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Home » Articles » Geology - the Carboniferous PeriodGeology - the Carboniferous Period
Rocks and fossils dating from the Carboniferous Period.
Rocks and fossils dating from the Carboniferous Period.
In the early part of the Carboniferous Period, Wales lay just south of the equator and parts of south and north Wales were covered by a shallow tropical sea. Fine lime mud was precipitated onto the floor of this warm sea, and now forms the thick deposits of the grey Carboniferous Limestone. The sea teemed with life, and the remains of animals such as corals, brachiopods and crinoids are common as fossils in the limestone. In the mid Carboniferous, the sea-level fell and much of South Wales was covered by vast river deltas. Here, changing water levels and periodic flooding led to thick deposits of grits and sandstones interbedded with shales and marine limestones. Gradually the seas retreated even further and the deltas were colonised by dense tropical forests. These periodically flooded and regenerated so that cyclic deposits were formed. The compressed and fossilised remains of these early forests are preserved today as coal.
