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Scaled analogue models explored the role of different boundary conditions in intra‐caldera resurgence processes. Models investigated the role of magma intrusion depth (Series 1), asymmetric and symmetric caldera collapse (Series 2), as well as the presence of existing discontinuities in the pre‐volcanic substratum (Series 3) on the style of caldera resurgence. Experimental results indicate that different intrusion depths resulted in different resurgence styles and structural patterns, which evolved from piston‐like resurgence, for deeper intrusions, to intra‐caldera resurgent domes for shallower intrusions. Asymmetric collapse was typically accompanied by a tilted roof block above the emptied analogue magma reservoir, while inherited faults influenced significantly the deformation pattern of piston‐like resurgence. Experiments simulate many of the principal characteristics of calderas. We compare our modelling results primarily to the Los Potreros caldera nested within the Los Humeros Volcanic Complex, where the largest Mexico’s Quaternary eruption occurred and which hosts an important geothermal field (eastern Trans‐Mexican Volcanic Belt). A structural field survey was conducted to identify the kinematics of faults within the caldera and outside the volcanic edifice. The Los Potreros caldera shows a sub‐orthogonal fault pattern strikingly similar to that of models deformed with shallow intrusion depth. We interpret this correlation as an evidence of similarity in dynamic processes, whereby modelling results would indicate a scaled intrusion depth of approximately 4.5 km. The Acoculco caldera complex, in Mexico, shows a fault pattern similar to the Los Potreros caldera, and geological information corroborates the attribution of renewed magmatic pressure to similar intrusion depths.

This study is based upon a stratigraphic and structural revision of a Middle Jurassic-Upper Cretaceous mostly continental succession exposed between Boumalne Dades and Tinghir (Southern Morocco), and aims at reconstructing the relation among sedimentary, tectonic and magmatic processes that affected a portion of the Central High Atlas domains. Basalts interbedded in the continental deposits have been sampled in the two studied sites for petrographic, geochemical and radiogenic isotope analyses. The results of this study provide: (1) a robust support to the local stratigraphic revision and to a regional lithostratigraphic correlation based on new 40Ar-39Ar ages (ca. 120 Ma) of the intervening basalts; (2) clues for reconstructing the relation between magma emplacement in a structural setting characterized by syn-depositional crustal shortening pre-dating the convergent tectonic inversion of the Atlasic rifted basins; (3) a new and intriguing scenario indicating that the Middle Jurassic-Lower Cretaceous basalts of the Central High Atlas could represent the first signal of the present-day Canary Islands mantle plume impinging, flattening, and delaminating the base of the Moroccan continental lithosphere since the Jurassic, and successively dragged passively by the Africa plate motion to NE. The tectono-sedimentary and magmatic events discussed in this paper are preliminarily extended from their local scale into a peculiar geodynamic setting of a continental plate margin flanked by the opening and spreading Central Atlantic and NW Tethys oceans. It is suggested that during the late Mesozoic this setting created an unprecedented condition of intraplate stress for concurrent crustal shortening, related mountain uplift, and thinning of continental lithosphere.

This paper illustrates the results of a stratigraphic, sedimentologic and structural study of the continental succession exposed at the core of the Adrar Aglagal syncline, located at the southern front of the Central High Atlas (Morocco). This structure deforms a Lower Jurassic-Upper Cretaceous succession, resting unconformably on Triassic clastic and volcanic deposits. Marine-transitional Lower Jurassic limestone, dolomite and gypsum crop out at the syncline's limbs whereas the core is characterized by a continental clastic succession which is the local expression of a sedimentary complex regionally known as Couches Rouges (red beds). These continental successions, attesting to a Middle Jurassic-Lower Cretaceous regressive phase, have different interpretations in the frame of the tectono-sedimentary evolution of the Central High Atlas. According to some authors these red beds record localized early compressive-transpressive stages of deformation, others refer them to a period of tectonic quiescence. Facies analysis and recognition of unconformities have allowed a stratigraphic revision and a new subdivision of these, mostly fluvial, deposits in five units. Paleocurrent analysis, compositional data and the evidence of syn-depositional growth of the syncline support a picture of crustal shortening that affected this axial portion of the Central High Atlas in a period considered tectonically quiescent. This case study supports the hypothesis that the Moroccan Atlas system experienced significant relief formation, as the consequence of the peculiar geodynamic setting in which the northern margin of the Africa plate was located during the Mesozoic.

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Located at the south-western slope of the Mt. Amiata volcano (Tuscany, Central Italy), the Bagnore spring has been investigated for geochemical precursors of earthquakes from 2004 to 2015. Over this period, several parameters of the spring have been monitored by discrete and continuous sampling. An automatic continuous monitoring station, equipped with sensors for the measurement of temperature, pH, redox potential, electrical conductivity, CO2 and CH4 dissolved concentration, is transmitting the registered signals to the remote server in Pisa 150 km northwest of Mt. Amiata. The Bagnore spring drains a shallow, short-circuiting aquifer hosted in the volcanic rocks of the volcano. Its emergence point is located in proximity of the intersection of two major fault systems that are supposed to provide a preferential ascent path to hydrothermal gases, mainly represented by CO2(g) and H2S(g), locally rising from depth. The most evident change occurred in the registered signals over the period is represented by the sudden increase in CO2 concentration measured starting from April 2010. Along with this increase in CO2, a slight increase in water temperature and in SO4 concentration, associated to a decrease in pH, was also recorded. This trend has been interpreted as an evidence for the augmented inflow of deep gases into the shallow aquifer. The CO2 continuous signal recorded by the Bagnore automatic station has been then processed by applying multiple statistical techniques (i.e. artificial neural network analysis and Census I method) in the search for anomalies possibly related to local seismic activity. Anomalous signals have been detected starting from April 24, 2010, and the correlation with the most energetic seismic events has been tentatively proposed.

Two main magmatic events occurred during the Mesozoic evolution of the Atlas System, the first one dated to Late Triassic-Early Liassic (200-195 Ma), tied to the opening of the Central Atlantic Ocean (CAMP - Central Atlantic Magmatic Province - Event), the second dated from Middle-Late Jurassic to Early Cretaceous (~ 165-110Ma), within which K-Ar ages seem to cluster into two distinct groups, 175-155 Ma and 135-110 Ma. The post-Liassic magmatic rocks, possibly representing the last magmatic phases related to the CAMP event, are specific for the High Atlas domain, with the emplacement of (1) subvolcanic intrusive complexes, often cropping out in the cores of anticlinal ridges, and (2) basaltic lava flows, interbedded in the Middle-Late Jurassic to Early Cretaceous red beds. Their magmatic signatures, ranging from transitional basalt series to weakly/moderately alkaline series, are typical of continental intraplate magmatism and are usually considered as rift-related. In our work, we studied magmatic bodies (1) cropping at the core of anticlines and/or (2) interbedded in the red beds of the High Atlas, in the chain and at its southern front. The relationships observed between the magmatic products (2) and both the stratigraphic succession and structures, faults and folds, point to their possible emplacement as sills and to a development of the magmatism within an active, Jurassic-Cretaceous, compressive stress field. In particular, we present the first results obtained on two mafic magmatic bodies outcropping in correspondence of the South Atlas front. They are intruded at the core of anticlines folding Late Jurassic-Cretaceous rocks, or are interbedded within the vertical Late Jurassic-Cretaceous succession as a sub-effusive body. We present an important first radiometric 40Ar-39Ar dating obtained on a lava flow rock sample; the obtained age of 119 Ma, allows us to refer it to the second magmatic event of the High Atlas. We also present preliminary petrographic and geochemical compositional data of collected rock samples that display porphyritic and fluidal textures in the lavas and porphyroid textures with poikilitic crystals set in an ophitic matrix in dykes and sills. The studied rocks display a restricted compositional range, falling across the fields of basalts, trachybasalts and basaltic trachyandesites with alkaline to subalkaline affinity. We report here major and trace elements and isotopic compositions (87Sr/86Sr and 143Nd/144Nd) obtained on representative lava flow, dyke and sill rock samples.

Several large earthquakes reaching up to M>7 have affected Bulgaria, and testify a significant active tectonics whose associated seismicity threatens large portions of the territory. A detailed knowledge of the main active faults and the understanding of the current tectonic activity and seismicity is therefore fundamental to get a comprehensive picture of the seismotectonics of the region. We have undertaken a study based on field survey, seismicity and paleostress analysis, remote sensing and digital topography interpretation, and integrated this information in a comprehensive map of active faults. This exhaustive dataset provides fundamental information on the state of stress and the seismic proneness of different areas, and represents a first valuable step toward the elaboration of a complete and actualized seismotectonic map of Bulgaria. This has obvious implication for the study of seismic hazard, urban planning and civil protection and gives basic information to the knowledge of the active deformation and geodynamics of the region. Few examples highlight the information that can be derived from such a seismotectonic map. Southern Bulgaria, south of the Balkan mountains, is mainly affected by normal active faults, which accommodate a roughly N-S to NNE-SSW extension, which is likely related to the northern extent of the Aegean extensional system. Activity of these extension-related structures is responsible for some of the destructive earthquakes which affected Bulgaria in historical times, notably the 1904 Krupnik earthquake (7.2

This paper reports new data on biostratigraphy, stratigraphy and syn-sedimentary deformation of the so-called "Boeotian Flysch" cropping out in key areas in Central Greece (Levadhia, Parnassus, Iti). Because of its age, sedimentary evolution and mechanisms of the syn-sedimentary deformation, the Boeotian Flysch represents a key element providing useful hints on the Cretaceous paleogeography reconstruction of the Dinaric-Hellenic Chain and in particular on the obduction at the Jurassic-Cretaceous transition in the eastern continental margin of the Adria plate. We provide here a new detailed study of different features of the Boeotian Flysch, with particular emphasis on reconstructing and dating its stratigraphy. In particular, we recognized two distinct turbiditic systems: the Lower Boeotian Flysch (Tithonian?-Aptian) and the Upper Boeotian Flysch (Cenomanian-Coniacian), which are separated by a main unconformity marking a sedimentary hiatus lasting from Aptian p.p. to Albian. By means of the improvement of the age, stratigraphy and deformation history of this syn-tectonic turbidite deposit, we therefore contribute to better define the chronology of the early phases of the continental stage of obduction, and the following continental collision between Adria and Eurasia. The analyses of the collected data allowed us to propose for the Boeotian Flysch a deposition within an obduction-related foredeep basin associated with a flexural depression/flexural bulge due to crustal loading of westerly-directed ophiolite obduction.

The paper reports a revision of the tectonic-depositional evolution of the continental Cinigiano-Baccinello and Velona basins, located in the Amiata Volcano region, with special emphasis on the Messinian dynamics. Integration of facies analysis, magnetostratigraphy, and structural geology allowed a comparison of the evolution of these basins and a discussion of possible local to regional implications. At a local scale, crustal shortening, accommodated by thrust faults and related anticlines delimiting the basins, determined a dynamic physiographic and hydrographic scenario during the Messinian. Uplift of the tectonically-controlled shoulders was paired with pulses of subsidence in the basins that favoured the development of palustrine-lacustrine settings or endorheic alluvial plains. Stages of quiescent tectonics favoured fluvial incision of structural thresholds and the development of a south-directed drainage system, particularly developed during the late Messinian in coincidence with the Mediterranean Messinian Salinity Crisis. The dominant fluvial and clastic depositional pattern recorded in these basins during such a regional scale event points to local tectonic activity of the Northern Apennines playing a major role than the climatic, eustatic and geodynamic factors that controlled the Mediterranean region.

This paper and the associated 1:50,000 geological map are devoted to describe the geological features of the Monte Amiata region. The tectono-stratigraphic setting of Monte Amiata region includes, from bottom to top, 1) the pre-Neogene stack of tectonic units, made up of Tuscan, Sub-Ligurian and Ligurian Tectonic Units, 2) the Neogene sedimentary deposits and 3) the Plei -stocene Radicofani and Monte Amiata volcanoes. The pre-Neogene stack of tectonic units includes, from bottom to top, the Tuscan Nappe, belonging to the Tuscan Domain, and Canetolo Tectonic Unit, belonging to the Sub-Ligurian Domain. These tectonic units, regarded as representative of the thinned continental margin of the Adria plate, are topped by the Santa Fiora and Ophiolitic Tectonic Units, interpreted as remnants of the Ligure-Piemontese oceanic basin and its transition to the Adria continental margin. All the tectonic units of the pre-Neogene stack have been affected by folds and thrusts originated during the convergence related to the Europe-Africa motion during the Middle Eocene-Early Miocene. Subsequently, these tectonic units were affected by a widespread reduction of thickness of their successions due to low-angle normal faulting related to the Middle Miocene extensional tectonics. The Neogene sedimentary deposits unconformably overlie the pre-Neogene stack of tectonic units. They consist of Upper Miocene to Pliocene continental and marine sediments, filling the Cinigiano-Baccinello, Velona, and Siena-Radicofani basins, adopting an informal hierarchy of different stratigraphic units where the first order units are synthems. The Pleistocene Radicofani and Monte Amiata volcanoes are made up by high-K basaltic andesitic to shoshonitic volcanic rocks and by trachydacitic to trachytic and olivine-latitic volcanic rocks, respectively. The geological mapping has provided evidences of a complex tectonic setting resulting from a long-lived history shifting from Cretaceous to Early Miocene compressive events to Middle Miocene extensional tectonics and Late Miocene-Pleistocene contractional and extensional events during which the Pleistocene magmatic activity occurred. In this regard, the Monte Amiata region can be regarded as a key area where the final result of a 200 Ma long geological history of the Northern Apennines is exposed.

We use new structural and apatite fission-track data together with apatite fission-track and (U-Th)/He data from literature to examine the tectonic evolution of the continental Upper Valdarno Basin, in the hinterland sector of the Northern Apennines fold-andthrust belt. This basin is located in-between two structural ridges, the Chianti Mountains to the southwest and the Pratomagno to the northeast. In our interpretation, the Upper Valdarno Basin developed at ca. 3.4-3.3 Ma as pop-down synformal-shaped depression bounded and controlled by oppositely-verging thrust-related structures, namely the thrust system lifting the Chianti Mountains and the southwest-facing backfolds at the base of the Pratomagno. This evolution is compatible with the accelerated exhumation rates at 4-5 Ma documented through apatite fission-track data along both the Pratomagno and Chianti ridges. Shortening suffered by basin deposits is clearly manifested by the outcrop-scale reverse faults and thrust-related folds affecting the Late Pliocene sediments (Castelnuovo dei Sabbioni Synthem), which are well exposed in the Santa Barbara mine. These strongly folded deposits are overlain unconformable by Early Pleistocene sediments (Montevarchi Synthem), which display evidence for syn-depositional normal faulting. This suggests that the Upper Valdarno Basin experienced a phase of normal faulting that started at the base of Pleistocene (ca. 2.6-2.5 Ma) and likely produced the large southwest-dipping "Trappola Fault", which affects the southwestern margin of the Pratomagno displacing the earlier backthrusts and backfolds. Basin evolution can be thus basically framed into a two-phase history, with extensional tectonics superposed onto compressional structures that were deactivated by ca. 2.7 Ma. Being the Chianti Mountains part of the 250 km-long regional line of thrusts and thrust-related folds (the so-called "Tu - scan Nappe front"), the results of this study may also involve regional implications, as they would also hint for the tectonic history of other sectors and basins settled along-strike this regional element.

This paper describes a new tectonosedimentary model for the evolution of the Plio-Quaternary Sant'Arcangelo Basin, located in the Southern Apennines of Italy. To this purpose, we carried out a new field survey of the basin fill, closely integrating stratigraphy, facies analysis, and structural and tectonic analyses. The geological map at 1:50 000 scale of the whole basin is the first result of this work. We present a new stratigraphic framework for the Sant'Arcangelo Basin succession, which has been subdivided into five major stratigraphic groups, classified as synthems, following the recognition of major basin-wide unconformities. The synthems include smaller-scale stratigraphic units, which are classified as depositional sequences or sub-synthems. These sub-units are composed of different lithofacies assemblages recording cyclic activation of fluvial, deltaic, shallow marine and lacustrine environments throughout the evolution of the basin. Integration of facies analysis and tectonic data led to the definition of a series of palacogeographical sketches, encompassing the Piacenzian and late Pleistocene, which mark the main steps in the evolution of the Sant'Arcangelo Basin. Basin-scale hinterland-verging thrust faults and folds controlled the development of sub-basins and the progressive isolation of the Sant'Arcangelo Basin from the Ionian foredeep. The new model presented here defines the Sant'Arcangelo Basin as a triangular-shaped basin, bounded by oppositely verging thrusts. The hinterland-verging Valsinni thrust anticline limited its eastern margin and exerted a major control on the basin evolution.

The Sassa-Guardistallo Basin (SGB) is located close to the Tyrrhenian Sea and represents one of the most internal Neogene-Quaternary hinterland basins of the Northern Apennines fold-and-thrust belt. Its sedimentary succession consists of ca. 400-m-thick Late Tortonian-Messinian continental - largely conglomeratic - units overstepping a mainly shaly substratum (Palombini Shales) and overlain by Late Messinian evaporites and marine to continental Pliocene-Pleistocene sediments. This stratigraphic succession can be approximated to a composite rheological multilayer that dictated the style of basin deformation. Detailed geological mapping and structural analysis revealed that basin deposits were affected by compressional deformations that can be found both at map and outcrop scales. Decametric splay thrusts emanating from the substratum-conglomerate interface locally double the continental succession and are bounded by a roof thrust along the Late Messinian evaporite decollement, defining a deformation pattern consistent with a duplex-like structure. The time-space structural evolution of the basin inferred from the fieldwork was addressed and tested by analogue modelling that approximated the rheological stratification of the study area to a layered brittle-ductile system. The model results support the hypothesis that the evolution of the thrust system affecting the SGB started as an early floor imbricate fan thrust system that successively evolved to a duplex structure as the link thrusts propagated into the upper decollement layer that resulted from the deposition of the Late Messinian evaporites. Models display many structural features that may be compared with the natural prototype, and highlight the importance of syntectonic sedimentation in the development and evolution of tectonic structures. The results of this study retain relevant implications for the Neogene evolution of the Tyrrhenian Basin-Northern Apennines system. This study also supports that combining between field structural analyses and analogue modelling can give useful hints into the evolutionary history of tectonically complex areas.

This paper presents the results of an extensive chemical and isotopic investigation on natural thermal and cold fluids (spring waters and associated gases) discharging throughout the main geological domains of Morocco. The chemical features of the thermal springs are mainly dependent on rock dissolution involving Triassic evaporite formations, producing either Na-Cl or Ca-SO(4) composition, although mixing with shallower connate high-saline waters in Neogene post-orogenic sedimentary layers cannot be ruled out. Only in the Moroccan Meseta and Anti-Atlas domains have spring discharges probably undergone equilibration as a result of water-rock interaction in granites. Of the chemical and isotopic features of the gas seeps, (3)He/(4) He ratios and delta(13)C -CO(2) values indicate the occurrence of a significant contribution of mantle-derived gas, especially at Oulmes (Moroccan Meseta) and Tinejdad-Erfoud (Anti-Atlas), where associated waters are found to equilibrate at relatively high temperatures (c. 130 degrees C). These areas are also characterized by the presence of Pliocene to Quaternary basaltic volcanic rocks. Thermal discharges located along the Rif front and related to the NE-SW-oriented main strike-slip faults are associated with a CH(4)(-) and/or N(2)-rich gas phase, derived respectively from a crustal or an atmospheric source. Some of them have significant contents of 3 He that could indicate the rising of mantle fluids. Such a striking isotopic signature, which is not related to any recent volcanism visible at surface, is likely to be associated with cooling magma at depth related to transpressive fault systems. Similarly, in the northeastern area, the small, although significant, enrichment of (3)He in the gas discharges seeping out along the Nekor seismic active fault and related to Pliocene-Quaternary basalts also suggests a deep-seated (magmatic) contribution. The distribution of thermal discharges is strongly related to the main active tectonic structures of Morocco. Moreover, this study indicates the presence of deep active tectonic structures in areas until now considered as stable. In particular, the NE-SW-trending Nekor fault may be part of a major system that extends to the Moroccan Meseta and into the Smaala-Oulmes fault system, thus emerging as a deep structure with crustal significance.