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Late Caradoc graptolitic faunal gradients across the Iapetus Ocean

Published online by Cambridge University Press:  01 May 2009

J. A. Zalasiewicz ,
A. W. A. Rushton  and
A. W. Owen
J. A. Zalasiewicz
Affiliation:
British Geological Survey, Key worth, Nottingham NG12 5GG, UK
A. W. A. Rushton
Affiliation:
British Geological Survey, Key worth, Nottingham NG12 5GG, UK
A. W. Owen
Affiliation:
Department of Geology and Applied Geology, Lilybank Gardens, University of Glasgow, Glasgow G12 8QQ, UK
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Abstract

Late Caradoc graptolite assemblages across the Iapetus Ocean in Wales and Scotland became progressively more disparate despite the narrowing of the ocean. We compare faunal distributions in continuous sections from opposite sides of Iapetus, at Whitland in South Wales and Hartfell Score in the Southern Uplands of Scotland. A comprehensive graptolite range-chart is given for each. The graptolite assemblages from the clingani Biozone are subdivided into a lower Ensigraptus caudatus Subzone and upper Dicellograptus morrisi Subzone at both localities, though the faunas differ in detail. Higher in the sequence, the distinctive Scottish linearis Biozone fauna is not recognizable at Whitland, its presumed equivalent being a fauna dominated by variable morphotypes of the genus Normalograptus. This suggests that environmental gradients (depth and/or temperature) were changing more rapidly than the geography. Significantly, the subsequent inception of limestone deposition at Whitland was approximately contemporaneous with widespread replacement of black mudstones by oxic, bioturbated sediments elsewhere in the Welsh Basin and in Scotland. This was possibly a response to an early phase of cooling prior to the end-Ordovician glaciation. In Wales the claimed hiatus at the Caradoc-Ashgill boundary may rather reflect biofacies variation.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 5 , September 1995 , pp. 611 - 617
Copyright
Copyright © Cambridge University Press 1995

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References

Barnes, C. R., 1992. The uppermost series of the Ordovician. In Global perspectives on Ordovician geology (eds Webby, B. D. and Laurie, J. R.), pp. 185–92. Rotterdam: Balkema.Google Scholar
Berry, W. B. N., Wilde, P., & Quinby-Hunt, M. S., 1989. Paleozoic (Cambrian through Devonian) anoxitropic biotopes. Palaeogeography, Palaeoclimatology, Palaeoecology 74, 3–13.CrossRefGoogle Scholar
Brenchley, P. J., Marshall, J. D., Carden, G. A. F., Robertson, D. B. R., Long, G. D. F., Meidler, T., Hints, L., & Anderson, T. F., 1994. Bathymetric and isotopic evidence for a short-lived late Ordovician glaciation in a greenhouse period. Geology 22, 295–8.2.3.CO;2>CrossRefGoogle Scholar
Cocks, L. R. M., & Fortey, R. A., 1982. Faunal evidence for oceanic separations in the Palaeozoic of Britain. Journal of the Geological Society, London 139, 465–78.CrossRefGoogle Scholar
Cooper, R. A., Fortey, R. A., & Lindholm, K., 1991. Latitudinal and depth zonation of early Ordovician graptolites. Lethaia 24, 199–218.CrossRefGoogle Scholar
Cope, J. C. W., Ingham, J. K., & Rawson, P. F., (eds) 1992. Atlas of Palaeogeography and Lithofacies. Geological Society, London, Memoir no. 13.Google Scholar
Davies, J. R., Fletcher, C. J. N., Waters, R. A., Wilson, D., Woodhall, D., & Zalasiewicz, J. A., In press. The geology of the Rhayader and Llanilar districts. Memoir of the British Geological Survey.Google Scholar
Elles, G. L., & Wood, E. R. M., 1901–1918. A monograph of British graptolites. Palaeontographical Society (Monograph).Google Scholar
Finney, S. C., 1986. Graptolite biofacies and the correlation of eustatic, subsidence, and tectonic events in the Middle to Upper Ordovician of north America. Palaios 1, 435–61.CrossRefGoogle Scholar
Fortey, R. A., Bassett, M. G., Harper, D. A. T., Hughes, R. A., Ingham, J. K., Molyneux, S. G., Owen, A. W., Owens, R. M., Rushton, A. W. A., & Sheldon, P. A., 1991. Progress and problems in the selection of stratotypes for the bases of series in the Ordovician System of the historical type area in the U.K. Geological Survey of Canada, Paper 90–9, 5–25.CrossRefGoogle Scholar
Fortey, R. A., Harper, D. A. T., Ingham, J. K., Owen, A. W., & Rushton, A. W. A., 1995. A revision of Ordovician series and stages from the historical type area. Geological Magazine 132, 15–30.CrossRefGoogle Scholar
Lapworth, C., 1878. The Moffat Series. Quarterly Journal of the Geological Society of London 34, 240–346.CrossRefGoogle Scholar
Legrand, P., 1986. The lower Silurian graptolites of Oued in Djerane: a study of populations at the Ordovician-Silurian boundary. In Palaeoecology and Biostratigraphy of Graptolites (eds Hughes, C. P. and Rickards, R. B.), pp. 145–53. Geological Society Special Publication no. 20.Google Scholar
Legrand, P., 1987. Modo de desarrollo del Suborden Diplograptina (Graptolithina) en el Ordovícico superior y en el Silúrico. Revista Española de Paleontologia 2, 59–64.Google Scholar
Pratt, W. T., 1991. The Nod Glas décollement of the Welsh Basin. Geological Magazine 128, 279–82.CrossRefGoogle Scholar
Price, D., 1973. The age and stratigraphy of the Sholeshook Limestone of Southwest Wales. Geological Journal 8, 225–46.CrossRefGoogle Scholar
Price, D., 1977. Species of Tretaspis (Trilobita) from the Ashgill Series in Wales. Palaeontology 20, 763–92.Google Scholar
Price, D., 1984. The Pusgillian Stage in Wales. Geological Magazine 121, 99–105.CrossRefGoogle Scholar
Riva, J., 1969. Middle and Upper Ordovician graptolite faunas of St. Lawrence lowlands of Quebec, and of Anticosti Island. In North Atlantic — Geology and Continental Drift (ed. Kay, M.), pp. 513–56. American Association of Petroleum Geologists Memoir no. 12.Google Scholar
Rushton, A. W. A., 1990. Ordovician graptolite biostratigraphy in the Welsh Basin: a review. Journal of the Geological Society 147, 611–14.CrossRefGoogle Scholar
Rushton, A. W. A., 1993. Hartfell Score. In Scottish Borders Geology. An excursion Guide (eds McAdam, A. D., Clarkson, E. N. K. and Stone, P.), pp. 173–79. Edinburgh: Scottish Academic Press.Google Scholar
Rushton, A. W. A., & Stone, P., 1991. Terriginous input to the Moffat Shale sequence, Southern Uplands. Scottish Journal of Geology 21, 167–9.CrossRefGoogle Scholar
Skevington, D., 1974. Controls influencing the composition and distribution of Ordovician graptolite provinces. Special Papaers in Palaeontology 13, 59–73.Google Scholar
Stone, P., Floyd, J. D., Barnes, R. P., & Lintern, B. C., 1987. A sequential back-arc and foreland basin thrust duplex model for the Southern Uplands of Scotland. Journal of the Geological Society 144, 753–64.CrossRefGoogle Scholar
Stow, D. A. V., 1994. Deep sea processes of sediment transport and deposition. In Sediment Transport and Deposition Processes (ed. Pye, K.), pp. 257–91. Oxford: Blackwell Scientific Publications.Google Scholar
Strahan, A., Cantrill, T. C., Dixon, E. E. L., Thomas, H. H., & Jones, O. T., 1914. The geology of the South Wales Coalfield, part XI, the country around Haverfordwest. Memoirs of the Geological Survey, England and Wales (Sheet 228). HMSO.Google Scholar
Temple, J. T., & Cave, R., 1992. Preliminary report on the geochemistry and mineralogy of the Nod Glas and related sediments (Ordovician) of Wales. Geological Magazine 129, 589–94.CrossRefGoogle Scholar
Toghill, P., 1970. Highest Ordovician (Hartfell) Shales graptolite faunas from the Moffat area, south Scotland. Bulletin of the British Museum (Natural History) 19, 1–26.Google Scholar
Vandenberg, A. H. M., & Cooper, R. A., 1992. The Ordovician graptolite sequence of Australasia. Alcheringa 16, 33–85.CrossRefGoogle 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. Geological Society Special Report no. 3.Google Scholar
Williams, S. H., 1982. Upper Ordovician graptolites from the top Lower Hartfell Shale Formation (D. clingani and P. linearis zones) near Moffat, southern Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 72, 229–55.CrossRefGoogle Scholar
Williams, S. H., 1987.Upper Ordovician graptolites from the D. complanatus Zone of the Moffat and Girvan districts and their significance for correlation. Scottish Journal of Geology 23, 65–92.CrossRefGoogle Scholar
Williams, S. H., 1994. Revision and definition of the C. wilsoni graptolite Zone (Middle Ordovician) of southern Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 85, 143–57.CrossRefGoogle Scholar
Woodcock, N. H., 1990. Sequence stratigraphy of the Palaeozoic Welsh Basin. Journal of the Geological Society, London 147, 537–47.CrossRefGoogle Scholar