Abstract

A snow-covered plateau hundreds of miles long extends from the northern to the southern part of the Palmer Peninsula, Antarctica. It is approximately 2000 feet high at the northern end and more than 6000 feet high at the southern end. The plateau presumably is a middle or late Tertiary peneplain which has been differentially uplifted. The peneplain was dissected after the uplift; depression of more than 1000 feet since then has resulted in a shore line of submergence.

Wright, Priestley, and Gould thought that glaciation started in the Antarctic in the middle Tertiary because they interpreted breccias as tillites. The writer concludes after an examination of the literature that these breccias are probably volcanic; he believes that there is no good evidence for Tertiary Antarctic glaciation.

U-shaped valleys, cirques, horns, truncated spurs, arêtes, glacially formed bedrock basins, erratics, and moraine are common.

Evidence of deglaciation is widespread. Land ice extended more than 15 miles beyond the present strand line during the most advanced stage of glaciation. Three thousand feet of ice covered areas now deglaciated. The southwest terminus of the shelf ice in King George VI Sound retreated approximately 30 miles from 1940 to 1949. The Northeast Glacier retreated measurably from 1940 to 1947.

A strand flat 1500 feet long, 400 feet wide, and in places as much as 20 feet above sea level was mapped. Till buried in places by elevated beach gravels veneers its bedrock platform. The strand flat was formed by a local glacier. Since its formation, sea level has dropped as much as 20 feet with respect to the land. Other strand flats have had a somewhat similar history.

More than 20 elevated beaches were studied. The highest is approximately 110 feet above sea level. Elevated beaches have also been reported from South Victoria Land and from the northern part of the Palmer Peninsula. The elevations of these beaches suggest that on the average more than 300 feet of ice has been removed from the margin of the continent during deglaciation.

The average depth of the break in the slope of the Antarctic continental terrace is approximately 1600 feet. The world average depth of the break in slope is approximately 430 feet. If the great depth of the Antarctic break in slope is due solely to the weight of the icecap, the icecap must average between 3550 and 4800 feet thick.

More than 75 per cent of the area is covered with permanent ice. Valley, piedmont, tidewater, cliff, cirque, reconstructed, outlet, transection, and fringing glaciers are common; so too are highland, snowdrift, shelf, and island ice.

The insignificant quantity of alluvium and the small size of the meltwater streams in the summer months prove that running water is of only minor importance as a geologic agent.

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