Free State Geological Adventures in Pursuit of the Mundane

I have to avoid the temptation to discount the familiar.  I have lived with geology for 30 years of my life and it is part of my reality.  However I remember being enthralled by the new knowledge I had acquired when I first began this adventure as a student – suddenly the rocks on the patio took on a new significance, and I began to look at every outcrop I came across to try to determine the rock type and formation, and I venture that there is a new generation out there who would be very interested in the landforms and geology of what I sometimes relegate to the mundane. 

And so, without further ado, let us begin our adventures.

In search of new horizons and some space after a hectic year, I headed the truck in the direction of the Cape without thought of an ultimate destination.  However, averse to the trials of the Eastern Cape roads I opted for the grand sweep of the Free State and the vast landscapes of the Karoo.  Which if course forces one to drive the road up van Reenen’s Pass,  delivering one onto the high plateau which makes up the great African hinterland.  There is the usual mix up with trucks and motorists as everyone jockeys their way up the great escarpment, but while I dice with trucks I always find myself reflecting on the geology during the long climb to nearly 2000 m.  For those in the know, this escarpment is a result of Gondwana disintegration , formed in the order of 120 million years ago during one of the major ructions in Earth history.  So as we climb to the summit, consider that not only are we like mere ants in the vastness of the landscape, but also mere triflings in the immense passage of time.   

Let us take a closer look at the geology.  We are driving across sediments of the Karoo Supergroup, a vast pile of rocks that preserve nearly 200 million years of Earth history, ranging from rocks of glacial origin at the base to desert conditions  at the top of the pile.  Van Reenen’s Pass of course is near the top of this vast accumulation of sediments and those lofty peaks, so often wreathed in mist, are of Clarens Formation sandstones – which are the remnants of a fossilised desert of Saharan proportions. 

 Sandstones of the Clarens Formation

Dinosaur footprints and dinosaur bones are to be found preserved in the Clarens Formation.  Capping all of this are basaltic lavas which form the high Drakensberg.  Imagine an outpouring of lava on a continental scale – a veritable flood of incandescent, all consuming, molten rock flowing across an ancient desert floor, enveloping life, plants and water in its fiery embrace.   

 Dinosaur footprints in the Clarens Formation

Perhaps the best place to view some of this geology is the Golden Gate National Park, which was exactly on my way.  In fact I chose to make it so, for I am never one to pass up on an opportunity to take the road less travelled.  Golden Gate is indeed a gem not only in terms of its scenery but also its geology and accessibility thereof.  In many ways the geology is relatively simple, but there are some wonderful examples not only of the Drakensberg basalts and Clarens Formation sandstones, but the underlying Elliot Formation.  The Elliot rocks are remnants of ancient floodplain deposits and seasonally-flooded pans.  More than this, there are spectacular examples of dolerite dykes which can be traced for kilometres across country and which were the feeder pipes for the overlying basalts.  One of these is well signposted on the roadside.  Then there are faults to be seen in the road cuttings, and for those with some time on their hands the contact between the basaltic lavas and the underlying Clarens Formation sandstones is a must see – the very point where red hot lava met the shifting sands of an ancient desert. 

So now you know – the yellowish sandstones with their black staining which you see on the climb up van Reenen’s Pass are the remnants of an ancient desert, and the dark, resistant capping the first exhalations of lava as Earth went into convulsions as Gondwana began to pull apart.  Those basalts covered nearly the whole of southern Africa and extended into other Gondwana continents which is pretty awesome to say the least.