Concretions in sandstones of the Inner Hebrides, Scotland

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

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Rudists: A fossil story

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

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Three-dimensional photographs of fossils (Part 1): Gastropods from the Paratethys Ocean

Dr Robert Strum (Austria) About 23Ma, the Paratethys Ocean covered a large area, including what is now the Vienna basin and Alpine Foreland. This mostly shallow ocean was a habitat for a large number of plant and animal species, which included numerous marine gastropods, some of which are discussed in this article. This is the first of three articles on three dimensional photograph of fossils. In this article, to give the reader a better impression of their volume and shape, the fossil shells have been photographed by using the stereoscopic technique I describe in Three dimensional photography of fossils (Part 3): Ammonites from the Northern Limestone Alps of Austria. Today, beautiful shells with various shapes and patterns, of recent marine gastropods, can be collected in large numbers along Mediterranean and tropical coasts. While this seems normal to us, finding marine molluscs in Austrian sandpits, far away from any ocean, is a little more surprising. Of course, the simple answer is that these shells are fossils from the ocean referred to above, which once covered what is now Central Europe. The fossils commonly originate from the Tertiary period, which lasted from 65Ma to about 1.8Ma. More precisely, the fossils are from the Eggenburgian of the Miocene (23Ma to 5.3Ma), named after Eggenburg, a lovely village north-west of Vienna. (The Eggenburgian is a Lower Miocene stage of the Central Paratethys regional chronostratigraphic classification.) Fig. 1. Map exhibiting the position of Eggenburg in Austria and the arrangement of single sampling localities and related sights:1. … Read More

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Saltwick Bay, North Yorkshire

Emily Swaby (UK) Saltwick Bay is located along the Yorkshire Coast, between Whitby and Robin Hood’s Bay, and can be accessed from the Cleveland Way, which passes the spectacular Whitby Abbey. The geology of the area is predominantly Jurassic in age, with the site often being described as a ‘fossil treasure trove’. The bay yields a wide variety of specimens, including common ammonites and belemnites to rarer finds such as marine reptiles, Whitby Jet and even dinosaur footprints. Even though Saltwick Bay is close to Whitby, it is still a very productive locality and you never leave empty handed. In fact, it is a good location for families and beginners. The walk to Saltwick Bay from Whitby itself is approximately 2.4km and provides many picturesque views of the abbey, the harbour entrance and the remarkable coastline. The steps leading down to the beach are located just past Whitby Holiday Park, but can sometimes be slippery during winter months. It is also recommended that you check tide times for the area before arriving, as high tide can limit the extent of accessibility and could potentially cut you off. Fig. 1. The steps descending down the cliff to the bay. Once you have made your way down the steps, fossils can be found immediately among the scree or in the shingle. However, it is advisable stay away from the base of the cliffs, as rock falls are common, with loose fragments of shale constantly falling down. Fig. 2. The Nab is a … Read More

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

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

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Trouble with pyrite

 Fred Clouter (UK) On Wednesday, 26 April 1882, the Queenborough Chemical and Copperas Works were auctioned off, heralding the demise of the copperas industry on the Isle of Sheppey. Green copperas was used to make sulphuric acid or vitriol, chemical manures and dye stuffs. Being in Queenborough Castle in the year 1579 I found there one Mathias Falconer, A Brabander, who did in a furnace that he had erected there, trie to drawe very goode brimstone and copperas oute of a certain stone that is gathered in great plenty upon the shoure near untoe Minster on the isle”. This extract is from ‘Lambard’s Perambulations of Kent’ and is probably the earliest known reference to a ‘chemical’ factory in Britain. Fig 1. Poster advertising the sale of Queenborough Chemical and Copperas Company. The first reference that I have that links copperas with the collection of fossils is found in the ‘Life and letters of Edward Lhwyd (second Keeper of the MUSEUM ASHMOLEANUM) Oxford March 28th. 1695’. Below is an excerpt from ‘A Museum of the Early seventeenth Century’ By Cyril Edward Nowill Bromhead, BA, FGS, FRGS. (Read 18Th. June, 1947) referring to the Lhwyd letter: If you could setle a correspondent in the Isle of Shepey to save us all the Crampstones the copras-women pick up for a month or two, I would now fall about a Lithologia Britannica: and so contrive it that the first tome shall consist of onely teeth and bones of fish.” (Sharks’ teeth were called ‘cramp … Read More

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Jurassic Coast (or is it?) with the Geologists’ Association

Mervyn Jones (UK) Since 2012, the Geologists’ Association (GA) has put on annual field trips to the Dorset coast led by Prof John CW Cope (of the National Museum Wales), who is author of the definitive Field Guide No 22. The second edition was published in April 2016 (Geology of the Dorset Coast (2nd ed)). In fact, the trips were started to celebrate the publication of the first edition of the guide. The Dorset Coast is often equated with the ‘Jurassic Coast’ when, in fact, the geology stretches from the topmost Triassic, near the Devon border, through Jurassic and Cretaceous successions, to Eocene deposits at Studland. For this and other reasons, it attracts amateur geologists in large numbers. John’s guide provides essential information including descriptions of the succession and practical guidance about access. What’s missing are the entertaining stories that John Cope can provide and the context provided by exploring inland a bit. Day 1 – Saturday (1 October) For our fifth field meeting, we met up in Lyme Regis (in the car park next to the newly-restored house originally owned by John Fowles – see below) – a town to stir the heart of any geologist. Our mission for the weekend was to look at the unconformity below the Cretaceous, as it oversteps the older Jurassic and Triassic strata progressively in a westerly direction. En route, we observed the instability of the cliffs and suffered the same ourselves, as we scrambled over the boulders and shingle. On this occasion, … Read More

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Fossil crustaceans as parasites and hosts

Adiël Klompmaker (USA) Who would like to carry a parasite? I bet not many people would like to have one or more. They are nevertheless very common in humans and in other organisms, and can affect entire food webs including keystone species. They tend to be small compared to the host and the vast majority of them are soft-bodied. Despite their small size and soft appearance, they can affect the host substantially, for example, leading to a reduced growth rate and less offspring. Much of the same holds true for crustaceans – they are affected by parasites and can act as parasites themselves. For example, parasitic crustaceans are found among the isopods and copepods. Given the widespread occurrence of parasitism in and by crustaceans today, a fossil record of such parasitism may be expected. Swellings in fossil crabs and squat lobsters So what does the fossil record look like? I have been fortunate to have worked on this under-studied field of research. During my PhD research, I found various swellings in fossil crabs and squat lobsters (decapods from the superfamily Galatheoidea) during and after field work in northern Spain in reef carbonates from the mid-Cretaceous (upper Albian). They appeared to occur regularly in the back part of the carapaces of these crustaceans. Fig. 1. Bopyrid isopods from the species Orthione griffenis (large female and small male), removed from the right gill chamber of a modern mud shrimp (Upogebia pugettensis). (Photo by Stephen Ausmus, USDA Agricultural Research Service, http://www.bugwood.org.) This swelling … Read More

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Interesting borings

Stephen K Donovan (The Netherlands) It is unfortunate that the miscellaneous holes, pits and depressions produced in wood, rocks and skeletons (bones, shells and tests), both pre- and post-mortem, by a wide range of invertebrates, plants and fungi, are called borings. A less inspiring name for a fascinating suite of structures is hard to imagine. Borings represent a range of activities, although most can be interpreted as feeding – predation or parasitism – or construction of a domicile (=home). Borings may or may not be assignable to a particular species, although shelly borers, such as gastropods, may rarely be preserved in situ (see, for example, Baumiller, 1990, text-fig. 1). And borings are real evidence of ancient organism-organism or organism-substrate interactions that would be impossible to determine based on the evidence of skeletal remains alone. Therefore, borings breathe life into a dead fossil record and, in truth, are exciting. Small round holes in shells Borings vary in complexity from the complicated interconnected chambers of clionoid sponges and the trace fossil (ichnogenus) Entobia Bronn (Fig. 1), to the simplicity of small round holes, formerly included in the ichnogenus Oichnus Bromley, although this is now considered a junior synonym of Sedilichnus Müller (Zonneveld and Gingras, 2014). Fig. 1. Entobia cretacea (Portlock, 1843), the Natural History Museum, London (BMNH) S.9015, clionoid sponge boring preserved in flint, chalk drift (=clay-with-flints?), Croydon, Surrey (after Donovan and Fearnhead, 2015, fig. 2). Note the cushion-shaped chambers connected by fine canals; the small tubercle-like structures in the centre of … Read More

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Hunting the Dutch beach of Hoek van Holland for fossils

Bram Langeveld (The Netherlands) Holland is a small country that lies for the most part below sea level, which can be quite problematical. However, if you are a fossil collector hunting for the fossils of animals from the Weichselian (Last Ice Age) and early Holocene, it is not such a bad thing. That is because the Dutch government regularly has sand deposited on Dutch beaches, which is dredged up from the bottom of the North Sea to fight erosion of the beaches by the sea. Taking this one step further, Holland also has large scale land reclamation projects, where whole new parts of Holland are made by spraying sand from the bottom of the North Sea onto a location close to shore until it rises above sea level. Fig. 1. Map of The Netherlands showing Hoek van Holland. Much of this sand is dredged up by big, specially equipped vessels, called trailing suction hopper dredgers, from a location known as ‘Eurogeul’, which is the route for big vessels to reach the port of Rotterdam. Here, the sea is approximately 13m deep, but is deepened to 30m, by removing sand from the bottom. Much of this sand is used to reinforce beaches and for land reclamation projects. However, it is not just sand that is dredged up … Fig. 2. Simple timescale of the late Pleistocene and Holocene.The North Sea Plain If we could travel back in time – approximately 30,000 to 100,000 years ago – we would find ourselves in … Read More

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