The listed coordinates will bring you to the western entrance of the Golden Gate Highlands National Park, which is located in the Free State. This will allow you to view the spectacular sandstone cliffs as you proceed to the Brandwag Mountain. There is also an eastern entrance to the Park on the R712.
The Brandwag Mountain is at S28 30.185 E28 36.940
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Logging Tasks:
1) What is the defining formation of the Brandwag cliffs? Answer is in the listing.
2) Describe this formation.
3) Estimate how high the Brandwag Mountain is (from road level) and give your opinion as to how thick the layers in this formation are that you see.
Optional - Take a picture of you/your team and GPS with the Brandwag Mountain visible in the background and upload this with your log (optional) .
The Golden Gate Highlands National Park covers an area of 340 km². The park's most notable features are its golden, ochre, and orange-hued deeply eroded sandstone cliffs and outcrops, especially the Brandwag rock. Another feature of the area is the numerous caves and shelters displaying San rock paintings. Wildlife featured at the park includes mongoose, eland, zebra, and over 100 bird species. It is the Free State's only national park, and is more famous for the beauty of its landscape than for its wildlife. Numerous paleontology finds have been made in the park including dinosaur eggs and skeletons.
"Golden Gate" refers to the sandstone cliffs that are found on either side of the valley. In 1875 J.N.R. van Reenen named the location "Golden Gate" when he saw the last rays of the setting sun fall on the cliffs.
The park is situated in the Rooiberge of the eastern Free State, in the foothills of the Maluti Mountains. The Caledon River forms the southern boundary of the park as well as the border between the Free State and Lesotho. The highest peak in the park is Ribbokkop at 2,829 m.
Geology
The geology of the park provides very visual "textbook" examples of Southern Africa’s geological history. The sandstone formations in the park form the upper part of the Karoo Supergroup. These formations were deposited during a period of aeolian deposition towards the end of the Triassic Period. At the time of deposition the climate of the area the park covers was becoming progressively drier until arid desert conditions set in, resulting in a land of dunes and sandy desert, with occasional scattered oases. The deposition of the sandstones ended when lava flowed out over the desert 190 million years ago.
The following sequence of geological formations are visible in the park (starting from the top):
1) The Drakensberg formation comprises the basaltic lava that flowed over the desert. It forms the mountain summits in the park. On Ribbokkop it is 600 meters thick.
2) Just below the basaltic lava is a thin layer of quartzite, which is formed from heat and pressure of the molten lava that ‘cooked’ the sandstone layer underneath it and turned it into quartzite—a metamorphic rock. The sand grains in the quartzite have melted together making the rock much tougher than normal sandstone.
3) The Clarens Formation is buff coloured, fine grained and well-sorted aeolian sandstone and is the defining formation. These were deposited about 200 million years ago.
Almost dissecting the Clarens Formation is a layer of Calcified Sandstone (probably not visible to the untrained eye), which formed over the years, of water moving through the sandstone which caused a buildup of calcium carbonate in some layers. The calcium carbonate acts as cement and holds the rock particles together making the rock harder.
4) The Elliot Formation is a geological formation dating to roughly between 210 to 190 million years ago and covering the Norian to Sinemurian stages. The Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone, sandstone, and red mudstone. Fossils of the prosauropod dinosaur Massospondylus have been recovered from the upper Elliot Formation. The Elliot Formation is the red mudstone one sees.
5) The Molteno Formation is a palaeontological formation located in South Africa. It dates to the Upper Triassic period. The Molteno formation was deposited on tropical, well-vegetated, braided river flood plains and wetlands, as revealed by an enormous wealth of plant fossils.
Then there are the Karoo dolerite dykes and sills that cut the sandstone formations, which have in places baked and hardened the sandstone. A good example of this is Brandwag buttress that is 'backed' by a thick dolerite dyke.
And those black marks? All around the park you can see black stripes on the rock, even long after it has rained. These are areas where water seeps out of the rocks. Minerals from the top basalt layer (manganese dioxide) are carried in the water and these stain the rocks black. The water enables organisms like algae and moss to live on the rock as well.
Reference: Wikipedia
Geological Journeys - Nick Norman & Gavin Whitfield
SanParks Geology Golden Gate Highlands