Number 2 October 2004
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Price £2.50 Number 2 October 2004 It seems amazing that a whole year has passed since the firstNewsletter appeared, and in that time a lot has happened. The Forum has had a highly successful first year and has run a number of well supported field meetings throughout Wales, reports of which occur elsewhere in this newsletter. The Council’s thanks go out to those who have organised and led the various meetings. Membership currently stands at about 60, which is a good start, but there must be many other potential members out there who either may not be aware of the Forum or just haven’t got around to joining yet. It needs every one of us to spread the word and entice others into the fold. One problem associated with a small membership is finding enough bodies to fill the roles required to keep the organisation running smoothly. At this stage Council feels that there is a need for someone to take on the role of Meetings Organiser, currently one of the multitude of roles that Tim Palmer is covering. If anybody would be willing to fill such a role would they please contact Tim. During the summer the Forum presented a poster display at the Sennybridge Agricultural Show. Dyfed Elis Gruffydd fronted the display and he was kept busy answering questions from the many members of the public who showed interest in the presentation. Attending such events is a profitable way to spread the word about the Forum’s existence. Hopefully, soon to appear should be a promotional and membership leaflet, an A1 size poster as well as a Forum web site. It is hoped that the latter will serve as a repository for reports on current and completed projects, which will form a useful reference source to all things stone. Forthcoming Meetings The meetings until October 2005 have now been agreed. Full meeting details and further information will be available closer to the dates and also posted on the web site. It is a varied programme that we hope will be of interest to you all. Saturday 26th March The Museum of Welsh Life, St Fagans, Cardiff 11.30am. AGM followed by a talk by Gerallt Nash about stone-built reconstructed buildings and a tour of the site. Saturday 9th April St David’s, Pembrokeshire. Field meeting. Meeting co-ordinators: John Davies and Judi Loach. Meet at 11.00am at the Cathedral Gatehouse (Porth-y-Twr). Saturday 7th May Monmouth, Monmouthshire Field meeting. Meeting co-ordinator Edward Holland. Start time 11.00am. Saturday 25th June Barmouth and Egryn, Gwynedd Field meeting. Meeting co-ordinator Tim Palmer. Start time 11.00am September/October The Carboniferous sandstones of Flintshire Weekend field meeting based in Wrexham. Meeting co-ordinator Graham Lott. Full details to follow later. 1 Trefor Granite Ferricrete at St Dogmaels The northern skyline of the Lleyn Peninsula in north Wales is punctuated by a series of rugged and steep hills, which are In the summer of 2002, following up ideas hatched at the Stone in Wales conference, a number of members of the formed from a series of medium-sized granite or, more strictly, granitoid intrusions. There are several, mainly disused committee travelled into west and mid Wales seeking out ‘exotic’ limestone occurring in the fabric of medieval quarries scattered around this vicinity but the Trefor granite is still exploited commercially as an ornamental stone. monastic sites. More specifically, we were looking for what might be identified as the “Dundry Stone” of previous The Trefor Granite Quarry is located on the north coast of Lleyn about 20 km SSW of Caernarfon, above the records. Was that yellow Jurassic limestone from Bristol really taken in quantity by the Cistercian builders for the small village of Trefor, after which it takes its name. The quarry is accessed (with the permission of the owner) by a steep finer mason work to counter the rough textures of greywackes and slates of the immediate surroundings of the site? incline, which rises to a height of almost 150m above the village. It contains about six benches, each approximately Could there even be French limestones from the Paris Basin sites of the parent communities? 30-50 m high, which face north towards the sea. The total height of the quarry from the top to the bottom is about 300m When we reached St Dogmaels, just south of Cardigan, Dyfed Elis Gruffydd was keen to show columns and (1000 feet) and quarrying has removed a considerable chunk of the mountain. Today, much of the quarry is redundant window tracery of yellow limestone which pose the question, is this Dundry or is it still more ‘exotic’ and transported as volumetrically the demand for the stone is very small. from France as it could have been thanks to the coastal setting? Well, the Like the numerous slate quarries, Trefor jury is still out on that question, but, if as often happens, when chasing one Quarry is part of the industrial heritage of north question another turns up in the process. In the case of St Dogmaels, that Wales. In the early part of the 19th century Samuel diversion was the occurrence in the mixed lithologies of the rubble walling Holland, businessman and quarry owner, was of irregular blocks of highly ferruginous sandstone and sandstone pebble heavily involved in the slate mining industry of stone. Colours range from a light chestnut-brown to reddish-brown and north Wales. He had also opened up a quarry at in extreme cases, a purple tone. In the last instance, the broken surfaces Penmaenmawr to provide road surfacing and after can have a metallic lustre. The grains are coated with the pigmenting iron some exploration around the granitoid intrusions of oxides, creating at the same time the effective cementation of the stone. the Lleyn, he concluded that the Trefor granite was In my experience of working in the stoneless wastes of the London Basin well suited for producing setts, which were in great and nearby regions of poorly consolidated Pleistocene and Tertiary soft demand in the burgeoning cities of the industrial rocks, areas occur where iron-rich groundwaters locally cement sands and revolution. He opened the quarry in the 1830s to terrace gravels into what Lamplugh termed ferricrete (1902 Geol Mag). supply this market and as a result a small village Locally, and in subsurface cuts to create foundationing, these hard lenses grew up at the base of the hill near the pier from which the rock was exported. It was named after Trefor Jones who was provide useful building material in regions of stone poverty. As such, Holland’s first foreman at the quarry. Extraction of the granite for setts maintained the quarry through much of the 19th the ferricretes were much used by Saxon and Norman church builders of century but, inevitably as roads became paved with aggregate and tarmacadam, the demand subsequently declined. the period between the 9th and 13th centuries and would be familiar to the Today Trefor Granite is famed for its use for curling stones. Indeed, it was Trefor Granite curling stones that monastic builders of St Dogmaels. were used in the last winter Olympics in Salt Lake City. The quarry owner, Mr Trevor Davis, insists that Trefor Granite My excitement at the discovery was hardly shared by my companions, (understandably one has to admit), is superior to Eilsa Craig Granite, which was historically the most important rock for making curling stones. It is also partly because the next question was, where is the local source of ferricrete in west Wales? My lack of knowledge used as an ornamental stone for walls, columns, fireplaces etc. The stone is brought down in large blocks from the quarry of local geology gave me no chance of answering, although I could and did prophesy that coastal, dune sand or river to the masons’ yard at Trefor where it is sliced up using a diamond wire saw and then cut to shape and size on demand alluvial sands would have to be examined for a possible source, particularly if there was a trace of yellow ‘iron-water’ in the workshop using cutting machines and stone lathes. springs. That was how the matter was left when we moved on to Strata Florida and more exciting stonework. In the geological literature the Trefor Granite is referred to as The Garnfor Multiple Intrusions. This indicates One year on, and without much direct application to the question, a breakthrough has come from a new publication that it is composed of several different types of granitoid rock, three types can be identified in the quarry. These are from BGS, which offers useful information. The source is one of the new mini-memoirs explaining the geology of referred to by the quarrymen as pink, blue and grey granite, all of which are used for curling stones. The pink granite Cardigan, Sheet 193 (Davies et al 2003). Not only do these short accounts summarise the kind of detail which used forms the core of the intrusion, at least in the higher levels of the quarry, and merges into the grey granite. The blue to fill out the full sheet memoir of the past, but also they have a focus upon environmentally important aspects. In granite forms the margins of the overall structure and its boundary with the pink is quite sharp. this case, there are seven out of twenty five pages devoted to the Quaternary possibly because there is a history of The granite is probably about 450 million years old and at the time of its formation this part of Wales was a landslipping, with one at St Dogmaels as recently as 1994.