Carboniferous continental margin deposits in southern Tuscany, Italy: results from geological mapping of the geotopes Farma Valley and San Antonio Mine Area

Abstract

AbstractRelics of the Carboniferous shelf, slope and basin margin section occur as intensely tectonized slices within the middle Tertiary Monticiano‐Roccastrada metamorphic core complex in southern Tuscany. These sedimentary successions are interpreted as predominantly siliciclastic second‐order sequence stratigraphic cycles, deposited in a successor basin (Farma Basin) established near the Southern Convergence Front of the westmediterranean Hercynides. The units developed as highstand systems tracts above a downlap surface and buried pelagites of a starved, moderately deep‐water basin (Risanguigno Basin). The Risanguigno Basin was characterized by dys‐ and anoxic conditions and underwent partial tectonic inversion during the early Carboniferous. Detailed mapping has revealed that Carboniferous turbidites deposited on the slope, base of slope and Farma Basin margin are present in the eastern part of the Farma Valley and in the San Antonio Mine Area. Coeval lithologies—storm influenced deposits of the inner shelf and lower shoreface—crop out in the western part of the Farma Valley. Both units, considered to be related to storm‐triggered offshore bottom currents bypassing the outer shelf, are covered by offlapping shallow marine and littoral clastics probably of Permian age. Subsequent tectonic uplift and partial inversion of the Farma Basin resulted in subaerial exposure, erosion of the upper part of the basin fill and deposition of the terrestrial Verrucano Group (middle Triassic), which sealed these early Carboniferous to late Permian sequences considered to represent a late Palaeozoic preligurian failed rift. Copyright © 2008 John Wiley & Sons, Ltd.