The Grosmont Formation is a

stratigraphical Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrati ...

unit of

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during th ...

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

in the Western Canadian Sedimentary Basin. It takes the name from the hamlet of

Grosmont, Alberta Grosmont is a locality located within Athabasca County in Alberta, Canada. It is located on Highway 2, approximately northwest of the Town of Athabasca and north of Edmonton. It is northwest of Island Lake and has an elevation of . The commu ...

, and was first described in well Imperial Grosmont No. 1, in 13-17-67-23W4M, central Alberta by H.R. Belyea in 1952.

Lithology

The Formation is composed of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

and

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

with minor argillaceous dolomite, siltstone and shale. Anhydrite and anhydritic dolomite occur in the upper part ( Hondo Member) in the west and south. Porous and fractured dolomite is predominant in the eastern extent of the Formation.

Hydrocarbon production

Bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

is present from the Grosmont Formation in north-eastern Alberta. The Energy Resources Conservation Board of Alberta estimates 406 billion barrels bitumen in place. While most reserves can not be extracted economically with current technology, several production pilots target the Grosmont Formation. The first attempts to produce oil from the Grosmont dates back to the 1970s, when the Alberta Oil Sands Technology and Research Authority and industry partners Union Oil Canada and Chevron Resources Canada conducted an unsuccessful production pilot. Companies currently involved in Grosmont exploration include Shell Canada, Laricina Energy, Athabasca Oil Corporation, OSUM Oilsands Corp,

Husky Energy Husky Energy Inc. is a company engaged in hydrocarbon exploration, headquartered in Calgary, Alberta, Canada. It operates in Western and Atlantic Canada, the United States and the Asia Pacific region, with upstream and downstream business segm ...

and Sunshine Oilsands.

Distribution

The Grosmont Formation occurs mostly in the sub-surface in

central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

and northern Alberta. It was observed in outcrop along the

Peace River The Peace River (french: links=no, rivière de la Paix) is a river in Canada that originates in the Rocky Mountains of northern British Columbia and flows to the northeast through northern Alberta. The Peace River joins the Athabasca River in th ...

at Vermilion Chutes at To the east and north, the Grosmont Formation disappears along the pre-

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

erosional edge. Where present, the Grosmont formation is to thick.

Relationship to other units

The Grosmont Formation is conformably overlain by the Nisku Formation of the

Winterburn Group The Winterburn Group is a stratigraphical unit of Frasnian age in the Western Canadian Sedimentary Basin. It takes the name from Winterburn area located west of Edmonton, and was first described in well ''P.A. Pyrcz No. 1'' by Imperial Oil Limi ...

or by a thin part of the Ireton Formation (to which it is equivalent in the south). It conformably overlays the Ireton Formation or Duvernay Formation. At the

subcrop Subcrop is a term in geology. It is a contrast to the term ''Rocky outcrop, outcrop'', if not a perfect Opposite (semantics), antonym. If rocks exposed at the present-day erosion surface are referred to as outcrops, then now-buried rocks that wer ...

edge at its northeastern limit it is

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the McMurray Formation of the

Mannville Group The Mannville Group is a stratigraphical unit of Cretaceous age in the Western Canadian Sedimentary Basin. It takes the name from the town of Mannville, Alberta, and was first described in the ''Northwest Mannville 1'' well by A.W. Nauss in 1945 ...

. The lower Grosmont is equivalent to the Mikkwa Formation in northern Alberta. The entire Grosmont is equivalent to the lower Twin Falls Formation (Alexandra Member) and part of the Hay River Formation in the

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

. The Grosmont Formation is part of the Woodbend Group.

Subdivisions

The Hondo Member is an anhydritic sub-division present in the western and southern extents of the Grosmont Formation.

References

{{Western Canadian Sedimentary Basin, Northeast_Plains=yes Stratigraphy of Alberta Frasnian Stage