Proceedings of the Geologists’ Association 130 (2019) 752–769 Contents lists available at ScienceDirect Proceedings of the Geologists’ Association journal homepage: www.elsevier.com/locate/pgeola Microvertebrates from the Wadhurst Clay Formation (Lower Cretaceous) of Ashdown Brickworks, East Sussex, UK a,b a c d Pernelle Turmine-Juhel , Richard Wilks , David Brockhurst , Peter A. Austen , a,e,f a, Christopher J. Duffin , Michael J. Benton * a School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK b Géosciences, UMR 6118, Université Rennes-1, 263, Avenue du Général-Leclerc, 35000, Rennes, France c 8 Crowmere Avenue, Bexhill-on-Sea, East Sussex, TN40 2BA, UK d 3 Bromley Road, Seaford, East Sussex, BN25 3ES, UK e 146 Church Hill Road, Sutton, Surrey, SM3 8NF, UK f Earth Sciences Department, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK A R T I C L E I N F O A B S T R A C T Article history: Ashdown Brickworks, near Bexhill, East Sussex, has produced a large number of vertebrate fossils from Received 14 May 2019 the Wadhurst Clay Formation, part of the Wealden Supergroup (Hastings Group; Valanginian; Lower Received in revised form 16 August 2019 Cretaceous). Here we describe the microvertebrate fauna of the ‘conglomerate bed’, representing a rich Accepted 17 August 2019 sample of taxa. While most of the recovered teeth and bones are abraded, some heavily, most can be Available online 28 August 2019 identified to species level. The taxa include four species of hybodont sharks (Egertonodus basanus, Planohybodus ensis, Polyacrodus parvidens, P. brevicostatus), three taxa of bony fishes (an unidentified Keywords: Lepidotes-like semionotiform, the pycnodontiform Ocloedus, and an albuliform), three taxa of Wadhurst Clay Formation crocodyliforms (the goniopholid Hulkepholis, a bernissartiid, and the atoposaurid Theriosuchus), and Wealden Cretaceous the theropod dinosaurs Baryonyx and an allosauroid. Sediments of the Wadhurst Clay Formation as a Valanginian whole indicate freshwater to very slightly brackish-water environments of deposition, and the mainly Hybodontidae aquatic time-averaged mixture of fishes and tetrapods recovered from the ‘conglomerate bed’, together Semionotiformes with isolated terrestrial species, confirms this interpretation. Crocodyliformes © 2019 The Geologists' Association. Published by Elsevier Ltd. All rights reserved. Palaeoenvironment Brackish environments 1. Introduction from bone-rich accumulations, especially on the Isle of Wight (e.g., Sweetman, 2011a, 2016; Sweetman and Evans, 2011a, 2011b; The Wealden Supergroup of south-east England has been one of Sweetman et al., 2014). He reported a diverse vertebrate the most productive continental Mesozoic units for fossil assemblage including chondrichthyan and osteichthyan fishes, vertebrates, with the first reported finds dating back to before lissamphibians, lizards, turtles, crocodyliforms, pterosaurs, non- 1800 (Martill and Naish, 2001). The Wealden Supergroup, avian dinosaurs, birds and mammals from the plant debris beds of especially in Surrey, East and West Sussex and Kent, comprises the Wessex Formation (Barremian), and a sparser fauna of many formations and members, characterized by diverse fluvial, chondrichthyans and osteichthyans, and a small number of teeth lacustrine and terrestrial facies, that have been studied intensely of crocodyliforms, from the overlying Vectis Formation (late by geologists and palaeontologists (e.g., Topley, 1875; Allen, 1975; Barremian–early Aptian). Batten, 2011). Over 200 years, hundreds of skeletons of dinosaurs, Microvertebrates had been reported from the Wealden of the crocodyliforms, turtles, and rare pterosaurs and plesiosaurs have Weald, particularly some important fossil mammals from Hast- been reported, with additional finds of fishes, lissamphibians, ings, East Sussex, and other locations (Clemens and Lees, 1971). lizards and mammals based on microvertebrate remains (Allen, Intensive sampling efforts around Hastings through the 1960s and 1949; Martill and Sweetman, 2011). More recently, Steve Sweet- 1970s by Kenneth Kermack and his team from University College man has conducted a series of investigations into microvertebrates London revealed many new specimens, but only the mammals have been described. There are few accounts of the Wealden bone beds of the Weald Sub-basin since Allen (1949) and Cook (1995) described the sedimentology and taphonomy of numerous * Corresponding author. E-mail address: [email protected] (M.J. Benton). examples. https://doi.org/10.1016/j.pgeola.2019.08.003 0016-7878/© 2019 The Geologists' Association. Published by Elsevier Ltd. All rights reserved. P. Turmine-Juhel et al. / Proceedings of the Geologists’ Association 130 (2019) 752–769 753 The aim of this paper is to report the microvertebrate fauna A brick works has operated continuously at this site since the from a unit that is older than the Isle of Wight Wealden fossil beds 1890s. Formerly known as Lunsford Brickworks, and owned by the (Valanginian versus Barremian–early Aptian), but with many taxa Sussex and Dorking Brick company, the site produced around in common. The location is the Ashdown Brickworks near Bexhill, 350,000 bricks per week, and was then taken over by Redland Brick East Sussex, where collecting since the 1990s has yielded abundant in the 1970s. The site was redeveloped in 1978 to produce around vertebrate fossils, initially larger remains, such as partial dinosaur 750,000 bricks per week and was then taken over by Ibstock Brick skeletons, but also isolated teeth of a diversity of dinosaurs, Ltd in 1996. crocodyliforms, and pterosaurs (Austen et al., 2010). We concen- The Wadhurst Clay was named as a distinct rock unit by Drew trate on the microvertebrate fauna from the ‘conglomerate bed’, (1861) and was later formally made the Wadhurst Clay Formation, one of five bone-bearing horizons at the site. a subdivision of the Wealden Group of Rawson (1992) and Hopson Institutional abbreviation: BEXHM, Bexhill Museum, 47 Egerton et al. (2008), and clarified by Batten (2011) as the Wadhurst Clay Rd, Bexhill-on-Sea, TN39 3HL, U.K. Formation within the Hastings Group of the Weald Sub-basin, a division of the Wealden Supergroup (Fig. 3A). It is part of what was 2. Geological setting and previous work formerly referred to as the ‘Hastings beds’, and ranges in thickness from 30 m at Rye to 70 m at Cuckfield and 78 m at Worth (Hopson The Wealden sandstones around Hastings and Bexhill have long et al., 2008, p. 10). The unit extends over most of the Weald Sub- been a rich source of fossils, both from the inland stone quarries and basin, from Bexhill and Hastings on the coast, inland to Uckfield, from the coastal sections (Topley, 1875; Batten, 2011). Ashdown Crowborough, Royal Tunbridge Wells, and Tenterden, and it is Brickworks (TQ 720095), on Turkey Road, near Bexhill, East Sussex dated as early to early late Valanginian. The Wadhurst Clay (Fig.1), has long been recognised as a prolific fossil locality (Batten and Formation overlies the Ashdown Formation (Fig. 3A), and consists Austen, 2011; Austen and Batten, 2018). There are two pits, the mainly of dark grey and soft shales and mudstones, with minor southerly Crowborough Pit and the northerly Pevensey Pit, and they sandstones, conglomerates, calcareous gravels, ferrous clays and are separated by the Whydown Fault, which runs west–east (Figs.1, 2). lignite, interpreted collectively as the deposits of freshwater to The pits expose two stratigraphic units, the Wadhurst Clay Formation slightly brackish-water lagoon environments (Anderson et al., overlain by the Lower Tunbridge Wells Sand Formation. The fossils 1967; Allen, 1975; Lake and Young, 1978). The upper boundary is described here come from the Wadhurst Clay Formation, which is marked by a sharp change from siltstones to the fine-grained silty exposed only in the Pevensey Pit. sandstones of the overlying Tunbridge Wells Sand Formation. The A summary section through numerous sedimentary logs top of the Wadhurst Clay is commonly red-stained at this junction, around the quarry shows the beds dipping at around 10 north marking the occurrence of pene-contemporaneous weathering. (Fig. 2). The Wadhurst Clay Formation is divided into three units The sediments at Ashdown Brickworks show many aspects of locally - a lower clay, some 30 m thick, a middle sandstone unit, Allen’s (1975) classic environmental model for the Wealden of the the Northiam Sandstone, 2–3 m thick, and an upper clay, about Weald. He interpreted the overall environment as “a variable- 10 m thick. salinity coastal mudplain with lagoons and sandy water-courses Fig. 1. Geological map showing the region north of Bexhill-on-Sea (English Channel coast at bottom right), with the site of Ashdown Brickworks marked (red star), and the regional geology indicated. The Whydown Fault runs from west to east, through the middle of the works. Top right: Bexhill is indicated on the regional geological summary map of SE England. © Crown Copyright and Database Right 2017. Ordnance Survey (Digimap Licence). Regional map courtesy of Steve Sweetman. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 754 P. Turmine-Juhel et al. / Proceedings of the Geologists’ Association 130 (2019) 752–769 Fig. 2. Sketch cross section through the two pits at Ashdown Brickworks, showing the Whydown Fault between the two pits, and how this re-sets the observed successions