Urban geology: A failed example of gabions as false urban geology from the Netherlands

Stephen K Donovan (The Netherlands) The provinces of Noord and Zuid Holland, including much of the Dutch North Sea coast and adjacent inland areas, are devoid of rocky exposures. In a region of flat-lying Pleistocene siliciclastic successions (Burck et al, 1956), there are no quarries, cliffs or other man-made or natural exposures of lithified rocks. The topography is slight, with the highest natural structures being the coastal sand dunes, in part preserved as a national park (Jelgersma et al, 1970). To offset this lack of geological ‘furniture’, the Dutch have enterprisingly imported and installed sundry rocks that fill what may be an unattractive void in the environment. These rocks vary from the minimalist, such as roadside boulders (in part, possibly erratics) (Donovan, 2015), to reconstructions of structures such as a replica of a natural bridge in Mississippian limestone slabs (Donovan, 2014). But, in some instances, reconstructions are unsuccessful or, at least, inaccurate, such as the false (Pennsylvanian) Coal Measure strata without identifiable coal beds in the national railway museum (Het Spoorweg Museum) in Utrecht (Donovan, 2018a). In this article, I describe further mock geological structures that fail in the details. Gabions are tools of the engineering geologist. Yet, when packed with cobbles of imported, grey Mississippian limestone, they may make convincing false sedimentary ‘beds’, at least from a distance, and are a not uncommon feature of the environment of Noord and Zuid Holland (Donovan, 2018b). (Vertical, dyke-like structures are rarer and are less successful as false geology; Donovan, research in … Read More

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Urban geology: The strange tale of a windowsill

Stephen K Donovan and John WM Jagt (The Netherlands) Leiden, in the Dutch province of Zuid-Holland, is a city with a fine selection of fossiliferous building stones, mainly Mississippian (Visean, Lower Carboniferous) limestones. which preserve an array of fossils, such as rugose and tabulate corals, brachiopods, bryozoans, molluscs, and crinoids. However, this fine diversity of body fossils is not supplemented by a similar composition of trace fossils. Despite having examined these rocks over many years, when leading student fieldtrips and in collusion with co-workers, SKD has found no evidence of burrows, nor any borings in bioclasts, which can be locally common at some localities where Mississippian strata are exposed (for example, Donovan and Tenny, 2015). It is therefore of note to recognise an uncommon rock type among the building stones of Leiden that is dominated by burrows and lacks body fossils. This article highlights this distinctive building stone that has engrossed SKD for some years. The street Rapenburg (Fig. 1) in Leiden is a favourite route for building stone tours of the city. Although the dominant building materials are bricks, there are ample rocks to make a visit worthwhile. When SKD has led groups of students from the University of Leiden on geological excursions down the Rapenburg, the start is commonly at the North End Pub (Fig. 1). Fig. 1. Map of the centre of Leiden (modified after Van Ruiten & Donovan, 2018, fig. 1); Leiden Centraal railway station is north of the north-west corner of this map and less … Read More

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Invertebrate fossils from the Lower Muschelkalk (Triassic, Anisian) of Winterswijk, The Netherlands

Henk Oosterink (The Netherlands) During the Muschelkalk part of the Ansian (240mya), the Central European area (Germany, Poland, Denmark, The Netherlands and north-eastern France) was covered by a shallow sea, referred to as the Muschelkalk Sea. While there were frequent regressions and transgressions (leading to both marine and terrestrial fossil being present in these regions), it is from this sea that the limestones from this quarry were deposited and in which most of the fossilised animals discussed in this article lived. The quarry in the Muschelkalk at Winterswijk, in the east of the Netherlands (Fig. 1), is especially well known for the skeletons, bones, footprints and tracks of Middle Triassic reptiles. I wrote about these in Issues 15 and 20 of Deposits. However, fossils of invertebrates, such as molluscs, brachiopods and arthropods can also be found. Included in the molluscs are bivalves, cephalopods and gastropods, and from the brachiopods, the Inarticulata are present. From the arthropods, there are Malacostraca, Merostomata and insects. Fig. 1. Lower Muschelkalk quarry near Winterswijk (Eastern Netherlands). Mollusca Bivalves Some strata contain a large number of moulds of bivalves. These are situated quite high in the profile and, if you find this level, it is important to split the rock along an irregular dark-grey line (Fig. 2). If you do this, you will find the moulds of the convex upper side of the separated shells on one slab, with the negative impression visible on the other. This makes clear that these are valves swept together by … Read More

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Triassic reptiles from the Lower Muschelkalk of Winterswijk

Henk Oosterink (Netherlands) The Lower Muschelkalk (from the Anisian age of the Middle Triassic) of the quarry at Winterswijk in The Netherlands is well known for its beautiful and sometimes abundant finds of reptile footprints and bones. A few, almost complete, skeletons have even been found. Most of the bones come from marine reptiles within the Sauropterygia (that is, ‘winged lizards’, referring to their paddle-like flippers) group. The quarry is one of the most important sites for Triassic reptiles in the world. Every year, between 2,000 and 3,000 people visit this quarry on excursions and during open days, most being fossil collectors. Many new forms of life The Triassic Period is characterised by an explosive development of many reptile groups. For instance, at the end of this period, the dinosaurs appeared. Many new forms of life developed in terrestrial and marine environments. In the Tethys Ocean and its epicontinental seas, some reptiles adopted a semi-aquatic lifestyle allowing them to be functional in the sea as well as on land. Many of these reptiles belonged to the Sauropterygia. Sauropterygians are diapsids – reptiles are divided into two groups, anapsids that include turtles and diapsids that have two holes in the skull behind the orbit. Their skulls have upper temporal openings and, on the back of the skull, the quadrate is immovable and is connected to the squamosal. The sauropterygians lived mainly in the sea, but they did come ashore, for instance, to lay their eggs. This reptile group appears for the … Read More

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