Multiple Ice Advances Suggested by Rock Glacier Stratigraphy and Surface Weathering in the McMurdo Dry Valleys, East Antarctica
Abstract
In Taylor Valley of the McMurdo Dry Valleys, cold-based Sollas Glacier extends from the Kukri Hills to a plateau above Lake Bonney. Adjacent to the eastern margin of the glacier is the 1200-m long Sollas rock glacier, which flows from an icefall deposited by Doran Glacier as it overtops a steep sidewall. Ground-penetrating radar lines from upper to lower Sollas rock glacier indicate a thin debris cover overtopping 3-6 m of clean ice, which in some areas overlies a second debris layer above deeper clean ice. This configuration is similar to observed englacial stratigraphy in the higher-elevation Mullins Glacier in Beacon Valley, where it is interpreted to result from episodic advances of the source ice. Major ion analyses of seven meltwater ponds extending from the central to lower Sollas rock glacier show fresh water in central ponds, but highly saline water in isolated lower ponds. This salinity distribution is consistent with the observed weathering pattern along the rock glacier, with fresh, angular granitic boulders dominating the upper and central sections, and heavily grussified granitic boulders dominating the lower sections. Weathering, pond salinities, and subsurface stratigraphy all point to successive advances of the Sollas rock glacier, likely induced by fluctuations of Doran Glacier. These relationships have two implications: 1) Sollas Glacier itself has not laterally expanded more than 50 m beyond its current extent over the past few local climate fluctuations, and 2) glacial ice buried under 10-50 cm of debris has survived these fluctuations. This supports research that indicates subsurface ice persisted, even in the low elevation McMurdo Dry Valleys, through Marine Isotope Stages 1, 2, and possibly 5. Such persistence preserves the record of local ice advances that may in turn reflect the behavior of Taylor Dome.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C41B0659W
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 0774 Dynamics;
- CRYOSPHEREDE: 0798 Modeling;
- CRYOSPHEREDE: 1621 Cryospheric change;
- GLOBAL CHANGE