10.6084/m9.figshare.3453146.v1 Baptiste Sucheras-Marx Baptiste Sucheras-Marx Fabienne Giraud Fabienne Giraud Vincent Fernandez Vincent Fernandez Bernard Pittet Bernard Pittet Christophe Lecuyer Christophe Lecuyer Davide Olivero Davide Olivero Emanuela Mattioli Emanuela Mattioli Duration of the Early Bajocian and the associated δ<sup>13</sup>C positive excursion based on cyclostratigraphy Geological Society of London 2016 cyclostratigraphic analysis carbonate content ocean eutrophication duration marine invertebrates climax isotope values carbon isotope values Bajocian δ 13 C latitude French Subalpine Basin palaeoenvironmental changes δ 13 C excursion 172 Ma tectonic changes 2.72 Ma greyscale variations Les Dourbes section Chaudon 4.082 Ma 1.36 Ma Geology 2016-06-21 11:10:38 Dataset https://geolsoc.figshare.com/articles/dataset/Duration_of_the_Early_Bajocian_and_the_associated_sup_13_sup_C_positive_excursion_based_on_cyclostratigraphy/3453146 <p>The Early Bajocian, about 172 Ma ago, was a period of tectonic changes, a global carbon-isotope positive excursion, and biological diversification of marine invertebrates (e.g. ammonites, radiolarians and coccolithophores). Unfortunately, both the duration of the Early Bajocian and the associated palaeoenvironmental changes are still poorly constrained. We propose here an estimate of the duration of this sub-stage based on a cyclostratigraphic analysis of the carbonate content from the Chaudon–Norante section, French Subalpine Basin, France. The Chaudon–Norante succession has been correlated with Les Dourbes section using greyscale variations to detect possible local hiatuses. The duration estimated here for the entire Early Bajocian is 4.082 Ma. Two intervals were identified in the positive δ<sup>13</sup>C excursion: an increase of carbon isotope values lasting 1.36 Ma and climax isotope values lasting for 2.72 Ma. A cooling at high latitudes and warming at low latitudes may have enhanced the Earth’s temperature gradient leading to an increase in humidity, which in turn triggered ocean eutrophication at the origin of the δ<sup>13</sup>C positive excursion. </p>