Millions of years in the baking…
While the Park is habitat to a range of plant, animal and bird species, it was the outstanding geological features of the Park that secured its protection status at national level in September 1963. Subsequent to this the Park has further distinguished itself as the site of the oldest dinosaur embryo discovery on the planet. Scientists have put the estimated age of these fossils at 190 million years.
At around this time a vast desert was encroaching on this area from the north. Most of what is now central southern Africa had, for more than a hundred million years, been a relatively flat swampy area that had gradually grown warmer and drier. Now, windblown sand was accumulating, diminishing the wetter areas where floodplains of former meandering rivers remained exposed. So it was in these ancient muddy watercourses and floodplains that our local dinosaurs lived out their declining age in our area.
Over several million years, layer upon layer of sand built up over a vast area stretching south and far north of this area in the proportions of the Sahara. The sandstone cliffs that we see at The Golden Gate Highlands National Park and all around the eastern Free State were built by this sand, blown in over vast distances, over an inconceivable time frame. But that is only half the story. Another event was about to unfold that dramatically changed the direction of the geological formation of most of southern Africa.
Scientists tell us that here in southern Africa we live on top of a “superswell”. This is thought to be caused by something called a mantle plume, which is a vast amount of hot molten material that is rising up steadily deep beneath the earth’s crust, pushing the crust upwards. The hypothesis is that this has caused the phenomenally high altitude of the central southern African subcontinent.
Scientists believe that it is probable that an earlier superswell resulted in the catastrophic event that struck 180 million years ago. At this time southern Africa lay at the centre of the super-continent Gondwana. Severe pressure beneath the central region of this vast mass of land resulted in parts of it breaking off and moving away to form other continents. At the same time a dramatic break in the earth’s crust formed on the eastern side of southern Africa, from in the region of what is now the Eastern Cape through KwaZulu Natal and further north. Volcanic material spewed east and west and lava spread across most of what is now the South African interior. The region took on an east to west tilt resulting in all the water drainage from our entire central regions flowing west to the Atlantic.
Southern Africa has been in a state of perpetual erosion since this event. The molten lava, once cooled and becoming basalt rock, had completely covered the desert of sand, in some places to over 1 600 meters deep. The newly formed Indian Ocean brought warm moist air into the eastern regions and a wet climate started. The weathering of the rock has continued for the most part of 180 million years, stripping most of the basalt away in some regions, with much of it still standing in others. And the great legacy of these events is the mighty basalt range of the Maloti Drakensberg, and our very own Clarens Sandstone Formations, nowhere more spectacular than at Golden Gate.
Without the volcanic lava our sandstone cliffs would never have formed as they have. Several forces came into play. The compressing weight of the lava and its heat stabilised and strengthened the sandstone layer directly under it. Some of the lava never escaped into the atmosphere but instead penetrated into horizontal sills and vertical dykes within the sandstone. Most of the sandstone cliffs are still topped with a layer of grass covered basalt protecting it from erosion from above. The exposed walls of the sandstone cliffs erode at a rate dependent on the lava effect. Just below the cap of basalt there is usually a section of sandstone that has been strengthened through its initial proximity with the lava, where the heat has brought about chemical changes to the particles causing a cementing effect. Below this the weaker sandstone often recedes, creating an overhang.
The characteristic dark streaks down the face of the pale sandstone walls are also due to the basalt caps. Minerals from the molten magma delivered from deep within the core of the earth, then trapped in basalt rock, gradually seep from the rock and find their way down sandstone walls in the manner of dripping strokes on canvas.
Like San rock art, they tell an ancient story in these high sandstone galleries, an unimpassioned testament to the herculean drama that, so long ago, shaped these golden monuments of rock.
The picture insert is taken from the Glen Reenen side of Golden Gate and features as the cover picture of the 2014 calendar produced by and sold in aid of Cluny Animal Trust. Calendars can be purchased at The Gallery, Clementines Restaurant and the Old Stone Bottle Store, in Clarens. Alternatively they can be ordered from Katherine on 0827886287, Jan on 0782462553, Helen on 0582230918 or by email to email@example.com .
Article and photograph by Mary Walker
Clarens News: September 2013
Golden Gate Highlands National Park (Activities and Tours)
Exploring the Golden Gate with Maluti Tours (Clarens News)