Thomas, Michael F., Nott, Jonathan, and Price, David M. (2001) Late Quaternary stream sedimentation in the humid tropics: a review with new data from NE Queensland, Australia. Geomorphology, 39 (1-2). pp. 53-68.

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Abstract

There is now a wide agreement that temperature depression in the humid tropics during the Last Glacial Maximum (LGM) was at least 5°C. Most estimates of precipitation reduction at the LGM range from 25–30% to 50–65%, based on proxy data, but the recent CCM1 model envisages only around 12%. Dates obtained from river sediments indicate major changes to fluvial activity in the late Quaternary. Isotope Zone 3 sediments (58–28 ka BP) are widespread and possibly indicate cooler conditions. Post-28 ka BP, and certainly post-21 ka BP, river regimes altered radically towards fan building, braiding or major reduction in all activity. This paper reports on fan formation in NE Queensland between 26 and 14 ka BP and reviews evidence for comparable changes in humid tropical areas of S America, W Africa and SE Asia, including records of Holocene sedimentation. Within a global rhythm of major changes to river regimes in the humid tropics during the late Quaternary, it is now possible to detect regional variations in stream response to climatic change. At the LGM, reductions in stream power may have led to fan formation in NE Queensland, while vegetation changes may have contributed to increased sediment loads and braiding in some forest marginal areas. But, in W Africa, greater aridity may have been responsible for enfeebled streams leaving few records.

Channel cutting, then deposition of coarse sediment in braided rivers marked the transition to the early Holocene in W Africa, and fans became entrenched in NE Queensland. This regime persisted until forest recovery was complete by 9.5–8.5 ka BP, when widespread overbank deposition occurred and a change towards meandering channels took place widely across the humid tropical zone, followed by several cut-and-fill episodes in the middle and late Holocene.

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