Age determination of the Lower Watrous red-beds of the Williston Basin, Saskatchewan, Canada

Abstract

The age of the Lower Watrous red-beds, which host hydrocarbon reserves in the Williston Basin, along with equivalent formations in Manitoba (Lower Amaranth Formation) and the U.S.A. (Saude Member of the Spearfish Formation) is a controversial subject, with this succession being assigned ages from Mississippian to Middle Jurassic; a timespan of over 150 million years. Using existing published data and new geochemical analyses on the Watrous Formation, we present a Triassic age for the Lower Watrous red-beds.An established well-log correlation dates the Saude Member red-beds as post-Middle Permian.Some previously published geochemical and palynological data from equivalent formations are in agreement with this age, but several palaeomagnetic studies have provided conflicting results, with age assignments of Mississippian through to Late Triassic. Our study demonstrates the equivalency of the Saude Member and Lower Watrous red-beds by extending the well-log correlation north, from the U.S.A. into Saskatchewan. The combined new strontium, sulfur and oxygen isotopic analyses of isolated Lower Watrous anhydrite nodules are most consistent with an Early or Late Triassic age, which is in agreement with the well-log correlation and potassiumargon dating of a pre-red-beds impact structure. A Pennsylvanian age for the Lower Watrous red-beds is considered most unlikely.

The Late Great Unconformity of the Central Canadian Shield

“…Although Paleozoic units in the Williston Basin extend into the Mississippian (e.g., Porter et al, 1982), in the Hudson Bay Basin, the top of the preserved stratigraphic section is late Devonian (e.g., Norris, 1993). In the Williston Basin, Triassic and Jurassic terrestrial deposits overlie Ordovician through Mississippian units above a widespread angular unconformity, followed by Middle Jurassic to Paleocene strata that mark a shift to foreland basin deposition (e.g., Butcher et al, 2012;Husain, 1991;Porter et al, 1982).…”

“…Additionally, for samples closest to the Williston and Hudson Bay Basins (MB-04 and 96-10), we restrict the early-mid Paleozoic temperatures to below 70 °C, based on ∼2 km of preserved strata of that age in each basin (e.g., Burrus et al, 1996;Sanford & Grant, 1990), although simulations without this constraint were also tested (Figure S2). At 325-220 Ma, we impose another near-surface constraint based on an angular unconformity between Mississippian and Triassic/Jurassic units in the Williston Basin (e.g., Butcher et al, 2012;Husain, 1991). We also require that all paths reach surface temperatures by present-day.…”

3D stratigraphic architecture, sedimentary budget, and sources of the Lower and Middle Triassic strata of western Canada: evidence for a major basin structural reorganization

“…1) and (2) the Williston Basin (North Dakota and South Saskatchewan, Edwards et al, 1994). In the Williston basin, the Triassic interval consists of poorly-dated, continental red bed deposits (Cumming, 1956;Carlson, 1968;Edwards et al, 1994, Butcher et al, 2012 whereas in the WCSB, the Lower to Middle Triassic strata preserves a variety of marine and marginal marine environments (Armitage, 1962, Davies, 1997Davies et al, 1997;Zonneveld et al, 1997;Dixon, 2000;Zonneveld et al, 2001;Zonneveld, 2001;Zonneveld, 2009, Furlong et al, 2018 a). In the subsurface of the WCSB marine deposits of the Lower and Middle Triassic (approx.…”

Alluvial Fans, Loess Plains, Lakes, and Distributive Fluvial Systems: Depositional Systems of the Permian-Triassic Red Beds and Evaporites of Wyoming (USA)

“…Defining characteristics of these fine-grained, chemically immature sandstones and siltstones are a red-orange color, spatially-extensive layer-cake bedding, an association with gypsum and halite, a paucity of body and trace fossils, and a distinctive alternating resistant-recessive bedding pattern. Examples of similar red beds include the Spearfish Formation of the Black Hills and Williston Basin (USA; (Dow, 1964), the Lower Watrous red beds of south-central Canada (Cumming, 1956;Butcher et al, 2012), and the Cumbrian Coastal and Sherwood Sandstone Groups in northwestern England and southwestern Scotland (Brookfield, 2004). The red pigmentation in the Red Peak Formation has been interpreted as originating during post-compaction diagenesis .…”