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

Abstract

ABSTRACT Samples from six outcrop sections were examined for calcareous nannofossils and correlated to the zonations of Sissingh (1977) and Perch-Nielsen (1979, 1983, 1985). Units studied are from the upper Lower Taylor Marl, the Wolfe City Sand, and the lower Pecan Gap Chalk of the Taylor Group in North-Central Texas. The Cryer Creek section contains the contact between the Wolfe City Sand and Lower Taylor Marl. Based on the presence of Marthasterites furcatus in the Lower Taylor Marl samples and its absence in the Wolfe City Sand, the uppermost Lower Taylor Marl is placed in the top of the Aspidolithus parcus Zone (CC 18c), and the lowermost Wolfe City Sand in the lower Calculites ovalis Zone (CC 19a). The formation contact approximately coincides with the zonal boundaries. The Arroyo Lane and Tomlinson sections contain lower to middle Wolfe City Sand 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 Sand and is placed in the upper Calculites ovalis Zone (CC 19b) as Bukryaster hayi is no longer present in the section. The lower portion of the Pecan Gap Chalk was sampled 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 Chalk in the Quadrum sissinghii Zone (CC 21).