The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada

Outcrops of pebbly mud (diamict) at Scarborough in Southern Ontario, Canada (the so-called Sunnybrook ‘Till’) are associated with the earliest incursion of the Laurentide Ice Sheet (LIS) into mid-continent North America some 45,000 years ago. The Sunnybrook is a blanket-like deposit containing deepw...

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Published in:Quaternary Research
Main Authors: Eyles, Nicholas, Eyles, Carolyn H., Woodworth-Lynas, Christopher, Randall, Todd A.
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press (CUP) 2005
Subjects:
Online Access:http://dx.doi.org/10.1016/j.yqres.2004.12.002
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spelling crcambridgeupr:10.1016/j.yqres.2004.12.002 2024-10-13T14:08:06+00:00 The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada Eyles, Nicholas Eyles, Carolyn H. Woodworth-Lynas, Christopher Randall, Todd A. 2005 http://dx.doi.org/10.1016/j.yqres.2004.12.002 http://api.elsevier.com/content/article/PII:S0033589404001577?httpAccept=text/xml http://api.elsevier.com/content/article/PII:S0033589404001577?httpAccept=text/plain https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400013259 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Quaternary Research volume 63, issue 2, page 171-181 ISSN 0033-5894 1096-0287 journal-article 2005 crcambridgeupr https://doi.org/10.1016/j.yqres.2004.12.002 2024-09-18T04:03:17Z Outcrops of pebbly mud (diamict) at Scarborough in Southern Ontario, Canada (the so-called Sunnybrook ‘Till’) are associated with the earliest incursion of the Laurentide Ice Sheet (LIS) into mid-continent North America some 45,000 years ago. The Sunnybrook is a blanket-like deposit containing deepwater ostracodes and occurs conformably within a thick (100 m) succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake. Contextual evidence (associated facies, sedimentary structures, deposit geometry and landforms) indicates a low energy depositional setting in an ice-dammed ancestral Lake Ontario in which scouring by floating ice masses was an important process. U-shaped, iceberg-cut scours (with lateral berms) up to 7 m deep, occur on the upper surface of the Sunnybrook and are underlain by ‘sub-scour’ structures that extend several meters below the scour base. Ice-rafted concentrations of clasts (‘clast layers’), grooved surfaces formed by floating ice glissading over a muddy lake floor (‘soft sediment striations’) and melanges of sand and mud mixed by grounding ice keels (‘ice keel turbates’) are present and are all well known from modern cold environments. The wider significance of this depositional model is that the LIS margin lay east of Scarborough and did not overrun Southern Ontario. This finding is in agreement with recent data from the Erie Basin of Canada, Ohio, and Indiana where deposits formerly correlated with the Sunnybrook (and thus implying an extensive early Wisconsin ice sheet) are now regarded as Illinoian. A speculative hypothesis is proposed that relates deposition of the Sunnybrook and two younger deposits of similar sedimentology, to surge-like instabilities of the southern LIS margin. Article in Journal/Newspaper Ice Sheet Cambridge University Press Canada Dammed Lake ENVELOPE(-68.258,-68.258,68.496,68.496) Scarborough ENVELOPE(-96.000,-96.000,60.000,60.000) Quaternary Research 63 2 171 181
institution Open Polar
collection Cambridge University Press
op_collection_id crcambridgeupr
language English
description Outcrops of pebbly mud (diamict) at Scarborough in Southern Ontario, Canada (the so-called Sunnybrook ‘Till’) are associated with the earliest incursion of the Laurentide Ice Sheet (LIS) into mid-continent North America some 45,000 years ago. The Sunnybrook is a blanket-like deposit containing deepwater ostracodes and occurs conformably within a thick (100 m) succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake. Contextual evidence (associated facies, sedimentary structures, deposit geometry and landforms) indicates a low energy depositional setting in an ice-dammed ancestral Lake Ontario in which scouring by floating ice masses was an important process. U-shaped, iceberg-cut scours (with lateral berms) up to 7 m deep, occur on the upper surface of the Sunnybrook and are underlain by ‘sub-scour’ structures that extend several meters below the scour base. Ice-rafted concentrations of clasts (‘clast layers’), grooved surfaces formed by floating ice glissading over a muddy lake floor (‘soft sediment striations’) and melanges of sand and mud mixed by grounding ice keels (‘ice keel turbates’) are present and are all well known from modern cold environments. The wider significance of this depositional model is that the LIS margin lay east of Scarborough and did not overrun Southern Ontario. This finding is in agreement with recent data from the Erie Basin of Canada, Ohio, and Indiana where deposits formerly correlated with the Sunnybrook (and thus implying an extensive early Wisconsin ice sheet) are now regarded as Illinoian. A speculative hypothesis is proposed that relates deposition of the Sunnybrook and two younger deposits of similar sedimentology, to surge-like instabilities of the southern LIS margin.
format Article in Journal/Newspaper
author Eyles, Nicholas
Eyles, Carolyn H.
Woodworth-Lynas, Christopher
Randall, Todd A.
spellingShingle Eyles, Nicholas
Eyles, Carolyn H.
Woodworth-Lynas, Christopher
Randall, Todd A.
The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
author_facet Eyles, Nicholas
Eyles, Carolyn H.
Woodworth-Lynas, Christopher
Randall, Todd A.
author_sort Eyles, Nicholas
title The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
title_short The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
title_full The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
title_fullStr The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
title_full_unstemmed The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada
title_sort sedimentary record of drifting ice (early wisconsin sunnybrook deposit) in an ancestral ice-dammed lake ontario, canada
publisher Cambridge University Press (CUP)
publishDate 2005
url http://dx.doi.org/10.1016/j.yqres.2004.12.002
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https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400013259
long_lat ENVELOPE(-68.258,-68.258,68.496,68.496)
ENVELOPE(-96.000,-96.000,60.000,60.000)
geographic Canada
Dammed Lake
Scarborough
geographic_facet Canada
Dammed Lake
Scarborough
genre Ice Sheet
genre_facet Ice Sheet
op_source Quaternary Research
volume 63, issue 2, page 171-181
ISSN 0033-5894 1096-0287
op_rights https://www.cambridge.org/core/terms
op_doi https://doi.org/10.1016/j.yqres.2004.12.002
container_title Quaternary Research
container_volume 63
container_issue 2
container_start_page 171
op_container_end_page 181
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