Quaternary fans and colluvium as indicators of environmental change and landscape sensitivity

Abstract

Unconsolidated sediments in the humid tropics range from highly altered weathering products involved in minimum, low energy transport, to coarse fans and landslide deposits. But most can be regarded as colluvium and alluvium showing imprints of episodic sedimentation. These deposits may span the entire Cenozoic, but 14C dating has led to a focus on Late Quaternary sediments. Many studies have indicated concentration of activity between the Last Glacial Maximum (LGM) and the early Holocene ‘pluvial’, but recent use of Optically Stimulated Luminescence (OSL) dating indicates episodic sedimentation throughout the Last Glacial Cycle in some landscapes. The low resolution of most OSL studies limits attempts to construct true event stratigraphies. But, despite this restriction, these sediments record the detailed history of landscape sensitivity to environmental change, and this history includes the effects of continuing weathering and pedogenesis. Bringing together studies of weathering, landscape sensitivity to environmental change, and source-to-sink models of sedimentation, provides a conceptual framework to understand earth surface systems within a Quaternary time frame.