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Prehistoric Polynesian voyaging into high latitudes with landfall in Antarctica remains a widely credited proposition. We examine it through archaeological and environmental evidence from the Subantarctic region of the southwest Pacific, focussing upon an extensive archaeological site at Sandy Bay on Enderby Island. Combining a new set of radiocarbon ages with former, older, ages we show that the site is now within the same rapid expansion phase in which South Polynesia was first colonised. Radiocarbon ages across the site indicate a single continuous settlement, probably of some decades. Consideration of limiting factors in Subantarctic settlement, including of seafaring capability and critical resources, suggests that the site was about as far south as prehistoric habitation could be sustained and was probably vacated at the onset of the Little Ice age (LIA) in the late 14th century. An absence of prehistoric remains on islands further south also suggests that Polynesian exploration reached a boundary 2000 km short of Antarctica. The southern case is discussed briefly in the wider context of Polynesian expansion. Les voyages polynésiens préhistoriques vers les hautes latitudes avec atterrissage en Antarctique restent une proposition largement reconnue. Nous l'examinons à travers des preuves archéologiques et environnementales provenant de la région subantarctique du sud‐ouest du Pacifique, en nous concentrant sur un vaste site archéologique à Sandy Bay sur l'île Enderby. En combinant un nouvel ensemble d'âges au radiocarbone avec des âges antérieurs, plus anciens, nous montrons que le site se trouve désormais dans la même phase d'expansion rapide dans laquelle la Polynésie du Sud a été colonisée pour la première fois. Les âges au radiocarbone sur l'ensemble du site indiquent un seul établissement continu, probablement de plusieurs décennies. La prise en compte des facteurs limitants du peuplement subantarctique, notamment la capacité de navigation et les ressources critiques, suggère que le site se trouvait à peu près aussi au sud que l'habitation préhistorique pouvait être soutenue et qu'il a probablement été libéré au début du Petit Âge Glaciaire (LIA) à la fin du XIVe siècle. L'absence de vestiges préhistoriques sur les îles plus au sud suggère également que l'exploration polynésienne a atteint une frontière située à 2 000 km de l'Antarctique. Le cas méridional est brièvement discuté dans le contexte plus large de l'expansion polynésienne.

ABSTRACTMining is an environmentally destructive human activity. Consequently, community expectations and legislation require minimisation of impacts and rehabilitation once mining ceases. Rehabilitation standards now include restoration of structural and functional attributes of pre-disturbed landscapes. However, insufficient baseline data before, and during, mining often makes it difficult to assess impacts and develop rehabilitation objectives. Techniques that retrospectively document the pre-impact condition and environmental history of wetlands affected by mines can provide this information. We demonstrate how this can be achieved using data from palaeoecology and remote sensing, to understand mine impact on Fishermans Wetland, North Stradbroke Island (Minjerribah), by inferring its environmental history from formation to present. Fishermans Wetland is a small, clear, open water, wetland with extensive macrophyte growth. A lack of information about the wetland’s pre-mine condition created uncertainty about the effects of upstream sand mining. Contrary to local community concerns that Fishermans Wetland was ancient and hydrologically modified by mining, it only formed in the 1950s. Moreover, changes to site hydrology predated mining. Consequently, ongoing supplementation of water is unnecessary for maintaining the wetland’s ecological character. Similar techniques could be used elsewhere where mine impacts are poorly understood or contested.

ABSTRACTTree-ring series offer considerable potential for the development of environment-sensitive proxy records. However, with traditional increment cores, only small amounts of wood are often available from annual tree-ring sequences. For this reason, it is important to understand the reliability (and reproducibility) of radiocarbon measurements obtained from small-sized samples. Here we report the F14C results from the Chronos 14Carbon-Cycle Facility of modern tropical Australian tree samples over a range of four graphite target sizes from the same rings. Our study shows that similar precision can be obtained from full-sized, half-sized, as well as small-sized graphite targets using standard pretreatment and analysis procedures. However, with a decline in sample size, there was an increase seen in the associated variance of the ages and the smallest target weights started showing a systematic bias. Wiggle-matching accuracy tests, comparing the Southern Hemisphere post-bomb atmospheric calibration curve to the different sample weight sequences, were all significant except for the 200 μgC graphite targets. Our results indicate that samples smaller than 350 μgC have limited accuracy and precision. Overall, reliable measurements of F14C sequences from tree-ring records across a range of sample sizes, with best results found using graphitized samples >350 μgC.

ABSTRACTWetland sediments are valuable archives of environmental change but can be challenging to date. Terrestrial macrofossils are often sparse, resulting in radiocarbon (14C) dating of less desirable organic fractions. An alternative approach for capturing changes in atmospheric 14C is the use of terrestrial microfossils. We 14C date pollen microfossils from two Australian wetland sediment sequences and compare these to ages from other sediment fractions (n = 56). For the Holocene Lake Werri Berri record, pollen 14C ages are consistent with 14C ages on bulk sediment and humic acids (n = 14), whilst Stable Polycyclic Aromatic Carbon (SPAC) 14C ages (n = 4) are significantly younger. For Welsby Lagoon, pollen concentrate 14C ages (n = 21) provide a stratigraphically coherent sequence back to 50 ka BP. 14C ages from humic acid and >100 µm fractions (n = 13) are inconsistent, and often substantially younger than pollen ages. Our comparison of Bayesian age-depth models, developed in Oxcal, Bacon and Undatable, highlight the strengths and weaknesses of the different programs for straightforward and more complex chrono-stratigraphic records. All models display broad similarities but differences in modeled age-uncertainty, particularly when age constraints are sparse. Intensive dating of wetland sequences improves the identification of outliers and generation of robust age models, regardless of program used.

ABSTRACTThe Chronos 14Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Measurements on international standards, known-age and blank samples demonstrate the facility is capable of measuring 14C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world.

Sowhile more carbon was stored in plants, it took longer forcarbon in soil to be safely buried in the lake. The key question we sought toanswer was whether carbon stored in Australia's trees,shrubs, and soils contribute to the pool of carbon storedsafely in lake sediment. [Extracted from the article]