The Beattie Peaks Formation is a geologic formation of

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

( Valanginian) 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 ...

that consists primarily of marine

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. ...

. It is present in the northern 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 ...

and the adjacent plains in northeastern British Columbia.Stott, D.F. 1998. Fernie Formation and Minnes Group (Jurassic and lowermost Cretaceous), northern Rocky Mountain foothills, Alberta and British Columbia. Geological Survey of Canada, Bulletin 516.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. .

Lithology

The Beattie Peaks Formation consists primarily of dark grey to brownish grey or black mudstones that contain abundant

organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

and are extensively burrowed. Interbeds of argillaceous

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 ...

and fine-grained sandstone increase toward the top of the formation.

Environment of deposition

The Beattie Peaks Formation was deposited in marine and prodeltaic environments within the Western Interior Seaway.

Paleontology and age

The age of the Beattie Peaks Formation has been determined from its fossil fauna, primarily species of the

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

''Buchia''. The formation has also yielded other fossil bivalves, ammonites, and microfossils. Trace fossils made by burrowing organisms are common in its mudstones.

Thickness and distribution

The Beattie Peaks Formation is present in the foothills of the

and the adjacent plains in northeastern British Columbia, extending from the Prophet River to south of the Pine River. It reaches a maximum thickness of in the western foothills and thins eastward.

Relationship to other units

The Beattie Peaks Formation is part of the Minnes Group. It was deposited conformably on the

Monteith Formation The Monteith Formation is a geologic formation of Early Cretaceous ( Valanginian) age in the Western Canada Sedimentary Basin that consists primarily of sandstone. It is present in the northern foothills of the Canadian Rockies and the adjacent ...

and is conformably overlain by the Monach Formation, both of which also belong to the Minnes Group. To the south it grades into the lower part of the Gorman Creek Formation.

References