Upper Cambrian faunas from the subsurface Deadwood Formation, Williston Basin, Montana

The Deadwood Formation was cored from the base of the Winnipeg to the Precambrian schist. The upper 347 feet was assigned to the Lower Ordovician, the middle 300 feet to the Upper Cambrian Trempeleauan and Franconian stages and the lower 257 feet to the Dresbachian. BBrachiopods, trilobites, and dendroid graptolites, including 10 new species, are systematically described for each faunal (trilobite) zone. The faunules support physical evidence that eastern Montana was part of a wide coastal shelf during LateCambrian time and that sporadic sedimentation continued across the Upper Cambrian-Lower Ordovician boundary.--V.M.J

This record provided courtesy of AGI/GeoRef.

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