Sedimentology and palaeontology of the Withycombe Farm Borehole, Oxfordshire, England


The pre-trilobitic lower Cambrian of the Withycombe Formation is a 194 m thick siliciclastic succession dominated by interbedded offshore red to purple and green pyritic mudstone with minor sandstone. The mudstone contains a hyolith-dominated small shelly fauna including: orthothecid hyoliths, hyolithid hyoliths, the rostroconch Watsonella crosbyi, early brachiopods, the foraminiferan Platysolenites antiquissimus, the coiled gastropod-like Aldanella attleborensis, halkieriids, gastropods and a low diversity ichnofauna including evidence of predation by a vagile infaunal predator. The assemblage contains a number of important index fossils (Watsonella, Platysolenites, Aldanella and the trace fossil Teichichnus) that enable correlation of strata around the base of Cambrian Stage 2 from Avalonia to Baltica, as well as the assessment of the stratigraphy within the context of the lower Cambrian stratigraphic standards of southeastern Newfoundland. The pyritized nature of the assemblage has enabled the study of some of the biota using micro-CT, augmented with petrographic studies, revealing pyritized microbial filaments of probable giant sulfur bacteria. We aim to produce the first complete description of the core and the abundant small pyritized fossils preserved in it, and develop a taphonomic model for the pyritization of the “small” shelly fossils

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