Pleistocene Terrestrial Mammal Faunas from the North Sea

Pleistocene terrestrial mammal faunas from the North Sea Th van Kolfschoten Institute of Prehistory, Leiden University. P.O. Box 9515,2300 RA Leiden, the Netherlands C. Laban Rijks Geologische Dienst, P.O. Box 157,2000 AD Haarlem, the Netherlands Van Kolfschoten, Th. & Laban. C., 1995: Pleistocene terrestrial mammal faunas from the North Sea - Meded. Rijks Geol. Dienst, 52. p. 135-151 Manuscript: received April 26.1994; accepted after revision June 6,1994 Keywords: North Sea, Pleistocene, stratigraphy, terrestrial larger mammal faunal associations Abstract Many thousands of (sublfossil mammalian remains have been collected trom the bottom of the North Sea by fishermen using beamtrawls. The larger mammal fossils have been found mainly in a restricted area in the southern pan of the North Sea notably the Deep Water Channel and the Brown Bank. The list of mammal species are divided into two main groups: a group which Itve in a marine environment and a group of terrestrial mammals. The terrestrial mammals from the North Sea are divided in four fauna-associations which are regarded as groups of larger mammals with a compar- able age although not necessarily regarded as contemporaneous. Heavily mineralized mammalian remains are referred to fauna-associations I and II. Fauna-association I, with Anancus arvernensis and Mammuthus meridionalis, of Early or Middle Villafranchian age is correlated with the Tigliart. Fauna-association II with e.g. Mammuthus meridionalis {advanced type!. Mammuthus trogomherii, Hippopotamus antiquus and Cervalces latifrons, of Late Villafranchian age is correlated with the late Early/early Middle Pleistocene. The fossil remains referred to fauna-association / originate most probably from the IJmuiden Ground Formation and fauna-association II from the Yarmouth ffoads Formation. Fauna-association III, with e.g. Elephas antiquus, Mammuthus primigenius, Coelodonta antiquitatis and Ovibos moschatus, of Late Pleistocene age originates from the Brown Bank Formation. Fauna- association IV with e.g. Sus scrora, Alces alces and Bos primigenius of early Holocene age originates from the Elbow Formation which occurs in the eastern part of the Flemish Bight area. NrS2 1995 Pleistoceng terrestrial mammal faunas from the North Sea 135 Introduction mammal molars is largely restricted to sediments obtained from boreholes. Since historical times many towns along the coast of the North Sea and the former "Zuiderzee" had their own fish- Trawling over the sea bed (Figure 3) takes on average ery fleets. The fishing technique employed to catch flat- about 1 hours at a speed of 5 to 7 knots, the tracklength fish was the beamtrawl, the use of which dates from the varying between 10 and 13 kilometres, fishing mostly be- Middle Ages when sailing boats with tiny gears fished ing carried out in loops. The penetration depth of a beam- over the sea bed in the coastal areas. Up until the late fif- trawl into the sea bed varies between 4 and about 8 centi- ties of this century most fishing boats had small engines metres, depending on the composition of the sea bed and and the fishing gears used were not heavy. With the re- the weight of the fishing gear used (Laban & Lindeboom, placement of the fishing fleet by much heavier modern 1990). Below a depth of up to 8 centimetres no deforma- vessels (Figure 1), more sophisticated fishing gear towed tion of the sedimentary structures is visible. Studies car- over the sea bottom resulted in a higher pressure to be ried out by other institutes have also pointed to a penetra- exerted on the sea bed. The amount of material collected tion depth of about 7 cm (Bridger, 1970, 1972; De Groot, off the sea bed (in addition to fish!) including much man- 1973); during one of these studies a video camera mount- derived debris and (sub)fossil remains of mammals has ed on one of the gears confirmed that the penetration was increased considerably since the fishery fleet was moder- indeed only some centimetres.The mammal remains that nised. Only remains of larger mammals (Figure 2I are col- have been exposed at the sea bed are overgrown by al- lected by the beamtrawls due to the large diameter (about gae and bryozoa and are saturated by seawaler. After de- 5 cm) of the meshes of the nets; the occurrence of smaller salination the bones are impregnated with a solution of Figure I Beamtrawlers in the harbour ofStellendam (Delta area, Province of South-Holland, the Netherlands!. 136 Mededelingen Rijks geologische dienst Nr52 1995 _ glue and acetone to prevent the remains disintegrating the more spectacular finds. Erdbrink (e.g. 1981, 1983b, into pieces. The acetone evaporates while the glue re- 1983c, 1985) published a large number of fossil remains mains in the pores, thus ensuring preservation. mainly from large carnivores and Hooijer (1984a. 1984b, 1985) described some mammoth and ass remains from Many thousands of fossils have been collected during the the North Sea. More general reviews of the faunas from past 30 years and most of the material is stored in a large the North Sea have been published by Kortenbout van number of mainly small private collections. A restricted der Sluijs (1970-71; 1983), Drees (1986) and Van number of fossils have found their way into the National Kolfschoten & Van der Meulen (1986). Museum of Natural History, Leiden, the Net- The study of the fossils from the North Sea is hampered herlands which houses the largest national collection. by the fact that although the number of fossils is very The most important private collections are owned re- large they are dispersed over many collections. In addi- spectively by D. Mol IHoofddorp. Netherlands), H. van tion, and possibly of more importance, however, was the Essen (Dieren), C.F.G. van Tuyll van Serooskerken lack, until recently, of adequate stratigraphical informa- (Oostkapelle) and L.C.J. Stolzenbach (St. Michielsgestel). tion. With the publication by the Geological Survey of the There is much interest in the mammal fossils from the Netherlands and the British Geological Survey of the North Sea and they are sold all over the world, especially Quaternary map of the Flemish Bight (Cameron et al., in Europe, the U.S.A. and Japan. 1984), a much better insight into the outcrop of formations has now been obtained. Combination of the avail- The faunal remains have never been studied and de- able information of the locations where the material was scribed properly to any great extent apart from some of obtained from the seafloor together with the recent geo- Figure 2 Fossils from the bottom of the North Sea collected by Mr. P. van Es, Stellendem within a period of a few weeks. NrSZ 1995 Pleistocene terrestrial mammal faunas from the North Sea 137 logica! data, enable conclusions to be drawn about the Geological setting of the south-west part possible age of the faunal remains and the environment of the North sea in which the sediments were deposited. The geological setting of the south-west part of the North Sea, the com- The Neogene, Early and Middle Pleistocene deposits in position of the different faunal assemblages and their bio- the south-west part of Flemish Bight, the area between and chronostratigraphical position are discussed below. the coordinates 52° - 53° N/2° - 4° E, form a complex sequence of marine, brackish-marine, deltaic and fluviatile sediments (Cameron et al. 1984, 1989) (Figure 4-6). Late Pleistocene and Holocene deposits cover most of the area and are up to 30 metres thick. Pliocene and Early Pleistocene sediments crop out or subcrop close to the sea bed only in the extreme south-west part of the area. The oldest sediments exposed belong to different formations notably the Brielle Ground Formation (Pliocene, Reuverian), the Red Crag Formation (Praetiglian), the Westkapelle Ground Formation (Praetiglian to early Tiglian), the Smith's Knoll Formation and the Umuiden Ground Formation (both Tiglian). All these formations were mainly deposited in a marine pro-deltaic environment. The succeeding Winterton Shoal Formation (late Tiglian to Eburonian), which partly covers the Smith's Figure 3 Knoll and the Umuiden Formations, may include fluvia- A schematic impression of a beamtrawler trawling tile, delta and pro-delta facies of the Rhine, Meuse and over the sea bed. North German river systems. The Winterton Shoal Formation is mainly covered by younger deposits al- Legend lithostratigraphy Pleistocene map + prof îles I I Holocene formations J Twente Formation I.1 i I Kreftenheye Formation l"~-^' i Brown Bank Formation I Eem Formation i 3 Ice pushed sediments ty/W/\ Egmond Ground Formation I* .xxx N Yarmouth Roads Formation E~~~-^ Wmterton Shoal Formation ': : • •:" '•• ' Umuiden Ground Formation t::: :^:::::1 Smith Knoll Formation i i Westkapelle Ground Formation t-:-:::::-:-:-l Red Crag Formation \~:•'.'•'•'•.'] Brielle Ground Formation ^ —j Tertiaryformations undivided figure The lithostratigraphy of the top of the Pleistocene of the geological sheet Flemish Bight of the southern bight of the North Sea between 5Ï and 53°NK' and 4° £ Location of sections shown in 5A and B. 138 Mededelingen Rijks geologische Dienst NrS2 1995 though scattered outcrops occur in the south-east part of Pollen analytical investigations on a number of cores the North Sea. The overlying Yarmouth Roads For- show that deposition mainly took place during the early mation (late Tiglian to Elsterian) is composed of a pre- Weichselian, pollen zone EWIa (Zagwijn, 1983). The sedi- dominantly non-marine sequence of fine or very fine- ments were thought to have been initially deposited in a grained sands and clay. The surface outcrops of this for- lacustrine environment during the sealevel lowering dur- mation are restricted to the western part of the Flemish ing the late Eemian at the onset of the Weichselian glacia- Bight area.

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