Glossary of geological terms
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MN OP QRSTU VW X Y Z
Hafod Fawr Formation / Ffurfiant Hafod Fawr
A succession of sandstones, siltstones and mudstones laid down during the Ludlow Epoch of the Silurian Period. It includes the Cwar Glas Member which contains a number of thick sandstone beds.
Halfway Farm Formation / Ffurfiant Halfway Farm
A succession of mudstones laid down during the Wenlock Epoch of the Silurian Period.
Hirnantian / Hirnantaidd
Uppermost stage of the Ordovician Period. See Ordovician timechart.
Holocene / Holosen
The current epoch which began around 11,500 years ago. See Quaternary timechart.
Honeycombed Sandstone / Tywodfaen Dil Mel
A sandy limestone deposited during the Carboniferous Period.