A Record of Fluvial Response for the Australian Wet Tropics and Relationships to Regional Climate Change

Abstract:

The reconstruction of fluvial dynamics from alluvial sedimentary sequences has contributed to our understanding of the link between global Quaternary climate change and landscape response. However, the geographical bias in such studies towards middle and higher latitudes leaves a gap in our understanding of climate change and landscape evolution in the tropics. The Wet Tropics biogeographic region in the tectonically-stable northeast Australia provides an ideal setting to study the history of fluvial response: catchments are small and steep; receive high annual rainfall; and cyclones are common which collectively, promotes short catchment response times. Additionally, the region benefits from an extensive range of paleoclimate reconstructions based on pollen, coral and speleothem proxies. The aim of this field-based research is to establish the nature of the relationship between fluvial response and Quaternary climate change in the Australian Wet Tropics region. To construct a temporal record of fluvial response, forty sediment cores (4-12m in length) were extracted from floodplains and terraces in similar geomorphic settings across five catchments. The stratigraphy of each core was described and 40 samples from select cores dated using optically stimulated luminescence. This temporal record of landscape response was then compared to the regional climate record to examine the relationship between fluvial response and tropical climate change. This work provides the first systematic study of fluvial sedimentary records in the Wet Tropics and in doing so makes valuable contribution to understanding of landscape evolution in the tropics.