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Integrated Upper Ordovician graptolite–chitinozoan biostratigraphy of the Cardigan and Whitland areas, southwest Wales

Published online by Cambridge University Press:  17 December 2007

THIJS R. A. VANDENBROUCKE ,
MARK WILLIAMS ,
JAN A. ZALASIEWICZ ,
JEREMY R. DAVIES  and
RICHARD A. WATERS
THIJS R. A. VANDENBROUCKE*
Affiliation:
Research Unit Palaeontology, Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium
MARK WILLIAMS
Affiliation:
Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK
JAN A. ZALASIEWICZ
Affiliation:
Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK
JEREMY R. DAVIES
Affiliation:
British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK
RICHARD A. WATERS
Affiliation:
Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK
*
†Author for correspondence: [email protected]
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Abstract

To help calibrate the emerging Upper Ordovician chitinozoan biozonation with the graptolite biozonation in the Anglo-Welsh, historical type basin, the graptolite-bearing Caradoc–Ashgill successions between Fishguard and Cardigan, and at Whitland, SW Wales, have been collected for chitinozoans. In the Cardigan district, finds of Armoricochitina reticulifera within strata referred to the clingani graptolite Biozone (morrisi Subzone), together with accessory species, indicate the Fungochitina spinifera chitinozoan Biozone, known from several Ordovician sections in northern England that span the base of the Ashgill Series. Tanuchitina ?bergstroemi, eponymous of the succeeding chitinozoan biozone, has tentatively been recovered from strata of Pleurograptus linearis graptolite Biozone age in the Cardigan area. The T. ?bergstroemi Biozone can also be correlated with the type Ashgill Series of northern England. Chitinozoans suggest that the widespread Welsh Basin anoxic–oxic transition at the base of the Nantmel Mudstones Formation in Wales, traditionally equated with the Caradoc–Ashgill boundary, is of Cautleyan (or younger Ashgill) age in the Cardigan area. In the broadly time-equivalent, graptolite-rich Whitland section, also in SW Wales, two Baltoscandian chitinozoan biozones and a subzone have been recognized (again using accessory species), namely the Spinachitina cervicornis Biozone?, the Fungochitina spinifera Biozone and the Armoricochitina reticulifera Subzone. The new chitinozoan data provide a more precise means of correlation between the Whitland and Cardigan successions and suggest that the Normalograptus proliferation interval of the Whitland section is at least partly attributable to the Dicellograptus morrisi Subzone of the Dicranograptus clingani Biozone, rather than equating with the overlying Pleurograptus linearis Biozone.

Keywords

chitinozoansgraptolitesOrdovicianbiostratigraphyWales
Type
Original Article
Information
Geological Magazine , Volume 145 , Issue 2 , March 2008 , pp. 199 - 214
Copyright
Copyright © Cambridge University Press 2007

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References

Bettley, R. M., Fortey, R. A. & Siveter, D. J. 2001. High-resolution correlation of Anglo-Welsh Middle to Upper Ordovician sequences and its relevance to international chronostratigraphy. Journal of the Geological Society, London 158, 937–52.CrossRefGoogle Scholar
Davies, J. R., Fletcher, C. J. N., Waters, R. A., Wilson, D., Woodhall, D. G. & Zalasiewicz, J. A. 1997. Geology of the country around Llanilar and Rhayader. Memoir of the British Geological Survey, Sheets 178 and 179 (England and Wales), 268 pp.Google Scholar
Davies, J. R., Waters, R. A., Wilby, P. R., Williams, M. & Wilson, D. 2003. The Cardigan and Dinas Island district – a brief explanation of the geology. 1:50000 Series England and Wales Sheet 193 (including part of sheet 210). Keyworth: British Geological Survey, 26 pp.Google Scholar
Fortey, R. A., Harper, D. A. T., Ingham, J. K., Owen, A. W., Parkes, M. A., Rushton, A. W. A. & Woodcock, N. H. 2000. A revised correlation of Ordovician Rocks in the British Isles. Geological Society of London Special Report no. 24, 83.CrossRefGoogle Scholar
Henry, J.-L., Nion, J., Paris, F. & Thadeu, D. 1974. Chitinozoaires, Ostracodes et Trilobites de l'Ordovicien du Portugal (serra de Buçaco) et du massif Armoricain: essai de comparaison et signification paléogéographique. Comunicações dos Serviços Geológicos de Portugal 57, 303–45.Google Scholar
Lowman, R. D. W. & Bloxam, T. W. 1981. The petrology of the Lower Palaeozoic Fishguard Volcanic Group and associated rocks E of Fishguard, N Pembrokeshire (Dyfed), South Wales. Journal of the Geological Society, London 138, 47–68.CrossRefGoogle Scholar
Nõlvak, J. 2005. Distribution of Ordovician Chitinozoans. In Estonian Geological Sections, Bulletin 6, Mehikoorma (421) core (ed. Poldvere, A.), pp. 20–2. Geological Journal of the Geological Survey of Estonia. Tallinn.Google Scholar
Nõlvak, J. & Grahn, I. 1993. Ordovician chitinozoan zones from Baltoscandia. Review of Palaeobotany and Palynology 79, 245–69.CrossRefGoogle Scholar
Page, A., Zalasiewicz, J. A., Williams, M., & Popov, L. E. 2007. Were transgressive black shales a negative feedback modulating glacioeustasy in the Early Palaeozoic Icehouse? In Climate Change through Deep Time (Williams, M., Haywood, A., Gregory, J. & Schmidt, D.), pp. 123–56. The Micropalaeontological Society, Bath: London. Geological Society Publishing House.Google Scholar
Paris, F. 1981. Les chitinozoaires dans le Paléozoïque du sud-ouest de l'Europe (cadre géologique – étude systématique – biostratigraphie). Mémoire de la Société géologique et minéralogique de Bretagne no. 26, 496 pp.Google Scholar
Paris, F. 1990. The Ordovician chitinozoan biozones of the Northern Gondwana Domain. Review of Palaeobotany and Palynology 66, 181–209.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 Tetraspis (Trilobita) from the Ashgill Series in Wales. Palaeontology 20, 763–92.Google Scholar
Price, D. 1980. A revised age and correlation for the topmost Sholeshook Limestone formation (Ashgill) of South Wales. Geological Magazine 117, 485–9.CrossRefGoogle Scholar
Price, D. 1984. The Pusgillian Stage in Wales. Geological Magazine 121, 99–105.CrossRefGoogle Scholar
Rickards, R. B. 2002. The graptolitic age of the type Ashgill Series (Ordovician) Cumbria. Proceedings of the Yorkshire Geological Society 54, 1–16.CrossRefGoogle Scholar
Rickards, R. B. 2004. The significance of the graptoloid Amphigraptus divergens from the (mid-Rawtheyan) type section of the Ashgill Series, Ordovician. Geological Magazine 141, 735–8.CrossRefGoogle Scholar
Strahan, A., Cantrill, T. C. 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. Memoir of the Geological Survey, England and Wales (Sheet 228), 262 pp.Google Scholar
Vandenbroucke, T. R. A. In press a. An Upper Ordovician Chitinozoan Biozonation in British Avalonia (England & Wales). Lethaia.Google Scholar
Vandenbroucke, T. R. A. In press b. Upper Ordovician Chitinozoans from the British Historical Type Areas and Adjacent Key Sections. Palaeontographical Society Monograph.Google Scholar
Vandenbroucke, T. R. A., Ancilletta, A., Fortey, R. A. & Verniers, J. 2008. A modern assessment of Ordovician chitinozoans from the Shelve and Caradoc areas, Shropshire, and their significance for correlation. Geological Magazine 145, in press.Google Scholar
Vandenbroucke, T. R. A., Rickards, R. B. & Verniers, J. 2005. Upper Ordovician Chitinozoan biostratigraphy from the type Ashgill Area (Cautley district) and the Pus Gill section (Dufton district, Cross Fell Inlier), Cumbria, Northern England. Geological Magazine 142, 783–807.CrossRefGoogle Scholar
Van Nieuwenhove, N., Vandenbroucke, T. R. A. & Verniers, J. 2006. Chitinozoan biostratigraphy of the Upper Ordovician Greenscoe-roadcutting, Southern Lake District, U.K. Review of Palaeobotany and Palynology 139, 151–69.CrossRefGoogle Scholar
Verniers, J. & Vandenbroucke, T. R. A. 2006. Chitinozoan biostratigraphy in the Dob's Linn Ordovician–Silurian GSSP, Southern Uplands, Scotland. Geologiska Föreningens i Stockholm Förhandlingar 128, 195–202.Google Scholar
Webby, B. D., Cooper, R. A., Bergström, S. M. & Paris, F. 2004. Chapter 2: Stratigraphic framework and time slices. In The Great Ordovician Biodiversification Event (eds Webby, B. D., Droser, M. L., Paris, F. & Percival, I.), pp. 41–7. New York: Columbia University Press.CrossRefGoogle Scholar
Williams, M., Davies, J. R., Waters, R. A., Rushton, A. W. A. & Wilby, P. R. 2003. Stratigraphical and palaeoecological importance of Caradoc (Upper Ordovician) graptolites from the Cardigan area, southwest Wales. Geological Magazine 140, 549–71.CrossRefGoogle Scholar
Zalasiewicz, J. A., Rushton, A. W. A. & Owen, A. W. 1995. Late Caradoc graptolitic faunal gradients across the Iapetus Ocean. Geological Magazine 132, 611–17.CrossRefGoogle Scholar