Remnants of Gondwanides Mountain Range Reveal Mass Extinction Secrets

“The Gondwanides not only influenced how and where rivers flowed (depositing sediment), it also had a significant effect on the climate, and thus the ancient fauna of the Karoo Basin,” says Viglietti.

Large mountain ranges put a lot of weight on the Earth’s crust, creating a depression in the crust. This can be described by using the analogy of a person standing on the edge of a diving board. The person represents the “load” (or weight) of the mountain while the diving board is the earth’s crust. The depression causes sediment to accumulate around the mountain’s base. It is in this sediment, where rocks and fossils are preserved.

As mountains erode, they put less weight on the Earth’s crust, and the depression decreases, just like the diving board would react to the diver jumping off it. This was the effect that the Gondwanides had on the sedimentation in the Karoo Basin over a 100 Million years. The traces of this tectonic dance are preserved by periods of deposition and non-deposition.

The sediments during this loading event also provided evidence of climatic changes as well as evidence of a previously overlooked “faunal turnover”, that points to the start of the end Permian mass extinction event.

“Within the last million years before this major biotic crisis, the animals had already started to react. I interpret this faunal change as resulting from climatic effects relating to the end-Permian mass extinction event – only occurring much earlier than previously identified,” says Viglietti.

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