Anatomy and evolution of the Astoin diapiric complex, sub-Alpine fold-and-thrust belt (France)

The structure of the southwestern branch Alpine orogen is affected by extensive Late Triassic evaporites. These evaporites have been involved in polyphased salt tectonics since early Liassic, coeval with Tethyan rifting, and are décollement level for thrusts external parts during orogeny. role this arc re-evaluated order to determine relative importance deformation related motion respect main compressional events. This paper focuses on one identified as diapiric 1930’s: Astoin diapir (Goguel, 1939). Analysis geological maps together new field work allowed better define diapirism Upper outcrops around Astoin. Study surrounding depocenters reveals a major involvement structuration area, Liassic. Several ridges linked structure, explaining why we call it “diapiric complex” Salt was initiated Liassic few locations show evidence reactive whereas others passive seen. Passive continued post-rift stage margin history Jurassic Cretaceous when an allochthonous sheet emplaced. Diapirism also occurred Oligocene while foreland basin developing part European Alps. Serial interpretative cross-sections drawn illustrate lateral variations structural style. Sequential evolutions each cross-section proposed reconstruct complex evolution through time. shows framework important along-strike variation activity. Most geometries inherited from that extension, some places these structures overprinted structures.