The ‘coprolite’ bearing Woburn Sands Formation, Lower Greensand Group (Aptian) at Upware, Cambridgeshire, UK

Abstract

Upware, about 15 km north of Cambridge, eastern England, was heavily involved in the ‘Coprolite’ Industry during the 19th century. Rich phosphate deposits especially at the base of the Lower Greensand (Early Cretaceous) were dug by hand and after processing supplied the Victorian agricultural industry with fertiliser. They were also a source of abundant reworked and indigenous fossils which feature in the original accounts and descriptions of the geology and palaeontology of the area including those in the classic award-winning Sedgwick Prize essays of Harris Teall in 1873 and Walter Keeping in 1879. Today, however, there are no permanent exposures of the Lower Greensand in the area. The sites of the original commercial excavations have been returned to agricultural land and traces of phosphatic lithoclasts and bioclasts may only be encountered in ploughed fields and the debris from animal burrows. In 2015 temporary trenches were dug by the authors in the base of the Lower Greensand Group, Woburn Sands Formation (Late Aptian). Much poorly bedded and phosphate depleted Woburn Sands was exposed which is attributed to backfilled ‘Coprolite’ workings. However, one site provided exposure of undisturbed Woburn Sands resting unconformably upon the Upware Limestone Member, West Walton Formation (mid-Oxfordian, Late Jurassic) and the feather edge of the Ampthill Clay Formation (mid-Late Oxfordian). The sand contains rich concentrations of reworked phosphatised fossiliferous concretions of original Jurassic-Cretaceous boundary to mid-Aptian age and indigenous calcitic fossils, of Late Aptian age. This is the first time that in situ Woburn Sands have been exposed in the Upware area since the time of the coprolite workings and are documented photographically for the first time. A detailed stratigraphic succession has been recorded and new geological and palaeontological collections have been made from accurately known levels at a precisely known site. New observations allow us to re-evaluate the early geological accounts and provide the opportunity to discuss more closely the relationships of the reworked faunas of Oxfordian to Aptian age, and in particular we draw attention to those faunas with affinities to the Jurassic-Cretaceous boundary deposits of the Spilsby Basin to the north. This work confirms the basic accuracy of Keeping’s earlier seminal account.