Amy L Prendergast | University of Melbourne (original) (raw)

Papers by Amy L Prendergast

Libyan Studies, 2012

The paper reports on the fifth (2012) season of fieldwork of the Cyrenaican Prehistory Project. T... more The paper reports on the fifth (2012) season of fieldwork of the Cyrenaican Prehistory Project. The primary focus of the season was the continuation of the excavation of the prehistoric occupation layers in the Haua Fteah cave. A small trench (Trench U) was cut into Holocene (Neolithic) sediments exposed on the south wall of Charles McBurney's Upper Trench. Below this, the excavation of Trench M was continued, on the southern side of McBurney's Middle Trench. In previous seasons we had excavated Oranian ‘Epipalaeolithic’ layers dating toc.18,000–10,000 BP (years before the present). In 2012 the excavation continued downwards through Dabban ‘Upper Palaeolithic’ occupation layers, one of which was associated with a post-built structure and likely hearths. There are indications of an occupational hiatus separating the oldest Dabban from the youngest Levallois-Mousterian (Middle Palaeolithic or Middle Stone Age) lithic material. The Deep Sounding excavated by Charles McBurney in...

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Scientific Reports, 2019

elemental analysis of biogeochemical archives is an established technique used to study climate i... more elemental analysis of biogeochemical archives is an established technique used to study climate in a range of applications, including ocean circulation, glacial/interglacial climates, and anthropogenic climate change. Data from mollusc archives are especially important because of their global abundance and sub-annual resolution. Despite this potential, they are underrepresented among palaeoclimate studies, due to enigmatic physiological influences skewing the elemental record. Understanding the patterns behind these influences will improve data interpretation and lead to the development of new climate proxies. Here, we show for the first time that extensive spatial mapping of multiple mollusc specimens using Laser Induced Breakdown Spectroscopy (LIBS) across a wider region can resolve enigmatic patterns within the elemental record caused by physiological influences. 2D elemental (Mg/Ca) maps of whole limpet shells (Patella caerulea) from across the Mediterranean revealed patterns of variability within individual mollusc records as well as within isochronous parts of specimens. By registering and quantifying these patterns, we established previously uninterpretable correlations with temperature (R 2 > 0.8, p < 0.01). This outcome redefines the possibilities of accessing sub-annual climate proxies and presents the means to assess annual temperature ranges using oxygen isotope analysis requiring only 2 samples per shell. Seasonally resolved climate proxies are a valuable tool for overcoming the biases of records reflecting only mean annual conditions 1 as they trace the full extent of variability that is experienced throughout the year rather than only within a specific growth-window 2. This information is essential for evaluating short-term ecological responses 3 , as well as long-term changes of seasonal variability across millenia 4. Most mollusc shells provide this information as biogeochemical archives of their growth-increments and are commonly analysed using oxygen isotope ratios (δ 18 Ο) or elemental ratios (e.g. Mg/Ca, Sr/Ca, Ba/Ca). Their availability along modern and ancient shorelines as well as their good preservation facilitate climatic analyses at a high temporal and spatial resolution 5,6 , in addition to ecological responses across a large population 7-9. Obviously sufficiently resolved geochemical studies require large sample sizes per shell specimen and with elemental analysis being more cost-effective 10 , this approach is becoming increasingly popular within the last decade 11-14. Yet, elemental ratios in mollusc shells are more difficult to establish as climate proxies relative to δ 18 Ο values 15-17. Studies have had mixed success in developing general equations that link elemental ratios of shell car-bonate to specific sea surface temperatures (SST) even within a single species 11. The amount of unpublished negative results is unknown but likely substantial 18. Specifically, for Patella sp. shells a variety of correlations between elemental ratios and SST were found 19-22 , with no consistent explanation for any of the variabilities or anomalies that were encountered. Generally, it is argued that variations in study location as well as vital or physiological effects working between and within individual mollusc specimens prevent a comprehensive and unambiguous interpretation of their elemental records 11,21-28 .

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Recent studies have shown that the use of aquatic resources has greater antiquity in hominin diet... more Recent studies have shown that the use of aquatic resources has greater antiquity in hominin diets than previously thought. At present, it is unclear when hominins started to habitually consume marine resources. This study examines shellfish exploitation from a behavioural ecology perspective, addressing how and when past hunter-gatherers from the Levant used coastal resources for subsistence purposes. We investigate the seasonality of shellfish exploitation in the Levantine Upper Palaeolithic through oxygen isotope analysis on shells of the intertidal rocky shore mollusc Phorcus (Osilinus) turbinatus from the key site Ksâr 'Akil (Lebanon). At this rockshelter, multi-layered archaeological deposits contained remains of both marine and terrestrial molluscs in relatively large quantities, which were consumed and used as tools and ornaments by the occupants of the site. Our results indicate that at the start of the Initial Upper Palaeolithic (IUP), there is no evidence for shellfish consumption. Humans started to take fresh shellfish to the rockshelter from the second half of the IUP onward, albeit in low quantities. During the Early Upper Palaeolithic (EUP) shellfish exploitation became increasingly frequent. Oxygen isotope data show that shellfish exploitation was practised in every season throughout most of the Upper Palaeolithic (UP), with an emphasis on the colder months. This suggests that coastal resources had a central role in early UP foraging strategies, rather than a seasonally restricted supplementary one. Year-round shellfish gathering, in turn, suggests that humans occupied the rockshelter at different times of the year, although not necessarily continuously. Our oxygen isotope data is complemented with broader-scale exploitation patterns of faunal resources, both vertebrate and invertebrate, at the site. The inclusion of coastal marine resources signifies a diversification of the human diet from the EUP onward, which is also observed in foraging practices linked to the exploitation of terrestrial fauna.

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Geochemical signatures from biogenic carbonates are being increasingly employed as palaeoenvironm... more Geochemical signatures from biogenic carbonates are being increasingly employed as palaeoenvironmental proxies. In turn, many of these proxy archives including mollusc shells, corals, and otoliths have periodic growth structures, which allow the reconstruction of chronologically constrained records of palaeoenvironmental variability at unparalleled high temporal resolution. Studying the growth and chemistry of these periodic growth structures is known as sclerochronology. Biogenic hard parts accumulate in geological or archaeological deposits, and can be directly dated using radiometric and racemisation methods. They therefore offer the opportunity for high-resolution palaeoenvironmental reconstructions across many time intervals, all over the globe. Such data are important for several reasons: (1) understanding past climate and environmental change provides a means of contextualising current and future climate change and ecological disturbance; (2) high-resolution palaeoenvironmental records are essential for constraining, testing and validating global and regional numerical climate models; (3) palaeoenvironmental records from biogenic carbonates can provide an environmental framework from which to understand the behav-ioural changes and interactions of peoples with their environment. However, inter and intra-species differences in growth rate, physiology, and environmental response can cause variations in the chemical profiles of biogenic car-bonates. Before geochemical data is employed for palaeoenvironmental reconstructions, it is thus necessary to examine modern specimens of the target species, or related taxa, to understand how geochemical variations are influenced by local environmental conditions, kinetic and vital effects. This allows the generation of quantitative and more reliable proxy records of environmental change. This special issue brings together the latest research on palaeoenvironmental proxy development and validation in biogenic carbonates. It includes studies on marine, freshwater and estuarine organisms (molluscs, corals and echi-noderms), and on traditional as well as novel geochemical proxies. The papers presented here include in situ field calibration studies, laboratory growth experiments as well as methodological studies into the effects of sampling and pre-treatment. The geographical scope is broad, encompassing both the northern and southern hemispheres including South Africa, South America, Australia, Asia, the Mediterranean Sea and the North Atlantic.

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Terrestrial gastropods are problematical for radiocarbon (14 C) measurement because they tend to ... more Terrestrial gastropods are problematical for radiocarbon (14 C) measurement because they tend to incorporate carbon from ancient sources as a result of their dietary behavior. The 14 C ecology of the pulmonate land snail, Helix melanostoma in Cyrenaica, northeastern Libya, was investigated as part of a wider study on the potential of using terrestrial mollusk shell for 14 C dating of archaeological deposits. H. melanostoma was selected out of the species available in the region as it has the most predictable 14 C ecology and also had a ubiquitous presence within the local archaeology. The ecological observations indicate that H. melanostoma has a very homogenous 14 C ecology with consistent variations in F 14 C across sample sites controlled by availability of dietary vegetation. The majority of dated specimens from non-urbanized sample locations have only a small old-carbon effect, weighted mean of 476 ± 48 14 C yr, with between ~1% and 9% of dietary F 14 C from non-organic carbonate sources. Observed instabilities in the 14 C ecology can all be attributed to the results of intense human activity not present before the Roman Period. Therefore, H. melanostoma and species with similar ecological behavior are suitable for 14 C dating of archaeological and geological deposits with the use of a suitable offset.

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Limpet shells are common components of many archaeological sites in the Mediterranean. To test wh... more Limpet shells are common components of many archaeological sites in the Mediterranean. To test whether δ 18 O values from archaeological Patella caerulea shells can serve as a reliable palaeothermometer for the Mediterra-nean and a reliable archive of season of collection information, we collected live P. caerulea from eight Mediter-ranean locations in Croatia, Israel, Libya, Malta, Tunisia, and Turkey. Shell growth patterns were studied in section, and samples for oxygen isotope analysis were milled from the shells and used to calculate sea surface temperature (SST). As with other species of limpet, SST reconstructed from P. caerulea δ 18 O values were lower than expected from observational records. However, when a correction factor of −0.72‰ was applied, the shells recorded SST within the range of instrumental SST. SST calculated from δ 18 O shell values of the most recently formed shell portion of monthly-collected shells from one site in Libya were strongly and significantly correlated with instrumental SST in the region (R 2 = 0.95). Oxygen isotope curves from individual shells sampled at high resolution from each of the study sites across the Mediterranean exhibited sinusoidal patterns. Annual growth lines correlated with the lowest δ 18 O shell values and were thus formed in summer. However, shell growth rates varied markedly between the sites. Some sites with larger shells recorded less than a year of growth in broad, highly irregularly shaped increments. At other sites, medium sized shells recorded several years of growth with clear, regular growth increments. A sclerochronological approach can therefore be used to pre-screen limpet shell sections before geochemical sampling. The δ 18 O shell values from shells sampled at high-resolution recorded the full seasonal range of instrumental SST at each collection site. This reinforces the potential of this species as one of the few sub-seasonal resolution palaeoenvironmental archives in the region. Additionally, the pattern of δ 18 O shell variation from the last formed shell portion was studied to determine whether accurate season of collection information could be identified from P. caerulea shells. The correct season was interpreted N 80% of the time indicating that this species is a good candidate for seasonal shellfish foraging studies using archaeological shells.

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ABSTRACT The Haua Fteah cave in Libya contains one of the longest and most complete sequences of ... more ABSTRACT The Haua Fteah cave in Libya contains one of the longest and most complete sequences of human occupation in North Africa. This rich archaeological assemblage occurs in tandem with abundant material for paleoenvironmental reconstruction. In this study, stable isotope analyses of the archaeological mollusc assemblage from the Haua Fteah have allowed the reconstruction of paired marine and terrestrial climate records that extend from c.22,000 to 5,500 cal BP. In the marine topshell Osilinus turbinatus, δ18O records fluctuations in sea surface temperature. In the terrestrial mollusc Helix melanostoma, δ18O varies according to the water ingested by the animal as the shell grows, which in turn is linked to water and air temperature at the moment of precipitation whilst δ13C provides a proxy for palaeovegetation patterns and water stress. Intrashell stable isotope series from these shells record snapshots of sub-seasonal climatic variations covering rapid and profound climatic fluctuations from MIS 2 to MIS 1. This high-resolution climatic framework coupled with the well-dated record of cultural change, allows an examination of human-environment interactions during critical periods of late Pleistocene to Holocene climate change.

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Proceedings of the National Academy of Sciences, 2015

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Mollusk shells excavated from archeological sites have been used to reconstruct paleoenvironment,... more Mollusk shells excavated from archeological sites have been used to reconstruct paleoenvironment, human foraging , and migratory patterns. To retrieve information on past environment or human behavior, chemical signatures such as oxygen stable isotopes (δ 18 O shell) are analyzed. Shell archeological remains usually represent food waste. Thermal treatments such as boiling and roasting may influence shell structure and biochemical composition. However, little is known about the relationship between changes at macro-, microstructural and chemical levels. This work is a calibration study on modern Phorcus (Osilinus) turbinatus shells. A simulation of two different cooking methods (boiling and roasting) was carried out at four temperatures (100 °C, 300 °C, 500 °C and 700 °C) for two durations (20 min and 60 min). The structure and biochemistry of shells boiled at 100 °C did not significantly change. However, treatments at higher temperatures strongly affected both the structure and the biochemistry of the shells. At 300 °C the external coloration, as well as nacre iridescence, were altered. Raman spectroscopy revealed that, at this temperature, the aragonite-calcite polymorphic transformation starts. Scanning electron microscope (SEM) analysis showed drastic changes in the microstructural organization also beginning at 300 °C. Furthermore, the isotopic δ 18 O shell values were significantly affected. Increasing cooking temperatures resulted in an enhancement of the above-mentioned alterations. These results provide a set of temperature-related morphological, structural and biochemical characteristics for investigating the thermal behavior of biocarbonates and for estimating different cooking treatments in archeological record.

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The late Pleistocene to Holocene archaeological record of North Africa is key to understanding th... more The late Pleistocene to Holocene archaeological record of North Africa is key to understanding the emergence of anatomically modern humans into West Asia and Europe, and the broadening of subsistence strategies in the shift from hunter-gatherer to pastoral-agricultural lifeways. Some contend that these developments were modulated by major shifts in climate and environment. Evaluation of this hypothesis requires the pairing of local and regional climate records with well-dated archaeological sequences. The Haua Fteah archaeological site in the Gebel Akhdar region of Libya provides a key site to test this hypothesis as the cave contains one of the longest and most complete sequences of human occupation in North Africa as well as abundant material for palaeoenvironmental reconstruction. This study uses stable isotope analyses (d 18 O and d 13 C) of the terrestrial mollusc Helix melanostoma to construct a palaeoenvironmental framework for interpreting North African human-environment interactions from the Upper Palaeolithic to the Neolithic (~30,000 to 5000 years ago). The land snail stable isotope records from Haua Fteah suggests that cool arid conditions in the cave peaked during marine isotope stage (MIS) 2. This stage was, however, only marginally drier than previous and subsequent stages and coincided with an increase in occupation density in the cave. This suggests that the Gebel Akhdar may have served as an environmental refugium from the more extreme aridity in the surrounding Sahara and arid coastal plains for Late Stone Age (LSA) populations in North Africa. Conditions became progressively wetter towards the Holocene. However, generally wetter conditions were interrupted by two arid episodes at c. 8.0 ka and 7.3 ka that appear to coincide with regional changes reflected elsewhere in the Mediterranean basin.

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A detailed assessment of the impact of a far-field tsunami on the Australian coastline was carrie... more A detailed assessment of the impact of a far-field tsunami on the Australian coastline was carried out in the Steep Point region, West Australia, following the July 17th 2006 Java tsunami. Tsunami impact was surveyed by collating eye-witness accounts, measuring run-up heights, local flow depths, inundation distances and examining tsunami deposit sedimentology. The tsunami inundated the Steep Point coastline close

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On July 17th 2006, an Mw = 7.7 earthquake south of Java generated a tsunami that devastated parts... more On July 17th 2006, an Mw = 7.7 earthquake south of Java generated a tsunami that devastated parts of the Javanese coast, killing more than 500 people. The tsunami also affected parts of the Western Australian coast. Within a week of the event, a post tsunami survey was carried out near Steep Point, Western Australia. Tsunami inundation and run-up were mapped on the basis of eyewitness accounts, debris lines, vegetation damage and the occurrence of recently deposited fish, starfish, corals and sea urchins well above high-tide mark. Eyewitnesses reported three waves in the tsunami wave train, the second being the largest. A topographic survey using kinematic GPS with accuracies of 0.02 metres in the horizontal and 0.04 metres in the vertical recorded inundation depths of between 1-2 m, inundation of up to 200 m inland, and a maximum recorded run-up of 7.9 m AHD (Australian Height Datum). The tsunami caused widespread erosion in the littoral zone, extensive vegetation damage, destroyed...

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The seasonal pattern of shellfish foraging at the archaeological site of Haua Fteah in the Gebel ... more The seasonal pattern of shellfish foraging at the archaeological site of Haua Fteah in the Gebel Akhdar, Libya was investigated from the Epipaleolithic to the Neolithic via oxygen isotope (d18O) analyses of the topshell Phorcus (Osilinus) turbinatus. To validate this species as faithful year-round palaeoenvironmental recorder, the intra-annual variability of d18O in modern shells and sea water was analysed and compared with measured sea surface temperature (SST). The shells were found to be good candidates for seasonal shellfish forging studies as they preserve nearly the complete annual SST cycle in their shell d18O with minimal slowing or stoppage of growth. During the terminal Pleistocene Early Epipaleolithic (locally known as the Oranian, with modeled dates of 17.2e12.5 ka at 2s probability, Douka et al., 2014), analysis of archaeological specimens indicates that shellfish were foraged year-round. This complements other evidence from the archaeological record that shows that the cave was more intensively occupied in this period than before or afterwards. This finding is significant as the period of the Oranian was the coldest and driest phase of the last glacial cycle in the Gebel Akhdar, adding weight to the theory that the Gebel Akhdar may have served as a refugium for humans in North Africa during times of global climatic ex- tremes. Mollusc exploitation in the Latest Pleistocene and Early Holocene, during the Late Epipaleolithic (locally known as the Capsian, c. 12.7 to 9 ka) and the Neolithic (c. 8.5 to 5.4 ka), occurred predominantly during winter. Other evidence from these archaeological phases shows that hunting activities occurred during the warmer months. Therefore, the timing of Holocene shellfish exploitation in the Gebel Akhdar may have been influenced by the seasonal availability of other resources at these times and possibly shellfish were used as a dietary supplement when other foods were less abundant.

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Diatom assemblages in the 2004 tsunami deposits of Phra Thong Island, Thailand represent flow con... more Diatom assemblages in the 2004 tsunami deposits of Phra Thong Island, Thailand represent flow conditions during the tsunami. The tsunami deposit consists of single or multiple graded beds. Diatom assemblages in the lowermost part of the deposit predominantly comprise beach and subtidal species. In the middle part of the deposit, the assemblages are dominated by marine plankton with increasing finer fractions. A mixed assemblage of freshwater, brackish, and marine species occupies the uppermost part of the deposit. Changes in flow conditions during the tsunami can explain these diatom assemblage variations. During fast current velocities, medium sand is deposited; only beach and subtidal diatoms that live attached to the sand can be incorporated into the tsunami deposit under these flow conditions. It is difficult for diatoms in suspension to settle out under fast current velocities. With decreasing current velocities, marine plankton can settle out of the water column .Finally, duri...

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Nature, 2008

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PNAS, 2015

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Libyan Studies, 2012

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Scientific Reports, 2019

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Proceedings of the National Academy of Sciences, 2015

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Nature, 2008

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PNAS, 2015

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This study presents the first stable isotopic and sclerochronological calibration of the bivalve ... more This study presents the first stable isotopic and sclerochronological calibration of the bivalve Anomalocardia flexuosa (Linnaeus, 1767) in relation to environmental variables in a subtropical coastal area of southern Brazil. We investigate incremental shell growth patterns and δ 18 O and δ 13 C values of modern specimens collected alive from the Laguna Lagoonal System (LLS). Shells of Anomalocardia flexuosa are also one of the main biological components of pre-Columbian archaeological shell mounds and middens distributed along the Brazilian coastline. We therefore selected archaeological specimens from a local late Holocene shell mound (Cabeçuda) to compare their stable carbon and oxygen isotope values with those of modern specimens. Shell growth increments, δ 18 O and δ 13 C values respond to a complex of environmental conditions, involving, for example, the effects of temperature and salinity. The isotopic information extracted from archaeological specimens from Cabeçuda shell midden in the LLS indirectly indicates that environmental conditions during the late Holocene were different from present day. In particular, intra-shell δ 18 O and δ 13 C values of archaeological shells reveal a stronger marine influence at 3 ka cal BP, which is in contrast to the seasonal freshwater/seawater balance that currently prevails at the LLS.

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