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Field Trip to Askham Fell 1st June 2016

The party met on the open fell at 6.30pm on a fine sunny evening. John Rodgers, our leader, began by describing the features of the Lowther Valley to the south. This valley is bordered on the east by Carboniferous limestone escarpments and on the west by the rugged terrain of the Borrowdale Volcanics. Between the two the relatively easily eroded Skiddaw Group rocks occur and underlie the lower part of the valley.

We then walked northwards over the fell, noticing sink holes and one small exposure of the limestone. We crossed the narrow sandstone band of the Ravonstonedale Group, which is very poorly exposed but members located a few specimens of the well-sorted, gingery coloured sandstone. A pause was made to consider a line of enigmatic depressions which were probably man made rather than sink holes. The party continued to Heughscar Hill to enjoy the magnificent view along Ullswater. Again the underlying geology was reflected in the topography. Here the BVG group form the high rugged fells to southern and southeastern boundaries of the Lake. To the north west Great Mell Fell and Little Mell Fell and the smaller fells of Soulby Fell and Bowerbank are smooth, rounded hills of the Mell Fell Conglomerate. Closer to the viewpoint the low land is again a reflection of the erosion of the Skiddaw Group rocks which underlie this area.

From this panorama the group moved eastwards to a small exposure of limestone pavement and a tumbledown limestone wall where a range of fossils – colonial and solitary corals, and a variety of brachiopods – were identified.

This was the last stop after which the party returned to the cars and thanked John for a very enjoyable evening.

Excursion Report

A small group of members examined the Carrock Fell Complex spending most of their time in the southern mafic plutonic component considered to be associated with the Eycott Volcanic Group.  Discussion covered the range of published interpretations for this body of layered cumulate gabbros pooling our collective knowledge of magma-chamber processes and guided by Prof. Joe Cann.  The gabbroic body is bounded by sub-vertical faults and the internal igneous layering is steeply inclined.  Published explanations cover a spectrum from layered gabbro accumulation in a sub-horizontal sheet followed by high degrees of rotation to crystallisation on an inclined floor of a magma chamber with no subsequent rotation.  If the former proposal is correct, the challenge is to understand how and when the very significant rotation happened; could it have been in the murky events associated with the initiation of subduction at the leading edge of Avalonia or a volcano-tectonic fault, or a younger event?  Lighter and darker banding in the gabbro was first seen in the quarry along the road from Mosedale Bridge.  Within the mafic body we observed the layering mainly dipping at around 50 degrees though steeper dips are found on the margin.  The party climbed up the steep slopes of Carrock Fell, approximately along the steep contact of the gabbro with the metamorphosed and deformed Skiddaw Group.  Some large xenoliths of intensely folded hornfelsed Skiddaw rock were seen within the intrusion in amongst moderate-sized exposures of layered gabbro.

On the summit of Carrock Fell, the group encountered the second, and younger, component of the complex which is a gabbro to microgranite intrusive suite unrelated to the gabbro cumulates.  Here exposed granophyre weathers to a distinctive pinkish colour.  Boulders of gabbro on the summit occur as sparse erratics, carried upwards and northwards by ice.

All agreed that the Carrock Fell complex is indeed complex, and would merit further study.

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Non-members are welcome to join excursions and lectures on a try out basis free of charge. Further information can be found on the events and membership pages of the website.

Cumbria GeoConservation (CGC) is the group formerly known as Cumbria RIGS Group. The group was set up in 1992 and operates as a special interest group of Cumbria Wildlife Trust (CWT). There are now around 280 Local Geological Sites in Cumbria reflecting all aspects of the county’s geology and geomorphology. Through the local planning system the designation is intended to protect important geological sites from inappropriate development, as well as to encourage everyone to appreciate and enjoy the geology of our county.

Since 2014 the CGC group has met informally in the field to visit and review geological sites, and has recently started negotiating more active conservation management with landowners and managers. Over time many sites have become overgrown, their access lost or quarries infilled. Recent discussions with LDNP Rangers will hopefully lead to clearance of obscuring vegetation from some LGS quarries, such as Brown How, Blawith, LGS 7/027 (SD 289901) and Scout Scar Quarries near Kendal LGS 7/128 (SD 487925).

We have recently been working with Marshalls Stone at Birkhams quarry, St Bees Head, LGS 4/030 (NX 956154), where St Bees Sandstone is extracted, outside the bird nesting season, for conservation building stone. Two interpretation panels, one for geology and one describing the quarrying process, will be mounted on blocks of quarried stone and placed just outside the quarry, at a strategic location on two long distance paths; Wainwright’s Coast to Coast and the England Coast Path.

Great progress has also been made at Eycott Hill, CWT’s latest reserve. Geological interpretation panels, designed by Elizabeth Pickett, are in preparation, for the car park and for a viewing platform on the first lava outcrop encountered on a waymarked trail around the reserve. A geological trail is also planned. A short video film featuring John Rodgers of the CGS explaining the geology for non-specialists has stimulated a wish list for similar videos for other LGS.

Recent survey visits have identified certain problem sites, for example Hodgson Howe Quarry, Keswick LGS 7/079, (NY 242236) where despite being by the roadside, access and visibility is made next to impossible by a locked gate, barbed wire, soft slurry in the quarry floor and abundant tree growth obscuring the steeply dipping Skiddaw Group exposure in the quarry walls. This quarry is the site where Edgar Shackleton found the graptolite Azyograptus lapworthii, which was formerly displayed in Keswick Museum. For this reason the site should be archived, but it cannot be recommended for a visit. At Park Wood, Isel LGS 7/125 (NY 167348), the contacts between the underlying Skiddaw Group, the Cockermouth Lavas and Carboniferous Limestone can no long be seen, while the adjacent site of Clints Crag and Thackray Wood LGS 7/067 (NY 160357) also needs a thorough review. A good LGS site for Cockermouth Lavas is required and Gill Beck, Blindcrake (NY149343) is currently being considered. We are looking to make use of the expertise of CGS members in surveying and reviewing sites and suggesting new ones. Please contact Sylvia Woodhead if you are interested in being involved in the work of Cumbria GeoConservation.

SW 16 March 2016

A few places are available on this 3 day field trip which will look at the Palaeozoic rocks with particular emphasis on the mineralization.   The party will gather at Melrose Guest House, Douglas, on the evening of 11th July for briefing and disperse on the morning of Friday 15th July.

Bed and breakfast accommodation has been booked at the Melrose Guest House in Douglas and transport on the Island will be by minibus.   Accommodation is available in twin or one triple bedroom.   There are no single rooms.

Cost £170 per person to cover B&B accommodation for 4 nights and minibus transport for the three days in the field, handouts and leader’s expenses.    Lunch and evening meals are not included.

If you would like to go on this trip please contact our event organizer using the online form available here.

Please report by between 9.45 and 10.00 at the originally arranged point i.e. outside the Tourist Information Office (temporarily closed) at the main Glenridding  car park. You will then be re-directed to a nearby location where you can park for the whole time ( a single all day charge of £3 per vehicle is due in the box by the gate of this location).

We will then walk from this location back to Glenridding pier to start the trip. We will return to the cars for a lunch stop and then walk to the other side of the valley via Side Farm for the afternoon session. This will involve a short ascent up to a rough path which will give us fine views over the surrounding area and access to outcrops of the local volcanic rocks.

Facilities [toilets, hot drinks, shop] are available at Glenridding.  Leader John Rodgers 01768 895743  mob. number removed but be aware there is poor network single around this area.

The World’s Largest Caves, by Richard Walters

The speaker started with some spectacular images of the UK’s longest cave system, across the borders of Cumbria, Yorkshire and Lancashire – hence the Three Counties cave.

He explained his interest in locating, and measuring by laser, the largest cave caverns in the world. The overall largest is the Miao Room in China, where it took seven days underground to record its size.

He explained the technology which enables 3D images of the inside walls of the chambers to be produced. These images can then be rotated and linked to surface topography. After much computer manipulation, animations can show the entrance into the caves, views of the enormous stalagmite formations, and an idea of the extent of the cave, which cavers themselves cannot see at the time. Using simple diagrams, the formation of large caverns was explained.

Water meeting from different channels underground becomes aggressive again, and can dissolve more limestone. Stress on the arch structure of the cavern roof was explained as keeping these enormous cavern roofs standing, while unstressed rocks collapses into loose blocks. The fate of all large cavern chambers is to collapse, especially when chambers have an open roof. Yorkshire’s Hull Pot is believed to be a collapsed cavern.

3D images of the underground workings of Nenthead mines were shown, and finally the 3D laser plotted the inside of the meeting room, together with all CGS members. It was a truly memorable illustrated talk, taking us underground without having to make any effort.

A write-up of the event on 10th February 2016 by Sylvia Woodhead.