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TitleLate glaciation in the eastern Beaufort Sea: contrasts in shallow depositional styles from Amundsen Gulf, Banks Island Shelf and M'Clure Strait
AuthorKing, E L
SourceArcticNet, 2015 Annual Scientific Meeting: oral presentation abstracts/ArcticNet, 2015 Réunion scientifique annuelle: oral presentation abstracts; 2015 p. 63
LinksOnline - En ligne (complete volume, volume complet, 1.17 MB)
Alt SeriesEarth Sciences Sector, Contribution Series 20150335
MeetingArcticNet, 2015 Annual Scientific Meeting / Réunion scientifique annuelle; Vancouver, BC; CA; December 7-11, 2015
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS87C; 87D; 87F; 87G; 88B; 88C; 88D; 88E; 88F; 88G; 88H; 97C; 97D; 97E; 97F; 97G; 97H; 98
AreaAmundsen Gulf; M'Clure Strait; Banks Island; Beaufort Sea
Lat/Long WENS-128.0000 -112.0000 76.0000 69.0000
Subjectsmarine geology; surficial geology/geomorphology; stratigraphy; sedimentology; geophysics; continental margins; continental shelf; continental slope; glacial history; glaciation; ice flow; ice margins; deglaciation; ice retreat; depositional environment; depositional models; geophysical surveys; acoustic surveys, marine; core samples; glacial deposits; glacial features; tills; moraines; moraine, lateral; glacial erosion; erosional surfaces; unconformities; lineations; glacial flutings; landslide deposits; debris flow deposits; muds; marine sediments; terraces; sea level changes; submarine features; submarine troughs; submarine terraces; facies analyses; Last Glacial Maximum; Banks Island Shelf; Amundsen Trough; Amundsen Ice Stream; M'Clure Ice Stream; M'Clure Trough; till blanket; iceberg turbation; glaciomarine sediments; glaciomarine blanket; ice-flow directions; megascale glacial lineations; shelf breaks; iceberg scour; ice streams; Phanerozoic; Cenozoic; Quaternary
ProgramPublic Safety Geoscience, Marine Geohazards
Released2015 12 01
AbstractAmundsen Gulf and M'Clure Strait were the major glacial outlets to the Beaufort Sea. Amundsen Gulf has abundant shallow (3.5kHz) sub-bottom profiler coverage, yet the first sub-bottom coverage in M'Clure Strait was collected by ArcticNet Seabed Mapping Program (P. Lajeunesse, Laval) in 2015. Though coverage is sparse, supplemented with 2011 USCG Healy data there and across the Banks Island Shelf, it allows a preliminary insight into the latest glacial events. Recent land-based and short marine core work allows inference of a Last Glacial Maximum (LGM) reaching the shelf break at both trough mouths and a deglacial event chronology; absolute chronology is yet available for LGM deposits. Beyond the shelf break, the depositional record was largely lost through mass failures. Shelf-based stratigraphy and geometry of tills and till-like blankets, slope-based glacigenic debris flows (GDFs), iceberg turbates and stratified glacimarine mud blankets allow initial deciphering of glacier extent, direction, and margin dynamics. Amundsen Trough mouth has a single thin till-like blanket, GDF time equivalents on the slope and a complex younger sequence of tills and flow tills on the trough flanks (>50m thick), locally interbedded with stratified glacimarine muds. More than ten stacked till-like units along the southern flank (far fewer on the northern), represent a combination of basal till, lateral moraines, ice stream flank erosional remnants and ice-margin deposits recording frontal fluctuations punctuated with plume sedimentation. The mid- to inner Banks Island Shelf has a sea-level low-stand constrained terrace at 40-50 m depth built up to 50m thick. It comprises crudely prograding (0.5° to 1°) and locally channelized glacially-derived muds, with basal-transgressive and sub-littoral components. Seaward, is a thick (20+m), structurally complex stratified glacimarine blanket, fully iceberg turbated on its upper surface and with local buried morainic mounds or megascale glacial lineations (MSGLs). Its outermost margin has flutes and ice-marginal flow tills. This and an erosion bench demonstrate broad splaying of both Amundsen and M'Clure ice streams across the bank. Direct glacial deposition from island-based ice is still in question. The M'Clure trough floor exhibits a smooth, broadly uniform surface interpreted as the glacial erosional surface (GES) unconformity sculpted by the last ice sheet. Three stratigraphically different facies overly the GES: 1. The lower is acoustically attenuating and has a constructional geometry suggesting a moraine-like or MSGL origin, similar to Amundsen Gulf, but thinner and with little till-stacking. This, and sparse GDFs on the slope, indicate a short-lived shelf-break position and simple retreat pattern. 2. Overlying this is a thin, near-continuous blanket forming the surficial unit. Only in the deepest basins, below 520m (shallower westward) does otherwise ubiquitous iceberg scouring abate, revealing the originally stratified blanket. This enables its differentiation from till. It is a glacimarine mud, deposited from plumes with ice-stream calving and retreat, completely turbated by icebergs. 3. Locally, and the thickest of all, (0-30m) are mounded deposits with acoustically transparent and homogeneous character, post-dating the main calving event. Their geometry and stratigraphic position suggests very late stage, localized and rapid deposition but a meltwater versus glacial re-advance is not yet clear.
Summary(Plain Language Summary, not published)
Amundsen Gulf and M'Clure Strait were major glacial outlets to the Beaufort Sea- troughs draining the western Canadian Archipeligo. Glaciation and associated low-stands of sea-level are the primary influence on surficial geology; a basic framework is necessary to put a process and timing constraint on potential geohazards. Good geophysics survey coverage in Amundsen Gulf contrasts with M'Clure Strait and Banks Island Shelf, between them. A summer 2015 ArcticNet cruise aboard CCGS Amundsen helps remedy this, supplemented with 2011 USCG Healy cruise data. Glacier erosion, discontinuous till blankets and other deposits and features are examined towards an initial reconstruction of the glaciers. Ice streams filling both troughs splayed greatly where they briefly entered deep Beaufort water, covering large parts of Banks Island Shelf. Many ice front fluctuations occurred in Amundsen Trough in contrast to a simpler retreat through M'Clure though some enigmatic deposits need further study.