Programme: 2002 - 2003

© Craven & Pendle Geological Society

Indoor Meetings

Friday, 11th October
The New BGS Regional Guide to the Pennines
Neil Aitkenhead, Ph.D., BGS

Friday, 15th November
Lead Mining in the Pennines
John Varker, Ph.D

Friday, 20th December
Volcanoes and wine
Roger Suthren, Ph.D., Oxford Brooks University

Friday, 17th January
Members Evening

Friday, 14th February
UK's energy needs...in a future without North Sea oil and gas
Nick Riley, Ph.D., BGS

Friday, 21st March
New research on Iceland's Subglacial Volcanoes
Dave McGarvie, Ph.D., Open University

Field Meetings

Saturday, 10th May
Carboniferous rocks of Anglezarke Moor
Paul Kabrna

Saturday, 14th June
Windermere rocks around Tarn Hows, the Lake District
Paul Kabrna

Saturday, 30th August
The geology and glaciation around Ilkley Moor
Neil Aitkenhead

Saturday, 13th September
The Ingletonian of the River Doe section Jack Soper; A joint meeting with Leeds Geological Association

Saturday, 27th September
The geology of Alderley Edge
Bob Perris

The Pennines and adjacent areas (4th Ed.)
Authors:  N. Aitkenhead, W.J. Barclay, A. Brandon, R.A. Chadwick, J.I. Chisholm, A.H. Cooper and E.W. Johnson.  Contributions from: G.R. Chapman, C.S. Cheney, T.B. Colman, D.E. Highley, G.K. Lott, T.C. Pharaoh, N.J. Riley, C.N. Waters, G. Warrington.

Published: 2002 On-line price at BGS: £18 - Product Code: BRG08  www.geologyshop.com ISBN 0-85272-424-1

The Pennines and Adjacent Areas has long been a classic account of the geology of the region at the heart of the Yorkshire Geological Society's territory. The third edition was published nearly 50 years ago and has been reissued many times since however, it was definitely getting very long in the tooth. Members of the YGS will therefore be pleased to see that an all new fourth edition is now available. This maintains the same format as the third edition with a series of stratigraphically-ordered chapters succeeded by one on structural geology and one on the economic aspects of the regions geology. A nice fold out map (1:625 000 scale) is also included in a back pocket. A measure of the growth of knowledge on Pennine geology can be had from the fact that the 86 pages of the third edition are replaced by the 206 pages of the fourth. As with all recent British Geological Survey (BGS) publications the quality of the diagrams is unrivalled, although the frequent use of subtle, pastel shades will probably render most 'unphotocopyable'!

Following an introduction, the 'meat' of the book begins with the Pre-Carboniferous rocks of the Craven Inliers which draws on both outcrop and borehole information. As you would expect with a BGS publication, the latest stratigraphic name is always given. Thus, the Ordovician Coniston Limestone Group has become the Dent Group. Sometimes this tendency to rename is a bit of a shame because famous, long-established names disappear. For example, the classic cross section of the Askrigg Block from the third edition is rightly retained but you look in vain for the Yoredale Beds. Only in the text does it become clear that they are now the Wensleydale Group. This is only a minor gripe but it would be nice if stratigraphic names were accorded the same stability as biological species. Another significant and better change is the much greater emphasis given to the origin of the rocks being described i.e. palaeoenvironments as well as lithologies are discussed. For example, the first thing we are told about Windermere Supergroup is that it is a shelf succession that records shoreface and storm depositional processes.

Chapters 3 to 6 are packed with information about the Carboniferous that provides an excellent introduction to much of the geology of the Pennines. Chapter 7 covers Permian and Triassic strata and Chapter 8 is a further in-depth review of the Quaternary geology of the region, backed up by superb illustrations such as the excellent satellite image of the north-west region that shows the position of drumlin fields.  Chapter 9, on the structural geology of the region, is perhaps the one that has changed the most since the third edition, 4 brief pages having been replaced by 14, reflecting the great advances that have been made in understanding deeper structural controls. And, of course, all the deformation is related to plate tectonic reconstructions a very definite change since the 1954 edition.

In summary, this is an excellent account of the geology of northern England that provides a detailed and thoroughly up-to-date introduction that will be of interest to all members of the Craven & Pendle Geological Society.

Reviewed by Paul Wignall & Paul Kabrna

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Lead Mining in the Pennines
John Varker, University of Leeds

Minerals In Veins
Other minerals often accompanying galena include calcite, copper, fluorite, barytes and perhaps rarer still, silver, zinc and mercury. The lead miners regarded calcite, fluorite and barytes as 'gangue' - a term used to indicate a mineral of no commercial value. Through time the concept of what is gangue and what isn't would change.

Being one of the first metal ores to be mined, lead is well known and its usefulness has long been recognised. It is a dense bluish-grey metallic element with the chemical symbol Pb (Latin Plumbum, a lead weight). Due to its toxicity, its reputation has become somewhat 'tarnished'. Its relatively low melting point made is easy to smelt; it is also a soft malleable ductile metal of low tensile strength and a poor conductor of electricity. Its malleability makes it easy to work i.e. bend and shape. Its early use was in drinking water pipes and as a paint pigment. The former though is no longer considered good practice for obvious reasons!

Origin Of Pennine Ores
The original idea behind Pennine ore formation has magma cooling with volatiles escaping through cracks and fissures into the surrounding country rock. The high temperature of the volatiles made it possible for them to carry chemical substances in solution subsequently to become deposited in cracks and joints which precipitate out to become the veins.

Today evidence suggests a different origin for these Pennine ores. Following analysis of deep borehole cores in Weardale, ores appear not to be related to deep-seated granitic intrusions as previously thought. The veins containing the ores cut the granite (therefore are older) and are overlain by Triassic rocks. This suggests the veins are Permo-Carboniferous in age. So what of their origin? In fact water (brine) is known to be circulating at depth. It is highly corrosive and hot (+300C) and able to readily dissolve elements. These mineralised fluids were then transported into sedimentary rocks over a 100 million years ago where they became locked up in deep basins. In time they gradually migrated upwards and onto the Askrigg Block. As the sediments were slowly compacted into rock the solutions were squeezed out. Eventually in late Carboniferous and early Permian times, the minerals were precipitated from solution to form the many mineral veins found throughout the Yorkshire Dales. To its commercial advantage, Harrogate and its Spa baths successfully 'tapped' into these 300 millions of year old waters.

A Brief History Of Lead Mining
It is thought that early small-scale lead mining began in the Bronze age. When the Romans arrived lead mining increased as they used lead for lining cisterns and baths. It was not until the 12th century that lead ore once again found a common niche especially during the building of castles and cathedrals.

As a result of the industrial revolution, lead mines were transformed from the chaotic assemblages of shafts to a more systematically planned and worked series of mining operations. Like so many industries, cheaper foreign imported galena eventually led to the demise of the industry. The miners switched their attention to other minerals of commercial value such as fluorspar and barytes (a lubricant for the drill bit in oil wells).

The most recent 20th century activity in lead mining is associated with Greenhow Hill, Grassington Moor and Swaledale with the last underground mining taking place at Gillheads Mine near Appletreewick in 1981. Now all that remains are sites frequently preserved as industrial archaeological walks.

Galena's twentieth century value lies with x-ray protection, and as a protective shielding around radioactive materials. Even today the public are wary of its toxic effects. Also, the environmental impact of mining and smelting lead is still felt today.

Lead mining: Conditions
The working conditions of a lead miner were horrendous and could knock 10 years off their life span from about 55 years to 45 years. Lead miners had to deal with rock dust - the reason for chest problems that contributed to their premature deaths. As the miners worked on piece-rate they seldom waited for the levels in which they were working to become safe following blasting. The fumes and dust were heavy in the air as ventilation was generally poor. The working conditions were no better in the smelt mills. The smelting process produced much sulphur dioxide gas in combination with lead that got into the vapour that was released during the process of smelting. At the surface women and children as young as 10 may well have been involved in some kind of lead mining activity - it's hardly surprising then that their life span was not what it should have been! At least one danger that lead miners were spared was that of potentially explosive gases that coal miners had to face.

Reading Material
A nice little publication is Lead Mining In The Yorkshire Dales by John Morrison (1st Edition 1998) and published by the Dalesman Publishing Co. in Skipton (ISBN: 1855 68 138 2).

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Volcanoes and Wine
Roger Suthren, Oxford Brooks University

Introduction
The Earth's rocky outer shell (the lithosphere) is fragmented with the larger pieces being termed 'Plates'. The average thickness is about 100 kilometres and they drift around the earth's surface on the hot rock found in the asthenosphere that lies beneath them. The boundary between the plates is where most of the Earth's dramatic geological activity takes place. At transform boundaries, plates grind past one another, frequently causing earthquakes e.g. San Francisco 1906 on the San Andreas Fault. At divergent plate boundaries, plates separate, allowing magma to pour out of large cracks e.g. the Mid-Oceanic Ridge. At convergent boundaries, plates collide causing volcanoes to erupt and mountains to form e.g. Mount Etna (at the boundary between the African and Eurasian plates).

Lavas, Pyroclasts and Volcanic Gases
When molten rock pours from a volcano non-explosively it's called lava. Lava cools and hardens into volcanic igneous rocks. When magma erupts explosively it is blasted into fragments called pyroclasts e.g. pumice and ash.

Volcanoes erupt explosively when gases within the magma violently expand as it nears the surface of the Earth. During an eruption some of these gases are released into the atmosphere, where sulphur compounds rapidly change into sulphuric acid droplets, which then fall to the surface as acid-rain. Very large eruptions can temporarily lower the temperature of the earth e.g. the year following the great 1815 eruption of Indonesia's Tambora volcano (the largest eruption in history) became known as 'the year without a summer'. The eruption of Pinatubo in the Philippines in 1991 is thought to have lowered global temperatures by ½°C. The dangers of such eruptions is illustrated in the photograph on the previous page. Pyroclastic flows racing down the valleys at high speed are perhaps the most dangerous aspect of volcanic eruptions.

CASE STUDY: Wines of Napa Valley, California
Adapted from 'The Geology Of Fine Wines' by John Livingston (1998)

To a visitor to Napa Valley individual vineyards look much the same. However, for the grape growers and winemakers there are subtle differences. These differences are related to how the land influences the character of wines.

There are many factors that determine a wine's character and quality. Of all these factors the four critical ones are soil, bedrock, climate, and topography. Napa Valley contains at least 60 soil types, three out of five recognised grape-growing microclimates, and topography that spans from sea level to 4,500 feet in elevation. "If anything can be said to characterise this valley, it is the diversity of growing conditions. That's what makes it so exciting," according to sedimentary geologist David Howell of the U.S. Geological Survey.

If you get the opportunity to sample some Carneros chardonnay or Howell Mountain cabernet, take a moment to reflect on the series of geological accidents over the past several million years. David Howell observed that "the rocks exposed on the flanks of Napa Valley include oceanic crustal fragments, deep-sea sediments, and volcanic ash. Many of the rocks are, in geologists" jargon, allochthonous, or brought here from elsewhere by plate tectonics. I describe this strata from distant parts of the Pacific as 'geologic flotsam and jetsam' carried to California aboard the drifting Pacific plate.

Factors that influence soil variability include the parent rock, time, topography, and climate. The successful vineyards of the Napa Valley understand that soil condition is inextricably linked to the geology. At one extreme there are meagre and sometimes toxic soils of the oceanic ultramafic rocks, typically marked by sparse vegetation and deep-rooted grey pines. Efforts to grow grapes on such soils usually meet with limited reward. In contrast, the valley floor harbours deep, well-drained soils rich in minerals and organic matter where grape-growing opportunities abound. High permeability, ample water retention and rich nutrients, however, create their own challenges. Growers curtail vigorous growth, which can impart too much vegetal or grassy taste to a wine, by choosing suitable rootstocks, planting vines closer together, and employing other techniques to coax the varietal character from the fruit.

Between these two extremes lie the upland slopes and benches along the hillsides, where thinner, less fertile but mineral-rich and well-drained soils create the natural stress associated with intensely flavoured grapes from low-yield, high-quality vineyards. Early viticulturists in the nineteenth century purposefully selected alluvial fans, broad deposits of eroded sediment that form where a stream channel emerges onto flatter land.

In Europe, winemakers have long acknowledged the role of what the French call terroir, a concept that encompasses the geology and ecology of a vineyard site and how aspects of a specific setting, such as soil, topography, and climate, may influence both the chemistry of the grapes grown there and the flavour of the wines they produce. California grape growers and winemakers have sought to simplify Napa Valley's complex patchwork array of distinctive geologic and climatic growing zones by demarcating regions with similar terroir as subappelations or viticultural areas within the valley.

To summarise:
The main factors required for controlling wine quality are as follows:
a) Climate: vines need sunlight and water
b) Terroir
c) Grape variety
d) The wine-making process

Vines depend on soils for anchorage, regulation of water supply, nutrients and temperature regulation. Many varieties prefer well-drained soils, often stony and on a slope. These stony soils reflect and diffuse sunlight to lower leaves, absorb heat by day and release it by night, and conserve moisture very well. As vines have very low nutrient requirements they make good use of poor soils. It is advantageous to keep the vines under stress thus producing smaller quantities of more concentrated juice (more flavour and higher quality wine). There is however no direct connection proved between specific soil minerals and flavour of grape or wine.

The French term terroir is commonly used worldwide although there is no direct English translation. As suggested above it may best be described as the vinery's combined attributes of geographical location; sub-soil / bedrock; soil composition and properties; slope, slope aspect and drainage; shade, climate / microclimate i.e. day and night temperatures, rainfall distribution and hours of sunlight; and finally the ecosystem / human influence.

Happy Wine Tasting

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UK's energy needs . . . in a future without North Sea oil and gas
Nick Riley, British Geological Survey

The first challenge we face is environmental. Levels of carbon dioxide (CO2) in the atmosphere, one of the main causes of climate change, have risen by more than a third since the industrial revolution and are now rising faster than ever before. This has led to rising temperatures: over the 20th century, the earth warmed up by about 0.6°C largely due to increased greenhouse gas emissions from human activities. The 1990s were the warmest decade since records began. The rise in temperatures has been accompanied by changes in the world around us:

a) Ice caps are retreating from many mountain peaks like Kilimanjaro;

b) Global mean sea level rose by an average of 1-2mm a year during the 20th century;

c) Summer and autumn arctic sea ice has thinned by 40% in recent decades;

d) Global snow cover has decreased by 10% since the 1960s;

e) El Nino events are more frequent and through the last 20-30 years;

f) Usage of the Thames Barrier has increased from once every two years in the 1980s to an average six times a year over the past 5 years;

g) Weather-related economic losses to communities and businesses have increased ten-fold over the last 40 years.

In this century, without action to reduce emissions, the earth's temperature is likely to rise at a faster rate than any time in the last 10,000 years. In the UK, the risks of droughts and flooding are likely to increase with sea levels at unprecedented heights and a clear threat to the east coast by the end of the century. In addition, there is a risk of large scale changes such as the shut-down of the Gulf Stream or melting of the West Antarctic ice sheet, which although they may have a very low probability of occurring, would have dramatic consequences.

The second challenge is the decline of the UK's indigenous energy supplies - oil, gas, nuclear and coal. Already we import nearly half the coal we use. Much of the UK's economically viable deep mined coal is likely to be exhausted within ten years. By around 2006 we will also be a net importer of gas and by around 2010 of oil. By 2020 we could be dependent on imported energy for three quarters of our total primary energy needs.

As we shift from being a net energy exporter to being once again a net energy importer we may become potentially more vulnerable to price fluctuations and interruptions to supply caused by regulatory failures, political instability or conflict in other parts of the world. But being an energy importer does not necessarily make it harder to achieve energy reliability. Of the world's leading industrial nations only two - Canada and the UK - are net energy exporters. The others have all achieved economic growth as energy importers. We will be able to do the same - just as we did before North Sea oil and gas. The best way of maintaining energy reliability will be through energy diversity. We need many sources of energy, many suppliers and many supply routes. Renewables will help us avoid over-dependence on imports and can make us less vulnerable to security threats.

Norway will be a major source of our gas imports over the next decade. But we will also need to look for supplies from elsewhere eg from Russia, the Middle East, North Africa and Latin America. This trade in energy will involve relationships of mutual dependence their energy being as important to us as their income from us is to them. Our growing interdependence also means that securing reliable energy supplies will need to be an increasingly important part of our European and foreign policy. We will work internationally to promote regional stability, economic reform, open and competitive markets and appropriate environmental policies in the regions that supply most of the world's oil and gas - Russia, the Middle East, North Africa and Latin America. We have already secured a commitment to energy liberalisation in the European Union for industrial customers by 2004 and overall by 2007. This is vital not only to improve our own access to diverse sources of supply but also to allow UK companies to compete in wider markets

Our third challenge is the need to update much of the UK's energy infrastructure over the next two decades. During the 1990s there was significant new investment in generating capacity, especially for gas-fired plant. This was a response to the high electricity prices and market structure of the time. Some generating capacity has since been mothballed and interest in building new plant, other than renewables, has declined. However, European measures to limit carbon emissions and to improve air quality are likely to force the modernisation or closure of most older coal-fired plant. In the absence of new build or life extensions, nuclear power's share of electricity production will shrink from its current level: there would be only one plant still operating by 2025. And renewables will become a more significant source of electricity as we seek to tackle climate change.

The energy system in 2020

We envisage the energy system in 2020 being much more diverse than today. At its heart will be a much greater mix of energy, especially electricity sources and technologies, affecting both the means of supply and the control and management of demand. For example:

1. Much of our energy will be imported, either from or through a single European market embracing more than 25 countries.

2. The backbone of the electricity system will still be a market-based grid, balancing the supply of large power stations. But some of those large power stations will be offshore marine plants, including wave, tidal and windfarms. Generally smaller onshore windfarms will also be generating. The market will need to be able to handle intermittent generation by using backup capacity when weather conditions reduce or cut off these sources.

3. There will be much more local generation, in part from medium to small local/community power plant, fuelled by locally grown biomass, from locally generated waste, from local wind sources, or possibly from local wave and tidal generators. These will feed local distributed networks, which can sell excess capacity into the grid. Plant will also increasingly generate heat for local use.

4. There will be much more micro-generation, for example from CHP plant, fuel cells in buildings, or photovoltaics. This will also generate excess capacity from time to time, which will be sold back into the local distributed network.

5. Energy efficiency improvements will reduce demand overall, despite new demand for electricity, for example as homes move to digital television and as computers further penetrate the domestic market. Air conditioning may become more widespread.

6. New homes will be designed to need very little energy and will perhaps even achieve zero carbon emissions. The existing building stock will increasingly adopt energy efficiency measures. Many buildings will have the capacity at least to reduce their demand on the grid, for example by using solar heating systems to provide some of their water heating needs, if not to generate electricity to sell back into the local network.

7. Gas will form a large part of the energy mix as the savings from more efficient boiler technologies are offset by demand for gas for CHP (which in turn displaces electricity demand).

8. Coal fired generation will either play a smaller part than today in the energy mix or be linked to CO2 capture and storage (if that proves technically, environmentally and economically feasible).

Conclusion

In order to meet these three challenges the following must take place:

a) to put ourselves on a path to cut the UK's carbon dioxide emissions - the main contributor to global warming - by some 60% by about 2050.

b) to maintain the reliability of energy supplies;

c) to promote competitive markets in the UK and beyond, helping to raise the rate of sustainable economic growth and to improve our productivity;

d) and finally: to ensure that every home is adequately and affordably heated.

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New research on Iceland's Subglacial Volcanoes
Dave McGarvie, Open University

Iceland

Introduction

For the past five years a team of OU, Lancaster University, and British Antarctic Survey geologists have been researching what happens when volcanoes erupt under glaciers. Such subglacial eruptions only occur every few decades, so rather than wait around for the next one to happen, our work has focussed on those volcanoes that have been revealed over the past few thousand years as the ice above and around them has melted. These newly-emerged volcanoes are always steep-sided mountains, their summits guarded by scree and snow slopes, and often capped by thick lavas. They owe their shape to the inability of the erupting material to escape sideways, because everywhere it tries to escape it meets ice or water, and chills, and has nowhere else to go but vertically upwards.

The work takes us into remote and un-tramped country, where a high degree of self-sufficiency is required. (A satellite phone has to be carried in case of emergencies.) Jeeps and horses can’t get where we need to go, so everything we need for the month or two in field is carried on the back. One camp for last summer’s month-long trip was at 720 m elevation in the Kerlingarfjöll mountains, on a small terrace above a stream. During the 30 days spent there, there were only two when rain gear was not needed. And about six when the party was tent-bound due to storms. But there were times when the sun shone and the landscape sparkled with immense clarity. Glaciers 100 km away looked within a day’s walk, and from the tops of the mountains the ‘big sky’ of Iceland took the breath away.

Brief account of 2002 work

Having worked on Torfajökull for the past six years (Iceland’s largest active rhyolite volcanic complex, which has been the locus of numerous subglacial rhyolite eruptions during the Pleistocene), the research has shifted to two new field areas – Kerlingarfjöll in the central highlands, and Snaefellsnes in western Iceland. Plus we did a recce of another area (Öraefajökull) for fieldwork in 2003.

Snaefellsnes

Last summer’s trip to Snaefellsnes was focused on collecting samples for a geochemical study involving age dating of rhyolites, to get a better understanding of the timing and timescales of eruptions. This work is being undertaken by a Manchester-based PhD student (Steph Flude). Although Snaefellsnes is not within the active rift zone, there have been basalt eruptions during the last 10 000 years.

Kerlingarfjöll

In order to understand better what happens during the early phases of subglacial eruptions, rhyolitic ash shards from subglacial volcanoes at Kerlingarfjöll are currently being looked at by John Stevenson (Lancaster-based OU PhD student). Their distinctive shapes and surface textures relate to a variety of fragmentation mechanisms, and we are seeing evidence that eruptions can take place during magma interactions with water/ice present, and with no water/ice present. The work is still at a preliminary stage, but results have been encouraging.

Öraefajökull

This was an area we did a recce of for future fieldwork. It is a massive ice-covered stratovolcano, which rises 2 km above sea-level. It last erupted in 1727 AD (basalt) and 1362 AD (rhyolite), and both eruptions produced destructive floods (jokulhlaups) through ice melting. For our work Öraefajökull is fascinating because it may be a unique example of ‘thin-ice’ subglacial rhyolite volcanism, which contrasts with the ‘thick-ice’ work carried out at Torfajökull and more recently at Kerlingarfjöll. In glacier-carved valley walls, thick rhyolite lava flows are well-exposed, but are difficult to access. There are also ‘sheets’ of columnar-jointed rhyolite lavas that appear to infix pre-existing valleys. We have noted a dearth of fragmental (ash) material and a dominance of lavas, and this may be a characteristic of the ‘thin-ice’ environment. This hypothesis will be tested further during this summer’s fieldwork in 2003.

Final thoughts

Although the fieldwork is demanding, the rewards justify the effort. One OU postgraduate student recently completed his PhD, and the team have published three key papers on our work, plus there’s another two papers nearly ready for submission. Two further postgraduate students (John Stevenson and Steph Flude) are both in their second year of PhD study. We’re gradually pushing forward the Science, and getting glimpses and insights into one of Nature’s most spectacularly-contrasting phenomena.

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Field Meetings


Carboniferous rocks of Anglezarke Moor
Leader: Paul Kabrna

Time / Date: 10:15am, Saturday, 10th May 2003

Meeting at: Anglezarke car park at Grid Ref: 620 160. Carry packed lunch and / or visit the Yew Tree pub.

Geological setting: Anglezarke Moor is situated about 4½km east of Chorley. The localities seen today lie along the western edge of the Rossendale Anticline and are characterised by rocks belonging to the Millstone Grit Group. To the west lies the Lancashire Plain where Millstone Grit is seen to give way firstly to Coal Measures and then to Permo-Triassic rocks. The entire area has been affected by glaciers, in particular, the North West Irish Sea ice sheet, which covered the Lancashire plain and banked up on to the Rossendale Fells.

The morning session will be spent at Lead Mines Clough (five localities) and a quick look at Leicester Mills Quarry. The minerals that can be found on the spoil heaps include barytes, witherite, galena and calcite. The marine bands in this area have been known to yield the bivalves Posidonia and Dunbarella. The goniatite horizons in the Marsdenian are dominated by the genus Bilinguites (formerly Reticuloceras).

The afternoon session is a 4km walk beginning at White Coppice. This is also dominated by rocks of the Millstone Grit Group. White Coppice lies on the Brinscall Fault and has a distinguished history of lead and baryte mining.

References:
O.S. 1:50 000 Sheet 109, Manchester

Geol. Survey 1:63 360 Sheet 75, Preston. Solid and Drift Editions

Price, D. et al, 1963: Geology of the Country around Preston. Memoir of the Geological Survey.

Suggitt, D. & Williams, K. White Coppice Geological Trail Guide. Published by the Lancashire RIGS Group.

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Windermere Supergroup rocks around Tarn Hows, the English Lake District
Leader: Paul Kabrna

Time / Date: 10:30am, Saturday, 14th June 2003

Meeting at: On arriving in Ambleside take the A593 Coniston road. Turn left at Clappergate along the B5286 towards Hawkshead. After about 1½ kilometres turn right along a road signposted Tarn Hows and Coniston. Park your car 250 metres along the roadside near a gate and stile on the left.

Practical details: Large natural exposures are uncommon so the day will be spent mainly examining old quarries. There are three localities altogether. The morning session will be in the Brathay Formation and the Wray Castle Formation (both of Wenlock age). The afternoon will spent at Tarn Hows where BVG and Windermere Group rocks will be seen. Carry packed lunch although a pub stop is possible at the Outgate Inn.

O.S. Maps:
1: 50 000 Sheets 90 and 97
1: 63 360 (one inch), Touring Map No. 3. The English Lake District
1:25 000 Outdoor Leisure Map; The English Lakes South Eastern Area

View across Tarn Hows

Geological setting: Following on from the mass outpourings of lava and ash of the Borrowdale Volcanic Group, by contrast, the Windermere Supergroup is predominantly composed of argillaceous rocks, particularly siltstones, turbidite sandstones and mudstones. Unlike the BVG which is confined to the mid-Ordovician (Caradoc), the Windermere Supergroup rocks span the Ashgill (late Ordovician) through the entire Silurian system. These rocks were deposited unconformably on the BVG. The Dent Subgroup (formerly the Coniston Limestone) was the first notable marine transgression. Later the remnant Iapetus Ocean floor began to subside resulting in the deposition of thick sequences of dark mudstones and siltstones. All this took place at the southern margin of the Iapetus Ocean as it closed.

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The geology and glaciation around Ilkley Moor
Leader: Neil Aitkenhead

Time / Date: 10 am; Saturday 30th August, 2003

Meeting at: Cow and Calf Rocks [SE 131 467] about 1 mile south-east of Ilkley town centre. There is a free car park but no toilets. However, the Cow and Calf Hotel is nearby where facilities are available. Participants are strongly advised to carry a packed lunch and to wear suitable footwear for rough moorland walking over a distance of about 7km (4.3 miles). We will also walk through two disused quarries where hardhats are desirable for those who wish to make a close inspection of the faces.

Cow & Calf Rocks, Ilkley Moor

Purpose: Ilkley Moor is formed by the outcrop of rocks of the Millstone Grit Group, here of Kinderscoutian to Yeadonian (R1c - G1b zones) age (Waters, 2000; Stephens et al.1953). Particular attention will be paid to an evenly laminated fine-grained sandstone and siltstone facies of probable tidal origin (Aitkenhead & Riley, 1996). This immediately underlies the Addingham Edge Grit, the lowest sandstone in the local R1c succession and a probable incised valley infill, well exposed at the Cow and Calf Rocks. From this locality, we will walk over the top of the moor tracing the prominent feature of the Lanshaw Delves Moraine (esker?) for some 3.5km to Reva Reservoir where it is revealed in cross section. We will also examine some mysterious markings known as Cup & Ring thought to be of Neolithic origin.

In the event of bad weather with hill fog, an alternative low-level walk along the banks of the River Wharfe downstream from Bolton Abbey can be undertaken, by looking at the Bowland Shale and Millstone Grit groups.

Maps:
O.S. 1:50 000 Sheet 104 Leeds & Bradford.
O.S. 1:25 000 Sheet Explorer 297 Lower Wharfedale & Washburn Valley
British Geological Survey 1:50 000 Sheet 69 Bradford – Solid and Drift Edition.

References:

AITKENHEAD, N & RILEY, N. J. 1996. Kinderscoutian and Marsdenian successions in the Bradup and Hag Farm boreholes near Ilkley, West Yorkshire. Proceedings of the Yorkshire Geological Society, 51 , 115-125.

STEPHENS, J.V., MITCHELL, G.H. & EDWARDS, W. 1953. Geology of the country between Bradford and Skipton. Memoir of the Geological Survey of Great Britain, Sheet 69 (England & Wales).

WATERS, C.N. 2000. Geology of the Bradford district. Sheet description of the British Geological Survey, 1:50 000 Series Sheet 69 Bradford (England & Wales) 41pp.

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The Ingletonian of the River Doe section
Leader: Jack Soper

A joint meeting with the Leeds Geological Association

Time / Date: 10.30 am, Saturday, 13th September 2003

Meeting at: Roadside car park Grid Ref: [SD 703 734].

Practical details: Meet at the small car park on the B6255 Ingleton to Hawes road at Storrs Common just up the hill out of Ingleton. Carry a packed lunch.

Purpose: To examine the enigmatic Ingletonian strata adjacent to the River Doe by considering way-up criteria and cleavage relationships with a view to ascertaining the stratigraphical age of these rocks.

Geological setting: The Craven Inlier, as exposed in Chapel le Dale, Ingleton, is composed of pre-Carboniferous rocks of Ordovician and Silurian age. Similar exposures of these rocks can be found in Crummack Dale, Ribblesdale and Malham. The Craven Inliers also mark the southern edge of the Askrigg Block.

The Ingleton Group exposed in Chapel le Dale represents the oldest rocks of the Craven Inlier and is of Arenig age (early Ordovician). They are primarily turbidite sandstones (greywackes) with interbedded siltstones and conglomerates. The Ingletonian were originally described as Precambrian in age. This conclusion was essentially based on the total absence of macrofaunas.

Subsequently, borehole analysis by isotope dating, and the presence of microfaunal evidence, suggests that the Ingleton Group be ascribed to the late Ordovician. Recent work by Jack Soper suggests that an early Ordovician age is not ideal - in fact the current evidence may well place the Ingletonians back into the Precambrian Period!

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The geology of Alderley Edge
Leader: Bob Perris

Time / Date: 10:30am, Saturday, 27th September 2003

Meeting at: the Wizard car park (National Trust), Macclesfield Road, Alderley Edge: Grid Reference SJ 859773.

Practical details: Cars will be left here for the day so carry packed lunch. The day will involve walking over modestly rugged ground with a walking distance of about 4 kilometres. Collecting and the use of a hammer is not permitted on National Trust property. Carry a packed lunch.

References:
G.Warrington 'The Copper Mines of Alderley Edge and Mottram St Andrew, Cheshire' JCAS Volume 64 (1981)

J.D. Sainter 'Scientific Rambles Round Macclesfield', Silk Press reprint (1999)

British Geological Survey: Geology of the country around Macclesfield.

Geological setting: The Alderley Edge area consists of a series of escarpments and dip slopes which have been fashioned by differential erosion from mineralised sandstone units of the Sherwood Sandstone Group (Lower Triassic) which lie in a N-S 3km-wide horst cutting the Wilmslow anticline. The whole belongs to the Wem-Red Rock Fault zone, an inherited Palaeozoic lineament on the NE of the basin. The latter stages of the evolution of the Edge relate to it being covered, and then exposed, during the passage of the Devensian ice sheet. During the Holocene the area was occupied by Neolithic and Mesolithic peoples and by Bronze Age, Roman and 17th-19th century copper miners.

Castle Rock (Hardegsen Disconformity)

The Alderley Edge mines of were mined from the Bronze Age (c. 4000 years ago) until the early 20th century. Some of the minerals mined at Alderley Edge include malachite, azurite, copper, galena, barytes and iron. Most of the mines are still accessible although many surface features have been obscured by vegetation over the years.

Many of the mines are owned by the National Trust and have been leased by them to the Derbyshire Caving Club which maintains access and continues to explore the network for areas of mining that have been closed for centuries.

In recent years, a fairly comprehensive study has been made of the mines by a project team lead by the Manchester Museum and the National Trust. This study is due to be published soon.

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