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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).

 
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Figure 1. Location of the Kaapvaal Craton
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Figure 2. Stratigraphic Section, KwaZuluNatal
 
Special to KZN, the Kaapvaal Craton also holds meaning for all passionate about geology as it represents one of the very few remaining areas for study of pristine crust on Earth (University of Kwazulu-Natal).   This makes for fascinating present-day geologic study, however at the time of its formation, the Kaapvaal Craton was a simple crust of barren, desolate and dark basalt stabilized by granitoid batholiths and void of life (in fact, scientists have dated the first sign of primitive life on Earth to this time, give or take a few hundred million years!).  This is in dramatic contrast to the beautiful rolling hills, pristine grasslands, monumental cliffs and flowing canyons so full of life at Madaka today (Pictures 1-4). Although the many birds, game, grasses and flowers of Madaka Game Ranch were not to be found during the barren Archaean, the ancient action in this area would have been something to behold – the Mozaan Subgroup rocks of Madaka River canyon were deposited in the World’s Oldest Preserved Rift (Burke, 1985).

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).
 
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Figure 3. Location of the 3 Billion Year Old Pongola Rift, the World’s Oldest Preserved Rift - the geologic episode that led to some of the World’s oldest preserved rocks being deposited at today’s Madaka Game Ranch.

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).

 
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Figure 4. Geologic Map of the Pongola Structure. Note the location of Madaka Game Ranch (just northwest of Louwsburg). The ranch is literally at the crossroads of 300 Million and 3 Billion year old geology!
 
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Figure 5. Distribution of Nsuze (a; here labelled ‘Insuzi’) and Mozaan (b) sediments. Note the greater extent of Mozaan deposition, suggesting less active rifting (sedimentation is outpacing rift subsidence). Modified from Burke, 1985
 
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Figure 6. Pongola Supergroup with locations of numbered gold deposits (Bullen, 1994). The Eldorado placer gold mine is just north of Madaka Game Ranch.
 
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Figure 7. Eldorado mine (Ithala Game Reserve, note ‘Au’ designation…GOLD!) is found in the same formations as those intersected by the Madaka and Mbizane Rivers of Madaka Game Ranch. While finding even a single flake of gold is uncertain, it would be hard to beat a day panning and swimming the beautiful rivers of the Ranch!
 
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Picture 1. The high rolling hills of Madaka Ranch. These Precambrian beds are comprised of rocks of the Mozaan Subgroup, the upper siliciclastic section of the Mesoarchaean Pongola Supergroup. This succession has been locally age dated through study of Nzuse Subgroup felsites and Usushwana Complex intrusions as being 2.87-2.98 Billion Years Old (Nhleko, 1998).
 
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Pictures 2 and 3. Madaka Canyon – five minute ranch drive, or a continuous streambed hike, from Nyala Lodge. Walk down through time, older-and-older bed-by-bed, through rocks of the Mozaan Subgroup (up to 3 Billion Years Old!!). This succession consists predominantly of alternating shales, quartz arenites, conglomerates and minor iron formation, representing braided alluvial plain, tidal flat and offshore shelf facies (Burke, 1985). Swimming in the Madaka River plunge pools in the warmth of the South African sun amongst the oldest exposed rocks in the World is sure to make your African experience truly once-in-a-lifetime.
 
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Picture 4. High bluffs of Madaka Ranch and Ithala Game Reserve. While giraffes, rhinos or elephants may occasionally obscure the view, any time one looks up, they are struck by the dramatic cliffs of sandstones with dolerite intrusions of the Ecca Series of the Karoo System – the most famous of South African rock systems (analogous rock types and stages occur in all the daughter continents of Gondwana, proving the existence of this series of rocks before the breakup of the supercontinent (King, 1982); also of significance, geologists from around the world regularly study the Karoo system to get a hands-on understanding of ancient and modern deep water depositional systems, both for oil and gas exploration and comprehension of modern Earth processes). Locally, these rocks host economically important coal measures and serve as important aquifers.
 

Usushwana Complex


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.

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!).
 
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Figure 8. In the Late Jurassic the Central Atlantic Ocean was a narrow ocean separating Africa from eastern North America.   Eastern Gondwana had begun to separate from Western Gondwana.
 

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.

Dwyka Series


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.
 
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Figure 9. Gondwana ice cap. Note the position of the South Pole within present day South Africa. Through the actions of plate tectonics, several lands of Gondwana drifted across the southern polar region and were covered in polar ice caps, much as Antarctica is today.
 
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Figure 10. Diagrammatic cartoon of glacial processes.
 
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Figure 11. Stratotype A of the Dwyka Series, Madaka Game Ranch. Top left is diamictite, top right is clast supported conglomerate (Von Bunn). Bottom photo taken 2014 on a typical sunny Autumn day at Madaka Game Ranch (Mbizane River).
 

Ecca Series


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).
Not only does this make for a unique souvenir, but it also points to another type of treasure being had from the Ecca – Coal (Figure 12). The coals of the Vryheid Formation have long been known for their high quality, and although major companies have sold these aging assets to mid and minor operators, new exploration is ongoing that may again see Vryheid Formation coal rise to prominence.
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Figure 12. Coal fields of eastern South Africa. Note the Ecca Series (Group) fields noted near Vryheid. In fact, the most prolific section for coal from the Ecca Series is from the Vryheid Formation (Hancox, 2014).
 

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).

 
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Figure 13. Axis of the Natal Monocline (King, 1982). Note the position of Madaka Game Ranch on the axis of the monocline. The pivot point of the structural movement has been centered more or less at the present coastline, driving inland uplift and continued headward erosion to the west of Madaka.

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!

 
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Figure 14. Emergence of the beauty of Madaka Game Ranch. Through crustal movement and associated erosion, what was once a flat, undulating plain has emerged into the dramatic, breathtaking scenery that is Madaka Game Ranch today. Not only does this give today’s visitor amazing sites to behold, but this continued erosive revealing of the ancient rocks underfoot provides visitors a chance to truly step back in time through some of the most ancient rocks and exciting geologic events in Earth’s history!

References

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.