Paleoenvironments in the Calcaire a gryphees of the Lias of Lorraine, fromthe Xeuilley quarry to the Paris Basin

A multidisciplinary study of the Lower Liassic outcrop of Xeuilley (central Lorraine, France) is presented here in order to rest the validity of subsu rface correlations at the scale of the Paris basin. The study involves an i ntegrated biostratigraphical, sedimentological, palynological and palaeoeco logical analysis of a single outcrop located within Calcaire a Gryphees For mation. 1. All of the ammonite biozones are present ranging from the Lower Hettangi an up to the Lower Sinemurian. Several environments follow one another in a n offshore situation in which the hydrodynamic control on sedimentation is related to periodic storms. The fossil assemblages indicate deposition with in the infra- to circa-littoral zones. Benthic communities lived mainly on soft to firmgrounds in poorly agitated euhaline waters, periodically deplet ed in oxygen at the sediment-water interface. 2. The instability may be partly explained by the paleogeographical situati on of the study area within the Paris Basin. The area of deposition was loc ated near the source of terrigenous sediments and sheltered from the influe nces of the open Tethys by a topographic high in the South. 3. Different orders of cyclicity may be successfully deciphered from the se quence. The global deepening-up trend is well recorded. Third order descrip tive cycles are proposed but not unambiguously interpreted. Fourth order cy cles are not well defined and therefore care needs be exercised if these cy cles are to be used for stratigraphic well logging correlations. Well defin ed fifth order cycles correspond to marl-limestone alternations induced by climatic fluctuations.