ORCID Profile
0000-0002-0007-5753
Current Organisation
Australian National University
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Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.JHEVOL.2012.07.006
Abstract: While it is generally accepted that modern humans evolved in Africa, the specific physical evidence for that origin remains disputed. The modern-looking Omo 1 skeleton, discovered in the Kibish region of Ethiopia in 1967, was controversially dated at ~130 ka (thousands of years ago) by U-series dating on associated Mollusca, and it was not until 2005 that Ar-Ar dating on associated feldspar crystals in pumice clasts provided evidence for an even older age of ~195 ka. However, questions continue to be raised about the age and stratigraphic position of this crucial fossil specimen. Here we present direct U-series determinations on the Omo 1 cranium. In spite of significant methodological complications, which are discussed in detail, the results indicate that the human remains do not belong to a later intrusive burial and are the earliest representative of anatomically modern humans. Given the more archaic morphology shown by the apparently contemporaneous Omo 2 calvaria, we suggest that direct U-series dating is applied to this fossil as well, to confirm its age in relation to Omo 1.
Publisher: Elsevier BV
Date: 09-2004
Publisher: American Geophysical Union (AGU)
Date: 22-02-2007
DOI: 10.1029/2006GL028525
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 11-2013
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 04-2010
Publisher: Springer Science and Business Media LLC
Date: 04-1992
DOI: 10.1007/BF00310752
Publisher: Springer Science and Business Media LLC
Date: 04-1992
DOI: 10.1007/BF00310753
Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2020PA004022
Abstract: Boron proxies in the calcium carbonate shells of planktic foraminifera are sensitive to seawater acidity, but B/Ca ratios and isotopic composition (i.e., δ 11 B) recorded by different foraminifer species grown under identical environmental conditions differ significantly and systematically. Specifically, Globigerinoides ruber displays higher B/Ca and δ 11 B than Trilobatus sacculifer and Orbulina universa . It has been hypothesized that these differences are caused by species‐specific rates of symbiont photosynthesis and habitat depth with greater symbiont photosynthesis elevating the microenvironmental pH of G. ruber relative to T. sacculifer and O. universa . Here we test this hypothesis by applying fast repetition rate fluorometry (FRRF), Chlorophyll a quantification, and symbiont counts in laboratory grown specimens of G. ruber (pink), T. sacculifer and O. universa to study species‐specific differences in symbiont photochemical quantum efficiencies. In addition, we report B/Ca shell profiles measured by laser ablation on the same specimens previously monitored by FRRF, and δ 11 B data of discrete populations of all three species grown under high and low light conditions in the laboratory. While the light experiments document that symbiont photosynthesis elevates pH and/or δ 11 B in the calcifying microenvironment of all three foraminifer species, the FRRF, Chl. a and symbiont abundance data are relatively uniform among the three species and do not scale consistently with intrashell B/Ca, or with observed species‐specific offsets in B/Ca or δ 11 B. Implications of these findings for foraminiferal physiology and biomineralization processes are discussed.
Publisher: Elsevier BV
Date: 2005
Publisher: Elsevier BV
Date: 02-2009
Publisher: Elsevier BV
Date: 07-03-2011
Publisher: Oxford University Press (OUP)
Date: 08-2000
Publisher: PERSEE Program
Date: 2011
Abstract: Contexts and age of the new dental human fossils from Middle Pleistocene deposits at Thomas Quarry I (Casablanca, Morocco) – The Thomas Quarry I locality became famous in 1969 with the discovery of a human half-mandible in a cave. From 1988 onwards, modern controlled excavations took place within the framework of the Franco-Moroccan co-operative project “ Casablanca.” The stratigraphy of Thomas I Quarry is complex and represents several major episodes of coastal sedimentation that are dated to the final Lower and early Middle Pleistocene on the basis of a detailed regional lithostratigraphical and microfaciological study and form the Oulad Hamida Morpho-stratigraphic Unit. Within this MSU, some lithostratigraphic units fossilize a polyphase palaeo-shoreline in which caves have developed. A continental sediment series dated to the Middle and Upper Pleistocene on lithostratigraphical and biochronological evidence and by OSL is preserved in the Hominid Cave (GH). The top of the GH general stratigraphy shows a red complex with abundant microfauna (stratigraphic unit 1). Below this, a multilayer dripstone floor interbedded with loose red sands (stratigraphic units 2-3) caps the lower stratigraphic units (4 and 5). Stratigraphic unit 4 contains artefacts, fauna and hominid fossils and rests on collapsed eolianite blocks imbedded in coarse sands which form stratigraphic unit 5 this lowermost intertidal unit fossilizes a notch in the polyphase shoreline. The Acheulean lithic assemblage recovered by recent excavations in GH stratigraphic unit 4 is similar to the series collected at the time of the discovery of the first Homo fossil in 1969. It is manufactured mainly on various quartzites available close to the site as pebbles of small to medium size and some blocks as well as a few flint nodules collected in a secondary position from beach deposits. The flint nodules derive from the phosphatic plateau of the Meseta hinterland and were carried to the ocean by wadis. The assemblage consists of chopper-cores (mainly unifacial unidirectional cores with a retouched cutting edge) and cores, semi-cortical flakes obtained by direct and bipolar knapping, along with rare handaxes made from large flakes or from flat pebbles, handaxe-like cores, hammerstones and anvils. Stone knapping was mainly oriented towards flake production and a few handaxes were probably imported to the site. A rich mammalian macrofauna supplemented by the addition of a few reptiles and birds is associated with the lithics in GH stratigraphic unit 4. The abundance and ersity of carnivores attest to their use of the cave. The most common species is a middle-size canid, with enlarged crushing part of the dentition. The fauna indicates an open woodland environment and suggests an age younger than Tighenif in Algeria, but the remoteness of this latter site, its distance from the seashore, and the fact that it is an open-air site may account for some of the differences. Preliminary taphonomic analysis of the megafauna indicates that the carcasses were processed by carnivores. Cut-marks are still absent from this assemblage despite the association with refitted lithic artefacts, which raises the question of any human role in the bone accumulations. Similar cases of accumulations created by humans, carnivores and porcupines have already been described in the Mediterranean area. However, the studied assemblage comes from inside the cave, whereas any human occupation may well have been concentrated closer to the entrance. Geological studies have demonstrated that unit 4 containing the assemblage results from several sedimentary processes having possibly mixed artefacts with bones previously accumulated by predators. Between 1994 and 2005, four teeth of Homo were recovered in stratigraphic unit 4, a right upper premolar (ThI 94 OA 23-24), another right upper premolar (ThI 95 SA 26 no 89), a first left upper incisor (ThI 95 SA 26 no 90) and a left upper premolar (ThI 2005 PA 24 no 107). The teeth are larger than those of modern humans and show moderate to heavy wear Laser ablation ICP-MS dating combining tESR and U-series data for modelling U-uptake has given an US/ ESR age of 501 ka for a human premolar while new OSL measurements yielded an age of 420 ± 34 ka for sediments immediately above the dated tooth and 391 ± 32 ka below. Nevertheless, biostratigraphy and lithostratigraphy point to greater antiquity, towards the base of the Middle Pleistocene. + 94 − 76
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 10-2017
Publisher: Wiley
Date: 12-1997
Publisher: Elsevier BV
Date: 04-2011
Publisher: Copernicus GmbH
Date: 25-03-2014
Abstract: Abstract. Strontium isotope ratios (87Sr / 86Sr) are a key geochemical tracer used in a wide range of fields including archaeology, ecology, food and forensic sciences. These applications are based on the principle that the Sr isotopic ratios of natural materials reflect the sources of strontium available during their formation. A major constraint for current studies is the lack of robust reference maps to evaluate the source of strontium isotope ratios measured in the s les. Here we provide a new data set of bioavailable Sr isotope ratios for the major geologic units of France, based on plant and soil s les (Pangaea data repository doi:10.1594/PANGAEA.819142). The IRHUM (Isotopic Reconstruction of Human Migration) database is a web platform to access, explore and map our data set. The database provides the spatial context and metadata for each s le, allowing the user to evaluate the suitability of the s le for their specific study. In addition, it allows users to upload and share their own data sets and data products, which will enhance collaboration across the different research fields. This article describes the s ling and analytical methods used to generate the data set and how to use and access the data set through the IRHUM database. Any interpretation of the isotope data set is outside the scope of this publication.
Publisher: American Geophysical Union (AGU)
Date: 03-07-2009
DOI: 10.1029/2008PA001664
Publisher: Elsevier BV
Date: 10-2001
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 10-2006
Publisher: Informa UK Limited
Date: 03-2005
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.FORSCIINT.2014.04.040
Abstract: A commercially available laser-induced breakdown spectroscopy (LIBS) instrument was evaluated for the determination of elemental composition of twenty Australian window glass s les, consisting of 14 laminated s les and 6 non-laminated s les (or not otherwise specified) collected from broken windows at crime scenes. In this study, the LIBS figures of merit were assessed in terms of accuracy, limits of detection and precision using three standard reference materials (NIST 610, 612, and 1831). The discrimination potential of LIBS was compared to that obtained using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray microfluorescence spectroscopy (μXRF) and scanning electron microscopy energy dispersive X-ray spectrometry (SEM-EDX) for the analysis of architectural window glass s les collected from crime scenes in the Canberra region, Australia. Pairwise comparisons were performed using a three-sigma rule, two-way ANOVA and Tukey's HSD test at 95% confidence limit in order to investigate the discrimination power for window glass analysis. The results show that the elemental analysis of glass by LIBS provides a discrimination power greater than 97% (>98% when combined with refractive index data), which was comparable to the discrimination powers obtained by LA-ICP-MS and μXRF. These results indicate that LIBS is a feasible alternative to the more expensive LA-ICP-MS and μXRF options for the routine forensic analysis of window glass s les.
Publisher: Canadian Science Publishing
Date: 03-2014
Abstract: Transgenerational marking enables mass-marking of larval fishes via transmission of enriched stable isotopes from mother to offspring, but potential impacts on the resultant progeny are poorly understood. We injected enriched stable isotopes ( 137 Ba and 87 Sr) into female purple-spotted gudgeon, Mogurnda adspersa, to produce multiple batch markers and examined larval morphology at hatch as well as survival and growth to 31 days posthatch in marked and unmarked offspring. Transgenerational marking had minimal effects on larval growth and survival, whereas body depth at hatch was significantly reduced in marked larvae. A meta-analysis of transgenerational marking effects on larval morphology at hatch and growth rates across multiple fish species found a nonsignificant positive effect of enriched stable barium isotopes on larval morphology at hatch, but a significant negative effect on growth. There were no significant effects of strontium on morphology or growth. Meta-regression analysis revealed that larval size at hatch increased with the dose of injected stable barium isotopes, but this result should be interpreted cautiously. Because of high levels of between-study heterogeneity, we caution against assuming there are no effects of transgenerational marking on fish offspring any such effects should be validated and incorporated into transgenerational marking studies of fish dispersal.
Publisher: Copernicus GmbH
Date: 18-04-2019
Abstract: Abstract. We construct a carbon cycle box model to process observed or inferred geochemical evidence from modern and paleo settings. The [simple carbon project] model v1.0 (SCP-M) combines a modern understanding of the ocean circulation regime with the Earth's carbon cycle. SCP-M estimates the concentrations of a range of elements within the carbon cycle by simulating ocean circulation, biological, chemical, atmospheric and terrestrial carbon cycle processes. The model is capable of reproducing both paleo and modern observations and aligns with CMIP5 model projections. SCP-M's fast run time, simplified layout and matrix structure render it a flexible and easy-to-use tool for paleo and modern carbon cycle simulations. The ease of data integration also enables model–data optimisations. Limitations of the model include the prescription of many fluxes and an ocean-basin-averaged topology, which may not be applicable to more detailed simulations. In this paper we demonstrate SCP-M's application primarily with an analysis of the carbon cycle transition from the Last Glacial Maximum (LGM) to the Holocene and also with the modern carbon cycle under the influence of anthropogenic CO2 emissions. We conduct an atmospheric and ocean multi-proxy model–data parameter optimisation for the LGM and late Holocene periods using the growing pool of published paleo atmosphere and ocean data for CO2, δ13C, Δ14C and the carbonate ion proxy. The results provide strong evidence for an ocean-wide physical mechanism to deliver the LGM-to-Holocene carbon cycle transition. Alongside ancillary changes in ocean temperature, volume, salinity, sea-ice cover and atmospheric radiocarbon production rate, changes in global overturning circulation and, to a lesser extent, Atlantic meridional overturning circulation can drive the observed LGM and late Holocene signals in atmospheric CO2, δ13C, Δ14C, and the oceanic distribution of δ13C, Δ14C and the carbonate ion proxy. Further work is needed on the analysis and processing of ocean proxy data to improve confidence in these modelling results.
Publisher: American Geophysical Union (AGU)
Date: 09-2005
DOI: 10.1029/2005GC000930
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 12-2014
Publisher: Springer Science and Business Media LLC
Date: 02-11-2017
DOI: 10.1038/S41467-017-00955-0
Abstract: The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polymorph vaterite, implying a non-classical crystallisation pathway involving metastable phases that transform ultimately to calcite. The current understanding of how planktic foraminifer shells record climate, and how they will fare in a future high-CO 2 world is underpinned by analogy to the precipitation and dissolution of inorganic calcite. Our findings require a re-evaluation of this paradigm to consider the formation and transformation of metastable phases, which could exert an influence on the geochemistry and solubility of the biomineral calcite.
Publisher: Informa UK Limited
Date: 09-2011
Publisher: American Geophysical Union (AGU)
Date: 10-2023
DOI: 10.1029/2023PA004613
Publisher: Springer Science and Business Media LLC
Date: 1993
DOI: 10.1007/BF01161564
Publisher: IEEE
Date: 03-2019
Publisher: Elsevier BV
Date: 05-2013
Publisher: Elsevier BV
Date: 02-2011
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 2015
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/MF13150
Abstract: Transgenerational marking is increasingly being used to study the early life history, biology and ecology of fishes. However, the timeframe over which the injected enriched stable isotopes remain in the mother and are passed onto her offspring is largely unknown. Similarly, we have relatively little knowledge of the effects of isotope labelling on the morphology of offspring. In this study, we injected adult female eastern rainbowfish (Melanotaenia splendida) with two doses (20 µg g–1 and 40 µg g–1) of enriched 137Ba or 87Sr stable isotopes to mark the otoliths of their larvae and examine the effects of isotope labelling on larvae morphology. Isotope ratios in larval otoliths were significantly different from controls in larvae hatched up to 174 days post-injection, indicating that enriched isotopes can mark the larvae of this daily spawning species up to 6 months after a single injection. Isotope-marked larvae displayed variable, but generally increased physical size, indicating that enriched stable isotope labelling may have some unintended effects on larvae morphology. Consequently, transgenerational marking provides a long-term tool for marking the offspring of M. splendida to disentangle their patterns of survivorship and dispersal, with the caveat that such studies should be interpreted in light of potential isotope-related changes in offspring morphology.
Publisher: Inter-Research Science Center
Date: 31-01-2013
DOI: 10.3354/MEPS10085
Publisher: American Geophysical Union (AGU)
Date: 03-2008
DOI: 10.1029/2007PA001452
Publisher: Elsevier BV
Date: 05-2003
Publisher: Elsevier BV
Date: 04-2012
Publisher: Elsevier BV
Date: 12-2017
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 09-2011
Publisher: Mineralogical Society of America
Date: 11-2018
Publisher: Emerald Group Publishing Limited
Date: 2010
Publisher: Informa UK Limited
Date: 06-1998
Publisher: Informa UK Limited
Date: 2006
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.CHEMOSPHERE.2014.05.065
Abstract: Reptiles are ideal organisms for the non-invasive monitoring of mercury (Hg) contamination. We have investigated Hg bioaccumulation in tissue layers of reptile dermis as a basis for establishing a standardized collection method for Hg analysis. Tissue s les from freshwater turtle species Podocnemis unifilis and Podocnemis expansa and caiman species Melanosuchus niger and Caiman crocodilus, all from the Amazonian region, were analysed in this study. We first tested the relationships between Hg concentrations in keratin and bone to Hg concentrations in muscle to determine the best predictor of Hg concentration in muscle tissue. We then investigated the potential for measuring Hg concentrations across turtle carapace growth rings as an indicator of longer term changes in Hg concentration in the environment. Hg concentrations were significantly lower in bone (120 ng g(-1) caimans and 1 ng g(-1) turtles) than keratin (3600 ng g(-1) caimans and 2200 ng g(-1) turtles). Keratin was found to be a better predictor of exposure to Hg than muscle and bone tissues for both turtles and caimans and also to be a reliable non-invasive tissue for Hg analysis in turtles. Measurement of Hg in carapace growth rings has significant potential for estimating Hg bioaccumulation by turtles over time, but full quantification awaits development and use of a matrix-matched reference material for laser ablation ICPMS analysis of Hg concentrations in keratin. Realising this potential would make a valuable advance to the study of the history of contamination in mining and industrial sites, which have until now relied on the analysis of Hg concentrations in sediments.
Publisher: American Geophysical Union (AGU)
Date: 08-2008
DOI: 10.1029/2008GC001974
Publisher: Mineralogical Society of America
Date: 11-2018
Publisher: Wiley
Date: 08-2015
Publisher: Springer Science and Business Media LLC
Date: 04-05-2011
Publisher: Elsevier BV
Date: 06-2015
Publisher: Elsevier BV
Date: 04-2006
Publisher: Oxford University Press (OUP)
Date: 2016
Publisher: Springer Science and Business Media LLC
Date: 11-1987
DOI: 10.1007/BF00372004
Publisher: Elsevier BV
Date: 07-2003
Publisher: IEEE
Date: 10-2013
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 02-1993
Publisher: Wiley
Date: 07-2003
Publisher: Springer Science and Business Media LLC
Date: 03-2003
DOI: 10.1038/NATURE01482
Publisher: Informa UK Limited
Date: 10-1997
Publisher: Elsevier BV
Date: 10-2017
Publisher: American Geophysical Union (AGU)
Date: 07-2008
DOI: 10.1029/2008GC002018
Publisher: Elsevier BV
Date: 07-1987
Publisher: Elsevier BV
Date: 10-2012
Publisher: Elsevier BV
Date: 07-2009
Publisher: Elsevier BV
Date: 09-2017
Publisher: Geological Society of America
Date: 2000
Publisher: American Geophysical Union (AGU)
Date: 11-2003
DOI: 10.1029/2002GC000427
Publisher: American Geophysical Union (AGU)
Date: 07-2016
DOI: 10.1002/2016PA002929
Publisher: Informa UK Limited
Date: 03-07-2016
Publisher: Geological Society of America
Date: 2003
DOI: 10.1130/G19832.1
Publisher: American Geophysical Union (AGU)
Date: 09-2007
DOI: 10.1029/2007GC001619
Publisher: Geochemical Society of Japan
Date: 2014
Publisher: American Geophysical Union (AGU)
Date: 12-2005
DOI: 10.1029/2005GC000973
Publisher: Society of Economic Geologists
Date: 08-2001
Publisher: Elsevier BV
Date: 06-2002
Publisher: Geological Society of America
Date: 1999
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 03-2002
Publisher: Copernicus GmbH
Date: 25-02-2015
Abstract: Abstract. The boron isotopic (δ11Bcarb) compositions of long-lived Porites coral are used to reconstruct reef-water pH across the central Great Barrier Reef (GBR) and assess the impact of river runoff on inshore reefs. For the period from 1940 to 2009, corals from both inner- and mid-shelf sites exhibit the same overall decrease in δ11Bcarb of 0.086 ± 0.033‰ per decade, equivalent to a decline in seawater pH (pHsw) of ~0.017 ± 0.007 pH units per decade. This decline is consistent with the long-term effects of ocean acidification based on estimates of CO2 uptake by surface waters due to rising atmospheric levels. We also find that, compared to the mid-shelf corals, the δ11Bcarb compositions of inner-shelf corals subject to river discharge events have higher and more variable values, and hence higher inferred pHsw values. These higher δ11Bcarb values of inner-shelf corals are particularly evident during wet years, despite river waters having lower pH. The main effect of river discharge on reef-water carbonate chemistry thus appears to be from reduced aragonite saturation state and higher nutrients driving increased phytoplankton productivity, resulting in the drawdown of pCO2 and increase in pHsw. Increased primary production therefore has the potential to counter the more transient effects of low-pH river water (pHrw) discharged into near-shore environments. Importantly, however, inshore reefs also show a consistent pattern of sharply declining coral growth that coincides with periods of high river discharge. This occurs despite these reefs having higher pHsw, demonstrating the overriding importance of local reef-water quality and reduced aragonite saturation state on coral reef health.
Publisher: Elsevier BV
Date: 15-09-2004
Publisher: Geological Society of America
Date: 1995
Publisher: Springer Science and Business Media LLC
Date: 05-1993
DOI: 10.1007/BF00307867
Publisher: Oxford University Press (OUP)
Date: 19-02-2009
Publisher: Springer Science and Business Media LLC
Date: 15-03-2017
Publisher: Informa UK Limited
Date: 09-2005
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 07-2008
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B505020K
Publisher: Springer Science and Business Media LLC
Date: 11-2003
Publisher: Mineralogical Society
Date: 12-2001
Abstract: The construction of zirconium (Zr) budgets for metamorphic reactions in high-grade rocks provides new insight into zircon growth during metamorphism. In this study we target reactions involving garnet, as they enable zircon growth to be related to known pressure and temperature conditions. Two reactions involving the breakdown of Zr-bearing garnet from Rogaland, SW Norway have been investigated in detail, showing contrasting behaviour of Zr, with zircon formation being subject to the solubility of Zr in product phases. In the decompression reaction garnet + sillimanite + quartz → cordierite, Zr released during garnet breakdown cannot be incorporated into the cordierite structure, resulting in zircon nucleation and growth. In contrast, for the reaction garnet + biotite + sillimanite + quartz → osumilite + orthopyroxene + spinel + magnetite, no new zircon growth takes place, despite the garnet involved containing more than double the Zr concentration of the former reaction. In the latter case, all the Zr released by garnet breakdown can be detected in the product phases osumilite and orthopyroxene, thereby preventing growth of new metamorphic zircon. This study highlights the potential for high resolution geochronology in metamorphic rocks by relating zircon growth to specific metamorphic reactions.
No related grants have been discovered for Stephen Eggins.