The Arfon Group is a stratigraphically defined geological group of rocks that are present in the Cymru Terrane around Bangor in North Wales, United Kingdom. The group contains volcanogenic conglomeratic sandstone, fine-grained tuffite and tuffaceous sediment.[1]
This Precambrian volcano-sedimentary group incorporates over 4000 m of deposits and were previously considered to be of Cambrian age. Uranium–lead (U–Pb) isotope ratio data suggests that the whole succession is indeed Precambrian Neoproterozoic age.[2] Exposure of the lower unit (Padarn Tuff) is exhibited on a ridge between Bangor and Caernarfon (both located in North Wales) and also on a ridge near Llyn Padarn.[3] This is noted to be a thick sequence of acid ash flow tuffs and exhibits welding and are thought to be rapid deposition of thin air-fall tuffs and rhyolite flows placed in a bounded half-graben (or graben).[2]
Zircon (U–Pb) radioisotopic datingEdit
Isotope data shows a zircon from the lower part of the succession as having a U–Pb isotope date of 614±2 Ma[4] and 604.7±1.6 Ma[5] and as such confirms a Neoproterozoic age.[3]
ReferencesEdit
^"BGS Lexicon of Named Rock Units - Result Details".
^ abA. J. Reedman, B. E. Leveridge, R. B. Evans, The Arfon Group (Arvonian) of North Wales., 1984, Proceedings of the Geologists Association, 95, 313-321
^ abP. J. Brenchley, P. F. Rawson The Geology of England and Wales, 2006, 2nd Ed
^R. D. Tucker & T. C. Pharaoh, U-Pb Zircon ages for late-Precambrian rocks in southern Britain., 1991, Journal of the Geological Society of London, 148, 435-433
^W. Compston, A. E. Wright, P. Toghill, Dating the Late Precambrian volcanicity of England and Wales. 2002, Journal of the Geological Society of London. 159 323-339.
arfon, group, stratigraphically, defined, geological, group, rocks, that, present, cymru, terrane, around, bangor, north, wales, united, kingdom, group, contains, volcanogenic, conglomeratic, sandstone, fine, grained, tuffite, tuffaceous, sediment, contents, l. The Arfon Group is a stratigraphically defined geological group of rocks that are present in the Cymru Terrane around Bangor in North Wales United Kingdom The group contains volcanogenic conglomeratic sandstone fine grained tuffite and tuffaceous sediment 1 Contents 1 Lithology and outcrop 2 Zircon U Pb radioisotopic dating 3 References 4 External linksLithology and outcrop EditThis Precambrian volcano sedimentary group incorporates over 4000 m of deposits and were previously considered to be of Cambrian age Uranium lead U Pb isotope ratio data suggests that the whole succession is indeed Precambrian Neoproterozoic age 2 Exposure of the lower unit Padarn Tuff is exhibited on a ridge between Bangor and Caernarfon both located in North Wales and also on a ridge near Llyn Padarn 3 This is noted to be a thick sequence of acid ash flow tuffs and exhibits welding and are thought to be rapid deposition of thin air fall tuffs and rhyolite flows placed in a bounded half graben or graben 2 Zircon U Pb radioisotopic dating EditIsotope data shows a zircon from the lower part of the succession as having a U Pb isotope date of 614 2 Ma 4 and 604 7 1 6 Ma 5 and as such confirms a Neoproterozoic age 3 References Edit BGS Lexicon of Named Rock Units Result Details a b A J Reedman B E Leveridge R B Evans The Arfon Group Arvonian of North Wales 1984 Proceedings of the Geologists Association 95 313 321 a b P J Brenchley P F Rawson The Geology of England and Wales 2006 2nd Ed R D Tucker amp T C Pharaoh U Pb Zircon ages for late Precambrian rocks in southern Britain 1991 Journal of the Geological Society of London 148 435 433 W Compston A E Wright P Toghill Dating the Late Precambrian volcanicity of England and Wales 2002 Journal of the Geological Society of London 159 323 339 External links EditThe Geology of Wales BGS 1 The BGS Online Rock Lexicon 2 Retrieved from https en wikipedia org w index php title Arfon Group amp oldid 1095248776, wikipedia, wiki, book, books, library,
