Distribution of sedimentary facies in Muir Inlet, Glacier Bay, Southeast Alaska
Seramur, Keith C.
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Seismic facies analysis was applied to high resolution, single channel, analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, Alaska. Sedimentary facies have been interpreted from seismic facies identified on the profiles. The interpretations are based on relection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflector terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining the paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat, a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The occurrence of outwash deposits and submarine moraines (stratified and push-moraines) is described and the style of basin sedimentation is discussed.