I was shocked and more than a tad surprised to find the entire Forest of Dean earmarked for the latest, and most important yet, round of licensing for onshore oil and gas… aside from all the battles we’ve had since 2010 stopping it from being sold/ leased/ wrecked by development, it seemed the very special geology of the area would make it unfeasible for oil or gas prospectors.
Which begs the question, where do they hope to find gas or oil? And do they have a hope in hell?
There are basically two sources of gas that frackers or “unconventional” extractors are seeking – coal and shale gas. Shale is dark grey or black, soft, fine grained rock which is very common – 70% of the world’s surface rocks are sedimentary (ie from either solidified sand, mud or silt rather than volcanic), and 50% of those are shale. Shales contain 95% of organic matter in sedimentary rock. Organic matter is from plants or animals which have died, sunk to the bottom of lakes, sea or rivers, and subsequently buried. The deeper it’s become buried, the more cooked or baked the rock becomes, and shale gas is generally found 2km to 6km below ground.
Shales are dense rocks with the space between the grains (where gas accumulates) glued in very tight spaces. That’s why they need to be pumped with colossal amounts of water mixed with sand and chemicals at extreme pressures in order to fracture them to release the gas, if the shale contains gas.
Coal is a fossil fuel – the solidified remains of 300 million-year-old trees and plants – buried under sand and mud, but again needs to be a fair distance underground (though hundreds rather than thousands of metres) to contain methane.
In tranches of South Wales, stretching from the west of Swansea to the Gwent levels, licences have already been granted for coalbed methane exploration. The fight is on to prevent this from happening, and solidarity with all those communities on the fracking frontline.
Nowhere else in Wales or Scotland is included in the latest (14th) round of licensing consideration, because both the Welsh Assembly and Scottish Parliament have put up massive opposition to it.
In England though, the Infrastructure Act 2015, despite our best efforts last year, makes it a “legal objective” to get any gas out of the depths of the earth wherever it can be found. The Government can also step in and override councils’ decisions if they’re not determined within 15 weeks.
The thing is, though, would it be worth any gas or oil company’s time, money and effort in even looking for it in the Forest of Dean area? I’ve been speaking to people with industry knowledge and they say as there has been such little research into shale gas potential here, including no boreholes which reach deeper than the coal levels (a few hundred metres), it would cost millions of pounds to even explore for it. It would require boreholes a few kilometres, at least, deep, and rock being extracted from that level, brought to the surface and heated in laboratories to determine whether they contained gas.
Forest of Dean MP Mark Harper, and two local geologists I have communicated with, have all said there is no potential for shale gas. Another thinks there could be in silurian shales, but while rocks of that age (more than 400 million years old) have been tapped for shale in parts of the US and Poland, this is what those in the industry might term a “risky play” – ie not really viable unless you have loads of money to burn.
Mark Harper tells the Forest Review (August 26, 2015 edition)
According to information provided by the British Geological Survey there are no shale deposits in or around the Forest of Dean. However, given the mining heritage in the Forest there are coal deposits in the areas which may contain natural gas.
If Mr Harper, the Tory Chief Whip, has read this in a report it’s a confidential one – I’ve ploughed through all the public BGS reports on shale gas. Maybe he has consulted the BGS (which is a Governmental organisation) himself to ascertain these facts.
After emailing the BGS asking that very same question I was invited to phone a representative at their Cardiff office, and she couldn’t say definitively there wasn’t any, but that there was no data either way – the area hasn’t been explored, unlike the Carboniferous Bowland Shales area in Lancashire, for instance.
So how about gas from the coalfield? A 2004 report into unconventional gas extraction from coal, cited by the Gloucestershire minerals survey, says there is no potential for recovering gas from the Forest of Dean coalfield. I’ve been informed that this is the most up to date report on the subject.
Here’s the advice of another local geologist – as I haven’t asked his permission to cite his advice in a blog, I won’t name him, but he is respected in the field and teaches it:
“Although the Forest may be included as part of the Licence scheme; it is extremely unlikely that any geologist worth their salt would risk spending money (or their job!) drilling for shale gas in this area –
- The Carboniferous rocks nearest the surface have not been buried deeply enough to allow maturation of the undoubted organic matter they contain (coal etc) into oil and /or gas
- The underlying Old Red Sandstone has no organic matter in it (laid down in a desert), and therefore no oil or gas
- the Silurian rocks below the ORS consist of a series of sandstones and volcanic sediments (May Hill variety) and overlying shallow water limestones and siltstones, none of which contains anything but traces of organic matter, and therefore no oil or gas
- Below the Silurian it is possible (but unproven) that there are Cambrian/early Ordovician deeper water. Shales, similar to those exposed at the surface west of the south Malverns and near Sharpness over the river, preserved in the area between the Forest and Cwmbran which may have the potential for oil/gas maturation and storage. Such rocks were explored in the 1970s and 80s in the area west of the Malverns, with no success.. These rocks are probably absent below the Forest, where it is likely that the Silurian rests directly on PreCambrian volcanic basement, due to uplift along the Malvern Fault (Blaisdon – Hagloe Fault in our area), and therefore no oil or gas.Drilling near fault lines, especially near major ones like the Malvern or Glasshouse Faults, would be totally unproductive, even if there were a possibility of hydrocarbons, because the rocks near faults have been highly fractured naturally, due to fault movement, involving hundreds of major earthquakes – any oil or gas would have leaked to the surface between 330 and 220 million years ago – the last time these faults moved more than the minor 2 or 3 small earthquakes per century currently experienced.”
Another geologist I know, however, thinks the Silurian limestone layer – probably about 3km down in the centre of the Dean – might indeed have enough organic matter in its shales to contain gas. And while the expert quoted above thinks the layers below that, known as Tremadog and Cambrian, might not be below the Forest of Dean, they have been found in the nearest deep borehole in Fownhope, Herefordshire (on the edge of the Woolhope dome, a geological structure which the ridges to the east of the Dean between Mitcheldean and May Hill culminate) and outcrops (meaning is the bedrock found immediately below the soil and subsoil) near Sharpness and Berkeley, just south across the river from Blakeney and Hagloe, along the major fault line that runs north across Pope’s Hill to May Hill and beyond to the Malverns…
At this stage maybe I’m getting too technical for those with none or very little knowledge of geology? Though I have had no formal education in the subject, I’ve been fascinated by geology for years. It’s like history in DEEP TIME. By deep time I mean millions, and hundreds of millions of years.
So let me attempt to give readers (if there should be any) a quick crash course in geology and…
THE MAKING OF THE FOREST OF DEAN…
This is how the Dean looks now just beneath the tree canopies and metre or so of soil… (though not literally these colours!)
Here’s a cross-section view (thanks Gloucestershire Geology Trust):
Hopefully you can decipher this graphic below I laboriously made using MS Paint (the most sophisticated graphics software I have). You’ll need to click on it and zoom in on it for a decent look. It shows what lies below our feet if we’re standing at Speech House, the centre of Newent and near the Severn at Rodley.
Now the rocks I have described in green are an assumption that what outcrops in the Malvern hills – Cambrian era rocks (from 500 million years ago-plus) – also underlies the Forest of Dean area. This is unproven (but see my reasoning just above re the Fownhope deep borehole and the outcrop just south of the Severn) – there might just be volcanic rock (orange writing) underneath the Silurian (in purple). As you can see in Newent and Rodley there are much younger rocks above all the levels found below Speech House and also what is known as a “superficial” level of muds in the process of turning into rocks because of their proximity to existing rivers (Severn and Ell Brook) which during the past two million years would have periodically covered these bits of land. The youngest rock in the centre of the Forest of Dean, however, is about 300 million years old – although parts of it also contains recent mud or alluvium, while the raised land at Coppet Hill, Drybrook and Cinderford got there because of melting glaciers from the north and west transporting rock about 10,000 years ago.
As you can see (check the rulers on the left of the rock faces), the sedimentary rock layers go down about 4km to 5km, and then there is 1km or more of rock that was formed from volcanic eruptions/ lava (the only place in the area you can see this lava rock above ground is at Huntley Quarry, just beside the A40 and just west of the village) and magma, the stuff spewed from the bowels of the earth from under the sea or below rather than into the air.
The continental crust, 40km or so deep, lies beneath this bedrock – known as precambrian basement – and is pretty much constantly being added to at its base from the alternating solid and liquid molten levels below… ultimately determined by the mysterious raging hot iron inner core at the centre of the earth. Older bits of crust will also be periodically flaking off and descending into the fiery depths where they are consumed.
Nowadays, this crust stretches continuously from far out under the sea to the west of Ireland to the far east of Russia and the Philippines. Like it or not, we are very much part of Europe, and anchored by much deeper, older crust that lies beneath Ukraine. And currently moving at about the same rate our fingernails grow, Britain and the entire Eurasian plate (or crust) is moving to the northeast… the Mid Atlantic Rift which bisects Iceland (hence all the volcanoes there) and stretches down to the South Atlantic – making it the longest mountain range in the world, albeit almost entirely deep under the sea – is pulling Eurasia further and further apart from America.
It’s all part of a cycle that lasts hundreds of millions of years where land masses accumulate, and then disperse to the four corners of the globe, before coming together again in different formations and shapes. There has probably never been as much land mass as now, however.
Here’s a rough account of the Forest of Dean’s travels round the world over deep time, as well as the various continents that have existed and then ceased to exist…
Once upon a time, between 1.6 billion and a billion years ago, the crust on which the Forest of Dean stands on was created by the earth’s volcanic movements… it probably began as fragments of magma cooled to rock in the middle of a long-gone ocean in the Southern Hemisphere, the magma welding bits together to create what geologists call the WREKIN TERRANE.
This roughly triangular slab of land gradually drifted over to the massive Gondwana continent (which at its peak included Australia, India, South America and Africa), and was either annexed to what is now the Tocantin province of Brazil or Liberia in west Africa (which were then situated not far north of the then ice-free South Pole). As you can see from the map below (based on the West Africa hypothesis rather than Brazilian one), May Hill and Malverns were on the eastern coast/ edge. It’s impossible to determine where the southern edge of the Wrekin Terrane was, as thanks to an event called the Variscan Orogeny (see further below for explanation), all the land was smashed up south of Bristol. Of course, there were no towns when it was formed – there were no people, and indeed no life on land at all, and if there were hills they’d be barren rocky ridges – some ridges could be in the same pattern of today’s hills, and the source of the various faults which shape our landscape.
The various components of England and Wales as well as northern Europe probably developed in a similar way to the Caribbean islands today – as a series of volcanic arcs that gradually meshed together. During the process they would have cracks and fissures, known today as faults, which could be activated when under pressure or crushed by colliding land masses.
By about 540 million years ago, the Wrekin Terrane was sandwiched between a much younger triangular piece of land called the Charnwood Terrane, which stretched as far east as London at its base (and Charnwood in Leicestershire near its northern tip), and another chunk of land which now forms the western part of Wales. They had formed part of a larger land mass, a mini-continent known as AVALONIA, which also included Belgium, Holland, most of Germany, a corner of Poland in the east, and Newfoundland and the eastern seaboard of Canada and the US (above Connecticut). Scotland and the top two-thirds of Ireland were on the other side of the world at that time, but England and Wales was intact. Here’s a map of Avalonia…
It should be noted that the blue areas on the map are the current places where there are sea… Britain as an island only took its current shape about 6,000 years ago. Various parts of the continental crust – including the Forest of Dean – have been under shallow and deep seas over the past 500 million years. And from about 540 million years ago, still in the southern hemisphere, Avalonia headed northwards, towards the continent of Laurentia (which included most of north America, Scotland and the northern two-thirds of Ireland). On its way Avalonia collided with the Baltica continent (which includes Scandinavia and western Russia), a roughly circular shaped mass of rock which was also rotating, and like a pinball game in extremely slow motion also bounced away again… by this time there were jellyfish, and algae, and then later small land plants. Their corpses formed sediment, later solidified into the various sedimentary rock layers.
Around 400 million years ago, Avalonia docked with Laurentia (North America), the coastal crust (being more brittle but thinner than continental crust) being crushed and subducted (ie slid underneath) what is now almost exactly the border between England and Scotland – Britain and Ireland were now united. The collision formed massive mountain ranges such as the Appalachians of Northeast America, the Caledonian mountains and Cambrian mountains of Wales, which would have been far, far higher when the excrutiatingly slow collision, happening over millions of years, took place. Parts of the Forest of Dean area were affected, to the north at Wigpool and Howle Hill, west of what is now the Wye Valley (the Wye Valley was only formed about 10,000 years ago), and perhaps south of the Forest near Lydney. The resulting combined continent, called either Laurussia or Euroamerica, is known as the Old Red Sandstone continent, as the mountains were crumbling/ eroding at the same time as forming, with a thick layer of sandstone accumulating southwards of the Scottish, Welsh and northern English mountains.
Gradually the Dean became a river delta, then by about 360 million years ago, when Baltica had locked on to the northeast of Avalonia, a shallow, tropical sea. It was full of crinoids, a weird sea animal which still exists, which is also known as a stone lily, spending its adult life rooted into the sea bed (and incidentally has its mouth right next to its anus and about five pairs of fern-like arms, which it uses to feed on snails and things). The segmented skeletons of the crinoids (and brachiopods) eventually became different layers of limestone above the sandstone layers – which now forms a pavement stretching west almost as far as Newport and as far east as Plump Hill above Mitcheldean and down to Staple Edge and Moseley Green, south of Cinderford. It forms a rim around all but a corner of the Forest (this limestone-less corner includes Danby Lodge, Yorkley and Viney Hill).
By now the Dean was on or close to the Equator, and after the sea receded, a swampy rainforest sprung up… life was a bit different then (about 320 to 305 million years ago). Everything was giant – centipedes the size of articulated lorries, dragonflies as big as albatrosses, and ferns bigger than oak trees, with incredibly thick bark. The air was thick with sulphur, from loads of electrical storms and instead of being eaten by bacteria (which didn’t exist then), trees and plants rotted on the spot after they reached the end of their lives, ending up as a kind of massive jelly. This swamp was unstable, and the forest was regularly buried by mud, forming a slurry which after millions of years, eventually became the Forest of Dean coalfield.
The last major event we know about in the Dean was known as the variscan orogeny, a mountain-building process, with its peak 280 million years ago. What had happened was that another mini continent known as Armorica (comprising most of France, Spain and other parts of western Europe) had slammed into the south of England at an oblique angle, and was then crushed by the huge Gondwana continent, the Africa part of it, to the south of Armorica. This created the hills of Cornwall and Somerset, among others, and also reactivated the split between the Wrekin and Charnwood terranes – which for about 200 million years had become a stable piece of land known as the Midland Platform or Wales-Brabant High, during various eras.
This reactivation of the papered-over crack meant the area which is now Worcester down to Huntley and Newnham, being a younger and less thick piece of land, was thrown down about 2,000 metres, and the Malvern Hills and May Hill created as the Wrekin terrane buckled as the Charnwood terrane crumbled beneath it. Then the hills were mountains as tall as the Alps (themselves only about 30 million years old).
When I was banging on about the Infrastructure Bill in 2014 and its fracking clauses (see earlier blog), my concern was that the map below showed that the area along the Severn east of Westbury was mooted on the margin of possible shale gas locations for its Jurassic (174-million-year-old) blue lias outcrop. Information from boreholes along the Severn was often classified unlike others on the BGS website, which could only rouse my suspicions…
Perhaps, as the grid squares mark where the drilling is taking place at ground level and not necessarily where the holes go horizontally (they are often 5km long), the actual fracking could take place along the Severn with just the well and drill-heads above the Dean? (Except, of course, the strength of resistance and the renowned spirit of Foresters isn’t going to let drillers NEAR to the Dean.) The Severn has a recommended 1km buffer zone, but this is only at the above-ground level.
Back to the variscan orogeny (mountain-building episode): another faultline, between May Hill, Blaisdon and Longhope, forced the rocks to be upended and folded downwards, forming a ridge (now three or four ridges, due to erosion) of old red sandstone. The same kind of uplift and folding was happening at the western end of the Dean, from the Usk valley – red sandstone layers, but in more gentle downward folds. In the middle of these two sets of ridges, the embryonic coalfield basin – the core of the Forest of Dean – was, thanks to being squeezed from either side, raised up and folded several times – most decisively in the Cannop valley. At its edges, the thinner layers of limestone were lifted up to form a rim around and above the basin. In the process there would have been earthquakes, volcanoes and general chaos all round.
When it first happened, the Dean would have resembled a massively high unconquerable plateau, perhaps like the mesas of New Mexico or Monument Park in the wild west of America. It remains a plateau to this day, and the scenery we enjoy is the result of this plateau eroding – it’s probably about one-tenth the height it originally was.
This last collision episode formed the Pacman-shaped super-continent of Pangaea (Greek for ‘all land’). The Dean wasn’t too far from its eastern coast – perhaps a few hundred miles – but like much of the continent spent a lot of that time in desert conditions, as the earliest dinosaurs evolved following a mass extinction. The lowlands east of the Dean (the former Charnwood terrane) also experienced shallow seas and lakes over the ensuing 100 million years or so – with many wonderful beasts which can now be found in fossil form along the eastern end of Westbury Cliff – as well as the entire landmass sinking below rising sea levels as the Pangaea began to break up. The Jurassic limestone of the Cotswolds formed even further east and south (but didn’t become hills until several million years ago).
The best way of seeing the Malvern line around these parts is travelling from Gloucester along the A40. As you go through Huntley, a line of hills marks the boundary. Here is a map of the various fault lines (in black) that produced the ‘syncline’ (downward folding hills) of the Forest of Dean and its inner folds and the Malvern line to the east, with its core filled with coal and Pennant sandstone.
Mainly occuring on the crease limestone layer along the folded rim, scowles were long thought to be entirely man-made iron-ore workings, but were recently proven to be natural geological phenomena (utterly unique to the Dean), formed about 150 million years ago, from massive amounts of acidic rain and a mix of mud, sand and unformed liquid coal, which oxidised into iron ore.
The hundreds of scowles are marked here in brown either side of the Dean coalfield. Ironworking has being going on since perhaps 500BC, with the Romans probably destroying a fair bit of the Forest after they arrived in about AD50. Coal was probably mined from Roman times as well, and freeminers (first mining iron, then coal and quarrying stone) were probably long established by the time the Normans arrived in about 1060 (they got to the Welsh borderlands perhaps a decade before William I conquered). In 1282 they were recognised as a tradition since “tyme out of mind”.
In the late 16th-century, the blast furnace arrived, sparking a second major industrial revolution in the Dean, which culminated in ironmaster Sir John Wintour chopping down all but 200 trees in the 1660s, partly to feed his many iron-making furnaces.
As you can see by this current map (actually a bit out of date as there are now more and different freemines), fairly small-scale extraction of the Dean’s minerals continues.
Freemining is only done small scale, as is most of the quarrying.
But at this time, the Forest is facing the prospect of quarrying on an unprecedented scale, with a huge chunk of rich farmland to the west of the Forest between Stowe and Clearwell earmarked for a massive limestone quarry.
Here’s a video explaining more:
Coupled with fracking, could we see devastation on a parallel which we can only imagine that happened with the iron industry in the Roman era (which seemed to have exhausted all the timber needed for bloomeries after a century or so), and the 17th century (with Wintour leaving only 200 trees standing in the Dean during the 1660s), and more so than the 100 million tons of coal that was mined between the 18th and mid-20th century from the Dean (amounting to six per cent of the UK’s energy consumption).
The daft thing is, if politicians weren’t so compromised by corporate interests and actually considered the environmental logic of fossil fuels versus clean, forever available, renewable energy – which, as this report shows, could fulfill all our energy needs with some left over, there would be no need for us having sleepless nights and trying to solve this puzzle over what are they looking for on and around our public forest land? And how we must stop them every step of the way…
But it’s all about money, ain’t a damn thing funny... as Grandmaster Flash rapped, “you gotta have a con in this land of milk and honey…”
Meanwhile, Greenpeace is cheering the fact that much less than 60% of the country (which was mooted) is up for fracking licences.
That still doesn’t get the Forest of Dean off the fracking hook even though, as this blog indicates, there is quite probably no shale gas to be found nor coalbed methane. It has been suggested to us the only reason the Dean is included along with other English coalfields (and the South Wales coalfield already licenced) is “to make it look complete”. Another possibility is that one or more oil and gas exploration companies has indicated to the Government a speculative interest in the area. To make that interest solid the company/ies will need to attract millions of pounds in inward investment.
Here’s a message to would-be investors should they find this blog in the course of their research, this will be a very “risky play”… or in layperson’s terms, it just isn’t worth your while.
(this lovely graphic by Squiff Creative Media)