Exposed Units: Gully Oolite Formation/Llanelly Formation
Conservation Status: Local Geological Site
This is a quarry in Gully Oolite Formation, a grey-white oolitic limestone containing occasional brachiopod and crinoid fossils. In the middle section of the quarry, current bedding can be seen showing that these beds were formed in very shallow water. At the southwestern end of the site, there are lenses of yellow sandstone. The Llanelly Formation, seen at the very top of the quarry face, unconformably overlies the Gully Oolite Formation. Between the Gully Oolite Formation and the Llanelly Formation there is a striking change in sedimentation which has been referred to as the ‘mid-Avonian break’. The Llanelly Formation is a pale grey, thinly bedded, calcareous mudstone.
This site is part of the Community Earth Heritage Champions Project.
Terminology
Oolite – rock made up of ooliths, small spheres made up of successive concentric layers of calcium carbonate which accumulated as the ooliths rolled on the sea bed.
Photos
Sandstone lenses seen at the south east end of the quarry north of King Arthur’s cave.
East face of quarry showing Gully Oolite Formation. There are faint traces of current-bedding. Gully Oolite is overlain by thinly bedded Llanelly Formation at the very top of cliff.
General view of north face.
References
Dreghorn, W., 1968, Geology explained in the Forest of Dean and Wye Valley, David and Charles, Newton Abbot, pp. 196.
Howard, M.A., 1994, A landscape history of Ganarew, Herefordshire, Ross-on-Wye & District Civic Society, Ross-on-Wye, pp. 25.
Symonds, P.B., 1924, ‘King Arthur’s cave and the Great Doward’, Transactions of the Woolhope Naturalists’ Field Club, vol. 25, 1, pp. 28-29.
Barton, R.N.E., 1995, ‘An interim report on the survey and excavations in the Wye valley, 1995’, Proceedings of the University of Bristol Spelaeological Society, vol. 20, 2, pp. 153-159.
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