Jointing and minor tectonics of the S. Crop of the South Wales Coalfield between Machen and Bridgend

Roberts, John C.

doi:10.1002/gj.3350100204

Cited by 7 publications

(4 citation statements)

References 10 publications

(7 reference statements)

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“…This demonstrate how poor data coverage may cause misinterpretations of fault zones as folds, due to their fold-like geometries at lower resolutions. (Roberts 1966(Roberts , 1975Dixon & Strahan 1977;Roberts 1979;Wright et al 2009;Woodcock et al 2014;Morgan 2015) (c) Post-Variscan to Mesozoic extensional regime. (Roberts 1966(Roberts , 1975(Roberts , 1979Nemčok et al 1995;Glen et al 2005;Morgan 2015) (d) Alpine compressive regime, specifically the Pyrenean Phase (Parrish et al 2018).…”

Section: Discussionmentioning

confidence: 99%

“…(Roberts 1966(Roberts , 1975Dixon & Strahan 1977;Roberts 1979;Wright et al 2009;Woodcock et al 2014;Morgan 2015) (c) Post-Variscan to Mesozoic extensional regime. (Roberts 1966(Roberts , 1975(Roberts , 1979Nemčok et al 1995;Glen et al 2005;Morgan 2015) (d) Alpine compressive regime, specifically the Pyrenean Phase (Parrish et al 2018). Additional sources include: (Skempton et al 1969;Ameen & Cosgrove 1990;Nemčok et al 1995;Belayneh & Cosgrove 2004;Glen et al 2005 Fig.…”

Section: Discussionmentioning

confidence: 99%

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Major faulting in London: evidence for inherited basement faults in the London Basin

Morgan

Ghail

Lawrence

2020

QJEGH

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The near-surface of London is faulted, although the locations, architecture and tectonic origins of the faults are broadly unknown. This presents serious issues for geotechnical engineering in London and has implications for our structural understanding of the London Basin. The region is a product of Alpine compression, yet it is unclear whether these major faults are new Alpine shears or reactivated basement faults. We assess the plausibility of Alpine reactivation and inheritance of basement faults in London through three investigations: analysing structures in the near-surface; mechanically assessing the feasibility of basement fault reactivation under Alpine stress conditions; and comparing inheritance mechanisms with observations in London and the Thames Estuary. Three major en echelon fault sets are identified. These appear to have compartmentalized London's near-surface geology and are all interpreted to be products of Alpine reactivation of the underlying basement faults. Fault interaction and linkage is evidenced by complex zones of intense faulting identified by tunnelling projects. The role of new structural development in accommodating Alpine compression is considered to have been comparatively minor. The lack of major faulting in the basin's interior may reflect the competence of the underlying Anglo–Brabant Massif in restricting Alpine strains to its margins.Thematic collection: This article is part of the Geology of London and its implications for ground engineering collection available at: https://www.lyellcollection.org/cc/london-basin

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Major faulting in London: evidence for inherited basement faults in the London Basin

Morgan

Ghail

Lawrence

2020

QJEGH

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“…Well‐defined fracture planes are recorded from the Gondwana, Dafla, and Bomdila Gneisses. Note that joints and faults cannot be regarded as kinematic equivalents, but under similarly oriented stress fields, both structures can form (Roberts, 1975). Prefaulting damage may be initiated with pervasive fracturing.…”

Section: Discussionmentioning

confidence: 99%

“…The ~E‐W subvertical joint sets are also nearly parallel to the trend of the MBT and axis of folded Gondwana and Dafla sequence in the area (Figure 2). All joint sets and faults are not coeval and require the maximum compressive stress to be oriented subparallel to the trend of the bedding and intermediate compressive axis perpendicular to the bedding (Roberts, 1975). Near‐vertical faults in the Siwalik sequence of the western Himalaya can be related to isostatic adjustments and strike‐slip tectonics.…”

Section: Discussionmentioning

confidence: 99%

Brittle tectonics in the western Arunachal Himalayan frontal fold belt, northeast India: Change in stress regime from pre‐collisional extension to collisional compression

et al. 2022

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The study of brittle deformation of the collisional mountains can explain its shallow crustal tectonic evolution and the palaeostress regime. The Main Boundary Thrust (MBT) zone in the western Arunachal Himalaya displays imbrication in the Permian Gondwana sequence between the MBT‐1 (/Bome Thrust/MBT‐Upper) in the north and MBT‐2 (/MBT‐Lower) in the south with consistent northerly dip. The Lower Gondwana rocks occur in the footwall of the MBT‐1 with the Proterozoic Bomdila Group in the hangingwall. The upper Gondwana rocks constitute the hangingwall sequence for the MBT‐2 with Neogene Siwalik rocks in the footwall. This article analyses palaeostress using brittle fractures in the Gondwana rocks that crop out for ~120 km2 in the study area. The fault‐bounded imbricate zone depicts eight brittle shear indicators and four sets of joints (J1 and J2: inclined and J3 and J4: subvertical). The signatures of the inherited pre‐Himalayan extensional deformation are preserved in the Lower Gondwana Miri Formation. The Bichom and Bhareli rocks exhibit brittle deformation features of the Himalayan Orogeny under strong ~N‐S compression. The palaeostress analysis of all joint sets indicates three phases of brittle deformation in the Gondwana and Siwalik rocks of the area. The subvertical joint sets and normal faults in the Miri Formation indicate a north‐northwest (NNW)‐directed extensional phase of the pre‐Himalayan origin. The inclined joint sets of the Bichom and Bhareli formations of the Gondwana sequence depict Himalayan orogeny with ~N‐S compressional phases. The third phase of brittle deformation in the Siwalik sequence depicts an east‐west (~E‐W) extension. The arc‐parallel extension in the frontal fold belt of the Arunachal Himalaya may be due to oblique India‐Asia collisional tectonics.

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Jointing and minor tectonics of the South Gower Peninsula between Mumbles Head and Rhossilli Bay, South Wales.

Roberts

1979

Geological Journal

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Joints and other minor structural elements were recorded at 429 stations on the S. Gower coast. A systematic pattern exists comprised of up to 6 set3 of joints which strike at 360°, 340°, 290°, 270°, 240" and 200". Joint set maxima are frequently parallel to the strike of major and minor faults, but no simple geometric relationship exists between joint orientation and fold axis trend. Axial-trace-fracturing has been recognized, whilst en echelon gash arrays, mineralized joint sets and their crosscutting relationships enable a tectonic sequence of events to be determined. The systematic joints are thought to have developed during the folding under the infl ence of a N-S compression, but variation in the strike of minor structures suggests a swing in orientation suites.of a Y through time. Subsequent stress relaxation facilitated dilation and the production of mineralized vein Geol.

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Jointing and minor tectonics of the S. Crop of the South Wales Coalfield between Machen and Bridgend

Cited by 7 publications

References 10 publications

Major faulting in London: evidence for inherited basement faults in the London Basin

Major faulting in London: evidence for inherited basement faults in the London Basin

Brittle tectonics in the western Arunachal Himalayan frontal fold belt, northeast India: Change in stress regime from pre‐collisional extension to collisional compression

Jointing and minor tectonics of the South Gower Peninsula between Mumbles Head and Rhossilli Bay, South Wales.

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