Apulia Foreland Research Articles

Geological Uniqueness and Potential Geotouristic Appeal of Murge and Premurge, the First Territory in Puglia (Southern Italy) Aspiring to Become a UNESCO Global Geopark

At the end of November 2021, a large area of Puglia (an administrative region in Southern Italy) was officially nominated as new aUGGp (aspiring UNESCO Global Geopark) by the Italian National Commission of UNESCO. This area comprises the northwestern part of the Murge territory, where a Cretaceous sector of the Apulia Carbonate Platform crops out, and part of the adjacent Premurge territory, where the southwestward lateral continuation of the same platform (being flexed toward the Southern Apennines Chain) is covered by thin Plio-Quaternary foredeep deposits. The worldwide geological uniqueness of the aspiring Geopark (Murge aUGGp) is that the area is the only in situ remnant of the Adria Plate, the old continental plate almost entirely squeezed between the Africa and Eurasia Plates. In such a context, the Murge area (part of the Apulia Foreland) is a virtually undeformed sector of Adria, while other territories of the plate are and/or were involved in the subduction/collision processes. In the aspiring Geopark, the crust of Adria is still rooted to its mantle, and the Cretaceous evolution of the continent is widely recorded in the Murge area thanks to the shallow-water carbonate succession of one of the largest peri-Tethys carbonate platforms (the Apulia Carbonate Platform). The aspiring Geopark also comprises the Premurge area, which represents the outer Southern Apennines foredeep, whose Plio-Quaternary evolution is spectacularly exposed thanks to an “anomalous” regional middle-late Quaternary uplift. Despite the presence of numerous geological singularities of international importance, it would be important, from a geotourist point of view, to propose a regional framework of the geology of the aUGGp before introducing visitors to the significance of the individual geosites, whose importance could be amplified if included in the geoevolutionary context of the Murge aUGGp.

Petrographic and Geochemical Inferences for Genesis of Terra Rossa: A Case Study from the Apulian Karst (Southern Italy)

Terra rossa is a reddish clay soil which is often present on the surface of limestone in regions with a Mediterranean-type climate. Its genesis is a controversial subject in terms of the origin of the parent material, from the residuum of underlying (carbonate/dolomite) bedrock in the absence/presence of an external silicate contribution (e.g., aeolian dust). Within this context the main goal of the present work was the understanding of the geochemical processes leading to the formation of the terra rossa starting from the carbonate bedrock. We report the results of a multi-method analysis on a terra rossa deposit occupying the bottom of a Quaternary karst depression on Mesozoic limestones exposed in the Murge area (Apulia Foreland, southern Italy). Geological, petrographic, textural, and chemical data were collected on karst products (reddish calcite incrustations and nodules, and fine-grained portion of terra rossa) by a detailed field mapping, optical microscopy, XRF and fusion ICP/MS analyses and by scanning electron microscope. New collected data show that the mineralogical composition of reddish incrustations and nodules is comparable, consisting of fibrous and impure calcite, detrital fragments of quartz, K-feldspar, zircon and authigenic minerals as (Mn, Ba, Ca) phases, (Al, Si, Mn, Fe, Mg, Ba, Ca) minerals, Fe-kaolinite and anatase. The prevailing minerals, instead, in the fine-grained portion of terra rossa are hematite, kaolinite, and goethite. Based on the chemical composition, and especially on REE patterns, a progressive interaction of silicate aqueous solutions (with Al, Si, Fe), containing pelite material, with the calcareous bedrock, as a source of carbonic acid, was the process driving the formation of terra rossa. Obtained results add new elements to the definition of the long-lasting question about the genetic processes responsible for the formation of terra rossa, corroborating their polygenetic origin, as result of limestone alteration in conjunction with the chemical interaction with allochthonous siliciclastic material.

‘Isolated base‐of‐slope aprons’: An oxymoron for shallow‐marine fan‐shaped, temperate‐water, carbonate bodies along the south‐east Salento escarpment (Pleistocene, Apulia, southern Italy)

AbstractThis paper regards the lower Pleistocene temperate‐water carbonate deposits disconformably overlying an escarpment made up of faulted Cretaceous to Miocene limestones of the Apulia Foreland (southern Italy). Study deposits discontinuously crop out along the present‐day eastern Salento sea cliff, and form isolated fan‐shaped bodies, up to 1 km wide and up to 40 to 50 m thick, each of them covering an area of a few square kilometres. The internal arrangement of beds is represented by up to 25° to 30° lobate, seaward dipping clinobeds thinning and onlapping onto a rocky foreslope in the proximal sector and passing to gently inclined to sub‐horizontal strata in the distal sector. Seven facies were distinguished, mainly composed of coarse‐grained skeletal carbonates made up of a heterozoan association including coralline algae, large and small benthic foraminifera, echinoids, molluscs, bryozoans and serpulids. Since clinobeds were formed thanks to hyperconcentrated density flows (grain flows) bypassing the upper part of the inherited escarpment, these skeletal grains represent ex situ deposits whose shallow‐marine factory was located upward (landward) with respect to the bypassed zone, likely in the almost flat area on top of the Salento Peninsula. Clinobeds are often affected by tens of metres wide and long channel‐like structures interpreted as landslide scars. Inside these gullies, contorted beds (slumps) or matrix‐supported intra‐bioclastic floatstone/rudstone (massive deposits) are present. The occurrence of supercritical‐flow structures (for example, backset‐bedded beds) indicates the development of hydraulic jumps along the steep slope of gullies. Since these clinostratified, fan‐shaped carbonate bodies represent carbonate slopes, and that the latter are known as aprons, normally related to linear sourced sediments, an acceptable oxymoron for studied fan‐shaped carbonate bodies is suggested: ‘isolated base‐of‐slope aprons’.

Multidisciplinary approach for assessment of the factors affecting geohazard in karst valley: the case study of Gravina di Petruscio (Apulia, South Italy)

Management plans, actions and strategies for preventing and mitigating natural disasters require detailed information on natural and human-induced geohazards for the area under evaluation. Karst areas are particularly prone to instability due to the natural fragility of their environment but are also vulnerable due to human activity. In-depth studies of the factors controlling mass movement processes, including land use over time, become crucial for understanding instability mechanisms and future landscape evolution, as well as for designing preventive measures and control techniques. The Murge area, in the central part of Apulia (South Italy), is crossed by a vast network of dry valleys, locally named lame and gravine, whose morphology may resemble the most well-known canyons and gorges of the world. The genesis of these dry valleys is controversial and still the subject of continued debate, although their origin is directly related to the geostructural setting and the uplift of the Apulia foreland since the middle Pleistocene. Each of these karst valleys has particular morphometric characteristics as well as their own morpho-evolutionary history strongly linked to the different types of fault or fracture on which they developed. Also, geological and geotechnical characteristics of the rock substrate channel, and historic human-made slope excavation or remodeling play an important role. Unfortunately, several tragic events which occurred during the last decades have shown the susceptibility of the Apulian dry valleys to natural hazards, sometimes caused by human activities. This paper proposes, by means of a case study on a dry valley called Gravina di Petruscio in the Arco Ionico Tarantino subregion, a multidisciplinary approach using traditional methods of investigation and combining results to arrive at a critical appraisal of information that are suitable for a geohazard susceptibility analysis in karst environments. Geological, geostructural and geomechanical surveys, together with petrographic observations in thin sections of the outcropping materials, allow to understand the genesis of the valley and then its evolution mainly due to slope retreat processes. Both sides of the valley have been found to be affected by planar slides, wedge slides, direct toppling and falls, while the caves, mostly modified by humans, are affected by thinning, spalling and crushing of pillars, and partial or total collapse of cave roofs. The predisposing and triggering factors of the most common mass movements are presented and discussed. Mitigation and prevention measures for future planning, and remedial engineering structures are reported.

The contribution of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) to “Adria LithosPHere investigAtion (ALPHA)” active seismic experiment

During the winter 2012, from 20 January to 4 February, the German oceanographic FS METEOR cruise (M86/3) took place in the central-southern Adriatic Sea in the frame of “Adria LithosPHere InvestigAtion” (ALPHA [Kopp et al., 2013]). The primary goal of the project was high-resolution tomographic imaging of the crust and lithospheric mantle underneath the southern Adriatic Sea, the Apulia eastern margin and the external zone of the Dinaric thrust-belt by collecting offshore-onshore seismic data along three multi-fold wide-aperture profiles. The definition of reliable velocity models of the Adriatic lithosphere was considered crucial for a better understanding of the structure, fragmentation, geodynamic evolution, and seismotectonics of the Adria-Apulia microplates. The ALPHA Project was coordinated by Helmholtz Centre for Ocean Research Kiel, Germany (GEOMAR), former Leibniz Institute of Marine Sciences (German: Leibniz-Institut fur Meereswissenschaften, IFM-GEOMAR) and conducted in close cooperation with different European institutions of Germany, Albania, Croatia, Italy and Montenegro. The Istituto Nazionale di Geofisica Vulcanologia (INGV) participated by deploying land stations along two transects in the Apulia and Gargano Promontory to extend westwards the seismic profiles. The primary goal was to record shallow-to-deep seismic phases travelling along the transition between the Adriatic basin and the Apulia foreland. In this paper we present the field work related to the two Italian onshore transects, the recorded data, and the processing flow developed to highlight crustal and mantle refractions and wide-angle reflections.

Following Writings and Paintings by Carlo Levi to Promote Geology Within the “Matera-Basilicata 2019, European Capital of Culture” Events (Matera, Grassano, Aliano—Southern Italy)

The prestigious designation as “European Capital of Culture 2019” assigned to the town of Matera (southern Italy) may offer the perfect opportunity to divulge the culture of geology, especially to non-expert audiences. For this purpose, local institutions and tour operators could organise touristic field trips containing thematic tours (historical, literary, archaeological…) coupled with geological information. The present paper proposes a sample itinerary which touches upon three towns, all situated within the province of Matera, and connected to one another not only because they are the setting of Carlo Levi’s political exile in the 1930s, but also because each town lies within one of the three important orogenic elements characterising the geology of southern Italy. These elements are the Apulia Foreland, the Bradanic Trough and the southern Apennines Chain. The proposed itinerary sets off from the town of Matera, located within the Apulia Foreland, continues through the small town of Grassano, located within the Bradanic Trough, and ends in the small town of Aliano, located within the southern Apennines Chain. During his exile, Carlo Levi narrated and described these three places through his paintings and renown book Christ Stopped at Eboli. In his works, Levi captured both the human aspects, as well as the historical and geological ones. The authors of the present paper believe that a selection of Levi’s artworks can be utilised to guide tourists along the journey, illustrating the geology of the area through the eyes (i.e. the paintings) and, above all, the words (i.e. the book) of Carlo Levi. Today, the increased knowledge of Carlo Levi’s works has been made possible also thanks to the constitution of a Literary Park dedicated to the writer/artist.

Insights on the seismotectonics of the western part of northern Calabria (southern Italy) by integrated geological and geophysical data: Coexistence of shallow extensional and deep strike-slip kinematics

We assess the seismotectonics of the western part of the border area between the Southern Apennines and Calabrian Arc, centered on the Mercure extensional basin, by integrating recent seismicity with a reconstruction of the structural frame from surface to deep crust. The analysis of low-magnitude (ML≤3.5) events occurred in the area during 2013–2017, when evaluated in the context of the structural model, has revealed an unexpected complexity of seismotectonics processes. Hypocentral distribution and kinematics allow separating these events into three groups. Focal mechanisms of the shallower (<9km) set of events show extensional kinematics. These results are consistent with the last kinematic event recorded on outcropping faults, and with the typical depth and kinematics of normal faulting earthquakes in the axial part of southern Italy. By contrast, intermediate (~9–17km) and deep (~17–23km) events have fault plane solutions characterized by strike- to reverse-oblique slip, but they differ from each other in the orientation of the principal axes. The intermediate events have P axes with a NE-SW trend, which is at odds with the NW-SE trend recorded by strike-slip earthquakes affecting the Apulia foreland plate in the eastern part of southern Italy. The intermediate events are interpreted to reflect reactivation of faults in the Apulia unit involved in thrust uplift, and appears aligned along an ~WNW-ESE trending deep crustal, possibly lithospheric boundary. Instead, deep events beneath the basin, which have P-axis with a NW-SE trend, hint to the activity of a deep overthrust of the Tyrrhenian back-arc basin crust over the continental crust of the Apulia margin, or alternatively, to a tear fault in the underthrust Apulia plate. Results of this work suggest that extensional faulting, as believed so far, does not solely characterizes the seismotectonics of the axial part of the Southern Apennines.

Pliocene‐Quaternary orogenic systems in Central Mediterranean: The Apulia‐Southern Apennines‐Tyrrhenian Sea example

AbstractIn the Central Mediterranean the Africa‐Eurasia convergence led to the development of complex orogenic systems and back‐arc basins. Throughout Pliocene‐Quaternary times the Southern Apennines accretionary prism migrated toward the Apulia foreland and, contemporaneously, the Tyrrhenian Sea back‐arc basin opened. In this study, we investigated the offshore of the southern Apulia foreland and the Southern Apennines. Using seismic reflection profiles and well data in a dedicated GIS software, we made a detailed stratigraphic analysis, reconstructed the structural pattern, and built 2‐D geological models of the main geological surfaces. The structure of the Apulia region formed during two main tectonic stages: lower Pleistocene complex extensional faulting developed in a transtensional regime and middle‐upper Pleistocene transpression/shortening. The Southern Apennines accretionary prism developed through the Pliocene‐early lower Pleistocene and was overprinted by late lower Pleistocene‐middle Pleistocene NW‐SE sinistral faults. Through linking new data from the accretionary prism and the foreland with previous information from the Tyrrhenian Sea back‐arc, we provide an original interpretation for the relationships between the various provinces that make the Central Mediterranean crustal puzzle and reconstruct the main phases of the evolution of its Pliocene‐Quaternary orogenic cycle. We recognized collisional stages of uncoupled plates, followed by late lower‐middle Pleistocene postcollisional stages of coupled continental plates. This Pleistocene plate reorganization of Central Mediterranean was probably due to the rupture of the Apulia/Ionian slab or to NNW intraplate shortening transmitted from Africa.

Active tectonic structures and submarine landslides offshore southern Apulia (Italy): a new scenario for the 1743 earthquake and subsequent tsunami

The southern Apulia foreland recorded a strong (Imax=X MCS) earthquake in 1743 and a concomitant tsunami, which struck the southeastern Salento coast. The seismo-genetic fault and the triggering factors of the tsunami are unknown. Three-dimensional interpretation of multichannel seismic profiles calibrated by wells using a GIS software enabled the recognition of the stratigraphic succession, structural framework, and submarine landslides offshore Salento. A thin Pliocene unit overlying the Mesozoic-Cenozoic substrate is covered by a Pleistocene succession separated by a Middle Pleistocene unconformity that formed during the regional uplift of Salento. The latter gave rise to the morphologic conditions for the deposition of a prograding wedge off the Salento coast, with a shelf break located at 150 m depth. Normal faults, mainly oriented NW–SE, displaced the early Lower Pleistocene succession and are buried by younger deposits. Since the Middle Pleistocene, a compressional event gave rise to the Apulia uplift and large folds and basement-involved reverse faults that are active in the eastern part of Apulia. A huge (58 km3) slump affecting the Middle Pleistocene prograding wedge has been documented offshore the southeast coast of Salento. The proposed geological scenario of the 1743 earthquake and subsequent tsunami is (1) an initial strong earthquake (Imax=X MCS) associated with a thrust fault located in the eastern sector of the Apulia offshore, (2) a shacking-induced large-volume slump offshore Otranto, and (3) landslide-triggered tsunamis that struck the Salento coast.

Seismotectonic of Southern Apennines from recent passive seismic experiments

We used data of local earthquakes collected during two recent passive seismic experiments carried out in southern Italy in order to study the seismotectonic setting of the Lucanian Apennine and the surrounding areas. Based on continuous recordings of the temporary stations we extracted over 15,600 waveforms, which were hand-picked along with those recorded by the permanent stations of the Italian national seismic network obtaining a dense, high-quality dataset of P- and S-arrival times. We examined the seismicity occurring in the period 2001–2008 by relocating 566 out of 1047 recorded events with magnitudes ML ≥ 1.5 and computing 162 fault-plane solutions. Earthquakes were relocated using a minimum one-dimensional velocity model previously obtained for the region and a Vp/Vs ratio of 1.83. Background seismicity is concentrated within the upper crust (between 5 and 20 km of depth) and it is mostly clustered along the Lucanian Apennine chain axis. A significant feature extracted from this study relates to the two E–W trending clusters located in the Potentino and in the Abriola–Pietrapertosa sector (central Lucania region). Hypocentral depths in both clusters are slightly deeper than those observed beneath the Lucanian Apennine. We suggest that these two seismic features are representative of the transition from the inner portion of the chain to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, seismicity is generally deeper and more scattered. The sparse seismicity localized in the Sibari Plain, in the offshore area along the northeastern Calabrian coast and in the Taranto Gulf is also investigated thanks to the new recordings. This seismicity shows hypocenters between 12 and 20 km of depth below the Sibari Plain and is deeper (foci between 10 and 35 km of depth) in the offshore area of the Taranto Gulf. 102 well-constrained fault-plane solutions, showing predominantly normal and strike-slip character with tensional axes (T-axes) generally NE oriented, were selected for the stress tensor analysis. We investigated stress field orientation inverting focal mechanism belonging to the Lucanian Apennine and the Pollino Range, both areas characterized by a more concentrated background seismicity.

Rheological behaviour of the crust in Southern Apennine (Italy): results from a thermal and seismological study

AbstractTo add information on the brittle/ductile transition of the Southern Apennine, we investigated a rheological profile of the crust along a WSW–ENE‐oriented cross‐section running from Neapolitan Volcanic Zone to Apulia foreland. The rheological model was obtained computing a thermal modelling and constrained by a relocalization of earthquakes of the area. Results show that the area is characterized by horizontal rheological variations, with two horizons interlayered with ductile horizons, that are quite predominant with respect to vertical ones. The horizontal stratification of lithospheric rheology has important geodynamic consequence and could provide new insights to better understand the tectonic processes which have played a major role to construct the Southern Apennine belt. Results of this study suggested that well‐constrained rheological models, built integrating information from both relocated earthquakes and thermal state, could give important hints on the mechanical behaviour of the crust and its related tectonic processes.

Trace element and isotopic variations from Mt. Vulture to Campanian volcanoes: constraints for slab detachment and mantle inflow beneath southern Italy

New Sr–Nd–Pb isotopic ratios and trace element data for volcanic mafic rocks outcropping along a E–W transect in southern Italy, from Mt. Vulture to Neapolitan volcanoes, are reported. The variation of LILE/HFSE, HFSE/HFSE and radiogenic isotopes along this transect indicates that all of these volcanoes contain both intra-plate and subduction-related signatures, with the former decreasing from Mt. Vulture to Campanian volcanoes. New data are also reported for the Paleocene alkaline rocks from Pietre Nere (Apulia foreland), which show isotopic ratios mostly overlapping the values for Mediterranean intra-plate volcanoes as well as the Eocene–Oligocene alkaline mafic lavas from the northern Adria plate. Pietre Nere provides evidence for an OIB mantle composition of FOZO-type, free of subduction influences, that is present beneath the Adria plate (Africa) before its collision with Europe. After this collision, and formation of the southern Apennines, westward inflow of mantle from the Adria plate to the Campanian area occurred, as a consequence of slab break off. Interaction of subduction components with inflowing Adria mantle generated hybrid sources beneath the Vulture–Campania area, which can explain the compositional features of both Mt. Vulture and the Campanian mafic rocks. Therefore, mafic magmas from these volcanoes represent variable degrees of mixing between different mantle components.

Inferences on the upper crustal structure of Southern Apennines (Italy) from seismic refraction investigations and subsurface data

This paper presents an interpretation of crustal seismic refraction data from the northern sector of the Southern Apennines thrust belt, a region that in historical times experienced large destructive earthquakes. The data were acquired in 1992 along a seismic line 75 km long and parallel to the Apenninic chain, in order to determine a detailed 2-D P-wave velocity model of the upper crust in an area that had not been deeply investigated by geophysical methods previously. We have used a 2-D ray tracing technique based on asymptotic ray theory to model travel times of first and reflected P-wave arrivals. Synthetic seismograms have been produced by finite difference simulations in order to check the reliability of the velocity model inferred by ray-tracing modelling. The interpretation of the velocity model is constrained by stratigraphic and sonic velocity logs from wells for oil exploration located close to the seismic line. Gravity data modelling allows to check the velocity model and to extend the structural interpretation in 3-D. In the shallow crust, up to a depth of 3–4 km, strong lateral variations of the modelled velocities are produced by the overlapping of thrust sheets formed by: (1) Cenozoic flyschoid cover and basinal successions that underlie the seismic profile with P-wave velocities in the 2.8–4.1 km/s range and thicknesses varying between 0.5 and 4.5 km; (2) Mesozoic basinal sequences with a velocity of 4.8 km/s and a depth of 1.5–2.1 km in the northern part of the profile; (3) Mesozoic limestones of the Western Carbonate Platform with a velocity of 6.0 km/s and a depth of 0.1–0.8 km in the southern part of the profile. At a greater depth, the model becomes more homogeneous. A continuous seismic interface 3.0–4.5 km deep with a velocity of 6.0 km/s is interpreted as the top of the Meso-Cenozoic Carbonate Multilayer of the Apulia Platform, characterized by an increase in seismic velocity from 6.2 to 6.6 km/s at depths of 6–7 km. A lower P-wave velocity (about 5.0 km/s) is hypothesized at depths ranging between 9.5 and 11 km. As inferred by commercial seismic lines and data from two deep wells located in the Apulia foreland and Bradano foredeep, this low-velocity layer can be related to Permo-Triassic clastic deposits drilled at the bottom of the Apulia Platform. Seismic data do not allow us to identify possible deeper seismic interfaces that could correspond to the top of the Paleozoic crystalline basement; this is probably due to the low-velocity layer at the bottom of the Carbonate Multilayer that reflects and attenuates a great part of the seismic energy. The joint interpretation of seismic refraction and well data, in accordance with gravity data, provides the first detailed P-wave velocity model of the upper crust of the northern sector of the Southern Apennines, which differs considerably from previous 1-D velocity models used to study the seismicity of the region, and reveals new information about the structure of the thrust belt.

Depth and modes of Pliocene–Pleistocene crustal extension of the Apennines (Italy)

Since early Pliocene times the Apenninic chain has been dissected by normal faults propagating towards the Adriatic foreland. In the Tyrrhenian Sea extension involved deep crustal sections, whereas in the ‘Central Apennines Downfaulted Area’ it affected the shallow crust. The Tyrrhenian back‐arc domain is connected to the overall flexural retreat of the Adriatic–Apulia plate in front of the Apenninic collisional wedge. In the outer Apenninic belt thin‐skinned delamination and gravitational collapse occurred in the hanging wall of a thickened wedge, overthrusting the uplifted, buoyant crust of the Apulia foreland. Differential sinking velocity of the foreland plate results from the inherited competence contrast between the rigid Gargano–Apulia carbonate platform to the south, and the low‐competence lithology of the pelagic sequence of the Adriatic basin to the north. During late Messinian–early Pliocene times this palaeogeographical boundary acted as a lithospheric tear, separating segments of the Apulia plate subjected to different subduction modes.

A P-wave velocity model of the upper crust of the Sannio region (Southern Apennines, Italy)

This paper describes the results of a seismic refraction profile conducted in October 1992 in the Sannio region, Southern Italy, to obtain a detailed P-wave velocity model of the upper crust. The profile, 75 km long, extended parallel to the Apenninic chain in a region frequently damaged in historical time by strong earthquakes. Six shots were fired at five sites and recorded by a number of seismic stations ranging from 41 to 71 with a spacing of 1-2 km along the recording line. We used a two-dimensional raytracing technique to model travel times and amplitudes of first and second arrivals. The obtained P-wave velocity model has a shallow structure with strong lateral variations in the southern portion of the profile. Near surface sediments of the Tertiary age are characterized by seismic velocities in the 3.0-4.1 km/s range. In the northern part of the profile these deposits overlie a layer with a velocity of 4.8 km/s that has been interpreted as a Mesozoic sedimentary succession. A high velocity body, corresponding to the limestones of the Western Carbonate Platform with a velocity of 6 km/s, characterizes the southernmost part of the profile at shallow depths. At a depth of about 4 km the model becomes laterally homogeneous showing a continuous layer with a thickness in the 3-4 km range and a velocity of 6 km/s corresponding to the Meso-Cenozoic limestone succession of the Apulia Carbonate Platform. This platform appears to be layered, as indicated by an increase in seismic velocity from 6 to 6.7 km/s at depths in the 6-8 km range, that has been interpreted as a lithological transition from limestones to Triassic dolomites and anhydrites of the Burano formation. A lower P-wave velocity of about 5.0-5.5 km/s is hypothesized at the bottom of the Apulia Platform at depths ranging from 10 km down to 12.5 km; these low velocities could be related to Permo-Triassic siliciclastic deposits of the Verrucano sequence drilled at the bottom of the Apulia Platform in the Apulia Foreland.

No tectonic rotation of the Tuscan Tyrrhenian margin (Italy) since Late Messinian

Extensive paleomagnetic sampling of 38 late Miocene and Pliocene sites has been carried out in the western Tuscan basins in Italy. These basins are located along the Tyrrhenian margin, and the studied formations were deposited at the same time as the opening of the Tyrrhenian Sea. The laboratory analyses show that, in most of the sites, pseudo‐single‐domain magnetites are the main magnetic carrier. The paleomagnetic data obtained from 27 suitable sites indicate that the Tuscan Tyrrhenian margin has not been affected by significant regional rotation since at least the late Messinian‐early Pliocene (about 5.5 m.y.). These data demonstrate that the rotations previously measured in the Meso‐Cenozoic units of the Apennines and of the Apulia foreland cannot be directly related to the late Messinian‐Pliocene phases of rifting in the Tyrrhenian Sea. Moreover, the data presented here conflict with published results from coeval formations in the Apennines and Sicily, in areas subjected to strong thrusting and shortening. In these areas the rotations control the orientation of the main compressional structures and give rise to the typical arcuate shape of the Apenninic chain. We suggest that the tectonic evolution of the northern Tyrrhenian Sea‐Apenninic chain system involved thrusting and shortening of the external (eastern) domains, with rotations of the allochthonous units, followed by gravitational collapse of the western sector. This second phase involved no tectonic rotation of the newly formed extensional basins.

The Gargano promontory: An important Italian seismogenic-tsunamigenic area

Gargano is a small mountainous promontory protruding into the Southern Adriatic and, from a structural point of view, it is part of the Apulia foreland. Deformative structures, both inland and offshore the promontory, are quite common and can partially be associated with a substantial Quaternary uplifting. Seismogenically this area is well known, because several historical strong earthquakes have been reported to occur here and recent important seismic sequences have been recorded. This paper is a contribution to evaluate the seismogenic as well as the tsunamigenic potential of this region. Particular attention has been given to study the major events, some of which were able to produce tsunamis. The epicenter location of some of these earthquakes computed solely on the basis of macroseismic data would point to focal regions on land, but this is questionable if tsunami generation is taken into account. As regards the tsunamigenic potential, statistical analysis is used to evaluate the local geographical distribution of expected tsunamis and the mean return periods. It is found that large events are expected on average every 228 years, while a tsunami of any size is generated every about 84 years, which is in good agreement with the experimental observations.

Geometric and kinematic complexities in the Marche-Abruzzi external zones (Central Apennines, Italy)

In the Central Apennines (Italy) three major domains can be recognized: the Umbria and Marche pelagic domains and the Lazio-Abruzzi carbonate platform. Their Mesozoic-Tertiary sequences are separated by major low-angle thrust systems, which superpose the Umbria domain onto both the Marche and Lazio-Abruzzi domains, the Lazio-Abruzzi platform onto the Marche sequence, and all of them onto the Apulia foreland.