Tuesday, 27 October 2015

November 5th - Decorative & Building Stones / November 7th - Geologists' Association Festival

November 5th - The Geology of Decorative and Building Stones at Kingston Lacy; the William Bankes Palladian Mansion and Park, near Wimborne, Dorset.
Peter Bath, Dorset Geologists' Association Group
Kingston Lacy Hall is a major, but little known, competitor to Chatsworth for decorative polished stone; notably for foreign stones of Grand Tour Provenance. Two dozen notable rocks from the African Precambrian basement, Mesozoic Sediments and many resulting from the Alpine and Apennine Orogenies have been used extensively. They will be named, described and their provenance explored.
Further details - Bath Geological Society
7.30p.m. at BRLSI 16 Queen Square, Bath - everyone welcome - visitors £4 - free refreshment

November 7th - Geologists' Association Festival

Thursday, 15 October 2015

Rock clearance day at Saltford - 20th November

Rock clearance day at Saltford
Friday 20 November 
Meet: 10:30am at the clearance site. Finish at 4pm.
Simon Carpenter is organising a rock clearance day on Friday 20 November to clean up a late Triassic/White Lias site close to the Railway Path at Saltford ST 691668. The site will eventually be part of a new geology trail around the village and I need your help.
The rock outcrop occurs along the rim of the cutting and I need a team to help clear ivy and vegetation covering the current rock face as well as removing a substantial talus slope that covers and obscures the lower part of the exposure. It should be possible to complete this work in one day.
If you are interested (volunteer days can be real fun, especially if the weather is nice), please ring or email me to register your interest: 01373 474086 and/or simonccarpenter@gmail.com
You will need to bring a spade, thick work gloves, secateurs and or loppers - some extra tools will be available if you don't have any of your own.  Bring packed lunch or there is the Bird in Hand pub a short distance away.  Bring lots to drink and warm clothing, if it's cold. 
There is a regular bus service to Saltford (X39) from Bath and Bristol or the site can be reached by bicycle of walking.  There is some car parking near the River Avon at 'The Shallows' and the rock exposure can be reached from here by a short walk.  There will be signs placed on the railway path adjacent to the rock exposure so that you don't miss it.  

Wednesday, 7 October 2015

Field trip to Anglesey, May 2016 - Lecture December 3rd 2015

Bath Geological Society
Field trip to Anglesey, Cemaes Bay in north Anglesey
27th to 30th May 2016
Dave Green, Geostudies
The course will start at 7.30 pm on 27th and is based at the Harbour Hotel in Cemaes Bay. The course ends at lunch time on 30th May near the Menai Straits bridge, but details will be given of other sites to visit for those who wish to stay on.
The cost for tuition is £40 of which only £20 is refundable.
Transport is by private car to the location. Sharing is advisable during the course due to narrow roads. Book your own accommodation, but if you do not stay at the Harbour Hotel, please be nearby and be prepared to eat the evening meal there, to enable discussion in the evening session.

3rd December this year, Dave Green is giving a talk on the complex and controversial geology of Anglesey. 
Firm expressions of interest are requested after that date, with payment shortly after (cheques to Bath Geological Society). There is a maximum of 20 places on the course.
Further details from the secretary.

Tuesday, 6 October 2015

Mystery object found on the Bath GS Manor Farm trip

The object above was found at Borrow Pit, Manor Farm, Aust - a Triassic mystery.  An expert's opinion is as follows:-
"My interpretation of this is that it lacks the symmetry and detail to be a fossil animal in its own right, though algal activity may have played a part in producing the lumps on the surface.  It has a slightly laminated appearance and I believe it to be a sedimentary accretion.  Whether it has a nucleus of any kind could only be resolved by sectioning and polishing it, but I did notice the tell-tale signs of pyrite decay products around the edge of the central lamina.
Pyrite is widespread in the Westbury Formation.  It exists as individual cubes, clusters (framboids) and granules, and is largely responsible for the bluish black colour of the sediment. It arose as a result of the reaction between iron hydroxide gels (these are excreted by algal blooms) and sulphur liberated by sulphur-reducing bacteria sourced from organic matter such as coprolites or decaying plant material. The effect of one of these FeS clusters (they only need to be a few microns in diameter) at the sediment/water interface is to create a patch wherein the pH of the pore seawater is considerably reduced in relation to its surroundings; an acid bubble, if you like. Trapped within the sediment, this can have the effect of attracting, dissolving and then precipitating any calcareous material suspended in the seawater.
Bear in mind that the environment at this time was in the process of changing from the brackish marine conditions of the first Upper Triassic incursion, to the fluvial channel conditions of the much more calcareous Cotham Member, and ultimately culminated in the lagoonal, nodular calcareous mudstone strings of the pre "White Lias"  After the desert conditions of the Keuper, things became more and more propitious for shelled marine life, so it sort of fed off itself and there would have been more and more calcareous material present in the water, starting from small beginnings. Rhythmic precipitation of this sort, discussed by Tony Hallam in about 1966 I think, responds to seasonal and even diurnal temperature and salinity changes and proceeds from small pea-sized "nummular" nodules to gradually bigger ones and finally coalescing into continuous beds. Hope this helps."
It certainly does, thank you!