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Newsletter - March 2015

The full, illustrated newsletter is available as a pdf for download. Text extracts are given below.


A belated Happy New Year to all our readers! The AGM has now taken place and I am pleased to announce that I am being released to go and work full time for Santa as Lyn Relph has been elected as your new Newsletter Editor. Lyn also currently edits the Open University Geological Society newsletter.

Talking of the Annual General Meeting where we had a very interesting talk by Ray Burgess on Mars, there are still vacancies on the MGA Council. Not to do any specific job (well apart from Indoor Meetings!) but just to help in the running of the Association. If you would like to find out what this actually means in practice, why not come along to one of the Council Meetings?

The next one is on Saturday 7 March 2015 at 10am at Manchester Museum. The following one is on Saturday 6 June, same time, same venue. If you would like to come along, then please let our Secretary Sue Plumb know by email or phone (her details can be found on the back page of the newsletter).

So it's farewell from your House Elf - thank you for reading my newsletter over the last 12 months. I am sure you will give Lyn your full support by sending her trip reports and other bits of geology related information.

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Forthcoming Outdoor Events

The coal measures of Todmorden Moor: Saturday 30 May 2015

Joint trip with GeoLancashire

The field excursion will be led by John Knight, President of the Yorkshire Geological Society and an expert on the Coal Measures.

The first part of the day will follow the itinerary of the Todmorden Moor Geology and Heritage Trail. In a gully we will see a good exposure of the 6 Inch Mine. Immediately above this coal seam we will also see the Gastrioceras subcrenatum Marine Band, which marks the base of the Westphalian. The coal is underlain by a seat earth paradoxically containing some fossils, as yet not conclusively identified.

For more information see the trail guide and the Todmorden Moor website.

We will also visit a sandstone quarry with spectacular sedimentary features and fossil tree fragments. A local tip contains "bullions", carbonate concretions with well preserved goniatites and also occasional coal balls, well cemented nodules which preserve fossil plant matter in astonishing detail.

The afternoon itinerary is not yet fixed but the general plan is to visit part of Green's Clough, to the north-west of the Todmorden Moor Trail; here we will hope to see a rather lower succession of latest Namurian age.

Boots, waterproof clothing and a packed lunch will be required. The trail is especially exposed to easterly winds.

Field Excursion to the Wirral: Sunday June 28 2015

Leader: Hilary Davies

Joint trip with GeoLancashire

This excursion will visit a number of sites on the west coast of Wirral in West Kirby, Hoylake and Thurstaston to examine a variety of Triassic exposures and a thick layer of Irish Sea Till, which is being eroded by the sea, revealing a variety of erratic boulders.

It will be necessary to travel by car between locations using as few cars as possible. Extra cars can be left in the pay and display car park at the start, which is also the finishing point.

Packed lunches are preferable, although there are cafes and pubs in the area.

Criggion Quarry: Tuesday July 28 2015

Leader: John Peate, Principal Geologist, Hanson UK

Criggion Quarry, located south of Oswestry, produces aggregates for use in ready-mix concrete, asphalt production and the construction industry. The quarry works an olivine dolerite intrusion, forming Breidden Hill. Originally the intrusion was thought to be laccolithic but it is now believed to have a more discordant 'plug' shape. Drilling to 274 metres failed to reach the base of the intrusion. The Breidden Hills inlier is a SW-NE trending igneous complex consisting of the shales, tuffs and conglomerates of the Breidden Volcanic Group, the Caradoc andesitic intrusion of Moel Y Golfa, and the olivine dolerite Criggion intrusion.

Geological features include the relationship between the Breidden Hill doleritic intrusion and the Ordovician shales and tuffs, the mineralogy and porphyritic texture of the olivine dolerite and alterations to the underlying shales at the contact with the dolerite.

It will also be possible to investigate geological structures such as joint sets related to grain size, fine grained chilled margin dolerite on the edge of the intrusion being well jointed, becoming more massive and coarser-grained towards the centre (the area currently being worked); shales and tuffs close to the intrusive contact near the western base of the hill along the quarry haul road have a consistently steep dip to the west; a zone of major faulting between the 'old' quarry and the present quarry, with two NW trending faults; a zone of block faulting, perpendicular to the margin, occurs along the western edge of the intrusion.

Aspects of engineering geology including problems due to the relationship between the joint sets and quarry faces, and the potential for toppling and planar failure can be illustrated. For those with an interest in geomorphology, scree development can also be examined.

It is proposed to link this visit with one to Llanymynech a few miles north of Criggion, led by Peter del Strother and Jennifer Rhodes. This area is an extensive country park with the restored remains of a Hoffmann lime kiln set in the quarries which supplied the limestone. (An article by Peter about Hoffmann kilns can be found in North West Geologist No 19)

The Criggion quarry visit will be in the morning, after which the party will drive to Llanymynech, where packed lunches can be eaten (alternatively there are cafes, pubs and shops in the village) before exploring the area.

Bosley Cloud: Saturday 22 August 2015

Leader: Paul Aplin

Joint trip with OUGS

Building Stones of the Trafford Centre: Sunday 18 October (morning only)

The Fred Broadhurst Memorial Trip

Leader: Jane Michael

This trip will be based round Fred Broadhurst's leaflet produced for the Trafford Centre in 2000. It is an ideal low-mobility trip as it is on the flat and, although we will be visiting both floors of the Trafford Centre, lifts are available for participants.

Further details will be available to participants and numbers are limited, so book early.

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Cobbles acquire Museum Accession Status at Knutsford Heritage Centre

Members may recall that the MGA supported the creation of a display of eleven geologically interesting cobbles, recovered from the redevelopment of the Royal George yard, Knutsford, in 2004. They are glacial erratics comprising fine examples of a variety of intrusive and volcanic rocks from the Lake District and sedimentary rocks from the region south towards Knutsford. They are set in a bed of the pure glacial sand, used to make glass, taken from a quarry near to Jodrell Bank. The display was unveiled by Fred Broadhurst in 2006 in the presence of John Price, the then President. The information poster was revised to the new house style in March 2013. The display replaces Location 7 in my Geology of Knutsford's Building Stones and Cobbles trail.

The Heritage Centre is aiming to achieve Museum Status and so the cobbles and sand have been assigned Accession Numbers, KHC/2014/1288/1-11 as they will become permanent objects in the museum. Is this a first for some lowly cobbles and sand? It is surprising how dirty and unkempt such a simple display can become with atmospheric dirt, moss and weeds. I give it some TLC twice a year and have to remove and wash the top 5 cm of sand every two years to keep it looking attractive.

The display can be seen at the Knutsford Heritage Centre, 90A King Street, Knutsford, WA16 6ED. For opening times, phone 01565 650506 or visit the Heritage Centre website.

This is also the home of the well-known Knutsford Millenium Tapestry triptych and is well worth a visit.

Fred Owen

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Geo Web Watch

Most of us have access to the web either via our own computer or using our local library. There are many geo-themed websites out there and so your Editor thought it might be useful to highlight some of these each quarter. If you have any favourite sites which you use, please let me know and I'll be pleased to include them next time.

This quarter I am going to introduce you to the Facebook site Geology Page. You can look at this page but to delve further you do need to log into Facebook. Geology Page puts all sorts of interesting information on the Facebook site every day.

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