Stratigraphy and facies of Cambrian to Lower Ordovician strata in Saskatchewan

Abstract

Abstract Cambrian to Lower Ordovician strata in Saskatchewan are present only in the subsurface and are mostly siliciclastic. They are divided into three units which, in ascending order, are the informally named Basal Sandstone Unit overlain by the Earlie Formation and Deadwood Formation. Strata of the Basal Sandstone Unit and Earlie Formation are Middle Cambrian and those of the Deadwood Formation range from the Upper Cambrian to Lower Ordovician. Sedimentary facies indicate that all units were deposited in environments ranging from shoreface to shallow-water shelf. Two major transgressive-regressive sequences are identified in these strata; the older is comprised of the Basal Sandstone Unit and most of the Earlie Formation, and the younger one is mostly the Deadwood Formation. The boundary between the two sequences shows very little evidence of erosion but the younger sequence overlaps the older sequence in an easterly direction. The upper boundary of the younger sequence is a major erosional surface. Facies trends in the sequences indicate an eastern to northeastern source of the siliciclastic sediment. The Saskatchewan succession is comparable to similar age strata in north-central and western USA, and the Interior Plains of Western Canada and the Northwest Territories. Many sandstone beds in the succession are porous and would be suitable petroleum reservoirs but the source rock potential of the associated shale appears poor. However, the reported presence of Gloeocapsomorpha sp., a fossil with known hydrocarbon-producing potential, could be a positive indicator if it can be found concentrated in organic-rich laminae or thin beds.