Skip to main content
Article thumbnail
Location of Repository

Structural Analysis and Tectonic Significance of the Carmel Head Thrust Belt, Anglesey, North Wales.

By Abdullah Omar Bamousa

Abstract

The Carmel Head Thrust Belt (CHTB) is a major tectonic feature that records a complex history of polyphase deformation in N Anglesey, NW Wales, British Isles. This thesis tests the hypothesis that the CHTB developed by S-directed contraction that was subsequent to SE-directed ductile contraction (D1-D2) which is recorded elsewhere in western Anglesey, and on Holy Island. Also, this study tests whether the CHTB was formed as part of a Palaeozoic accretionary wedge complex. Detailed structural analysis and synthesis of data collected along three coastal transects in NE, N and NW Anglesey form the basis for the study. Major lithological units were examined in thin-section for petrographic textures, microstructures and deformation processes.\ud The macro- and the micro-structural data indicate that lithological units in N Anglesey underwent S-directed brittle contractional deformation (D3), associated with anchizonal metamorphism. Structures associated with brittle shortening cross-cut SE-directed folds and shear zones (D1-D2) recorded in the greenschist-grade New Harbour and South Stack groups schists and phyllites. D1-D2 occurred after early Cambrian time, synchronous with the Caledonian orogeny. The D3 event occurred during the early Devonian Acadian\ud orogeny and involved southward propagation of the CHTB with a dextral component.\ud Since Ordovician time and prior to Acadian thrusting, transtensional basins were developed which were then locally inverted within a S-vergent thrust wedge. D3 CHTB structures are cut by E-W and N-S extensional faults. The E-W normal faults are related to a Permo-Triassic extensional event and considered D4, whereas the N-S normal faults are considered D5 and formed subsequent to emplacement of a regional Tertiary dyke swarm that affected Anglesey and NW Wales.\ud The Gwna Group and Ordovician rocks were not affected by pre-D3 tectonism and regional metamorphism. The Gwna Group is affiliated with Ordovician rather than Monian rocks. The Gwna mélange is the youngest unit of the Gwna Group, underlain by the Fydlyn beds and the Skerries Formation. The Gwna mélange contains crude stratigraphy, was originally olistostromal and became tectonosomal during CHTB development.\ud The CHTB in N Anglesey documents a major S-directed collisional event, whereas western, central and SE Anglesey record two separate and opposite dipping lower Palaeozoic subduction zones. The NW-dipping subduction zone is beneath NW Wales, and is in the same polarity as the SE-directed D1-D2 deformation. Central Anglesey represents a micro-continent, and the SE-dipping subduction zone was beneath southeastern-most Anglesey and NW Wales. The results of this study shed new light on the Palaeozoic amalgamation history of the British Isles

Publisher: University of Leicester
Year: 2009
OAI identifier: oai:lra.le.ac.uk:2381/4535

Suggested articles

Citations

  1. (1991). A discussion of Monian stratigraphy in northwest Wales, doi
  2. (1986). A greenschist protolith for blueschist in Anglesey, doi
  3. (1963). A Lower Ordovician gastropod from Anglesey. doi
  4. (1979). A new look at the Mona Complex, Anglesey, North Wales, volume 136. doi
  5. (2004). A practical guide to rock microstructure. doi
  6. (1922). A short summary of the geological history of Anglesey.
  7. (1988). Anomalous vergence patterns on the Rhoscolyn Anticline, Anglesey : implications for structural analysis of refolded regions. doi
  8. (1974). Aspects of magmatism and plate tectonics doi
  9. (1996). Avalonian magmatism and terrane linkage: new isotopic data from the Precambrian of North Wales, volume 153. doi
  10. (2007). British Regional Geology: Wales. British Geological Survey. doi
  11. (1992). Caledonian structures in Britain, south of the Midland Valley. doi
  12. (1908). Composition and origin of the crystalline rocks of Anglesey - report of the committee. Report of the British Association for the Advancement of Science for
  13. (1990). Conditions of fault-valve behavior. doi
  14. (2004). Continental growth at convergent margins facing large ocean basins: a case study from Mesozoic convergent-margin basins of doi
  15. (1990). Contrasting metamorphic terranes in northwest Wales. In doi
  16. (1990). Control of fluids on deformation of rocks. doi
  17. (1999). Debris flows on the Ordovician margin of Avalonia, Lady Port Formation, Manx Group. doi
  18. (1991). EDGE deep seismic reflection transect of the eastern Aleutian arc-trench layered lower crust reveals underplating and continental growth, doi
  19. (2002). Evolution and Kinematics of an ancient decollement zone, melange in the Shimanto accretionary complex of Okinawa Islan, Ryukyo Arc, doi
  20. (1969). Evolution of the Appalachian/Caledonian orogeny, doi
  21. (1989). Extended Abstract: Correlation of the Monian Supergroup doi
  22. (1981). Field meeting in Anglesey and Southeast Ireland, volume 92.
  23. (2005). Fitting the Anglesey piece into the Avalonian-Iapetan puzzle. Abstract in: Recent Developments
  24. (1984). Flow melanges and the structural evolution of accretionary wedges. doi
  25. (2003). Fluid flow at the toe of convergent margins: interpretation of sharp pore-water geochemical gradients, volume 213. Earth and Planetary Science Letters. doi
  26. (1930). Foliation researches on the succession and metamorphism in the Mona doi
  27. (1923). Further researches on the succession and metamorphism in doi
  28. (1993). Geochemistry and eruptive environment of metavolcanic rocks from the Mona Complex of Anglesey, North Wales, U.k., volume 130. Geological Magazine. doi
  29. Geological description of Anglesea, doi
  30. (1921). Geological itineraries in Anglesey. Tinling and Co, doi
  31. (1985). Geology and paleobiology of islands in the Ordovician Iapetus Ocean: review and implications by R.B. doi
  32. (1984). Geology and paleobiology of islands in the Ordovician Iapetus Ocean: review and implications, volume 95. doi
  33. (1992). Geology of England and Wales. doi
  34. (2007). Geotectonic framework of the blueschist unit on Anglesey-Lleyn,UK, and its role in the development of a Neoproterozoic accretionary orogen, volume 153. Precambrian Research. doi
  35. (1981). Glaucophanic amphibole in a Monian shear zone on the mainland of N Wales. doi
  36. (1979). Gwna Melange, Upper Precambrian Olistostromal Sequence, North Wales, United Kingdom: doi
  37. (2005). Internal dynamics of a paleoaccretionary wedge: insights from combined isotope tectonochronology and sandbox modelling of the South-Central Chilean forearc, volume 231. Earth and Planetary Science Letters. doi
  38. (1988). Is the Welsh Borderland Fault System a terrane boundary? 145. doi
  39. (1999). Kinematic analysis of melange fabrics: examples and applications from the McHugh Complex, doi
  40. (1985). Large scale sediment underplating in the Makran accretionary prism, southwest Pakistan, doi
  41. (1979). Late Precambrian igneous activity in Southern Britain. doi
  42. (1999). Lateral growth of the continental crust through deep level subductionaccretion: a re-evaluation of central Greek Rhodope, doi
  43. (1998). Material transfer in accretionary wedges from analysis of a systematic series of analog experiments, volume 20. doi
  44. (2002). Mechanical decoupling and basal duplex formation observed in sandbox experiments with application to the Western Mediterranean Ridge accretionary complex. 186. Marine Geology. doi
  45. (1995). Mechanisms of melange formation: examples from SW Japan and southern Scotland, volume 17. doi
  46. (1989). Melanges and olistostromes in the Appalachians of the United states and mainland Canada; an assessment. doi
  47. (1987). Menai Strait fault system: an early Caledonian terrane boundary in North Wales, doi
  48. (2006). Mineral isograds and metamorphic zones of the Anglesey Blueschist belt, UK: implications for the metamorphic development of a Neoproterozoic subdcution-accretionary complex, volume 24. Metmorphic Geology. doi
  49. (1989). Monian terrane in northern Wales.
  50. (1985). New exposures of old blueschists in Anglesey, North Wales. 142. journal of the Geological Society of London.
  51. (1956). Notes on the structure and relations of the Pre-Cambrian and doi
  52. (1999). Numerical modelling of focussed fluid flow in the cascadia accretionary wedge, doi
  53. (1972). Ocean floor basalt affinity of Precambrian glaucophane schist from Anglesey. doi
  54. (1900). On photographs of sandstone pipes in the Carboniferous Limestone at Dwlbau Point, east Anglesey. Abstract in: Report of the British Associattion for the Advancement of Science for 1899(69th, Transactions Section C.
  55. On Quartzite lenticles in the schist of southeastern Anglesey. Report of the British Association for the Advancement of Science Meeting (66th), Transaction Section C.
  56. (1997). On the deformation sequence in the New Harbour group of Holy Island, Anglesey, North Wales, volume 32. doi
  57. On the Monian System of rocks, volume 44. doi
  58. (1896). On the occurrence of sillimanite gneisses in central Anglesey. doi
  59. (1913). On the origin of some of the mica-schists of Anglesey. Report of the British Association for the Advancement of Science for 1912 (82nd), Transaction Section C.
  60. (2004). On the structural age of the Rhoscolyn antiform, Anglesey, North Wales, volume 39. doi
  61. (1974). Ophioilites, melanges, blushcists, and ignimbrites: early Caledonian subduction in Wales? In doi
  62. (1999). Orogens and slabs vs. their direction of subduction, volume 45. Earth-Science Reviews. doi
  63. (1996). Palaeogene dyke swarm, NW Wales: evidence for Cenozoic sinistral fault movement, volume 153. doi
  64. (1979). Palaeontological evidence for the age of some supposedly Precambrian rocks in Anglesey, North Wales. doi
  65. (1966). Petrology of an irregular-nodule bed, Lower Carboniferous, Anglesey, North Wales. doi
  66. (1990). Pre-arenig terranes of North Wales. doi
  67. (1986). Pre-Mesozoic lawsonite in Anglesey, North Wales: preservation of ancient blueschists. doi
  68. (1975). Precambrian of Wales. In
  69. (1994). Precambrian rocks in Anglesey, southwest Llyn and southeast Ireland.
  70. (1984). Principles of rock deformation. doi
  71. (1991). Progressive deformation of the South Stack and New Harbour Groups, Holy Island, doi
  72. (1984). Prologue the melange problem - a review. In doi
  73. (2004). Provenance and age constraints of the South Stack group, Anglesey, UK: U-Pb SIMS detrital zircon data, volume 161. doi
  74. (1986). Reclassification of blueschist amphiboles from Anglesey, North Wales. doi
  75. (1996). respectively after Horak et al.,
  76. (2005). Scandinavian Caledonides (with Greenland). In doi
  77. (1985). Sedimentological studies in the Ordovician rocks of Anglesey. Ph.D.,
  78. (1978). Serpentinite textures in Anglesey, doi
  79. (2004). Shear zones - an introduction and overview. doi
  80. (2001). Smectite diagenesis, pore-water freshening, and fluid flow at the toe of the Nankai wedge, volume 194. Earth and Planetary Science Letters. doi
  81. (1948). Some Anglesey glacial problems.
  82. (1992). Southern Patagonian plateau basalts and deformation: backarc testimony of ridge collisions, doi
  83. (1937). Spring pits and sandstone pipes. 74. Geological Magazine. doi
  84. (1983). Stratigraphy, subduction and strike-slip faulting in the Mona Complex of North Wales-a review, volume 94. doi
  85. (1996). Structural geology of rocks and regions.
  86. (2003). Structural style of the offscraped Ligurian oceanic sequences of the Northern Apennines: new hypothesis concerning the development of melange block-in-matrix fabric, volume 25. doi
  87. (1985). Structural styles in Mesozoic and Cenozoic melanges in the western doi
  88. (1995). Structure and morphotectonics of the accretionary prism along the Eastern Sunda-Western Banda Arc, doi
  89. (1949). Studies in the Mona Complex - the base of the succession. 86. geological Magazine. doi
  90. (2003). Superposed deformations and their hybrid effects: The Rhoscolyn anticline unravelled, volume 160. doi
  91. (1992). Superposed structures in the Mona Complex at Rhoscolyn, Ynys Gybi, North Wales. doi
  92. (1989). Suspect terrane definition in Anglesey, North Wales. In doi
  93. (2002). Tectonic and metasomatic mixing in a high-T, subductionzone melange:insights into the geochemical evolution of the slabmantle interface, volume 187. Chemical Geology. doi
  94. (1987). Tectonic collision processes after plate rupture, doi
  95. (1992). Tectonic context of fluid venting at the toe of the eastern Nankai accretionary prism: Evidence for a shallow detachment fault, volume 109. Earth and Platenary Science Letters. doi
  96. (1979). Tectonic emplacement of ophiolite rocks in the Precambrian Mona Complex of Anglesey. doi
  97. (1978). Tectonic emplacement of ophiolitic rocks in the Precambrian Mona Complex of Anglesey. doi
  98. (1988). Tectonic evolution of northern Anglesey.
  99. (1989). Tectonics and hydrogeology of accretionary prims: role of the decollement zone, volume 11. doi
  100. (1995). Tectonics. Freeman and Co., doi
  101. (1987). The age of blueschist metamorphism in Anglesey, North Wales: evidence from 40Ar/39Ar mineral dates of the Penmynydd schists, volume 144. Journal ofthe Geological Society, doi
  102. (1900). The age of the later dykes of Anglesey. doi
  103. The Archean geology of Anglesey. 37.
  104. (1998). The Cambrian-Silurian tectonic evolution of the northern Appalachians and British Caledonides: history of a complex, west and southwest pacific-type segment of iapetus. doi
  105. (2004). The chemistry of subduction-zone fluids, volume 223. Earth and Planetary Science Letters. doi
  106. (1948). The cleavages of Mon and
  107. (1995). The Geolgy of the Irish Sea, volume United Kingdom Offshore Regional Report.
  108. (1919). The geology of Anglesey, doi
  109. (1896). The geology of the eastern corner of Anglesey. doi
  110. (1989). The Geology of the Monian Supergroup, doi
  111. The Hereford earthquake of 1896 considered in relation to the geological sturcture in the Bangor-Anglesey region. doi
  112. (1991). The lithostratigraphy, sedimentology and tectonic setting of the Monian Supergroup, western Anglesey, North Wales, volume 148. doi
  113. (2003). The lost Lower Old Red Sandstone of England and Wales: a record of post-Iapetan flexure or Early Devonian transtension, volume 140. doi
  114. (1928). The Lower Carboniferous rocks of the Menaian region of Caernarvonshire. 84. doi
  115. (1968). The Lower Palaeozoic brachiopod and trilobite faunas of Anglesey.
  116. (1990). The Mechanics of Earthquakes and Faulting. doi
  117. (1902). The origin and associations of the jaspers of southeastern doi
  118. (1928). The Precambrian complex and associated rocks of S.W. doi
  119. (1969). The Precambrian of North Wales. doi
  120. (1965). The sedimentation and palaeogeography of the Old Red Sandstone of Anglesey, North Wales. doi
  121. (1977). The serpentinite and related rocks of Anglesey. 12. doi
  122. (1972). The stratigraphy of the Ordovician rocks of Anglesey, doi
  123. (1993). The structural controls on mineralisation at
  124. (1954). The structure and succession of Anglesey and the Lleyn Peninsula, volume 11. Advancement of Science.
  125. (1974). The structure of the Lower Palaeozoic rocks of Anglesey, with special reference to faulting, volume 9. doi
  126. (1979). The tectonic evolution of the Welsh Caledonides, doi
  127. (2000). Thrusting and sinistral wrenching in a pre-Eocene HP-LT Caribbean accretionary wedge (Saman Peninsula, Dominican Republic), volume 13. Geodinamica Acta. doi
  128. (1990). Transcurrent ductile sher zones and the dispersal of the Avalon superterrane. In doi
  129. (1981). Transcurrent faulting and the anomalous position of precarboniferous Anglesey, doi
  130. (1975). Ultramafic rocks in Anglesey, their non-tectonic emplacement. doi
  131. (2003). Understanding Earth. Freeman and Company,
  132. (2005). Volatiles in subduction zone magmas: concentrations and fluxes based on melt inclusion and volcanic gas data, volume 140. doi
  133. (2001). Volcanic Sequence and Alteration at the Parys Mountain Volcanic-Hosted Massive Sulfide Deposit, Wales, United Kingdom: Applications of Immobile Element Lithogeochemistry, volume 96. Economic Geology. doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.