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Refinement of the stratigraphic framework for the Regional C depositional unit of the McMurray Formation and implications for the early transgression of the Alberta Foreland Basin, Canada

Chloe C. F. Chateau, Shahin E. Dashtgard and James A. MacEachern
Refinement of the stratigraphic framework for the Regional C depositional unit of the McMurray Formation and implications for the early transgression of the Alberta Foreland Basin, Canada
Journal of Sedimentary Research (October 2020) 90 (10): 1322-1345

Abstract

The Lower Cretaceous McMurray Formation in Alberta and Saskatchewan, Canada, comprises a series of depositional units (DUs) consisting of stacked parasequences bounded by flooding surfaces and incised by fluvio-estuarine channel belts. The fluvio-estuarine channel belts of the McMurray Fm have been the focus of numerous studies whereas the regional DUs have received substantially less attention. Of the regional DUs, Regional C (equivalent to the middle McMurray) is the most understudied, yet this interval records the history of the McMurray Formation between deposition of fluvial strata in the lower McMurray and marine facies in the upper McMurray and overlying Clearwater Formation. Determining the history of the Regional C DU is fundamental for accurately reconstructing the stratigraphic evolution of the McMurray Fm and, by extension, the early evolution of the Alberta Foreland Basin. The Regional C is divided into two DUs separated by a regionally mappable flooding surface. This surface occurs 11 to 15 m below the top of the Regional C and is traceable over a 2,550 km2 area. This flooding surface divides the thick interval of undifferentiated Regional C into a lower C2 DU and an upper C1 DU, each with a maximum thickness of <15 m. The thickness of the C2 and C1 DUs indicates that deposition at this time also occurred in a setting of low to moderate accommodation creation, which is consistent with the rest of the McMurray Formation. The limited available accommodation space was easily surpassed by sediment supplied by the paleo-distributive channel system, leading to a basinward progradation of the shoreline. The C2 and C1 DUs are retrogradationally stacked, with the maximum regressive paleo-shoreline of C1 lying landward of that of C2. This stacking arrangement indicates that the shoreline backstepped during the early stages of transgression of the Boreal Sea. The backstepping of the paleo-shoreline from C2 to C1 time is consistent with previous studies that show continued and stepwise retrogradation and/or transgression of the paleo-shoreline from the onset of deposition in the lower McMurray Formation through to maximum transgression in the Clearwater Formation. Together, these studies demonstrate that the early drowning of the Alberta Foreland Basin was persistent and slow.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 90
Serial Issue: 10
Title: Refinement of the stratigraphic framework for the Regional C depositional unit of the McMurray Formation and implications for the early transgression of the Alberta Foreland Basin, Canada
Affiliation: Simon Fraser University, Department of Earth Sciences, Applied Research in Ichnology and Sedimentology Group, Burnaly, BC, Canada
Pages: 1322-1345
Published: 202010
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 70
Accession Number: 2021-003321
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 3 tables, sketch maps
N49°00'00" - N60°00'00", W110°00'00" - W101°19'60"
N49°00'00" - N60°00'00", W120°00'00" - W110°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 2021
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