15 research outputs found
Numerical modelling of Cretaceous Pyrenean Rifting: The interaction between mantle exhumation and synârift salt tectonics
International audienceThe preshortening Cretaceous Pyrenean Rift is an outstanding geological laboratory to investigate the effects of a preârift salt layer at the sedimentary base on lithospheric rifting. The occurrence of a preârift kmâscale layer of evaporites and shales promoted the activation of synârift salt tectonics from the onset of rifting. The preâ and synârift sediments are locally affected by highâtemperature metamorphism related to mantle ascent up to shallow depths during rifting. The thermoâmechanical interaction between dĂ©collement along the preâexisting salt layer and mantle ascent makes the Cretaceous Pyrenean Rifting drastically different from the type of rifting that shaped most Atlanticâtype passive margins where salt deposition is synârift and gravityâdriven salt tectonics has been postrift. To unravel the dynamic evolution of the Cretaceous Pyrenean Rift, we carried out a set of numerical models of lithosphereâscale extension, calibrated using the available geological constraints. Models are used to investigate the effects of a kmâscale preârift salt layer, located at the sedimentary cover base, on the dynamics of rifting. Our results highlight the key role of the dĂ©collement layer at cover base that can alone explain both salt tectonics deformation style and highâtemperature metamorphism of the preârift and synârift sedimentary cover. On the other hand, in the absence of dĂ©collement, our model predicts symmetric necking of the lithosphere devoid of any structure and related thermal regime geologically relevant to the Pyrenean case