The upper Silurian Downton Bone Bed of Weir Quarry, Herefordshire, England
Student thesis: Doctoral Thesis
The Downton Bone Bed is a multitaxic Fossil Concentration-Lagerstätte located in the Platyschisma Shale Member of the Downton Castle Sandstone Formation c.1.5m above the Ludlow Bone Bed. The Downton Bone Bed has received little direct study since its discovery over a century ago. This study focuses on the Downton Bone Bed from one locality, Weir Quarry (SO 4561 7520) on the Herefordshire/Shropshire border. The focus is to look at the palaeontology and sedimentology of the Downton Bone Bed, to understand how it formed and what fauna and flora is present in the bone bed providing new insights into the formation and palaeoenvironment of the bed. An integrated method of processing well-indurated bone beds was developed using paraffin impregnation and a microwave oven. The fossils of the Downton Bone Bed represent a restricted fauna and flora. Vertebrates comprise Paralogania ludlowiensis, Thelodus parvidens, Gomphonchus sp., Nostolepis sp. and Onchus murchisoni. P. ludlowiensis is the most common vertebrate in the Downton Bone Bed. There is also evidence to support the presence of an osteostracan and heterostracan. There are also three poorly preserved conodonts present. Organic walled fossils comprise Cooksonia pertoni /Hollandophyton colliculum, Synorisporites downtonensis, Nematothallus pseudo-vasculosa, Prototaxites sp. and Pachytheca spherica. Invertebrates are Modiolopsis complanata, Turbocheilus helicites, Tunisiglossa? cornea, Lingula missendenensis, Frostiella groenvalliana, Londinia arisaigensis and Leperditia sp. There is also evidence for eurypterids. The sedimentology provides evidence of two energy conditions shifting between a quiet low-energy setting, indicated by planar and quasi-planar laminations with trace fossils present (Teichichnus and Planolites) and periods of rapid burial in which all the body fossils were deposited. It is suggested here that the formation of the Downton Bone Bed was caused by storms. The environmental setting for the Downton Bone Bed is a lower shoreface of an epeiric sea, in proximity to a terrestrial freshwater source.
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