The Upper Carboniferous S. Giorgio succession (Iglesiente, SW Sardinia): stratigraphy, depositional setting and evolution of a Post-Hercynian molassic basin

BARCA S.;COSTAMAGNA, LUCA GIACOMO

2003-01-01

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Abstract

A lithological and sedimentological analysis of the Upper Carboniferous S. Giorgio basin succession has provided a deeper understanding of its stratigraphy and depositional environment and allowed us to outline the tectonosedimentary evolution. Several stratigraphic sections have been measured, sampled and fitted into a comprehensive framework. Microfacies analyses of the samples have also been made. Collected data suggest the S. Giorgio succession could be related to a progradational-retrogradational cycle caused by the late orogenic movements of the Variscan Chain. Deposition of the sequence is thought to have taken place in an alluvial plain to transitional environment, comprising something between fan-delta fronts and a marsh-coastal lake-deltaic l.s. context, with a significant contribution of carbonate deposition during periods of low to zero terrigenous input. No evidence of a real lake has been found. The siliciclastic infilling of the basin might have been the result of the gradual slowing of subsidence and the termination of extensional tectonic activity. The informal name of S. Giorgio Fm. is suggested for the studied succession.