Cwm Gwrelych and Nant Llyn Fach Streams
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Geology & landscape
Geological Period: Carboniferous
Description
Description The best sequence of Westphalian (Carboniferous) rocks in the South Wales Coalfield. About 500 metres of strata are exposed, representing a more or less complete section through the Westphalian A, Westphalian B and lower Westphalian C. Thicker sequences have been shown in boreholes near Swansea, but this is the thickest sequence available in natural exposures. All of the principal marine bands are visible (except the Amman Marine Band), and there are numerous fossil bands yielding non-marine bivalves and plants. Such a complete and well exposed section through rocks of this age is unique in Europe, and will probably be selected as the standard reference section for the lower half of the Westphalian. A site of outstanding international significance.