Theoretical constraints and chronological evidence of Holocene coastal development in central and southern New South Wales, Australia

Abstract

Holocene coastal evolution in New South Wales has been interpreted essentially as the unfolding of the impact of marine transgression. Sea level on this coast supposedly reached its present height at 6–6.5 ka, and varied < 1 m since then. The early Holocene rise of the sea has been considered the key factor (“forcing function”) in dune migration, coastal sand barrier development, and the evolution of estuaries. Episodic storminess during the late Holocene has been seen as an important, though secondary, factor in beach erosion and dune mobilisation. An alternate interpretation presented here challenges the concept of the marine transgression as the primary “forcing function”. It (a) attributes early Holocene dune mobilisation to climate rather than the rising sea; (b) shows that the sea reached its present level by 7 ka and rose to at least + 2 m until ∼ 1.5 ka; (c) links late Holocene dune activity to local disruption of vegetation rather than to regional episodic storminess; (d) demonstrates a fall of 2°C in sea surface temperature after 3 ka that coincides with the onset of barrier erosion; (e) recognises the imprint of at least three tsunamis in the coastal sedimentary record.