View at Drumadoon, south-west Arran, Buteshire


Drumadoon, south-west Arran, Buteshire. Composite sill of quartz porphyry with quartz dolerite margin. Beds of Triassic sandstone and shale below. Raised beach in foreground.

Composite sill. Basaltic and granitic magmas have partly mixed prior to intrusion. The main body of the sill is quartz porphyry, an acid rock which, however, contains inclusions of more basic rock.

The outer skin of quartz dolerite contains quartz xenocrysts, indicating some mixing of magma before intrusion. Columnar jointing well developed in the main quartz porphyry. Scree slope with large blocks below sill. Flat grassy area in foreground is raised beach.

SCRAN ID: 000-000-146-245-R: British Geological Survey