Because of Covid-19 restrictions, lecture meetings for Session 163 (2020 -2021) will take the form of online Zoom meetings. They will still be held on the second Thursday of the month, but will start in September rather than October. The meetings will start at 7:30 pm and finish at around 9:00 pm. Because of the unusual circumstances this session, the lecture programme has not yet been finalised. Further details will be posted on the website when they become available.
Society members for whom we have email addresses will be sent an invitation a few days before each meeting. If you are a member but are not on our email list, or a non-member who would like to join a particular meeting, please email the society’s meetings secretary to request an invitation.
10th September 2020
Professor Simon Cuthbert, AGH University of Science and Technology, Krakow
The geology of Mercury
8th October 2020
Professor Matthew Thirlwall, Royal Holloway, University of London
New isotopic age determinations from the Northern Highlands and their implications
12th November 2020
Professor Bruce Levell, University of Oxford
The Argyll Group: two beauts
10th December 2020
Dr Daniel Field, University of Cambridge
Bird evolution from the Late Cretaceous onwards
14th January 2021
Dr Tim Kearsey, British Geological Survey, Edinburgh
Palaeosols as evidence of terrestrial climate change at major Palaeozoic vertebrate evolutionary events
4th February 2021
Dr Doug Robinson, University of Bristol (retired)
The geology of the Mendip Hills
11th February 2021
Professor David Beerling, University of Sheffield
Large-scale CO2 removal via enhanced rock weathering
11th March 2021
Dr Dave Schofield, British Geological Survey, Edinburgh
Terrane evolution of southern Great Britain
8th April 2021
Dr Queenie Chan, Royal Holloway, University of London
Catch a shooting star
13th May 2021
Mercury has been recognised as a “wanderer” of the night sky since Babylonian times, but its proximity to the Sun has made it a difficult body to study. The situation has changed dramatically since the recent MESSENGER mission, which has revealed a fascinating and distinctive member of the family of terrestrial planets.
Dubbed the “iron planet” it has a huge metallic core and a relatively thin rocky mantle. In some ways the geology and landforms of Mercury resemble Earth’s Moon with its heavily cratered surface, extensive smooth lava plains and lack of an atmosphere, but it is unusually dark – a possible vestige of a primordial crust made of graphite! Tectonic features suggest that the entire planet has shrunk by several kilometres since it originally solidified.
This presentation will explore current knowledge about this rather uncelebrated planet and consider how its curious nature might be inherited from the special environmental conditions close to the Sun during the very earliest history of the Solar System. A look ahead to the upcoming Bepi-Colombo mission will anticipate some exciting new insights about this mysterious “pink dot”.
Over the last 15 years we have carried out a large number of new age determinations on metamorphic rocks from the Moine and its basement inliers. Some of these are published and some not. They include Lu-Hf and Sm-Nd ages on garnets and Rb-Sr ages on white mica and biotite. Lu-Hf garnet ages are probably close to crystallization ages, while Sm-Nd garnet ages in most cases represent stages on a cooling trajectory. This can clearly be demonstrated on a few samples where core Sm-Nd ages are younger than rim Lu-Hf ages. White mica ages are in some cases substantially younger than Sm-Nd garnet, and in other cases agree well.
We see a long record of Proterozoic events, but there are few if any Archean ages on the basement inliers. There are almost no Silurian ages, neither from garnets, nor from white micas, implying that Scandian events did not result in substantial new garnet or mica growth. White mica ages largely cluster in the late Ordovician around 445Ma, and are clearly too old to reflect final collision.
Bird, Anna; Cutts, Kathryn; Strachan, Rob; Thirlwall, Matthew F.; Hand, Martin. (2018): First evidence of Renlandian (c. 950–940 Ma) orogeny in mainland Scotland : Implications for the status of the Moine Supergroup and circum-North Atlantic correlations. Precambrian Research, 305, p. 283-294.
The Neoproterozoic Argyll Group (Dalradian Supergroup), is a well-exposed, 10 km thick, sequence recording a transition from glacial through shallow marine to slope and deep-water sediments and pillow lavas. It probably represents the rift-to-drift sequence of the Laurentide margin of Iapetus.
Two units are presented: the Port Askaig Formation, probably the Sturtian phase of “Snowball Earth”, and the Jura “Quartzite”, a 5 km thick cross-bedded, sandstone. These allow general points to be made about “Snowball Earth” and preservation bias in the sedimentary record respectively.
Daniel will talk about evolution of birds across mass extinctions, and the timescale of the modern bird radiation. The end-Cretaceous (K–Pg) mass extinction dramatically affected vertebrate life worldwide. He and his colleagues are trying to decipher how this event affected birds and other vertebrates through fieldwork and lab-based studies. When in Earth history did the first evolutionary divergences among modern birds take place? How old are the major avian clades?
Field, D.J., Benito, J., Chen, A., Jagt, J.M.W., Ksepka, D.T. 2020. Late Cretaceous neornithine from Europe illuminates the origins of crown birds. Nature, 579 397-401.
Field, D.J., Berv, J.S., Hsiang, A.Y., Lanfear, R., Landis, M.J., Dornburg, A. 2020. Timing the extant avian radiation: The rise of modern birds, and the importance of modeling molecular rate variation. PeerJ Preprint of in-review manuscript: https://peerj.com/preprints/27521/
Climate change is a major driver of evolution. Palaeosols (fossil soils) are one of the few direct indicators of terrestrial climate and provide a record of climate changes and landscape architecture, and are critical in understanding the terrestrialization of vertebrates in the Carboniferous and the Earth’s largest mass extinction at the end of the Permian.
Otoo, B., Clack, J., Smithson, T., Bennett, C., Kearsey, T. & Coates, M. 2019. A fish and tetrapod fauna from Romer’s Gap preserved in Scottish Tournaisian floodplain deposits. Palaeontology, 62, 225-253.
Somerset is a unique county with more geological periods present than most other English counties. The city of Wells is well known as England’s smallest city but within its immediate backdrop the rocks record a longer geological history than any other English city – a 200 million year (Devonian to Jurassic), 6,000 km journey from the southern tropics across the equator into northern latitudes.
Enhanced silicate rock weathering (ERW), deployable with croplands, has potential use for atmospheric carbon dioxide (CO2) removal (CDR), which is now necessary to mitigate anthropogenic climate change. ERW also has possible co-benefits for improved food and soil security, and reduced ocean acidification. The talk will discuss the challenges and opportunities of ERW deployment, including the potential for excess industrial silicate materials (basalt mine overburden, concrete, and iron and steel slag) to obviate the need for new mining, as well as uncertainties in soil weathering rates and land–ocean transfer of weathered products.
Beerling, D.J. 2020. Potential for large-scale CO2 removal via enhanced rock weathering with croplands. Nature, 583, 242–248.
During the 1970s, the recognition of allochthonous terranes as discrete lithospheric fragments gave geologists a new tool kit to help describe the mosaic-like complexity of orogenic belts. Understanding that terranes could be dispersed and recombined accompanied realisation that strike-slip translation contributed significantly to orogenic development.
In applying this to understanding the, largely concealed, late Neoproterozoic and Lower Palaeozoic record of southern Britain, conflicts in nomenclature, scales of observation and focus of the geologist’s themselves has led to a confusing picture where terranes are essentially reduced to snapshots in time rather than lithospheric entities evolving in both time and space.
This talk takes a look at this problem and uses summaries of isotopic data to contrast Neoproterozoic rocks with their Cambrian cover successions in southern Britain and those in the Caledonian-Appalachian Orogen as a whole, and looks at when the component terranes may have been assembled and largely stabilised.
Earlier interpretations of the orogeny compare southern Britain with Avalon Peninsula in Newfoundland based on the similarity of their Cambrian shelfal sedimentary successions and cold water faunas, known as East and West Avalonia respectfully. However, isotopic studies of the Precambrian basement to southern Britain show that it more closely resembles that of other terranes that formed around the continental margin of West Gondwana, Meguma of Nova Scotia and Ganderia of Central Newfoundland and New Brunswick of the northern Appalachians.
Similarly, U-Pb zircon provenance studies of the overlying Cambrian cover successions show that North Wales and the Midland Platform of England most closely resemble Meguma while those of Anglesey (Monian Composite Terrane) and the Leinster-Lakesman Terrane most closely resemble Ganderia. While in the northern Appalachians these terranes largely travelled separately before their accretion in a piecemeal fashion onto the continental margin of Laurentia; in the UK they were juxtaposed during the Early Ordovician Monian Orogeny, after which southern Britain and Ireland probably travelled as a single terrane before arriving on Laurentia during the Silurian.
It is not easy to catch a shooting star, but when we find one, we make the most out of it by studying it in every detail to learn its secrets. Although the building blocks of life in meteorites could be vulnerable to extreme conditions, e.g. toasty temperature during a meteorite’s fiery entry into the atmosphere, the interiors of meteorites are buffered from those conditions. Trapped liquid water and life’s precursor molecules could have been preserved like “mosquito in amber” and therefore studied in the laboratory.
Queenie Chan is a planetary scientist. Her work involves the analysis of the chemical and organic contents of astromaterials including meteorites and asteroidal/cometary samples returned by space missions. In this talk, she will discuss how water and life’s simple building blocks were delivered to the early Earth.
13th May 2021
A series of short presentations by society members