Ice streams of the Late Wisconsin Cordilleran Ice Sheet in western North America. (1st January 2018)

• Record Type: Journal Article
• Authors: Eyles, Nick; Arbelaez Moreno, Lina; Sookhan, Shane
• Is Part Of: Quaternary science reviews. Volume 179(2018)
• Page Start: 87
• Page End: 122
• Publication Date: 2018-01-01
• Subjects: Cordilleran Ice Sheet -- Drumlins -- Megascale glacial lineations -- Paleo ice streams; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2017.10.027
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: The Late Wisconsin Cordilleran Ice Sheet (CIS) of western North America is thought to have reached its maximum extent (∼2.5 × 10 6 km 2 ) as late at c. 14.5 ka. Most (80%) of the ice sheet's bed consists of high mountains but its 'core zone' sited on plateaux of the Intermontane Belt of British Columbia and coterminous parts of the USA, shows broad swaths of subglacially-streamlined rock and sediment. Broad scale mapping from new digital imagery data identifies three subglacial bed types: 1) 'hard beds' of variably streamlined bedrock; 2) drumlinized 'soft beds' of deformation till reworked from antecedent sediment, and 3) 'mixed beds' of variably-streamlined bedrock protruding through drumlinized sediment. Drumlins on soft beds appear to be erosional features cut into till and antecedent sediments, and identify the catchment areas of paleo ice streams expressed downglacier as flow sets of megascale glacial lineations (MSGLs). 'Grooved' and 'cloned' drumlins appear to record the transition from drumlins to MSGLs. The location of paleo ice streams reflects topographic funneling of ice from plateau surfaces through outlet valleys and a soft bed that sustained fast flow; rock-cut MSGLs are also present locally on the floors of outlet valleys. CIS disintegrated in <1000 years shortly after c. 13.0 ka releasing very large volumes of meltwater and sediment to the Pacific coast. Abrupt deglaciation may reflect unsustainable calving of marine-based ice streams along the glacio-isostatically depressed coast; large deep 'fiord lakes' in the ice sheet's interior may have played an analogous role. Mapping of the broad scale distribution of bed types across the Cordilleran Ice Sheet provides key information for paleoglaciological modelling and also for understanding the beds of modern ice masses such as the Greenland Ice Sheet which is of a comparable topographic setting. Highlights: Mapping from new digital imagery data identifies three subglacially streamlined bed types on the bed of the former Cordilleran Ice Sheet in western North America. Drumlins appear to be erosional features, identify the catchment areas of ice streams identified down glacier by MSGLs. 'Grooved' and 'cloned' drumlins appear to record the transition from drumlins to MSGLs. Location of paleo ice streams reflects topographic funneling of ice from plateau surfaces through outlet valleys. Provides key information for paleoglaciological modelling and also for understanding the beds of modern ice masses such as the Greenland Ice Sheet.