3 - Aberdaron to Porth Oer
Dolerite Sill
Another photo of the Pen Y Cil Dolerite Sill
Sill is a Geological term for an Igneous intrusion between layers of older rocks.
These rocks are associated with the Mynydd Penarfynydd Igneous complex.
Ref: NW 666
Date: 08/04/2022
Location: SH 1564 2406
