Sometimes referred to in literature as 'Bwlch y Gaseg' and in very close proximity to the area of the same name.[2] It was described by Rushton et al. (2000)[3] and exposes Late Ordovician micaceous siltstones and mudstones of the Dolhir Formation (Ashgill Series, Rawtheyan Stage) which yields a rich shelly (brachiopod) fauna. Trilobites are represented by several genera although the fauna is dominated by Gravicalymene arcuata Price, 1982.[4]Bivalves, bryozoans and various Echinodermata (Crinoids and Cystoids) are also present. Examples of most of the fossils listed below are illustrated and briefly described (or remarked upon) in "Fossils of the Upper Ordovician" by Harper and Owen (Eds.).[5]
^RUSHTON, A. W. A., OWEN, A. W., OWENS R. M. and PRIGMORE J. K. 2000. Cambrian to Ordovician stratigraphy. Joint Nature Conservation Council Peterborough, xxi + 435 pp. [dated 1999]
^PRICE, D. 1982. Calymene quadrata King, 1923 and allied species of trilobites from the Ashgill Series of North Wales. Geological Magazine, Volume 119, Issue 1, January 1982, pp. 57 - 66. DOI: https://doi.org/10.1017/S0016756800025656
^HARPER, D. A. T. and OWEN, A. W. (Eds.) 1996. Fossils of the Upper Ordovician. Palaeontological Association Field Guide to Fossils Volume: 7, 312 pages, 52 plates with b/w photos; 34 b/w photos and b/w line drawings.
