Arguments for the pre‐rift uplift and rift propagation in the Ligurian‐Provencal Basin (northwestern Mediterranean) In the light of Pyrenean Provencal Orogeny

Abstract

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.

Reconstruction of the Provence Chain evolution, southeastern France

“…For the Provence belt, we used new structural data and the previously published Bestani et al [] section. For the Ligurian basin, the Sardinia domain, and the Tethyan subduction system, we integrated data published by Guieu and Roussel [], Rollet et al [], Dèzes et al [], Lacombe and Jolivet [], Bache et al [], and Malusà et al [] (Figures and ). We also integrated tectonic reconstruction maps of Choukroune et al [], Matte [], Guillot and Menot [], Molli and Malavieille [], and Advokaat et al [] for location of the Sardinia during Late Paleozoic to present day.…”

History of subduction and back-arc extension in the Central Mediterranean

“…This event is marked by large scale folding mainly localized along the southern, North African (Bosworth et al . 1999) and northern, Iberian–European (Guieu & Roussel 1990; D'Argenio & Mindszenty 1991), Tethyan passive margins of the Ligurian–Piedmont ocean (Dercourt et al . 1986) and subordinately along the Apulia microplate (D'Argenio & Mindzenty 1991).…”

“…Along the northern margin, in particular in Sardinia and in the Provençal area, this event is followed by a rapid subsidence as marked by the presence of a large‐scale angular unconformity (∼90–85 Ma, Fig. 3; Guieu & Roussel 1990; D'Argenio & Mindzenty 1991). Soon after this widespread compressional episode, the first evidence of the formation of a trench and the subduction process along the northern, Iberian–European margin occur.…”

“…The whole Mediterranean region was subjected to a large-scale rapid pulse of in-plane compressional stress during the Late Cretaceous (y95-85 Ma). This event is marked by large scale folding mainly localized along the southern, North African (Bosworth et al 1999) and northern, Iberian-European (Guieu & Roussel 1990;D'Argenio & Mindszenty 1991), Tethyan passive margins of the Ligurian-Piedmont ocean (Dercourt et al 1986) and subordinately along the Apulia microplate (D'Argenio & Mindzenty 1991). Along the northern margin, in particular in Sardinia and in the Provençal area, this event is followed by a rapid subsidence as marked by the presence of a large-scale angular unconformity (y90-85 Ma, Fig.…”

Subsidence history, crustal structure, and thermal evolution of the Valencia Trough: A young extensional basin in the western Mediterranean

“…In the Paleogene, for example, the Iberian plate subducted to the north beneath the European plate that led to the development of the Pyrenees and Iberian chains. The compression resulted in crustal thickening and, probably, was accompanied by uplift and erosion of a broad region of the northwestern Mediterranean [e.g., Guieu and Roussel, 1990]. England and McKenzie [1982] have proposed that extension may follow compressional thickening of the crust owing to a gravitational instability in the lower part of the lithosphere, such as in the case of a Himalayan-type orogenic belt.…”