Research-paper
Lithostratigraphy and correlation of the Cenomanian - Turonian boundary sequence
Pomerol, B.; Mortimore, R. N.
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Abstract
The Cenomanian - Turonian boundary (CTB) is characterized by worldwide lithological and geochemical events and faunal turnovers which outline one of the major Oceanic Anoxic Event (SCHLANGER & JENKYNS 1976) of the Cretaceous period. Following the works of JEFFERIES (1970), the stratigraphy of the boundary sequence (the Actinocamax plenus Zone of the ancient authors) has been described in the Anglo - Paris basin by many authors. Including the classical section of Beachy Head (Sussex), recent data (field work and geophysical) on that Zone, while displaying the repartition of various trace fossils, allow a better definition of the lithological units such as the Melbourn Rock. Equally better correlations from the Southern England to the Eastern Paris basin can be propounded, even when the boundary sequence is highly condensed. In addition, the CTB is characterized by geochemical shifts (manganese and 13C for example) which, firstly described in the Anglo - Paris basin, have a worldwide occurrence. In the absence of markers fossils, they probably are one of the keys in the correlations between different palaeogeographical realms (boreal, tethyan, central atlantic etc.) and also with regions where the biostratigraphy of the boundary sequence is more detailed (Western Interior, USA, for example).