30 m of sediments are exposed in a terrace face near the upstream end of the Rangitata Gorge, mid Canterbury, New Zealand. Two radiocarbon age determinations indIcate that lake sedimentation predominated from probably over 11 500 years ago until shortly after 7380 years ago. This was followed by a period of fluvial sedimentation derived from local tributary streams. Alluvial fan sedimentation in several South Island valleys after about 7500 years ago may have been caused by a change to cooler and increasingly stormy climatic conditions.