A càrrec de César R. RANERO (Institut de Ciències del Mar, CSIC, Barcelona)
Organitzat conjuntament CSIC-UB

Dia: 10-03-2011
Hora: 12:00 h
Lloc: Sala d'actes de l'Institut Jaume Almera

Descripció:
Sedimentary rift basins are created by thinning and progressively subsidence of continental lithosphere during the first phases of extension. If the extension process persists it may ultimately cause the break of the plate. The greatly thinned lithosphere, split in two plates, subsides deep below sea level to form a conjugate pair of rifted continental margins. Despite the fact that rift basins and conjugate margins are ubiquitous structures, the deformation processes that lead from a moderately extended basin to a highly-stretched pair of conjugate margins are still greatly debated. An unresolved problem is the common report that crustal thinning (estimated from seismically-measured thickness) is greater than extension caused by the brittle faulting imaged on seismic records.

We present a new model developed using pre-stack depth-migrated seismic images that have permitted to accurately measure extension on faults and compare it to thinning estimated from seismic measurements of crustal thickness. We have used the seismic observations to create an area-balanced kinematic model of extension during rifting that solves the paradox of the extension discrepancy by generating a fault-controlled crustal thinning that evolves from a rift basin to the asymmetric structure and extreme crustal thinning of conjugate pairs of rifted margins. Our observations support 1) that crustal thinning is to a first degree caused by simple Andersonian faulting, and 2) that the causal faults are unequivocally visible on seismic images. (Authors: César R. Ranero, Marta Pérez-Gussinyé).