Late quaternary deglaciation and sea-level history of eastern Juan de Fuca Strait, Cascadia

Eastern Juan de Fuca Strait of southwestern British Columbia/northwestern Washington State is near the western and southern terminus of Late Wisconsinan glaciation in North America. Seismic-reflection profiles, bathymetric data, sediment core data and 41 new radiocarbon dates provide insight into the history of ice retreat and sea-level change in the eastern portion of the strait. The retreating ice margin appears to have passed through the area between 14,460 +/- 200 and 13,595 +/- 145 C-14 yr. Glacial marine sediments date between 12,889 +/- 50 and 11, 110 +/- 50 C-14 yr BP. Wave-eroded unconformities, drowned prograded deposits and a partially isolated low-stand basin are evidence attributed to low-stand sea levels following deglaciation and five new control points on the local eustatic sea level curve are assigned based on radiocarbon dating of these features. Sea-level change was rapid: from + 75 in immediately after deglaciation to possibly -60.4 in at 9920 +/- 60 C-14 yr BP. After this time, gradual sea level transgression took place. Relative sea level reached its approximate present position by 5470 +/- 115 C-14 yr BP. Since then, relative sea level has remained constant suggesting eustatic rise is balanced by crustal uplift. (C) 2004 Elsevier Ltd and INQUA. All rights reserved.