Imagine piecing together a puzzle that is 3, 2 billion years old. That’s the essence of detailed geological mapping being done in the Barberton Greenstone Belt by two students from the Freie Universität in Berlin, Germany. A geological map shows the distribution of different rocks over an area. The current focus is on the Saddleback syncline next to the Bulembu and Shiyalongubu Roads and in the southern area of Mountainlands Nature Reserve.
A syncline is like a layered cake that has folded back on itself so that the original horizontal layers are now curved. This specific syncline forms part of the Moodies Group of rocks dating back 3,2 billion years and contains, among others, ancient ocean floor sediments and the oldest known record of tides. Meike Gröschke is mapping the outer, southern limb of the syncline and Jonathan Engelhardt is working on the central hinge. It has previously been mapped on a 1:50 000 scale, but the students are now doing more detailed 1:2000 scale mapping. The new details will be used, among others, to establish the rate of sediment deposition and may therefore even be used to declare certain structures as seasonal. Eventually, their work will contribute to a better understanding of the geological processes of the young Earth.
Field exploration mapping is an invaluable technique and good practice for the students. “We have now spent more than three weeks mapping and also went on excursions with some of the numerous scientists that were here. We have also collected rock samples and when we return to Germany we will both analyze them and continue creating the detailed map,” says Jonathan who is doing his Masters Degree on the Moodies Group lava and ash layers. He hopes to be able to determine the age of the Basalt lavas that he is currently collecting on an outcrop that is the only igneous (formed through lava or magma) rock in a 35km thick formation of sediments. “In my opinion, the pillow lavas on this ridge could have been delivered through a massive volcanic eruption and now just a thin layer is all that is left,’’ says Jonathan.
Jonathan Engelhardt of Freie Universität in Berlin, investigating pillow lavas on the Saddleback syncline.
Prof. Christoph Heubeck, under whom they study, has already done detailed mapping of most of the syncline, and their information will be added onto his. “Mapping is just part of our training as geologists,” adds Jonathan whilst he makes notes on several aerial photographs that he takes with him into the mountains everyday. The data that he collects is again fed into a Geographical Information Systems programme with which the university is compiling the map.
Meike’s exercise is to search for environmental information about the oldest, large scale ecosystem that existed on earth and consists of fossilized, tidal microbial mats. She is trying to establish if these microbial mats lived in marine shallow waters, beaches, river beds or in all of these environments. She will relate sedimentary structures and those of the biomats to modern structures and try to find analogies between known modern microbial organisms and the ancient ones she mapped, sampled and described.
Through the work of Prof. Heubeck and his students they have already discovered pillow lavas and microbial mats that are exposed for some 11km’s in Mountainlands Nature Reserve. These mats contain some of the earliest known life forms on earth and both the mats and pillow lavas were previously thought to only occur further south towards the Swaziland border.
“What is great about geology is the variety in the work and the different scales that can range from billions of years to seasonal and from kilometers to micrometers. Working in the Barberton Mountains is a big honor for me. The greenstone belts are rare and the Barberton one provides the best preserved archive of the early earth worldwide. And who wouldn’t like to spend his days hiking and climbing between groups of wild zebras, wildebeest and baboons in this beautiful landscape?” says Jonathan.
“Thankfully a lot of people in and around Barberton help us to realize our project, because they know that the area’s geology is one of several awesome natural attractions of the area. Helpful and friendly people let us feel very comfortable here, which is the base of an exquisite experience and memorable work in every case,” concludes Meike.
