Glossary of geological terms
D1 or D2 limestone / calchfaen D1 neu D2
See ‘Vaughan’s biozones’
Devensian / Defensaidd
Name given to the period of time during which the last ice age occurred. Beginning about 120,000 years ago, it gave way to the Flandrian 10,000 years ago. See geological timescale.
Devonian / Defonaidd
Geological period which lasted 60 million years from 419 to 359 million years ago. See geological timescale.
Dimlington Stadial / Is-gyfnod Rhewlifol Dimlington
The coldest and most intense period of the last (Devensian) ice age. The time of the ‘Late Devensian Glaciation’ between 26,000 and 15,000 years ago.
Dinantian / Dinantaidd
Subdivision of the Carboniferous Period. See Carboniferous timechart.
disturbance / cylchfa ffawtio-plygu
Name given in South Wales to any of several linear zones of geological faults and folds. They include the Neath, Cribarth and Carreg Cennen Disturbances.
Ditton Series or Dittonian / Cyfres Ditton
Local stage name of the lower Devonian during which the rocks of the St Maughans Formation were laid down. See Devonian timechart.
Dowlais Limestone Formation / Ffurfiant Calchfaen Dowlais
A part of the Pembroke Limestone Group (formerly the ‘main limestone’) of the Carboniferous Limestone in South Wales.
Downtonian or Downton Series / Cyfres Downton
Lowermost stage of the Devonian Period. See Devonian timechart.