The Morrissey Formation is a stratigraphic unit of Late Jurassic (

Portlandian The Portland Group (defining the Portlandian) is a Late Jurassic ( Tithonian) lithostratigraphic group (a sequence of rock strata) in South East England. The name is derived from the Isle of Portland in Dorset where the strata are exposed and ...

) age in the

Western Canada Sedimentary Basin The Western Canadian Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary ...

. It is named for outcrops on

Morrissey Ridge Morrissey Ridge is a mountain range of the Border Ranges (Rocky Mountains), Border Ranges located south-east of Fernie, British Columbia, Fernie. See also *Ranges of the Canadian Rockies References External links

* Canadian Rockies ...

, southeast of Fernie, British Columbia, and is present in southeastern British Columbia and southwestern Alberta.

Stratigraphy and lithology

The Morrissey Formation is the basal unit of the Kootenay Group. It consists of massive, cliff-forming, fine- to coarse-grained sandstone, with minor beds and lenses of conglomeratic sandstone, and rare beds of

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

, carbonaceous

, and coal. The sequence coarsens upward and, in most areas, it can be subdivided into two members, the Weary Ridge Member at the base, and the Moose Mountain Member at the top:Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. .

Environment of deposition

The Morrissey sediments were derived from newly rising mountain ranges to the west and transported eastward by river systems. They were deposited along the edge of the Western Interior Seaway in extensive littoral, deltaic and beach environments. Thin beds of carbonaceous mudstone and coal near the top of the formation may have been deposited in interdune, lacustrine or

swale Swale or Swales may refer to: Topography * Swale (landform), a low tract of land ** Bioswale, landform designed to remove silt and pollution ** Swales, found in the formation of Hummocky cross-stratification Geography * River Swale, in North ...

environments.

Paleontology and age

Fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

, including microfossils, are very rare in the Morrissey Formation. Several genera of molluscs (e.g., '' Oxytoma'', '' Modiolus'', and possibly ''

Pachyteuthis ''Pachyteuthis'' is a genus of belemnite that lived from the Early Jurassic to the Early Cretaceous, and has been found in Asia, Europe and North America.

'') have been collected from the Weary Ridge Member. A single impression and a few fragments of the

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

'' Titanites occidentalis'', which have been recovered from the top of the Moose Mountain Member, indicate a Late Jurassic (Portlandian) age. Impressions of logs are also known from the top of Moose Mountain Member.

Thickness and distribution

The Morrissey Formation extends from the Flathead River area of southeastern British Columbia near the

Canada–United States border The border between Canada and the United States is the longest international border in the world. The terrestrial boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Can ...

to the North Saskatchewan River in western Alberta. It has a maximum recorded thickness of near

Mist Mountain Mist Mountain is a mountain located alongside Highway 40 in the Canadian Rockies of Alberta, Canada. It reaches an elevation of and is visible from Alberta Highway 40 and the Sheep River. The mountain was named in 1884 by George M. Dawson. ...

and the

Highwood Pass Highwood Pass is a mountain pass in Kananaskis Country, Alberta, Canada. It lies west of Mount Rae and Mount Arethusa of the Misty Range, south of the Elbow Pass. It lies within the Peter Lougheed Provincial Park on Alberta Highway 40. The Highwoo ...

in Alberta, and it thins eastward, reaching a zero edge along the eastern foothills of the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part ...

in Alberta.

Relationship to other units

The Morrissey Formation abruptly but conformably overlies the "Passage Beds" at the top of the

Fernie Formation The Fernie Formation is a stratigraphic unit of Jurassic age. It is present in the western part of the Western Canada Sedimentary Basin in western Alberta and northeastern British Columbia.Poulton, T.P., Tittemore, J. and Dolby, G. 1990. Jurassic ...

, and is in turn abruptly but conformably overlain by the

Mist Mountain Formation The Mist Mountain Formation is a geologic formation of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin that is present in the southern and central Canadian Rockies. It was named for outcrops along the western ...

. To the north in the vicinity of the North Saskatchewan River it interfingers with and grades into the

Nikanassin Formation The Nikanassin Formation is a stratigraphic unit of Late Jurassic (Portlandian) to Early Cretaceous (Barremian) age.Poulton, T.P., Tittemore, J. and Dolby, G. 1990. Jurassic strata of northwestern (and west-central) Alberta and northeastern Britis ...

. To the east it was truncated by pre-

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

erosion and 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

Cadomin Formation The Cadomin Formation is a stratigraphic unit of Early Cretaceous (Barremian to Aptian) age in the western part of the Western Canada Sedimentary Basin. It is extends from southeastern British Columbia through western Alberta to northeastern Bri ...

. Its correlation south of the Canada-United States border in Montana is uncertain.

References

{{WCSB, Northwest_Plains=yes, Canadian Rockies=yes Geologic formations of Canada Tithonian Stage Stratigraphy of Alberta Stratigraphy of British Columbia