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Stable isotope compositions of a late Jurassic ammonite shell: a record of seasonal surface water temperatures in the southern hemisphere?
Laboratory “Paléoenvironnements & Paléobiosphèreâ€?, UMR CNRS 5125 , Bâtiment “Geodeâ€?, Université Claude Bernard Lyon I et Institut Universitaire de France, 27–43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, France
Paläontologisches Institut und Museum, Universität Zürich, Karl Schmid-Strasse 4, 8006 Zürich, Switzerland
Abstract. Exceptional preservation of aragonite secreted by ammonites offers an opportunity to determine the seasonal temperature variations of Mesozoic surface waters. Ontogenetic profiles of carbon and oxygen isotope compositions have been obtained from the nacreous layer of a well-preserved Late Jurassic (Oxfordian) ammonite (Perisphinctes) from Madagascar. A similar range of oxygen isotope compositions was also obtained from an associated benthic bivalve (Astarte) which suggests the absence of sampling bias. Late Jurassic seasonal variations in the southern Hemisphere were close to 2.5°C and relatively weak when compared to the 2.5–6.5°C temperature range prevailing in the present-day Indian ocean at a paleolatitude of 40±1° S. According to the hypothesis of an ice cap-free Late Jurassic Earth, average sea surface temperatures may have been up to 7°C higher than now.
Discussion Paper (PDF, 2483 KB) Interactive Discussion (Closed, 3 Comments) Final Revised Paper (eE)
Citation: Lécuyer, C. and Bucher, H.: Stable isotope compositions of a late Jurassic ammonite shell: a record of seasonal surface water temperatures in the southern hemisphere?, eEarth Discuss., 1, 1-19, 2006. Bibtex EndNote Reference Manager
