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[Abstract The diagenetic history of the Ediacaran sedimentary rocks in the East European Craton (EEC) over the area extending from Arkhangelsk (Russia) in the north to Podolia (Ukraine) in the south was revealed by means of the XRD characterization and K–Ar dating of clay fractions, mudstone porosity measurements and organic geochemistry investigations. Mudstone porosity measurements produced direct evidence of shallow maximum burial of the Ediacaran sediments on the craton (Russia, Lithuania, Belarus, Volyn), not exceeding 1.5 km, and much deeper burial at the cratonic margin, in Podolia and Poland. In general, illitization of smectite and biomarker indices indicates more advanced diagenesis at the cratonic margin. K–Ar dating of authigenic illite–smectite and aluminoceladonite revealed the Palaeozoic age of mineral diagenesis (ca. 450–300 Ma) both on the craton and its margin, with older ages generally observed in the north. When the maximum palaeotemperatures were evaluated from illite–smectite and biomarkers, based on the calibrations from the conventional burial diagenetic sections, a major mismatch was detected for the cratonic area: 100°C–130°C from illite––smectite and tens of oC lower from the lipid biomarkers. This diagenetic pattern was interpreted as the result of short‐lasting (in ky scale) pulses of potassium‐bearing hot fluids migrating from the Caledonian and Variscan orogens deep in the craton interior, effectively promoting illitization in porous rocks without altering the organic matter. Analogous short pulses of fluids were responsible for numerous diagenetic phenomena, including Mississippi Valley‐Type ore deposits, in the American Midwest, in front of the Appalachians. K–Ar dating indicates that the entire Proterozoic sedimentary cover of the Great Unconformity on the EEC remained untouched by measureable post‐sedimentary changes until the early Palaeozoic, thus for over 1000 My, which is an unprecedented finding., Short‐lasting pulses of potassium‐bearing hot fluids migrated from Caledonian and Variscan orogens deep into the craton interior, effectively promoting illitization without altering the organic matter in Ediacaran sediments of EEC. ]

The NW Iberian Allochthon and the Tepla-Barrandian and Moldanubian zones represent the internal parts of the Variscan belt in their respective domains. A correlation based on the lithological association, protolith ages, metamorphic evolution, detrital zircon age spectra and tectonic setting is attempted between the NW Iberian Massif and SE Bohemian Massif in order to check whether they could have formed part of the same allochthonous stack. The Galicia-Tras-os-Montes Zone of the Iberian Massif and the internal zones of the Bohemian Massif include from bottom to top a Parautochthon and Lower Allochthon representing the outer edge of the northern Gondwana margin, an oceanic Middle Allochthon with Cambro-Ordovician and Early Devonian ophiolites and an Upper Allochthon interpreted as a peri-Gondwanan terrane. Early Variscan, subduction-related high-pressure metamorphism characterizes many of the allochthonous units, with ages younging from the structurally upper to the lower units from 400–385 Ma to 370–360 Ma, respectively. High- and ultrahigh-pressure metamorphism occurred also in the Saxothuringian Autochthon at 360–340 Ma, but not in the NW Iberian Autochthon. The different behavior of the Autochthon in the Iberian and Bohemian massifs accounts for their distinct evolutions from 360 Ma onward. We conclude that the Upper Allochthon was a unique peri-Gondwanan terrane, whereas the Middle Allochthon represents units of the same peri-Gondwanan ocean, opened at the Cambro-Ordovician boundary, and having recorded localized renewed activity in the Silurian–Early Devonian. No other oceans separated the Lower Allochthon, Parautochthon and Autochthon.

The Intra-Sudetic Basin, a ~ 12 km deep Variscan intramontane basin, has the best preserved post-orogenic sedimentary record available at the NE margin of the Bohemian Massif. Apatite fission track (AFT) analyses have been performed on 16 sedimentary and volcanic samples of Carboniferous to Cretaceous age from the Intra-Sudetic Basin to improve understanding of the post-Variscan thermal evolution. AFT central ages range from 50.1 ± 8.8 to 89.1 ± 7.1 Ma (Early Eocene to Coniacian), with 13 of them being Late Cretaceous. The mean track length values range from 12.5 ± 0.4 to 13.8 ± 0.5 (except for one sample 14.4 ± 0.2) µm. This relatively short mean track length together with the unimodal track length distributions and rather low standard deviation (0.8 to 1.7 µm) in most samples indicate a long stay in the partial annealing zone during slow cooling. However, in the northern part of the Intra-Sudetic Basin, samples show a wider track length distribution (standard deviation of 1.8 to 2.1 µm) that could indicate a more complex thermal evolution possibly related to Mesozoic reheating. Vitrinite reflectance data combined with thermal models based on the AFT results indicate that the Carboniferous strata reached maximum palaeotemperatures in the latest Carboniferous to Early Permian time, corresponding to a major coalification event. The second phase of temperature rise occurred due to Late Mesozoic sedimentary burial, but it had no influence on maturation of the Carboniferous organic matter. Final cooling phase in the Late Cretaceous–Paleogene was related to tectonic inversion of the Intra-Sudetic Basin, which occurred after deposition of a significant thickness of Cenomanian–Turonian sediments. Thermal modelling demonstrates that ~ 4 km thick cover of Upper Cretaceous sediments is required to obtain a good match between our AFT data and modelled time–temperature paths. This outcome supports a significant amount of Late Cretaceous–Paleogene inversion within the Variscan belt of Central Europe.

The authors of the Comment suggest that our geological overview map of the European Variscides is incorrect in the section showing SW Iberia (our Fig. 1a). However, our paper reports results of the provenance study from the northern Rhenish Massif, and does not attempt to discuss the architecture and tectonic evolution of the Appalachian-Variscan belt. The aim of Fig. 1 is to locate the study area in the geological context of the European Variscides and not to extrapolate the implications of our findings down to southern Portugal. The map is mostly based on Franke (2014) that is explicitly stated in the caption. Our results are neutral towards the hypothetical correlation between the Mid-German Crystalline High and the southern domains of the Ossa-Morena Zone that is shown on the map[…]

Our paper demonstrates how two-dimensional density models can deliver critical constraints that permit construction and validation of geological models in an underconstrained subcropped fold-and-thrust belt. As a case study, we use a newly discovered thrust-and-fold belt developed above the margin of the East European Craton (EEC) in SE Poland. A geological model constructed using gravity data resolved the basement-cover interface and a top-Cambrian horizon. This model was used as a framework for cross-section construction employing at this step also borehole and seismic evidence. Two cross-sections were created to address a source of uncertainty related to non-uniqueness of gravity modelling with different emphasis on gravimetric vs geological evidence. Model 1 strictly obeys the top-Cambrian derived from gravity modelling that was treated as an envelope of deeper structures. Model 2 allowed for local departures from the gravity model, especially in the case of conflicts with formation thicknesses. The comparison between the present structure and restorations allowed for separating effects of Caledonian and Variscan shortening. Although the fit of both models to the gravity data is satisfactory, model 2 better complies to geological constraints, resolving the long-discussed problem concerning the distribution and intensity of Caledonian tectonics across the SW periphery of the EEC.

The Eastern Siberian Arctic Shelf (ESAS) represents a geologically complex realm with a tectonic history that is related to the final stages of the formation of the Pangaea supercontinent during the Mesozoic and its subsequent disintegration during the Late Cretaceous and Cenozoic. It is a key region to constrain the origin of the deep-water basins and intervening ridges of the Amerasia Basin. We present results of gravity modeling of published seismic refraction and reflection profiles acquired between 1989 and 2012 over the ESAS and adjacent Arctic Ocean along five composite geotransects using Getech’s satellite altimeter-derived gravity data. Our main goal was to examine published crustal models and to present new models for the ESAS that are constrained by both seismic data and 2D gravity forward modeling. We consider several topics important for understanding Arctic geology: (i) hyperextension within the Laptev Rift System and the possible extent of the exhumed mantle, (ii) the relationship between the New Siberian Shelf and the Lomonosov Ridge, (iii) the nature of the collapsed upper Mesozoic fold belt in the southern part of the East Siberian Sea, (iv) the character of transition between the De Long Massif and the deep-water Podvodnikov Basin, (v) the lateral extent of the hyperextended North Chukchi Basin and the nature of its basement, and (vi) relationship between the Mendeleev Ridge and Chukchi Plateau crustal domains. Our results do not confirm the previously inferred extent of continental crust beneath the oceanic realm. The latter is dominated by High Arctic Large Igneous Province (HALIP) igneous crust. We discuss the existence of a dismembered continental Bennett-Barrovia block that is currently represented by three smaller fragments/massifs. When restored to its possible single state, this block can play a crucial role in reconstructing the pre-Canada Basin Arctic.

Baltica was one of continents formed as a result of Rodinia break-up 850–550 Ma. It was separated from Amazonia(?) by the Tornquist Ocean, the opening of which was preceded by Neoproterozoic extension in a network of continental rifts. Some of these rifts were subsequently aborted whereas the Tornquist Rift gave rise to splitting of Rodinia and formation of the Tornquist Ocean. The results of 1-D subsidence analysis at the fossil passive margin of Baltica provided insight in the timing and kinematics of continental rifting that led to break-up of Rodinia. Rifting was associated with Neoproterozoic syn-rift subsidence accompanied by deposition of continental coarse-grained sediments and emplacement of continental basalts. Transition from a syn-rift to post-rift phase in the latest Ediacaran to earliest early Cambrian was concomitant with deposition of continental conglomerates and arkoses, laterally passing into mudstones. An extensional scenario of the break-up of Rodinia along the Tornquist Rift is based on the character of tectonic subsidence curves, evolution of syn-rift and post-rift depocenters in time, as well as geochemistry and geochronology of the syn-rift volcanics. It is additionally reinforced by the high-quality deep seismic reflection data from SE Poland, located above the SW edge of the East European Craton. The seismic data allowed for identification of a deeply buried (11–18 km), well-preserved extensional half-graben, developed in the Palaeoproterozoic crystalline basement and filled with a Neoproterozoic syn-rift volcano-sedimentary succession. The results of depth-to-basement study based on integration of seismic and gravity data show the distribution of local NE–SW elongated Neoproterozoic depocenters within the SW slope of the East European Craton. Furthermore, they document the rapid south-eastwards thickness increase of the Neoproterozoic succession towards the NW–SE oriented craton margin. This provides evidence for extensive crustal thinning occurring prior to the break-up of Rodinia and formation of the Tornquist Ocean.

The Paleoproterozoic suture between Sarmatia and Fennoscandia (SFS), two major components of the East European Craton, extends SW-ward from Russia through Belarus to SE Poland. The exact character of this suture remains speculative, despite the results of the wide-angle reflection and refraction (WARR) soundings. Here, we show results of newly reprocessed deep reflection seismic data of the PolandSPAN™ survey, portraying the whole crust and uppermost mantle in SE Poland. Their interpretation is supported by the unsupervised clustering of seismic reflectivity patterns. From the integration of PolandSPAN™ data with both magnetic and WARR data, we conclude that the SFS cannot be interpreted as a localised lithospheric discontinuity coincident with the Minsk Fault. Instead, we observe a so-called diffuse cryptic suture zone, c. 150 km wide, where materials from two colliding plates are mixed over large distances to form a unified continental crust. The suture-related reflections are interpreted as a thrust-wedge rooted at the lower-middle crust interface underneath the Ivanowo-Borisov zone. We support Bogdanova et al. (2015) view that the Okolowo-Holeszow Belt and Belarus-Podlasie Granulite Belt have affinities to the NW margin of Sarmatia. We interpret both units as belonging to the diffuse SFS.

A main goal of this study was to understand the character of the Caledonian Deformation Front in Pomerania, NW Poland and its relationship to the adjoining Teisseyre-Tornquist Zone (TTZ), in the context of the Avalonia-Baltica early Palaeozoic collision. Since the Pomeranian Caledonides are concealed beneath 1–4 km thick platform cover of upper Palaeozoic and Mesozoic sediments, we used a combination of potential field, seismic and well data to investigate the basement architecture and structure of the lower Palaeozoic rocks. Starting from a qualitative review of gravity and magnetic data, we built a 2D gravity and magnetic model upon the PolandSPAN™ PL1-5600 seismic reflection line and applied 3D gravity inversion for a depth-to-basement study. Using well tops, a top lower Palaeozoic horizon and lower Palaeozoic isopach map were created. We found out that the Pomeranian Caledonides represent a thin-skinned fold-and-thrust belt involving Ordovician and Silurian sediments of the Caledonian foreland basin. The deformation front was developed due to the buttressing effect of a basement ramp occurring directly above the TTZ. The latter corresponds to a Precambrian suture zone overprinted by successive extensional tectonics and buried beneath the foreland basin. In northern Poland, the suture is defined by a remnant crustal keel still preserved underneath the TTZ, probably resulting from Precambrian collision during formation of the Rodinia paleocontinent. We propose that the extension of the Thor suture separating Baltica and Avalonia must exist west from the TTZ, probably in the Rugen area. In our interpretation, the TTZ represents an intra-cratonic crustal discontinuity comparable to its NW prolongation, the Sorgenfrei-Tornquist Zone that runs across the Baltic Sea, Sweden and Denmark. Consequently, the basement underlying the Palaeozoic Platform in NW Poland may be considered to have been part of Baltica in early Palaeozoic times.

In NE Poland, Eastern European Craton (EEC) crust of Fennoscandian affinity is concealed under a Phanerozoic platform cover and penetrated by sparse, deep research wells. Most of the inferences regarding its structure rely on geophysical data. Until recently, this area was covered only by the wide-angle reflection and refraction (WARR) profiles, which show a relatively simple crustal structure with a typical three-layer cratonic crust. ION Geophysical PolandSPAN™ regional seismic programme data, acquired over the marginal part of the EEC in Poland, offered a unique opportunity to derive a detailed image of the deeper crust. Here, we apply extended correlation processing to a subset (∼950 km) of the PolandSPAN™ dataset located in NE Poland, which enabled us to extend the nominal record length of the acquired data from 12 to 22 s (∼60 km of depth). Our new processing revealed reflectivity patterns, which we primarily associate with the Paleoproterozoic crust formed during the Svekofennian (Svekobaltic) orogeny, that are similar to those observed along the BABEL and FIRE profiles in the Baltic Sea and Finland, respectively. We propose a mid- to lower-crustal, orogeny-normal lateral flow model to explain the occurrence of two sets of structures that can be collectively interpreted as kilometre-scale S–C′ shear zones. The structures define a penetrative deformation fabric invoking ductile extension of hot orogenic crust in a convergent setting. Localized reactivation of these structures provided conduits for subsequent emplacement of gabbroic magma that produced a Mesoproterozoic anorthosite–mangerite–charnockite–granite (AMCG) suite in NE Poland. Delamination of thickened orogenic lithosphere may have accounted for magmatic underplating and fractionation into the AMCG plutons. We also found sub-Moho dipping mantle reflectivity, which we tentatively explain as a signature of the crustal accretion during the Svekofennian orogeny. Later tectonic phases (e.g. Ediacaran rifting, Caledonian orogeny) did not leave a clear signature in the deeper crust; however, some of the subhorizontal reflectors below the basement, observed in the vicinity of the AMCG Mazury complex, can be alternatively linked with lower Carboniferous magmatism.

In NE Poland, the Eastern European Craton (EEC) crust of the Fennoscandian affinity is concealed under a Phanerozoic platform cover and penetrated by the sparse deep research wells. Most of the inferences regarding its structure rely on geophysical data. Until recently, this area was covered only by the refraction/wide-angle reflection (WARR) profiles, which show a relatively simple crustal structure with a typical cratonic 3-layer crust. ION Geophysical PolandSPAN™ regional seismic program, acquired over the marginal part of the EEC in Poland, offered a unique opportunity to derive a detailed image of the deeper crust. Here, we apply extended correlation processing to a subset (~950 km) of the PolandSPAN™ dataset located in NE Poland, which enabled us to extend the nominal record length of the acquired data from 12 to 22 s (~60 km depth). Our new processing revealed reflectivity patterns, that we primarily associate with the Paleoproterozoic crust formation during the Svekofennian (Svekobaltic) orogeny and which are similar to what was observed along the BABEL and FIRE profiles in the Baltic Sea and Finland, respectively. We propose a mid- to lower-crustal lateral flow model to explain the occurrence of two sets of structures that can be collectively interpreted as kilometre-scale S-C' shear zones. The structures define a penetrative deformation fabric invoking ductile extension of hot orogenic crust. Localized reactivation of these structures provided conduits for subsequent emplacement of gabbroic magma that produced a Mesoproterozoic anorthosite-mangerite-charnockite-granite (AMCG) suite in NE Poland. Delamination of overthickened orogenic lithosphere may have accounted for magmatic underplating and fractionation into the AMCG plutons. We also found sub-Moho dipping mantle reflectivity, which we tentatively explain as a signature of the crustal accretion during the Svekofennian orogeny. Later tectonic phases (e.g. Ediacaran rifting, Caledonian orogeny) did not leave a clear signature in the deeper crust, however, some of the subhorizontal reflectors below the basement, observed in the vicinity of the AMCG Mazury complex, can be alternatively linked with lower Carboniferous magmatism.

The blueschist occurrence at the Kopina Mt. is situated at the eastern margin of the Karkonosze–Izera Massif in the West Sudetes of the northern Bohemian Massif. Metabasic rocks with continental crust affinity occur as lenses within the prevailing metasediments. The metabasites consist mainly of garnet, blue amphibole, epidote, chlorite-I, titanite, hematite and quartz forming the high-pressure assemblage. Synkinematic garnet exhibits prograde zoning, a feature allowing for assessment of the prograde course of the pressure–temperature ( P–T ) path. Phase equilibrium modelling has been used to estimate prograde and peak metamorphic conditions. Based on the P–T pseudosections, calculated in the system Na 2 O–CaO–K 2 O–FeO–MgO–MnO–Al 2 O 3 –SiO 2 –H 2 O–TiO 2 –O 2 (NCKFMMnASHTO), the garnet + glaucophane + epidote + chlorite + white mica(?) + Fe oxide + quartz ± titanite assemblage was formed between 12–15 kbar and 480–520 °C. These results are based on garnet and Na-amphibole compositional isopleths. Garnet shows a prograde zoning expressed by the rapid rim-ward decrease of spessartine, moderate increase of almandine and as light increase of other components. It is inferred here that white mica must have decomposed to secondary albite–chlorite-II–K-feldspar. The obtained results point to the formation of the Kopina blueschists along a low-temperature P–T gradient of 8–10 °C/km, typical of rocks from a subduction–exhumation channel. We postulate that the Kopina blueschists were formed in a subduction system developed along the eastern termination of the Saxothuringian Ocean and operating beneath the Tepla–Barrandian upper plate. When combined with previous data on continental crust affinity for the protolith, our results demonstrate a derivation of the Kopina blueschists from subducted part of the Saxothuringian margin.

The Laptev Shelf in the East Siberian Arctic represents a rare tectonic setting where an active oceanic spreading centre, the Gakkel Ridge, intersects a continental margin. The North America–Eurasia plate boundary follows the Gakkel Ridge and passes into a continental shelf; this has resulted in the development of a wide rift system that has been active since the Late Cretaceous. The new long-offset seismic profiles provide a reliable basis for deciphering the structural characteristics of this rift system. We use two new seismic profiles, along with one acquired in the 1990s, to examine the crustal architecture of the rift system. Our approach combines seismic interpretation, time to depth conversion of seismic profiles and 2D gravity forward modelling. The obtained results indicate the presence of hyperextended continental crust beneath the Ust9 Lena Rift Basin and exhumed continental mantle at the base of the syn-rift succession along the rift axis. The upper crust was removed by brittle stretching, while the lower crust experienced extreme ductile thinning. Our results show that continental crust can be eliminated in the course of rifting without a considerable heat input from asthenospheric mantle.

Four detrital zircon concentrates from the metasediments and metavolcanics of the Central Sudetes, Bohemian Massif, have been dated using SHRIMP II. The Wyszki paragneiss yielded Precambrian age spectra similar to those characteristic of the Cadomian terranes: (1) Archaean and Palaeoproterozoic zircons are scattered between 2830 and 1867 Ma, and (2) there are abundant Neoproterozoic zircons dated at 803–577 Ma. The estimated maximum sedimentation age for this rock is 566 ± 4 Ma. The Klodzko Fortress pyroclastic metarhyodacite gave an igneous emplacement age of 536 ± 2 Ma. The magmatic precursor to the subvolcanic Gniewoszow metarhyolite was dated at 501 ± 3 Ma. Finally, the Ścinawica subvolcanic rhyolite yielded an igneous emplacement age of 338 ± 3 Ma and a large population of inherited zircons dated at: Palaeoproterozoic, Neoproterozoic, Cambro-Ordovician and Late Devonian–early Carboniferous. The dated samples come from two adjacent suspect terranes —the Orlica–Śnieznik dome and the Klodzko massif in the Central Sudetes that are characterised by contrasting timing of metamorphism and exhumation. Despite this difference, the results obtained show, in conjunction with earlier data, a similar provenance of the studied units and their common affinity to the Saxo-Thuringian terrane. Since the Central Sudetes are separated from Saxo-Thuringia by a collisional suture, the pre-Variscan rocks must represent the deformed and metamorphosed, allochthonous equivalents to Saxo-Thuringian lithologies. They were probably subducted together with the Saxo-Thuringian passive margin during a Variscan collision and then exhumed within an accretionary wedge in front of Brunia/East Avalonia. The Central Sudetic suspected terranes must have been derived from a dismembered single accretionary complex and were then juxtaposed by strike–slip faults.

New SHRIMP II data from the Strzegom–Sobotka composite granitoid intrusion show a successive emplacement of four magma batches with different modal compositions over the period of c. 10–15 m.y. The first emplaced was the two-mica granite that crystallised at 304.8 ± 2.7 Ma. This was followed by the biotite granodiorite the three samples of which were dated at 301.9 ± 3.6, 299.3 ± 2.4, and 297.9 ± 3.7 Ma, respectively. The biotite and hornblende–biotite granites yielded practically an identical age, 301.1 ± 2.7 Ma, 297.7 ± 2.2 Ma, and 297.1 ± 3.0 Ma, but are considered slightly younger based on the field cross-cutting relationships. The final rock type is the Łazany granodiorite dated at 294.4 ± 2.7 Ma. The temperature estimates along with the zircon crystal morphology show the gradual but significant rise of magma temperature with the decreasing age of intrusion. The temperature increased from c. 720 °C in the two-mica granite to 740–780 °C in the biotite granodiorite and 800–860 °C in the biotite–hornblende granites and Łazany granodiorite. Based on the ages obtained, the emplacement of the Strzegom–Sobotka granitoids immediately followed the cessation of compression in the Variscan externides of SW Poland. Moreover, the intrusion was synchronous with rapid uplift of the Variscides and abundant bimodal volcanism in the nearby intramontane troughs. Consequently, the gradual heating of the crust, as recorded by the data acquired, must have been caused by thermal influx into the lower crust related to the ascent of basaltic magmas. Since the latter were probably formed during the decompressional melting of lithospheric mantle, the emplacement of Strzegom–Sobotka granitoids, along with bimodal volcanism, signalled the commencement of lithospheric thinning beneath Central Europe.

International audience; The sedimentary cover of the East European Craton (EEC) is unique because of its low degree of diagenetic alteration that allows preservation of the original “source to sink” relationships. The present study provides U-Pb and Hf zircon data for the entire Proterozoic sedimentary section of the EEC based on samples from five boreholes in Belarus within the Volyn-Orsha Basin, one of the most important sedimentary basins of the craton. Twenty-one samples of mudstones and sandstones were selected for detrital zircon U-Pb geochronology, supplemented by the Hf isotope analyses of zircons from 6 samples representing different U-Pb age spectra and bulk rock XRD mineralogy of all mudstone samples collected from the studied boreholes. Five clastic successions in the Volyn-Orsha Basin are characterized by different sources of detrital material: (1) The Mesoproterozoic Pinsk Suite with a narrow population of c. 2.0 Ga zircons, (2) The Orsha Suite with a broad 1.3–3.2 Ga zircon age distribution, (3) Glacial sediments of the Vilchitsy Series with an age spectra similar to the Orsha Suite, except for a c. 1.0 and 1.2 Ga cluster, (4) The Volyn and Valdai Series, including lowermost Cambrian, with a narrow trimodal population of 0.5, 1.5, and 1.8 Ga zircons, and (5) lower Cambrian (?) sediments with a diffused zircon age spectrum, including a 500–700 Ma cluster. Maximum depositional ages were constrained for the Vilchitsy Series at 977 ± 6 Ma and for the Volyn Series at 579–545 ± 4 Ma. Combined Hf zircon data indicate four episodes of new continental crust generation at 3.3, 2.8, 2.1–2.3 and 1.8 Ga, suggestive of source terrains within the crust of the present-day EEC. These sources experienced subsequent reworking of crust at c. 1.8 Ga and 550–600 Ma. Only a lower Cambrian sample lacks any trend or clustering within the Hf data probably due to mixing of zircons from exotic and local sources. Paleogeographic models explaining these provenance signals in terms of intracratonic erosion and sediment transport are presented.

The Muglad basin, Sudan, is a good example of polyphase rifting with at least three major phases of basin development. Each phase has resulted in the generation of source rock, reservoir and seal geology with structural traps often closely linked to basement highs. In this contribution we investigate the tectonic processes that have contributed to basin development at both macro and micro scales. The macro perspective investigates the basin?s evolution as part of an Africa wide rift system and how it is intimately linked to global plate tectonics and to changes in plate interactions. These changes in plate interactions have caused significant modifications in the orientation and magnitude of the African stress field which in turn has controlled the development of the rift system. On the micro basin scale, the methods used to investigate structure include the compilation of structural maps for different time periods of the individual rift basins into regional structural maps, the role and importance of stratigraphic unconformities within basins and geophysical mapping of the basement morphology of the Muglad basin using an integrated interpretation approach.

IntroductionThe Variscan orogen of Europe con-tains a collection of terranes that weredispersed along the northern marginof West Gondwana in the late Neo-proterozoic and early Palaeozoic (e.g.Murphy et al., 2002; Linnemannet al., 2007; Nance et al., 2008). Theseperi-Gondwanan terranes show anumber of common features as: (1)voluminous late Neoproterozoic(c. 640–550 Ma) arc magmatism, (2)extensive volcano-sedimentary succes-sions of cogenetic arc-related basins,(3) a widespread Cadomian unconfor-mity separating deformed Precam-brian rock units from their EarlyPalaeozoic (Cambro-Ordovician)overstep sequence and (4) an overlyingEarly–Middle Cambrian shallow-marine platform (e.g. Murphy andNance, 1989; Nance et al., 1991,2002). The peri-Gondwanan terranesrepresent dismembered fragments ofthe Avalonian – Cadomian orogenthat was formed in the late Neoprote-rozoic (c. 700–540 Ma) at the north-ern edge of Gondwana (e.g. Nanceet al., 2002; Linnemann et al., 2007).In the early Palaeozoic, several peri-Gondwanan terranes were separatedfrom West Gondwana (e.g. Avalonia)while others, including the Cadomianterranes, remained attached toGondwana and were accreted intothe Appalachian – Variscan orogenwith the closure of the Rheic Ocean inthe late Palaeozoic (e.g. Linnemannet al., 2004; Nance et al., 2008). Pres-ently, the Cadomian terranes areincluded within the Variscan belt ofEurope as separate blocks that stretchout from the Iberian Massif to theSaxo-Thuringian and Tepla´-Barran-dian zones (Fig. 1; e.g. Linnemannet al., 2008; Nance et al., 2008).The occurrences of Neoproterozoicrocks have long been known from theCentral Sudetic segment of the easternVariscides (Fig. 2), although their pre-cise age and provenance remainedunclear (e.g. Aleksandrowski and Ma-zur, 2002). Only recently, Jastrze˛bskiet al. (2010) reported from the Orlica-S´nieznik dome in the Central Sudetes_a metamorphosed volcano-sedimen-tary succession continuing from thelate Neoproterozoic into the early Pal-aeozoicwithoutaCadomianunconfor-mity. If uninterrupted sedimentationwas actually the case across theNeoproterozoic–Palaeozoic boundary(c. 542 Ma), the Orlica-S´nieznik dome_would lack a Cadomian affinity. Con-sequently, the Central Sudetes wouldrepresent an exotic terrane insertedbetween the Cadomian terranesand East Avalonia. In such a case,existing plate tectonic models for theclosure of the Rheic Ocean wouldrequiresubstantialrevision.In this article, we present new Sen-sitive High Resolution Ion Micro-probe (SHRIMP) U–Pb data fordetrital zircon grains to constrain theage and provenance of selectedmetasediments from the Orlica-S´nieznik dome (Fig. 2). These geo-_chronological data, in combinationwith field relations and publishedresults, are used to identify the plate-tectonic setting(s) of Neoproterozoicto Cambro-Ordovician rock units ofthe Orlica-S´nieznik dome. We then_compare the new results with theNeoproterozoic to early Palaeozoicstratigraphy of the Saxo-Thuringianzone to test the Cadomian affinity ofthe Central Sudetes. Our goal is toconstrain the eastern extent of theCadomian terranes and the location ofthe Rheic suture in Central Europe.Geological settingThe Orlica-S´nie_znik dome (Fig. 2) isdominated by amphibolite-grade or-thogneiss, locally containing lenses of(U)HP rocks, alternating with belts ofstaurolite-grade supracrustal rocks(Don et al., 1990). The orthogneiss istraditionally subdivided into two maintextural varieties (Fig. 2): the por-phyric augen to banded S´nieznik_ABSTRACT

The Carboniferous foreland basin of western Poland contains a coherent succession of late Visean through Westphalian turbidites derived from a uniform group of sources located within a continental magmatic arc. Detrital zircon geochronology indicates that two main crustal components were present in the source area of Namurian A sediments. They represent Late Devonian and Early Carboniferous ages, respectively. The detritus from Westphalian D beds is much more diversified and contains admixture of Late Carboniferous zircons suggesting rapid unroofing of Variscan igneous intrusions in the hinterland between Namurian A and Westphalian D times. Tectonic repetitions of tens of metres thick fault-bounded stratigraphic intervals, recorded in several wells, provide evidence for compressional regime that occurred in the SW part of the Carboniferous basin not earlier than during the Westphalian C and produced NW-SE trending folds, concordant with the structural grain of the adjacent, NE part of the Bohemian Massif.

SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates input from late (550–750 Ma) and early Proterozoic to Archaean sources (∼2.0–3.4 Ga, the latter being the oldest recorded age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks of early Palaeozoic age. Rather, they indicate provenance from Cadomian and older rocks that currently form part of other, geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone. Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift succession deposited at the northern margin of Gondwana, cannot yet be precluded.

The Sudetes in southwestern Poland and northern Bohemia expose a Palaeozoic collage of the northeastermost extremity of the Variscan belt. One of presumed terrane boundaries occurs in the Orlica Mts, along the contact between the phyllite-amphibolite complex (Neoproterozoic?) of the Nove Město unit of probable Tepla-Barrandian affinities in the SW and the orthogneiss (Early Ordovician protolith) and mica-schist (Neoproterozoic?) complexes of the Orlica-Śnieznik unit in the NE, most likely representing the Moldanubian terrane. The synmetamorphic structural evolution of both adjacent units comprised four deformation events. The Nove Město rocks have recorded an early stage of ductile, top-to-the SE thrusting (D1), which must have resulted in an early juxtaposition of the both terranes within a nappe pile. The original overthrust contact was subsequently modified by a dextral shear-dominated event (D2), which produced a 1–2 km wide shear zone at the boundary of both units, in which earlier fabric elements were overprinted and mostly obliterated. This deformation brought the lower-grade Nove Město rocks into present-day strike-slip contact with those of the regionally uplifted, higher-grade Orlica-Śnieznik unit. Postdating this juxtaposition are E–W trending folds F3, which affect both the adjacent units. The contact shear zone also contains record of a late, top-to-the SW, semi-brittle, normal-slip displacement (D4), downthrowing the Nove Město unit. The peak, amphibolite facies metamorphic conditions were attained in the Orlica-Śnieznik unit and in the contact shear zone prior to the D2 event. They corresponded to maximum temperatures and pressures of ca. 600 °C and 10 kbar, respectively. The D1 thrusting event in the phyllites of the Nove Město unit took place under greenschist facies conditions (ca. 350 °C and 4.5 kbar) and its effects mostly survived the later amphibolite-facies metamorphism. These structural relationships are equivalent to those observed elsewhere in the Bohemian Massif on the Tepla-Barrandian/Moldanubian terrane boundary. The characteristic features of this boundary are a high metamorphic gradient but lack of metamorphic inversion; the occurrence of mid-Carboniferous stitching plutons; and the importance of mid-Carboniferous deformation that resulted in significant downwards movement of the low-grade Tepla-Barrandian terrane relative to the uplifted high-grade and hot lower to middle crust of the Moldanubian terrane. The downthrow of the Tepla-Barrandian occurred on ductile shear zones showing either down-dip-slip kinematics or that of transfer strike-slip, as was the case with the Orlica Mts., both kinematics being associated within the same, regional-scale, linked shear zone extensional system. The extensional crustal collapse must have been preceded by a SE-directed crustal stacking achieved through overthrust emplacement of the Tepla-Barrandian on top of the Moldanubian terrane.

The Klodzko Metamorphic Complex (KMC) in the Central Sudetes is a composite outcrop of pre-Upper Devonian metasedimentary and metaigneous rocks, formed of several thrust units. The metaigneous rocks are geochemically diversified, and were interpreted to reflect a complex geodynamic setting of emplacement. The association of large amounts of felsic and mafic rocks is reminiscent of the model of Cambro-Ordovician bimodal, rift-related suites developed along the northern periphery of Gondwana. However, the felsic rocks are potash-poor, calc-alkaline in character, while the associated mafic rocks are, in part, metagabbros and cumulates resembling N-MORB, which is consistent with neither typical ensialic rift nor evolved MOR tectonic environments. Combined with published data, our new geochemical and Nd isotope results show that the metabasic rocks of the northeastern part of the KMC, not associated with felsic volcanics, are of within-plate type, with an ϵNd400 (assuming approximate youngest possible Silurian/Devonian age) of +6.8, typical of magmas derived from time-integrated depleted mantle sources. The metagabbros of the southwestern part of the KMC (associated with felsic rocks) range from slightly enriched to depleted rocks, and their ϵNd560 (assuming a Neoproterozoic age, K. Turniak, personal communication) scatters from +2.2 to +8.6, suggesting that hybrid sources and/or variable degrees of crustal contamination of a strongly depleted mantle source were involved. The intermediate and acidic rocks are peraluminous to metaluminous rhyolites, rhyodatites/dacites, and andesites (and volcaniclastics), with Na2O > K2O and large negative anomalies of Nb, Sr, and Ti. Their highly variable, but distinctly positive, ϵNd560 values (from +2.9 to +8.6, mostly clustered around +5.5) overlap those measured in the associated metagabbros, thereby substantiating close genetic relationships. Metarhyolites produced by crustal melting are conspicuously missing. A subduction-related environment is suggested for this peculiar mafic–felsic association of probable Neoproterozoic age. The overall geochemical variations, combined with the new age data, indicate that the KMC is a composite domain that displays fragments of a Pan-African active margin, telescoped during Variscan nappe tectonics, with rift-related volcanics and passive margin sequences probably related to the Palaeozoic break-up of Gondwana.

The Nagssugtoqidian orogen and its transition into the Rinkian orogen to the north were the main focus of the field activities of the Geological Survey of Denmark and Greenland (GEUS) in West Greenland in the summer of 2001. This work was carried out within the framework of the Survey’s three-year programme of bedrock mapping and mineral resource evaluation to enhance the understanding of the Archaean and Palaeoproterozoic crustal evolution in the transition zone between the Nagssugtoqidian and Rinkian orogens (Fig. 1). The work in the field season of 2001 comprised geological mapping of the 1:100 000 Kangaatsiaq map sheet described in this paper (Fig. 2), an investigation of the supracrustal rocks at Naternaq / Lersletten (Østergaard et al. 2002, this volume), a geochronological reconnaissance of the southern Rinkian orogen in the northern Disko Bugt region (Garde et al. 2002, this volume), a resource evaluation of the Nagssugtoqidian orogen (Stendal et al. 2002, this volume), a synthesis and interpretation of geophysical data of the central part of the Nagssugtoqidian orogen (Nielsen et al. 2002, this volume) and a report on investigations of the kimberlites and related intrusive rocks in the southern Nagssugtoqidian orogen and its foreland (Jensen et al. 2002, this volume).

The southern and eastern Karkonosze–Izera massif (northern Bohemian Massif) exposes blueschist facies rocks and MORB-type magmatic complexes. During Late Devonian to Early Carboniferous times, these were overthrust within a nappe pile toward the NW onto the pre-Variscan Saxothuringian basement composed of the Izera–Kowary metagranitoids and their envelope. The lowermost nappe (or parautochthonous?) unit of the pile is the low-grade metamorphosed Jestěd complex, comprising a Devonian to Early Carboniferous sedimentary succession of the Saxothuringian passive margin. This is tectonically overlain by the South Karkonosze complex, which represents Ordovician–Silurian volcano-sedimentary infill of the Saxothuringian basin, affected by Late Devonian HP metamorphism. The uppermost nappe is the Early Palaeozoic epidote–amphibolite grade Leszczyniec MORB-like complex, cropping out on the eastern margin of the Karkonosze–Izera massif. It probably represents a fragment of obducted Saxothuringian basin floor. The nappe pile was stacked beneath the overriding upper plate margin, now concealed below the Intra–Sudetic basin and hypothesized to represent a fragment of the Tepla–Barrandian terrane. The nappe stacking, triggered by buoyancy-controlled upward extrusion of the subducted continental slab, was the main mechanism for the exhumation of HP rocks. The final stages of the NW-ward nappe stacking were accompanied and followed by SE-directed Early Carboniferous extensional collapse. The lower plate of the suture zone was uplifted at that time and intruded by the ~330-Ma-old, nearly undeformed Karkonosze granite pluton. As a result of the collapse, the Tepla–Barrandian(?) upper plate was downthrown on shear zones and brittle faults and buried under several km-thick synorogenic Late Tournaisian(?) through Namurian and post-orogenic Late Carboniferous–Early Permian succession of the Intra–Sudetic basin. The south and east Karkonosze suture most probably is a fragment of the Tepla/Saxothuringian (Munchberg–Tepla) suture belt known from the western Bohemian Massif.

The still highly disputable terrane boundaries in the Sudetic segment of the Variscan belt mostly seem to follow major strike-slip faults and shear zones. Their kinematics, expected to place important constraints on the regional structural models, is discussed in some detail. The most conspicuous is the WNW–ESE Intra-Sudetic Fault Zone, separating several different structural units of the West Sudetes. It showed ductile dextral activity and, probably, displacement magnitude of the order of tens to hundreds kilometres, during late Devonian(?) to early Carboniferous times. In the late Carboniferous (to early Permian?), the sense of motion on the Intra-Sudetic Fault was reversed in a semi-brittle to brittle regime, with the left-lateral offset on the fault amounting to single kilometres. The north–south trending Niemcza and north-east–southwest Skrzynka shear zones are left-lateral, ductile features in the eastern part of the West Sudetes. Similarly oriented (northeast–southwest to NNE–SSW) regional size shear zones of as yet undetermined kinematics were discovered in boreholes under Cenozoic cover in the eastern part of the Sudetic foreland (the Niedźwiedź and Nysa-Brzeg shear zones). One of these is expected to represent the northern continuation of the major Stare Mesto Shear Zone in the Czech Republic, separating the geologically different units of the West and East Sudetes. The Rudawy Janowickie Metamorphic Unit, assumed in some reconstructions to comprise a mostly strike-slip terrane boundary, is characterized by ductile fabric developed in a thrusting regime, modified by a superimposed normal-slip extensional deformation. Thrusting-related deformational fabric was locally reoriented prior to the extensional event and shows present-day strike-slip kinematics in one of the sub-units. The Sudetic Boundary Fault, although prominent in the recent structure and topography of the region, was not active as a Variscan strike-slip fault zone. The reported data emphasize the importance of syn-orogenic strike-slip tectonics in the Sudetes. The recognized shear sense is compatible with a strike-slip model of the northeast margin of the Bohemian Massif, in which the Kaczawa and Góry Sowie Units underwent late Devonian–early Carboniferous southeastward long-distance displacement along the Intra-Sudetic Fault Zone from their hypothetical original position within the Northern Phyllite Zone and the Mid-German Crystalline High of the German Variscides, respectively, and were juxtaposed with units of different provenance southwest of the fault. The Intra-Sudetic Fault Zone, together with the Elbe Fault Zone further south, were subsequently cut in the east and their eastern segments were displaced and removed by the younger, early to late Carboniferous, NNE–SSW trending, transpressional Moldanubian–Stare Mesto Shear Zone.

This contribution has two aims – to reinforce the plate tectonic linkage between the evolving Atlantic Ocean ridge system with the poly-phase development of the West and Central African Rift system by correlating the stratigraphic unconformities of the Muglad rift basin with the changes in relative plate motions within the Atlantic Ocean. Then by using the newly compiled gravity and magnetic data for the Muglad basin to generate a new structure and depth to basement map that confirms the close relation between basement structure and known oil accumulations and to spatially identify new targets areas worthy of investigation.

We analyse the deformation pattern along the south-western margin of the Central European Basin System (CEBS) where Upper Carboniferous–Mesozoic rocks are uplifted due to the Late Cretaceous basin inversion. The geometry of mesoscale faults and associated striae are used to calculate the stress state(s) responsible for the observed deformation. Each reduced stress tensor obtained comprises (i) the directions of the principal stress axes σ1, σ2, and σ3 (σ1 ≥ σ2 ≥ σ3) and (ii) the ratio of principal stress differences R = (σ2 − σ3) / (σ1 − σ3). We present a stress inversion technique that allows each stress state inherent in a heterogeneous fault population to be identified by integrating the results of the PBT-Method [Turner, F.J., 1953. Nature and dynamic interpretation of deformation lamellae in calcite of three marbles. American Journal of Sciences, 251(4): 276–298; Sperner, B., Ratschbacher, L. and Ott, R., 1993. Fault-striae analysis: a Turbo Pascal program package for graphical presentation and reduced stress tensor calculation. Computers & Geosciences, 19: 1361–1388] and the Multiple Inverse Method [Yamaji, A., 2000. The multiple inverse method; a new technique to separate stresses from heterogeneous fault-slip data. Journal of Structural Geology, 22(4): 441–452]. This comprehensive approach not only facilitates the separation of complex data sets into homogeneous subsets but also guarantees that each stress state derived fulfils both the criteria of low-misfit angles (Wallace–Bott hypothesis) and high shear-to-normal-stress ratios (Mohr–Coulomb criterion). The reliability of our technique is confirmed by the fact that irrespective of (i) the number of fault-slip data from an outcrop, (ii) the number of subsets they represent and (iii) the proportion of newly formed and reactivated faults, we obtain consistent results from outcrops of variously aged rocks. This consistency concerns both calculated stress states as well as locally observed deformation sequences. Such local chronologies are derived from cross-cutting relationships and superimposition of different fault-slip data which individually are assigned to a consistent stress state. A synthesis of results from different locations of the study area argues for the superposition of two main deformation events. Most prominently, the area was affected by a stress state with a horizontal N–S- to NE–SW-directed maximum compression (σ1) and a low stress ratio which induced reverse and strike-slip faulting. A pure strike-slip regime of E–W- to NW–SE-directed compression with moderate stress ratios is less prevalent and probably younger. The age of the youngest rocks documenting these two phases proves the stress fields to correspond to the polyphase Late Cretaceous–Tertiary basin inversion of the CEBS during post-Cenomanian times. The youngest tectonic imprints detected in the study area correspond to locally appearing extensional stress states with varying directions of σ3. At many sites, the youngest derived paleostress state coincides with the present-day stress field in terms of the direction of the maximum horizontal stress axis, SHmax. The only stress state detected which pre-dates the basin inversion corresponds to an extensional regime with an WNW-ESE- to NW–SE-directed σ3-axis observed only locally in the N–S striking Leine Graben and its prolongation to the North. The fact that the majority of variously aged rocks exhibit only the traces of the latest deformation phases indicates a high degree of fault plane reactivation in the study area.

(1) The SUDETES 2003 seismic experiment investigated the lithospheric structure of the eastern part of the Variscan belt of central Europe. The key profile of this experiment (S01) was 630 km long and extended southwestward from the margin of the East European craton, across the Trans-European suture zone (TESZ) and Sudetes, and across the Bohemian Massif that contains the active Eger (Ohre) rift, which is an element of the European Cenozoic rift system. Good quality first arrivals and later phases of refracted/reflected P and S waves were interpreted using 2-D ray-tracing techniques. The derived seismic model shows large variations in the internal structure of the crust, while the depth to the Moho varies in the relatively narrow depth interval of 28-35 km. Except for the Polish basin on the northeast end of the profile, the sedimentary cover is thin. The crystalline upper and middle crust with velocities of 5.9-6.4 km s 1 is about 20 km thick, and the 7-10 km thick lower crust can be divided into three regions based on P wave velocities: a low-velocity region (6.5-6.6 km s 1 beneath Eger rift and Sudetes) that is bounded on the southwest and northeast by regions of significantly higher velocity (6.8-7.1 km s 1 beneath the Saxothuringian and Moldanubian in the southwest and Fore-Sudetic Monocline and Polish Basin in the northeast). High-velocity bodies (Vp > 6.5 km s 1 ) were delineated in the upper crust of the Eger rift region. The seismic structure along the S01 profile images a Variscan orogenic wedge resting on the down warped margin of the plate margin containing the TESZ. This situation implies the northerly directed subduction of the Rheic Ocean that existed between the southern margin of the Old Red Continent and the Armorican terranes presently accreted into the Variscan belt. Closure of this ocean produced the Rheic suture between low-velocity crust of the Variscan orogenic wedge and higher-velocity crust of the TESZ.

Ca. 500 Ma orthogneisses and bimodal suites are widespread along the northern part of the Bohemian Massif (central European Variscides) and are interpreted to document intense magmatism during a continental break-up episode along the northern periphery of Gondwana. Based on geological setting, and geochemical and isotopic evidence, these felsic igneous rocks record the generation of: (1) magmas of pure or predominantly crustal derivation, represented by minor extrusives and much more voluminous orthogneisses similar to S-type granitoids; (2) subordinate magmas of exclusively mantle origin (ranging from within-plate alkali trachytes to oceanic plagiogranites) corresponding to felsic derivatives of associated basalts; and (3) magmas of hybrid origin, produced either as a result of large degrees of contamination of mantle-derived magmas ascending through the crust, or alternatively, generated by partial melting of mixed sources, such as interlayered sediments and mafic rocks or graywackes containing a juvenile component. The high-temperature dehydration melting process responsible for the generation of the most abundant rock-types necessitated the advection of mantle heat, in a context of continental lithosphere extension, as documented by broadly coeval basaltic magmatism at the scale of the igneous province. The large volumes of felsic magmas generated during the 500-Ma anorogenic event are interpreted to result from the combination of a hot extensional tectonic regime with the widespread availability in the lower crust of fertile lithologies, such as metagraywackes. This in turn reflects the largely undifferentiated nature of the crustal segment accreted some 50–100 m.y. earlier during the Cadomian orogeny.

Several selected seismic lines are used to show and compare the modes of Late-Cretaceous–Early Tertiary inversion within the North German and Polish basins. These seismic data illustrate an important difference in the allocation of major zones of basement (thick-skinned) deformation and maximum uplift within both basins. The most important inversion-related uplift of the Polish Basin was localised in its axial part, the Mid-Polish Trough, whereas the basement in the axial part of the North German Basin remained virtually flat. The latter was uplifted along the SW and to a smaller degree the NE margins of the North German Basin, presently defined by the Elbe Fault System and the Grimmen High, respectively. The different location of the basement inversion and uplift within the North German and Polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the WNW-ESE trending Elbe Fault System and by the NW-SE striking Teisseyre-Tornquist Zone, the latter underlying the Mid-Polish Trough. Therefore, the inversion of the Polish and North German basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis. The inversion of the Mid-Polish Trough was connected with the reactivation of normal basement fault zones responsible for its Permo-Mesozoic subsidence. These faults zones, inverted as reverse faults, facilitated the uplift of the Mid-Polish Trough in the order of 1–3 km. In contrast, inversion of the North German Basin rarely re-used structures active during its subsidence. Basement inversion and uplift, in the range of 3–4 km, was focused at the Elbe Fault System which has remained quiescent in the Triassic and Jurassic but reproduced the direction of an earlier Variscan structural grain. In contrast, N-S oriented Mesozoic grabens and troughs in the central part of the North German Basin avoided significant inversion as they were oriented parallel to the direction of the inferred Late Cretaceous–Early Tertiary compression. The comparison of the North German and Polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field. A thick Zechstein salt layer in the central parts of the North German Basin and the Mid-Polish Trough caused mechanical decoupling between the sub-salt basement and the supra-salt sedimentary cover. Resultant thin-skinned inversion was manifested by the formation of various structures developed entirely in the supra-salt Mesozoic–Cenozoic succession. The Zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution. Only in parts of the NGB and MPT characterised by either thin or missing Zechstein evaporites, thick-skinned inversion directly controlled inversion-related deformations of the sedimentary cover. Inversion of the Permo-Mesozoic fill within the Mid-Polish Trough was achieved by a regional elevation above uplifted basement blocks. Conversely, in the North German Basin, horizontal stress must have been transferred into the salt cover across the basin from its SW margin towards the basins centre. This must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion-related basement faults are seismically detected apart from the basin margins. This strain decoupling in the interior of the North German Basin was enhanced by the presence of the Elbe Fault System which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred Late Cretaceous–Early Tertiary far-field compression.

The southern and eastern margins of the Karkonosze-Izera massif in the West Sudetes expose a nappe pile overthrust toward the NW onto the pre-Variscan continental basement of the Saxothuringian basin. The uppermost thrust sheet, the Leszczyniec nappe, shows an entirely different structural pattern in comparison to all underlying units. Although this contrast of structural trends has been long recognized, the irregular distribution of structural data prevented its reliable tectonic interpretation. Therefore, the AMS method was applied in the area to collect more structural information from meta-igneous, often massive and weakly foliated and lineated rocks of the Leszczyniec unit. An analysis of the magnetic fabric confirms the general difference of structural plan between the Leszczyniec nappe and the underlying tectonic units, interpreted below to result from the juxtaposition of entirely decoupled crustal segments. Furthermore, the AMS data reveals a discrepancy of the magnetic fabric within the Leszczyniec unit itself, between the metabasites and penetrating them metagranitoids. The latter rocks demonstrate a continuous transition of a structural trend towards that, typical of the underlying nappe pile. This abrupt change probably reflects an uplift of the Leszczyniec unit into the shallower crustal level dominated by a different deformation regime.