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Biostratigraphy and palaeoenvironment of the Kimmeridgian/Tithonian transition beds of the Boulonnais (Pas-de-Calais): new paleontological data (ammonites), sequential organization and organic-matter content

Abstract:

Newly discovered ammonites and detailed sedimentological studies of the Argiles de Chatillon precisely locate the Kimmeridgian/Tithonian boundary within this formation, which contains two members. The sedimentary palaeoenvironments form part of a homoclinal carbonate ramp. The sequence through the Argiles de Chatillon reflects fluctuating sea levels and shows two complex superimposed prograding units corresponding to the two members of the formation. The distribution of organic matter is analysed and compared with that of successions of the same age in Great Britain. It reflects the many factors affecting deposition. Sequence stratigraphy and the distribution of organic matter show the influence of sea level variations on ammonite populations. -P.Wallace