Olivier Serrano

Meso-Cenozoic geodynamic evolution of the Paris Basin: 3D stratigraphic constraints

Abstract 3D stratigraphic geometries of the intracratonic Meso-Cenozoic Paris Basin were obtained by sequence stratigraphic correlations of around 1 100 wells (well-logs). The basin records the major tectonic events of the western part of the Eurasian Plate, i.e. opening and closure of the Tethys and opening of the Atlantic. From earlier Triassic to Late Jurassic, the Paris Basin was a broad subsiding area in an extensional framework, with a larger size than the present-day basin. During the Aalenian time, the subsidence pattern changes drastically (early stage of the central Atlantic opening). Further steps of the opening of the Ligurian Tethys (base Hettangian, late Pliensbachian;...) and its evolution into an oceanic domain (passive margin, Callovian) are equally recorded in the tectono-sedimentary history. The Lower Cretaceous was characterized by NE–SW compressive medium wavelength unconformities (late Cimmerian–Jurassic/Cretaceous boundary and intra-Berriasian and late Aptian unconformities) coeval with opening of the Bay of Biscay. These unconformities are contemporaneous with a major decrease of the subsidence rate. After an extensional period of subsidence (Albian to Turonian), NE–SW compression started in late Turonian time with major folding during the Late Cretaceous. The Tertiary was a period of very low subsidence in a compressional framework. The second folding stage occurred from the Lutetian to the Lower Oligocene (N–S compression) partly coeval with the E–W extension of the Oligocene rifts. Further compression occurred in the early Burdigalian and the Late Miocene in response to NE–SW shortening. Overall uplift occurred, with erosion, around the Lower/Middle Pleistocene boundary.

Reassessment of the structural framework of western Provence (France): consequence on the regional seismotectonic model

Reprocessing and interpretation of the petroleum seismic profile 81SE5b, located between the Luberon Massif and the Arc Basin, have provided new data on the Pyrenean and Alpine thrusting in western Provence. Among the principal results, it is shown that a) the repetition of the Mesozoic succession observed in the Eguilles1 borehole is due to a north-dipping south-verging thrust, and b) the Trévaresse and Aix-Eguilles thrusts are deep structures rooted in the Triassic at a depth of between 7 and 8 km. The implication of this new knowledge on the seismotectonic model of western Provence is that the front of the Alpine deformation between the Aix-en-Provence and Salon-Cavaillon fault systems, which acted as lateral ramps, lies some 7 km farther south near the northern limb of the Arc syncline. In addition, it is seen that the Alpine-Provence thrusts, considered as still active (having given rise to the 1909 earthquake with an epicentral intensity of VIII-IX), are not shallow reverse faults but correspond to major tectonic structures affecting the full thickness of the Meso-Cenozoic cover.