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Probing the deep shelf: a Lagerstätte from the Upper Ordovician of Girvan, southwestern Scotland




Sarah E. Stewart [], Department of Natural Sciences, National Museums Scotland, National Museums Collection Centre, 242 West Granton Road, Edinburgh EH5 1JA, Scotland, UK; Alan W. Owen [], Department of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, Scotland, UK; manuscript received on 10/08/2006; manuscript accepted on 16/12/2007.


A deep-water Konservat Lagerstätte from the lower Caradoc (Sandbian) at Girvan is dominated by the trilobite Diacanthaspis trippi, the carpoids Anatifopsis n. sp.? and a new genus of ctenocystoid together with the polyplacophoran Solenocaris solenoides and the brachiopod Onniella williamsi. Most of these are multi-element organisms, with many specimens preserved in an articulated state in finely laminated rocks, indicating minimal disturbance and suggesting that the fauna is largely an in situ association. It contains few of the species known from other deep-water sites of similar age at Girvan which contain diverse assemblages of trilobites and brachiopods absent from the Lagerstätte. The taphonomy of the site indicates preservation by rapid burial followed by early diagenesis under dysaerobic conditions. It provides a ‘taphonomic window’ on otherwise unknown faunas from distal shelf facies on the Ordovician Laurentian margin, and, moreover, is an important reminder of the hidden biodiversity that resided in thin-shelled, multi-element organisms.