Taphonomy and sedimentology of an echinoderm obrution bed in the Lower Devonian Voorstehoek Formation (Bokkeveld Group, Cape Supergroup) of South Africa Mhairi Reid, Emese M. Bordy ⇑ , Wendy Taylor Department of Geological Sciences, University of Cape Town, Cape Town, South Africa article info Article history: Received 2 January 2015 Received in revised form 15 April 2015 Accepted 16 April 2015 Available online 19 June 2015 Keywords: Taphonomy Lower Devonian obrution bed Malvinokaffric Ophiuroid–stylophoran assemblage SW Gondwana 3D microCT scanning abstract The Lower Devonian Voorstehoek Formation is a lithostratigraphic unit within the Ceres Subgroup of the Bokkeveld Group (Cape Supergroup) in South Africa comprised of essentially mudstones and siltstones. This fossiliferous unit contains typical cool to cold water benthic biota (e.g., brachiopods, trilobites, crinoids) from the Malvinokaffric Realm of SW Gondwana, however, to date, not only the taphonomy of Voorstehoek invertebrates is understudied, but in general those of the Early Devonian marine communities of this Realm. The palaeontological and sedimentological features of the Emsian Voorstehoek Formation suggest that deposition took place in a shallow marine environment within the storm-influenced, proximal part of an offshore transition zone. 3D microCT scanning of this obrution bed allows us to report, for the first time from South Africa, on the co-occurrence of fully-articulated remains of both ophiuroids and stylophorans within the same sedimentary layer. Taphonomic analyses of this ophiuroid–stylophoran assemblage suggest a marine obrution deposit, which formed due to the rapid burial of the benthic community during high-energy storms, smothered both autochthonous and allochthonous taxa. This uniquely preserved, mixed ophiuroid–stylophoran assemblage provides a taphonomic window into the marine ecosystems of the Early Devonian, including the structure of a benthic community within the Malvinokaffric Realm of SW Gondwana. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction The Devonian Bokkeveld Group of South Africa comprises inver- tebrate fossil assemblages that belong to the unique cool to cold water, high latitude Malvinokaffric Realm, a biogeographic term first introduced by Richter (1941) and originally used to denote the highly endemic, benthic marine, Devonian invertebrate faunas of the Southern Hemisphere. Initially defined based on the distribution of endemic Devonian trilobites and brachiopods (Clarke, 1913; Richter and Richter, 1942; Boucot et al., 1969; Eldredge and Ormiston, 1979), this polar latitude biogeographic unit now encompasses the Early Palaeozoic (Late Ordovician to Middle Devonian (Eifelian)) invertebrate fossil assemblages of south-western Gondwana (i.e., South America, southern Africa, Falkland Islands, Antarctica; see inset in Fig. 1)– Boucot, 1985, 1988; Melo, 1988). Generally, the Malvinokaffric Realm is characterised by a low-diversity fauna with abundant conulariids and hyolithids and the absence of certain major groups such as stromatoporoids, conodonts, nautiloids, and graptolites and almost no thermophilic reef-building corals or bryozoans (Oliver, 1980; Bigey, 1985; Boucot, 1985, 1988; Hiller and Theron, 1988; Meyerhoff et al., 1996). The Malvinokaffric biota of the Bokkeveld Group comprises both highly endemic species (e.g., certain bivalves and bra- chiopods) as well as several shared taxon (e.g., Australospirifer sp., Australocoelia sp., Burmeisteria sp.) that are also found in the Devonian of the Falkland Islands and southern parts of South America (Ponta Grossa Formation in the Parana Basin – e.g., Reed, 1906; Clarke, 1913; Richter and Richter, 1942; Melo, 1988; Almond et al., 1996; Boucot, 1999). The fossiliferous nature of the Lower Devonian Bokkeveld Group was first recorded in 1830 and onwards (e.g., Grisbrook, 1830; Thom, 1830; Bain, 1856; Salter, 1856) and in comprehensive reviews by Reed (1925), Theron (1972) and Oosthuizen (1984). Furthermore, the Lower Bokkeveld stylophorans were described by Rennie (1936) and revised in detail Ruta and Theron (1997). Additionally, Jell and Theron (1999) provided an extensive revision of the Bokkeveld crinoids, blastoids and asterozoans. http://dx.doi.org/10.1016/j.jafrearsci.2015.04.009 1464-343X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, South Africa. E-mail address: emese.bordy@uct.ac.za (E.M. Bordy). URL: http://www.geology.uct.ac.za/emese/bordy (E.M. Bordy). Journal of African Earth Sciences 110 (2015) 135–149 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci