The internal structure of glacial landforms: an example from the Halton till plain, Scarborough Bluffs, Ontario

Sharpe, D R

doi:10.1111/j.1502-3885.1988.tb00119.x

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…Passive sedimentation is documented by the generally conformable contact with NT and the undeformed Thorncliffe basin sequence. This style of passive sedimentation is supported by local evidence of melt-out (Sharpe 1988) based on boulder scour marks and NT draped on sandy Thorncliffe fans (Fig. 10c).…”

Section: Laurentide Till Depositionmentioning

confidence: 58%

“…10c; Sharpe et al 2002b); such draping was also identifiable along lake bluff sections to the east of the LT (Brookfield and Martini 1999). At the Scarborough Bluffs, boulders were observed to project below the base of NT (Sharpe 1988, fig. 12; note, originally misidentified as Halton Till); bedding in underlying stratified TF sand displays scouring around the clast projecting from the till.…”

Section: Newmarket Tillmentioning

confidence: 90%

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Geological framework of the Laurentian trough aquifer system, southern Ontario

2018

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The Laurentian trough (LT), a depression >100 km long, >3000 km2 in area, and 100 m deep at the base of the Niagara Escarpment, extends from within Georgian Bay to Lake Ontario. It has a complex erosional history and is filled and buried by up to 200 m of interglacial and glacial sediment. The primary depression fronts a cuesta landscape and is attributed to differential erosion by fluvial, glacial, and glaciofluvial processes, exposing Ordovician rocks along the Canadian Shield margin. The fill succession includes sediments from the last two glacial periods (Illinoian, Wisconsinan) and the intervening interglacial time (Sangamonian), a poorly dated succession with at least three regional unconformities. A subaerial (interglacial, Don Formation) unconformity relates to low base level mainly preserved in lows of the LT, succeeded by a long period of rising water levels and glaciolacustrine conditions as ice advanced into the Lake Ontario basin. A second unconformity, within the Thorncliffe Formation, is the result of rapid channel erosion to bedrock, forming an ∼north–south network filled with coarse-grained glaciofluvial, transitional to fine-grained glaciolacustrine subaqueous fan sediment. The overlying drumlinized Newmarket Till, up to 50 m thick, is a distinct regional unit with a planar to undulating base. A third unconformity event eroded Newmarket Till, locally truncating it and underlying sediment to bedrock. Three younger sediment packages, Oak Ridges Moraine (channel and ridge sediment), Halton, and glaciolacustrine overlie this erosion surface. Significant regional aquifers are hosted within the LT. Upper Thorncliffe Formation sediments, north–south glaciofluvial channel–fan aquifers, are protected by overlying mud and Newmarket Till aquitards. Similarly, Oak Ridges Moraine sediments comprise a north–south array of glaciofluvial channel–fans and east–west fan aquifers, locally covered by silt–clay rhythmite and till aquitards.

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Section: Laurentide Till Depositionmentioning

confidence: 58%

Section: Newmarket Tillmentioning

confidence: 90%

Geological framework of the Laurentian trough aquifer system, southern Ontario

2018

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“…Newmarket Till surface between ORM and Lake Ontario Sharpe 1988;Golder and Associates 1999). ice advancing out of Lake Ontario basin (Karrow 1967;Eyles 2002).…”

Section: R a F Tmentioning

confidence: 99%

A revised depositional setting for Halton sediments in the Oak Ridges Moraine area, Ontario

Sharpe

Russell

2016

Can. J. Earth Sci.

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Outcrop and continuous core descriptions, high-resolution seismic profiling, and downhole geophysical data are integrated with detailed mapping to update sedimentary and stratigraphic frameworks for Halton sediment, a complex mud-rich lithofacies succession. Halton sediment has a gradational transition from underlying Oak Ridges Moraine (ORM) sediment and can abruptly overlie Newmarket Till. Halton strata thin and fine upwards from ORM sand and gravel to graded sand, silt, and clay rhythmites, with muddy diamicton and sand and gravel interbeds. These strata fill basin lows and drape ORM sediment lobes and Newmarket Till drumlins. These distinct sedimentary units are here informally referred to as Halton formation. Formal Halton Till is a proposed subunit of Halton formation, a clay-rich diamicton mapped from Niagara Peninsula to ORM and eastward. Halton Till has traditionally been inferred to represent a late, climatically induced readvance of grounded ice from Lake Ontario basin, which deposited drumlinized till. Halton sedimentary architecture and facies are interpreted as deposition in an ice-marginal or subglacial lake bounded by Niagara Escarpment, ORM, and grounding line oscillation of a semi-buoyant ice shelf or ice lid over Lake Ontario. Large volumes of transported mud are distal equivalents of ORM high-energy gravelly sand deposits to the east. Glaciolacustrine sedimentation is indicated by mud-rich texture and laminations. Clay–silt rhythmites, diamicton interbeds, and intraclasts indicate ponding, debris flow, and periodic ice loading. Halton depositional model may apply to other muddy diamictons in Great Lakes basins. Halton formation facies are not compatible with proposed grounded ice stream events in Lake Ontario basin.

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