2022, Articolo in rivista, ENG
D'Orazio M.; Fulignati P.; Gioncada A.; Cavalcante F.
This work describes the first occurrence of albitite rocks in the Middle Triassic Verruca Formation, Monti Pisani, Northern Apennines, northern Tuscany, Italy. The albitite formed by Na-metasomatism of phyllites ('potassic white mica' + quartz + 'chlorite' + hematite + albite) in an amagmatic environment. The albitisation process took place after the Miocene main phases of Apenninic deformation and was followed by the formation of veins of Fe-carbonate + quartz. Hydrothermal alteration progressed with the ingression, possibly favoured by the increase of permeability due to albitisation, of a slightly acidic, oxidising, aqueous fluid that led to the pervasive kaolinisation of the albitite and to the complete transformation of the Fe-carbonate of the veins into Fe-hydroxides. This stage was followed by supergene alteration that led to the formation of a pervasive network of halloysite veinlets and colloform (P-Al-Si)-bearing Fe-hydroxides. Finally, the hydrothermally altered rock underwent a localised brittle fracturing without new minerals being formed. The prominent compositional changes occurring during this multi-stage hydrothermal process were the inversion of the Na2O/K2O ratio of the whole rock (from 0.07 in the pristine phyllite to up to 200 for the kaolinised albitite), the loss of Fe and Mg, and the enrichment of Sb. The MREE were partially lost, whereas LREE and HREE behaved conservatively. Though pervasive hydrothermal alteration occurrences are common in central-southern Tuscany, mostly related to the post-collisional extensional regime, lithospheric thinning and emplacement of magmatic bodies in the crust, the rare Monti Pisani kaolinised albitite described in this investigation expands the effects of post-collisional hydrothermal activity in Tuscany northwards, far from potential magmatic sources.
2021, Articolo in rivista, ENG
Guerra V.; Lazzari M.
The aim of this paper is to present the geomorphological map of the right side of the middle Marecchia valley, in the northern Apennines (Italy), as a basis to enhance the geotouristic potential of the area. This area has been chosen because it is representative of the geological, geomorphological and geodynamic context characterizing the whole Marecchia basin, where a massive allochthonous body (known as Valmarecchia Nappe) widely outcrops. This area consists of Ligurian and Epiligurian formations that overthrust the Umbro-Marchean autochthonous units, drawing a peculiar landscape characterized by high geodiversity and marked above all by landforms developing into various formations. In order to map the main geomorphological features, multi-temporal aerial photos analysis, field survey and bibliographical research, concerning both the geomorphological and cultural values, have been carried out. The landforms highlighted in the map include stream terraces, vertical cliffs, alluvial fans, badlands and landslides; additional geomorphological points of interest have been described and mapped as they represent the most distinctive events in the area. The geomorphological features have been integrated with the additional (ecological, aesthetic, cultural) values to quantify the value of each geosite using an adapted version of Reynard et al. (2016)'s method, from which it emerged that the sites have high scores both in terms of scientific and additional values, making the study area an ideal territory in which implement actions and proposals for geotouristic fruition.
2021, Articolo in rivista, ENG
Festa A.[1], Meneghini F.[2], Balestro G.[1], Pandolfi L.[2,3], Tartarotti P.[4], Dilek Y.[5], Marroni M.[2,3]
The Jurassic ophiolites in the Northern Apennines and the Western Alps represent fossil mid-ocean ridge (MOR) oceanic lithosphere that formed in the Mesozoic Ligurian-Piedmont Ocean Basin (LPOB). Their sedimentary covers include chaotic rock units containing ophiolite-derived material. The processes of formation and the lithostratigraphic position of these chaotic units in the Western Alps remain a matter of debate, unlike their counterparts in the Northern Apennines. This is because of pervasive tectonic deformation and high-pressure metamorphism that affected their internal structure during collisional tectonics. A comparative analysis of these chaotic units in both mountain belts reveals the nature of processes involved in their formation. Chaotic deposits of gravitational origin occur both below and above the extrusive sequences in the ophiolites. They represent synextensional, hyperconcentrated deposits associated with the seafloor-spreading evolution of the LPOB lithosphere during Middle and Late Jurassic times. Mass transport deposits (MTDs) occur as intercalations within turbiditic sequences above the ophiolites. They represent syncontractional submarine slides that occurred on frontal accretionary prism slopes during the Late Cretaceous-Paleocene closure of the LPOB. The results of our comparative analysis imply that (1) the structure-stratigraphy of the chaotic deposits and MTDs of the Northern Apennines can be used as a proxy to better identify their metamorphosed and highly deformed counterparts in the Western Alps, (2) sedi-mentological processes associated with slow-spreading MOR tectonics and accretionary prism development in convergent-margin tectonics contributed to the sediment budgets of the cover sequences, and (3) magmatic, tectonic, and sedimen-tological processes that occurred during the formation of the Jurassic oceanic lithosphere and its sedimentary cover in the LPOB were remarkably uniform and synchronous.
2021, Articolo in rivista, ENG
Esposito C. (1), Di Luzio E. (2), Baleani M.(3), Troiani F.(1), Della Seta M. (1), Bozzano F. (1), Mazzanti P. (1,3)
This research illustrates the case of a deep-seated gravitational slope deformation (DSGSD) affecting a folded structure that developed during Miocene tectonics in the Northern Apennines of Italy, deforming a heterogeneous turbiditic sequence characterised by pelitic-marly and arenaceous intervals. The investigated area includes the headwater portion of the Bidente River basin that has experienced intensive valley incision during the late Quaternary and the sizeable Poggio Baldi landslide with failure episodes in 1914 and 2010. The aim of this work was to unravel the local morphostructural setting determined by the interplay between the active DSGSD, inherited fold geometry, and fluvial dynamics. Dip data collection and structural analysis were used to reconstruct the fold geometry. A complex type of fault-propagation fold was outlined, with later breakthrough thrusts causing the backlimb rotation. Gravity-driven geomorphological features were inventoried and displayed on two geological cross-sections together with Geological Strength Index measurements, while their distribution was analysed to conceive a conceptual model for the development of the DSGSD. Fold setting and lithological anisotropies were considered as the predisposing factors of the gravitational slope deformation, whereas the multi-step entrenchment of the Bidente River valley, testified by the presence of the remnants of at least three generations of fluvial erosional terraces, was considered as the main cause of its initiation. Finally, the reconstruction of the original slope topography in the Poggio Baldi area and the results of structural analysis performed in the landslide detachment zone through remote sensing techniques allowed for the estimation of the size of the wedge-shaped rock block which detached in 1914, an event that occurred in the wider frame of the DSGSD.
2021, Articolo in rivista, ENG
Andrea Di Capua, Federica Barilaro, Gianluca Groppelli
This work critically reviews the Eocene-Oligocene source-to-sink systems accumulating volcanogenic sequences in the basins around the Alps. Through the years, these volcanogenic sequences have been correlated to the plutonic bodies along the Periadriatic Fault System, the main tectonic lineament running from West to East within the axis of the belt. Starting from the large amounts of data present in literature, for the first time we present an integrated 4D model on the evolution of the sediment pathways that once connected the magmatic sources to the basins. The magmatic systems started to develop during the Eocene in the Alps, supplying detritus to the Adriatic Foredeep. The progradation of volcanogenic sequences in the Northern Alpine Foreland Basin is subsequent and probably was favoured by the migration of the magmatic systems to the North and to the West. At around 30 Ma, the Northern Apennine Foredeep also was fed by large volcanogenic inputs, but the palinspastic reconstruction of the Adriatic Foredeep, together with stratigraphic and petrographic data, allows us to safely exclude the Alps as volcanogenic sources. Beyond the regional case, this review underlines the importance of a solid stratigraphic approach in the reconstruction of the source-to-sink system evolution of any basin.
2020, Articolo in rivista, ENG
1Basch V.; 2Borghini G.; 2Fumagalli P.; 1Rampone E.; 1Gandolfo A.; 3Ferrando C.
Plagioclase peridotites are an important marker of the shallow geodynamic evolution of the lithospheric mantle at extensional settings. Based on low-pressure experiments, a recent study by Fumagalli et al. (2017) defined and calibrated a geobarometer for peridotitic bulk compositions, based on the Forsterite-Anorthite-Ca-Tschermak-Enstatite (FACE) pressure-sensitive equilibrium. The Suvero plagioclase-bearing peridotites, on which the FACE geobarometer was calibrated, are primarily associated to plagioclase pyroxenites. Assuming that the pyroxenites record the same Pressure-Temperature evolution than the plagioclase peridotites, they represent ideal candidates to test the applicability of the FACE geobarometer on pyroxenitic compositions. As documented in the plagioclase peridotites, the pyroxenites are characterized by the development of fine-grained neoblastic assemblages, indicative of partial recrystallization under plagioclase-facies conditions. Chemical zonations in these neoblastic mineral aggregates suggest equilibration stages at variable pressure and temperature and allowed to document two re-equilibration stages corresponding to the onset of plagioclase-facies recrystallization (830-850°C, 6.9-8.1 ± 0.5 kbar) and a shallower colder re-equilibration (770-790°C, 5.8-5.9 ± 0.5 kbar), respectively. The decompressional evolution reported for pyroxenitic bulk compositions is consistent with the exhumation history documented in the associated Suvero peridotite, although at slightly higher equilibrium pressures (~ 1 kbar). Remarkably, the much lower XCr in pyroxenites reflects in lower Cr incorporation in pyroxenes and, consequently, in significantly higher Ca-Tschermak activity in clinopyroxene that might introduce the systematic pressure overestimation by FACE geobarometer.
2019, Articolo in rivista, ENG
Spina A.[1], Capezzuoli E.[2], Brogi A.[3,4], Cirilli S.[1], Liotta D.[3,4]
Recent studies on the stratigraphy of Paleozoic successions belonging to key sectors of the inner Northern Apennines provide data that can be used to propose new hypotheses about the palaeogeography of the western Mediterranean domain during post-Hercynian times.We report here the first evidence of mid- to late Permian (Guadalupian-Lopingian) palynomorphs in the chronostratigraphically highly debated metamorphic units of the Northern Apennines (the Rio Marina Formation, the Mt Calamita Formation and the Le Cetine Formation) and consider the stratigraphic implications for the Tuscan 'basement' to which the study rocks belong and their palaeogeographical attribution considering their Gondwana affinity. These results agree with the interpretation that the Alpine Tethyan sedimentary cycle was already active during the mid- to late Permian
2019, Articolo in rivista, ENG
Bianco C.[1], Godard G.[2], Halton A.[3], Brogi A.[1,4], Liotta D.[1,4], Caggianelli A.[1]
Evidence for high-P blueschist-fades metamorphism was found in metabasites embedded in calcschists of Eastern Elba Island (Northern Apennines, Italy). Study of immobile trace elements (REEs and HFSEs) in the metabasites indicates an affinity with T- and E-MORBs, and they are interpreted as sill or dykes intruded in the western margin of the Adria continental plate. The minerals are heterogeneously distributed in the rock, constituting mafic and Ca-Al-rich microdomains inherited respectively from the magmatic pyroxene- and plagioclase-rich zones of the original doleritic rock. The peak pressure paragenesis consisted of lawsonite, aegirine-omphacite, glaucophane and chlorite. Former rhombic prisms of lawsonite have been replaced by pseudomorphic clinozoisite (0.1 mm in size) with inclusions of Ms. +/- Ab +/- Qz. The inclusions are preferentially oriented parallel to one of the diagonals of the basal rhombic sections, indicating that the two diagonals were not crystallographically equivalent. This implies that the protocrystals were orthorhombic prisms with (110) faces, which is the case of lawsonite. The different compositions shown by white mica and epidote in the pseudomorphs (muscovite and Fe3+-poor clinozoisite) and in the matrix (phengite and Fe3+-rich epidote) also suggest the former presence of Mg- and Fe-poor lawsonite in these rocks. Thermodynamic modelling, using the THERMOCALC software and dataset, suggests that metabasites experienced a clockwise P-T path from the lawsonite-blueschist to epidote-blueschist subfacies, down to greenschist facies. The estimated peak pressure conditions are P >= 1.6 GPa and 450 < T < 500 degrees C. Glaucophane grew mainly during the lawsonite-to-epidote transition and is dated at 19.8 +/- 1.4 Ma by the Ar-40/Ar-39 method. This evolution is interpreted in terms: (i) intrusion of basic magmas in carbonatic and pelitic sediments (post-late Cretaceous, pre-Oligocene), (ii) subduction (Oligocene), (iii) collision (early Miocene: 19.8 +/- 1.4 Ma), (iv) exhumation and granite intrusion (middle-late Miocene), favored by extensional tectonics. We underline that the eastern part of Elba Island belongs to a blueschist-facies belt that extends from Gorgona Island, in the northwest, to Argentario and Giglio Island in the southeast, so many of the conclusions of this study can be extended to the whole of this belt. (C) 2019 Elsevier B.V. All rights reserved.
2019, Articolo in rivista, ENG
Pauselli C.[1], Gola G.[2], Mancinelli P.[1], Trumpy E.[2], Saccone M.[1], Manzella A.[2], Ranalli G.[3]
A revised surface heat flow map of a sector of the Northern Apennines is presented, constrained by recently available thermal and petrophysical logs from 174 wells drilled for geothermal and hydrocarbon exploration purposes. The borehole temperatures have been corrected for drilling, inclination, and palaeoclimate effects. The corrected temperature data, combined with petrophysical parameters for each individual formation, have been used to derive shallow geotherms (down to a maximum depth of 8 km), which have yielded site-specific heat flow values. These values, once corrected for palaeoclimatic topographic and erosion/sedimentation effects, have been contoured by a kriging procedure to obtain the heat flow map. The map shows a clear distinction between a western zone (the Tyrrhenian Domain) of high heat flow (> 150mW m-2), with closely spaced heat flow isolines, and an eastern zone (the Adriatic Domain) of relatively low (< 70mW m-2), spatially uniform heat flow. The boundary between the two zones is roughly parallel to the axis of the Apennines. Five crustal geotherms (extending to the Moho) and the corresponding rheological profiles confirm that the 70mW m-2 isoline corresponds to a major tectonic boundary, across which the thermal, structural, and seismic properties of the lithosphere go through a significant change.
2018, Articolo in rivista, ENG
Livani, Michele; Scrocca, Davide; Arecco, Paola; Doglioni, Carlo
The external part of the Northern Apennines accretionary wedge in northern Italy is buried beneath its fast subsiding and asymmetric foreland basin in the Po Plain. It is characterized by a diffused noncylindrical geometry resulting in salients and recesses in the study area, namely, the Cremona salient, the Parma recess, and the Ferrara salient. The interpretation of borehole and seismic reflection data suggests that the thrust belt is characterized by thin-skinned tectonic style. Two main décollement levels have been identified: a basal décollement located in the Upper Carnian units (San Giovanni Bianco Clay and Raibl Group) and a shallow décollement located in the late Eocene-Oligocene formations (Gallare Marls). The décollement surfaces dip SSW toward the hinterland of the accretionary prism, parallel to the steep (>10°) regional monocline. The geometry of the seismically active Northern Apennines system of salients and recesses is essentially controlled by the interplay of two factors: (i) the lateral facies variations of the stratigraphic units hosting and controlling the location and depth of the décollement levels and (ii) the slope of the basal décollement. Salients occur where, due to the inherited variable stratigraphy of the Mesozoic-Cenozoic Tethyan passive margin, the shaly formations hosting the two décollements are well developed allowing larger forward propagation of the thrust wedge. Recesses are instead associated to erosional-nondepositional areas. Moreover, salients are more pronounced where the flexural behavior of the Adriatic subducting slab has generated a steeper geometry of the foreland monocline and consequently of the basal décollement.
2018, Articolo in rivista, ENG
Maestrelli D.[1,2] Benvenuti M.[2] Bonini M.[3], Carnicelli S.[2], Piccardi L.[3], Sani F. [2,3]
The Pede-Apennine margin (Northern Italy) is a major WNW-ESE-trending morpho-structural element that delimits the Po Plain to the southwest and consists of a system of southwest dipping thrusts, generally referred to as Pede-Apennine Thrust (PAT). The leading edge of the chain lies further north-east and is buried beneath the Plio-Quaternary marine and fluvial deposits of the Po Plain. Whereas the buried external thrust fronts are obvious active structures (as demonstrated by the 2012 Emilia earthquakes; e.g. Burrato et al., 2012), ongoing activity of the PAT is debated. Using a multidisciplinary approach that integrates structural, seismic, sedimentological and pedological field data, we describe the recent activity of the PAT structures in a sector of the Pede-Apennine margin between the Panaro and the Enza Rivers (Emilia-Romagna). We found that the PAT is emergent or sub-emergent and deforms Middle Pleistocene deposits. We also infer a more recent tectonic phase (~ 60-80 ka) by Optically Stimulated Luminescence (OSL) dating of soil profiles that have been deformed by a recent reactivation of the PAT. Furthermore, we show evidence that the PAT and its external splay thrusts strongly influenced the drainage pattern, causing fluvial diversions and forcing paleo-rivers to develop roughly parallel to the margin. Finally, numerical Trishear modelling has been used to calculate deformation rates for the PAT along two transects. Extrapolated slip rates vary between 0.68 and 0.79 mm·yr-1 for about the last 1.2-0.8 million years.
2017, Articolo in rivista, ENG
Martelli L.[1], Santulin M.[2] Sani F.[3], Tamaro A.[4], Bonini M.[5], Rebez A.[4], Corti G.[5], Slejko D. [4]
Seismic hazard has been computed for the Northern Apennines in northern Italy based on a new seismogenic zonation. This zonation considers inclined (dipping) planes as seismogenic sources, defined on the basis of all the seismotectonic information available so far. Although these geometries are extremely rough because they simplify with a few inclined elements the totality of faults constituting a source, this model mimics the tectonic style better than that based on horizontal planes. Nevertheless, for a comparison between the new ground motions obtained and those available in the literature, the plane version of the zonation has been developed, where horizontal areas (the standard seismogenic zones), representing the surficial projection of the inclined planes, are used as seismogenic sources.
2017, Articolo in rivista, ENG
Balestrieri M.L.[1], Benvenuti M.[2], Catanzariti R.[3]
Detrital apatite fission-track (AFT) thermochronology has been applied to lower Pleistocene lacustrine fan-delta sediments of the NE shoulder of the Mugello Basin, the youngest and closest to the main watershed among the Northern Apennines intermontane basins. The aim was to decode the shoulder uplift dynamics during the development of the basin through the analysis of the Quaternary fluvio-lacustrine deposits. Bedrock shoulder analysis, performed to match the detrital AFT data with their source, revealed the presence of a unexpected only partially annealed portion of a turbidite foredeep unit (AFT ages >7-5 Ma) belonging to the structural complex that constitutes the shoulder bedrock. These data disagree with the AFT age distribution pattern of the well-studied Northern Apennines chain, suggesting a segmentation of the foredeep basin. The latter may have been related to the presence of a tectonically induced topographic high (pre-late Langhian) in the area limiting the thickness of the overriding Ligurian lid. On the other hand, detrital AFT data provided arguments for understanding the dynamics of Mugello Basin shoulder uplift and rotation. The proportion in the different stratigraphic units of the fan-delta sediments of single grains showing young (reset) and old (non-reset) ages points to late Early Pleistocene timing of the development of the SW-verging backthrust that characterizes the study area. These data confirm and detail the picture of an early Quaternary development of the Mugello Basin under a compressional setting, only later (middle Pleistocene to present) superimposed by normal faultings.
2017, Articolo in rivista, ENG
Marchi A.[1], Catanzariti R.[2], Pandolfi L.[1,2]
The Mt. Modino Unit succession (Northern Apennines) is mainly composed of turbiditic sediments deposited during the collisional and post-collisional stages of the Northern Apennines fold-and-thrust belt. Within this succession we have studied a thick interval of shales with arenitic beds, marls and arenites, of the Fiumalbo Shale, the Marmoreto Marl and the Mt. Modino Sandstone formations. Calcareous nannofossil assemblages of the eight investigated stratigraphic sections contain middle-late Eocene to Oligocene-early Miocene biozones. Zones CNE12 to MNN1 have been identified through quantitative analyses of a set of 200 samples, and the precise ages of the Fiumalbo Shale, the Marmoreto Marl and the Mt. Modino Sandstone were identified as well. The biostratigraphic analyses enable stratigraphic correlations between the investigated sections which were used to propose a stratigraphic architecture of the Mt. Modino Unit succession. Physical and biostratigraphic data available for the Mt. Modino Unit succession suggest a subsiding wedge-top basin fed since the Rupelian by both Apennine and Alpine sources. After the late Oligocene shortening phase, the Mt. Modino Basin occupied the inner part of the foredeep basin, sharing the same turbiditic deposits with the Macigno formation.
2015, Articolo in rivista, ENG
Catanzariti, Rita; Perilli, Nicola
An accurate biostratigraphic study of the Paleocene-middle Eocene calcareous nannofossils was performed on the turbiditic successions that characterize the Northern Apennines Mt. Caio, Farini d'Olmo, Mt. Sporno and Mt. Penice Units, belonging to the "Tertiary Flysch Auctt." and referable to the External Ligurides. These succession accumulated in a link key area, located between the oceanic Ligure-Piedmontese domain and the Adria continental margin. The reference biostratigraphic scheme used in the study is the recently published calcareous nannofossil biozonation proposed for the Paleogene by Agnini et al. (2014). The obtained biostratigraphic and chronostratigraphic data suggest that further investigation is needed to clarify the tectono-sedimentary evolution and to unravel the complex architecture of the External Ligurides.
2015, Articolo in rivista, ENG
Liotta D. (1), Brogi A. (1), Meccheri M. (2); Dini A. (3), Bianco C. (1), Ruggieri G. (4)
In this paper we deal with the kinematic and chronological relationships among low angle normal faults and high angle strike- to oblique-slip faults in an exhumed mineralized area, where shear veins and minor associated structures filled with the same mineral assemblage has been interpreted as indicators of coeval fault activities. The study area is located in the eastern Elba Island, where a mineralized late Miocene-early Pliocene low-angle normal fault (Zuccale fault) and high-angle strike- to oblique-slip faults extensively crop out, the latter giving rise to the Capoliveri-Porto Azzurro shear zone. The field study highlighted that: (a) the damage zones of both fault sets are mineralized by syn-kinematic tourmaline, graphite, Fe-oxides and/or Fe-oxyhydroxides shear veins, thus indicating their coeval activity during the hydrothermal event (5.9-5.4. Ma); (b) the Capoliveri-Porto Azzurro shear zone is constituted by a network of fractures, whose geometry and kinematics display the evolution of a NE-trending left-lateral oblique-slip transtensional shear zone; (c) its internal architecture is defined by tourmaline and Fe-oxides and/or Fe-oxyhydroxides mineralized veins, framed in the same kinematic field characterizing the Zuccale fault evolution; for this reason, the Capoliveri-Porto Azzurro shear zone is interpreted as a transfer zone active during the low-angle fault activity; (d) the Capoliveri-Porto Azzurro shear zone played the role of a significant normal fault during the Late Pliocene-Pleistocene, therefore favouring the deepening of the Tyrrhenian Basin with respect to the uplift and exhumation of the mid-crustal rocks of the Elba Island. It is finally argued that the interaction between the low-angle normal fault and the almost vertical shear zone determined an increase of permeability, favouring the mineralizing fluid flow during the hydrothermal stage and, reasonably, the previous emplacement of the Porto Azzurro magmatic body.
2015, Abstract in atti di convegno, ENG
MARCHI, Alessandra1, PANDOLFI, Luca1, 2, CATANZARITI, Rita2
2014, Articolo in rivista, ENG
Caricchi, Chiara; Cifelli, Francesca; Sagnotti, Leonardo; Sani, Federico; Speranza, Fabio; Mattei, Massimo
We report on an extensive paleomagnetic study (36 sites) of the Tuscan Nappe succession from the Northern Apennines Arc, aimed to reconstruct the tectonic evolution of the internal sector of this chain. We analyzed Eocene pelagic foreland ramp deposits (Scaglia Toscana Formation) and Oligocene-lower Miocene siliciclastic turbidites (Macigno and Falterona Formations). Paleomagnetic results show that the internal sector of the Northern Apennines underwent large counterclockwise (CCW) rotations with respect to the Adria-Africa foreland. A decrease in the rotation magnitude was observed from the southern to the northern sector of the arc (from 91 to 36). This trend is opposite to that observed in the more external units of Northern Apennines and demonstrates that the oroclinal bending model, which has been proposed for the external units of the chain, is not appropriate to explain the evolution of the internal sector of the arc. On the basis of the observed paleomagnetic pattern, we propose a new tectonic model in which the Tuscan and Falterona-Cervarola units in the southern area were first rotated CCW along with the Corsica-Sardinia block during its lower Miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector (Umbria domain), thus yielding the final curved shape of the Northern Apennines chain. Data from this study represent the first paleomagnetic evidence of the influence of the Corsica-Sardinia CCW rotation in the Apennines orogenic wedge deformation, in the general framework of the geodynamic evolution of the Central Mediterranean subduction system. © 2014. American Geophysical Union. All Rights Reserved.
2014, Articolo in rivista, ENG
Bonini M.[1], Sani F.[2], Stucchi E.M.[3], Moratti G.[1], Benvenuti M.[2], Menanno G.[3], Tanini C.[4]
The inner Northern Apennines (western Tuscany and Tyrrhenian basin) is characterized by a relatively thin continental crust (~20-25 km), high heat flow (>100 mW m-2), and the presence of relevant tectonic elision of stratigraphic sequences, a setting known as Serie Ridotta. These features are normally ascribed to an extensional deformation that affected the back-arc area above the subducting Adria plate since the Early-Middle Miocene (~16 Ma). However, various geophysical studies image the continental crust to becurrently affected by W-dipping thrust faults (and associated basement uplifts) that have not been obliterated by this claimed long-lasting extensional process. These observations raise the question whether the thrusts are older or younger than the continental extension. To address this question we have reprocessed and interpreted the deep seismic reflection profile CROP03/c that crosses the onshore hinterlandsector, and investigated the structural setting of some of the Late Miocene-Pliocene hinterland basins(Cinigiano-Baccinello, Siena-Radicofani, Tafone, Albegna and Radicondoli basins) that are situated at the front or in-between the basement uplifts. The analysis of field structures and commercial seismic profiles has allowed the recognition that both substratum and basins' infill have been intensely shortened.These findings and the architecture of the basins suggest that the latter developed under a contractional regime, which would have started around 8.5 Ma with the onset of the continental sedimentation. This compressive stress state followed an earlier phase of continental extension that presumably started at ~16 Ma (with the blocking of the Corsica-Sardinia rotation), and thinned both the continental crust and sedimentary cover producing most of the Serie Ridotta. The main phases of basin shortening are bracketed between 7.5 and 3.5 Ma, and thus overlap with the increase in the exhumation rate of the metamorphic cores at ~6-4 Ma determined through thermochronological data. We therefore propose a correlation between the basin deformation and the activity of the nearby basement thrusts, which would have thus shortened a previously thinned continental crust. This chronology of deformation may suggest a geodynamic model in which the back-arc and hinterland sector of the Northern Apennines was recompressed during Late Miocene-Early Pliocene times. This evolution may be explained through different speculative scenarios involving a blockage of the subduction process, which may vary between end members ofcomplete slab detachment and stalled subduction.
2013, Articolo in rivista, ENG
Maesano, Francesco Emanuele; Toscani, Giovanni; Burrato, Pierfrancesco; Mirabella, Francesco; D'Ambrogi, Chiara; Basili, Roberto
We present a reconstruction of the central Marche thrust system in the central-northern Adriatic domain aimed at constraining the geometry of the active faults deemed to be potential sources of moderate to large earthquakes in this region and at evaluating their long-term slip rates. This system of contractional structures is associated with fault-propagation folds outcropping along the coast or buried in the offshore that have been active at least since about 3 Myr. The ongoing deformation of the coastal and offshore Marche thrust system is associated with moderate historical and instrumental seismicity and recorded in sedimentary and geomorphic features. In this study, we use subsurface data coming from both published and original sources. These comprise cross-sections, seismic lines, subsurface maps and borehole data to constrain geometrically coherent local 3D geological models, with particular focus on the Pliocene and Pleistocene units. Two sections crossing five main faults and correlative anticlines are extracted to calculate slip rates on the driving thrust faults. Our slip rate calculation procedure includes a) the assessment of the onset time which is based on the sedimentary and structural architecture, b) the decompaction of clastic units where necessary, and c) the restoration of the slip on the fault planes. The assessment of the differential compaction history of clastic rocks eliminates the effects of compaction-induced subsidence which determine unwanted overestimation of slip rates. To restore the displacement along the analyzed structures, we use two different methods on the basis of the deformation style: the fault parallel flow algorithm for faulted horizons and the trishear algorithm for fault-propagation folds. The time of fault onset ranges between 5.3 and 2.2 Myr; overall the average slip rates of the various thrusts are in the range of 0.26-135 mm/yr. (C) 2012 Elsevier Ltd. All rights reserved.