Coastal geology of the King Point area, Yukon Territory, Canada

Abstract

At King Point, on the Yukon coast of the Canadian Beaufort Sea, a sand/gravel barrier is migrating landward across a sequence of lacustrine muds which were deposited in a thermokarst lake. The lacustrine deposits were laid down between 12 ka and the time of breaching of the thermokarst lake. Breaching occurred at some point after 1.7 ka, probably a few hundred years ago. Estimates of sediment supply and barrier growth can be best reconciled if a model is assumed that involves initial erosion of a 1 km wide headland, an extension of a diamict ridge which forms King Point itself, followed by straightening of the coast and an increased sediment supply from gravel-rich cliffs north of the ridge. This is compatible with historical evidence for development of the barrier. Comparison of sediment supply, retreat rates and longshore sediment transport potential lead to the conclusion that the development of the barrier and coastal retreat are limited by the longshore transport potential. The evolution of the King Point barrier is similar to that of gravel barriers in temperate regions, but short-term increases in sediment supply through thermal erosion of adjacent bluffs and erosion of the lower shoreface by ice scouring may be important additional factors.