Controls on facies distributions in the Charlie Lake Formation, Peace River Arch, Alberta

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1 Controls on facies distributions in the Charlie Lake Formation, Peace River Arch, Alberta E.L. Percy 12, C. Frostad 2, A. Juska 2, C. Schmidt 2, C. Sitzler 2, and J.P. Zonneveld 3 University of Calgary, Tourmaline Oil Corp, University of Alberta Summary The Triassic marks a transition from a passive margin to a foreland basin setting in Western Canada, resulting in the transition from carbonate-dominated deposits of the Paleozoic to clastic-dominated successions in the Mesozoic (eg. Ferri and Zonneveld, 2008; Beranek and Mortensen, 2007; 2011; Zonneveld and Moslow, in press). The sediments of the Upper Triassic Charlie Lake Formation record a portion of this important structural and paleogeographic transition, and host significant volumes of hydrocarbons. Despite the geologic and economic importance of this formation, it is underrepresented in the geologic literature and is arguably one of the least understood intervals in Western Canadian Sedimentary Basin. This study aims to describe and map the distributions of lithofacies in the Charlie Lake Formation in the Peace River Arch area to understand how this succession was accumulated. Introduction and Study Area The Upper Triassic Charlie Lake Formation is a complex heterolithic succession dominated by sabkha-style deposits (Arnold, 1994) deposited during an interval of global aridity, resulting in an unusual mixture of siliciclastic, carbonate and evaporite rocks (Zonneveld et al., 2001). The Charlie Lake Formation was deposited along the western margin of the North American craton, with the thickest accumulation occurring in the vicinity of the collapsed Peace River Arch (Davies, 1997). The Peace River Arch area is characterized by southwest and northeast striking normal faults that formed during the Precambrian to Carboniferous and were reactivated during Triassic sedimentation (Davies, 1997). Recent research suggests that the Western Canadian Foreland Basin started to form during the Triassic, rather than in the Early Jurassic (Unterschutz et al., 2002; Ferri and Zonneveld, 2008; Beranek and Mortensen, 2011; Golding et al., 2016a; Golding et al., 2016b; Rohais et al., 2016). The onset of compression in the fold and thrust belt resulted in significant angular unconformities (such as the Coplin Unconformity), as well as synand post-depositional controls on facies and pay distributions within the strata of the Charlie Lake Formation in the Peace River Arch area.

2 The study area for the present project covers the Peace River Arch (PRA) area within Alberta. In this study well logs, 3D seismic, and core descriptions were integrated to understand the stratigraphic architecture and depositional model of the Charlie Lake for the study area. Results and Interpretations The Charlie Lake in the study area is divided into an upper unit, a Middle Boundary Lake unit, and a lower unit for this study. The top of the lower unit is marked by the Coplin unconformity. This angular unconformity overlies strata that dips significantly westward due to post depositional uplift of the North American craton. The lower unit is composed of three members dominated by sabkha style deposits of dolomitic algal mats, red beds, and anhydrite. Significant vertical and lateral facies heterogeneity occur within the lower unit. The Middle Unit (the Boundary Lake Member) occurs between the Coplin and Boundary Lake unconformities; however, this unit was outside the scope of the present study and is not further discussed. The upper unit overlies the Boundary Lake unconformity and consist of alternating clastic-dominated members and members composed of sabkha deposits (Figure 1). The top of the upper unit is truncated by the Worsley unconformity, or by the base of the Baldonnel Formation in some areas. The clastic members are composed of relatively uniform distributions of dolomitic siltand sandstone beds deposited in tidal flat/tidal channel environments. The members dominated by sabkha deposits are composed of similar facies as the lower unit. Members within the upper unit are erosionally truncated by unconformities towards the eastern erosional edge of the Charlie Lake Formation. Controls on the distribution of reservoir-quality lithologies (i.e. pay distribution) are dominated by two factors: the lateral distribution and thicknesses of reservoir facies within syn-depositional fault-basins; and secondary dissolution caused by post-depositional erosion. The control on reservoir facies distribution differs for members dominated by sabkha deposits versus those dominated by clastic lithologies. The distribution of dolomitic stromatolites and anhydrite within the sabkha deposits correlate with reactivated Mississippian aged faults identified through seismic and residual maps. During deposition of the sabkha lithologies subtle topographic relief, caused by the uplift and down-dropping of basement blocks, resulted in syn-depositional control on the distribution of pay and non-pay lithologies. For the clastic members, pay coincides with the updip erosional edge of each member indicating post-depositional porosity enhancement due to secondary dissolution. Conclusions The onset of compressional tectonics during the Upper Triassic had a significant influence on facies distributions, as well as on syn-depositional and post-depositional erosion of the various members of the Charlie Lake Formation. Controls on reservoir distribution within the Charlie Lake Formation depend on the lithology of each member. Clastic members are more homogenous allowing for post-depositional porosity enhancement due to groundwater dissolution where they are overlain by subaerial unconformities whereas syn-depositional structural control dominated reservoir distribution in sabkha-style units.

3 References Arnold, K. J., 1994, Origin and distribution of aeolian sandstones in the Triassic Charlie Lake Formation, northeastern British Columbia, MSc thesis, University of Alberta, 320 p. Beranek, L.P. and Mortensen, J.K A Triassic link between Yukon-Tanana and North America; anew detrital zircon age, geochemical, and biostratigraphic data. Geological Society of America, Cordilleran Section, Abstracts with Program, v. 38, p Beranek, L.P., J.K. Mortensen, M.J. Orchard, and T. Ulrich Provenance of North American Triassic strata from west-central and southeastern Yukon: correlations with coeval strata in the Western Canadian Sedimentary Basin and Canadian Arctic Islands. Canadian Journal of Earth Sciences, 47: Ferri, F. and Zonneveld, J-P Were Triassic rocks of the Western Canada Sedimentary Basin deposited in a Foreland. Canadian Society of Petroleum Geologists Reservoir, v. 35, p Furlong, C.M., Gingras, M.K., and Zonneveld, J.P Bioturbation influence on reservoir quality: A case study from the Anisian Wedge of the Lower Triassic Montney Formation. British Columbia Unconventional Gas Technical Forum Golding, M. L., J. K. Mortensen, J. P. Zonneveld, and M. J. Orchard, 2016a, U-Pb isotopic ages of euhedral zircons in the Rhaetian of British Columbia: implications for Cordilleran tectonics during the Late Triassic, Geosphere, v. 12, no. 5, p Golding, M. L., J. K. Mortensen, F. Ferri, J. P. Zonneveld, and M. J. Orchard, 2016b, Determining the provenance of Triassic sedimentary rocks in northeastern British Columbia and western Alberta using detrital zircon geochronology, with implications for regional tectonics, Canadian Journal of Earth Scienes, v. 53, p Rohais, S., V. Crombez, T. Euzen, and F. Baudin, 2016, The Lower and Middle Triassic of Western Canada: passive margin, back-arc, or fore-arc geodynamic setting?, Geoconvention abstract, Calgary CA, March Unterschultz, J. L. E., R. A. Creaser, P. Erdmer, R. I. Thompson, and K. L. Daughtry, 2002, North American margin origin of Quesnel terrane strata in the southern Canadian Cordillera: inferences from geochemical and Nd isotopic characteristics of Triassic metasedimentary rocks, GSA Bulletin, v. 114, no. 4, p Zonneveld, J. P., M. K. Gingras, and S. G. Pemberton, 2001, Trace fossil assemblages in a Middle Triassic mixed siliciclastic-carbonate marginal marine depositional system, British Columbia, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 166, p

5 Figure 1: Described core and corresponding logs for part of the upper Charlie Lake Formation. The lithology alternates between dolomitic and anhydrite-bearing stromatolite shallow subtidal/sabkha facies, and siliciclastic intertidal facies.

Carboniferous Stoddart Group: An integrated approach

Carboniferous Stoddart Group: An integrated approach Abu Yousuf*, Department of Geoscience, University of Calgary, Calgary, Alberta yousufabu@hotmail.com and Charles M. Henderson, Department of Geoscience,