New Tremadoc strata at outcrop in the Bristol Channel

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Abstract
In September 1972, as part of its offshore mapping programme, the Institute of Geological Sciences, using the chartered drillship MV Whitethorn, drilled a shallow borehole in the southern part of Carmarthen Bay. The hole, 72/60, was sited at latitude 51°34-80'N, longitude 4°34-71'W on Continuous Seismic Profile (CSP) 71/3/9 to determine the nature of the Palaeozoic rocks at this location. 5 m of sandy gravel, 3 m of stiff brown clay and 2-5 m of grey mudstone were cored. The mudstone was found to contain a rich assemblage of microplankton including the following taxa: Acanthodiacrodium ubui? Martin Micrhystridium shinetonense Downie Cymatiogalea cf. multarea Deunff Cymatiogalea cf. membranispina Deunff Acanthodiacrodium angusta (Downie) Leiofusa squama Deunff Saharidia fragile (Downie) Possible chitinozoa fragments Acanthodiacrodium sp. nov. Acanthodiacrodium cf. decipiens Timofeyev Dasydiacrodium sp. nov Vulcanisphaera africana Deunff Micrhystridium robustum Downie Polygonium sp. nov. Polygonium sp. nov Vulcanisphaera sp. nov. Priscotheca complanata Deunff Archaeohystrichosphaeridium pungens Timofeyev The above assemblage is indicative of the Tremadoc and can be equated with that from the Brachiopod Beds of the Shineton Shales. It includes records of several new species, as yet undescribed, which have been recorded by Rasul (1971, unpublished Ph.D. Thesis) from Shropshire. No macrofossils have been found in the core. The mudstone core is 2.5 m in length and vertically cleaved. It is dark grey, thinly laminated and micaceous. Examination in thin section reveals angular to sub-angular quartz grains tightly packed within a dense matrix of chlorite, which is in places iron stained. Muscovite flakes are orientated along

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