| Titre | Deeply channeled Precambrian rivers depicted in the 1.9 Ga Burnside [River] Formation of Kilohigok Basin (Nunavut, Arctic Canada) |
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| Auteur | Ielpi, A; Rainbird, R H |
| Source | Margins through time: GAC-MAC 2016; Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 39, 2016 p. 38  Accès ouvert |
| Liens | Online - En ligne (complete volume - volume
complet, PDF, 1.3 MB)
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| Année | 2016 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190440 |
| Éditeur | Association géologique du Canada |
| Réunion | GAC-MAC 2016; Whitehorse, YK; CA; juin 1-3, 2016 |
| Document | publication en série |
| Lang. | anglais |
| Media | en ligne; numérique |
| Formats | pdf |
| Province | Nunavut |
| Sujets | sédimentologie; Sciences et technologie; Nature et environnement |
| Programme | GEM2 : La géocartographie de l'énergie et des minéraux Chantrey-Thelon de la province de Rae |
| Diffusé | 2016 06 01 |
| Résumé | (disponible en anglais seulement)
We present outcrop evidence for deeply channeled fluvial drainage in the 1.9 Ga Burnside River Formation of Kilohigok Basin (Nunvaut, Arctic Canada), a feature
that contrasts with the dominant sheet-like geometry observed in many ground-based studies of Precambrian fluvial sandstones. In the Burnside River Formation, sheeted sandbodies with ubiquitous cross-bedding observed at the outcrop scale 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 paleovalleys hosting clustered, km-scale, channel bodies with
attached large foreset bars, sand sheets with width to thickness ratio > 2500, and scattered eolian intervals. The association of these architectural elements points to the coexistence of fluvial piedmonts generated by braidplain channels, at time
wind-winnowed, and weakly-sinuous channel belts up to 25 m deep. Channel geometries comparable to those of late Paleozoic to modern braided channels disprove the inference that all Precambrian streams readily widened in response to increased
discharge. The current facies models for large-scale Precambrian sheetdominated fluvial sandstones did not include large channel forms because the latter could not be resolved by ground-based observations alone. Based on the abundance of
architectural elements with very high width to thickness ratio, and on their limited geomorphic variability in fluvial style, we recommend that large sheet-braided fluvial systems should still be considered a separate entity from post-Silurian (i.e.,
vegetated) and modern braided rivers. Parallels between sheet-braided and modern dryland rivers do not reconcile with the deep and perennial channelized morphodynamics evident from the Burnside River Formation. On the other hand, the distal and
sand-bed reaches of modern humid sandur plains bear possible analogies to Precambrian sheetbraided rivers. This conclusion contradicts the assumption that all Precambrian rivers simulated seasonal behaviors independently from their original climate
regime. |
| GEOSCAN ID | 321715 |
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