Strontium isotope age-dating of fossil shark tooth enameloid from the Upper Cretaceous Strata of Alabama and Mississippi,USA |
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| Institution: | 1. Department of Integrative Biology & Museum of Paleontology, University of California, Berkeley, 1005 Valley Life Sciences Building #3140, Berkeley, CA 94720,USA;2. Department of Earth and Ocean Sciences, University of North Carolina Wilmington, Wilmington, NC 28403-5944, USA;3. Department of Earth Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur WB-741246, India;4. Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway;5. Department of Biological and Environmental Sciences, University of Gothenburg, Sven Lovén Centre for Marine Sciences – Kristineberg, Fiskebäckskil 45178, Sweden;6. Department of Geological Sciences, University of Missouri, 101 Geology Building, Columbia, MO 65211, USA;7. Florida Museum of Natural History, University of Florida, 1659 Museum Road, Gainesville, FL 32611, USA;1. Institute of Geosciences, Goethe-University, Altenhöferallee 1, 60438 Frankfurt am Main, Germany;2. Geochemistry and Isotope Biogeochemistry Group, Leibniz-Institute for Baltic Sea Research, Seestraße 15, D-18119 Warnemümde, Germany;3. Institute of Geosciences, Johannes Gutenberg University, Johann-Joachim-Becher-Weg 21, 55128 Mainz, Germany;4. Biodiversity and Climate Research Center, Senckenberganlage 25, 60325 Frankfurt, Germany |
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| Abstract: | Cretaceous strata in Alabama and Mississippi (USA) represent one of the most complete records of shallow marine deposition worldwide for the Upper Cretaceous. The age assignment of these strata in the eastern Gulf Coastal Plain is difficult due to the comparative lack of radiometrically datable beds and sometimes conflicting results of biostratigraphy using different taxonomic groups. Numerical age dating using strontium isotope ratios (87Sr/86Sr) preserved in diagenetically resistant fossil shark tooth enameloid had been proposed by previous researchers as a solution to dating some geologic units. Here we apply this methodology to the whole Upper Cretaceous, using teeth of two fossil shark genera (Scapanorhynchus and Squalicorax) collected from variable facies. Shark teeth collected from a bentonite mine in Monroe County, Mississippi, were also analyzed and compared with the radiometric date of the bentonite layer. Results indicate a strong correlation between stratigraphic position of the fossil teeth and numerical age determination based on 87Sr/86Sr content. Furthermore, this method is equally effective for both of the fossil shark genera analyzed in the study. Because of the nearly uniform distribution of strontium in ocean water, numerical age dating using strontium isotope ratios preserved in fossil shark tooth enameloid can be a useful method to employ in the correlation of marine geological strata on both regional and global scales. |
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| Keywords: | Biogeochemistry Gulf Coastal Plain Mississippi Embayment Paleontology Stratigraphic correlation Stratigraphy |
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