Papers by Robin Twaddle
Queensland Archaeological Research
Archaeological survey, excavations, and analyses of the Murdumurdu shell midden on Bentinck Islan... more Archaeological survey, excavations, and analyses of the Murdumurdu shell midden on Bentinck Island, Gulf of Carpentaria are reported. Patterns of subsistence as well as the timing and periodicity of site use are investigated through quantification of cultural materials, AMS radiocarbon dating, stable isotopic analysis of <em>Marcia hiantina</em> shell carbonates (δ18O and δ13C), magnetic susceptibility analysis of the deposits and palaeoenvironmental reconstruction. Exploitation of shellfish focused on sandy-mud flat species (especially <em>M. hiantina</em> and <em>Gafrarium pectinatum</em>) with occupation occurring exclusively during the dry season (May-August). Radiocarbon dating reveals that the main period of occupation was short, albeit intense and occurred c.300 years ago. Initiation of occupation closely follows the establishment of freshwater conditions in the adjacent Marralda Swamp. These factors suggest that use of Murdumurdu was limit...
Changing relationships between people and their environments result in modified patterns of land-... more Changing relationships between people and their environments result in modified patterns of land-use and occupation as populations respond to fluctuating conditions across space and through time. Understanding these relationships occurring on a variety of scales is integral to achieving nuanced interpretations of fundamental Aboriginal lifeways. This is particularly salient in contexts characterised by stark seasonal shifts in climate, which have long been suggested to act as key drivers behind fundamental decision-making processes. For Aboriginal groups living along Australia's tropical north coast these seasonal changes coincide with the monsoonal cycle, with ethnographic data demonstrating that seasonality permeates associated behavioural and cultural systems. Numerous authors have attempted to explain change evident in the archaeological record using broad models based upon wide-ranging concepts such as shifts in ENSO intensity. However, these broad models map poorly onto lo...
Complexities in the palaeoenvironmental and archaeological interpretation of isotopic analyses of the Mud Shell Geloina erosa (Lightfoot, 1786)
Isotope signals derived from molluscan shell carbonates allow researchers to investigate palaeoen... more Isotope signals derived from molluscan shell carbonates allow researchers to investigate palaeoenvironments and the timing and periodicity of depositional events. However, it cannot be assumed that all molluscan taxa provide equally useful data owing to species-specific biological and ecological traits. The Mud Shell, Geloina erosa (Lightfoot, 1786) (syn. Polymesoda coaxans, syn. Polymesoda erosa), an infaunal mangrove bivalve, is a common component of archaeological deposits along Australia's tropical north coast and throughout the Indo-West Pacific. The ubiquity of G. erosa has led to numerous researchers incorporating this taxon into interpretations of associated deposits, particularly in the generation of radiocarbon chronologies and as a palaeoenvironmental proxy. Despite this, concerns have been expressed regarding the impact of G. erosa physiology and ecology on associated geochemical signals. Adaptations allowing the survival of this species within its highly changeable mangrove environment may introduce complexities into radiocarbon and environmental data archived within its shell. This study combines local environmental and hydrological data with isotopic analysis (δ18O, δ13C, and 14C) of live-collected specimens to explore the interpretability of geochemical proxies derived from G. erosa. Results suggest a number of factors may impact geochemical markers in unpredictable ways, eroding the usefulness of associated interpretations.
Sclerochronological analysis of archaeological mollusc assemblages: methods, applications and future prospects
Archaeological and Anthropological Sciences, 2016
Accreting skeletal tissues found in bone, teeth, otoliths and molluscan shell act as sensitive re... more Accreting skeletal tissues found in bone, teeth, otoliths and molluscan shell act as sensitive recorders of local environmental and climatic conditions. Owing to their robust nature, ubiquity and abundance in the archaeological record as well as the potential for high-resolution data acquisition, the accreting skeletal tissues of archaeological molluscs are increasingly employed as palaeoenvironmental proxies. Researchers have chiefly utilised such proxies to extend instrumental records of environmental conditions through palaeoenvironmental reconstruction and explore the impact of environmental and climatic change on human populations. However, the use of environmental proxies from the archaeological record can be hampered by a number of methodological challenges including inadequate sampling strategies, appropriate calibration, the use of inappropriate proxies and the broad extrapolation of localised results. This paper reviews the use of molluscan shell from archaeological contexts as palaeoenvironmental proxies. We focus on the application of sclerochronology—a suite of high-resolution physical and geochemical data recovery methods widely used in conjunction with molluscan shell. This paper presents an overview of the potential of these techniques in approaching more nuanced understandings of human-environment interactions and how they can be more successfully incorporated into archaeological research.
Theses by Robin Twaddle
Reliable speciation protocols used for identifying shellfish from prehistoric archaeological site... more Reliable speciation protocols used for identifying shellfish from prehistoric archaeological sites provides robust data for interpreting prehistoric human behaviour. Because prehistoric Hawaiian shell middens are dominated by the limpet Cellana spp., this taxon has previously been utilised to document anthropogenic impacts on the marine environment and for reconstructing subsistence practices. However, without accurate species-level identifications of marine shellfish from archaeological sites and an understanding of the surrounding coastal marine environment, it is difficult to differentiate culturally from environmentally influenced variations in shellfish size and abundance. This research presents newly designed and tested speciation methods developed specifically for whole and fragmentary archaeological limpet shell. Species-level identifications are then made using assemblages from four prehistoric archaeological sites situated along the northern coast of Moloka„i, Hawai„i. Results reveal that analysis of temporal and spatial fluctuations in the size and abundance of Cellana spp. provides detailed information regarding human subsistence behaviour. However, these variations alone do not provide irrefutable evidence of anthropogenic impact. In order to make meaningful inferences about prehistoric subsistence practices and human impact on marine resources, a holistic approach encompassing ecological information about marine ecosystems, ecology of targeted shellfish, and the variation of shellfish diversity and size in archaeological midden sites throughout a study area is required.
Posters by Robin Twaddle
The interpretation of geochemical signals derived from molluscan shell carbonates allows research... more The interpretation of geochemical signals derived from molluscan shell carbonates allows researchers to reach a variety of understandings related to palaeoenvironments and the timing and periodicity of depositional events. However, it cannot be assumed that all molluscan taxa provide equally accurate data owing to species-specific biological and ecological variability. Polymesoda coaxans, an infaunal mangrove bivalve, is a common component of archaeological deposits along Australia’s tropical north coast. The ubiquity of this species has led to numerous researchers incorporating P. coaxans into interpretations of associated deposits, particularly in the generation of radiocarbon chronologies and as a palaeoenvironmental proxy. Despite this, concerns have been expressed regarding the impact of P. coaxans physiology and ecology on the accuracy of associated geochemical signals. Adaptations allowing the survival of this species within its highly changeable mangrove environment may also introduce latent inaccuracies into radiocarbon and environmental data archived within its shell. This study combines understandings of local environmental and hydrological cycles as well as live-collected specimens to explore the efficacy of incorporating geochemical signals derived from P. coaxans into archaeological interpretation. Preliminary results suggest a number of factors may offset geochemical markers in unpredictable ways, eroding the accuracy of associated interpretations.
This research aims to generate detailed understandings of seasonal environmental and hydrological... more This research aims to generate detailed understandings of seasonal environmental and hydrological cycles and their effects on the growth and isotopic composition of important economic shellfish taxa endemic to Bentinck Island, Gulf of Carpentaria, as part of a broader investigation of Kaiadilt occupation patterns.
The skeletal hard parts of molluscan shells contain detailed records of tidal, seasonal, and annual environmental cycles manifesting as discrete growth banding and isotopic variation (Burchell et al. 2013; Deith 1983; Shackleton 1973). Analysis of shellfish remains from archaeological deposits permits complex questions of occupation periodicity, mobility, and demography to be approached. However, the effects of environmental shifts on the growth regimes and isotopic composition of molluscan shell are not uniform, with significant variation derived from different taxa and geographic locations (Bernstein 1990; Carré et al. 2005; Jones and Quitmyer 1996). It is therefore necessary to construct detailed modern baseline analogues to characterise causality between environmental/hydrological cycles and changes in molluscan growth regimes/isotopic composition, providing a contextual framework from which accurate high-resolution interpretations of archaeological material can be made.
These findings provide crucial baseline analogues for a high-resolution study of the seasonality and periodicity of Kaiadilt occupation in the South Wellesley Islands during the mid-to-late Holocene. Novel applications of sclerochronology and scleroisotope analysis will allow more nuanced understandings of Australian offshore island use – including higher-order interpretations of mobility and demography – to be approached
"This research aims to generate detailed understandings of seasonal environmental and hydrologica... more "This research aims to generate detailed understandings of seasonal environmental and hydrological cycles and their effects on the growth and isotopic composition of shellfish endemic to Bentinck Island, Gulf of Carpentaria, as part of a broader investigation of island occupation patterns. Shellfish have long been recognised as sensitive environmental recorders documenting their ambient environment within the chemical and physical structures of their skeletal tissues. When collected from archaeological assemblages such data allow for high-resolution determinations of seasonal occupation. However, the effects of environmental shifts on the growth regimes and isotopic composition of molluscan shell are not uniform, with significant variations derived from different species and geographical locations. It is therefore necessary to construct detailed modern baselines in order to 1) understand the effects of local environmental and hydrological cycles on targeted species; 2) give context to data acquired from archaeological material; and, 3) provide comparative baselines from which archaeological specimens can be analysed.
Snapshots of local environmental and hydrological cycles are generated from data collected using water sampling and environmental monitoring instruments deployed over the course of an annual cycle. It is expected that the wet season (December – March) will be characterised by more negative isotopic values owing to greatly increased temperatures, decreased salinity, and influxes of freshwater from heavy precipitation and continental runoff. The dry season (April – November) is expected to exhibit the opposite with more positive isotopic values, lower temperatures, and higher salinity. By aligning and comparing this data to isotopic signals and growth patterning of live collected shellfish a high-resolution understanding of the effects localised seasonal cycles have on geochemical and physical aspects of molluscan shell will be acquired.
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Conference Presentations by Robin Twaddle
Using Stable Isotopes in Marine Shell to Explore Occupation Patterns: A Preliminary Chronology of Thundiy, South Wellesley Islands, Queensland
Changing interactions between humans, culture, and environment modify patterns of land-use and oc... more Changing interactions between humans, culture, and environment modify patterns of land-use and occupation as populations respond to fluctuating conditions. Broad interpretations of human responses to Holocene environmental change in northern Australia suggest far-reaching cultural and behavioural transformations, including the increasing use of offshore islands. Occupation patterns in these contexts are often characterised as unidirectional, implying a gradual shift from ephemeral to permanent use as offshore islands are reincorporated into the foraging territories of mainland-based groups. However, regional sequences indicate multiple instances of abandonment and reoccupation as well as seasonal exploitation and visitation, suggesting complex patterns of island use. To better understand these changing occupation strategies, researchers can interpret stable oxygen and carbon isotope values derived from archaeological mollusc shell. Aspects of the environment, including temperature and water composition, imprint a chemical signal within the shell matrix allowing the timing (i.e. season) of resource consumption to be determined. While fast becoming a staple in the interpretative frameworks of many international projects, stable isotope analyse of molluscs is rarely applied in Australian contexts. Thus, a unique opportunity exists for this internationally accepted method to be deployed in Australia. This paper presents a preliminary site-use chronology for the expansive midden complex of Thundiy located on Bentinck Island, South Wellesley Islands, with a focus on understanding trajectories associated with changes in the timing and permanency of occupation.
High-Resolution Scleroisotope Analysis: Preliminary Stable Isotope Values from the South Wellesley Islands, Gulf of Carpentaria
Detailed understandings of local environmental conditions and their impact on growth and isotopic... more Detailed understandings of local environmental conditions and their impact on growth and isotopic fractionation in constituent molluscan taxa are required to accurately contextualise archaeological results. Molluscs have long been recognised as sensitive recorders of local environmental conditions. Aspects of the environment, including temperature and water constitution, imprint a chemical signal within the shell matrix. Archaeologists use stable oxygen and carbon isotope profiles derived from archaeological shellfish assemblages to address questions related to palaeoenvironments, including extending instrumental records, characterising subannual environmental oscillations, and determining the timing and periodicity of resource collection and siteuse. This paper reports preliminary findings of research characterising subannual environmental cycles and their effects on extant shellfish taxa from Bentinck Island, southern Gulf of Carpentaria using subannual stable isotope profiles. Distinct shifts in local environmental conditions owing to the Australian Monsoonal Cycle are reflected within observed environmental data and molluscan isotope profiles, suggesting similar patterns will be present within archaeological assemblages from this region. These results form the basis for modern analogues through which archaeological data can be accurately contextualised.
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Papers by Robin Twaddle
Theses by Robin Twaddle
Posters by Robin Twaddle
The skeletal hard parts of molluscan shells contain detailed records of tidal, seasonal, and annual environmental cycles manifesting as discrete growth banding and isotopic variation (Burchell et al. 2013; Deith 1983; Shackleton 1973). Analysis of shellfish remains from archaeological deposits permits complex questions of occupation periodicity, mobility, and demography to be approached. However, the effects of environmental shifts on the growth regimes and isotopic composition of molluscan shell are not uniform, with significant variation derived from different taxa and geographic locations (Bernstein 1990; Carré et al. 2005; Jones and Quitmyer 1996). It is therefore necessary to construct detailed modern baseline analogues to characterise causality between environmental/hydrological cycles and changes in molluscan growth regimes/isotopic composition, providing a contextual framework from which accurate high-resolution interpretations of archaeological material can be made.
These findings provide crucial baseline analogues for a high-resolution study of the seasonality and periodicity of Kaiadilt occupation in the South Wellesley Islands during the mid-to-late Holocene. Novel applications of sclerochronology and scleroisotope analysis will allow more nuanced understandings of Australian offshore island use – including higher-order interpretations of mobility and demography – to be approached
Snapshots of local environmental and hydrological cycles are generated from data collected using water sampling and environmental monitoring instruments deployed over the course of an annual cycle. It is expected that the wet season (December – March) will be characterised by more negative isotopic values owing to greatly increased temperatures, decreased salinity, and influxes of freshwater from heavy precipitation and continental runoff. The dry season (April – November) is expected to exhibit the opposite with more positive isotopic values, lower temperatures, and higher salinity. By aligning and comparing this data to isotopic signals and growth patterning of live collected shellfish a high-resolution understanding of the effects localised seasonal cycles have on geochemical and physical aspects of molluscan shell will be acquired.
"
Conference Presentations by Robin Twaddle