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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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The Wann Formation (Missourian) of northeastern Oklahoma is primarily a regressive marine sequence of calcareous shale, shale, and sandstone with a characteristic molluscan fauna traceable along much of the outcrop. The replacement of a crinoid-brachiopod fauna by the molluscan fauna in Washington County
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reflects the change from deeper water to a nearshore marine environment. This environmental change was caused by the northward expansion of a deltaic area which generally was on the south. The deltaic sediments are well developed in the southern outcrops of the Wann.
The rich molluscan fauna, a "Drum-type assemblage," is similar to those found in other Middle and Upper Pennsylvanian formations in Oklahoma indicating a repetition of environments. Trepospira, Worthena, Euphemites, and Glabrocingulum are the predominant elements of the fauna although other gastropods and pelecypods are prominent locally. The relative abundance of a species at any location within the assemblage zone appears to be depth controlled.
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