Abstract
Rates of basal till deposition ranging from 0.5 to 2.5 cm year–1 have been obtained from the Burroughs Glacier in southeast Alaska. Unlike minimum rates of till deposition which are derived by dividing the thickness of till deposited by the length of time the area was ice covered, these values are believed to more closely represent an actual rate of deposition.Because of the emergence of hills during deglaciation, a change in ice flow direction of up to 90° has occurred near the southeast terminus. Since this change is recorded by maps and photographs dating to 1892, a rate of change of ice flow direction can be estimated. Till fabric measurements and till composition at two or three depths in the till at seven localities reflect this change. Estimates of the rate of till deposition are obtained by assuming that the fabric azimuth represents the ice flow direction at the time the till was deposited.Most till deposition seems to have taken place during late stages of deglaciation since at two locations fabric of till just above bedrock or a paleosol records a post-1892 flow direction. The rate obtained by dividing the average thickness of till by the number of years the area was ice covered is an order of magnitude lower than those calculated above.
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