The Cretaceous Section at Lanigan in South-Central Saskatchewan
Date
1978-10
Authors
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Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
The Cretaceous section in the second Alwinsal potash mine shaft
at Lanigan is a thin, discontinuous sequence of entirely terrigenous
clastic rocks, 327 m thick, with an age-span of Middle Albian to Early
Campanian. The Cretaceous rocks rest disconformably on Jurassic rocks
and are overlain disconformably by Pleistocene sediments. The basal
Cantuar Formation of the Mannville Group is composed of fluviatile
deposits; the overlying Pense Formation of the Mannville Group introduces
the shallow-water marine deposits that persist to the top of the
section. Succeeding formations, identified as the Joli Fou, Viking,
'Unnamed Shale', Upper White-Speckled Shale, and Lea Park Formations,
were deposited in littoral, infralittoral, and circalittoral environments
(or a combination of these) and represent the deposits of locally
and regionally transgressive and regressive marine waters.
The Cretaceous section is intermittently fossiliferous; there are
thick sequences barren of megafossils. In terms of the established
molluscan zones usually recognized in the Western Interior of Canada
and of the United States, the Joli Fou Formation almost certainly falls
within the Inoceramus comaneheanus Zone, the Upper White-Speckled
Shale carries the CZioscaphites vermiformis and Inoceramus cordiformis
Zones, and the Lea Park Formation carries at least the Baculites
perplexus and Hoploscaphites gilli Zones.
The lower Joli Fou Formation contains a varied molluscan fauna
hitherto unrecorded in Canada; it has most in common with the fauna
of the Late Albian Kiowa Formation of Kansas. The presence of this
fauna, which has both distinctive boreal and tethyan elements, provides
important new evidence on the date of establishment of the
Western Interior seaway in North America.
The Cretaceous section at Lanigan contains at least one important
unconformity (expressed as a paraconformity): the Early to Middle
Santonian Upper White-Speckled Shale sits directly on the Late Albian
(and possibly also Late Cenomanian) 'Unnamed Shale', and rocks of
Turonian and Coniacian age are totally absent. Other paraconformities
also may be present.
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Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geology