Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago
The Beaufort Formation (BF) braided river deposit contains exceptionally well-preserved logs, leaves, peat, insects, and vertebrate fossils that provide key evidence for Arctic environmental conditions during the Pliocene. Its wide geographic range along the western edge of the Canadian Arctic Archi...
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ftdalhouse:oai:DalSpace.library.dal.ca:10222/56765 2023-05-15T14:28:44+02:00 Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago Braschi, Lea Department of Earth Sciences Master of Science Andrew MacRae John Gosse Martin Gibling Natalia Rybczynski Not Applicable 2015-05-04T17:45:35Z http://hdl.handle.net/10222/56765 en eng http://hdl.handle.net/10222/56765 geochronology stratigraphy sedimentology paleoclimatology Beaufort Formation High Terrace Sediments Canadian Arctic Archipelago Banks Island Ballast Brook cosmogenic nuclides 2015 ftdalhouse 2021-12-29T18:12:04Z The Beaufort Formation (BF) braided river deposit contains exceptionally well-preserved logs, leaves, peat, insects, and vertebrate fossils that provide key evidence for Arctic environmental conditions during the Pliocene. Its wide geographic range along the western edge of the Canadian Arctic Archipelago suggests that its deposition and incision history were dictated by regional drivers of sediment transport (e.g., eustatic sea-level, permafrost thaw, ice sheet erosion, and dynamic topography). Hence, the BF provides clues about both environmental and depositional conditions, but available chronology in the last few decades has not been able to identify these as having occurred either 1) during the polar amplification of global warming (Pliocene Climate Optimum, 3.3-3.0 Ma) or 2) during the onset of northern hemisphere glaciations (Plio-Pleistocene transition, 2.6 Ma). We use cosmogenic nuclide burial dating at the southernmost BF locality (Ballast Brook on Banks Is.) to obtain: a) a minimum age of 2.72 (+0.34)⁄(-0.24) (1 σ) Ma, and b) a maximum catchment-wide paleo-erosion rate of 49-86 ± 2 cm/ka. The description of a previously unreported glaciofluvial gravel (which occurs at the same stratigraphic level as a potential ice-wedge pseudomorph and coincides with the base of a previously-mapped 3-km wide cut-and-fill channel) dates the earliest evidence of CAA glaciation, at 2.72 Ma. The presence of a large channel that runs parallel to the northern coast of Banks Is. also suggests that M’Clure Strait (and the Northwest Passage) was not open at that time. Furthermore, such a large (correlative with part of the 3-km Iperk Formation offshore) and quick (49-86 ± 2 cm/ka) deposition event must have required the stripping of unconsolidated material (e.g, part of the Eureka Sound Group or Hassel and Isachsen Formations). The deposition system was likely a transport-limited system, and like the White Channel Gravels of the Yukon (Hidy et al. 2013), may have been controlled by changing climate in the Pliocene (e.g., melting permafrost, increased precipitation). Other/Unknown Material Arctic Archipelago Arctic Banks Island Canadian Arctic Archipelago Eureka Sound Global warming Ice Ice Sheet Northwest passage permafrost wedge* Yukon Dalhousie University: DalSpace Institutional Repository Arctic Ballast Brook ENVELOPE(-123.227,-123.227,74.440,74.440) Canadian Arctic Archipelago Eureka ENVELOPE(-85.940,-85.940,79.990,79.990) Eureka Sound ENVELOPE(-84.999,-84.999,79.002,79.002) Hassel ENVELOPE(-164.467,-164.467,-86.467,-86.467) Isachsen ENVELOPE(-103.505,-103.505,78.785,78.785) Northwest Passage Yukon |
institution |
Open Polar |
collection |
Dalhousie University: DalSpace Institutional Repository |
op_collection_id |
ftdalhouse |
language |
English |
topic |
geochronology stratigraphy sedimentology paleoclimatology Beaufort Formation High Terrace Sediments Canadian Arctic Archipelago Banks Island Ballast Brook cosmogenic nuclides |
spellingShingle |
geochronology stratigraphy sedimentology paleoclimatology Beaufort Formation High Terrace Sediments Canadian Arctic Archipelago Banks Island Ballast Brook cosmogenic nuclides Braschi, Lea Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
topic_facet |
geochronology stratigraphy sedimentology paleoclimatology Beaufort Formation High Terrace Sediments Canadian Arctic Archipelago Banks Island Ballast Brook cosmogenic nuclides |
description |
The Beaufort Formation (BF) braided river deposit contains exceptionally well-preserved logs, leaves, peat, insects, and vertebrate fossils that provide key evidence for Arctic environmental conditions during the Pliocene. Its wide geographic range along the western edge of the Canadian Arctic Archipelago suggests that its deposition and incision history were dictated by regional drivers of sediment transport (e.g., eustatic sea-level, permafrost thaw, ice sheet erosion, and dynamic topography). Hence, the BF provides clues about both environmental and depositional conditions, but available chronology in the last few decades has not been able to identify these as having occurred either 1) during the polar amplification of global warming (Pliocene Climate Optimum, 3.3-3.0 Ma) or 2) during the onset of northern hemisphere glaciations (Plio-Pleistocene transition, 2.6 Ma). We use cosmogenic nuclide burial dating at the southernmost BF locality (Ballast Brook on Banks Is.) to obtain: a) a minimum age of 2.72 (+0.34)⁄(-0.24) (1 σ) Ma, and b) a maximum catchment-wide paleo-erosion rate of 49-86 ± 2 cm/ka. The description of a previously unreported glaciofluvial gravel (which occurs at the same stratigraphic level as a potential ice-wedge pseudomorph and coincides with the base of a previously-mapped 3-km wide cut-and-fill channel) dates the earliest evidence of CAA glaciation, at 2.72 Ma. The presence of a large channel that runs parallel to the northern coast of Banks Is. also suggests that M’Clure Strait (and the Northwest Passage) was not open at that time. Furthermore, such a large (correlative with part of the 3-km Iperk Formation offshore) and quick (49-86 ± 2 cm/ka) deposition event must have required the stripping of unconsolidated material (e.g, part of the Eureka Sound Group or Hassel and Isachsen Formations). The deposition system was likely a transport-limited system, and like the White Channel Gravels of the Yukon (Hidy et al. 2013), may have been controlled by changing climate in the Pliocene (e.g., melting permafrost, increased precipitation). |
author2 |
Department of Earth Sciences Master of Science Andrew MacRae John Gosse Martin Gibling Natalia Rybczynski Not Applicable |
author |
Braschi, Lea |
author_facet |
Braschi, Lea |
author_sort |
Braschi, Lea |
title |
Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
title_short |
Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
title_full |
Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
title_fullStr |
Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
title_full_unstemmed |
Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago |
title_sort |
chronostratigraphy of the beaufort formation, western canadian arctic archipelago |
publishDate |
2015 |
url |
http://hdl.handle.net/10222/56765 |
long_lat |
ENVELOPE(-123.227,-123.227,74.440,74.440) ENVELOPE(-85.940,-85.940,79.990,79.990) ENVELOPE(-84.999,-84.999,79.002,79.002) ENVELOPE(-164.467,-164.467,-86.467,-86.467) ENVELOPE(-103.505,-103.505,78.785,78.785) |
geographic |
Arctic Ballast Brook Canadian Arctic Archipelago Eureka Eureka Sound Hassel Isachsen Northwest Passage Yukon |
geographic_facet |
Arctic Ballast Brook Canadian Arctic Archipelago Eureka Eureka Sound Hassel Isachsen Northwest Passage Yukon |
genre |
Arctic Archipelago Arctic Banks Island Canadian Arctic Archipelago Eureka Sound Global warming Ice Ice Sheet Northwest passage permafrost wedge* Yukon |
genre_facet |
Arctic Archipelago Arctic Banks Island Canadian Arctic Archipelago Eureka Sound Global warming Ice Ice Sheet Northwest passage permafrost wedge* Yukon |
op_relation |
http://hdl.handle.net/10222/56765 |
_version_ |
1766302883944333312 |