Allochthonous salt in the sub-Alpine fold–thrust belt of Haute Provence, France
Rod Graham, Martin Jackson, Robin Pilcher, Bill Kilsdonk, 2012. "Allochthonous salt in the sub-Alpine fold–thrust belt of Haute Provence, France", Salt Tectonics, Sediments and Prospectivity, G. I. Alsop, S. G. Archer, A. J. Hartley, N. T. Grant, R. Hodgkinson
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In the sub-Alpine chains of Haut Provence, SE France, a very well-exposed Mesozoic sequence showing rapid thickness and facies changes associated with Jurassic and Cretaceous extension on the margin of the Ligurian Tethys has been deformed by ‘Alpine’ compression which occurred from the Late Cretaceous to the Pliocene. Although the geology has been very well known for decades, aspects of the structure remain enigmatic and cannot be explained by either Mesozoic extension or Alpine shortening alone. We infer that some deformation resulted from salt tectonics. A completely overturned, highly condensed Jurassic section near Barles village resembles the elevated roof of a Triassic salt body in a deep-marine basin. This carapace became overturned as a flap in the Middle Jurassic when salt broke out at the seafloor and overran the inverted flap as an allochthonous extrusion, comparable to those in the deepwater Gulf of Mexico or Angola. Later, Alpine compression exploited the weakness of the salt sheet as the Digne Thrust moved over the inverted flap. Although the flap is in the footwall of the thrust, evidence of soft-sediment deformation and other anomalous structures within the flap suggest that it did not originate as an overturned footwall syncline.