Late Pleistocene Alpine Glaciers and the Cordilleran Ice Sheet at Washington Pass, North Cascade Range, Washington

1975 ◽  
Vol 7 (1) ◽  
pp. 25 ◽  
Author(s):  
Richard B. Waitt
Keyword(s):  
Late Pleistocene ◽  
Ice Sheet ◽  
Cascade Range ◽  
Alpine Glaciers ◽  
Cordilleran Ice Sheet

Reconstructing the Cordilleran Ice Sheet in northern British Columbia during the Late Pleistocene climate reversals

2020 ◽  
Author(s):  
Helen Dulfer ◽  
Martin Margold
Keyword(s):  
British Columbia ◽  
Late Pleistocene ◽  
Regional Scale ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Western Canada ◽  
Alpine Glaciers ◽  
Pleistocene Climate ◽  
Cordilleran Ice Sheet ◽  
Exposure Ages

<p>The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet. Deglaciation of the CIS following the Last Glacial Maximum (LGM) directly affected atmosphere and ocean circulation, eustatic sea level, and human migration from Asia to North America. It has recently been shown that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. Data on glacial isostatic adjustment and cosmogenic nuclide exposure ages indicate that abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the Younger Dryas cooling caused the expansion of alpine glaciers across the mountains of western Canada. However, the mountainous subglacial terrain makes it challenging to reconstruct the regional-scale deglaciation dynamics of the ice sheet, and its configuration during this period of rapid change remains poorly constrained. </p><p>Here we use the glacial landform record to reconstruct the ice sheet configuration for the central sector of the CIS, over the Cassiar and Omineca Mountains in northern British Columbia, during the Late Pleistocene climate reversals. We present the first regional-scale reconstruction of the CIS following the Bølling-Allerød warming, whereby the ice sheet was reduced to a labyrinth of valley glaciers fed by ice dispersal centres located over the Skeena Mountains in the south and Coast Mountains in the west. Additionally, numerous lateral and terminal late glacial moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS during the Younger Dryas. Cross-cutting relationships indicate that the valley glaciers of the CIS were slower to respond to the Younger Dryas cooling than the mountain glaciers.</p>

Tephrochronologic Constraints on the Late Pleistocene History of the Southern Margin of the Cordilleran Ice Sheet, Western Washington

1997 ◽  
Vol 47 (2) ◽  
pp. 140-146 ◽  
Author(s):  
James E. Begét ◽  
Mary J. Keskinen ◽  
Kenneth P. Severin
Keyword(s):  
Lake Sediments ◽  
Late Pleistocene ◽  
Ice Sheet ◽  
Cascade Range ◽  
Southern Margin ◽  
Ash Layer ◽  
History Of ◽  
Western Washington ◽  
Cordilleran Ice Sheet ◽  
Eastern Washington

An ash layer that appears geochemically correlative with Mt. St. Helens tephra set S occurs in a sequence of Pleistocene lake sediments in the Ohop Valley of the southern Puget Lowland, below Vashon till deposited during the maximum late Pleistocene advance (Fraser Glaciation) of the Puget Lobe of the Cordilleran Ice Sheet. The Puget Lobe reached its maximum southern extent ca. 14,000–14,500 yr B.P., and at least part of set S is evidently somewhat older. Previous radiocarbon and thermoluminescence dates for set S have ranged from 13,000 to 16,000 yr B.P.Geochemically correlative deposits of set S tephra occur in slackwater sediments coeval with the Missoula Floods in eastern Washington, produced by jökulhlaups through the Purcell Trench Lobe of the Cordilleran Ice Sheet. These relationships suggest that advances of glacier lobes on the southern margin of the Cordilleran Ice Sheet were nonsynchronous, as the Pucell Trench lobe east of the Cascade Range advanced to its maximum southern extent prior to the time of the eruption of set S, before the Puget Lobe west of the Cascades reached its maximum southern extent.

scholarly journals Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene

2017 ◽  
Vol 43 (2) ◽  
pp. 467 ◽  
Author(s):  
J.L. Riedel
Keyword(s):  
British Columbia ◽  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Cascade Range ◽  
North Cascades ◽  
Alpine Glacier ◽  
The North ◽  
Alpine Glaciers ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a punctuated retreat to valley heads. In the south, beyond the reach of ice sheet glaciation, several end moraines were deposited after the LGM. Moraines marking a re-advance of alpine glaciers to <5 km below modern glaciers were deposited from 13.7 to 11.6 ka.The Cordilleran Ice Sheet flowed south from near 52° north latitude in British Columbia into the North Cascades. At its maximum size the ice sheet covered more than 500 km2 and had a surface elevation of 2200 m in upper Skagit valley. Deglaciation commenced about 16 ka by frontal retreat of ice flanking the mountains. Surface lowering eventually exposed regional hydrologic divides and stranded ice masses more than 1000 m thick in valleys. Isolated fragments of the ice sheet disintegrated rapidly from 14.5 to 13.5 ka, with the pattern of deglaciation in each valley controlled by valley orientation, topography, and climate. Like alpine glaciers to the south, retreat of the ice sheet remnants was slowed by millennial scale climate fluctuations that produced at least one large recessional moraine, and multiple lateral moraines and kame terraces from elevations of 200-1400 m in most valleys. Large volumes of glacial meltwater flowed through the North Cascades and was concentrated in the Skagit and Methow rivers. Outburst floods from deep proglacial lakes spilled across divides and down steep canyons, depositing coarse gravel terraces and alluvial fans at valley junctions.Climate at the LGM was characterized by a mean summer temperature 6 to 7 ºC cooler than today, and 40% lower mean annual precipitation. Persistence of this climate for thousands of years before the LGM caused a 750-1000 m decrease in alpine glacier equilibrium line altitudes (ELA). In the southern North Cascades at 16 ka, glacial ELAs were 500-700 m lower than today, and during advances from 13.7 to 11.6 ka alpine glacier ELAs were 200-400 m lower.

Lake Tapps Tephra: An Early Pleistocene Stratigraphic Marker in the Puget Lowland, Washington

1987 ◽  
Vol 28 (3) ◽  
pp. 340-355 ◽  
Author(s):  
J. A. Westgate ◽  
D. J. Easterbrook ◽  
N. D. Naeser ◽  
R. J. Carson
Keyword(s):  
Early Phase ◽  
Ice Sheet ◽  
Early Pleistocene ◽  
Southern Sector ◽  
Alpine Glaciers ◽  
Cordilleran Ice Sheet

AbstractThe rhyolitic Lake Tapps tephra was deposited about 1.0 myr ago, shortly after culmination of the early phase of the Salmon Springs Glaciation in the Puget Lowland. It is contained within sediments that were deposited in ponds or lakes in front of the reteating glacier. An herb-dominated tundra existed in the southern Puget Lowland at that time. Lake Tapps tephra is most likely the product of an eruption that in part was phreatomagmatic. It forms an early Pleistocene stratigraphic marker across the southern sector of the Puget Lowland and provides a link between Puget lobe sediments of the Cordilleran Ice Sheet and sediments deposited by Olympic alpine glaciers.

10Be dating of late Pleistocene megafloods and Cordilleran Ice Sheet retreat in the northwestern United States

Geology ◽  
2017 ◽  
Vol 45 (7) ◽  
pp. 583-586 ◽  
Author(s):  
Andrea M. Balbas ◽  
Aaron M. Barth ◽  
Peter U. Clark ◽  
Jorie Clark ◽  
Marc Caffee ◽  
...  
Keyword(s):  
United States ◽  
Late Pleistocene ◽  
Ice Sheet ◽  
10Be Dating ◽  
Cordilleran Ice Sheet

Glacier Peak Tephra in the North Cascade Range, Washington: Stratigraphy, Distribution, and Relationship to Late-Glacial Events

1978 ◽  
Vol 10 (1) ◽  
pp. 30-41 ◽  
Author(s):  
Stephen C. Porter
Keyword(s):  
Far East ◽  
Ice Sheet ◽  
Late Glacial ◽  
Cascade Range ◽  
Time Layer ◽  
Terminal Moraine ◽  
The North ◽  
Stratigraphic Position ◽  
Cordilleran Ice Sheet ◽  
Glacial Time

Pumiceous tephra, resulting from multiple eruptions of Glacier Peak volcano in late-glacial time, mantles much of the landscape in the eastern North Cascade Range and extends eastward beyond the Columbia River as a thinner discontinuous deposit. Within about 25 km of the source, the tephra is divisible into as many as nine layers, distinguishable in the field on the basis of color, grain size, thickness, and stratigraphic position. Three principal layers, designated G (oldest), M, and B, are separated from one another by thinner, finer layers. Layer G has been found as far east as Montana and southern Alberta, whereas layer B has been identified as far as western Wyoming. By contrast, layer M trends nearly south, paralleling the crest of the Cascade Range. Available 14C dates indicate that the tephra complex was probably deposited between about 12,750 and 11,250 years ago. Glacier Peak tephra overlies moraines and associated outwash east of the Cascade Crest that were deposited about 14,000 years ago. Unreworked tephra occurs within several kilometers of many valley heads implying that major valley glaciers had nearly disappeared by the time of the initial tephra fall. Distribution of tephra indicates that the southern margin of the Cordilleran Ice Sheet had retreated at least 80 km north of its terminal moraine on the Waterville Plateau by the time layer G was deposited. Late-glacial moraines of the Rat Creek advance lie within the fallout area of layer M but lack the tephra on their surface implying that they were built subsequent to the eruption of this unit. Moraines of the Hyak advance at Snoqualmie Pass, which are correlated with the Rat Creek moraines farther north, were constructed prior to 11,000 14C years ago. The late-glacial advance along the Cascade Crest, therefore, apparently culminated between about 12,000 and 11,000 14C years ago and was broadly in phase with the Sumas readvance of the Cordilleran Ice Sheet in the Fraser Lowland which occurred between about 11,800 and 11,400 14C years ago.

Vashon Drift: definition of the formation in the Georgia Depression, southwest British Columbia

1985 ◽  
Vol 22 (5) ◽  
pp. 748-757 ◽  
Author(s):  
Stephen R. Hicock ◽  
John E. Armstrong
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Southwestern Part ◽  
Maximum Expansion ◽  
Source Areas ◽  
Alpine Glaciers ◽  
Time Space ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet ◽  
Definition Of

Vashon Drift was deposited during the Fraser Glaciation (late Wisconsinan) at the time of maximum expansion of the southwestern part of the Cordilleran ice sheet when it filled the Georgia Depression about 14 500 years ago. The drift is present throughout the depression and comprises till and glaciofluvial and glaciolacustrine sediments derived from source areas surrounding the coastal trough. It is overlain by Capilano Sediments and underlain by Quadra Sand, also of Fraser age. Drift deposition was diachronous and complex, probably caused by alpine glaciers coalescing in the trough with the ice margin repeatedly grounding and floating in seawater. Studies of bedrock striae, till fabrics, and clast provenance reveal that Vashon ice movement was generally southward, although locally controlled by topography. A time–space diagram is presented that confirms the long-held hypothesis that advance and decay of Vashon ice were rapid.

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