Buried bedrock valleys and glacial and subglacial meltwater erosion in southern Ontario, Canada

2011 ◽  
Vol 48 (5) ◽  
pp. 801-818 ◽  
Author(s):  
Cunhai Gao
Keyword(s):  
Drainage System ◽  
Geological Mapping ◽  
Glacial Erosion ◽  
Diagnostic Features ◽  
Simple Modification ◽  
Southern Ontario ◽  
Georgian Bay ◽  
Niagara Escarpment ◽  
Mechanical Weathering ◽  
Subglacial Meltwater

Morphometric features from a recently compiled bedrock topography map by the Ontario Geological Survey suggest a glacial erosion origin for the buried large bedrock valleys and troughs in southern Ontario. The bedrock valleys at Milverton, Wingham and Mount Forest are tunnel valleys, resulting from subglacial meltwater erosion beneath the Huron ice lobe, probably during or shortly after the Late-Wisconsinan glacial maximum. Diagnostic features for this interpretation include abrupt valley beginning and termination, uneven longitudinal valley profiles and up-slope gradients. The Dundas bedrock valley is the western extension of the Lake Ontario Basin. No comparable bedrock valleys were found to connect it to the Milverton valley for a joint drainage system as previously suggested. The Laurentian bedrock trough is the southeastward extension of the Georgian Bay Basin, both developed along shale bedrock between the Precambrian shield highlands and the Niagara Escarpment, resulting from long-term mechanical weathering associated with Pleistocene glacial erosion. This bedrock low has a floor that exceeds 50 km in width and is 26 m and more below the current water level of Georgian Bay. It could drain Georgian Bay should the drift cover be removed. There is no evidence to suggest that a preglacial river channel, if it existed, is still preserved in the floor of the Laurentian trough as previously suggested. The framework for an intensely glacially sculpted bedrock surface differs from the previous view for simple modification of a preglacial landscape and is, therefore, important in regional subsurface geological mapping and groundwater studies.

Storm-deposited sandstones (tempestites) and related ichnofossils of the Late Ordovician Georgian Bay Formation, southern Ontario, Canada

1991 ◽  
Vol 28 (2) ◽  
pp. 266-282 ◽  
Author(s):  
Michael Kerr ◽  
Nicholas Eyles
Keyword(s):  
Foreland Basin ◽  
Detailed Examination ◽  
Middle Part ◽  
Late Ordovician ◽  
Southern Ontario ◽  
Georgian Bay ◽  
Fine Grained ◽  
Delta Plain ◽  
Niagara Escarpment ◽  
Taconic Orogeny

The Late Ordovician Geogian Bay Formation of southern Ontario, Canada, comprises up to 250 m of grey to blue–grey shales interbedded with highly fossiliferous calcareous sandstones. These strata were deposited in equatorial paleolatitudes after 448 Ma in a shallow foreland basin created by overthrusting along the eastern margin of North America (the Taconic orogeny). The Georgian Bay Formation comprises the middle part of an upward-shallowing progradational sequence from deep-water transgressive shales of the underlying Whitby Formation to muddy tidal-flat sequences of the overlying Queenston Formation. Exposures in brickyard and river cuts near Toronto, and northwards along a narrow outcrop belt along the foot of the Niagara Escarpment, show laterally extensive (100 m+), sharp-based sheets of sandstone up to 1 m thick, with gutter casts and washed-out (hypichnial) trace fossils (dominantly Planolites and Paleophycus) on their lower bedding surfaces. Detailed examination of sandstone beds in outcrop and in three boreholes that penetrate the formation shows that the beds are composed internally of a basal fossil hash layer overlain by flat, hummocky, and wave-rippled divisions. Bed tops show a variety of wave-ripple forms and are heavily bioturbated (dominantly Bifungites, Conostichus, Diplocraterion, Didymaulichnus, Teichichnus). Sandstone sheets are interpreted as storm deposits (tempestites) resulting from tropical storms (hurricanes) transporting fine-grained suspended sediment from a delta plain onto a muddy shelf to the west.

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 Large-scale integrated subglacial drainage around the former Keewatin Ice Divide, Canada reveals interaction between distributed and channelised systems

2020 ◽  
Author(s):  
Emma L. M. Lewington ◽  
Stephen J. Livingstone ◽  
Chris D. Clark ◽  
Andrew J. Sole ◽  
Robert D. Storrar
Keyword(s):  
Spatial Distribution ◽  
Dynamic Response ◽  
Large Scale ◽  
Water Pressure ◽  
Pressure Fluctuations ◽  
Drainage System ◽  
Different Types ◽  
Form Part ◽  
Subglacial Meltwater ◽  
Subglacial Drainage

Abstract. We identify and map traces of subglacial meltwater drainage around the former Keewatin Ice Divide, Canada from ArcticDEM data. Meltwater tracks, tunnel valleys and esker splays exhibit several key similarities, including width, spacing, their association with eskers and transitions to and from different types, which together suggest they form part of an integrated drainage signature. We collectively term these features 'meltwater corridors' and propose a new model for their formation, based on observations from contemporary ice masses, of pressure fluctuations surrounding a central conduit. We suggest that eskers record the imprint of a central conduit and meltwater corridors the interaction with the surrounding distributed drainage system. The widespread aerial coverage of meltwater corridors (5–36 % of the bed) provides constraints on the extent of basal uncoupling induced by basal water pressure fluctuations and variations in spatial distribution and evolution of the subglacial drainage system, which will modulate the ice dynamic response.

scholarly journals Sculpted Bedrock Forms along the Niagara Escarpment, Niagara Peninsula, Ontario

2007 ◽  
Vol 46 (2) ◽  
pp. 195-207 ◽  
Author(s):  
Keith J. Tinkler ◽  
Ronald E. Stenson
Keyword(s):  
Flow Velocity ◽  
Continuous Spectrum ◽  
Niagara Escarpment ◽  
Site Mapping ◽  
A Site ◽  
Subglacial Meltwater ◽  
Small Obstacle

ABSTRACT Assemblages of subglacial sculpted bedrock forms (p-forms; Dahl, 1965) are identified on resistant units of the Niagara Escarpment in the Niagara Peninsula, and on the Onondaga Escarpment. The scale of the features is much larger than previously recorded for bedrock glacial features in the Peninsula (Feenstra, 1981) and we suggest that there is a continuous spectrum of forms from small obstacle marks with dimensions of a few centimetres, through ridges and furrows measured in tens of metres, to promontories on the order of kilometres. Such assemblages comprise fluted surfaces with a consistent orientation between N40E and N45E, and which show very little variation within a site. Mapping the features has increased our awareness of their extent, and of the problems they pose for mechanisms proposed to explain them. The morphometry of the forms is similar to that described elsewhere, and the irregular edge of the Niagara Escarpment to oncoming flows is thought to be responsible for the prominent features described. The apparent removal of substantial bedrock blocks implies flow velocity well in excess of 3 m/s. Therefore the sculpting of the forms is attributed to fast flowing subglacial meltwater which may have had a discharge of the magnitude of 2.1 x 106 cumecs.

THE STATUS OF PARASITES OF THE APPLE MAGGOT, RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE), IN ONTARIO

1971 ◽  
Vol 103 (4) ◽  
pp. 507-512 ◽  
Author(s):  
L. G. Monteith
Keyword(s):  
Lake Ontario ◽  
Rhagoletis Pomonella ◽  
Southern Ontario ◽  
Niagara Escarpment ◽  
The Status

AbstractOpius melleus Gah. and O. lectus Gah. were the only parasites of Rhagoletis pomonella (Walsh) found in southern Ontario during a 4-year survey. The parasites were found only in the Niagara Region on the slope of the Niagara Escarpment and between it and Lake Ontario. The population of parasites was low though they appeared to be well adapted to attack R. pomonella. They were found in, or adjoining, unsprayed sites where there was shrubby growth under the trees infested by R. pomonella.

The extent of old-growth Thuja occidentalis on cliffs of the Niagara Escarpment

1991 ◽  
Vol 69 (7) ◽  
pp. 1628-1636 ◽  
Author(s):  
D. W. Larson ◽  
P. E. Kelly
Keyword(s):  
Cross Sections ◽  
Forest Ecosystems ◽  
Forest Ecology ◽  
Eastern North America ◽  
Old Growth ◽  
Southern Ontario ◽  
Thuja Occidentalis ◽  
Selective Sampling ◽  
Niagara Escarpment ◽  
Old Growth Forest

Extensive random sampling of populations of Thuja occidentalis growing on vertical cliffs of the Niagara Escarpment in southern Ontario, Canada, was conducted to determine the extent of an old-growth forest that had recently been described. Nine sites distributed along the length of the escarpment were intensively sampled and from these, 1254 increment cores or cross sections were obtained from 872 trees in all age categories. The results show that all cliffs support a broadly similar old-growth forest of stunted trees, but that statistically significant differences were found in the numbers of trees among sites. No large differences among sites were found in heights or diameters of trees. Maximum ages of 532 (sampled) and 814 years (estimated) were found in the random census, although in subsequent selective sampling, intact stems up to 1032 years were found. The incidence of fire and cutting by humans was also measured, but little evidence of such disturbances was found. It is concluded that exposed cliff faces of the Niagara Escarpment support one of the oldest, most extensive, and most intact old-growth forest ecosystems yet described for eastern North America. The opportunities for the study of basic forest ecology and especially for dendrochronology are considerable. Key words: Thuja occidentalis, old growth, Niagara Escarpment, cliff, age structures.

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