Carboniferous Limestone

330m million years old

Here, and just down the hill, are two different sorts of limestone that come from the same quarries in Clwyd.

This is a very muddy limestone full of shelly fossils. Its mottled appearance is the result of animals burrowing into the soft sediment and churning it about as they searched for food and shelter. The biggest fossil is a sea-shell which is similar to a scallop, though it is not at related to it.

Smooth Rock

Further down the hill, the other limestones are pale grey, smooth and mainly includes ooliths. These are small spherical grains formed as concentric layers of calcium carbonate accumulated around small grains of shell or grains of sand.

Special Soil

Acidic water and lichens are able to dissolve Limestone. Over a long time, dissolved rock, nutrients from dead lichens, and wind-blown dust help to contribute to the formation of lime-rich soil. This sort of soil is good for dairy farmers and for one of Wales’ rarest wild flowers, limestone woundwort Stachys alpina, the county flower of Denbighshire.

Where do these rocks come from? RMC Halkyn Quarry and Tarmac NW Quarry, Clwyd.