The Edinburgh Geologist

Magazine of the Edinburgh Geological Society Issue No 50 Autumn 2011 The Edinburgh Geologist Issue 50 Autumn 2011

Cover Illustration Since this is the 50th issue of The Edinburgh Geologist, it seemed appropriate to have some gold on the front cover. These grains (the largest only a few mm across) were panned from the Kildonan Burn, a tributary of the Helmsdale River in Sutherland (BGS image P243790). For more on the story see Graham Smith’s article — Does Scotland have a golden future? BGS images are reproduced by permission of the British Geological Survey ©NERC. All rights reserved. Acknowledgements Production of The Edinburgh Geologist is supported by grants from the Peach and Horne Memorial Fund and the Sime Bequest. Published September 2011 by The Edinburgh Geological Society (Charity registered in Scotland number SC008911) www.edinburghgeolsoc.org Editors Phil Stone Bob McIntosh [email protected] [email protected] British Geological Survey Murchison House West Mains Road Edinburgh EH9 3LA ISSN 0265-7244 Price £2 net editorial

A 50th birthday, our debt to the Torridonian, a new National Museum and some very fancy steps.

An editorial ramble by Phil Stone

This issue of The Edinburgh Geologist Services centre) is not complete. is number 50. I wonder how many Perhaps something should be done people still have a complete run? about that. Elsewhere EG appears It goes out to all members of the more cherished, and I was much Edinburgh Geological Society (that’s cheered to note the beautifully about 500) and though most of you bound copies preserved in the are local to the city there are plenty London library of The Natural History spread across the rest of Scotland, Museum, sharing shelf-space with the quite a few in other parts of the UK adjacent Scottish Journal of Geology and a fair number based in far-flung and Transactions of the Royal Society parts of the world, where EG seems of Edinburgh. Overall, the implication particularly appreciated. Example: is clear: if you seek literary prestige at Our Dynamic Earth I recently write for The Edinburgh Geologist. met Professor Ian Dalziel (Clough Not convinced? Remember in the Medallist 2003–04) of the University last issue we featured an article of Texas at Austin. Ian was in town on early life in Scotland by Martin for a symposium on Antarctic geology Litherland — it was picked-up and but assured me that when EG arrives the story re-run by The Oban Times he takes it to his favourite bar and no less. enjoys it with a margarita. The EG is also sent to places where its survival Progress to number 50 has not been is pretty-much guaranteed, such as entirely smooth and painless, as is the British Library and the National evident from the irregular publication Library of Scotland. Its fate in some timetable and the missing years. of the Scottish University Libraries Nevertheless, we have arrived, is a bit more hit and miss, and I thanks to the joint efforts of a discovered that even the set held succession of editors and scores of by the British Geological Survey in contributors, and reaching our 50th the Murchison House library (now anniversary is obviously worthy of rebranded as a Research Knowledge some celebration. Looking back

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to issue number one, put together Bound copies of The Edinburgh by the founding editors, Helena Geologist in The Natural History Mansbridge assisted by Andrew Museum’s library, London. Note McMillan, we find contributions that there is still plenty of space on the Dalradian, the Southern for future issues. Thanks to Adrian Uplands, and a newly discovered Rushton for the photograph. mineral deposit in Shetland. What could be more appropriate than a scientific retrospective? The original authors — Doug Fettes, Euan Clarkson anniversary is Graham’s focus on gold and Graham Smith — all agreed to in Scotland. the proposal and their reappraisals of the same topics, together with So what of the future? Can we look editorial reflections from Helena and forward to The Edinburgh Geologist Andrew, make up the bulk of this, number 100? Should it appear, it will issue 50 of The Edinburgh Geologist. undoubtedly be in a very different Particularly felicitous for our 50th format, and probably medium, to

2 editorial number 50. Despite the style changes 2011, came even more remarkable experienced by EG so far, it has evidence, not just for bacterial remained a printed document, with activity but for multicellular life hard copy posted to recipients. That (Paul Strother and others, Nature, mode of operation seems unlikely doi: 10.1038/nature09943). What’s to last. Whilst relative printing costs more, this multicellular life had have diminished, postal rates have made it out of the ocean into the risen to near-punitive levels and there lacustrine, Torridonian environment, has been a general flight of scientific to become the Earth’s earliest non- publication from words and pictures marine eukaryotes. Organic-walled on paper to digital files on the web. It microfossils had first been described seems to me inevitable that sooner or from the Torridonian in 1907, in later EG will follow the same route. I, the Geological Survey’s ‘North-west for one, shall regret the passing of the Highlands’ memoir, but the recent printed page and the consequential resampling and modern investigation metamorphosis of libraries into takes the interpretation a lot farther. research knowledge centres housing I doubt whether these early Scottish nothing but computer screens. But of colonisers were much to look at, but course there will be compensations. just possibly we are all descended EG 100 may be part of an from that Torridonian slime. interactive geo-social network as yet unimagined. Even so, for my part, in Edinburgh rock the highly unlikely event that I am The summer saw the opening in still around, I’d hope to have my feet Edinburgh of two splendid new up and be enjoying a good book. geological attractions; one designed as such, one conceived as something More early life in Scotland very different. In the previous issue of The Edinburgh Geologist, number 49, we At the end of July we celebrated the featured evidence for the first signs long-awaited opening of the National of life in Scotland. One report from Museum of Scotland after the November, 2010, claimed a chemical mammoth redevelopment of what signature of bacterial activity from 1.2 had been the Royal Museum. I’ve billion year-old Torridonian strata, only had the opportunity of a quick reinforcing previous interpretations look around so far but am much of sedimentary structures from the impressed by what I’ve seen — and Diabaig Formation as indicative relieved that real rocks and fossils of microbial mats. Then, in April still form the core of the geological

3 editorial exhibits, even if some specimens Steps are now Martin Creed’s ‘Work seem a bit short on explanation. No. 1059, 2011’. The geological In this issue of Edinburgh Geologist connection comes from this piece we have an excellent ‘insiders’ of public sculpture having involved viewpoint from Yves Candela and Creed in resurfacing each of the steps Peter Davidson describing the (originally Carmyllie Flagstones from philosophy behind the new displays Angus) with a different ornamental and providing an introduction to marble — which means that sizeable what can be seen. I’m sure that many slabs of 105 of such rocks are now of you reading this will have visited laid out for inspection in close already, or be intending to, so let’s juxtaposition. The ornamental stones, hear your opinions for inclusion provided by an Italian supplier but in the next issue of EG. For some cut to size and shape in Leith, are reason, I was particularly pleased to sourced from all over the world, spot a coelacanth. What item caught from as far afield as Afghanistan your eye? and Bolivia, but I can’t help but be disappointed that not a single Scottish In complete contrast to the carefully rock was included, nor indeed any planned museum displays was the from the rest of Britain. But of course fortuitous geological extravaganza that wasn’t the point. To quote from provided in June by the opening the Fruitmarket Gallery’s informative of the refurbished Scotsman Steps. brochure (which lists the trade names This landmark spiral stairway runs of all of the stone varieties used — I down from Edinburgh’s North particularly like the sound of Fior di Bridge adjacent to The Scotsman Pesco Fantastico): Hotel (formerly the HQ of The Scotsman newspaper) to Market “Creed himself has described the Street, and is contained within an work as a microcosm of the whole octagonal tower constructed of world – stepping on the different Prudham Sandstone from the north marble steps is like walking through of England. The Steps had fallen the world. into disrepair and had been closed off for a number of years, but have Work No. 1059 . . . is an exercise in now been colourfully restored as an adding and subtracting by degrees. To artwork commissioned by Market make it, Creed started from nothing, Street’s Fruitmarket Gallery with the and added something. The process support of various other public and of addition, though immensely private benefactors. Accordingly, the complicated, involving architects,

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planners, engineers, stone cutters, A selection of the renovated builders etc, results in an intervention Scotsman Steps. whose deceptive simplicity seems almost to take the addition away (though extravagantly marble and chromatically beautiful, the steps are Scotsman Steps’. Any volunteers? still only steps, after all).” Quite apart from Martin Creed’s intention that his work should I guess that geologists, if involved emulate walking through the world, at all, are lumped above into the geological perspective would add ‘etc’. But geological interest is to that experience journeys through certainly there in abundance, with time, through long-lost environments, textural, petrographic and even and through the depths of the Earth’s palaeontological features all laid out crust. Of course, Creed has also set for inspection. So what we urgently up a technical experiment into the need is a ‘Geological Guide to the relative durability of the different

5 editorial lithologies. The different types were selected and positioned on aesthetic considerations within an artistic concept and some, I suspect, are not generally used for paving. How they stand up to the assault of myriad feet, aggressive cleaning and winter salt remains to be seen but first impressions of a few steps are not encouraging. My advice is to take a good look as soon as possible before any deterioration sets in — and don’t forget to send your impressions to The Edinburgh Geologist.

Another image perhaps?

6 a few words from our founding editors

A few words from our founding editors

Helena Mansbridge (Butler) writes: telling the story of geological research and endeavour in an accessible When I graduated with a geology manner has remained an essential degree in 1974 I joined the feature. Keep up the good work! Edinburgh Geological Society, as many of us did. I looked forward Andrew McMillan writes: to receiving the Scottish Journal of Geology and read it enthusiastically This is a piece of sheer indulgence. but was aware that many of the Back at the beginning of the eighties amateur members of the society when I was Membership Secretary, would find it very academic and of someone (may be it was Colin Will) limited interest. In 1976 over ‘high gave me a Peanuts cartoon which I tea’ in Crief, after a very enjoyable unearthed recently. Snoopy is seen EGS fieldtrip to Glen Lednock, I drafting the minutes of the Cactus suggested that there might be a Club. It went as follows: “The place for a more general-interest Secretary will read the minutes of publication of the Society in which the last meeting.” “A suggestion was current research in geology would be made that we purchase a computer discussed with an amateur audience to keep track of our membership.” in mind. There was considerable “After the laughter died down, we interest in the idea and after a period had refreshments”. of due deliberation, the Edinburgh Geologist was born. I edited the first That’s just one perspective on 17 issues with invaluable assistance what life was like in the formative from Andrew McMillan — and many years of The Edinburgh Geologist, others who contributed a wide range first published in 1977. Before the of enlightening articles during my days of mass usage of PCs, word time as editor. processing was only just emerging as the ultimate solution to document I am delighted that the Edinburgh and magazine production. For the Geologist is still going strong after 34 early editions we used to provide years and has reached its ‘Golden typed up clean copy to printers at Edition’. It is clear from the content of the University of Edinburgh, and they recent issues that the original aim of would run off the required number

7 a few words from our founding editors of A4 stapled copies – sufficient to mind with his ‘Strange Earth’ for members who were resident in series which ran and ran. And then and around Edinburgh. I had been there were excursion reports, the delighted when the concept of the sort that didn’t suit more formal magazine for members became a Proceedings. These accounts could reality in 1977 with Helena Butler as be very amusing although the poetry editor. Thank you to Euan Clarkson, was usually worse than William Norman Butcher and the late Wally MacGonagall. Mykura for their support for this new enterprise. The Scottish Journal I’m really pleased that Phil Stone and was not everyone’s cup of tea and Bob McIntosh have picked up the it was good, particularly for non- baton of editorship thus reviving the professional geologists, to have an fortunes of this excellent magazine informal magazine in which short which went into hibernation for a articles, local geological news, book year or so. They have succeeded reviews and even crosswords (I in matching their predecessor Alan had great fun drafting some) were Fyfe’s editions which really did put welcome. I joined Helena in a co- The Edinburgh Geologist up there editorial role in 1979, and used as an attractive and professional the position to cajole colleagues to compilation. Of course, today’s produce interesting material. There technology allows them to do was no house style for diagrams formatting things that we could only and the editors were sole referees. dream of, but the standard of articles A more professional looking format makes for a very readable magazine. was introduced in 1980 when Congratulations on reaching the my sister-in-law Val suggested she half century! Here’s to all of the could produce the camera ready editors who have had a hand in copy on her new word processor steering the magazine. I hope it goes and the university printed issues in from strength to strength even if, as a neat A5 format. Over the years the pace of change accelerates, it we were blessed with some regular becomes necessary to transmit our contributors. Bill Baird springs contributions electronically!

8 new geology exhibits in the redeveloped national museum of scotland

New geology exhibits in the redeveloped National Museum of Scotland

by Yves Candela and Peter Davidson

More than six years after the start of the project and three years after the closure of the Royal Museum, the redeveloped National Museum re-opened to the public on the 29th of July. The outside of this familiar Survival Window on the World Adventure Victorian building has largely retained Planet its unique character, but a major new feature is apparent: two street-level entrances have been opened into the bowels of the museum, the basement area where collections used to be stored.

Window on the World

Restless Sixteen new galleries have emerged Earth from the redevelopment project and L3 nine of these now feature a mixture of geological and palaeontological specimens (Figure 1). Geology is

most prominent in ‘Restless Earth’ Animal Discoveries World + and ‘Earth in Space’ which focus Wildlife Panorama on the geology of the Earth, and its Window on the World

Earth in place in the solar system and the Space

L1

Figure 1 Maps of the redeveloped museum. © National Museums Scotland. EiS — Earth in space, Wild Pano — Wildlife Panorama, Discov — Discoveries, Rest Window on the World

Earth — Restless Earth, Adv Planet — Entrance Hall Adventure Planet.

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9 new geology exhibits in the redeveloped national museum of scotland universe, respectively. ‘Restless Earth’ educated. They may be there to drink is entirely dedicated to displaying in the sheer beauty of objects and geological specimens and showcasing their environment. For that reason, the geological processes that have we have designed the museum’s shaped, and continue to shape, the displays to be aesthetical as well Earth. as educational, and this approach is fully applied to the geological Displaying the specimens specimens. Our objects are used in The newly refurbished galleries three different ways: 1) to interpret present exhibits in a more the main themes of the exhibition; multidisciplinary manner than 2) to showcase the collections, by previously. The systematic display displaying adjacently specimens with of fossils by species within a no apparent relationship to each phylum is often seen by the public other — a similar philosophy to a as too didactic or patronising. In traditional ‘cabinet of curiosities’; and developing these new galleries, we 3) as aesthetic or fascinating objects, have taken the best ideas of the with interesting stories related to creators of 19th Century museums, them. who wanted to establish a special dialogue with the visitor. Our We will now give a quick overview galleries retain their emphasis on of some of the geological specimens the specimens but merge them with you will encounter on entering the the most recent developments in museum, then talk about ‘Earth exhibition technology and design to in space’ and ‘Restless Earth’ in form an exciting mix of interactive more details. First of all, a cut and exhibits featuring some outstanding polished monolith of fossiliferous items from the collections of the limestone with Gryphaea arcuata National Museums Scotland. We (a.k.a. ‘the Devil’s Toenail’) stands seek to demonstrate that a modern in the ‘Entrance Hall’ to welcome museum can combine real objects the visitors. The interpretation of with modern technology and up-to- the specimen includes a mixture of date design concepts to create truly scientific fact and popular myth. This exhilarating experiences for the visitor specimen was chosen as an ‘attractor’ that will inspire them and excite their and fits into the third category curiosity to learn more. mentioned above. It is a new acquisition, collected by museum Of course, many members of the staff from a Site of Special Scientific public don’t visit museums to be Interest on the Isle of Skye, with

10 new geology exhibits in the redeveloped national museum of scotland the kind consent of Scottish Natural Universe. Most specimens in this Heritage. Access to the original Main gallery are exhibited in showcases Hall, now renamed ‘Grand Gallery’ and are organised in three main is possible either by a new staircase areas: ‘Matter’, ‘Space’ and ‘Origin or via glass panelled lifts. Here an of Life’, with the geological content 18-metre high wall displaying over concentrated in the first and last 800 specimens from across the full sections. These feature fossils, breadth of the collections confronts minerals and rocks. In ‘Matter’, the visitor. Inspired by an ancient visitors see that the ‘stuff’ we are ‘cabinet of curiosities’, it contains made of is found throughout the specimens that illustrate the wide Universe and that elements or range of the NMS collections. A combinations of elements can give similar feature, though more modest rise to a wonderful diversity of in scale, can be seen at ‘Die neue minerals — gold from Australia (Figure Sammlung — The International Design 2), platinum from Russia, sulphur Museum’, part of the Pinakothek from Italy, calcite from Scotland. der Moderne’ in Munich, Germany. Meteorites are featured in this Prominent in our ‘wall of wonders’ is section and play an important role in a one-metre high, 19th century carved connecting matter from space with vase of Derbyshire ‘Blue John’ fluorite matter on Earth. The public is able to from the NMS mineralogy collection. get close to and even touch a 150kg The banded blue and yellow (bleu fragment of a meteorite collected et jaune in French — hence Blue in Sweden. Other open display John) fluorite was once extensively specimens include a large hematite mined for its ornamental value but mass from the North of England and today only a few hundred kilograms smoky quartz from Brazil. are mined each year. From the Grand Gallery, visitors may enter In ‘Origin of Life’, the audience the new galleries. Let’s look first ‘meets’ ancient life-forms found in at ‘Earth in Space’ (my personal Scotland and elsewhere through recommendation — Yves). actual fossils and life-size (or larger) models and reconstructions; they Earth in Space include Ediacaran and Burgess Shale This gallery uses a mixture of fossils. The visitor is also able to travel specimens, graphics, text and back in time even farther, to within audiovisual presentations and a few hundreds of million of years of interactive displays to tell the story the formation of the Earth: the oldest of the Earth and its place in the rock on Earth, the Acasta Gneiss from

11 new geology exhibits in the redeveloped national museum of scotland

Figure 2 Gold from Ballarat, Australia (longest dimension = 80 mm). © National Museums Scotland

Scottish connection are featured. Among these are a group of minerals named after Scots (for example Jamesonite, named after Robert Jameson, professor of Natural History at Edinburgh and founder of the museum) or Scottish places (for example Strontianite, named after the village of Strontian, Argyll, which also gave its name to the element Strontium). The largest known Scottish meteorite that fell through the roof of a house in Strathmore, and a saltire flag which went up in the space shuttle and was signed by astronaut Nick Patrick are also examples of the Scottish connection showcased in the gallery.

Restless Earth: the gallery of geology Northern Canada at about 4000 The visitor to this gallery is led million years old, and the oldest rock on a journey of discovery and in Scotland, the Lewisian Gneiss understanding of how the Earth dating to almost 3000 million years works. A succession of exhibits ago, are astonishing examples from mingling specimens, graphics and the NMS collection. text together with exciting audiovisual and interactive displays across the Visitors with an interest in local gallery floor brings this whole topic geology will strongly engage with to life. In ‘Journey to the Centre the displays in this gallery as some of the Earth’ for example, the choice specimens with a strong showcase dealing with the internal

12 new geology exhibits in the redeveloped national museum of scotland structure of the Earth, both sides of the case are cleverly utilised: one side displays an interpretative illustration with peepholes through which specimens are seen in their context of origin, while the other side thematically displays specimens from the collection. In addition to this, an interactive audiovisual brings to life the concepts highlighted in the display.

‘Earth Events’ presents a series of four showcases that give the visitors an overview of the geological events that are shaping the planet, from plate tectonics to volcanism to earthquakes and finally to erosion. Once again, both sides of the showcases are used: the graphic side of each case is the base for a large illustration with cut-out windows (peepholes) that allow the visitor to see some specimens from two different angles. These specimens are displayed in the context of their formation so, for example, in the showcase dealing

Figure 3 (Top) Sapphire from Loch Roag, Lewis, Scotland (width of crystal in matrix = 120 mm, width of cut crystal = 12.5 mm); (Middle) Opals from San Juan Del Rio, Mexico (height of the opal set in matrix = 190 mm); (Bottom) Malachite from Siberia, Russia (width = 175 mm). All © National Museums Scotland.

13 new geology exhibits in the redeveloped national museum of scotland with volcanism and volcanic rocks, curriculum. It also engages the public the peepholes are positioned in with geology through events that are such a way to allow the visitor to see widely covered in the media, such as the rocks located in their zone of earthquakes, tsunamis and volcanic formation within a vertical section of eruptions. an idealised volcano. Double-sided panels with text and images assist in ‘Story of Rocks’ looks at the interpretation. On the other side the three fundamental of the showcase, a range of rocks types — igneous, sedimentary and and minerals are displayed which metamorphic — using many fine relate to the topic, selected both for examples. An entire showcase is educational and aesthetic purposes. devoted to a display of minerals, Highlights from this four-case section include a slab with two preserved skeletons of Mesosaurus, a sample of Figure 4 Orbicular granodiorite fine and fragile Pele’s hair and a large from Mount Magnet, Australia sample of snowflake obsidian. By (orbicules are about 120 mm in design, this section of the gallery has diameter). © National Museums strong links with the Scottish schools’ Scotland.

14 new geology exhibits in the redeveloped national museum of scotland which includes a unique Scottish granodiorite from Australia (Figure sapphire, some exquisite Mexican 4), a part and counterpart of a opal and a beautiful polished large amethyst geode (each half specimen of Russian malachite weighs about 1000 kg), a boulder of (Figure 3). But the public will not peridotite xenoliths in basalt, with only be able to see specimens inside a cut and polished section, from cases. Some large specimens are Arizona and a large example of ropey exhibited on open display. These lava (also known as pahoehoe) from include not only specimens that the 1783 eruptions of the Laki fissure had been on display in the former in Iceland, an event that caused galleries, but a large number of new much hardship in Europe at the end acquisitions brought to NMS either of the 19th century. by purchase or through fieldwork by NMS’ geology section staff. The Yves Candela and Peter Davidson public can enjoy the physical contact National Museums Collection Centre and accessibility of these specimens 242 West Granton Road from all sides, leading to a greater Edinburgh EH5 1JA sense of engagement. Some of the recently acquired specimens include [email protected] a polished monolith of orbicular [email protected]

15 reflections on the lower palaeozoic of south and central scotland Reflections on the Lower Palaeozoic of south and central Scotland — where do we stand now?

By Euan Clarkson

There are certain regions in European of Charles Lapworth, who was the geology, which may be taken as a first to use the graptolites commonly coherent whole, yet which display found in the oceanic black shales remarkable diversity within a in the south, and to correlate those confined area. For the Palaeozoic rocks stratigraphically with the one thinks, for example, of the shallow marine sediments to the Ardennes-Eifel massif, the Armorican north. This short article reviews some peninsula (Brittany and adjacent of the changes that have taken place regions), the Barrandian syncline in our understanding since 1899, of the western Czech Republic. considers our current perspective, And surely the Lower Palaeozoic of and wonders where we go from here. southern Scotland belongs here too. Let’s look at the kinds of rocks The monumental Geological Survey that are present, their depositional memoir by Ben Peach and John environments and their Horne on the Lower Palaeozoic rocks interpretation. Strata across the vast of Southern Scotland, published in area to the south of the Southern 1899, was so comprehensive that it Upland Fault were deposited in seemed to act as a damper on further deep water, as Lapworth recognised research for many years, and only in the 1870s. But for a time there a few papers were published, apart were alternative models, and until from some monographs on fossils, greywackes were recognised as until after WW2. The area covered turbidity current deposits in the in this massive work included the 1950s, at least some geologists Ordovician and Silurian mountain believed that deposition had taken country in the south (chiefly cherts, place in a great expanse of shallow shales and above all greywackes) water mud and sand flats. It is now but also the Ordovician and Silurian clear that radiolarian cherts were of the Girvan area and the Midland formed in deep water, lying on Valley Inliers. Peach and Horne top of ocean floor basalts, and that built upon the splendid research these were succeeded by graptolitic

16 reflections on the lower palaeozoic of south and central scotland

A selection of graptolites from the Birkhill Shales Formation at Dob’s Linn, Moffatdale: a) Rastrites sp., b) Campograptus communis, c) a climacograptid. BGS image P772042.

of greywacke. Southwards, the greywacke was deposited on progressively younger and younger shale, for reasons that we now interpret in terms of plate tectonics — progressively younger oceanic crust being carried north by sea floor spreading towards a trench and subduction zone, where the greywacke was deposited. Occasional tsunamis brought down shales; the graptolites are eminently shallow water fossils into deep water, suitable for biostratigraphy and their including the coral Kilbuchophyllia, excellent stratigraphical control previously unknown, which occupies has enabled a valuable elucidation a critical position in the evolutionary of events. Subsequently, turbidity history of corals. The greywackes currents swept in to cover the graptolitic shale with thick successions

The coral Kilbuchophyllia recovered from a debris flow deposit in the late Ordovician Kirkcolm Formation at Wallace’s Cast, beside the Wandel Burn to the north-east of Abington. BGS image P521144.

17 reflections on the lower palaeozoic of south and central scotland themselves, once thought to be represented, by several sedimentary boring and monotonous are now cycles each beginning with known, through petrography and conglomerate and ending with shale, geochemistry, to be differentiable the result of successive intervals of into several groups, of different unroofing and uplift. Alwyn Williams, origins. These greywacke bands can in the early 1960s, was able to show be mapped out in detail; compare that Ordovician sedimentation the common purple tint of the older in Girvan was controlled by maps with the elegant coloured contemporaneous faulting, with stripes of the maps of today. conglomerates cascading over the edges of the submarine fault scarps. The inliers to the north, lying in As is now known, and even more the southern Midland Valley, are of arresting, is that the fault-bounded surpassing interest for palaeontologists, blocks were moving laterally as well since they are replete with splendidly as vertically, sliding into their present preserved, undistorted fossils. Only position only later. The other inliers, in the Girvan area is the Ordovician Knockgardner, Lesmahagow, the Hagshaw Hills, Carmichael and the Pentland Hills are all Silurian. Now in all cases the succession in these inliers begins with marine sediments, eventually passing upwards into redbeds of continental origin as the sea receded. Whereas each of these inliers represents a former part of the Laurentian continental shelf, the faunas in each are different. The central Hagshaw and Lesmahagow inliers are dominated by fish and arthropod faunas; these may have been deposited in brackish-water conditions. The Knockgardner

The late Ordovician trilobite Stenopareia shallochensis recovered from the Drummuck Subgroup at Lady Burn, near Girvan. BGS image P521133.

18 reflections on the lower palaeozoic of south and central scotland and Pentland Hills inliers are not faults. This process built up a huge dissimilar faunally, but whereas the accretionary complex at the margin former represents an open shoreface of the Laurentian continent, before environment, the fossiliferous its oblique collision with the Avalonia sediments of the Pentland Hills were continent advancing from the south. deposited in a broad, quiet-water This overall concept is not in doubt, lagoon, separated from the open but can we say more about it? There ocean by an offshore barrier system. are persistent problems, and there The changes in faunas, as related to have been two related but separate this system have been meticulously interpretational models. The first documented, and this work is still is that the Southern Uplands did continuing. indeed form as an accretionary prism, the top of which rose above The original structural model adopted sea level to form a chain of eroding by Peach & Horne for the Southern islands, known as Cockburnland. Uplands was that of an isoclinally To the north lay an ‘upper slope folded complex; it was based directly basin’, an elongated part of the on the interpretation of Lapworth Laurentian continental shelf in which and held sway until the 1960s, accumulated the successions now when ENE-WSW strike faults rather seen in the Midland Valley Inliers. than folds were recognised as truly Although this seems to fit very well the dominant structural control. with the evidence, there are some Paradoxically, one of these great additional complexities, for to the strike faults passed almost directly south was an andesitic island arc below Birkhill Cottage, in Moffatdale, complex, known from southerly where Lapworth stayed during his derived turbidites rich in andesite field work. And when the plate and quite different from the quartz- tectonic revolution began in earnest rich turbidites derived from the in the 1960s it became clear that north. Might the area of the Southern the Southern Upland region was Uplands have been a back-arc originally an ocean basin (the Iapetus basin, rather than an accretionary Ocean), underlain by a subduction prism? It is certainly possible, but zone dipping to the north. As since we do not really know the subduction continued, northward, palaeogeography of the basin before the shales and greywackes covering continental collision there the matter the oceanic plate were stripped rests, though most recent research off along great thrust planes, now has favoured the accretionary prism seen as the great ENE-WSW strike model. It has also become clear that

19 reflections on the lower palaeozoic of south and central scotland lateral as well as vertical movements not only of tectonic effects but of sea- have taken place through time, level change also. Recent preliminary and these require much further studies in these fields are excellent investigation and serve to show what else might be done in the Silurian Midland In terms of modern tectonic theory Valley Inliers. And then there are the we now have a pretty good idea of graptolites, which remain available the geological history of this area, for meticulous stratigraphical and but much more remains to be done. ecological studies. I can only hope Firstly, refinements in biostratigraphy that future generations will delight in are much required, and nowadays the geology of this marvellous area organic-walled microfossils such as much as people of my generation as chitinozoans, acritarchs and have been able to do. And it is radiolarians are proving increasingly scenically beautiful too . . . useful. Next, we need more basic mapping — not a fashionable pursuit Further reading: these days. The Geological Survey’s Euan Clarkson & Brian Upton. 2006. excellent programme of mapping, Edinburgh Rock; the Geology of extending from the south west has Lothian. Dunedin Acadmic Press. reached as far as St Mary’s Loch. 239pp But with extra pressures on the Survey, and with key staff retiring Euan Clarkson & Brian Upton. 2010. or being reassigned, it has stalled. Death of an Ocean. A Geological Then there is the effect of global sea- Borders Ballad. Dunedin Academic level change, which has hardly been Press. 210 pp. applied yet, though it is undoubtedly very important in interpreting the Nigel Trewin (editor). 2002. The successions. In the Girvan area, Geology of Scotland. Chapter 5, The for example, chitinozoans have Midland Valley terrane, 149–166; recently been used effectively for Chapter 6, The Ballantrae Complex biostratigraphy but the sedimentology and Southern Uplands terrane, and palaeoenvironments of 167–200. The Geological Society, Ordovician and Silurian successions London. still need to be considered in terms

20 progress on understanding the dalradian Progress on understanding the Dalradian

by Doug Fettes

The Dalradian Supergroup is one of the major structures owe much to that the great icons of Scottish geology. great character of Highland geology, It comprises a varied sequence of Sir Edward Battersby Bailey. And, metamorphic rocks of Neoproterozoic more recently, it was geologists such to Early Ordovician age, which as Basil King, Nick Rast and Mike stretches from the west coast of Johnson who were inspirational in Ireland to Shetland, some 700 km. establishing the different structural In Scotland it forms most of the and metamorphic phases of the ground between the Highland Grampian Event. These geologists and Boundary and Great Glen faults, those who followed have provided ranging from the craggy indented a very detailed understanding of the coastline of Argyll to the lowlands Dalradian succession and its history. of Buchan. To the geologist the However, it would be wrong to think fascination of the Dalradian is its it has surrendered all its secrets and key role in the evolution of Scottish considerable research continues. In Geology. The metamorphic sequences recent years the focus has moved to established by Barrow and Read the wider setting of the succession and underpin modern systematics. The important aspects of this are the age lithostratigraphy and elucidation of and nature of the sedimentary basin.

Greenland Figure 1 The breakup of Norway the Rodinia Laurentia GGF supercontinent and the birth of Scotland Baltica Iapetus, c. 590 Ma., showing Amazonia the position of the Dalradian X Dalradian Supergroup sedimentary basin.

Iapetus Ocean 60S Simplified from GGF Great Glen Fault Leslie et al. 2008. 30S

21 progress on understanding the dalradian

How did the Dalradian form? series of linear fault-bounded basins. The Dalradian was formed as the The sediments are dominated by supercontinent of Rodinia broke up, siliciclastic turbidite fan systems. and specifically as the continental Towards the top of the group more masses of Laurentia, Baltica and stable conditions developed marking Amazonia drifted apart opening a transition into the Appin Group, up the Iapetus Ocean (Figure 1). which is characterised by shallow The Dalradian sedimentary basin shelf sediments. The Appin Group developed as the crust thinned and divisions, which are marked by rifted. Then, following continental limestones, black mudstones and rupture, deposition continued quartzites, can be traced across the on the margin of Laurentia as whole strike length of the Dalradian Iapetus opened and closed. The from the west coast of Ireland to lithostratigraphical groups of the Banffshire. This remarkable degree Dalradian reflect stages in the of continuity reflects a lack of rifting evolution of this process.The with uniform subsidence along the basement to the Dalradian is likely basin. These conditions changed to be varied but, where seen, markedly with the onset of the Argyll the lowermost beds rest on the Group. Crustal stretching increased Dava-Glen Banchor succession (Figure 2), a Neoproterozoic unit broadly equivalent to the Moine assemblage.

The Grampian Group marks the start of sedimentation. Great Glen Fault Fault Crustal extension led to subsidence, Boundary active rifting and the

Highland

development of a p

u o

r Southern Highland Group

g r

e Appin & Argyll groups

p

u S Figure 2 Lithostrati- Dalradian Grampian Group graphical divisions of Dava & Glen Banchor the Scottish Dalradian successions succession. Faults

22 progress on understanding the dalradian with the development of complex rift emphasise that rupture would have basins marked by rapid deepening been complex in space and time with and sediment deposition. The an almost certain ragged continental thinned crust led to decompression margin and the creation of several and major volcanism along the micro-continental bodies. Dalradian belt, the products of which are well seen on Farragon Hill and Current thinking regards the greater Ben Vrackie. Ultramafic bodies, part of the Highland Border Complex possibly derived from the mantle, as a contiguous part of the Dalradian the presence of ultramafic detritus succession and has ascribed it to a in many of the lithostratigraphical new group, the Trossachs Group. units, and the chemistry of the This unit consists of metamorphosed volcanic rocks all suggest there may sandstones, limestones and black have been actual local rupture of the mudstones and represents deposition crust at this time. Another indicator on the Laurentian margin as of these extreme conditions is the the Iapetus Ocean opened and presence of stratabound exhalitive eventually closed, marking the end of orebodies particularly within the Dalradian sedimentation. Easdale Subgroup; for example, as found in the Foss barytes mine, How old is the Dalradian near Aberfeldy. The top of the Argyll The age of the Dalradian succession Group is marked by the dominance is critical in interpreting regional of coarse clastic turbidite fans, events. The Dalradian has to which characterise the succeeding be younger than its basement, Southern Highland Group, wherein elements of which have been dated individual lithostratigraphical units at 815 Ma, and older than the are difficult to distinguish and latterly Grampian tectontothermal event discontinuous. It seems probable that at c. 470 Ma. Direct radiometric the extreme crustal stretching and and fossil evidence is limited and is potential rupture characteristic of the summarised on Figure 3. Argyll Group ceased as a result of full scale rupture offshore from the Recently a considerable effort has Dalradian basin. Thus the marked gone into establishing global glacial change in sedimentation at the top events. These are marked by the of the Argyll Group represents the development of glacigenic deposits start of deposition on the foundering or tillites. These tillites may be margin of the Laurentian continent, correlated globally using, inter alia, as it broke free. It is important to the distinctive isotopic signature

23

progress on understanding the dalradian

n

a

i

c i

v Grampian Event

Ma o d

r ? Lower Arenig 476 Ma** O ? Margie Limestone 485 Ma**

n

a 500 i r Trossachs

b Palaeozoic

m Leny Limestone c . 515 Ma**

a

C

? Southern Highland Inishowen/Macduff tillites =Gaskiers glacials at c . 580 Ma 600 Ash bed 601Ma (U-Pb age) Edicardian Argyll Stralinchy-Reelan tillite Port Askaig tillite * Appin Ballachulish Slate Formation 660 Ma (Re-Os age)

700 n Grampian

a

i

c

n

i

e o Flooding surface

g z

o

o

r

y

r

e

t C Uplift and erosion

o

r

p

o

800 e Pegmatite intrusion c . 807 Ma N (U-Pb age)

Dava -Glen Migmatites 840 Ma Banchor (U-Pb age) ‘basement’

n

a

i

n

o 900 T * = Marinoan glacials at c. 640 Ma? ** = Fossil age

Figure 3 Dalradian stratigraphical section showing dated points.

24 progress on understanding the dalradian of associated carbonates. Using However, taking all the data together radiometric or fossil evidence, these the best estimate is that Dalradian tillite/carbonate horizons may be sedimentation lasted from c. 730 Ma dated and potentially provide global to c. 470 Ma with the main rupture time planes. However, the necessary and break away of Laurentia around database is still incomplete, and so 630–620 Ma. far the defined glacial events appear to comprise several phases and in Final thoughts some cases to extend over millions of As the global database increases so years. our understanding of the accretion and disruption of supercontinents There are three tillite horizons in and the processes involved develops. the Daradian succession. The best Discovering the position of the developed is the Port Askaig Tillite Dalradian in these bigger pictures (and its correlatives), which lies at maintains the fascination of this the base of the Argyll Group, above intriguing piece of Scottish geology. are the Stralinchy-Reelan formations in Donegal, which lie close to the Further reading (and references base of the Easdale Subgroup (lower therein) Argyll Goup), and finally the Macduff Leslie, A.G., Smith, M. & Soper, N.J. Boulder Bed (correlated with the 2008. Laurentian margin evolution Inishowen beds in Donegal), which and the Caledonian orogeny – a lies within the Southern Highland template for Scotland and East Group. The Macduff unit has been Greenland. In: Higgins, A.K., correlated with the Gaskier global Gillotti, J.A. & Smith, M.P. (eds) The event at c. 580 Ma, consistent with Greenland Caledonides: Evolution of the radiometric dates. The Port the Northeast margin of Laurentia. Askaig and Donegal units are fairly Geological Society of America, tightly constrained by the radiometric Memoirs, Vol. 202 307-343. dates and are also stratigraphically close (Figure 3). As such it seems Fettes, D J, Macdonald, R, Fitton, J G, probable that both represent stages in Stephenson, D & Cooper, M R. in the Marinoan global event at c. 640 press. Geochemical evoution of Ma. Dalradian metavolcanic rocks: implications for the break-up of the There is still considerable debate Rodinia supercontinent. Journal of about these correlations and they the Geological Society, London. Vol. have to be treated with caution. 168.

25 does scotland have a golden future?

Does Scotland have a golden future? [Not a comment on independence, but a review of the nation’s gold resources]

by Graham Smith

The existence of gold in Scottish Thereafter, although no visible rocks has been known for over gold was recorded, the metal was 950 years. Adamson (1980) cites discovered in late 19th and early 20th over 180 localities where gold was century ore assays at a number of historically recorded, pre-eminent lead and copper mines and trials. amongst which were those at These included Wood of Cree, Leadhills and in the Helmsdale Talnotry, Stronchuillin, Inverneil, River. Leadhills produced c. Kilmartin, Castleton, Clachan Beag, £500 000 worth of gold, including McPhun’s Cairn and Loch Duich. In the source material for the present the early 1960s, an assay of a grab Scottish regalia, in the 16th and 17th sample taken from Halliday’s Vein at centuries. Helmsdale was the site of Tyndrum recorded 122 g/t gold. Scotland’s only gold rush in 1868– 69 during which time around 400 Modern gold exploration in Scotland ‘miners’ produced over 3500 ozs. commenced in the early 1980’s, In both areas the metal was found initially encouraged by advances in river gravels and like all the in analytical technology, which other historical occurrences had effectively made detection more accumulated by alluvial processes. rapid and cost effective, thus enabling There were two unsubstantiated a greater throughput of material. This accounts of gold being traced to in turn, coupled with comparisons bedrock in the Leadhills area, but with overseas occurrences, led to a probably the first authenticated better understanding of which rock account of primary gold in Scotland types might have the potential to was by Thost (1860) who reported contain economic grades of gold. up to 6 oz per ton of native gold in Other early stimuli included the work gossans in the Lochearnhead area. of the British Geological Survey’s He also notes gold being discovered (BGS) Mineral Reconnaissance during crushing of the lead ore at Programme and the funding the Corrie Buie Mines in Perthshire. offered under the Government’s

26 is the earliest animal scottish?

Mineral Exploration and Investment based on the initial premise that Grant Act. However, probably gold is often found in association the greatest incentive came from with base metal sulphides such as the BGS’s Regional Geochemical pyrite, chalcopyrite and galena. Survey Programme (now known as G-Base), which comprised a UK-wide The Gairloch deposit is the collection and analysis of stream oldest known gold concentration sediments. Although, G-Base does in Scotland, occurring within not routinely analyse for gold it does 2000–2200 ma Lewisian rocks record where gold is noted in panned of the Loch Maree Group in a concentrates of the stream sediments. volcanogenic, massive-sulphide- It also analyses concentrations of type deposit; native gold occurs the ‘pathfinder elements’ antimony, along with pyrite and chalcopyrite arsenic and bismuth, so called in a sequence of metabasalts and because they frequently accompany metasediments. Gairloch was gold. When incorporated into a amongst the first of the deposits GIS system the three plots can to be investigated in the modern be superimposed and if they are era of exploration, the target being assigned a primary colour then a identified by comparisons with white spot will result if all three are Precambrian massive sulphide sufficiently concentrated, thereby deposits in Canada and Scandinavia identifying possible targets for gold and a literature reference to copper exploration. mineralisation in that area.

Establishing the likely bedrock Subsequent investigations source of alluvial gold grains is now involved a wide range of targets aided by microchemical analysis, in terms of age, rock type and whereby the silver content and geographical area, undertaken by the geochemistry of inclusions both academic and commercial within the grains is utilised. By organisations and the BGS. These this method it is possible to show included: Dalradian-hosted that the Leadhills gold may have deposits in Unst; porphyry-copper several sources. Some exploration style mineralisation in Devonian targets are indentified by modelling intrusions, some sub-volcanic, through comparisons with deposits at Lagalochan, Black Stockarton elsewhere in the world. For Moor, and Foreburn; igneous example, the discovery of the contact veinwork at Moorbrock Gairloch and Cononish deposits was Hill; and the Devonian chert-

27 does scotland have a golden future? hosted occurrence at Rhynie. The concentrations. For example 1000 ground south of Loch Tay, has grams of gold were obtained from a attracted considerable exploration 10 tonne bulk sample, some of which interest mainly because of the was used to produce a number of unusually large number of small gold-plated replica James V ‘bonnet sulphide deposits These include pieces’. The upper few metres of the Calliachar vein suite, south- many veins are deeply weathered west of Aberfeldy, which along and hence would be amenable to with the Cononish veins are the limited surface mining. only occurrences currently being economically assessed. Cononish could be the first ever bedrock gold mine in Scotland. Its The Calliachar suite comprises 14 discovery was the result of some north-west trending, sub-vertical extremely innovative sleuthing by quartz veins cutting Dalradian metasedimentary rocks. Although generally only a few cm wide, they The entrance to the exploratory adit locally contain significant gold at Cononish. BGS image P550931.

28 does scotland have a golden future?

Inside the exploratory adit. BGS image P001604.

EGS member Richard Parker. Initially attracted to the Tyndrum area by the abundance of vein- hosted sulphides (although none of the structures other than Halliday’s Vein had recorded gold), and aware that there were historical records of alluvial gold in the area, he panned up the Cononish River and discovered a mineralised mineable bedrock gold deposits. boulder, which was eventually traced With the exception of Calliachar to a vein close to the former Eas Anie and Cononish most of the modern lead mine. Subsequent assessment, gold exploration in Scotland was which included extensive drilling undertaken by major international and driving a 0.9 km exploratory mining companies by who’s adit, concluded that the deposit had standards the Scottish prospects mineable reserves of 450 000 tonnes would be regarded as very small of rock grading 11 g/t gold and 60 g/t beer. This, coupled with the silver. A recent application to mine significantly lower gold price of was turned down by Loch Lomond yesteryear might explain why they National Park Planning Board and a were never brought to fruition. It revised application is in preparation. is possible then that some of these deposits could now be attractive to Modern exploration has thus ‘junior’ mining companies, if the high demonstrated that Scotland has a gold price (currently about $1500 number of small, but potentially per oz) is maintained. However,

29 does scotland have a golden future?

A sheared breccia vein in the Cononish mine. Gold occurs with pyrite and galena scattered through the host quartz. BGS image P244649.

their development would have to References contend with objections from the Adamson, G F S. 1988. At the end of environmental lobby and with ever- the rainbow. The occurrence of gold burgeoning planning legislation, in Scotland. Albyn Press Ltd. (especially if more designated areas such as National Parks are created); Thost, C H G. 1860. The together, these constitute the greatest Breadalbane Mines. Quarterly Journal barrier to Scotland becoming a gold of the Geological Society of London, producing country. Vol. 16, 425.

30 book reviews

Book reviews

31 book reviews

32 book reviews

33 book reviews

34 book reviews

35 book reviews

36 epilogue

37 This issue: No. 50, Autumn 2011

1 Editorial ramble A 50th birthday, our debt to the Torridonian, a new National Museum and some very fancy steps.

7 A few words from our founding editors by Helena Mansbridge (Butler) and Andrew McMillian

9 New geology exhibits in the redeveloped National Museum of Scotland by Yves Candela and Peter Davidson

16 Reflections on the Lower Palaeozoic of south and central Scotland — where do we stand now? by Euan Clarkson

21 Progress on understanding the Dalradian By Doug Fettes

26 Does Scotland have a golden future by Graham Smith

23 Book reviews

ISSN 0265-7244 Price £2 net