Geology of the Golden Gate Highlands National Park

Abstract

The Golden Gate Highlands National Park is underlain by stratigraphic units belonging to the upper part of the Karoo Sequence. These units include part of the Beaufort Group and the Molteno, Elliot, Clarens and Drakensberg Formations. Dolerite dykes and sills are intruded into the succession while recent alluvium and scree cover the valley floors and mountain slopes. The Beaufort Group is represented by red mudstone and light brown fine-grained feldspathic sandstone of the Tarkastad Subgroup. The Molteno Formation consists of medium- to coarse-grained trough cross-bedded sandstone, while the Elliot Formation comprises a thick succession of red mudstone, siltstone and interlayered fine- to medium-grained, light yellow-brown sandstone. The most characteristic feature of the park is the yellowish sandstone cliffs of the Clarens Formation. Cave formation is caused by exudation, differential weathering due to different degrees of carbonate cementation and undercutting of the sandstone. The highest peaks are capped by numerous layers of amygdaloidal and massive varieties of basaltic lava of the Drakensberg Formation. A possible volcanic pipe occurs in the eastern part of the park. The Elliot and Clarens Formations are rich in vertebrate fossil remains, especially Massospondylus sp. Remains of Notochampsa sp., Pachygenelus monus, Clarencea gracilis, Lanasaurus scalpridens and a cluster of unidentified dinosaur eggs have also been found. The formations underlying the Golden Gate Highlands National Park were formed during the Late Triassic Epoch and the Jurassic Period (roughly 150 to 230 million years ago). The strata in the park show very little structural deformation and the only obvious structures are faults which are intruded by dolerite.