice-shelf facies passes upward into a siliceous mud and ooze unit that represents deposition in an open-marine setting. A sandy, volcaniclastic-rich subfacies marks the transition from ice shelf to open-marine environments found at the calving line. The 86 AMS radiocarbon dates on organic matter provide an accurate chronology for 19 cores. Ice-shelf conditions were established in the outer Drygalski Trough by 11±0.25 ka and perhaps earlier. This transition took place in the JOIDES Basin by 10-8 ka. The calving front of the Ross Ice Shelf passed over the Drygalski Trough at 74°S by 9.5±0.25 ka. The timing of deglaciation in the Ross Sea calls into question current models for the contribution of Antarctic glacial ice to Holocene sea-level rise and suggests that recession was relatively gradual and more closely aligned with Northern Hemisphere deglaciation and its associated eustatic pulse.
Sections:Geochemistry
Subsections:Sedimentary rocks
Subjects:Absolute age; Bathymetry; C-14; Carbon; Cenozoic; Cores; Dates; Deglaciation; Glacial geology; Glaciation; Grain size; Holocene; Ice sheets; Isotopes; Lithostratigraphy; Marine sediments; Pleistocene; Quaternary; Radioactive isotopes; Sediments; Upper Pleistocene; Antarctic ice sheet; Antarctica; Ross Sea; Southern Ocean; West Antarctica; Antarctic Ocean
Abstract Numbers:01M/3027
Record ID:1999066498
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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