Approximately 250 million years ago, the Karoo was a vast inland sea. It covered an area of around 400 000 square kilometres, becoming a gigantic swamp as the planet warmed during this period.
Reptiles and amphibians flourished in this environment, and through the epochs of almost unimaginable time this massive swampy area became the breeding ground for the early history of major groups of land vertebrates, including dinosaurs and mammals; along with a group of vertebrates known as therapsids or ‘mammal-like reptiles’ which fit into the evolutionary map of the transition of reptiles to mammals.
Walking the barren stretches of the Karoo today, it’s hard to imagine it was once an ancient lush landscape, teeming with lizards and life of all sorts and sizes. But here and there the desert offers a glimpse of the past in the eroded shapes of broken hills and layers of sediment in flat basins now surrounded by crenelated outcrops of koppies and cliffs. If you squint a little, and let the mind warp slightly, it’s not hard to conjure up muddy stretches of water, and bodies slithering and glistening in the primal sun.
Key points about this ancient world
- More than 200 million years ago, South Africa was part of the southern area of the Pangaea, which was the great single supercontinent before it split into two: the Pangaea and Gondwanaland.
- The Beaufort Group of rocks within the Karoo was already being deposited by rivers draining into a vast, but shrinking inland sea. As these rivers filled the basin with sediment they entombed the remains of land animals that lived around them.
- The Molteno and Elliot formations formed after the Beaufort sequence. The red rocks of the Elliot formation have recorded some of the earliest dinosaur communities, which are of assistance to paleontologists seeking to understand the rise of the giant sauropod dinosaurs of the Jurassic Period.
- The area is internationally noted for its record of fossil therapsids which are “mammal-like” reptiles depicting the path to mammals as they evolved from their early tetrapod forebears.
- How fossil bones are preserved provides rich insight. Changes in preservation style between skeletons in the latest Permian Period to those in the earliest Triassic Period can be attributed to changes in climate. The region at this time was developing from seasonally dry floodplains with high water tables to predominantly dry floodplains.
- The abundance of fossil tetrapods found in Karoo rocks is of great value in the reconstruction of global patterns of diversity. They have been used to divide the rock succession into fossil zones, called biozones. This has enabled the biozones to be correlated with equivalent sequences elsewhere in the world. A comprehensive database of all the Karoo fossil vertebrate collections in South Africa has been built – the first database of Permian-Jurassic continental vertebrates – an invaluable tool available to scientists globally.
- The Karoo holds evidence of two great extinction events at this time, the end-Permian (252 million years ago) and the end-Triassic (200 million years ago). The end-Permian mass extinction, the greatest, was responsible for the elimination of 90% of species living in the sea, and 70% of species living on land. This extinction lasted for approximately 300,000 years, terminating at the Permian-Triassic boundary. It was followed by a lesser extinction pulse approximately 160,000 years later in the Early Triassic.
- Then around 182 million years ago, during the early part of the Jurassic Period, enormous amounts of lava flowed across the landscape of the area that we now call the Karoo, transforming the environment into a land of fire. But intrepid dinosaurs and other animals managed to inhabit this region during the quieter periods between the volcanic eruptions.
- Ultimately, there were several major extinctions of species, especially in the oceans, caused mostly by gases emitted from immense lava flows that poured onto the land surface in South Africa. Even as it incinerated the landscape, the lava flows changed the chemistry of the atmosphere and seas. But despite the threat of devastation from further eruptions, some ecosystems managed to function and survive.
- Today, more than 30,000 fossils of vertebrate animals from the Karoo reside in museum collections across the world.
But for all the questions we have answered about this lengthy past, there are still many more. Were the early mammal ancestors of the Karoo warm-blooded? What can the Karoo tell us about the survival modes of ecosystems in this distant and tumultuous past? What can we learn about the intriguing mystery of evolution?
These are deep questions to ponder in the great silence of Karoo, under the endless stars and with a mug of cheery hot coffee in your hand when you join us on one of our extremely popular walks and guided tours through this fascinating landscape.
Heuningland: African & Karoo tours to stir the heart and lift the soul
We are proudly South African and have a fervent love of the Great Karoo, its people and its unique vegetation and animals. We are passionate conservationists of nature and would like to share our knowledge acquired through years of travel and touring experience. We are therefore able to offer custom-designed and distinctively different tour options:
- Hiking/camping trails or guided self-driving tours through the ancient landscape of the Karoo.
- Tailor-made safaris to any destination in South Africa, Namibia, Zimbabwe, Zambia, Mozambique, and Botswana.
Find out more at: www.heuningland.com