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Abstract: Calcareous Nannofossil Biostratigraphy of the Taylor Group (Campanian) of North-Central Texas

Kathleen A. Locke, Stefan Gartner

Samples from six outcrop sections were examined for calcareous nannofossils and correlated to the zonations of Sissingh (1977) and Perch-Nielsen (1983). Units studied are from the upper Ozan, Wolfe City, and lower Pecan Gap formations of the Taylor Group in north-central Texas.

The Cryer Creek section contains the contact between the Wolfe City and Ozan. Based on the presence of Marthasterites furcatus in the Ozan samples and absence in the Wolfe City, the uppermost Ozan is placed in the top of the Aspidolithus parcus zone (CC 18c) and the lowermost Wolfe City in the lower Calculites ovalis zone (CC l9a). The formation contact approximately coincides with the zonal boundaries.

The Arroyo Lane and Tomlinson sections contain lower to middle Wolfe City and are assigned to the lower Calculites ovalis zone (CC 19a) based on the presence of Bukryaster hayi and absence of both Marthasterites furcatus and Ceratolithoides aculeus. The Lane Ranch section contains the upper Wolfe City and is placed in the upper Calculites ovalis zone (CC 19b) because Bukryaster hayi is no longer present in the section.

The lower portion of the Pecan Gap was observed at the Cedar Springs location. The presence of Ceratolithoides aculeus and absence of Bukryaster hayi and Uniplanarius nitidum place this section in the Ceratolithoides aculeus zone (CC 20) or younger. In the Poole Creek section, Uniplanarius nitidum has appeared but Uniplanarius trifidum is not yet present, placing the middle Pecan Gap in the Quadrum sissinghii zone (CC 21).

AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994