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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Pangea: Global Environments and Resources — Memoir 17, 1994
Pages 589-619
Sedimentation

The Permian Ambition Formation of Northwestern Stikinia, British Columbia

M. H. Gunning, E. W. Bamber, D. A. Brown, L. Rui, B. L. Mamet, M. J. Orchard

Abstract

The name Ambition Formation is proposed for a thick, well bedded Permian carbonate succession of the Stikine assemblage in the Scud River area of northwestern Stikinia. The formation locally lies conformably on Upper Carboniferous or lowest Permian ash tuff and grades upward into an unnamed Upper Permian succession of tuff and radiolarian chert. Lateral discontinuity resulted from nondeposition, erosion, folds, faults and disruption by plutons.

The type section consists of about 1000 m of strata in two shallowing upward successions comprising basal, non-calcareous argillite which grades up into neritic, fossiliferous limestone. The reference section is composed of about 30 m of sparry packstone which forms the uppermost part of the formation. Fossils from the formation range in age from Gzhelian or Asselian to Roadian or early Guadalupian.

The formation has a locally abundant, stenohaline, benthic fossil assemblage of low diversity and open marine affinity. Carbonate sedimentation took place in low energy environments, possibly on a ramp, generally below fair weather wave base but periodically disturbed by storms. Although the formation accumulated on a subaqueous, predominantly mafic volcanic succession there was no influx of volcanic, volcaniclastic or terrigenous clastic sediment during carbonate sedimentation, but there was renewed volcanism in Late Permian time.

The formation accumulated in an extensional, oceanic tectonic setting isolated from the west margin of ancestral North America, and in a subtropical region south of its present latitude. It was within the realm of dispersion of some shelly benthos along western and northern Pangea, near or within the McCloud Belt of allochthonous terranes.


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