The Trans-European Suture Zone (TESZ) is the boundary between ancient Precambrian lithosphere of the East European Craton (EEC) and the younger lithosphere beneath the latest Neoproterozoic–Palaeozoic mobile belts of western Europe. The former is characterized by a thick crust (c. 45 km), low heat flow and a tectono-thermal age of about 3000 to 800 Ma, the latter by a thinner crust (c. 30 km), higher heat flow and a tectonothermal age of 560 to 290 Ma. These contrasting types of crust were juxtaposed during the Caledonian and Variscan orogenic episodes. The crystalline basement of the TESZ is largely concealed by sedimentary basins controlled by the reactivation of structures within the suture zone during Permian–Mesozoic extension and Cenozoic inversion. The pre-Permian evolution of the craton and the mobile belts, and the location of the sutures, is inferred from isolated outcrops, hundreds of boreholes and geophysical evidence. Existing seismic data demonstrates that the TESZ is rather narrow and has an expression at all levels of the lithosphere and deep into the asthenosphere. Teleseismic studies have demonstrated that the differences in the velocity structure of the asthenospheric and lithospheric mantle across the TESZ persist to depths of c. 400 km (Zielhus & Nolet, 1994).

A passive seismological experiment across the northern boundary of the Tornquist Fan was carried out from December 1994 until April 1995 along a 100 km long profile in Denmark and Sweden. Observed PS converted seismic waves indicate an abrupt increase in Moho depth of 4–5 km within 5 km horizontal distance at about 50 km to the northeast of the Øresund. This is a much sharper jump than that inferred from the wide-angle data of EUGENO-S line 1. Preliminary analysis of seismic shear wave anisotropy indicates asthenospheric mantle flow parallel to the Sorgenfrei-Tornquist Zone. These parallel directions are already observed between the Elbe Line and the Sorgenfrei-Tornquist Zone while further south in central Europe the flow directions follow the trend of the Alpine belt.

The Tornquist Fan is a northwestward widening splay of late Carboniferous–early Permian fault zones in the region of Denmark emanating from the Teisseyre-Tornquist Zone in northern Poland. The crust–mantle boundary shows an undulating topography which correlates with the main tectonic features of the area. Zones of high average velocity through the consolidated crust coincide with pronounced positive Bouguer gravity anomalies in the deep basins and in the border zone of the shield. Less pronounced, similar correlation to gravity is found for the thickness of the lower crust, whereas the thickness of the upper crust in parts is inversely related to the gravity anomalies. Some magnetic anomalies appear to be related to the gravity anomalies. The positive features are interpreted as magmatic bodies that formed during late Carboniferous to early Permian transtensional movement along the faults of the Tornquist Fan, which explains pull-apart structures in the area and the Ringkøbing-Fyn basement High. The magmatism has strong implications for the subsequent formation of the regional Mesozoic basins. Localized dextral strike-slip movement on the Teisseyre-Tornquist Zone became distributed over the Tornquist Fan, which formed part of the rigid Baltic Shield and was situated at the northwestern end of this major, long-reaching Central European zone. As defined by late Cretaceous–early Tertiary compressional inversion structures, the Sorgenfrei-Tornquist Zone cuts across the Tornquist Fan area.

New data implying crustal activation of Eastern Avalonia along the Anglo-Brabant fold belt are presented. Late Ordovician subduction-related magmatism in East Anglia and the Brabant Massif, coupled with accelerated subsidence in the Anglia Basin and in the Brabant Massif during Silurian time, indicate a foreland basin development. Final collision resulted in folding, cleavage development and thrusting during the mid-Lochkovian to mid-Eifelian. In the southeast of the Anglo-Brabant fold belt, Acadian deformation produced basin inversion and the regional antiformal structure of the Brabant Massif. The uplift, inferred from the sedimentology, petrography and reworked palynomorphs in the Lower Devonian of the Dinant Synclinorium is confirmed by illite crystallinity studies. The tectonic model discussed implies the presence of two subduction zones in the eastern part of Eastern Avalonia, one along the Anglo-Brabant fold belt and another under the North Sea in the prolongation of the North German–Polish Caledonides.

The Tremadoc to early Llanvirn is the time interval in the Ordovician for which a global acritarch distribution pattern can be proposed. It is possible to differentiate a high latitude, cold- to temperate-water realm and a low latitude, warm-water realm. The cold-water assemblages, recorded from numerous localities at the northern border of Gondwana in the southern hemisphere, include some diagnostic morphotypes, such as Arbusculidium filamentosum, Arkonia, Aureotesta, Coryphidium-Vavrdovella, Dicrodiacrodium, Frankea and Striatotheca. Assemblages related to warm-water areas are described from Canada, the United States, northern China, Australia, and Baltica. Although a distinction of separate provinces within the cold-water and warm-water realms is difficult, the differentiation between these two units appears evident and a distinction of the assemblages from peri-Gondwana and the microfloras from Baltica is possible. This enables a recognition of the Trans-European Suture Zone in the early to middle Ordovician.

During Cambrian and earliest Ordovician times, Avalonia was an area forming an integral part of the huge Gondwanan continent, probably along the northern margin of Amazonia, until in early Ordovician (late Arenig or Llanvirn) time it split off from Gondwana, leaving a widening Rheic Ocean to its south. Today, its southern margin with Gondwana extends northeast from east of Cape Cod, Massachusetts, through Nova Scotia north of the Meguma terrane, and thence below sea level to the south of Newfoundland. On the eastern side of the present Atlantic, the southern margin may separate southwest Portugal from the rest of the Iberian Peninsula; it can be traced eastwards with more certainty from the south Cornwall nappes to a line separating the Northern Phyllite Belt (on the southern margin of the Rhenohercynian terrane) and the Mid-German Crystalline High. There is no certain evidence of Avalonian crust to the northeast of the Elbe Line. The northern margin of Avalonia extends westwards from south of Denmark to the British Isles, where it merges with the Iapetus Ocean suture between Scotland and England. Traced westwards, it crosses Ireland and reappears in northern Newfoundland to the east of New World Island, where it may follow the trace of the Dog Bay Line and the Cape Ray Fault. Recent work suggests that the northern margin of Avalonia may clip the northern tip of Cape Breton Island in Nova Scotia, and then enter the North American mainland at the Bay of Chaleur; it may then be traced from north and west of the Popelogan and Bronson Hill arcs to Long Island Sound near Newhaven, Connecticut. The Cambrian to Devonian faunas reflect the history of Avalonia: initially they were purely Gondwanan but, as Ordovician time proceeded, more genera crossed firstly the Tornquist Ocean as it narrowed between Avalonia and Baltica to close in latest Ordovician and early Silurian times, and secondly the Iapetus Ocean, so that by the early Silurian most of the benthic shelly faunas, apart from the ostracods, were the same round the adjacent margins of all three palaeocontinents.

The Caledonian deformation of the Brabant Massif and the Rügen Early Palaeozoic has been compared by structural analysis including strain determinations, X-ray texture analysis, illite crystallinity and vitrinite reflectivity. Both areas have experienced weak internal deformation under anchimetamorphic to very low-grade metamorphic conditions. The deformation of the Brabant Massif is characterized by (a) a pronounced diagenetic foliation which resulted from compaction and weak extensional tectonics; (b) tilting or weak folding of the Cambrian strata around the Cambrian/Ordovician boundary without internal deformation; (c) a main phase of Caledonian deformation in the Lower Devonian which was associated with open folding and an axial-plane pressure solution cleavage; (d) bending of Caledonian structures from northwest–southeast to northeast–southwest. The internal deformation appears homogeneous with decreasing strain values towards upper structural levels. The strain ellipsoid is predominantly prolate with the main axis of extension parallel to the bedding–cleavage intersection lineation. It is interpreted as the result of superposition of compaction, tectonic shortening and volume loss through pressure solution. The Rügen Early Palaeozoic is less deformed and less metamorphosed under anchizonal conditions. While the upper structural level is almost undeformed, towards the deeper structural levels a spaced and then a continuous slaty cleavage is developed which is successively crenulated by a fracture cleavage. The internal deformation appears inhomogeneous due to several thrust zones with somewhat higher strain values. Outside the thrust zones strain values increase towards lower structural levels, but not significantly. The strain ellipsoid is prolate with a strongly varying orientation of the X-axis. The structural inventory of both areas is comparable with other fold-and-thrust belts. While the Rügen Palaeozoic represents an imbricated thrust-fan of an upper structural level with discrete thrusts and inhomogeneous strain, the Brabant Massif represents a deeper structural level dominated by folding and more homogeneous internal deformation.

Crystalline crust examined along the seismic profile LT-7 is subdivided into four blocks separated by distinct vertical fractures. The northeastern block belongs to the East European Craton (Baltica). Its three-layer structure is similar to that of the Svecofennian crust farther to the northwest. The southeastern block reveals typical, two-layer Variscan crust. Both central blocks have a peculiar structure not comparable with the crust of the Danish and North German areas: two lower layers, with velocities identical or close to that of the cratonic lower and middle layers, are extremely thin, and an upper layer, 8–11 km thick, shows surprisingly low velocities. This upper layer probably represents the folded and weakly metamorphosed Lower Palaeozoic sequences, although the connection with undeformed epicratonic cover cannot be excluded. Significant differentiation of crustal types in different segments of the Trans-European Suture Zone favours the concept of tectonostratigraphic terranes which collided with Baltica.

A new gravity model of the crustal structure of the Trans-European Suture Zone in the northwestern Poland has been constructed. The Bouguer anomaly map, obtained after stripping off the three-dimensional gravity effect of the sedimentary cover down to the Zechstein formations, is characterized by a 50 mGal gravity anomaly. We have assumed that the short-wavelength components derive from upper crustal intrusions and the long-wavelength components reflect crustal thickness and lateral heterogeneity which are strongly supported by the new seismic data along the LT-7 geotraverse. Quantitative modelling of gravity data along three profiles crossing the area indicate the presence of anomalous masses within the Lower Palaeozoic sequence, mainly along the Teisseyre-Tornquist Zone. Two of the profiles crossing the long-wavelength ‘stripped’ gravity high suggest the existence of a zone of 35 km crust above a dense upper mantle along the Teisseyre-Tornquist Zone. The extent of the zone can be determined based on the Bouguer anomalies interpretation.

The Upper Silesian and Małopolska blocks are situated near the southwestern boundary of the East European Platform within the Trans-European Suture Zone. The Lower Palaeozoic lithologies of the blocks reveal different stratigraphic and diastrophic development. In the Upper Silesian Block, unmetamorphosed and gently folded Lower Cambrian to Ordovician sedimentary rocks rest on a Cadomian basement. The Lower Cambrian is represented by an older (sub-Holmia) Borzęta Formation and a younger (Holmia) Goczałkowice Formation. The thickness of the Cambrian lithologies increases from the southwest towards the lateral part of the block. In the Małopolska Block Palaeozoic and Precambrian lithologies are represented by regionally metamorphosed and intensely folded Lower Cambrian–Vendian clastic rocks which are unconformably overlain by Ordovician–Lower Silurian carbonates and Upper Silurian clastic rocks. The crystalline basement of the Małopolska Block has yet to be recognized. The Lower Palaeozoic sediments of both blocks are overlain by Devonian and Carboniferous rocks. The blocks are in direct contact along a narrow tectonic zone, a part of the largely concealed Hamburg–Kraków fault zone, in which tectonic evolution has taken place spasmodically with strike-slip movements predominating.

All Cambrian series and several Cambrian biozones have been recognized using acritarch biochronology within the siliciclastic successions underlying Upper Silesia in southern Poland. The entire Cambrian succession is around 580 m thick and contains rare Lower Cambrian trilobites of the Acado-Baltic faunal province. Acritarch associations are taxonomically comparable to those recorded in Baltica, Laurentia and Gondwana, but their closest taxonomic affinity is with Iberia. The Cambrian succession accumulated in a shallow shelf environment and is almost flat-lying, unmetamorphosed, uncleaved and in normal stratigraphic order. It underlies paraconformably Lower Devonian deposits and overlies unconformably steeply dipping metasediments of undetermined Precambrian age. Tectonic deformation and metamorphism to greenschist grade in these Precambrian strata must have occurred in the Proterozoic, and are attributed to the Cadomian orogeny because similar Cadomian basement complexes occur in the adjoining Brno Massif and in the East Avalonian and Armorican terranes. Upper Silesia appears to be a stable crustal block bordered by deep faults whose sedimentary cover has not been affected by tectonic deformation other than faulting. Based on the recognition of Cadomian age basement, the distribution of trilobites and acritarchs and the tectonostratigraphic relationships to adjacent areas, the Upper Silesia terrane is interpreted to be a distal segment of East Avalonia that in Cambrian times faced Iberia. An extension of the Tornquist Suture from the Intra-Sudetic Fault is seen in the Kraków-Myszków Fault Zone at the margin of Upper Silesia. The Intra-Sudetic Fault zone and the Kraków-Myszków Fault Zone contain Early Palaeozoic rocks deformed during the Caledonian orogeny, and mark the boundary between the Caledonian accretionary belt and areas unaffected by this orogeny.

Two metasedimentary complexes are exposed in the Sudetes Mountains of Poland, Germany and the Czech Republic. Succession I comprises pelites and greywackes of Neoproterozoic–Cambrian age, deformed and metamorphosed prior to intrusion by S-type porphyritic granites at 515–480 Ma. Succession II comprises a sandstone–mudstone–chert sequence and turbidite sequence of Ordovician–early Carboniferous age accompanied by bimodal volcanogenic rocks. Both successions were intruded by late- to post-orogenic granitoid intrusions at 340–300 Ma. The sedimentary rocks of succession II show increasing maturity until mid–late Devonian times. Inversion of the basins, commencing in late Devonian–early Carboniferous times, was reflected in the emplacement of turbidites and olistostromes, concurrent with the uplift of a metamorphic core complex of succession I rocks. The original stratigraphic order of the successions was maintained, thus crustal imbrication was not significant. Instead, extensional faulting became important, followed by transpression on almost orthogonal fault zones, resulting in the presently observed juxtaposition of crustal blocks. The Palaeozoic sequences developed in mainly ensialic basins on Cadomian and older basement, parts of which became strongly reworked (2.6 to 0.54 Ga zircon inheritance ages) and incorporated into the Palaeozoic structures. The orogen developed either on the rifted margin of peri-Gondwana or on a rifted-away fragment of pre-Baltica. The Sudetic section of the Variscan Orogen is of broadly Alpine style, with significant basement involvement, but apparently without evidence for long-lived subduction of wide oceans or the accretion of numerous exotic terranes.

The mafic metavolcanic rocks (blueschists and greenschists) of the Rýchory Mountains crystalline complex (West Sudetes) experienced sea-floor hydrothermal alteration (spilitization?) prior to regional metamorphism. The metabasite geochemistry (namely trace element and REE abundances) indicates that the protolith was comparable in composition with (1) tholeiitic to transitional ocean-floor basalts and (2) transitional and alkaline intra-oceanic island basalts. Two main metamorphic events affected the Rýchory Mountains metabasites. In an earlier high pressure–low temperature metamorphic event, the rocks experienced blueschist facies metamorphism. The results of 40Ar–39Ar geochronology studies on phengites from the mafic blueschists date the end of the earlier metamorphism to 360 Ma. The greenschist metamorphic overprint followed around 340 Ma. The elongated bodies of mafic metavolcanic rocks are situated within the prominent NNE–SSW Leszczyniec shear zone following the trend of the Rýchory Mountains and the Rudawy Janowickie Mountains. Both the geochemical affinities and the blueschist facies metamorphism of the metabasites suggest that this shear zone evolved from the Variscan suture dividing western and central terranes of the West Sudetes. According to the radiometric age for the end of the high pressure–low temperature metamorphism, the terranes accreted during the Famennian. A considerable time-span between the formation of the metabasite protolith and the blueschist metamorphism may indicate long-lasting subduction of a large oceanic plate between Gondwana and Laurussia, possibly accompanied by terrane accretion, prior to the Variscan orogeny.

In the Sudetes, seven distinct lithostratigraphic terranes exhibit a symmetric distribution. A central region of basinal/oceanic and ophiolitic rocks, the Central Sudetic terrane is bordered, respectively to the northwest and southeast, by the sialic Saxothuringian and Moldanubian terranes. These exhibit contrasting metasedimentary/metavolcanic successions and tectonic-metamorphic sequences, but both are characterized by Palaeozoic plutonism. These are in turn bordered (again respectively to the northwest and southeast) by the Lusatian and Moravian terranes, which are also sialic, but contain Cadomian granitoids and represent rifted and now widely separated fragments of Gondwana. Along the southwestern flank of the Sudetes, the Barrandian terrane, largely covered by younger sediments, extends to the southwestern margin of the Bohemian Massif. The Sowie Góry terrane forms a klippe of high grade gneisses tectonically emplaced on top of low-grade, sheared ophiolites of the Central Sudetic terrane. The Sowie Góry terrane exhibits a history of three distinct, probably multi-orogenic, regional metamorphic events: an early high-pressure granulite/eclogite metamorphism followed by medium- to low-pressure granulite, and in turn by amphibolite facies metamorphism. All the terrane boundaries are complex zones of ductile to brittle shearing, modified by later brittle movements. Some, such as the Leszczyniec shear zone, mark lines of old, pre-Variscan rift and suture zones, reactivated and overprinted during a series of Variscan ductile to brittle events of extensional shearing with related metamorphism and plutonism.

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.