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A Building Stones Guide to Central Manchester
Third Edition (2014)
Four self-guided walks through the city centre
Now available to purchase

Newsletter - June 2018

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

MGA Field Excursion - Trowbarrow Quarry, Silverdale and Keer, near Carnforth

On May 8th 2018, there was a joint excursion with Geolancashire to Trowbarrow Quarry, near Silverdale and to Keer, near Carnforth.

Trowbarrow Quarry, near Silverdale SD 481759

Trowbarrow is a limestone quarry in the Arnside Silverdale AONB, which operated from the 1850s to 1959. The rocks are Lower Carboniferous, laid down on the southern shelf of the South Lake District High, part of the same group as those on the Furness coast in Cumbria. The main rock within the quarry is the Urswick limestone, a pale grey rock, which forms massive thick beds that can form prominent scars and pavements. These quarry walls are very popular with climbers.

These walls are actually vertical bedding planes; a result of a monoclinal fold (the Silverdale Disturbance), which runs from just north of Leighton Moss to Storth, near Arnside on the Kent estuary.

A number of the beds are full of fossils, in particular large colonial corals and trace fossils in the form of "stick beds".

At the North end of the quarry three distinct bedding planes are visible with thin red clay fillings. These are paleokarst surfaces, believed to be associated with falling sea levels due to glaciation events that occurred during the period that the beds were being laid down.

A further paleokarst surface is visible on the western wall of the quarry, colloquially known by the climbers as the "Red Wall". This surface is covered in a number of large circular depressions. It is speculated that these are the location of tree roots, which produced carbon dioxide, producing excess local erosion.

One rock which is not visible within the quarry is the Woodbine Shale, which lies between the Upper and Lower Urswick beds. However, this was visible as we subsequently walked from the quarry down the footpath to Leighton Moss RSPB for lunch.

Here the vertical beds of the soft Woodbine Shale have been eroded out to form what is locally known as "The Trough", Trowbarrow originally being known as Troughbarrow. This Trough can be traced the length of the Silverdale Disturbance, and is seen again at Throughs Lane, Storth, at the northern end of the disturbance. Beyond this the beds can be tracked back to the horizontal.

So, down to the RSPB at Leighton Moss, where we had an enjoyable lunch before heading towards Carnforth.

Many thanks to Peter Standing and the other members of the Westmorland Geological Society (as referenced) who have produced all the information on the quarry and surrounding area. Peter Standing has produced a number of Geotrails for the area which are available by email.

References

Patrick, C. (2010) 'the Silverdale Disturbance' WGS proceedings (38) 18-22.

Keer, near Carnforth

An embankment of 'igneous rock' extends for about a kilometre along the north bank of the River Keer from NGR SD487713 to SD478705. Although the material was once molten it isn't igneous in the geological sense. It is slag from the works of the Carnforth Haematite Iron Co. Ltd., which operated from 1864 to 1930. This was no small operation. In 1871 they erected six Bessemer converters and by 1873 had installed plate and rail mills.

I am indebted to Duncan Woodcock for drawing attention to this locality, see bibliography, and to Brian Jeffery for research into the history of local and regional ironworking.

The picture illustrates one method of slag tipping used at Keer. Slag was also allowed to cool in hexagonal crucibles and the resulting solid blocks tipped in a similar manner.

For those interested in steam locomotives David Longman's website includes many great pictures.

Over many years the huge pile of slag has largely been quarried away; in 1958 some was used for the foundations of the M6. What remains is a 4 metre high cliff facing south across the river and largely unvegetated.

The reason for visiting was that the tipped slag possesses many characteristics of relatively recent volcanic activity - and the nearest place to see such characteristics is rather more than a one-day MGA field excursion away!

If you make this excursion yourself, be aware that the base of the exposure is on the River Keer flood plain. I do not know how often the river floods but it would be prudent to avoid times of high tides. The first igneous characteristics seen were chilled margins and vesicles.

In places the slag had partly solidified prior to tipping but was still sufficiently plastic for the fragments to weld together, see below, in the form of an anticline.

The chaotic nature of the exposure is illustrated with Brian Jeffery relishing the sunshine on the day when he, Barbara Gordon and I did the recce. Disappointingly, on the afternoon of the MGA visit, it drizzled. Nevertheless the hardy souls present had an enjoyable day.

Bibliography

Duncan Woodcock. Anthropocene volcano-analogue deposits near Carnforth, Lancashire: an introduction and field guide. OUGS Journal 35 (1-2) 2014; published 2015.
Phillip Grosse. The Railways of Carnforth - the town and its ironworks. ISBN 978-0 9569709-0-9

Peter del Strother and Barbara Gordon

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Letter by Grahame Miller (July 1973)

An article (July 1973) has come into my possession for the MGA archives by Grahame Miller on 'Practical Difficulties in Studying Geology at Home' together with a letter of comment from Fred Broadhurst in which he says 'The subject matter is very much one that is in my mind and I see my own future as moving away from 'pure' academic research towards a liaison job, placing geology at everybody's front door'

'In fact the sooner our student population ranges from 18-80 yr olds the better... Morven Simpson and I have just completed 6 programmes for Radio Manchester's 'Prospect Manchester' which will go on the air next autumn. We are also completing a guide on building stones which have been used in the city centre (Manchester) and which the Town Hall promise to publish and issue free of charge to all schools and interrelated parties - provided we satisfy their requirements!'

How right he was !

[Did the Town Hall do this? I don't know. There is no mention about it in the original 1975 Guide].

Derek Brumhead

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Force Crag Mine

A communication from the National Trust:

Thanks to the work of an amazing group of volunteers, Force Crag Mine has undergone a two year project to conserve and protect its nationally important collection of mining machinery. The project was led by Tim Martin of Context Engineering, one of the UK's leading machinery conservation consultants, so don't miss the opportunity to see what they got up to.

This year's open day dates are:
  • Saturday 5 May
  • Friday 1 June
  • Wednesday 8 August
  • Saturday 8 September
  • Saturday 15 September
Located near Keswick, in the Lake District, Force Crag Mine has it all, history, engineering, geology, geography, archaeology you name it. The last mineral mine worked in the Lake District, it was once a hive of industry, mining lead, zinc and barytes for over 200 years. Production ceased in 1990 yet you could almost believe the miners had just left for the day as the complete processing plant still exists.

Nestled in the stunning Coledale Valley, it's a hidden gem in the Lakeland landscape that gets missed by many, so don't be afraid to bring along friends and family who may not be as interested in mining as you are!

We offer a guided tour to explore the processing mill and surrounding remains, to get a feel for the harsh lives of the miners working away on the side of the fell. The tour takes about 1 hour, all tickets are £6 and we do provide transport up to the site.

To find out more visit our web page, call 017687 74649 or email.

Many thanks and I hope that we may see you at Force Crag Mine soon.

Cath Tyrrell
Marketing Assistant North Lakes Outdoors

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