R. A. Fortey, J. K. Ingham, A. W. Owen, A. W. A. Rushton, 2000. "International correlation", A revised correlation of Ordovician Rocks in the British Isles, R. A. Fortey, D. A. T. Harpe, J. K. Ingham, A. W Owen, M. A. Parkes, A. W. A. Rushton, N. H. Woodcock
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For the convenience of workers wishing to use the British charts in a global context, we include a scheme for the international correlation of the standard graptolite biozonation (Fig. 34). The base of the Middle Ordovician at the base of the Tripodus levis/Isograptuslunatus Biozone cannot be correlated into the Gondwana palaeocontinent and associated terranes with confidence and its mid-Arenig placement is speculative. The base of the Upper Ordovician is at the base of the gracilis Biozone. The base of gracilis Biozone is taken at the first appearance of N. gracilis itself, and the end of the zone at its last appearance. Work in progress by Richard Bettley indicates that first appearances of graptolite species such as Orthograptus apiculatus may eventually provide greater stratigraphic utility, but conservative usage is followed here.
Recent revisions are used for correlation into other regions important for the development of the Ordovician; however, where older names are still familiar and in use we have indicated them by square brackets below. Chronostratigraphic revisions to the North American terminology are after Ross et al. (1997). Bohemian chronostratigraphic standards were updated by Havli?ek et al. (1994); the lithological units that have been much employed previously are also indicated. For the East Baltic area the biostratigraphic scheme used by Männil & Meidla (1994) has been somewhat updated from Dronov & Holmer (1999). We have taken the Chinese standard from Chen et al. (1995) to whom reference should be made for correlation within China; standard lithological units of the Yangtze platform are also shown. We have not attempted to include the many terranes of the former Soviet Union.
Figures & Tables
This Report is revised and expanded from the 1972 publication providing an up-to-the-minute account of the British Ordovician formations and their correlation nationally and internationally. It also includes the most comprehensive treatment of Ireland ever attempted. The reference list of a comprehensive bibliography of papers on the subject published since 1970.
The British sections are the type for the Ordovician System and classical in stratigraphical, tectonic and volcanic studies. The Charts bring together 30 years of research over the period in which plate tectonics has revolutionized our understanding of the Lower Palaeozoic rocks of the British Isles.
This Special Report will be a valuable reference for research and applied geoscientists working with rocks of Ordovician age. It will be of particular interest to those working in, or visiting, the Welsh mountains and the English Lake District.