SEDIMENT RECORD OF SHORT-LIVED ICE-CONTACT LAKES, BURROUGHS GLACIER, ALASKA

Sediments deposited in two small ice-contact lakes with low rates of s ediment input have been studied in subaerial exposures. Sediment chara cteristics are a function of the water sourer (glacial meltwater versu s non-meltwater), proximity to the glacier margin and lake shore, amou nt of supraglacial debris, and lake duration. Calving Lake expanded (a nd later partially drained) as a calving ice margin retreated. Nearsho re deltas contain 1 x 10(5) m(3) stratified sand and gravel deposited at rates up to m/yr during a 9-yr interval. Deltaic sediment contains types A and B ripple-drift cross-lamination, draped lamination, and sc our surfaces caused by variations in water-flow velocity and the amoun t of sediment settling from suspension. Must water inflow came From no n-subglacial meltwater sources and was sediment-poor, so overflow and interflow sedimentation processes dominated the offshore environment. Offshore sediment generally contains massive sill or silt interbedded with fine-grained sand deposited at rates of 1.3-1.5 cm/yr. Iceberg gr avity craters observed on the lake plain were formed when icebergs imp acted the lake Boor during calving events. In Bruce Hills Lake, proxim ity to glacier ice and the presence of supraglacial sediment formed co arsening-upward successions when debris Fell directly from an ice ledg e onto silty lacustrine sediment.