Category: geology

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Philadelphia fossils and ferns

Paul Murdoch and Clay Carkin (USA) Our hectic, 48-hour adventure had its beginning many years ago, courtesy of the WWW. My friend, Clay, a sixth grade science teacher in Freeport, Maine, had originally contacted the Calvert Marine Museum fossil club’s website about purchasing fossils to use in his classroom. Although I live outside of Philadelphia in Pennsylvania, I visit the Calvert County Maryland area quite frequently and have a keen interest in the fossils there. Clay and I chatted a few times, and I subsequently agreed to stop by his school and do a fossil presentation. We also discussed going fossil hunting together. However, our schedules never worked until this year. Clay will tell you that Maine is a poor state to live in, if your passion is fossil collecting. Therefore, he and I planned a 48-hour blitz of the better-known fossil localities within a 100 mile or less radius of my home. My wife and I met Clay and his wife Joye at the airport at noon on Friday and, immediately, Clay and I set off to some fossil-hunting grounds. On Friday, the first and only stop for Clay and me was a trip up I-95 and the New Jersey turnpike to the Cretaceous outcrops of marine fossils in the brooks of Monmouth County, New Jersey. After a short detour due to road construction, we were in the Ramanesson Brook, sifting through the sand and pebbles and finding sharks’ teeth. Clay was a natural, finding a shark’s tooth, Squalicorax … Read More

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A field guide to Barbados (Part 4): Bridgetown and the South Coast

Stephen K Donovan (The Netherlands) The area considered in this part of the guide is outlined in Donovan & Harper (2010, fig. 1C) and Fig. 1 of this article. As in other articles in this series, the starting point is Bridgetown. Fig. 1. Locality map showing the positions of Stops 1 to 5 on or near the south coast of Barbados (after Donovan & Harper, 2005, fig. 8). Only those roads relevant to this excursion are shown. This map should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: A = Grantley Adams International Airport; abc = ABC Highway; C = Six Cross Roads; O = Oistins; 1 = the Barbados Museum, Bridgetown (Stop 1); 2 = South Point Lighthouse (Stop 2); 3 = Foul Bay (Stop 3); 4 = Woodbourne Oilfield (Stop 4); 5 = Chapel Quarry (Stop 5); coastline stippled.  Stop 1: The Barbados Museum The Barbados Museum and Historical Society was founded in 1933. Its museum occupies St Ann’s Garrison, a nineteenth century British military prison. It is situated in the parish of St Michael, southeast of the central part of Bridgetown, behind the Garrison Savannah racetrack. The museum has displays covering many aspects of Barbadian history and life, including natural history, prehistory and maps. The library is an important research resource, containing 5,000 books, monographs and articles on the culture and natural history of the island. Articles about the island’s natural history, culture and history are … Read More

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A field guide to Barbados (Part 3): Northern Barbados

Stephen K Donovan (The Netherlands) Stop 1: Arawak Cement Quarry The area considered in this part of the guide is outlined in Donovan & Harper (2010, Fig. 1b) and Fig. 1. As with other articles in this series, the starting point is Bridgetown. Drive north from the Bridgetown area on Highway 1, the main west (or leeward) coast road, which is constructed on the Lower Coral Rock and overlies superficial deposits. Fig. 1. Locality map showing the positions of Stops 1 to 4 in northern Barbados (after Donovan & Harper, 2005, fig. 7). Only those roads relevant to this excursion are indicated (including the track to Stop 4). This map should be used in conjunction with the geological map of Poole & Barker (1983) and any tourist road map. Key: C = Content; Ch = Checker Hall; G = Greenidge; T = Trents; 1 = Arawak Cement Quarry (Stop 1); 2 = Animal Flower Cave, North Point (Stop 2); 3 = limestone cliffs west of North Point (Stop 3); 4 = Cluff’s Bay (Stop 4); coastline stippled. The First High Cliff and the Middle Coral Rock are close by in the east (Speed & Cheng, 2004). This coast has been developed for tourism and has neither the magnificent sea cliffs of the east coast, nor the impressive Atlantic breakers seen in the previous excursion. To the west, two submerged barrier reefs, at 22m and 70m water depth, are separated from the coast by a submerged wave cut terrace (MacIntyre, 1967). … Read More

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A field guide to Barbados (Part 2): The coastal geology of southeast Barbados

Stephen K Donovan (The Netherlands) and David AT Harper (Denmark) Introduction This article is the second part of a field guide to Barbados, the first part of which is A field guide to Barbados (Part 1): Introduction. The areas visited by different the excursions outlined in Parts 2 to 6 of this guide are shown in Fig. 1. All itineraries commence from the Bridgetown area and the itinerary outlined in this part is rewritten after Donovan and Harper (2002). The words in italics and bold appear in the glossary at the end of the Part 1. Fig. 1. Relative positions of field excursions described in this field guide (after Donovan & Harper, 2005, fig. 5). (a) Southeast Barbados (Part 2). (b) North Barbados (Part 3). (c) South Barbados (Part 4). (d) Scotland District (Part 5). (e) Central Barbados (Part 6). Charles Taylor Trechmann DSc, FGS (1885-1964) (Fig. 2) was an anachronism, a twentieth century gentleman geologist and archaeologist. He was an amateur with sufficient private means to dedicate his time and use his scientific abilities to make an original contribution to his chosen field of study, an original thinker with a desire to use his observations to interpret broad geological phenomena. He devoted his time to research on Malta, Gibraltar, New Zealand and, particularly, northeast England and the Caribbean. He published over 80 monographs and research papers on geology and archaeology, including at least 40 on the Caribbean (Donovan, 2003, 2008, 2010a). Fig. 2. Charles Taylor Trechmann, DSc, FGS (1884-1964) … Read More

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BOOK REVIEWS dinosaurs england fossils geology palaeontology scotland

Book review: Fossils of the Kimmeridge Clay Formation, edited by David M Martill and Steve Etches (pictures editor, Robert F Loveridge)

I always wait expectantly for the publication of a new Palaeontological Association guide to fossils and, when they turn up, I am never disappointed. This is undoubtedly another triumph. This guide attempts to bring the diversity of its flora and fauna together in a single work, for the first time.

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Book review: Measures for Measure: Geology and the Industrial Revolution, by Mike Leeder

I sat down to read this over Christmas and what a good read it turned out to be. The appropriate word is ‘eclectic’ – because Measures for Measure is written for all us with an interest in the industrial history of Great Britain, and its impact on the landscape, economy, social history and culture. It’s a great read as it dots about linking places and ideas together, with the link always being the geology.

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Agates: A brief introduction to agates in the UK

P W Forster (UK) I have many years of experience collecting and cutting agates. It was my wife who originally had an enthusiasm for these beautiful semi-precious stones and it was because of her enthusiasm that I developed an interest that has now become an obsessive hobby for the both of us. Cabinets in our home evidence the wide range of specimen stones that an amateur collector can discover. Each specimen has identification labels and is catalogued to show the date and the region where it was found. Before starting my first collecting foray, I obtained as much information on the subject as was available. To this end, I found the book ‘Agates’ by H G McPherson most useful. (This book, together with ‘Agate collecting in Britain’ by P R Rodgers, has been extensively used in the writing of this article.) From my research, it became apparent that the Midland Valley of Scotland contained many of the best deposits of agates in Great Britain. With this in mind, we paid the first of many visits to the region. We started searching along the east coast of Ayrshire. This coast abounds with small coves of pebble beaches and large stretches of andersite larvas that stretch out to sea. During the first year, we amassed a large amount of what we thought were agates, but closer examination revealed that we had collected some colourful specimens of jasper as well as some lovely quartz pebbles. This first attempt had revealed that those agates … Read More

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A field guide to Barbados (Part 1): Introduction

Stephen K Donovan (The Netherlands) This is the first of six articles that will introduce the geology of the Antillean island of Barbados. It is an expanded and more detailed guide derived from two earlier publications (Donovan & Harper, 2005, 2009). The structure of the guide will include a summary of the geology of the island (in this part) and five, one-day field excursions for the geologically-biased tourist. These excursions will introduce the stratigraphy, structure and geological history of Barbados (Figs. 1 and 2), a small Antillean island shaped like a contorted teardrop, about 34km long by 24km at its widest. Fig. 1. The principal features of the geological history of Barbados summarised in a single section at Spring Bay, parish of St. Phillip, on the southeast coast. Professor David Harper (University of Copenhagen) is looking northwest, towards Ragged Point (Fig. 2) and admiring the angular unconformity between the allochthonous Palaeogene basal complex (=Scotland Beds) and the overlying autochthonous bedded limestones of the Pleistocene Coral Rock. A visitor to the island, who wants to undertake fieldwork, should hire a car. The only other reliable forms of transport are bus and taxi. While cheap, buses tend to stick to the main routes, particularly in the countryside. However, the size of the island means that localities are rarely more than a few kilometres from a bus stop. If money is no object, a taxi driver will be happy to drop you at a site in the morning and collect you at a … Read More

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Bringing the best out of your fossils: Tips on the preparation of fossils

Byron Blessed (UK) As many of us know, a good day’s fossil hunting rarely stops when we leave the beach. However, many people do not know what to do with a fossil once they’ve found it. So, here are a few pointers in the art of fossil preparation. This article will not only outline what equipment you will need but will also give you general guidelines on how to use it. Fig. 1. The various stages of prep-work. Nautilusastercoides, found in the Upper Lias, Sandsend,near Whitby in North Yorkshire, UK. The first thing that any fossil preparator needs (and it isn’t something you can buy) is a lot of patience. The second thing you need is … a lot of patience! This cannot be stressed enough. Fossil preparation is a long, sometimes boring and laborious process and it is all too easy to damage specimens by being too hasty! It must also be noted that fossil preparation is not something that can easily and successfully be taken up overnight. Most of the best preparators have been in the business for decades. To think that you can immediately match their skills over night is naïve to say the least. Like any good hobby or job, practice makes perfect. In addition, it can be very costly to get all the right kit so this can become an expensive hobby. Washing specimens under the tap is a good, first step and will reveal hidden detail by removing unwanted mud and sand. Many clays … Read More

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The Deccan Traps, India (Part 3): Evidence of recent tectonic activities in Deccan basalts

Mugdha Chimote (India) The term ‘Quaternary’ is derived from the Latin word “Quaternarius” (meaning “four”, such that the Quaternary is “the fourth great epoch of geological time” in the now-abandoned system of dividing geological time). It refers to the most recent period of the Earth’s history, covering a span of about 1.77 million years extending up to the present day. The Quaternary System is divided into Pleistocene and Holocene Series. The term Holocene was introduced for the part of Quaternary that contains only living species. It covers the last 10,000 period of the Quaternary. The Quaternary has witnessed some very important events of great consequence, characterised by dramatic climatic changes. It witnessed repeated glacial and interglacial periods, more so than any other period of geological history. Monsoonal wind patterns also developed during this period, and deserts were formed during the latter part of the Quaternary. Although the Quaternary recorded a few extinction events, a great biological diversity still exists on Earth. Most of the present-day species of vertebrates, invertebrates and plants are believed to have remained unchanged during this period. By now, you must have realised, the Quaternary is not a separate entity of geology. It rather refers to the time period ‘Quaternary’ and all the geological processes pertaining to that period. Quaternary rocks and sediments are the most recent geologic strata, which lie on the uppermost layers of earth and have been exposed to the least amount of erosion. As such, they are one of the most well studied … Read More

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How to identify a pterosaur tooth

Paul Pursglove (UK) Take a close look at the three teeth labelled A, B and C in Fig. 1. All of these teeth could have been sold by unscrupulous fossil dealers as pterosaur teeth. So, which is the real pterosaur tooth? Pterosaur teeth are very rare fossils and they tend to be difficult to identify in isolation. However, they do command a high price to a collector. Most people who research pterosaurs will take time to study the teeth and to compare them with reference collections and scientific papers which are held in repositories at universities and major museums. So let us look at some of the general rules for identifying the teeth of pterosaurs. Fig. 1. What teeth are these? Triassic pterosaurs These little beasties are as rare as it gets. They are only known from a few sites worldwide, and the major finds come from the Zorzino Limestone of Cene, near Bergamo in Italy and from the Preon Valley. Other isolated specimens are known from Greenland, Luxembourg, Austria and Texas. There is also a speculative specimen from the Rhaetic bone beds in the UK. Most of these pterosaurs have three cusped teeth which are very distinctive. I am not aware of any Triassic pterosaur teeth in private collections. Jurassic pterosaurs These pterosaurs are more numerous, but tend to be predominated by Dimorphodon, Pterodactylus or Rhamphorhynchus-like specimens. Rhamphorhynchus is a good example of the pterosaurs that have long dagger-like teeth; several other species have very similar teeth, which can occasionally … Read More

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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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Marvellous microfossils (Part 2): The fascination of Microfossils from the Gault of Folkestone

Joe Shimmin (UK) The beauty and variety of the microfossils of Folkestone’s Gault Clay cliffs has amazed me ever since I was about 14 years old. At about this time, I had the good fortune to see some samples sent to me by Jim Craig, who I had met at the site. These microfossils roused in me such enduring enthusiasm that I eventually wrote an article entitled Marvellous microfossils (Part 1): Collecting Microfossils from Folkestone on how to process Gault Clay to obtain. This is the second article on this topic. Apart from the fact that the Forams, Ostracods and other microfossils found in the residue left by wet- sieving Gault Clay are interesting and unusual, in themselves it is also a bonus that there are vastly more of these fossils, in terms of numbers, to be found than the larger fossils that people usually go there to collect. If you collected hundreds of these larger fossils from a site in one go, you might be seen to be selfishly depriving other collectors of the opportunity to collect some for themselves. However, within 1kg of Gault Clay, there are literally thousands of microfossils. Therefore, removing a few kilograms of Clay from the site will do no damage whatsoever. So, within reason, you can build up a huge collection of a vast variety of microfossils with minimal impact on the site. These reasons have led me from writing the article referred to above to attempting to write a small book (or, … Read More

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Book review: Strata: William Smith’s Geological Maps, with contributions by Oxford University Museum of Natural History, with a foreword by Robert Macfarlane

This book is truly sumptuous, and yet is also a comprehensive discussion of William Smith’s maps (including the revolutionary ‘A Delineation of the Strata of England and Wales, with part of Scotland’) and career. It is beautifully produced, printed on quality paper and the full colour illustrations are outstanding.

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Marvellous microfossils (Part 1): Collecting microfossils from Folkestone

Joe Shimmin (UK) The  Gault  Clay   outcrop,  at Folkestone  in  Kent,  is  a wonderful place to find all manner of fossils. Over 100 species of ammonite have been found and there are also barnacles, belemnites, bones (reptile and fish), coprolites, corals, crinoid pieces, crabs, crocodile teeth, fish teeth, gastropods, (deep breath) nautiluses, ccaphopods, shark teeth, vertebrae (bony fish, shark and, occasionally, reptile), worm tubes and more. These fossils can be found in the clay cliffs and also at the base of the cliffs, washed out from above. But there are other fossils to be found at Folkestone that are less conspicuous. Fig. 1. The cliffs at Folkestone. An individual, who is new to the site, may be forgiven for thinking that the larger fossils are all that Folkestone has to offer. If this were so, it would still be a fantastic location. The fact is, however, that this is not the case. Folkestone’s Gault Clay also has a rich and varied, beautifully preserved, microfossil fauna. Fig. 2. Enlarged images of microfossils from the Gault Clay at Folkestone. Microfossils are trickier to find and collect than their larger counterparts. They are hard to see, often quite fragile and difficult to handle. However, with a small amount of perseverance, along with a good technique and a few pieces of apparatus, anyone will be able find hundreds of these beautiful and intricate fossils and, in no  time,  build  up  quite  a collection. While on a fossil hunting trip to Folkestone, it is well … Read More

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The Deccan Traps, India (Part 2): Its geomorphology and stratigraphy

Mugdha Chimote (India) Fig. 1. The natural arch/bridge at Ahmednagar, Maharashtra (see text box below). The Deccan Traps occupy approximately 25% of the total of peninsular India, that is, the triangular shaped landscape of southern India. They traverse the states of Maharashtra, Karnataka, Madhya Pradesh, and Gujarat. The Deccan Traps are currently believed to occupy about 500,000km2 of northwest peninsular India. It is estimated that the total exposure prior to erosion (including the region beneath the Arabian Sea) is of the order of 15 million square kilometres (Krishnan, 1956) or even up to 18 million square kilometres (Todal and Eldham, 1999). The differences in estimations of the total area of the Deccan Traps resulted from the fact that, an unknown area of the Deccan Volcanic Province (DVP) was rifted away as the Cambay rift system moved south and the Seychelles-Mascarene Plateau, along with part of the DVP, migrated to the west. The earliest basaltic eruptions took place along the north-western margins of the Indian continent, that is, in the Nashik-Narmada region. Later lava successions were emplaced on the southern flank of the evolving volcanic edifice as India migrated northwards over the plume head. The last of the flows were erupted in the southern DVP near Belgaum in Karnataka. As a result, the thickness of the flows gradually reduces from north-western to southern region of Indian subcontinent. Given the massive extent and volumes of Deccan Basalts, extensive studies have been carried out over the years to better understand the petrography, geochemistry, … Read More

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The Deccan Traps, India (Part 1): The story of its genesis

Mugdha Chimote (India) Fig. 1: Deccan Traps exposed in Mahabaleshwar region of Maharashtra, India. Introduction Sandwiched between the Arabian Sea to the west and the vast Indian subcontinent to the east, the Western Ghats, a haven for trekkers and travellers, are a 1,600km long range of mountains along western edge of Deccan Plateau. Also known as “Great Escarpments of India”, the range extends from Gujarat in the north to Kanyakumari in the south. The Ghats traverse the states of Maharashtra, Karnataka, Kerala, and Tamil Nadu. They comprise of more than 39 wildlife sanctuaries, reserve forests and national parks. The Western Ghats were declared as one of the eight hottest ecological hotspots in the world in the year 1988, as the area is home to nearly 325 globally threatened floral, amphibian, fish, bird and faunal species. Famous hill stations such as Mahabaleshwar, Panchgani, Munnar, Wayanad, Coorg and Ooty are among some of the perfect weekend getaways and popular tourist attractions here. Thanks to the rich ecological reserve and tourist attractions, Western Ghats were awarded the title of UNESCO World Heritage Site in 2012. The Western Ghats however cover just a small portion of Deccan Traps (see also box: Kaas Pathar below). Deccan is an anglicised word derived from the Sanskrit word “Dakshin”, meaning south (the region is located in the southern part of Indian subcontinent). “Traps” mean step-like features. Thus, the Deccan Traps are step-like volcanic features found mainly in Southern India. The laterally extensive basaltic lava flows of the Deccan … Read More

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On the origins of buffalo wings and chicken fingers by means of unnatural connexion, or the preservation of flavoured races in the struggle for clarity

Carl Mehling (USA) Things aren’t always what they seem. The fluidity of information and the frailties of human memory allow for a lot of corruption. Innocent assumptions are made. Sloppy mistakes take place. Unforeseeable accidents occur. And deliberate subterfuge is always there as an option when these others fail. Throw a little time at them and mis- and disinformation get lithified, entrenching them in the human psyche and culture. Fighting for accuracy is a continuous battle. A wing and a prayer Once almost considered throw-away parts of the bird, chicken wings have soared to unimaginable heights since their transformation into ubiquitous bar food in the 60s. Buffalo wings are so absurdly popular in the US that possibly-calculated rumours often circulate that a wing drought is coming, causing the requisite panic. Sports bars riot over this dearth, prompting half-serious suggestions of breeding chickens with more than the pathetic pair that their lineage has provided. Anything this popular inevitably spawns feuds over priority: Who gets to claim bragging rights for such a powerful, lasting and lucrative phenomenon? Fig. 1. Were the origins of Buffalo Wings in a science pub or a brew pub? This certainly happened with Buffalo wings. I’ll spare you the gory details, but although hard to prove definitively, most have settled on the idea that the Anchor Bar in Buffalo, NY began this tangy trend in 1964. However, as it turns out, it can be demonstrated that the origin of buffalo wings actually happened elsewhere, and in 1962. Or, … Read More

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Bryozoans in the British Jurassic

Dr Paul D Taylor (UK) Fossil collectors often overlook, or worse discard, bryozoans. There are several reasons: some bryozoans are small and not easily spotted in the field, others are mistaken for non-descript sponges or algae, while bryozoans cemented to the surfaces of other fossils can be cursed for detracting from the value of the main fossil. But bryozoans are fascinating fossils in their own right and ought not to be ignored. Bryozoans are a morphologically varied phylum of colonial invertebrates. The myriad of colony-forms they exhibit reflect adaptations that evolved to allow them to prosper as immobile colonial animals living on the seabed and feeding on passing plankton (Taylor, 2020). The majority of the more than 6,000 bryozoan species living today possess resistant skeletons of calcium carbonate, and the calcareous skeletons of fossil bryozoans are abundant globally in rocks ranging back to the Early Ordovician, some 480 million years. Fossil bryozoans in Britain occur in marine sedimentary rocks from every post-Cambrian geological period except the Triassic. Ordovician bryozoans can be found in the Welsh Borderlands and in southern Scotland, Silurian bryozoans in the West Midlands and Shropshire, Devonian bryozoans in Devon, Carboniferous bryozoans in the Pennines and other places where the Carboniferous Limestone outcrops, and Permian bryozoans in the Magnesian Limestone of northeast England. Previous contributions to Deposits have described bryozoans from the Chalk of Late Cretaceous age (Taylor, 2018) and the Pliocene Coralline Crag of Suffolk (Taylor and Milne, 2009). Here, I focus on British Jurassic bryozoans. Jurassic … Read More

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BOOK REVIEWS dinosaurs england fossils geology historical / biographies palaeontology

Book review: Dinosaurs, Evolution and the Woman whose discoveries changed the World: the Fossil Hunter, by Shelley Emling

Mary Anning was clearly one of the most significant characters of eighteenth century science and possibly of all time, particularly in the realm of palaeontology. I am not sure that she is quite as unknown (certainly in the UK) as the American author this excellent little biography claims, but she certainly should be better known.

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Baths and batholiths

Deborah Painter (USA) “Look over there!” I exclaimed as I stood on the grounds of a manufacturing plant and stared across the tracks of the Atchison, Topeka and Santa Fe Railroad to the east of the plant. I was pointing at several mountains a few kilometres in the distance. “That mountain is glowing!” Standing alongside me was James, the plant’s maintenance supervisor. “I guess because I’ve seen this for the past 14 years, I don’t even pay attention anymore” was his reply. The mountain was not glowing due to any internal source but because exceptionally light toned granites captured and reflected rays of sun streaming from behind a December cloud cover (Fig. 1). Fig. 1. The mountain glowed in the shaft of light, as the sun peeked from behind a cloud. (Credits: Deborah Painter.) The mountains looked like this for most of that chilly day and the glow shifted from mountain to mountain (Fig. 2). Fig. 2. A remarkable combination of December light and greyish-white toned granites produced this day-long glow in the Bernasconi Hills. (Credits: Deborah Painter.) The granitic mountain cluster was in Perris, a city in Riverside County, California in the USA. I have had the good fortune to visit this county twice recently on two separate and unrelated trips a few years apart. And my friend, Mike Ramsey, had been with me on both trips to this same county. He was with me and a friend late in November when we visited another friend in nearby Moreno … Read More

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Earth history in miniature: Zircon under the microscope

Dr Robert Sturm (Austria) The mineral zircon (more correctly, orthosilicate zircon or ZrSiO4) is an important accessory mineral in various rocks of the earth’s crust, but most of all of igneous rocks with the mineral composition of granite. An accessory mineral is a mineral comprising less than about 10% of a rock and which therefore plays little or no role in naming or classifying that rock. Fig. 1. The typical appearance and morphology of zircon crystals that have been separated from various granitic rocks. As well as its ubiquitous appearance in magmatic, metamorphic and sedimentary rocks, zircon is a remarkable mineral due to its high resistance to mechanical and chemical processes within the earth crust. Therefore, it is very useful as a protolith indicator in different types of crustal rocks (Speer, 1982). (A protolith indicator is a mineral in a metamorphic assemblage that provides information on the chemistry of the host rock, within which it had originally grown.) As a result of the repeated formation of magmatic overgrowths around older ‘inherited’ zircon cores (like the rings of an onion), evidence of several stages of earth history are preserved within a single grain and can be scientifically analysed (Sturm, 1999, 2004). Once these overgrowths have been identified, the phases of crystallisation included in accessory zircon can be attributed to geological time periods. This is achieved by radiometric dating, based on the mineral’s content of radioactive uranium and thorium, and the redistribution of these isotopes and their daughter products. Another important characteristic … 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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europe fossils geology palaeontology

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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europe fossils geology palaeontology

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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europe fossils geology palaeontology

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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Geological field trip through Scotland: Basalts from the Isle of Skye

Robert Sturm The Isle of Skye is a part of the Inner Hebrides in the north-west of Scotland. It has a total area of 174,000 hectares and has an irregularly shaped coastline that is typical of the British Isles. Since the early nineteenth century, the island has become a centre of geological research, because rocks of different geological periods are exposed there. For instance, the gneisses of the Lewisian complex were formed in the Proterizoicum, 2,800Ma and, therefore, are some of the oldest rocks in Europe. On the other hand, intrusive and extrusive igneous rocks can be assigned to magmatic events that covered wide parts of the island during the Tertiary. This event, which took place about 60Ma, resulted in the development of the Atlantic Ocean in its present form. In more recent times, two ice ages, which affected the island 26,000 years ago (the Dimlington glacial) and 11,000 years ago (the Loch Lomond glacial), resulted in the formation of a partly spectacular glacigen landscape (a landscape formed by the ice) with sediments that are of high interest for geological research. Fig. 1. Geological map of the Isle of Skye (modified after Anderson & Dunham 1966) illustrating the high variability of rocks that can be found on the island. Impressive evidence for the Tertiary volcanism is provided by the plateau lava series (these are horizontally stacked layers of lava), mainly exposed in the north and west of the island. These extrusive rock formations probably reached a thickness of 1,200m before … Read More

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