Cymdeithas Daeareg Gogledd Cymru
North Wales Geology Association
Programme :
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Which way to meetings?

Saturday July 15th 2017
Field Meeting: Penrhyn Quarry, Bethesda
Leader: David Jameson

Sunday August 6th 2017
Field Meeting: FossilPlants Garden, Llanberis
Leader: Robbie Blackhall-Miles

Wednesday 6th December 2017
Annual Members' Evening - Short Presentations
Speakers: See below

Saturday January 27th 2018
Annual General Meeting

Wednesday February 21st 2018
Monitoring subsidence related to relict salt mine, Marston, Cheshire.
Speaker: Cathrene Rowell, Keele University

Wednesday March 28th 2018
Epic seafloor off North Wales.
Speaker: Katrien Van Landeghem, Bangor University

July 15th 2017
Field Meeting:
Penrhyn Quarry, Bethesda
Leader: David Jameson, GWP Consultants
Based on the Llanberis Slates outcrop, Nant Ffrancon, Bethesda

Visits to this site are not easily organised due to its status as a working quarry and home to the iconic ZIPWORLD attraction for adrenalin junkies. We are therefore very pleased that we have been assisted in this task by David Jameson, who has worked in this site for many years as a consultant.

Penrhyn Quarry
Image ©Eric Jones. #225970

We will start with a 30 minute introductory briefing in the canteen/workshop area giving a brief history, geological background and structural setting with respect to quarry stability and production. In the quarry we will look at the detailed stratigraphic sequence within the slates and cross cutting dykes and the major faults which delimit the productive slate strata.

High visibility jackets, hard hats and solid boots are mandatory for all participants because this is a working site. Please provide your own jacket and hat where possible as the quarry is not set up for large numbers of visitors, and only a limited supply is available. It is an exposed, upland area and participants must be prepared for the conditions. Please contact Gary Eisenhauer to register your interest. Numbers will be limited by transport arrangements, as this cannot be a walking trip due to the distances involved. There is a short technical paper which can be distributed to anybody with a wish to read a bit more about the site before the visit.

Joining details will be given to participants when they are finalised, but a 10:00h start in Bethesda should be assumed.

August 6th 2017
Field Meeting:
FossilPlants Garden, Llanberis
Leader: Robbie Blackhall-Miles
Avisit to Robbies specialist garden in Llanberis

Llyn y gafr
Image ©RB-H.

FossilPlants is the North Wales garden of Robbie and his partner Ben. A backyard Botanic Garden working to promote the conservation, education and scientific understanding of those plants that were around before the extinction event that saw the demise of the non-avian dinosaurs; the K-Pg boundary.

This very small garden hosts an impressively large collection of plants from all over the world. Many of these plants are threatened with extinction and it is for this reason that the garden became a institutional member of of BGCI (Botanic Gardens Conservation International).

The garden houses many members of the Proteaceae and is working towards a Plant Heritage National Plant Collection of South East Australian Banksias. Other notable groups of plants in the garden are Illicium, Chloranthus and Southern hemisphere ferns.

Please contact Gary Eisenhauer to register your interest. Numbers are not particularly limited, but the size of a tour party is restricted by the small size of the garden so splitting into groups may be necessary. This will be a relaxing trip, and services in the town are nearby, as is the lakeside resort of Padarn Country Park.

Joining details will be given to participants on application to Gary.

December 6th 2017
Annual Members' Evening
Speakers: See below (in no particular order):
Meeting Room, Pensychnant, Conwy.
Meeting to commence at 19:30h
Refreshments and Nibbles from 19:00h
Location details and map: Contact/Find

Keith Nicholls:
The geology of Deeside, with particular reference to the Shotton Steel Works Site

The Shotton, or Summers, Steel Works was one of the hallowed places which seemed to be incredibly exciting to a young proto-geologist living in southern England. Remarkable, in fact, that it was even known of - BUT it was also a location famous for a very modern way of handling bulk commodities (i.e. iron ore) in big trains with big steam locomotives (the Riddles Standard class 9F for cognoscenti) between Birkenhead Docks and the steel works. The last steam locomotive to do so became rather famous and is still operating today, I am pleased to say. Not quite what Keith is going to say, pehaps.......

Richard Birch:
The Origin of Fish

For the obvious reason that fish live in water and are more likely to be fossilised than terrestrial vertebrates, fish are the most common vertebrate fossils. This offers a unique opportunity to trace vertebrate evolution. The Devonian Age of Fishes (419-358 mya) is well represented in UK rocks, and presents a fascinating window into a period where the modern phenotype of a fish as a slimline scaly form with fins was in the minority. This short film explores the Devonian rocks of Britain and their equivalents elsewhere, and the diversity of early fish they contain. Richard will also bring a display case to demonstrate.

Jonathan Wilkins:
Slate quarrying and petrology

drilling rig The heritage of slate quarrying in North Wales has produced unrivalled outcrop sections for the study of ancient mudrocks.

This talk is in two parts which cover the quarries visited during field trips and personal exploration, and the petrological examination of specimens collected for "What-if" studies.

January 27th 2018
Speaker: Dr Servel Miller, University of Chester
Meeting Room, Pensychnant, Conwy.
Location details and map: Contact/Find

Annual General Meeting commences 10:00h
Refreshments at 11:00h
Lecture to commence at 11:30h
From Diatoms to Drones: A Journey from Mapping Tsunami on the shores of Jamaica to Slope Instability along UK Coastlines.

Recent events such as the January 2018 mudslide event in Montecito, California are stark reminders of the disproportionate impact that such natural phenomena can have on society. In areas that have not experienced the effects of an adverse natural hazard in living memory, raising awareness can be challenging, particularly if there is limited knowledge and understanding of the risk posed to society. Identifying, mapping and quantifying these hazards is thus one of the most important steps in their management.

Within areas affected by natural hazards such as tsunami and slope instability, deposits and/or geomorphological features left in the landscape can provide vital evidence of hazard existence, extent and magnitude. In Jamaica for instance, the last tsunami was in 1906. The island as such has very limited plans to mitigate the potential impact of a tsunami, mostly due to the lack of evidence for their existence. In the UK landslides, unlike flooding, are rarely considered during the planning processes but there has been a three-fold increase in landslide incidents in the last decade, costing millions of pounds each year. One problem that geologists face is the difficulty in obtaining accurate records of landslide events, especially in more remote areas. This talk will explore the use of novel techniques such diatom analysis to determine the extent of tsunami deposits in Jamaica and the use of drone mapping techniques to map landslides in inaccessible valleys and unstable cliffs around the UK. However, these tools/techniques are not without their challenges and limitations, which will be explored as part of the talk.

Dr Miller is senior lecturer and programme leader for the BSc. Natural Hazard Management course in the Department of Geography and International Development at the University of Chester.
February 21st 2018
Monitoring subsidence related to relict salt mine, Marston, Cheshire.
Speaker: Cathrene Rowell, School of Geology, Geography and the Environment, Keele University
Meeting Room, Pensychnant, Conwy.
Location details and map: Contact/Find

Meeting to commence at 19:30h

The Cheshire Basin contains >4.5km of Permo-Triassic red beds, including the Mercia Mudstone Group (MMG) which accumulated in playa and tidal-flat environments. The MMG is the host to two major halite formations: The Northwich and Wilkesley Halite formations, which have been commercially exploited. Both rock salt and brine has been extracted from mainly two horizons of the Northwich Halite Formation in the Cheshire Basin in various locations, and rock salt is still mined in nearby Winsford, Cheshire.

canal subsidence Surface subsidence resulting from salt mining and brine pumping in Northwich, and the surrounding areas in Cheshire, has occurred since Medieval times. This has varied in severity, with evidence of subsidence ranging from topographic depressions to catastrophic surface collapse from the mid-18th Century onwards.

To detect, characterise and monitor areas susceptible of subsidence, near-surface geophysics has been applied. A section of the Trent and Mersey Canal, in Marston (Northwich), crossing 3 abandoned salt mines has been the focus of long-term microgravity surveys for >10 years. The data collected over this period shows consistent, deepening negative anomalies at the margin between the Adelaide and Old Marston relict mine workings, as opposed to over the mines themselves. By correlating microgravity data with mine plans, boreholes and sedimentary logs, 2D gravity models have been produced: the anomalies are interpreted as upwardly propagating voids, and associated collapse material. A void feature at the point of the microgravity excursion has been confirmed by intrusive investigations. Further investigation of the canal water depths and the underlying silt accumulation on the canal floor has been undertaken, in addition to water / sampling and analysis, to ascertain any connection to underlying mines and potential canal collapse. This study further demonstrates the importance of time-lapse microgravity surveys to facilitate the identification and monitoring of at-risk areas, with a view to mitigating the risk of catastrophic surface subsidence.

Cathrene Rowell is studying for her PhD at Keele.

March 28th 2018
Epic seafloor off North Wales shows rapid ice retreat during the last ice age. The fate of West-Antarctic ice?
Speaker: Dr. Katrien Van Landeghem, School of Ocean Sciences, Bangor University
Meeting Room, Pensychnant, Conwy.
Location details and map: Contact/Find

Meeting to commence at 19:30h

antarctic science cruise A spectacular 2100 km2 seafloor image dataset collected on behalf of Celtic Array Ltd between Anglesey and the Isle of Man reveals the geomorphology and subsurface geology of a wide, submerged glacial landscape. With this data, we investigated how the Irish Sea Ice Stream advanced and retreated about 20,000 years ago (during the last ice age). This ice stream was the largest of its type to drain the interior of the former British-Irish Ice Sheet, and this study thus provides a conceptual model of how large ice streams retreat and cause the instability (even collapse) of large ice sheets. Why is that so interesting or important? Some ice streams in West Antarctic Ice Sheet are currently also unstable and there are concerns that their retreat can cause an onset of rapid collapse of parts of this massive ice sheet. That in turn would cause a huge global sea level rise (in the order of metres), and warrants our greatest attention.

Katrien is a lecturer and researcher in the School of Ocean Sciences at Bangor. Her current research includes sand dredging, sediment transport, shipwreck sites and the future of the Antarctic Ice Sheet. She is an engaging speaker and this talk will appeal to anybody with an interest in the special area we call the Irish Sea. N.B. This sea has equal claim to be Scottish, English and Welsh, and it matters to all of us! Her image (left) bears an uncanny resemblance to the view of the Carneddau from the Menai Strait during chilly times, don't you think?