Advance and retreat of Cordilleran ice sheets in Washington, USA

Abstract

Cordilleran Ice Sheet glaciations show characteristic patterns of advance and retreat, consisting of 1) advance outwash, 2) glacial scouring, 3) deposition of till, 4) deposition of recessional outwash. The pattern of events in the northern Puget Lowland includes: 1) glacial loading under 1800 m of ice during the Vashon maximum; 2) rapid glacial thinning and floating of the ice deposited Kulshan glaciomarine drift 12-13 ka yrs BP; 3) emergence and deposition of fluvial Deming sand ~11.5 ka yrs BP; 4) resubmergence and deposition of Bellingham glaciomarine drift up to ~200 m, well beyond global eustatic sea level rise; 5) emergence ~10.5-11.5 ka yrs BP and deposition of Sumas outwash on Bellingham glaciomarine drift; 6) Holocene eustatic sea level rise kept pace with isostatic rebound, thus, post-Sumas marine terraces are absent. -from Author