View of Black Cave, Bennan Head, south coast of Arran, Buteshire

A recent sea cave cut into a sill of columnar dolerite.

The dolerite is part of the Tertiary Bennan composite intrusion which consists in the main part, of a quartz feldspar-porphyry with minor hypersthene dolerite above and below. Black Cave represents part of the lower basaltic sheet. Several intercalations or floats of sedimentary rock are exposed in the cave, one is ten feet by three feet in cross-section.

SCRAN ID: 000-000-146-238-C; British Geological Survey