We review currently available Canadian and international lithostratigraphic and lithodemic schemes and find most of them inadequate for classifying intrusive and strongly metamorphosed rocks of Canada and beyond. A new system is proposed, one that unifies, complements, and extends components of the revised North American Stratigraphic Code, the British Geological Survey Rock Unit Classification System of 2021, and the International Stratigraphic Guide of 1999. This new Cooperative Lithodemic and Stratigraphic System (CLASS) is intended to serve as a practical guide to geoscientists who need to classify and report on lithodemic units in North America and has broad applicability to other jurisdictions. It is built with database management practices in mind and employs the concept of inheritance of root characteristics between seven formal rock unit ranks, which will allow incorporation of the scheme into compact object-oriented and relational databases designed for purpose. Broad application of CLASS, especially to historically problematic lithodemic units, should help to foster jurisdictional interoperability, data sharing, global compilations, and thematic studies. At the heart of this proposed system is a subdivision and accompanying nomenclature that allows classification of rocks into seven formal ranks. Following the well-established lithostratigraphic supergroup, group, subgroup, formation, member, submember, and bed approach, CLASS proposes three classes of lithodemic subdivisions for formally naming lithodemic rock units.

Lithostratigraphic correlation and mapping of formations and units within the Upper Elk Point subgroup provide updated information on their extent and distribution within the province of Alberta. Together with detailed bed-scale evaporite mapping of three evaporite minerals — halite, anhydrite, and gypsum — within evaporitic successions for net-thickness maps, these data allow new representations of the paleogeography of these units across the province. Paleogeographic maps of the Keg River, Prairie Evaporite and Muskeg formations reveal new details on the location of the La Crete sub-basin in northern Alberta, and the distribution and nature of Keg River Formation buildups and the overlying evaporite strata within this depositional realm. Net-evaporite mapping gives a robust picture of the distribution of Upper Elk Point subgroup evaporites, and allows for a detailed characterization of heterogeneities, halite dissolution, and sulphate karstification. Mapping of gypsum reveals that rehydration of anhydrite to gypsum (gypsification) through meteoric inflow is most pronounced within the La Crete sub-basin in northeastern Alberta, particularly where thick anhydrite deposits are associated with interbuildup basinal areas east of the Prairie Evaporite halite dissolution scarp. This association provides an explanation for the location of where active gypsification, dissolution and associated karstification is occurring and where it can be expected to occur. The process of gypsification, and ultimately sulphate dissolution, is requisite for the formation of porous dedolomite zones within the carbonates of the Prairie Evaporite Formation. Dedolomitized beds are recognized as aquifer units that are known to have contributed to Devonian-sourced, high-salinity water inflows to mine pits in the mineable oil sands area. Evidence is provided for a top-down advancement of halite and sulphate dissolution in all evaporites in northeastern Alberta. Circular, chain-like karst lakes are likely surficial expressions of the meteoric conduits for top-down karstification of sulphates east of the Prairie Evaporite halite dissolution scarp, similar to that observed in the well-documented sulphate karst district of Wood Buffalo National Park.

Dedolomitization is a common diagenetic process in shallow burial environments and is often associated with sulphates in mixed carbonate‐evaporite successions. In these settings, elevated Ca2+/Mg2+ ratios necessary for dedolomitization result from the dissolution of sulphate phases by the incursion of undersaturated groundwater. Reported dedolomite textures from other studies are varied, but the most prevalent is a rhombic texture interpreted to result from the partial to complete pseudomorphic replacement of secondary dolomite rhombs formed in the burial diagenetic realm. In this study of primary cryptocrystalline to finely crystalline dolomicrites in the Prairie Evaporite Formation of north‐eastern Alberta, dedolomitization has resulted in sutured to loosely packed mosaics of dedolomite that range from subhedral to distinctly euhedral (rhombic) crystal fabrics; however, no prior aggrading neomorphism producing dolomite rhombs is evident in the precursor dolomicrites. Non‐pseudomorphic dedolomitization of the dolomicrites results in textures that include rhombic dedolomite crystals with cloudy cores comprising remnant dolomicrite and clear rims. These textures are similar to those observed in the pseudomorphic dedolomitization of secondary dolomite rhombs. The Prairie Evaporite Formation of north‐eastern Alberta has experienced extensive karstification near the erosional margin of the sedimentary succession. Dedolomitization of dolomicrites occurs in marker beds within the Prairie Evaporite succession associated with evaporite karstification. Along with stratigraphic and petrographic considerations, stable isotope results support the interpretation of a shallow dedolomitization event influenced by meteoric waters derived from the basin margin. Negative δ18O and low δ13C values (averages of −13·6‰VPDB and 0·5‰VPDB, respectively) of the dedolomite, compared with those of the primary dolomicrite (averages of −6·0‰VPDB and 1·2‰VPDB, respectively), point to isotopically light diagenetic fluids. These results show that rhombic dedolomite textures can form through shallow, non‐pseudomorphic dedolomitization of dolomicrites by meteoric fluids in the presence of sulphates, with resulting textures that are similar to the pseudomorphic dedolomitization of secondary dolomite rhombs.

Elk Point Group outcrops in the Athabasca Oil Sands mining region (AOSMR) and adjacent areas include exposures of the La Loche, Contact Rapids, Keg River, and Prairie Evaporite formations. Here, we review prior investigations of these formations in outcrop, followed by new descriptions of some outcrops, including those previously unpublished or newly discovered.The fluvial to marginal marine sandstone and conglomerate of the La Loche Formation, informally known as the granite wash, outcrops along the Clearwater River in Saskatchewan, where it is sandwiched between the Precambrian basement and the Contact Rapids Formation. In Alberta, the La Loche Formation is exposed at a locality along Whitemud Falls, where it directly underlies the Keg River Formation as a lithic sandstone and fills paleokarst crevices in the Keg River dolostone. From these two outcrops we recognize three facies in the La Loche Formation: regolith, lithic conglomerate, and lithic to arkosic sandstone. The marginal marine shale, silt, and dolomite of the Contact Rapids Formation outcrops in Saskatchewan at its namesake Contact Rapids, but is exposed only as a slumped bank of grey to greenish mud. We examined Keg River Formation dolostone from three outcrops along the Clearwater River at Contact Rapids in Saskatchewan and Whitemud Falls and Cascade Rapids in Alberta. We also describe an outcrop on the Firebag River in Alberta. From these outcrops, we recognize three general facies: bedded to laminated cryptalgal dolomitized bindstone (originating from an intertidal paleoenvironment), coral and stromatoporoid-bearing dolomitized floatstone to rudstone (originally a reef), and crinoid and brachiopod dolomitized floatstone (from off-reef or inter-reef areas). A newly recognized outcrop of the collapse residue from the dissolved Prairie Evaporite Formation occurs along the Clearwater River, where cobbles and boulders of breccia and other less soluble Prairie Evaporite rock weather out of the river bank between several sulfur springs.

The distribution and extent of Paleozoic strata within an area encompassing 874 townships in northeast Alberta have been updated based on detailed regional-scale lithostratigraphic mapping and modelling. Precambrian basement paleotopography strongly influenced the distribution of Keg River Formation carbonate buildups and interbuildup basins, which in turn largely controlled the depositional patterns in the overlying Prairie Evaporite Formation. Keg River paleotopography controlled the type of evaporites that were deposited, particularly at the Whitkow Member level of the Prairie Evaporite Formation. Keg River paleotopography continued to have an effect on the overlying sedimentary succession including the Cretaceous strata in areas where evaporites in the Prairie Evaporite Formation were removed by intrastratal dissolution. East of the regional Prairie Evaporite halite dissolution scarp, enhanced structuring of the sub-Cretaceous unconformity occurs by the draping of Waterways strata over Keg River paleotopography, especially along the Athabasca Arch. Structural mapping and modelling of the Prairie Evaporite Formation, and isopach mapping of halite and anhydrite therein using modern well control, provide the basis for an updated version of the location and extent of the Prairie Evaporite halite dissolution scarp. A new regionally correlatable marker bed, the Conklin, is introduced within the Prairie Evaporite Formation. Detailed correlation of this marker bed, along with previously established member and marker bed stratigraphy from the Prairie Evaporite Formation, reveals a well-defined pattern of evaporite karst within the halite dissolution scarp, and provides evidence for the top-down removal of halite throughout the study area. A regional Devonian subcrop model, together with a paleogeographic reconstruction of the sub-Cretaceous unconformity, highlight the control that karst processes in the Prairie Evaporite Formation and resulting Devonian structure have had on accommodation space and depositional patterns in the overlying lowermost formations within the Mannville Group.

A number of potential geothermal targets have been previously identified in the Alberta Basin (Canada). These targets were identified mainly based on temperature data collected by the oil and gas industry, which are known to be inherently biased by drilling activities and contain large measurement errors. Utilizing the vast number of measurements available from the oil and gas industry we have determined which measurements are statistically reliable in order to re-evaluate the previous temperature estimates for these anomalies, and provide a regionally accurate temperature model. Over 70% of the available measurements were removed from the temperature database based on this method, resulting in a regionally consistent database with average standard deviations of 3°C across all measurement locations.

Recent geothermal exploration indicated that the Cambrian Basal Sandstone Unit (BSU) in central Alberta could be a potential target formation for geothermal heat production, due to its depth and extent. Although several studies showed that the BSU in the shallower Western Canada Sedimentary Basin (WCSB) has good reservoir properties, almost no information exists from the deeper WCSB. This study investigated the petrography of the BSU in central Alberta with help of drill cores and thin sections from six wells. Porosity and permeability as important reservoir parameters for geothermal utilization were determined by core testing. The average porosity and permeability of the BSU is 10% and <1 × 10−14 m2, respectively. A zone of high porosity and permeability was identified in a well located in the northern part of the study area. This study presents the first published geomechanical tests of the BSU, which were obtained as input parameters for the simulation of hydraulic stimulation treatments. The BSU has a relatively high unconfined compressive strength (up to 97.7 MPa), high cohesion (up to 69.8 MPa), and a remarkably high friction coefficient (up to 1.22), despite a rather low tensile strength (<5 MPa). An average geothermal gradient of 35.6 °C/km was calculated from about 2000 temperature values. The temperature in the BSU ranges from 65 to 120 °C. Results of this study confirm that the BSU is a potential geothermal target formation, though hydraulic stimulation treatments are required to increase the permeability of the reservoir.

Summary We present an updated correlation and composite section of the Moberly Member (Waterways Formation) outcrops in the Athabasca Oil Sands mining region in Alberta. Notable trends in the lithology and paleontology of the outcrops include (a) a southward increase in the argillaceous portion of the sediment in the lower part of the section and a northward increase in argillaceous sedimentation in the upper portion of the section; (b) a general decline in fossil abundance and richness diversity in the upper portion of the section, along with the disappearance of some fossil taxa; (c) a northeastsouthwest trend in the Moberly Member biostrome unit from one dominated by branching, bulbous, and tabular forms in the northeast to one with only massive stromatoporoids surrounded by Radiatrypa brachiopods in the south to a presumably offshore, non-biostromal unit containing a diverse fauna and heavily bioturbated with Thalassinoides burrow networks in the southwest.