Re-examination of Changes in Fluvial Stacking Pattern Across the P-t Boundary in the Central Transantarctic Mountains, Antarctica

Abstract

A change in fluvial style and a change in the stacking pattern of fluvial channel sandstone bodies occur across the Buckley‒Fremouw formational contact in the central Transantarctic Mountains in Antarctica. Strata in the Buckley Formation are characterized by thick floodplain deposits in the Middle to Upper Permian Buckley Formation; whereas, stacked interconnected sandstone bodies occur in the Triassic Fremouw Formation (Barrett et al., 1986; Isbell & Macdonald, 1991a, 1991b; Collinson et al., 1994; Isbell et al., 1997; 2005). Such changes in fluvial stacking patterns have been attributed to changes in the creation of accommodation within basins due to changes in relative sea level, changes in accommodation due to tectonism, and changes in sediment flux associated with loss of vegetation and increased erosion rates following the end-Permian mass extinction event. To explain the changes in the Buckley-Fremouw Formation in Antarctica, Isbell & Macdonald (1991a, 1991b) and Isbell et al. (1997) argued for changing tectonic conditions in the basin while Retallack et al. (2006) suggested the changes were associated with the P‒T mass extinction event causing the loss of peat forming plants. This study found that the change in the accommodation across the PTB was a result of tectonism based on evidence of changing sandstone composition, changing paleocurrent orientations, and changing fluvial stacking patterns between the Buckley Formation and the Fremouw Formation. This suggests differential subsidence in the Transantarctic foreland basin with an under-filled basin in the Late Permian changing to an over-filled basin in the Early Triassic.