RIASSUNTO

Dati sismici e di sottosuolo suggeriscono che le successioni carbonatiche mesozoiche affioranti in alcuni settori dell’Appennino centro-meridionale costituiscano una parte affiorante della Piattaforma Apula Interna (PAI). Sono state studiate in dettaglio alcune successioni cretaciche affioranti nei rilievi del Gruppo del Matese e del Taburno-Camposauro, confrontandole con coevi sedimenti carbonatici della unità Apula interna raggiunta in perforazione nel Campo Benevento e dal pozzo Morcone 1bis.I dati di sottosuolo evidenziano come a partire dal tardo Aptiano vengano ad individuarsi piccoli bacini o solchi intrapiattaforma, in alcuni casi fortemente subsidenti. Anche i dati raccolti in superficie documentano una tendenza simile e, confrontati con quelli del sottosuolo, permettono di riconoscere 3 fasi principali di strutturazione riferibili all’Aptiano medio, all’Aptiano superiore-Albiano e al Cenomaniano inferiore-medio. I principali lineamenti tettonici, individuatisi a seguito della prima fase di strutturazione, sono stati ripetutamente riattivati nelle fasi successive condizionando l’evoluzione paleoambientale dei differenti subdomini. L’analisi delle facies sia dei corpi affioranti che di quelli raggiunti nel sottosuolo mostrano trend deposizionali confrontabili e soprattutto evidenziano come, a partire dall’Aptiano medio-superiore, le aree a sedimentazione carbonatica mostrino una netta variazione: da uniformi sistemi lagunari pre-aptiani a complessi sistemi di produzione e accumulo di sedimenti, creatisi in relazione con le fasi di strutturazione tettonica. Infine, lo studio delle sezioni sismiche permette di effettuare una correlazione tra il massiccio del Matese, il pozzo Morcone 1 e il Campo di Benevento, mostrando una struttura costituita da una serie di thrust in cui i piani di scollamento portano unità più antiche(Piattaforma Apula) su terreni più giovani (Avanfossa miocenica).Un elemento di conferma di tale interpretazione è rappresentato dalla polarità temporale dei sedimenti silico-clastici cui evolvono le facies neritiche mioceniche, in un trend di annegamento passante per depositi relitti, palinsesto ed emipelagici, spostandoci dal Matese orientale verso i pozzi Morcone 1 e Benevento. Tale polarità temporale permette, infatti, di ricostruire il timing deformativo di questo settore della catena.

TERMINI CHIAVE: Cretacico, Appennino campano-molisano,Piattaforma Apula.

ABSTRACT

The Cretaceous evolution of a sector of the Apulia Platformfrom subsurface and outcrop data (Campania-Molise Apen-nines).

Seismic and outcrop data suggest that the Mesozoic carbonate successions cropping out in the Matese and Camposauro Groups, inthe central-southern Apennines of peninsular Italy, can be inter-preted as an exposed part of the Inner Apulia Platform (PAI). Cretaceous sequences have been studied in detail in the field and com-pared with the coeval carbonate sediments of the Inner Apulia Unit cored in the Benevento oilfield and in the Monte Taburno 1 and Morcone 1bis wells. Subsurface data show that, starting from the late Aptian time onwards, the Inner Apulia Platform was dismem-bered into a series of sub-domains which included shelf al productive areas and a series of small intra-platform basins (or elongated depressions). These basins have a mean Apennine orientation and were locally affected by significant subsidence. Outcrop analyses indicate similar tectono-sedimentary trends and led to the recognition of three main structuring phases, that can be ascribed Middle Aptian, Late Aptian-Albian and Early-MiddleCenomanian time intervals, respectively. The main structural features, formed during the first structuring phase, were repeatedly reactivated during the subsequent phases and controlled the palaeo-environmental evolution of the various sub-domains, that were characterised by different facies and facies associations. The facies analysis from integrated outcrop and core data shows analogous evolutionary trends. In particular, starting from the middle-late Aptian, the carbonate factories display a sharp variation in the sedimentary dynamics and depositional architectures: the uniform pre-Aptian shallow-lagoon rimmed system rapidly evolved into a much complex system in which shallow-water rudist-dominated carbonate factories were located alongside by-pass and deeper basinal areas. At outcrop, the steering toward open marine conditions can be correlated with the early (middle Aptian) structuring phase of the platform. This trend is marked in the easternmost studied areas by the formation of tectonically active margins, characterised by the presence of complex channel networks, but is also evident in the innermost sectors (western areas) of the shelves, by the increase in frequency and intensity of high-energy events. The varied time-span of the «mid-Cretaceous» stratigraphic gaps (see CARANNANTE et alii, 1987, 1994; RUBERTI, 1992) supports the hypothesis of a complex tectonically-controlled palaeo-topographyand of a differential evolution of the related sub-domains. Since the late Turonian, a shallow sea encroached on the exposed lands. Deposition of shallow water rudist-rich sediments followed. The peculiar features of the benthic assemblages which dwelled patchily in loose substrata resulted in the lack of real reefs at the shelf margins. This enhanced the water circulation and controlled the 3D arrangement of the sedimentary bodies made up mainly of large coalescing sheets of winnowed fine to coarse skeletal sands. The skeletal fraction, produced by intensive bioerosive and mechanical processes acting on mainly diagenetically stable calcite-shelled organisms, covered most of the open shelf. This large amount of loose silt to pebble-sized bio-clastic debris was periodically removed from the shelf, transported (often through submarine channels) and resedimented in the adjacent strongly subsiding intra-platform basins formed during the Lower Cretaceous and Cenomanian structuring phases. Finally, the study of available seismic lines allowed for correlation between the Matese Mountains and the Morcone 1 well and the Benevento oilfield. These lines, tied to well data, show a complex structure formed by several thrusts where older units pertaining to the Apulia Platform are piled up over younger siliciclastic units of the Miocene Foredeep. Further, the foredeep siliciclastic deposits areas old as lower-middle Tortonian in the Eastern Matese, while as young as late Tortonian in the Morcone 1 well and Pliocene in the Benevento oilfield. This remarkable time-polarity appears to support the hypothesis presented in this contribution, and makes it possible to constrain the timing of the thrust emplacement for this sector of the Apennine Chain.

KEYWORDS: Cretaceous, Campania-Molise Apennines, Apulia Platform.

FULL TEXT>>