Improvements in sub-basalt imaging combined with petrological and geochemical observations from the Ocean Drilling Program (ODP) Hole 642E core provide new

Structural analysis of the southern Tunisian Atlas was carried out using field observation, seismic interpretation, and cross section balancing. It shows a mix of thick‐skinned and thin‐skinned tectonics with lateral variations in regional structural geometry and amounts of shortening controlled by NW‐SE oblique ramps and tear faults. It confirms the role of the Late Triassic–Early Jurassic rifting inheritance in the structuring of the active foreland fold and thrust belt of the southern Tunisian Atlas, in particular in the development of NW‐SE oblique structures such as the Gafsa fault. The Late Triassic–Early Jurassic structural pattern is characterized by a family of first‐order NW‐SE trending normal faults dipping to the east and by second‐order E‐W trending normal faults limiting a complex system of grabens and horsts. These faults have been inverted during two contractional tectonic events. The first event occurred between the middle Turonian and the late Maastrichtian and can be correlated with the onset of the convergence between Africa and Eurasia. The second event corresponding to the principal shortening tectonic event in the southern Atlas started in the Serravalian‐Tortonian and is still active. During the Neogene, the southern Atlas foreland fold and thrust belt propagated on the evaporitic décollement level infilling the Late Triassic–Early Jurassic rift. The major Eocene “Atlas event,” described in hinterland domains and in eastern Tunisia, did not deform significantly the southern Tunisian Atlas, which corresponded in this period to a backbulge broad depozone.

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The provenance of middle Eocene to early Miocene sedimentary rocks cropping out in the Sulaiman fold and thrust belt has been determined examining the mineralogy, bulk-rock major and trace elements, and Nd-Sr isotopes. The older (50-30 Ma) deposits are characterized by a mixed orogenic provenance with a major contribution from the Karakorum and the Tethyan belt (c. 80%). As the 50-30 Ma deposits have a provenance distinct from that of coeval Subathu, Khojak and Ghazij shallow marine formations of India and Pakistan, we propose that they were deposited as a distinct delta system that once fed the Palaeo-Indus fan. We document a major change in provenance that occurred before the early-late Oligocene transition at c. 30 Ma. This change in provenance is marked by the appearance of chlorite and monazite and a shift toward more radiogenic Nd-Sr isotopic compositions. We interpret this change as the result of the exhumation and erosion of the proto-Higher Himalaya. The 30-15 Ma sampled rocks are characterized by a major contribution from the Tethyan belt and the Higher Himalayan Crystallines (70-90%) and a subordinate contribution (10-30%) from the Karakorum, Ophiolitic Suture and Trans-Himalaya. As the åNd(0) values of our 30-15 Ma samples are similar to those of the Palaeo-Indus fan deposits, we suggest that the 30-15 Ma sedimentary rocks of the Sulaiman fold and thrust belt were the fluvial onshore record of the Indus fan. Other coeval deposits of India and Pakistan recorded similar increasing exhumation of the Higher Himalaya range, so that we postulate that these sedimentary rocks all derived from the Palaeo-Indus drainage basin. This would suggest that the modern Indus drainage basin is no younger than 30 Ma.