Tour of newly renovated sites in the northern Malvern Hills
We visited seven sites freshly cleared in the last 20 months by EHT volunteers. There was no common theme, except that they are all very local, but this is a chance to see these important sites in good condition, prior to their deterioration.
Another visit to the East Malvern Fault, visible at North Quarry car park. The surface we were standing on is now flat, having been levelled to accommodate the machinery for the neighbouring North Quarry. The removal of the sandstone allowed the fault to be visible. The fault is not a single line, but is made up of many branches. We examined both fault breccias and slickensides associated with the fault.
Looking at the East Malvern Fault
The rocks here were exposed in around 1960 when the playing fields were made; previously there was a slope. Looking along the slight ridge we could see red rocks, then grey, and finally shale. They are from the lower Silurian period and were deposited prior to the uplifting of the Malvern Hills. At that time the sea was advancing from the west and there were a number of shale and limestone bands which were later thrust up by the Variscan orogeny.
We examined the rocks. The red rocks are a breccia conglomerate, coated in red haematite. These were laid down in fluvial (rivers) conditions and are known as the Cowleigh Park Beds. There is then an unconformity leading to the grey rocks and, some metres further on, finely bedded shales which are easily eroded. These are named the Wyche beds and are a marine deposit.
Looking along the ridge, the red breccia conglomerate on the left
The breccia conglomerate
Wyche Formation beds
The Sycamore Tree Quarry is a famous location to see Miss Phillips' conglomerate. She was the sister of John Phillips, an early 1840s geologist who became Professor of Geology at Oxford University. He also wrote the first geological memoir of our region. The quarry was not there when Miss Phillips found the conglomerate and showed it to her brother, there is some debate as to the exact location (see ref 1). The find was important because it helped resolve a long running debate as to the age of the Malverns - these Silurian beach rocks were deposited on top of the Malvernian igneous rocks, showing the igneous rocks were older.
The conglomerate itself has rounded pebbles in a sandy matrix and is interpreted as a beach deposit. It appears all the way up to the Wyche Cutting. It is early Silurian, of the Llandovery formation. Trace fossils of worm tracks can be seen here, as well as shelly remains, a coral and ripple marks.
Sycamore Tree Quarry
Miss Phillips conglomerate plus a coral
Worm tracks and ripple marks
This location is round the back of the toilets at the Wyche cutting. There is a fault at the Wyche, creating a weakness which meant that the rock could be easily cut out. The fault has pink granite on one side, and diorite on the other. It was created in Carboniferous times by the Variscan orogeny, which produced faults running along a north south axis as well as east-west across the ridge.
The granite is a stronger rock than the diorite. There is an amount of foliation and due to the relative strengths this is less likely to spread to the granite. The foliation direction seemed to alter quite a bit. In areas the pink pegmatite granite was in pods rather than veins, possible stretching produces boudinage. In one corner we found an extreme form of foliation, mica schist, aligned along the foliation planes.
The fault at the Wyche Cutting
Pods of pink granite within the diorite, maybe boudinage
Gardiners Quarry is one of the many aggregate quarries located on the hills, now being used as a car park. The dominant rock type is diorite. There is a large dolerite dyke running through the centre of the quarry.
Throughout the quarry there are a series of granite pegmatite dykes. These cut through the diorites.
At the southern end there is a large granitic intrusion forming a shear zone. It is thought that this represents the end of the Colwall Fault (although John was not entirely convinced by this).
Pegmatite dykes (in pink), cutting through the diorite (grey)
We drove to Earnslaw Quarry and looked at the rocks on the right hand side of the car park. John explained that these were not the normal rocks of the Malverns, and there has been interest in them for at least the last 100 years. We still lack a full description of them.
There is a large pink pegmatite dyke running through the underlying diorite. Its direction is east to west, running through the "Gold mine" area. This pegmatite has strongly interacted with the underlying diorite, swapping some of the potassium in the orthoclase feldspar. The result is a collection of new minerals, notably black biotite. John commented that biotite is a weak rock, but there seems to be no weakness associated with its presence here.
It saw originally thought that this altered rock was Shonkinite, but recent experts now disagree.
Earnshaw Quarry (to the right of the car park)
Pink pegmatite veins in grey diorite
Altered rock, with pink pegmatite, black biotite, within grey diorite
Knight’s Quarry features exposures of the Woolhope limestone sequence. This is the third, and smallest, of the three Silurian limestone bands found in the Malvern area. It lies almost directly adjacent to the Llandovery sandstone. John explained that the Woolhope limestone is a bit of a mystery as its width is uncertain, and it occasionally appears in two bands. It is a nodular limestone with both silt and lime being deposited together. The deposits were laid down in moderately deep water and, over time concretions are formed.by segregation of the lime.
We searched for fossils and found a number of brachiopods.
Note that permission is required to visit this site.
Brachiopod fossil #1 (Atrypa reticularis ?)
Brachiopod fossil #2 (Resserella canalis ?)
Ref 1: The Miss Phillips’s Conglomerate of the Malvern Hills - Where is Phillips’s original site?
Author: M. J. P. Payne