G

Glossary of geological terms

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glaciofluvial deposits / gwaddodion ffrwdrewlifol

Sands and gravels laid down by water originating from glaciers and ice-sheets during the ice ages.

Gondwana(land) / (Tir) Gondwana

Former super-continent which came into being towards the end of the Precambrian era.  It comprised modern-day Africa, South America, Australia, Antarctica and India.  Its collision during the Carboniferous period with the former continent of Laurasia resulted in the super-continent of Pangaea.

Goniatites / Goniatites

Fossil shells of an extinct group of molluscs resembling ammonites. They can be found within ‘marine bands’ within the Carboniferous age rocks of the area where they are useful as marker horizons.

Grammysia Beds / Gwelyau Grammysia

A succession of fossil-bearing mudstones laid down during the Ludlow Epoch of the Silurian Period.

Grey Grits / Grutiau Llwyd

Coarse sandstones which in some places overlie the Plateau Beds and laid down during the upper Devonian Period.

grike / ?

See Limestone pavement.