Abstract

The Cleistopora typa gorbyi faunule, characterized by C. typa gorbyi and Microcyclus blairi, is of earliest Mississippian age and is present in the Caballero Formation of New Mexico, and the Compton Limestone and the Sedalia dolomite (in part) in Missouri. The Northview Shale fauna from the lower part of the Northview Shale in the Northview basin may be in part the equivalent of the C. typa gorbyi faunule. The Cleistopora typa typa faunule characterized by C. typa typa, C. placenta, Homalophyllites calceolus, Vesiculophyllum sedaliense, Lithostrotionella microstyla, and Michelinia expansa, overlies the C. typa gorbyi faunule in New Mexico and Missouri. The stratigraphic units of Early Mississippian age in New Mexico are laterally persistent, and the coral faunules are sharply confined to certain parts of the section. The coral zonation is not as obvious in Missouri where the Compton Limestone and the Sedalia dolomite interfinger and the Northview Shale and the Sedalia dolomite interfinger. The C. typa typa faunule occurs in the top of the Sedalia dolomite (in part), the top of the Northview Shale, and the Pierson Limestone. It is found in the Andrecito and perhaps in the Alamogordo members of the Lake Valley Formation in New Mexico. The faunule is Early Mississippian in age and younger than the Cleistopora typa gorbyi faunule. In the Northview basin the C. typa typa faunule is replaced, at least in part, by a molluscan assemblage which occurs with Scalarituba and Taonurus. In New Mexico, elements of the C. typa typa faunule occur with Scalarituba and Taonurus. The corals of the older C. typa gorbyi faunule are minor elements in a dominantly brachiopod-rich assemblage. On the other hand, corals of the younger C. typa typa faunule are a conspicuous part of the total fossil assemblage. The C. typa typa faunule is widespread in the United States, but the C. typa gorbyi faunule is more restricted geographically.

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