Sedimentology and sequence stratigraphy of the middle and upper Eocene succession from Jebel Kabbara (central Tunisia)

Abstract

During the Maastrichtian-Middle Eocene interval, a resistant area (Kasserine Island) occurred in central Tunisia. The emerged area narrowed especially on its northern edge because of the eustatic rise and associated compressive tectonics having marked central Tunisia during the Paleocene-Eocene transition. Located at the NE boundary of the Kasserine Island, the study area saved the shoreline variations and therefore the sedimentary environment evolution. In this area, sedimentological and sequence stratigraphy analysis of middle and upper Eocene deposit are scarce in previous works. In this context, this paper aims to study the depositional facies, early diagenesis and sequence stratigraphy of the Cherahil Formation (Middle and Late Eocene) in Jebel Kabbara (central Tunisia) in order to refine the deposit facies and environment and paleographic variations in the NE boundary of the Kasserine Island during Middle and Late Eocene.The studied succession (Cherahil Formation) outcrops at Jebel Kabbara, SW of Jebel Cherahil and is located 42 km from Kairouan city. This Formation is subdivided into lower and upper lithostratigraphic members separated by Siouf member. The field examination and microscope observation of thin sections and XRD clays mineralogy set apart five carbonate facies. The depositional facies occurred broadly within a shallow-water carbonate platform with alternatively episodes of open marine conditions and episodes of restricted lagoonal conditions.The analysis of the depositional facies stacking and the field examination of the unconformity surfaces allow subdividing the Cherahil Formation into eight third-order depositional sequences, including only transgressive and high-stand systems tracts. The sequence boundaries generally consist of erosive surfaces corresponding to superimposed subaerial exposure surfaces and transgressive ones. According to the available biostratigraphic data, the depositional sequences of Cherahil Formation may be broadly correlated with the Haq's et al. TA3 2nd order global eustatic cycles.