High-resolution biotratigraphy and chemostratigraphy of the Cenomanian/Turonian boundary event in the Vocontian Basin, southeast France

The Cenomanian/Turonian boundary black shale has been traced in southeastern French subalpine ranges in several sections correlated over tens of kilometres, both on a bed-by-bed basis and with the control of δ13C isotope curves. Correlations show a thickness increase slopeward and a slight increase in the time span of black shale deposition basinward. They also show that the Vergons section cannot be used as a local reference section for Ocean Anoxic Event 2 (OAE2) because it has probably been affected by synsedimentary sliding. Finally they show that the vertical range of the Whiteinella archaeocretacea Zone changes considerably over short distances. This could be easily understood in widely separated basins but is harder to explain at such a local scale. In addition, using results obtained in the US Western Interior Basin, we question the validity of this Partial Range Zone.