Geology

See Geological walk from Cradley Church.

Useful links:

A thousand years of Building with Stone (see resources)

The Geology of Cradley

Update from Earth Heritage Trust of February 2010.

We have 20 sites overall, across both Herefordshire and Worcestershire and hoping to attain 5 Champions per site. The total at the moment for voluntary Champions is 60, so we are just over half way of the quota we wanted. This is encouraging, as there are still 2 sites to go through the recruitment process. Response to the project has been superb. We will have the minimum amount we want by the time the project moves into its next phase. This next phase is the actual training days that are being held at the Worcestershire Countryside Centre and the University of Worcester. One day for Practical training vegetation clearance, guided walk training etc. and the other for Theory based training (this is for information on the geology of the counties and the individual sites relevance to this). These days are scheduled for the 13th, 20th, 27th of March and the 3rd April 2010. Whitmans Hill is a popular site at the moment [but as of spring 2022 beware locked access lane], and we have only one more Champion to recruit to meet the minimum that we wanted to have for it.

Message from Natalie Watkins received 8 August 2006.

I am writing to you from Herefordshire and Worcestershire Earth Heritage Trust in regards to one of our most recent projects that the parishioners of Cradley may find of interest.

The project is called 'The Geopark Way' and has been funded through Defras' Rural Enterprise Scheme.

In short, the project is to write and research a long distance walking trail guide running through the Abberley and Malvern Hills Geopark. The trail will start in Bridgnorth and will run down to Gloucester following public rights of way, passing through, or close by to, Cardley Parish.

Primarily the guide will be a walking trail guide interpreting the landscape and geology found along the route. Additionally, the guide will highlight all that geology has influenced in the area: biodiversity, archaeology, wildlife, land use, industrial history and social history. Accompanying the walking trail route will be details of cycling and public transport routes covering the same ground. There is potential here to include travel by the water routes and bridle trails. The guide will also serve as a tourist guide listing accommodation providers, eateries, events and tourist attractions. We wish the guide to be rurally focused reflecting the local character of the regions through which it will pass by promoting local produce, crafts and independent businesses. The project will run for 20 months. The guide will be published at the end of the project in May 2008 and will come in the form of a 110 page A5 ring-bound booklet.

A significant aspect of this project is to invite members of local communities to participate in the project. Whether it is to share their stories on local history and character, test possible trail routes, input their interpretation on the many aspects that will be highlighted in the guide or simply to come to community meetings that we will be holding to inform people about the project and how it is developing.

A ‘Geopark Way’ project public meeting is being held at Martley Village Hall on the 11th of Septeber at 7pm. The meeting will include talks and displays on the project, the local geology, history and wildlife. Another is being arranged in Ledbury - dates to be confirmed.

Yours sincerely, Natalie Watkins, Researcher, H&W EHT, Geological Records Centre, University Worcester, Henwick Grove, Worcester, WR2 6AJ, 01905 855184

Fossil finds confirm Malvern's seaside past

STAND aside Southend and Clacton. Scientists have revealed the original coastal hot-spot - Malvern-on-Sea.

Experts from Herefordshire and Worcestershire Earth Trust have finally shored up theories that the town was once by the sea, after identifying rocks found on the Malvern Hills.

These were identified as a conglomerate formed by different rocks being washed up and deposited against a cliff face and bound together with compressed sand and mud.

All of which confirms that 440 million years ago, the once much higher Malvern Hills would have been coastal. It also means Colwall and Ledbury would have been underwater, possibly as part of an extensive shallow tropical sea.

Peter Oliver, director of the trust based at University College Worcester, said: "This is an exciting discovery. It was always one of the theories but we're now fairly convinced that this is the case.

"We had a visit this week from two eminent palaeontologists, one from the National Museum in Cardiff and the other from Aberystwyth University, both keen to find fossil evidence to confirm what we thought. It seems from the fossils we found that the evidence is pretty much irrefutable but we'll continue to look for more." Much of the evidence relies on the identification of the fossil, called graptolite.

One of the specialists, Dr Dennis Bates, said: "It's possible that those found originally by the team from Worcester were just a few of these creatures washed in to the shore and laid down in a very thin layer of mud. To find more would mean splitting the rock in exactly the same timeframe.

"If they were drifting in over many thousands of years, they would be easier to find, but if only for a short time span, it's like looking for a needle in a haystack! It really does bring home to you the amazing timeframe in which we work, where fifty thousand years can be represented by as little as half an inch of compacted sediment."

To find more evidence, Prof Mike Brooks, from the National Museum of Wales, will analyse limestone samples and look for ancient microfossils called conodonts, which would give a precise date for the age of the rocks.

By Ally Hardy, Friday 2 August 2002

The geology of the Malverns

Here is an item by the webmaster's mother, Vera Copp (1916 - 2013), who went on a field trip on the Malverns Spring 2000 and wrote it up for a Geology magazine. She looked after the Bournemouth Natural Science Society's Geology section (was president twice and was Chairman of the BNSS Council).

A weekend to remember

Looking down from Herefordshire Beacon, 338 metres up on the Malvern Hills, the landscape spread out in front of us under a clear blue sky like a geological map come to life. We were standing on top of a great monoclinic fold produced by the collision of Europe and Asia at the end of the Carboniferous when the Urals were raised.

On the skyline to the east were the Cotswold Hills and in the graben between us was the flat Severn Plain, the Worcester Basin. This rift valley is controlled by major north-south faults of Permo-Triassic age with the Malvern Hills forming the western edge of the structure. Recent seismic studies have discovered 2-2 kms. down in the Worcester Basin the Precambrian rocks which have been thrust up to the top of the Malverns over the Silurian. We were there to do a bit of detective work to find out for ourselves this sequence of events which had formed an eight mile ridge of one of the oldest outcrops in England. The Malvern ridge separates Worcestershire and Herefordshire. The valley on the west, the Herefordshire side, stretched away to the Shropshire Hills in gentle folds, ripples from the pressure on the east side which had raised up the monocline. On the west side lies a thick succession of alternating mudstones and limestones, the Wenlock limestone ridges forming curves marked out by belts of trees. This was the Silurian over which the monocline had been thrust.

We walked along the ridge in glorious sunshine. To our north was Worcestershire Beacon, at 425 metres the highest point of the Malverns, and to our south lay Hollybush Hill and Midsummer Camp. Compression in the crust during these earth movements had led to the development of low angle thrusts and Hereford Beacon had been carried westwards forming a prime defensive position for the Iron Age people who had built a fort here. It's called British Camp and the earthworks are impressive.

The Precambrian diorite of the ridge was intruded just east of the Beacon by the Warren House Volcanics and this outcrop threw more light on to the early history of the Malverns. 600 million years ago the area was 60 degrees south of the equator and probably an island arc off the coast of South America. Palaeomagnetism suggests somewhere near Brazil. New continental crust generated at the subduction zone spread away from the back arc to reach the surface about 100 million years later. Here in the doorway of the Giant's Cave are the unmistakeable outlines of pillow lavas. These iron-rich lavas have been modified by sea water and show the formation of secondary minerals producing a purply blue spilitic basalt with crisscrossing veins of calcite and epidote, typical of present-day island arcs. We examined fresh surfaces in the scree and the more knowledgeable members produced names like andesites and rhyolites. Recent zircon dating has helped enormously to pinpoint dates with great accuracy and the Warren House Volcanics have been dated at over 600 million years.

In the afternoon we visited Dingle Quarry where Dave Green, our leader, managed to squeeze out of us every little clue we could find as to the sequence of events forming the Malvern Complex. Dave didn't spoonfeed us but under his skilled prodding we managed to work out the geological puzzle. No animals with hard parts in the Precambrian so no fossils to help us, but a sequence of cross-cutting intrusions and faults. The pink pegmatite intrusions were a give-away, big quartz and feldspar crystals with some nice compression foliation. These were coming up through the early diorite and by working forward with this we built up a picture of the sequence. Our clues were fault breccias and shearing, slickensides, mineralisation along the fault, sometimes difficult to judge which came first the chicken or the egg. But a very satisfying dark dolerite sill cutting across everything proved to our satisfaction that this was really the youngest rock.

There was just time to visit a quarry in the Silurian which showed the marine incursion over the old land surface, 400 to 500 million years ago, showing shallow water limestones and shales. Some of our more talented members found trilobites but most of us found bits of crinoid and coral and brachiopods. Lesser prizes were the tail-end of Dalmanites, a lovely Halycites and a perfect Atripa.

Time flew - time to go back to our very comfortable hotel for supper. The last man out got his car well and truly wedged in the mud. Despair! Thanks to his mobile phone four strong men were extricated from their baths and more or less lifted the car out bodily. There was much mirth when one fell flat on his face and the other was spattered with mud from head to toe by a spinning wheel. However all were placated with drinks in the bar in the evening by the shame-faced car owner. No names, no pack drill!

On Sunday morning, well fortified by a Full English Breakfast (wot, no black pudding!), we set off to Hollybush Quarry to test our skills on the sequence of events leading up to the Precambrian/cambrian unconformity. There are big quarries at Hollybush where aggregate for the M5 was quarried, but we went to the smaller one where we could literally get to grips with the rock. Again we traced faults, intrusions, depositional and erosional junctions, mineral alteration at junctions, some of the rock showing blue-green chlorite weathering, haematite staining making the rock rusty and brown, perhaps giving a clue to humid temperate conditions. Some of the shears had tell-tale broken bits in them, another indication of the sequence of events. With fifteen pairs of eyes there someone was always coming up with something interesting, like Liesegang rings, water penetrating the rock and weathering it.

We finally worked out that in the Malvernian Complex diorite was the first comer, the massive Malvernian. Pegmatite pods and veins cut across the diorite. Then came a dolerite intrusion about the same time as the pegmatites. Dolerite didn't show the same kind of metamorphism as the diorite. This dolerite dyke was clearly showing chilled margins as it had been intruded into the already cold diorite. There are different sorts of diorite - amphibole turned into mica makes it flaky but feldspar remains unaltered. If this is sheared it becomes soft and flaky. We saw some sparkly mica in some medium grain diorite. Mineralisation at junctions was interesting. A thin layer of clay at a junction of the diorite showed fine grained limonite, a lemony weathering surface caused by iron-rich solutions washing down through the joints The pegmatites were truncated by dolerite bands. Then there were at least two faults, one cutting across the other. After this there must have been uplift and erosion before deposition of the basal conglomerate showing re-working of the old surface. This could be plainly seen as there was a different jointing pattern from the underlying diorite. The Cambrian rocks had a closely spaced series of joints which were at right angles to the bedding whereas the Precambrian showed an irregular pattern of joints. We found fallen lumps of conglomerate in the scree. It has a yellow brown colour when weathered and is composed mostly of well-rounded quartz pebbles set in a sandy matrix. The Malvern Quartzite. There were angular chips in it which could have been bits of Malvernian diorite. There were reported to be infills of sand on the eroded surface - Neptunian dykes. Finally the whole lot had been tipped over. This Cambrian unconformity has been dated at 530 - 540 m.y.

A pub lunch at The Farmers Arms sunning ourselves in the garden - still lovely weather. Then we were ready to move up the succession to the Lower Silurian at Eastnor Quarry, a treasure-house of fossils from the Wenlock limestones and shales. The sea which had transgressed over the eroded surface of the Precambrian and Cambrian was warm and shallow with still waters. There was no evidence of coral reefs or sessile corals as might be expected from rougher waters. This was a fine-grained limestone with lovely examples of Favosites, Heliolites and trilobites like Calymene. There were brachiopods of the shallow waters like Lingula. In the shales we found deeper water brachiopods. The bottom of the quarry was nodular limestone with nodules with crystalline interiors. The top of the quarry was crinoidal limestone and here we found lots of crinoids. even a calyx, a very handsome stromatoporoid, a gastropod Eumphalus, corals like Leptina, mostly rugose corals.

We tore ourselves away from here to follow the succession to the Permian. Evidence for the Devonian and Carboniferous has been eroded away on the Malverns. We wandered up through Bromsberrow Lane at the southern end of the Malvern Hills to find the Haffield Breccia, the basal bed of the Permian which is highly unconformable. The coarse-grained deposits of haematite coated pebbles showed small sub-angular clasts of Malvernian diorite. This was the third of the big unconformities in the area. The Malverns have been unroofed in Cambrian, Silurian and Permian times.

Above the Haffield Breccia lie the red-brown aeolian desert sandstones of the dune-bedded Bridgnorth Sandstone. At this time Britain was part of a giant land-locked continent and lay just north of the equator so conditions were similar to those experienced in parts of the Sahara desert today. Here there was rapid erosion, particularly in the hills where the greatest uplift had occurred, forming wind-blown deposits of sand dunes. The Bridgnorth Sands are well rounded with the large-scale cross-bedding structure showing that the dunes were migrating south, a Permian wind coming from the north just as today the Sahara winds blow from the north east to the equator. The rock has a red colouration, probably haematite staining or from bacteria which precipitate iron. These deposits were laid down immediately after the formation of the Malvern Monocline and great thicknesses of these sediments were deposited on the floor of the Worcester Basin.

Our grateful thanks go to Sheila Alderman for organising everything so smoothly and pleasantly and to Dave Green for teaching us so much about the Malverns in such a skilful way that we felt like the early geologists discovering it all for ourselves. A most rewarding field trip.