RIASSUNTO Il rilevamento geologico-strutturale e l’analisi biostratigrafica di dettaglio delle successioni carbonatiche in facies neritica affioranti nella dorsale del Monte Fellino (Appennino Campano), hanno per- messo di ricostruire a scala chilometrica una anticlinale rovesciata a geometria serrata associata ad un sovrascorrimento vergente a nord- ovest. La piega rovesciata, con direzione assiale N50-70°, ed il sovra- scorrimento risultano ripiegati da una seconda fase plicativa caratte- rizzata da pieghe aperte ad andamento N100-120°. La ricostruzione geometrica delle strutture analizzate è stata ef- fettuata mediante due sezioni geologiche realizzate sulla base di sti- me attendibili degli spessori ricavati dall’analisi stratigrafica di suc- cessioni carbonatiche. Le successioni coinvolte sono di età compresa tra il Lias inferiore e il Cretacico superiore e affiorano sia nella dor- sale di Monte Fellino che in aree contigue (Monti d’Avella e di Nola- Lauro). Inoltre, l’analisi di facies e del contenuto fossilifero delle successioni esaminate ha permesso di distinguere cinque unità cro- nostratigrafiche. La vergenza verso nord-ovest del sovrascorrimento e della piega N50-70°, anomala rispetto all’andamento appenninico potrebbe esse- re connessa ad una rotazione passiva in senso antiorario indotta dal- la formazione di una struttura ad arco che si sviluppa dal Monte Cervialto ai Monti di Caserta, responsabile anche della formazione delle pieghe N100-120° (in quest’area). TERMINI CHIAVE: strutture da interferenza, analisi biostra- tigrafica, carbonati mesozoici, Appennino meridionale. ABSTRACT Interference pattern in the Mesozoic carbonates of Mt. Fellino Ridge, Campania Apennines, Italy. Geological mapping and detailed biostratigraphic analysis of the shallow-water carbonate successions of the Mt. Fellino Ridge (Campania Appennines), has led to the recognition of a km-scale overturned anticline characterized by tight geometry and associated with a NW-verging thrust which brought Jurassic over Cretaceous successions. The overturned fold is a N50-70°-trending non-cylindrical struc- ture, whereas the thrust is refolded by a N100-120°-trending open anticline. Such a structure is recognizable also toward the south-east not far from the investigated area (i.e. Nola-Lauro Ridge). The angle between the two fold hinges is 40°-60°, as shown by geological mapping. The geometric reconstruction of the geological structures out- cropping in the study area has been realized by means of two viable cross-sections (called AA' and BB' in fig. 6). The construction of the geological sections has been carried out considering the thickness obtained by the stratigraphic analysis of carbonate successions outcropping along the Mt. Fellino Ridge (fig. 2). Further, the stratigraphic analysis of several carbonate succes- sions outcropping both along the Mt. Fellino Ridge and in the wider area of the Avella Mts-Nola-Lauro Ridge allowed five chronostrati- graphic units to be characterized, showing different litho-sedimento- logical features and biostratigraphic content. In particular, the five chronostratigraphic Mesozic units are, from bottom to top: – Lias: about 700 m of limestones and dolomite containing mainly Palaeodasycladus mediterraneus (PIA), Orbitopsella praecursor (GÜEMBEL) and, in the upper part, large spathic shells of bivalves of the «Lithiotis facies» Auct.; – Dogger: about 400 m of oolitic and pseudo-oolitic limestones and subordinate dolomite, containing mainly Valvulina lugeoni SEPTFONTAINE, Mesoendothyra croatica GUSIC, the dasycladaceans Selliporella donzellii SARTONI & CRESCENTI, Pfenderina salernitana SARTONI & CRESCENTI, Pfenderella arabica REDMOND, Satorina apuliensis FOURCADE & CHOROWICS; – Malm: about 400-450 of limestones which consist of calcilu- tites and rarely of calcarenites, sometimes oolitic, containing Clado- coropsis mirabilis FELIX, Kurnubia palastiniensis HENSON, Valvulina lugeoni SEPTFONTAINE, Parurgonina caelinensis CUVILLIER, FOURY & PIGNATTI-MORANO, Clypeina jurassica FAVRE, Salpingoporella annu- lata CAROZZI and Campbelliella striata (CAROZZI); – Lower Cretaceous (Neocomian-Albian): about 600 m of whitish limestones (from mudstones to grainstones) containing mainly Praechrysalidina infracretacea LUPERTO SINNI, Orbitolina (Mesorbitolina) texana (ROEMER), Orbitolina (Mesorbitolina) parva DOUGLAS, Cuneolina laurentii SARTONI & CRESCENTI, Cuneolina scarsellai DE CASTRO, Sabaudia minuta (HOFKER), Ovalveolina reicheli DE CASTRO, Paracoskinolina tunesiana PEYBERNES, Neoiraqia insolita (DECROUEZ & MOULLADE), dasycladacean algae among which, in the lower part of the succession, Salpingoporella cemi RADOICIC, Salpingoporella annulata CAROZZI, Praturlonella danilovae (RADOICIC), and in the upper part Salpingoporella dinarica RADOICIC and Salpingoporella turgida RADOICIC. – Upper Cretaceous (Cenomanian-Senonian): about 650 m of limestones (mainly mudstones-wackestones), sometimes loferitic and stromatolitic, with rare intercalations of dolomites in the lower portion, and greenish marls. This interval contains Sellialveolina viallii COLALONGO, Pseudorhapydionina dubia (DE CASTRO), Biplanata peneropliformis HAMAOUI & SAINT-MARC, Nezzazata sim- plex OMARA, Biconcava bentori HAMAOUI & SAINT-MARC, Cisalve- olina fraasi (GÜEMBEL), Pseudolituonella reicheli MARIE, Chrysalid- ina gradata D’ORBIGNY, Cuneolina pavonia parva HENSON, Nezzazatinella cf. aegyptiaca (SAID & KENAWY), Dicyclina schlum- bergeri MUNIER-CHALMAS, Accordiella conica FARINACCI, Monchar- montia apenninica (DE CASTRO), Scandonea samnitica DE CASTRO. Among the macrofossils fragments and shells of Rudists are abun- dant. The trace of the cross-section AA' is N120°-trending (i.e. sub- orthogonal to the first phase fold axis), whereas the trace of the cross-section BB' is N20° (i.e. perpendicular to the second phase fold axis). In the geological section AA', one can observe the N50-70°- trending overturned fold with a tight geometry (FLEUTY, 1964), in the hangingwall of the thrust. Moreover, a splay thrust cuts the Malm deposits, causing the imbrication of two different slices. The tight geometry of the plicative structure could be linked to the evolu- tion of a previous blind-thrust into a breakthrough thrust (SUPPE & MEDWEDEFF, 1990). In the geological section BB' is possible to detect the refolding of the first phase fold by a N100-120°-trending open fold. Boll. Soc. Geol. It., 125 (2006), 105-116, 9 ff. La struttura da interferenza nei carbonati mesozoici della dorsale di Monte Fellino (Appennino Campano) SERGIO BRAVI (*), DARIO CIVILE (*), CLAUDIO MARTINO (**) & MARIA LUISA PUTIGNANO (***) (*) Dipartimento di Scienze della Terra, Università di Napoli Federico II, Largo San Marcellino, 10 - 80138, Napoli. E-mail: sergiobravi@libero.it; civile@unina.it (**) Dipartimento di Scienze Geologiche, Università della Basi- licata, campus Macchia Romana - 85100, Potenza. E-mail: claudio.martino@imaa.cnr.it (***) Dipartimento di Scienze Ambientali, II Università di Napo- li, via Vivaldi 43 - 81100, Caserta.