<li>Eruption of the small Weaklaw volcano, as described by Upton ''et al''. (2019), was probably contemporaneous with petrographically and geochemically similar basanitic volcanoes associated with the basal North Berwick Member of the GHVF (McAdam and Tulloch, 1985; Upton, 2003, p 54). A low but upstanding volcanic edifice with gentle slopes probably survived for some time, until….</li>
<li>Eruption of the small Weaklaw volcano, as described by Upton ''et al''. (2019), was probably contemporaneous with petrographically and geochemically similar basanitic volcanoes associated with the basal North Berwick Member of the GHVF (McAdam and Tulloch, 1985; Upton, 2003, p 54). A low but upstanding volcanic edifice with gentle slopes probably survived for some time, until….</li>
<li>After possibly a significant time interval, eruption of the mugearite lava at the top of the Hailes Member. The lava is not seen in contact with the Weaklaw Tuffs, so does the mugearite lap up against the remains of the Weaklaw volcano below current erosion level or maybe it was deflected around it?</li>
<li>After possibly a significant time interval, eruption of the mugearite lava at the top of the Hailes Member. The lava is not seen in contact with the Weaklaw Tuffs, so does the mugearite lap up against the remains of the Weaklaw volcano below current erosion level or maybe it was deflected around it?</li>
Geologically surveyed by Rich'd G. Symes and Alex. McHenry. Carboniferous boundary revised in 1906 by Alex. McHenry (also minor revisions) Edition of 1907.
BGS175: 175th Anniversary Science Symposium of the founding of the British Geological Survey, 28th September, Royal Institution, London
The British Geological Survey is the world's oldest national geological survey and commemorated its 175th anniversary in 2010.
The event was marked by a one-day science symposium on 28 September 2010.
The symposium showcased our world-class science and technologies, demonstrating their relevance, societal benefits and positive impacts in addressing 21st century challenges; including living with environmental change, energy and natural resource security, rising CO2 emissions and geohazards.
Peak metal: Scarcity of supply or scare story?
Bronze Age Mediterraneans may have visited Stonehenge
Modelling of Icelandic volcanic ash particles
The event was attended by influential stakeholders including representatives from government, industry, academia, international geological surveys, students and the national media.
Acuity, accuracy and application: from systematic geological mapping to responsive 3D+ surveys
Martin Smith, Head Geology & Landscape, BGS
From watercolour to web
Keith Westhead, Head Knowledge Exchange, BGS
Keynote: Facing tomorrow’s challenges with integrated science
Marcia McNutt, Director, USGS
Morning session B
OneGeology: improving access to geoscience globally
Ian Jackson, Chief of Operations, BGS
North American liaisons
Garth Earls, Director, GSNI
Arabian adventures: geological mapping and climate change in Arabia
Andrew Farrant, Geologist, BGS
Groundwater animals: extending our understanding of biodiversity in the UK
Louise Maurice, Groundwater ecologist, BGS
Life just got complicated
Dr Phil Wilby, Geologist, BGS
Afternoon session A
Predict or prepare: natural hazards and human disasters
David Kerridge, Head Earth Hazards & Systems, BGS
Groundwater, health and livelihoods in Africa
Alan MacDonald, Hydrogeologist, BGS
Marine exploration
Robert Gatliff, Head Marine Geoscience, BGS
Carbon capture and storage (CCS):demonstrating the concept
Andy Chadwick, Head CO2 Storage Research, BGS
Future energy: renewable energy dividends from our coal mining legacy
Diarmad Campbell, Chief Geologist, Scotland, BGS
Keynote: The human planet
Iain Stewart, Professor of Geosciences, Communication, University of Plymouth
Afternoon session B
Malthus revisited? Population growth, environmental change and resource limits
Andrew Bloodworth, Head Minerals & Waste, BGS
Looking forward to making predictions: BGS’s role in the next decade and beyond.
Andrew Hughes, Hydrogeologist, BGS
Panel session
Featuring: Sir David Attenborough, Marcia McNutt (Director, USGS) Iain Stewart (Chair), Randy Parrish (Head of NIGL), Kathryn Goodenough (Geologist, BGS), Mike Ellis (Head of Climate Science, BGS).
Closing remarks
Closing remarks by Jon Gluyas (BGS Board Chair), and BUFI poster prize presentation.
Cofir am Edward Greenly yn bennaf am ei arolwg daearegol o Ynys Môn, gwaith y bu wrthi am bron pum mlynedd ar hugain o’i fywyd.
Image caption: Edward Greenly. Llun trwy garedigrwydd Terry Williams
Edward Greenly (1861–1951)
Campwaith pennaf Edward Greenly oedd cwblhau arolwg daearegol manwl o Ynys Môn. Cyhoeddwyd The Geology of Anglesey (Volume 1 and Volume 2) mewn dwy gyfrol yn 1919 ac yna yn 1920 fap daearegol ar y raddfa un fodfedd i’r filltir. Er bod rhannau o’r gwaith wedi’u diweddaru yn ystod y degawdau dilynol, erys ei astudiaeth yn glasur o fri rhyngwladol.
Mapio Môn
Wrth fapio ynys Môn, gwnaeth Greenly ddefnydd mawr o syniadau tectonig a ddatblygodd wrth iddo fynd i’r afael â gwaith maes cynharach yn Ucheldiroedd yr Alban. Roedd tair prif broblem yn ei wynebu: prinder brigiadau da, yn enwedig mewn ardaloedd mewndirol allweddol bwysig; presenoldeb creigiau gorchuddiol clytiog yn cuddio yn aml y baslawr Cyn-Gambriaidd hŷn; a phresenoldeb toriadau tectonig megis ffawtiau a chylchfaoedd croesrym a oedd yn aml yn rhwystro’r gwaith o gydberthyn gwahanol ddilyniannau o greigiau. Chwaraeodd ei wraig Annie Greenly (Barnard gynt), a oedd yn rhannu ei ddiddordeb mewn daeareg a diwinyddiaeth, rôl hollbwysig drwy baratoi’r mynegai i’w gyfrol.
Ganed Greenly ym Mryste ac fe’i haddysgwyd yng Ngholeg Clifton. Bu’n fyfyriwr yng Ngholeg y Brifysgol, Llundain, cyn ymuno â’r Arolwg Daearegol yn 1889. Yn gyntaf, bu gofyn iddo baratoi arolwg o Ucheldiroedd gogledd-orllewin yr Alban. Daeth yn ffrind agos ac yn gydweithiwr i Ben Peach yr oedd ei archwiliadau wedi bod yn gyfrwng i ddatrys adeiledd cymhleth yr Alban (gan gynnwys adnabod a sylweddoli arwyddocâd Gwthiad Moine). Rhoddodd Greenly y gorau i’w waith gyda’r Arolwg yn 1895 er mwyn iddo, o’i ben a’i bastwn ei hun. roi cychwyn ar ei arolwg o Ynys Môn.
Cyfraniadau pwysig i ddaeareg
Yn gydnabyddiaeth am ei gyfraniadau pwysig i ddaeareg, cafodd Edward Greenly ei dderbyn yn aelod er anrhydedd o gymdeithasau daearegol Caeredin a Lerpwl, a Chymdeithas Hynafiaethwyr Môn. Dyfarnwyd iddo Fedal Lyell, fawr ei bri, y Gymdeithas Ddaearegol yn 1920, medal Cymdeithas Ddaearegol Lerpwl yn 1933 a doethuriaeth er anrhydedd Prifysgol Cymru yn 1920.
Ar y cyd â Howel Williams, cyhoeddodd GreenlyMethods of Geological Surveying yn 1930 a’i hunangofiant A Hand through Time: Memories Romantic and Geological a ymddangosodd yn 1938. Bu farw ym Mangor yn 1951 ac yn briodol iawn fe’i claddwyd ym mynwent Llangristiolus, Ynys Môn. Mae ei fedd wedi’i gyfnodi’n Safle Geoamrywiaeth o Bwysigrwydd Rhanbarthol (RIGS).
Table
Geologists' Association photograph albums [Green bound]
These two key albums of the GA focus on photographs of members.
The first volume contains portraits of early GA members and then photographs of individuals or groups of members taken on GA field excursions 1922–1977.
The second volume contains photographs of individuals or groups of members taken on GA field excursions 1979 to 1996.
Eruption of the small Weaklaw volcano, as described by Upton et al. (2019), was probably contemporaneous with petrographically and geochemically similar basanitic volcanoes associated with the basal North Berwick Member of the GHVF (McAdam and Tulloch, 1985; Upton, 2003, p 54). A low but upstanding volcanic edifice with gentle slopes probably survived for some time, until….
After possibly a significant time interval, eruption of the mugearite lava at the top of the Hailes Member. The lava is not seen in contact with the Weaklaw Tuffs, so does the mugearite lap up against the remains of the Weaklaw volcano below current erosion level or maybe it was deflected around it?
The Marine Villa Tuffs were deposited, mainly by pyroclastic flow, directly upon a very fresh, perfectly preserved, rubbly to spiky top of the mugearite lava. There is no sign of reddening, weathering or erosion of the mugearite, so this was almost certainly after only a short time interval. The gently undulating hummocky surface of the tuffs is most probably primary, possibly also reflecting underlying topography on the top of the mugearite but the contact is generally subhorizontal and very close to low-water mark on the rock platform. Cross-bedding in the pyroclastic flows consistently indicates flow towards the Weaklaw volcano. Did the flows completely overtop what was left of the volcano or were they too deflected around it - or maybe both? It seems possible that the little open syncline in the Marine Villa Tuffs at the key locality might be a primary feature, at least in part i.e. is it a result of the basal pyroclastic flow 'colliding' with a low-angled remnant of the Weaklaw volcanic edifice?
Some 250 m farther west, at the Hanging Rocks (Locality 7), two masses of pyroclastic breccia form prominent bluffs protruding from the full height of the cliff section (figures 5 and 6). Previous authors have suggested that the breccias represent a volcanic conduit, or conduits, possibly emplaced along faults, and in continuity with exposures of similar breccias extending for a considerable distance to the NE across the rock platform. The affinities of the rocks in the cliff section adjacent to and behind the Hanging Rocks are of vital importance and can be examined most easily a short distance west of the Hanging Rocks at the Smugglers Caves. On the rock platform and at the base of the cliff they are clearly Weaklaw breccias. But most authors, from Day (1923) through to Upton et al. (2019, 2020), with varying degrees of confidence, have assigned the rocks that overlie the Weaklaw breccias at the base of the cliff to what we now term the Marine Villa Tuffs, overlain by a rotten feldspar-phyric lava. In particular, Upton et al. (2020, fig. 8b) showed flattened devitrified fiamme in the tuffs. They also argued from trace elements that the lava is most likely an altered mugearite (earlier workers thought it was a trachyte).
The breccias that compose the Hanging Rocks are indistinguishable from the pyroclastic breccias of the Weaklaw Vent exposed on the rock platform, with a similar range of clasts, including the characteristic ‘cored bombs’ enclosing mantle xenoliths, as described by Upton et al. (2019). However, they cannot have been intruded through the demonstrably younger Marine Villa Tuffs, as has been suggested or implied by previous authors. On both sides of both of the Hanging Rocks, the breccias are clearly seen to be bounded by fractures dipping seawards (NW) at 40 to 50 degrees. The fault planes so defined cut the buttresses on their seaward sides up to about a metre above their bases. Where the dominant fault planes project onto the horizontal surface of the rock platform, a few metres from the base of the rocks, Day (1916, 1923) claimed to have traced a fault for some distance. That is difficult to identify today, possibly due to shifting beach deposits, but short lengths of slickensided surfaces were identified on a recent visit.
So, the Hanging Rocks breccias are truly ‘hanging’ in both a topographical and a geological sense i.e. they expose the hanging wall of a high-angle reverse fault-zone, parallel to and possibly controlling the location of the cliff line. Breccias of the Weaklaw Vent have been thrown up on the NW side of the fault-zone and juxtaposed against a near-horizontal upward succession of Weaklaw breccias, Marine Villa Tuffs and mugearite lava, exposed in the cliff behind the erosional remnants (Figure 2). T. Cuthbert Day had identified the geometry more-or-less correctly (e.g. see Day, 1916, figs 1 and 2) but he misinterpreted the angle of the fault plane and the direction of throw. ‘Tongues’ of breccia and ‘white trap’ apparently extending from the hanging wall breccias into the footwall succession at the western Hanging Rock were, understandably, taken as support for an intrusive contact. These features are difficult to access in a crumbly cliff but ideally, they should be investigated, together with the NW-dipping planes of dislocation. An intrusive nature of the Hanging Rocks breccias has been followed by most subsequent authors and the three-dimensional exposures, as interpreted here, could be interpreted as an intrusive contact but that would present serious problems regarding the age relationships. A faulted contact is by far the simplest and most likely interpretation and apparent ‘tongues’ of Weaklaw-type lithologies are probably tectonic slices within the complex fault-zone.
West of the exposures of the Weaklaw Vent, and after about 200 m of beach sand, there is a well-exposed closed syncline, well seen from the dunes above the beach at low tide (Locality 8) (Day, 1923, fig. 1, plate XXIV). The syncline is mainly in sedimentary rocks (siltstones and dolostones) above the GHVF but its lowest beds include a c. 1m-thick bed of tuff, which can be traced all around the syncline. This tuff is unlike either the Weaklaw Tuffs or the Marine Villa Tuffs. It is a coarse ash- to lapilli-grade lithic tuff, composed of matrix-supported equidimensional angular clasts of almost entirely sedimentary material, probably mainly dolostone (‘dolomitic ash’ of Day, 1923). Some fine-grained, siliceous igneous clasts might be present but this has not been confirmed. Bedding is poor or absent. Other beds in ephemeral exposures to the west are of similar tuffs or ‘tuffaceous dolomitic rocks’ (McAdam and Tulloch, 1985). Given the dominance of clasts of sedimentary rock, maybe these tuffs are the products of sporadic eruptions associated with the ‘cryptovents’ around Cheese Bay, a short distance to the south-west?
