New Evidence for Salt Tectonics in Bannu Basin, Northern Pakistan from Seismic Imaging

Abstract:

The Trans Indus-Salt Range, located in northern Pakistan, is one of the most tectonically active fold-and-thrust belts and comprises three main regions of Potwar-Salt Range, Kohat-Surghar Range and the Bannu Basin-Khisor Range. Of these, Bannu Basin is the least studied and only a handful of publicly accessible datasets and publications are available.

2D seismic profiles and well data from this area have been recently made public and provide a more comprehensive picture of the structural geology and stratigraphy of the Bannu Basin. Well data analysis plus structural and stratigraphic interpretation of seismic profiles were integrated with existing data from the Bannu Basin to generate structural cross sections and fence diagrams. The fence diagrams indicate the presence of salt and salt diapirism that is concentrated along the Marwat anticline.

Salt diapirs and transpressive structures were identified at the terminations of wrench zones. Evidence of salt enables the concept that Infra-Cambrian salt may have been the sole detachment for Bannu Basin and not Cambrian shale as previously proposed. A shallower Eocene/Paleocene detachment has also been identified.

Bannu Basin indicates structural and stratigraphic similarities with the Potwar-Salt Range and exhibits thin-skinned deformation. Our results suggest that these similarities are likely due to the presence of salt and its role as a detachment in both regions. Therefore, we consider the Bannu Basin as the western extension of the Potwar-Salt Range and that the Infra-Cambrian salt extends westward of the Kalabagh fault.