Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Geology Dept.


Robert A. Gastaldo


The Permian-Triassic Boundary (252.6 Ma) is an interval under intense study as changes across it represent the greatest loss of life in Earth history. Although the event is well understood and constrained in the marine realm, questions remain about extinction, climate, and environmental conditions on land. The Karoo Basin of South Africa is a focus of study due to the complete nature of its terrestrial record, specifically across this boundary.

The identification of pedogenic mud aggregates document the presence of soils with abundant clays produced in a seasonally arid environment. The occurrence of these aggregates in low-sinuosity Early Triassic fluvial samples, but not in high-sinuosity Middle Permian samples, supports the hypothesis of increasing aridity following the extinction event. Additionally, the identification of two generations of aggregates in Early Triassic channel deposits (a carbon-rich signature and a carbon-poor signature) and only one generation in paleosol deposits indicates the removal of earlier generations of paleosols from the landscape.


Permian, Triassic, fluvial, pedogenic mud aggregate

Multimedia URL

Included in

Geology Commons