Facies distribution and stratigraphic architecture of the Lower Cretaceous McMurray Formation, Lewis Property, northeastern Alberta

Abstract

Research Article| June 01, 2007 Facies distribution and stratigraphic architecture of the Lower Cretaceous McMurray Formation, Lewis Property, northeastern Alberta Erin E. Crerar; Erin E. Crerar Nexen Inc., 801 - 7 Avenue SW, Calgary, AB T2P 3P7 Search for other works by this author on: GSW Google Scholar R.W.C. Arnott R.W.C. Arnott Department of Earth Sciences, Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, ON K1N 6N5 Search for other works by this author on: GSW Google Scholar Author and Article Information Erin E. Crerar Nexen Inc., 801 - 7 Avenue SW, Calgary, AB T2P 3P7 R.W.C. Arnott Department of Earth Sciences, Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, ON K1N 6N5 Publisher: Canadian Society of Petroleum Geologists Received: 24 Jan 2005 Accepted: 20 Apr 2007 First Online: 03 Oct 2017 Online ISSN: 2368-0261 Print ISSN: 0007-4802 © The Society of Canadian Petroleum Geologists Bulletin of Canadian Petroleum Geology (2007) 55 (2): 99–124. https://doi.org/10.2113/gscpgbull.55.2.99 Article history Received: 24 Jan 2005 Accepted: 20 Apr 2007 First Online: 03 Oct 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Erin E. Crerar, R.W.C. Arnott; Facies distribution and stratigraphic architecture of the Lower Cretaceous McMurray Formation, Lewis Property, northeastern Alberta. Bulletin of Canadian Petroleum Geology 2007;; 55 (2): 99–124. doi: https://doi.org/10.2113/gscpgbull.55.2.99 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of Canadian Petroleum Geology Search Advanced Search Abstract Within the Lewis study area (Townships 91–92, and Ranges 6–8W4), McMurray Formation strata comprise four facies associations that form a depositional continuum of braided-fluvial (FA1), tidally-influenced braided- or low-accommodation meandering-fluvial and meandering-tidal channel-fills (FA2), associated overbank (FA3), and open-estuarine tidal flat deposits (FA4). The primary reservoir occurs in transgressive FA2 deposits.Lower-FA2 channels incise older water-saturated FA1 sand and consist of medium to locally-coarse, bitumen-saturated sand with rare to locally common pin-stripe laminated and/or 1–5 cm thick mud beds. Channels were initially confined by steep valley walls formed along the sub-Cretaceous unconformity. As a consequence, coeval interchannel sediment (FA3) was cannibalized by lateral channel migration and occurs only as common mud-clasts. The net result was the accumulation of a sand-rich, sheet-like deposit with locally-preserved fine-grained interchannel deposits, suggesting a high rate of lateral versus vertical accretion.With the filling and elimination of the irregular paleotopography along the unconformity, upper-FA2 channels became unconfined and formed thick, areally extensive inclined heterolithic stratification (IHS) deposits. Similarly, coeval interchannel deposits are more widely-distributed and thickly preserved compared to underlying strata. The position of upper-FA2 channels was indirectly influenced by paleotopography along the unconformity because IHS strata are thickest and sandiest along trends that overlie earlier channel systems, suggesting that syn-depositional salt dissolution controlled channel position and infilling history. Stratigraphically-upward there is a gradational change to tidal-flat deposits (FA4), suggesting abandonment of the main north-south channel system and a condition of coarse-grained bedload sediment starvation.Although most point-bar deposits within the Lewis study area consist of 10–30 m thick vertically-stacked successions of incomplete IHS deposits, several complete successions from channel base to overbank deposits are preserved. The geometric similarity between meandering-fluvial channels of different scales, climatic regimes, and substrate conditions suggest that the geometry of meanders is governed by mechanical principles. Although the applicability of these relationships to meandering-tidal channels is equivocal, using these formulas on IHS deposits of the McMurray Formation can provide a first order approximation of channel width (W=1.5h/tanβ ), depth (0.595h), meander wavelength (λ=10.9w1.01), and point-bar length (1/2λ). For two examples of complete point-bar deposits, channel widths were estimated to be at 148 m and 336 m; channel depth 12.6 m and 18.7 m; meander wavelength 1718 m and 3930 m; and point-bar length 859 m and 1965 m. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.