Ante-Stephanian paleogeography
During its collapse in the Stephanian-Permian period, the Variscan chain was folded and segmented by numerous detachments. It is therefore important to reconstruct the geometry of the chain during the Variscan orogenic climax of the Visean, taking into account that the orogen is constituted, on at least one part, by 2 diachronous collision chains: between Armorica and Avalonia on the one hand and between Armorica and Gondwana on the other.
Comparison of the southern and northern foreland basins of the chain
The southern and northern foreland basins contain crucial records of the volumes, nature and climatic/alterological signature of materials eroded from the chain. Reconstruction of the basins will allow testing of current piedmont and lithospheric flexure models to estimate the orogenic load of associated topographies.
Extension of the sedimentary covers during the Stephanian
The late-orogenic phase, i.e. the deconstruction of the chain relief, is well documented in the so-called “Limnic” or “Stephanian” basins. In terms of relief, however, it is important to be able to witness individualized and isolated depocenters or sedimentary covers extending over large areas.
A mass balance of coal
On a global scale, it is important to determine the share of coal in CO2 sequestration at the end of the Paleozoic and the link with climate and orogeny. A literature synthesis would allow a first order estimate of the mass of coal preserved by the orogenic system, when, where and how. This will allow discussion of whether the Paleozoic 13C “peak” is really due to coal accumulations. More generally, we will try to understand the significance of the abrupt transition, classically described in the Permian-Carboniferous, from “black” (deposition of coal in a period considered wet) to “red” (deposition of red series in a period considered dry) on the ancient orogenic domain and on the scale of continental masses.
Variscan Source – to – Sink
Paleogeographic syntheses will eventually allow us to consider a Source-to-Sink perspective in order to evaluate the relative contribution of cratonic and orogenic domains in the sediment budget and global biogeochemical cycles over a complete orogenic cycle.