GEOLOGICAL INTERPRETATION OF THE CROP-11 SEISMIC LINE BETWEEN THE ADRIATIC COAST AND THE TIBER VALLEY

The CROP 11 is 1 w-e orientec, deep seismic profile (156 Km) that crosses the Cenrral Aoennines from the Tyrrhenian to the Adriatic coast.The shallow structure of the Adriatic crust consists of Mesozoic-Tertiary carbonates 6-7 Km thicK (Apulia Platform) and of Plio-Pleistocene foredeep deposits 2-Km thick. The top of the Apulian Platform is represented on the line by a low-frequency and high-amplitude seismic signal thai evidences a continuous horizon gently dipping westwards beneath the Apennine domain. From 4.2 s TWT (about 10 Km) to 5,7 s TWT, a reflecrive seismic facies, corresponds to the Permo-Triassic terrigenous deposits, stratigraphically underlying the shallow-water carbonates of ihe Apulia Plarform drilled bv the Puglia 1 and Gargano I wells. Below this package of reflectors, a transparent seismic facies, interreted as a crystalline upper crust, extends as far as 10 s TWT. Between 10 and 12 s TWT, finally, a new package of well-organized reflectors should represent a layered lower crust. An Adriatic Moho at about 12 s TWT, which corresponds to a depth of 32-35 kilometres, fits the results of previous geophisical experiments.Moving westwards, the line enters the Apennine belt. This is organized as a duplex structure formed by Mesozoic-Tertiary carbonates and Permo-Triassic terrigenous deposits detacned from ihe Apulian basement. Tne roof thrust of the duplex system corresponds to the base of a basin-derived allochtnous sheets (Molìse nappes). Stratigraphic information contained in the Ponte 1 well suggest that the Apennine frontal ramp was active in this area during Early Plelsiocene times. Backthrusts are common features within the thrust-belt and may account for ihe regional elevation of positive structures (i.e. Bomba, Maiella and Marsica anticlines). The Pemo-Triessic terrigenous deposits have been severely involved in tne compressional deformation in the periadriatic area. On thee contrary the Apennine sole-thrust system seems to be locate at the base of the Upper Triassic dolomites and anhydrites in ihe Marsica and Simbruini regions. An eastward deepening of the sole-thrust during the forward thrust propagation, as also suggested by an important deep-seated duplex structure recognised between Tiber Valley and Marsica regions from 4.5 s to 9 s TWT. Reflection events at 10 s TWT below the Fucino Plain could be attributed to the downgoing Adriaric crust or, alternatively, to the uprising Tyrrhenien mantle