Upper Devonian and Lower Carboniferous Miospore Assemblages from Hook Head, County Wexford, Ireland

Abstract

Three successive miospore assemblages are described from the Upper Devonian and Lower Carboniferous strata of Hook Head in southeast Ireland. Their stratigraphic significance and position within the existing miospore zonation schemes of western Europe are discussed. Comparisons are made with Tournaisian microfloras described from eastern Canada. Twenty-two new species are erected, four new spore types are described, and one new combination is proposed. Upper Devonian and Lower Carboniferous miospore assemblages from Hook Head, County Wexford, Ireland INTRODUCTION AND STRATIGRAPHY The miospore assemblages described were obtained from samples of the Upper Old Red Sandstone facies, the overlying Porter's Gate Formation, and base of the Hook Head Formation of Hook Head, County Wexford, southeast Ireland. These sediments range from ?Famennian-Tournaisian to middle Tournaisian in age and represent a continuous transition from fluviatile to marine conditions. The present study was undertaken to investigate the stratigraphic distribution of miospores in this section and thereby enable the author to describe in detail the microfloral changes that had been observed during a preliminary investigation by Dolby (1970). The Old Red Sandstone succession is approximately 360 m. in thickness and consists of coarse conglomerates resting unconformably on Lower Palaeozoics and overlain by red sandstones, siltstones, and conglomerates. There follows a sequence of red and grey sandstones, and siltstones with occasional conglomerates and mudstones. This succession has not yet been fully described but has been subdivided by MacCarthy, Gardiner, and Horne (1971) and Gardiner and Horne (1973). There is no macropalaeontological evidence for the age of these sediments, but Dolby (1 970, p. 271, fig. 2) tentatively correlated a horizon approximately 11 5 m. below the top of the Old Red Sandstone with the Tnla-Tnlb boundary in Belgium. The strata overlying the Old Red Sandstone have recently been described by Sleeman et al. (1974) and is divided into the Porter's Gate Formation and the overlying Hook Head Formation. The Porter's Gate Formation consists of two members, the lower of which has been termed the Houseland Sandstone Member; the upper, the Lyraun Cove Shale Member. This scheme of stratigraphic subdivision has been adopted in the present study. Strata comprising the Porter's Gate Formation were considered by Smyth (1930) to be of K-Zone age in terms of Vaughan's (1905) coralbrachiopod zonation. The age of the formation based on conodont evidence was discussed by Sleeman et al. (1974), who closely compared faunas from the Lyraun Cove Shale Member with those recorded by Butler (1973) from the upper part of the Lower Limestone Shales at Maesbury in the eastern Mendips, England. Faunas from the Houseland Sandstone Member are similar to those obtained from the lower part of the Lower Limestone Shales in the same area. The strata referred to in this study are the basal metre of the Hook Head Formation, the Porter's Gate Formation, and the upper 99 m. of the Old Red Sandstone. micropaleontology, vol. 21, no. 4, pp. 393-419, pls. 1-7, october, 1975 393 This content downloaded from 207.46.13.179 on Tue, 18 Oct 2016 06:18:15 UTC All use subject to http://about.jstor.org/terms