Glacial landforms on German Bank, Scotian Shelf: evidence for Late Wisconsinan ice‐sheet dynamics and implications for the formation of De Geer moraines

The extent and behaviour of the southeast margin of the Laurentide Ice Sheet in Atlantic Canada is of significance in the study of Late Wisconsinan ice sheet-ocean interactions. Multibeam sonar imagery of subglacial, ice-marginal and glaciomarine landforms on German Bank, Scotian Shelf, provides evidence of the pattern of glacial-dynamic events in the eastern Gulf of Maine. Northwest-southeast trending drumlins and megaflutes dominate northern German Bank. On southern German Bank, megaflutes of thin glacial deposits create a distinct northwest-southeast grain. Lobate regional moraines (>10km long) are concave to the northwest, up-ice direction and strike southwest-northeast, normal to the direction of ice flow. Ubiquitous, overlying De Geer moraines (<10 km long) also strike southwest-northeast. The mapped pattern of moraines implies that, shortly after the last maximum glaciation, the tidewater ice sheet began to retreat north from German Bank, forming De Geer moraines at the grounding line with at least one glacial re-advance during the general retreat. The results indicate that the Laurentide Ice Sheet extended onto the continental shelf.

[1]  A. Dyke,et al.  Major end moraines of Younger Dryas age on Wollaston Peninsula, Victoria Island, Canadian Arctic: implications for paleoclimate and for formation of hummocky moraine , 2000 .

[2]  Julian A. Dowdeswell,et al.  Evolution of subglacial bedforms along a paleo‐ice stream, Antarctic Peninsula continental shelf , 2002 .

[3]  J. Schlee.  Atlantic continental shelf and slope of the United States; sediment texture of the northeastern part , 1973 .

[4]  D. Belknap,et al.  Deglaciation of the Gulf of Maine , 2001 .

[5]  G. Fader,et al.  Morphology and seismic stratigraphy of the inner continental shelf off Nova Scotia, Canada: Evidence for a −65 m lowstand between 11,650 and 11,250 C14 yr B.P. , 1994 .

[6]  Chris D. Clark,et al.  Geomorphological criteria for identifying Pleistocene ice streams , 1999, Annals of Glaciology.

[7]  A. Elverhøi,et al.  Glacial geomorphic features in the northern Barents Sea: direct evidence for grounded ice and implications for the pattern of deglaciation and late glacial sedimentation , 1990, Geological Society, London, Special Publications.

[8]  G. Steeves,et al.  Canadian imaging and sampling technology for studying marine benthic habitat and biological communities , 2000 .

[9]  J. Menzies,et al.  Subglacial bedforms—an introduction , 1989 .

[10]  G. Drapeau,et al.  Surficial geology of the Yarmouth-Browns Bank map area , 1972 .

[11]  W. Barnhardt,et al.  Late Quaternary relative sea-level change in the western Gulf of Maine: Evidence for a migrating glacial forebulge , 1995 .

[12]  G. Fader,et al.  WISCONSINAN GLACIAL AND SEA-LEVEL HISTORY OF MARITIME CANADA AND THE ADJACENT CONTINENTAL SHELF : A CORRELATION OF LAND AND SEA EVENTS , 1998 .

[13]  G. Fader,et al.  New data from Halifax Harbour: paleoenvironment and a new Holocene sea-level curve for the inner Scotian Shelf , 1999 .

[14]  G. Prichonnet,et al.  Formation of De Geer Moraines Deposited Subglacially, Central Québec , 2007 .

[15]  John B. Anderson,et al.  Distribution of glacial geomorphic features on the Antarctic continental shelf and correlation with substrate: implications for ice behavior , 2001 .

[16]  G. Fader,et al.  Wisconsinan glaciation of the Atlantic continental shelf of southeast Canada , 1986 .

[17]  L. H. King.  Late Wisconsinan ice retreat from the Scotian Shelf , 1996 .

[18]  J. L. Sollid.  Comments on the genesis of De Geer moraines , 1989 .

[19]  De Geer,et al.  Geochronologia suecica principles , 1946 .

[20]  J. Andrews,et al.  The Laurentide and Innuitian ice sheets during the Last Glacial Maximum , 2002 .

[21]  W. Peltier.  GLOBAL GLACIAL ISOSTASY AND THE SURFACE OF THE ICE-AGE EARTH: The ICE-5G (VM2) Model and GRACE , 2004 .

[22]  W. Warren,et al.  Origins of the Ice-contact Stratified Ridges (Eskers) of Ireland , 1994 .

[23]  G. M. Young,et al.  Global glacial chronologies and causes of glaciation , 2002 .

[24]  R. Stea.  The appalachian glacier complex in maritime canada , 2004 .

[25]  C. Clark,et al.  A highly mobile Laurentide ice sheet revealed by satellite images of glacial lineations , 1990, Nature.

[26]  R. S. Williams,et al.  Evidence against a late Wisconsinan ice shelf in the Gulf of Maine , 1990 .

[27]  H. Zilliacus.  Genesis of De Geer moraines in Finland , 1989 .

[28]  D. Mickelson,et al.  Till Ridges Presently Forming above and below Sea Level in Wachusett Inlet, Glacier Bay, Alaska , 1974 .

[29]  J. Piotrowski,et al.  Influence of bedrock permeability and till grain size on the formation of the saadjärve drumlin field, Estonia, under an east‐Baltic Weichselian ice stream , 2003 .

[30]  G. Fader,et al.  Sonography of a glaciated continental shelf , 1994 .

[31]  J. Wright,et al.  Stratigraphy, paleoceanography, chronology, and environment during deglaciation of eastern Maine , 2001 .

[32]  J. Dowdeswell,et al.  Assemblages of submarine landforms produced by tidewater glaciers in Svalbard , 2006 .

[33]  G. Boulton.  Push-moraines and glacier-contact fans in marine and terrestrial environments , 1986 .

[34]  N. Glasser,et al.  Fast-flowing outlet glaciers of the Last Glacial Maximum Patagonian Icefield , 2005, Quaternary Research.

[35]  B. Maclean,et al.  Geology of the Scotian Shelf , 1976 .

[36]  B. Tucholke,et al.  Late Wisconsin Glaciation of the Southwestern Gulf of Maine: New Evidence from the Marine Environment , 1973 .

[37]  Mike J. Smith,et al.  Methods for the visualization of digital elevation models for landform mapping , 2005 .

[38]  K. Blake.  Common origin for De Geer moraines of variable composition in Raudvassdalen, northern Norway , 2000 .

[39]  L. Mayer.  Frontiers in Seafloor Mapping and Visualization , 2006 .

[40]  G. Prichonnet,et al.  Late Glacial De Geer moraines with glaciofluvial sediment in the Chapais area, Québec (Canada) , 2008 .

[41]  Chris D. Clark,et al.  Mega‐scale glacial lineations and cross‐cutting ice‐flow landforms , 1993 .

[42]  J. Menzies.  A review of the literature on the formation and location of drumlins , 1979 .

[43]  V. K. Prest,et al.  Late Wisconsinan and Holocene History of the Laurentide Ice Sheet , 2008 .

[44]  H. Josenhans,et al.  Dynamics of the Laurentide Ice Sheet in Hudson Bay, Canada , 1990 .

[45]  E. Larsen,et al.  Formation of De Geer moraines and implications for deglaciation dynamics , 1991 .

[46]  B. Loncarevic,et al.  Offshore continuation of Meguma Terrane, southwestern Nova Scotia , 1989 .

[47]  M. Canals,et al.  Deep sea-floor evidence of past ice streams off the Antarctic Peninsula , 2000 .

[48]  Drumlinization and drumlin-forming instabilities: viscous till mechanisms , 1998 .

[49]  H. Sejrup,et al.  Configuration, history and impact of the Norwegian Channel Ice Stream , 2003 .

[50]  C. Wentworth.  A Scale of Grade and Class Terms for Clastic Sediments , 1922, The Journal of Geology.

[51]  Mattar,et al.  Tributaries of West Antarctic Ice Streams Revealed by RADARSAT Interferometry. , 1999, Science.

[52]  P. Möller,et al.  Marginal formation of De Geer moraines and their implications to the dynamics of grounding‐line recession , 2005 .

[53]  G. Fader,et al.  A conceptual model of the deglaciation of Atlantic Canada , 2006 .

[54]  J. Shaw,et al.  Palaeogeography of Atlantic Canada 13–0 kyr , 2002 .