The Edinburgh Geologist

Magazine of the Edinburgh Geological Society Issue No 65 Spring 2019 The Edinburgh Geologist Issue 65 Spring 2019

Cover Illustration Serpentinite cut by a network of carbonate veins, part of the mantle-crust transition in the Lizard Ophiolite exposed at Coverack, Cornwall. Image ©Beverly Bergman. x1. For more on the Cornish geology seen during the Edinburgh Geological Society’s ‘long excursion’ in 2018 see the article by Beverly Bergman and others on page 13. BGS images are reproduced by permission of the British Geological Survey ©UKRI. Published February 2019 by The Edinburgh Geological Society (Charity registered in Scotland number SC008011) www.edinburghgeolsoc.org

Editors Phil Stone Bob McIntosh [email protected] [email protected] British Geological Survey The Lyell Centre, Research Avenue South, Edinburgh EH14 4AP ISSN 0265-7244

The Edinburgh Geological Society was founded in 1834 with the twin aims of stimulating public interest in geology and advancing geological knowledge. We organise a programme of lectures and excursions and also publish leaflets and excursion guides. For more information about the Society and membership, please visit www.edinburghgeolsoc.org. editorial

From Pangaea to the Anthropocene by way of South Uist, Cornwall and Glasgow

An editorial ramble by Phil Stone

One of the many delights of geology is the way in which unexpected connections crop up in unlikely places. Our first article in this issue of The Edinburgh Geologist was initiated by a chance discovery in an Outer Hebridean library on the Isle of Benbecula, yet interacts neatly with one of my own recent encounters in a disused quarry in the village of Kirtlington, about eight Figure 1 The dedication plaque to miles north of Oxford. Visiting friends Stuart McKerrow at the beginning in that area, I was taken to see a of the Kirtlington Quarry geological local geological trail, set up in the trail, near Oxford. old limestone quarry which, from 1907 to 1928 had been worked for cement production. But the surprise came, not from the Middle Jurassic Ordovician to Silurian, Southern (Bathonian) rocks, but from the Uplands terrane in terms of dedication plaque at the beginning subduction of the Iapetus Ocean of the trail that acknowledged the at the margin of Laurentia. With ‘renowned Scottish geologist W Stuart his background in palaeontology, McKerrow’ (Figure 1). Stuart hailed he had also been one of the first from Glasgow but spent his academic to show the sequential merging career at Oxford University. of faunas as the Iapetus Ocean narrowed. Appropriately enough, the From the perspective of Scottish centrepiece of his memorial plaque geology, Stuart McKerrow is probably is a reconstruction of the Pangaea best known for his initiation of the supercontinent, with the north of ‘accretionary prism’ model that Scotland nestled into the south-east explained development of the coast of Greenland.

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Stuart’s involvement with the England in 1215 AD? Probably not, quarry at Kirtlington started with beyond acknowledging that neither his palaeontological work on arose until considerable pressure brachiopods early in his career, hence had been brought to bear. But our the contrasting views of, I think, a first article describes a much more rhynchonellid brachiopod on either benevolent association in a detective side of the Pangaea map. He bought story pieced together by Jean Archer a house in the village in 1979 and that takes us from South Uist to thereafter campaigned successfully for Washington D.C., following the the quarry to be recognised as a local trail of a grand diplomatic gesture. nature reserve and SSSI: it is estimated Crucial to Jean’s account is the that a thousand students of geology palaeogeography of the Precambrian visit the quarry annually. But now the supercontinents Rodinia (complete invertebrate fauna has been eclipsed about 750 Ma) and Pannotia by vertebrates, with the quarry yielding (complete about 580 Ma — Figure remains of dinosaurs, sharks, crocodiles 2), wherein Scotland’s North-west and plesiosaurs and, it is claimed, the Highlands terrane lay close to what quarry is amongst the richest mammal- is now southern Greenland. Its bearing localities of Middle Jurassic unification with the rest of Scotland age known anywhere in the world. as the history of the Iapetus Ocean All of which sounds rather like a piece unfolded is a story that owes much of Scottish geology that has recently to Stuart McKerrow’s seminal acquired much significance for its contributions. His memorial illustrates vertebrate fauna, the Middle Jurassic of the Pangaea supercontinent (formed Skye. How apposite if Stuart McKerrow, about 300 Ma), the break-up of a palaeontologist from Glasgow, is which left the North-west Highlands commemorated in southern England’s behind as the opening of the Atlantic equivalent of the Bathonian succession Ocean carried Scotland apart from around the Trotternish peninsula. Greenland and North America. Jean’s Perhaps unsurprisingly, shallow marine story derives from the perceived to coastal lagoon environments are geological connection between represented in both areas. Scotland and the United States, rather than Greenland, but in context Oceans apart but geologically united we can let that pass. Now, keeping Pangaea in mind, can you quickly make a connection It’s now commonplace for the Lewisian between Lewisian gneiss and the Gneiss Complex to be cast as an Magna Carta signed by King John of outpost of North American geology,

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distinguished services in connection with the geological interpretation of our Earth’. Wegener, who had ignited the continental drift debate, had died in 1930 on an expedition to Greenland, but despite Du Toit’s expressed admiration, he must have despaired at some of Wegener’s ideas. For example, not content with correlating the solid geology in his continental reconstruction, Wegener also noted a correspondence in the extent of glacial deposits on either Figure 2 A reconstruction of the side of the North Atlantic Ocean. palaeogeography of the Pannotia From that, and displaying little supercontinent at about 580 Ma. regard for the geological timescale, The red ‘ladders’ show the rift zones he deduced that the North Atlantic that developed into the Iapetus must have opened since the retreat Ocean. BGS image. of the Quaternary ice sheets. Such an unlikely circumstance made it very easy for his opponents to dismiss but it was not always thus. We now continental drift in its entirety. smile smugly when thinking about the initial American reaction to continental We can stay with the themes of drift and celebrate the championing closing oceans and the development of the cause by the likes of Arthur of Pangaea into our second article Holmes — not least, and recently, but move south from the Early in EG64. Another name that should Palaeozoic Iapetus Ocean to the be celebrated for the same reason is Late Palaeozoic Rhenohercynian Alex. (he always signed himself Alex.) Ocean, the ocean that separated Du Toit, the South African geologist Avalonia from Gondwana. As the whose seminal book Our Wandering Iapetus Ocean closed, bringing the Continents (1937) was for many years Avalonia and Baltica continental a solitary and influential beacon for the plates to the margin of Laurentia, ideas of continental drift. the Rhenohercynian Ocean opened behind Avalonia as it moved away Du Toit dedicated his book to the from its original position at the memory of Alfred Wegener ‘for his margin of Gondwana. Eventually,

3 editorial in its turn, the Rhenohercynian gone to plan, as you read this issue Ocean closed and by the end of of EG what was billed as the UK’s the Carboniferous, Gondwana deepest ever borehole (projected was reunited with Avalonia to depth of 4.5 km) should be making complete the supercontinent of good progress near Redruth, on the Pangaea. Whereas the remains of the northern flank of the Carnmenellis Iapetus Ocean can be found in the pluton. Caledonian orogen across Scotland and northern England, the remains Sadly, Scottish granites are not so of the Rhenohercynian Ocean form hot. Whilst the Cornubian granites part of the Variscan orogen that commonly generate in excess of 120 extends from central Europe across milliWatts per square metre (mWm-2) to the peninsula of south-west with wide areas showing in excess of England. And it is there, to Cornwall, 100, the best Scotland can manage, that our second article takes us in from a small area of the Cairngorm the company of the participants in granite is about 80 mWm-2. But that the EGS ‘long excursion’ of 2018, coordinated by Beverly Bergman.

Hot rocks and warm water Cornwall clearly has some fascinating geology: Devonian marine strata variously deformed, the enigmatic Lizard ophioilite, the Early Permian Cornubian granites and their associated mineralisation. The granites at outcrop are a bit like the tips of icebergs, in that they are but the visible cupolas of a huge buried Figure 3 A heat-flow map of batholith. The Cornubian granites Cornwall produced by the British also produce a lot of heat and the Geological Survey. In the red areas extent of the batholith is dramatically the maximum heat-flow exceeds 120 shown by a heat-flow map of the milliWatts per square metre (mWm-2), region (Figure 3). It’s an aspect of whereas the pale blue area has a the geology that has often been regional background heat flow of considered in terms of geothermal about 50 mWm-2. Compare with the energy potential, and perhaps its geological map on page 13. time has finally come. If all has

4 editorial doesn’t mean Scotland is without its place is a very different range of geothermal potential, as explained by Scottish industry — Stoats Porridge Alison Monaghan in our third article. Bars, Stewart Brewing and Macsween It is hoped that the warm(ish) water Haggis amongst others. in abandoned coal workings can be exploited for neighbourhood heating Of course, the scene at Bilston Glen schemes via a heat pump system, is a familiar one across all of the and Alison describes a pilot project once-productive Scottish coalfields underway in Glasgow that aims to so it’s appropriate that one of our test the concept. book reviews is concerned with the geological controls on mining in the It’s a remarkable turn-around in the East Neuk of Fife — and complements face of anthropogenic climate change geology with a fascinating account when coal mines become a source of of the social history that the industry renewable energy. And the speed of generated. Another book review that turn-around was brought home introduces metamorphism and shows to me when I recently came across a that there is much more to it than picture of Bilston Glen colliery, in the is demonstrated by those old, hard, Midlothian coalfield just to the south- Lewisian rocks of northern Scotland. east of Edinburgh, under construction in 1956 (Figure 4). At the time it was Whither the Anthropocene? predicted that the mine would have Having touched on anthropogenic a working life of 100 years, but this climate change I expect that, given proved unduly optimistic; production its wide publicity and broad cultural started in 1963 and the mine closed in 1989. The site is now occupied by an industrial estate and no trace of the colliery remains. In

Figure 4 Bilston Glen colliery under construction in 1956. BGS image P001468.

5 editorial assimilation, you have got used to of geological events and the science living in the Anthropocene. Perhaps of where we are now, the concept you even saw it performed by of the Anthropocene has proved Scottish Opera earlier this year. invaluable. As an example of its explanatory value I can offer one of But wait: the final word on these my 2018 Christmas books, indeed it’s arcane matters of nomenclature one of the most satisfying geological is usually pronounced by the books that I’ve come across recently. International Union of Geological The main title, Timefulness, might Sciences (IUGS) and a formal conjure-up ideas of New Age decision was expected last year. meditation but the sub-title should Would the Holocene be declared prove irresistible — How thinking like at an end, and a brave new world a geologist can help save the world. begun? That result was widely The author, Marcia Bjornerud, is expected, but instead IUGS declared a structural geologist at Laurence that the Holocene was in fact still University, Appleton, Wisconsin, up and running and, going further, and is clearly a fan of Hutton and divided it into three divisions, the last Lyell; her second illustration is a of which continues to the present sketch of the unconformity at Siccar day. So, since 4250 years ago, we Point. She vividly and succinctly have been in a stage called the contrasts the processes enduring Meghalayan. To quote from New through ‘deep time’ with their abrupt Scientist, 28 July 2018, p. 24: “This acceleration by the unintended age is defined by a mega-drought consequences of human activities, that caused a number of civilisations, hence the Anthropocene. Quite including Mesopotamia, to collapse. apart from championing the cause It is named after the north-eastern of long-term thinking if the issues Indian state of Meghalaya, where a of anthropogenic climate change stalagmite was recovered from a cave are to be first appreciated and then that provides chemical evidence of addressed, the book is an excellent the drought.” ‘grown-up’ introduction to geology and its comprehensive importance. Somehow, I don’t think that will be The author’s concluding call to the end of the story. In general, the arms has an understandable North finer divisions of geological time American bias, but it doesn’t take arouse little public excitement, but a genius to make the trans-Atlantic in terms of the wider understanding correlations. Recommended!

6 a special stone for a very special pedestal

A special stone for a very special pedestal

By Jean B Archer

‘The material for the base of the by King John in June 1215. It was Parliamentary gift to Congress of the to be replaced at the end of the Magna Carta was obtained from the bicentennial year by a replica Magna pegmatitic gneiss at Ardivachar Point’ Carta, worked in gold. To contain first (Black 1977). the original Magna Carta, and then its golden replica, architect turned This enigmatic statement caught my goldsmith Louis Osman (1914– eye whilst I was browsing through the 1996) was commissioned, on the pages of an unpublished geological recommendation of the Goldsmiths’ report on the Outer Hebrides Company, to create a fitting reached down from the reference showcase. There is no mistaking the shelves of my local library, a few miles magnificence of this goldenobject from Ardivachar. The claim appears d’art which sparkles with gemstone over the names of three well-known insets and enamelled detail all geologists, but when was the gift worked into a plethora of symbolic made and under what circumstances? motifs appropriate to a document Ardivachar Point (Rubha Aird na held in just as high esteem in the USA Machrach) is at the north western as it is in the UK (see https://www/ corner of the Isle of South Uist, but aoc.gov/art/commemorative-displays/ apart from that geographical fact all magna-carta-replica-and-display). else was obscure. I was intrigued. After embarking on several false lines With only a year to work on this of enquiry a chance encounter with major commission Osman lost no an islander — Billy MacPhee — set me time in completing a design in which off on the correct trail. The Magna his ‘golden box’ would stand on a Carta was the British government’s mushroom-shaped pedestal carved in gift to the USA on the occasion of the a stone that would match the Virginian Bicentennial of 1976. sandstone flooring and walling of the Rotunda in the Capitol Building. The The gift entailed a year-long loan to pedestal would have a polished stone Congress of one of only four known table top, but where might there be original copies of Magna Carta signed found a suitable British stone? That

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The Magna Carta display case and pedestal — following conservation in 2010 and flanked by the team that installed the display in the Crypt of the Capitol Building, Washington D.C. Courtesy of the Architect of the Capitol. is where Ardivachar Point came to (Ray) Dearnley, was remarkably the goldsmith’s notice as the source difficult to trace. of a rock that he came to call Eygon Pegmatite. In 1968 Ray co-authored with Frederick (Fred) Weir Dunning Osman required the pedestal to a paper in which they identified possess a symbolism appropriate the Ardivacher rocks as an early both to the event and its location. (Scourian) part of the Lewisian Gneiss He therefore sought geological Complex essentially unscathed by advice. That much is on record; Laxfordian reworking. In 1975 Fred Osman’s biographer refers to held the post of Curator in the South his ‘corresponding with eminent Kensington Geological Museum geologists’ (Moore 2006). In my which was a likely place for Osman search for their identity the records to have turned for geological advice. of the Goldsmiths’ Company were When I approached Fred about his of no assistance, but another likely knowledge of the Magna Carta gift he source of information was one or was approaching the end of his life other of the authors of the above- and unable to help (he passed away mentioned geological report. on 12 April 2018). However, Janet Watson had passed away in 1985, Rod Graham denied Wendy Cawthorne of the Geological all knowledge of the gift to Congress, Society, London, Library interested while the third author, Raymond herself in the search for Ray. She

8 a special stone for a very special pedestal made the breakthrough when she pad of Uist’s missile range, and which discovered, from the Geological terminates in the rocky foreshore Survey’s Annual Report for 1976, that on the southern approaches to Ray had indeed served as Osman’s Ardivachar Point. advisor. Furthermore, she found that the Report outlined reasons for Ray returned to Ardivachar with Osman’s selection of Ardivachar Osman and a film crew led by stone. Besides aesthetic appearance, Jon Schorstein (1949–1978) who Ardivachar rocks were described was commissioned to shoot a at the time as the oldest in the UK documentary on the making of having ‘pre-drift geological linkage the Magna Carta gift. The South with the USA’ (Anon 1977) — so Uist footage, which Ray viewed in making them a combined token of London in Osman’s company, is now liberty and former unity. seemingly lost along with the rest of the never completed film. Ray also Wendy had a further success when disclosed that he recommended she traced and established contact a Millstone Grit quarry near with Ray Dearnley. In a face-to- Huddersfield operated by Johnsons face encounter, Ray reminisced Wellfield Ltd as the source of about his association with Osman. stone for the massive, mushroom- Ray told a veteran of the Lewisian, shaped Magna Carta pedestal. Douglas Fettes of BGS, and myself Osman opted for another, similar- that he had discussions in London looking, York Stone (sandstone with Osman and then travelled from West Yorkshire). This was Coal north with him in his ‘campervan’ to Measure Sandstone from the Bolton view the oldest rocks in the British Woods quarry near Bradford, then Isles in a geographic location closer operated by the long-established to North America than most other firm of Waterhouse Denbigh which parts of Great Britain. Together, in also fashioned the pedestal. In the summer of 1975, they inspected recommending York Stone, Ray had various locations where outcrop led Osman to material which, by all interrupts, and helps stabilize, the accounts, is an excellent match of long, remarkably straight, beach and the Virginia Sandstone flooring and dune-lined Atlantic coastline of South walling of the Rotunda in the Capitol Uist. Their search came to its happy Building. conclusion on the rocky foreshore at the northern termination of the long Ray took no part in the removal of beach which is home to the launch the stone from Ardivachar and from

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shore, told me the stone was about the size of his kitchen fridge and had been removed from the foreshore by Uist Builders Ltd.

The founder and managing director of Uist Builders, the late Donald Joseph Peteranna, proved to be a rich source of information which I now very gratefully acknowledge. He recalled borrowing from Askernish Quarry (now MacCaulay Askernish) the digger normally used to lift rock blasted from the quarry face. The digger, operated by its usual driver (Duncan Campbell), cleared a track across the foreshore to a boulder some three tons in weight and hoisted it onto the back of a waiting lorry. The boulder was then transported by sea and land Contactor Donald Joseph Peteranna for cutting and polishing in the sizing-up the boulder preparatory stonemason’s yard of J & A Milligan to its removal from the Ardivachar at Creetown, in Dumfries and foreshore. From original photograph Galloway. There, the boulder was in the possession of Duncan first sliced along cut-lines oriented at Campbell — the operator of the a high angle to the rock’s gneissose digger seen in the background. foliation/banding to ensure maximum exposure of the banding on the flat surfaces of the cut rock. We do not the Outer Isles. I spent some time know how many individual (circa hunting for the site of extraction 4-inch thick) slabs were cut, only before I knew that the stone was that four of them were trimmed not cut from country rock, but was for eventual fitting together into a selected from one of the numerous single five foot square slab before boulders strewn on the Ardivachar one face of each slab was polished. wave-cut platform. Ronald John Fitted together the individual pieces MacEachan, who lives close by the became the beautiful polished

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in the Rotunda preparatory to the arrival of the display case.

Following it’s unveiling on 2 June 1976 the Magna Carta display stood in the Rotunda of the Capitol for more than three decades. In 2010 it was removed for conservation and cleaning and afterwards installed in the so-called Crypt of the Capitol Building. Few of the multitude who J A Milligan and sons in the annually pass through those hallowed Creetown yard where the pegmatitic halls will have any understanding of gneiss table top of the Special the story, both ancient and modern, Pedestal was fashioned and polished. attached to the beautiful Hebridean Reproduced, courtesy of David rock which once lay on the opposite Thornton, from his image 58586 shores of an opening Atlantic. For posted on-line at www.aditnow. Osman the venture ended in disaster. co.uk. The casket and its pedestal left him bankrupt. slab of pegmatitic gneiss that is the It was financially unfortunate too in immediate support of Osman’s Uist and West Yorkshire. None of Magna Carta display case. the firms behind the making of the Special Pedestal were paid for their In one of Osman’s Northamptonshire contribution to Osman’s masterpiece, workshops there was inscribed aka the British government’s around the sides of the stone permanent bicentennial gift to the the words ‘PRESENTED TO THE USA. CONGRESS OF THE UNITED STATES OF AMERICA BY THE PARLIAMENT Acknowledgements OF THE UNITED KINGDOM OF It is my pleasure to thank the already GREAT BRITAIN AND NORTHERN named individuals who made this IRELAND IN THE BICENTENNIAL article possible as well as thanking YEAR 1976’. The two parts of the for their assistance the following: Eleni pedestal were airlifted to Washington Bide (Goldsmiths’ Company Library), in a military transport plane at the Jennifer Blancato (Office of the Curator, end of May 1976 and assembled Architect of the Capitol), Simon Lowe

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The pegmatitic top of the special pedestal exposed during the installation of the Magna Carta display in the Crypt of the Capitol Building in 2010. Courtesy of the Architect of the Capitol.

(Aditnow), Gordon Herries Davies, Dearnley, R and Dunning, F Alistair MacCaulay, Jane Osborne, W. 1968. Metamorphosed and David Schorstein and Laura Smith. deformed pegmatites and basic dykes in the Lewisian complex of the References Outer Hebrides and their geological Anon 1977. Annual Report for 1976, significance,Q. J. Geol. Soc. Lond., Institute of Geological Sciences, p. 123, 335–378. 122. Jenny Moore 2006. Louis Osman Black, G P. (ed) 1977. Outer (1914–1996) The life and times of an Hebrides Localities of Geological Architect and Goldsmith, Halsgrove, and Geological Importance. 184 pp. Unpublished report prepared by the Nature Conservancy Council for Na Jean B Archer h-Eileanan Siar, 91 pp. [email protected]

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The EGS long excursion to Cornwall

By Beverly P Bergman, David Blythe, Douglas Holliday, Stephen Livera, Richard A Smith, Christine L Thompson and Alison Tymon

The EGS Long Excursion 2018 took At the start of the first day, Peter Scott place in Cornwall from 19–26 May took us to the elevated viewpoint, and was led by Professor Peter Scott Carn Brea, overlooking Camborne, of Camborne School of Mines and numerous mines and much of the Exeter University, and Dr Mike Styles Cornish coast, where he introduced of the British Geological Survey. The us to Cornish geology. The granite group was based in Falmouth and on which we stood formed typical the aim of the excursion was to study tors; less typical were the scalloped the geology of the Lizard Peninsula and basin-shaped hollows formed by and neighbouring localities. Broadly prolonged exposure to the elements the geology of Southern Cornwall (other than the last glaciation which comprises predominantly Devonian this area escaped) (Figure 2). Peter mudstones deformed and overthrust pointed out the surrounding hills from the south during the Variscan orogeny by the spectacular ophiolites exposed on the Lizard; subsequently the central Cornubian granite batholith intruded the mudstones and produced an extensive metamorphic aureole characterised by widespread mineralisation (Figure 1).

Figure 1 Simplified geological map of Cornwall after BGS 1:625 000 Scale, Bedrock Geology UK South.

13 the egs long excursion to cornwall which were underlain by granites, saw skarn mineralisation, composed and the numerous chimneys and of tourmaline, garnet and magnetite, engine houses of the tin mines in that had replaced metabasalts close the adjacent valleys, which mainly to the granite. Cross-cutting mineral worked lodes away from the granite. veins had been exploited along the We paused to imagine how the area coast and we searched the old mine might have looked today if modern dumps for samples of cassiterite, mining had proceeded to form one wolframite, chalcopyrite, arsenopyrite vast open-cast pit. and molybdenite as well as secondary minerals. Warm, sunny weather also led us to sample the excellent Cornish ice cream!

The second day began at Chapel Porth west of St. Agnes, looking at Middle to Upper Devonian slates

Figure 2 Sculpted granite tor, Carn Brea ©Beverly Bergman.

We then drove west past South Crofty mine, the last to produce tin in the area, onto Cape Cornwall to observe the contact of the Land’s End Granite with Upper Devonian mudstones, locally known as ‘killas’, which have been metamorphosed in the granite aureole. The metamudstones were invaded by numerous early quartz veins and folded in zig-zag folds on several scales. Farther north, at Botallack, picturesque mines and engine houses are sited near the cliffs, inspiring the popular Poldark Figure 3 Crowns Engine House, stories (Figure 3). In former adits we Botallack Mine ©Alison Kerr.

14 the egs long excursion to cornwall of the Porthowan Formation of the The next stop was Cligga Head Gramscathco Basin. These sediments where the small, eponymous contain sandstones with a distinctly granite intrusion has been discordant deformation style completely mineralised and is compared to the softer metapelites. A famous for its greisen and tin- worked vein in the hanging wall of a tungsten mineralisation (Figure 5). normal ‘relaxation’ fault mineralised High temperature late-stage fluids by the St. Agnes granite showed turned the feldspars into micas and copper sulphides (chalcopyrite). deposited an array of minerals, including wolframite, cassiterite and A pleasant walk across the beach an arsenopyrite variety, lollingite, in warm sunshine led to the which breaks down to a distinctive workings below Wheal Coates. The secondary, green iron arsenite, mineralisation was extensive and scorodite. At Roche Rock an outlier formed against a rhyolitic elvan1 of resistant granite stands above the located along a fault where the ore surrounding countryside and has fluids were trapped (Figure 4). The been used as a place of worship mine was initially down to sea level over the generations. The intrusion and then a pumping house was is a quartz-tourmaline rock (with built for drainage to enable deeper no feldspar) intruded into Lower excavation. Devonian clastic sedimentary rocks (‘killas’). Is such an unusual rock a result of hydrothermal alteration by boron-rich fluids or could it have crystallised from a magma? Current theories favour crystallisation following the late separation of an immiscible boron- and fluorine-rich liquid phase from a granitic magma and there was much discussion, without resolution, about the nature and temperature of such a residual Figure 4 Mineralisation at Chapel melt from which tourmaline forms Porth, below the Wheal Coates instead of feldspar. The final stop of Engine House ©Beverly Bergman. the day was at Carclase, a disused china clay pit in the St. Austell 1 An elvan is the Cornish mining term for a vein of granite, where those who had seen feldspathic or porphyritic rock crossing a metalliferous the china clay pits in their heyday vein

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Lizard peninsula. The rocks of the Lizard represent an ophiolite — an upthrust sliver of oceanic lithosphere with a characteristic sequence of rocks. The ophiolite rode up and onto the northern margin of a closing ocean basin during the Upper Palaeozoic Variscan orogeny. Our first stop was at the lifeboat station at the south end of Coverack beach. Here we stood on an exposure of ancient mantle in the form of peridotite, an ultramafic igneous rock consisting mainly of olivine and pyroxene. Running through the peridotite were sub-parallel veins of another ultramafic rock, dunite, composed Figure 5 Black quartz-tourmaline almost entirely of olivine. Mike told veins and extensive wall-rock us that the veins served as pathways greisening of granite are both for magma rising-up through the controlled by steeply inclined, peridotite and feeding magma closely spaced joints in the quarry on chambers at the base of the crust. Cligga Head. Kaolinised phenocrysts of feldspar are aligned subparallel Working our way northwards, we to the joints. The notebook is about saw evidence of those magma 15 cm long. ©Steve Livera. chambers in outcrops of troctolite (named for its resemblance to the skin of a trout), a rare type of gabbro were disappointed to see how these that collected as a crystal mush at unique features of the Cornish the base of a magma chamber while landscape had deteriorated. gabbro crystallised higher up. We were now in a transitional zone Day 3, led by Mike Styles, promised between upper mantle and lower an excursion with a difference: a crust, probably corresponding to the descent into the former mantle, palaeo-Moho, and gabbro became returning via the Moho and the more dominant rock the further lower crust. This entailed going to north we walked. We then moved Coverack, a fishing village on the on to Porthoustock quarry, about 5

16 the egs long excursion to cornwall kilometres north of Coverack, and 200°C) lead-zinc mineralisation in marvelled at a sheeted dyke complex N-S trending veins. very similar to a mid-oceanic dyke swarm. And so, in one day, we had After lunch in Porthleven, our progressed from bottom to almost the examination of Rinsey Cove was top of a typical ophiolite sequence, curtailed by a rising tide. The wave- the only rocks missing being the pillow cut platform here comprises a roof lavas and deep-sea sediments that pendant of the Mylor Slate Formation, would normally cap the sequence. locally with andalusite and cordierite, surrounded and metamorphosed by Peter Scott was again our leader on the c. 284 Ma Tregonning-Godolphin Day 4, in the Portleven-Polurrian Granite. Several xenoliths of country area, where the Frasnian Porthscatho rocks occur within the granite Formation was thrust (Carrick which is pegmatitic in places. The Thrust) over the Famennian Mylor easternmost, low angle junction with Slate Formation, intruded by the the granite contrasts with the vertical Godolphin-Tregonning Granite, western boundary. Above the cove during the Variscan Orogeny, together we briefly examined the remains with associated mineralisation. The of the Wheal Proper Engine House Portscatho Formation at Church before proceeding towards Trewavas Cove, south-west of Gunwalloe, Head, noting the highly sculptured comprises strongly deformed grey granite outcrops below (Figure 6). turbiditic sandstones, siltstones and Beyond, more mine buildings were mudstones (slates), locally isoclinally reached, and search of the waste folded, and exhibiting cleavage. rocks suggested that the copper Sole structures occur on the bases of mineralisation hereabouts was largely several sandstone beds. These rocks confined to the granite itself. With the are overlain by Quaternary wind- aid of a Geiger counter, our leader blown sand with a thin basal deposit was able to demonstrate increased containing numerous fragments of levels of background radiation in the Devonian strata. At Porthleven Sands, mine dumps as evidence of uranium the Mylor Slate Formation is sheared ore. From this locality, there were and heavily deformed. Here, N-S fine distant views to the SE of cliffs trending quartz veins cross-cut earlier (Megiliggar Rocks) showing horizontal quartz veining. Nearby, beautifully sill-like granitic intrusions. restored historic mine workings, Wheal Rose and Wheal Penrose, had Day 5 began with a brief stop at St. exploited low temperature (100– Keverne, after which we inspected

17 the egs long excursion to cornwall exposures of Landewednack deformed with a strongly flasered (hornblende) schist, with a distinct fabric and significant colour variation. north-westerly foliation, in the old Some of the material was distinctly pale coastal quarry workings at Porthkerris. and feldspathic while darker, more The schists were also found to be mafic types approached pyroxenite variously folded and deformed, in composition. The metagabbro is some cases with detached fold limbs; thought to be derived from a layered the degree of deformation increased igneous intrusion which is referred to towards the north. Metagabbro was as the ‘Traboe Cumulate Deposit’. encountered on the north side of the cove. This has been subjected to At Porthallow, a northerly traverse granulite temperature and pressure was again made along the coastal levels before being retrogressively exposures, first examining the metamorphosed under amphibolite metagabbro on the south side of conditions. It was observed to be highly the cove. Outcrops of serpentinised dunite with prominent relict crystals of spinel were also encountered. The location of the Lizard Boundary Fault to the north was identified by a gully in the cliff, a number of sheared fragments of mica schist of possible Cambrian age and a zone of sheared and deformed rock extending over a total distance of about 100 m. Beyond this zone, there was a complete contrast in the geology with an outcrop of altered rhyolite thought to represent a large clast in an olistostrome. This, together with an adjacent exposure of metamorphosed basaltic rock and a succession of clastic sediments, is collectively referred to as the ‘Meneage mélange’ and is now generally considered to be of Devonian age.

Figure 6 Sculptured granite outcrops, For our final day, Mike Styles guided Trewavas Head ©Doug Holliday. us around the Lizard looking for

18 the egs long excursion to cornwall evidence of the obduction of the the xenoliths and the talc alteration Rheic Ocean ophiolite complex of the peridotite. during the Variscan collision. Below the Lizard lighthouse, cliffs of black As the group headed for home, we foliated amphibolite (hornblende reflected that in the space of a week, schists), originally basalt lava flows on we had examined mineralisation, the ocean floor, form the dramatic mine workings, ophiolite sequences coastline. Near Lizard Point, where and much else, and had come to the cafés and RSPB centre do a appreciate both the complexity brisk trade, a headland to the west and the economic importance of exposed 500 Ma pale, sillimanite- Cornish geology. Most of all though, cordierite schists of the Old Lizard our appreciation is extended to our Head Series. The isoclinally folded leaders, Peter Scott and Mike Styles schists also form the cliffs at Polpeor and, as ever, our organiser Anne Cove at the old lifeboat station. Burgess for making it all happen. The advice of David Stephenson helped Pebbles of white and black banded in the preparation of this article. Man of War gneiss (the oldest rocks in Cornwall), which forms the Bibliography offshore islands at Lizard Point, could Hall, A. 2005. West Cornwall. Geologists’ be found on the beach, evidence of Association Guide Number 31. Gondwanan crust. Leveridge, B E and Hartley, A J 2006. The Variscan Orogeny: the development After lunch at Lizard village, with and deformation of Devonian/ Carboniferous basins in SW England enough time to peruse the carved and South Wales. In: Brenchley, P and serpentinite souvenirs in the tourist Rawson, P. (eds) The Geology of England shops, we visited Landewednack and Wales, 226–255. Church where red and green Scrivener, R. Cornubian granites and serpentinite has been used to great mineralization of SW England. In: effect in the pulpit and font. Finally, Brenchley, P and Rawson, P. (eds) The at Kennack Sands, the group tackled Geology of England and Wales, 257–267. the origin of the so-called Kennack Styles, M T, Cook, C A and Holdsworth, Gneiss, a coarsely-banded felsic and R E. 2000. The geology of the Lizard mafic rock with a complex history complex; 100 years of progress. of intrusion and deformation. Using Geoscience in South-West England, 10, 92–98. field observation, we concluded that granitic and mafic magmas had been Corresponding author: Dr B P Bergman intruded into peridotite, judging from [email protected]

19 how things change — a uk geoenergy observatory in glasgow

How things change — a UK Geoenergy Observatory in Glasgow

By Alison Monaghan

When I started work as a geologist at Energy and Industrial Strategy, to gain BGS over 20 years ago my job was a better understanding of subsurface to make maps and 3D digital models change beneath our feet. of the subsurface in western central Scotland. By integrating fieldwork, One Geoenergy Observatory in the coal mine plans and boreholes I Thornton area of Cheshire will focus mapped and modelled the lithology, on a range of subsurface energy stratigraphy and structure of technologies to over a kilometre Carboniferous rocks and basins of below the ground. The other the Midland Valley. The results were Geoenergy Observatory will focus on a ‘static’ representation of what’s low-temperature geothermal energy beneath our feet. from the flooded mine workings below the east end of Glasgow to Fast forward to today and the way a depth of a few hundred metres. a geologist works has changed Here, scientists will be able to significantly — towards understanding move from knowledge of say, their competing resources, impact and underpinning static geological models change in the subsurface e.g. for of Carboniferous Coal Measures rocks, waste disposal, for energy resources to answer key research questions on and energy storage. However, low carbon, renewable, heat resources impartial, freely available data to within those rocks — and enable more constrain a ‘dynamic’ understanding widespread use of the subsurface in a of subsurface change can be hard sustainable way. to come by. The UK Geoenergy Observatories project is an ambitious First of all, I’ll describe the concepts £31 million investment that will behind mine water geothermal see BGS set up and operate two energy and then summarise what subsurface research laboratories on is planned for the Geoenergy behalf of the Natural Environment Observatory in Glasgow, the Glasgow Research Council and the UK Geothermal Energy Research Field Government department for Business, Site.

20 how things change — a uk geoenergy observatory in glasgow

What is mine water geothermal fractures have been termed an energy? ‘anthropogenically-enhanced Many parts of the UK are underlain aquifer’. By taking advantage of this by abandoned coal mines. Upon anthropogenic aquifer, warm water closure, the mines became naturally can be abstracted through a borehole flooded with water which becomes and passed through a heat pump to warmed due to the naturally provide a heat source for homes and increasing geothermal gradient with businesses, before being returned depth. For the relatively shallow within a sealed loop to a different mine workings in eastern Glasgow part of the mine system (Figure 1). the water is thought to be around 12°C, with a stack of seven worked A number of mine water geothermal coal seams. These man-made schemes have been run successfully workings have greatly increased for tens of years. For example, a permeability for groundwater and scheme in Shettleston in Glasgow the mine working galleries, shafts, provides for a small number of roadways and collapse-related homes, and a much larger scheme

Heat pumps Getting heat from the ground Using mine water to heat your home The interior of the Earth is hot, so, the deeper you go, the warmer it gets. Water in ﬂooded mine workings A device called a heat pump can turn warm groundwater into absorbs this heat – if we can extract it, we might be able to harness this energy to heat our homes. water that is hot enough to heat your radiators or ﬁll a bath.

1. Water is extracted from 3. The used (and now cooler) 4. The returned water slowly fllters back through flooded mineworkings minewater is pumped back the flooded mine system and warms back up. 1. Warm groundwater (around 4. The gas then passes underground and brought to the underground – far enough away 10-15˚C) is pumped into a tank. through a compressor which surface. This water is warm from the extraction point to ensure The research we will be carrying out heats it to around 50˚C. because it has been heated by it doesn’t cool down the water we will find out if extracting geothermal geothermal energy. want to extract. energy in this way is safe and efficient 2. A liquid called a Although the compressor enough to be worthwhile. refrigerant is pumped through does use some electricity, tubes in the water tank. Heat you get out about 4 times The minewater is pumped into 2. from the groundwater turns as much energy out of the homes where its energy is extracted the liquid into a gas and the heat pump as you put in. and used to power a heat pump groundwater cools. (see right-hand side of poster). 5. The hot gas is pumped 3. The cooled groundwater through a water tank. 2 3 is pumped away and It heats up the water and Warm Cooled reinjected underground to be the gas cools. groundwater groundwater warmed up again. pumped from returned back mine underground workings 1

Warm groundwater 1 enters tank 7

Collapsed HEAT PUMP 6 The cooled gas mine 6. 2 Hot water turns back into a sent to house liquid and returns to be heated up again. Coal seam 7. The hot water is used to heat the Refrigerant house and then extracts heat returned to the heat Flooded mine from pump for reheating. workings groundwater Cooled water returned for reheating Compressor 5 3 Water temperature increases with depth 4 Groundwater Cooled reheats as it groundwater ﬁlters through returned back 4 the mine system underground

Many of the mineworkings are likely to be collapsed and Copyright: NERC, Ben Gilliland blocked by rubble, but water can easily ﬁlter through

21 how things change — a uk geoenergy observatory in glasgow that also includes heat storage and geoscientific challenges. Some is running in Heerlen in the geoscientific examples include: Netherlands. Several schemes e.g. at Markham in Derbyshire, have • how quickly warm water is targeted mineshafts or roadways. replenished — resource value and However, few schemes target sustainability the much more extensive mine • what minerals are in the water and workings — either stoop and room, how to minimise clogging of pipes or ‘waste’ from total extraction — that etc. — hydrogeochemistry it is planned to test at the Glasgow • costs and risks of borehole site. Also, most existing schemes have drilling — does it matter what type limited subsurface and environmental and depth of mine working is monitoring to record what happens targeted? to the subsurface environment when • subsurface connections between the warm mine water is abstracted, near surface land contamination and the cooler mine water returned. and mine waters — environmental protection Mine water geothermal energy is a potentially significant source of This is where the UK Geoenergy low-cost, continuous low-carbon Observatory in Glasgow comes in. heat that is sustainable long-term. However, its contribution to the UK’s What’s going to be at the Glasgow energy mix, and to decarbonisation Geothermal Energy Research Field of its energy, is, as yet, largely Site? unrealised. The Glasgow site was The subsurface Observatory will chosen as it has much in common feature a number of boreholes of with other parts of the UK with a various depths, which will enable mining history, relatively complex research into the area’s geology, Carboniferous geology and a legacy underground water systems and the of former industrial land use. Mine potential for mine water geothermal water geothermal, on its own or heat. Measurements will be taken in combination with other heat from the boreholes, such as sources, could provide community temperature, water movement, water scale heat via district heating chemistry and of microorganisms networks in former coalfield areas (geomicrobiology). Environmental which commonly suffer from fuel baseline monitoring of near-surface poverty. Yet to achieve this there are chemistry, gases and waters will also a number of economic, regulatory be measured, to provide a record

22 how things change — a uk geoenergy observatory in glasgow of ‘what is normal’ before any to characterise and monitor water geothermal research takes place. in the Glasgow Upper and Glasgow Main coal workings (Figures 2, 3). Planning approval and permitting Five boreholes will be used to record for the current characterisation and the environmental baseline near the monitoring phase have been granted top of the bedrock and superficial with the majority of the boreholes deposits. The boreholes are planned located at the Cuningar Loop, to have range of sensors such as Rutherglen (Figure 2). Planned drill resistivity and temperature cables, lengths are between around 10 to 90 water data monitors will be installed, metres. Six boreholes are targeted and regular water samples will be

23 how things change — a uk geoenergy observatory in glasgow taken. In addition, there is one seismic overlain by a variable thickness of monitoring borehole of around 200 m artificial (made) ground. These deposits drill length at Dalmarnock (Figure rest on approximately 300 m of Scottish 2), which is planned to provide a Coal Measures Group bedrock. borehole core. A new core scanning Underlying this are older Carboniferous facility at BGS Keyworth will be used strata of the hundreds of metres thick to give a geophysical, mineralogical, Clackmannan and Strathclyde groups. and geochemical and optical/X-ray downcore record. The Quaternary deposits are of variable thickness, up to 30 m. Subsequent to the current phase and The upper surface of bedrock was permissions for the installation of the incised, with thicker accumulations of pipes and heat pumps that will allow superficial deposits infilling a broadly geothermal research, the observatory NW-SE trending channel following will be open to the whole of the UK the modern-day River Clyde. There science community to undertake is widespread made, filled and research. Continuous data from state-of- landscaped ground relating to a the-art sensors from the boreholes will be variety of prior industrial land use, in open, free and accessible to the public, some places this is 10–15 m thick. government, regulators, academia, and industry via an online portal. Bedrock strata of the Scottish Upper, Middle and Lower Coal Measures Timescale formations of the Westphalian Scottish Planning permission and various Coal Measures Group are cyclical permits are in place, with borehole sedimentary rocks of sandstone, drilling work started on site in siltstone, mudstone and coal. November 2018. The aim is for all Recorded coal mine workings in the boreholes and monitoring equipment area were active from 1810–1934 to be ready for research use from with total extraction and stoop and 2020 for a 15-year lifespan. room workings shown. It is expected that total extraction areas collapsed Geology of the research site within a few years of mining to form The Glasgow Geothermal Energy a waste, and that the mines will be Research Field Site is located on the flooded. Figure 3 illustrates a cross- western side of the Central Coalfield section of the geology and two of of the Midland Valley of Scotland. the planned sets of boreholes in It is located within glacial and post- the Cuningar Loop area — our static glacial Quaternary superficial deposits, model of the geology before we start

24 how things change — a uk geoenergy observatory in glasgow

Figure 3 Cross-section of the geology in the Cuningar Loop area with the planned borehole target depths shown. Note that the thick black lines represent areas recorded on abandonment plans as mine workings. British Geological Survey © UKRI 2019. All Rights Reserved. drilling, monitoring and sensing the with locally sourced, decarbonised heat/ subsurface. heat storage, reinvigorated with local engineering and science expertise. To conclude In a few years’ time I hope this project Further information and references will have enabled us to reflect not can be found on the BGS website only on ‘how things change’ for a BGS http://www.bgs.ac.uk/research/ geologist’s work, or our significantly energy/esios/glasgow/home.html improved knowledge of ‘how things change’ in the subsurface environment Alison Monaghan, above and in old coal mines, but British Geological Survey, because with the results of this national- The Lyell Centre, Research Avenue good science we’ll be on the way to South, Edinburgh EH14 4AP, changing old coalfield communities [email protected]

25 book reviews

Book reviews

Coal Mining in the East Neuk of In his introduction, Professor Fife by John McManus. Dunedin McManus claims that it is the Academic Press, Edinburgh. 2017. underlying geological controls that Hardback, 200 pp. Price £24.99. are the principal focus of his account, ISBN: 978-1-78046-072-7. and whilst this rather underplays his fascinating social commentary, geology is very much to the fore at the beginning of the book. We start with the big picture. The first of four short chapters takes the reader from the origin of the Earth to plate tectonics and sea floor spreading. This is followed by a summary of Scotland’s geology from the Proterozoic Lewisian to the Early Permian amalgamation of Pangaea, then by the story of We have an ambivalent attitude to life emerging from the sea and the coal these days, so it’s always salutary evolution of terrestrial vegetation. to see recorded the contribution That leads naturally to a discussion of that mining has made to Scotland’s coal formation, with Carboniferous economic development and cultural cyclothems in Fife originating in heritage. However, when recalling response to the effect on sea-level of the heyday of the Scottish coalfields, distant glacial fluctuations. perhaps the East Neuk of Fife does not immediately spring to mind. From the broad geological All the more welcome therefore perspective, McManus moves to the is Professor John McManus’s history of mining in the East Neuk. impressively researched account The 18th and 19th centuries saw of the geological basis of mining the peak of activity, but few mines in that region, well-illustrated survived past the 1920s and only one throughout, skilfully integrated with was still working at nationalisation the complementary social history, and in 1947. The developments in Fife rounded-off by a good glossary and are integrated into the broader index. picture of coal mining across Britain

26 book reviews and improvements in transport, found it necessary to have at hand most notably the expansion of Figure 9.3 from the Read et al. the railway network. A wealth of (2002) chapter in The Geology of detail emphasises the hardship and Scotland; I recommend a similar deprivation of life in the mining tactic. Otherwise the descriptions communities. That theme also are well illustrated, and indeed in permeates the description of the part the detailed account of “The ways in which coal has been won, coal seams and mines of the East from stoop and room and bell pits to Neuk” (Chapter 10) reads like a field modern longwall mining. Illustrations guide (complete with a couple of include a series of seven evocative illustrations from MacGregor’s classic pictures of underground work based of 1968). Further detail is then added on original paintings by Derek Salter, from two major 20th century coalfield himself a former miner and now an reviews (Chapter 11) before the most art teacher. The paintings have a important sector of the coalfield, muscular, almost heroic feel, but in around Largoward, is given individual no way glamorise the claustrophobic attention (Chapter 12) although it conditions. had featured prominently in the earlier chapters. The overall result is The first nine chapters occupy only challenging, but persevere, and there 60 pages, but thereafter, in the is much reward in this exhaustive real heart of the book, the next account which delivers equally on its four chapters take up just over 100 disparate themes. pages. Although given separate status they are intricately interconnected A final brief chapter provides some and contain a plethora of detail, ‘closing thoughts’. These extend facts and figures. The range and to fracking but avoid the issues intensity of Professor McManus’s around anthropogenic climate research is manifest, but the change in which coal is now cast as result is not easy reading; this is the principal villain. That’s a sad, if not a lightweight book. Nor is an inevitable epitaph. John McManus understanding of ‘The geology of the has done a great service to both coal-bearing succession’ (Chapter geologist and socio-economic 9) made easier by the omission of historian by bringing together a a detailed correlation chart for the different side of the story from the Carboniferous stratigraphy. Table East Neuk of Fife. 1, early in the book, is inadequate and to keep up with the author I Phil Stone

27 book reviews

Introducing Metamorphism by Ian minerals, the main techniques Sanders. Dunedin Academic Press, for studying metamorphic rocks Edinburgh. 2018. Paperback, 148 pp. including microscopy, the scanning Price £14.99. ISBN 978-1-78046-064-2. electron microscope, and isotopic age dating. The main text is an excellent description of the different styles and settings of metamorphism both with progressive and retrogressive developments. Technical terms are introduced and clearly defined.

The first chapter starts with the fundamentals. The six main parent lithologies (protoliths) are defined. This is a fascinating book: although The main types of metamorphism entitled ‘Introducing Metamorphism’ and their settings are described, it is much more than a simple including burial, contact, shock, guide to the subject as it covers dynamic and hydrothermal. in considerable detail the causes, geological settings and development The second chapter deals in of the wide range of metamorphic considerable detail with the phenomena. petrography of metamorphic rocks. This examines the mineralogical The book is structured in three parts, changes, in the main rock types, as a comprehensive glossary, three a result of increasing PT conditions appendices and the main text in five with variable crystal growth rates. chapters. The concept of particular index minerals reflecting specific pressure/ In the preface the author temperature conditions is introduced, acknowledges that some readers for example biotite zone, garnet zone may have a limited background etc. Also, changes in the structure of in geological processes and lack the rock under directed stress with the familiarity with some of the methods consequent development of cleavages, used to study metamorphic rocks. folds and lineations, and how these The appendices are designed to may be overgrown by new mineral provide this information with a growth is discussed. The variable synopsis of earth processes, the mineralogy and textural changes in chemistry of common metamorphic the various lithological types when

28 book reviews subjected to differing metamorphic In summary, the author has styles is well illustrated. Different succeeding in producing a text that fields on a PT grid for metabasic provides a comprehensive description rocks are defined and the concept of of metamorphism ranging from the metamorphic facies is introduced. simple fundamental definitions to complex metamorphic processes. The third chapter examines, inter It is superbly illustrated with, in alia, the critical role of water in particular, excellent photographs promoting and controlling grain and microphotographs illustrating growth and its role in retrogression. mineral textures, the relationship of The production of rock melts can also minerals to structures and the relative be determined by the presence or development of minerals. In addition, absence of water. The nature of grain there are many very clear and useful growth is also covered. diagrams covering mineral types, their stability fields and their development The fourth chapter considers contact under evolving metamorphic metamorphism and develops conditions, simplified facies maps, the facies concept. Metamorphic the relationship of minerals within belts, reflecting differing styles of triangular chemical diagrams, etc. metamorphism (e.g. Barrovian and Buchan) are discussed as well as This is a well-produced book and a their relationship, in part, to different comprehensive modern account of tectonic regimes. For example, the metamorphism. development of paired metamorphic belts at subduction zones as Each chapter contains a wealth of well as other tectonic regimes. It detail. It covers items of interest to concludes with a discussion of shock the novice and those with experience metamorphism basically related to in metamorphic rocks. Because of meteorite impact. the depth of information, the relative novice might find a straight read The fifth chapter examines the use of rather overwhelming and might find geothermometers and geobarometers. it better to skim the essence of each The resultant data, related to textural section and then go back and study evidence (for example the growth or the detail as desired. Either way, all retrogression of component mineral users will enjoy and gain from this species), allows the history and book. character of metamorphic complexes to be determined. Doug Fettes

29 This issue: No. 65, Spring 2019

1 Editorial ramble From Pangaea to the Anthropocene by way of South Uist, Cornwall and Glasgow

7 A special stone for a very special pedestal By Jean B Archer

13 The EGS long excursion to Cornwall By Beverly P Bergman, David Blythe, Douglas Holliday, Stephen Livera, Richard A Smith, Christine L Thompson and Alison Tymon

20 How things change — a UK Geoenergy Observatory in Glasgow By Alison Monaghan

26 Book reviews Coal Mining in the East Neuk of Fife Introducing Metamorphism

All previous issues are available online at www.edinburghgeolsoc.org/publications.

Cert no. SGS-COC-003231 ISSN 0265-7244