Depositional Facies, Sequence and Diagenesis of the Middle-Upper Eocene in Jebel Cherahil (Central Tunisia)

Abstract

This paper is set out to study the Cherahil Formation (middle-upper Eocene) in Jebel Cherahil. In this area, the Cherahil Formation is subdivided into three lithostratigraphic units: the lower, the middle and the upper Cherahil members. The field examination and microscope observation of thin sections and the DRX clays mineralogy allowed us to distinguish six depositional facies (marly and five carbonate facies) that have been developed broadly within a shallow water carbonate platform with episodes of open marine conditions and others of restricted lagoon conditions. The depositional environment was subjected to variable continental inputs. According to the vertical variation of the depositional facies and the examination of the discontinuity surfaces, the Cherahil Formation may be subdivided into eight third-order depositional sequences. Each one of them includes transgressive and high-stand systems tract developed in a platform setting. Moreover, the sequence boundaries generally consist of erosive surface that corresponds to superimposed subaerial exposure surface and transgressive surfaces. The sea level fluctuation has, in addition, controlled the carbonate digenesis, in particular dissolution.