Pore network connectivity anisotropy in Jurassic argillite specimens from Eastern Paris Basin (France)

In order to scientifically test the feasibility of storage of high activity nuclear wastes, ANDRA, the French radioactive waste management agency, gave us the opportunity to study entirely preserved specimens of Jurassic clay-rich rocks from eastern Paris Basin. The collection was realised in the frame of a reconnaissance study that now leads to the building, under progress, of a -400 m-deep Laboratory, close to the village of Bure. The rocks under study consist in dark- to light-grey silty marls, or clay-stones, that were deposited during the Callovian and the beginning of the Oxfordian, called Cox (Callovo-Oxfordian) argilites. According to pyrolysis data of the organic fraction and to fluid inclusion studies, these argilites never reached 50 C in temperature nor have been buried deeper than 800 m, hence retain most of their original physical and chemical properties that were examined through microstructural and SEM observations. (authors)