John has a wealth of information about the ORS which he has investigated and mapped extensively, in particular looking at similarities and hence correlations between the facies here and in Pembrokeshire.
First stop was in Brampton Abbots where there are exposures in a sunken lane. John explained that the outcrop is wide on the map because the dip is so shallow.
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| Shallow, south dipping thinly bedded sediment of the Senni Fm in the lane section |
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| Rooting around in the rockery on someone's bank looking for a bit with more pebbles in! This is the overlying Lawrenny Cliff Fm and has many exotic pebbles: quartz, rhyolite, greywacke, various igneous rocks and sedimentary clasts. Very rounded, and the provenance indicates a source to the north |
The dip steepens closer to Ross, possibly because of a fault structure that ties in with the Caledonian Lower Usk Valley fault system.
Just a little way down the lane we came to an exposure of the Lawrenny Cliff Fm on a junction. The was a coars, angular sandstone with a scattering of rounded pebbles and more angular clasts. It is cross-stratified, dipping to the S-SW which ties in with interpretation of bars in a braided river moving downstream.
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| The Lawrenny Cliff Fm in Brampton. |
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| The A40 road section (Allen, 1974) |
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| The ENE end of the section |
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| Most of the section is now not visible. Also the road is now too busy to allow easy examination |
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| The New Shipping Fm in Ross River Cliff. |
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| Ross River Cliff: planar stratified sediments separated by packets of cross- stratified sandstone |
From here we headed up to the terrace of the Royal Hotel from where there is an excellent view of the country to the north: the ridge formed by the Lawrenny Cliff Fm, then lower ground occupied by the Bryn Melyn Mudstone, before the ridge of New Shipping Fm sandstone on which we are standing. John has correlated these beds from his type areas in Pembrokeshire to this area.
After lunch we moved on to Goodrich Castle which is built on an exposure of New Shipping Fm rocks along the same ridge. From the track to the castle we stopped to look at the view to the SE where a mudstone valley (at the top of the New Shipping Fm) separated us from a ridge formed by two beds of conglomerate, the lower has large quartz pebbles but has not been identified. The upper, which caps the hills, is of the Upper ORS.
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| View SE from Goodrich Castle. Mudstone valley in the foreground, then conglomerate caped hills on the skyline |
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| Goodrich Castle from the ditch. The builders made use of natural rock exposures |
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| The square Keep is earlier than the round towers and curtain walls. It is also built of a more grey-green sandstone possibly Tintern Sandstone which could have been brought upriver by barge |
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| Close up of Keep walls |
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| At first floor level in the Keep is the original doorway with round topped, Romanesque arch. This was later converted to a window when a ground floor entrance was created. |
A final stop was to have been at Craig y dorth, further down the Wye valley but although we found the grid reference (nothing to see there!) we temporarily lost our leader who had overshot the turning and Jan and I decided it was time to go home!
I should just explain that John Davies is in the process of writing up his work and the names he has currently given to the formations could change!
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