Professor Brian Bluck, University of Glasgow
Scottish Highland Border rocks and their role in the Caledonides

Rocks along the Highland Border have provided geologists with a wide range of interpretations, partly because they are very poorly dated, partly because of their structural complexity and partly because they are thin and yet contain such a wide range of lithologies. However, meticulous fossil collecting by several workers has shown the rocks to be Lower Cambrian, possibly later Cambrian and Ordovician (Arenig) in age.
The Highland Border sequence is dominated by rocks which, when combined, would strongly suggest that they form part of a dismembered ophiolite. These rocks include black shales and cherts, pillow lavas, fragments of dolerite, gabbro and trondhjemite and sheets of serpentinite. The ophiolite is unconformably overlain by conglomerates and limestones one of which contains Lower Arenig fossils, implying that the ophiolite is Arenig or older. The only dates so far suggest that the ophiolite was possibly obducted during the Cambrian (c.540 Ma).

This ophiolite spread its debris widely to younger rocks within the Complex and some of the ‘external’ clasts in these sediments have ages of c.1.8 Ga. The structural complexity of the complex is partly due to Devonian strike slip movements and partly due to the enormous contraction which had taken place during and since the ophiolite formed. The relationship of the Highland Border Complex to the blocks on either side is difficult to establish, but geophysical and xenolithic evidence suggests that the older Dalradian block may overly rocks of similar type.

Professor Tony Harris, University of Cardiff
The Moine Rocks of southwest Mull

The Moine rocks of southwest Mull are cut by the Ross-of-Mull granite and by numerous Tertiary and Caledonian minor intrusions. They are faulted against the Tertiary volcanic rocks that lie to the northeast and the older rocks of Iona to the west. The Moine rocks are the most southwesterly occurrence of the Moine, because the Moine Supergroup does not re-appear in Ireland. They suffered polyphase deformation and regional metamorphism to kyanite grade prior to the emplacement of the Ross of Mull granite, which in turn imposed a substantial contact aureole on the metasediments. The complex history of these rocks will be explored and their relationships with the remainder of the Moine of the South-West Highlands speculated on.

Dr Brian Baptie, British Geological Survey
The magnitude 7.9 earthquake of May 12, 2008 in Sichuan, China

The magnitude 7.9 earthquake of May 12, 2008 in Sichuan was the most devastating earthquake to strike China in over thirty years and resulted in over 70,000 deaths and left more than 4.8 million homeless. This has also drawn direct attention to the complex tectonic and geologic history of the Longmen Shan and eastern margin of Tibetan Plateau. On a continental scale, the seismicity of central and eastern Asia is a result of northward convergence of the India plate against the Eurasia plate with a velocity of about 50 mm/y. The convergence of the two plates is broadly accommodated by the uplift of the Asian highlands and by the motion of crustal material to the east away from the uplifted Tibetan Plateau. However, the steep, high-relief eastern margin of the Tibetan Plateau (including Longmenshan) has undergone rapid Cenozoic cooling and denudation, yet shows little evidence for large-magnitude shortening.

Teleseismic recordings show that the earthquake occurred as the result of motion on a northeast striking thrust fault dipping at 33º to the northwest. There was also a significant component of dextral slip. Fault dimensions constrained by the seismic moment and finite fault modelling suggest that the rupture was approximately 300 by 20 km and that the rupture propagated from the epicentre in the southwest, over two hundred and fifty kilometres to the northeast in around two minutes. The aftershock distribution also shows excellent agreement with the rupture zone. The shallow depth of initial rupture and the fault slip, place the surface rupture close to the Bechuan Fault, a previously identified fault at the margin of the Seichuan Basin that can be traced continuously for up to 200 km along the plateau margin. Surface ruptures of several meters were observed after the earthquake.

In August 1933 a magnitude 7.5 earthquake, approximately 90 km northeast of the 12 May earthquake, destroyed the town of Diexi, killing 9,000. In terms of seismic hazard, return periods for earthquakes in the Longmenshan are greater than on some of the other fault zones around the Tibetan plateau. However the potential for catastrophic events in this region has been dramatically demonstrated and it seems possible that the seismic hazard may have been underestimated.

Dr Sue Loughlin, British Geological Survey
The interaction of groundwater and an active volcano - could a magma chamber influence spring flux?

The Soufriere Hills volcano, Montserrat in the eastern Caribbean began its current eruption in 1995. From 1998 the natural springs on which the island's population relied for their water resources appeared to be in terminal decline. Then, within a few months of the largest lava dome collapse ever documented worldwide in July 2003, there was a dramatic recovery. Could this have been due to 'unloading' of the crust or consequent pressure effects in the magma chamber? There is now another large dome at the summit of the volcano - will springs be affected when/if that collapses? Montserrat has a tropical climate - the rainfall typically triggers lahars (floods loaded with volcanic debris) and mudflows; however mudflows have also been observed on the volcano when it is dry - how are they generated? Intense rainfall may trigger partial or total lava dome collapse but we don't know exactly how, and the onset of lava extrusion is commonly preceded by phreatic (steam-driven) explosions. Groundwater flow and volcanic activity are closely linked but we still don't fully understand this interesting and complex relationship.

The James Wright Memorial Lecture
Professor John Dewey, University College Oxford
Arc-continent collision: complex geology and the growth of continents.

The collision of a supra-subduction zone ophiolite or oceanic arc with a continental margin, followed by a flip in subduction polarity, would lead to the addition of oceanic arc complexes to the edges of continents and, hence, continental growth. Three examples are the mid-Ordovician Grampian Orogen of the western Irish Caledonides, the Miocene Bismarck Orogen of New Guinea, and the early Cretaceous Nevadan Orogen of the Sierra Nevada. In each, imminent collision is heralded by a switch from mafic to silicic magmatism. Fore-arc/successor basins preserve a clastic records of collisional events and unroofing of the obducted supra-subduction zone ophiolite and underlying metamorphic complexes. Ancient zircons from subducted crust appear in the immediately pre-collisional and post-collisional arc, and the crust was returned to normal thickness, mainly by extension, not erosion.

The preservation of low-grade rocks in these collisional zones may be the result of four factors, the principles of which can be illustrated by reference to the Grampian Orogeny, the Nevadan Orogeny, and the Bismarck Orogeny:
1. Subduction systems commonly show a general subsidence of the over-riding lithosphere resulting from the colder negative buoyancy of the subducting slab(s);
2. The subducting, thinned and stretched, continental margins probably contain substantial amounts of rift-related mafic igneous rocks, which if converted to eclogite during continental thickening would contribute to depression of the orogen and reduce erosion;
3. The 12 km-thick obducted arc/ophiolite nappes had an average density of about 3200 kg/m3, beneath which the evolving orogens were depressed below sea level;
4. The Grampian Orogen in western Ireland enjoyed a period of late-orogenic extensional denudation, when only very recently-generated staurolite-bearing garnet amphibolites were drawn up beneath an extensional detachment(s) to contribute a statistically significant pulse of detritus, as the ophiolite/arc hanging wall was drawn down. Subduction flip led to extensional collapse and, probably, delamination/detachment of the eclogitised Laurentian root, which would have generated uplift of the Grampian core from which the high-level obducted sheet was withdrawn. Similar processes probably occurred in the Bismarck and Nevadan Orogens.

Dr Ed Stephens St Andrews University
Enlisting geology in fighting disease and organised crime

Evolution has ensured that our respiratory, digestive and other bodily systems are well adapted to cope with most geological products in the environment, but cultural and industrial innovations of recent centuries have exposed us to new toxins at a rate far exceeding our ability to adapt. Human activities now displace more continental material than the sum of all natural denudation processes with the consequence that enormous quantities of pollutants are liberated into our living environments, some of which are hazardous to health. When natural defences are inadequate it becomes important to understand the environmental pathways and toxic responses in order, wherever possible, to protect those exposed to these hazards. Two examples of such geological health hazards will be described. Quartz, perhaps surprisingly for such an ubiquitous mineral, is implicated in various lung diseases including cancer, yet it appears only to be highly toxic under very particular circumstances related to its surface properties. New work on these properties will be presented. The second example concerns the influence of minerals and trace elements on the hazardous effects of tobacco smoke. Minerals account for a substantial part of tobacco (much ending up in ash) and we can now show that some of the most hazardous emissions in smoke have geological or mineralogical origins. An unexpected spin-off from these health investigations has been the discovery that useful forensic information is contained in the mineralogy and geochemistry of tobacco leaf. The global trade in illicit tobacco products is enormously lucrative (some $50 billion annually) and is largely controlled by organised crime with consequent adverse health, social, criminal and revenue implications. Examples will be presented to show how geology is now a key tool in constraining the origins and tracing the supply routes of counterfeit products across continents.

Professor Simon Harley, Edinburgh University and CoRWM (UK Committee on Radioactive Waste Management)
Towards Deep Geological Disposal of UK Radioactive Waste - Joint lecture with Mining Institute of Scotland

The UK has been generating electricity from a variety of nuclear power stations for the past fifty years, and even without ‘New Build’ will continue to do so beyond 2025. The wastes already produced from our nuclear reactors and committed through their operation up to and including decommissioning, our ‘Legacy Waste’, pose one of the most important ethical, environmental and safety issues facing the UK. The objective of responsible long-term management of such waste is to isolate it from both unwarranted human intervention and natural occurrences, so as to protect both the environment and those who live in it, from the radioactivity. For some kinds of radioactivity this requires long-term plans spanning generations. Low level wastes (LLW) are already committed to long-term surface or near-surface storage at sites in the UK. The safe management of the more radioactive intermediate and high-level legacy waste (and potentially spent fuel) is the goal of the ‘Managing Radioactive Waste Safely’ (MRWS) programme. The MRWS strategy is to manage higher activity radioactive waste in the long-term through geological disposal, coupled with safe and secure interim storage and ongoing research and development to support its optimised implementation. Geology is very important in this – the geological barrier is the ultimate one in deep disposal – but the process is based on ‘volunteerism’: communities have been invited to express an interest in opening up discussions with Government on the possibility of hosting geological disposal facilities (GDF) at some point in the future. This presentation will describe what our legacy waste inventory is, outline the MRWS programme, explain where we are in the process, describe who the various players are and what roles they play (including the role of CoRWM), and explain the geoscience challenges that will need to be addressed in order to enhance confidence in geological disposal and enable implementation of GDF – wherever that may be in the light of volunteerism.

February 11th - Professor Richard Worden, University of Liverpool
Animal-sediment interaction since the Precambrian: the worm gut as a natural clay mineral factory

Recent work at Liverpool University has shown that animal-sediment interaction has a profound effect upon mineral dissolution and mineral growth. The simple action of animals ingesting and excreting sediment changes the minerals. Using a set of artificial marine experiments and the common lugworm, Arenicola marina, it has been shown that sediment ingestion and excretion by macrobiota represents a new way in which to precipitate clay minerals or ‘bio-clays’. Significant quantities of clay minerals can be the product of biological interaction within sediment.

Animals such as worms have lived in sediment at the Earth’s surface since the later Precambrian. Over that time, they have been burrowed, excavated, and excreted within sediments. Bioturbation fabrics are well known and are routinely used to characterise sedimentary environments. However, it is not known whether animals modify the mineralogy of their host sediments. This research has been designed to test the mineralogical and geochemical effects of animal-sediment interaction.

Mesocosm tanks, with experiment and control sides, were constructed with artificially layered sediment and natural seawater. Lugworms, chosen because they are hardy, ubiquitous, non-selective filter feeders, were introduced to the experimental side of the tanks. Lugworms excrete on the sediment surface enabling simple collection of their faeces for analysis. The experiments were conducted at room temperature for a total duration of 24 months. The silicate material in the layered sediment and ingested by the worms was crushed, recently-erupted and totally fresh basalt from Iceland. Such material is free of indigenous clay minerals. Fine sediment fractions from faecal casts from the lugworm tanks, examples of primary material and samples from the unbioturbated control tank, were periodically collected and analysed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM. Faecal casts showed extensive mineral alteration as denoted by relative loss of primary minerals, especially plagioclase. New authigenic minerals in faecal casts from the lugworms included kaolinite, illite, quartz and smectite. It is likely that inorganic weathering of similar parent basalt would probably produce an identical mineral assemblage but many more times slowly than with the macrobiotic mechanism demonstrated here.

The experiments reported here show that a range of early diagenetic clay minerals can develop within ingested sand in the guts of creatures at a rate that is many orders of magnitude greater than in an abiotic environment. Early diagenesis in marine environments may thus be strongly influenced by the occurrence of sediment ingestion and excretion by animals.

Dr Neil Clark
Scottish Dinosaurs, Jackalopes, and Guinness

The first evidence in Scotland of Jurassic dinosaurs was the discovery of a large single three-toed footprint of a dinosaur in 1982. It was not until 1994 that the first dinosaur bones were brought to the attention of palaeontologists. The earliest is from rocks of about 205 million years old, and is a hind limb bone of a ceratosaur (a small meat-eating dinosaur). Herr Matthias Metz of Germany found the bone in the south of the Isle of Skye in 1992 and later donated it to the National Museums of Scotland. At about the same time, a local collector found a small piece of a sauropod bone in 165 million year old rocks in the north of Skye.

Since then, many new fossil remains of Scotland’s dinosaurs have come to light. Nearly every year there is a new discovery. Footprints; a leg bone, a tail bone, and a tooth of a Cetiosaurus, a tail bone and a tooth of a small meat eating dinosaur related to the American Coelophysis; the elbow bone of a thyreophoran dinosaur; a set of giant theropod (meat-eating dinosaur) footprints; a tooth of a giant titanosaur sauropod (large plant-eating dinosaur) amongst other discoveries. Surprisingly, Scotland’s dinosaurs even made it into the 2006 Guinness World Records book with the World’s smallest dinosaur footprint! Footprints of adult and juvenile theropod dinosaurs from here suggest the first evidence worldwide for parental care in theropod dinosaurs.

Although Middle Jurassic dinosaur remains are quite rare world-wide, there are some dinosaur footprints of a similar age in Wyoming, USA. When the footprints on Skye were compared to the ones of similar age from sites in Wyoming, it was found that they were the same type. Perhaps, when North America and Scotland were closer, dinosaurs were able to migrate over the great distances in migrating herds, or perhaps the animals in Wyoming were the western extent of the population and Scotland was the eastern part of the range. Dinosaurs have only been found on the Isle of Skye in Scotland so far. There are rocks of the same age and environment on other islands in the west of Scotland, but there are also exposures of Jurassic rocks near Inverness to Helmsdale. Perhaps one day soon, someone will find new dinosaurs from these areas as well.

Dr Alec Livingstone (Presentation of the Clough Medal)
Mineralogy and the Museum: an overview

During the seventeenth century mineral collections were amassed in Scotland and around 200 years ago museum and personal collections, upon which a coterie of Edinburgh people worked, became vital elements in early mineralogical developments. Large mineral collections are latent databases with intellectual capital but how large are national collections? How are collections managed and what benefits accrue?

A mineralogists work is diverse; public duties, curation and research being core functions. Work on the collections can throw light on the stories behind them and the personalities involved, topographical inventories, fundamental mineralogy, new species, taxonomy, and villains.

Between 1791-1987 twenty-eight new species, some collection-based, have been described from Scotland. Scottish geology is complex, could there be more?

Rob Strachan, University of Portsmouth
New ideas on the Neoproterozoic geology of Shetland

The Shetland Islands expose a fascinating section across the Scottish Caledonides from rocks that have been correlated with the Hebridean Foreland in the west to the well known Unst ophiolite exposed in the east. Much of our knowledge of this area derives from the work of Derek Flinn and his PhD students over many years. Inliers of orthogneisses have been correlated with the Lewisian basement, and extensive tracts of metasedimentary rocks have been correlated with the Moine and Dalradian successions of mainland Scotland. Although the area has been mapped in great detail, virtually no modern geochronology has been carried out on any of these rock units. The results of geochronological and geochemical studies carried out on metasedimentary rocks of Yell and Unst provide crucial new evidence for a complex series of Neoproterozoic tectonothermal events with implications for regional correlations in Scotland and further afield.

Fellows’ Night

Presentations will include: "The Storegga Slide: Scotland's Tsunami" by Christine Skinner, "New view on the Highland Border", by Graham Leslie and "Glacial erratics in eastern Orkney" by Adrian Hall.

Further contributions for Fellows’ Night are invited. These may be short talks of up to 15 minutes, or demonstrations of specimens, posters, photographs, microscopy, or anything else you would like to share with fellow members. If you have something you would like to offer, contact our Secretary Angus Miller (see Contact Details).