120 Million Years of Gondwana's Past Held in South Africa's Karoo Rocks

A new review led by Professor Emese Bordy at the University of Cape Town brings together more than two decades of research on the Karoo Supergroup, a rock sequence in southern Africa recording about 120 million years of Earth history, from the Late Carboniferous to the Early Jurassic. Published as an open-access article in the South African Journal of Geology, it synthesizes advances in sedimentology, stratigraphy, paleontology and basin analysis since 2000.

The Karoo preserves evidence of climate change, volcanic and tectonic activity, ecosystem turnover and several major extinction events across Gondwana, the supercontinent that once united Africa, South America, Antarctica, India, Madagascar and Australia. A key finding of the review is that the Karoo's climate history was more complex than earlier interpretations suggested: rather than a simple, gradual shift toward drier conditions, research over the past 25 years points to nonlinear climatic changes, especially in the younger parts of the Karoo rock sequence.

Advances in high-resolution imaging and evolutionary analysis have led to new fossil discoveries and refined fossil-based correlations across Gondwana, improving understanding of ecosystem change during major biological crises, including the end-Capitanian, end-Permian, end-Triassic and end-Pliensbachian extinction events. The new evidence also points to ecosystem resilience during periods of profound environmental change.

Researchers have separately improved the Karoo's chronological framework using techniques such as radioisotopic dating through detrital zircon geochronology and magnetostratigraphy, helping determine the ages of rock layers more accurately and strengthening correlations with equivalent rock records across former Gondwanan continents.

Questions that remain include exactly when and how key formation boundaries formed and how much of the basin's rock record reflects climate versus tectonic forces. The same Karoo rock layers that record Gondwana's past are also being assessed for groundwater resources, critical minerals and carbon storage potential.