Madaka Game Ranch: the heart of Zululand, the heart of the most exciting geology in the world!
The geologic formations of Madaka Game Ranch, the Natural Heritage Site home of Wow Africa, record many of the most significant geologic events in Earth's history. At the core of KwaZulu-Natal (KZN) lies the Kaapvaal Craton (Figure 1), the most ancient (Archaean, Figure 2) crustal block in Southern Africa (3 Billion Years Old).
The World’s Oldest Preserved Rift
As shown in Figure 3, Madaka Game Ranch was in the heart of the World’s Oldest Preserved Rift long before it was in the heart of Zululand. Study of the Pongola Supergroup, composed of both the Nsuze and Mozaan Subgroups (Figure 4), has revealed great variation in stratigraphic thickness of Pongola Sediments, and a large proportion of volcanic rocks – telltale signs of rifting (Burke, 1985). Detailed study of the areal distribution of the Mozaan Subgroup (Nsuze Subgroup rocks have been eroded in the Madaka Game Ranch area) reveals a ‘Steers Head’ geometry, a feature that typifies two stage stretching and thermal recovery of a rift system. It follows, therefore, that Nsuze rocks record the rapid initial phase of subsidence and filling of the Pongola Rift Basin, and Mozaan rocks of Madaka record the thermal subsidence phase of the rift system (Figure 5, Burke 1985).
Anyone with a gleam in their eye for gold may want to note that quartzites and shales of the Mozaan Subgroup account for the bulk of Natal’s gold production (Figure 6). The Wonder and Ngotshe gold mines, the largest and second largest gold producers in Natal, respectively, were actively operated in the early 1900’s (Bullen, 1994). While both mines are now shut and noted on driving loops within Ithala Game Reserve, visitors to Madaka Game Ranch may want to grab a gold pan and head to the streambeds of the Madaka and Mbizane Rivers – the same rocks mined within Ithala are those being ever eroded and revealed through the gentle yet constant force of these rivers (Figure 7).
Following deposition of the Nsuze and Mozaan Subgroups, dikes and sills of the Usushwana Complex (2.8 Billion Years Old) intruded throughout the Pongola Supergroup, and are interpreted as renewed rifting of the Pongola Rift Basin. While visiting Usushwana rocks requires a short drive from Madaka Game Ranch (Figure 4 – a great addition to a Blood River ‘Bloedrivier’ excursion!), the renewed phase of rifting in this area can well be viewed as the precursor to the geologic event that gave us the World on the maps and globes that we all know today – the breakup of Gondwana.
Some 120 million years ago or so, all the southern continents, along with India, Iran and Arabia, were united in the single Continent Gondwana (Figure 8). At this point in its history, Madaka Game Ranch had been roughly at the center of this mega continent for some time, with a walk to today’s Antarctica possible without getting your boots wet (although humanity as we know it took another 100+ million years to arrive!).
The Karoo System (Dwyka and Ecca Series)
Driven by the forces of plate tectonics, Gondwana began to break up during the Early Jurassic (Figure 2). Prior to this rupture, Gondwana looked similar to the continental landscapes that we know today – high mountain chains, and large intracontinental basins. Thousands of meters of sediments accumulated in these basins, which at the onset of the rupture of the Super Continent, were topped off by vast outpourings of basaltic lava. After the break up, each daughter continent carried away sections of these rocks, which in South Africa are termed the Karoo System. In Natal, the exposed rocks of the Karoo are the shales and sandstones of the Dwyka and Ecca Series; while to the west and south, baslatic lava floods from this time form the heart of the dark mountain wall of the High Drakensberg (King, 1982) – it must be noted, however, that prior to the strong forces of the Madaka, Mbizane and Pongola Rivers, and their ancient ancestors, similar dark dramatic peaks of the Drakensberg were also found at Madaka – but this story can wait (see Figure 14 if you can’t wait!); the Dwyka and Ecca Series of Madaka Game Ranch have their own story to tell.
The Dwyka Series overlies the Natal Group (the Natal Group/Series is not found at Madaka, however it is preserved nearby just south of Ulundi) and is a thick unit of tillite that was deposited in a glacial environment by retreating ice sheets about 300 million years ago (Figure 9, University of KwaZuluNatal Geology Education Museum). Just as can be studied in modern glacial valleys, this environment was characterized by slow moving ice sheets, entraining rocks of all sizes (some as large as a house…or elephant…or bigger) grinding and polishing the surface that they slowly marched across under the force of gravity towards standing bodies of water or open seas (Figure 10). The dwyka tillite of Madaka witnesses this ancient episode, characterized by highly variable lithology (diamictite, matrix- and clast-supported conglomerate, sandstone, siltstone and mudrock), with crustacean trackways preserved on some laminated mudrock surfaces. This assemblage of rock records debris flow and turbidity current sediment gravity processes, reflecting meltwater plumes, tidewater glaciers, suspension settling and sediment rain-out from floating ice during a period of widespread deglaciation (Von Brunn, 1999). Excellent exposures of the Dwyka are found on Madaka Game Ranch. In fact, Stratotype ‘A’, the ‘Mbizane Stratotype’ (Figure 11) is housed in the Mbizane river bed of Madaka! Walk these 300 Million Year Old rocks towards where they abruptly and unconformably abut the previously incised Archaean terrain – this is one of the very few places in the World where one can place one foot 300 Million Years in the past, and the other 3 Billion years in the past! Madaka truly is a magical place that brings the history of Earth to life.
Overlying the Dwyka Series, and forming many of the slopes viewable to the south and east of Madaka Game Ranch, are the shales, coals and sandstones of the Ecca Series. The fluvial deltaic depositional story of the Ecca is not as exotic as the glacial story of the Dwyka, however fossil leaf impressions of Glossopteris can be found (Inset picture).
The Natal Monocline
The geologic story of Madaka Game Ranch has so far highlighted the central role the area played in the formation and breakup of ancient earth, the coming and going of glaciers and the hunt for Earth’s riches. This brings us to the last, and still ongoing, geologic phase in which the area of Madaka Game Ranch has played a central role.
The breakup of Gondwana brought the Indian Ocean to Madaka’s doorstep. As the new sub-continental margin was drawn out and thinned through the continued separation of the newly ‘single’ continents, giving way to the forming Indian Ocean, the thick Karoo sandstones and lava flexed down towards (and below) the new coast. This singular flexing to the east initiated formation of the Natal Monocline, named by German geologist Albrecht Penck in 1908 (King, 1982). Of course, as has been the case throughout its geological evolution, the area of Madaka Game Ranch features as the key player of this exciting geologic episode as well – the ranch is placed at the axis of the Natal Monocline (Figure 13).
As described by King, primitive Natal was a smoothly undulating and mostly flat lying landscape (Figure 14, top left). Through time, and the impact of several episodes (shown here 1-6, older to younger respectively) of uplift and tilting of the province, coast-seeking streams and rivers took advantage of fault-driven weaknesses in the rocks to dissect the landscape, stranding younger (Ecca, for example) rocks on interfluves and ever exposing older rocks working down to the Archaean layer-by-layer. The ancient Drakensberg, once east of and then coincident with the Madaka Game Ranch area, continued (and continues) a westward march as the streams and rivers push the scarp ever away from the coast in their quest to achieve an equilibrium gradient. Only time will tell how Mother Nature concludes the geologic story of KwaZuluNatal and Madaka Game Ranch; however this deep 3 Billion Year Old history, one that is still active today, is yours to take in – guaranteed that one visit isn’t enough!
Burke, Kevin, W.S.F. Kidd and T.M. Kusky, 1985. The Pongola Structure of Southeastern Africa: The World’s Oldest Preserved Rift? Journal of Geodynamics, 2, 35-49.
Bullen, W.D., Thomas, R.J. and /mcKenzie, A. Gold Mineralization in Natal, South Africa. Journal of African Earth Sciences, Vol. 18, No. 2, 99-109.
Geology of KZN. Retrieved from www.stec.ukzn.ac.za/GeologyEducationMuseum/KZNGeology.aspx
Hancox, P. John and GÖtz, Annette E. South Africa’s Coalfields – a 2014 Perspective. 2014. International Journal of Coal Geology. 132, 170-254.
King, Lester. The Natal Monocline: explaining the Origin and Scenery of Natal, South Africa. 1982. Second Edition, University of Natal Press, Pietermaritzburg. 134 pgs.
Nhleko, Noah, 1998. Stratigraphy of the Archean Mozaan Group in the Kubuta-Mooihoek Area, Swaziland. Master of Science, Rand Afrikaans University. 132 pgs.
Von Brunn, V. and Visser, J.N.J. Lithostratigraphy of the Mbizane Formation (Dwyka Group). South African Committee for Stratigraphy, No. 32, 10 pgs.