Grosmont Formation
Encyclopedia
The Grosmont Formation is a stratigraphical
unit of Frasnian
age
in the Western Canadian Sedimentary Basin
.
It takes the name from the hamlet of Grosmont, Alberta
, and was first described in well Imperial Grosmont No. 1, in 13-17-67-23W4M, central Alberta
by H.R. Belyea in 1952.
and dolomite
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.
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.
and northern Alberta
. It was observed in outcrop along the Peace River
at Vermilion Chutes at 58°22′N 114°55′W
To the east and north, the Grosmont Formation disappears along the pre-Cretaceous
erosional edge. Where present, the Grosmont formation is 100 metres (328.1 ft) to 230 metres (754.6 ft) thick.
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 edge at its northeastern limit it is unconformably
overlain by the McMurray Formation
of the Mannville Group
.
The lower Grosmont is equivalent to the Mikkwa Formation in northen 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 Grosmont Formation is part of the Woodbend Group
.
sub-division present in the western and southern extents of the Grosmont Formation.
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
unit of Frasnian
Frasnian
The Frasnian is one of two faunal stages in the Late Devonian epoch. It lasted from 385.3 ± 2.6 million years ago to 374.5 ± 2.6 million years ago. It was preceded by the Givetian stage and followed by the Famennian stage...
age
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
in the Western Canadian Sedimentary Basin
Western Canadian Sedimentary Basin
The Western Canadian Sedimentary Basin is a vast sedimentary basin underlying of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock...
.
It takes the name from the hamlet of Grosmont, Alberta
Grosmont, Alberta
Grosmont is an unincorporated area in Alberta.The Grosmont Formation, a bitumen bearing stratigraphical unit of the Western Canadian Sedimentary Basin was first observed in well Imperial Grosmont No. 1 and was named for the community....
, and was first described in well Imperial Grosmont No. 1, in 13-17-67-23W4M, central Alberta
Central Alberta
Central Alberta is a region located in the Canadian province of Alberta.Central Alberta is the most densely populated rural area in the province...
by H.R. Belyea in 1952.
Lithology
The Formation is composed of limestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
and dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
with minor argillaceous dolomite, siltstone and shale. Anhydrite
Anhydrite
Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...
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 is present from the Grosmont Formation in north-eastern Alberta. The Energy Resources Conservation BoardEnergy Resources Conservation Board
The Energy Resources Conservation Board is an independent, quasi-judicial agency of the Government of Alberta. It regulates the safe, responsible, and efficient development of Alberta's energy resources: oil, natural gas, oil sands, coal, and pipelines...
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.
Distribution
The Grosmont Formation occurs mostly in the sub-surface in centralCentral Alberta
Central Alberta is a region located in the Canadian province of Alberta.Central Alberta is the most densely populated rural area in the province...
and northern Alberta
Northern Alberta
Northern Alberta is a region located in the Canadian province of Alberta.Its primary industry is oil and gas, with large heavy oil reserves being exploited at the Athabasca Oil Sands and Wabasca Area in the east of the region...
. It was observed in outcrop along the Peace River
Peace River (Canada)
The Peace River 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 flows into the Slave River, a tributary of the Mackenzie River. The Mackenzie is the 12th longest river in the world,...
at Vermilion Chutes at 58°22′N 114°55′W
To the east and north, the Grosmont Formation disappears along the pre-Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
erosional edge. Where present, the Grosmont formation is 100 metres (328.1 ft) to 230 metres (754.6 ft) thick.
Relationship to other units
The Grosmont Formation is conformably overlain by the Nisku Formation of the Winterburn GroupWinterburn 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...
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 edge at its northeastern limit it is unconformably
Unconformity
An unconformity is a buried erosion 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 of time before deposition of the younger, but the term is used to describe...
overlain by the McMurray Formation
McMurray Formation
The McMurray Formation is a stratigraphical unit of Cretaceous age in the Western Canadian Sedimentary Basin.It takes the name from Fort McMurray, and was first described in the outcrop occurring on the banks of the Athabasca River by F.H...
of the Mannville Group
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...
.
The lower Grosmont is equivalent to the Mikkwa Formation in northen 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
Northwest Territories
The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...
.
The Grosmont Formation is part of the Woodbend Group
Woodbend Group
The Woodbend Group is a stratigraphical unit of Frasnian age in the Western Canadian Sedimentary Basin.It was first described in the British American Pyrcz No...
.
Subdivisions
The Hondo Member is an anhydriticAnhydrite
Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...
sub-division present in the western and southern extents of the Grosmont Formation.