ARGUMENTS FOR THE PRE-RIFT UPLIFT AND RIFT PROPAGATION IN THE LIGURIAN-PROVENCAL BASIN (NORTHWESTERN MEDITERRANEAN) IN THE LIGHT OF PYRENEAN PROVENCAL OROGENY

The Cenozoic Provencal orogeny and the subsequent opening of the Ligurian‐Provencal basin were caused by a geodynamic mechanism that originated in the Cretaceous. It is evident from the arguments presented that (1) regional doming preceded rifting of the continental margin and this uplift widened and/or migrated during the ensuing opening of the Ligurian‐Provencal basin; (2) clastic sedimentation on the Provencal platform was initiated during the early Cenomanian; (3) deformation in the Provencal block, which varies from Late Cretaceous to Miocene, reflects a migration of the north‐south compression from west to east accross the block; (4) the Languedoc‐Provencal fold belt was initiated during the Eocene as a result of tectonic uplift and sinistral displacement of the Paleozoic basement toward the north. Significant geologic features of the region associated with these events include (1) similarities in shape of the Languedoc virgation and the Provencal thrust front with the shape of geophysical features over the Golfe du Lion; (2) the unusual width of the young, stretched continental margin in the Golfe du Lion; (3) the distinctive V‐shaped form of the Ligurian oceanic crust; and (4) the concordance in age of the earliest post‐rift deposits, which increasingly young toward the east, and magnetic anomalies that parallel the basin axis. These events and structures are attributed to the uplift of a Paleozoic block situated to the south in the Golfe du Lion and previously buried under the Mesozoic cover. The development of this crustal uplift since upper Aptian, and its northeastwards migration and/or gradual widening account for both sedimentary events and tectonic deformation that occurred on the Provencal platform until upper Eocene, and the later stage of rifting and formation of the Provencal margin. In the Ligurian‐Provencal basin, the synthesis of marine data as well as relevant terrestrial data indicates that rifting propagated towards the Gulf of Genoa, while the Corsica‐Sardinia block rotated to the southeast. Copyright 1990 by the American Geophysical Union.