General geology

Abstract

We may think of the Plateau as consisting of two main, nearly horizontal, layers of rock resting on a basement of older, steeply tilted rocks. The surface layer, a few hundred metres thick, is dolerite about 165 million years old. This was injected into marine and non-marine sedimentary rocks deposited during a span of about 90 million years beginning about 290 million years ago. The part of this sequence originally over the dolerite has been removed by erosion, that beneath the dolerite is preserved as an almost continuous band around the northern base of the Plateau from Travellers Range to Table Mountain. The basement consists of metamorphic, sedimentary and igneous rocks some older than 570 million years, intruded by granite over 480 million years ago and again about 345 million years ago, and folded into a mountain range about 370 million years ago.