The late Palaeozoic coal-bearing Madzaringwe Formation of the Karoo Supergroup in the Tshipise-Pafuri Basin in the Limpopo Province, South Africa, records part of the infill of a passive continental margin terrain. Lithofacies analysis was performed with a view to deduce the nature of depositional environments of the Formation. Sedimentological and sequence stratigraphic evidence indicates that this unit represents a complex siliciclastic facies that reflects a fluvial paleodepositional environment. Eleven facies, which were grouped into five facies associations, were recognised. The base of the Madzaringwe Formation (Lower Member) represents a sequence deposited by braided channels. The coal deposits represent flood plain and swamp deposits, which is characterised by shale, thick coal seams, siltstone, and sandstone. The Middle Member is characterised by both clast and matrix supported conglomerates, major tubular and lenticular sandstones, and finely calcareous, micaceous siltstone. The deposition represents a sequence being formed from fluvial and particularly braided channels. The crudely stratified, coarse to pebbly sandstone indicates channel lag deposits within a heavy loaded fluvial system. The fine-grained sandstone represents deposition by shift channel and side bar deposits during lower flow conditions. The Upper Member is characterised by facies associations similar to the Lower Member, representing a new depositional cyclothem. 1. Introduction The Madzaringwe Formation is a coal-bearing sequence of the late Palaeozoic Karoo Supergroup in the Tshipise-Pafuri Basin in the Limpopo Province, South Africa (Figure 1). It overlies the diamictite Tshidzi Formation. Although the Madzaringwe Formation represents one of the coal-bearing late Palaeozoic units of the Karoo Supergroup, no detailed facies analysis has been presented yet and only a few papers have dealt with paleoenvironmental aspects [1–4]. The Madzaringwe Formation is approximately 220？m thick and constitutes two main coal seams. The lower seam, 2.5？m in thickness, forms the bottom part of the composite unit directly above the diamictite [4] while the upper main seam is about 3.5？m thick and consists of up to nine coal bands separated by carbonaceous shale. The Mikambeni Formation is a fluvial origin [1]. Development of a more precise depositional model for this unit will provide valuable insights into basin evolution and role of syndepositional tectonism. The purpose of this study is to describe and interpret the facies and depositional environments of the poorly understood Madzaringwe
References
[1]
G. Brandl, “The geology of the Messina area,” Tech. Rep. Explanation sheet 2230, Geological Survey of South Africa, Messina, Italy, 1981.
[2]
G. Brandl, “The geology of the Alldays area,” Tech. Rep. Explanation sheet 2228, Geological Survey South Africa, Alldays, South Africa, 2002.
[3]
G. Brandl and S. McCourt, “A lithostratigraphic subdivision of the Karoo Sequence in the north-eastern Transvaal,” Annals Geological Survey of South Africa, vol. 14, pp. 51–56, 1980.
[4]
J. H. Sullivan, The geology of the coal-bearing rocks of the Karoo Sequence in the Tshikondeni mine area, northern Transvaal [M.S. thesis], University of Pretoria, 1995.
[5]
A. D. Miall, “Architectural elements and bounding surfaces in fluvial deposits: anatomy of the Kayenta formation (lower jurassic), Southwest Colorado,” Sedimentary Geology, vol. 55, no. 3-4, pp. 233–262, 1988.
[6]
A. D. Miall, “Lithofacies types and vertical profile models in braided river deposits: a summary,” in Fluvial Sedimentology, A. D. Miall, Ed., vol. 5, pp. 597–604, Canadian Society of Petroleum Geologists Memoir, 1978.
[7]
A. D. Miall, The Geology of Fluvial Deposits: Sedimentary Facies, Basin Analysis and Petroleum Geology, Springer, New York, NY, USA, 1996.
[8]
A. D. Miall, “Alluvial sedimentary basins. Tectonic setting and basin architecture,” in Sedimentation and Tectonics in Alluvial Basins, A. D. Midall, Ed., vol. 23, pp. 1–33, Geological Association of Canada, 1981.
[9]
I. C. Rust, “Tectonic and sedimentary framework of Gondwana basins in southern Africa,” in Gondwana Geology, K. S. W. Campbell, Ed., pp. 537–564, Australian National University Press, Canberra, Australia, 1975.
[10]
A. D. Miall, “Alluvial deposits,” in Facies Models: Response to Sea-Level Change, R. G. Walker and N. P. James, Eds., pp. 119–142, Geological Association, Canada, 1992.
[11]
R. G. Walker and D. J. Cant, “Sandy fluvial systems,” in Facies Models, R. G. Walker, Ed., Reprint Series 1, pp. 71–89, Geoscience, Canada, 2nd edition, 1984.
[12]
E. M. Bordy and O. Catuneanu, “Sedimentology of the lower Karoo Supergroup fluvial strata in the Tuli Basin, South Africa,” Journal of African Earth Sciences, vol. 35, no. 4, pp. 503–521, 2002.
[13]
R. M. Flores, “Coal deposition in fluvial paleoenvironments of the paleocene tongue river member of the fort union formation, powder river area, powder river basin, wyoming and montana,” in Recent and Ancient Non-Marine Depositional Environments: Models for Exploration, F. G. Ethridge and R. M. Flores, Eds., vol. 31, pp. 169–190, SEPM Special Publications, 1981.
[14]
C. F. K. Diessel, Coal-Bearing Depositional Systems, Springer, Berlin, Germany, 1992.
[15]
E. M. Bordy and O. Catuneanu, “Sedimentology of the upper Karoo fluvial strata in the Tuli Basin, South Africa,” Journal of African Earth Sciences, vol. 33, no. 3-4, pp. 605–629, 2001.
