Stephen K Donovan (The Netherlands)
A misconception shared by many non-palaeontologists is that fossils are rare. For example, when governments pass legislation to protect their fossil heritage, they are stopping the export of complete and well-preserved specimens, such as those of Mesozoic dinosaurs, hominids and Ice Age mammoths. There can be little argument that protecting their prehistoric heritage is responsible. Yet, these same politicians will support, for example, the export of cement. This may seem unrelated, but, of course, limestone is rich in fossils, most particularly invertebrates (Bathurst, 1971), and is an essential component of cement. These fossils are not dinosaurs or mammoths, admittedly, but they are fossils nonetheless. Legislation needs careful wording to ensure that exporting cement is not an illegal activity.
The Netherlands is an exporter of cement from the Upper Cretaceous limestone quarries in Limburg, in the far south of the country (Felder and Bosch, 2000) and therefore trades fossils in a rather ground-up, broken state after roasting them in a kiln. This is the type area of the mosasaur, but, hopefully, not too many bones get into the mix. However, fossils have also been imported to the Netherlands in limestones from elsewhere in Europe and these are recognisable. Most commonly, fossils have arrived in Amsterdam, Leiden and elsewhere in limestones used as curb and paving stones, gravestones, facing stones for buildings and other decorative applications (van Roekel, 2007; Donovan, 2014a, b).
These limestones are commonly grey, and most were deposited as lime sands and muds in shallow, warm seas during the Early Carboniferous (Mississippian), between about 360 and 320Ma, although some may be Devonian. They will have been imported from Belgium, Germany and elsewhere in Europe. Outside Amsterdam Zuid station, just one stop by train away from Amsterdam Schiphol International Airport, Carboniferous limestones form the sides of raised flower beds (the ends of these same beds are a pink gneiss) (Fig. 1). Particularly after rain, white fossils are readily apparent against a background of darker grey limestone. These rocks are commonplace – once you ‘get your eye in’, you will see them again and again in the Netherlands. For something a little more exotic, both geologically and gastronomically, visit the Wagamama restaurant while you are at Zuid station and examine the floor (Fig. 2).
It must have cost a small fortune to import this floor with a limestone the colour of wet straw to various shades of grey. By comparison with photographs in Broadhurst and Simpson (2008, pp. 34, 37, figs 4-6), this rock has been identified as what is referred to, in stonemason’s jargon, as Jura Grey limestone from southern Germany (see http://www.juragreylimestone.com) and is of Late Jurassic age (about 160 to 145Ma). The fossils are distinctly different from those of the Carboniferous limestones. Commonest are sponges.
Apart from the borings of clionoid sponges in shelly substrates – that is, the trace fossil Entobia isp. – my experience of fossil sponges is limited. They have a skeleton that disarticulates into separate microscopic spicules soon after death, so complete specimens are rarely preserved (Donovan and Stemann, 2007). I have visited the Cretaceous Faringdon Sponge Gravels Member (of the Faringdon Formation, Lower Greensand Group) in Oxfordshire (Rawson et al., 1978, p. 43), but that is my only experience of rocks where sponges are as common as in the floor of this restaurant. The Jurassic sponges in this floor would have been vase-shaped and the sections seen in these limestones vary from rounded to V-shaped, depending on whether they have been cut transversely or longitudinally (Fig. 2B-E).
Less common are the brown, cigar-like guards (=shells) of belemnites (Fig. 2A; compare with Clarkson, 1998, fig. 8.32a, b). I collected my first belemnites from the Gault Clay Formation at Folkestone in Kent in 1975 (the tiny Neohibolites) and family holidays in Norfolk would often find me looking for them on the beach, reworked out of the Upper Chalk (Donovan and Lewis, 2010). Seeing them in Wagamama 40 years later was like an unexpected meeting with an old friend. And, of course, they immediately told me that this was a Mesozoic rock. Other groups are present, but rare. Gentlemen visiting the bathroom should note an ammonite(?) or gastropod in spiral section in the wall above the cistern (Fig. 2F). Now you’ve seen the sites, it is surely time to eat – and enjoy!
Bathurst, R.G.C. 1971. Carbonate Sediments and their Diagenesis. Elsevier, Amsterdam, xix+620 pp.
Broadhurst, F.M. and Simpson, I.M. 2008. A Building Stones Guide to Central Manchester. Second edition. Manchester Geological Association, Manchester, 45 pp.
Clarkson, E.N.K. 1998. Invertebrate Palaeontology and Evolution. Fourth edition. Blackwell Science, Oxford, xvi+452 pp.
Donovan, S.K. 2014a. Urban geology: A sunny Sunday in Hoofddorp. Deposits, 38: 8-10.
Donovan, S.K. 2014b. An unnatural bridge in an artificial limestone environment, the Netherlands. Cave & Karst Science, 41: 118-119.
Donovan, S.K. and Lewis, D.N. 2010. Notes on a Chalk pebble from Overstrand: ancient and modern sponge borings meet on a Norfolk beach. Bulletin of the Geological Society of Norfolk, 59 (for 2009): 3-9.
Donovan, S.K. and Stemann, T.A. 2007. Where have all the sponges gone? The significance of spicules from the Upper Pliocene Hopegate Formation of Jamaica. Caribbean Journal of Science, 42 (for 2006): 239-243.
Felder, W.M. and Bosch, F.W. 2000. Krijt van Zuid-Limburg. Nederlands Instituut voor Toegepaste Geowetenschappen TNO, Delft/Utrecht, 192 pp.
Rawson, P.F., Curry, D., Dilley, F.C., Hancock, J.M., Kennedy, W.J., Neale, J.W., Wood, C.J. and Worssam, B.C. 1978. A correlation of Cretaceous rocks in the British Isles. Geological Society of London, Special Report, 9: 70 pp.
Roekel, A. van 2007. Discover Fossils in Downtown Amsterdam. Second revised edition. Uitgeverij De Vuurberg, Amsterdam, 17 pp.