Abstract
Basin-scale models are required to interpret ancient continental sedimentary successions, and reduce uncertainty in assessing geological resources in basins. Recently, modern studies show distributive fluvial systems to comprise a substantial proportion of modern sedimentary basins, but their role in ancient basin fills has yet to be quantitatively documented at the basin scale. This study analysed key fluvial characteristics to construct a detailed basin-wide model of the Palaeogene Fort Union and Willwood formations (Bighorn Basin, Wyoming), using observations from modern studies, and ancient system scale studies of distributive fluvial systems, to guide interpretations. Mapping showed these formations to be highly heterogeneous with channel-body proportion (from 12 to 81%) and geometry types (large amalgamated bodies to isolated channels), grain size (silt to conglomerate), average channel-body thickness (4 to 20 m) and average storey thickness (3 to 10 m) varying significantly across the basin. Distributive fluvial systems in the form of alluvial and fluvial fans in transverse configurations were recognized as well as a wide axial system, with heterogeneity in the formations being closely aligned to these interpretations. Furthermore, numerous individual depositional systems were identified within the formations (Beartooth Absaroka, Washakie, Owl Creek and axial). Predicted downstream distributive fluvial system trends (i.e. downstream decrease in channel proportion, size and grain size) were identified in the Beartooth, Absaroka and Owl Creek systems. However, predicted trends were not identified in the Washakie system where intrabasinal thrusting disturbed the sequence. Importantly, a wide axial fluvial system was identified, where reverse downstream distributive fluvial system trends were present, interpreted to be the result of the input of transverse systems of variable size. This study provides a new level of detail in the application of basin-scale models, demonstrating their usefulness in trying to understand and predict alluvial architecture distribution and heterogeneity, with important implications for economic resources and palaeogeographic reconstructions.
| Original language | English |
|---|---|
| Pages (from-to) | 736-763 |
| Number of pages | 28 |
| Journal | Sedimentology |
| Volume | 66 |
| Issue number | 2 |
| Early online date | 19 Aug 2018 |
| DOIs | |
| Publication status | Published - 28 Feb 2019 |
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Keywords
- Basin scale
- Bighorn Basin
- distributive fluvial system
- fluvial
- Fort Union Formation
- Willwood Formation
ASJC Scopus subject areas
- Geology
- Stratigraphy
Cite this
Basin-scale predictive models of alluvial architecture : Constraints from the Palaeocene–Eocene, Bighorn Basin, Wyoming, USA. / Owen, Amanda (Corresponding Author); Hartley, Adrian J.; Ebinghaus, Alena; Weissmann, Gary S.; Santos, Maurício G.M.
In: Sedimentology, Vol. 66, No. 2, 28.02.2019, p. 736-763.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Basin-scale predictive models of alluvial architecture
T2 - Constraints from the Palaeocene–Eocene, Bighorn Basin, Wyoming, USA
AU - Owen, Amanda
AU - Hartley, Adrian J.
AU - Ebinghaus, Alena
AU - Weissmann, Gary S.
AU - Santos, Maurício G.M.
N1 - This work was supported by Phase 2 of the Fluvial Systems Research Group (BP, BG, Chevron, ConocoPhillips and Total). AE thanks the University of Aberdeen for additional funding and MGMS thanks the São Paulo Research Foundation (FAPESP 2014/13937‐3). The authors also wish to thank numerous residents of the Bighorn Basin for their kind hospitality and access to land, and Isobel Buchanan and Alistair Swan for assistance in the field. The authors also thank reviewers Luca Colombera and Sian Davies‐Vollum and AE Christopher Fielding for helpful comments on this manuscript.
PY - 2019/2/28
Y1 - 2019/2/28
N2 - Basin-scale models are required to interpret ancient continental sedimentary successions, and reduce uncertainty in assessing geological resources in basins. Recently, modern studies show distributive fluvial systems to comprise a substantial proportion of modern sedimentary basins, but their role in ancient basin fills has yet to be quantitatively documented at the basin scale. This study analysed key fluvial characteristics to construct a detailed basin-wide model of the Palaeogene Fort Union and Willwood formations (Bighorn Basin, Wyoming), using observations from modern studies, and ancient system scale studies of distributive fluvial systems, to guide interpretations. Mapping showed these formations to be highly heterogeneous with channel-body proportion (from 12 to 81%) and geometry types (large amalgamated bodies to isolated channels), grain size (silt to conglomerate), average channel-body thickness (4 to 20 m) and average storey thickness (3 to 10 m) varying significantly across the basin. Distributive fluvial systems in the form of alluvial and fluvial fans in transverse configurations were recognized as well as a wide axial system, with heterogeneity in the formations being closely aligned to these interpretations. Furthermore, numerous individual depositional systems were identified within the formations (Beartooth Absaroka, Washakie, Owl Creek and axial). Predicted downstream distributive fluvial system trends (i.e. downstream decrease in channel proportion, size and grain size) were identified in the Beartooth, Absaroka and Owl Creek systems. However, predicted trends were not identified in the Washakie system where intrabasinal thrusting disturbed the sequence. Importantly, a wide axial fluvial system was identified, where reverse downstream distributive fluvial system trends were present, interpreted to be the result of the input of transverse systems of variable size. This study provides a new level of detail in the application of basin-scale models, demonstrating their usefulness in trying to understand and predict alluvial architecture distribution and heterogeneity, with important implications for economic resources and palaeogeographic reconstructions.
AB - Basin-scale models are required to interpret ancient continental sedimentary successions, and reduce uncertainty in assessing geological resources in basins. Recently, modern studies show distributive fluvial systems to comprise a substantial proportion of modern sedimentary basins, but their role in ancient basin fills has yet to be quantitatively documented at the basin scale. This study analysed key fluvial characteristics to construct a detailed basin-wide model of the Palaeogene Fort Union and Willwood formations (Bighorn Basin, Wyoming), using observations from modern studies, and ancient system scale studies of distributive fluvial systems, to guide interpretations. Mapping showed these formations to be highly heterogeneous with channel-body proportion (from 12 to 81%) and geometry types (large amalgamated bodies to isolated channels), grain size (silt to conglomerate), average channel-body thickness (4 to 20 m) and average storey thickness (3 to 10 m) varying significantly across the basin. Distributive fluvial systems in the form of alluvial and fluvial fans in transverse configurations were recognized as well as a wide axial system, with heterogeneity in the formations being closely aligned to these interpretations. Furthermore, numerous individual depositional systems were identified within the formations (Beartooth Absaroka, Washakie, Owl Creek and axial). Predicted downstream distributive fluvial system trends (i.e. downstream decrease in channel proportion, size and grain size) were identified in the Beartooth, Absaroka and Owl Creek systems. However, predicted trends were not identified in the Washakie system where intrabasinal thrusting disturbed the sequence. Importantly, a wide axial fluvial system was identified, where reverse downstream distributive fluvial system trends were present, interpreted to be the result of the input of transverse systems of variable size. This study provides a new level of detail in the application of basin-scale models, demonstrating their usefulness in trying to understand and predict alluvial architecture distribution and heterogeneity, with important implications for economic resources and palaeogeographic reconstructions.
KW - Basin scale
KW - Bighorn Basin
KW - distributive fluvial system
KW - fluvial
KW - Fort Union Formation
KW - Willwood Formation
UR - http://www.scopus.com/inward/record.url?scp=85052439685&partnerID=8YFLogxK
UR - http://www.mendeley.com/research/basinscale-predictive-models-alluvial-architecture-constraints-palaeoceneeocene-bighorn-basin-wyomin
U2 - 10.1111/sed.12515
DO - 10.1111/sed.12515
M3 - Article
VL - 66
SP - 736
EP - 763
JO - Sedimentology
JF - Sedimentology
SN - 0037-0746
IS - 2
ER -