Characterization of Permian mixed carbonate-clastic systems in the Jeffara area, Central Tunisia
C. Kougioulis (TU Delft - Civil Engineering & Geosciences)
P.B.R. Bruna – Mentor (TU Delft - Applied Geology)
G. Bertotti – Graduation committee member (TU Delft - Applied Geology)
A. W. Martinius – Graduation committee member (TU Delft - Applied Geology)
A Barnhoorn – Graduation committee member (TU Delft - Applied Geophysics and Petrophysics)
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Abstract
Permian deposits are found in outcrops and in the subsurface of Southern Tunisia, in the Jeffara Basin. Their stratigraphic and tectonic evolution is not yet fully understood and represents the main focus of this work. Aspects of the Permian system such as, lateral extend of formations, dating and paleo environments are not well constrained. Answering these questions will impact future hydrocarbon exploration and also improve the geological understanding of Tunisia. To achieve this, seismic lines and well data of the Jeffara Basin have been re-interpreted and re-correlated.
The results of the study indicate a lagoon depositional environment for the Early Permian, a carbonate self environment for the Middle-Upper Permian successions, with dimensions of 80 square kilometers and a general east-west orientation. The thickness of the carbonate deposits reaches a maximum of 2500 kilometers to the north of the reconstituted paleoshore. A Sabkha environment has been interpreted for the Upper Permian with significant deposits of anhydrite. Structurally, it was observed that the Permian is not affected by major normal faults.
Conversely, significant folds have been identified at the seismic data, with a general east-west strike and a northwards dip. Based on the displacement of seismic reflectors, two tectonic episodes have been identified. The first is dated to the Upper Carboniferous - Early Permian and the second to the Early-Middle Triassic. Decompaction calculations indicate low subsidence rates and general stability during the Early Permian. This was followed by significantly increased subsidence rates during the Middle and Upper Permian.