The layers upon layers of rock tucked away among the valleys and mountain passes of the Maloti Drakensberg reveal treasures attesting to the formation of this dramatic region over millions of years. Peeking out of the pages of the region's geological history are dinosaurs with their eggs, the very first mammals and the ancient vegetation they browsed amongst, perpetually frozen into the rock. Each layer tells a silent story of the life that once thrived in these mountains.
As you travel up the mountain passes in this dramatic landscape, rising from the river valleys to the high peaks, you pass through a succession of very distinct layers in the rock. The impressive Drakensberg escarpment and the deep gorges of Lesotho expose these rock layers. In so doing they reveal fossils of the numerous plants, reptiles (including a number of dinosaur species) and mammals that lived here, and the traces that they left behind.
Why was this region so full of life?
To help us understand what this region was like so long ago, geologists encourage us to look for similar landscapes in our present world. The eastern part of present-day southern Africa was once largely covered by giant marshes. Sediments settled there over many millions of years, forming the rocks of the Beaufort Group.
The continents then were not separate as they are now, but still joined together as a vast landmass called Gondwanaland. At that time the area where the Maloti Drakensberg Mountains now stand was very far from the sea. This area would have been very dry had it not been for the presence of huge snow-covered mountains in the south and east of Gondwanaland.
The melt-water from these mountains fed the huge inland marshes, sustaining plant and animal life over a period of approximately 60 million years. The fossil evidence of this is abundant. There are numerous places where dinosaurs and other animals walked across mudflats and left their footprints. Where marshes dried up, as they did from time to time, the remains of literally thousands of creatures were buried in the mud and turned into the fossils that we now discover in the mudstones.
What fossils can be seen?
The fossils of two reptiles, Dicynodont and Lystrosaurus, occur repeatedly in the Beaufort rocks. Their presence in these sediments tells of widespread marshy conditions. Trirachodon, a mammal-like reptile, survived harsh conditions by burrowing. The remains of these burrows were preserved in the red rocks of the upper Beaufort Group. Above this, in the Molteno Formation, fossilized ferns are found.
Around 200 million years ago the water supply from the mountains diminished and the region became far less hospitable. Silt was still carried down the rivers into the marshes, but there was much less water – resulting in the red rocks of the Elliot Formation. As the climate became drier still, the whole area was covered by sand dunes, still visible today in the yellow sandstone of the Clarens Formation. The fossil record shows, however, that many animals still inhabited the region, including two dinosaurs, Massospondylus and Lesothosaurus.
Fossils of Massospondylus have been found throughout the region. This was a bird-like reptile approximately six metres long which lived near water and laid eggs in the sand – much as crocodiles do today. One of the most dramatic fossil finds was a cluster of six eggs found in the Golden Gate Highlands National Park by Professor James Kitching in 1978. Just as the Massospondylus babies were about to hatch they must have been buried by a sandstorm. They are believed to be the oldest known fossilized embryos in the world.
Lesothosaurus, a small meat-eating dinosaur, was better adapted to this desert. Its fossilized remains are known mostly from Lesotho. Also living in the region throughout this period was a shrew-like creature, Megazostrodon, considered one of the earliest mammals. Its burrows and fossilized remains are found occasionally in the Elliot and Clarens rocks.
The formation of the Maloti and Drakensberg mountains
About 180 million years ago a new era began. The supercontinent of Gondwanaland began to break apart. Molten magma from beneath the earth’s crust erupted through fissures stretching for hundreds of kilometres across southern Africa. These eruptions continued intermittently over 45 million years, layer upon layer of liquid basalt oozing out and covering the surrounding earth. The eruptions ended 135 million years ago, leaving a layer of basalt up to 3 km thick covering much of what is now southern Africa. After the weathering which has taken place through all the millenia since then, the thickest layers remain now as the high mountain land of Lesotho.
In places the magma forced its way through cracks and between layers of the sedimentary rock, but solidified before it reached the surface. These vertical and horizontal intrusions of hard dolerite rock are known as dykes and sills. Some very good examples can be seen in the Impendle area of KwaZulu-Natal, and in the Golden Gate area, where the dolerite has been exposed by the weathering of the surrounding rock. It is interesting that the Lets’eng la Terai diamond pipe erupted only about 75 million years ago, thus indicating the continuation of intermittent volcanic activity. By 135 million years ago, due to plate tectonics and continental drift, Antarctica and India had split from Africa. A very high escarpment was formed where the African coastline is today. Ever since then the escarpment has been weathered by the relentless effects of sun, rain and snow, which have eroded it back to where the Drakensberg escarpment is now, far inland. This process continues to this day, causing the edge of the escarpment to recede about 3 cm every 100 years. The same weathering forces continue to carve the myriad valleys of Lesotho ever deeper into the rock.