Mercia Rocks
OUGS West Midlands Branch Newsletter
Issue No 4 December 2020
High Tor Limestone Reef, Matlock, Derbyshire. Jun 2015 - Mike Hermolle
Branch Officers Contents Branch Organiser – David Green Branch Treasurer - Susan Jackson Branch Organiser’s report p 2 Newsletter Editor – Mike Hermolle Message on events p 2 AGM 2021 p 3 Branch Committee Quiz p 4 Emma Askew Summary of a research topic p 6 Sandra Morgan Local Geology p 9 Alan Richardson Geo-etymology p 11 Adrian Wyatt Other Societies P 14 Stop Press p 15 If you would like to join the Online Talks p 16 committee please do get in touch 2020 AGM Draft Minutes p 17 [email protected]
[email protected] 1 Branch Organiser’s Report
This year has been a year we may be remembering for quite a while, unfortunately the Branch has not been able to organise any events this year and is not likely we will be able to have any events until the lock down restrictions are lifted. You will see in this newsletter that the AGM will be held virtually via Zoom this time. The meeting is being held in February and I hope by then we may have some better news regarding what events we may be able to hold next year.
I would be very happy to try to help anyone who would like to join the AGM meeting but is unsure of using ZOOM. It is easy to use to join in meetings and is not that hard if anyone is unsure. We will not be having a speaker this year so it will only take up an hour or so of your time. There of course will not be any travelling required to be at the AGM so hopefully members who may have been put off by having to give all day to the meeting may be able to log in to the meeting.
As far as my activities this year as BO I have attended some Zoom meeting myself this year on behalf of the Branch as well as the Society’s AGM. For next year at the moment the AGM is also planned to be online and for the Branch we hope to be able plan for some day events and workshops just as soon as restrictions are lifted.
I hope everyone is keeping well and will be looking forward to be seeing as many members as possible at the AGM in February
Dave Green
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 20/21 – In abeyance due to COVID19 restrictions
20 February 2021 Branch AGM
[email protected] 2 Notice of OUGS West Midlands Branch
Annual General Meeting
Saturday 20th February 2021 at 11:30 Meeting to be held virtually via Zoom Agenda 1. Apologies
2. Minutes of previous meeting on 25th January 2020 3. Matters Arising 4. Officers Reports 5. Election of Officers 6. Appointment of Committee
7. Meeting close Discussion of any items raised by members present If anybody would like to raise any matters to be included in the meeting please contact me on [email protected]. The details for the meeting are Join Zoom Meeting https://us02web.zoom.us/j/87016372237?pwd=SzZsakZpO GsvSjZuWXRzdWN1NkprQT09 Meeting ID: 870 1637 2237 Passcode: 717856
Draft Minutes of the previous meeting were published in the March Mercia Rocks and are available in the WMi Branch members Area of the OUGS website. [email protected] 3 Quiz
Adrian Wyatt has sent photos that members might like to puzzle over:
I don't think that there are many places in the Midlands that specimens like this are to be readily seen (Figs 1 & 2). Yes, it is from the Midlands, in particular from the Malvern Hills.
Fig 1
Fig 2
This specimen has been well weathered so it has been a long time since it was in situ. The only location thought to represent this type of rock is a SSSI owned by the Malvern Hills Trust (MHT) and thus hammering and sampling is not allowed. [email protected] 4 The location, once a small quarry, has recently been 'freshened up' during a clearance session by volunteers supporting the MHT. This has given visitors the best chance of seeing the features shown in this sample in the actual rock face. During the clearance small patches of rock surface have been hand ground to reveal the structure. The sample photographed was found some distance away in loose scree but there is only one known quarry where it has been noted. The location has been described in the GA Guide No. 4 ^1 where it is location number 4 on Itinerary 1.
Adrian Wyatt
Which of the following best describes this type of rock?
A) Folded white marble, a metamorphosed limestone sediment.
B) Angular style micro-folding in quartz-plagioclase-mica schist.
C) Malvern 'gneiss', a rock having a 'gneissic' texture.
D) Mylonite, a rock that has been subjected to metamorphic alteration.
Answer on page 12
References:
^1 Geologists' Association Guides No. 4: The Malvern Hills, Penn & French, 1971.
Rocks and Minerals, C. Pellant, Dorling Kindersley, 2000, p211.
[email protected] 5 The hyperthermal events of the Palaeogene - a summary of my research topic for the OU Earth Science MSc
I retired in 2013 having decided that I wanted to fulfil a lifelong desire to learn more about geology. I began my studies by following several L2 and L3 course with the Open University and by joining the Open University Geological Association (OUGS). Attending meetings and fieldtrips organised by the OUGS enabled me to learn more about the landscape and its evolution from people who like me had a keen interest in the subject. In 2016 I enrolled on an online course at York University entitled - The geology of Yorkshire and northern England and it was whilst studying this course that I visited Whitby and learnt about the effects of the Toarcian Oceanic Event (TOAE). Schangler and Jenkyns, (1976) described Oceanic Anoxic Events (OAEs) as episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen-deficient bottom waters. In the case of Whitby, the most extreme episode of this event was seen in the deposition of Whitby Jet (Fig 1), a finely laminated black bituminous shale which is been used to make ornaments and jewellery.
Fig. 1. An image of Whitby Jet. (Geology.com, 2017
The trigger for the TOAE is thought to have been volcanogenic and/or methanogenic sources which caused a rapid release of carbon dioxide into the atmosphere resulting in global warming, a warming of the oceans and a fall in oxygen levels leading to the deposition of the dark shales.
The link between the environmental changes during the TOAE and present-day global warming has attracted many researchers. Often major warming events are associated with the release of large amounts of igneous material which formed large igneous [email protected] 6 provinces (LIP). In the case of the TOAE, the Karoo- Ferrar LIP was the likely source. An excellent book by Paul B. Wignall – The Worst of Times (2015) provides detailed information on mass extinction events during the late Permian and Triassic Periods. A further example of severe environmental disruption associated with igneous activity is the more recent Palaeocene-Eocene Thermal Maximum (PETM) ~56 Ma.
Fascinated by LIPs, mass extinction events and OAEs and their environmental consequences I decided to explore this as my research topic for the OU Earth Science MSc which I submitted in September 2020. I was advised by my tutor to define a series of objectives that could be measured and evaluated through appropriate data. In 1985, the Ocean Drilling Programme (ODP) commenced. Analysis of a number of marine sediment cores extracted by these programmes have revealed that in the early-mid Palaeogene (65 to 40 Ma) many global warming events occurred. The first and largest event to be identified was the Palaeocene-Eocene Thermal Maximum (PETM) by Kennett and Stott (1991) in their study of ODP Site 690 in the South Atlantic. ODP records show changes in temperature and the carbon cycle and reveal a large number of short rapid warming events, termed hyperthermals. Hyperthermals are described as intervals of rapid, pronounced global warming associated with negative excursions of oceanic δ13C and with clay-rich layers indicative of reduced sedimentary calcium carbonate (CaCO3) content commonly interpreted as a response to increased CaCO3 dissolution. The hyperthermal events of the Palaeogene became the focus for my research.
I established four objectives:
(i) To identify the major hyperthermal events of the Palaeogene based on the criteria identified in the definition above. (ii) Using ODP data measure the magnitude, duration and shape of these events. (iii) Determine the cause of the events. (iv) Describe the environmental consequences of the events.
My research identified over 50 hyperthermal events but 10 events, including the PETM, met the criteria and the availability of data and previous research enabled an evaluation of these events.
For each event the ODP records were used to construct graphs showing the size of the event, its duration and shape. The largest event, the PETM was about five times the size of the other events. The magnitude of the events was measured by the negative excursion in the stable carbon isotope record (δ 13C); whilst the PETM recoded a negative shift of ~ 3‰ most other events registered smaller negative excursions between 0.5 and 1.0‰. The events varied in duration from about 50 to 200 thousand years, some had an asymmetrical shape whilst other had a more symmetrical appearance. The shape reflects how the carbon cycle was affected and responded to Earth system feedback mechanisms. Figure 2 illustrates the magnitude duration and shape of Eocene Thermal Maximum 2 (ETM2), one of the major events studied in my research.
[email protected] 7 The Magnitude and Duration of ETM2, ODP Site 1263, Walvis Ridge, SE Atlantic 0.6
0.4
0.2 C 13 0
-0.2
Change in δ in Change δ -0.4
-0.6
-0.8
-1 54080 54060 54040 54020 54000 53980 53960 53940 53920 53900 Age in Ma 54.08 to 53.90 Ma
Fig. 2. The magnitude and duration of ETM2 based on the benthic stable carbon isotope record from ODP Site 1263, Walvis Ridge, SE Atlantic. (Lauretano et al., 2015, Supplementary Material, PANGAEA.854818 – Benthic stable carbon isotope record for ODP 1
The different impact these events had on the marine environment is shown by comparing records for ocean warming, changes in ocean chemistry and changes to the marine life. Figure 3 illustrates the change in iron content (Fe) as a measure of carbonate dissolution during event Eocene Thermal Maximum 3 (ETM3). The higher the iron content the greater the rate of carbonate dissolution. Other measures used showed the changes in calcium carbonate content.
Changes in Fe content as an indicator of carbonate dissolution for ETM3 at ODP Site 1262, Walvis Ridge, SE Atlantic 4000 3500 3000 2500 2000 1500 1000
500 Changes incontent Fe 0 52510 52500 52490 52480 52470 52460 52450 Age in Ma 52.10 to 52.45 Ma
Figure 3. Changes in Fe content as an indicator of carbonate dissolution for the ETM3 at ODP Site 1262, Walvis Ridge, SE Atlantic. (Littler et al., 2014, X-ray fluorescence (XRF) of iron (Fe) core scannings at ODP Site 1262, PANGAEA.833209.) [email protected] 8 The analysis of the literature shows many of the events were caused by variations in the orbit of the Earth around the sun. When the Earth was closest to the sun temperatures increased, the oceans and the land were warmed causing the release of greenhouse gases which led to further warming. For the PETM, volcanic activity could have also been a cause. Evidence showed that initial warming often trigged the release of additional carbon dioxide (and methane) from carbon sinks such as wetlands and permafrost.
Significantly, five of the ten events occurred during a four million-year-period (53 to 49 Ma) when temperatures and levels of atmospheric carbon dioxide reached a maximum. I proposed that investigating these events could improve our understanding of present- day global warming and provide more realistic models than the larger PETM and other major global warming events of the Permian, Triassic, Jurassic and Cretaceous periods.
Further Reading and references
Kennett, J.P. and Stott, L.D. (1991). Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Palaeocene. Nature, 353(6341), pp.225-229. Lauretano, V., Littler, K., Polling, M., Zachos, J.C. and Lourens, L.J. (2015). Frequency, magnitude and character of hyperthermal events at the onset of the early Eocene Climatic Optimum. Climate of the Past, 11, pp. 1313-1324. Littler, K., Röhl, U., Westerhold, T. and Zachos, J.C. (2014). A high-resolution benthic stable- isotope record for the South Atlantic: Implications for orbital-scale changes in Late Palaeocene– early Eocene climate and carbon cycling. Earth and Planetary Science Letters, 401, pp.18-30. PANGAEA database www.pangaea.de. Wignall, P.B. (2015). The Worst of Times: How life on Earth survived eighty million years of extinctions. Princeton University Press.
Ken Madrell December 2020
A Short Section of the Geopark Way
The Geopark Way is a 109 mile path that stretches from Bridgnorth to Gloucester following the line of the Malvern and Abberley Hills. Each section of the Way is checked by volunteers to ensure that the Way is waymarked and in good repair and is not blocked.
I volunteer to check the section from Hollybush which is near to Eastnor Castle down to Ketford on the River Leadon. The section passes over the complete range of rocks in the Geopark from Precambrian Malvern Complex to Glacial Meltwater Deposits. Going from the car park at Hollybush the way goes over and around Ragged Stone hill which is made up of the Malvern Complex and being comprised of harder rocks stands up from the softer surrounding sedimentary rocks. Between the hill and White Leaved Oak small pits of White-Leaved Oak shale can be found this is dated to the Cambrian and are fine grained shale laid down in deep water. Ridges can be seen in the fields in this area which show where there are underlying Ordovician Dolerite which was intruded into the older Shales. Passing through the hamlet of White Leaved Oak the wall at [email protected] 9 Cider Cottage provides a chance to see some of this Dolerite in the wall of an old bread oven.
A short steep climb goes up to the triangulation point on top of Chase Hill from where there are views over the Severn Plain and the Limestone hill of the Cotswold Hills. Some small pits allow a glimpse of the Malvern Complex with a quarry towards the base of the hill. The quarry is very overgrown and can be difficult to enter. The quarry is in the Malvern Complex with some pegmatites but the overall view has been very much overgrown. Continuing on to Bromsberrow there is a change in geology with the underlying rocks being softer sedimentary rocks forming low-lying land instead of the harder Igneous and Metamorphic rocks which form Chase Hill and Ragged Stone Hill. The Bridgnorth Sandstone can be seen just before arriving at the village of Bromsberrow. The Permian Sandstone shows some signs of cross-bedding. The war memorial in the village shows some small shell fossils (Fig 1) in the base plinth of the cross.
Fig 1. Shell fragments at Bromsberrow
Between the village and the Church the path goes past mounds which are formed from glacial meltwater depositing sands and gravels. At the church some good examples of the Bridgnorth Sandstone also can be seen.
Returning from Bromsberrow Church to the car park at Hollybush the opportunity was taken to call in to three locations described in the Geologists Association Guide to the Malvern Hills. The guide was published in 1971 and the locations shown are now very overgrown but can still be found. The first quarry to be visited was that shown as location 3 (Figs 2 & 3) in the guide.
Fig 2. Folding at Location 3 Fig 3 Location 3
This quarry is within the Malvernian which the guide describes as being of intensely sheared granite with large bodies of pegmatite. Some shearing can be seen as well as some pegmatite (Fig 4) where small areas are still visible.
Fig 4. Pegmatite at Location 3
[email protected] 11 The pegmatite is a course grained igneous rock which was intruded into the surrounding rocks around 600 million years ago. Moving on towards Hollybush a small valley is crossed which divides Ragged Stone hill into two peaks the valley is likely to be on a fault, “location 4” of the guide is reached This is a small outcrop of quartz-plagioclase schists but is also very overgrown and it is difficult to see a great deal. The last location visited is shown as Location 1 in the guide this is a roadside cutting on the A438. The Hollybush Sandstone is also very overgrown with only a few parts still visible.
A guide to the Geopark Way can be obtained from the Herefordshire and Worcestershire Earth Heritage Trust.
The Geologists Association Guide is No4 The Malvern Hills was published in 1971 and which may now be out of print.
Dave Green
Geo-Etymology
Talus - Simpson & Weiner, (2009)
Geology. A sloping mass of detritus lying at the base of a cliff or the like, and consisting of material which has fallen from its face; also, the slope or inclination of the surface of such a mass.
Etymology: Latin via French and derived from talus, ankle
Allaby & Allaby, (1990)
(scree slope). A sloping mass of coarse rock fragments accumulated at the foot of a cliff or slope
Tephra - Simpson & Weiner, (2009)
Dust and rock fragments that have been ejected into the air by a volcanic eruption.
Etymology: Swedish tefra (S. Thórarinsson 1944, in Geografiska Annaler XXVI. 114), < Greek τέϕρα ash. (Thórarinsson suggests (volcanic) ash or (better) tephra as a collective term for all clastic ejectamenta.
Allaby & Allaby, (1990)
Collective term applied to all pyroclastic particle of fragments ejected from a volcano, irrespective of size shape or composition. The term is usually applied to all air-fall material rather than pyroclastic flow deposits.
[email protected] 12 Tethys (Sea) - Simpson & Weiner, (2009)
Geology. The name of a large sea that formerly lay between Eurasia and Africa.
Etymology: Latin Tēthys, Greek Τηθύς, a sea-goddess
Allaby & Allaby, (1990)
The sea that more or less separated the two great Mesozoic supercontinents of Laurasia and Gondwana.
Lempriere, (n.d.)
The greatest of the sea deities was the wife of Oceanius and daughter of Uranus and Terra. She was the mother of the chiefest rivers, such as the Nile, Alpheus, Meander….The word Tethys is poetically used to express the sea.
References
Allaby, A. and Allaby, M. (eds.) (1990) The Concise Oxford Dictionary of Earth Sciences, Oxford, Oxford University Press. Lempriere, J. (n.d.) Lempriere’s Classical Dictionary, London, Routledge, George & Sons. Simpson, J. A. and Weiner, E. c (2009) Oxford English Dictionary [Online]. Available at https://www.mendeley.com/catalogue/oxford-english-dictionary-vol-vi/ (Accessed 18 November 2020).
(The Classical Dictionary was presented to my father in 1934 as a prize for Classics. It provides an interesting diversion when investigating naming of paleontological species. MAH)
Answer to the quiz
Answer: B) The rock is a type of micro-folded schist with noticeable small scale folds and equi-spaced alternating bands of mica and quartz, plagioclase feldspar. The texture is likely to have been formed under moderate pressure and temperature, deep in the crust.
[email protected] 13 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 Indoor meetings will be held in the Abbey Room at the Dudley Archives, Tipton Road, Dudley, DY1 4SQ, 7.30 for 8.00 o'clock start unless stated otherwise Visitors are welcome to attend BCGS events but there will be a charge of £1.00. 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 December 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
Stop Press Save the Branch Money
For those of you who have received a black & white printed copy of this newsletter:
You have received this printed copy because you have not explicitly requested electronic delivery. If you wish to receive the Mercia Rocks electronically in full colour, please e-mail the Membership Secretary at [email protected] with subject "OUGS emails: please revert Branch Newsletter to email", giving your surname and OUGS membership number and we will add you to the email delivery list for the Mercia Rocks which will then revert to a colour email copy. This will save the Branch the cost of postage
Contributions to the Newsletter are always welcome. The subject matter can be anything geological that you think other members would like to read. New items this month are Rock of the Month and Local Geology; please let me have your contributions for the next issue
We use photographs at the head of the title page to make Mercia Rocks a little bit more interesting, attract your attention and show some geology. I need more pictures! Email (to [email protected]) your favourite (preferably local) picture and I will include it in a future issue. It can be a distant general view, or a close up.
Mike Hermolle Items for inclusion in the next Newsletter, by email to: [email protected] by 31 December 2020
Photographs on Field Trips
Extract from Field Trip Guidelines:
There is a sentence on the Attendance Form stating that participants give consent for any photographs taken at events to be used in print and/or online OUGS publications. Please ensure that if any participant does not wish their photograph to be include in any such material, they make this known at the start of the event and that they remove themselves from view when photos are being taken. The leader must also be allowed to withdraw from being photographed. Any person documenting the event for OUGS must not take photographs of any under 16s that may be attending.
Please note that the social media sites of Facebook (OU Geological Society) and Twitter ([email protected]) are official OUGS sites. [email protected] 15 Online talks
Lapworth lecture Thursday 17th December 2020 (19:00-20:00) Ruiz Revisited: New Insights on Colombian Volcanoes Part of the Lapworth Lecture Series
The eruption of Nevado del Ruiz volcano in Colombia thirty-five years ago is remembered as one of the worst volcanic disasters in history. The events of that day not only changed lives forever, but led to a focus of study on Colombia's volcanoes to prevent such a disaster ever occurring again. David Cavell, who has spent his PhD studying the formation and history of Colombia's volcanoes, will take us through the deadly events of the 1985 eruption, the legacy it created in the study of volcanoes, and how this has led to new insights into the geological story of Colombia.
Speaker: David Cavell, University of Birmingham
Find the link to register at: https://www.birmingham.ac.uk/facilities/lapworth-museum/events/lectures/2020/17dec- onlinelapworthlecture.aspx
BCGS
19.00, 14 December – Talk by a young geologist. 'Phytoplankton and the response of ocean ecosystems to ancient and future climate change'.
I will forward the invitation once it is received.
Other Online sources
There are numerous places on line to access geological information. If you have not already done so, a visit to the OUGS website should be your first stop:
https://ougs.org/.
You will need to sign in to get access to the Members’ Only area where you will find numerous links on the pages including to OUGS Forums and an OUGS You Tube Channel which It currently hosts 3 talks for members
The Branch Facebook page is at:
West Midlands Branch of the Open University Geological Society
Come and join us