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TitleA revised depositional setting for Halton sediments in the Oak Ridges Moraine area, Ontario
AuthorSharpe, D RORCID logo; Russell, H A JORCID logo
SourceCanadian Journal of Earth Sciences vol. 53, 2016 p. 1-23, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150259
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
NTS30M; 30N; 31D; 31C
AreaOak Ridges Moraine
Lat/Long WENS -80.0000 -76.0000 45.0000 43.0000
Subjectshydrogeology; sedimentology; surficial geology/geomorphology; groundwater; groundwater resources; depositional environment; terrain analysis; terrain types; sedimentary facies; grain size analyses; sedimentary rocks; moraines; glacial deposits; glaciolacustrine deposits; drumlins; Halton sediments; Oak Ridges Moraine; Halton Till; Newmarket Till; Quaternary; Paleozoic
Illustrationslocation maps; block diagrams; stratigraphic columns; photographs; ternary diagrams; geological maps
ProgramGroundwater Geoscience Aquifer Assessment & support to mapping
Released2016 03 01
AbstractOutcrop 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 mudrich 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.
Summary(Plain Language Summary, not published)
High-resolution geophysical profiles, outcrop description, core logs, and downhole geophysical data, are integrated with detailed mapping to update a 3D sedimentary and stratigraphic framework of Halton Formation, in the Greater Toronto Area (GTA), using a modern basin analysis framework. Sedimentation relates to ice-meltwater dynamic events rather climatically-induced re-advance of late-glacial ice from the Lake Ontario basin. A revised conceptual model links complex Halton Formation sediments and likely processes within a re-interpreted depositional setting that aids groundwater assessment in the GTA. The Halton Formation depositional model may be applicable to other late-glacial muddy sediment units around the Great Lakes basin.

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