Skip to main content

Publications Ynyslas Dunes. Dyfi National Nature Reserve. [General leaflet] (1979). Ynyslas. Dyfi National Nature Reserve. Sand dune nature trail. (1981). Ynyslas dunes. Dyfi National Nature Reserve. Teachers Pack. (1981) 1. Introduction to the Dyfi National Nature Reserve for teachers. 2. Geography of Ynyslas Dunes. 3. Plant life on the dunes. 4. The Ynyslas saltmarsh. 5. Intertidal sand and mudflats. 6. Management of Ynyslas dunes. 7. Project suggestions for field studies at Ynyslas. 8. Geology & physiography. 9. Bibliography. 10. Environmental education resources list. 5 maps. 5 identification guides. Dyfi National Nature Reserve. Ynyslas. Middle school guide. (1982). Dyfi National Nature Reserve. Ynyslas. Students guide. (1982). Dyfi National Nature Reserve. Ynyslas. A primary school teachers handbook. (1982). Ynyslas dunes. Dyfi National Nature Reserve. Information Sheets. (1983). 1. Butterflies. 2. Insects. 3. Mammals. 4. Sand 6. Ogof Ffynnon Ddu NNR, Powys The cave system Ogof Ffynnon Ddu (Cave of the Black Spring), often referred to in its abbreviated form "OFD", is situated on the south-western edge of the upland range of Fforest Fawr, in the south of the Brecon Beacons National Park. Lying approximately 4 km east of Craig-y-Nos, it forms part of the rugged hill land known as Y Wern. Its impressive rocky desolate landscape overlooks the Upper Tawe Valley into which the bulk of the surface area drains. OFD, which has a land surface area of approximately 413 ha, was purchased by the Nature Conservancy Council from the Forestry Commission and declared a National Nature Reserve in October 1975. The reserve was established to protect a major portion of one of the largest, deepest and biologically the best studied cave systems in Europe (Ratcliffe 1977). Currently, including cave passages which lie beyond the reserve boundary, the "system" covers some 45 km of complex passages with an altitudinal range of approximately 300 m. The reserve has the unique distinction of being the first NNR to be declared with the specific object of conserving and managing a large cave system. The cave system lies in Carboniferous rocks at the northern margin of the South Wales coalfield, to the south of the high Old Red Sandstone hills that form the core of the Brecon Beacons National Park. A narrow band of Carboniferous Limestone is exposed dune flowers. 5. Marine fish & jellyfish. 6. Birds. 7. The submerged forest. 8. Pebbles. 9. Mollusca. 10. Sand dunes. The wildlife of the Dyfi estuary. 1983. Gwarchodfa Natur Genedlaethol Dyfi. Ynyslas. Llwybr natur: Ysgolion Cynradd. n.d. Further information and advice can be obtained from: Ynyslas Information Centre and Conservation Shop, Nature Conservancy Council, Ynyslas, Borth, Dyfed, (Telephone Borth 640) General enquiries should be made to: The Reserve Warden, Nature Conservancy Council, Llwyn Awel, Talybont, Dyfed, (Telephone Talybont 485). Field Studies enquiries should be made to: The Field Studies Officer, Nature Conservancy Council, Plas Gogerddan, Aberystwyth, Dyfed, (Telephone Aberystwyth 828551). RJ. Haycock as a series of hummocks or knolls with scree and collapsed pavement along the northern edge of the reserve at the foot of an extensive Millstone Grit plateau. The rocks dip to the south and south-west and the northern scarp of the Millstone Grit is sharply defined between the outcrops Carreg Cadno (537 m. OD) and Carreg Llwyd (457 m. OD) whence it slopes away across Y Wern, to its lowest altitude within the reserve at approximately 290 m. OD. The Millstone Grit exhibits shallow crags, boulder scree and extensive areas of pavement. A large portion of the grit slabs are bare of vegetation and show particularly good examples of glacial striae (surface scratches), indicating the direction of ice flow during the periods of glaciation. Numerous shake holes or swallow holes are an important feature of the area between the gritstone plateau and the limestone hummocks. The sequence of development of the cave system is still not completely understood and continues to be the subject of research. O'Reilly et al, (1969), consider that initiation (i.e. the development of tiny capillary sized tubes in the limestone, enlarged by the corrosive action of water) probably occurred more than two million years ago during the Pliocene period and that cave development continued throughout the succeeding Pleistocene period, largely by solution of rock in a water saturated zone at or beneath the then existing water table. During the Pleistocene period, sea levels