T18 Sea Level and Ice-Sheet Changes, Glacial Isostatic Adjustment, and Landscape Evolution I

Monday, 26 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

MILLION-YEAR-OLD ICE FOUND BURIED UNDERNEATH THIN LAYER OF DIRT; ONG VALLEY, ANTARCTICA

Paper number: T18-5
Program: Technical Sessions
Time: 2:20 PM – 2:35 PM

Authors

Abstract

We have collected two 10-meter ice cores from a newly discovered massive buried ice mass in Ong Valley, Transantarctic Mountains, Antarctica. This ice mass is buried under a thin layer (< 1 m) of sublimation till and exposure dating from the overlying till have revealed a minimum age of > 1.1 Ma, therefore making this one of the oldest ice bodies found on Earth.

Measured concentration of the cosmic-ray produced nuclides 10Be, 26Al, and 21Ne in englacial sediment down core are used obtain additional constraints on the age, sublimation rate, and origin of this buried ice mass. These cosmogenic nuclides are produced by cosmic-ray interactions with minerals near the Earth’s surface, and in this case suspended material embedded in the ice. As the production rate decreases rapidly with depth below the Earth’s surface, the cosmogenic nuclide concentration yield information about the exposure history. In addition to the measured cosmogenic nuclides, we have analyzed for deuterium and oxygen isotopes throughout the ice core.

Unexpected large variation in both cosmogenic nuclide concentrations and water isotopes downcore, suggests that the last few meters of the ice core may belong to a separate, older ice mass that has previously been exposed at the surface. Lateral moraines and measurements of cosmogenic nuclides in glacial till further up valley suggest that this deeper, older ice may be > 2.6 Ma old, and was most likely buried during glacial advancement into Ong Valley.

Further, resulting age and sublimation rate will be coupled and validated with GPS measurements of lateral and end moraines. During periods of glaciation, glacial ice advanced uphill into the glacier valley, resulting in lateral moraines deposited sloping down toward the head of the valley. These moraine elevations provide an independent indication of the mass of ice and debris lost to sublimation and erosion. With this we hope to understand past glacial advancement and extent both locally and regionally within the Transantarctic mountain range.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359283

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