The Morrissey Formation is a

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characteriz ...

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

(

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 ha ...

) age in the

Western Canada Sedimentary Basin The Western Canada 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 ba ...

. It is named for

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s on Morrissey Ridge, southeast of

Fernie, British Columbia Fernie is a city in the Elk Valley (British Columbia), Elk Valley area of the East Kootenay region of southeastern British Columbia, Canada, located on British Columbia provincial highway 3, BC Highway 3 on the western approaches to the Crows ...

, and is present in southeastern

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

and southwestern

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

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 Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, 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. Although its permeabil ...

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.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

, carbonaceous

, and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

. 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 The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...

in extensive

littoral The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely i ...

deltaic A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creati ...

and

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from Rock (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological s ...

environments. Thin beds of carbonaceous mudstone and coal near the top of the formation may have been deposited in interdune,

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

or swale 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 ...

, including

microfossils A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

, are very rare in the Morrissey Formation. Several genera of

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

(e.g., '' Oxytoma'', '' Modiolus'', and possibly '' Pachyteuthis'') have been collected from the Weary Ridge Member. A single impression and a few fragments of the

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

'' 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 The Flathead River (, , ), in the northwestern part of the U.S. state of Montana, originates in the Canadian Rockies to the north of Glacier National Park and flows southwest into Flathead Lake, then after a journey of , empties into the Cla ...

area of southeastern British Columbia near the

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

to the

North Saskatchewan River The North Saskatchewan River is a glacier-fed river that flows from the Canadian Rockies continental divide east to central Saskatchewan, where it joins with the South Saskatchewan River to make up the Saskatchewan River. Its water flows event ...

in western Alberta. It has a maximum recorded thickness of near

Mist Mountain Mist Mountain is a mountain located alongside Alberta Highway 40, Highway 40 in the Canadian Rockies of Alberta, Canada. It reaches an elevation of and is visible from Highway 40 and the Sheep River (Alberta), Sheep River. The mountain was name ...

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 Elbow Pass. It lies within the Peter Lougheed Provincial Park on Alberta Highway 40 (Kananaskis Tr ...

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

Canadian Rockies The Canadian Rockies () 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 of the Canadian Cordillera, w ...

in Alberta.

Relationship to other units

The Morrissey Formation abruptly but conformably overlies the "Passage Beds" at the top of the Fernie Formation, and is in turn abruptly but conformably overlain by the Mist Mountain Formation. To the north in the vicinity of the North Saskatchewan River it interfingers with and grades into the Nikanassin Formation. To the east it was truncated by pre-

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

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

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

is uncertain.

References

{{WCSB, Northwest_Plains=yes, Canadian Rockies=yes Tithonian Stage Geologic formations of Alberta Geologic formations of British Columbia Sandstone formations of Canada Siltstone formations of Canada Mudstone formations of Canada Coal formations