Dick Mol 1,2, Klaas Post 1,Jelle W.F.Reumer 1,John de Vos 3 & Cees Laban 4 1 Natuurmuseum Rotterdam 2 Cerpolex, Paris 3 Naturalis, Leiden 4 NITG, Utrecht Het Gat: preliminary note on a Bavelian fauna from the North Sea with possibly two mammoth species Mol, D., Post, K., Reumer, J.W.F., De Vos, J. & Laban, C., 2003 - Het Gat: preliminary note on a Bavelian fauna from the North Sea with possibly two mammoth species - in: Reumer, J.W.F., De Vos, J. & Mol, D. (eds.) - ADVANCES IN MAMMOTH RESEARCH (Proceedings of the Second International Mammoth Conference, Rotterdam, May 16-20 1999) DEINSEA 9: 253 - 266 [ISSN 0923-9308] Published 24 May 2003 We describe the fossil vertebrate remains from a site (‘Het Gat’) on the bottom of the North Sea, between the United Kingdom and the Netherlands. The site is a maximally c. 46 m deep gully that cuts through layers of Holocene and Eemian sediments and reaches into the Yarmouth Roads Formation. This part of the Yarmouth Roads Formation is a complex of fluvial sediments of late Early-Pleistocene, most probably Bavelian, age. The age of the Bavelian is considered to be some 1.000.000 - 750.000 years (1 - 0.75 Ma). As the fossils originate from the Yarmouth Roads Formation, the fauna is thus attributed a late Early Pleistocene age; we correlate it to localities such as Untermassfeld (Germany) and Saint-Prest (France), which both have an estimated age of c. 1 Ma. The faunal content of the site ‘Het Gat’ is provisionally as follows: (Proboscidea) Mammuthus meridionalis and/or Mammuthus trogontherii; (Artiodactyla) Hippopotamus antiquus, Alces lati- frons, Megaloceros dawkinsi, Megaloceros savini, Eucladoceros ctenoides, Bison menneri; (Perissodactyla) Equus major, Stephanorhinus etruscus; (Carnivora) Homotherium cf. latidens, Ursus cf. etruscus. These finds necessitate us to discuss whether or not two different species of mammoth can have coexisted and can thus be present in one fossil faunal assemblage. There appe- ars to have been a continuous evolutionary development leading from Early Pleistocene M. meri- dionalis to Late Pleistocene and Holocene M. primigenius. Most authors recognise an intermedia- te species M. trogontherii, of supposedly Middle Pleistocene age. The differences are in the den- tition, while postcranially the taxa are difficult to distinguish. The molars we found in ‘Het Gat’ can either be interpreted as advanced M. meridionalis or as M. trogontherii. Until the taxonomy of Pleistocene Mammuthus species is clarified we doubt the presence of two species in one locality. Correspondence: Dick Mol, Klaas Post, and Jelle W.F. Reumer, Natuurmuseum Rotterdam, Postbus 23452, 3001 KL Rotterdam, the Netherlands, e-mail [email protected]; John de Vos, Nationaal Natuurhistorisch Museum, Naturalis, Postbus 9517, 2300 RA Leiden, the Netherlands; Cees Laban, Nederlands Instituut voor Toegepaste Geowetenschappen TNO, Postbus 80015, 3508 TA Utrecht, the Netherlands Keywords: North Sea, Het Gat, Bavelian fauna, Mammuthus. 253 ADVANCES IN MAMMOTH RESEARCH DEINSEA 9, 2003 INTRODUCTION by one single ship on one single locality, Early and/or Middle Pleistocene mammalian named Het Gat. Geological details of this site fossils from the bottom of the North Sea were are known and the Cerpolex/Mammuthus first recognised by Kortenbout van der Sluijs Expedition 2001 thoroughly investigated the (1970-1971, 1971). Drees (1986) attempted locality, enabling us to be reasonably exact to give a paleontological and geological con- about the geological context of the fossils. text to these 'black and heavy' fossils. In the most recent and detailed treatment of this THE LOCALITY AND ITS subject an early Early Pleistocene association GEOLOGIGAL CONTEXT (with mastodon and southern mammoth) is Nearly all localities of fossil bones (both Late described in addition to a late Early and/or Pleistocene and older) are situated S or SW early Middle Pleistocene association (Van of the so-called Brown Bank. The fauna Kolfschoten & Laban 1995). This latter asso- described in the present paper, however, ori- ciation comprised Mammuthus meridionalis, ginates from an aberrant, narrow and very Mammuthus trogontherii, Equus major, elongate trench N and NE of the Brown Stephanorhinus etruscus, Hippopotamus anti- Bank. The site is situated between 52º35'- quus, Alces latifrons, and an (as yet) uniden- 52º50' N and 3º20'-3º25' E (Fig. 1). tified deer and bison. The fauna would date Fishermen call this trench 'Het Gat' or 'Het to a period between Late Tiglian (TC5-6) and Gat binnen de Bruine Bank' (meaning The Pit Early Cromerian. According to Van Kolf- or The Pit within the Brown Bank). The schoten & Laban (1995) the fossils originate Brown Bank itself lies at c. 18 m below from several associations with different geo- sealevel and the sides of the Bank steeply dip logical ages. This conclusion was substantia- to c. 36-40 m. The maximum depth of Het ted by doubting the occurrence of both Gat is about 46 m. Mammuthus meridionalis and Mammuthus Fishermen consider the area to be difficultly trogontherii within a single fauna. fishable due to the presence of small erratic All such studies about the oldest mamma- boulders and irregularly folded layers of lian fossils from the North Sea are based on coarse brown sands and fine clays. The folded accidental finds without accurate locality sediments and the erratica are caused by, and data. Often it is only known that the fossils deposited by, glacial action. They cause originate from the deeper parts of the sout- damage to the nets or even the loss of entire hern North Sea, and as a rule the term ‘Deep equipments. The trench Het Gat therefore is Water Channel’ is used for the lack of better. only rarely visited and the vessel that provi- In reality the rare finds originate from several ded our fossils is the only ship that frequents different deeper pits. The distances between the trench on a regular basis. The vessel, these pits (of up to 40 nautic miles) and the GO41 with captain G.‘t Mannetje, always complex geological situation of the bottom of follows the same route: a N-S directed stretch the southern part of the North Sea necessitate at 40-42 m depth, at 3º20'30" E and 52º41' N a critical evaluation of the general conclu- to 52º36'30" N. Below 42 m depth, problems sions published so far. arise with lots of stones. Turning the ship is Most fishermen do not discriminate between to be avoided. After five subsequent pulls the older (Early and Middle Pleistocene) fossils bottom becomes too loose and fishing is halt- and the ones from the Late Pleistocene and ed. hence precise locality data are rare. Yet an The geological map of the area (Cameron increasing interest among the fishermen led et al. 1984) shows that thin layers of Eemian to a better localisation of the fossils and to a and Holocene sediments lay directly on top wealth of new data. The importance of the of the Yarmouth Road Formation (YRF). As present paper is the restriction to data collected these layers are being exposed, both Eemian 254 MOL et al.:a Bavelian fauna from the North Sea 3 o 10' E 3 o 30' E 53o 25' N NORTH SEA P 5-4 UK NL P 8-7 52 o 25' N Brown Bank Het Gat locality of fossil bones (52 o 37' / 52oo 39'30" N - 3 20'30" / 3o 20'80" E) bore-hole (52o 37'N - 3 o 21' E) bore-hole (52o 45'N - 3 o 25' E) section of figure 2 Figure 1 Map of the Brown Bank area with Het Gat and indications of the locations of borings P 8-7, P 5-4 and of the profile of Figure 2. 255 ADVANCES IN MAMMOTH RESEARCH DEINSEA 9, 2003 sediments and YRF sediments can be found border of Het Gat (52º45’ N - 03º25’ E; water at or near the surface. Profile 4 of Cameron depth 33.80 m) contained the YRF at 30 - et al. (1984; our Figure 2) cuts through the 47.20 m below the bottom surface (RGD middle part of the trench (52º43’ N, 3º18’- report 560). Boring P8-7 in the centre of Het 3º22’ E) and shows that glacial pushing Gat (52º37’ N -03º21’ E; water depth 40 m) during the Elsterian brought the YRF at or has the YRF directly at the bottom surface. near the bottom surface. Comparison with Zagwijn (1971) performed a pollen analysis Profiles 2 at 52º48’ N and 3 at 52º18’ N of a clay layer at 2.45 m below the bottom (Cameron et al. 1984; here not reproduced) surface (RGD report 581). He found a flora shows that the YRF is present throughout Het with a characteristically interglacial composi- Gat and that the lowermost depth of the YRF tion (comprising e.g. Tsuga, Eucommia and lies at 60 - 200 m below sea level. Thus, Azolla filiculoides) that is typical for either older layers can not have been exposed. the Waalian or the Bavelian. The YRF must be interpreted as a fluviatile sedimentary complex deposited between the Three fossil faunas Early Waalian and the Early Cromerian. At least three fossil faunas are to found in Laban (1995) shows that the boulders and the Het Gat. These are the Mammoth Steppe irregular structures are due to glacial pushing Fauna, a warmer Eemian fauna and a possi- by Elsterian ice. The gravel and the stones bly older fauna from the YRF. The well- are most probably of Scandinavian origin. known Late Pleistocene fossils of mammoth Two borings by the Rijks Geologische Dienst and its companions are rarely encountered. (RGD, the Dutch Geological Survey) are an Sometimes animals are found that could date important reference.