FORAMINIFERS OF THE CLARITA FORMATION (LATE LLANDOVERY-EARLY LUDLOW, SILURIAN) FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA

The study, identification, and classification of Silurian foraminifers from the Arbuckle Mountains in Oklahoma have attracted little attention since the work of Moreman and Ireland in late 1930’s. These authors described 48 new species and several new genera, some of which are synonyms in recent taxonomy. Diverse shelly faunas have been described from Silurian strata in the Arbuckle Mountain region, especially brachiopods, trilobites, and conodonts, as well as corals, bryozoans, and rare graptolites. Rich assemblages of foraminifers occur in the Fitzhugh Member of the Clarita Formation of the Hunton Group, in association with abundant and diverse conodont faunas. Based on these conodont faunas, the Clarita Formation has been shown to range in age from the late Telychian (latest Llandovery) through the Wenlock into the early Gorstian (earliest Ludlow). A cryptic, but significant unconformity that coincides with the early Homerian Mulde Event separates the Sheinwoodian sequence of the lower Fitzugh Member from the overlying Homerian to early Gorstian sequence of the upper Fitzugh Member. Foraminifers have been studied from residues processed for conodonts allowing the conodont species to be used as a key reference to the age of foraminiferal assemblages. Approximately 26 species of 11 genera of well preserved and relatively abundant agglutinated foraminifers have been identified in samples from eight stratigraphic sections located in the Arbuckle Mountains area. The genera identified include Lagenammina, Thurammina, Colonammina, Shidelerella, Sorosphaera, Webbinella, Psammosphaera, Glomospira, Ammodiscus, and Hyperammina. A modern study of Silurian foraminifers recovered from conodont producing strata in the Arbuckle Mountains area provides an updated taxonomy and platform for correlation to Silurian strata in the United States and other countries.