Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario
Outcrop exposures along the Attawapiskat River in the Hudson Bay Lowlands of northern Ontario clearly reveal the morphology of Silurian (upper Llandoverian) reefs of the Attawapiskat Formation and the relationships between reef cores, flanking beds, and post-reef beds. These relationships indicate t...
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crcansciencepubl:10.1139/e93-044 2023-12-17T10:27:29+01:00 Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario Suchy, Daniel R. Stearn, Colin W. 1993 http://dx.doi.org/10.1139/e93-044 http://www.nrcresearchpress.com/doi/pdf/10.1139/e93-044 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 30, issue 3, page 575-590 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1993 crcansciencepubl https://doi.org/10.1139/e93-044 2023-11-19T13:39:09Z Outcrop exposures along the Attawapiskat River in the Hudson Bay Lowlands of northern Ontario clearly reveal the morphology of Silurian (upper Llandoverian) reefs of the Attawapiskat Formation and the relationships between reef cores, flanking beds, and post-reef beds. These relationships indicate that the reefs had a syndepositional relief of at least 8–10 m. The relief of the reefs is indicated by debris-flow lenses encased within flanking beds, a debris-flow fan at the base of a reef, thin reef-flanking beds truncated against a vertical reef face, penecontemporaneous brachiopod beds on the flanks of reefs, and three large slide blocks that apparently slid over the side of a reef.Reefs of the Attawapiskat Formation are largely limestones with a wide range of lithologies, from stromatoporoid-, coral-, and cement-rich boundstones to alga–cement-rich boundstones. Thick, laterally extensive Nuia grainstone beds, a product of widespread Nuia monocultures in supratidal to intertidal ponds, are present above the reefs. The most important diagenetic processes were early marine cementation (predominantly radial-fibrous calcite), shallow burial diagenesis, and pervasive neomorphism.Schematic reconstructions of the depositional history of the Attawapiskat Formation in outcrop, constructed from observations of outcrop relationships, show a stratigraphic succession that was controlled by relative-sea-level changes. Reefs growth was terminated by a relative-sea-level fall, but subsequent minor relative-sea-level fluctuations resulted in alternating deposition of supratidal to shallow subtidal sediments for a short time before the final retreat of the Silurian seas from the Hudson Bay Platform; only supratidal evaporite facies are present in the remainder of the Silurian section above the Attawapiskat Formation. Article in Journal/Newspaper Attawapiskat Hudson Bay Canadian Science Publishing (via Crossref) Hudson Bay Hudson Attawapiskat ENVELOPE(-82.417,-82.417,52.928,52.928) Attawapiskat River ENVELOPE(-82.300,-82.300,52.950,52.950) Canadian Journal of Earth Sciences 30 3 575 590 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Suchy, Daniel R. Stearn, Colin W. Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
topic_facet |
General Earth and Planetary Sciences |
description |
Outcrop exposures along the Attawapiskat River in the Hudson Bay Lowlands of northern Ontario clearly reveal the morphology of Silurian (upper Llandoverian) reefs of the Attawapiskat Formation and the relationships between reef cores, flanking beds, and post-reef beds. These relationships indicate that the reefs had a syndepositional relief of at least 8–10 m. The relief of the reefs is indicated by debris-flow lenses encased within flanking beds, a debris-flow fan at the base of a reef, thin reef-flanking beds truncated against a vertical reef face, penecontemporaneous brachiopod beds on the flanks of reefs, and three large slide blocks that apparently slid over the side of a reef.Reefs of the Attawapiskat Formation are largely limestones with a wide range of lithologies, from stromatoporoid-, coral-, and cement-rich boundstones to alga–cement-rich boundstones. Thick, laterally extensive Nuia grainstone beds, a product of widespread Nuia monocultures in supratidal to intertidal ponds, are present above the reefs. The most important diagenetic processes were early marine cementation (predominantly radial-fibrous calcite), shallow burial diagenesis, and pervasive neomorphism.Schematic reconstructions of the depositional history of the Attawapiskat Formation in outcrop, constructed from observations of outcrop relationships, show a stratigraphic succession that was controlled by relative-sea-level changes. Reefs growth was terminated by a relative-sea-level fall, but subsequent minor relative-sea-level fluctuations resulted in alternating deposition of supratidal to shallow subtidal sediments for a short time before the final retreat of the Silurian seas from the Hudson Bay Platform; only supratidal evaporite facies are present in the remainder of the Silurian section above the Attawapiskat Formation. |
format |
Article in Journal/Newspaper |
author |
Suchy, Daniel R. Stearn, Colin W. |
author_facet |
Suchy, Daniel R. Stearn, Colin W. |
author_sort |
Suchy, Daniel R. |
title |
Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
title_short |
Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
title_full |
Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
title_fullStr |
Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
title_full_unstemmed |
Lower Silurian reefs and post-reef beds of the Attawapiskat Formation, Hudson Bay Platform, northern Ontario |
title_sort |
lower silurian reefs and post-reef beds of the attawapiskat formation, hudson bay platform, northern ontario |
publisher |
Canadian Science Publishing |
publishDate |
1993 |
url |
http://dx.doi.org/10.1139/e93-044 http://www.nrcresearchpress.com/doi/pdf/10.1139/e93-044 |
long_lat |
ENVELOPE(-82.417,-82.417,52.928,52.928) ENVELOPE(-82.300,-82.300,52.950,52.950) |
geographic |
Hudson Bay Hudson Attawapiskat Attawapiskat River |
geographic_facet |
Hudson Bay Hudson Attawapiskat Attawapiskat River |
genre |
Attawapiskat Hudson Bay |
genre_facet |
Attawapiskat Hudson Bay |
op_source |
Canadian Journal of Earth Sciences volume 30, issue 3, page 575-590 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e93-044 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
30 |
container_issue |
3 |
container_start_page |
575 |
op_container_end_page |
590 |
_version_ |
1785579354645856256 |