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The role of inherited weaknesses in metamorphic basements with respect to the geometry and tectonic evolution of subsequent orogens formation forms a cornerstone of structural reconstructions, especially in non-inverted orogens with old Variscan basements. In this study, we analyse the geometry, kinematics, and tectonic evolution of the complex western termination of the Alpine Pyrenean–Cantabrian orogen using an integrated approach based on analogue modelling, constrained by structural mapping and geochronology, to provide new insights into the role of pre-existing structures and the shift in the orientation of the stress field. Our results demonstrate that pre-existing structures are necessary to explain the complex western termination, which does not follow the same tectonic architecture as the rest of the orogen. The reason for this is the different orientation of the pre-existing Variscan structures in this area, which do not follow the general E–W trend. These western structures (including NNE–SSW and NW–SE strike-slip fault systems and a greater number of E–W thrusts) accommodate the shortening, but have a less favourable orientation. The reactivation of the NNE–SSW strike-slip faults and the southern E–W thrusts in the recent stages indicates a late intraplate tectonic regime, mainly following the shift of the Shmax (from N–S to NNW–SSE) which occurred when the convergence between the Iberian, Eurasian, and African plates changed. • NW Iberia Variscan structures control the lateral termination of Alpine orogen. • Multiple inherited structures accommodated Alpine shortening in wider region. • The wide variety of structure orientations generate more complex tectonic models. • Iberian plate convergence shifts, reactivated structures in intraplate regimen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lateritic clays occur in fault contact with granites in a Cenozoic basin. • Geochemical data indicates an allochthonous mafic source for the lateritic clays. • Hydrothermal fluids interacted with the lateritic clays and the granites. • Faults had extensional component and were re-activated with inverse strike-slip. • Faults were not effective seals for the hydrothermal fluids. Continental basin evolution can be influenced not only by tectonic activity, but by hydrothermal and weathering processes. This is displayed on the basement rocks (granites and xenoliths) and sedimentary cover (clays, sands and conglomerates) in the Cenozoic Ferreira basin of NW Spain. In this study, we applied petrological, geochemical and structural proxies to investigate a red clay unit and adjacent granitic basement rocks in a fault contact. Red clays have a lateritic composition (SiO 2 : 38–42 wt%, Fe 2 O 3 : 13–20 wt% and Al 2 O 3 : 24–29 wt%) with moderate to high contents in V (267 – 324 ppm) and Ni (46–71 ppm), and are characterized by (La/Yb) n and TREE that vary from ∼5 to 12 and ∼55 to 110 ppm, respectively. The basement rocks are peraluminous biotite granites (A/CNK: 1.12–13.57) with (La/Yb) n and TREE that vary from 7.7 to 27.42 and from 82.79 to 244.64 ppm, respectively. The xenoliths are peraluminous shales (A/CNK: 3.48–4.48) with (La/Yb) n and TREE varying from 7.66 to 11.10 and from 228.61 to 344.42 ppm, respectively. This geochemistry indicates that the lateritic red clays come from residual weathering of mafic ± intermediate rocks. They are interpreted to have been generated under the tropical climate conditions in the Late Cretaceous (∼70 Ma). Afterwards red clays were remobilized in subsequent tectonic events (Alpine), deposited in faulted grabens, and together with adjacent basement granites, affected by hydrothermal events that caused element mobility (e.g., REE leaching and Ce positive anomalies). Fault reactivations, under strike-slip stresses with a reverse component, channelized these hydrothermal fluids and uplifted part of the landscape. This uplift is interpreted as the trigger of an erosional regime that affected the lateritic red clay unit in the Ferreira basin. The conclusions of this study highlights the important interplay of different geological processes in small continental basins. [ABSTRACT FROM AUTHOR]

In the Cuesta del Rahue area, located in the Precordillera Neuquina (northern Argentine Patagonia), late Paleozoic turbiditic rocks with maximum depositional age of ca. 389 Ma were affected by three orogenic events. The oldest orogenic event is the Chanic orogeny (Late Devonian–early Carboniferous) that is characterized by folds with NNE vergence. This deformation is developed in low-grade to very low-grade metamorphic conditions, which allowed the development of a slaty/rough cleavage. The main Chanic structure is an asymmetric fold with a large normal limb tilted by the more recent orogenic events. The characteristics of the deformation and metamorphism allows us to assign the Cuesta del Rahue outcrop to the external hinterland of the western wedge of the Chanic orogen. Early to late Carboniferous igneous rocks intruded the Paleozoic rocks of the Cuesta del Rahue area and crosscut the Chanic structures. After the Chanic orogeny, the Gondwanan orogeny (late Carboniferous–early Permian) took place. The main structures of the Gondwanan orogen are thrust and related folds with SSW vergence that fold the large Chanic normal limb and also affect Carboniferous igneous rocks. The Gondwanan deformation was developed under non-metamorphic conditions, and Permian igneous rocks crosscut the Gondwanan structures. Mesozoic regional extension related to the beginning of the Andean cycle and the formation of the Neuquén Basin gave rise to normal faults and small-scale extensional folds. Finally, the Andean orogeny, developed during the Cenozoic in the study area, also affected the Cuesta del Rahue Paleozoic rocks, with the development of compressional structures related to the Aluminé thrust and fold belt. The main Andean structure in the study area is the NW–SE Rahue fault, which links the E–W Piedra Santa tear fault with the NNE–SSW Catán Lil reverse fault. The Rahue fault has a SW tectonic transport direction. It uplifted the Cuesta del Rahue area and placed Paleozoic rocks on top of Mesozoic and Cenozoic rocks. The Piedra Santa fault partially reactivated the Huincul right-lateral and left-lateral Chanic transverse faults that define the southern end of the doubly vergent Chanic orogen, giving rise to the current Huincul lineament. • New insights on the evolution of the Paleozoic basement of the Andes in the southern end of the Cuyo Sector are presented. • In the Cuesta del Rahue outcrop the Paleozoic basement is a turbiditic succession, Middle to Late Devonian in age. • The Cuesta del Rahue is located on the southern end of the western wedge of the Chanic orogen. • The Paleozoic rocks were deformed by the late Paleozoic Chanic and Gondwanan orogenies and the Cenozoic Andean orogeny. • Th Huincul lineament is a wrench fault, limiting by the south the Chanic orogen, partially reactivated during the Gondwanan and Andean orogenies. [ABSTRACT FROM AUTHOR]

During the late Carboniferous–middle Permian, the basement of the Chilean Coastal Cordillera was deformed by the Gondwanan Orogeny, developed by the subduction of the Paleo-Pacific plate under Gondwana from the early Carboniferous. In the Maule sector (35.4°S), the following metamorphic rock units are distinguished: (i) Western Series, formed by metapelites, metabasites, metacherts, metaconglomerates, and marbles, mixed in a subduction channel, with probably ages between the Cambrian and the Carboniferous; (ii) Eastern Series, consisting of metasediments of a fore-arc basin, Carboniferous in age. In the Eastern Series two units are recognized in terms of lithology and deformation style: the Eastern Pelitic Series and the Eastern Sandy Series. Three Gondwanan deformation episodes have been distinguished, affecting both series unequaly. In the Western Series, D1 structures consist of a foliation (S 1) developed under high-pressure and low-temperature conditions, while in the Eastern Series it comprise tight east-verging folds, with the associated S 1 developed under low PT metamorphic conditions (greenschist facies). D2 structures are only present in the Western Series and Eastern Pelitic Series and represent the exhumation of the accretionary prism and its emplacement to the east over the fore-arc basin, with the development of east-verging recumbent folds and a thick shear-zone. Difficulties in the propagation of the deformation by the presence of the Coastal Batholith to the east led to the development of the D3 deformation event, only well developed in the Eastern Sandy Series, and represented by the Los Tablones Back-thrust and associated folds, as well as N–S open right folds formed under low PT metamorphic conditions. • New data on the lithology, structure and metamorphism of the Paleozoic rocks of the Chilean Coastal Range are presented. • Paleozoic rocks of the Maule River were deformed during the Gondwana orogeny under different metamorphic conditions • The Western Series deformed in HP metamorphic conditions during D1 in the subduction channel and was exhumed by an east-directed thrust during D2 • Structures D1, D2 and D3 of the Oriental Series were developed under LP-LT metamorphic conditions. The D1 and D2 have East vergence and the D3 West [ABSTRACT FROM AUTHOR]

One of the most important geological effects generated by the seismic events of Emilia Romagna (Italy, 2012) was the liquefaction. The first earthquake took place on 20th May (5.9 M w ) and generated liquefaction in the locality of San Carlo, mainly recorded as large fissure sand volcanoes. Detailed stratigraphic and sedimentology analyses of these sand bodies indicated the assemblage of rhythmic normal graded beds of sand for many individual sand volcanoes. This is interpreted as repeated individual sand extrusions generating polygenetic sand blows for a single earthquake. This original analysis, made for first time in a case of extensive seismic liquefaction, indicates that the different pulses sand extrusion occurred after seismic shaking, and therefore no related to the cyclic seismic shearing stimulated by surface seismic waves. Underground liquefaction of shallow sandy layers and ground cracking, assisted by relevant lateral spreading, promoted water and sand ejections (E–W direction). Localised and repeated ground subsidence and bulging supported by the ejection of the underlying fluidized sediments feedback transient ground undulations and repeated sand ejections. The unstable undulating behaviour of the ground reinforced and sustained the liquefaction process through time after the seismic shaking, leading the occurrence of polygenetic sand volcanoes. In summary, the seismic liquefaction is the starting point of the process, although only if these sand ejections could promote the instability of the ground since underground sand depletions feedback the liquefaction process through time. The process stops when the hydrostatic balance is recovered in the affected zone. [ABSTRACT FROM AUTHOR]