%0 Journal Article
%T Early Aptian ¦Ä13C and manganese anomalies from the historical Cassis-La B¨¦doule stratotype sections (S.E. France): relationship with a methane hydrate dissociation event and stratigraphic implications
%A Renard Maurice
%A Raf¨¦lis Marc de
%A Emmanuel Laurent
%A Moullade Michel
%J Carnets de G¨¦ologie
%D 2005
%I Carnets de G¨¦ologie
%X Comparison of oxygen and carbon isotope and manganese evolution curves in bulk carbonate from the historical Bedoulian stratotype (Cassis-La B¨¦doule area, Provence, France) reveals an important geochemical event (negative ¦Ä13C and high Mn content) located within the D. deshayesi ammonite Zone and at the base of the R. hambrowi ammonite Subzone. This worldwide event, which can be observed in environments ranging from the fluvial to the pelagic realm (Selli/Goguel level), seems to be related to methane hydrate destabilization. Scenarios for manganese, carbon and oxygen evolutions are proposed for early Bedoulian oxic conditions and for dysoxic/anoxic conditions related to methane hydrate destabilization at the early/late Bedoulian transition. The impacts of this global event on the biosphere (nannoconid crisis) and its stratigraphic implications are considered. Comparison of geochemical and biostratigraphical data from the Cassis-La B¨¦doule stratotype with that of the Cismon-Apticore reference borehole shows that the La Bedoule sequence records geochemical evolution during the Goguel/Selli Event in more detail than that of any other previously published section.
%K Lower Aptian
%K Bedoulian
%K carbon and oxygen isotopes
%K manganese
%K methane hydrates
%K nannoconid crisis
%K Selli and Goguel levels
%U http://paleopolis.rediris.es/cg/CG2005_A04/index.html