Plettenberg Bay Gilead Cave

Peter Swart 31 July 1998

Plettenberg Bay Gilead Cave

Geology

A few kilometres to the west of Robberg, the coast is characterized by a narrow, rocky strip at sea level, backed by 80m to 100m high quartzite cliffs. The quartzite beds dip steeply towards the sea in the south, with the strike running approximately parallel to the coast. The beds have been differentially lifted along joints that run parallel to the dip, and give the impression of large, steeply sloping steps.

Gilead Cave was formed when a light gray shale band was eroded from between two quartzite beds. The remains of the shale band can be seen on the northern ceiling of the cave (see cross section bb'). The north wall/floor of the cave is a series of quartzite slabs, covered in a light grey powdery dust, and littered with rubble that has fallen from the ceiling.

Minerals

Most of the visibly interesting minerals occur towards the back of the cave. White crystals and short silica stalagmites have formed along joints in the ceiling, while a bank of dark red clay has formed in an alcove in the northern wall. A 1m high column of red clay, which reaches to the ceiling, tops a bank of the same red clay. The clay is possibly allophane (Durrheim et al, 1994).

Biota

Although we did not search the cave for small animals, we noted signs of porcupines and bats in the cave. The floor of the cave was littered with quills and we found a small pile of bat droppings on the ledge that runs along the northern wall. A number of 3cm long, white hairy moth caterpillars weas feeding on the bat droppings. These caterpillars appear similar to the ones that occur in Woolly Worm Cave at De Hoop.

Archaeology

There are two large shell middens at the entrance to the cave, and judging by the size of the shells in the middens, they don't make limpets the way they used to. Mrs Leggat showed us a small digging weight, and parts of a stone tool that they had found in the cave. Apparently (Leggat pers comm) the slanting floor of the cave made it unsuitable for habitation, so the cave was just used as a stop over, or shelter. There were also a number of fossilized bones on the floor of the cave, all baring fairly new teeth marks on them.

Plettenberg Bay Nelson Bay Cave

Gilead Cave - Plettenberg Bay