Low-accommodation foreland basin response to long-term transgression: A record of change from continental-fluvial and marginal-marine to open-marine sequences over 60,000 km2 in the western Canada foreland basin

• Published in: Marine and petroleum geology Vol. 139; p. 105583
• Main Authors: Peng, Yang, Hagstrom, Cynthia A., Horner, Sean C., Hodgson, Cheryl A., Martin, Harrison K., Leckie, Dale A., Pedersen, Per K., Hubbard, Stephen M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2022
• Subjects: Deltas; Low-accommodation foreland basin; Meandering channel-belt deposits; Strandplain/shoreface; Tidal channels and bars; Transgressive sequence; Deltas; Transgressive sequence; Tidal channels and bars; Meandering channel-belt deposits; Low-accommodation foreland basin; Strandplain/shoreface
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2022.105583

Low-accommodation foreland basins have been of recent interest because their stratigraphic architectures provide insight into the interaction of tectonic subsidence and eustasy. Aptian-aged strata in Alberta, Canada (McMurray Formation and Wabiskaw Member) were deposited under the influence of a continental-scale river that longitudinally transported and debouched sediment into the southward-transgressing Boreal Sea in the distal, low-accommodation Western Canada Foreland Basin (WCFB). In this study, we present a high-resolution stratigraphic framework for the McMurray-Wabiskaw interval, which was deposited during a long-term transgression. Using wireline logs from >20,000 wells and more than 500 cores, regional mapping focused on resolving stratigraphic relationships and the distribution of depositional environments across approximately 60,000 km2 in the Athabasca Oil Sands Region of northeastern Alberta. The studied stratigraphic interval is part of a third-order sequence: the McMurray Formation developed during a period of relative sea-level fall, lowstand, and early transgression, while the overlying Wabiskaw Member was deposited during late transgression. Within the McMurray Formation, superimposed fourth-order sea-level fluctuations in this low accommodation setting created a complex amalgam of deltaic strata vertically and laterally juxtaposed with valley-fill deposits. Relative sea-level rises resulted in rapid transgressions in which the shorelines migrated >400 km landward. Thin (5–15 m thick), widespread deltaic parasequence sets were deposited during subsequent sea-level highstands. During relative sea-level falls, fluvial meandering channel belts developed in downcutting valleys, with associated shorelines dramatically prograding basinward. In the Wabiskaw Member, continued sea-level rise coupled with potentially decreasing sediment supply resulted in the development of tide-influenced/dominated channels and bars in estuaries. The final phase of the third-order transgression was marked by a regional transgressive ravinement event and several southwestward backstepping wave-dominated shorefaces/strandplains. This low-accommodation foreland basin succession demonstrates a transition from deposition in continental fluvial and marginal-marine settings subject to high-frequency eustatic changes, to open-marine conditions over a long-term transgression. •The McMurray-Wabiskaw interval demonstrates a high-resolution stratigraphic framework in a distal, low-accommodation foreland basin•The stratigraphy illustrates a transition from deposition in continental fluvial and marginal-marine settings to open-marine conditions over a 3rd-order transgression.•4th-order sea-level fluctuations led to the deposition of repeated packages of meandering channel belt strata and deltaic deposits in the basin•The juxtaposition of fluvial meandering channel belts and deltas was more influenced by eustatic changes given its low accommodation and topographic relief•Later stage of the overall transgression was marked by tide-influenced channels and bars in estuaries and backstepping wave-dominated shorefaces/strandplains