Séverine Fauquette

The environment of the Marseille basin in the Early Pleistocene was reconstructed through a multiproxy study of fluvial tufa deposits. Palaeomagnetic measurements revealed the Jaramillo subchron and dated the tufa to within the 0.8–1.5 Ma interval, probably between 0.9 and1.2 Ma. Sedimentological studies show varied depositional environments comprising natural dams formed by accumulations of plants promoting the development of upstream water bodies. The very negative δ¹³C values indicate that the Marseille tufa is not travertine sensu stricto but tufa deposited by local cold-water rivers. Palynological analyses indicate a semi-forested, diverse, mosaic vegetation landscape dominated by a Mediterranean pine and oak forest. Along the streams, the riparian forest was diverse and included Juglans, Castanea, Platanus and Vitis. The potential diet reconstructed from pollen was varied. The most surprising discovery was the presence of proto-cereals, which could potentially enrich the diet with carbohydrates. The identification of spores of coprophilous fungi seems to indicate the presence in situ of large herbivore herds. It is possible that, as in Anatolia, the disturbance of ecosystems by large herbivores was responsible for the genetic mutation of Poaceae and the appearance of proto-cereals. Climatic reconstructions indicate a slightly cooler and wetter climate than the present.

Based on detailed sedimentological analyses of cores, interpretation of well logs and a set of geochemical measurements performed on lacustrine sedimentary rocks, the palaeoenvironmental evolution and the sedimentary architecture of the Paleogene continental Vistrenque Basin (SE France) have been reconstructed. The analysis of sedimentary archives revealed three main stages of basin infill evolution: (1) a deep-lake basin (Priabonian-earliest Rupelian) whose sedimentation was dominated by terrigenous gravity-driven deposits during a period of high subsidence rate and strike-slip fault activity and under a prevailing humid climate; (2) an evaporative deep lake (early Rupelian) characterized by a drastic reduction in lake volume (forced-regression), terrigenous supplies and deposition of evaporites in disconnected sub-basins; (3) an overall long-term normal regressive stage (middle Rupelian to earliest Chattian) of lake infill characterized by an increase in terrigenous supplies and a vertical upward transition from deep-lake gravity-driven deposits to marginal lake and floodplain sedimentation. The onset of lake volume reduction and forced regression during the early Rupelian is associated with (1) the reworking of marginal lake carbonates into the deep lake areas, (2) the deposition of organic-rich sediments (TOC > 10%) coupled with sulphate-reduction processes in the deepest areas of the lake, (3) an important decrease in terrigenous supplies and (4) a long-term increase in δ¹⁸O of matrix-supported carbonates. This early Rupelian forced regression of the Vistrenque lacustrine system is interpreted to result from a regional decrease in precipitation in response to global cooling during the Eocene-Oligocene Transition (EOT). The final infill of the Vistrenque lake system (late Rupelian-early Chattian) and the onset of a floodplain occurred in more humid conditions during a stage of decreased activity of the Nîmes Fault, prior to or during an early stage of the Liguro-Provençal rifting.

We describe the new frog Telmatobius achachila sp. nov. from the late Middle to earliest Late Miocene of Achiri, based on a partial skeleton found at 3960 m above sealevel in the Bolivian Altiplano. This skeleton, attributed to a male adult, constitutes the first documented fossil record of the speciose living genus Telmatobius, endemic to the Andean Cordillera and the Altiplano. Phylogenetic analysis confirms the new species as being part of the crown group, and diverging both later than the T. verrucosus group and earlier than the T. bolivianus, T. marmoratus and T. macrostomus groups. Coupled with its accurate stratigraphic provenance and age, this phylogenetic position provides a relevant calibration point for timing the evolutionary history of these highland, mostly aquatic frogs. The skeleton of T. achachila indicates that several of the osteological peculiarities of extant Telmatobius were already acquired at c. 12 Ma, including some that might be linked to their aquatic lifestyle. Together with mixed montane–rainforest pollen vegetation uncovered in the same level, this fossil specimen further provides key data enabling a more accurate reconstruction of ancestral habitats and elevation ranges of Telmatobius, agreeing with the previously postulated conditions in which these water frogs might have first evolved. Ultimately, this discovery adds to the sparse evidence of a humid tropical Bolivian Altiplano just prior to: (1) the Late Miocene uplift pulse of the Central Altiplano; and (2) the drastic climate deterioration that occurred from Late Miocene time onward, leading to the harsh highland‐steppe environments reigning there today.

The Mio-Pliocene succession of Andalusia on the Atlantic coast (Guadalquivir Basin) is known as one of the former stratotype candidate for the Andalusian Stage, proposed during the seventies as the last stage of the Miocene. Its type section is located in Carmona, east of Seville. Our investigation includes the drilling of three cored boreholes, which provide bio- and magnetic-stratigraphic data in complement to pre-existing industrial information, and a high-resolution palynological analysis (pollen grains, spores and dinoflagellate cysts). The pollen flora and its climatic quantification provide the mean to correlate the section to the oxygen isotope curve from the Montemayor-1 borehole, located about 80 km to the West of Carmona. The variations in the ratio between dinoflagellate cysts and pollen grains are used to identify high and low oceanic levels, consistently with a recent paleobathymetric reconstruction based on foraminifera: the two lowest levels being successively marked by the deposit of a littoral calcarenite (the Calizza Tosca Formation) then by a subaerial erosive episode. Based on the correlation with the Montemayor-1 regional drilling, the two major lowerings in oceanic level observed at Carmona are linked with the two episodes of the Messinian Crisis. The interlocking position of the high-energy sandstone deposits inscribed in the Messinian valley leads to an assessment of a drop in the global oceanic level of about 114 m at the beginning of the paroxysm of the Messinian Crisis, amplitude to be moderated with respect to the potential effect of isostatic readjustements due to the Messinian Crisis. Comparisons are discussed with the amplitude of the Messinian Erosional Surface in the West-Alboran Basin which potentially remained suspended and fed with Atlantic waters during the height of the crisis and isolated from the rest of the almost totally dried Mediterranean Basin. The quantified climate constructed from the pollen records confirms that dry conditions existed before the Messinian Crisis in Southern Mediterranean latitudes including the Atlantic side, making the Mediterranean Sea climatically predisposed to desiccation. Atlantic sea-level variations observed in the Guadalquivir region and measured at Carmona suggest that global glacio-eustatism somewhat facilitated the onset and completion of the Messinian Crisis in the Mediterranean Basin. At last, this work allows to discriminate two regional erosive events: the first one, dated at 5.60 Ma, of fluvial origin in relation with global eustasy; the second one, submarine, occurred just before 5.33 Ma, and referred to the strain exerted by the Guadalquivir olistostrome.

The French Massif Central is a key basement relief. This region experienced an intense period of alkaline volcanism, beginning with the Cantal Stratovolcano at 11 Ma and ending at 3 Ma. To quantify the palaeoelevation of the Cantal Stratovolcano and to replace it in the frame of the uplift history of the Massif Central, we first reconstructed the vegetation and climate based on a pollen analysis of the Murat diatomites, which were deposited in a maar lake. The vegetation was organized in three different belts: a Glyptostrobus swamp around the lake; a mixed forest; and, at higher altitudes, a conifer forest. The climate estimated using the climatic amplitude method indicates temperatures between 11.4 and 17°C. Using these estimates and comparison with contemporaneous sites, we infer a palaeoelevation for Murat between 710 and 930 m a.s.l. This site was therefore uplifted by 130 to perhaps 350 m during the Early Pliocene, leading to a reorganization of the drainage pattern and the capture of rivers flowing from the northern edge of the Massif Central towards the Atlantic Ocean. Our study confirms that the Cantal Stratovolcano was a high volcano (>2500 m) before its progressive dismantling during glacial episodes in the Pleistocene.