Abstract This paper examines the role of mechanical stratigraphy on the evolution of normal fault geometry and fault zone internal structure, using a well-exposed normal fault system from the Permian Lodève Basin, southern France. Faults formed early during the syn-deformation tilting history of the basin tend to have steeper segments in the competent sandstone layers due to refraction, assisted by pre-existing early bedding-perpendicular joints, where displacement remained on the order of bed thickness. Faults which continued to slip during tilting have a more complex structure of splays due both to the space incompatability problem of slip at fault bends of this irregular geometry, and because tilting favours the generation of new splays at a different angle to the earlier faults experiencing rotation. Continued deformation between faults and their splays often causes both distributed deformation in between the two, and reconnection of splays to the main fault forming isolated lenses. Thus, fault zone complexity increases greatly as slip exceeds competent bed thickness, owing both to the presence of the mechanical layering, and the fact that this layering is being tilted.

Abstract In order to take into account the studies of the European and American (USA) collections carried out by one of the authors, and of the recent nomenclatural revisions from new footprint discoveries, which have occurred during the last decade, the authors present a critical review of the French Permian palichnofauna. The distribution of the ichnospecies in the stratigraphy of the Lodève Basin, taken as a reference, is outlined. The ichno-associations are then compared with those of other French (Provence), European (Italy, Germany) and USA basins. Based on the ages of different ichnofossiliferous formations, three successive ichnofaunal units can be distinguished in the Permian of Europe. The first developed in the Cisuralian (Asselian to Kungurian). The second is found in the south of France in Kazanian to Lower Tatarian strata, equivalent to the Roadian-Wordian. The third and youngest, dated as Lopingian, is only found in Italy, in the Bolzano Basin. Because of sedimentary gaps, limited observations, sometimes erroneous determinations, and ichnospecies with great vertical distribution, it currently appears that footprints have a low utility for biochronological resolution. Nevertheless, they allow us to discriminate three time intervals in the Permian, as is also the case for skeletal remains.