Ferrar Dolerites

Intruding the basement and the Beacon group are near-horizontal sills of the Ferrar dolerites. A sill intruding the basement has a uniform thickness of about 800 feet, and dips westwards at 5°. The Beacon group is shattered and complexely intruded by a dolerite of different composition. This upper dolerite is at least 4-5000 feet thick, and the Beacon sediments can be considered as rafts floating within the dolerite. Bifurcation and complexity of intrusion of this upper sill increase towards the west.

Many specimens were collected for laboratory investigation.