An integrated study (geochemistry,stable oxygen and carbon isotopes,nannofossils, planktonic foraminifera,inoceramid bivalves,ammonites and crinoids) of the Waxahachie Dam Spillway section,north Texas: a possible boundary stratotype for the base of the Campanian Stage |
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| Institution: | 1. Department of Earth Sciences, UCL, Gower Street, London WC1E 6BT, UK;2. Department of Earth Sciences, RHUL, Egham, Surrey TW20 0EX, UK;4. Department of Geology, University of Leicester, Leicester LE1 7RH, UK;5. NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;6. Observatoire de Lyon, Laboratoire de Géologie de Lyon UMR-CNRS 5276, Université Lyon 1 (UCBL1, La Doua). Bâtiment Géode, 2 Rue Raphaël Dubois, 69622 Villeurbanne, France;1. Institute of Atmospheric and Environmental Sciences, Department of Environmental Analytical Chemistry, Goethe-University, 60438 Frankfurt am Main, Germany;2. Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel;3. Institutes of Mineralogy and Geochemistry, Fridericiana University of Karlsruhe, Karlsruhe, Germany;4. Geological Survey of Israel, Jerusalem, Israel |
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| Abstract: | The spillway of Lake Waxahachie, Ellis County (Texas), exposes a >17 m section of the Hutchins Member of the Austin Chalk Group, unconformably overlain by Taylor Clay. The Austin sequence was regarded as a potential Global Stratotype Section for the base of the Campanian Stage at the 1995 Brussels meeting on Cretaceous Stage boundaries, with the last occurrence of the crinoid Marsupites testudinarius (von Schlotheim, 1820) as the potential boundary marker. An integrated study of the geochemistry, stable carbon and oxgen isotopes, nannofossils, planktonic foraminifera, inoceramid bivalves, ammonites and crinoids of this section place the last occurrence of M. testudinarius in a matrix of eighteen ancillary biostratigraphic markers, while the boundary can also be recognised on the basis of a δ13C excursion that can, in principle, be detected globally in marine sediments. A new forma of the crinoid Marsupites testudinarius is introduced. The Waxahachie section fulfils sufficient geological criteria as to be an excellent candidate GSSP for the base of the Campanian Stage, if problems of ownership and access to the section can be resolved. |
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