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Definition of the Tremadoc Series and the series of the Ordovician System in Britain

Published online by Cambridge University Press:  01 May 2009

H. B. Whittington ,
W. T. Dean ,
R. A. Fortey ,
R. B. Rickards ,
A. W. A. Rushton  and
A. D. Wright
H. B. Whittington
Affiliation:
Sedgwick Museum, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ
W. T. Dean
Affiliation:
University College, P.O. Box 78, Cardiff CF1 1XL, Wales
R. A. Fortey
Affiliation:
British Museum (Natural History), Cromwell Road, London SW7 5BD
R. B. Rickards
Affiliation:
Sedgwick Museum, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ
A. W. A. Rushton
Affiliation:
Institute of Geological Sciences, Exhibition Road, London SW7 2DE
A. D. Wright
Affiliation:
Queen's University, Belfast B17 INN, Northern Ireland
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Abstract

The Tremadoc Series and series of the Ordovician System are widely used in international correlations, and this review explains and summarizes how the base of each of these series is recognized in Britain. No type section in which the base of any one of them is displayed has ever been selected and formally designated, hence the basal horizon of each series is a matter of general understanding rather than precise definition. This general understanding is of particular biozones, or of assemblages of fossils and their relative ages. The geographical separation between type sections of series, and differences in facies, complicate the understanding of relative ages of biozones. Brachiopod and trilobite faunas of the Llandeilo, Caradoc and Ashgill Series have been studied in detail in recent years, and biozones proposed. These biozones have proved difficult or impossible to recognize outside their type areas in Britain, and brachiopod–trilobite faunas of the Tremadoc, Arenig and Llanvirn Series are likewise highly provincial. Thus for correlation within and outside Britain attention has been focused on the ‘standard’ graptolite biozones, particularly since such conodont faunas as have been found have not proved useful. Yet there are problems associated with these ‘standard’ biozones; for example, the Tetragraptus approximatus Biozone is unknown in Wales or England, the relationship between the base of the Glyptograptus teretiusculus Biozone and the earliest Llandeilo shelly faunas requires clarification, and at what level the base of the Caradoc Series may lie in the Nemagraptus gracilis Biozone is unknown.

Thus to bring precision to definitions of Ordovician Series in Britain the identification of continuous, fossiliferous sequences that will serve as stratotypes, is required. Such a section for the basal portion of the Tremadoc Series has recently been proposed. Systematic studies related to particular biozones are needed, for example early Caradoc and early Ashgill brachiopods, and graptolites of the Didymograptus bifidus and Glyptograptus teretiusculus Biozones. The stratigraphical ranges and abundances of species in particular sections require documentation, so that the type of biozone (assemblage, acme, concurrent-range, etc.) may be recognized. Such work could lead towards chronostratigraphy, the provision of a standard stratigraphical scale in Britain for the Tremadoc Series and Ordovician series.

Type
Articles
Information
Geological Magazine , Volume 121 , Issue 1 , January 1984 , pp. 17 - 33
Copyright
Copyright © Cambridge University Press 1984

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References

Banroft, B. B. 1928. The Harknessellinae. Memoirs and Proceedings of the Manchester Literary Philosophical Society 72, 173–96, pls. 1, 2.Google Scholar
Bancroft, B. B. 1929. Some new species of Cryptolithus (s.l.) from the Upper Ordovician. Memoirs and Proceedings of the Manchester Literary and Philosphical Society 73, 67–98, pls. 1, 2.Google Scholar
Bancroft, B. B. 1933. Correlation Tables of the Stages Costonian–Onnian in England and Wales. Blakeney, Glos. (privately printed), 1–4.Google Scholar
Bancroft, B. B. 1945. The brachiopod zonal indices of the Stages Costonian to Onnian in Britain. Journal of Paleontology 19, 181–252, pls. 22–38.Google Scholar
Barnes, C. R., Norford, B. S. & Skevington, D. 1981. The Ordovician System in Canada. Correlation Chart and explanatory notes. International Union of Geological Sciences, Publication 8.Google Scholar
Bassett, D. A., Ingham, J. K. & Wright, A. D. 1974. Field Excursion Guide to Type and Classical Sections in Britain. Palaeontological Association, Ordovician Symposium, Birmingham, 1974. 66 pp.Google Scholar
Bassett, M. G. 1981. The Ordovician brachiopods of Cornwall. Geological Magazine 118, 647–64, pls. 1–4.CrossRefGoogle Scholar
Bassett, M. G. (ed.) 1982. Geological Excursions in Dyfed, South–west Wales. Cardiff: National Museum of Wales.Google Scholar
Bassett, M. G. & Dean, W. T. (eds.) 1982. The Cambro–Ordovician boundary: Sections, Fossil Distributions and Correlations. National Museum of Wales, Geological Series No. 3, Cardiff. 227 pp.Google Scholar
Bates, D. E. B. 1968. The Lower Palaeozoic brachiopod and trilobite faunas of Anglesey. Bulletin of the British Museum (Natural History) London. Geology series 16, 127–99.Google Scholar
Bates, D. E. B. 1969. Some early Arenig brachiopods and trilobites from Wales. Bulletin of the British Museum (Natural History) London. Geology series 18, 1–28.Google Scholar
Belt, T. 1867. On the ‘Lingula Flags’ or‘Festiniog Group’ of the Dolgelly district. Part 1. Geological Magazine 4, 493–5.CrossRefGoogle Scholar
Bergström, S. M. 1971. Conodont biostratigraphy of the Middle and Upper Ordovician of Europe and eastern North America. Memoir of the Geological Society of America 127, 83–157.CrossRefGoogle Scholar
Bergström, S. M. 1973. Correlation of the late Lasnamagian Stage (Middle Ordovician) with the graptolite succession. Geologiska Föreningens; Stockholm Förhandlingar 95, 9–18.CrossRefGoogle Scholar
Bulman, O. M. B. 1927–1967. A monograph of British Dendroid Graptolites. Palaeontographical Society, London (Monographs), xiv + 97 pp., 10 pls.Google Scholar
Callaway, C. 1874. On the occurrence of a Tremadoc area near the Wrekin in South Shropshire, with a description of a new fauna. Quarterly Journal of the Geological Society of London 30, 196.CrossRefGoogle Scholar
Cantrill, T. C. & Thomas, H. H. 1909. Pp. 44–48 in ‘The geology of the South Wales Coalfield. Part X. The country around Carmarthen.’ By Strachan, A., Cantrill, T. C., Dixon, E. E. L. & Thomas, H. H.. Memoir Geological Survey of Great Britain 229, 1–177.Google Scholar
Cave, R. 1965. The Nod Glad sediments of Caradoc age in North Wales. Geological Journal 4, 279–98.CrossRefGoogle Scholar
Cave, R. & Price, D. 1978. The Ashgill Series near Welshpool, North Wales. Geological Magazine 115, 183–94.CrossRefGoogle Scholar
Cocks, L. R. M. 1978. A review of British Lower Palaeozoic brachiopods, including a synoptic revision of Davidson's monographs. Palaeontographical Society, London(Mono–graphs), pp. 1–256.Google Scholar
Cooper, R. A. & Fortey, R. A. 1982. The Ordovician graptolites of Spitsbergen. Bulletin of the British Museum (Natural History) London. Geology series 36, 157–302, pls. 1–6.Google Scholar
Cowie, J. W., Rushton, A. W. A. & Stubblefield, C. J. 1972. A correlation of Cambrian rocks in the British Isles. Special Report. Geological Society of London 2, 1–42.Google Scholar
Curtis, M. L. K. 1968. The Tremadoc rocks of the Tortworth Inlier, Gloucestershire. Proceedings of the Geologists' Association 79, 349–62, pls. 8, 9.CrossRefGoogle Scholar
Dean, W. T. 1958. The faunal succession in the Caradoc Series of south Shropshire. Bulletin of the British Museum (Natural History) London. Geology series 3, 191–231, pls. 24–6.Google Scholar
Dean, W. T. 1959. The stratigraphy of the Caradoc Series in the Cross Fell Inlier. Proceedings of the Yorkshire Geological Society 32, 185–228.CrossRefGoogle Scholar
Dean, W. T. 1960. The Ordovician trilobite faunas of south Shropshire, I. Bulletin of the British Museum (Natural History) London. Geology series 4, 71–143, pls. 11–19.Google Scholar
Dean, W. T. 1961. The Ordovician trilobite faunas of south Shropshire, II. Bulletin of the British Museum (Natural History) London. Geology series 5, 311–58, pls. 49–55.Google Scholar
Dean, W. T. 1962. The trilobites of the Caradoc Series in the Cross Fell inlier of northern England. Bulletin of the British Museum (Natural History) London. Geology series 7, 65–134, pls. 6–18.Google Scholar
Dean, W. T. 1963. The Ordovician trilobite faunas of south Shropshire, IV. Bulletin of the British Museum (Natural History) London. Geology series 9, 1–18, pls. 1, 2.Google Scholar
Dean, W. T. 1964. The geology of the Ordovician and adjacent strata in the southern Caradoc district of Shropshire. Bulletin of the British Museum (Natural History) London. Geology series 9, 257–96.Google Scholar
Dean, W. T. 1980. The Ordovician System in the Near and Middle East. Correlation chart and explanatory notes. International Union of Geological Sciences, Publication 2.Google Scholar
Dean, W. T. & Dinneley, D. L. 1961. The Ordovician and associated Pre–Cambrian rocks of the Pontesford district, Shropshire. Geological Magazine 98, 367–76.CrossRefGoogle Scholar
Elles, G. L. 1904. Some graptolite zones in the Arenig rocks of Wales. Geological Magazine 41, 199–211.CrossRefGoogle Scholar
Elles, G. L. 1940. The stratigraphy and faunal succession in the Ordovician rocks of the Builth–Llandrindod Inlier, Radnorshire. Quarterly Journal of the Geological Society of London 95 (for 1939), 383–445.CrossRefGoogle Scholar
Fearnsides, W. G. 1905. On the geology of Arenig Fawr and Moel Llyfnant. Quarterly Journal of the Geological Society of London 61, 608–40.CrossRefGoogle Scholar
Fearnsides, W. G. 1910. The Tremadoc Slates and associated rocks of south–east Carnarvonshire. Quarterly Journal of the Geological Society of London 66, 142–88.CrossRefGoogle Scholar
Fortey, R. A. & Owens, R. M. 1978. Early Ordovician (Arenig) stratigraphy and faunas of the Carmarthen district, south west Wales. Bulletin of the British Museum (Natural History). London. Geology series 30, 225–94.Google Scholar
Greig, D. G., Wright, J. E., Hains, B. A. & Mitchell, G. H. 1968. Geology of the country around Church Stretton, Craven Arms, Wenlock Edge and Brown Clee. (Sheet 166). Memoir. Geological Survey of the United Kingdom, i–xiv, 1–380.Google Scholar
Hamman, W., Robardet, M. & Romano, M. 1982. The Ordovician System in southwestern Europe (France, Spain and Portugal). Correlation Chart and explanatory notes. International Union of Geological Sciences, Publication 11.Google Scholar
Harper, D. A. T. 1979. The environmental significance of some faunal changes in the Upper Ardmillan succession (upper Ordovician), Girvan, Scotland. Pp. 439–45. In The Caledonides of the British Isles – reviewed (ed. Harris, A. L., Holland, C. H. & Leake, B. E.). Geological Society of London & Scottish Academic Press, Edinburgh, xii + 768 pp.Google Scholar
Henry, J.–L. 1980. Trilobites ordoviciens du Massif Armoricain. Mémoires de la Sociéte Géologique et Minéralogique de Bretagne 22, 1–250, pls. 1–48.Google Scholar
Henningsmoen, G. 1973. The Cambro–Ordovician boundary. Lethaia 6, 423–39.CrossRefGoogle Scholar
Hicks, H. 1875. On the succession of the ancient rocks in the vicinity of St David's, Pembrokeshire, with special reference to those of the Arenig and Llandeilo Groups, and their fossil contents. Quarterly Journal of the Geological Society of London. 31, 167–95.CrossRefGoogle Scholar
Hicks, H. 1881. The classification of the Eozoic and Lower Palaeozoic rocks of the British Isles. Popular Science Review 5, 289–308.Google Scholar
Higgins, A. C. 1967. The age of the Durine member of the Durness Limestone Formation at Durness. Scottish Journal of Geology 3, 382–8.CrossRefGoogle Scholar
Holland, C. H. 1982. The state of Silurian stratigraphy. Episodes 1982 (3), 21–3.CrossRefGoogle Scholar
Holland, C. H., Audley–Charles, M. G., Bassett, M. G., Cowie, J. W., Curry, D., Fitch, F. J., Hancock, J. M., House, M. R., Ingham, J. K., Kent, P. E., Morton, N., Ramsbottom, W. H. C., Rawson, P. F., Smith, D. B., Stubblefield, C. J., Torrens, H. S., Wallace, Peigi & Woodland, A. W. 1978. A guide to stratigraphical procedure. Special Report. Geological Society London, 11, 1–18.Google Scholar
Hopkinson, J. & Lapworth, C. 1875. Descriptions of the graptolites of the Arenig and Llandeilo rocks of St David's. Quarterly Journal of the Geological Society of London 31, 631–72, pls. 23–7.CrossRefGoogle Scholar
Hughes, C. P. 1969. The Ordovician trilobite faunas of the Builth–Llandrindod Inlier, central Wales. Part 1. Bulletin of the British Museum (Natural History) London. Geology series 18, 39–103, pls. 1–14.Google Scholar
Hughes, C. P. 1971. The Ordovician trilobite faunas of the Builth–Llandrindod Inlier, central Wales. Part II. Bulletin of the British Museum (Natural History) London. Geology series 20, 115–82, pls. 1–16.Google Scholar
Hughes, C. P. 1979. The Ordovician trilobite faunas of the Builth–Llandrindod Inlier, central Wales. Part III. Bulletin of the British Museum (Natural History) London. Geology series 32, 109–81.Google Scholar
Ingham, J. K. 1966. The Ordovician rocks in the Cautley and Dent districts of Westmorland and Yorkshire. Proceedings of the Yorkshire Geological Society 35, 455–505.CrossRefGoogle Scholar
Ingham, J. K. 1970. A monograph of the Upper Ordovician trilobites from the Cautley and Dent districts of Westmorland and Yorkshire. Part I. Palaeontographical Society, London (Monographs), 1–58, pls. 1–9.Google Scholar
Ingham, J. K. 1974. The Upper Ordovician trilobites from the Cautley and Dent districts of Westmorland and Yorkshire. Part II. Palaeontographical Society, London (Monographs), 59–87, pls. 10–18.Google Scholar
Ingham, J. K. 1977. The Upper Ordovician trilobites from the Cautley and Dent districts of Westmorland and Yorkshire. Part III. Palaeontographical Society, London (Monographs), 89–121, pls. 19–27.Google Scholar
Ingham, J. K. 1978. Geology of a contintental margin. 2. Middle and late Ordovician transgression, Girvan. In Crustal evolution in northwest Britain and adjacent regions (ed. Bowes, D. R. and Leake, B. E.). Geological Journal (Special Issue) 10, 163–176.Google Scholar
Ingham, J. K. & Wright, A. D. 1970. A revised classification of the Ashgill Series. Lethaia 3, 233–42.CrossRefGoogle Scholar
Jaanusson, V. 1960. On the Series of the Ordovician System. International Geological Congress, Report of 21st Session, Nordern, part VII, 70–81.Google Scholar
Jackson, D. E. 1961. Stratigraphy of the Skiddaw Group between Buttermere and Mungrisdale, Cumberland. Geological Magazine 98, 515–28.CrossRefGoogle Scholar
Jackson, D. E. 1962. Graptolite zones in the Skiddaw Group in Cumberland, England. Journal of Paleontology 36, 300–13.Google Scholar
Jenkins, C. J. 1983. Ordovician graptolites from the Great Paxton borehole, Cambridgeshire. Palaeontology 26, 641–53.Google Scholar
Kaljo, D. & Koren', T. (eds.) 1976. Graptolites and Stratigraphy. Tallin: Academy of Science, Estonian SSR, Institute of Geology, 256 pp.Google Scholar
King, W. B. R. & Williams, A. 1948. On the lower part of the Ashgillian Series in the north of England. Geological Magazine 85, 205–12.CrossRefGoogle Scholar
Kitchin, F. L. 1930. Sectional Report, Palaeontological Department. In Summary of Progress. Geological Survey of Great Britain, 1929, 1, 87–94.Google Scholar
Lamont, A. & Lindström, M. 1957. Arenigian and Llandeilian cherts identified in the Southern Uplands of Scotland by conodonts, etc. Transactions of the Geological Society of Edinburgh 17, 60–70.CrossRefGoogle Scholar
Lapworth, C. 1879–1880. On the geological distribution of the Rhabdophora. Annals and Magazine of Natural History, series 5, 3, 245–57, 449–55; 4, 333–41, 423–31; 5, 45–62, 273–85, 358–69; 6, 16–29, 185–207.CrossRefGoogle Scholar
Lockley, M. G. & Williams, A. 1981. Lower Ordovician Brachiopoda from mid– and southwest Wales. Bulletin of the British Museum (Natural History) London. Geology series 35, 1–78.Google Scholar
Löfgren, A. 1978. Arenigian and Llanvirnian conodonts from Jämtland, northern Sweden. Fossils and Strata 13, 1–129, 16 pls.CrossRefGoogle Scholar
Lynas, B. D. T. 1973. The Cambrian and Ordovician rocks of the Migneint area, North Wales. Journal of the Geological Society of London 129, 481–503.CrossRefGoogle Scholar
Marr, J. E. 1905. (The classification of the sedimentary rocks.) Quarterly Journal of the Geological Society of London 61, lxi–lxxxvi.Google Scholar
Marr, J. E. 1913. The Lower Palaeozoic rocks of the Cautley district. Quarterly Journal of the Geological Society of London 69, 1–17.CrossRefGoogle Scholar
Marr, J. E. 1916. The Ashgillian succession to the west of Coniston Lake. Quarterly Journal of the Geological Society of London 71, 189–204.CrossRefGoogle Scholar
Mosseley, F. (ed.) 1978. The Geology of the Lake District. Leeds: Yorkshire Geological Society (occasional publication 3) vii + 284 pp.Google Scholar
Murchinson, R. I. 1839. The Silurian System Founded on Geological Researches in the Counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester and Stafford; with Descriptions of the Coal–fields and Overlying Formations. London: Murray (in 2 vols.).Google Scholar
Neuman, R. B. & Bates, D. E. B. 1978. Reassessment of Arenig and Llanvirn (early Ordovician) brachiopods from Anglesey, northwest Wales. Palaeontology 21, 571–613, pls. 63–8.Google Scholar
Orchard, M. J. 1980. Upper Ordovician conodonts from England and Wales. Geologica et Palaeontologica 14, 9–44, pls. 1–6.Google Scholar
Owen, A. W. 1980. The trilobite Tretaspis from the upper Ordovician of the Oslo region, Norway. Palaeontology 23, 715–47, pls. 89–93.Google Scholar
Owen, A. W. & Bruton, D. L. 1980. Late Caradoc–early Ashgill trilobites of the central Oslo Region, Norway. Palaeontological Contributions, University of Oslo, no. 245, 1–42, pls. 1–10.Google Scholar
Owens, R. M. 1973. British Ordovician and Silurian Proetidae (Trilobita). Palaeontographical Society, London (Monographs), 98 pp., pls 1–15.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, 8 pls.CrossRefGoogle Scholar
Paul, C. R. C. & Cope, J. C. W. 1982. A parablastoid from the Arenig of South Wales. Palaeontology 25, 499–507, pl. 51.Google Scholar
Pocock, R. W., Whitehead, T. H., Wedd, C. B. & Robertson, T. 1938. Shrewsbury district, including the Hanwood Coal–field (Sheet 152). Memoir Geological Survey of the United Kingdom i–xxi, 1–297.Google Scholar
Postlethwaite, J. & Goodchild, J. G. 1886. On some trilobites from the Skiddaw Slates. Proceedings of the Geologists' Association 9, 455–69, 4 pls.CrossRefGoogle Scholar
Price, D. 1977. Species of Tretaspis (Trilobita) from the Ashgill Series in Wales. Palaeontology 20, 73–92, pls. 98–103.Google Scholar
Rhodes, F. H. T. 1953. Some British Lower Palaeozoic conodont faunas. Philosophical Transactions of the Royal Society of London series B 237 (for 1952–1954), 261–334, pls. 20–3.Google Scholar
Romano, M. 1976. The trilobite genus Placoparia from the Ordovician of the Valongo area, North Portugal. Geological Magazine 113, 11–28.CrossRefGoogle Scholar
Ross, R. J. Jr, Naeser, C. W., Izett, G. A., Obradovich, J. D., Bassett, M. G., Hughes, C. P., Cocks, L. R. M., Dean, W. T., Ingham, J. K., Jenkins, C. J., Rickards, R. B., Sheldon, P. R., Toghill, P., Whittington, H. B. & Zalasiewicz, J. 1982 a. Fission–track dating of British Ordovician and Silurian stratotypes. Geological Magazine 119, 135–53.CrossRefGoogle Scholar
Ross, R. J. Jr, Adler, F. J., Amsdent, T. W., Bergstrom, D., Bergstrom, S. M., Carter, C., Churkin, M., Cressman, E. A., Derby, J. R., Dutro, J. T., Ethington, R. L., Finney, S. C., Fisher, D. W., Fisher, J. H., Harris, A. G., Hintze, L. F., Ketner, K. B., Kolata, D. L., Landing, E., Neuman, R. B., Sweet, W. C., Pojeta, J., Potter, A. W., Rader, E. K., Repetski, J. E., Shaver, R. H., Thompson, T. L. & Webers, G. F. 1982 b. The Ordovician System in the United States: Correlation Chart and Explanatory Notes. International Union of Geological Sciences, Publication 12.Google Scholar
Rushton, A. W. A., Fortey, R. A. & Owens, R. M. 1979. Excavation of two candidate sections for stratotypes in Wales by the Nature Conservancy Council. Earth Science Conservation (Nature Conservancy Council), Newbury, no 16, 1–5.Google Scholar
Rushton, A. W. A. & Hughes, C. P. 1981. The Ordovician trilobite fauna of the Great Paxton Borehole, Cambridgeshire. Geological Magazine 118, 623–46, pls. 1–6.CrossRefGoogle Scholar
Salder, P. M. 1974. Trilobites from the Gorran Quartzites, Ordovician of south Cornwall. Palaeontology 17, 71–93, pls. 9, 10.Google Scholar
Salter, J. W. 1866 a. On the fossils of North Wales. Appendix, pp. 239–363, pls. 1–2. In Ramsay, A. C., The Geology of North Wales. Memoir Geological Survey of Great Britain 3, viii + 381 pp., 28 pls.Google Scholar
Salter, J. W. 1866 b. A monograph of the British Trilobites, Part 3. Palaeontographical Society, London (Monographs) (vol. for 1864), 129–76, pls. 15–25.CrossRefGoogle Scholar
Sedgwick, A. 1847. On the classification of the fossiliferous slates of North Wales, Cumberland, Westmorland and Lancashire. Quarterly Journal of the Geological Society of London 3, 133–64.CrossRefGoogle Scholar
Sedgwick, A. 1852. On the classification and nomenclature of the Lower Palaeozoic rocks of England and Wales. Quarterly Journal of the Geological Society of London 8, 136–68.CrossRefGoogle Scholar
Sedgwick, A. & McCoy, F. 1851–1855. A Synopsis of the Classification of the British Palaeozoic rocks, with a Systematic Description of the British Palaeozoic Fossils in the Geological Museum of the University of Cambridge. xcviii + 661 pp., pls. 1 A–L, 2 A–D, 3 A–K, Appendix A by Salter, J. W. (1852), viii pp. London and Cambridge.Google Scholar
Sheng, Shen–Fu. 1980. The Ordovician System in China: Correlation Chart and Explanatory Notes. International Union of Geological Sciences, Publication 1.Google Scholar
Skevington, D. 1969. The classification of the Ordovician System in Wales, pp. 161–79. In Wood, A. (ed.), The Pre–Cambrian and Lower Palaeozoic Rock of Wales, 461 pp. University of Wales, Cardiff.Google Scholar
Skevington, D. 1970. A Lower Llanvirn graptolite fauna from the Skiddaw Slates, Westmorland. Proceedings of the Yorkshire Geological Society 37, 395–444.CrossRefGoogle Scholar
Skevington, D. 1971. The significance of the Hendre Shales graptolite fauna described by Toghill (1970). Proceedings of the Geological Society of London 1664, 199–203.Google Scholar
Stone, P. & Rushton, A. W. A. 1983. Graptolite faunas from the Ballantrae ophiolite complex and their structural implications. Scottish Journal of Geology (in press).CrossRefGoogle Scholar
Strachan, I. 1971. A synoptic supplement to ‘A Monograph of British Graptolites by MissElles, G. L. and MissWood, E. M. R.’. Palaeontographical Society, London (Monographs), pp. 1–130.Google Scholar
Strachan, I. 1981. The sequence of graptolite faunas in the Ordovician of the Shelve Inlier, Welsh Borderland. Ada Palaeontologica polonica 26, 19–26.Google Scholar
Stubblefield, C. J. 1930. A new Upper Cambrian section in south Shropshire. Summary of Progress. Geological Survey of Great Britain (for 1929), part 2, 54–62.Google Scholar
Stubblefield, C. J. & Bulman, O. M. B. 1927. The Shineton shales of the Wrekin District: with notes on their development in other parts of Shropshire and Herefordshire. Quarterly Journal of the Geological Society of London 83, 96–146, pls. 3–5.CrossRefGoogle Scholar
Sweet, W. C. & Bergström, S. M. 1976. Conodont biostratigraphy of the Middle and Upper Ordovician of the United States Midcontinent. In Bassett, M. G. (ed.), The Ordovician System: Proceedings of a Palaeonto–logical Association Symposium, Birmingham, September 1974. 696 pp., University of Wales Press and National Museum of Wales: Cardiff.Google Scholar
Toghill, P. 1970. A fauna from the Hendrer Shales' (Llandeilo) of the Mydrim area, Carmarthenshire. Proceedings of the Geological Society of London 1663, 121–9.Google Scholar
Watts, W. W. 1885. On the igneous and associated rocks of the Breidden Hills in east Montgomeryshire and west Shropshire. Quarterly Journal of the Geological Society of London 41, 532–46.CrossRefGoogle Scholar
Watts, W. W. 1925. The geology of south Shropshire. Proceedings of the Geologists' Association 36, 321–63.CrossRefGoogle Scholar
Webby, B. D. (compiler and ed.) 1981. The Ordovician System in Australia, New Zealand and Antartica: Correlation Chart and Explanatory Notes. International Union of Geological Sciences, Publication 6.Google Scholar
Wedd, C. B. 1932. Notes on the Ordovician rocks of Bausley, Montgomeryshire. Summary of Progress. Geological Survey of Great Britain (for 1931). part 2, 49–55.Google Scholar
Whittard, W. F. 1931. The geology of the Ordovician and Valentian rocks of the Shelve country, Shropshire. Proceedings of the Geologists' Association 42, 322–39.CrossRefGoogle Scholar
Whittard, W. F. 1955–1967. The Ordovician trilobites of the Shelve Inlier, West Shropshire. Palaeontographical Society, London (Monographs), 350 pp., 50 pls.Google Scholar
Whittard, W. F. (ed.) 1960. Lexique Stratigraphique International. Congrès Géologique International–Commission de Stratigraphie. Vol. 1. Europe. Fascicule 3a, England, Wales and Scotland, Part 3a, IV: Ordovician, pp. 1–296. Centre National de la Recherche Scientifique, Paris.Google Scholar
Whittard, W. F. 1979. An account of the Ordovician rocks of the Shelve Inlier in West Salop and part of the North Powys. Bulletin of the British Museum (Natural History) London. Geology series 33, 1–69.Google Scholar
Whittington, H. B. 1966. Trilobites of the Henllan Ash, Arenig Series, Merioneth. Bulletin of the British Museum (Natural History) London. Geology series 11, 489–505, pls. 1–5.Google Scholar
Whittington, H. B. & Williams, A. 1964. The Ordovician period. In Harland, W. B., Smith, A. G. and Wilcock, B. (eds.). The Phanerozoic time–scale. Quarterly Journal of the Geological Society of London 120s, 241–54.Google Scholar
Wilcox, C. J. & Lockley, M. G. 1981. A reassessment of facies and faunas in the type Llandeilo (Ordovician), Wales. Palaeogeography, Palaeoclimatology, Palaeo–ecology 34, 285–314.CrossRefGoogle Scholar
Williams, A. 1953. The geology of the Llandeilo district, Carmarthenshire. Quarterly Journal of the Geological Society of London 108, 177–208.CrossRefGoogle Scholar
Williams, A. 1969 a. Ordovician faunal provinces with reference to brachiopod distribution. In Wood, A. (ed.) The Pre–Cambrian and Lower Palaeozoic rocks of Wales, pp. 117–54. University of Wales Press, Cardiff.Google Scholar
Williams, A. 1969 b. Ordovician of the British Isles. In Kay, M. (ed.), North Atlantic – geology and continental drift: a symposium. Memoir American Association of Petroleum Geologists 12, 236–64.Google Scholar
Williams, A. 1974. Ordovician Brachiopoda from the Shelve District, Shropshire. Bulletin of the British Museum (Natural History) London. Geology series, supplement 11yes, 163 pp., 28 pls.Google Scholar
Williams, A., Strachan, I., Bassett, D. A., Dean, W. T., Ingham, J. K., Wright, A. D. & Whittington, H. B. 1972. A correlation of Ordovician rocks in the British Isles. Special Report. Geological Society of London 3, 1–74.Google Scholar
Williams, S. H. & Bruton, D. L. (in press). The Caradoc–Ashgill boundary in the central Oslo region and associated graptolite faunas. Norsk Geologisk Tidsskrift.Google Scholar
Zalasiewicz, J. (in press). A re–examination of the type Arenig Series. Geological Journal.Google Scholar