Climate as a Stratigraphic Tool for Basin Margin Deposition in Intracontinental Basins

Amy Gough, Stuart M Clarke, Philip C Richards

In intracontinental basins stratigraphic packages are not as predictable as those deposited in marine settings, namely due to a lack over an overriding control on deposition. Deposition in intracontinental basins is controlled by tectonics, climatic variations, and sediment supply. Complexity is added as deposition is affected by both autocyclic localised variations (e.g., lobe switching) and larger scale allocyclic variations such as climate forcing, leading to rapid changes in depositional environment. This research considers a basin margin depositional system predominately controlled by climatic variations and presents a model to highlight how the individual depositional environments respond to wetting and drying events. Alluvial fan related environments (e.g., talus cone, debris flows, sheetfloods) prograde into the basin during increased humidity, whereas increased aridity leads to retrogradation. Fluvial environments (e.g., fluvial, palaeosol) react in the same manner, prograding during humid climates and retrograding during increasing aridity. Lacustrine environments expand in the basin centre during increased humidity, and desiccate and shrink during arid climates. Finally, aeolian environments decrease in magnitude and migration is reduced during increased humidity but grow in extent during increased aridity. A case study from the end-Carboniferous to Permian Cutler Group (undifferentiated) in the western U.S.A. is used to build the model as it comprises an exceptionally well-preserved basin margin system.