Le passage cénomanien-turonien dans les Monts des Ksour (Atlas Saharien Occidental， Algérie): biostratigraphie， géochimie et milieux de dép?t

摘要

two levels with rare ammonites of the Ghoundja?a Formation at the M’daouer section allow to characterize the Vibrayeanus， Gamai and Cauvini zones. So， for both sections， it seems useful to apply an isotopic study which showed a positive excursion zone of the δ 13C lying along the Lower Member and the lower part of the Middle Member Ghoundja?a Formation. This anomaly zone is marked by three well-defined and characteristics peaks of the Cenomanian-Turonian transition and the boundary between these two stages stands between peaks 2 and 3 coincident with the transition from Gamai to Cauvini zones. The recording of these three peaks allowed the local correlation with the Tamedna?a section where fauna of biostratigraphic value is missing.