The distribution of Gondwana-derived terranes in the Early Palaeozoic

The present day Variscan basement areas of Europe have been recognized as generally derived from Gondwana, based on fauna, facies and detrital zircons distributions. These areas represent only a portion of Europe (Iberia, France, Central Europe), but it is obvious that similar Variscan basements are present in the whole Alpine and Mediterranean areas too, up to the Caucasus. In tracing these terranes back to their possible position around Gondwana, it became obvious that they could not all be positioned north of Africa, as generally shown on reconstructions. We developed the concept of a ribbon like Galatian superterrane that comprised most of these “European” Variscan elements. In Ordovician times, this superterrane extended from the north of South America to South China (located in continuity to Africa). Along such a length, the geodynamic evolution was not the same, but presents strong similarities. Geodynamic scenarios for the whole Paleozoic have been developed for the different segments, thus allowing us to re-distribute the subterranes in a coherent way. The diachronous openings of the Rheic s.l. ocean, then of the Paleotethys, represent the main reconstruction guidelines, together with major magmatic activity distribution in space and time

Kimmeridgian-Tithonian sea-level fluctuations in the Uljanovsk-Saratov Basin (Russian Platform)

Abstract The Uljanovsk-Saratov Basin, located in the southeast of the Russian Platform, presents an intriguing record of the Kimmeridgian-Tithonian sea-level fluctuations. In the Late Jurassic, this basin was a trough within the Interior Russian Sea. The data available from both outcrops and boreholes have permitted outlining a number of lithostratigraphic units and regional hiatuses in the northeastern segment of the Uljanovsk-Saratov Basin, thus permitting a precise reconstruction of transgressions/regressions and deepenings/shallowings. In total, three transgressive-regressive cycles and two deepening pulses have been established. These regionally documented changes were both related in part to global eustatic changes, and they also corresponded in part to the regional sea-level changes in some basins of Western Europe and Northern Africa, but not to those of the Arabian Platform. Differences observed between the global and regional curves as well as rapid Tithonian sea-level oscillations are explained by the influences of tectonic activity. It is hypothesized that the regional Tithonian oxygen depletion might have been a consequence from the rapid flooding of a densely vegetated land

Exotic terrains in the Alps - A solution for a single Jurassic ocean

The Brianconnais area is explained as a large scale exotic terrain separating from Europe during the opening of the Valais ocean. It's displacement history during the Alpine evolution allows to replace older concepts of multiple oceans separating narrow strips of continental crust