Sedimentology, Palaeobotany and Coal Geology of the Upper Permian Emakwezini Formation (Lebombo Basin, South Africa)

Emese Bordy¹, Rose Prevec¹, and David Grant^2
1Department of Geology, Rhodes University, Grahamstown, South Africa
²Applied Geology and Mining (Pty) Ltd, Rivonia Johannesburg, South Africa

The Emakwezini Formation (lower Beaufort Group, Karoo Supergroup) crops out in narrow, faulted, north-south trending strips in northern KwaZulu-Natal (South Africa). Its fining-upward successions of coarse- to fine sandstones and coal-bearing mudstones contain a fossil assemblage of trace fossils, insect, mollusc, arthropod, fish and plant species. Previously, poorly provenanced collections only described Glossopteris leaves and Phyllotheca australis from this Formation.
Of its four coal seams (A-D), seam B is being exploited in open pits at Somkhele Mine where it is ~11 to 15 m thick and contains two mudstone partings and vitrinite-rich (>75%) semi-anthracite to anthracite with a vitrinite reflectance of 2.4 to 3.1%. The coal has a raw ash of ~25% (reducible to 9 to 18% with beneficiation), low phosphorus (<0.015%) and sulphur (0.7 to 0.8%) contents. The other seams are much thinner, higher in ash and not considered economic at current prices.

Recent regional-scale investigations of the Formation, consisting of sedimentary facies analysis (field relationships, provenance studies, palaeocurrent and subsurface data) as well as palaeobotanical studies of a newly-discovered, well-preserved and diverse palaeoflora, allowed an improved reconstruction of the environment. Moreover, the current investigation also documents, for the first time, the occurrence of a suite of taxa (Dictyopteridium flabellatum, Rigbya arberioides, Lidgettonia spp., Raniganjia sp., Trizygia speciosa and Benlightfootia sp.) that strongly support a Late Permian age for the Formation, and provide a reliable correlation with other Upper Permian floras.

Sediments of the Formation were derived from east, northeast and southeast, and were deposited rapidly in a moist fluvio-lacustrine environment with a diverse biota.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery