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Cambrian and early Tremadoc rocks of the Llangynog Inlier, Dyfed, South Wales

Published online by Cambridge University Press:  01 May 2009

J. C. W. Cope  and
A. W. A. Rushton
J. C. W. Cope
Affiliation:
Department of Geology, University of Wales, P.O. Box 914, Cardiff CF1 3YE, U.K.
A. W. A. Rushton
Affiliation:
British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
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Abstract

Until recently no Cambrian rocks were known in the Llangynog area. Detailed mapping has now revealed a succession of ?Lower and Upper Cambrian rocks overlain by Tremadoc rocks. The Allt y Shed Sandstones (new) rest unconformably on the Precambrian, but have yielded no diagnostic fossils and are tentatively assigned to the Comley Series. Succeeding with faulted or unconformable contact is an Upper Cambrian Merioneth Series succession which includes in ascending order: conglomerates, sandstones and siltstones with olenid trilobites and resembling the Treffgarne Bridge Beds of the Haverfordwest area; micaceous shales and siltstones referred to the Ffestiniog Flags Formation; and black mudstones with calcareous concretions and a rich olenid fauna referred to the Dolgellau Formation. Succeeding the latter with possible disconformity is a succession belonging to the lower part of the Tremadoc Series and earlier than any rocks of that series hitherto recorded from the area.

Type
Articles
Information
Geological Magazine , Volume 129 , Issue 5 , September 1992 , pp. 543 - 552
Copyright
Copyright © Cambridge University Press 1992

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References

Bulman, O. M. B. 1954. The graptolite fauna of the Dictyonema Shales of the Oslo region. Norsk Geologisk Tidsskrift 33, 1–40, pls 1–8.Google Scholar
Cobbold, E. S. & Pocock, R. W. 1934. The Cambrian area of Rushton (Shropshire). Philosophical Transactions of the Royal Society of London, Series B, 223, 305–409, pls 38–45.Google Scholar
Cope, J. C. W. 1977. An Ediacara type fauna from South Wales. Nature 268, 624.CrossRefGoogle Scholar
Cope, J. C. W. 1979. Early history of the southern margin of the Tywi anticline in the Carmarthen area, South Wales. In The Caledonides of the British Isles - Reviewed (eds Harris, A. L. Holland, C. H. and Leake, B. E.), pp. 527–32. Geological Society of London.Google Scholar
Cope, J. C. W. 1982. Geology of the Llanstephan Peninsula. In Geological Excursions in Dyfed, South-West Wales (ed. Bassett, M. G.), pp. 259–69. National Museum of Wales, Cardiff.Google Scholar
Cope, J. C. W. & Bassett, M. G. 1987. Sediment sources and Palaeozoic history of the Bristol Channel area. Proceedings of the Geologists' Association 98, 315–30.CrossRefGoogle Scholar
Cope, J. C. W. & Bevins, R. E. 1993. The stratigraphy and setting of the Precambrian rocks of the Llangynog Inlier, Dyfed, South Wales. Geological Magazine 130, [in press].Google Scholar
Cope, J. C. W., Fortey, R. A. & Owens, R. M. 1978. Newly discovered Tremadoc rocks in the Carmarthen district, South Wales. Geological Magazine 115, 195–98, pl.CrossRefGoogle Scholar
Cowie, J. W., Rushton, A. W. A. & Stubblefield, C. J. 1972. A correlation of Cambrian rocks in the British Isles. Special Report of the Geological Society, London, No. 2, 42pp.Google Scholar
Fortey, R. A. & Owens, R. M. 1992. The Habberley Formation: youngest Tremadoc in the Welsh Borderland. Geological Magazine 129, 533–66.CrossRefGoogle Scholar
Henningsmoen, G. 1957. The trilobite family Olenidae. Skrifter utgitt av Det Norske Videnskaps-Akademi i Oslo. I. Matematisk Naturvidenskapelig Klasse, for 1957, no. I, 303 pp., 31 pls.Google Scholar
Old, R. A., Sumbler, M. G. & Ambrose, K. 1987. Geology of the country around Warwick. British Geological Survey, Memoir for 1:50,000 geological sheet 184 (England and Wales), H.M.S.O., London.Google Scholar
Owens, R. M., Fortey, R. A., Cope, J. C. W., Rushton, A. W. A. & Bassett, M. G. 1982. Tremadoc faunas from the Carmarthen district, South Wales. Geological Magazine 119, 1–38, pls 1–8.CrossRefGoogle Scholar
Peng, , Shanchi, , 1990. Trilobites from the Panjiazui Formation and the Madaoyu Formation in Jiangnan Slope Belt. Beringeria 2, 55–171, 23 pls.Google Scholar
Robison, R. A. & Pantoja-Alor, J. 1968. Tremadocian trilobites from the Nochixtlán region, Oaxaca, Mexico. Journal of Paleontology 42, 767–800, pls 97–104.Google Scholar
Rushton, A. W. A. 1968. Revision of two Upper Cambriantrilobites. Palaeontology 11, 410–20, pls 77–8.Google Scholar
Rushton, A. W. A. 1974. The Cambrian of Wales and England. In Cambrian of the British Isles, Norden, and Spitsbergen (ed. Holland, C. H.), pp. 43–121. Wiley.Google Scholar
Rushton, A. W. A. 1983. Trilobites from the Upper Cambrian Olenus Zone in central England. Special Papers in Palaeontology 30, 107–39, pls 14–19.Google Scholar
Schrank, E. 1973. Trilobiten aus Geschieben der oberkambrischen Stufen 3–5. Paläontologische Abhandlungen, Abteilung A, Paläozoologie, 4, 806–57, 15 pls.Google Scholar
Strahan, A., Cantrill, T. C., Dixon, E. E. L. & Thomas, H. H. 1909. The geology of the South Wales Coalfield. Part X. The country around Carmarthen. Memoir of the Geological Survey of Great Britain, viii + 177pp.Google Scholar
Stubblefield, C. J. 1930. A new Upper Cambrian succession in south Shropshire. Summary of Progress of the Geological Survey for 1929, part II, 54–62.Google Scholar
Stubblefield, C. J. 1933. Notes on the fossils. In S. Smith. On the occurrence of Tremadoc Shale in the Tortworth Inlier (Gloucestershire). Quarterly Journal of the Geological Society, London 89, 357–78, pI. 34.Google Scholar
Taylor, K. & Rushton, A. W. A. 1972. The pre-Westphalian geology of the Warwickshire Coalfield. Bulletin of the Geological Survey of Great Britain 35, vii +150 pp., 12 pls (dated 1971).Google Scholar
Thomas, A. T., Owens, R. M. & Rushton, A. W. A. 1984. Trilobites in British Stratigraphy. Special Report of the Geological Society, London, No. 16, 78 pp.Google Scholar
Westergård, A. H. 1944. Borrningar genom Skånes Alunskiffer 1941–42. Sveriges geologiska Undersökning, Avhandlingar och uppsalser, Serie C, no. 459, 45 pp., 6 pls.Google Scholar
Williams, T. G. 1934. The Pre-Cambrian and Lower Palaeozoic rocks of the eastern end of the St. David's Pre-Cambrian area, Pembrokeshire. Quarterly Journal of the Geological Society, London, 90, 32–75, pl. 2.CrossRefGoogle Scholar