Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage
Abstract The repetitive sedimentology of many Precambrian sheet‐dominated fluvial sandstones favoured their attribution to unconfined depositional processes. This article presents outcrop evidence for deep‐channelled drainage in the 1·9 Ga Burnside River Formation of Kilohigok Basin, Arctic Canada....
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crwiley:10.1111/sed.12273 2024-09-15T18:00:32+00:00 Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage Ielpi, Alessandro Rainbird, Robert H. Natural Sciences and Engineering Research Council of Canada 2016 http://dx.doi.org/10.1111/sed.12273 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fsed.12273 https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12273 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Sedimentology volume 63, issue 6, page 1550-1581 ISSN 0037-0746 1365-3091 journal-article 2016 crwiley https://doi.org/10.1111/sed.12273 2024-07-25T04:20:39Z Abstract The repetitive sedimentology of many Precambrian sheet‐dominated fluvial sandstones favoured their attribution to unconfined depositional processes. This article presents outcrop evidence for deep‐channelled drainage in the 1·9 Ga Burnside River Formation of Kilohigok Basin, Arctic Canada. On the ground, sheet‐like sandbodies with ubiquitous cross‐bedding are at first consistent with classic, unconfined depositional models. However, satellite and oblique‐aerial imagery of sections up to 15 km wide and 500 m thick reveals the occurrence of incised palaeovalleys hosting clustered, kilometre‐scale, channel bodies with attached large foreset bars pointing to downstream‐lateral accretion, sand sheets with aspect ratios (i.e. width to thickness) as high as 2500, and scattered aeolian intervals. The genetic association of these architectural elements points to aggradational fluvial piedmonts composed of low‐relief unit bars generated by braidplain channels several metres deep. Preservation of aeolianites was facilitated by fluctuating groundwater table and accommodation. Fluvial piedmonts were transected by weakly sinuous channel belts up to 25 m deep and characterized by through‐going or tributary planform. Aspect ratios comparable with those of late Palaeozoic to modern braided channels disprove the inference that all Precambrian streams readily widened in response to increased discharge. Previous facies models for large‐scale Precambrian sheet‐braided rivers failed to depict entire channel forms, possibly because they could not be resolved by ground‐based observations. Based on their limited geomorphic variability and abundance of architectural elements with very high aspect ratios, this study recommends that large sheet‐braided fluvial systems should still be considered separately from their post‐Silurian (i.e. vegetated) braided counterparts. Parallels between sheet‐braided and modern dryland rivers do not, however, reconcile with the deep, perennial, channelized processes described here. Yet, distal ... Article in Journal/Newspaper Burnside River Wiley Online Library Sedimentology 63 6 1550 1581 |
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Wiley Online Library |
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crwiley |
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English |
description |
Abstract The repetitive sedimentology of many Precambrian sheet‐dominated fluvial sandstones favoured their attribution to unconfined depositional processes. This article presents outcrop evidence for deep‐channelled drainage in the 1·9 Ga Burnside River Formation of Kilohigok Basin, Arctic Canada. On the ground, sheet‐like sandbodies with ubiquitous cross‐bedding are at first consistent with classic, unconfined depositional models. However, satellite and oblique‐aerial imagery of sections up to 15 km wide and 500 m thick reveals the occurrence of incised palaeovalleys hosting clustered, kilometre‐scale, channel bodies with attached large foreset bars pointing to downstream‐lateral accretion, sand sheets with aspect ratios (i.e. width to thickness) as high as 2500, and scattered aeolian intervals. The genetic association of these architectural elements points to aggradational fluvial piedmonts composed of low‐relief unit bars generated by braidplain channels several metres deep. Preservation of aeolianites was facilitated by fluctuating groundwater table and accommodation. Fluvial piedmonts were transected by weakly sinuous channel belts up to 25 m deep and characterized by through‐going or tributary planform. Aspect ratios comparable with those of late Palaeozoic to modern braided channels disprove the inference that all Precambrian streams readily widened in response to increased discharge. Previous facies models for large‐scale Precambrian sheet‐braided rivers failed to depict entire channel forms, possibly because they could not be resolved by ground‐based observations. Based on their limited geomorphic variability and abundance of architectural elements with very high aspect ratios, this study recommends that large sheet‐braided fluvial systems should still be considered separately from their post‐Silurian (i.e. vegetated) braided counterparts. Parallels between sheet‐braided and modern dryland rivers do not, however, reconcile with the deep, perennial, channelized processes described here. Yet, distal ... |
author2 |
Natural Sciences and Engineering Research Council of Canada |
format |
Article in Journal/Newspaper |
author |
Ielpi, Alessandro Rainbird, Robert H. |
spellingShingle |
Ielpi, Alessandro Rainbird, Robert H. Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
author_facet |
Ielpi, Alessandro Rainbird, Robert H. |
author_sort |
Ielpi, Alessandro |
title |
Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
title_short |
Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
title_full |
Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
title_fullStr |
Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
title_full_unstemmed |
Reappraisal of Precambrian sheet‐braided rivers: Evidence for 1·9 Ga deep‐channelled drainage |
title_sort |
reappraisal of precambrian sheet‐braided rivers: evidence for 1·9 ga deep‐channelled drainage |
publisher |
Wiley |
publishDate |
2016 |
url |
http://dx.doi.org/10.1111/sed.12273 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fsed.12273 https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12273 |
genre |
Burnside River |
genre_facet |
Burnside River |
op_source |
Sedimentology volume 63, issue 6, page 1550-1581 ISSN 0037-0746 1365-3091 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/sed.12273 |
container_title |
Sedimentology |
container_volume |
63 |
container_issue |
6 |
container_start_page |
1550 |
op_container_end_page |
1581 |
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1810437687639801856 |