Urban geology: Productid brachiopods in Amsterdam and Utrecht

Stephen K Donovan (The Netherlands) and David AT Harper (UK) The most obvious manifestations of geological materials in the urban environment are building and facing stones, and similar rocks used in street furniture, such as kerbstones. As a Londoner, SKD was impressed as a boy by the massive kerbstones that he saw in the City and locally where he lived. It was only as his knowledge of geology grew that he discovered such stones to be truly exotic, being largely crystalline rocks (mostly granites in the broad sense) and probably derived from the southwest or the north of the British Isles. A field guide to the kerbstones of London would have accelerated his education in geology at that time. More satisfactorily to palaeontologists, such as the authors of this article, are building stones that are fossiliferous. We have particular interests in the palaeontology of Palaeozoic limestones. These are common building stones and street furniture in many cities in the Netherlands (and elsewhere). These rocks are all imported (Van Ruiten and Donovan, 2018; Dr Bernard Mottequin, email to DATH, 9 May 2018) and are mainly Mississippian, although there are some limestones of Devonian age here and there (Van Roekel, 2007; Reumer, 2016). However, the Mississippian limestones are the more widespread and contain abundant fossils, from the well-known, such as bryozoans (Donovan and Wyse Jackson, 2018), brachiopods, crinoids, and rugose and tabulate corals (Van Ruiten and Donovan, 2018) to the more exotic, such as rostroconch molluscs (Donovan and Madern, 2016). This article … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Geo junkets: New Zealand, North Island (Part 1)

Jesse Garnet White (USA) Fig. 1. Legend/Key:1 = Sediments (Cretaceous and Cenozoic).2 = Greywacke (Permian and Triassic).3 = Schist (Carboniferous to Cretaceous).4 = Volcanic rocks (Cretaceous and Cenozoic).5 = Sediments and ophiolites (Northland and East Coast allochthon) (Cretaceous and Oligocene).6 = Pyroclastic rocks (Triassic and Jurassic).7 = Limestone, clastics and volcanic rocks (Central and Eastern sedimentary zone) (Cambrian to Devonian).8 = Granitoids (Paleozoic and Cretaceous).9 = West Fiordland metamorphic zone (Paleozoic and Cretaceous).10 = Ophiolites and pyroclastics (Permian).11 = Volcanic rocks (including pyroclastics) (Permian).12 = Mafic and ultramafic complexes (Paleozoic and Cretaceous).13 = Greywacke (Western sedimentary zone) (Cambrian to Ordovician). Auckland and the AVF In a thick brain fog, crusty eyed and yawning, I sat up in bed at 4:30 am. I was in Auckland, New Zealand. It was still dark outside when I drove to Mount Eden (Maungawhau), where I hiked up a narrow dirt trail lined by tall grass stippled with dew. Coming out of the verdure, my shoes, socks and shorts were soaked through. On top of the hill, a shadow-black grouping of trees blocked the creeping morning light from behind the Hanua Ranges. The burnt orange sunrise, obstructed by cumulous, lit up like a distant mountain wildfire. Auckland city centre was under puffy, lavender-white cirrus clouds, reflecting pastel colours across the harbour. Alone in the cool and crisp pre-dawn air, I viewed the various scoria cones in the Auckland Volcanic Field (AVF) bursting through the city neighbourhoods. Fig. 2. Map of New Zealand showing place names. … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Crinoids at Hartington

Stephen K Donovan (The Netherlands) Much of the secondary railway route in Derbyshire, from Buxton south to Ashbourne, was closed in the 1950s and 1960s. Today, only the northern section is still in use as a railway, providing a route for major limestone quarry traffic (Roberts and Emerson, 2018). But the remainder of the line, from about 2.25km north of the closed Hurdlow station (Rimmer, 1998, p. 102), all the way to Ashbourne – a distance of about 27.5km – is now open as a cycle path called the Tissington Trail. This is part of the High Peak Trail north of High Peak Junction, which is south of Parsley Hay, and provides excellent access. For a map, see http://www.peakdistrict.gov.uk/__data/assets/pdf_file/0009/90486/hptisstrails.pdf. The interest of this route for the geologist is that most of it is through the Carboniferous limestones (Mississippian) of the Derbyshire plateau. The beauty of the scenery combines with the accessibility of exposures in railway cuttings to provide much of interest to the geologist on foot or bicycle. The northern part of the route, from south of the site of Hurdlow station, through Parsley Hay (with cycle hire and a cafe) to Hartington, is described in a brief field guide by Simpson (1982, pp. 102-107). My interest in these limestones is for their fossil crinoids. These are commonly difficult to see in the massive beds of limestone, which, over many years, have developed a surface patina that conceals internal features such as fossils. As this is a national park, there … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Geomodels in engineering: An introduction

Peter Fookes, Geoff Pettifer and Tony Waltham (UK) This article is based on the introduction to the newly published book Geomodels in Engineering Geology – An Introduction. What, why and when? The Earth is an active planet in a constant state of change. These changes can take place over both long and short periods of geological time (thousands or millions of years) or much more quickly on an engineering timescale (minutes, hours or days). Geological processes continually modify the Earth’s surface, destroying old rocks, creating new ones and adding to the complexity of ground conditions: the so-called ‘geological cycle’. The all-important concept that drives this geological plate tectonics. The benefits geologists bring to construction projects must exceed the cost of their services — that is, they must accurately improve the engineer’s ground knowledge more cheaply and effectively than any other method. They must reduce the risk of geological hazards by anticipating situations perhaps unseen by the engineers and also help to determine effective ways of dealing with risks and any problems arising during design and construction. The main role of the engineer geologist is to interpret the geology and ground correctly. Creating an initial model for the geology of the site is an excellent start. Geology (the study of the Earth) and its closest geo-relative, geomorphology (the study of the Earth’s surface), are concerned with changes over time and any geomodel has to build in any changes likely to occur in the near future, especially when the construction project may … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Concretions in sandstones of the Inner Hebrides, Scotland

Mark Wilkinson (UK) Concretions are a common feature in many sedimentary rocks, yet they seem sometimes to be misunderstood. So, how do concretions form? As well-studied examples, let’s look at the ones found in some of the sandstones of the Scottish Inner Hebrides, notably the islands of Eigg and Skye. The concretions are found in several formations, but perhaps the largest and most spectacular are in the Valtos Sandstone Formation of the Great Estuarine Group. This was originally named the Concretionary Sandstone Series after the prominent metre-scale concretions. It is Bathonian in age (Middle Jurassic) and is interpreted as having been deposited in a coastal environment. The Great Estuarine Group is becoming famous for its abundant dinosaur footprints and much rarer skeletal material. The concretions themselves vary from spherical to elongate volumes of rock and are typically from around 50cm to one metre or more in diameter. They are also often coalesced into groups (Fig. 1). Inside the concretions, the spaces between the sand grains are filled completely with a calcite cement. The concretions are resistant to weathering compared to the host sandstone, which is fairly soft, so stick out from the cliff in a sometimes rather alarming manner as you walk below them. I’ve been visiting the concretions sporadically for around 30 years and some of the ones that I photographed in the cliffs in the 1980s are now lying loose on the beach. None of them have fallen while I’ve been there, touch wood. Fig 1. Concretions on … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Rudists: A fossil story

Jack Shimon (USA) This article is adapted from a presentation given at the Denver Gem Show, September 17, 2016 by me, Jack Shimon. When I was six and a half years old, my Grandpa took me fossil hunting in central Texas. We went to a Carboniferous Limestone quarry that he had visited earlier and was given permission to enter and collect from. This was one of my first fossil hunting trips and I really enjoyed it. The ancient reef we went to (now a quarry) had huge boulders of limestone and tube-like things in it we later to be found to be rudist bivalves. This article is all about these finds and the efforts we went to, to find out what they were. Fig 1. The author at the quarry. (Photo credit: Mike Hursey.) Fig. 2. This Google satellite image shows the reef we collected from. Two of the three lobes have been excavated for limestone. You can also see smaller pinnacle reefs marked with the short arrows. All of the reefs rise above the flat Texas landscape. (Permission from Google.com: ‘Special Use Guidelines’.) Fossils We spent a lot of time at the quarry observing the massive specimens onsite and then collected some smaller pieces to bring home and look at closer. A simple way of thinking about fossils is to consider them either as a cast or a mould. A mould is formed when an object is placed into a soft substrate and then decomposes or is washed away … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

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

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Stop the press: The Jurassic Coast starts in the Permian

Mervyn Jones (UK) This Geologists’ Association field meeting followed the publication of Professor John Cope’s Geologists’ Association (GA) Guide No 73, Geology of the South Devon Coast. It is also the companion to GA Guide No 22, Geology of the Dorset Coast. John retired in 2003 after lecturing at Swansea and Cardiff universities. Since then, he has been an Honorary Research Fellow at the National Museum Wales in Cardiff, and has a wide field experience in the UK and Europe, with publications covering many fossil groups over a wide stratigraphical range. Most recently he has been working on redrawing the geological map of South Wales, the subject of an upcoming GA lecture. And, each year, for the past six years, he has provided weekend geological trips to the West Country. Fig. 1. Prof Cope demonstrates bedding and cleavage. We met up at Meadfoot Strand to the east of Torquay Harbour. Our mission for the weekend was to examine the complex Devonian succession in the Torbay area and its unconformable relationship to the Permo-Triassic cover. Of great interest was the marine Devonian, first described by Adam Sedgwick, assisted by Roderick Impey Murchison, who finally realised that these facies were contemporaneous with the familiar Old Red Sandstone found north of the Bristol Channel. Since then, the Devonian Stages have been named after rocks in the Czech Republic, Germany and Belgium. The base of the Devonian was the first ‘Global Boundary Stratotype Section and Point’ (GSSP), defined by graptolite zones at Klonk, in … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Rocks in Roslin Glen: A record of a swampy past

Mark Wilkinson and Claire Jellema (UK) Midlothian is an area of central Scotland that lies to the west of Edinburgh and is an area with strong geological connections due to a history of mining for both coal and oil shale. As a part of the annual Midlothian Science Festival (http://midlothiansciencefestival.com/), the School of GeoSciences at the University of Edinburgh offered a walk to look at some local geology and a talk about climate change research on the Greenland icecap. In addition, a ‘Dino and Rocks Day’ was attended by 380 people, proof (as if it were needed) that dinosaurs continue to fascinate the general public. The Edinburgh Geological Society also contributed with a session about Midlothian Fossils and a local historian talked about the history of coal mining in the area. The geology walk visited local exposures, in this case Carboniferous sediments including what may be the best exposed fluvial sediments in the area. The walk was advertised as “Rocks in Roslin Glen: a Record of a Swampy Past” and all 25 spaces were quickly booked. The location was Roslin Glen, which may sound familiar if you’ve seen the film, The Da Vinci Code, based on the novel by Dan Brown. We have not misspelled the name of the glen incidentally. For some reason, Rosslyn Chapel lies on the edge of Roslin Glen and the country park of the same spelling. The glen itself is a steep-sided valley of around 20m in depth, which carries the River North Esk roughly … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

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

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Triassic beasts and where to find them

Sue Beardmore (UK) Located amid the scenic Southern Alps, on the Swiss-Italian border, is Monte San Giorgio, a mountain that rose up like many across Central Europe as a result of continental collision between Africa and Europe during the Alpine Orogeny. It is not particularly big or distinct by alpine standards but it is special, a status emphasised by the designation of its slopes as a UNESCO World Heritage site initially in 2003 for the Swiss part with the neighbouring Italian area added in 2010. To begin, the rocks outcropping on the mountain form an almost complete stratigraphic sequence from the Permian through to the Jurassic (Fig. 1), not only an extended interval of time but an important one around the massive Permo-Triassic extinction. The same rocks provide a context for the equally important Middle Triassic vertebrate, invertebrate and plant fossils, now numbering more than 20,000, that have been found at the locality over the last 170 years. Fig. 1. A stratigraphic section of the rocks at Monte San Giorgio. © Commissione Scientifica Transnazionale Monte San Giorgio, 2014. In particular, it is the diversity, relative abundance and excellent preservation of the vertebrate fossils that has thrown the locality into the spotlight. These occur in six main fossiliferous horizons deposited in a shallow marine basin, the Monte San Giorgio Basin, one of many depressions on a carbonate platform between the Eurasian continent to the north and west, and the open waters of the vast Tethys Ocean to the south and east. … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Carbonate platforms and coral reefs: The Coralline Oolite of the Yorkshire Upper Jurassic – a prime source of palaeontological information

Keith Eastwood (UK) The Malton Oolite Member of the Coralline Oolite Formation (Corallian Group), as exposed in the Betton Farm South Quarry (TA00158555) at East Ayton, near Scarborough (Fig. 1), provides a wealth of fascinating palaeontological and sedimentological information. Examination of outcrops within this small quarry enables the geologist to reconstruct the palaeoenvironment of deposition of the Betton Farm Coral Bed, a localised system of patch, ribbon and framework reefs that developed during the Upper Jurassic. Fig. 1. Locality map of the Betton Farm and Spikers Hill quarries. Geological outcrops from BGS Sheet 54 (Scarborough) (1998), (Wright, 2001, p.157, fig.4.20). Total image © Joint National Conservation Committee; geological outcrop map – British Geological Survey © NERC. Redrawn and reproduced with permission. The lithology and textural characteristics of the Malton Oolite Member provide a sedimentological basis for the interpretation, but the fossil content adds definitive ecological and climatic insights. The Malton Oolite is the upper of two oolite members in the Coralline Oolite Formation (Fig. 2). The lower one, the Hambleton Oolite Member, is not seen in the Betton Farm Quarries (which consist of two quarries: Betton Farm North Quarry and Betton Farm South Quarry, north and south of the A170, respectively) but is fully exposed in the Spikers Hill Quarry (SE 980863) just 3km to the WNW (Fig. 1). This location is important in providing a regional depositional context for the Betton Farm deposits, even though the upper surface of the intervening Middle Calcareous Grit Member is a minor unconformity. … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Urban geology: Gabions in the Dutch townscape

Stephen K Donovan (The Netherlands) Gabions are tools of the engineering geologist, facing elements that are used to stabilize over-steep slopes, such as sea cliffs or railway/roadway cuttings; they also have military applications. The word is derived from the French, gabion, and Italian, gabbione, and originally referred to “A wicker basket, of cylindrical form, usually open at both ends, to be filled with earth, for use in fortification and engineering” (Little et al., 1983, p. 823). A modern gabion used in engineering geology is a cage, box or cylinder, commonly infilled by rocks or concrete, and sometimes sand or soil (https://en.wikipedia.org/wiki/Gabion). Fig. 1. A gabion wall, lacking subtlety, outside the restaurant, ‘De Blausse Engel’, at Amsterdam Zuid railway station. A: General view of castellated wall, separating restaurant patrons (chairs and tables to left) from passers-by. B: Detail of one cobble in the gabion, showing a vein (sphalerite?). Essentially, gabions provide a stable retaining wall that is semi-permanent. That is, they can be more easily removed, modified or replaced than a permanent structure made in concrete, brick or steel. Although they may be aesthetically unpleasing, gabions provide stability in situations where serious erosion problems may exist, which cannot be controlled by alternatives such as re-vegetation (Freeman and Fischenich, 2000). This is a simplification and studies such as that of Druse (2015) explain something of the complexities. So, in the low-lying Netherlands, what uses might be and are found for gabions? It is reasonable to suggest that they might be used in … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Fossil fish from northern Scotland

 Bob Davidson (UK) The north of Scotland is famous to scientists and amateur collectors for its wealth of localities where fossil fish of Devonian age can be collected. From plate tectonics, we know that in Devonian times Scotland was situated just below the equator, as part of a continent that was largely arid desert and where land plants were only just emerging. Most life on earth was still aquatic and fishes were the most successful backboned animals. The fossil fish of the area are unique in many ways. They present a window on the development of vertebrates, in which many of the innovations necessary to pave the way for the next great evolutionary step (the invasion by tetrapods of the land) were already in place. The fauna contains the acanthodians, one of the first group of vertebrates to evolve jaws, and the lobe finned fishes, so called because of their fleshy lobes supporting their pectoral and pelvic fins. The lobe fins also include the lungfish. Their fleshy fin lobes played an important role in the development of the limbs of early four-legged animals (tetrapods) and ultimately to all terrestrial vertebrates today – including ourselves. The classic Middle Devonian (380 to 375Ma old) locality is Achanarras Quarry in Caithness, where exquisitely preserved fish can be collected in an old roof tile quarry. Many such quarries existed in the past and fish have been widely collected from several localities over the years. The fish are preserved in thinly laminated siltstones and limestones, … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Agate: A mineral that develops with age, water and moganite

Terry Moxon (UK) Agate is banded or variegated chalcedony and this distinctive appearance allows a ready identification from any source. Many agate thick sections from basic igneous hosts are reminiscent of a series of distorted onion-like rings with the initial bands closely replicating the shape of the supporting gas cavity. However, the banding is frequently distorted and this general pattern is known under various names, for example, fortification or wall lining. A second type is less common and demonstrates apparently gravity-controlled horizontal bands. Agate host rocks are varied but the most abundant agate sources are the gas cavities of basic igneous rocks. This article limits discussion to agates from these basic hosts. However, agates can also be found in some igneous acidic hosts (for example, rhyolite), sedimentary rocks (for example, limestone) and in some fossils. Agate is greater than 97% silica (SiO2) and shows little variation between different samples. Under normal earth surface conditions, silica occurs in a number of forms. It is most commonly found as alpha-quartz and this is the major component in agate. A second silica constituent is moganite with a concentration at 2 to 25%. Moganite is found in agate that has not been heated by metamorphism or in the laboratory. Together with alpha-quartz, they are usually the only forms of silica identified in agate. However, other forms of silica such as cristobalite and tridymite have been occasionally identified in agate. In agates from basic igneous hosts, calcite is a rarity, as demonstrated by an examination … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

What’s so special about South Devon?

Professor John CW Cope (National Museum of Wales, Cardiff UK) Take a trip to the South Devon coast around Easter time and you are bound to come across student parties from universities engaged in fieldwork. What is it about this area that makes it so popular as a centre for this? The simple answer lies in a single word — variety. There is probably no other area in the UK where such a wide variety of rock types and ages is well-exposed in such a small geographical compass. Let’s have a look at some of the factors. The geological succession The oldest rocks exposed in South Devon are of Devonian age and, unlike many other areas of the UK, the Devonian rocks are in marine facies virtually throughout. Looking back over the history of geology, the age of these rocks had initially proved difficult to identify and it was only after Murchison had seen the marine successions in The Rhineland and Russia that he realised that these marine rocks were the equivalent of the Old Red Sandstone farther to the north. The Devonian rocks present a variety of marine facies, with the Middle Devonian limestones being of particular note. The limestones are a local development whose presence, in an otherwise deeper water succession, is due entirely to local shallowing of the water caused by thicknesses of volcanic rocks extruded along extensional fault lines as the local basins developed. This shallowing allowed reef-building organisms to flourish and the principal ones of … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Seeing into the ‘Stone Age’: The stone tools of early man

Bob Markham (UK) In the early part of his evolution, man made great use of rock and stone to assist him in his activities. The term ‘Stone Age’ has been given to the period of time during which stone was the main material used for the manufacture of functional tools for daily life. It is generally thought to have commenced about 3.3Ma and was the time when man firmly established his position on earth as a ‘tool-using’ mammal. However, it should be remembered that stone was not the only material used for this purpose. More perishable materials, such as wood, reeds, bone and antler, were also used, but very few of these materials have survived to be found today (but see the box: Non-stone tools). Non-stone toolsA notable exception to the general rule that non-stone tools have not been preserved is the Palaeolithic wooden spear shaft that was recovered in 1911 from a site in Clacton in Essex. At 400,000 years old, the yew-wood spear is the oldest, wooden artefact that is known to have been found in the UK (see http://piclib.nhm.ac.uk/results.asp?image=001066).A number of wooden spears dating from 380,000 to 400,000 years ago were also recovered between 1994 and 1998 from an open-cast coal mine in Germany (see https://en.wikipedia.org/wiki/Schoningen_Spears). Other items are found from time to time from peat-bog conditions, which offer the most favourable medium for the preservation of such material.The stones used to make tools Being a non-perishable material, stone has survived the ravages of time and is … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Urban geology: A rostroconch in Hoofddorp

Stephen K Donovan (The Netherlands) Part of my job is to provide service teaching for the University of Leiden. The university lacks a geology department, but my colleagues and I provide tuition in stratigraphy and palaeontology for life science students at the undergraduate and masters degree level. One of my favourite practical classes is a building stones tour of a part of Leiden that is rich in Mississippian (Lower Carboniferous) limestones, which are packed with fossils. These have been used for facing stones, external stairs and paving slabs. Many have been in place for some hundreds of years and many have been etched by slow solution by rainwater as a result. Common fossils include crinoid columnals, tabulate and rugose corals, brachiopods, and molluscs (Donovan, 2016; van Ruiten and Donovan, in review). These are most commonly seen in two dimensions and random sections, a different view of life to what the life scientists are usually accustomed. One group of fossils in these rocks were a mystery until recently, but we now know they are sections through rostroconchs (Donovan and Madern, 2016, p. 349), an extinct group of Palaeozoic molluscs. Rostroconchs were formerly considered to be an ancient group of bivalves and they are certainly bivalve-like in appearance, but lack an articulation of interlocking teeth and a ligament. That is, the shell is a univalve, a one-piece structure. I had only seen the sections of rostroconchs in building stones in Leiden. It was therefore gratifying, shortly after publication of these fossils, to … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Carbon Capture and Storage (CCS): Using geology to fight climate change

Mark Wilkinson (UK) Practically everyone has an opinion on climate change by now, although for the vast majority of scientists, the weight of evidence is overwhelming – emissions of carbon dioxide and other greenhouse gases are causing climate change, sometimes referred to as global warming. One possible technology for fighting climate change is Carbon Capture and Storage (CCS) in which geology plays an important role. In fact, future generations of geologists may be employed searching for CO2 storage sites in the subsurface, rather than for the more traditional search for oil and gas. The aim of CCS is simple – to allow the continuing use of fossil fuels while reducing the emissions of greenhouse gases into the atmosphere. In the long term, the burning of fossil fuels will probably cease, but until we can rely on renewable sources of energy, we are stuck with these fuels as a cheap and reliable energy source. CO2 is emitted during many activities, including driving cars and heating homes, but the largest single sources are fossil fuel power plants, which generate electricity, followed by industries, such as steel works and cement plants. It is these that most research has been focussed on. And, in principle, the technology is simple – capture the CO2 from a source (such as a power plant; Fig. 1) before it gets into the atmosphere, then transport it to a suitable storage site and inject it into the ground where it will remain for tens of thousands of years. Fig. … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Erzberg Mine in Austria: An iron ore reserve with a long tradition

Dr Robert Sturm (Austria) The Erzberg Mine is situated in the Austrian county of Styria. From a geological point of view, it belongs to the so-called greywacke zone, which represents a band of Palaeozoic metamorphosed sedimentary rocks intercalated between the Northern Limestone Alps and the Central Alps. The Erzberg Mine is the world’s largest deposit of the iron mineral siderite (FeCO3), which is mixed with ankerite (CaFe[CO3]2) and dolomite (CaMg[CO3]2). Due to this mixture of different mineral phases, the concentration of iron ranges from 22% to 40% and adopts an average value of 33%. The annual output amounts to about two million tons of iron ore, which is transported to blast furnaces in Linz and Leoben-Donawitz. According to current estimations, the ore reserves will allow mining activity for another 30 to 40 years. History of the Erzberg Mine There are lots of myths regarding the founding date of the iron mine on the Erzberg. According to the opinion of several scholars and a few written documents of dubious veracity, the mine was already established in the year 712, which would imply a use of the deposit by Slavic peoples. However, there exists better evidence that foundation of the mine took place in 1512, which was also the inauguration year of the Oswald church in the village Eisenerz. Fig. 1. The Erzberg Mine with its characteristic appearance, photographed from the north (Pfaffenstein). First documentary mention of the Erzberg Mine is from 1171. In the fourteenth century, the Reigning Prince of Styria … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Jamaica’s geodiversity (Part 2): Highlights from the Neogene

Stephen K Donovan (The Netherlands) and Trevor A Jackson (Trinidad) This is the second and concluding part of our introduction to Jamaica’s geodiversity. Here, we are concerned with more Neogene ‘highlights’ dating from the Middle or Late Miocene, about 10mya, when the island became, once again, sub-aerially exposed. The glossary provided in Part 1, as well as the maps (Donovan & Jackson, 2012, figs 1 and 2), are also relevant to this article and first appearance of the relevant terms in the text are highlighted in bold italics. Highlights 1 to 5 were discussed in Part 1 and 6 to 12 are described below. Highlight 6. Wait-A-Bit Cave Jamaica is a land of caves and sinkholes (Fincham, 1977). About two thirds of the rocks exposed at the surface of the island are limestones, which are soluble in acidic groundwaters, that is, those that are more or less rich in dissolved CO2. The percolation of these waters ‘excavated’ extensive cave systems throughout Jamaica, mainly by dissolution, since the island was sub-aerially exposed about 10mya (Miller, 2004). Wait-a-Bit Cave, south of Green Town in the parish of Trelawny (Fig. 1), is unusual among these myriad caves for reasons apart from its euphonious name. Fig. 1. Cave survey and selected passage cross-sections (A-A’ to G-G’) of the Wait-a-Bit Cave, parish of Trelawny, Jamaica (after Miller & Donovan, 1996, text-fig. 2). The thick dashed line to the west of E’, and south of F’ and G’, marks the edge of the limestone overhang from … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Blue John: Remarkable fluorite from a limestone cavern

Steven Wade Veatch (USA) Blue John stone is the name given to banded fluorite found in the Castleton area of Derbyshire in England (Ollernshaw, 1964). It has been prized for centuries. Chemically, it is a calcium fluoride (CaF2) and occurs in distinct bands of different colours: blue, white, purple and yellow. The colour banding is thought to be from periodic changes in the composition of the mineralising solution and the physical conditions during its formation (Mackenzie and Green, 1971). The name of this distinctive material is thought to have come from the French “bleu et jaune”, referring to its blue and yellow colours. Blue John is mined from only two places – Treak Cliff Cavern and Blue John Cavern in Castleton. It occurs either in veins up to 7.5cm thick or as nodules in a limestone unit found inside natural caverns beneath a hill west of Castleton. The caverns are now tourist attractions, where visitors can go on underground tours (British Council, 2008). Castleton is an excellent example of a quintessential English town. A beautiful stream quietly flows through this picturesque community of quaint tea shops, inviting pubs, charming cottages and old stone houses. Peveril Castle is a short walk up the hillside. Fig. 1. Located in limestone, deep witihin the Treak Cliff and Blue John Caverns, Blue John has been mined for its beautiful colours for centuries. (D Veatch specimen, photo by S Veatch.) Blue John was first discovered about 2,000 years ago when the Romans mined lead and … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.