bluuebunny/crossref_metadata_2025_split huggingface dataset:
Late events in the tectonic history of the Saxothuringian zone
Authors: Franke Wolfgang 
Published: September 2007

Summary
The Saxothuringian zone lies between the Moldanubian block (largely consolidated in late Precambrian time) to the south and the Rhenohercynian zone to the north. It is characterized by exotic blocks of relatively high-grade metamorphic rocks set among very low-grade Palaeozoic sequences. These ‘Zwischengebirge’ (Münchberg, Wildenfels, Frankenberg) were formerly interpreted as metamorphic ‘diapirs’. Recent investigations have led to a revival of the nappe concepts previously proposed by Suess, Wurm, Kossmat and others.
The Münchberg complex is a pile of later Proterozoic to early Palaeozoic volcanic and sedimentary rocks, some now at advanced states of metamophism, in which both stratigraphic sequences and metamorphic grades appear in inverted order. These rocks rest upon a Carboniferous wildflysch, which, in its turn, rests upon an autochthonous Devonian and, locally, a Lower Carboniferous sequence. The flysch material, like the nappes above, was derived from sources in the SE.
Special features of the sedimentary facies, the tectonic deformation, and the state of very low-grade metamorphism, combine with the evidence of a well-developed thrust at the base of the wildflysch sequence to suggest that this sequence should be treated as the lowest tectonic unit in the Münchberg pile of nappes.

Tectonic deformation of the Palaeozoic sequence began with the production of tight to isoclinal, recumbent, NW-facing folds, accompanied and outlasted by subhorizontal thrusting. It was at this time that the nappe-like tectonic units (already in their metamorphic state) were emplaced. An F
2
refolding produced open, upright to SE-facing folds.

A study of illite crystallinity has indicated the significance of a transverse zone, which was the locus of enhanced heat flow throughout the time of deformation, and has confirmed that a metamorphic inversion was introduced when the (relatively strongly metamorphic) wildflysch was thrust over the autochthonous Devonian and Carboniferous.
The Saxothuringian zone shows the closest approach to an alpino-type character found in the northern part of the Variscides. Basin development, deformation and metamorphism are best explained in terms of a model based on horizontal tectonism.
Inverted metamorphic zonation and large-scale thrusting in the Variscan Belt: an example in the French Massif Central
Authors: Burg J. P. , Matte Ph. , Leyreloup A. , Marchand J. 
Published: September 2007

Summary
Half of the northern part of the French Massif Central has been shown to be allochthonous. In the allochthonous rocks, preserved high-pressure granulites represent an early tectonometamorphic event which took place before thrusting. During the southward-directed overthrusting of this high-grade metamorphic slab a plurifacial inverted metamorphism was developed in the underlying sediments. Adjacent areas show different types of metamorphism in the autochthonous and parautochthonous pelites. The climax of the metamorphism is shown to have been reached by the end of the thrusting episode. This was followed by the retrogression of the high-grade rocks and the establishment of a low-pressure metamorphism in both the thrust unit and the autochthonous-parautochthonous terranes beneath. We describe this example of inverted metamorphic zonation associated with the large-scale thrusting of an already metamorphosed series.
Palaeozoic evolution of the Plateau d’Aigurande (NW Massif Central, France)
Authors: Quenardel Jean-Michel , Rolin Patrick 
Published: September 2007

Summary
The Plateau d’Aigurande represents the north-westernmost part of the French Massif Central. It is overlain by the sediments of the Paris Basin to the north and bounded by the La Marche shear zone to the south. Detailed mapping, mainly from the Creuse Valley region, indicates thrust and nappe tectonics.
Beginning at the base of the sequence one can recognize: (1) the Fougères unit (schists of low to medium grade) intruded by syntectonic leucogranites; (2) the Eguzon unit (medium- to high-grade schists which are partly diaphtoretic in the lower part of the unit); (3) the Gargilesse unit (high-grade schists); and (4) the Migmatitic unit.
The metasediments of the Fougères, Eguzon and Gargilesse units were originally coarse grained clastics. They are interbanded with magmatic units (orthogneisses and amphibolites). The migmatites are derived from greywacke-type rocks intruded by magmatic rocks (orthogneisses and amphibolites).
Following a high-pressure (Silurian?) tectonometamorphic event, the piling up of tectonostratigraphic units occurred during two periods of deformation. The main one, probably of late Caledonian (Acadian?) age, was synchronous with or slightly after the climax of metamorphism. The second, of Westphalian age, was accompanied by the emplacement of leucogranitic magma and by retrograde metamorphism. The shear-sense appears to have been from SW to NE during the Acadian phase and from NW to SE during the Westphalian. Structural and lithological studies suggest that the three lowermost units may have been derived from the same palaeogeographic domain while the migmatites have a distinctly different history.
Northern margins of the Variscides in the North Atlantic region: comments on the tectonic context of the problem
Authors: Matthews S. C. 
Published: September 2007

Summary
Some of the misconceptions which have figured in discussions of Variscan geology are analysed. Subduction (but not in the obvious sense), strike-slip movement and sole thrusts may all have a part to play, but none of these alone explains the Variscides. Kossmat’s scheme of tectonic zones still deserves attention. So, too, do questions concerning the pre-Variscan geology, especially the prevalence of rift-structures, in central and western Europe. The problem of integrating the pattern of Palaeozoic tectonism in Europe with that in eastern North America is briefly explored. It is suggested that Caledonian and Variscan be treated as parts of one chapter of tectonism and that much of the early tectonic history of central and western Europe be regarded as Pan-African. It is argued that western Europe is unlikely to produce evidence of structural transpositions on the scale recently revealed by seismic reflection profiling in the southern Appalachians. It is also suggested that the idea of a Variscan front is largely illustory.
Thrust nappe tectonics in the Devonian of south Cornwall and the western English Channel
Authors: Leveridge B. E. , Holder M. T. , Day G. A. 
Published: September 2007

Summary
A review of stratigraphical data from south Cornwall, considered in conjunction with information obtained during a current re-survey by the British Geological Survey of 1:50,000 Sheet 352 (Falmouth), indicates the presence of a major thrust nappe in the Devonian rocks of the district. Seismic records from the western English Channel contain a prominent event that is interpreted as the offshore extension of the thrust. A model of the thrust nappe system of the area is proposed which is consistent with obduction from a small oceanic basin to the south.
Thin-skinned tectonics, basement control and the Variscan front
Authors: Shackleton Robert M. 
Published: September 2007

Summary
The thin-skinned interpretation of Variscan structures in southern England, Wales and Ireland, based on structural and seismic evidence, is used to define the Variscan front as the northern limit of the thin-skinned structures. The original front was where displacement on the décollement surface diminished to zero. The present front, eroded back from its original line, is near the line previously accepted as the Variscan front. Caledonian (and in places older) structures control the Variscan deformation north of the front. They can also be traced south of it, as post-Variscan structures which have propagated up through the décollement. A zone of ENE-WSW structures in south Cornwall is thought to reflect the influence of Cadomian basement where the basal thrust has cut down into it.
Variscan tectonics of the Alston block, northern England
Authors: Critchley M. F. 
Published: September 2007

Summary
Several ‘blocks’ can be recognized in the Carboniferous of northern England. These acted as rigid units and were only affected by the last phases of Variscan deformation.
The Alston block provides an example of the deformational history of block regions during the Variscan orogeny. A pre-Carboniferous granite provided resistance to deformation of the block until late Carboniferous times, and fracturing of the Carboniferous sediments above cupolas of the granite is less intense than elsewhere. Away from the cupolas, where a thick succession of Lower Palaeozoic rocks underlie Carboniferous strata, there is a more random and denser distribution of faults and vein fractures.
There were three tectonic phases to the structural evolution of the Alston block during the Variscan orogeny. The first phase, occurring prior to the intrusion of the Stephanian Whin sill, resulted in local folding of the block sediments and the formation of early shear joints under E-W compression. The second tectonic phase was a period of uplift of the Alston block, and resulted in a reticular pattern of ENE and NNW normal faults and extension joints. The third phase was characterized by renewed E-W compression. This resulted in the formation of ESE sinistral strike-slip faults, and horizontal reactivations along existing fractures.
Structural variation across the northern margin of the Variscides in NW Europe
Authors: Sanderson David J. 
Published: September 2007

Summary
Four areas which cross the northern margin of the Variscan fold belt are examined and models of their structural evolution, from basin development to folding etc., are compared.
Foreland Britain is characterized by heterogeneous deformation localized in basins, whose development accompanied E-W dextral shear. The Munster basin in Ireland contains steep folds and cleavage. A variety of minor structures indicates an important dextral shear component to the deformation, and basin inversion by transpression is proposed. SW England is dominated by thrust tectonics, including the obduction of the Lizard ophiolite. Deformation was preceded by south to north migration of basin development. Brittany is characterized by major dextral shear zones delimiting areas of variable ductile strain.
The structural geometry and history of these areas is interpreted in terms of regional dextral transpression. The common transport direction is to the NNW or NW and oblique to the belt. Variable amounts of thrusting and dextral shear produced the different structural patterns. A case is made for an essentially ‘thick-skinned’ style of heterogeneous deformation produced in a dextral, oblique collision orogen, which involved microplates and a small back-arc basin.
Structural style, shortening estimates and the thrust front of the Irish Variscides
Authors: Cooper M. A. , Collins D. , Ford M. , Murphy F. X. , Trayner P. M. 
Published: September 2007

Summary
Previous work in the Irish Variscan orogen has emphasized the significance of the major folds in the overall structure. A series of three balanced sections through the orogen reveals that thrusts are an equally important element of the orogenic structure. The ‘thrust front’ is not a fundamental structural line delimiting different deformational zones as previously proposed. Major thrusts occur along the ‘thrust front’ between Killarney and Mallow, but are absent east of Mallow. This change in character of the ‘thrust front’ is a function of a change in the stratigraphic level of the sole thrust to the orogen and the current erosion level. The deeper level of the sole thrust produces the numerous Silurian cored inliers to the NE of Mallow. The balanced sections show that the overall bulk shortening in the orogen increases from 33% in the east, to 42% in the central areas. This increase may be related to the arcuate nature of the orogen.
Does the Variscan front in Ireland follow a dextral shear zone?
Authors: Max M. D. , Lefort J. P. 
Published: September 2007

Summary
The line commonly taken in Ireland as marking the ‘Variscan front’ passes in a gentle arc from Dungarven Bay in the east to Dingle Bay in the west. This is the most convenient course for the northern margin of the Rheno-Hercynian zone through Ireland and marks a primary Variscan structural line. The line follows thrusts and steep faults in the west and a series of less well seen strike faults along the southern limb of a tight syncline in the east from Mallow to Dungarvan. Although the line is thus structurally composite, and stratigraphic evidence shows that it was locally of indirect influence during deposition of the Upper Palaeozoic sediments, both structural and geophysical evidence suggests that a dextral strike-slip component was associated with this line.
Strike-slip movement along with N-S compression is shown by widespread E-W horizontal strain markers, strike faults and rotated fold traces which formed at the same time as the cleavage. Basement control of structures to the south of the line is not discernible while to the north rejuvenation of Lower Palaeozoic structures in the basement is common.
Variscan structures in the Upper Palaeozoic rocks of west central Ireland
Authors: Coller D. W. 
Published: September 2007

Summary
The western half of central Ireland is part of a low strain zone on the northern margin of the Variscan orogen in which the structures in the Upper Palaeozoic ‘cover’ rocks appear largely to be controlled by ENE-WSW and NNE-SSW trending structures in the Caledonian, and possibly the pre-Caledonian basement.
Preceding the main ductile phase of Variscan deformation, there was an important period of mid-Dinantian faulting which is closely associated with major base metal mineralization. New structural evidence suggests that the main movement on these faults involved an important component of dextral transcurrent shear.
The main ductile deformation, between post-Westphalian and pre-Upper Permian in age, is characterized by kilometric scale open folds and mainly ENE-WSW trending vertical transcurrent ductile-brittle shear zones. The model of deformation is considered to be one of regional, heterogeneous transpression where the main compression, or pure shear component was approximately N-S, and the simple shear component was an ENE-WSW dextral shear. A major NNE-SSW trending sinistral shear zone, the Fergus shear zone, appears to be the western limit of the dextral shear component.
Geophysical evidence for the extension of the Variscan front on to the Canadian continental margin: geodynamic and palaeogeographic consequences
Authors: Lefort Jean-Pierre , Haworth Richard T. 
Published: September 2007

Summary
Dextral transcurrent movement and thrusting induced by transcurrent movement have been identified along a roughly east-west line across the continental shelf NE of Newfoundland at approximately 52°N. The location of that boundary correlates well on a pre-Mesozoic fit of the North Atlantic with the terminus of the Variscan front on the European margin. Seismic reflection, refraction, gravity and magnetic data show a structural succession across the boundary that correlates with that across the front in Europe. This North American continuity of the Variscan front has subsequently acted as the locus for Mesozoic tectonics.
A revised nomenclature for Upper Permian strata in eastern England
Authors: Smith D. B. , Harwood G. M. , Pattison J. , Pettigrew T. H. 
Published: September 2007

Summary
Revised names of some Upper Permian strata in eastern England are proposed and defined, together with new names for some strata previously without formal names; the new and revised names are based on nominated type localities and are intended to replace existing names that were confusing or inappropriate. We propose that the names Lower and Upper Magnesian Limestone in the Yorkshire Province be replaced by the new names Cadeby (Magnesian Limestone) Formation and Brotherton (Magnesian Limestone) Formation respectively and that the Lower and Middle Magnesian Limestone in the Durham Province should become the Raisby (Magnesian Limestone) and Ford (Magnesian Limestone) formations respectively. The Middle Marls are renamed the Edlington Formation in both provinces and the new names Sherburn (Anhydrite) Formation, Sneaton (Halite) Formation and Littlebeck (Anhydrite) Formation are proposed for the Upper Anhydrite, Upper Halite and Top Anhydrite formations. The term Roxby Formation is proposed to replace the present name Upper (or Saliferous) Marls.
Sedimentology of sandwaves in an oolite shoal complex in the Cadeby (Magnesian Limestone) Formation (Upper Permian) of eastern England
Authors: Kaldi J. 
Published: September 2007

Summary
Four depositional facies are recognizable in the Sprotbrough Member of the Cadeby Formation (formerly the Lower Magnesian Limestone) in eastern England; they are sabkha, semi-restricted lagoon, oolite shoal complex and open marine shelf. Of these, the oolite shoal complex occupies most of the present outcrop in the Yorkshire Province, i.e. south of the Cleveland High. It comprises large-scale cross-stratified oolite bedforms that are interpreted as sandwaves from their size, type of sediment and internal features. The sandwaves probably originated from the concentration of wave energy by eminences on the floor of the Zechstein Sea. Biogenic structures in the sandwaves show that they were inhabited by marine organisms.
A complex pattern of palaeocurrent styles and azimuths is present within the sandwaves. At many exposures, the long axes of the sandwaves trend NW-SE, suggesting predominant currents normal to this direction. A predominant current from the NE is further indicated by the preferential abutment of SW-dipping beds on the NE flanks of bedforms; this was caused by sandwaves that climbed the backs of others. Occasional storms from the SE produced spillover lobes oriented towards the NW. Storms were also probably responsible for the formation of internal structures such as hummocky cross-stratification, fan-shaped bedding and contemporaneous erosion surfaces.
Mineralization in Upper Permian carbonates at outcrop in eastern England
Authors: Harwood G. M. , Smith F. W. 
Published: September 2007

Summary
Upper Permian carbonates in eastern England at outcrop feature subeconomic syngenetic and epigenetic Pb-Zn-Cu-Fe-Ba-F mineralization. Pb-Zn-Fe sulphides occur in vugs and breccias of sedimentary origin whereas much barite replaces the host carbonate. Vein mineralization is rare. The majority of occurrences are within the Cadeby Formation (Lower Magnesian Limestone; EZ1 Ca).
More than 70 occurrences of mineralization have been recorded, clustered on centres at Farnham, Bramham, Edlington and Mansfield. Host carbonates at the first three of these centres overlie major cross-cutting structures in pre-Permian strata; these structures were possible flow channels for mineralizing solutions. Mineralization in the Mansfield area can be explained by the upwards leakage, on a broad scale, of formation fluids from Carboniferous strata that overlie the South Pennine basement high.
The Trow Point Bed—a deposit of Upper Permian marine oncoids, peloids and columnar stromatolites in the Zechstein of NE England
Authors: Smith D. B. 
Published: September 2007

Summary
An extensive thin bed of oncoids, peloids and columnar stromatolites occurs at the top of the Cycle 1 carbonate of the English Zechstein sequence in NE England; here termed the Trow Point Bed, it lies on the lower part of the basin-margin slope, basinward of a linear shelf-edge reef in the Ford Formation. The bed is generally 0.05–0.20 m thick but locally ranges to 0.60 m; it rests on an uneven surface that has a local relief of up to 15 m and slopes exceeding 35° in places. It contains a sparse marine fauna of foraminifera, ostracods and bivalves; there are only a few traces of current action and sorting, and terrigenous sediment nowhere comprises more than 2% of the bed.
The Trow Point Bed is generally similar to deposits described at a comparable stratigraphical position in Germany and Poland and although environmental indications are partly mutually contradictory, it seems likely that the bed accumulated in oxic conditions on the basin floor under water perhaps 25–100 m deep.
Subsidence and foundering of strata caused by the dissolution of Permian gypsum in the Ripon and Bedale areas, North Yorkshire
Authors: Cooper A. H. 
Published: September 2007

Summary
Underground dissolution of thick gypsum beds in the Edlington Formation and Roxby Formation of the Zechstein sequence in North Yorkshire, England, has resulted in a 3 km-wide and 100 km-long belt of ground susceptible to foundering. Within this belt a large subsidence depression at Snape Mires, near Bedale, was largely filled with lacustrine deposits in the later part of the Late Devensian and during the Flandrian. South of Snape Mires the Nosterfield-Ripon-Bishop Monkton area has suffered about 40 episodes of subsidence in the past 150 years, and the presence of several hundred other subsidence hollows indicates considerable activity from the later part of the Devensian onwards. The linear and grid-like arrangement of these subsidence hollows indicates collapse at intersections in a joint-controlled cave system. Linear subsidence features at Snape Mires are also joint-controlled. The transition from anhydrite at depth to secondary gypsum near surface marks the down-dip limit of the subsidence-prone belt. Cavities are propagated upwards by roof collapse of caverns in the gypsum, leading to the formation of breccia pipes. Choking of the pipes can reduce the surface expression of the underground collapse, but the larger cavities are liable to produce pipes that reach the surface even at the eastern boundary of the 3 km-wide belt described. Further subsidence in the Ripon area is predicted and some suggestions for remedial measures are given.
Stratigraphy of the Lower Werra Cycle (Z1) in West Germany (preliminary results)
Authors: Paul J. 
Published: September 2007

Summary
The Zechstein Limestone (Cal) of Western Germany has a clear stratigraphical subdivision. A lower unit (subcycle a) is separated from an upper unit (subcycle b) by a discontinuity, which is best exposed at the Solhops-Berg at the Harz Mountains and is here termed the ‘Solhops Discontinuity’. The discontinuity was caused by an extensive regression of the Zechstein Sea which led to subaerial exposure of large areas of the Zechstein basin. Based on this discontinuity, a preliminary stratigraphy of the Lower Werra cycle in Germany is established and compared with that of the English Zechstein sequence.
On the Zechstein Copper Shale lithofacies and palaeoenvironments in SW Poland
Authors: Oszczepalski S. 
Published: September 2007

Summary
Microfacies and geochemical studies on the Copper Shale in the Sudetic Foreland of SW Poland show the strong influence of palaeorelief on the distribution of lithofacies. Spatial variability in microlithofacies and lithofacies indicate sedimentation in the following palaeoenvironments: (1) offshore—deep shelf, characterized by the black shale lithofacies (30–50 cm thick) and shallow shelf, where the Copper Shale is either absent or is represented by red shale lithofacies (up to 60 cm thick), and (2) nearshore, characterized by grey shale lithofacies (40–100 cm thick or more). Shorewards the Copper Shale is replaced by carbonate and/or terrigenous rocks of the first Zechstein cycle.