The Campanian stage

The Campanian working party in Brussels did not wish to make a conclusive recommendation but there was a strong feeling that the base of the stage should be fixed at the extinction-level of the crinoid Marsupites. Other criteria discussed included ammonites, belemnites, foraminifera, calcareous nannofossils and magnetostratigraphy. Candidates for a boundary-stratotype occur in central Texas and south-east England. Until these sections have been described in detail, it will not be possible to choose a boundary-stratotype, and hence make a firm recommendation to the International Subcommission for the base of the stage. It was felt that three substages should be used for the Campanian, but international correlations within the stage are still too uncertain to make recommendations for the definitions of these substages

The Turonian stage and substage boundaries

Formal definitions of the Cenomanian-Turonian and lower-middle Turonian boundaries are proposed, following discussions at the Second International Symposium on Cretaceous Stage Boundaries, held in Brussels, 8-16 September 1995. The Global boundary Stratotype Section and Point (GSSP, "golden spike") for the Cenomanian-Turonian boundary should be placed at the base of Bed 86 in a section at Rock Canyon Anticline, west of Pueblo, Colorado, USA, coincident with the first occurrence of the ammonite Watinoceras devonense WRIGHT and KENNEDY, 1981. A GSSP for the lower-middle Turonian boundary is proposed at the level of first occurrence of the ammonite Collignoniceras woollgari (MANTELL, 1822) in the same section (Bed 120). For the middle-upper Turonian boundary no GSSP can be proposed at present

The Santonian stage and substages

The recognition of the Coniacian-Santonian boundary is easy with good correlation of macro- and microfossil evidence. The Santonian Working Group (SWG) recommends the lowest occurrence of Cladoceramus undulatoplicatus (Roemer) as the marker for the Coniacian-Santonian boundary. As yet, the SWG cannot make a formal proposal for a Boundary Stratotype Section, because the biostratigraphy must be better known and integrated first. Three candidates for Boundary Stratotype Section, Olazagutia Quarry (Navarra, Spain), Seaford Head (Sussex, England) and Ten Mile Creek (Dallas, Texas, USA) were selected for further decision. To achieve a useful subdivision of the Santonian into substages a better understanding of taxa ranges and correlation through different biogeographic realms is needed. Formal proposals for subdivision would be premature at present, but a three-fold division is favoured

The Cretaceous Period

International audienceThe breakup of the former Pangea supercontinent culminated in the modern drifting continents. Increased rifting caused the establishment of the Atlantic Ocean in the middle Jurassic and significant widening in Cretaceous. An explosion of calcareous nannoplankton and foraminifers in the warm seas created massive chalk deposits. A surge in submarine volcanic activity enhanced supergreenhouse conditions in the middle Cretaceous with high CO2 concentrations. Angiosperm plants bloomed on the dinosaur-dominated land during late Cretaceous. The Cretaceous dramatically ended with an asteroid impact, which resulted in a mass extinction