Upper Coquetdale

This is a mainly car-based expedition to examine various features in this beautiful dale. We drive straight to Fulhope to sample the limited exposures of Cheviot rhyolite. The geological survey classifies the rock as ‘mica-felsite’. It is a purplish rock with white feldspar phenocrysts. There is little evidence of mica to the naked eye. In the dry stone walls it has a rather more crinkly texture than the commoner andesite.
We then drive to Blindburn to view the excellent exposures of blocky andesite resting on a bed of tuff and ignimbrite on the opposite (South) side of the Coquet. We drive past the traditional hay meadows of Barrowburn, and notice that the Wood Cranesbill is in flower beside the road.
We stop at Bygate to try to locate the Acklington Dyke in the river bed. We find it in a rather inaccessible spot in the river. The Dyke has nothing to do with either the Devonian Cheviot volcanics or the Permian Whin Sill. It is one of a series of tholeiitic dolerite dykes radiating from the Eocene Mull volcano, and reaching right on to the Northumberland coastal plain.
Our final port of call is Kateshaw Crag at the roadside between Bygate and Shillmoor. The andesite here has weathered to produce beautiful blue-green phenocrysts of chlorite. We were trying to find the quartz-porphyry dyke which has been mapped in the river bed here. We could see a bed of rock on the opposite bank which looked more granitic than the surrounding andesite but the river was too deep to wade so confirmation eluded us.