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. NMS G.210.1271. of the Midland Valley, particularly agates are often all that is left once towards the north east (Figure 2). the host rock has weathered away. Agates are most commonly found Loose agates, or ‘Scottish Pebbles’ in situ in vesicular andesite but are as they are locally known, are often occasionally found in basaltic rock found in ploughed fields and on or lining fractures as in the example beaches. from Burn Anne in Figure 3a. Harder wearing than the encompassing lava,
Figure 2 Map of central Scotland showing many of the locations where Heddle collected agates. For geological explanation see BGS 1:625 000 scale Bedrock Geology UK North.
5 heddle’s agates
Figure 3 (a) Vein Agate with moss texture from Burn Anne, Ayrshire, x 0.6 (NMS G.210.486), (b) Agate exhibiting the green colouration of its skin and with a sealed fracture or ‘rent’, location unknown, x 0.8 (NMS G.210.1658), (c) Stalactitic Agate from the Blue Hole, x 0.7 (NMS G.210.1542), (d) Sheared ‘fortification’ agate, location unknown, x 0.6 (NMS G.210.1120), (e) Heddle’s famous Seascape agate from the Blue Hole, one of two halves, x 0.8 (NMS G.210.453), (f) Agate exhibiting pendulous celadonite skin coated in chalcedony, location unknown, x 0.5 (NMS G.210.1639). The location of many Heddle agates was not recorded.
6 heddle’s agates
Heddle the collector (1837–1925) of St Andrews. Not Collecting agates was a sociable only did these friends provide activity for Heddle. We can’t be companionship but they shared good sure when he started to assemble finds (Figure 4). his agate collection, but he was certainly active by the 1850s when The most important agate locality he met his life-long friend Patrick was the Blue Hole in Angus. One Dudgeon (1817–1895). Together third of Heddle’s collection comes they collected vein agates from Burn from this locality alone, not to Anne located close to Dudgeon’s mention substantial parts of Miln’s house in Cargen, Dumfriesshire, and Thoms’ collections. Agates from but they mostly focussed on areas this locality were noted for their closer to St Andrews where Heddle delicate beauty and bright green taught Chemistry, areas such as mineralised skin or ‘paint’ as it was Fife, Perthshire and Angus. Other locally known. These days, the companions were Robert Miln precise location of the Blue Hole is (1824–1905) who lived in Broughty uncertain, although we know it is on Ferry, Angus, and Alexander Thoms the shore near Usan, no more than 3
Figure 4 Heddle shared a lot of agates with friends. The Blue Hole agate on the left is from the Heddle collection (NMS G.210.1311), the counterpart (right) is from the Miln collection (NMS 210.1891), x 0.8.
7 heddle’s agates miles south of Scurdie Ness in Angus companions, which were primarily (Heddle and Thomson, 1894). a representation of geographical diversity, Heddle paid relatively Agates were not collected just for little attention to the source of the their aesthetic value, however. specimens judging from the extant Unlike the collections of his labels found with them (Figure 5a). Rather, he was fascinated by how they formed. For example, he collected broken agates as they revealed a lot about their 3-dimensional structure and sequence of formation (Figures 3b). If they revealed interesting textures he cut and polished them irrespective of how small they were; he had some specimens only 1 cm in diameter. He also collected anything unusual, for example uncut agates that reveal the flow direction of the lava or agates in vesicles that crystallised just as they started to coalesce. He spent weeks digging the Blue Hole, partly because the skin on agates there was particularly thick and soft and good for analysing. Thin sections and thick sections were used to Figure 5 (a) Label of Heddle’s analyse composition of non-silica with one edge glued to an agate minerals and he conducted a range from Montrose, (NMS G.210.1120). of experiments to identify the ‘skin’ Heddle’s main motivation for minerals coating the agates and those collecting agates was to understand minerals within the agates. He found their formation through careful that some layers stuck to the tongue observation. (b) Labels put on when licked and that chalcedony fortification and onyx agate from becomes stained when boiled in Montrose which was displayed in honey (Heddle 1899)! the Scottish Mineral Gallery after Heddle’s death (late 1890s–1940s) Heddle published dozens of papers (NMS G.210.929), x 0.5. but two of his last were on agate
8 heddle’s agates composition and formation. One ‘stalactites’ (Figure 3c and e). Next paper written with a colleague, J. come the bands of either onyx Stuart Thompson, concerned the (horizontal bands in Figure 1), or chemical composition of the green more chalcedony. If the agates are micaceous mineral celadonite partly unfilled, then they may have 2+ 3+ K(Mg,Fe )(Fe ,Al)[Si4O10](OH)2 a core of quartz, amethyst or more which together with delessite rarely calcite, or even an empty (a type of chlorite (Mg,Fe,Fe,Al) space (Figure 3e). Finally, one of
(Si,Al)4O10(O,OH)8)) commonly coats the unique features of agates with agates (Heddle & Thomson 1894). A a name coined by Heddle that is second more substantial paper was still in common usage: the so-called on the sequence of crystallisation ‘tube of escape’. These are routes of agate and the resulting patterns through which excess silica was (Heddle 1899). He was liberal expelled from the core of the agate with inventing new terms for his back into the host rock (Figures 1 observations, for example, discachtæ, and 3b). oonachatæ and hæmachatæ for the small disk-like, white and red spotted Heddle made many thin sections textures observed in some agates which are now housed in the respectively. Not all of these terms Hunterian Museum in Glasgow. Using are still used although some have these, he noted that chalcedony has a survived, for example ‘fortification fibrous texture with fibres orientated agate’ (Figure 5b) and ‘tube of at right angles to the growth or escape’ (Figure 1). banding directions. Heddle suggested that these might be the very high In his 1899 paper, Heddle suggested temperature form of silica — tridymite. that the minerals lining vesicle walls We now know that these are actually were formed from the alteration formed by spirals of chalcedony and and mixing of host rock minerals, moganite, the latter being a hexagonal particularly augite. Sometimes these form, low-temperature polymorph initial layers of chlorites, micas or of quartz that was discovered quite even zeolites were so thick or loose recently (Heany & Post 1992). that they would flake off or dangle Another important suggestion by into the cavity space, producing Fallick et al. (1984) is that the silica gel Moss Agate (Figure 3a), within the from which agates formed originated next layer of clear chalcedony; in water at only about 50°C rather the chalcedony sometime casts than at high temperature. These loose lining material forming corrections aside Heddle’s paper
9 heddle’s agates
Industrial Museum in Edinburgh (now part of National Museums Scotland) for several months to develop a new gallery of Scottish Minerals. He used almost all the 7000 minerals that he donated and partly sold to the museum. They were located on the top, northwestern-most gallery of what is now the National Museum of Scotland (Figure 6). In this display he exhibited 300 agates, half of which were his own. When Heddle died, he bequeathed 1000 of his best specimens to Thoms, who donated them to the museum the following year. John Goodchild, the curator at the time, added most of them to the gallery where they were arranged to show the origin, variety, ‘unmaking’ Figure 6 Plan of the Scottish (fracture and alteration) of agates, Mineral Gallery as it was in 1896, all explained in an accompanying two years after Heddle set it up in museum guide (Goodchild 1899). what is now the National Museum Many of these agates remained on of Scotland. Cases containing agates display for several decades until are outlined in red. John Goodchild they were hastily packed away at later added the agates which Thoms the advent of the Second World donated, putting them into the War. Today there are a few Heddle hexagonal case in the centre and agates on display in the Restless Earth four additional upright cases. Gallery with most now housed in the National Museums Collection Centre. They are accessible to interested remains a very useful resource to parties by prior arrangement. There understand agate formation and a was nothing nostalgic or egotistical great tribute to his observational skills. about Heddle and his collection, he simply loved collecting minerals and In 1894, when Heddle was 65 understanding the stories that they years old, he was employed by the told. Agates were no exception.
10 heddle’s agates
You might be able to view this broken agate (NMS G.210.1671) in 3-dimensions by looking at the two images and slightly crossing your eyes until both images become superimposed. [Good luck, I can’t manage this trick – Ed.]
Acknowledgements Heany, P J, and Post, J E. 1992. The Thanks to Phil Stone for his widespread distribution of a novel encouragement and patience and to silica polymorph in microcrystalline Bill Crighton for the images of agates. quartz varieties. Science, 255, 441– 443. References Johnston, H H. 2015. Matthew Heddle, M F. 1899. On the structure Forster Heddle, Mineralogist and of agates. Transactions of the Mountaineer. National Museums of Geological Society of Glasgow, 11, Scotland. 153–173.
Fallick, A E, Jocelyn, J, Donnelly, T, Heddle, M F, and Thomson, J Guy, M, and Behan, C. 1985. Origin S. 1894. On the skin of agates. of agates in volcanic rocks from Mineralogical Magazine, 10, 248– Scotland. Nature, 313, 672–674 250.
Goodchild, J G. 1899. Guide to Dr Rachel Walcott the Heddle Collection of Scottish Principal Curator, Earth Systems, Agates. National Museums Scotland.
11 tracking down scotland’s dinosaurs
Tracking down Scotland’s dinosaurs
By Paige dePolo
When one imagines the places where insights into dinosaur behaviour fossils are found, the locations evoked and paleoecology from this poorly are remote, challenging to work in… recorded time period. and dry. Classic localities like the Gobi Desert, the Badlands of South Working on the Isle of Skye presents Dakota, and the deserts of Utah are a series of unique challenges that characterized by blinding sunlight, are driven by uncontrollable factors little shelter, and an abundance of like the weather and the tides. The dust. Where would a dinosaur hunter dinosaur track sites were located on be in these types of environments intertidal platforms, which meant without a trusty broad-brimmed that there was a narrow window hat a la Indiana Jones? Folks with of opportunity for examining the this mental image of fossil hunters footprints each day. Additionally, may have a difficult time imagining the platforms were covered with palaeontologists working in the wet, seaweed, limpets, and other marine coastal environment of the Isle of life which served to obscure fine Skye, Scotland. Yet the coastlines details of the footprints. The final and tidal platforms of the Trotternish challenge from nature at the sites Peninsula (the northernmost was the weather — sunny, clear days, peninsula on Skye) preserve while not unheard of on Skye, are sedimentary rocks with footprints, decidedly less common than in the teeth and bones from a wide variety average desert. of animals, including dinosaurs. Even more excitingly, these rocks are When first encountering one of from the Middle Jurassic (174–164 these track sites, the magnitude of million years ago), a time where the task is a bit overwhelming. How dinosaur fossils are rare globally. The is a person supposed to understand fossils from this part of the world are, the information contained in the therefore, quite special. In particular, footprints if the area is large, flat, and several recently discovered, laterally covered in slippery things? How is extensive, in-situ dinosaur track sites the careful, painstaking, slow work possess the potential to provide of a good paleontological description
12 tracking down scotland’s dinosaurs going to be accomplished if one Once the tracks were better exposed, is persistently being chased by the the challenge arose of how to incoming tide or being rained on and precisely figure out their spatial blown about by high winds? How relationships. It seemed like the can one confidently and consistently best way to overcome the logistical recognize footprints in this heavily challenges of mapping the footprints eroded environment? and documenting the sites was to fly a drone over them and collect a Large problems can often be solved series of photographs that could later by breaking them down into smaller be used to make three-dimensional pieces and fieldwork on these track models of the outcrops. Indeed, the sites started in the simplest way drone was flown with great success possible — with clearing the platforms at two of the four sites being studied. of seaweed. This job was certainly However, drone flight is extremely nothing to sneeze at — one of the dependent on ideal weather platforms spanned approximately conditions (low wind, no rain) that 3000 square meters and the work of occur infrequently on Skye. Although partially clearing it took four people most of the winter and spring were a full tidal cycle (about five and a half spent trying to find the perfect time hours). to fly the drone on Skye, only two
A panoramic photograph of one of the tracksites investigated along the Duntulm foreshore on a rare, sunny day. The outcrop is flat, large, and some parts of it still have extensive weed coverage even after much was cleared away. Photo credit; Paige dePolo.
13 tracking down scotland’s dinosaurs
The drone taking flight over one of the platforms. All flights were coordinated and executed by the inestimable Tom Wade (Airborne Geosciences Facility, University of Edinburgh). Photo credits; Rob Parry.
days between the end of November the weather was emphatically out of in 2016 and the end of May in 2017 our control. We had to figure out a manifested with the right combination way to take photographs of a similar of all factors. Since only one site could quality and with a similar amount of be documented in a day, thanks to the overlap to a drone without relying narrow tidal time window, that meant on said drone. It turns out that a that photographs still needed to be quite simple solution was at hand collected for two sites. using the resources available at the University of Edinburgh — a couple As PalAlba’s (a research consortium of point-and-shoot cameras and a of Scotland-based palaeontologists) few pieces of scrap metal were used annual fieldwork approached in May to construct an intervalometer (or 2017, the pressure of figuring out more wryly, ‘camera on a stick’). a way to get the data necessary to The cameras were programmed to make good maps of these track sites trigger every couple of seconds and became more intense. How could spaced to have enough overlap to the team ensure that a good dataset generate a three-dimensional model. was collected during this last major Then, mounted on a pole, they were window of opportunity? After all, carried at shoulder height by two
14 tracking down scotland’s dinosaurs
‘dancing partners’ and sweeps were Armed with these hard-won made across the outcrop following a descriptions and models, some gridded pattern. The intervalometer interesting conclusions can be made was waterproofed so that it could about Skye’s dinosaurs. About 170 be used under the extreme weather million years ago, this part of the conditions on Skye. The major world was a coastal margin connected limitation on its operation became to the larger Scottish landmass. The consideration of the safety and footprints found on Skye’s intertidal resilience of its operators. platform come in many different shapes and sizes and indicate that When May rolled around, the long-necked sauropods, plate- intervalometer was successfully backed stegosaurs, theropods, and used on the sites that did not yet ornithopods all were making tracks have a photo dataset for creating on Skye during the Middle Jurassic. three-dimensional models. From them, the raw descriptive work of The footprints found on Skye understanding how many tracks there extend and nuance the story told by were at each site, what each track the island’s dinosaur body fossils. looked like, and how the tracks were Bipedal ornithopod dinosaurs, which spatially related to one another could were herbivorous grazers, are only finally be completed! known on Skye from the footprints
My ‘dancing partner’, Amelia, and I manoeuvring the intervalometer over some tricky terrain at one of the track sites. High-tech science facilitated by cameras on a stick. Photo credit; Shasta Marrero.
15 tracking down scotland’s dinosaurs
These images illustrate variations in size and shape of the footprints preserved on Skye. From left to right and top to bottom, we see footprints from stegosaurs, theropods, sauropods, and ornithopods. The red/white gradations on the scale card are 1 cm, the diameter of the lens cap is 5 cm, and the black scale bar and grey pencil are both 15 cm. Photo credits; Davide Foffa and Paige dePolo.
they left behind in ancient mudflats. of dinosaurs preferred to walk on Stegosaurs and theropods also the drier, subaerial mudflats. left their tracks on these transient surfaces which later dried out, This diverse dinosaur fauna is developed mudcracks, and then only one part of the story told by were flooded by the nearby ocean Skye’s fossils. Tantalizing hints of to form lagoons. Sauropods trampled salamanders, frogs, turtles, lizards, through the sediments deposited in crocodylomorphs, early mammals, these lagoons. This pattern seems ichthyosaurs, and plesiosaurs also are consistent across multiple track sites found in rocks of the same geological on the Isle of Skye and possibly age on the island. These animals indicates that different clades of occupied a variety of ecological dinosaurs preferred different living niches within the same geographical environments. Sauropods dominated areas and indicate that the coastal the lagoons while other smaller types ecosystems of Scotland were thriving
16 tracking down scotland’s dinosaurs
Maureen Moss, the Edinburgh Zoo, and Edinburgh Geological Society.
Bibliography Brusatte, S L. 2015. PalAlba and the dinosaurs of Skye. Edinburgh Geologist, 58, 18–22.
Brusatte, S L, Challands, T J, Ross, D My field helpers Moji, Davide, A, and Wilkinson, M. 2015. Sauropod and Rachel posing with ‘Seaweed dinosaur trackways in a Middle Jurassic Mountain’ in mid-November 2016. lagoon on the Isle of Skye, Scotland. Photo credit; Paige dePolo. Scottish Journal of Geology, 52, 1–9.
Clark, N D L. 2018. Review of the during the Middle Jurassic. Thus, the dinosaur remains from the Middle Isle of Skye is a globally important Jurassic of Scotland, UK. Geosciences, 8, location for studying this enigmatic doi:10.3390/geosciences8020053. time period. dePolo, P E, Brusatte, S L, Challands, T Acknowledgements J, Foffa, D, Ross, D A, Wilkinson, M, and This piece is adapted from the Yi, H.-Y. 2018. A sauropod-dominated outreach portion of the author’s tracksite from Rubha nam Brathairean MScR. in Palaeontology and (Brothers’ Point), Isle of Skye, Scotland. Geobiology at the University of Scottish Journal of Geology, 54, 1–12. Edinburgh. I gratefully acknowledge the advice and guidance of my Romano, M, Clark, N D L, and Brusatte, supervisors, Steve Brusatte and Tom S L. 2018. A comparison of the dinosaur Challands. This research could not communities from the Middle Jurassic have happened without a veritable of the Cleveland (Yorkshire) and horde of cheerful field assistants: Hebrides (Skye) Basins, based on their Davide Foffa, Moji Ogunkanmi, ichnites. Geosciences, 8, doi:10.3390/ Rachel Bartlett, Amelia Penny, geosciences8090327. Michela Johnson, Shasta Marrero, and Paulo Pereira. Funding for Paige dePolo PalAlba’s fieldwork comes from School of GeoSciences, National Geographic, the Association University of Edinburgh of Women Geoscientists, Derek and [email protected]
17 how the past can influence the future: why buried landscapes matter!
How the past can influence the future: why buried landscapes matter!
By Carol Cotterill, Emrys Phillips and Kirstin Johnson
Dogger Bank — named after medieval most recent updates to the 1992 Dutch fishing boats called Doggers; Regional Report by Cameron et al., famous for the numerous Battles of were undertaken in 2008/2009 as Dogger Bank in 1696, 1781,1904, part of a Joint Nature Conservation 1915 and 1916, and now maybe Committee project on Special Areas best known for the Dogger shipping of Conservation. However, as this forecast — as I write this the wind report was predominantly associated is northwest 5 or 6, moderate to with seabed features and habitats, no rough sea states with showers but updates to the deeper Quaternary good visibility. Now we are not geology were carried out. So, the naval historians or keen ocean-going scene was set for a new detailed look seafarers, so why, may you ask, have at Dogger Bank! we spent the last nine years of our careers researching this isolated The Dogger Bank is approximately topographic high in the central North 100 km wide by 250 km long and Sea? lies in an area of shallow water. The majority of the bank lies within the In June 2008 The Crown Estate UK sector of the North Sea (Figure announced the opening of nine 1) but it also extends into Dutch development zones within UK waters and German territorial waters. for offshore windfarm leasing, the The proposed windfarm zone is largest of which was the Dogger Bank situated 125 to 290 km northeast zone. Forewind, a consortium of of Yorkshire coast and is the largest Equinor (previously Statoil), Statkraft, of the Round 3 zones, covering Innogy SE (previously RWE nPower) an area of 8660 km2, with water and SSE committed to a detailed depths ranging from 18 to 63 m site survey and Environmental Lowest Astronomical Tide (LAT), Impact Assessment towards securing and is located entirely within the UK the necessary Zone Appraisal and sector. The lack of understanding Planning consents for construction regarding the sedimentary and and development. Prior to this, the structural architecture of the
18 how the past can influence the future: why buried landscapes matter!
Quaternary sediments on Dogger Bank presented a major issue for the development of a windfarm in this area. The stratigraphy and structure of the Dogger Bank was believed to be a relatively simple ‘layer-cake’ with much of the upper 60 m (the foundation depth for the windfarm) of this unconsolidated sedimentary sequence being assigned to the Dogger Bank Formation (Balson & Cameron, 1985; Cameron et al., 1992). However, the acquisition of new high-resolution survey data during the site investigation of the DBZ has proven that this is far from the case. Figure 1 Map showing the location The earliest reference to the Dogger of the Dogger Bank in the southern Bank being glacial in origin was made North Sea Basin, and the Round by Thomas Belt (1874) who stated 3 windfarm zone indicated by the that “The ice north was now gradually red polygon. The limit of the UK receding, and leaving great banks of territorial waters is also marked in red. moraine rubbish in the old ocean EMODNET DigBath bathymetry (UK bed, to be ultimately levelled by the waters) and GEBCO bathymetry (Non- sea when it long afterwards returned, UK waters). Coloured lines indicate and which now form the Dogger and a compilation of published Last other great submarine banks”. But the Glacial Maximum ice sheet extents, modern seabed gives no indication highlighting the degree of uncertainty: of this kind of geomorphology at further details and references all…….so what was hidden beneath available in Phillips et al. (2017). the modern marine sands?
The first piece of the puzzle came of unconsolidated sediments or from the geotechnical results. ‘soils’) indicated that the Dogger Downhole measurements acquired Bank Formation was lithologically using a Cone Penetrometer (CPT) very similar throughout, and yet the (a method for testing the strength geotechnical results varied wildly with
19 how the past can influence the future: why buried landscapes matter! both depth and geographical location. of a change in lithology, a change Spot core samples, taken roughly in water content, or a change in every 3 m downhole for the length of the density due to compression or the CPT showed that the dominant desiccation. One of these seismic sediment type in the Dogger Bank horizons, chosen due to its laterally Formation was stiff to very stiff clays continuity across most of the with multiple sand layers/lenses. study area and the fact that the These deposits range in thickness from geotechnical data suggested a major 30–50 m. Below the Dogger Bank change in something occurring at Formation deposits are a sequence this level, revealed a buried glacial of dense to very dense poorly sorted, landscape which has been hidden silty to fine-grained sands containing from view since the end of the last interbeds of hard clay and silty fine ice age. The resultant sub-bottom sand. The presence of shell fragments horizon map is shown in Figure 2a. and organic matter within the sands The red and yellow colours represent has been used to suggest that they highs (minimum depth below the were deposited in a marine (possibly seabed c. 2.5 m). In contrast, the nearshore) environment, consistent green and blue colours indicate areas with their belonging to either the Eem where this surface occurs at a much and/or Egmond Ground formations. deeper level (maximum depth c. Above the Dogger Bank Formation 60 m). The resultant pattern reveals are an overlying sequence of fine- to elongate, arcuate features (Figure 2a), medium-grained Holocene sands that which are interpreted as a series of are being reworked by contemporary moraines (purple colours on Figure marine processes. The sands range in 2b) — glacially formed accumulations thickness from a thin veneer (<1 m of glacial debris. thick) to localised channel infill deposits of up to 35 m. The final piece of the puzzle came to light through a detailed analysis The second puzzle piece came of some of the seismic survey lines. in the form of a seismic horizon. Three areas across this buried glacial Sub-seafloor information, acquired landscape were selected running using sound, revealed a number of perpendicular to the main moraine strong reflections. These reflections complex (MC1, Figure 2a) as well correspond to changes in acoustic as one area of longer lines crossing impedance, or the speed that the multiple moraines as well as low- sound wave travels through the lying basins and troughs (Area D, sediments. This is a good indicator Figure 2a). An example interpretation
20 how the past can influence the future: why buried landscapes matter!
Figure 2 (a) Horizon map constructed for the top of the Older Dogger Bank within Tranche A; (b) Landform map of the buried glacial landscape concealed within the Dogger Bank Formation comprising a suite of topographically higher arcuate moraine ridges separated by lower lying basinal areas and meltwater channels (after Cotterill et al., 2017b).
is included as a supplement in the sedimentological features dominate online version of Edinburgh Geologist this buried landscape (supplementary 66. It reveals an unprecedented level figure; Cotterillet al., 2017a; Cotterill of detail across a now buried thrust et al., 2017b; Phillips et al., 2018): moraine complex which formed due to the bulldozing effect (glacitectonic • Although predominantly clay, deformation) at the margin of a major the Dogger Bank Formation is ice sheet. actually formed of three distinct sub-units, identified by their The interpretations showed that a geotechnical responses and number of key geomorphological and seismic character — a basal, highly
21 how the past can influence the future: why buried landscapes matter!
consolidated unit that appears to • Meltwater channels with multiple form primitive, early moraines; a stages of infill, often from different lower unit that is highly deformed directions/(?)sources, incised and ranging in thickness from a into the underlying sediments. few metres to >35 m in thickness; The channels often start and end and finally an upper unit that is less abruptly, suggesting that they deformed with more draping of the represent sub-glacial ‘tunnel sediments, infilling the topography valleys’ which were eroded by created by the deformed lower highly pressurised meltwater unit. flowing beneath the ice sheet. However, the site also includes • The large moraine complexes are a network of much later wide, composed of highly deformed laterally extensive pro-glacial lower clays that have been folded, channels that formed in front of thrusted, over-ridden and over- the retreating ice sheet. These consolidated. The largest of these complex channels are infilled with moraines is up to 15–20 km across. fan sediments and debris flow The geometry of the deformation deposits which flowed off the structures within these moraines nearby moraine highs. indicates that they were formed by ice moving across the area The detailed analysis of high- from north to south. This suggests resolution seismic data from the the main influence building the Dogger Bank has shown that the Dogger Bank was probably Fenno- multiple units comprising the Dogger Scandian ice which is thought to Bank Formation record a complex have covered a large part of the history of sedimentation and large- North Sea during the last ice age scale, ice-marginal to proglacial (Weichselian glaciation). glacitectonism associated with the active retreat of the Weichselian ice • Large low-lying basinal areas sheet. This complex glacial landscape between the moraines which was later buried beneath a thin are dominated by the upper sequence of Holocene sediments. less deformed clays. The style of sedimentary deposition is All of this new geological information indicative of ice-marginal or pro- is being used to help guide the glacial outwash laid down as the siting of turbine foundations as ice retreated northwards towards well as reducing the risk of jack- the end of the last ice age. up platforms de-stabilising during
22 how the past can influence the future: why buried landscapes matter! turbine installation due to sudden Cotterill, C J, Phillips, E, James, L, and unexpected penetration from Forsberg, C F, and Tjelta, T I. 2017a. increased loading. By integrating How understanding past landscapes can geophysics, geotechnics and inform present day site investigations: geology, the team have developed A case study from Dogger Bank, a methodology to interpret buried southern central North Sea. Near landscapes, the lateral variability Surface Geophysics Marine Special of these environments and the Publication, 15, 403–413. https://doi. impact of these unseen features on org/10.3997/1873-0604.2017032 renewable energy developments in the offshore realm. Cotterill, C J, Phillips, E, James, L, Forsberg, C F, Tjelta, T I, and Dove, D. Acknowledgments 2017b. The evolution of the Dogger This research is an ongoing Bank, North Sea: a complex history collaboration between BGS and the of terrestrial, glacial and marine energy companies developing the environmental change. Quaternary Dogger Bank project areas. Thanks to Science Reviews, 171, 136–153. https:// the Forewind Consortium for access doi.org/10.1016/j.quascirev.2017.07.006 to the survey datasets, and to Equinor and SSE for their continuing support. Phillips, E, Hodgson, D M, and Emery, A M. 2017. The Quaternary Geology of the References North Sea Basin. Journal of Quaternary Balson, P S, and Cameron, T D G. 1985. Science, 32. https://doi.org/10.1002/ Quaternary mapping offshore East Anglia. jqs.2932 Marine Geology, 9, 221–239 Phillips, E, Cotterill, C, Johnson, K, Belt, T. 1874. An examination of the Crombie, K, James, L, Carr, S, and theories that have been proposed to Ruiter, A. 2018. Large-scale glacitectonic account for the climate of the glacial deformation in response active ice sheet period. Quarterly Journal of Science, 44, retreat across Dogger Bank (southern 421–464. central North Sea) during the Last Glacial Maximum. Quaternary Science Reviews, Cameron, T D J, Crosby, A, Balson, P 179, 24–47. https://doi.org/10.1016/j. S, Jeffery, D H, Lott, G K, Bulat, J, and quascirev.2017.11.001 Harrison, D J. 1992. United Kingdom offshore regional report: the geology of Dr Carol Cotterill ([email protected]) the southern North Sea. London: HMSO and colleagues for the British Geological Survey. British Geological Survey,
23 eustatic drift
Eustatic Drift
By Keira Greene everything about us now is rock without tongues everything about us then was wet we wrote everything down how did it all begin? in tunics of dark grey and pelagic mudstone sleep-wake over soft cherty ribs wake-sleep thick bands of volcanic ash all that solidifies eventually speaks fragmented crystal clasps this and much more we remember under the dandled sun in the heat of the day we toll we were found ancestral calendars sleep turning to wake skeletal signifiers turns to wake again and sleep again all that solidifies eventually speaks and later we were named in the mud of a new dawn we listlessly quiver most things are named as bodies climb into our beds bearing resemblance to hieroglyphs their front pressed to our front they arrived at graptolite feet rubbing gradient folds graptos after written and lithos after rock we’ve been collecting in a deep communion once we were plankton slouched in the ocean a fever but now we are code a complex juice of aeons surfaced and held in the laminae of rock like open scores we’ve shifted across vast territories of encounters in a torrid spike we were stilled subversions there and not there and on our way we learned the path is lost an endless vacation where one face looks to the future flowing and the other to the past forming laterally in the middle distance to when we raked the ocean like cream no longer a path but a gap and the pass you go will write you billions of architects trust us we built micro-utopias to live together in common corridors listen to our voices float on the underside in horny sheaths we can see the exposed shoulders they are rising irresistible time passed they rise and fall perhaps we were swimming? and over their tips we hear and sticky temporal sequences the locking and unlocking time jelly strong and knotted together the locking unlocking of doors stretched out like a ribbed mirror
24 eustatic drift
“once we were plankton slouched in the ocean but now we are code, surfaced and held in the laminae of rock like open scores”
This narrative voice comes to us In a studio environment dancer Katye from the fossils of Graptolites, our Coe performs the Graptolite as an open long extinct plankton ancestry. Their score. She unfolds the rock and imagines speculative voice speaks to us from how the species may’ve moved. In within deep time as they coil past one instance we read in their script: and future, blending evidence of our interspecies story. In Eustatic Drift we “perhaps we were swimming?” experience the real and imaginary potential of the Graptolites, as a Coe’s performance bears tangible index of a once dominant resemblance to the development species, and as a latent oracle. It of a seedling in the dark. She draws investigates graptolites through film, upon the depth of our interspecies dance, images and words. memory in the absence of scientific knowledge as to how the Graptolite The film opens with wide images of species moved or how deep in the the remote landscape of Dob’s Linn, Ocean they lived. Scotland, significant for its graptolite- bearing strata. The landscape is In Eustatic Drift the camera meditates richly complex in these singled-out on the surface of images, preoccupied moments, held at a distance. History with that which runs beneath “there is sunk into the fabric of the rock and and not there”. Immanence is at the same time in constant change; rooted in the dialectic of embodied change is its constant truth. The experience that is critical to all humans. landscape is cut with images of the And to embody an awareness of fossils; they remind us of the certainty our interaction with other species is that everything is vulnerable, of critical for human survival. trauma that has lost all meaning, but the Graptolites present a post- literative world, in which language and hybridity must evolve.
25 eustatic drift
26 eustatic drift
Graptolites were small marine Keira Greene is an artist who works across moving image and performance. Her colonial organisms, the fossilised practice is critically engaged with the remains of which are commonly filmed image of dance and the moving found in black shale rocks that once body on screen. Often she works with were muddy sea floors; they look like language, exploring how text, speech impressions of tiny hacksaw blades and images can be turned into scores for movement, music and script. Her on the rock surfaces. Graptolites work is often collaborative and she works first appear in the fossil record closely with dance artists and musicians to about 520 million years ago, part of develop this research. the explosion of diverse life in the Cambrian Period, and disappeared in She has exhibited and screened her the early Carboniferous, 350 million work widely with recent exhibitions and years ago. For about 100 million screenings including Cubitt, London, Jerwood Space, London, Whitechapel years, mainly through the Ordovician Gallery, London, Tate, London, The and Silurian periods, they evolved Commons Bolinas, San Francisco, CA. quickly and were widely distributed She is performance curator for Whitstable throughout the world’s oceans. Their Biennale 2018 and a founding trustee rapid evolutionary change make of the Stuart Croft Foundation. She is currently undertaking a practice-based these fossils particularly valuable PhD at Kingston University, supported by for dating and correlation of marine Techne¯ . sedimentary rock successions worldwide. Credits for Eustatic Drift: Dob’s Linn in southern Scotland Dance — Katye Coe exposes mudstone spanning Cello — Ute Kanngiesser about 25 million years through Sound — Paul Abbott the late Ordovician and early Special thanks to Jan Zalasiewicz, Silurian periods. The original Rob Barnes and Siobhan Davies Studio sediment was deposited in a wide With the support of a Jerwood Visual ocean — Iapetus — separating Arts Artists Bursary and The Elephant ‘Scotland’ from ‘England’, both Trust parts of larger land masses at the © Keira Greene 2018 time. It is the defining locality for the Ordovician–Silurian boundary Keira Greene worldwide, with particular For more information on Eustatic species of graptolites being key to Drift see http://keiragreene.com/ identifying this fundamental point in time.
27 book review
Book review
Introducing Geology by Graham between the text and the tables, Park. Dunedin Academic Press, diagrams and photos, makes the facts Edinburgh. Third edition 2019. easy to read, learn and remember. Paperback, 134 pp. Price £9.99. Technical words are highlighted in ISBN 978-1-78046-075-8. bold in the text and each appears, with a clear definition and a page reference, in the twenty-page glossary which serves as a basic geological dictionary.
The book is structured so that the more immediately attractive topics — minerals, volcanoes — are found in the first few chapters. Those on sedimentary and igneous rocks go into enough detail to satisfy most people, though there is limited information on how to identify rocks and those who live in or visit Scotland This book provides an approachable may be disappointed by the very introduction for interested adults who short section on metamorphic rocks. are studying the subject. I have been It was sad to read the old chestnut recommending it to U3A geology about rivers in mountainous areas groups for a few years and it is good flowing faster than rivers in lowlands, to see a new edition. The revision years after experiments have shown has allowed the author to improve that velocity due to kinetic energy the line drawings, in particular in rivers with high discharge is exchanging symbols for colour, which greater than the velocity of rivers in makes many of the diagrams easier mountains, where potential energy to understand. The text is clear and has to overcome friction. However, easy to follow, though, inevitably very there is an excellent section on densely written in order to compress glacial processes and landforms, with a huge amount of information into a helpful photos. The two consecutive book of a little more than a hundred chapters on geological time and pages. Clear cross-referencing fossils are nicely linked by discussion
28 book review of absolute and relative dating A few errors have survived the respectively, with well-chosen photos revision for this third edition, such of examples of most of the fossil as a caption to a photo of a calcite groups and a particularly beautiful cleavage rhomb, unfortunately image of insects preserved in amber. labelled as a crystal. Dolerite is described as fine-grained in a photo The chapter on plate tectonics caption, but (correctly) as medium- contains exemplary explanations grained in the igneous rocks table linking continental drift, ocean-floor on the following page. The common spreading, distribution of climatic misunderstanding of the difference zones, palaeomagnetism, plate between exposure (rocks visible movements, subduction, mountain- at the surface) and outcrop (the building and continental rifting. area where a rock is found, though From experience, it is not easy to it may be obscured by soil and teach global plate tectonics to an vegetation) has not been eliminated. adult audience, but this chapter will Weathering and erosion are not provide excellent further reading to clearly distinguished and this has led reinforce complex ideas. The section to an error in the caption for Fig. is well illustrated with maps and 3.1, which describes a granite tor as diagrams and it is helpful that arrows an example of erosion, instead of have been added to the world map weathering. I was sorry to see the of plate boundaries. A long chapter use of the words ‘acid’ and ‘basic’ to on the history of the Earth, well- describe magma composition. These illustrated with palaeogeographic terms were superseded some years maps, will challenge the beginner ago by the words ‘silicic’ and ‘mafic’, but will be helpful for those who so it is unfortunate that they have re- are interested in the global picture, emerged here. particularly how Scottish geology fits into world plate tectonics. For the audience for which it is intended, Graham Park’s book is A brief look at economic geology straightforward and well-illustrated concludes the book, though no and provides the basis for a good doubt the author would have liked to understanding of geological features have added examples and diagrams and processes. to explain mineral extraction, the processes of ore formation and how Alison Tymon roads and tunnels are built, had there been space.
29 This issue: No. 66, Autumn 2019
1 Editorial ramble Ladies’ Day
4 Heddle’s Agates By Rachel Walcott
12 Tracking down Scotland’s dinosaurs By Paige dePolo
18 How the past can influence the future: why buried landscapes matter! By Carol Cotterill, Emrys Phillips and Kirstin Johnson
24 Eustatic Drift By Keira Greene
28 Book review Introducing Geology
All previous issues are available online at www.edinburghgeolsoc.org/publications.
Cert no. SGS-COC-003231 ISSN 0265-7244