Newsletter - September 2011
A PDF version (3MB) of this newsletter is available for download.
The nights are drawing in already and after a very busy summer in the field (thanks Jane), we are looking forward to an excellent programme of lectures (thanks Jim).
We kick off next week on Wednesday 12th October with wine, juice and nibbles at 6.00 pm followed by two entertaining lectures at 7.00 pm, entitled "Whodungit?" and "Dead in the Water" (abstracts).
You will need to book with Jim Spencer if you want to come to the Broadhurst Day in November, as numbers are limited and we are providing a buffet lunch. The cost for the day is £7. (Booking form).
Details of our December meeting will be announced at meetings and on the website in due course.
Reports of the first three field excursions follow and the rest will be in our December edition. I hope you all enjoyed your summer excursions as much as I have done.
With best wishes to all,
MGA Newsletter Editor
An "Update Your Skills" DayPractical geology for members
I am considering putting together a Skills Day in October 2012 which will comprise 3 sessions. These are, in very general terms:|
However, before I put more effort into organising this, I would like to know whether people would be interested in attending.
- Geological Maps
- Making Thin Sections (the simple way)
So far I only have Duncan Woodcock on board (Thin Sections) as a lecturer/demonstrator - he and I have discussed the day in general and come up with the above. Each session would probably last 2 hours and everyone would have an opportunity of attending each one (i.e. there will be three groups). I would be looking at the maximum number of attendees being 18-21 to ensure the groups are small. I think this could be a really exciting and informative day.
Please email your comments to me by 30 November 2011 or phone on 07917 434598.
The Greater Manchester Building Stones Collecting Project
Greater Manchester has some iconic and much loved buildings. Many of these buildings are made from local stone and form an important part of our geological heritage.|
The Manchester Museum is putting together a building stones collection that shows examples of Greater Manchester's building stones and we are looking for people who might be able to help collecting specimens and gathering information. A wealth of fascinating clues can also be found in the old papers and transactions of geological and naturalist societies, which were often written when many of the building stone quarries were still producing stone and some of you may want to help with this aspect of the project by searching through these papers for useful references.
In addition you may have useful contacts with local history societies or old stone masons, builders and drystone wallers who used the local building stone. Local stone names such as Chocolate Drop and Old Mother Rock have already been saved from obscurity through research so far.
The collection will complement the Strategic Stone Study that Chantal Johnson has worked on for English Heritage which links key Manchester buildings to the rocks they are made from. The report builds on the work of Fred Broadhurst and Morven Simpson. The collection will bring together information on the specimens, buildings, quarries and geology and will be an invaluable resource for researchers, building conservation officers and anyone else who is interested.
If you'd like to help with this project or find out more please contact David Gelsthorpe, Curator of Earth Science Collections, The Manchester Museum, Tel: (0161) 306 1601
An Introduction to Geological Structures & Maps 8th Edition|
George M Bennnison, Paul A Olver and Keith A Moseley
Hodder Education PB £21.99
Publisher's description: This is a concise and accessible textbook providing simple structural terminology and map problems which introduce geological structures. It is a perfect introduction to mapping for students of geology, engineering geology and civil engineering.
Each topic is explained and illustrated by figures, and exercises follow on successive maps. If students are unable to complete an exercise, they can read on to obtain more specific instructions on how theory may be used to solve the problem. An appendix at the end of the book provides the solutions.
This new, eighth edition contains simplified introductory matter to make the subject as easy to grasp as possible. Colour photographs illustrating geological structures bring the subject to life and a new map from the British Geological Survey illustrates a real area. There is more on outcrop patterns, which will help students to think in 3D, and on structures and the relationship of topography to geological structure. Cliff sections have been added to reinforce the concept of apparent dip. The section on planetary geology has been more closely tied to igneous geology to aid understanding of the connection between the two. Finally, a new map on economic geology has been added for the benefit of engineering students.
A geological glossary helps students to understand and memorise key terms and a new, colourful, text design enlivens the appearance of this popular book. Colour photographs bring geological structures to life Introductory matter is expanded and explained in more detail making the subject more accessible.
A British Geological Survey map is included illustrating a real area.
Jane Michael recommends another useful book. She says, "This looks a really useful book with excellent diagrams. Some interesting appendices where you can make box models to actually demonstrate how various structures map on the ground. Lots of inter text questions. It makes a valuable addition to my library."
A Geological Excursion Guide to the North-West Highlands of Scotland
Edited by Kathryn M. Goodenough and Maarten Krabbendam, co-published with Edinburgh Geological Society
228 pages, 210 x 148 mm, 115 colour illustrations
Paperback (flexiback binding for ease of reference and carrying) £15.99
ISBN 978 1 905267 53 8
The area covered largely corresponds to the North-west Geopark. The 16 excursions:
This is the companion volume to An Excursion Guide to the Moine Geology of the Northern Highlands of Scotland by Rob Strachan, Ian Alsop, and Suzanne Miller published in 2010 ISBN 978 1 905267 33 0, £17.99, as is A Geological Excursion Guide to Rum by C H Emeleus and V R Troll ISBN 978 1 905267 22 4, £12.99.
- Loch Assynt and the Achmore Duplex
- A Transect through the Canisp Shear Zone
- Stoer Group at Stoer Peninsula
- Stoer Group at Enard Bay
- Ullapool River, Creag nam Broc and Glen Achall
- Knockan Crag and the Knocken Klippen
- Traligill and Bealach Traligill
- Conival and Ben More Assynt
- Glen Oykel and the Loch Ailsh Pluton
- Cam Loch, Ledmore and the Loch Borralan Pluton
- Scourie Mor
- Durness, Balnakeil Bay and Faraid Head
- The Moine Thrust Zone at Loch Eriboll
- Roadside Stops around the North-west Highlands
Editor: Here's another new book, not seen it yet but I've heard Kathryn Goodenough talk ...so it's sure to be good!
Park Bridge, Ashton-under-Lyne, 9 April 2011
Following her interesting and informative though somewhat wet trip to Park Bridge in July 2010, Chantal Johnson led another excursion covering areas which hadn't been visited last time. She was also blessed with much better weather.|
This time seven members met up at the Visitor Centre where Chantal showed us copies of some old photographs of how the area looked in its industrial heyday as an iron works. This included the railway viaduct which was demolished in the 1970s. The railway was part of the Stockport/Ashton/Oldham/ Delph line and went across the River Medlock. She also explained about the Forges where the men would have to try and 'catch' the hot snake-like lengths of metal with heavy tongs as they passed it from one set of rollers to the next, to make the wrought iron to the required length and thickness and the 'Bright shop' where items were pickled in acid to make them 'bright and shiny'. The Lees family owned much of the area. The iron works closed in 1962 - it had made good quality iron reputedly including the rivets in the Eiffel Tower.
Chantal asked us to think about why the iron works were situated here. Was there iron? Well scrap iron was actually brought in although iron rich nodules can be found in the rocks. The Copperas Works made sulphuric acid locally (and Hannah Lees made her fortune here) and this used iron pyrites dug from the local rocks but were any leftovers usable as a source of iron? Chemists might be able to answer that one. There was coal - we saw the Foxholes seam which was not brilliant quality but usable. There were many other seams and mining had been undertaken since at least the 17th century. There was water as a source of power - the River Medlock.
We walked up to look at an area we had visited in July where there is a thin coal seam, the Foxholes seam, visible together with a seat earth below where rootlets can sometimes be seen.
Most of the area is in the Lower Coal Measures - approx. 300 million years old. Many fossils have been found in rocks of this age including Meganeura, large dragonfly-like insects, and Arthropleura, millipedes the size of dogs. George Wild, who was involved in the local mining industry in Victorian times, collected many local fossils and his collection is in the Manchester Museum. In particular he found amphibian rib bones and fish spines (some around 18 inches long). From the fossil clues of this area and other areas with similar rocks it is likely to have been part of a large delta type environment with channel switching and brackish water in some areas. There is a marine band, no longer exposed, which shows that relative sea level did rise.
As we walked back to the river Chantal pointed out a possible fault in the bank where the sediments have been dragged down to form a small fold. The mining started on the surface often where coal was exposed along the valley sides, bells pits may have been dug and finally shafts. The rock is much faulted and the strata is dipping which would not have helped mining.
Dick Crofts from the BGS had indicated that some of the small dry valleys such as above Dingle Terrace are glacial in origin and probably formed by meltwater. Sand and gravel deposits and also glacial erratics can be found along stretches of the Medlock valley around Park Bridge. Walking alongside the river, we were following an old tram line which went from Rocher New Pit to the Fairbottom Branch Canal. At least part of the tunnels cut for this tramway had also later been used as air raid shelters. Another problem with the rock was that it contained a lot of methane. This caused the Bardsley Pit disaster of 1858 when over 50 men and boys were killed by a gas explosion and many more seriously burnt and injured.
Fairbottom Bobs is the area where a bobbing Newcomen type beam engine was situated. This removed water from the coal mine. This stopped working around the 1830s and was not in use in 1890s when George Wild led a field excursion. We had a good look round the ruins. The engine itself was rescued by Henry Ford in 1929 after a visit and is in the Henry Ford Museum in the United States. There were cottages nearby but they have been knocked down.
A reed bed has been set up to clean up the iron ochre which is coming out of the ground. This is working to the extent that whilst the water entering the bed is orange, it is a very pale colour at exit. Apart from water from the mine, there is good fresh water from springs at Alt Hill but its source is not known for certain - it runs all year and during WWII it was one of the many local springs that were surveyed as a potential water source in case the main supply was poisoned.
We moved to the river again to look at a landslip where a tree has almost fallen into the river. The river bank also shows some interesting geology. There is a layer of round and oval nodules. Further along the river there is some definite arching over of the rocks. But is this a fold or the result of faulting as seen earlier - a possible thrust? Here orange ochre seeps out into the river, against the backdrop of green mosses and liverworts.
The Fairbottom Branch Canal mentioned earlier at one time extended up towards Fennyfield Bridge. It is now filled in and is now a cycle path and bridleway. Chantal took the opportunity to give a brief history of what it would have been like working in pits - from the age of 7! We walked along the disused railway line to Rocher Vale where there had been two known coal pits. This still gives good views of some of the geology (when not obscured by spring growth!). At Rocher Vale we were able to see the cross bedding in the sandstone and evidence of channel swopping - this was much clearer than last July due to the better weather! The wedges of coarser sandstone in the sediments confirmed a dynamic environment.
It was then just a short walk back to the Visitor Centre. Chantal had given us even more insight into the geology and how it instructed the industrial development of the area.
You'll have another chance to visit Park Bridge next year, there will be an MGA sponsored geology day there in June 2012.
Cutacre Field Event, 8 May 2011
The group met at the offices of UK Coal's 322 hectare surface mine site at Cutacre, Little Hulton, Greater Manchester. Kitted out in hard hats and high visibility jackets, the group took close notice of Mr. Joe Brooks (Foreman) as he described the layout and dangers of Cutacre's everchanging topography. He pointed out particular danger areas to keep clear of. Care was necessary in the working void and backfill area, as they were made up of tipped rocks and spoil, which could be very slippery after rain. He drew attention to the remains of a slag heap which had once been the largest in Europe. After a period of internal combustion in the heap, the resultant red shaley material was used for tennis courts.|
Surface mining in the area had been proposed in the early 1980s but planning permission had been refused on several occasions. However, more recently with coal once again in demand due to lack of confidence in other fuels, permission was granted in 2001 and 900,000 tonnes of coal has been extracted between work commencing in 2006 and the site's closure in mid 2011.
Surface mining in the Little Hulton area can be traced back to the sixteenth century, and Cutacre's workings are on the site of the former Walton Hall deep mine, operational from the 1860s to the mine's closure in 1928. It was part of the vast colliery complex controlled by the Trustees of the Duke of Bridgewater, accessed by surface winding and by the Worsley underground canal system comprising of 52 miles of underground canals on four levels. During the recent excavations, old workings from around the 1880s have been uncovered, including tunnels, brick shafts, remains of pit tubs and rails. (See the Cutacre website for some splendid photographs of these fascinating artefacts). In the most recent activity coal was excavated from the Crombouke, Brassey, Rams and Bickershaw 7 feet seams at the site and was taken overnight by road to Drax power station in Yorkshire.
We travelled partway to the working area (the void) in Land Rovers, then slithered the rest of the way down to the void through grey, heavy, sticky mud, stopping at times to avoid the huge bulldozers and trucks coming towards us, and to gather nodules, some elliptical and containing shark eggcases. Near the bottom embedded in the rock, could be seen a pit prop from the old deep mine.
On reaching the sloping floor, the vastness of the void could be appreciated. By now the party was strung and out busily searching among the layers of shale and sandstones, and tipped rock and back fill, with the hope of finding some of the spectacular examples of Coal Measures fossils. Here was a rare chance to collect Carboniferous Westphalian B coal measure material such as sigillaria, calamites, neuropteris, lepidodendron and rarities such as spiders, all indicators of the conditions in the tropical swampy deltas throughout the Upper Carboniferous, over 300 Ma. Further down the void, water was emerging, under pressure, from the old deep mine workings and was being pumped through a pipe up the excavated high, vertical walls into a filter system, which rendered the water less acidic. Amongst the back fill and tipped rock was the exposed, platform-like top surface of the southerly dipping Bickershaw 7 feet seam - a sight few of us will ever have the luck to see again.
It took some persuasion to round everyone up from their fossil hunting and back into the Land Rovers. Only the prospect of the long, slippery, muddy climb back up to the offices made stragglers move with alacrity. Back on top fossil finds were shown - some luckier that others, but no one disappointed.
This was a very stimulating and exciting experience, thanks to Alan Davies, the leader, and Joe Brooks, the foreman. Thank you also to Jane for organizing the clement weather and this unique trip, as the mine has now been completely in-filled. Restoration of the area will create 100 hectares of amenity woodland and wetlands for newts and birds.
Marjorie E. Mosley
MGA Excursion to the Great Orme, 16 July 2011
In the morning Dr. Jacqui Malpas had planned to lead the group to see both the exposures of Asbian / Brigantian limestones in Bishop's Quarry and the extensive limestone pavement with solution hollow on the top of the Great Orme. The weather was so wet and windy that it was decided that the limestone pavement would be too hazardous so the excursion was confined to Bishop's Quarry.|
The north face of Bishop's Quarry exposed the Summit Limestone resting upon Bishop's Quarry Limestone. Both 'limestones' consisted of limestone units with calcareous mudstone partings. The transition from limestone to calcareous mudstone and vice-versa was observed to be abrupt rather than gradational. The limestone units were between about 0.3 and 0.7 m thick. The precise stratigraphic position has not been agreed but the Bishop's Quarry Limestone is thought to be at the top of the Asbian stage of the Carboniferous period.
The Bishop's Quarry Limestone was well exposed in the southern outcrop in faces up to about 4 metres high. Lower units were seen to be fine grained with few macrofossils. However the bases of most of the upper limestone units displayed abundant productid brachiopods in life position. It was postulated that the depositional conditions following the deposition of the calcareous mudstone were more favourable to carbonate productivity which could also have been stimulated by the nutrients available from the siliciclastics in the mudstone. Jacqui advised that the productid brachiopods Productina margaritacea and Gigantoproductus edelburgensis had been identified from this location.
The south face has been exposed to weathering for sufficient time that many of the fossils now stand proud of the weathered surface. Several limestone units displayed abundant brachiopods in life position throughout the unit. These brachiopods were not preserved in any clearly defined horizons. A debate took place regarding the lifetime of a single brachiopod in relation to the time taken for the deposition of the limestone unit. No agreed conclusion was reached.
Previous reports on this locality had suggested that there was evidence of emergent surfaces. No reddening was seen, nor evidence of calcrete horizons. Nor was any evidence of burrowing seen, at least not on the scale of Thalassinoides burrows seen in other Asbian exposures in North Wales. In at least one of the upper units could be seen solitary and colonial corals. Jacqui showed a fossil list for this location and based on that list the corals were tentatively identified as Siphonodendron junceum and a species of Diphyphyllum. Caninia is reported but no example was found. Two different species of Syringopora were also seen. The corallites of one were much smaller in diameter than the examples with which most of us were familiar.
Very little crinoid debris was seen, just a few fragmentary ossicles. Productid brachiopods often have spines but despite the excellent exposure and a careful search no examples were found. Some vertical joints displayed slickensides, preserved both as scratches and as calcite crystal growth. It was clear that some strike slip faulting had occurred, without vertical displacement.
For wild flower buffs there was abundant white stonecrop and purple toadflax near the copper mine. Despite the weather a good time was had by all and at the end of the morning's excursion Jane Michael proposed a well-earned vote of thanks to Jacqui.
In the afternoon most of the group visited the Bronze Age copper mines. Carbon dating from charcoal found in the mine, where fires were used to weaken particularly hard rock faces, has indicated Bronze Age mining activity between about 1800 and 900 BC. After leaving the mine the sun was shining so the author of these notes returned to Bishop's Quarry to see it in almost ideal conditions. His only difficulty was holding his camera steady in the strong winds. The photographs were taken in conditions far removed from that of the morning.
Thanks are also due to Jane Michael for her part in the organisation of the day.
Peter del Strother
Greater Manchester RIGS Group
Repairs on the third floor of the Manchester Museum have almost been completed, so we are back in our usual working space.|
The GMLGAP is now almost ready for printing. There are still a few errors to be corrected. The restoration work at Rochdale Cemetery is almost complete. Thanks to Terry and Roger for their hard work.
After meeting Anna Cocker, a Warden of Redisher Wood, Holcombe, in June, and sending her details of the geology there, David Dutton, the Wildlife Officer at Bury, has contacted GMRIGS Group for support with their bid for DEFRA funds for the Ash Clough SSSI site. I am awaiting more details from him.
I have almost completed a write up of the seven sites in Redisher and Saplin Wood, Holcombe, assessed by Jane Michael and me.
This, combined with the completed Harcles Hill circular walk of ten sites, is an interesting observation of the succession from the Holcombe Brook Grit to the Woodhead Hill Rock; providing we can find the elusive site in Saplin Wood, of the Lower Haslingden Flags.
You will be able to find details of these walks on the MGA web site in the near future.
Jane has kindly taken over the assessment of the Oldham Peak District National Park Sites. Thank you Jane.
Jim Spencer is proving invaluable with his help and advice with site assessment, and we have site visits planned for Wigan, Salford and Manchester, using public transport.
Thanks to Phyllis Stoddart for her help in the Manchester Museum Resource Centre over the past three months.
Marjorie E. Mosley
Secretary, GMRIGS Group