The Variscan Orogeny: the Welding of Pangaea

Warr, Laurence N.

doi:10.1002/9781118274064.ch15

Cited by 18 publications

(28 citation statements)

References 19 publications

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“…Continuing Variscan deformation resulted in northward-directed thrusting in south Wales and widespread basin inversion during the last stages of the assembly of the Gondwana-derived microplates into the supercontinent of Pangaea (Warr 2002). The LISPB DELTA profile crosses the Variscan Front in the vicinity of the Mendip Hills to the south of the Bristol Channel, and to the south passes across the Avalonian foreland Rheno-Hercynian Cornubian zone affected by Variscan folding and thrusting.…”

Section: Regional Geology and Tectonicsmentioning

confidence: 96%

“…The southern margin of the Welsh Basin was controlled by the Welsh Borderland Fault System, which underwent significant strike-slip displacement when rifting of the western Midland Platform Bamford et al 1978;Barton 1992) and DELTA (reported here). (b) Tectonic map of western UK, showing LISPB DELTA from north Wales to the English Channel (after Soper 1986;Bluck et al 1992;Warr 2002;Woodcock & Strachan 2002b;Woodcock et al 2007). MSFS, Menai Strait Fault System; BF, Bala Fault; WBFS, Welsh Borderland Fault System; BCFZ, Bristol Channel Fault Zone.…”

Section: Regional Geology and Tectonicsmentioning

confidence: 99%

“…In SW England, offshore deep marine and marine shelf basins were supplied with marine and alluvial sediments off the southern margin of Avalonia. The Early to Mid-Devonian Acadian event in the Welsh Basin records uplift and crustal thickening as a result of encroachment of the Armorican microcontinent (c. 400 Ma) from the south (Warr 2002), with closure resulting in a major unconformity between the Lower and Upper Old Red Sandstone. Subsequent episodic sea-level rise in Late Devonian times provided widespread alluvial and marginal marine sedimentation to generate the Upper Old Red Sandstone in south Wales and across the Cornubian basins of SW England (Fig.…”

Section: Regional Geology and Tectonicsmentioning

confidence: 99%

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LISPB DELTA, a lithospheric seismic profile in Britain: analysis and interpretation of the Wales and southern England section

Maguire

England

Hardwick

2011

JGS

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The Lithospheric Seismic Profile in Britain (LISPB), shot in 1974, included a 310 km profile LISPB DELTA, crossing the Palaeozoic Welsh Basin, the western extent of the Midland microcraton and the Cornubian zone of southern England. This first comprehensive analysis of these data has produced a sub-horizontally layered seismic and associated gravity model that correlates well with surface geology. A north-south decrease in crustal velocity and density corresponds to the change from Avalonian crust into the Rheno-Hercynian zone at the south end of the profile. High velocities and densities in the lowest crustal layer beneath north Wales are proposed to result from Cenozoic and possibly Ordovician igneous intrusive rocks, the former derived from an upwelling plume associated with the opening of the North Atlantic. Examination of the load distribution throughout the model shows that it is strongly correlated with the earthquake distribution along LISPB DELTA. Earthquake focal depth also correlates with heat flow. A simple heat-flow profile has been derived, and the seismic velocity model used to constrain crustal heat production values. A long-wavelength excursion from published data can be explained in terms of an increase in mantle heat flow resulting from a previously identified deep thermal anomaly beneath the Irish Sea. Supplementary material: normalised, synthetic and true amplitude seismic record sections including picks and modelled phases for shots SP04, SP05, SPS1, SPS2 are available at http://www.geolsoc.org.uk/SUP18450. The 1974 Lithospheric Seismic Profile in Britain (LISPB) (Bamford et al. 1976; Fig. 1a) was one of the first projects undertaken at the start of the era of long-range controlled source seismic profiling in Europe before the advent of deep seismic reflection and present teleseismic studies. The aim of the crustal profiles (ALPHA to DELTA) was 'to provide velocity crosssections that would be useful to discussions of tectonic problems in the British Isles, in particular the evolution of the Caledonian orogenic belts ' (Bamford et al. 1978). LISPB's northern section has been extensively reported elsewhere, most recently by Barton (1992). Preliminary results from LISPB DELTA from north Wales to the English Channel have been reported (Nunn 1978) and discussed elsewhere (Edwards & Blundell 1984;Griffiths & Westbrook 1992). This paper is the outcome of applying well-established 2D seismic ray-tracing and amplitude modelling techniques to LISPB DELTA data, combined with analysis of associated gravity data along the profile to develop the model of crustal structure and processes beneath this region of the British Isles. It provides the first comprehensive analysis of these data.Long-range refraction-wide-angle reflection profiles such as LISPB form the basis for our understanding of the physical properties of the crust, its evolution and behaviour. It could be argued that the UK crust is typical of large parts of the continental crust. It records major past orogenic events and now lies some distanc...

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Section: Regional Geology and Tectonicsmentioning

confidence: 96%

Section: Regional Geology and Tectonicsmentioning

confidence: 99%

Section: Regional Geology and Tectonicsmentioning

confidence: 99%

See 1 more Smart Citation

LISPB DELTA, a lithospheric seismic profile in Britain: analysis and interpretation of the Wales and southern England section

Maguire

England

Hardwick

2011

JGS

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“…It is adapted from Hallsworth et al . () and Warr () and employs the reconstructions of Matte () for Armorica, Pollock et al . () for Ganderia, and De la Rosa et al .…”

Section: Introductionmentioning

confidence: 99%

The provenance of Western Irish Namurian Basin sedimentary strata inferred using detrital zircon U–Pb LA‐ICP‐MS geochronology

2011

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The Western Irish Namurian Basin (WINB) preserves classic examples of basin floor sequences through to slope deposits and deltaic cyclothems. Despite over 50 years of research into the WINB, its sediment provenance remains highly contested. Sedimentological arguments, including palaeocurrent vectors and palaeoslope indicators have been invoked to propose a sediment source from the NW or the west (i.e. from within Laurentia). These same indicators have been subsequently reinterpreted to reflect a southern provenance. It is not clear from sedimentological arguments alone which interpretation more accurately reflects the infilling of the WINB. Regional-scale constraints on WINB provenance may be obtained with detrital zircon U-Pb geochronology.U-Pb LA-ICP-MS detrital zircon analysis was undertaken on samples from three sandstone units at different stratigraphic levels within the WINB siliciclastic sedimentary fill (Ross Formation, Tullig Sandstone, Doonlicky Sandstone). The samples are dominated by 500-700 Ma zircons, which can be correlated with Cadomian-Avalonian orogenic activity within terranes to the south of the WINB (Avalonia/Ganderia, Armorica and Iberia). In contrast, Eastern Laurentia, to the north of the WINB, was devoid of orogenic activity at this time. WINB samples also yield age populations younger than 500 Ma, and older than 700 Ma. These are not diagnostic of a particular source terrane and thus could be derived from terranes north and/or south of the WINB. WINB detrital zircon age spectra can be reconciled by an Avalonian or combined Avalonian-Laurentian provenance for WINB sedimentary strata. Further research is required in order to distinguish between these two possibilities.

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“…Today, these foreland successions are separated from their deformed counterparts within the Variscan Orogen by the northern limit of large-scale Variscan thrustingthe so called 'Variscan Front'and by the fundamental Bristol Channel-Bray Fault line (e.g. Waters and Davies, 2006;Leveridge and Hartley, 2006;Warr, 2012; Fig. 1).…”

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confidence: 99%

The Corwen Outlier and its implications for the Mid Mississippian palaeogeography of North Wales, UK

Davies

Riley

Wilson³

2013

Geol. J.

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The isolated outlier of Visean (Mid Mississippian) limestones and sandstones near Corwen, North Wales, UK, provides a critical constraint on regional tectonic and palaeogeographical models. The late Asbian to Brigantian succession comprises a series of shoaling-upwards cycles (parasequences). These were the product of forced, glacioeustatic regressions and have boundaries that testify to emergence, karstic dissolution and soil formation on a low gradient carbonate platform prior to flooding and the resumption of marine deposition. The recognition of two of the main marker beds within the North Wales Visean succession (Main Shale and Coral Bed) together with a newly applied foraminiferal and algal biozonation allow the outlier succession to be correlated with other Visean outcrops in the region and more widely throughout the British Isles. In revealing regional thickness and facies variations, these comparisons show that the outlier succession was deposited landward of the early Asbian shoreline in a region of enhanced subsidence localized along the Bala Lineament. The Corwen Outlier suggests that, within narrow gulfs associated with the region's major tectonic lineaments, Mississippian carbonate facies extended farther south into the contemporary hinterland of older rocks and that, in response to Brigantian climate change, these topographic features likely also influenced fluvial catchments supplying siliciclastic sediment to the platform's landward margin and, subsequently, Namurian deltas. Contrary to earlier suggestions, Visean outcrop patterns, facies distributions and thicknesses in the vicinity of the Bala Lineament can be explained without the need to invoke extensive post-depositional lateral displacements. BGS ? NERC 2013. Geological Journal ? John Wiley & Sons Ltd.Peer reviewe

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The Variscan Orogeny: the Welding of Pangaea

Cited by 18 publications

References 19 publications

LISPB DELTA, a lithospheric seismic profile in Britain: analysis and interpretation of the Wales and southern England section

LISPB DELTA, a lithospheric seismic profile in Britain: analysis and interpretation of the Wales and southern England section

The provenance of Western Irish Namurian Basin sedimentary strata inferred using detrital zircon U–Pb LA‐ICP‐MS geochronology

The Corwen Outlier and its implications for the Mid Mississippian palaeogeography of North Wales, UK

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