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A mineralogical tour of Ireland (Part 3): Connaught

Stephen Moreton (UK) In the first two articles of this series, we looked at Leinster and Munster. Continuing in a clockwise fashion brings us to Connaught. Some of Ireland’s oldest rocks are to be found here, forming the Ox Mountains. The rugged and mountainous west is dominated by metamorphic rocks and a series of granite intrusions. Inland, Carboniferous limestone prevails. Fig. 1. The four regions of the island of Ireland. Fig. 2. Connaught in more detail. Where the latter abuts Devonian sediments is found the jewel in the crown of Irish mineralogy – Tynagh Mine. This giant polymetallic deposit, near Loughrea in County Galway, was discovered in the 1960s and yielded close to a million tonnes of lead, zinc and copper. Much of this was as sulphides dispersed through black mud filling a huge depression in the limestone. This was formed by acid from rotting pyrite dissolving the country rock. Extensive oxidation and remobilisation of the primary ores produced hundreds of thousands of tonnes of smithsonite, cerussite, malachite and azurite. Scores of rarer species, such as linarite, anglesite, brochantite, native silver and numerous arsenates were also present. Fig. 3. Malachite, from Tynagh, Co. Galway. 64mm x 35mm botryoidal and stalactitic mass dug out of the tips. Sadly, collectors were slow to learn of this treasure and most was sent to the crusher. By the time they did realise something glorious was going on, most was already turned into smelted metal. A fickle attitude on the part of management did not … Read More

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A mineralogical tour of Ireland (Part 2): Munster

Stephen Moreton (UK) In the second part of our tour of Ireland, we head for Munster, which occupies the southwest corner of the island. Geologically, the rocks are mostly inland Carboniferous shales and limestones, with Devonian sandstones forming the coastal peninsulas. All host mineral localities of note. Fig. 1. The four regions of the island of Ireland. Fig. 2. Munster in more detial. Starting in County Waterford, mineral collectors will tend to head for the copper coast – a group of nineteenth century copper mines centred on the coastal village of Bunmahon. The magnificent crystallised native copper and cuprite these mines yielded in the past are elusive nowadays. On the other hand, post-mining oxidation in the dumps and sea cliff levels and outcrops has produced an array of vividly coloured and sometimes rare secondary minerals. These include connellite, langite, atacamite, botallackite, brochantite, lavendulan and erythrite. The soft, wet, blue and green substances that coat the mine walls are amorphous gels that dehydrate and crumble to powder when removed to a dry environment. They are best left where they are. Fig. 3. Tankardstown Mine, Co. Waterford. The author is examining post-mining deposits of an amorphous copper-bearing gel. Mention should be made of the Croaghaun Hill beryl occurrence inland from the copper mines. In a small outcrop of conglomerate, one of many among the scrub, patches and sprays of slender, sky blue beryl prisms occur in a quartz matrix. Unfortunately, the rock is so tough it defeats even the largest sledgehammer. The … Read More

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A mineralogical tour of Ireland (Part 1): Leinster

Stephen Moreton (UK) The island of Ireland has much to offer the mineral collector, but is relatively unknown to most. This may in part be due to a lack of published information, although, for years, the troubles in the north also served to deter visitors for many years. This series of articles briefly summarises the principal mineral locations on a region by region basis. Fig. 1. The four regions of the island of Ireland. Fig. 2. Leinster in more detial. As the island is divided into four regions, Leinster, Munster, Connaught and Ulster (Fig. 1), which are in turn subdivided into counties, it seems appropriate to cover the island in this way. As the main ferry terminals for the Irish Republic are in Leinster many a trip to the country will start here. Leinster occupies the southeast region of the island and is the driest (or rather least wet) part of Ireland. Geologically, it offers the largest granite batholith in the British Isles, complete with metamorphic aureole, Carboniferous and Ordovician sediments and a scattering of basic igneous intrusions. County Wicklow dominates the mineral scene in Leinster. Fractures along the margin of the Wicklow granite have acted as conduits for much later mineralising solutions, giving rise to lead/zinc veins. These reach their best development in Glenmalure, Glendasan and Glendalough. Fig. 3. One centimetre spinel law twinned crystals of galena, from North Hero lode, Glendasan, Co. Wicklow. Fine schieferspar calcite and dark brown sphalerite have recently been found in Glendasan, while some … Read More

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Fossil bones from the North Sea: An easy to way to collect fossil remains from the Ice Age?

Dick Mol (The Netherlands) Introduction In 1874, the first known mammoth remains were brought ashore, trawled off the coast of the province of Zeeland, The Netherlands. Fishermen, fishing for flatfish, caught these fossils as bycatch in their nets. (A bycatch is a fish or other marine species that is unintentionally caught while catching certain target species and target sizes of fish, crabs and so on) A museum associate in Middelburg described these bones in an extensive research report. This resulted in a sound basis for ongoing study of the lost life found on the bottom of the North Sea between the Netherlands and the British Isles, about two million to 10,000 years ago. For years the fishermen brought their bycatches ashore. Usually, these were large bones and teeth, both of mammoths and whales. In fact, the North Sea bottom used to be a vast plain during the Ice Age with mammoths walking around in large herds and this area must have been a paradise for large mammals. Apart from the mammoth remains, other species like wild horses, giant deer, deer, lions, bears, wolves, rhinos and others have also been found. Fig. 1. An upper molar of a woolly rhino, Coelodonta antiquitatis (BLUMENBACH). Thousands and thousands of woolly rhino remains have been fished from the southern bight of the North Sea between Britain and the Netherlands. Thousands and thousands of these remains ended up in Naturalis, the National Natural History Museum in Leiden. Today, this museum holds one of the largest … Read More

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Urban geology: The battery on the Sloterweg

Stephen K Donovan (The Netherlands) The city of Amsterdam in the Netherlands is surrounded by a great defensive earthwork on its landward side, the Stelling van Amsterdam (= Defence Line of Amsterdam), along which are a series of forts and batteries (Figs. 1A-E and 2). This major structure was built between 1880 and 1914. The principle feature of this defensive system is a raised earthen embankment or dyke, still imposing today although breached or flattened in many places to make way for modern developments, most commonly roads. The embankment is often flanked by two canals, one on either side. Fig. 1. (A, B) The Battery on the Sloterweg, Hoofddorp, Noord Holland, the Netherlands.(A) General view of the Battery, looking approximately northwest.(B) Nameplate.(C-E) Three views of the restored embankment between the Battery on the Sloterweg and Hoofddorp station.(C) The view southeast on the northeast side of the embankment from the R-Net bus stop (routes 300 and 310) at Hoofddorp station, looking towards the Battery. The cycle path crosses the bridge and continues away from the photographer. Note the blue tractor scraping the embankment.(D) The view southeast on the southwest side of the embankment from the R-Net bus stop at Hoofddorp station, looking towards the Battery (at the end of the path in the distance). Again, note the tractor scraping the surface.(E) The view northwest from the Battery, looking towards Hoofddorp station, showing the ‘exposure’ in the foreground, which was particularly productive of builders’ rubble, including lithic fragments.(F) Details of the granite … Read More

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Urban geology: An inselberg in Rotterdam

Stephen K Donovan (The Netherlands) The Low Netherlands, much of which is below sea level, is a broad area of the country that (very approximately) parallels the coast and is kept ‘dry’ by major works of civil engineering (IDG, 1985, pp. 6-7). Geologically, it is a flat expanse of Holocene deposits; most of the author’s experience is in the coastal plain (de Gans, 2007), where I both live and work. There is no significantly older geological deposit or feature anywhere in this region – no coastal cliffs, mountains or quarries to tempt the attention of the wandering Earth scientist. So, it is commonly the ex situ that demands the geologist’s attention rather than the in situ. For example, I have commented previously on such diverse topics as the use of imported limestone to make a false natural bridge (Donovan, 2014), various aspects of building stones (for example, Donovan, 2015, 2019) and gabions mimicking sedimentary bedding, at least from a distance (Donovan, 2018). Of these examples, the natural bridge is the most exotic; although such a bridge might be expected in karstified limestone landscapes almost anywhere, my own experiences of them are limited to the Antilles (Miller and Donovan, 1999; Donovan et al., 2014). In this article, I describe a further man-made structure mimicking an even more exotic geomorphological phenomenon, most closely associated in the minds of Earth scientists with Africa. It is a structure that I have, until now, only known from textbooks – I refer to a mock inselberg … Read More

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Urban geology: Brush up your neoichnology

Stephen K Donovan (The Netherlands) It was a dry Saturday in February (2014), but it was blowing a gale such that some gusts stopped me dead in my tracks. My son, Pelham, and I were out for a walk in the Haarlemmermeersebos, which roughly translates as ‘the wood of the lake of Haarlem’. The area where we live, which includes the nearby Amsterdam Schiphol International Airport, is the bed of a lake that was drained over 160 years ago. So it is a flat, featureless, polder landscape (Ministry of Foreign Affairs, 1985, pp. 10-11), apart from what man has put into it; and is criss-crossed by canals and, less commonly, dotted by lakes. The canals in the Haarlemmermeersebos landscape that are intended for water transport are few; rather, most are part of the water management system in a landscape that is below sea level. In such a landscape, the weekend geologist must look hard for ‘exposures’. Building and decorative stones are always of interest (Donovan, 2014). Beachcombing on the nearby North Sea coast can be rewarding, particularly after storms when Quaternary peat clasts are washed up on the shore (Donovan, 2013). But, in truth, there is more potential for the geomorphologist than the geologist or palaeontologist. The point of our excursion in a gale was to model palaeontological collecting and to hone our observational skills in the open air. I had discovered a path paved with many hundreds of recent sea shells and rare flint pebbles in the Haarlemmermeersebos (Fig. … Read More

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Alluvial gold: A geological model (Part 2)

Philip Dunkerly (UK) In A geological model for the alluvial gold environment (Part 1), the first part of this article, I discussed how alluvial gold is found and suggested a geological model for alluvial gold deposits. (Readers are recommended to have another look at that part to remind them of the model.) In this second part, I now turn to the nature of the gold itself. Fig. 1. Gold bullion bars of 400 troy oz. Fig. 2. Sites from around the world. Gulch gold Gulch gold is the coarsest that exists in any part of a river system. If nuggets (pieces of gold weighing more than 0.1g) are present, they will mostly be found in gulches (narrow ravines), provided suitable traps are present, such as irregular bedrock. In gulch alluvium, the vast majority of the gold will be found on, or in crevices within, the bedrock. Gulch gold is often coarse and angular and may contain silicate debris, especially quartz. As examples, gold from Victoria Gulch on the Klondike was described as “sharply angular”. In the Ballarat gullies, some enormous nuggets were found and Canadian Gully yielded nuggets of 50.4, 34.7 and 31.4kg. At Bendigo, White Horse Gully, a 17.8kg nugget (including some quartz) was found. (Interestingly, of a list of 92 Victorian nuggets, 34 came from localities specifically named “gullies”.) Finally, in the Sierra Nevada of California, most of the gold is from gulches or minor streams close to croppings. Fig. 3. Old hydraulicking operation of terrace gravels, note … Read More

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Alluvial gold: A geological model (Part 1)

Philip Dunkerly (UK) Mankind almost certainly first found gold when a yellow, glint from the bottom of a stream bed attracted the attention of one of our ancestors in pre- historic Africa. Ever since, the allure of gold – its colour, improbable density, malleability and scarceness – meant it has been prized, and great efforts have been made to accumulate it. Most ancient peoples venerated and coveted gold and used it for decoration, and empires used gold as a store of value and a medium of exchange. The Egyptians are known to have used gold as early as about 5000 BC, followed by many others, including the Romans, the Incas, the Spaniards and, of course, the Anglo-Saxon invaders of North America, Africa, Australia and New Zealand. Fig. 1. Spectacular Roman paleogravel workings at Las Medulas, NW Spain, now a World Heritage site. The mouth of one of the tunnels through which water was released from a header tank is visible in the shadow. Fig. 2. Panoramic view of Las Medulas, worked by sluicing using water brought through canals up to 60km long. Though gold was won from hard-rock deposits in ancient times, most gold until perhaps 1900 was won from riverbeds, and was traditionally called alluvial or placer gold. Prospecting for alluvial gold required relatively little equipment and always attracted hardy pioneers willing to forego the comforts of society in the hope of ‘getting rich quick’. The gold they found – if they were lucky – could almost instantly be … Read More

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Book review: Fossilien im Alpstein: Kreide und Eozän der Nordostschweiz (Fossils in the Alpstein: The Cretaceous and Eocene of north-eastern Switzerland), by Peter Kürsteiner and Christian Klug

This is clearly one for our German speakers, of which I am glad to say there are many. However, this glossy and excellently produced hardback, covering the fossils of the Alpstein region of Switzerland, may have general appeal to anyone interested in the identification and study of fossils from various parts of the world, despite being written in German.

Small is beautiful: fossil voles as stratigraphic aids

David Mayhew (The  Netherlands) When you walk through the countryside,youwill not often come across a vole. However, they are present in most habitats and are one of the most successful groups of small mammals, widely distributed in both Eurasia and North America. Broadly speaking, Voles are blunt- nosed, short-eared, mouse-like rodents and many of them are specialised for burrowing. They can eat hard vegetation such as grasses that are very abrasive due to the presence of silica spicules. Therefore, many species of voles haveevolvedcontinuously growing cheek teeth (that consist of molar teeth: three upper and three lower) as well as the continuously- growing incisors that are typical of rodents. Finding fossil remains of voles This evolution took place largely in the last three million years.For this reason, fossil remains of voles are very useful for helping us unravel the stratigraphy of deposits from the Pliocene and Pleistocene periods. And, as you can see from the photographs, they are beautiful objects in their ownright. We are talking here of quite small fossils, for example, the molar teeth are between 1 and 3mm in size. So, where and how are they found? Many, even thousands of specimens, can be found in cave and fissure deposits, such as Foxholes at High Wheeldon in Derbyshire. Often, such localities have no stratigraphic context other than the fauna contained in the sediments. However, the material may be very complete (skulls, lower jaws and limb bones). Fig. 1. Remains of vole Microtus sp. from Foxholes cave, High … Read More

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From sharks’ teeth to sea urchins: A palaeontological expedition through the Northern Alpine foreland in Austria

Dr Robert Sturm Over the last few decades, local amateur collectors, as well as professional palaeontologists, have collected a large number of fossils from quarries and sandpits on the northern margin of the Central European Alps. With the help of these marine and terrestrial fossils, it has been possible to reconstruct a picture of the animal life in the early Tertiary (about 50Ma). Interestingly, many animals that lived in these ancient tropical habitats can still be found in the oceans and on the coasts today. Main geological characteristics of the area Fig 1. Upper image: geological map of the Northern Alpine Margin and the alpine foreland near Salzburg in Austria. Lower image: north-south profile through the northern alpine lithology and the alpine foreland clearly indicating that single geological units are superimposed from south to north as a result of the movement of the African plate northwards. As you can see from the map in Fig. 1, the geology of the northern Alpine margin can be subdivided into three main, east-west striking units: The Flysch Zone (green) is situated directly north of the limestone Alps, the exposed part of which reaches a width of up to 20km. The grey marls and sandstones belonging to this unit were deposited in a deep, oceanic basin during the Cretaceous (144 to 65Ma) and measure more than 3,500m in thickness. In the south, the Flysch Zone was successively superimposed on by the Northern Limestone Alps.The Helvetic zone (violet) borders on the Flysch Zone in the … Read More

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Three dimensional photography of fossils (Part 3): Ammonites from the Northern Limestone Alps of Austria

Dr Robert Sturm As a result of their great diversity in shape and long-lasting occurrence in earth history (from the Devonian to the Cretaceous), ammonites are equally fascinating objects for the professional and amateur palaeontologist. By definition, ammonites exclusively comprise a group of extinct marine cephalopods that, according to the present store of knowledge, include about 1,500 genera and between 30,000 and 40,000 species. The shell size of adult animals ranged from a few centimetres to two metres in the case of Parapuzosia seppenradensis (Lehmann, 1981; Monks and Palmer, 2002). The introduction of ammonites into zoological systematics was carried out by Carl Alfred von Zittel in 1884, who defined the sub-class ‘Ammonoidea’. This unconventional term dates back to the first century AD, when the elder Pliny interpreted these fossils as horns of the ancient Egyptian god Amun. Since the petrified shells represent the most important relics of ammonites, information on their biology and anatomy is characterised by a number of uncertainties. For example, it is assumed that these cephalopods only possessed a small number of tentacles (eight to ten) and also an ink pouch, or bursa, for protection against natural enemies. Most species lived in a water depth of between 50m and 250m, where they mainly fed on crustaceans, foraminifers, and ostracods. Ammonites were also characterised by sexual dimorphism – the smaller individuals were males and the larger ones were females. Palaeontological determination of single species is chiefly based on the shape, size, sculpture and torsion of the shell, as … Read More

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The World’s longest death track: The last footsteps of an ancient horseshoe crab

Dean R Lomax (UK) A ‘big’ discovery In 2002, a wonderful discovery of a 9.7m-long trackway (ichnofossil) with the tracemaker (a horseshoe crab) preserved was made in a quarry near the village of Wintershof, north of the town of Eichstätt in Bavaria, Southern Germany (Fig. 1). Specifically, the specimen was collected from the Solnhofen Lithographic Limestones, Eichstätt Formation (Solnhofen Group), Hybonotum Zone, Riedense Subzone from the Late Jurassic (Tithonian). Fossils from Eichstätt are often confusingly thought to be from the area of ‘Solnhofen’, with the Solnhofen area being a world renowned Lagerstätte. Many exceptionally well-preserved fossil specimens have been collected from that area, including the famous fossils of Archaeopteryx. Fig. 1. Locality map of the fossil bearing localities within the Solnhofen area. Note the areas of Eichstätt and Wintershof, the locality of the trackway (WDC CSG-233). (Reproduced from Lomax and Racay, 2012.) However, many people are unaware that there are numerous localities that surround the area of Solnhofen, which yield many of the fossils from this famous geological unit. It has been suggested that several of the fossils found within the rocks originally laid down in the Solnhofen lagoons (which were part of an archipelago) are the result of mass storm events, during which organisms from the nearby Tethys Ocean were thrust into these anoxic lagoons during heavy storms. In many cases this was the beginning of the end. The horseshoe crab that produced this trackway was identified as Mesolimulus walchi. The taxon is fairly well recorded within the limestones … Read More

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Palaeozoic fossils from Central Europe: A geological expedition in the Southern Alps of Austria

Dr Robert Sturm (Austria) Unlike the British Isles, which contain large swathes of Palaeozoic rocks, Central Europe only features sporadic rock types belonging to this early geological era. Among the most salient geological terrains entirely or partially from the Palaeozoic are the Bohemian Massif, the Central Plateau in France, the Ardennes in Belgium and the Black Forrest in Germany. Within the alpine mountain belt, the frequency of Palaeozoic rock formations is even less, with such rock deposits being limited to the Greywacke Zone in the Central Alps, the Palaeozoic lithologies exposed around the city of Graz, the Gurktal nappe and the Carnic region/Karawanken in the Southern Alps. In this article, I will discuss some important Palaeozoic index fossils from the Carnic region that have been found by Austrian palaeontologists over the last few decades. Geology of the Carnian region in the Southern Alps – a brief overview When visiting the Carnic region in the early nineteenth century, the famous natural scientist, Leopold von Buch, expressed his fascination of the virgin landscape he came across with the statement that it was “a fully unknown area [that] has to be discovered and comprehensively described”. Since then, the Carnic region has acquired a high reputation among geologists and palaeontologists in Europe and, indeed, all over the world, because it represents an outstanding ‘picture-book’ containing 500myrs of earth history. In this area, there is a considerable amount of evidence of specific sections of this long period of geological time and especially for those prehistoric … Read More

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The “thick-shelled mussel” Pycnodonte (Phygraea) vesiculare: Germany’s “Fossil of the Year” 2017

Jens Lehmann (Germany) Thick-shelled oysters of the species Pycnodonte (Phygraea) vesiculare (Lamarck, 1806) are among the most common fossils of the late Cretaceous period of Europe. They are also known as “thick-shelled mussels” in the popular wisdom and the reason for this name is obvious when you have a look at a typical example (Fig. 1). Fig. 1. A large specimen of Pycnodonte (Phygraea) vesiculare, as typically occurring in the latest Cretaceous of Europe. From the Campanian of Haldem near Lemförde in Germany. This is an historically important specimen, because it belongs to the reference material of Arnold (1968) from this famous locality, which has produced many type specimens of fossils. GSUB L559. They can be seen in many museums, but, even more often, they are encountered during walks along the beaches under the chalk cliffs of England or around the Baltic Sea in continental Europe. A famous locality is the island of Rügen in Germany, where tourists can easily spot them (Fig. 2). Fig. 2. Collecting Pycnodonte from Late Cretaceous (early Maastrichtian) chalks is popular among tourists on the Isle of Rügen (Promoisel pit near Saßnitz) in northeastern Germany. (Photo by Martin Krogmann, 2014.) Therefore, it is not surprising that this extinct oyster species was selected as “Fossil of the Year” 2017 by the German Palaeontological Society (Paläontologische Gesellschaft) due to its ease of recognition (Kutscher 2017). Further reasons for the vote include its scientific and scientific-historical significance. This is the second time the society voted for a fossil … Read More

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Arthropleura – Germany’s ‘Fossil of the Year’ 2016

Jens Lehmann (Germany) Since 2008, the largest palaeontological association in Germany – the Paläontologische Gesellschaft – has awarded the crown for ‘Fossil of the Year’ for fossils that are of special scientific interest or that are commonplace in that they are on display in many institutions. A ‘Fossil of the year’ can also be easy to collect species, encountered by many amateur enthusiasts. Among others, the largest ammonite in the world in the museum of Münster and the spectacular dinosaur skeleton of Brachiosaurus from East Africa in Berlin have won the title. This is the fifth time the award has been given, but is actually the first time the crown has been given to a fossil species and not to an individual fossil find. This year’s title went to Arthropleura armata, a remarkable arthropod species resembling recent millipedes and centipedes (Fig. 1). However, details of the phylogenetic relationships of the order Arthropleurida to millipedes are still debated (for example, Krauss, 2003a, b). And the arthropleurids reached significantly larger dimensions, with a total length of more than two metres (Fig. 1) and, therefore, are the largest arthropods ever to have lived on land. The first occurrence of the genus Arthropleura dates back into the period of the massive coal swamps of the late Carboniferous and they became extinct at the end of the early Permian – during the first phase of the supercontinent Pangaea. Arthropleura lived 280 to 340mya, but related arthropleurids (order Eoarthropleurida) continued to exist into the Silurian. Fig. … Read More

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Tauern gold: The history of gold mining in the Central Alps

Dr Robert Sturm (Austria) Exploitation of gold deposits in the Hohe Tauern, in the Central Alps of Austria, has a long history: occurrences of this noble metal were explored for the first time about 2,000 years ago. Since the fourteenth century, the search for gold has been conducted on an industrial level, resulting in the production of 130km of tunnels and shafts, with the main centres of medieval gold production being the Gastein Valley, Rauris, Heiligenblut, Fusch and, later on, Schellgaden. In the second half of the fifteenth century, all of the gold found in the Central Alps was sold to Venice, but from the year 1501, the noble metal was exclusively used for indigenous minting and, therefore, all gold mines came under the archbishop’s control. Fig. 1. Map showing the position of the Hohe Tauern National Park (green) in Austria and the main locations of historical and current gold exploration. The economic zenith of gold exploitation in the Central Alps was reached in the middle of the sixteenth century. At this time, three families – the Weitmosers, Zolts and Strassers – dominated the mining industry in the Gastein Valley and in Rauris. In 1557, 830kg of gold (corresponding to about 27,000 ounces) and 2,723kg of silver were hauled from the mines. However, 50 years later, gold mining ceased completely. The main reason for this economic collapse was the total exhaustion of all lodes of ore that had been exploited in the Hohe Tauern until that time. Furthermore, only ‘visible’ … Read More

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Cameos from Ancient Greece and Rome: Small but precious treasures

Dr Robert Sturm (Austria) When talking about precious or semi-precious gemstones, most people think of the diamonds they cannot afford or rubies, agates and similar well-known minerals. But, only a few people know that gemstones have been subjected to various carving techniques since ancient times, making from them small but marvellous works of art. Basically, the most commonly applied technique of gem carving is the so-called cameo, which, in most cases, features a raised relief and, therefore, differs from the so-called intaglio that has an engraved or negative image. Ancient cameos date back as far as the third century BC and were first produced in Greece, where they mainly served as jewellery for the Hellenistic kings and their retinues. In ancient Rome, cameos and similar works of art were highly popular, especially in the family circle of the Emperor Augustus (27 BC to 14 AD), who developed a great affection for this kind of art. Roman cameos generally continued Hellenistic styles and were marked by only very few innovations. The extremely high quality of gem carving (which will be discussed more in detail below) was maintained until the end of the second century AD, but, with the beginning of the third century AD, it was subject to a sharp decline that can also be seen in other fields of art. During the European Middle Ages, cameos were highly appreciated by the aristocracy, but, nevertheless, the production practices developed in the ancient world found their application only in very rare cases, … Read More

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Peñon de Ilfach: Did it jump or was it pushed?

Mark Wilkinson (UK) The Spanish coastal town of Calpe is dominated by the towering massif of the Peñon de Ilfach (Fig. 1). The 332m, steep-sided summit is surrounded by the Mediterranean Sea on three sides and connected to the land by a relatively narrow neck, rather like a gigantic sea stack. Unless you are prepared to do some serious rock climbing, the summit is accessible only through a tunnel bored for the purpose, complete with rope hand-rails. The half-hour walk to the summit, through a small nature reserve and visitors centre, gives fantastic views of the surrounding coast and mountains. Fig. 1. The Peñon de Ilfach with Calpe in the foreground. Tower blocks for scale. To the geologically minded, the Peñon offers another aspect. It gleams white in the Mediterranean sunshine, so it’s not too difficult to guess that it is made of limestone. But bedding is quite tricky to spot, especially from a distance. I’ve often wondered as to how such an isolated feature came to be there – and why is the bedding so hard to see? It was almost a relief to purchase the Geologists Association guide to the area and discover that “even experienced geologists may find the bedding hard to locate”. Phew, it’s not just me then! And how did the Peñon come to be so isolated from the other limestone hills in the area, the nearest of which is several kilometres away? Was there a massive sheet of limestone, which has simply been eroded … Read More

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Milos: A must-visit island destination for the geo-traveller

Ken Madrell (UK) Introduction Most visitors to the Cyclades islands will gravitate to the island of Santorini to see its stunning caldera and the magnificent sunsets from the northern town of Oia. The island is part of the Aegean volcanic arc formed by the subduction of the African plate under the Aegean Sea. About 3,600 years ago, the island suffered a violent volcanic eruption in which much of the rocks were removed, causing the volcano to collapse and produce the caldera. About 160km northwest of Santorini and also situated on the volcanic arc is the island of Milos. The island is a more peaceful alternative to the bustling crowds of Santorini and the rich volcanic soils are renowned for producing excellent wines and vegetables. Milos is a ‘must-visit’ island for any traveller with an interest in geology visiting this area of the Greek Islands. Fig. 1. Santorini. Northward view of the eastern caldera wall and rim. There are a number of designated Geo Walks on the Milos (see How to Explore the Island below). These can be up-loaded at https://www.milosminingmuseum.com/en/the-museum/miloterranean-geo-walks/. Readers may also wish to refer to these while reading the text of this article. The geology of Milos The oldest rocks are a basement of metamorphic rocks, such as schists, gneiss and quartzites of Mesozoic to Palaeogene ages (250 to 25Ma). The basement rock is overlain by Miocene to early Pliocene (25 to 5Ma) conglomeratic and calcareous rocks. The main character of the island we see today was formed … Read More

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De Kaloot: A fossil treasure trove in The Netherlands

Frank Wesselingh (The Netherlands) In the southern Delta area of the Netherlands, several beaches exist where the collector can collect a wide variety of Tertiary and Quaternary fossils. One of the well-known beaches is that of Cadzand that has been particularly rich in fossil shark teeth (but also fossil shells). The richest of the Dutch localities, a beach called De Kaloot, was under threat because of a proposed container terminal that would obliterate most, if not all, of the beach. Fig. 2. A view down the bank at De Kaloot. Fig. 3. A walk along the beach at De Kaloot. De Kaloot is located on the North bank of the Westerschelde estuary. Tidal currents are very powerful, eroding the seabed in front of the beach down to 60m in depth. As a result, five different fossiliferous formations in the subsurface are revealed. The fossils from these deposits find their way to the beach, especially after heavy SW storms. The fossil finds are diverse but comprise mainly fossil shells of Pliocene and Quaternary age. We estimate that over 500 species have been collected from De Kaloot. In addition, from these shells, shark teeth, vertebrate remains, bryozoans and other fossil groups have been collected. On some days, about 75% of the shell banks consist of fossil shells. This locality is unrivalled in its species richness, and it is said that it is under threat. In 1999, the Province of Zeeland, where De Kaloot is located, announced plans to build a container terminal. The … Read More

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Giant file clams: A common fossil as an exciting document of Earth history

Jens Lehmann (Germany) Plagiostoma – a record of about 200 million years Are there any boring fossils out there in the ground? I do not think so and to demonstrate this, an “ordinary” fossil find is focussed on here. We are talking about “just” a mussel, but one that belongs to an extinct group and even this alone makes it exciting. Plagiostoma is a member of the file clam family. This genus is only known from the fossil record and appeared probably in the Permian and certainly by the Mid-Triassic period, about 240 million years ago. This genus became extinct at the Cretaceous-Palaeogene boundary – according to the most recent timescale dated 66 million years ago. At least two dozen of species have been described so far. The shells of Plagiostoma are moderately inflated and can reach the size of a hand, with an oblique oval outline. It is a common fossil, for example, in the Muschelkalk (Middle Triassic) in the Germanic Basin and quite a few continental countries. It is also well known from the Blue Lias of Southern England and stratigraphic equivalents, and can be frequently found at Monmouth Beach in Lyme Regis, a world-famous spot for fossil hunting. The giant Plagiostoma The species frequently encountered at Lyme Regis is Plagiostoma gigantea and the name already suggests that it is a giant amongst the representatives of the genus. The specimens figured here (Fig. 1) are of moderate size, with a total length of each about 8cm, but there … Read More

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Flints in the Late Cretaceous Chalk of NW Europe

Rory Mortimore (UK) Flint in the Late Cretaceous Chalk: links across the European platform In a recent issue of this journal Paul Taylor wrote “We are very fortunate in Britain to host one of the most remarkable deposits in the entire geological record, the Chalk” (Deposits Issue 55, 2018, p.35, see Bryozoans in the English Chalk). Perhaps equally remarkable are the bands of flint associated with the pure white chalks (Figs. 1 to 3). Flints have attracted human attention since pre-historic times with some flint bands providing the preferred source rock for manufacturing stone-age tools (for example, the Late Turonian Floorstone Flint at Grimes Graves near Brandon in Norfolk, England (Figs. 4 to 6a and b; Mortimore and Wood, 1986), or the geologically much younger Early Campanian flints in the Harrow Hill Flint Mines in Sussex, England Fig. 7). Subsequently, Brandon flints were used as the vital spark for guns (that is, gun-flints, Skertchley, 1879; Shepherd, 1972) and these have been found as far afield as eastern North America (used in weapons of the American revolution) to the Fijian Islands in the Pacific (from Royal Navy guns). In the modern era flint remains a material of concern in engineering causing damage to core-drilling operations, tunnelling machines (Fig. 8) and cable trenching machines onshore and offshore northwest Europe. Flint also impacts the ease with which piles can be driven into chalk. To fully appreciate flint as a material and to assess the impact of flints on engineering operations has required establishing … Read More

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Colonising skeletal substrates: Encrusters and borers from the Upper Jurassic oyster shell beds of Central Poland

Michał Zatoń, Adrian Szewczuk and Mirosława Kuziomko-Szewczuk (Poland) Skeletons of live and dead marine animals very often serve as a secondary hard substrate for various organisms that either encrust it (encrusters) or bore into it (borers). The terminology for encrusters and borers varies. However, following Paul Taylor and Mark Wilson’s latest and widely accepted terminology for organisms inhabiting hard substrate, those associated with skeletal substrates should be referred to as episkeletobionts and endoskeletobionts, respectively. Another, more convenient term is ‘sclerobionts’, as it refers to any organisms (encrusters or borers) inhabiting any hard substrate (biogenic or lithic, including skeletons of both live and dead organisms). Sclerobionts are diverse in marine ecosystems today, being represented by such various groups as sponges, corals, bivalves, polychaetes, bryozoans and brachiopods. They were also diverse in the past, being represented by different taxa during different epochs. And like today, they inhabited various kind of hard substrate, such as stones, shells and reefs, creating specific benthic communities that changed and evolved over time. Sclerobiotic assemblages are also very useful in ecological studies. As encrusters firmly adhere or cement to, and borers drill into, the substrates they colonise, they are always found as fossils where they had actually colonised. And as they play a crucial role in ecosystems, being both constructive (for example, as a component of reef frame-builders – the so called ‘binders’) and destructive (for example, as reef bio-eroders), there is a growing scientific interest in their ecology, which focuses on both Recent and past environments. … Read More

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Geoarchitecture of some Romanesque churches in Aquitaine, France

Nouvelle-Aquitaine (New Aquitaine) is a vast region of southwest France covering more than 30,000 square miles. Between 1154 and the end of the Hundred Years War in 1453, much of the region was under British control. Links with Britain are still strong today, both through tourism and the large ex-patriate British population, particularly in the Dordogne, known jokingly to locals as ‘Dordogneshire’.

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Encrinus liliiformis – a crinoid from the Triassic that made a career for itself: Germany’s fossil of the year, 2019

Jens Lehmann (Germany) Despite their common name ‘sea lilies’, crinoids are animals but not plants, although they look like a flower (Fig. 1). They are related to the sea urchins, sea cucumbers and starfish, groups that are unified as echinoderms (see, for example, Broadhead and Waters, 1980). Crinoids consist of a “root”, a stem built of many disc-shaped elements (columnals) and a crown. Fig. 1. A crown of the famous crinoid, Encrinus liliiformis, from a Muschelkalk quarry in Northern Germany. The fossil shows a slightly opened crown, with a number of arms besides each other. The name “sea lily rock” is often associated with the basal plates of fossilised crowns that resemble a lily flower and were collected as “Lilienstein” (“lily rock”) by gentlemen collectors in Central Europe, particularly in the nineteenth century (Fig. 2). In fact, crinoids were encountered for many hundred years and thus were already known by the famous Swiss and German scientists (respectively), Conrad Gessner and Georgius Agricola, in the sixteenth century. However, these early geoscientists only found the fossils, since living crinoids can only be found in the deep sea and were not known by the scientific community before the eighteenth century. This is the reason why the isolated stem elements called columnals occur in millions of specimens in the German Muschelkalk (Middle Triassic) were mystically called “Boniface pennies” or “Witch money”, before they were recognised as parts of crinoids. Fig. 2: Even details of Germany’s “Fossil of the Year 2019” are beautiful, like these … Read More

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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

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