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Geological footprints – time capsules

19 July 2013

www.leopard.tvFor many people a rock is only that and is a hard object against which one may stub a toe. For someone with more insight, however, rocks contain clues about the origin of the Earth. Such knowledge is of inestimable value because, unlike humans, rocks are the product of countless millions of years of change in our environment.

At first glance the Waterberg may appear to be only a mass of deep-red rocks or cliffs. Closer inspection will reveal that every rock is a conglomerate of petrified sediment and pebbles that has formed in a body of water. However, it is only when one starts to wonder about where, when and how this occurred that the full picture emerges. These rock formations of the Waterberg also show a relationship with other sedimentary geological formations that occur the Soutpansberg, Olifantshoek in the Northern Cape province and Rehoboth in Namibia and indicate a similar origin.

The conglomerate rocks of the Waterberg developed in water that flowed sluggishly. Moreover, their uniform and intense red colour indicate that the water was rich in oxygen for the entire year. Dating of these rocks indicates that they were formed some 1.9 to 1.7 million years ago in a vast inland lake on an extensive floodplain that once covered much of the ancient Cape-Vaal tectonic plate or craton. This tectonic plate, which forms much of South Africa, originated some 2.7 billion years ago as an island in the primordial oceans that once covered the entire Earth. This tectonic plate was part of the first Supercontinent Ur on the Earth and the name Ur means the oldest. The Waterberg formation stretches from Bela-Bela in South Africa north to the eastern parts of Botswana, and in South Africa east to just north of Middelburg in Mpumalanga. In the Waterberg region the sediments were up to 7 km deep. This implies that the Waterberg originated from sediments which had accumulated in the deepest part of this ancient lake.

The conglomerate rocks consist mainly of pebbles and sandstone which wholly contains iron oxide. This indicates that the water was rich in oxygen when the sediments were formed and means that the Waterberg formations were the first of their kind in the history of the Earth. The oxygen was the product of cyanobacteria which were the first known form of life on the Earth with their fossils being found in rocks of the Barberton Mountains that are 3.5 billion years old. This oxygen transformed trace elements of iron in the sediments into iron oxide. In the primordial oceans the oxygen was dissolved in the water to bind with iron to form beds of iron. In sediments which show red and white layers of rock the surplus of oxygen was only seasonal and such rocks are older than those of the Waterberg... (To read and see more become a Green subscriber)

 

References

Anon 2013. Tsingy de Bamaraha Strict Nature Reserve. http://en.wikipedia.org/w/index.php?title=Tsingy_de_Bamaraha_Strict_Nature_Reserve&oldid=548461412

Anon 2013. The Pinnacles (Western Australia). http://en.wikipedia.org/w/index.php?title=The_Pinnacles_(Western_Australia)&

McCarthy, T & B Rubidge 2005. The story of Earth & life. Cape Town: Struik Nature.

Walker, C & J du P Bothma 2005. The soul of the Waterberg. Houghton: Waterberg Publishers & African Sky Publishing.

By: Prof J du P Bothma

 

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