South Tethyan passive margin paleoslope orientation inferred from soft-sediment deformation and fault kinematic analysis: a case study from the Cretaceous of Borj Cedria area, Tunisia

• Published in: Arabian journal of geosciences 2022-01, Vol.15 (1), Article 12
• Main Authors: Naji, Chahreddine, Amri, Zayneb, Masrouhi, Amara, Bellier, Olivier
• Format: Article
• Language: English
• Subjects: Analysis; Cretaceous; Deformation; Dipping; Earth and Environmental Science; Earth science; Earth Sciences; Fault zones; Geological faults; Jurassic; Kinematics; Ocean floor; Original Paper; Outcrops; Passive margins; Sediment; Sedimentary structures; Sedimentation; Sedimentation & deposition; Sediments; Slope gradients; Surveys; Thickness
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-021-09266-7

The Cretaceous outcrops of Borj Cedria-Bou Kournine area belongs to the NE-trending Atlas system of northern Tunisia. This area exposes sub-meridian folds associated with numerous N- to NW-trending major fault systems. This study together with previous surveys reveals that this N-trending folding is believed to be related to the inversion of the Jurassic and Early Cretaceous pre-existing fault zones and generated in response to the late compressive deformations. In addition, the study area provides evidence of soft-sediment deformations by good exposures of Cretaceous-aged slump sheets. Slump folds are usually associated with several meso-scale syn-sedimentary normal faulting together with frequent reworked blocs and occasional conglomeratic horizons. All these features indicate sedimentation on irregular seafloor topography. The aim of the present study is to investigate slump folds by applying techniques to reconstruct the contemporaneous slope gradient which has triggered soft-sediment deformations. Moreover, the brittle deformation is quantified using fault kinematic analysis together with the analysis of lithostratigraphic correlation and syn-sedimentary structures. Considerable thickness variations of Cretaceous deposits are interpreted as controlled by normal faulting activities. Likewise, fault kinematic analysis typifies a regional pure extension that trends NNW during Barremain, NNE during Albian, and probably NW during Cenomanian time. Based on slump folds analysis, the inferred sub-marine paleoslope is believed to have a northward dipping during Barremian and a NNE-dipping during Albian time. On the light of the over-mentioned interpretations, it is believed that Cretaceous sedimentation of the study area is highly controlled by major syn-depositional normal faults associated with intra basin growth faulting. These fault systems seem to be related to the Southern Tethyan expansion of the rifted continental passive margin.