ON THE ROCKS Newsletter of the Yorkshire Branch of the Open University Geological Society March 2018 A view of Great Gable (899m – the 9th highest mountain in England), Cumbria, looking northeast from the end of Wast Water, where the River Irt starts its short journey to the Irish Sea. Wast Water is the deepest lake in England (76m). The mountains are all from the Borrowdale Volcanic Group. (Peter Roberts 27.3.17 Grid Ref: NY 14535 03878) Welcome to the Spring edition of your newsletter Contents I hope you enjoy reading it and feel inspired to contribute to future issues. I must 1. Editor’s piece start with an apology. Unfortunately, the minutes of the AGM are not yet available 2. Rick’s musings but will be appearing in the next issue along with a copy of the accounts. 3. - 6. Blencathra report 7. Guide to minerals Our main article this time is the first of a number of reports by Peter Vallely on last 7. Obituary autumn’s Blencathra trip, and, if the photos are anything to go by, the hardy 8. Climate change article participants enjoyed a lovely sunny, if rather chilly, day out. 9. YOUGS 2018 field trips Peter Roberts has kindly provided the above photo, and we have another “simple 10. Snippets guide to minerals”, David Cousins’ personal view on surviving climate change, an 11. 2018 Blencathra obituary to Bill Graham who was a long-time Branch member, and a full listing of this year’s field trips, including separate details of this year’s Blencathra trip. Ann, our treasurer has asked whether I could include a puzzle or two in future issues, so if any members are expert at compiling crosswords or word searches etc, please let me know and I’ll be happy to include them. Peter Ellenger The Yorkshire Branch of the OUGS March 2018 Branch Organiser’s Musings Welcome to the first newsletter of the year. We held our AGM in a different location in Leeds, and more members attended this year than usual, with a total of 17 members turning up. As usual, and not surprisingly, our speaker Dr Phil Murgatroyd of Bradford University gave an interesting talk on Doggerland. A big thank you goes firstly to Phil for giving the talk, and secondly to Phil Robinson who for the last four years has always organised a very interesting lecture to follow the AGM. Personally, I would like to hold a day of talks maybe with three speakers. What do you think? As Branch Organiser I have always hated attending the Branch AGM with a passion. The reason for this has been that I have had to report that the works of Alan Stollery remain uncompleted. Although it was originally agreed before my time as BO that Alan’s Ramblings would be turned into some type of publication, from when I was first elected I have never been able to push it forward as fast as I would have liked. This year however all four volumes have been completed, and I now feel this is weight off my mind! All that needs to be done now is to create an index for the volume which our ex-newsletter editor Peter Roberts has volunteered to do. Once this is complete they will be put up on our YOUGS website so members can download them. In all honesty completing the Ramblings has been a fantastic experience. Through his works I really do feel that I have got to know Alan really well, even though I only knew him for all of one hour! We have a wide range of interesting and varied field trips planned for this year with our main leaders being Tony Felski, Paul Kabrna, Paul Hildreth and Bill Fraser. For any months where we don’t have a leader we will go out for a geologically-themed walk with no leader, but we will take Yorkshire Rocks and Landscapes along with Alan Stollery’s Ramblings because all the walks will be based on his diaries. Towards the end of the year we also have our annual excursion to Blencathra FSC, and if you have not been it really is a fantastic week in The Lakes. All our trips are on the YOUGS website. Our newsletters are an item I am extremely proud of, and I believe it represents our branch really well on a national level. However, it does rely on content being received by Peter our newsletter editor. It can be an interesting photo you have taken on holiday with a simple description of what is being seen, or a geologically-themed article you would like to write about somewhere you have been. Can I remind all members to keep your details up to date and to keep the Membership Secretary informed of any changes? I also recommend you that you take a look at the OUGS Facebook Group and also follow us on Twitter if you are so inclined. Finally, if you have any thoughts of places to go, things we can do better and so on, please do get in touch. Best wishes Ricky Savage - Yorkshire OUGS Branch Organiser 07761 409807 - [email protected] 2 The Yorkshire Branch of the OUGS March 2018 Blencathra 2017 – Part 1 Day 1. Cross Fell Inlier and High Cup Nick. “The Cross Fell Inlier is a slice of the Lake District in the Pennines”. I knew a bit about the Geology, but I was more concerned about the geo-psychology. How would our young leaders, James and Ellen, manage to drag a dozen oldies up a 2000-foot mountain on such a windy and icy day? Our planned walk followed the Pennine Way from the village of Dufton to High Cup Nick (see Figure 1). It allowed us to see rocks from five different geological periods (although our route did not actually cross the Silurian rocks in the Cross Fell Inlier – they were a few hundred metres to the north). We saw three major structural features: The Vale of Eden, the Cross Fell inlier, and the Whin Sill. All of these originated in the Late Carboniferous/Early Permian as a result of the Variscan Orogeny. The main collisions of the Variscan Orogeny occurred well to the south of the British Isles and there was limited deformation in Britain outside the south west. However, the newly-formed supercontinent of Pangea was subject to great stresses and started to rift in many places – such as Central Scotland. Much of northern Britain was under north-south extensional forces which led to large movements along faults, and emplacement of magma – most notably the Whin Sill. 3 5 4 High Cup Nick 2 1 Dufton 1 Cross Fell Inlier Whin Sill Pennines Vale of Eden (Early Permian) (Ordovician/Silurian) (Carboniferous) (Triassic) Figure1. Sketch map of route (red dashes) to High Cup Nick (6 km each way) Locality 1. Dufton - Le mur de la toilette (NY 689250) The village of Dufton lies in the Vale of Eden – which is a half-graben structure on the eastern side of the Lake District which deepens westwards towards the bounding Pennine Fault. Dufton is built on and built from the red Triassic St Bees sandstones. They are exposed in a small quarry at NY 691248 but to save time we examined good examples in the wall of the toilet block (photo 1). The sandstones were cross- bedded in places, coarse-grained, sub-angular and contained plenty of feldspar. They are interpreted as braided river sediments which were deposited under hot climatic conditions. Locality 2. Pennine Way Path (NY 715252) We then set off up the Pennine Way paying close attention to the path in front of us – to spot lithology changes but mainly to avoid slipping on the ice. After a while, shaley and volcanic material including ignimbrites became more prominent in the path which suggested that we had crossed into the Cross Fell Inlier. This was confirmed by in-situ examples of dark mudstones with prominent cleavage (photo2). Better exposures could be glimpsed in small quarries either side of the path but we pressed on into the biting headwind. 3 The Yorkshire Branch of the OUGS March 2018 [ Photo 1. St Bees Sandstone at St Bees Photo 2. Highly cleaved mudstones Head (we didn’t go there but it’s more within the Cross Fell Inlier on Pennine picturesque than the toilet block) Way (probably Murton Formation – equivalent to Skiddaw Slates). The Cross Fell Inlier is a narrow strip (about 25 km long and 2 km wide) where Lower Palaeozoic rocks have been uplifted a vertical distance of 1.5 km. The Cross Fell Inlier contains formations which can be correlated with the three major Lake District types i.e. the Skiddaw Group, the Borrowdale Volcanics and the Windermere Supergroup. The topography was also very convincing - either side of us we could see a narrow range of conical hills in the Cross Fell Inlier which contrasted dramatically with the broad plateau of the Pennines made from Carboniferous rocks straight ahead of us (photo 3). So the “slice of a Lake District” description is literally true rather than being just a fanciful metaphor. Photo 3. Looking north along the Cross Fell Inlier Photo 4. Lime kiln – in the Carboniferous Melmerby towards Dufton Pike – a prominent conical hill in the Limestone. narrow Cross Fell inlier 4 The Yorkshire Branch of the OUGS March 2018 Locality 3. Melmerby Limestone (NY 723 250) We stopped for lunch beneath a low but extensive outcrop of limestone, which was confirmed by the presence of a limekiln (photo 4).