Abstract

A single undescribed species from latest Givetian-earliest Frasnian strata of the Moose River Basin is the only known occurrence of possibly Upper Devonian rugose corals in eastern Canada. In contrast, a rich and diverse Frasnian rugosan assemblage, comprising at least 120 species, is currently recognized in western Canada. There, early Frasnian corals are sparsely represented with only rare occurrences in the Waterways Formation of NE Alberta and the Flume Formation of the Rocky Mountains. Overlying units in northern Alberta (Mikkwa Formation) and the southern Northwest Territories (Hay River Formation) yield a more diverse and abundant fauna. Diversity of coral faunas increases in younger Frasnian units, including the Mt. Hawk Formation of the Rockies, and Twin Falls and Redknife Formations of the southern N.W.T.A prominent rugosan fauna is also present in mid to late Frasnian clastics of the Fort Simpson and Imperial Formations of the Mackenzie River valley, N.W.T. By far the most prolific and varied coral assemblage is that of the latest Frasnian Ronde Member (and its equivalents) in the Rockies, and the Kakisa Formation of the southern N.W.T., where at least 60 species are now recognized.

Frasnian coral faunas are poorly developed in the U.S. east of the Mississippi River. Colonial phillipsastreids and scattered solitary rugosans are present in middle to late Frasnian beds of the Catskill clastic wedge, with deeper water metriophyllids in dark shales. In Iowa, the early Frasnian Shell Rock Formation and several members of the middle-late Frasnian Lime Creek Formation (both Cerro Gordo and Owen Members) contain diverse and abundant corals. An additional middle Frasnian fauna in Iowa is that of the Independence Shale, which bears a distinctive assemblage of small, solitary species. Equivalents are seen in New Mexico, where rugosans occur in middle to late Frasnian (= Lime Creek) rocks of the Sly Gap Formation, as well as the latest Frasnian Contadero Formation. The Martin Limestone of Arizona also contains middle to late Frasnian rugosan faunas. The thick sequence of Frasnian carbonates (Guilmette Formation) of western Utah and eastern Nevada has abundant corals at several levels. Rugosans are also present at several horizons within the more westerly Devil’s Gate Limestone of central Nevada, but are not yet well-placed stratigraphically.