The Ercall Granophyre is overlain by shallow dipping Cambrian rocks (in relation to the steeply dipping Uriconian volcanics) which contain Atdabanian fossils. The Granophyre is dated at 560+/-1Ma and is thought to be related to the volcanic events in the area. The thermal expansion of the area is likely to have assisted the formation of a sedimentary basin in which such volcaniclastic sediments accrued and were later folded. This has given rise to the steeply dipping sequences exposed at places such as the Forest Glen car park. The folding event is thought to be contemporaneous with uplift and a date of 526+/-28Ma has been put forward for this.