CONFIRMATION OF LATE PLEISTOCENE EXPANSION AND COALESCENCE OF BERING/STELLER/MARTIN RIVER GLACIER COMPLEX, ALASKA

Failure of reconnaissance reports early in the 20th Century to assess relevance of glacial drift beyond recent limits of Bering Glacier resulted in oversight of its great Pleistocene extent. This illusion persisted over 50 years, in spite of knowledge of the offshore Bering Trough. To resolve these inconsistent views, we examined diamict microstructures and verified the extent of muskeg-concealed glacial till. Field data from all sectors seaward of the Bering, Steller and Martin River Glaciers indicate widespread extent of till concealed beneath blanketing muskeg, as well as erratic rocks on beaches, lake strands and fluvial gravel bars. This evidence shows that the expanded Martin River Glacier spread west and south across the divide into the Katalla River valley. Eastward it coalesced with Steller Glacier in mounting stoss slopes and passing into upland through-valleys to join with alpine glaciers of local origin in the Don Miller Hills. To the south and farther east, Bering piedmont lobe extended several kilometers beyond previously known limits. These relationships indicate the Pleistocene confluence of trunk glaciers to be recognized as the Bering/Steller/Martin River Glacier Complex with probable seaward limits that support the presumed glacial origin of Bering Trough. Radiocarbon dating of basal peat, in contact with underlying till, supplements existing Late Pleistocene and Holocene retreat chronology. Yet to be cored are lake sediments from which detailed records of post-glacial sedimentation and Holocene environmental evolution will be obtained.