Contributions to the geology of the Table Mountain Group

Master Thesis


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University of Cape Town

Modern analysis of Table Mountain Group sediments began with I. C. Rust's D.Sc. thesis "On the sedimentation of the Table Mountain Group in the western Cape Province" in 1967. Rust defined the stratigraphy of the Table Mountain Group, produced computer generated isopach and palaeocurrent maps for each formation and attempted palaeoenvironmental analyses based on what data he had available. For work dated prior to 1967 the reader is directed to Rust's excellent review in Chapter 2 of his thesis. The thesis served as a basis for Rust's later published work on the Cape Supergroup. Current published palaeoenvironmental models of the lower Table Mountain Group (the Piekenierskloof, Graafwater and Peninsula Formations) are based on a transgressive fluvial - littoral - shallow shelf model (Tankard et al., 1982) following earlier facies and palaeoenvironmental analyses (Tankard and Hobday, 1977: Rust, 1977; Hobday and Tankard, 1978: Vos and Tankard, 1981). The validity of this model has recently been questioned (Turner, 1986; 1987) although no comprehensive alternative has been proposed to date. The sedimentology of the upper Table Mountain Group i.e. the Pakhuis, Cedarberg, Rietvlei, Skurweberg and Goudini Formations (the latter three the newly named Nardouw Subgroup) has not been studied systematically. Good progress has recently been made on the fossil content of the Cedarberg Formation (Gray et al., 1986; Cocks and Fortey, 1986) and palaeoenvironmental analyses initiated in the Nardouw Formation. This thesis documents contributions to the geology of the Table Mountain Group. It is not the intention of the author to present an extensive overview and treatise on the lower Table Mountain Group, but rather to concentrate on three topics that can provide some insight into Table Mountain Group geology. The following three topics were selected 1) Petrology and Diagenesis of lower Palaeozoic sandstones in the s.w. Cape Sandveldt (Clanwilliam and Piketberg Discricts). 2) Palaeoenvironmental indicators in the Faroo Member, (Graafwater Formation) at Carstensberg Pass, R364. 3) Facies analysis of conglomerates and sandstones in the Piekenierskloof Formation: Processes and implications for pre-Devonian braid-plain sedimentology. These topics form the basis of the thesis.