Earth’s biodiversity has changed over the millions of years recorded in geologic time. The plants and animals that are part of today’s landscape have not been here forever, and are witness to how the planet recovered following a catastrophic mass extinction some 65.6 million years ago with the demise of reptile dominance. The Cretaceous Mass Extinction Event is not the only time in Earth history when biodiversity loss was unimaginably large. It may be hard to believe, but the loss of biodiversity during the End-Permian Mass Extinction, 252.2 million years ago resulted in the extinction of at least 90% of all known marine animals, and up to 70% of plants and animals living on land. One of the best exposures to study the catastrophe that occurred on land is the Karoo Basin in South Africa.
The Department of Geology is studying the circumstances involved with this extinction event, and active research has occurred over the past decade with South African, Canadian, Dutch, and U.S. colleagues and students. In 2007, a Colby Geomajor, Sam Reid, stumbled across the first Late Permian-aged, forest floor litter horizon preserved above a fossil soil horizon. Not only are the leaves of the trees and groundcover preserved in this litter, but so are insects and other invertebrates. This horizon occurs below the presently accepted level where the mass extinction is believed to occur in the Karoo Basin geology. The unique aspect of this fossil assemblage is its method of preservation within a volcanic ash, which allows for the radiometric dating of the landscape.
This year, faculty and students will return to this area to resample the fossil horizon and the sediments preserving it, and expand their studies to other sites in the vicinity of Lootsberg Pass, Eastern Cape Province. The research team will spend 16 days in the field, undertaking a high resolution analysis of the rocks, fossil, and lateral relationships of units. Samples will be returned to laboratories in South Africa, Canada, and the U.S. for analyses upon the team’s return. The rocks exposed at the study sites play a key role in our understanding of how the plants and animals on land responded to what Doug Erwin of the Smithsonian calls the “Mother of All Extinctions.” We’ll be updating our discoveries and insights on our blog; stay tuned to learn more.