Process implications of chenier dates in Australia

Abstract

Chenier plains record changes in the mode of coastal progradation between periods of mudflat progradation and coarse sediment deposition. There are several environmental forces responsible for these changes, and these include both intrinsic and extrinsic processes. In Australia, the causes of these changes are still not well understood. The majority of Australian chenier plain studies have been conducted within a relatively narrow spatial scope, focussing on one or two individual plains. Compiling and assessing times of chenier ridge building across multiple sites can provide a broader-scale perspective on chenier plain development trends, potentially revealing broader scale morphodynamic relationships that may exist across a large region. One such assessment was undertaken by Lees and Clements (1987), and since then many more chenier ridge ages have been obtained. Our understanding of late Holocene environmental changes and computation methods have since improved. A new statistical assessment of Australian chenier ridge ages revealed periods of simultaneous chenier ridge building across multiple northern and southern Australian coastal plains between 2400 and 1300 yr BP, and possibly again in the last 1000 years. Previously such results were explained in terms of Holocene climate changes, however the spatial separation between sites in this new assessment suggests that other broad-scale extrinsic processes may provide a better explanation. A possible candidate for such a process is late Holocene sea level changes. • We conducted a statistical analysis of chenier ridge ages from 23 Australian sites. • Our results indicate that ridge formation was not affected solely by local events. • A common phase of chenier ridge formation occurred from 2400 to 1300 yr BP. • Further widespread ridge formation has occurred in the last 1000 years. • We suggest that sea level changes may have played a role in chenier ridge formation.