CONODONT BIOSTRATIGRAPHY OF THE MIDDLE-UPPER SILURIAN WINK FM. (WRISTEN GROUP) IN THE COBRA FRAZIER CORE, HOWARD COUNTY, TEXAS

The Cobra Frazier core penetrates the Wristen Group (represented by the Wink Fm.) and the uppermost Fusselman Fm. Preexisting integrated conodont biostratigraphy and carbon isotope chemostratigraphy from 2004 identified the upper Homerian 'Mulde' positive carbon isotope excursion within the core, although sampling resolution was insufficient to recover both peaks of the Mulde. The position of the Wenlock-Ludlow boundary was placed based on the occurrence of Kockelella crassa, and the top of the core was suggested to range into the Ludfordian, but was not well constrained. The Ludfordian 'Lau' excursion was not recovered, and the top of the core must be no younger than the Polygnathoides siluricus Zone due to the presence of kockelellids in the upper samples. Since 2004, global conodont biozonation has been revised, as has taxonomy, and ranges of kockelellid subspecies relative to the zonation are better known. Reexamination of the Cobra Frazier faunas focusing on identification of K. variabilis variabilis vs. K. variabilis ichnusae and K. absidata absidata vs. K. absidata sardoa allows further refinement of the age of the upper Wink Fm. Additionally, samples with Devonian (late Givetian-early Frasnian) species present due to stratigraphic leak help constrain episodes of karsting that affected the Wristen Group.