19A 2,400 year record of environmental change is reported from a wetland on Bentinck 20 Island in the southern Gulf of Carpentaria, northern Australia. Three phases of wetland 21 development are identified, with a protected coastal setting from ca 2,400 to 500 years 22 ago, transitioning into an estuarine mangrove forest from ca. 500 years ago to the 1940s 23 and finally to a freshwater swamp over the last +60 years. This sequence reflects the 24 influence of falling sea-levels, development of a coastal dune barrier system, prograding 25 shorelines and an extreme storm (cyclone) event. In addition, there is clear evidence of 26 1 the impacts that human abandonment and resettlement have on the island's fire regimes 1 and vegetation. A dramatic increase in burning and vegetation thickening was observed 2 after the cessation of traditional Indigenous Kaiadilt fire management practices in the 3 1940s, and was then reversed when people returned to the island. In terms of the longer 4 context for human occupation of the southern Wellesley Archipelago it is apparent that 5 the mangrove phase provided a stable and productive environment that was conducive 6 for human settlement of this region over the last 1,000 years. 7 8

A revised Holocene sea-level history for the southern Gulf of Carpentaria is presented based on new data from the South Wellesley Archipelago and age recalibration of previous research. Results confirm that rising sea levels during the most recent post-glacial marine transgression breached the Arafura Sill ca. 11,700 cal. yr BP. Sea levels continued to rise to ca. -30 m by 10,000 cal. yr BP, leading to full marine conditions. By 7700 cal. yr BP, sea-level reached present mean sea-level (PMSL) and continued to rise to an elevation of between 1.5 m and 2 m above PMSL. Sea level remained ca. + 1.5 between 7000 and 4000 cal. yr BP, followed by rapid regression to within ± 0.5 m of PMSL by ca. 3500 cal. yr BP. When placed into a wider regional context results from this study show that coastal landscape evolution in the tropical north of Australia was not only dependent on sea-level change but also show a direct correlation with Holocene climate variability. Specifically, the formation and preservation of beach-rock deposits, intertidal successions, beach and chenier ridge systems hold valuable sea-level and Holocene climate proxies that can contribute to the growing research into lower latitude Holocene sea-level and climate histories.

a b s t r a c tIn coastal areas of the globe, open shell matrix sites are commonly used to establish regional chronologies of human occupation and identify patterns of cultural change, particularly for the Holocene, postsea-level stabilisation period. Despite this, many basic sedimentary analyses that are routinely applied to rockshelter deposits (e.g. geophysical characterisation, particle size etc) are rarely applied to these sites. Magnetic susceptibility, occasionally used in rockshelters, has never been used to investigate shell matrix sites in Australia, despite several international studies identifying its efficacy for other types of open sites. This paper reports a pilot project applying a range of conventional sedimentary and archaeological analyses, as well as magnetic susceptibility at three anthropogenic shell mounds on Mornington Island, Gulf of Carpentaria, Australia. Results are compared to, firstly, assess site integrity and, secondly, to ascertain whether magnetic signatures are related to cultural or natural site formation processes. The results establish that the mounds were repeatedly visited, despite the archaeological evidence, including radiocarbon ages, suggesting effectively 'instantaneous' deposition. This has important implications for studies of other shell mounds where the limitations of radiocarbon dating precision may also mask multiple deposition events.

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