Deglaciation of Penobscot Bay, Maine, USA
The Pond Ridge and Pineo Ridge moraines in downeast Maine likely formed at ~16.1 and ~15.7 ka respectively, during cold episodes recorded by δ18O dips in the GRIP ice core. The elapsed time between these ages is broadly consistent with retreat rates recorded by intervening De Geer moraines, which ar...
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fterudit:oai:erudit.org:1070331ar 2023-05-15T16:39:16+02:00 Deglaciation of Penobscot Bay, Maine, USA Wrobleski, Emmy A. Hooke, Roger LeBaron 2020 http://id.erudit.org/iderudit/1070331ar https://doi.org/10.4138/atlgeol.2020.006 en eng Atlantic Geoscience Society Érudit Atlantic Geology : Journal of the Atlantic Geoscience Society vol. 56 (2020) http://id.erudit.org/iderudit/1070331ar doi:10.4138/atlgeol.2020.006 All Rights Reserved ©, 2020Atlantic Geology text 2020 fterudit https://doi.org/10.4138/atlgeol.2020.006 2021-09-18T23:34:50Z The Pond Ridge and Pineo Ridge moraines in downeast Maine likely formed at ~16.1 and ~15.7 ka respectively, during cold episodes recorded by δ18O dips in the GRIP ice core. The elapsed time between these ages is broadly consistent with retreat rates recorded by intervening De Geer moraines, which are readily visible on LiDAR imagery and are believed to be approximately annual. North-northwestward from the southwesterly extension of the Pond Ridge moraine there are three pairs of prominent moraines that are relatively continuous across the study area and could be reliably extrapolated across intervening water bodies. Retreat rates recorded by De Geer moraines suggest that these pairs formed at 15.7-15.8 ka, 15.5-15.6 ka, and ~15.5 ka. Although retreat appears to have occurred slightly faster across Penobscot Bay, a significant calving bay does not seem to have developed there. Instead, the ice margin remained relatively straight, retreating to the north-northwest. De Geer moraines become more widely spaced northward and vanish after ~15.5 ka when the ice margin was north of the head of Penobscot Bay and of Pineo Ridge. This likely reflects higher retreat rates during the initial phases of the Bølling warm period. Just south of Pineo Ridge there were two ice lobes; one retreated to the north and one to the northwest. The latter retreated more rapidly, while the former experienced numerous minor readvances and stillstands until finally pausing at the location of Pineo Ridge. A stillstand of this lobe then resulted in deposition of the Pineo Ridge moraine complex. Text ice core Érudit.org (Université Montréal) Pond Ridge ENVELOPE(-93.550,-93.550,-73.417,-73.417) Atlantic Geology 56 147 161 |
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Érudit.org (Université Montréal) |
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fterudit |
language |
English |
description |
The Pond Ridge and Pineo Ridge moraines in downeast Maine likely formed at ~16.1 and ~15.7 ka respectively, during cold episodes recorded by δ18O dips in the GRIP ice core. The elapsed time between these ages is broadly consistent with retreat rates recorded by intervening De Geer moraines, which are readily visible on LiDAR imagery and are believed to be approximately annual. North-northwestward from the southwesterly extension of the Pond Ridge moraine there are three pairs of prominent moraines that are relatively continuous across the study area and could be reliably extrapolated across intervening water bodies. Retreat rates recorded by De Geer moraines suggest that these pairs formed at 15.7-15.8 ka, 15.5-15.6 ka, and ~15.5 ka. Although retreat appears to have occurred slightly faster across Penobscot Bay, a significant calving bay does not seem to have developed there. Instead, the ice margin remained relatively straight, retreating to the north-northwest. De Geer moraines become more widely spaced northward and vanish after ~15.5 ka when the ice margin was north of the head of Penobscot Bay and of Pineo Ridge. This likely reflects higher retreat rates during the initial phases of the Bølling warm period. Just south of Pineo Ridge there were two ice lobes; one retreated to the north and one to the northwest. The latter retreated more rapidly, while the former experienced numerous minor readvances and stillstands until finally pausing at the location of Pineo Ridge. A stillstand of this lobe then resulted in deposition of the Pineo Ridge moraine complex. |
format |
Text |
author |
Wrobleski, Emmy A. Hooke, Roger LeBaron |
spellingShingle |
Wrobleski, Emmy A. Hooke, Roger LeBaron Deglaciation of Penobscot Bay, Maine, USA |
author_facet |
Wrobleski, Emmy A. Hooke, Roger LeBaron |
author_sort |
Wrobleski, Emmy A. |
title |
Deglaciation of Penobscot Bay, Maine, USA |
title_short |
Deglaciation of Penobscot Bay, Maine, USA |
title_full |
Deglaciation of Penobscot Bay, Maine, USA |
title_fullStr |
Deglaciation of Penobscot Bay, Maine, USA |
title_full_unstemmed |
Deglaciation of Penobscot Bay, Maine, USA |
title_sort |
deglaciation of penobscot bay, maine, usa |
publisher |
Atlantic Geoscience Society |
publishDate |
2020 |
url |
http://id.erudit.org/iderudit/1070331ar https://doi.org/10.4138/atlgeol.2020.006 |
long_lat |
ENVELOPE(-93.550,-93.550,-73.417,-73.417) |
geographic |
Pond Ridge |
geographic_facet |
Pond Ridge |
genre |
ice core |
genre_facet |
ice core |
op_relation |
Atlantic Geology : Journal of the Atlantic Geoscience Society vol. 56 (2020) http://id.erudit.org/iderudit/1070331ar doi:10.4138/atlgeol.2020.006 |
op_rights |
All Rights Reserved ©, 2020Atlantic Geology |
op_doi |
https://doi.org/10.4138/atlgeol.2020.006 |
container_title |
Atlantic Geology |
container_volume |
56 |
container_start_page |
147 |
op_container_end_page |
161 |
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1766029600271368192 |