Mississippian Conodonts from the Southern Texas Panhandle

A small but significant conodont fauna was recovered from four cores from the southern Texas Panhandle. These are the first conodonts to be documented in subsurface Mississippian rocks in the Southern Midcontinent region. The fauna comprises 18 single-element species representative of 8 genera and several indeterminate specimens of 4 additional genera. Cavusgnathus, Gnathodus, and Taphrognathus are the most abundant definitive genera. Apatognathus pinnata, a new species, was recovered from two cores. A middle to late Meramecian age is implied by the conodont faunas recovered from three cores; possible Chesterian elements are observed in the upper parts of two of these cores. The fourth core is probably early Meramecian, although a late Osagean age is possible. Temporal relationships indicated by the conodont faunas suggest that Mississippian deposition did not commence until early Meramecian time throughout most of the southern Texas Panhandle. Older rocks are indicated only in the extreme northern part of the area, where Osagean deposits accumulated along the margins of the Southern Oklahoma Aulacogen. These data suggest that many rocks referred to as Osage in the Palo Duro Basin may actually be Meramecian. Examination of conodont color indicates that previously suggested calibrations of the conodont color alteration index with other indices of thermal maturation may be in error. Levels of maturity in the Mississippian rocks of the southern Texas Panhandle are considerably lower than predicted by conodont color.