Browsing by Author "Mackenzie, LL"

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    Environmental context for late holocene human occupation of the South Wellesley Archipelago, Gulf of Carpentaria, northern Australia
    (Elsevier, 2015-10-22) Moss, PT; Mackenzie, LL; Ulm, S; Sloss, CR; Rosendahl, D; Petherick, LM; Steinberger, L; Wallis, LA; Heijnis, H; Petchey, F; Jacobsen, GE
    A 2400 year record of environmental change is reported from a wetland on Bentinck Island in the southern Gulf of Carpentaria, northern Australia. Three phases of wetland development are identified, with a protected coastal setting from ca. 2400 to 500 years ago, transitioning into an estuarine mangrove forest from ca. 500 years ago to the 1940s, and finally to a freshwater swamp over the past +60 years. This sequence reflects the influence of falling sea-levels, development of a coastal dune barrier system, prograding shorelines, and an extreme storm (cyclone) event. In addition, there is clear evidence of the impacts that human abandonment and resettlement have on the island's fire regimes and vegetation. A dramatic increase in burning and vegetation thickening was observed after the cessation of traditional Indigenous Kaiadilt fire management practices in the 1940s, and was then reversed when people returned to the island in the 1980s. In terms of the longer context for human occupation of the South Wellesley Archipelago, it is apparent that the mangrove phase provided a stable and productive environment that was conducive for human settlement of this region over the past 1000 years. © 2015 Published by Elsevier Ltd.
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    Geochemical investigation of the South Wellesley Island wetlands: insight into wetland development during the Holocene in tropical northern Australia
    (Sage, 2016-09-28) Mackenzie, LL; Heijnis, H; Gadd, PS; Moss, PT; Shulmeister, J
    The South Wellesley Islands in the Gulf of Carpentaria, northern Australia, were the recent focus of a palynological investigation which found vegetation change during the Holocene was driven by coastal progradation and regional climate. Here, we present new elemental data from x-ray fluorescence core scanning which provides non-destructive, continuous and high resolution analysis from three wetlands across Bentinck Island, the largest of the South Wellesley Islands. Elemental data and grain size analyses are combined with lead-210 (210Pb) and accelerator mass spectrometry (AMS) carbon-14 (14C) dates. An open coastal environment was present 1250 cal. a BP on the south east coast of Bentinck Island, with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock. Prograding shorelines, dune development and river diversion formed a series of swales parallel to the coast by ~800 cal. a BP, forming the Marralda wetlands. Wetlands developed at sites on the north and west coasts ~500 and ~450 cal. a BP, respectively. Geochemical and grain size analyses indicate that wetlands formed as accreting tidal mudflats or within inter-dune swales that intercepted groundwater draining to the coastal margins. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Elemental data provide new records of wetland development across Bentinck Island, highlighting the value of a multi-proxy approach to understanding environmental change during the Holocene in tropical northern Australia. © 2020 by SAGE Publications
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    Holocene sea-level change and coastal landscape evolution in the southern Gulf of Carpentaria, Australia
    (SAGE, 2018-09-01) Sloss, CR; Nothdurft, L; Hua, Q; O'Connor, SG; Moss, PT; Rosendahl, D; Petherick, LM; Nanson, RA; Mackenzie, LL; Sternes, A; Jacobsen, GE; Ulm, S
    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. © The Author(s) 2018
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    Holocene sea-level change and coastal landscape evolution in the southern Gulf of Carpentaria, Australia
    (International Union for Quaternary Research (INQUA), 2019-07-30) Sloss, CR; Northdurft, L; Hua, Q; O'Connor, SG; Moss, PT; Rosendahl, D; Petherick, LM; Nanson, RA; Mackenzie, LL; Sternes, A; Jacobsen, GE; Ulm, S
    A Holocene sea-level history for the southern Gulf of Carpentaria has been constructed based on a review of previously published data, combined with data collected for this study from a variety of sea-level proxies. These sea-level proxies include beach ridges, claypans, mangrove swamps, fossilized in situcoral reefs, beachrock and aeolinite deposits. Results confirm that rising sea-levels during the last Post-Glacial Marine transgression beached the Arafura Sill ca. 11,700 years ago (-53 m), resulting in a change from lacustrine to a marine environment. Sea levels continued to rise to ca. -30 m by 10,000 years ago. By 7,700 cal. yr BP sea-level reached PMSL and continued to rise an elevation of between 1.5 and 2 m above present mean sea-level by 7,000 years ago. Elevated sea levels resulted in the development of raised coral reefs, beach-rock and aeolinite deposits, and the initiation of chenier plains and beach ridges. Sea-level remained ca. +1.5 m above PMSL during the Holocene highstand, accompanied by distinct phases of beach-ridge and chenier plain development. The highstand was followed by arapid regression to within ±0.5 m of PMSL by ca. 3,500 cal. yr BP. When placed into a wider regional context results from this study show thatcoastal landscape evolution in the tropical north of Australia was not only dependenton sea-level change but also show a direct correlation with Holocene climatevariability. Specifically, the formation and preservation of beach-rock deposits,intertidal successions, beach and chenier ridge systems hold valuable sea-level and Holoceneclimate proxies that can contribute to the growing research into lowerlatitude Holocene sea-level and climate histories. ©2019 The Authors.
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    A Late Holocene record of environmental change from the east coast of New South Wales, Australia
    (International Union for Quaternary Research (INQUA), 2019-07-30) Mackenzie, LL; Fletcher, MS; Gadd, PS
    A multi-proxy palaeoenvironmental record from a lake (36° 5'37.33"S; 150° 7'26.02"E) on the east coast of Australia provides a record of coastal development and vegetation succession over the last 3,800 cal. yr BP. Lead-210 and 14C dating built a robust age-depth chronology for the 61cm long core. Pollen, charcoal and x-ray fluorescence analysis provide records of vegetation change, fire regimes and catchment dynamics during the late Holocene. This study finds that an open coastal environment dominated by Amaranthaceae and Eucalyptus was present between 3,800 and 3,000 cal. yr BP when sea level on the east coast of Australia was ~1.7-1.5m higher than present. Rainforest indicators including Cyathea, Pomaderris and Nothofagus suggest a mixed wet Sclerophyll community was present either regionally or locally. Low pollen concentration and relatively high counts of Fe, S and Ca suggest iron sulfides and shell hash accumulated in a shallow or periodically exposed basin. Microscopic charcoal counts varied between 4,000 and 3,500 cal. yr BP and may indicate an increase in regional fire events. From 3,000 cal. yr BP Casuarinaceae and Poaceae increased and aquatic types Typha and Cyperaceae first appeared in the record suggesting the falling sea level allowed a barrier dune to form and a brackish to freshwater wetland to develop. Between 3,000 and 2,000 cal. yr BP Sr and Ti counts varied significantly, suggesting terrestrial and marine sediments may have periodically washed over the barrier dune and accumulated in the wetland during a period when sea level was ~1.1m higher than present. Sclerophyll open forest dominated by Casuarinaceae expanded until 2,000 cal. yr BP and then remained constant until present. Local and regional fire indicators increased briefly at 2,000 cal. yr BP. The presence of European settlers in the region is clearly identified by the occurrence of Pinus and the significant increase in regional and local fire regimes from 1900 AD and 1920 AD respectively. This multi-proxy record from a coastal lake in eastern New South Wales identifies the impact of sea level change and coastal progradation on vegetation and fire regimes and investigates natural and anthropogenic driven environmental change during the late-Holocene.