Sedimentology, palaeontology and palaeo-environments of the Middle (?) to Upper Permian Emakwezini Formation (Karoo Supergroup, South Africa)

Abstract

The little-known Emakwezini Formation (Adelaide Subgroup, Beaufort Group, Karoo Supergroup) crops out in a narrow strip just inland of the eastern coast of South Africa in northern KwaZulu-Natal. It is an actively mined coal-bearing succession characterised by fining-upward successions of coarse- to fine-grained sandstones together with mudstones containing a fossil assemblage of animal traces, insects, molluscs, arthropods, fish and plants. Previously, only Glossopteris leaves and Phyllotheca australis had been described from this formation, on the basis of a few very small, scattered and poorly provenanced collections. Recent regional-scale sedimentary facies analysis (based on field relationships, provenance studies, palaeocurrent and subsurface data) together with palaeobotanical studies of a newly discovered, well-preserved and diverse palaeoflora from the Emakwezini Formation, have permitted a more detailed interpretation of the depositional environment. The current investigation also reveals the first evidence of the plant fossils Dictyopteridium flabellatum , Rigbya arberioides , Lidgettonia spp., and Trizygia speciosa in the upper parts of the Emakwezini Formation, strongly supporting a Late Permian age based on correlation with floras from Upper Permian units in the main Karoo Basin. In the lower part of the unit, within the partings of actively mined coal seams, our preliminary investigations also show the presence of a new flora including both the glossopterid fructification Ottokaria sp. (only known from the Lower Permian in South Africa) and the sphenopsid Schizoneura gondwanensis (typical of the Upper Permian in South Africa). With sediments sourced from a north-easterly continental interior, the Emakwezini Formation was deposited rapidly in a fluviolacustrine setting under moist conditions capable of supporting an abundant and diverse biota. The permanently moist environment in which the Emakwezini Formation was deposited contrasts with that of the time-equivalent lower Beaufort Group units in the main Karoo Basin where environmental indicators suggest deltaic, lacustrine and meandering fluvial systems developed in a seasonally dry and more arid setting. Thus, within southern Africa, during the Middle to Late Permian, the environmental conditions, including climate, were varied leading to a mosaic of continental depositional settings.