POST GLACIAL SEA LEVELS ON THE WESTERN CANADIAN CONTINENTAL-SHELF - EVIDENCE FOR RAPID CHANGE, EXTENSIVE SUBAERIAL EXPOSURE, AND EARLY HUMAN HABITATION

Grounded piedmont type glaciers inundated and isostatically loaded the deep troughs which indent the Western Canadian continental shelf, as far west as the shelf edge. Glaciers do not appear to have covered the offshore banks east of the Queen Charlotte Islands (Haida Gwaii). Ice retreated from the shelf at approximately 13,500 C-14 yr B.P. Rapid e mergence of the crust followed the ice retreat and resulted in a relat ive fall of sea level. At 10,400 C-14 yr B.P. relative sea level on th e continental shelf was more than 100 m below that of today and large areas of the Queen Charlotte Basin were subaerially exposed. Eustatic sea-level rise, coupled with subsidence of a glacioisostatic forebulge , allowed sea levels to rise very rapidly, and reach the present shore line on the Queen Charlotte Islands (Haida Gwaii) by about 9100 C-14 y r B.P. Dated shoreline deposits (shells), submerged wood remnants, and barnacles on stone tools at elevations between -110 m and +14 m sugge st a sea-level rise of 6.3 cm per year between 12,200 and 11,000 calen der years. Our reconstructions of the paleogeography and paleoenvironm ents suggest a hospitable environment for human habitation existed in areas that are now submerged. Stone tools excavated from intertidal de posits support this interpretation. Significant local variations in th e depth of synchronous shorelines are described and attributed to loca lized differences in isostatic load. The documented rates of crustal a djustment are much greater than those used in conventional geophysical (forebulge) models. Regional high-resolution seismic reflection data (3400 Line km) shows little evidence for post-glacial faulting and sug gest that most crustal adjustments appear to have been isostatically r ather than tectonically driven. Subaerial exposure and subsequent sea- level transgression were the dominant post-glacial processes that dete rmined the morphology, texture and paleoenvironment of the Western Can adian continental shelf.