Ice-wedge casts in Late Wisconsinan glaciofluvial deposits, southern Ontario, Canada

2005 ◽  
Vol 42 (12) ◽  
pp. 2117-2126 ◽  
Author(s):  
Cunhai Gao
Keyword(s):  
Window Of Opportunity ◽  
Southern Ontario ◽  
Braided Rivers ◽  
Drifting Snow ◽  
Close Proximity ◽  
Glaciofluvial Deposits ◽  
Ice Wedge ◽  
Late Wisconsinan ◽  
Sand And Gravel ◽  
Contraction And Expansion

Ice-wedge casts in Late Wisconsinan glaciofluvial sand and gravel deposits in southern Ontario taper downwards to form a V- or funnel-shaped morphology, ranging from 1 to over 3 m deep and from 1.0 to 2.5 m wide at the top. Pressure-derived primary structures, caused by repeated thermal contraction and expansion, include upturned strata, realigned stones, and small folds in the enclosing sediments. Although paleotemperature is difficult to estimate, the presence of ice-wedge casts testifies to the former presence of permafrost under prevailing periglacial conditions over this area. The regional till stratigraphy constrains the timing of ice-wedge growth to ca. 15 000 to ca. 13 000 BP. At this time, newly exposed terrains would have occurred in an interlobate area where severe climate created favourable conditions for permafrost to develop due to the close proximity to the receding ice. Inactive areas in braided rivers such as raised topographic surfaces and sand-filled channels with limited vegetation cover and minimal capability to trap drifting snow would have greatly enhanced ice-wedge growth. Rapid climatic amelioration and vegetation colonization across this area beginning ca. 13 000 BP probably slowed or stopped the growth of ice wedges. This limited window of opportunity, both geographically and in time, probably accounts for the limited occurrence of ice-wedge casts in southern Ontario.

Origin of vertical shafts in bedrock along the Eramosa River valley near Guelph, southern Ontario

2002 ◽  
Vol 39 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Micheal Kunert ◽  
Mario Coniglio
Keyword(s):  
Fine Sediment ◽  
River Valley ◽  
Precambrian Basement ◽  
Southern Ontario ◽  
Close Proximity ◽  
Late Wisconsinan

Numerous vertical to subvertical, cylindrical shafts occur in the rugged exposures of the Middle Silurian Amabel Formation bedrock along the Eramosa River, approximately 10 km northeast of Guelph. These shafts vary from < 1 m to 10 m in diameter, with depths as great as 12 m. They can occur as isolated depressions but more commonly are clustered closely together, and many coalesce to form sinuous bedrock walls. These depressions may contain soil, fine sediment, rubble from the surrounding dolomite bedrock, and rounded clasts of Precambrian basement lithologies. Till is conspicuously absent. These shafts occur in close proximity to cavernous pores that were formed during pre-Wisconsinan to Early Wisconsinan time, suggesting a possible karstic origin. The cylindrical shafts, however, with their greater midpoint diameters, sculpted interiors, and inclined axes, and their lack of vertical flutes and till, are more likely to have originated from glaciofluvial discharge at the end of the Late Wisconsinan. The development of these shafts may have been assisted by cavitation, which enhanced the erosional capacity of sediment-laden meltwaters.

Late Wisconsinan Ice-Wedge Polygons near Kitchener, Ontario, Canada

1972 ◽  
Vol 9 (6) ◽  
pp. 607-617 ◽  
Author(s):  
Alan V. Morgan
Keyword(s):  
Aerial Photographs ◽  
Air Temperatures ◽  
Ice Wedge ◽  
Late Wisconsinan ◽  
Sand And Gravel

Reconnaissance from a light aircraft has revealed areas of polygonal ground east of Kitchener, Ontario. Examination of aerial photographs of the same region has shown additional polygons all developed upon Port Stanley II Till. Trenching of a polygon has exposed wedge-shaped sand and gravel infilled structures interpreted as ice-wedge casts. The wedges are believed to have been active prior to 13 000 years B.P., probably under tundra conditions, with mean annual air temperatures some 25 °F (13–14 °C) cooler than present.

Trend surface analysis of major late Wisconsinan till sheets, Brantford–Woodstock area, southern Ontario

1978 ◽  
Vol 15 (6) ◽  
pp. 1025-1036 ◽  
Author(s):  
W. R. Cowan
Keyword(s):  
Strong Relationship ◽  
High Energy ◽  
Field Observations ◽  
Trend Surface Analysis ◽  
Southern Ontario ◽  
Niagara Escarpment ◽  
Regional Trends ◽  
Grade Material ◽  
Late Wisconsinan ◽  
Relationship Of

Linear and quadratic trend surfaces were computed for textural, carbonate, clast, and heavy mineral properties of the Catfish Creek (Nissouri Stadial), Port Stanley (Port Bruce Stadial), Tavistock (Port Bruce Stadial), and Wentworth (Port Huron Stadial) tills.Catfish Creek Till pebble grade material provided trend surfaces reflecting the underlying bedrock. However, an overall lack of regional trends in Catfish Creek Till is consistent with field observations that indicate remarkable uniformity for this till over several hundred square kilometres, a phenomenon that is believed to reflect the high energy of this ice sheet. Carbonates in Port Stanley Till were found to increase from east to west as the Silurian–Devonian contact was crossed. Tavistock Till was found to have increasing sand content and decreasing silt content from northwest to southeast owing to incorporation of underlying glaciofluvial sediments; pebble trends reflect the underlying bedrock for the most part. Wentworth Till trend surfaces for carbonates and pebbles show high dolomite near the Niagara Escarpment to the east and northeast with a dilution of dolomite and influx of limestone to the southwest.The strong relationship of the trend surfaces to substrate materials indicates the basal nature of the tills and the local origin of most glacial deposits. Pebble lithologies provide much information about local bedrock and drift prospectors should give close consideration to coarse fragments.

scholarly journals Glacial and Postglacial History of the White Cloud Peaks-Boulder Mountains, Idaho, U.S.A.

2007 ◽  
Vol 40 (3) ◽  
pp. 229-238 ◽  
Author(s):  
James F. P. Cotter ◽  
James M. Bloomfield ◽  
Edward B. Evenson
Keyword(s):  
Sediment Accumulation ◽  
Climatic Conditions ◽  
The North ◽  
Stratigraphic Model ◽  
Glaciofluvial Deposits ◽  
Dry Conditions ◽  
Minimum Age ◽  
Late Wisconsinan ◽  
Mount St Helens ◽  
Peak Set

ABSTRACT Glacial and glaciofluvial deposits are mapped and differentiated to develop new local, relative-age (RD) stratigraphies for the North Fork of the Big Lost River, Slate Creek and Pole Creek drainages in the White Cloud Peaks and Boulder Mountains, Idaho. This stratigraphic model expands the areal extent of the "Idaho glacial model". Volcanic ash samples collected from the study area are petrographically characterized and correlated, on the basis of mineralogy and glass geochemistry, to reference samples of identified Cascade Range tephras. Four distinct tephras are recognized including; Mount St. Helens-Set S (13,600-13,300 yr BP), Glacier Peak-Set B (11,250 yr BP), Mount Mazama (6600 yr BP) and Mount St. Helens-Set Ye (4350 yr BP). A core of lake sediments containing two tephra units was obtained from a site called "Pole Creek kettle". Pollen and sediment analyses indicate three intervals of late Pleistocene and Holocene climatic change. Cool and wet climatic conditions prevailed in the region shortly before and immediately following the deposition of the Glacier Peak-Set B ash (11,250 yr BP). Climatic warming occurred from approximately 10,500 to 6600 yr BP after which warm, dry conditions prevailed. Sediment accumulation in the kettle ceased by 4350 yr BP. The presence of Glacier Peak-Set B tephra in the base of the Pole Creek kettle core provides a minimum age of 11,250 yr BP for the retreat of valley glaciers from their Late Wisconsinan maximum position. A radiocarbon date of 8450 + 85 yr BP (SI-5181), and the presence of Mount Mazama ash (6600 yr BP) up-core support the Glacier Peak-Set B identification.

Periglacial Features Indicative of Permafrost: Ice and Soil Wedges

1976 ◽  
Vol 6 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Robert F. Black
Keyword(s):  
The United States ◽  
Pressure Effects ◽  
Freezing And Thawing ◽  
Wetting And Drying ◽  
Ice Wedge ◽  
Surface Patterns ◽  
Late Wisconsinan ◽  
Collapse Structures ◽  
Similar Soil ◽  
Permafrost Regions

Ice wedges are wedge-shaped masses of ice, oriented vertically with their apices downward, a few millimeters to many meters wide at the top, and generally less than 10 m vertically. Ice wedges grow in and are confined to humid permafrost regions. Snow, hoar frost, or freezing water partly fill winter contraction cracks outlining polygons, commonly 5–20 m in diameter, on the surface of the ground. Moisture comes from the atmosphere. Increments of ice, generally 0.1–2.0 mm, are added annually to wedges which squeeze enclosing permafrost aside and to the surface to produce striking surface patterns. Soil wedges are not confined to permafrost. One type, sand wedges, now grows in arid permafrost regions. Sand wedges are similar in dimensions, patterns, and growth rates to ice wedges. Drifting sand enters winter contraction cracks instead of ice. Fossil ice and sand wedges are the most diagnostic and widespread indicators of former permafrost, but identification is difficult. Any single wedge is untrustworthy. Evidence of fossil ice wedges includes: wedge forms with collapse structures from replacement of ice; polygonal patterns with dimensions comparable to active forms having similar coefficients of thermal expansion; fabrics in the host showing pressure effects; secondary deposits and fabric indicative of a permafrost table; and other evidence of former permafrost. Sand wedges lack open-wedge, collapse structures, but have complex, nearly vertical, crisscrossing narrow dikelets and fabric. Similar soil wedges are produced by wetting and drying, freezing and thawing, solution, faulting, and other mechanisms. Many forms are multigenetic. Many socalled ice-wedge casts are misidentified, and hence, permafrost along the late-Wisconsinan border in the United States was less extensive than has been proposed.

The Sisters Creek Formation: Pleistocene sediments representing a nonglacial interval in southwestern British Columbia at about 18 ka

1995 ◽  
Vol 32 (6) ◽  
pp. 758-767 ◽  
Author(s):  
Stephen R. Hicock ◽  
Olav B. Lian
Keyword(s):  
British Columbia ◽  
Glacial Maximum ◽  
Time Space ◽  
Late Wisconsinan ◽  
Sand And Gravel ◽  
New Time

Sisters Creek Formation is formally defined, stratotypes are established for it, and the time–space chart is updated for the Fraser Lowland, southwestern British Columbia. The Sisters Creek is a Pleistocene formation comprising in situ and reworked organic-rich sediments, and nonorganic silt, sand, and gravel. The formation was deposited during the Port Moody interstade (within the Late Wisconsinan Fraser Glaciation; δ18O stage 2) between the Coquitlam stade (early Fraser Glaciation) and the main Vashon stadial maximum that occurred about 14.5 ka. The Sisters Creek Formation represents a glacial recession in southwestern British Columbia that generally coincided with the timing of the last global glacial maximum. The new time–space chart implies that, in Fraser Lowland, the Fraser Glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains, which remained ice-covered during interstades.

A reconstruction of glacial events in southeastern New Brunswick

1991 ◽  
Vol 28 (10) ◽  
pp. 1594-1612 ◽  
Author(s):  
Marc Foisy ◽  
Gilbert Prichonnet
Keyword(s):  
New Brunswick ◽  
Ice Flow ◽  
Ice Cap ◽  
The North ◽  
Lithostratigraphic Units ◽  
Glaciofluvial Deposits ◽  
Southern Border ◽  
Late Wisconsinan ◽  
Radial Outflow ◽  
North And South

Sedimentological and petrographical data obtained from five sections located north and south of the Caledonian Highlands in southeastern New Brunswick demonstrate the existence of three main till units and one glaciofluvial unit, which have been grouped in four distinct lithostratigraphic units. The lower till was deposited by a glacier that overrode the Caledonian Highlands from northwest to southeast and advanced as far as Nova Scotia during Middle(?) to Late Wisconsinan times. The overlying middle till from the north provides evidence that ice continued to advance across the Highlands from northwest toward southeast and then was partially overwhelmed by another glacier that was advancing southwest along the southern border of the Highlands: this glacier deposited a coeval middle till. During Late Wisconsinan deglaciation, ice separated into two masses: a residual ice cap with radial outflow from the Highlands; and a lobe in the Chignecto Bay, retreating toward the northeast. The existence of a plateau ice cap is demonstrated by the presence of till and glaciofluvial deposits in the upper part of all surveyed sections, and is supported by the sequence of ice flow patterns recorded by striae and the centrifugal distribution of meltwater flow indicators. The weak development of soils, the fresh appearance of till and morainic landforms, and the lack of periglacial features throughout the area, especially on the Highlands, all favour the interpretation that the Caledonian Highlands were not a nunatak during the glacial maximum of the Late Wisconsinan Substage.

Pseudo-Ice-Wedge Casts of Connecticut, Northeastern United States

1983 ◽  
Vol 20 (1) ◽  
pp. 74-89 ◽  
Author(s):  
Robert F. Black
Keyword(s):  
United States ◽  
Water Table ◽  
Physical Environment ◽  
Northeastern United States ◽  
Complex Fracture ◽  
Ice Wedge ◽  
Sand And Gravel ◽  
Coated Sand ◽  
Horizontal Layers

AbstractSince 1965, ice-wedge casts have been reported in deposits of sand and gravel in Connecticut. These are wedge forms up to 1.1 m wide and many meters high. Most are single forms, not in polygonal array. They are found in adjoining states as well. Their distribution, dimensions, structure, and fabric and an assessment of the former physical environment preclude their origin as permafrost features. They appear to be tension fractures produced by the loading of coarse clastics on fine clastics near and below the water table where sediments creep toward a stream or depression. Locally movement started with kettle formation during deglaciation. However, some wedges cut horizontal layers of iron-coated sand and gravel and must be younger than those distinctly postglacial phenomena. Moreover, modern B horizons of the overlying soil have moved down into some wedges more than 2 m, indicating that fracturing is still active today. Complex fracture fillings in bedrock also have been attributed to a permafrost origin, but this too seems unlikely.

scholarly journals Significance of Sedimentological Studies on the Wisconsinan Stratigraphy of Southern Ontario

2007 ◽  
Vol 39 (3) ◽  
pp. 255-273 ◽  
Author(s):  
David R. Sharpe ◽  
Peter J. Barnett
Keyword(s):  
Lake Basin ◽  
Glacial Ice ◽  
Southern Ontario ◽  
Depositional Processes ◽  
Stratigraphic Framework ◽  
Large Channel ◽  
Late Wisconsinan ◽  
Subglacial Meltwater ◽  
Main Effects

ABSTRACTDetailed facies mapping along Lake Erie and Lake Ontario Bluffs, plus other studies illustrate that sedimentological studies, especially those with geomorphic or landform control, have had three main effects on the Wisconsinan stratigraphy of Ontario: (1) improved understanding of depositional processes and environments of several major rock stratigraphic units, without altering the stratigraphic framework, (2) aided correlation of drift sequences, and (3) questioned previous interpretations and stratigraphic correlations of drift sequences. Thus sedimentological analysis can not be separated from stratigraphy because the interpretation of depositional environnments of many mapped strata relies on their geometry and the inclusion of regional data. The geomorphic control provided by sedimentological study of surface landforms is also important because assessment of older buried sediments such as those at the Scarborough Bluffs has been hampered by the failure to determine landform control. The Late Wisconsinan stratigraphy of Southern Ontario generally remains unchanged, except for questions on the role of climate versus ice margin dynamics. The pre-Late Wisconsinan stratigraphy is scarce and not well defined, yet sedimentary studies support the presence of glacial ice in the Ontario Lake basin for all of the Middle Wisconsinan and possibly earlier, including the formation of the Scarborough delta. Large channel cut and fill sequences in the Toronto area (Pottery Road Formation), initially interpreted as resulting from subaerial erosion, were probably formed by subaqueous or subglacial meltwater erosion. If so, the pre-Late Wisconsinan stratigraphy in southern Ontario changes because the Pottery Road Formation may not be an Early Wisconsinan correlative of the St. Pierre beds. The channel example illustrates that stratigraphie correlation without sedimentological investigations may be misleading.

Laurentide glaciation in west-central Alberta: a single (Late Wisconsinan) event

1989 ◽  
Vol 26 (2) ◽  
pp. 266-274 ◽  
Author(s):  
David G. E. Liverman ◽  
N. R. Catto ◽  
N. W. Rutter
Keyword(s):  
Canadian Shield ◽  
Similar Sequence ◽  
Sedimentary Sequences ◽  
Base Level ◽  
The North ◽  
West Central ◽  
Braided Stream ◽  
Stream System ◽  
Late Wisconsinan ◽  
Sand And Gravel

The Grande Prairie region in west-central Alberta shows evidence of Late Wisconsinan Laurentide glaciation in the form of a widespread till, containing abundant erratic clasts derived from the Canadian Shield. Two sections, located on the Smoky River at Watino and on the Simonette River 80 km to the southwest, expose sediment lying stratigraphically below the till. A similar sequence is exposed in both localities: 5–10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt. The gravel contains no Laurentide erratics and is thus preglacial. The contact between the basal gravel and the overlying sand and silt is sharp and conformable. 14C dates from the base of the Simonette section and throughout the Watino section suggest a Middle Wisconsinan age. Thus, the sediment exposed is interpreted as a conformable Middle Wisconsinan sequence. The sedimentary sequences were deposited in a moderate- to low-energy braided stream system flowing towards the north. The general fining-up trend in the sections was produced as a result of channel abandonment, rather than by a change in regional base level. The sand and gravel units contain no material derived from the Canadian Shield. Consequently, the surface till is Late Wisconsinan, and represents the only Laurentide glaciation in this area of Alberta.

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