the second special geological feature that marks the little karoo is the 300-km-long fault line along the southern edge of the swartberg mountains. the swartberg mountains were lifted up along this fault, to such an extent that in the oudtshoorn region, the rocks that form the base of the cape supergroup are exposed. these are locally known as the cango group, but are probably continuous with the malmesbury group that forms the base of table mountain on the cape peninsula, and similar outcrops in the western cape. in the little karoo, the outcrop is composed of limestone, into which an underground stream has carved the impressively extensive cango caves.