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The Tricastin region in the lower Rhône Valley (France) is affected by an atypical seismic activity characterised by the development of long-lasting and recurrent seismic swarms. Indeed, since the 16th century, hundreds of seismic events sometime associated with underground noises of the explosion have been reported by local inhabitants. However, to date, none of the many scenarios of earthquake generation proposed for the area, involving either tectonics and/or hydrological forcings, appears consensual. To overcome that lack of comprehension, we compile and analyse an 880 seismic-events catalogue derived from both historical macroseismicity and instrumental records. The earthquakes appear to occur at shallow depths similar to those determined below a local network in 2002– 2003. We confront to this catalogue models involving hydrological mechanisms, including aquifers elastic loading and karst-drains responses, as well as tectonic mechanisms, including transient aseismic processes and their related effects on the fold hinges or on the local fault planes. Most of the earthquakes are located at short distances from karst drains and fractured fold hinges, possibly affected by transient hydrological changes. [ABSTRACT FROM AUTHOR]

Abstract: The ancient harbour of Fréjus, located in a Holocene ria, has been the subject of a research program in archaeology and, notably with regards to the sedimentary environment at its foundation. A core was extracted in the middle of the basin of Fréjus harbour. The objective is to understand the paleogeographical evolution of the pre-harbour and Roman harbour environments. The sedimentological and biostratigraphical proxies enabled us to: (1) confirm hypothesis in which the pre-harbour environment comprised a marine bay blocked by an artificial quay (). and , demonstrate the presence of a rocky coast (butte Saint-Antoine), at the time of the harbour''s foundation, which it has been progressively transformed into a sandy coast due to the sedimentary input of Argens delta. This study permitted: (2) to confirm the date of foundation of Fréjus’ harbor; and (3) to show different phases of protection. Indeed, the harbour facies attests to a euryhaline lagoon (B1 and B3) which was gradually transformed into a freshwater lake (B4) due to the progradation of the Argens. Low sedimentation rates (ca. 0.5mm/year), between the end of the last century BC until seventh century AD is consistent with the dredging of the harbour basin. [Copyright &y& Elsevier]

Abstract: The explanation normally given for the tectonics of Sainte-Victoire Mountain, a dozen kilometres east of Aix-en-Provence, to the north of the limestone Provence, is incorrect. To the east, the morphology of the Sainte-Victoire is subdued, whereas to the west, before the mountain breaks savagely, the morphology is that of a young mountain as appears in Alpine landscapes. This unusual aspect in the region and the large subvertical faults with vertically striated surfaces that mark the massif to the south and to the west, induce the idea of strong vertical uplifts and caste doubt on the tectonic interpretation given in 1962 by Corroy et al. According to those authors, the Sainte-Victoire is a unit of Jurassic and Cretaceous formations overthrusting 1800 m to the south conglomerates of the Late Cretaceous or Palaeocene. New observations about the conglomerate transgression over the Jurassic and Cretaceous beds, and about the faults around and on the massif do not give evidence of an overthrusting but, on the contrary, induce the idea of a uplift, perhaps still active, in the form of a ‘piano key’ inclined to the northeast. To cite this article: J. Ricour et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Abstract: The discovery of a level of lithophaga in the entrance of the karstic spring of the ‘Fontaine de Vaucluse’ indicates a pre-Pliocene age and supports a Messinian origin for the present spring. To cite this article: É. Gilli, P. Audra, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

A new geological map of the Palaeozoic units from the Porquerolles Island provides evidence for two main units joined along a north–south-trending shear zone: a western unit of schist, sandstone and microconglomerates, an eastern unit of schist including calcareous rocks, metabasite and various types of mineralisations. The shear zone has experienced a main strike-slip, sinistral movement in a ductile regime, and a late westward normal movement from ductile to brittle regimes. It crosscuts an early thrust fault, marked by penetrative syn-metamorphic deformation and the abundance of quartz rods. According to geometrical relationships, the regional conic fold is interpreted as a large-scale dragging of foliation related to strike-slip faulting. Combined folding and wrenching point out a main transpressional tectonics related to the continental collision dated Middle Visean in the central and eastern parts of the Variscan Maures massif. To cite this article: J.-P. Bellot, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]