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Thermoluminescence chronology of Toronto-area Quaternary sediments and implications for the extent of the midcontinent ice sheet(s)

1994; Geological Society of America; Volume: 22; Issue: 1 Linguagem: Inglês

10.1130/0091-7613(1994)022 2.3.co;2

1943-2682

Glenn W. Berger, N. Eyles,

Polar Research and Ecology

Research Article| January 01, 1994 Thermoluminescence chronology of Toronto-area Quaternary sediments and implications for the extent of the midcontinent ice sheet(s) Glenn W. Berger; Glenn W. Berger 1Department of Geology, Western Washington University, Bellingham, Washington 98225-9080 Search for other works by this author on: GSW Google Scholar Nicholas Eyles Nicholas Eyles 2Department of Geology, University of Toronto, Scarborough Campus, Scarborough, Ontario M1C 1A4, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Glenn W. Berger 1Department of Geology, Western Washington University, Bellingham, Washington 98225-9080 Nicholas Eyles 2Department of Geology, University of Toronto, Scarborough Campus, Scarborough, Ontario M1C 1A4, Canada Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1994) 22 (1): 31–34. https://doi.org/10.1130/0091-7613(1994)022 2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Glenn W. Berger, Nicholas Eyles; Thermoluminescence chronology of Toronto-area Quaternary sediments and implications for the extent of the midcontinent ice sheet(s). Geology 1994;; 22 (1): 31–34. doi: https://doi.org/10.1130/0091-7613(1994)022 2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We report direct dating, by thermoluminescence (TL) methods, of key Quaternary stratigraphic horizons in the Toronto area. TL ages indicate that (1) most of the exposed sediments of the Don Formation at the sampled site were probably deposited during the closing phase of the Sangamon Interglacial (∼80 ka; oxygen isotope stage 5a), not the climatic optimum substage 5e (∼120∼130 ka),as generally supposed; (2) overlying deltaic strata of the Scarborough Formation, which accumulated in an ice-dammed ancestral Lake Ontario, were deposited between 60 and 50 ka (early Wisconsin, oxygen isotope stage 4); (3) the Sunnybrook diamict, overlying the Scarborough Formation, was deposited in the middle Wisconsin at ∼40-45 ka (oxygen isotope stage 3), likely by glaciolacustrine processes, rather than before 65 ka, as previously supposed; (4) sediments of the Upper Thorncliffe Formation lying stratigraphically just beneath the last-glacial-maximum Hallton Till were deposited at ∼23 ka, consistent with reliable 14C dating. Thus, the earliest Wisconsin incursion of the (proto) Laurentide Ice Sheet into the Lake Ontario basin, as recorded by the Scarborough Formation, probably did not take place until at least 60 ka, and did not extend south and southwest of the Toronto area until after ∼25 ka. Ice-free conditions probably persisted over large areas of midcontinent North America from the end of the Illinoian glaciation at ∼130 ka to the late Wisconsin glacial maximum at ∼20 ka. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.