Marine terraces and extensional faulting in the Taranto Gulf, Bradanic Trough, Southern Italy

The front of the Southern Apennines in the Taranto Gulf is sealed by Pliocene-Pleistocene foredeep deposits, which represent the infill of the Bradanic Trough. The upper portion of the Middle Pleistocene succession consists of marine sands and conglomerates, that previous work considered arranged in several orders of terraces. The local drainage pattern appears controlled by priminent geomorphic lineaments. Some of these structures coincide with normal faults with vertical offsets of ca. 10 m each. Their trend defines an arcuate pattern that mimics the present coastline. Filedwork shows that all the terraced deposits belong to a single sedimentary body displaced by normal faults. The terraced deposits are related to an event of beach progradation, of Middle Pleistocene age, documented in other areas of the Italian peninsula. The recognition of normal faults offsetting a single terrace unit outline an intimate relationship between the arcuate trend of the mapped fault set and the present coaastline pattern. Normal fault development can be related to large-scalòe gravitational processes developed after the general tilting towards SE of the Bradanic Trough

La distensione tetidea ed il suo controllo sulle strutture compressive del sistema appenninico-maghrebide: l'esempio dei Monti delle Madonie (Sicilia centro-settentrionale)

L'assetto tettonico dei Monti delle Madonie (Sicilia centro-settentrionale) è caratterizzato dalla presenza di un importante lineamento orientato NNW-SSE che si estende per circa 20 Kkm da Gratteri fino a M. Mufara, individuando un settore orientale, dove affiorano le successioni della piattaforma carbonatica panormide, ed un settore occidentale, dove affiorano i depositi del bacino imerese. I risultati di uno studio stratigrafico-strutturale consentono di definire il ruolo svolto da questo lineamento tettonico dal Trias superiore al Pliocene. In particolare, l'analisi cinematica mostra che il lineamento corrisponde alla rampa òlaterale di un sovrascorrimento, attivo durante l'intervallo Miocene medio-Pliocene, lungo il quale le unità panormidi si sono sovrapposte tettonicamente alle unità imeresi. L'analisi stratigrafica ed i rapporti fra le facies delle successioni meso-cenozoiche mostrano che la rampa laterale mio-pliocenica si è impostata su una pre-esistente struttura attiva già dal Trias superiore. Durante l'intervallo Trias superiore-Cretaceo questa struttura ha agito come faglia diretta e/o transtensiva, individuando aree a sedimentazione neritica ed aree a sedimentazione pelagica. A partire dal Cretaceo superiore la struttura distensiva è stata riutilizzata come faglia di trasferimento fra sistemi di faglie dirette orientate W-E che si originano probabilmente in risposta ai movimenti convergenti orientati N-S ed attivi nella futura area mediterranea durante l'intervallo Cretaceo superiore-Oligocene

Pressure-solution fabrics and their overprinting relationships within a minor fold train of the Umbria-Marche Apennines, Italy

Analysis of mesoscopic folds that affect pelagic carbonates of the Upper Jurassic-Lower Cretaceous Maiolica Fm. in the Umbria- Marche Apennines reveals a complex structural history. Bedding- parallel stylolites, that were produced during or soon after deposi- tion as a consequence of an overall extensional deformation, are generally overprinted by bedding-normal pressure-solution cleavage related to the early stages of folding. These relationships are rever- sed in the steep fold limbs, where pressure-solution cleavage appears locally overprinted by bedding-parallel stylolites. The oblique rela- tionship among the stylolitic surfaces and the columnar peaks sup- ports the hypothesis of reactivation of dissolution processes along early, pre-folding stylolites during the advanced stages of folding. Systematic recognition of these relationships in other folded sequences is important, in that it may provide relevant constraints for the quantitative estimates of orogenic contraction across fold- and-thrust belts

Deformazioni distensive recenti nell’entroterra del Golfo di Taranto: implicazioni per la realizzazione di un deposito geologico per scorie nucleari nei pressi di Scanzano Ionico (Basilicata)

In questo studio viene segnalato un sistema di faglie dirette che interessa depositi marini terrazzati recenti nell’entroterra del Golfo di Taranto. L’area di indagine è collocata lungo il fronte dell’Appennino meridionale, una catena a pieghe e sovrascorrimen- ti originatasi in seguito alla chiusura del bacino oceanico mesozoico della Tetide, ed alla deforma- zione compressiva del margine passivo adriatico durante il Terziario ed il Quaternario. Il fronte della catena è parzialmente sepolto dai depositi sinoroge- nici del Pliocene-Pleistocene, che costituiscono il riempimento della Fossa Bradanica. La porzione superiore della successione del Pleistocene medio è costituita da sabbie e conglomerati di origine mari- na, la cui sommità modellata da terrazzi marini, che una precedente letteratura considera organizzati in ordini distinti. Le analisi di immagini da satellite e di foto aeree, e la realizzazione di una carta geomorfologica di dettaglio, indicano la presenza di numerosi linea- menti morfologici che controllano la distribuzione attuale del reticolo idrografico superficiale. Alcune di queste strutture coincidono con le tracce di faglie dirette che dislocano le superfici dei terrazzi marini producendo gradini di circa 10 m. Sebbene molti di questi gradini di faglia si esauriscono lateralmente, le scarpate principali raggiungono e a volte supera- no un’estensione di 4 km. Le scarpate hanno altez- za compresa fra 2 e 10 m, ma localmente è possibi- le quantificare rigetti verticali fino a 50 m. La maggior parte dei lineamenti morfologici osservati ha direzio- ne compresa fra ENE-WSW e N-S, il cui andamen- to cartografico evidenzia una prominente struttura arcuata. L’esame dei caratteri geomorfologici, sedimento- logici e stratigrafici dell’area analizzata consente di avanzare un’ipotesi originale sui rapporti fra le faglie dirette e lo sviluppo dei terrazzi. I depositi terrazzati si sono formati in seguito ad un evento di prograda- zione durante il Pleistocene medio, ben documenta- to anche in altre aree dell’Italia peninsulare. L’analisi dei lineamenti morfologici evidenzia una stretta rela- zione tra la distribuzione cartografica arcuata dei sistemi di faglie dirette e l’andamento della linea di costa attuale, indicando un forte controllo tettonico sulla morfologia del litorale ionico. Lo sviluppo delle faglie dirette potrebbe essere ricondotto a processi gravitativi di importanza regionale sviluppatisi in seguito ad un generale basculamento della Fossa Bradanica verso i quadranti orientali. I risultati di questo studio hanno un’importante ricaduta che investe il delicato aspetto della sicurez- za sociale. Nel novembre 2003 la zona di Scanzano Ionico è stata dichiarata, con Decreto Ministeriale n. 314 del 14/11/03, idonea alla realizzazione di un deposito geologico per scorie nucleari. La segnala- zione di importanti faglie dirette che dislocano depo- siti marini terrazzati indica che l’entroterra del Golfo di Taranto è stato soggetto a movimenti di origine tettonica in epoca recente. Le evidenze di superficie disponibili non consentono, inoltre, di escludere che alcune di queste strutture possano, in toto od in parte, essere ancora attive. Questi dati, pertanto, dovrebbero costituire elementi per un’approfondita riflessione sulla generale stabilità geologica dell’a- rea e sulla possibilità che l’area di Scanzano Ionico venga riproposta come sito per la realizzazione di un deposito geologico per scorie nucleari

The geodynamics of the southern Tyrrhenian Sea margin as revealed by integrated geological, geophysical and geodetic data

The recent and present-day deformation field of the southern Tyrrhenian Sea margin, as revealed from integrated geophysical, structural and space geodesy data, is characterised by subhorizontal NW-SE directed shortening and SW-NE directed extension. This def- ormation was mainly accommodated by development of an E-W trending, complex fault system that has the geometrical features of a strike-slip duplex, and that is here indicated as the Southern Tyr- rhenian Strike-Slip Duplex (STSSD). Most faults within the STSSD are recent. There are, however, local examples of ancient faults that were repeatedly reactivated through time, such as the Gratteri-Mt. Mufara Line. Structural measurements on these exposed fault sur- faces help constrain the kinematics of coeval structures offshore, and make it possible to interpret the latter as transtensional, rather than purely extensional structures, as proposed by many authors. The results of our study ultimately shows the effectiveness of an integrated, multidisciplinal approach in the study of active deforma- tion margins

A new Interpretation of Terraces in the Taranto Gulf: the Role of Extensional Faulting

The Taranto Gulf of southern Italy provides an excellent case where it is possible to document the importance of normal faults in displacing terraced deposits. The study area is located at the front of the southern Apennines, that is a fold-and-thrust belt developed following the closure of the Mesozoic Tethys Ocean, and the deformation of the Adriatic passive margin during Tertiary and Quaternary times. The outer, eastern parts of the belt were structured in Quaternary, i.e. up to Middle Pleistocene times. The front of the chain is partially sealed by Pliocene–Pleistocene foredeep deposits, which represent the infill of the Bradanic Trough. The upper portion of the middle Pleistocene succession consists of marine sands and conglomerates that in the previous literature have been arranged in several orders of terraces. Analysis of aerial photographs and geomorphological mapping has shown the occurrence of prominent geomorphic lineaments, which appear to control the local drainage pattern. Some of these structures coincide with the map trace of normal faults that produce vertical offsets of the marine terrace surfaces in the order of ca. 10 m each. Many of the fault escarpments reduce their elevation and terminate laterally. In other cases fault escarpments are laterally continuous and can be traced for up to 3–4 km. Scarp height is between 2 and 10 m. Their mean trend ranges from NNE– SSW to ENE–WSWand defines an arcuate pattern that mimics the present coastline. An accurate geomorphological, sedimentological and stratigraphic analysis has been carried out in a selected area of the Bradanic Trough (Pisticci transect) to investigate in detail the relationships between normal faults and the development of the terraces. This analysis allowed us to recognise five facies associations related to the upper and lower beachface and to the neritic clays which represent the substratum of the terraces. More importantly, we observed that all the terraced deposits in the Pisticci transect could be referred to a single sedimentary body displaced by faults. The terraced deposits are related to an event of beach progradation, of Middle Pleistocene age, which has been documented in other areas of the Italian peninsula. These results outline an intimate relationship between the arcuate trend of the recognised fault set and the present coastline pattern. The development of the normal faults can be related to large-scale gravitational processes developed after the general tilting towards the SE of the Bradanic Trough

Structural inheritance in mountain belts: an Alpine-Apennine perspective

The geological structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization and amplification of contractional structures during mountain building. In the Alpine-Apennine sector together with other sectors of the Tethyan orogenic system the pre-orogenic crustal template can include arrays of extensional faults. Other faults can form adjacent to the evolving mountain belt and subsequently become incorporated as the thrust belts migrate into their forelands. While in some areas these inherited features may simply reactivate under inversion, more commonly faults show complex, partial reactivation structures. In volumes of distributed strain, faults may serve to nucleate large-scale buckle folds, for example, along basement-cover interfaces. These different patterns of basement reactivation may reflect spatially varying strength-depth profiles in continental lithosphere that are themselves inherited from spatially-distinct geological histories. Even when not themselves reactivating, basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally extensive detachment horizons. The 3D form of thrust systems can be strongly compartmentalized by pre-existing cross-faults, such as the oblique lineaments of the Apennines. On a large-scale, the distribution of pre-existing faults and other weaknesses may affect the propensity for orogenic contraction in basement and therefore directly control larger-scale tectonic processes. In the central Mediterranean the evolution of slab roll-back and the related growth of overlying extensional basins (e.g. Tyrrhenian Sea) may be strongly modulated by the distribution of rift-related weak zones in the adjacent continental crust. The subduction of continental crust will strongly depend on the inherited structure of this crust, specifically the distribution of deep crust of basic composition. This develops relatively higher densities associated with eclogite metamorphism which act in turn to reduce the buoyancy of thickened continental crust that otherwise serves to inhibit further shortening. Investigating all these aspects, from the scale of bulk crustal compositions to the geometry, timing and strength of earlier fault zones preserved in orogenic belts requires the integration of substantial multidisciplinary geological data sets. The extent to which continental orogenic belts represent the amplification of inherited geological heterogeneities as opposed to self-ordered phenomena modulated by the syntectonic environment remains unclear. © 2006 Elsevier Ltd. All rights reserved