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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Disappearing Dunwich

Roy Bullard (UK) There are many places around the coastline of the British Isles that are quite simply majestic and, in their own unique ways, full of magic. Dunwich lies between the lovely town of Southwold and the village of Sizewell on the East Coast of England in the county of Suffolk. It is a coastal area that is easy to include in this category and is a place that I love to visit. However, as you sit there on the shore watching the cliffs and the North Sea, it is hard to imagine that so much has been lost since the time when Dunwich was once a large, thriving community. Fig. 1. Sandy cliffs of Dunwich. My aim in this short article is to take a look at the present state of this coastline and compare it with the coast as it once was before huge amounts of coastal erosion had taken place. In addition, I will take a look at the area’s history and mention, in passing, one of its well-worked, mythical tales. A steeply sloping shingle beach now lies in front of the cliffs at Dunwich. These cliffs have changed a lot over time but, over the past few years, erosion has decreased substantially. The cliffs today are overgrown and this indicates a significant slowdown in the rate of erosion. However, with the ongoing threat of climate change and rising sea levels, the local residents and council have joined together to act now to protect the northern … Read More

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Mysterious blue orbs of K2 granite

William Wray (USA) K2 granite is found near the base of K2, the mountain it is named after, in the Himalayas from a rarely visited site. K2, also called “Mount Goodwin Austen” is the second highest mountain in the world, rising to 8,611m (28,253 feet). K2 got its name from the British surveyor TG Montgomerie. The “K” comes from the Karakoram mountain range and the “2” means that it is the second tallest peak recorded. Fig. 1. An oval cabochon made from K2 granite found on K2, a mountain between Pakistan and China, revealing several bright blue azurite stains. The blue azurite stains formed after the granite cooled and hardened. (Photo by the author. Specimen from the William Wray collection.) K2 granite has impressive splashes of blue circles or orbs on its surface. The blue circles are azurite inside of white K2 granite rock. The white granite is fine-grained and composed of the minerals: quartz, feldspar, muscovite and biotite. The azurite stained parts of the granite, making blue dots, which range from a couple of millimetres to about two centimetres. Azurite has a relative hardness of 3.5 to 4 on the Mohs hardness scale, but assumes the hardness of the white granite, because the azurite is only a stain. The azurite formed after all the other minerals in the granite had cooled and hardened. With a hand lens or microscope, azurite spheres reveal that the azurite appears along the edges of mineral grains, in tiny fractures in the granite, and … Read More

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Colourful bluffs in Long Island recall the most recent ice age

Deborah Painter (USA) Imagine a tremendous piece of land moving equipment that scraped up the soil and some of the surface bedrock from four states within the United States’ Eastern Seaboard, carrying and dragging it all the way, before dumping it on a ridge off the shoreline. That is what essentially occurred with the final advance of the Wisconsinian ice sheet, the only one which left glacial deposits visible in New York State today. Long Island is a ridge of Cretaceous bedrock with glacial deposition. The moraines there have not been ground into sandbars and spits along the western end of the north shore as much as elsewhere, because of the sheltered nature of the Long Island Sound. Therefore, shoreline bluffs expose rocks as well as glacial loess. Fig. 1. Fishermen’s Drive takes you to the loess deposits. To park at the beach requires a permit. (Photo by JB Steadman.) If you find that your journeys take you to New York City, one of the world’s largest metropolitan areas, try to make time to visit Caumsett State Park at Long Island Sound. My own visit began when planning a visit to New York State’s Long Island to see my friend, Joyce Raber. She suggested various things that we might do: go to a Broadway play, go shopping and so forth. However, my list of things to do was typically “eco-tourist”. I wanted to visit the famed American Museum of Natural History in Manhattan, then see nearby Central Park, where the … Read More

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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

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Sand for arenophiles

 Dawn Walker (UK) As long as I can remember, I have collected interesting bits of rock, looking at their shapes and colours, and wondering what they were. This was fine as long as I had a garden shed of my own to keep them all in. I read some geology as a hobby and began to recognise a few of them, but then age caught up with me and I had to move to a smaller flat and there is simply no room for more rocks. In fact, I had to dispose of many of my old ones. Eventually, it dawned on me that sand is also rock, although made up of rather small pieces, and would not take up too much room, so why not collect that? After all, I was living at the seaside. Fig. 1. These translucent green grains from South Point, Hawaii, are olivine. The pounding surf erodes a forty-nine-thousandyear- old volcanic cinder cone made of olivine. As the cone erodes, the olivine crystals become beach sand. Very few beaches consist of pure olivine; however, if there is olivine in a sand, that indicates it is a volcanic region. Magnified 250 times. I really thought I had invented this hobby and was amazed to discover on the Internet that I was an arenologist or possibly an arenophile (from the Latin arena, meaning sand). There is an International Sand Collectors Society in America, which I joined, and now have email friends all over the place, with whom … Read More

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