The Edinburgh Geologist
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The Edinburgh Geologist Magazine of the Edinburgh Geological Society Issue No 66 Autumn 2019 The Edinburgh Geologist Issue 66 Autumn 2019 Cover Illustration Small agate-filled vesicles in Devonian lava from Scroggie, near Balmerino in Fife: x 0.9 approximately. Image courtesy of National Museums Scotland, NMS G.210.871 A. There are more than 5500 agates in the National Museums’ collection, and this specimen is from the Heddle agate suite, donated after Matthew Heddle died by Alexander Thoms, to whom it had been bequeathed. BGS images are reproduced by permission of the British Geological Survey ©UKRI. Published September 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 Ladies’ Day An editorial ramble by Phil Stone As usual, this issue of Edinburgh may become Britain’s largest offshore Geologist ranges across disparate windfarm — and graciously includes geological themes, but our articles a male co-author. Keira Greene gives have one unifying feature. All the graptolites a poetic appreciation, principal contributors are women. imaginatively celebrating these In this, the year that the Geological biostratigraphic wonders of the Society of London has celebrated Scottish Southern Uplands. The the centenary of its first admission graptolite palaeontologists Gertrude of female Fellows (at a momentous Elles and Ethel Wood were two of meeting on 21 May 1919), I rather the first eight women admitted to the wish the coincidence had been pre- Geological Society of London and planned. Such foresight cannot be would have appreciated Keira’s very claimed I’m afraid, but perhaps it different response to their mutual is more telling for that combination inspiration. Finally, our book review, of authors to have emerged Introducing Geology, is provided by unbidden.1 Alison Tymon. Rachel Walcott leads off with a Passing over the temptation to beautifully illustrated account link Paige DePolo’s dinosaurs with of Matthew Heddle’s agate London’s pre-1919 geological élite, collection — and provides our let’s move rapidly on to another striking front cover. Paige DePolo gender revolution that took place tracks dinosaurs on Skye and takes more locally seventy years ago. to the sky, kind of, in the process. Then, in 1949, five women were Carol Cotterill heads out into the admitted as the first female Fellows North Sea, to the Dogger Bank, and of the Royal Society of Edinburgh, explains the foundations of what and amongst them were two 1 And not to be outdone, the British Geological Survey will soon have its first female Director; DrKaren Hanghøj will take up the role on 14 October. 2 Keira’s contribution to EG is taken from her film Eustatic Drift, which premiered in May this year at the Alchemy Film Festival in Hawick – what an appropriate location. 1 EDITORIAL geologists: Doris Reynolds and Ethel to mammoths, deer and many of Currie. Reynolds developed the our human predecessors — but then controversial theory of ‘granitization’ the ice melted, and sea level rose. which, although later disproved, By about 5000 BC only a few low- focussed attention on the hard lying islands remained, although questions surrounding the origin of the coup de grâce for Doggerland’s granite. She was based at Edinburgh inhabitants may have been a tsunami University, perhaps overshadowed generated by the Storegga Slides somewhat by her famous partner — I (three huge submarine landslides off wonder if Arthur Holmes was ever the Norwegian coast) at about 6 200 introduced as Doris Reynolds’ BC. We’ll soon face our own battles husband. Currie, a palaeontologist with a rising sea level, and geology and Carboniferous stratigrapher, was will have an increasingly vital role. Assistant Curator at the Hunterian Just think about coastal defences Museum in Glasgow and in 1952 and relocation of infrastructure became the first female president of (and people) with the construction the Geological Society of Glasgow. materials and site investigations Here in Edinburgh, we didn’t take that will demand, not to mention that radical step until 2014 although the associated major changes in ladies were first admitted to our hydrogeological regimes. Then Society in 1865 — “in accordance there are the essential geological with the general progressive contributions to renewable energy tendency of Edinburgh”. They even developments and CO2 storage — I’m enjoyed half-price membership! sure you can add to the list. Welcome to the Anthropocene! Of course, today’s challenges and opportunities, for everyone with More cheerfully, let’s not forget geological inclinations are very our subject’s pleasures and their different to those that arose in the communication to new audiences. past — and the moraine complex Geologically inspired poetry has of the Dogger Bank provides plenty the potential ‘to reach those parts of food for thought. Around ten that others cannot’ and will enjoy a to twelve thousand years ago it showcase next year at Edinburgh’s was the rolling hill country at the Geopoetry Festival, scheduled for northern margin of Doggerland, the 1 October 2020. This gathering, to low-lying expanse of tundra that be held on National Poetry Day, is occupied much of what is now the to be hosted by EGS, the Geological southern North Sea. It was home Society of London, and the Scottish 2 EDITORIAL Poetry Library, and aims to bring Siccar Point together poets and geoscientists “to further encourage the rocks to Suddenly we see Red rocks from over the sea speak”. We hope to have more on River borne that in the next issue of EG but, in Now very worn the meantime, one of the Festival And then beneath conveners, Professor Patrick Corbett Something quite different of Heriot-Watt University, provides us with his own take on Siccar Point in our concluding editorial column. Geology? Don’t bet on it! Finally, here’s something for all those readers who were disappointed This rock is old as can be Hard and grey from undersea Standing proud from Deep down in Iapetus’ocean This rock is old as can be Hard and grey from undersea Standing proud from Deep down in Iapetus’s ocean This rock is old as can be Hard and grey from undersea Standing proud from Deep down in Iapetus’s ocean to discover that the editorial headline — Ladies’ Day — didn’t refer Patrick’s Unconformity to the Musselburgh Races. It is a well- known phenomenon that sometimes the eventual examination of long- neglected rock specimens can prove less entertaining than the content of the old newspapers in which they were wrapped. This was my recent experience when the packing material turned out to be the horse racing pages from the Scottish Daily Express of Monday 5 August 1968. Hutton’s Unconformity A creased, yellowing photograph of galloping horses was accompanied by An appropriately unconformable the results of the Kingsbury Handicap view of Siccar Point by Professor at Windsor on the previous Saturday, Patrick Corbett, kindly drafted by and carried the following caption: Grant Ross. Foxroy beats off 10 rivals to win from Phantom Jet and Chuffed. Edinburgh’s Geopoetry Festival Fourth was Geology. 1 October 2020 Can any punters out there tell us Deadline for contributions 1 March more about a racehorse called More information: Geology? https://www.geolsoc.org.uk/GSL-Geopoetry-2020 3 HEDDLE’S AGATES Heddle’s Agates By Rachel Walcott Professor Matthew Forster Heddle vesicular lava flows. The cavities, (1829-1897) FRSE was, indeed which act like molds, form through remains, Scotland’s most prolific the coalescence of volatiles that and thorough mineral collector and emerge during decompression as renowned mineralogist (Johnston the lava erupts and flows. As such, 2015). By the end of his life he had they have a number of interesting amassed a collection that included features; for example, the cavities one third of all known minerals at are often elongate in the direction the time. Heddle seems to have that the lava flowed before finally had a particular fondness for silica, crystallising. Unlike most minerals, as varieties of quartz make up one agates crystallise from the outside in, third of his 7000-strong collection. that is from the cavity wall inwards, Many of these, 1600 in all, are tending to become less hydrous in agates. While Heddle viewed the composition as they do so. Layers agate collection as separate from of chalcedony and/or opal may the main mineral collection, this completely fill the vesicle (Figure was not a collection assembled for 1) or a small pocket may remain its beauty. As with the minerals, he in the centre, which is often filled was primarily driven by the desire with crystalline quartz or amethyst. to discover, describe and identify Whereas the outside of the agate is new features and, where possible, usually a dull green, the layering and to understand how they formed. contaminants provide an array of This motivation is reflected in colours and textures inside, rendering the specimens and nature of his each agate unique. All of these collection, now housed in National features were of keen interest to Museums Scotland (NMS). Heddle. Scottish agates While some notable agate sites are in Agates are semi-precious gems largely the Palaeogene lavas of the western made from cryptocrystalline quartz. Scottish islands such as Mull, Rum They are colourful, banded nodules and Arran, most agates are found that typically form in the cavities of in the Permian and Devonian lavas 4 HEDDLE’S AGATES Figure 1 Agate from the Blue Hole near Usan, Angus, showing horizonal onyx banding and other features Heddle described in his final paper: ‘fortification’ banding (top left), and ‘tubes of escape’ (bottom left and middle right), x 1.