Revised dating of the major earliest Cretaceous transgression in S Aquitaine (SW France)

Abstract

The oldest dating of the earliest Cretaceous transgression in S Aquitaine (SW France) was long considered Aptian. In 1954, Cuvillier and Debourle report from the subsurface the find of a microfossil assemblage that they ascribe to the Valanginian. In 1968, Schroeder and Poignant cast some doubts on the identifications and state that this assemblage is characteristic of the Barremian, not of the Valanginian. Revision of the benthic foraminifers and Dasycladales from the bottom section of the Cretaceous at Lacq 104 borehole demonstrates that the oldest records of the transgression, per definition diachronous, are probably late Hauterivian in age. Due to the lack of any evidence for the occurrence of Berriasian or Valanginian strata, the hiatus related to erosion and non-deposition is there assumed to span the lower part of the Hauterivian, the Valanginian, most if not all of the Berriasian and possibly the uppermost part of the Tithonian.