One of the well-known features of Plio-Pleistocene early hominid sites in South Africa is that they are all associated with historic lime mines – think of Taung, Sterkfontein, Makapansgat, and others. As mentioned in earlier posts, this association is one of the critical factors that we used to develop our method and implement this field project, and thus has great practical value to us in the field – find the old lime mines, and we might also find some nice fossils!
However, there is also a very interesting historical component to this association. Mining, primarily of gold and other precious metals, was a principal factor supporting the economic development of the early South African state in the late 19th Century. The lure of vast riches associated with mining attracted migrants from many parts of the Western world. Lime mining was important for many industrial uses, literally providing the mortar and cement for building new towns and factories, and it was also an important component in the extraction process for gold and other economically important metals.
Speaking of gold, there were several early ‘gold rush’ events in South Africa, including Pilgrim’s Rest (1873), Ottoshoop (1879), Barberton (1881), Kaapsche Hoop (1882), and finally the Reef goldfields on the Witwatersrand (1886) which led to the establishment of the city of Johannesburg – and to conflicts that contributed to the start of the second Anglo-Boer War (1899-1902). We have covered some of these geographic regions in our survey activities, and read a great deal of information about their history in our archive work.
The people we have met in all of these areas are very knowledgeable about their local history, and of the historical importance of these events, and we have also located additional documentation about mining history through our archive work at the Wits University Historical Papers Library, Council for Geosciences, and other sources.
One example is the lime kilns near Ngodwana in Mupumulanga Province. We located them through a reference in a geological textbook1, and later determined that there was an old lime mine nearby. Our local contacts informed us that the kiln site (see photos) had been an important distribution centre for lime extracted from many mines in the area prior to 1899, and after processing the lime was shipped out to other areas by railroad. With this information, we were able to locate six additional lime mines within a few kilometers of the kiln site, and there are likely to be even more! (While we did not find fossil deposits at any of these mines, we did find in situ clastic cave sediments, or ‘rock breccia’, and some very thick remnant speleothem deposits. Definitely worth some future sampling!).
As it turns out, the geological formations in which the metallic ores occur – including gold, iron, and other mined resources – are closely related geographically to the dolomite formations of the Transvaal Supergroup. Thus, in the areas of our survey we have walked across other rock units in the Transvaal Supergroup such as quartzites and Banded Iron Formations (BIFS) [see previous posts], and encountered mines for resources such as gold, iron, and asbestos. In fact, some alluvial sources (i.e., those that have eroded out from original geological context and were redeposited elsewhere) actually occur in younger sedimentary context in dolomite regions. In both a geological sense, and historically, our observations in the field have led to a strong connection between the mines and our quest to locate new fossil localities in the dolomite formations. In learning more about mining history and practice in our study areas (focusing on lime mines, but requiring some understanding of more general issues), we believe that we will be able to refine our field methods to identify additional areas that hold strong potential to locate fossil sites. This is not a simple task, however, and will continue to be a focus of the research programme in the long term.