Apulian Platform Research Articles

Aptian dinosaur footprints from the Apulian platform (Bisceglie, Southern Italy) in the framework of periadriatic ichnosites

New dinosaur tracks have been found near Bisceglie (Bari, Apulia), on loose blocks ascribed to the Corato Member (late Bedoulian to early Gargasian) of the Calcare di Bari Fm. The material consists of isolated footprints as well as of short trackways of quadrupedal and bipedal dinosaurs. The new tracksite has yielded a quite differentiated dinosaur ichnocoenosis, including theropod, sauropod, thyreophoran and ornithopod footprints. The discovery of early Aptian dinosaur footprints in the limestone of the carbonate platform of southern Italy gives new insights on dinosaur distribution, and new palaeontological constraints for the palaeogeographic reconstruction of the Mediterranean Tethys during the Cretaceous. The analysis of this and others ichnosites of the periadriatic carbonate platforms, gives evidence of repeated emersions and of widespread land-vertebrates dwelling. The characteristics of the associations suggest that the trackmakers did not constitute a real coevolved association but the occasional co-occurrence of taxa after migration. The results emphasize the need of both structural and environmental continuity and walking ways between a southern continent and the periadriatic carbonate platforms during the Early Cretaceous.

SKS splitting in Southern Italy: Anisotropy variations in a fragmented subduction zone

In this paper we present a collection of good quality shear wave splitting measurements in Southern Italy. In addition to a large amount of previous splitting measurements, we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the CAT/SCAN temporary network. These new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the Apulian Platform. For our analysis we have selected well-recorded SKS phases and we have used the method of Silver and Chan to obtain the splitting parameters: the azimuth of the fast polarized shear wave ( φ) and delay time ( δt). Shear wave splitting results reveal the presence of a strong seismic anisotropy in the subduction system below the region. Three different geological and geodynamic regions are characterized by different anisotropic parameters. The Calabrian Arc domain has fast directions oriented NNE–SSW and the Southern Apennines domain has fast directions oriented NNW–SSE. This rotation of fast axes, following the arcuate shape of the slab, is marked by a lack of resolved measurements which occurs at the transition zone between those two domains. The third domain is identified in the Apulian Platform: here fast directions are oriented almost N–S in the northern part and NNE–SSW to ENE–WSW in the southern one. The large number of splitting parameters evaluated for events coming from different back-azimuth allows us to hypothesize the presence of a depth-dependent anisotropic structure which should be more complicated than a simple 2 layer model below the Southern Apennines and the Calabrian Arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer, at least at the edge of Southern Apennines and Apulian Platform. We interpret the variability in fast directions as related to the fragmented subduction system in the mantle of this region. The trench-parallel φ observed in Calabrian Arc and in Southern Apennines has its main source in the asthenospheric flow below the slab likely due to the pressure induced by the retrograde motion of the slab itself. The pattern of φ in the Apulian Platform does not appear to be the direct result of the rollback motion of the slab, whose influence is limited to about 100 km from the slab. The anisotropy in the Apulian Platform may be related to an asthenospheric flow deflected by the complicated structure of the Adriatic microplate or may also be explained as frozen-in lithospheric anisotropy.

Tectonic block rotation, arc curvature, and back-arc rifting: Insights into these processes in the Mediterranean and the western Pacific

The fastest modern-day tectonic block rotations on Earth (up to 9 degrees/Myr) occur in the forearcs of convergent plate margins where a transition from collision of a bathymetric high to subduction of normal oceanic crust occurs. GPS techniques have enabled accurate documentation of the kinematics of these rotations, leading us to develop a conceptual model where the change from collision to subduction exerts a torque on microplates within the plate boundary zone, causing them to spin rapidly about an axis at the collision point. We have investigated geophysical and geological data from several active plate boundaries (from the western Pacific and Mediterranean regions) to document a compelling spatial and temporal relationship between the transition from collision to subduction, plate boundary curvature, and rapid tectonic block rotations. In some cases, these microplate rotations can initiate back-arc rifting. We also present numerical modelling results supporting our conceptual model for block rotations at collision/subduction transition. Our results suggest that the rate of microplate rotation depends on the incoming indentor velocity, and can be greatly enhanced by: (1) extensional stresses acting at the subduction interface (possibly due to slab roll back), and (2) a low-viscosity back-arc. Where viscosity of the back-arc is low, forearc microplate rotation dominates. In contrast, tectonic escape of strike-slip fault-bounded microplates is predicted in areas where the back-arc viscosity is high. Previous workers have suggested that the kinematics of the Anatolian block and back-arc rifting in the Aegean are influenced by some combination of forces associated with Arabia/Eurasia collision, and/or subduction (including slab rollback) at the Hellenic trench. Based on previous work from active western Pacific arcs, we propose that the collision of two separate indentors (Arabian promontory in the east, Apulian platform in the west), is a fundamental tectonic mechanism for large-scale anticlockwise tectonic rotation of Anatolia and the opposing clockwise rotation of western Greece documented from paleomagnetic studies. The recognition of several global analogues for Mediterranean active tectonics may lead to new insights into the dominant forces behind tectonic processes there.

Tectonic burial and “young” (<10 Ma) exhumation in the southern Apennines fold-and-thrust belt (Italy)

In the southern Apennines fold-and-thrust belt, thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km. The thrust belt is made of allochthonous sedimentary units that overlie a 6–8-km-thick, carbonate footwall succession. The latter, continuous with the foreland Apulian Platform, is deformed by reverse faults involving the underlying basement. Therefore, a switch from thin-skinned to thick-skinned thrusting occurred as the Apulian Platform carbonates—and the underlying thick continental lithosphere—were deformed during the latest shortening stages. Apatite fission track data, showing cooling ages ranging between 9.2 ± 1.0 and 1.5 ± 0.8 Ma, indicate that exhumation marks these late tectonic stages, probably initiating with the buttressing of the allochthonous wedge against the western margin of the Apulian Platform. Pliocene-Pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that, based on cross-section balancing and restoration, could be transferred to the base of the allochthon from the underlying thick-skinned structures. This suggests that emplacement of the allochthon above the western portion of the Apulian Platform carbonates was followed by gravitational readjustments within the allochthonous wedge, coeval—and partly associated with—thick-skinned shortening at depth. The related denudation processes are interpreted to have played a primary role in tectonic exhumation.

Chronostratigraphy of Campanian–Maastrichtian platform carbonates and rudist associations of Salento (Apulia, Italy)

Late Cretaceous platform carbonates from the Salento peninsula (south Italy) were studied by strontium-isotope stratigraphy to improve their chronostratigraphy. Forty-three samples from nine localities were collected and the numerical ages were derived from fifteen geochemically well-preserved samples of rudist shells that were analyzed for 87Sr/ 86Sr values. Strontium isotope stratigraphy yielded new ages for the base of the Ciolo Limestone. The oldest successions studied in Salento are 85.9 Ma (+/− 0.6) and assigned to the Melissano Limestone. The youngest Cretaceous limestones observed at the Ciolo Limestone type locality (Ciolo cove) are 66.4 Ma (+/− 1.5), and the base of this formation is older than 72.8 Ma (+/− 0.4). Karstic cavities observed at the Cava Cocumola in the mid-Campanian S. Cesarea Limestone are tentatively interpreted to be linked to an intra-Campanian event which is related to a sea-level lowstand inferred also on the island of Brač (Adriatic coast of Croatia) and in the Boreal realm at 75–77 Ma. A new large recumbent rudist similar to Sabinia and Pseudosabinia is observed in the Ciolo and S. Cesarea Limestone and appears to be characteristic of the Apulian platform carbonates. Rudist associations from the S. Cesarea Limestone and the overlying Ciolo Limestone are remarkably similar, although they range over a time interval of more than 12 Ma.

Seismic anisotropy reveals focused mantle flow around the Calabrian slab (Southern Italy)

SKS splitting at the Calabrian subduction zone, with delay times (δt) up to 3s, reveals the presence of a strong anisotropic fabric. Fast directions (ϕ) are oriented NNE‐SSW in the Calabrian Arc (C.A.) and rotate NNW‐SSE to the north following the arcuate shape of the subducting plate. We interpret the trench‐parallel ϕ as local‐scale mantle flow driven by the retrograde motion of the slab; the absence of trench perpendicular ϕ below the Southern Apennines (S.A.) excludes the presence of a seismically detectable return flow at its NE edge. This may be due to the relative youth and limited width of the S.A. slab tear. A possible return flow is identified farther north at the boundary of the S.A. and Central Apennines. Different and weaker anisotropy is present below the Apulian Platform (A.P.). This implies that the influence of the slab rollback in the sub‐slab mantle is limited to less then 100 km from the slab.

Seismically-induced slumps in Lower-Maastrichtian peritidal carbonates of the Apulian Platform (southern Italy)

In the southeastern Murge (Apulian Foreland, southern Italy), a Lower-Maastrichtian carbonate section showing soft-sediment deformation structures is composed of peritidal lithofacies associations developed in a wide low-energy inner-platform system. Shear-induced soft-sediment deformation structures correspond to multilayer deformed horizons, 1.5 to 2 m in thickness, sandwiched between undeformed layers. Overturned and recumbent folds lying on décollement surfaces and asymmetrical fault-inception folds allow us to interpret the observed deformed horizons as slump sheets. The detailed description of the main morphological features of the deformed beds and the recognition of unconformable surfaces and undeformed beds between slumped beds allow us to distinguish three different events of deformation. Preferential orientation of slump folds has been measured and every slumped bed shows a different direction of shortening. Randomly oriented direction of shortening suggests that each deformation event was driven by the presence of local very gentle gradients developed in peritidal settings. By excluding other potential trigger mechanisms of deformation, the observed slumps are interpreted as seismically-induced slides. Even if no data about the distance of the seismic source may be obtained, near-field earthquake tectonics affected the Apulian Platform during Late Cretaceous times.

The regional record of Albian oceanic anoxic events at the Apulian Platform Margin (Gargano Promontory, southern Italy)

The Gargano Promontory, located on the eastern margin of the Apulia Platform, represents a distinctive Tethyan area where the transition from carbonate platform to adjacent basin is exposed on land. The Albian stratigraphic record, represented by shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to oceanic anoxic events (OAEs) in different depositional settings by using an integrated, high-resolution micropalaeontological (planktonic foraminifers and calcareous nannofossils) approach. Results show that organic matter preservation is confined to the more distal areas (Marne a Fucoidi Formation), and consists of black shale intervals from the middle and late Albian ( Ticinella primula/Prediscosphaera columnata Zones; upper Ticinella praeticinensis Subzone/ R. achlyostaurion Zone, respectively). Integrated biostratigraphic data correlate the intervals of black shale deposition to the Urbino and Amadeus levels, previously identified and named in the Umbria-Marche Basin. These black shales record the effects of OAEs 1b and 1c. The biotic changes in the pelagic Albian succession of the Apulian Platform Margin provide evidence for episodes of eutrophication that correlate to the deposition of these black shales. Genetic models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.

Deformation of western Greece during Neogene clockwise rotation and collision with Apulia

Following an Early Miocene phase of N–S extension affecting the entire Hellenides, 50° clockwise rotation affected western Greece. Modern GPS analyses show rapid southwestward motion in southwestern Greece over subducting oceanic lithosphere and no motion in the northwest, where Greece collided with Apulia. We aim to identify the deformation history of western Greece associated with the rotation and the collision with Apulia. The timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures. The results show that accompanying the onset of rotation, compression was re-established in western Greece in the early Langhian, around 15 Ma. Subsequently, western Greece collided with the Apulian platform, leading in the Late Miocene to a right-lateral strike-slip system running from the Aliakmon Fault Zone in northern Greece via the Kastaniotikos Fault and the Thesprotiko Shear Zone to the Kefallonia Fault Zone, offshore western Greece. NE–SW compression and uplift of the Ionian Islands was accompanied by NE–SW extension in southwestern Greece, associated with faster southwestward motion in the south than in the north. This led in the middle Pliocene (around 3.5 Ma) to collision without further shortening in northwestern Greece. From then onward, NW–SE to N–S extension east of Apulia, and gradually increasing influence of E–W extension in the south accommodated motion of the Hellenides around the Apulian platform. As a result, curved extensional basin systems evolved, including the Gulf of Amvrakikos-Sperchios Basin–Gulf of Evia system and the Gulf of Corinth–Saronic Gulf system.

Phylogenetic survey of metabolically active microbial communities associated with the deep-sea coral Lophelia pertusa from the Apulian plateau, Central Mediterranean Sea

Living deep-water coral assemblages were discovered recently inhabiting the Mediterranean Sea between the depths of 300 and 1000 m off the Cape of Santa Maria di Leuca (Apulian platform, Ionian Sea). This living assemblage was dominated by two colonial scleractinian corals, Lophelia pertusa and Madrepora oculata. Two other corals, Desmophyllum crystagalli and Stenocyathus vermiformis were also recovered from this site, but were much less common. The composition of the metabolically active fraction of the microbial community associated with living specimens of L. pertusa was determined. Dead corals, proximal sediments and overlying seawater were also sampled and analyzed. Complementary 16S ribosomal DNA (crDNA) was obtained from total RNA extracted from all samples that had been subjected to reverse transcription-PCR amplification. Domain-specific 16S PCR primers were used to construct four different 16S crDNA libraries containing 45 Archaea and 201 Bacteria clones. Using Archaea-specific primers, no amplification products were obtained from any coral samples (live and dead). Living specimens of L. pertusa seem to possess a specific microbial community different from that of dead coral and sediment samples. The majority of all coral-associated riboclones was related to the Holophaga-Acidobacterium and Nitrospira divisions (80%). Moreover, more than 12% of all coral-associated riboclones formed a separate deep-branching cluster within the α- Proteobacteria with no known close relatives. The metabolically active fraction of the bacterial community colonizing the dead corals was dominated by Proteobacteria related to the gamma and epsilon subdivisions (74% and 26% of all clones, respectively). Phylogenetic analysis of the Archaea clone library retrieved from proximal sediments indicated an exclusive dominance by the members of Crenarchaea Marine Group I (MGI), a lineage of unculturable microorganisms, widely distributed in marine habitats. In contrast, bacterial diversity was considerably higher in this sample than archaeal diversity, with four abundant eubacterial phylotypes: Proteobacteria, Verrucomicrobia, Actinobacteria and Planctomycetes (95% of all clones analyzed). This is one of the first phylogenetic evaluation of the presumed metabolically active microbial community structure associated with the deep-sea scleratinian coral L. pertusa.

Thrust sequences and evolution of the external sector of a fold and thrust belt: An example from the Southern Apennines (Italy)

Abstract The Southern Apenninic chain was built up from the late Oligocene–early Miocene to the middle Pleistocene. It consists of an upper wedge composed of strongly deformed deep marine and carbonate platform successions and a buried thrust and fold belt in the carbonate rocks of the Apulian Platform. This paper analyzes the frontal part of the Southern Apennines, where contractional structures display complex geometries related to progressive incorporation of accreted material, internal shortening and gravitational processes. Late normal faults, which hinder the interpretation of contractional structures in other sectors of the chain, are scarcely represented in the frontal part of the Southern Apennines. This allows a detailed analysis of thrust and fold geometry. In particular it is possible to recognize the relationships between gravity-driven nappes, foreland-vergent thrusts and backthrusts. New field observations allow us to depict a detailed structural framework of this area and to construct regional cross-sections, which illustrate the inferred evolution of the frontal sector of the Apenninic chain. The chronological constraints are given by the age of thrust-top basins and foredeep deposits of middle–late Miocene to Pleistocene age. Deepening of the decollement level during thrusting creates complicate overprinting relationships connected to the deformation of the older thrust surfaces. The inferred evolution can be summarized in two stages. During the first stage shortening of the wedge was associated to emplacement of thin thrust sheets, interpreted as gravity-driven nappes, before sedimentation of middle–late Miocene thrust top basins. The second stage, of middle Pliocene–middle Pleistocene age, was characterized by folding and breaching of the pre-existing structures, related to deep thrusting in the Apulian Platform. The examples shown suggest the presence of transfer zones and lateral ramps to explain lateral variations in thrust geometry and shortening amount. The along strike geometry of non-cylindrical structures provides a valuable tool to decipher the tectonic evolution of the thrust belt. The proposed scheme is well suited to interpret the structural setting of thin-skinned thrust and fold belts characterised by change in the geometry of the thrust systems through time.

DEEP SEISMIC REFLECTION DATA FROM OFFSHORE WESTERN GREECE: A NEW CRUSTAL MODEL FOR THE IONIAN SEA

Contractional structures recognised in a recent SW‐NE oriented seismic profile offshore western Greece, between the islands of Zakynthos and Kefallinia (Cephalonia), indicate that this part of the Pre‐Apulian geotectonic zone was involved in Quaternary shortening related to the westward propagation of the Hellenic fold‐and‐thrust system. Deep reflector horizons including the Moho and the top of the crystalline basement were identified on the profile. Shallower reflectors include those corresponding to the contacts between the Mesozoic/Miocene, Upper Miocene/Lower Pliocene, and Pliocene/Pleistocene sedimentary sequences. The Upper Cenozoic to Quaternary sequence rests unconformably upon Mesozoic carbonates. Triassic evaporites wedge‐out in the Paxos geotectonic zone, where the Palaeozoic passes up into Mesozoic deposits.We have identified contractional structures which were reactivated during the Plio‐Quaternary on pre‐existing high‐angle normal faults, and which gave rise to significant topographic anomalies. West‐dipping normal faults were also recognised both within the Palaeozoic and Cenozoic successions, and are related to regional extension during sedimentation. East‐dipping thrust faults which root in the evaporites were also identified on the seismic profile.Due to right‐lateral strike‐slip activity on the Kefallinia Transform Fault, east‐dipping normal faults were formed within the lonion abyssal plain. This abyssal plain together with the Hellenic Trench, an accretionary prism, and a forearc basin can be recognised on the seismic profile. A “triple junction” between the Apulian (African) Platform, the oceanic crust of the Ionian Abyssal Plain and the Eurasian Plate in the west of the line is related to the Kefallinia Transform Fault. Neotectonic structural deformation (i.e. Quaternary‐Holocene) is superimposed on the above‐mentioned structures. Finally, diapiric movement of Triassic evaporites has affected both the Alpine and the late Cenozoic to Holocene sedimentary sequences. Diapiric activity continues at the present day in the eastern part of the profile, in the lonian geotectonic zone. The forearc basin may be prospective for hydrocarbons. Target areas include the lonian channel where a play has already been located, and its extension to the south (the Kyparisiakos Gulf area). Here, thick late Cenozoic to Quaternary deposits may act as a top‐seal above a reservoir consisting of eroded Mesozoic to Eocene carbonates, as at the recent Katakolon discovery.

Rift-Drift, Seafloor Spreading, and Subduction Tectonics of Albanian Ophiolites

Albanian ophiolites in the Dinaride-Albanide-Hellenide mountain system in the Balkan Peninsula represent oceanic remnants of the Mesozoic Pindos-Mirdita basin and structurally overlie the peripheral tectonic units, composed mainly of volcanosedimentary rift assemblages and conjugate passive margin sequences. These tectonic units and the ophiolites collectively record the rift-drift, seafloor spreading, and subduction evolution of the Pindos-Mirdita basin, which developed as a Tethyan seaway between the Apulian and Korabi-Pelagonian microcontinents. The peripheral tectonic units on the west include, from west to east, the Apulian platform (Sazani, Ionian, and Kruja zones), Apulian passive margin sequences (Krasta-Cukali Zone), volcanosedimentary unit (Triassic-Upper Jurassic), subophiolitic mélange, and metamorphic assemblages; the Korabi-Pelagonian platform and its passive margin sequences bound the ophiolites on the east. Metamorphic assemblages include amphibolite, micaschist, and marble that generally display inverted field gradients, analogous to metamorphic soles beneath other ophiolites in the eastern Mediterranean region. Some metamorphic assemblages with cooling ages >169 Ma in southern Albania may represent, instead, dynamothermally metamorphosed volcanosedimentary rocks developed during advanced stages of continental rifting, prior to the onset of seafloor spreading. The subophiolitic mélange contains blocks and clasts of material derived from ophiolites, metamorphic units, platform carbonates, and passive margin sequences, and represents a subduction-accretion complex formed during initial displacement and tectonic emplacement of the ophiolites. The supra-opholitic mélange and the overlying flysch deposits (Tithonian-Valanginian) and neritic limestones (Barramian-Upper Cretaceous) unconformably rest on the ophiolites and the platform carbonates, and constrain the timing of ophiolite emplacement onto the Korabi-Pelagonian continental margin as the latest Jurassic-Early Cretaceous. The Pindos-Mirdita basin initially developed as a broad transtentional, intra-continental rift system with highly oblique, ultraslow rifting and spreading. Ophiolites in the Mirdita region show a transition from MORB to IAT and boninitic affinities from west to east and structurally upwards, indicating magma genesis from highly depleted, refractory mantle sources increasingly affected by subduction-derived fluids. These spatial, temporal, and chemostratigraphic relations point to a suprasubduction zone origin of the eastern ophiolites above a west-dipping, intra-oceanic subduction zone, whose rollback resulted in lithospheric extension and the formation of a boninitic "proto-arc" in the upper plate. This subduction-accretion system was terminated by collision of the Korabi-Pelagonian margin with the trench that facilitated eastward emplacement of the ophiolites. Subsequent oblique collision of Apulia with Eurasia during the Maastrichtian-Paleogene transported the Albanian ophiolites westward onto the Apulian margin. The bidivergent emplacement tectonics of the Albanian ophiolites is hence a result of two separate collisional events at different times.

Thermal maturity of the axial zone of the southern Apennines fold‐and‐thrust belt (Italy) from multiple organic and inorganic indicators

AbstractThe reconstruction of the thermal history of folded and thrust units is crucial to define the pattern of tectonic loading and the time‐space evolution of an orogen where tectonic exhumation processes occurred at shallow crustal levels. In the present study, a well‐constrained reconstruction of the thermal maturity in the axial zone of the southern Apennines has been achieved by the combined use of different thermal indicators in diagenesis. The major results are: (i) documentation of a jump in thermal maturity from the Apenninic Platform derived tectonic unit (from immature to early mature stages of hydrocarbon maturation) to the Lagonegro Basin derived tectonic units (late diagenetic zone); (ii) documentation of along‐strike slighter variations in the Lagonegro units, concerning thermal maturity (thus maximum burial temperatures). This can be related to changes in amounts of tectonic burial and erosion/exhumation because of the lack of cylindricity of contractional structures; (iii) recognition of an independent thermal evolution of the allochthonous chain compared with the Apulian Platform tectonic unit with Mt Alpi area (in the late mature stage of hydrocarbon generation) interpreted as a sector of localized, intense exhumation within the External Zone of the orogen.

Thin-skinned versus thick-skinned structural models for Apulian carbonate reservoirs: constraints from the Val d'Agri Fields, S Apennines, Italy

The Apulian Platform Carbonates form the reservoir unit in several major oil fields in the Val d'Agri area of southern Italy. Traps are formed by compressional fold structures developed in the hanging wall of major reverse faults. Published models for these structures emphasize a ‘thin-skinned’ tectonic style with a basal detachment located in Triassic evaporites. However, the generally poor quality of seismic data in the southern Apennines means that subsurface geometries are poorly constrained and seismic-structural interpretation becomes model-driven. The density of data associated with field development in the Val d'Agri area provides an opportunity to constrain structural models at a variety of scales. Good quality seismic data image the front of the Monte Alpi field and show involvement of the Base Apulian seismic reflection in compressional structures. Locally, well-defined fault plane reflectors image the moderate-steeply dipping, convex-up reverse faults that bound the structures. Integration of well, vertical seismic profiles and seismic data confirm the dominance within the reservoir of moderate-high angle reverse and normal faulting. Taken together these elements suggest that a thick-skinned structural model is most appropriate for the Val d'Agri Apulian structures, whilst the geometry of the main bounding faults suggests that they are inverted Permo-Triassic extensional faults.

Tectonic burial and exhumation in a foreland fold and thrust belt: the Monte Alpi case history (Southern Apennines, Italy)

The Monte Alpi area of the Southern Apennines represents the only sector of the thrust belt where the reservoir rocks (i.e. Apulian Platform carbonates) for major hydrocarbon accumulations in southern Italy are interpreted to crop out. Tectonic evolution and exhumation of this area were analysed by integrating stratigraphic and structural data with different organic and inorganic parameters The record the burial and thermal evolution of the sediments (vitrinite reflectance, fluid inclusions, and I/S mixed layers in clayey sediments). Our analyses suggest that the presently exposed Monte Alpi structure suffered a loading of ca. 4000 m, owing to the emplacement of allochthonous units in Early Pliocene times. Available geological data indicate that erosion of the tectonic load occurred since the Late Pliocene, when the area first emerged. This implies an average exhumation rate in excess of 1 mm/year. A model can be constructed which matches the maturity indices and also takes into account intermediate stages of the evolution, resulting from combined structural and fluid inclusion data. By this model, a first stage of exhumation would have taken place at an average rate of about 0.36 mm/year. This was controlled by uplift and erosion associated with both: (i) thrusting at depth within the Apulian carbonates (Late Pliocene), and (ii) strike-slip faulting (Early Pleistocene). A second exhumation stage would have occurred in the last 700 ky at a much faster rate (ca. 4 mm/year) as a result of extensional tectonics. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

Tectonic burial and exhumation in a foreland fold and thrust belt: the Monte Alpi case history (Southern Apennines, Italy)

The Monte Alpi area of the Southern Apennines represents the only sector of the thrust belt where the reservoir rocks (i.e. Apulian Platform carbonates) for major hydrocarbon accumulations in southern Italy are interpreted to crop out. Tectonic evolution and exhumation of this area were analysed by integrating stratigraphic and structural data with different organic and inorganic parameters which record the burial and thermal evolution of the sediments (vitrinite reflectance, fluid inclusions, and I/S mixed layers in clayey sediments). Our analyses suggest that the presently exposed Monte Alpi structure suffered a loading of ca. 4000 m, owing to the emplacement of allochthonous units in Early Pliocene times. Available geological data indicate that erosion of the tectonic load occurred since the Late Pliocene, when the area first emerged. This implies an average exhumation rate in excess of 1 mm/year. A model can be constructed which matches the maturity indices and also takes into account intermediate stages of the evolution, resulting from combined structural and fluid inclusion data. By this model, a first stage of exhumation would have taken place at an average rate of about 0.36 mm/year. This was controlled by uplift and erosion associated with both: (i) thrusting at depth within the Apulian carbonates (Late Pliocene), and (ii) strike-slip faulting (Early Pleistocene). A second exhumation stage would have occurred in the last 700 ky at a much faster rate (ca. 4 mm/year) as a result of extensional tectonics.

Geodetic control on recent tectonic movements in the central Mediterranean area

During the Neogene and Quaternary, the western Mediterranean geodynamics was apparently dominated by the nearly eastward migration of the Apenninic arc and the associated opening (spreading) of the back-arc basin (Tyrrhenian Sea). However, during the last 5 My, the collision of the arc with the Apulian platform led to a dramatic change in the tectonic setting of the area. As geological processes require a long period of time to register the displacements of the different blocks, it is indispensable to take into account the present-day motion given by space geodesy data analysis in order to better constrain the geological models. Geodetic motions were derived from Global Positioning System (GPS), Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) observations collected from different networks. All the geodetic solutions have been computed and combined at the Centre of Space Geodesy (CGS), at Matera, Italy. The geodetic results show a NNE motion of the Adriatic plate with a small component of counter-clockwise rotation, in good agreement with the geological and geophysical observations. In the southern Tyrrhenian area, the lengthening of the Matera–Cagliari baseline should imply that convergence cannot be considered as the driving mechanism for the Apenninic subduction process. The estimated motion of Noto is in quite good agreement with the estimated motion of the African plate.

Petrogenesis and evolution of Mt. Vulture alkaline volcanism (Southern Italy)

The Late Pleistocene Mt. Vulture strato-volcano developed at the intersection of NE-SW and NW-SE lithospheric fault systems, on the easternmost border of the Apennine compressional front overthrust onto the Apulian foreland. The initial phase of the volcanic activity is represented by pyroclastic deposits, including lava blocks, and subordinate eccentric domes, mostly phonolitic in composition. The later stages of activity formed the bulk of the strato-volcano (pyroclastic products and subordinate lavas), mostly tephritic in composition, with minor intercalations of basanite, mela-foidite and melilitite lavas and dikes. Variations in rock and mineral composition suggest that the volumetrically predominant basanite-tephrite (foidite)-phonotephrite-phonolite series can be accounted for by fractional crystallization processes starting from basanitic parental magmas, in agreement with the remarkably constant 87Sr/86Sr isotopes (0.70586–0.70581). Mass-balance calculations indicate that the variably differentiated magmas may have been produced by removal of wehrlite, clinopyroxenite and syenite cumulates, some of which are occasionally found as cognate xenoliths in the volcanics. Fractionation processes probably developed in multiple-zoned magma chambers, at depths of 3–5 km, corresponding to the tectonic discontinuity between the allochthonous Apennine formations and the underlying Apulian platform. Highly differentiated phonolitic magmas capping the magma chambers and their conduits thus appear to have fed the initial volcanic activity, whereas dominantly tephritic products were erupted in later stages. The least evolved mafic magmas, namely basanites, mela-foidites and melilitites, are characterized by diverse Na/K ratios and critical SiO2-undersaturation, which indicate their derivation as independent melts generated from distinct, heterogeneously enriched mantle sources and by variable partial melting degrees. Primitive mantle-normalized incompatible element patterns of Vulture mafic lavas invariably share analogies with both orogenic subduction-related magmas (high Low Field Strength Elements/High Field Strength Elements ratios, K, Rb and Th contents and marked Ti and Nb negative anomalies) and alkaline lavas from within-plate and rift settings (high Light Rare Earth Elements, P, Zr, Nb and Na). These geochemical features may be accounted for by magma generation from deep lithospheric mantle sources, enriched in Na-alkali silicate/carbonatite anorogenic components, subsequently affected by orogenic subduction-related K-metasomatism, analogous to that which modified magma sources of the Roman Magmatic Province along the internal Apennine Chain.

Upper Triassic platform margin biofacies and the paleogeography of Southern Apennines

The Upper Triassic dolomitic successions of the Monti della Maddalena area (Southern Apennines) consist of white, heavily recrystallized and cataclastic dolomites generally unsuitable for detailed facies analysis. Nevertheless, evidences of bioconstructions can be found in several localities. These evidences are represented by rudstones and possibly boundstones whose main components are fragments of sponges (sphinctozoans, inozoans, chaetetids) and corals generally encrusted by foraminifera, red algae and ‘problematica’. This association is much more diversified with respect to that of the microbial-serpulid buildups which characterize the platform margin facies of most Upper Triassic successions of the Southern Apennines. The Monti della Maddalena biofacies can be more readily compared with the bioconstructed facies of Sicily and in general with the Dachstein-type reef of the Tethyan realm. The studied successions are interpreted (according to the model of Cirilli et al., 1999) as formed at the margin of a carbonate platform facing a deep basin having good connection with the open sea, while the microbial-serpulid buildups formed on the margin of intraplatform restricted troughs with poorly oxygenated bottom waters. Our study discusses the relative paleogeographic position of the Apennine platforms and the Lagonegro Basin. The overall picture of the bioconstructed Triassic facies distribution in Southern Apennines, together with biofacies data from resedimented facies of Lucania, are compatible with paleogeographic reconstructions interpreting the Monti della Maddalena successions as representing the more external sector of the Apennine platforms system flanking the Lagonegro Basin. The latter, bordered on its external side by Apulia, was part of a deep Mesozoic domain comprising the Imerese–Sicani basin of Sicily and connected westward with the East Mediterranean branch of Western Tethys. Our data exclude the possibility that the Lagonegro Basin was located in an internal position with respect to all the Apenninic and Apulian platforms system.