Welsh Journals

about 18,000 feet of beds had been eroded away. The surface of Gower was somewhat irregular, though low-lying. The Port Eynon area, for example, formed a distinct hollow, in which were to accumulate coarse Triassic breccias. At this time, Gower's suface stood at a lower height than that of the neighbouring Coal- field, as of course it does today. The low-lying, but somewhat irregular, surface of Gower continued eastwards into what is today the Vale of Glamorgan and westwards into South Pembrokeshire. To the south, it stretched into what is now the Bristol Channel, but what was then a low arid waste, bounded on the south by the hills of Exmoor. All this low area was to receive a film of red Keuper marl by the close of Triassic times. Gower was beginning to be covered with its Mesozoic "Tar- paulin". In early Jurassic times a southern sea spread into parts of Britain, including at least the extreme south of Wales, and layers of mud and limestone completely blanketed the crudely-fashioned Gower surface and its thin veneer of Triassic dusts. As Jurassic, and then Cretaceous, times progressed, Gower sank beneath a thick cover of clays, limestones and eventually the pure, white Chalk. The laying of the "Tarpaulin" was complete. Much of the 100 million years or so which have elapsed since the end of the Cretaceous drowning has been needed to remove this blanket. Gradually the "cover" was removed, much more successfully in Gower than in the Vale of Glamorgan (where even some Jurassic strata are still preserved). The erosion of the blanket was probably accelerated by earth-movements which occured in mid-Tertiary times. These movements slightly warped the Gower surface and slightly downfolded the area between South Wales and Devon, i.e. the present Bristol Channel. Fracturing along the north coast of Devon, and very close to the present southern coasts of Gower and the Vale of Glamorgan further etched out the trough of the present Bristol Channel. Fracturing probably also occurred along what are now the east sides of Swansea and Carmarthen bays. The earth-movements were followed by an important marine advance in Pliocene, i.e. late Tertiary, times and much of the fringe area of South Wales was invaded by this sea. As it transgressed, it planed the rocks in its path. Relics of these planed marine platforms occur in the coastal areas of South Wales today. The sea level was not however static, as it fell (or the land rose) in a number of stages during later Pliocene and early Pleistocene times. Flat surfaces therefore occur at 600 feet (Rhosili Down), 400 feet and 200 feet, approximately, above present sea-level in Gower today. The "200 foot platform" is obvious to anyone looking at the cliff tops in the region from Caswell to Oxwich Point. It is important to remember, however, that these relatively recent seas did no more than provide a final