The Lea Park Formation is a stratigraphical unit of

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

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 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 ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

. It takes the name from the settlement of Lea Park, Alberta, located north-west of

Lloydminster Lloydminster is a city in Canada which has the unusual geographic distinction of straddling the provincial border between Alberta and Saskatchewan. The city is incorporated by both provinces as a single city with a single municipal administrati ...

on the banks of 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 ...

. It was first defined in an outcrop on the river banks, located in

section Section, Sectioning or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sig ...

15-11-54-3W4M by J.A. Allan in 1918.Allan, J.A., 1918. Sections along North Saskatchewan River and Red Deer and South Saskatchewan rivers;

Geological Survey of Canada The Geological Survey of Canada (GSC; french: Commission géologique du Canada (CGC)) is a Canadian federal government agency responsible for performing geological surveys of the country, developing Canada's natural resources and protecting the e ...

, Summary Report 1917, Part C, pp. 9-13. The early

campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

age was determined from its

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

and mollusks found in the formation.

Lithology

The Lea Park Formation is composed of dark shale with minor siltstone. Calcite veins and

ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be con ...

concretions, as well as

bentonite Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-m ...

beds are found throughout the formation.

Distribution

The Lea Park Formation reaches a maximum depth of in its eastern reaches. It occurs in the sub-surface in west-

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. Agriculture and energy are important to the area's economy. Geography Central Alberta is bordered ...

and extends eastwards through north-eastern

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

and north-western

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

Relationship to other units

The Lea Park Formation is conformably overlain (and laterally replaced )by the

Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It ...

and conformably overlies the First White Speckled Shale of the

Colorado Group Colorado is a geologic name applied to certain rocks of Cretaceous age in the North America, particularly in the western Great Plains. This name was originally applied to classify a group of specific marine formations of shale and chalk kn ...

. It is equivalent to

, Clagett Formation and Eagle Formation in northern

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

, and is replaced by the

Belly River Formation The Belly River Group is a stratigraphical unit of Late Cretaceous age in the Western Canadian Sedimentary Basin. It takes the name from the Belly River, a tributary of the Oldman River in southern Alberta, and was first described in outcrop ...

, Pakowki Formation and

Milk River Formation The Milk River Formation is a sandstone-dominated stratigraphic unit of the Western Canada Sedimentary Basin in southern Alberta, Canada. It was deposited in near-shore to coastal environments during Late Cretaceous (late Santonian to early Campani ...

southern Alberta Southern Alberta is a region located in the Canadian province of Alberta. In 2004, the region's population was approximately 272,017.Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

and in

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Winn ...

it is equivalent to the Gammon Ferruginous Member, Pembina Member and lower Millwood Member of the

Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Meek and Hayden in 1862 in th ...

. The Lower Lea Park correlates with the Puskwaskau Formation in north-western Alberta, and the entire formation is equivalent to part of the Wapiabi Formation in the northern Canadian Rockies

References

{{Western Canadian Sedimentary Basin, Northeast_Plains=yes, Central_Plains=yes Shale formations Western Canadian Sedimentary Basin Cretaceous Alberta