The history of phytolith research in Australasian archaeology and palaeoecology

Although phytolith research has come of age in archaeology and palaeoecology internationally, it has remained relatively marginalised from mainstream practice in Australasia. The region’s initial isolation from international scientific communities and uniqueness of its vegetation communities, has led to an exclusive set of challenges and interruptions in phytolith research. Examining a history of Australasian phytolith research presents the opportunity to recognise developments that have made phytoliths a powerful tool in reconstructing past environments and human uses of plants. Phytolith research arrived early in Australia (1903), after a convoluted journey from Germany (1835–1895) and Europe (1895–1943), but phytoliths were initially misidentified as sponge spicules (1931–1959). Formal understanding of phytoliths and their applications began in Australasia during the late 1950s, continuing throughout the 1960s and 1970s (1959–1980). After a brief hiatus, the modern period of phytolith analyses in Australasian archaeological and palaeoenvironmental research began in the 1980s (1984–1992), focusing on investigating the deep past. Advancements continued into the 1990s and early 2000s. Wallis and Hart declared in 2003 that Australian phytolith research had finally come of age, but more a fitting description would be that it had peaked. Since then phytolith research in Australasia slowed down considerably (2005-present). Local phytolith reference collections for Australasian flora, critical for identifying ancient phytoliths, are essentially no longer produced

Forty-thousand years of maritime subsistence near a changing shoreline on Alor Island (Indonesia)

We report archaeological findings from a significant new cave site on Alor Island, Indonesia, with an in situ basal date of 40,208-38,454 cal BP. Twenty thousand years older than the earliest Pleistocene site previously known from this island, Makpan retains dense midden deposits of marine shell, fish bone, urchin and crab remains, but few terrestrial species; demonstrating that protein requirements over this time were met almost exclusively from the sea. The dates for initial occupation at Makpan indicate that once Homo sapiens moved into southern Wallacea, settlement of the larger islands in the archipelago occurred rapidly. However, the Makpan sequence also suggests that the use of the cave following initial human arrival was sporadic prior to the terminal Pleistocene about 14,000 years ago, when occupation became intensive, culminating in the formation of a midden. Like the coastal sites on the larger neighbouring island of Timor, the Makpan assemblage shows that maritime technology in the Pleistocene was highly developed in this region. The Makpan assemblage also contains a range of distinctive personal ornaments made on Nautilus shell, which are shared with sites located on Timor and Kisar supporting connectivity between islands from at least the terminal Pleistocene. Makpan's early inhabitants responded to sea-level change by altering the way they used both the site and local resources. Marine food exploitation shows an initial emphasis on sea-urchins, followed by a subsistence switch to molluscs, barnacles, and fish in the dense middle part of the sequence, with crabs well represented in the later occupation. This new record provides further insights into early modern human movements and patterns of occupation between the islands of eastern Nusa Tenggara from ca. 40 ka.The fieldwork and dating for this project was funded by an Australian Research Council Laureate Fellowship to O’Connor (FL120100156) and analysis by the ARC Centre of Excellence for Australian Biodiversity and Heritage (CE170100015)

Luminescence Dating in Fluvial Settings: Overcoming the Challenge of Partial Bleaching

Optically stimulated luminescence (OSL) dating is a versatile technique that utilises the two most ubiquitous minerals on Earth (quartz or K-feldspar) for constraining the timing of sediment deposition. It has provided accurate ages in agreement with independent age control in many fluvial settings, but is often characterised by partial bleaching of individual grains. Partial bleaching can occur where sunlight exposure is limited and so only a portion of the grains in the sample was exposed to sunlight prior to burial, especially in sediment-laden, turbulent or deep water columns. OSL analysis on multiple grains can provide accurate ages for partially bleached sediments where the OSL signal intensity is dominated by a single brighter grain, but will overestimate the age where the OSL signal intensity is equally as bright (often typical of K-feldspar) or as dim (sometimes typical of quartz). In such settings, it is important to identify partial bleaching and the minimum dose population, preferably by analysing single grains, and applying the appropriate statistical age model to the dose population obtained for each sample. To determine accurate OSL ages using these age models, it is important to quantify the amount of scatter (or overdispersion) in the well-bleached part of the partially bleached dose distribution, which can vary between sediment samples depending upon the bedrock sources and transport histories of grains. Here, we discuss how the effects of partial bleaching can be easily identified and overcome to determine accurate ages. This discussion will therefore focus entirely on the burial dose determination for OSL dating, rather than the dose-rate, as only the burial doses are impacted by the effects of partial bleaching

Elevational Gradients in Bird Diversity in the Eastern Himalaya: An Evaluation of Distribution Patterns and Their Underlying Mechanisms

BACKGROUND: Understanding diversity patterns and the mechanisms underlying those patterns along elevational gradients is critically important for conservation efforts in montane ecosystems, especially those that are biodiversity hotspots. Despite recent advances, consensus on the underlying causes, or even the relative influence of a suite of factors on elevational diversity patterns has remained elusive. METHODS AND PRINCIPAL FINDINGS: We examined patterns of species richness, density and range size distribution of birds, and the suite of biotic and abiotic factors (primary productivity, habitat variables, climatic factors and geometric constraints) that governs diversity along a 4500-m elevational gradient in the Eastern Himalayan region, a biodiversity hotspot within the world's tallest mountains. We used point count methods for sampling birds and quadrats for estimating vegetation at 22 sites along the elevational gradient. We found that species richness increased to approximately 2000 m, then declined. We found no evidence that geometric constraints influenced this pattern, whereas actual evapotranspiration (a surrogate for primary productivity) and various habitat variables (plant species richness, shrub density and basal area of trees) accounted for most of the variation in bird species richness. We also observed that ranges of most bird species were narrow along the elevation gradient. We find little evidence to support Rapoport's rule for the birds of Sikkim region of the Himalaya. CONCLUSIONS AND SIGNIFICANCE: This study in the Eastern Himalaya indicates that species richness of birds is highest at intermediate elevations along one of the most extensive elevational gradients ever examined. Additionally, primary productivity and factors associated with habitat accounted for most of the variation in avian species richness. The diversity peak at intermediate elevations and the narrow elevational ranges of most species suggest important conservation implications: not only should mid-elevation areas be conserved, but the entire gradient requires equal conservation attention

Chronologies in context: reconciling the optical dating of quartz with its sedimentary environment

The occurrence of overdispersion (OD) in single-grain optically stimulated luminescence (OSL) equivalent dose (De) distributions is an issue affecting both natural and laboratory irradiated grains of quartz. The presence of this additional spread beyond statistical expectations is often explained as the result of factors either intrinsic or extrinsic to the grains being dated, or a combination of both. The designation of one, or both, of these factors to explain the OD is compounded by the destruction of the sedimentary context during sample preparation. With the original context destroyed, the De distribution and associated OD are disconnected from the sedimentary environment. The explanation of OD is often made using either macroscopic field observations or by comparison to previously published data. This thesis is motivated by the overarching aim to reconcile the De distribution, and the associated OD, with the sedimentary context from which the samples were collected. To address this aim, two locations – MacCauley’s Beach and Pech de l’Azé IV – were chosen as study sites. The former is a geogenic receded barrier beach deposit located near Wollongong, New South Wales, Australia, whereas the latter is a Neanderthal occupation site containing anthropogenic sediments located in the Department of the Dordogne, France. A total of 12 samples, six from each site, were collected as part of a broad aim to construct temporal frameworks and assess the site formation processes at each site. In 11 of the 12 samples the resulting De distributions were overdispersed, with OD values between 27 ± 2 and 87 ± 5%

Beta dose variability and its spatial contextualisation in samples used for optical dating: An empirical approach to examining beta microdosimetry

Beta microdosimetry (BM) has long been considered a leading cause in the amount of spread that is observed within samples dated using optically stimulated luminescence (OSL). We examined two samples from the site of MacCauley\u27s Beach, NSW, Australia that were considered to be influenced by BM but not quantifiably demonstrated. The beta dose rate (β-Dr ) environment of both samples was investigated using a series of methods that employ common laboratory equipment. Beta counting and inductively coupled plasma optical emission and mass spectrometry (ICP-OES/MS) measurements of constituent components (e.g., coarse sand quartz, fine sand heavy minerals, etc.) of the bulk sediment samples was used to assess beta dose rate (β-Dr ) variability within each sample. The result of this test showed significant variation in beta flux of sedimentary components, with the heavy mineral fraction of both samples having the highest β-Dr values (11.13 ± 0.40 Gy/ka, SP2; 22.03 ± 0.07 Gy/ka, SP5) of any of the measured components. Second, the spatial distribution of β-Dr was investigated using a geographic information system (GIS) analysis of sedimentary thin sections and portable x-ray fluorescence (pXRF) analysis of resin-impregnated sediments. The GIS results revealed a statistically significant non-uniform distribution of heavy mineral grains and associated hot- and coldspot regions. The pXRF results enabled the graphical display of a heterogeneous distribution of U, Th and K concentrations and also the resulting β-Dr map. However, the detection limit of the device meant that the lower β-Dr end of the distribution could not be resolved. It was concluded that BM plays a significant role in the OD of the single-grain OSL De distributions of those samples investigated, but could only be partially explained. It is recommended that characterisation of the beta dosimetric environment be carried out before assignation of BM is applied to De distributions

The history of phytolith research in Australasian archaeology and palaeoecology

Although phytolith research has come of age in archaeology and palaeoecology internationally, it has remained relatively marginalised from mainstream practice in Australasia. The region’s initial isolation from international scientific communities and uniqueness of its vegetation communities, has led to an exclusive set of challenges and interruptions in phytolith research. Examining a history of Australasian phytolith research presents the opportunity to recognise developments that have made phytoliths a powerful tool in reconstructing past environments and human uses of plants. Phytolith research arrived early in Australia (1903), after a convoluted journey from Germany (1835–1895) and Europe (1895–1943), but phytoliths were initially misidentified as sponge spicules (1931–1959). Formal understanding of phytoliths and their applications began in Australasia during the late 1950s, continuing throughout the 1960s and 1970s (1959–1980). After a brief hiatus, the modern period of phytolith analyses in Australasian archaeological and palaeoenvironmental research began in the 1980s (1984–1992), focusing on investigating the deep past. Advancements continued into the 1990s and early 2000s. Wallis and Hart declared in 2003 that Australian phytolith research had finally come of age, but more a fitting description would be that it had peaked. Since then phytolith research in Australasia slowed down considerably (2005-present). Local phytolith reference collections for Australasian flora, critical for identifying ancient phytoliths, are essentially no longer produced

A high-resolution late Quaternary depositional history and chronology for the southern portion of the Lake Mungo lunette, semi-arid Australia

© 2020 Elsevier Ltd The Willandra Lakes region sits on the southern margin of Australia\u27s arid core and is one of the oldest localities on the continent known to have been occupied by Australia\u27s First People. The archaeological traces that accumulated in the Lake Mungo lunette paint a picture of changing land use over the past ∼50 thousand years (ka) and some of these are likely to have been responses to changes in palaeoenvironmental conditions. This study set out to determine the finest temporal resolution that can be used to study the depositional and palaeoenvironmental history of the Lake Mungo lunette. The investigation focused on the depositional history documented within stratigraphy exposed in an eroding gully in the southern part of the lunette; Gully 10. A stratigraphic framework was developed using sedimentological and soil micromorphological analysis. This framework was then fixed in time by 56 single-grain optically stimulated luminescence (OSL) age estimates. These data sets were then combined into a Bayesian model that indicated three depositional phases: \u3e100 ka (LU1), ∼65–33 ka (LU2–LU3), and from ∼30 to 16 ka (LU4–LU9), with the late Pleistocene and Holocene samples (LU10–11) not being modelled. Furthermore, the redating of thirteen Lower and Upper Mungo OSL samples from Bowler et al. (2003)’s study of the southern tip of the lunette yielded younger age estimates for twelve of these, bringing them into line with previously published independent age control as well as the ages presented in this study. This study provides an approach for future efforts to establish consistency in age estimation and palaeoenvironmental interpretation along the length of the lunette

Shell Adzes, Exotic Obsidian, and Inter-Island Voyaging in the Early and Middle and Holocene of Wallacea

The environmental extremes of the Last Glacial Maximum and the subsequent warming and sea-level rise into the Holocene had profound implications for human behavior across much of the world. In northern New Guinea, the Maluku Islands, and the Philippines, shell adzes appear during this period alongside contact between islands. In this paper we present new data from the site of Asitau Kuru, Timor-Leste, to show that the creation of shell adzes and greater inter-island connectivity also characterizes the early and middle and early Holocene in the Nusa Tenggara archipelago of southern Wallacea. We suggest that one of the functions of these shell adzes was in making dugout canoes enabling regular access to neighboring islands; the import of exotic stone materials; long-term occupation of very small islands; and, with new hook and line technology, the capture of more fish. This evidence predates the Neolithic in the region and corroborates a linguistic hypothesis that there was a pre-Austronesian interaction sphere covering much of Wallacea

Establishing standardised growth curves (SGCs) for OSL signals from individual grains of quartz: A continental-scale case study

© 2020 Elsevier B.V. The standardised growth curve (SGC) procedure is a technique that can facilitate rapid De estimation. In this study, we apply a least-squares (LS) normalisation procedure to single grains of quartz from multiple sites across Australia to test its applicability for establishing common SGCs for individual quartz grains from the same continent. Seventy-two samples from 18 sites were divided into two groups: (1) forty samples were used to construct common SGCs for Australian quartz, and (2) thirty-two samples were used to blind test the reliability of single-grain dating, based on the continental SGCs. Individual grains of quartz from different sites exhibit significant variability in their OSL decay curves, inherent signal intensities and dose response curves (DRCs) constructed using the single-aliquot regenerative dose (SAR) procedure. Application of a LS-normalisation procedure can largely reduce between-grain variability in the shape of the DRCs, allowing for the establishment of a suite of continental SGCs for Australian quartz. For radiation doses below 50 Gy, all investigated grains share a single, common SGC. At higher doses, the DRCs can be divided into six groups, with each group represented by a common SGC. The proportion of grains belonging to each group shows no discernable dependence on OSL properties, but varies significantly among the different sites. The single-grain De values determined using the continental SGCs are consistent at 2σ with those obtained from their individual DRCs. Likewise, the single-grain De distributions obtained using the SGCs and the individual DRCs are similar for most of the blind-test samples. Discrepancies for a small number of samples can be explained by the inclusion in the SGC De dataset of a few outlying values associated with aberrant or saturated grains. Our results show that the establishment of a group of continental SGCs can significantly reduce the machine time required for single-grain OSL measurements, enabling more samples and/or more grains to be measured per unit time. Continental SGCs also yield single-grain De estimates with comparable accuracy and precision to those obtained from individual DRCs constructed using the full SAR procedure