Glossary of geological terms
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. It is found beneath the Penderyn Oolite and above the Dowlais Limestone. The name refers to the characteristic way in which it is affected by weathering.