Antarctic Science

EARTH SCIENCES

Shallow seismic surveys and ice thickness estimates of the Mullins Valley debris-covered glacier, McMurdo Dry Valleys, Antarctica

David E. Sheana1 c1, James W. Head IIIa1 and David R. Marchanta2

a1 Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912, USA

a2 Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA

Abstract

Several debris-covered glaciers occupy tributaries of upper Beacon Valley, Antarctica. Understanding their flow dynamics and ice thickness is important for palaeoclimate studies and for understanding the origins of ancient ice elsewhere in the McMurdo Dry Valleys region. We present the results of several shallow seismic surveys in Mullins Valley, where the largest of these debris-covered glaciers is located. Our results suggest that beneath a thin sublimation till and near-surface horizon of dirty glacier ice, lies relatively pure glacier ice (P-wave velocity ~3700–3800 m s-1), with total thickness estimates of ~90–95 m towards the valley head, and ~40–65 m near the entrance to Beacon Valley, ~2.5 km downglacier. P-wave velocities decrease downvalley, suggesting that the material properties of the ice change with increasing distance from the ice-accumulation zone. These new data are used to calibrate an ice thickness profile for the active portion of the Mullins Valley debris-covered glacier (upper ~3.5 km) and to shed light on the origin and spatial distribution of enclosed debris.

(Received August 25 2006)

(Accepted March 15 2007)

(Online publication August 16 2007)

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