Giant Grooves Made by Concentrated Basal Ice Streams
Abstract Glacial grooves are known on all the flat-lying limestone islands in western Lake Erie. The largest megagroove complexes are on Kelleys Island, each 2–6 m deep, 5–20 m wide, and 100–400 m long before quarrying. Each megagroove floor is rolling with second-order rounded ridges and “sine-shap...
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Language: | English |
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Cambridge University Press (CUP)
1979
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Online Access: | http://dx.doi.org/10.1017/s0022143000029919 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029919 |
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crcambridgeupr:10.1017/s0022143000029919 2024-04-07T07:53:41+00:00 Giant Grooves Made by Concentrated Basal Ice Streams Goldthwait, R. P. 1979 http://dx.doi.org/10.1017/s0022143000029919 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029919 en eng Cambridge University Press (CUP) Journal of Glaciology volume 23, issue 89, page 297-307 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1979 crcambridgeupr https://doi.org/10.1017/s0022143000029919 2024-03-08T00:34:51Z Abstract Glacial grooves are known on all the flat-lying limestone islands in western Lake Erie. The largest megagroove complexes are on Kelleys Island, each 2–6 m deep, 5–20 m wide, and 100–400 m long before quarrying. Each megagroove floor is rolling with second-order rounded ridges and “sine-shaped” grooves 10–90 cm deep, and 5–40 m long. Furthermore, these are gouged laterally by sharply curving and nesting gouges up to 10 cm deep. All grooves exhibit third-order striation up to 1–2 mm deep and 5–200 cm long made by individual tools of debris traveling mostly 240–260°. Ice of the Erie lobe was under compressive flow as it rose from 9 m below present lake level to 12 m above. Some sort of ice vortices (fixed eddies in the basal ice stream) are postulated to make the scoop marks and ridge ends. Fast-moving ice rather than water or a slurry is favored because there are no percussion marks. Very likely, a till mat of interfering engraving points is required. A strong convergence (2× to 10×) of striae into the deepest grooves indicates squeezing together of the debris tools and increase in local ice velocity. Interglacial subareal streams may well have shaped the initial trough up which these ice streams concentrated, because dendritic tributary grooves intersect, and main groove sets curve as much as 10° or 20°. Furthermore, sharp 100–180° meander curves are preserved at the bottom of the deepest grooves. Hiram-age clay-till with rare erratics half fills the original grooves; it shows that this groove cutting was completed before 15 500 14 C years ago. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Western Lake ENVELOPE(-128.106,-128.106,52.663,52.663) Limestone Islands ENVELOPE(-131.618,-131.618,52.909,52.909) Journal of Glaciology 23 89 297 307 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Goldthwait, R. P. Giant Grooves Made by Concentrated Basal Ice Streams |
topic_facet |
Earth-Surface Processes |
description |
Abstract Glacial grooves are known on all the flat-lying limestone islands in western Lake Erie. The largest megagroove complexes are on Kelleys Island, each 2–6 m deep, 5–20 m wide, and 100–400 m long before quarrying. Each megagroove floor is rolling with second-order rounded ridges and “sine-shaped” grooves 10–90 cm deep, and 5–40 m long. Furthermore, these are gouged laterally by sharply curving and nesting gouges up to 10 cm deep. All grooves exhibit third-order striation up to 1–2 mm deep and 5–200 cm long made by individual tools of debris traveling mostly 240–260°. Ice of the Erie lobe was under compressive flow as it rose from 9 m below present lake level to 12 m above. Some sort of ice vortices (fixed eddies in the basal ice stream) are postulated to make the scoop marks and ridge ends. Fast-moving ice rather than water or a slurry is favored because there are no percussion marks. Very likely, a till mat of interfering engraving points is required. A strong convergence (2× to 10×) of striae into the deepest grooves indicates squeezing together of the debris tools and increase in local ice velocity. Interglacial subareal streams may well have shaped the initial trough up which these ice streams concentrated, because dendritic tributary grooves intersect, and main groove sets curve as much as 10° or 20°. Furthermore, sharp 100–180° meander curves are preserved at the bottom of the deepest grooves. Hiram-age clay-till with rare erratics half fills the original grooves; it shows that this groove cutting was completed before 15 500 14 C years ago. |
format |
Article in Journal/Newspaper |
author |
Goldthwait, R. P. |
author_facet |
Goldthwait, R. P. |
author_sort |
Goldthwait, R. P. |
title |
Giant Grooves Made by Concentrated Basal Ice Streams |
title_short |
Giant Grooves Made by Concentrated Basal Ice Streams |
title_full |
Giant Grooves Made by Concentrated Basal Ice Streams |
title_fullStr |
Giant Grooves Made by Concentrated Basal Ice Streams |
title_full_unstemmed |
Giant Grooves Made by Concentrated Basal Ice Streams |
title_sort |
giant grooves made by concentrated basal ice streams |
publisher |
Cambridge University Press (CUP) |
publishDate |
1979 |
url |
http://dx.doi.org/10.1017/s0022143000029919 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029919 |
long_lat |
ENVELOPE(-128.106,-128.106,52.663,52.663) ENVELOPE(-131.618,-131.618,52.909,52.909) |
geographic |
Western Lake Limestone Islands |
geographic_facet |
Western Lake Limestone Islands |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 23, issue 89, page 297-307 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000029919 |
container_title |
Journal of Glaciology |
container_volume |
23 |
container_issue |
89 |
container_start_page |
297 |
op_container_end_page |
307 |
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1795669767745437696 |