Mercia Rocks
OUGS West Midlands
Branch Newsletter
Issue No 3 (2017) September 2017
Limestone slopes of the Eglwyseg Escarpment and Offa’s Dyke Sandra Morgan (Moyra Eldridge Competition—Highly Commended)
Branch Officers Contents
Branch Organiser – Sandra Morgan Branch Organiser’s report p 2 Branch Treasurer - Susan Jackson Field Trip programme p 3
Newsletter Editor – Mike Hermolle Geo-etymology p 6 Field trip reports P 7 Branch Committee Other Societies p 21
David Green,
Alan Richardson If you would like to join the committee please do get in touch
1 [email protected] BO Report September 2017
Dear all, I hope you had a great summer! Since the last newsletter, our branch programme has continued with a field trip on 2 July to the Lickey Hills, led by Julie Schroder with contributions from Alan Richardson. Here we examined different outcrops of the Ordovician Lickey Quartzite and various younger rock formations in the context of the wider landscape, and we learned about the geo conservation work of the Lickey Geo-Champions. See the trip report in this newsletter. There will be three more branch events this year. On Sunday 1 October we have a field trip to South Malverns, led by John Payne. This trip, organised by OUGS West Midlands, is a shared trip with the Black Country Geological Society. After this we can look forward to two more of Alan Richardson's popular labs: a Mineralogy Laboratory Workshop on 7 October and a Sedimentary Laboratory Workshop on 9 December. There are further details about all 3 events in this newsletter. The 2018 programme will start with our branch AGM on Saturday 20 January 2018. This will be held in the Lapworth Museum Education Room. Further information about the AGM will follow nearer the time, and for information about the Lapworth Museum, see the Museum website at http://www.birmingham.ac.uk/facilities/lapworth- museum/index.aspx. The branch AGM is your opportunity to elect your branch committee members for the coming year, and to give your feedback/suggestions. We would welcome new committee members. Do get in touch with me if you would like to discuss what this might entail. This year the OUGS Symposium, entitled A Festival of Geodiversity, took place in August at Queen Margaret University, Edinburgh. With good weather, interesting speakers and excellent field trips, the participants enjoyed a great weekend of geology. Next year's Symposium will be held at Worcester University – a great opportunity for West Midlands members! The organising committee (from the East Midlands, West Midlands and Severnside branches) are currently putting together the programme of events and other arrangements – look out for more information soon!
Best wishes,
Sandra
2 [email protected] Forthcoming Field Trips and Events
Each person attending a field meeting does so on the understanding that he/she attends at his/her own risk. The OUGS has Public Liability Insurance Cover for field and indoor meetings, but Personal Accident Cover and Personal Liability Cover remain the responsibility and personal choice of the participant.
There may be an element of appropriate cover included in house insurance or in travel insurance: although OUGS activities are not particularly dangerous, members are advised to check whether exclusions apply to activities in which they plan to participate in case they wish to arrange further cover. An annual travel insurance may be the best solution for any member who regularly attends field events: this again is a matter of personal choice.
Programme 2017/18 Sun 1 October South Malverns. Leader John Payne. Contact David Green [email protected] Sat 7 October Alan Richardson’s Mineralogy Lab Workshops—Lickey Hills Visitor Centre Sat 9 December Alan Richardson’s Sedimentary Petrology Lab Workshop—Lickey Hills Visitor Centre contact Alan Richardson [email protected] " Please note Alan's change of email address
Sat 20 January 2018 WMi Branch AGM—Lapworth Museum Education Room 20-22 April 2018 OUGS AGM and Social Weekend—Shap Wells Hotel 10-12 August 2018 OUGS Symposium “Music of the Earth” at Worcester Poster on last page
Contributions to the Newsletter are always welcome. The subject matter can be anything geological that you think other members would like to read. Duplication of field trip reports does not matter as you will see from this issue.
Items for inclusion in the next Newsletter, by email to: [email protected] by 30 November 2017 We particularly need trip reports, photographs for the header on Page 1 and you’ve seen my “Rocks Thru the Windscreen” —why not submit one for a regular journey you do. Mike Hermolle
3 [email protected] Sun 1 October South Malverns
Leader John Payne. Contact David Green [email protected] A shared trip with the Black Country Geological society Time and Location Start 10.00. Meet Hollybush car park (free) on north side of the Tewkesbury to Ledbury road at the crest of the Hollybush Pass over the Malvern Hills. Grid Reference SO 759 369. Overview and Geological Interest On this walk we will see the rocks of the south Malvern Hills and their immediate surroundings and discuss the geological aspects of the view from the hill top. The walk starts with a steep 100 metre climb but this is taken slowly and in stages. We visit first the site of a recently constructed earth house to see a thrust fault (an element of the East Malvern fault system). At the top of Raggedstone Hill the scenery, structure and geology of the hill and its surroundings will be described, followed by an early lunch. The first of several volcanic dykes which we shall see on the walk outcrops here. On the south ridge of the hill is an exposure of the Cambrian/Precambrian unconformity which here forms the western boundary of the igneous and metamorphic rocks of the Malvern ridge. Lower on the hill is a quarry showing some of the variety of Malvern’s metamorphic rocks, particularly a phyllonite. We will visit a small waterfall on a Triassic conglomerate of local rocks. A small quarry at Coal Hill shows interleaved Ordovician lava and Ordovician shales. On Chase End Hill, the most southerly of the Malverns, is an exposure of Malvern gneiss. The return to the cars passes an exposure of baked Cambrian shale and a quarry in andesitic lava with a nearby much decorated ancient oak. The final stop will be at the recently cleared roadside exposure at Hollybush, showing two distinct intrusions into the Cambrian Hollybush Sandstone.
Practicalities The tour is scheduled to take 6.5 hours. Estimated finish: 4:30pm
The length of the walk is about 7km and there are some hilly bits. There is one short but steep descent on rather mobile gravel (but on a well-used path) and another on grass.
There are no facilities of any sort on the route of this walk.
Bring a packed lunch.
Wear walking boots and clothing appropriate to the weather.
4 [email protected] 7 October 2017: Mineralogy Laboratory Workshop 1030 – 1530 Lickey Hills Visitor Centre, Warren Lane, Lickey, Birmingham B45 8ER The venue is signposted from the roundabout at Junction 4 (Lydiate Ash) of the M5. Last year saw the addition of a one-day mineralogy course to our annual programme of practical courses. While the structure remains the same, this year’s event benefits from a better range of specimens, a new laboratory guide, and access to two binocular microscopes. The course covers the essential elements of describing and identifying minerals. A range of rock- forming and ore mineral specimens will be provided, along with support materials which will allow individuals to work at their own pace, with the support of the tutor. All students will be e-mailed a pdf copy of the laboratory guide in advance: this booklet gives instructions for the systematic identification ofmineral properties. At the workshop you will be given a printed copy of the guide as well as an A3 sheet which records some of the properties of twenty four specimens: the object of the day’s work will be to complete the missing entries and identify the minerals. The price of this day school is £2.00. 9 December 2017: Sedimentary Petrology Laboratory Workshop 1030 – 1545 Lickey Hills Visitor Centre, Warren Lane, Lickey, Birmingham B45 8ER The venue is signposted from the roundabout at Junction 4 (Lydiate Ash) of the M5. This one-day lab-based course will cover the essential elements of describing, identifying and interpreting sedimentary rocks. A range of clastic and carbonate specimens will be provided, along with support materials which will allow individuals to work at their own pace, with the support of the tutor. The laboratory booklet gives instructions for the systematic identification of the rocks and pro- forma sheets for each specimen. All students will be e-mailed a pdf copy of the booklet in advance. The price of this day school is £2.00. If the weather is good, you may wish to make an independent visit to the Barnt Green Road Quarry, to see a recumbent fold in Ordovician quartzites (http://ehtchampions.org.uk/ch/?page_id=76), however, this is not part of the day course. The ground is rough and muddy so please wear appropriate footwear. Both of these day schools are tutored by Alan Richardson, a lecturer with 38 years’ experience of teaching geology. They are the first two of the annual series of five workshops, which progresses through igneous and metamorphic petrology, and concludes with a field skills training day in late spring. These events are especially suitable for those new to the study of geology, but are open to all. All sessions take place in the school room adjacent to the visitor centre, where there is a café and toilets.
5 [email protected] Handlens: You will need to bring a hand lens. Search on Amazon for a ‘Jeweller’s lupe’. I found one advertised for £4.85…or, for £4.99, you can buy one with built in illumination. Grain Size Scale: I recommend the ‘University of Leicester Grain Size Scale’, available from Geo- Supplies (www.geosupplies.co.uk) for £1.69. For more details see the OUGS website entry for these courses. All other testing materials will be provided. Alan Richardson [email protected]
Geo-etymology
In this issue two related words. We know what they are and have a good idea of their origin: Graben “A downthrown, linear, crustal block, bordered lengthways by normal faults. The upstanding blocks on either side may have been lowered by erosion…half-graben are bounded on only one side by one or more faults and are mainly associated with tilt-block tectonics.” (Allaby & Allaby, 1990). Graben “Geol. after German, graben ditch, introduced in its geological sense by E. Suess [Antlitz der Erde (1883) I. i. iii. 166]. A depression in the earth’s crust bounded by faults; a rift valley.” (Simpson & E. C. Weiner, 1989). Horst. “Upthrown block lying between two steep angled fault blocks”. (Allaby & Allaby, 1990). Horst. “Geol. After German horst heap, mass, cluster, sandbank etc.; introduced in its geological sense by E. Suess [Antlitz der Erde (1883) I. i. iii. 166]. A block of the earth’s surface which has been raised relative to the surrounding land and is bounded by faults on some or all sides.2 (Simpson & E. c Weiner, 1989). As well as finding the derivations interesting, it is also informative to discover exactly when terms came into use by the geological community. In the two cases here the OED quotes “graben” being used by W Gregory in in 1896: “…or, to use Prof. Suess’s term…”and “horst” being used in the Geol. Soc’s Quarterly Journal in 1893: “…in the sense originally applied by Suess.”
References Allaby, A. and Allaby, M. (eds.) (1990) The Concise Oxford Dictionary of Earth Sciences, Oxford,
Simpson, J. A. and Weiner, E. c (1989) Oxford English Dictionary Vol VI, 2nd ed. Oxford, Oxford Unoversity Press.
Simpson, J. A. and Weiner, E. C. (eds.) (1989) Oxford English Dictionary Vol VII, 2nd ed. Oxford, Oxford University Press.
6 [email protected] Field Trip Reports Lickey Hills Geology and Landscape
Led by Julie Schroder (Black Country Geological Society) with valuable input from Alan Richardson (OUGS WM member) both members of the Lickey Hills Geo-Champions. On Sunday 2 July we met on a warm sunny morning at the Lickey Hills Visitor Centre where Julie introduced us to the area and the work of the Lickey Champions. The ridge of the Lickey Hills runs approximately north-south and is composed of Lickey Quartzite from the early Ordovician, approximately 488 mya, with younger rocks on either side of the anticline.
Fig. 1 Cross section through the Lickey Hills…The dip of the beds west of the ridge is exaggerated. (Hardie, W.G. 1991, ‘A Guide to the Rocks and Scenery of the Lickey Hills Area)
We spent the rest of the morning following the Lickey Hills Champions' trail, examining different outcrops of the Lickey Quartzite in the context of the wider landscape. Our first stop was at Warren Lane Quarry. This quarry was used in WW1 as a bunker and firing range, and two large concrete structures (formerly the gun butts) still remain. In WW2 the quarry was used again, this time as a munitions store and weapons testing range. The exposure in this quarry has benefited greatly from the geo-conservation work of the Lickey Champions, removing earth and vegetation to reveal the rock face. Here we had our first encounter with the Lickey quartzite, an off-white, highly compressed, sedimentary rock composed of quartz grains deposited in a high energy shallow marine environment and later cemented with silica.
7 [email protected] Formerly quarried for road stone, this rock is very brittle and extensively fractured and jointed. Fig 2.
Fig. 2 Julie introduces us to Warren Lane Quarry In one area we observed traces of ripples, and in another area a few pebbles were visible in the quartzite indicating that they were laid down near the shore. A clay horizon was observed between several of the quartzite layers.
In this exposure we also saw a fissure (sometimes referred to as a neptunean dyke) filled with sandstone. This fissure would have been opened in the quartzite as a result of seismic events such as folding, and subsequently infilled. Fig 3.
From Warren Lane Quarry we followed the Champions' trail towards Bilberry Hill, stopping on the way to examine some boulders. Only the tops of these rocks were exposed, and there was some discussion as to whether they were boulders or bedrock. Fig 4.
Fig. 4 Brecciated Boulders on Bilberry Hill
These boulders were composed of brecciated Lickey quartzite, containing angular fragments of quartzite which had been re- cemented by silica. Fig 5.
Fig 5. Brecciated quartzite in the boulders
Next we proceeded to the viewpoint on Bilberry Hill. The views were excellent and we looked out across a flat region formed of Triassic Mercia mud to where Birmingham was clearly visible in the north east. From here we walked on to the Barnt Green Road 'overfold' quarry. Fig 6.
Fig. 6 Barnt Green Road Overfold Quarry
The rock here was again Lickey quartzite, but it was stained pink with iron and may contain tuffacious material. The rock was fragmented with a blocky fracture and we again observed layers of clay between the beds of quartzite. The quarry face was partly obscured by vegetation and by the strong shadows caused by the sunshine so we spent some time trying to discern the hinge of the overfold before returning to the Visitor Centre for a welcome lunch break.
10 [email protected] Our first stop after lunch was Rose Hill quarry, where the Lickey quartzite had undergone faulting and thrusting. Fig 7.
Fig. 7 Rose Hill Quarry
As evidence of thrusting, Alan showed us quartzite pebbles found in a clay layer between the quartzite beds. From the gorge we reached the Golf course which lies on Carboniferous Keele clay . This reddish muddy clay was deposited as mud on the floor of a shallow lake surrounded by a semi-arid landscape. Within the clay are thin sandstone beds, formed by heavy rain which carried the sand from the surrounding area into the lake.
11 [email protected] The group examined a small bank in the golf course which is very likely one of these sand ridges. Fig 8.
Fig. 8 Lickey Golf Course and possible sand ridge
Our next stop was Beacon Hill, formed Approx 299 mya. of Permian Clent Breccia which consists of angular clasts in a clay matrix. The rock fragments had been broken by flash floods and because they are still angular we can conclude that they were carried only a short distance before being deposited.
12 [email protected] Here we entered the castle-like toposcope building. Fig 9. From this viewpoint we had
Fig 9 Beacon Hill Toposcope Building excellent clear views and the toposcope assisted orientation with the landscape. We observed two types of granite used in the toposcope building: pink granite, perhaps from Scotland, used for the battlements, and grey granite, perhaps from Cornwall, used for the plinth of the toposcope.
13 [email protected] Our walk then took us past the Lickey monument, a monument erected 1834 in memory of Other Archer, the Sixth Earl of Plymouth, who owned land nearby. Fig 10.
Fig. 10 Lickey Monument The monument is made of Penmon marble, actually a Carboniferous limestone, from Penmon quarry in Anglesey. This rock is the same as that used to clad Birmingham Town Hall which was opened in 1834.
Next we passed Lickey church and examined the oldest part of the church which is built from Triassic Bromsgrove sandstone. Fig 11.
Fig 11 Lickey Church
In Lickey Warren, the final part of the trail, we observed the large rounded pebbles of the Kidderminster formation, formed in the Triassic, about 251 mya. These quartzite pebbles were rounded and transported by a large river system flowing northwards from France. They had been weakly consolidated in a sandy matrix which weathers easily. These pebbles could be seen on the path and within the roots of an upended tree. Fig 12.
Fig 12 Pebbles from Kidderminster Formation in upended tree roots
15 [email protected] Finally we drove a short distance to the Rubery Cutting where we examined a spectacular unconformable junction between the Lickey Quartzite and Rubery Sandstone formations. This unconformity represents a gap in time of approximately 100my. The basal bed of the sandstone contains clasts of Lickey quartzite, and the sandstone fills in the irregular surface of the quartzite. Fig 13.
Fig 13 Rubery cutting unconformity At Rubery cutting we found more “neptunean dykes”, and compared rock samples gathered earlier to the quartzite and sandstone found here, debating whether the rock types outcropping at Rubery were the same as the formations we had observed earlier. At the end of the day we thanked Julie Schroder for an excellent and informative trip, and Alan Richardson for his interesting discussions about the evidence for the geological processes that had shaped the area. Information about the Lickey Hills and the work of the Lickey Champions can be found on the Champions site at http://ehtchampions.org.uk/ch/worcestershire-sites/lickey-hills-quarries/ (Included on this site is an annotated image of Barnt Green Road Quarry showing the line of the overfold.) Sandra Morgan
16 [email protected] Lickey Hills (2) Fine summer day. Met at Visitor Centre where the leader Julie Schroder introduced us to the topic and showed us a number of available publications, from the historic to the modern. She also gave us a brief introduction to the Community Earth Heritage Champions, a Project which carries out conservation work on 19 geological sites in Herefordshire and Worcestershire. More information at www.EarthHeritageTrust.org.
The eastern element of the Lickey Hills is a long north/south ridge – the Lickey Ridge - comprising Cofton, Bilberry and Rednal Hills. Fig 1.
Fig 1. Geological Map. Copied from (H&W Earth Heritage Trust, 2005)
In cross section it is seen to be an anticline, faulted on both sides by faulting creating a raised Horst block. It is composed mainly of Lickey Quartzite, and forms an inlier of old strata surrounded by younger. Fig 2.
Fig 2. Cross section. Copied from (H&W Earth Heritage Trust, 2005)
17 [email protected] Lickey Quartzite. Initially included in the Cambrian but at 488Ma properly belongs in the Ordovician and is possibly the most easterly exposure of the Ordovician. Initially laid down as sand close to the shore of the sea, this was buried and compressed and the grains cemented with silica by circulating groundwater resulting in a sedimentary quartzite rather than one produced by full metamorphic processes. The sediments were subsequently folded possibly in the Caledonian or even the Variscan orogeny, leading to the anticline we see today. Lickey quartzite is thought to be the most easterly exposure of the Ordovician in the country. Warren Lane Quarry. After gathering outside the Visitor Centre Julie walked us across the road to Warren Lane Quarry, which is not open to the public. The immediate view of the quarry face is onto a bedding plane dipping steeply to the north-west about 600. The face of the quarry showed faint ripples, some minor faulting and included pebbles; the last two mainly at the southern end. Looking northwards along the strike, the bedding of the quartzite is clearly visible with the individual beds separated by thin clay horizons, which probably facilitated folding of the formation. At the northern end an exposure, cleared in the past year, reveals a neptunean dyke, a fissure in the quartzite infilled with a brown sandstone which is similar to that in a cutting at Rubery about 2 miles to the north. This is dated to the Silurian and suggests a 50-55Ma unconformity. After leaving Warren Lane Quarry Julie took us up onto the top of the ridge which is the crest of the anticline. On the footpath a number of brecciated boulders are exposed and appear to consist of broken quartzite cemented with silica. Although they are referred to as boulders, it is possible they are in situ and represent the hinge area of the fold which is where brecciation is most likely to take place. Continuing along the path we joined the Champions’ Trail at a viewpoint where we were able to look northwest across the Carboniferous Alveley Member and Beacon Hill, which is composed of Permian Clent Breccia. To the north the view towards Rednal Hill is across the Lickey Gorge created by the outflow of meltwater from a glacial lake. Returning to the South along the Champions Trail, we used a second viewpoint looking east, over an unseen exposure of Triassic Kidderminster Formation (previously Mercia Mudstone) and across a broad valley as far as the Cotswolds. The strata between the Lickey Hills and the Cotswolds is Triassic which has a depth of about 3km. Leaving the Trail we continued down the eastern limb of the anticline almost to the Barnt Green Road and its quarry. ‘Overfold’ Quarry. The Barnt Green Road Quarry is also referred to as the Overfold Quarry due to the prominent fold seen. In this quarry the quartzite beds are seen dipping from left to right where they thin out somewhat. The beds are again separated with thin clay beds. The clay has been said to be bentonite derived from weathering of Barnt Green volcanics to the south. However it has not been possible to date them which suggests they are not from a volcanic source. The fold can be seen to the left of the face and its structure suggests thrusting from the west. Rose Hill Quarry. After lunch Julie led us northwards to the west of Warren Lane Quarry passing another set of brecciated boulders. This time much lower than those seen in the morning although they appear to be below those and it is still not clear whether they are in situ beds or not. Continuing northwards we entered Lickey Gorge and found ourselves at Rose Hill Quarry. Another exposure of the Lickey Quartzite with the beds similarly tilted (dipping to the west at approximately 15o and a fairly evident thrust from the left evidenced by quartzite pebbles in a clay layer on the left and on the right hand side the beds thinning out.
18 [email protected] Golf Course and Beacon Hill. Moving to the west through Lickey Gorge we moved from the Ordovician onto Carboniferous bedrock crossing the Keele Clay with sandstone (Salop Formation) as we moved onto the golf course. A slight ridge line across the course may indicate thin beds of the Halesowen Sandstone. The climb up onto Beacon Hill took us onto the Permian Rocks of the Clent Breccia. Beacon Hill with its two-granite toposcope afforded all round views of the area from the Cotswolds in the east through Birmingham to Barr Beacon in the northeast and the Welsh mountains in the west. As we moved south off Beacon Hill, in the path, we found angular Clent Breccia pebbles changing, as we descended, to the rounded pebbles of the Kidderminster Formation. This conglomeritic rock is composed of pebbles of quartzite and quartz, originating in France and part of a major river system which created the Bunter pebble Beds which stretch from the Devon coast to the Midlands. Continuing our return to the Visitor Centre allowed us a short examinations of the Carboniferous Limestone of the Monument and the Triassic Bromsgrove Sandstone of Holy Trinity Church. At the Visitor Centre Julie gave us a quick summary before the party moved off to the Rubery Cutting. I had to leave at this point. I had no camera with me on the trip but Sandra’s photos picture the important points. You will find a map of the trip overleaf. References: H&W Earth Heritage Trust (2005) ‘Explore Lickey Hills - Landscape & Geology Trail’, Worcester, Herefordshire & Worcestershire Earth Heritage Trust. Mike Hermolle
Fig 3 GPS Track of trip. Produced with Garmin etrex 30 and Memory Map. The map is OS 1:10000 Streetview GB2015
20 [email protected] Other Geological Societies in the West Midlands
Please see the individual websites for events Black Country Geological Society For details go to www.bcgs.info Lecture meetings are held at Dudley Museum & Art Gallery, St James’s Road, Dudley, DY1 1HU, 7.30 for 8 o’clock start unless stated otherwise. Those wishing to attend field meetings please contact the Field Secretary, Andy Harrison email: [email protected] Shropshire Geological Society For details go to:- www.shropshiregeology.org.uk/SGS/SGSintro.html Lectures are held at Shire Hall, Shrewsbury, commencing at 7.15pm for 7.30pm A nominal charge is levied for attendance by non-Members. Warwickshire Geological Conservation Group For details go to www.wgcg.co.uk/ Lectures are held monthly from September to April, Starting at 7.00pm free to WGCG members with non-members £2.00 per lecture. North Staffordshire Group of the Geologists’ Association For details go to www.esci.keele.ac.uk/nsgga NSGGA is the regional group of the Geologist Association North Staffordshire. The winter lecture programme takes place on the second Thursday of the month from October to March at 7.30pm. All talks are held in the William Smith Building, Keele University. Woolhope Naturalists Field Club For details go to www.woolhopeclub.org.uk The geology section of the club is an affiliated member of the Geologist Association. Lectures are held in the Woolhope room, Hereford Library Broad Street. Field trip programme also available. For further information on all events email Sue Hay [email protected] Teme Valley Geological Society For details go to www.geo-village.eu
Meetings generally held at Martley Memorial Hall Martley Worcestershire