Un lac glaciaire dans la région du lac Minto—Nouveau-Québec

1983 ◽  
Vol 20 (9) ◽  
pp. 1488-1492 ◽  
Author(s):  
Bernard Lauriol ◽  
James T. Gray
Keyword(s):  
Main Part ◽  
River Valley ◽  
Glacial Lake ◽  
Glacial Ice ◽  
Isostatic Rebound ◽  
Raised Beaches

The presence of raised beaches around Lake Minto, northern Quebec, and the washing of till in the upper part of the Leaf River valley are attributed to the existence of a glacial lake. It drained westward into the Tyrrell Sea and was dammed in the east by glacial ice that occupied the main part of the Leaf River valley. The disappearance of this ice prior to 5200 years BP led to rapid drainage of the glacial lake into an arm of the D'Iberville Sea. Postglacial isostatic rebound has subsequently led to warping of the highest water plane associated with this glacial lake, as well as those of the postglacial seas.

The late Wisconsinan olistostrome of the lower Coppermine River valley, Northwest Territories

1986 ◽  
Vol 23 (11) ◽  
pp. 1700-1708 ◽  
Author(s):  
Denis A. St-Onge ◽  
Jean Lajoie
Keyword(s):  
Debris Flows ◽  
Late Quaternary ◽  
Fine Sand ◽  
Coarse Sand ◽  
Coarse Fraction ◽  
River Valley ◽  
Glacial Lake ◽  
The North ◽  
Geologic Record ◽  
Coppermine River

The late Quaternary olistostrome exposed in the lower Coppermine River valley fills a paleovalley that ranges in apparent width from 150 to 400 m and was cut into Precambrian bedrock before the last glaciation. The olistostrome is here named the Sleigh Creek Formation. The coarse fraction of the formation is matrix supported; beds are massive or reversely graded and have sharp, nonerosive contacts. These characteristics suggest deposition of the coarse fraction by debris flows. The olistostrome sequence is bracketed by, and wedged into, a marine rhythmite sequence, which indicates that deposition occurred in a marine environment.About 10 500 years BP glacier ice in the Coronation Gulf lowland dammed the valley to the south, which was occupied by glacial Lake Coppermine. Sediments accumulated in this lake in a 30 m thick, coarsening upward sequence ranging from glaciolacustrine rhythmites of silt and fine sand at the base to coarse sand alluvium, and deltaic gravels at the top. As the Coronation Gulf lowlands became ice free, the Coppermine River reoccupied its former drainage course to the north. The steep south to north gradient and rapid downcutting by the river through the glacial lake sediments produced unstable slope conditions. The resulting debris flows filled a bedrock valley network below the postglacial sea level, forming the diamicton sequence.The interpretation of the Sleigh Creek Formation raises questions concerning silimar diamicton deposits usually defined as "flowtills." More generally, the results of this study indicate that care must be used when attempting paleogeographic reconstructions of "glaciogenic" deposits in marine sequences in any part of the geologic record.

Status of Glacial Lake Columbia during the Last Floods from Glacial Lake Missoula

1987 ◽  
Vol 27 (2) ◽  
pp. 182-201 ◽  
Author(s):  
Brian F. Atwater
Keyword(s):  
Columbia River ◽  
River Valley ◽  
Glacial Lake ◽  
Grand Coulee

AbstractThe last floods from glacial Lake Missoula, Montana, probably ran into glacial Lake Columbia, in northeastern Washington. In or near Lake Columbia's Sanpoil arm, Lake Missoula floods dating from late in the Fraser glaciation produced normally graded silt beds that become thinner upsection and which alternate with intervals of progressively fewer varves. The highest three interflood intervals each contain only one or two varves, and about 200–400 successive varves conformably overlie the highest flood bed. This sequence suggests that jökulhlaup frequency progressively increased until Lake Missoula ended, and that Lake Columbia outlasted Lake Missoula. The upper Grand Coulee, Lake Columbia's late Fraser-age outlet, contains a section of 13 graded beds, most of them sandy and separated by varves, that may correlate with the highest Missoula-flood beds of the Sanpoil River valley. The upper Grand Coulee also contains probable correlatives of many of the approximately 200–400 succeeding varves, as do nearby parts of the Columbia River valley. This collective evidence casts doubt on a prevailing hypothesis according to which one or more late Fraser-age floods from Lake Missoula descended the Columbia River valley with little or no interference from Lake Columbia's Okanogan-lobe dam.

Glacial Lake Whittlesey: the probable ice frontal position in the eastern end of the Erie basin

1979 ◽  
Vol 16 (3) ◽  
pp. 568-574 ◽  
Author(s):  
Peter J. Barnett
Keyword(s):  
Lake Erie ◽  
Plane Curve ◽  
Glacial Lake ◽  
Glacial Ice ◽  
Data Points ◽  
Glacial Advance

Glacial Lake Whittlesey is related to the glacial advance during the Port Huron Stadial, approximately 13 000 radiocarbon years BP. This episode has previously been thought to be represented, in the eastern end of the Lake Erie basin, by the Paris and Galt Moraines and the deposition of the Wentworth Till in southern Ontario.However, the location of Whittlesey shoreline features suggests that this lake existed during the subsequent advance which deposited the Halton Till. A 'Halton' ice-contact delta, at Summit, Ontario, coincides with the Lake Whittlesey water plane curve constructed from 72 data points around Lakes Huron and Erie.It is suggested, therefore, that the glacial ice advance represented by the Halton Till, based on its relationship to Lake Whittlesey, has an age of about 13 000 radiocarbon years BP (Port Huron Stadial) and that the Wentworth Till (Paris and Galt Moraines) is of Port Bruce Stadial age.

Paleomagnetic Evidence for Repeated Glacial Lake Missoula Floods from Sediments of the Sanpoil River Valley, Northeastern Washington

1991 ◽  
Vol 35 (2) ◽  
pp. 197-207 ◽  
Author(s):  
William K. Steele
Keyword(s):  
Secular Variation ◽  
Geomagnetic Field ◽  
Remanent Magnetization ◽  
River Valley ◽  
Field Direction ◽  
Glacial Lake ◽  
Laboratory Measurements ◽  
Eastern Washington

AbstractRecent explanations of widespread rhythmically layered sediments in eastern Washington as the result of repeated great floods from glacial Lake Missoula implicitly suggest a paleomagnetic test for validity. If each conjectural flood layer is separated by years or decades, as hypothesized, a sequence of several such flood beds should record measurable secular variation in geomagnetic field direction. In the Sanpoil River valley where the rhythmite sequences are thought to have been deposited in glacial Lake Columbia, the paleomagnetic test consists of measuring remanent magnetization (RM) directions for thick, upwardly fining beds inferred to be sediments deposited by the influx of flood waters from glacial Lake Missoula into glacial Lake Columbia. Laboratory measurements of samples from three widely spaced sections along the Sanpoil River yield RM vectors with erratic inclinations, apparently affected by varying contributions of inclination error and (or) compaction shallowing, but with declinations that generally differ statistically from one flood to the next and that show the same west-to-east trend at all three locations. The rates of declination change inferred from these data are consistent with modern rates, thus providing the first geophysical evidence supporting the timing in the tens-of-floods theory.

Late Quaternary paleoenvironments and growth of intrusive ice in eastern Beringia (Eagle River valley, northern Yukon, Canada)

2010 ◽  
Vol 47 (7) ◽  
pp. 941-955 ◽  
Author(s):  
Bernard Lauriol ◽  
Denis Lacelle ◽  
Mélanie St-Jean ◽  
Ian D. Clark ◽  
Grant D. Zazula
Keyword(s):  
Late Quaternary ◽  
Maximum Level ◽  
River Valley ◽  
Bison Bison ◽  
Glacial Lake ◽  
Silty Clay ◽  
Uneven Surface ◽  
Ground Ice ◽  
Fluvial Terrace ◽  
Cut Marks

In this study, the sediments exposed in a fluvial terrace and in the headwall of a thaw slump in the Eagle River valley, northern Yukon, provide new data about the timing of flooding of glacial Lake Old Crow, the formation of massive ground ice bodies, and the vegetation and the fauna in eastern Beringia during the late Quaternary. The stratigraphy and radiocarbon ages establish the following chronology of events: (1) a gravel fluvial terrace was deposited by an overflow from glacial Lake Hughes into glacial Lake Old Crow; (2) a carbonate silty clay was deposited during the maximum level of glacial Lake Old Crow at 15 120 14C year BP; (3) permafrost and large intrusive ice bodies aggraded through the glaciolacustrine and underlying sediments following the drainage of glacial Lake Old Crow from the site; (4) at 11 290 14C year BP, a shrub–sedge tundra colonized an uneven surface deformed by the bodies of ground ice; (5) a thaw lake drained at 6730 14C year BP after flooding the site; (6) during the early Holocene and from the previous major event onwards, material from the slope nearby the site buried the previous organic and inorganic sediment and the ice bodies; and (7) a bison (Bison) vertebra with conspicuous cut marks was dated to 12 210 ± 70 14C year BP. The age from the bison bone is amongst the most recent of the late Pleistocene bison specimens yet found in eastern Beringia.

scholarly journals Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective from Kane Basin

2018 ◽  
Vol 14 (12) ◽  
pp. 1991-2010 ◽  
Author(s):  
Eleanor Georgiadis ◽  
Jacques Giraudeau ◽  
Philippe Martinez ◽  
Patrick Lajeunesse ◽  
Guillaume St-Onge ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Sediment Geochemistry ◽  
Glacial Ice ◽  
Isostatic Rebound ◽  
Nares Strait ◽  
Postglacial History ◽  
Marine Sedimentation ◽  
History Of ◽  
Ice Conditions ◽  
Insight Into

Abstract. A radiocarbon-dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that provide new insight into the evolution of ice sheet configuration in Nares Strait. Proglacial marine sedimentation at the core site initiated ca. 9.0 cal ka BP following the retreat of grounded ice. Varying contributions of sand and clasts suggest unstable sea ice conditions and glacial activity, which subsisted until ca. 7.5 cal ka BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. An interval rich in ice-rafted debris (IRD) is interpreted as the collapse of the ice saddle in Kennedy Channel ca. 8.3 cal ka BP that marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between ca. 8.3 and ca. 7.5 cal ka BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at about 8.1 cal ka BP as evidenced by a noticeable change in sediment geochemistry in our core. The gradual decrease in carbonate inputs to Kane Basin between ∼8.1 and ∼4.1 cal ka BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Reduced iceberg delivery from 7.5 to 1.9 cal ka BP inferred by our dataset may be linked to the retreat of the bordering ice sheets on land that decreased their number of marine termini.

scholarly journals III.—The Sea against Rivers: or the Origin of Valleys

1866 ◽  
Vol 3 (22) ◽  
pp. 155-160 ◽  
Author(s):  
D. Mackintosh
Keyword(s):  
Glacial Lake ◽  
Low Levels ◽  
Raised Beaches ◽  
Made In

In a former article I endeavoured to show that the more abrupt inequalities of the earth's surface, so far as they consist of escarpments with their associated phenomena, are chiefly due to the former action of the sea. Before proceeding to consider the origin of Valleys, I find it necessary to refer to a statement I made in the last article about Raised Beaches (page 69). My object was merely to show that the preservation of numerous terraces in the Cretaceous districts of Wilts and Dorset furnished an evidence of limited subaërial denudation since these terraces were formed. The terraces to which I alluded, principally occur at comparatively low levels; and that they are raised beaches can, I think, be clearly proved. But this is not necessary, so far as the present controversy is concerned; for the preservation of terraces in gravel (more easily worn away than chalk, according to the subaërialists), which all admit are either raised sea-beaches, or glacial-lake-beaches (such as those of Glenroy), afford an equally convincing proof of the impotence of rain as a denuding agent.

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