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The Pamir belts, located NW of the Himalaya, formed in response to the Cenozoic collision and indentation of India with Eurasia. Several crustal blocks separated by complex and scarcely studied suture zones form the present day tectonic architecture of the Pamirs. The extreme crustal shortening resulted in strong deformation and bending of pre-existing Paleozoic to Mesozoic orogens. Such deformation hinders straightforward correlations between tectonic terranes of the Himalaya-Tibetan area with their potential continuations through the Pamirs into Afghanistan and Iran. Central and SE Pamir, together with Karakoram and Qiangtang blocks separated from the Gondwana margin in the Early Permian, drifted northward, following the closure of the Paleotethys and other minor oceanic branches, and diachronously collided with Northern Pamir and Tian Shan. The Central and South Pamir are now separated by the poorly known Rushan-Pshart Suture Zone. South Pamir is separated into two units: SE Pamir consists of a Permian to Cenozoic sedimentary succession; SW Pamir is instead made of gigantic basement domes that are in contact with the SE block along crustal scale detachments. In SE Pamir, intensively folded and faulted Permian and Triassic units are unconformably covered by lowermost Jurassic terrigeneous deposits, testifying for Middle to Lower Triassic tectonics related to the Cimmerian orogenic events. Along the contact between the SE and SW Pamir, a small (a few tens of km2 wide) magmatic-metasedimetary unit occurs, reported in literature as the Bashgumbaz ophiolites. They consist of a low-grade metamorphic association of serpentinized harzburgites and gabbros, minor bodies of diorite and plagiogranite, basalts and intermediate volcanic rocks, metasediments, and a flyschoid unit containing olistolithic blocks with Triassic faunas attributed to Central Pamir block. Petrographic and geochemical data suggest a supra-subduction zone affinity for the gabbroic complex. U-Th-Pb dating of zircons from a diorite provides a Carnian crystallization age. Deformation and metamorphism (up to greenschist facies) that affected the Bashgumbaz complex should therefore been placed in the Late Triassic. We suggest that the Bashgumbaz unit formed in a supra-subduction setting and was later underthrusted and then obducted onto the southern margin of the closing Rushan-Pshart ocean. The obduction of the Bashgumbaz ophiolites could be considered as a time-marker for the accretion of the South Pamir terrane to the Eurasian margin.

Rockfall quantitative risk analysis in areas impended by high, subvertical cliffs remains a challenge, due to the difficult definition of potential rockfall sources, event magnitude scenarios and related probabilities. For this reasons, rockfall analyses traditionally focus on modelling the runout component of rockfall processes, whereas rock-fall source identification, mapping and characterization (block size distribution and susceptibility) are over-simplified in most practical applications, especially when structurally complex rock masses are involved. We integrated field and remote survey and rock mass modelling techniques to characterize rock masses and detect rockfall source in complex geo-structural settings. We focused on a test site located at Valmadrera, near Lecco (Southern Alps, Italy), where cliffs up to 600 m high impend on a narrow strip of Lake Como shore. The massive carbonates forming the cliff (Dolomia Principale Fm), normally characterized by brittle structural associations due to their high strength and stiffness, are here involved in an ENE-trending, S-verging kilometre-scale syncline. Brittle mechanisms associated to folding strongly controlled the nature of discontinuities (bedding slip, strike-slip faults, tensile fractures) and their attributes (spacing and size), as well as the spatial variability of bedding attitude and fracture intensity, with individual block sizes up to 15 m3. We carried out a high-resolution terrestrial photogrammetric survey from distances ranging from 1500 m (11 camera stations from the opposite lake shore, 265 pictures) to 150 m (28 camera stations along N-S directed boat routes, 200 pictures), using RTK GNSS measurements for camera station geo-referencing. Data processing by Structure-from-Motion techniques resulted in detailed long-range (1500 m) and medium-range (150 to 800 m) point clouds covering the entire slope with maximum surface point densities exceeding 50 pts/m2. Point clouds allowed a detailed reconstruction of 3D topography, fold mapping and characterization of orientation, intensity and size of slope-scale discontinuities. Due to the structural complexity, interpretation of discontinuity features associated to different fold sectors (i.e. limbs and hinge zone) required adetailed field description of small-scale structural features including slickensides, veins and joint associations, impossible to be detected in point clouds. This information allowed generating Discrete Fracture Network models in FracmanTM, which provided a robust description of rock mass structure, accounting for the controls of slope-scale folding processes on rock mass structure. Block size distributions and locations of potentially unstable blocks were derived from the DFN model of the cliff, providing valuable input to the definition of realistic scenarios for rockfall modeling and quantitative risk analysis.

The Pamir belts, located NW of the Himalaya, formed in response to the Cenozoic collision and indentation of India with Eurasia resulting in strong deformation and bending of pre-existing Paleozoic to Mesozoic orogens. Several crustal blocks separated by complex and scarcely studied suture zones form the present day tectonic architecture of the Pamirs. The extreme crustal shortening experienced by the Pamirs during the indentation of India hinders straightforward correlations between tectonic terranes of the Himalaya-Tibetan area with their potential continuations through the Pamirs into Afghanistan and Iran. Existing stratigraphic and paleontological data suggest that Central and SE Pamir, together with Karakoram and Qiangtang blocks separated from the Gondwana margin in the Early Permian, drifted northward, following the closure of the Paleotethys and other minor oceanic branches, and diachronously collided with Northern Pamir and Tian Shan. The Central and South Pamir are now separated by the Rushan-Pshart Suture Zone that extends E-W from the E-Pamir Fault ??? to the valley of the Panj River. South Pamir is separated into two units (SE and SW Pamirs) by a crustal scale detachment system that brought in contact the Permian to Cenozoic sedimentary succession of the SE block with the gigantic basement domes of the SW block, made of Precambrian metamorphic rocks with an high-T overprint of Miocene age. In SE Pamir the occurrence of Cimmerian tectonics is proved by lowermost Jurassic deposits resting in unconformity on intensively folded and faulted Permian and Triassic units. On the base of available data the suggested collision age of SE Pamir with Central Pamir is roughly bracketed between Middle Triassic to Early Jurassic. Along the contact between the SE and SW Pamir, a small (a few tens of km2 wide) ophiolitic unit occurs: the Bashgumbaz ophiolites. They consist of a low-grade metamorphic association of serpentinized harzburgites and gabbros with minor bodies of quartzdiorite and plagiogranite including olistolithic blocks with Triassic faunas related to Central Pamir by previous authors. Geochemical data suggest a supra-subduction zone affinity for the gabbroic complex. Significant enrichment in LILE and LREE compared to HREE, coupled with negative anomalies of Nb, Ti, Zr and other HFSE is coherent with this interpretation. U-Th-Pb dating of zircons from a quartzdiorite provides a Carnian crystallization age. Deformation and metamorphism (up to greenschist facies) that affected the Bashgumbaz complex should therefore been placed in the Late Triassic. We suggest that the Bashgumbaz ophiolites formed in a supra-subduction setting and were later underthrusted and then obducted onto the southern margin of the closing Rushan-Pshart ocean. The obduction of the Bashgumbaz ophiolites could be considered as a time-marker for the accretion of the South Pamir terrane to the Eurasian margin.

Deep seated gravitational slope deformations (DSGSD) evolve over several thousands of years in changing environmental conditions, under the influence of multiple triggering processes. Although glacial and fluvial erosion, deglaciation processes and slope hydrology perturbations are recognized to be common drivers of these phenomena in alpine environment, there is evidence of possible effects of seismicity on their initiation and development. A major difficulty in quantifying such effects is related to the involved timescales. In fact, while earthquake-induced, instantaneous slope instabilities can be studied with reference to specific earthquake scenarios, a considerably large number of seismic events of different magnitude and recurrence may contribute to slope instability and displacements on the typical DSGSD timescale, possibly leading to catastrophic rock slope instabilities over the long-term. In this work, we used numerical modelling to investigate the effects of long-term seismicity on a DSGSD, affecting the Piz Dora (Val Müstair, E Switzerland) over an area of 12 Km2 and with a 1500 m local relief. The slope is made of a sequence of Austroalpine conglomerates, meta-conglomerates and phyllites, folded into a kilometrescale anticline setting geometrical and geomechanical constraints on the large slope instability. The area has been experiencing tectonic uplift and fault activity since the Pliocene, and is characterized by frequent present-day shallow seismicity with maximum magnitude Mw>5 and dominant dip-slip mechanisms. After the Last Glacial Maximum (LGM), the slope experienced the removal of about 1000 m of ice. Morpho-structural characterization of DSGSD features and their relationships with glacial deposits and different generations of periglacial features (rock glaciers and protalus ramparts) allowed reconstructing a complex relative chronology of slope displacements and establishing local constraints on deglaciation. We used these constraints to validate a series of continuum 2D FEM dynamic simulations, set up starting from the signal characterization of a real earthquake occurred in 1999 few kilometers from the slope in a similar litho-structural seismo-tectonic setting. Available seismic hazard maps were used to scale in terms of PGA the dynamic input and describe events with specified return time. These were applied at the model base before, during and after slope deglaciation history, constrained by relative post-LGM paleoclimatic evidence. Comparison between static and dynamic simulations suggests a notable contribution of repeated seismic events to strain accumulation in different slope sectors, promoting the onset of DSGSD in marginally stable deglaciating alpine rock slopes.

The western Tauern Window is a key area for the reconstruction of the tectonic evolution of the Eastern Alps. Here basement units derived from the European margin are stacked together with their parautochthonous post-Variscan cover in a south-vergent crustal scale duplex that also involves the Glockner nappe (calcschists and ophiolites derived from the Penninic ocean). The major lithostratigraphic units comprise: i) a polymetamorphic basement consisting of mainly amphibolites, migmatites, orthogneisses, and locally pre-Mesozoic ultramafic to mafic bodies; ii) the Tux and Zillertal orthogneiss (part of the “Zentralgneiss Auct.”) that intruded unit (i) during early Permian times; iii) the parautochthonous metasedimentary cover including meta-conglomerates, calcitic and dolomitic marbles, calcareous micaschists, quartzites, and subordinate greenschists. iv) the Glockner Nappe, it consists of km-thick sequences of calcschists with interbeddings of prasinites, amphibolites and ultramafic bodies. Along the tectonic contact between the northern and southern duplex antiforms a slice (about 1km-thick, wedging out westward) of graphite-rich garnet micaschists with minor quartzites and calcschists (“Greiner schists” Auct.) occurs. Two phases of roughly coaxial isoclinal folding, the first one of these responsible for the regional foliation, have been recognized in the post-Variscan cover of the “Zentralgneiss”. A pronounced stretching lineation, parallel to fold axes and ascribed to a strong flattening is well developed in quartz-rich rocks. An amphibolite facies metamorphic stage characterized by static recrystallization of micas, garnet and amphibole (“Garbenschiefer” Auct.) is well recognizable in the post-Variscan metasedimentary units whereas its occurrence remains controversial in the Glockner nappe. This point still need to be resolved as the formation of the regional scale duplex, involving all described unit, is generally interpreted to had predated the static crystallization (“Tauercristallisation” Auct.). Late stage doming of the duplex, associated to folding at the mesoscale, caused eventually the present day structure with the two antiformal Tux and Zillertal domes. In the frame of the of the South Tyrol Province CARG project, devoted to 1:10000 mapping of the Vipiteno sheet, the goal of this work is to provide structural and petrological constraints to identify tectonometamorphic units with coherent structural and metamorphic evolution. Preliminary results display significant differences among the reconstructed P-T paths of the Glockner schists and metasedimentary rocks of the post-Variscan cover of the Tux and Zillertal gneisses. The generally accepted model for the tectonic evolution of the western Tauern Window does not provide full account for these features. Further analyses are therefore needed to unravel earlier stages of metamorphic history of the several units and define the ambient conditions at which nappe stacking occurred.

The Austroalpine nappe stack to the west of the Tauern Window is made of three main tectonometamorphic units that are, from top to bottom: the Ötztal-Stubai complex, the Schneeberg and the Texel units. The Ötztal-Stubai complex consists of a polymetamorphic basement and Permian-Mesozoic sedimentary rocks that underwent metamorphism and deformation during the Alpine orogeny. E and NE of Vipiteno (Schneeberg, Telfer Weissen, Tribulaun) the nonconformity surface between basement and the metasedimentary succession has been mapped in details in the frame of the CARG project of the Provincia Autonoma di Bolzano-Alto Adige. As the non-conformity is still roughly preserved, structural investigations across such discontinuity are useful to reconstruct the Alpine deformation history. Mafic to intermediate dikes that cut across the basement regional foliation but do not intrude the post-Variscan cover are additional structural markers. The Ötztal cover consists of a metaconglomerate (Basal Conglomerate Auct., Permian), containing quartz, gneiss and garnetite clasts, a thin level (1-20 meters thick) of quartz-carbonatic schists, calcitic-dolomitic marbles, graphitic calcschists and, at the top, dolomitic marbles. Even if the non-conformity between the basement and the overlying metaconglomerates is variably interested by shear zones, the occurrence in the metaconglomerate of clasts strictly deriving from the underlying basement suggests that displacement due to shearing is limited: garnetite clasts occur only in the Schneeberg area where garnetite levels, not found elsewhere, occur within Ötztal micaschists. Alpine deformation resulted in a penetrative foliation in the sedimentary cover coupled with a stretching lineation due to a top-to-W (NW) shearing. Mafic-intermediate dikes are substantially undeformed, displaying only a faint foliation close to the contacts with host gneisses. The Ötztal basement did not have suffered penetrative recrystallization and deformation during the Alpine cycle: dikes cut across not only the regional foliation but also the last fold system that fold it. P-T estimates constrain metamorphic condition in metaconglomerates and dikes at 450-500°C and 0.8-1.0 GPa. Ar-Ar dating of micas aligned along the main foliation in conglomerates and recrystallized biotite in dikes provide ages of about 85 Ma. These data are very close to the age of the eclogitic metamorphism in the Texel unit and the HP amphibolite facies metamorphism in the Schneeberg complex. All together these data suggest that metamorphic peak conditions were experienced roughly contemporaneously by the three units when they were at different crustal levels. During exhumation, the HP Texel unit was first coupled with the Schneeberg unit (the two units show a common evolution since the amphibolite facies re-equilibration of the Texel eclogites) and then the Schneeberg-Texel was brought in contact with the Ötztal basement and cover at shallow crustal level.

Deep-Seated Gravitational Slope Deformations (DSGSD) are widespread phenomena in alpine environments, where they affect entire high-relief valley flanks involving huge rock volumes. Slope scale inherited structures related to ductile and brittle tectonic deformation can control the onset and development of DSGSD and the localization of strain in deep gravitational shear zones. Slope unloading, rock mass damage and hydrological perturbations related to deglaciation are considered important triggers of these phenomena in formerly glaciated areas. Furthermore, earthquake shaking and the long-term effects of seismicity in active tectonic areas might provide an additional triggering component. Nevertheless, the role played by these different processes and their interplay is not obvious, especially in geological context less typically favourable to DSGSD and in low-magnitude seismicity settings as the axial European Alps. We analysed the Piz Dora sackung system (Val Mustair, Switzerland), which affects conglomerates, metaconglomerates and phyllites of the Austroalpine S-Charl nappe, involved in a slope-scale, WNW trending closed anticline fold. The area is actively uplifting, seismically active (maximum Mw>5) and experienced extensive glaciation during the LGM. The slope is affected by sharp gravitational morphostructures associated to the deep-seated sliding of 1.85 km3 of rock along a basal shear zone up to 300 m deep (Agliardi et al., 2014; Barbarano et al., 2015). We investigated the controlling role of inherited tectonic features and the relative influence of different candidate triggering processes (post-glacial debuttressing, related changes in slope hydrology, seismicity) through a series of 2D Distinct Element (DEM) numerical models set up using the code UDEC (ItascaTM). Based on field structural and geomechanical data, we discretized the slope into an ensemble of discontinuum domains, accounting for the slope-scale folded structure and characterised by unique combinations of rock mass properties and persistent brittle structural patterns related to folding or regional stress fields. We analysed the processes leading to DSGSD onset and evolution by testing combinations of: a) rock mass constitutive models; b) in situ stress fields; c) hydro-mechanical coupling; d) dynamic loadings. DEM results, validated using field evidence and discussed against the results of continuum-based Finite-Element models (Agliardi et al., 2014; Barbarano et al., 2015), suggest that DSGSD failure mechanisms are constrained by fold-related brittle structures, and stress and hydrologic conditioning of deglaciation were key triggers modulated by active tectonic processes.

The Iran microplate is part of the Cimmerian blocks which rifted off Gondwana in the Early Permian and collided with the Southern Eurasian margin in the Late Triassic due to the closure of the Palaeotethys ocean. The presence of several ophiolite belts in Iran dating between Late Palaeozoic to Triassic poses several questions on the possible existence of various sutures marking the closure of the Palaeotethys ocean between Eurasia and Iran. Late Palaeozoic complexes with a Carboniferous “Variscan” age have been also described in N Iran, along the Alborz range, and in NE Iran, along the Late Triassic Palaeotethys suture, and they are generally related to the Late Palaeozoic evolution of the southern Eurasian margin, consisting of a mosaic of small continental blocks. In this general frame, the Anarak Metamorphic Complex (AMC), located in Central Iran, presently far from the pre-Late Triassic suture zones, is still an open problem. Detailed structural, petrographic and geochemical analyses have been carried out in these last years through the DARIUS PROGRAMME and an Italian PRIN. The AMC, which consists of several metamorphic units including dismembered “ophiolites”, displays different tectono-metamorphic evolutions. The Morghab and Chah Gorbeh complexes, mainly consisting of metapelites associated with metabasites and thick marble layers display a M1 metamorphism characterized by blueschist relicts along the S1 foliation in the former, and greenschist assemblages in the latter. They share a similar D2 deformational and M2 metamorphic history showing a prograde metamorphism with syn- to post-kinematic growth of blueschist facies phase assemblages. Prograde metamorphism characterized by the syn- to post-D2 growth of sodic amphibole has been recognized also in marbles at the contact between this unit and serpentinites. Evidence of HP/LT metamorphism also occur in Mg-riebeckite-bearing metapillow lavas and serpentinites, which are characterized by the coexistence of lizardite with antigorite. Structural analyses showed that the Chah Gorbeh and Morghab units and the “ophiolites” have been tectonically coupled within an accretionary wedge before the D2 folding stage. The other units of the AMC lack evidence of HP metamorphism around Anarak, especially the Lakh Marble, a large thrust sheet that occupies the uppermost structural position in the AMC. Available radiometric ages of undeformed trondhjemites intrudeding the wedge, as well as our new data constrain the subduction event at the end of the Carboniferous, before 290 Ma. These data suggest that the AMC may be part of an allochthonous crustal fragment being part of the Variscan belt developed along the southern Eurasian margin before the Cimmerian collision of Iran. Subsequent deformational events occurring during the Mesozoic and the Cenozoic, up to the Miocene, dismembered the original structure of the wedge accompanying its displacement to the present day position.

Here we show that the sedimentary succession of SE Pamir comprises a syn-rift succession (Bazar Dara Group) in the Carboniferous-Early Permian, followed by a marked deepening from the late Early Permian, with increasing volcanic activity and synsedimentary tectonics in the Gan and Takhtabulak formations, related to the opening of the Rushan ocean between South and Central Pamir; carbonate deposition characterizes most of the Triassic, but then Upper Triassic flysches record the progressive closure of the Rushan ocean. We also show that this Permian-Triassic stratigraphic and biotic evolution broadly matches that of Karakoram. We consider these blocks plus Central Pamir equivalent to the Qiantang Terrane of Tibet, all of Palaeozoic Gondwanan ancestry, which detached from Gondwana in the Early Permian to form the Cimmerian belt. This was dissected into distinct terranes separated by deep extensional basins (i.e. the Rushan basin between SE Pamir and Central Pamir, the Wakhan basin between SE Pamir and Karakoram; the Shuanghu basin in Qiangtang). The northward drift of this composite belt from the Gondwanan margin since the late Early Permian onward is well supported by statistical palaeobiogeographical se analyses which show that the biotic affinity of its blocks shifted from Gondwanan in the Asselian-Sakmarian (Early Permian) to Palaeoequatorial in the Roadian-Wordian (Middle Permian). We also show the occurrence of lowermost Jurassic deposits suturing intensively faulted and folded Permian and Triassic units, which record a marked Cimmerian unconformity, suggesting that South Pamir collided against Central Pamir along the Rushan-Pshart suture at the T-J boundary. The closure of the Rushan ocean was at least in part coeval to the closure of the Palaeotethys, which caused the collision of Central Pamir against North Pamir, at that time located at the southern Eurasian margin. Collision of Karakoram to South Pamir happened slightly later along the TBZ zone. Progressive time shifting of deformation can thus be related to the complex setting of the Cimmerian belt, which was subdivided into minor blocks by incipient oceanic basins, providing strong crustal mobility

Current palaeotectonic models see the Alps chiefly as a collisional orogen, ith the Southalpine retrobelt developed only as a post-collisional feature. New structural and geochronological data show, instead, that the continental margin of Africa-Adria was being structured as a doubly vergent orogen during subduction of Alpine Tethys in the Cretaceous, tens of million years before collision with Europe. Subduction is envisaged here to have nucleated in the latest Albian/Cenomanian within the attenuated Adriatic margin. Most continental slivers exhumed as eclogites in the xial part of the Cretaceous orogen contain gabbros and relics of HT/LP metamorphic rocks, indicating inheritance from Permian to Jurassic rifting. Cretaceous shortening in the Southalpine retrobelt is indicated by several lines of evidence, including orogen-derived turbidites and syn-sedimentary compressional activity since the Cenomanian, Upper Cretaceous pseudotachylytes dating major S/SE verging thick-skinned thrusts, and widespread fold-and-thrust deformation cut by Eocene plutons and dikes

""Paleomagnetic results from Oligocene-Miocene sedimentary units in central Iran are used to reconstruct the history of Neogene tectonic deformation of this region. Paleomagnetic data show that in central Iran, crustal blocks bounded by sets of strike-slip faults are rotated to accommodate NNE-SSW shortening related to Arabia-Eurasia convergence. Counterclockwise rotations of 20 degrees-35 degrees have been measured in the Tabas and Anarak areas, south of the Great Kavir fault, characterized by the presence of N-S to NNW-SSE right-lateral strike-slip faults. Conversely, in the Great Kavir and Torud areas, where ENE-WSW left-lateral strike-slip faults have been recognized, paleomagnetic results are less conclusive because the small amount of measured clockwise rotation shows a statistical uncertainty, which also includes the possibility of no rotation. Some of these faults have been active during the Quaternary up to present day, suggesting the possibility that block rotation is still occurring in central Iran.""

The new Merano sheet (scale 1:50,000) depicts one of the most complex portions of the central-eastern Alps, extending across the Insubric line. The mapped area includes the Southern Alps, exposed SE of the fault system, and a large area belonging to the Austroalpine domain NW of it. Several tectono-metamorphic units have been distinguished in the Austroalpine domain, based on the definition of their structural and metamorphic evolution and on the occurrence of brittle to ductile shear zones along their boundaries. In the SW part of the sheet four units have been distinguished: the Ultimo and Tonale units belonging to the Tonale nappe, the Marlengo tectonic slice and the Pejo unit, the last one related to the Ortler-Campo nappe. The Ultimo unit extends in a small area between the N-Giudicarie and the S. Elena lines and consists of two-micas staurolite and kyanite paragneiss (TUN), and orthogneiss (TUO). The Tonale unit crops out along the lower segment of the Ulten Valley, forming the northern end of the unit. It is separated from the Ultimo unit by the mylonites of the S. Elena line and from the Marlengo tectonic slice by brittle-ductile shear zones. In the northern part, the Tonale unit is directly juxtaposed to the Southalpine basement along the N-Giudicarie line. The unit mainly consists of sillimanite gneiss (TTP) with minor amphibolites (TTA), often with garnet (TTAa). Pegmatite dykes (OGA) crosscutting the S2 foliation occur close to the Insubric line. The structural setting of this unit is very complex, due to the occurrence of pervasive cataclastic shear zones possibly coeval to the activity of the Periadriatic fault system. The Marlengo slice forms a 5 km wide, sinuous, NNE-SSW trending strip extending between Rifiano and the southern boundary of the sheet. The unit is bounded by the left-lateral cataclastic shear zones of the Forst fault, by the Pavicolo line, the N-Giudicarie line, and finally by the Passeier line N of Merano separating its NE part from the Scena and Punta Cervina units. The unit forms a complex wedge between the Ortler-Campo and the Tonale nappes to the south, whereas to the north it crops out between the Texel unit and the Southalpine basement. The Marlengo tectonic slice has been defined due to its peculiar composition. In fact, no pegmatite and marble layers, common in the Ortler-Campo nappe, occur in this unit. In addition, the regional trend of the S2 foliation is almost different from the one shown by the surrounding units, suggesting a sharp structural separation. The unit includes quartzite gneiss (OUP), banded gneiss (OUPa), garnet,staurolite and kyanite mica schists (OUM), with orthogneiss (OOR), leucocratic orthogneiss (OUO), quartzite (OUQ) and amphibolite (OUA). The Pejo unit forms the entire southern slope of the Vinschgau Valley between Naturno and Forst, extending from the Adige river up to the watershed and also beyond it. The Forst fault separates this unit from the Marlengo tectonic slice, whereas to the north it is separated from the Texel unit by the Thurnstein mylonites, which show a normal to left-lateral kinematics. The Pejo unit displays a medium-grade metamorphism, probably Variscan in age, followed by an Alpine greenschist facies re-equilibration. Two micas gneiss (OOP) with a pervasive mylonitic foliation dominate along the Vinschgau Valley below 1700 m a.s.l. They are often associated with migmatitic-like layers and lenses of foliated Permian pegmatite dykes (OGA), and orthogneiss (OOG). Amphibolite (OAF) and marble layers (OMA) also occur. In the upper part of the unit, garnet and staurolite mica schists (OMI) are exposed, with minor amounts of amphibolite (OAF), Marble (OMA), and quartzite (OQU). Metadiorites (OGD) and metagabbros (OGDa), possibly Permian in age, intrude the unit. The Texel (Tessa) unit, including most of the Tessa massif, crops out west of the Passirio river extending to the Monteneve unit to the north. The Passirio fault to the east and the Thurnstein mylonites to the south also bound the unit. Two main features characterize the Texel unit: the Parcines orthogneiss (OTH), which are considered Lower Palaeozoic (Caledonian) meta-intrusives, and the occurrence of a penetrative Alpine metamorphism. The Texel unit displays a polyphase metamorphic evolution with a dominant syn-D2 amphibolite facies imprint of Alpine age, followed by a pervasive greenschist facies retrogression during a D3 event. Eclogites (D1) are locally preserved as small boudins within garnet amphibolites. Garnet amphibolites with plagioclase or amphibole+plagioclase symplectites are also widespread. An HP syn-D1 metamorphic event is also recorded in the metapelites of the unit. Radiometric data constrain the eclogitic event at 85 Ma. The Texel unit mainly consists of banded paragneiss (OTP), garnet- and staurolite-mica schists (OTM), with amphibolite (OTF) with eclogitic relics (OTE), quartzite (OTQ), thick marble layers (OTB), and calc-schists (OTC). The upper part of the unit, rich in marble and calc-schists layers forming the transition between the Texel and the Monteneve unit, was previously related to the so called “Laas Serie” attributed by several authors to the Monteneve unit. Nice folds with superposed interference patters resulting from the D1+2 and D3 deformational events are exposed in the high peaks of the Tessa massif. Steeply plunging folds characterize the last important stage of ductile deformation (D3) especially in the Pfossen Valley close to the boundary with the Monteneve unit. The Parcines orthogneiss (OTH) largely extends in the central-southern part of the unit forming a large WSW-ENE trending body including also well preserved meta-intrusive (OTL) with relics of intrusive textures. The Monteneve unit is exposed in a small area along the high mountain ridge separating Italy from Austria in the NE part of the sheet. The contact with the underlying Texel unit is often marked by discontinuous mylonitic shear zones. The Monteneve unit here includes mica schists with large garnets (OSF), amphibolite (OSA), often rich in garnet (OSAa), thick garnet-rich quartzite layers (OSQ), marbles (OSB), and calc-schists (OSC). This peculiar lithological association has been traditionally considered as a monometamorphic unit, that experienced only Alpine metamorphism with peak metamorphic conditions close to the eclogiteamphibolite facies transition. We suggest that at least 3 different deformational events affected the unit, the last one (D3) being in common with the evolution of the Texel unit. The Monteneve unit is deeply involved in the D3 folds, also affecting the tectonic boundary with the Texel unit. East of the Passirio River, four tectono-metamorphics units are exposed: the Scena, Punta Cervina, Pennes and S. Leonardo units. Common features are a general pre-Alpine radiometric age of minerals, and the occurrence of important NNW-dipping shear zones marking their tectonic boundaries, which are sharply cut by the late Tertiary left-lateral Passirio fault. The Scena unit extends in the southernmost part of the area between the Insubric and Rio Masul lines. It mainly consists of garnet-staurolite-sillimanite gneisses (OVP) and mica schists (OVM) with minor amphibolites (OVA), and amphibolic gneisses. Mylonitic marble layers (OVB), and quartzite (OVQ) occur close to the Insubric line. The occurrence of sillimanite replacing garnet and, locally, of K-feldspar within garnet-biotite gneisses, indicates higher temperatures with respect to the nearby Punta Cervina and S. Leonardo units during the Variscan evolution. A large pegmatite dyke (OGA) crops out at the old mine of Rio Masul. The Punta Cervina unit is directly located north of the Scena unit forming a NW-SE trending belt developed in the hanging wall of the Rio Masul shear zone. The Punta Cervina unit is bounded to the north by the mylonites of the Pennes unit. The Punta Cervina unit consists of garnet-kyanite-staurolite gneiss (OCP and OCPa), with large kyanite crystals (up to 10 cm). Minor amounts of amphibolite (OCA), quartzite (OCQ), and thick layers of granitic gneisses (OCO) also occur. The km-thick high-angle NW-dipping shear zone of Rio Masul, forms the southern part of the unit; it consists of mylonitic gneisses (OCX) including other lithologies characterized by a pervasive mylonitic fabric with superimposed discrete cataclastic fault zones often injected by pseudotachylyte veins. Fine-grained ultramylonites show greenschist facies conditions with stable biotite. The kinematics of the shear zone strongly recalls the Merano-Mules line, showing an almost along-dip stretching lineation and a top-to-the SE shear sense. The Pennes unit forms a few km large stripe between the S. Leonardo unit to the north and the Punta Cervina unit to the south. This poorly known unit represents an important intra-Austroalpine shear zone extending from the Passirio Valley to Vipiteno out of the mapped area. It includes mylonitic orthogneiss (OPG) and deformed but poorly metamorphic metasediments. Metaconglomerates with metasandstones (OPC), and carbonates (OPD), belonging to the Permian to Triassic Austroalpine sedimentary cover, are preserved along the Sarentino-Passiria watershed. The shear zone shows a complex polyphase evolution recording a progressive exhumation from ductile to brittle condition. A mylonitic fabric with white mica, chlorite and quartz ribbons occurs both in metasandstones and in the deformed orthogneiss. Stretching lineations mainly suggest a motion of the top to the S/SW. The mylonitic shear zone is overprinted by right-lateral brittle-ductile shear zones. The S. Leonardo unit crops out in the NE part of the sheet, north of the Pennes unit. It extends up to the normal left-lateral Giovo fault out of the Merano sheet. It mainly consists of retrogressed garnet-staurolite gneisses (OJP), with orthogneiss derived from a granitic protholith (OJO), showing large K-feldspar porhyroclasts (OJF). Mica schists (OJM), quartzite (OJQ) and amphibolite boudins (OJA) have been also mapped. The Southern Alps domain is localized in the SE sector of the Sheet, SE of the Insubric Line, and is characterized by the absence of any Alpine metamorphic overprint. This domain includes a Variscan metamorphic basement, intruded by lower Permian acid plutons (Ivigna and Monte Croce bodies) and several related dykes. The basement is covered by: a) a thick Lower Permian sub-aerial volcanic sequence (Athesian Volcanic Group); b) an Upper Permian-Lower Triassic sedimentary cover of continental and shallow water marine sediments (Valgardena Sandstones and Werfen Fm). The metamorphic basement mainly consists of garnet bearing phyllites (+ biotite, muscovite, plagioclase, chlorite) and acid meta-volcanites (“porfiroidi” Auct.) with minor muscovite quartzites and metabasites. The metamorphism is Variscan (350-320 Ma) and the metamorphic grade reached the greenschist facies (garnet sub-facies) with a metamorphic peak around T ∼ 460-520°C (for P ∼ 0.3-0.5 GPa). The S2 schistosity is cut by many rhyodacitic dykes and by two huge intrusion bodies: the Ivigna Granodiorite and the Monte Croce Granodiorite; both of them form NE-SW elongated plutons emplaced ∼ 285 Ma very close to the Insubric Line and are composed by granodiorite - monzogranite calcalkaline rocks. Their emplacement was related to an extensional-transtensional regime in the Lower Permian, which produced voluminous basic to acid volcanic and plutonic rocks in the Southern Alps. The volcanic activity, during a span of 10 Ma (285-274 Ma), gave rise to the Athesian Volcanic Group and to the formation of large calderas: a thick succession (up to 2000 m outside this Sheet) of lavas and pyroclastic flow deposits (lapilli tuff - ignimbrites) with minor pyroclasic surge. The composition ranges from andesitic to rhyolitic with a general evolution from basic-intermediate to acid. Continental silico-clastic sedimentary deposits are present at the base (Conglomerato Basale) and inside the volcanic sequence. The basal conglomerate is clearly erosive on the metamorphic basement and starts the volcanic cycle, which is covered by the Upper Permian Valgardena sandstones, a continental silicoclastic formation, erosive on the upper volcanic formations (IGG or ORA). The sedimentary cover ends in this area with the Werfen Fm (Upper Permian p.p. - Olenekian p.p.): an alternation of carbonate-silico-clastic deposits of shallow water marine sediments, representing a general marine transgression. In the Merano sheet area, the Austroalpine units are juxtaposed to the South Alpine domain along the Insubric Line (Periadriatic fault system), which includes two different branches, both representing a restraining bend of the fault. They are: the NNE-SSW trending N-Giudicarie line south of S of Merano, and the NE-SW trending Merano-Mules line east of the town, both dipping at high angle respectively to WNW and NW, and showing an important N-side-up component. Oligocene magmatism is recorded along the line by the occurrence of thin foliated tonalite bodies (TLG). Radiometric ages on mylonites and pseudotachylytes along the North Giudicarie segment of the fault also suggest deformation around 30 Ma, possibly continuing up to 22 Ma (Müller et alii, 2001). The N-Giudicarie line forms the northern termination of the Giudicarie fault system. The hanging wall consists of paragneiss of the Tonale unit intruded by poorly deformed pegmatite dykes. Low grade S-C mylonites show a superimposed cataclastic fabric mainly indicating a left-lateral motion of the fault. The footwall comprises the low grade phyllite of the Bressanone unit showing contact metamorphism with the Permian Mt. Croce granodiorite. The Merano-Mules is a NW-SE trending high-angle reverse fault. Quartz-rich mylonites, calc-mylonites and phyllonitic layers showing an almost along-dip lineation occur along the fault, suggesting a top to SE motion of the Austroalpine domain. Strongly sheared pseudotachylytes injecting mylonitic gneiss belonging to the hanging wall of the fault near Merano. A late cataclastic imprint is given by discrete fault zones consistent with the ductile structures. The Merano-Mules fault is clearly displaced by a splay of the Passirio fault, showing a left-lateral offset of about 1 km across the Passirio River just N of Merano. As regards the Quaternary deposits, four main unconformity-bounded stratigraphic units (UBSU) have been recognized. The Monte Spinale supersyntheme (Upper and Middle Pleistocene) is set up: it includes a part which is subdivided into synthemes (Caldaro syntheme and Sonvigo syntheme) and another part which is undifferentiated. All deposits are formed before the LGM. The Caldaro syntheme is composed by alluvial and mixed (fluvial + debris flow + avalanche) deposits, which crop out in the Passiria Valley and at Castel Tirolo, with a thickness locally up to 200 m. These deposits testify a refilling phase of the Val Passiria, with a valley floor ~ 50-80 m higher then today, which is joined by the stream fans coming from both the valley mountainsides. Four C-14 ages allow attributing these deposits to the Upper Pleistocene, inside the Marine Isotope Stage (MIS) 3. Inside the Sonvigo syntheme (Upper and Middle (?) Pleistocene) are only present lodgement tills. The top of the unit is marked by a buried soil, over which there are tills attributed to the LGM. Carbons present inside this soil have given an age of 56000 yrs BP. This age allow attributing these deposits to a glacial event which can be set inside the lower part of the Upper Pleistocene or inside the Middle Pleistocene. The Garda syntheme (Upper Pleistocene) is made up of deposits formed during the phases of increase, maximum expansion and retirement of the local valley glaciers during LGM. The main unit is prevalently formed by till deposits up to 100 m thick. This unit is composed by two subsynthemes linked to the retirement phase: the San Pancrazio subsyntheme in the Ultimo Valley, characterized by glacigenic deposits associated to the first Late-glacial phases, and the Malga Fontana Bianca subsyntheme with glacigenic and rock-glacier deposits probably related to the last glacial re-advance phases. The Postglacial Alpine syntheme (PTG) (Upper Pleistocene p.p. - Holocene) formed after the local LGM expansion. It includes different kinds of deposits. In the Adige Valley there are mainly alluvial and debris-flow/torrential fan deposits; C-14 ages allow calculatating average sedimentation rates of 2-2,7 m/1000 years (in places with mainly coarse-grained sedimentation). Outside the Adige Valley gravitational and debris-flow deposits prevail. Inside the PTG there is also the Amola subsyntheme which includes deposits from the Little Ice Age to the present.

The Aghdarband Basin, consisting of a strongly deformed arc-related Triassic marine succession, is a key-area for the study of the Cimmerian events, as it is unconformably covered by mid-Jurassic gently folded sediments entirely sealing the Cimmerian compressive structures. The basin developed during part of the Triassic in a highly mobile tectonic context suggested by abrupt facies variations and local unconformities. In addition, syn-sedimentary tectonic activity is testified by the occurrence of carbonate olistholiths in the deepest parts of the basin. The marine succession, spanning from Olenekian to lowermost Carnian, shows at the base continental conglomerates andsandstones, as well as basaltic lava flows, possibly of Early Triassic age. They are followed by the shallow water Sefid Kuh Limestone, in which an intraformational unconformity has been now identified. This unit is locally covered by deep-water limestones of the Nazarkardeh Fm. which interfinger with slope facies of the Sefid Kuh Limestone. The volcaniclastic sandstone layers of the Sina Fm follow up-section with a deep unconformity, marked in several places by deep erosion and tilting of the underlying units. The Sina Fm. is in turn unconformably covered by the coal bearing shales of the Miankhui Fm., with a Norian-Rhaetian age testified by plant megafossils, marking the end of marine sedimentation and of volcanic-arc activity. The Triassic units are overthrusted to the south by Upper Palaeozoic siliciclastic successions showing in some cases a LG metamorphic imprint. They largely include the Qara Geithan Fm. consisting of granitic rocks, acidic to basic volcanics, and locally also large blocks of Permian bioclastic limestones derived from the erosion of the Palaeotethys accretionary wedge, exposed south of Aghdarband. The whole succession of the Aghdarband Basin, including the unconformable Miankhui Fm., is deeply involved in a north-verging thrust stack which interacts in the northern part of the area with an important strike-slip shear zone. Several tectonic units have been recognized within the Triassic succession, causing repetitions of the whole stratigraphic succession. Two main thrust sheets are exposed in the southern part of the basin under the Upper Palaeozoic thrust stack. Thrust faults and folds consistently show a N-directed tectonic transport, suggested by dip-slip motion along S-dipping reverse faults and axial plane geometry. Deformation occurred at shallow levels taking to the formation of cataclastic shear zones and to disjunctive and pencil cleavage in the shale layers of the succession. The thrust sheets comprise the Miankhui Fm. which shows a thick basal coal layer (up to 10 m) deeply excavated at the Aghdarband Mine. Nice examples of coal-related tectonics are exposed in open pits and tunnels of the mine. Intensive deformation of the coal, forming complex shear zones with s-c bands, causes the décollement of the Miankhui beds which show intensive tectonic thickening and repetitions mainly caused by polyphase thrust imbrications and disharmonic folding. The northernmost part of the Triassic basin shows a very complex setting, with traspressional structures given by vertical strike-slip faults and closed to tight folds with steeply plunging axes. According to our new data, up to four tectonic slices can be distinguished in this complex area. This structural zone is directly bounded to the north by severely deformed LG metamorphic rocks resulting from a volcaniclastic succession with Devonian and Carboniferous marble layers. Systematic asymmetry of major and parasitic folds, as well as rotation and torsion of axial surfaces indicate a general left-lateral transpressional regime, whereas kinematic indicators along the main fault planes show both left- and right-lateral motions. According to our relative chronology, dextral movements follow in time the sinistral ones reactivating previous Cimmerian structures and displacing also the surrounding Jurassic to Neogene succession of Kopeh Dagh in relatively recent times. Fold analyses along the area of interaction between thrust structure and the transpressional zone suggest an intricate interference pattern between thrust-related folds and strike-slip brittle shear zones, suggesting that the latter caused a strong reorientation of previously formed folds. The extension of the traspressional zone, which can be followed for some 20 km across the study area, indicates that important left-lateral movements, roughly parallel to the orientation of the convergence zone, were active during the last stages of the Late Triassic Cimmerian event, in contrast to what indicated by previous authors in the Mashhad area.

The Orobic Alps represent the central sector of the Southern Alps comprised between Lake Como and the Adamello batholith. Alpine deformation results in severe shortening by folding and thrusting of both cover and basement. The Orobic and Porcile thrusts form major, respectively E-W and ENE-WSW trending, tectonic structures along which the pre-Alpine basement is translated southward on the Permian-Triassic sedimentary cover. Both the Orobic and Porcile thrusts display a complex and long-lasting evolution with a first ductile stage defined by greenschist facies mylonites associated to folding and cleavage development in the footwall. The ductile-brittle transition is defined by the growth of cataclastic shear zones that overprints the ductile fabric. Pseudotachylyte fault and injection veins occur sporadically within both fault zones. All veins seems to originate from friction-induced melting of pre-existing cataclasites and ultracataclasites, derived from different lithologies (two mica gneiss, mica schists and K-feldspar gneiss). Pseudotachylytes occurring along melt generation surfaces are typically zoned with a thin black wall along contacts with the wall rock, and a lighter dark grey to brass-like coloured part in the vein centre. Clasts derived from the wall rock consist of quartz, lithic fragments and minor plagioclase. The clast/matrix ratio decreases towards the vein centre contrary to the increase of the clast grain size. Reservoir veins, usually occurring along existing fractures or veins, are mainly not zoned and display a clast/matrix ratio close to zero, probably due to the “bottleneck” effect. 40Ar/39Ar isotope dating of pseudotachylytes matrix indicates the presence of two age clusters: Late Cretaceous and Early to Middle Eocene. Pseudotachylytes belonging to the old age group occur both in the upper and lower structural part of the fault zone (up to 150 m wide), whereas Eocene pseudotachylytes are concentrated close to the basement-cover contact. In many cases re-melting phenomena of pre-existing pseudotachylytes were observed at the micro-scale. Old pseudotachylyte fragments with evident resorption features are present within new veins, and “intrusive” contact were locally observed between different vein generations. Different melt pulses along the same vein are differentiated on the base of clast/matrix ratios and chemical composition of both matrix and crystallites. Brittle deformation producing brecciation of old pseudotachylytes seems to be contemporaneous with new melt injection and flow, resulting in the coexistence, within the same vein, of old fractured pseudotachylyte layers and new, undeformed, ones. Structural data relative to fault veins point out that both old and young pseudotachylytes formed along reverse fault planes with similar geometric features. This suggest that no significant changes occurred in the main stress axes orientations and resulting deformation structures correlated to the Late Cretaceous and the Eocene compressive deformation events along the Orobic and Porcile fault zones. Field data, 40Ar/39Ar ages, microstructural and mineralogical data on pseudotachylytes along the Orobic and Porcile thrusts reveal that repeated coseismic friction-induced melting occurred along same faults with a time interval in excess of 15 Ma. This implies that the seismic history of regional scale faults could be very complex and polyphasic, with successive long time range re-activations that can be individuated exploring the geological record associated to fault zones.

New structural, sedimentological, petrological and palaeomagnetic data collected in the region of Nakhlak–Anarak provide important constraints on the Cimmerian evolution of Central Iran. The Olenekian–Upper Ladinian succession of Nakhlak was deposited in a forearc setting, and records the exhumation and erosion of an orogenic wedge, possibly located in the present-day Anarak region. The Triassic succession was deformed after Ladinian times and shows south-vergent folds and thrusts unconformably covered by Upper Cretaceous limestones following the Late Jurassic Neo-Cimmerian deformation. Palaeomagnetic data obtained in the Olenekian succession suggest a palaeoposition of the region close to Eurasia at a latitude around 208N. In addition, the palaeopoles do not support large anticlockwise rotations around vertical axes for central Iran with respect to Eurasia since the Middle Triassic, as previously suggested. The Anarak Metamorphic Complex (AMC) includes blueschist-facies metabasites associated with discontinuous slivers of serpentinized ultramafic rocks and Carboniferous greenschistfacies ‘Variscan’ metamorphic rocks, including widespread metacarbonates. The AMC was formed, at least partially, in the Triassic. Its erosion is recorded by the Middle Triassic Baqoroq Formation at Nakhlak, which consists of conglomerates and sandstones rich in metamorphic detritus. The AMC was repeatedly deformed during post-Triassic times, giving origin to a complex structural setting characterized by strong tectonic fragmentation of previously formed tectonic units. Based on these data, we suggest that the Nakhlak–Anarak units represent an arc–trench system developed during the Eo-Cimmerian orogenic cycle. Different tectonic scenarios that can account for the evolution of the region and for the occurrence of this orogenic wedge in its present position within Central Iran are critically discussed, as well as its relationships with a presumed ‘Variscan metamorphic event.

The Shanderman Metamorphic Complex, exposed along the Caspian foothills of the Talesh Mountain, western Alborz, Iran, has always been interpreted as an ophiolitic fragment of the Palaeotethys Ocean. According to our new data, this unit consists of metamorphic rocks mainly represented by garnet-staurolite micaschists with large bodies of metabasites containing well-preserved eclogitic-phase assemblages. The Shanderman Complex (SC) was later intruded at middle crustal levels by intermediate-basic intrusive bodies. New Ar/Ar ages of paragonitic white micas in equilibrium with the high-pressure assemblages have given a Late Carboniferous age (315 +/- 9 Ma). Our new data suggest that the SC was equilibrated in high-pressure conditions during an orogenic event that predates the Eo-Cimmerian orogeny by more than 100 Ma and that may be tentatively ascribed to the Variscan orogeny sensu latu. We suggest that the Shanderman Complex represents a fragment of the Upper Palaeozoic European continental crust. The occurrence of eclogites in these regions can be explained by two different hypotheses: (1) the SC high-pressure rocks can be related to the accretion of Gondwana-related Transcauscasian-Moesian microplate to the southern margin of Eurasia; or (2) the SC eclogites can represent a fragment of the Late Palaeozoic 'Variscan belt' sensu latu of central Europe, which has been translated eastwards during Permian along a dextral megashear zone taking from a Pangea-B to a Pangea-A plate configuration. This metamorphic unit was stacked southwards on the northern edge of the Iran Plate during the Eo-Cimmerian events occurring at the end of the Triassic. The eclogite-bearing basement of the SC was finally exhumed at the end of the Eo-Cimmerian orogeny, as suggested by the composition of the basal layers of the Shemshak Group dated here Middle Jurassic, that cover the crystalline rocks of the SC along a regional non-conformity. The SC was probably displaced further southwards during the Mesozoic opening of the South Caspian Basin and the Tertiary thrust stacking and dextral shearing accompanying the formation of the Alborz intracontinental belt.

New Late Ordovician and Triassic palaeomagnetic data from Iran are presented. These data, in conjunction with data from the literature, provide insights on the drift history of Iran as part of Cimmeria during the Ordovician–Triassic. A robust agreement of palaeomagnetic poles of Iran and West Gondwana is observed for the Late Ordovician–earliest Carboniferous, indicating that Iran was part of Gondwana during that time. Data for the Late Permian–early Early Triassic indicate that Iran resided on subequatorial palaeolatitudes, clearly disengaged from the parental Gondwanan margin in the southern hemisphere. Since the late Early Triassic, Iran has been located in the northern hemisphere close to the Eurasian margin. This northward drift brought Iran to cover much of the Palaeotethys in approximately 35 Ma, at an average plate speed of c. 7–8 cm year21, and was in part coeval to the transformation of Pangaea from an Irvingian B to a Wegenerian A-type configuration.

The Eo-Cimmerian orogen results from the Late Triassic collision of Iran, a microplate of Gondwanan affinity, with the southern margin of Eurasia. The orogen is discontinuously exposed along the northern side of the Alborz Mountains of North Iran below the siliciclastic deposits of the Shemshak Group (Late Triassic–Jurassic). A preserved section of the external part of the belt crops out in the Neka Valley (eastern Alborz) south of Gorgan. Here the Mesozoic successions (Shemshak Group–Upper Cretaceous limestones) overlay a pre-Jurassic Eo-Cimmerian thrust stack with a sharp unconformity. The stack includes the Gorgan Schists, an Upper Ordovician–Lower Silurian low-grade metamorphic complex, overthrusted southward above a strongly deformed Late Palaeozoic–Middle Triassic succession belonging to north Iran. In the Talesh Mountains (western Alborz), the Shanderman Complex, previously interpreted as an ophiolitic remnant isolated along the Eo-Cimmerian suture, is considered an allochthonous nappe of deeply subducted continental crust. The new evidence for this is the occurrence of previously unknown eclogites dating to the Carboniferous, and probably related to the Variscan history of Transcaucasia. South of the Shanderman Complex, Upper Palaeozoic slates and carbonates occurring below the Lower Jurassic Shemshak Group also record the occurrence of an Eo-Cimmerian metamorphic event. Based on our new data, the Eo-Cimmerian structures exposed in the Alborz appear to be remnants of a collisional orogen consisting mainly of deformed continental crust where no ophiolites are preserved.

An important, 2.4 km-thick Triassic succession is exposed at Nakhlak (central Iran). This succession was deformed during the Cimmerian orogeny and truncated by an angular unconformity with undeformed Upper Cretaceous sediments. This integrated stratigraphic study of the Triassic included bed-by-bed sampling for ammonoids, conodonts and bivalves, as well as limestone and sandstone petrographic analyses. The Nakhlak Group succession consists of three formations: Alam (Olenekian–Anisian), Ba¯qoroq (?Upper Anisian–Ladinian) and Ashin (Upper Ladinian). The Alam Formation records several shifts from carbonate to siliciclastic deposition, the Ba¯qoroq Formation consists of continental conglomerates and the Ashin Formation documents the transition to deep-sea turbiditic sedimentation. Petrographic composition has been studied for sandstones and conglomerates. Provenance analysis for Alam and most of the Ashin samples suggests a volcanic arc setting, whereas the samples from the Ba¯qoroq Formation are related to exhumation of a metamorphic basement. The provenance data, together with the great thickness, the sudden change of facies, the abundance of volcaniclastic supply, the relatively common occurrence of tuffitic layers and the orogenic calc-alkaline affinity of the volcanism, point to sedimentation along an active margin in a forearc setting. A comparison between the Triassic of Nakhlak and the Triassic succession exposed in the erosional window of Aghdarband (Koppeh Dag, NE Iran) indicates that both were deposited along active margins. However, they do not show the same type of evolution. Nakhlak and Aghdarband have quite different ammonoid faunal affinities during the Early Triassic, but similar faunal composition from the Bithynian to Late Ladinian. These results argue against the location of Nakhlak close to Aghdarband.