The northwest-directed “Bretonian phase” in the French Variscan Belt (Massif Central and Massif Armoricain): A consequence of the Early Carboniferous Gondwana–Laurussia collision

In the Variscan French Massif Central and Armorican Massif, the tectonic significance of a widespread NW–SE-trending stretching lineation, coeval with medium pressure–medium temperature metamorphism, is an open question. Based on a structural analysis in the southern part of the Massif Central, we show that this top-to-the-NW shearing is a deformation event, referred to as D2, which followed a D1 top-to-the-south shearing Devonian phase, and was itself re-deformed by a Late D3 Visean–Serpukhovian southward-thrusting event. We date the D2 phase at 360 Ma (Famennian–Tournaisian boundary). In the Armorican Massif, D2 is the “Bretonian phase” recorded in the metamorphic series and sedimentary basins. Geodynamically, D2 is related to a general northwestward shearing during the Laurussia–Gondwana collision, which occurred after the closure of the Rheic Ocean, as indicated by the emplacement of the Lizard ophiolitic nappe in Britain. The left-lateral Nort-sur-Erdre fault accommodated the absence of ductile shearing in Central Armorica.     

Spatial–temporal patterns of cloud-to-ground lightning over the northwest Iberian Peninsula during the period 2010–2015

The spatial–temporal patterns of cloud-to-ground (CG) lightning covering the period 2010–2015 over the northwest Iberian Peninsula were investigated. The analysis conducted employed three main methods: the circulation weather types developed by Jenkinson and Collison, the fit of a generalized additive model (GAM) for geographic variables, and the use of a concentration index for the ratio of lightning strikes and thunderstorm days. The main activity in the summer months can be attributed to situations with eastern or anticyclonic flow due to convection by insolation. In winter, lightning proves to have a frontal origin and is mainly associated with western or cyclonic flow situations which occur with advections of air masses of maritime origin. The largest number of CG discharges occurs under eastern flow and their hybrids with anticyclonic situations. Thunderstorms with greater CG lightning activity, highlighted by a higher concentration index, are located in areas with a higher density of lightning strikes, above all in mountainous areas away from the sea. The modeling of lightning density with geographic variables shows the positive influence of altitude and, particularly, distance to the sea, with nonlinear relationships due to the complex orography of the region. Likewise, areas with convex topography receive more lightning strikes than concave ones, a relation which has been demonstrated for the first time from a GAM.     

Juvenile granite in the Sanandaj–Sirjan Zone,NW Iran: Late Jurassic–Early Cretaceous arc–continent collision

The Sanandaj–Sirjan Zone (SSZ) of western Iran is characterized by numerous granitoids of mainly calc-alkaline affinities. Several leucogranite and monzonite bodies crop out in the eastern Sanandaj. Whole-rock Rb–Sr isochrons demonstrate that the Mobarak Abad monzonite (MAM) formed in two phases at 185 and 131 Ma. Low ⁸⁷Sr/⁸⁶Sr(i) (i represents initial) and high ¹⁴³Nd/¹⁴⁴Nd(i) ratios, resulting in positive ?^t _Nd, imply that the source magma originated from a depleted mantle; large ion lithophile element (LILE) and light rare earth element (LREE) enrichments imply that slab fluid was involved in the evolution of the parent magma. Geochemical characteristics of the MAM rocks show an affinity with I- and A-type granites, and the positive values of ?^t _Nd (+2 to +6), confirm that the MAM represents juvenile granite. Therefore, the MAM rocks are different from Himalayan, Hercynian, and Caledonian granites. Based on the geology of granitic host rocks that form the protoliths of metamorphic rocks, it is likely that the mafic part of the MAM formed in an island arc setting on Neo-Tethyan oceanic crust during Early to Middle Jurassic time. Subsequent collision of the island arc with the western part of the SSZ occurred in the Late Jurassic to Early Cretaceous. Metamorphism, accompanied by partial melting, occurred during collision. Finally, leucogranite magmas of the young Mobarak Abad dikes and the Suffi Abad body were generated in this collision zone. This new model suggests a Late Jurassic–Early Cretaceous arc–continental collision before final closing of the Neo-Tethys.     

U–Pb geochronology and petrology of the late Paleozoic Gil Marquez pluton: magmatism in the Variscan suture zone,southern Iberia,during continental collision and the amalgamation of Pangea

The origin of plutonic complexes that stitch suture zones developed during collision is not well understood. In southern Iberia, the Pulo du Lobo suture zone (PDLZ) is intruded by the syn- to postcollisional Gil Marquez pluton (GMP), thought to be part of the Sierra Norte Batholith. U–Pb (LA-ICPMS, zircon) data on various phases of the GMP yield from oldest to youngest: (1) a 354.4 ± 7.6 Ma unfoliated gabbro; (2) a 345.6 ± 2.5 Ma foliated intermediate phase; (3) a 346.5 ± 5.4 Ma unfoliated porphyritic granite; (4) a 335.1 ± 2.8 Ma unfoliated biotite granite. This sequence is consistent with cross-cutting relationships observed in the field. The range in ages is consistent with interpretations that the GMP is part of the composite (ca. 350–308 Ma) SNB. Inherited ages preserved in the GMP intermediate and felsic phases indicate that its magmas traversed through South Portuguese Zone and PDLZ crust during emplacement. The ca. 345 Ma emplacement of the late kinematic foliated intermediate phase constrains the age of late-stage strike slip deformation within the PDLZ, and the lack of a foliation in the older gabbro indicates that is was not proximal to a shear zone neither at the time of emplacement, nor during its subsequent history. The unfoliated porphyritic granite and unfoliated biotite granite cut the foliation of the intermediate phase indicating emplacement during the waning stages of collision, while the ca. 335 Ma biotite granite intrudes the Santa Ira Flysch, thereby providing a tight constraint for the latest stage of deformation in the PDLZ.     

Radiolarian paleobiogeography in the late Albian–Santonian

Radiolarian paleobiogeography for the late Albian–Santonian is proposed for the first time. The paleobiogeographic differentiation is found to be different for the Albian, Cenomanian, Turonian, and Coniacian–Santonian. The Tethyan and Boreal superrealms can be recognized for the Albian–Santonian. For the Albian–Santonian, the Tethyan Superrealm can be subdivided into realms: Atlantic-Mediterranean, Carpathian-Caucasian, and Tropical-Pacific. The boundaries of these realms changed throughout geological time. The Boreal Superrealm recognized for the Albian so far cannot be subdivided into realms, whereas in the Cenomanian it included the East European and Western Siberian realms without a clear definition of the boundaries and the Boreal-Pacific (in the North Pacific). The Boreal Superrealm is subdivided in the Turonian into two realms (European-Western Siberian and Boreal-Pacific), and in the Coniacian–Santonian, it is subdivided into three realms (European, Western Siberian, and Boreal-Pacific). The Austral Superrealm can be recognized only for the Albian and Cenomanian, and because of the lack of data, it cannot be delineated for the Turonian and Coniacian–Santonian.     

Subduction–accretion–collision history along the Gondwana suture in southern India: A laser ablation ICP-MS study of zircon chronology

We report the petrological characteristics and preliminary zircon geochronology based on laser ablation ICP mass spectrometry of the various units in an accretionary belt within the Palghat-Cauvery Shear/Suture Zone in southern India, a trace of the Cambrian Gondwana suture. Zircons extracted from a plagiogranite in association with an ophiolite suite within this suture possess internal structure that suggests magmatic crystallization, and yield mid Neoproterozoic ²⁰⁶Pb/²³⁸U age of 817 ± 16 Ma (error: 1σ) constraining the approximate timing of birth of the Mozambique Ocean floor. Compiled age data on zircons separated from a quartzite and metamorphosed banded iron formation within the accretionary belt yields a younger intercept age of 759 ± 41 Ma (error: 1σ) which we relate to a mid Neoproteozoic magmatic arc. Detrital zircons extracted from the quartzite yield ²⁰⁷Pb/²⁰⁶Pb age peaks of about 1.9–2.6 Ga suggesting that they were sourced from multiple protolithis of Neoarchean and Paleoproterozoic. Metamorphic overgrowths on some zircon grains record ca. 500–550 Ma ages which are in good harmony with the known ages for the timing of high-grade metamorphism in this zone during the final stage of continent collision associated with the birth of the Gondwana supercontinent in the latest Neoproterozoic-Cambrian. The preliminary geochronological results documented in our study correlate with the subduction–accretion–collision history associated with the closure of the Mozambique Ocean and the final amalgamation of the Gondwana supercontinent.     

The distribution of calcareous nannofossils in the late Santonian–Late Maastrichtian deposits in the southwest of Iran (Khuzestan Province)

The first data on the distribution of calcareous nannofossils in the Behbehan section, the Kuh-e-Rish, are considered. According to the distribution of nannofossils, the Upper Cretaceous deposits of the section are subdivided into nine biostratigraphic zones. CC17 (Calculites obscurus zone) indicate the Late Santonian. Biozones CC18 (Aspidolithus parcus zone), CC19 (Calculites ovalis zone), CC20 (Ceratolithoides aculeus zone), CC21 (Quadrum sissinghii zone), and CC22 (Quadrum trifidum zone) represent the Campanian. Biozone CC23 (Tranolithus phacelosus zone) indicate the Late Campanian–Early Maastrichtian. Biozones CC24 (Reinhardtites levis zone) and CC25 (Arkhangelskiella cymbiformis zone) suggest the Middle and Late Maastrichtian, respectively. In the late Late Maastrichtian, due to decreasing in water depth at the study area, Nephrolithus frequens zone (CC26) defined in Tethysian domain was not recognized. The boundary between Gurpi–Pabdeh Formations represented a non-depositional period from the late Late Maastrichtian to the end of Early Paleocene. Also, it seems that predominant conditions of the sedimentary environment of Neotethys basin with the presence of index species calcareous nannofossils specified, which itself indicates that the warm climate and high depth of the basin in Late Santonian to Late Maastrichtian, in low latitudes has been prevalent.     

U–Pb zircon dating of the Gruf Complex: disclosing the late Variscan granulitic lower crust of Europe stranded in the Central Alps

Permian granulites associated with noritic intrusions and websterites are a common feature of the post-Variscan European crust. Such granulites are common in the Southern Alps (e.g. Ivrea Zone), but occur only in the Gruf Complex in the Central Alps. To understand the geotectonic significance of these granulites, in particular in the context of Alpine migmatisation, zircons from 15 high-grade samples have been U–Pb dated by SHRIMP II analysis. Oscillatory zoned zircons from charnockite sheets, interpreted as melts generated through granulite facies fluid-absent biotite melting at 920–940°C, yield ages of 282–260 Ma. Some of these zircons contain inclusions of opx, unequivocally attributable to the granulite facies, thus confirming a Permian age for the charnockites and associated granulites. Two samples from an enclave-rich orthogneiss sheet yield Cambrian and Ordovician zircon cores. Two deformed leucogranites and six ortho- and augengneisses, which compose two-thirds of the Gruf Complex, give zircon ages of 290–260 Ma. Most zircons have milky rims with ages of 34–29 Ma. These rims date the Alpine amphibolite facies migmatisation, an interpretation confirmed by directly dating a leucosome pocket from upper amphibolite facies metapelites. The Gruf charnockites associated with metre-scale schlieren and boudins of opx–sapphirine–garnet–granulites, websterites and gabbronorites can thus be identified as part of the post-Variscan European lower crust. A geotectonic reconstruction reveals that this piece of lower crust stranded in the (European) North upon rifting of the Neotethys, such contrasting the widespread granulite units in the Southern Alps. Emplacement of the Gruf lower crust into its present-day position occurred during migmatisation and formation of the Bergell Pluton in the aftermath of the breakoff of the European slab.     

Evolution of radiolarians in the late Albian–Campanian

The dynamics of radiolarian evolution in the late Albian–Campanian is analyzed, and several stages are recognized. The first stage (late Albian–middle Cenomanian), related to the MCE regional anoxic event, showed low evolutionary tempos and hence lacked structural change in radiolarian communities. The second stage (late Cenomanian–early Turonian), corresponding to ОАЕ 2, which was a global anoxic event, is characterized by a decrease in the number of genera, while many genera showed increased diversification of species composition. At this stage, a considerable number of genera became extinct and appeared, suggesting an increased rate of the radiolarian evolution. The third stage (middle Turonian–early Coniacian), including the beginning of ОАЕ 3, is characterized by a stabilized number of genera. The fourth stage (late Coniacian–Santonian) completely encompasses ОАЕ 3 except for its very beginning. At this stage, the radiolarian communities underwent a significant structural change, while their rate of evolution increased considerably. Nevertheless, during the ОАЕ 3 stage, a distinct trend toward a decrease in generic diversity continued from the late Cenomanian to the middle Turonian. The fifth stage (Campanian) is characterized by quite significant changes in the assemblage composition, while the trend toward a gradual decrease in the number of genera steadily continued. At this stage, which coincided with a considerable cooling, twice as many genera became extinct as during ОАЕ 2. The analysis of the dynamics of radiolarian evolution showed that the anoxic MCE, ОАЕ 2, and ОАЕ 3 events did not result in degradation of radiolarian assemblages. This suggests that this group has significant stratigraphic potential. In general, the evolution of radiolarians in the Late Cretaceous was gradual. By the end of the Campanian, nearly half of the generic diversity was composed of genera which appeared at the beginning of the Cretaceous and earlier.     

A Middle Paleozoic shear zone in the Sierra de Valle Fértil,Argentina: Records of a continent-arc collision in the Famatinian margin of Gondwana

Geological, petrological and structural observations were obtained along a 30-km-long traverse across a segment of the Valle Fértil shear zone, central-western Argentina. On a regional scale, the shear zone appears as numerous discontinues belts over 25 km in width and is approximately 140 km in length, extended on the western section of the Sierras Valle Fértil – La Huerta mountain range. The steeply dipping shear zone with a vertical mylonitic lineation is composed of amphibolite facies ribbon mylonites and amphibolite to greenschist facies ultramylonites derived from Early Ordovician plutonic and metasedimentary parent rocks. Locally, syn-kinematic retrogression of mylonites formed greenschist facies phyllonites. During the later stages of deformation, unstrained parent rocks, mylonites, ultramylonites and phyllonites were affected by pervasive cataclasis under low greenschist facies conditions associated with localized faulting. One new ⁴⁰Ar/³⁹Ar age on biotite and published ⁴⁰Ar/³⁹Ar ages on amphibole in the shear zone yield an average cooling rate of 6.2 °C/Ma for a time period that crosses the Silurian–Devonian boundary. Since in metasedimentary rocks the youngest zircon's rims dated at 465 Ma marks the beginning of cooling, nearly continuous uplift of rocks within the shear zone occurred over a minimum time span of 55 Ma. During the period of active deformation, dip-slip movement can explain uplift of several kilometers of the Early Ordovician arc crust. The Valle Fértil shear zone, which was formed near above the inferred suture zone between the Famatinian arc and Cuyania microcontinent, is a major structural boundary nucleated within the Early Ordovician crust. The simplest geodynamic model to explain the evolution of the Valle Fértil shear zone involves the collision of the composite Cuyania/Precodillera microcontinent against the Famatinian arc.     

Late Palaeozoic–Early Mesozoic geological features of South China: Response to the Indosinian collision events in Southeast Asia

This paper provides some new evidences on stratigraphic sequence, zircon SHRIMP dating from ophiolite, granitoids, and fold-and-thrust tectonic styles in the South China Block (SCB). Stratigraphic studies suggest that the eastern and central parts of the SCB show a SW-dipping palaeoslope framework during the Late Palaeozoic–Early Mesozoic. These areas were not in a deep-sea environment, but in a shallow-sea or littoral one. Coeval volcanic rocks are missing. Deep-water deposits and submarine volcanism only took place in the western part of the SCB. The three ophiolitic mélanges of the eastern SCB formed in the Neoproterozoic, but not in the Permian or the Triassic. The sedimentary rocks associated with the Neoproterozoic oceanic relics contain abundant Proterozoic acritarchs, but no radiolarians. The Early Mesozoic granitoids (235–205 Ma) belong to the post-collision peraluminous S-type granites; they are widely exposed in the central-western SCB, and rare in the eastern SCB. The fold-and-thrust belt developed in the eastern SCB shows a top-to-the-south displacement, whereas the Xuefengshan Belt of central SCB indicates a north- or northwest-directed shearing. The geodynamic settings of the different parts of the SCB during the Triassic are discussed.     

Late Hercynian polymetallic vein-type base-metal mineralization in the Iberian Pyrite Belt: fluid-inclusion and stable-isotope geochemistry (S–O–H–Cl)

Late Variscan vein-type mineralization in the Iberian Pyrite Belt, related to the rejuvenation of pre-existing fractures during late Variscan extensional tectonism, comprises pyrite–chalcopyrite, quartz–galena–sphalerite, quartz–stibnite–arsenopyrite, quartz–pyrite, quartz–cassiterite–scheelite, fluorite–galena–sphalerite–chalcopyrite, and quartz–manganese oxide mineral assemblages. Studies of fluid inclusions in quartz, stibnite, and barite as well as the sulfur isotopic compositions of stibnite, galena, and barite from three occurrences in the central part of the Iberian Pyrite Belt reveal compelling evidence for there having been different sources of sulfur and depositional conditions. Quartz–stibnite mineralization formed at temperatures of about 200 °C from fluids which had undergone two-phase separation during ascent. Antimony and sulfide are most probably derived by alteration of a deeper lying, volcanic-hosted massive sulfide mineralization, as indicated by δ³⁴S signatures from ?1.45 to ?2.74‰. Sub-critical phase separation of the fluid caused extreme fractionation of chlorine isotopes (δ³⁷Cl between ?1.8 and 3.2‰), which correlates with a fractionation of the Cl/Br ratios. The source of another high-salinity fluid trapped in inclusions in late-stage quartz from quartz–stibnite veins remains unclear. By contrast, quartz–galena veins derived sulfide (and metals?) by alteration of a sedimentary source, most likely shale-hosted massive sulfides. The δ³⁴S values in galena from the two study sites vary between ?15.42 and ?19.04‰. Barite which is associated with galena has significantly different δ³⁴S values (?0.2 to 6.44‰) and is assumed to have formed by mixing of the ascending fluids with meteoric water.     

Topography of the Variscan orogen in Europe: failed–not collapsed

The Variscan orogenic collage consists of three subduction-collision systems (Rheno-Hercynian, Saxo-Thuringian and Massif Central-Moldanubian). Devonian to early Carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts, but also in post-tectonic basins within these foreland belts and on the Cadomian crust of peri-Gondwanan microcontinental fragments, which represent the upper plates of the subduction/collision zones. These marine basins preclude high elevations in the respective areas and also in their neighbourhood. Widespread late Carboniferous intra-montane basins with their coal-bearing sequences are likewise incompatible with high and dry plateaus. While narrow belts with high elevations remain possible along active margins within the orogen, comparison of the Variscides with the Himalaya/Tibetan plateau is unfounded. Plausible reasons for the scarcity of high Variscan relief include subduction of oceanic and even continental crust, subduction erosion, orogen-parallel extension and—most important—lithospheric thinning accompanied by high heat flow and magmatism. In many areas, timing and areal array of magmatism and HT metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse. It is suggested, instead, that lithospheric thinning and heating are due to mantle activities caused by the Tethys rift. The lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift: in terms of topography, the Variscides represent a failed orogen. The HT regime also explains the abundance of granitoids and HT/LP metamorphic rocks typical of the Variscides. Melting in the HT regime extracted mafic components from Variscan and Cadomian crust as well as from Cadomian metasomatized lithospheric mantle, thus mimicking subduction-related magmatism. The onset of the HT regime at c. 340 Ma may also have triggered the final ascent of HP/UHP felsic metamorphic rocks.     

Late Cretaceous tectono-magmatic activity in the Nize region,central Tibet: evidence for lithospheric delamination beneath the Qiangtang–Lhasa collision zone

ABSTRACT

The results of zircon U–Pb age dating and whole-rock geochemistry for the Late Cretaceous Nize granodiorite porphyries, combined with analysis of near-coeval structural deformation of the Lower Cretaceous Langshan Formation, provide new data to better understand the tectonic evolution of the northern Lhasa subterrane, central Tibet. Zircon U–Pb ages of 89.2 ± 0.3 Ma to 87.8 ± 0.3 Ma indicate emplacement during the Late Cretaceous. Granodiorite porphyry intrusions were contemporaneous with the development of a regional angular unconformity, overlain by the Upper Cretaceous Jingzhushan (or Abushan) Formation, within the collision zone between the South Qiangtang and Lhasa terranes. Geochemical data for Nize granodiorite porphyries indicate that they have a calc-alkaline composition enriched in large-ion lithophile elements and light rare earth elements and depleted in high-field-strength elements and heavy rare earth elements. High Al₂O₃ and Sr contents, low Yb and Y contents, and high Sr/Y ratios are similar to adakitic magmas.

Structural analysis indicates two stages of deformation (D₁ and D₂), with D₁ forming the focus of the present study. The D₁ deformation is represented by large-scale faults and records two periods of faulting. These periods are recognized as early compressional thrust faulting and a dominant late stage characterized by normal faulting and extension, with the latter stages of D₁ being near-coeval with the emplacement of the Nize granodiorite porphyries. The combination of zircon ages, geochemical data, and structural analysis indicates that the Nize granodiorite porphyries formed after collision of the South Qiangtang and Lhasa terranes. Adakitic magma derived from partial melting of the thickened lower or middle crust resulted from lithospheric delamination that may have been promoted by the convective removal of deeper lithospheric mantle.     

The Malpica–Lamego Line: a major crustal-scale shear zone in the Variscan belt of Iberia

The Malpica–Lamego Line (MLL) is a deformation zone in the Variscan belt of NW Iberia (NW Spain and N Portugal) that runs parallel to the chain for at least 275 km, bearing I-type granodiorite plutons along most of its length. The MLL affects previous structures by which high pressure and ophiolitic rocks were exhumed and emplaced on the Iberian plate during earlier deformation phases. Correlation and reconstruction of the stratigraphy of these sheets or tectonic units at both sides of the shear zone allows a preliminary estimate of the accumulated vertical and horizontal offsets after the tectonic activity of the fault. The value of the separations, of crustal-scale proportions, reaches a maximum 15 km of vertical offset that decreases gradually to the south. The structural record found in the rocks indicates a strike-slip regime that, in general, does not fit the geometry of the offsets. We suggest that the MLL went through two different stages during the same orogenic cycle: a first dip-slip episode, a reverse faulting event, overprinted by a later strike-slip reactivation.     

Cambrian–early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: Continental break-up and rifting of the northern Gondwana margin

The Cambrian–lower Ordovician volcanic units of the South Armorican and Occitan domains are analysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Cambrian–Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases: (1) basal Cambrian rhyolites, (2) upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, (3) upper lower–middle Cambrian continental tholeiites, (4) Tremadocian rhyolites, and (5) upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic continental rift is termed the “Tremadocian Tectonic Belt” underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that forecasted the South Armorican–Medio-European Ocean as a part of the Palaeotethys Ocean.     

Deciphering the Variscan tectonothermal overprint and deformation partitioning in the Cadomian basement of the Teplá–Barrandian unit, Bohemian Massif

The Teplá–Barrandian unit (TBU) has long been considered as a simply bivergent supracrustal ‘median massif’ above the Saxothuringian subduction zone in the Variscan orogenic belt. This contribution reveals a much more complex style of the Variscan tectonometamorphic overprint and resulting architecture of the Neoproterozoic basement of the TBU. For the first time, we describe the crustal-scale NE–SW-trending dextral transpressional Krakovec shear zone (KSZ) that intersects the TBU and thrusts its higher grade northwestern portion severely reworked by Variscan deformation over a southeastern very low grade portion with well-preserved Cadomian structures and only brittle Variscan deformation. The age of movements along the KSZ is inferred as Late Devonian (~380–370?Ma). On the basis of structural, microstructural, and anisotropy of magnetic susceptibility data from the KSZ, we propose a new synthetic model for the deformation partitioning in the Teplá–Barrandian upper crust in response to the Late Devonian to early Carboniferous subduction and underthrusting of the Saxothuringan lithosphere. We conclude that the Saxothuringian/Teplá–Barrandian convergence was nearly frontal during ~380–346?Ma and was partitioned into pure shear dominated domains that accommodated orogen-perpendicular shortening alternating with orogen-parallel high-strain domains that accommodated dextral transpression or bilateral extrusion. The synconvergent shortening of the TBU was terminated by a rapid gravity-driven collapse of the thickened lithosphere at ~346–337?Ma followed by, or partly simultaneous with, dextral strike-slip along the Baltica margin-parallel zones, driven by the westward movement of Gondwana from approximately 345?Ma onwards.