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TitleAulacostephanid ammonites from the Kimmeridgian (Upper Jurassic) of British Coumbia (western Canada) and their significance for correlation and palaeobiogeography
AuthorRogov, M; Poulton, T P
SourceBulletin of Geosciences vol. 90, no. 1, 2015 p. 7-20, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150066
PublisherCzech Geological Survey
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
NTS94D; 104A; 104H
AreaSkeena River; Nass River; Bower Lake
Lat/Long WENS-130.0000 -127.0000 57.5000 56.0000
Subjectspaleontology; Kimmeridgian; sea level changes; paleogeography; paleobiology; biogeography; fossils; systematic paleontology; faunas; Upper Jurassic; fossil zones; fossil distribution; aulacostephanids; Zenostephanus; Rasenia; ammonites; Bowser Lake Group; Bowser Basin; Jurassic
ProgramScience laboratory network
Released2015 01 26
AbstractWe present the first description of aulacostephanid (Perisphinctoidea) ammonites from the Kimmeridgian of Canada, and the first illustration of these ammonites in the Americas. These ammonites include Rasenia ex gr. cymodoce, Zenostephanus (Xenostephanoides) thurrelli, and Zonovia sp. A from British Columbia (western Canada). They belong to genera that are widely distributed in the subboreal Eurasian Arctic and Northwest Europe, and they also occur even in those Boreal regions dominated by cardioceratids. They are important markers for a narrow stratigraphic interval in the Cymodoce Zone (top of Lower Kimmeridgian) and the lower part of the Mutabilis Zone (base of Upper Kimmeridgian) of the Northwest European standard succession. In Spitsbergen and Franz Josef Land, the only Upper Kimmeridgian aulacostephanid-bearing level is the Zenostephanus (Zenostephanus) sachsi biohorizon, which very likely belongs to the Mutabilis Zone. Expansion of Zenostephanus from Eurasia, where it is present over a large area, into British Columbia, is approximately correlative with a transgressive event that also led to expansion of the Submediterranean ammonite genus Crussoliceras through the Submediterranean and Subboreal areas slightly before Zenostephanus.
Summary(Plain Language Summary, not published)
Archived fossils in GSC's collection, re-examined during the Bowser Basin project, were critical for understanding the geology of a resource-rich part of northern British Columbia, and they were referred to briefly in several geological publications. The short existence of this particular group of extinct ammonites, and their place in the evolutionary sequence, allows them to be used as geological time markers for the period about 155 million years ago. This report leverages the expertise of the European senior author, who showed an interest based on the early reports, to provide the first adequate North American documentation of that fossil group. This makes them known to the scientific community, and will erase doubts about their existence in North America.

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