Upper Ordovician graptolites from the D. complanatus Zone of the Moffat and Girvan districts and their significance for correlation

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Abstract
Synopsis: At its type development at Dob's Linn, southern Scotland, the Dicellograptus complanatus Zone is represented by two thin black shale bands some 9 m above the base of the Upper Hartfell Shale Formation. Contrary to previous reports, the fauna is moderately diverse with an assemblage including Dicellograptus complanatus Lapworth, D. minor Toghill, Climacograptus miserabilis Elles and Wood, C. tubuliferus Lapworth, Orthograptus socialis (Lapworth), Orthoretiolites ? pulcherrimus (Keble and Harris) and Plegmatograptus ? sp. indet. At Girvan the D. complanatus Zone is contained within the Mill Formation of the Upper Whitehouse Group and the lower part of the Shalloch Formation. The basal Mill Formation yields a still more diverse low D. complanatus Zone fauna, with the addition of Dicellograptus alector Carter? (? = D. gravis Keble and Harris), D. cf. minor Toghill, Orthograptus cf. calcaratus (Lapworth) and Glyptograptus ? cf. occidentalis Ruedemann. The D. complanatus Zone correlates with the D gravis (Ea4) and C. uncinatus (Bol) zones of Australia, and probably with the C. pygmaeus and C. manitoulinensis zones of north-eastern North America.