Periadriatic Zone Research Articles

Short-Term Kinematics of the Adria Plate and Space-Time Distribution of Major Peri-Adriatic Earthquakes

Seismic activity is quite strong in the peri-Adriatic zones, whereas the internal part of the Adria plate is almost aseismic. This pattern suggests that Adria is a solid block that interacts with the surrounding belts, trying to move roughly northward. Each major earthquake in a peri-Adriatic zone triggers the acceleration of the decoupled Adria sector, which induces a perturbation of the stress/strain fields in the still blocked boundaries of the plate. Step by step, the displacement of Adria involves more and more northern zones to finally reach the northern front of the plate (eastern Southern Alps). This interpretation seems to be compatible with the time patterns of seismic activity in the main peri-Adriatic zones since 1600 A.D., which may suggest repeated northward migrations of seismic crises. Each supposed migrating sequence involves major earthquakes in most zones. The main features of the first 4 seismic sequences (1600-1930) are used to get insights into possible regularities in the progressive activations of the peri-Adriatic zones. This information and the main features of the ongoing migrating sequence (since 1931) are then used to tentatively recognize the peri-Adriatic zones where the occurrence of next major earthquakes may be most likely.

Early Aptian rudist faunas from the Taurides (Southern Turkey): their stratigraphic, palaeogeographic and palaeobiogeographic significance

The eastern Taurides yield an early Aptian rudist fauna including Agriopleura libanica and Offneria murgensis, two key members of the Arabo-African biome, reported for the first time in Turkey. The presence of this assemblage which closely resembles that of the Shu'aiba Formation of Saudi Arabia, Oman and the United Arab Emirates, fills a distributional, geographical gap between its Arabian, North African and Apulian occurences. The rudist fauna and the composition of the associated micropalaeontological elements suggest an early Bedoulian age and a close palaeogeographic proximity with the regional outer platform margin. The presence in the Taurides of an Arabo-African fauna is consistent with the palaeotectonic placement of the Anatolides-Taurides in between the Arabian promontory and the peri-Adriatic zone.

How and why the present tectonic setting in the Apennine belt has developed

The building of the Apennine belt slowed down or ceased around the Early Pleistocene. Since then, the belt has undergone strong uplift and considerable distortion. This change, from belt-normal to belt-parallel shortening, has been determined by the fact that the continental Adriatic domain (Adria) was almost completely surrounded by buoyant orogenic structures. In that context, the mobility of Adria underwent a considerable reduction, whereas uplift and deformation of its southern part was strongly emphasized as an effect of the convergence of the confining plates. Around the middle Pleistocene, the deformation pattern in the peri-Adriatic zones changed again, in response to acceleration of Adria. The outer (Adriatic) sector of the Apennine belt underwent belt-parallel shortening, accommodated by uplift and outward escape of upper crustal wedges. The separation between the extruding wedges and the almost stable inner belt has generated a series of extensional or transtensional fault systems along the axial part of the Apennines, which now correspond to the main seismogenic sources. The spatio-temporal distribution of major tectonic events in the study area can plausibly be explained as an effect of the least-action principle. Thematic collection: This article is part of the ‘Apennines and Tyrrhenian system’ collection available at: https://www.lyellcollection.org/cc/the-apennines-tyrrhenian-system

Possible Location of the Next Major Earthquakes in the Northern Apennines: Present Key Role of the Romagna-Marche-Umbria Wedge

It is argued that in some zones of the Northern Apennines, in particular the Rimini-Ancona thrust system, the Romagna Apennines and the Alta Valtiberina trough, the probability of major earthquakes is now higher than in other Apennine zones. This hypothesis is suggested by the comparison of the present short-term kinematics of the Romagna-Marche-Umbria wedge in the Northern Apennines, deduced by the distribution of major shocks in the last tens of years, with the previous repeated behavior of the same wedge, evidenced by the distribution of major earthquakes in the last seven centuries. The seismotectonics of the Apennine region here considered is closely connected with the larger context that involves the progressive migration (from south to north) of seismicity along the peri-Adriatic zones. The information provided by this study can be used to better manage the resources for prevention in Italy.

Present Velocity Field in the Italian Region by GPS Data: Geodynamic/Tectonic Implications

The analysis of geodetic observations carried out by 478 continuous GPS stations in the Italian region since 2001 has allowed a fairly good definition of the ongoing horizontal velocity field with respect to Eurasia. It is argued that such evidence can provide important insights into the geodynamic context in the central Mediterranean area. Numerous velocity vectors in the Apulia zone coherently indicate that the southern Adriatic domain is moving roughly NE ward. Since no significant decoupling zone between this domain and Nubia has so far been recognized, one could expect that the kinematics of these two plates is compatible. However, this condition is not fulfilled if the Nubia-Eurasia relative motion is taken from the global kinematic models, either deduced by long-term evidence [1] or short-term geodetic data [2] [3]. This problem is considerably reduced if the alternative Nubia-Eurasia rotation pole suggested by [4] is taken into account. This choice is also suggested by other major long-term evidence in the Mediterranean region. The numerous geodetic vectors available in two Adriatic sectors, the Apulia zone and the Venetian plain, would imply an Adria-Eurasia rotation pole incompatible with all Nubia-Eurasia Eulerian poles so far proposed. Since a significant relative motion between these plates is not compatible with the absence of a tectonic decoupling zone, we suppose that the short-term kinematics of Adria might be influenced by a transient non-rigid behaviour of that plate. This hypothesis is compatible with the expected effects (post seismic relaxation) of the major decoupling earthquakes that have occurred along Periadriatic zones in the past tens of years. The compatibility of the GPS kinematic pattern in the Apennine belt, Calabria Arc and Sicily with the implications of the geodynamic/tectonic interpretations so far proposed for the central Mediterranean area is then discussed.

Pebble population dating as an additional tool for provenance studies - examples from the Eastern Alps

Abstract Detrital fission-track (FT) dating can be successfully used in provenance studies of siliciclastic sediments to define the characteristic cooling ages of the source regions during erosion and sedimentation. In order to obtain more specific information about potential source regions we have developed the pebble population dating (PPD) method in which pebbles of specific lithotype are merged and dated. Dating of both zircon and apatite crystals from such pebble populations yields age distributions, which reflect the cooling ages of the given lithotype in the source area at the time of sedimentation. By this technique it is possible to define ‘FT litho-terrains’ in the source regions and thus outline palaeogeological maps. Two examples are presented from the Eastern Alps. (i) Comparison of FT ages from a sandstone sample and a gneiss PPD sample from an Oligocene conglomerate of the Molasse Basin shows that the youngest age cluster is present only in the sand fraction and derived from the Oligocene volcanic activity along the Periadriatic zone. The lack of the youngest ages in the gneiss pebble assemblage excludes the Oligocene exhumation of the crystalline basement from mid-crustal level. (ii) Pebble assemblages of red Bunter sandstone, gneiss and quartzite were collected from an Upper Miocene conglomerate of the Molasse Foreland Basin and merged as PPD samples. Apatite and zircon FT grain age distributions of these PPD samples, representing the largest ancient East Alpine catchment, allow generating a new combination of palaeogeological and palaeo-FT-age maps of the Eastern Alps for the Late Miocene.

Petrology and geochemistry of Paleogene tonalites from the easternmost parts of the Periadriatic Zone

The Pohorje Mts. and Karavanke plutons occur in the easternmost parts of the Periadriatic Zone separating the Eastern Alps from the Southern Alps and the northwesternmost Dinarides, respectively. The plutons, which are composed largely of tonalites with subordinate granodiorites and rare diorites mainly of medium-K calc-alkaline affinity, are part of a series of mid-Tertiary intrusives emplaced over ∼700 km E-W along the Periadriatic Zone.

Eoalpine to Neoalpine magmatic and metamorphic processes in the northwestern Vardar Zone, the easternmost Periadriatic Zone and the southwestern Pannonian Basin

The occurrence of Eoalpine-Neoalpine, genetically different, granitoids and penecontemporaneous volcanics are characteristic for the Vardar Zone. These rocks are mostly associated with Late Cretaceous-Paleogene basinal sedimentary rocks underlain by ophiolites. The Late Cretaceous-Paleogene rocks were progressively metamorphosed under mediumpressure conditions and intruded by synkinematic Mesoalpine granitoids. The high-pressure blueschist metamorphism was related to a pre-Maastrichtian Eoalpine metamorphic event. Eoalpine and Mesoalpine magmatism and the related metamorphism of the Vardar Zone may have taken place along a magmatic arc, i.e., the subduction zone. The easternmost parts of the Periadriatic Zone are characterized only by Oligocene granitoids accompanied by penecontemporaneous volcanic rocks. Here, younger Alpine metamorphic phases only overprint and mylonitize older pre-Alpine formations. Most of the Mesoalpine granite plutonism both of the Vardar Zone and the easternmost area of the Periadriatic Zone was related to subsequent extension. The southwestern and southern parts of the Pannonian Basin contain the products of four pulses of Mesoalpine and Neoalpine synsedimentary volcanic activity (Egerian-Eggenburgian, Ottnangian-Carpathian, Badenian and post-Badenian) represented by predominant basalt-andesites, trachyandesites and trachydacites. This post-subduction volcanism was closely connected with the cyclic marine ingressions in the Pannonian Basin.