Luminescence Dating of Late Pleistocene Proximal Glacial Sediments in the Olympic Mountains, Washington

Abstract

Late Pleistocene glacial sediments from the South Fork Hoh River valley in the Olympic Mountains, Washington, USA, were dated using optically stimulated luminescence (OSL) on quartz sand. High sediment supply typical of glacial environments, short transport distances, and sediment newly eroded from bedrock sources were expected to pose problems for luminescence dating. Samples were collected from five distinct sedimentary facies, using approximated distances from the ice-front, to assess how luminescence results varied due to these factors and to determine which samples produced the most reliable age estimates. Results from the South Fork Hoh highlight the importance of transport environment and sedimentary facies on solar resetting. Sediments from better-sorted, ice-distal environments were determined to be more completely bleached and more reliable for OSL dating. Samples were collected as part of larger research goals to improve understanding of the glacial history of the South Fork Hoh River valley