Stratigraphy and stage boundaries in reference sections of the Upper Cretaceous Chalk in the east of the Paris Basin: the “Craie 700” Provins boreholes

Three tectonic phases are evident in the two boreholes. The pre-Ilsede phase is discrete in the Middle Turonian. The early Ilsede phase begins in the lower part of the Coniacian. The main Ilsede phase reduces the thickness of the middle part of the Coniacian (foraminiferal biozone S/b thin or absent). The Wernigerode phase seems to have reduced the thickness of the upper part of the Santonian (?lack of crinoid zones). The development of a thick dolomitic body in the Sainte-Colombe Borehole, and the presence of bored surfaces bounding the same stratigraphic interval in the Poigny Borehole, may be related to the Peine phase, active between the early and late Campanian.