New micropaleontologic datings within the intra- and postophiolitic sequences from the Balagne thrust sheet (Corsica) and attempt of reconstruction of a part of the Western Tethyan margin

In the Northern part of Corsica, the "Nappe de Balagne", derived from the L igurian-Piedmontese Zone, principally consists of ophiolites (gabbros and, particularly, pillow-lavas) with their sedimentary cover, Jurassic and Earl iest Cretaceous in age (radiolarites overlain by shelf carbonates, with ben thic Foraminifera then Calpionellids, including basinwards Radiolarian-bear ing pelitic intercalations and, locally, some calciturbidites), exceptional ly exempt of HP-LT metamorphism. The oceanic material is subdivided at Pian a-di-Castifao into two sucessive basaltic flows, poured out before the end of the Dogger and during the Kimmeridgian at least, because separated by a thin silici-elastic sequence where reworked bentbonic Foraminifera of these ages have been discovered. This intra-ophiolitic sequence might be subcont emporary with certain Kimmeridgian depositional sequences (BAL(2) to BAL(3) ) recognized and dated by their microfauna/microflora within the "Calcaires de San Colombano" Fm., farther North in a more proximal position, for us, on the West-Tethyan margin. The base of the underlying Radiolarite Fm. (BAL (1)), interbedded at San Colombano and Cima Corbaiola between the last basa lts/hyaloclastites and the first shelf limestones, is assigned to the Upper Bathonian-Callovian interval (Praekurnubia cursei-Pseudocyclammina maynci assemblage within lenticular sandy limestones from the "double bar" section of San Colombano) when its top, more or less eroded, is dated either as "U pper" Dogger or as "Lower" Maim. The sedimentary series is followed, above a major discontinuity, by a Berriasian sequence (BAL(5)), strongly influenc ed, as the previous ones, by extensional growth faults and characterized by a brecciated (debris-flow) low stand wedge corresponding to the "Calcaires a detritus of the San Colombano area. In conclusion, these new data and th eir interpretation allow us to propose, in Corsica, a hypothetic NW-SE pali nspastic reconstruction of a small part (about 20-30 km) of the Western mar gin of the Ligurian-Piedmontese Ocean during Mid-Late Jurassic and Berriasi an times showing that, during the post-rift phase, lilted blocks or steps, characterized by various Jurassic series, deeper and deeper to the East, ar e sealed by Berriasian high stand hemipelagites.