A Holocene record of coastal landscape dynamics in the eastern Kimberley region, Australia

Abstract

A 6-m-long sediment core from the King River region of north-west Australia has been analysed using sedimentological and palynological techniques. The core spans most parts of the Holocene and contains a detailed record of early to mid-Holocene landscape development. In the early Holocene an intertidal environment supported a diverse and probably extensive mangrove forest. Intensified fluvial activity, high mangrove biodiversity and the proximity of freshwater swamp vegetation reflect enhanced summer monsoon rainfall. From 7.4k cal a BP onwards, the mangrove forest starts to contract reaching minimum (and probably present-day) extent by 6.5k cal a BP. Late Holocene aridification led to shifts in mangrove composition, the expansion of hypersaline flats and the transition of freshwater swamps to intermittent wetlands. In addition, fire potentially played an increasing role in controlling ecosystem composition, in particular in the savanna/woodland vegetation. This record is the first of its kind from coastal north-west Australia and demonstrates that sea-level and climatic fluctuations, in addition to local geomorphological settings, are major controllers of landscape development. Although the general pattern of change is similar to other sites in tropical Australia, detailed analysis shows that the timing and character of vegetation shifts are considerably different.