VARIABILITY IN THE LATE PERMIAN LANDSCAPE OF THE UPPER BALFOUR FORMATION (BEAUFORT GROUP STRATA, KAROO BASIN, SOUTH AFRICA)

The End-Permian mass extinction is considered to represent the most severe ecological upheaval in the history of life. Compared to the well-studied marine record, the terrestrial expression of this extinction is poorly understood. Traditionally, it has been equated with the contact between the Daptocephalus and overlying LystosaurusAssemblage Zones in the Karoo Basin, South Africa. A recent age constraint shows that this faunal turnover, in the Elandsberg and Palingkloof Members of the uppermost Balfour Formation (Beaufort Group), predates the marine extinction. Nevertheless, many still consider this biozone transition to record phases of extinction, based on biostratigraphic data.

An accurate lithostratigraphic framework is essential for the development of any detailed, regional biostratigraphic database used to re-construct palaeobiological diversity models. This task is more difficult in terrestrial settings where landscape aggradation and degradation is the norm. To date, correlation between the isolated and widely distributed Changhsingian boundary sections in the Karoo are based on the purported presence of a unique boundary facies, ostensibly present at each section. Yet, the correlative utility of such "golden spike" horizons also has been called into question by assessments of facies relationships in the upper Balfour Formation where there is significant lateral lithofacies variation. Hence, it is impossible to accurately correlate between outcrops within a single locality without identifying datums and tracing their bounding surfaces in the field.

To determine whether similar lateral variation occurs on larger spatial scales, we have expanded an established lithostratigraphic framework from a single locality to an area spanning ~10 km, including a number of widely spaced measured sections. Provisional results show that current models underestimate the nature of the transitional Late Permian landscape, resulting in the conclusion that the uppermost Balfour Formation represents a laterally heterogenous landscape that preserves a variety of depositional sub-environments. This lateral variability necessitates a review of existing stratigraphic models and, by inference, also palaeobiological models for this interval.