Contributions of the Seismic 3D in the Interpretation and Comprehension of Geometry of the Paleovallees of the Ordovician

Many studies treat of deposits and processes of Ordovician paléovallées within the Illizi basin. Their limits and their extensions remain difficult to understind. These deposits are characterized by a short and glacial episode, which are responsible on the formation of irregular incisions in Ordovician. This results in depressions filled by the deposits of the various units of the upper Ordovician (IV-3/IV2/IV-1). They can reach 300m depths and rest on the various units under unclaimed of Ordovician, or on Cambrian unit II, even directly on the Précambrien base. Their widths are variable 1 with 3Km. Two types of orientations have summers met NW SE and WNW - ESE in the Illizi basin. The acquisition of 3D seismic in the study area, not only makes it possible to include/understand their geometry, their orientation but also to delimit them with precision. The seismic interpretations, combined with the geological data (ground, well, cores etc....) allow to have another design of these paléovalées, as well as the oil potential which is associated.