Submarine and onshore end moraines in southern Newfoundland: implications for the history of late Wisconsinan ice retreat

Shaw, John; Grant, Douglas; Guilbault, Jean-Pierre; Anderson, T. W.; Parrott, D R

doi:10.1111/j.1502-3885.2000.tb01212.x

Cited by 21 publications

(11 citation statements)

References 43 publications

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“…2), ice halted at the Trinity Moraine just prior to 16.0 14 C ka BP (19.3 ka cal. Shaw et al 2000Shaw et al , 2006Shaw et al , 2009Shaw 2003;Shaw & Potter 2015). The retreating ice margins did not stabilize at fjord mouths, unlike in south and west Newfoundland where large, arcuate, submarine moraines formed on fjord thresholds c. 14 14 C ka BP (e.g.…”

Section: Retreat Of the Ice Sheet After Lgmmentioning

confidence: 99%

Glacial geomorphology of the Northeast Newfoundland Shelf: ice‐stream switching and widespread glaciotectonics

Shaw

Longva

2017

Boreas

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Analysis of Olex bathymetry, multibeam sonar and seismic survey data, shows that, perhaps during the mid Pleistocene, grounded ice crossing the Northeast Newfoundland Shelf was topographically steered in Hawke Saddle, occupied a broad trough underlying much of Belle Isle Bank and present‐day Notre Dame Trough, and deposited ~100 m of stacked glacigenic sediment; grounded ice crossed southern Funk Island Bank and occupied Notre Dame Trough. During the Wisconsinan Stage, c. 30 cal. ka BP, flow remained topographically steered in Hawke Saddle, but due to flow switching two convergent ice streams incised the stacked sediments of the earlier phase, creating the modern Notre Dame Trough, and diverging around an erosional remnant near the shelf edge. The ice margin at the Last Glacial Maximum (c. 18 14C ka BP) was at the shelf edge in Trinity Trough but far to the west elsewhere. Retreating ice did not stabilize at fjord mouths, but halted several times within fjords. Shelf morphology was shaped by glaciotectonism. The large tectonized zone on the north flank of Notre Dame Trough was created by the northernmost of the two convergent streams. Glaciotectonism was most widespread in the enclosed St. Anthony Basin, where the Quaternary cover has been stripped away, arrays of composite ridges have formed and sediment blocks have been thrust onto the adjacent bank. A large hill‐hole pair was formed on the east side of the basin, extending onto Belle Isle Bank. A hill‐hole pair on the inner shelf was formed by ice flow from the northwest into Notre Dame Channel. Evidence of widespread glaciotectonism distinguishes this relatively deep shelf from the adjoining, relatively shallow, eastern Canadian shelves, but has strong parallels with parts of the Norwegian continental shelf where methane hydrates maybe played a role in regulating ice‐stream flow.

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Section: Retreat Of the Ice Sheet After Lgmmentioning

confidence: 99%

Glacial geomorphology of the Northeast Newfoundland Shelf: ice‐stream switching and widespread glaciotectonics

Shaw

Longva

2017

Boreas

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“…This land system is interpreted as evidence of the onset area for ice that formerly converged in, and streamed southward through, Placentia Bay. To the east, where the basement boundary is located at the coast, large submarine moraines are located at fjord mouths (Shaw et al 2000(Shaw et al , 2006Shaw 2003). 2.3c).…”

Section: Glacial Land Systemsmentioning

confidence: 99%

Chapter 2 Continental shelves of Atlantic Canada

Shaw

Todd

Mosher

et al. 2014

Memoirs

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The wide continental shelves of Atlantic Canada are characterized by a series of banks separated by transverse troughs. These shelves have been imprinted by repeated Quaternary glaciations, so that fluvial valleys have been deepened into fjords and shelf-crossing troughs, and a suite of glacigenic sediments has been deposited. In shallow areas the seafloor is shaped by waves and currents, including the strong tidal currents of the macrotidal Bay of Fundy. Glacigenic sediments have been reworked by modern processes to yield thick muds in basins, and thinner deposits of sand and gravel on wave-dominated banks and the littoral zone. As a result of a cold climate and the Labrador Current, seasonal sea ice occurs to varying degrees across the region, and iceberg impact continues on much of the Newfoundland and Labrador shelves. For the purpose of description, we divide Atlantic continental shelves into four regions and focus on advances in understanding over the past several decades relating to: (1) processes on upper continental slopes; (2) glacial history in the last glacial cycle; (3) glacial land systems; (4) geographical changes caused by glacio-isostasy; and (5) sediment mobility on the offshore banks. We conclude with a brief overview of the biota.

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“…Surficial geology map 4015-G, which accompanies the article by Fader et al (1982), shows the typical glacial and postglacial units mapped elsewhere in Atlantic Canada, but interpretation does not extend into the coastal waters of the study area. However, more recent mapping (Shaw et al 2000;Shaw 2003) shows a series of submarine moraines at the mouths of fjords postdating 14.2 kyr BP (radiocarbon years).…”

Section: Study Areasmentioning

confidence: 99%

“…In the east, where the basement boundary is located at the coast, large submarine moraines are located at fjord mouths. They have been described by Shaw et al (2000), Shaw (2003) and Shaw et al (2006), so an abbreviated description is given here. The moraines are arcuate in planform, commonly consist of several lobes and comprise up to several hundred metres of acoustically incoherent icecontact sediment that passes seaward into glaciomarine silt, the Downing Silt facies described by Fader et al (1982).…”

Section: Southwest Newfoundlandmentioning

confidence: 99%

“…A major calving episode beginning just before 14 kyr removed ice from the Gulf of St. Lawrence (Josenhans & Lehman 1999), triggering re-advances down secondary troughs. Isolation of a Newfoundland ice cap produced radial drainage via fjords (Shaw et al 2000) and the lowlands on the west coast (Shaw 2003;Bell et al 2001). By 13 kyr most remaining ice was on land, and was ablating by melting rather than calving.…”

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confidence: 99%

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Late Wisconsinan glacial landsystems on Atlantic Canadian shelves: New evidence from multibeam and single‐beam sonar data

Shaw¹,

Todd²,

Brushett³

et al. 2009

Boreas

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Multibeam sonar surveys in the past decade, augmented by single-beam data from the OLEX charting system, reveal landsystems on Atlantic Canadian shelves that are diagnostic of Late Wisconsinan ice-sheet dynamics. Four landsystems are described. (1) The Bay of Fundy landsystem comprises two contrasting sets of bedforms, and is interpreted as evidence of topographically controlled fast-flowing ice adjacent to slower-moving ice.(2) The German Bank landsystem off southwest Nova Scotia is comprised of glacially fluted terrain overprinted by De Geer moraines and arcuate recessional moraines. We infer that a flow of grounded glacial ice out of the Bay of Fundy was followed by steady retreat, punctuated by at least one major re-advance. (3) The Placentia Bay landsystem consists of a convergent field of streamlined landforms with superimposed De Geer moraines, overprinted in one area by flutings. We infer that this landsystem was formed in the onset zone of fast-flowing ice, and that overprinting was due to a re-advance of ice from offshore. (4) The south coast of Newfoundland landsystem, which includes arcuate, fjord-mouth moraines and a coast-parallel, fluted moraine, indicates strong topographic control on a retreating marine ice margin as it reached a fjord coastline. These submarine glacial landsystems are not inconsistent with a conceptual model showing Late Wisconsinan ice advance to shelf edges, rapid calving retreat along deepwater channels and slower retreat of ice margins grounded in shallow water. The re-advances documented two of the study areas have parallels in the Last British Ice Sheet, confirming that the reorganization of marine-based ice sheets, caused by calving in embayments, led to internally forced re-advances.

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Submarine and onshore end moraines in southern Newfoundland: implications for the history of late Wisconsinan ice retreat

Cited by 21 publications

References 43 publications

Glacial geomorphology of the Northeast Newfoundland Shelf: ice‐stream switching and widespread glaciotectonics

Glacial geomorphology of the Northeast Newfoundland Shelf: ice‐stream switching and widespread glaciotectonics

Chapter 2 Continental shelves of Atlantic Canada

Late Wisconsinan glacial landsystems on Atlantic Canadian shelves: New evidence from multibeam and single‐beam sonar data

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