ORCID Profile
0000-0003-4186-4828
Current Organisation
University of Wollongong
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Publisher: Elsevier BV
Date: 12-2011
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 04-2013
Publisher: Elsevier BV
Date: 08-2006
Publisher: Elsevier BV
Date: 10-2015
Publisher: Cambridge University Press (CUP)
Date: 14-08-2020
DOI: 10.1017/QUA.2020.61
Abstract: Here we report the findings from excavations at the open-air Middle Palaeolithic site of Alapars-1 in central Armenia. Three stratified Palaeolithic artefact assemblages were found within a 6-m-thick alluvial-aeolian sequence, located on the flanks of an obsidian-bearing lava dome. Combined sedimentological and chronological analyses reveal three phases of sedimentation and soil development. During Marine Oxygen Isotope Stages 5–3, the manner of deposition changes from alluvial to aeolian, with a development of soil horizons. Techno-typological analysis and geochemical sourcing of the obsidian artefacts reveal differential discard patterns, source exploitation, and artefact densities within strata, suggesting variability in technological organization during the Middle Palaeolithic. Taken together, these results indicate changes in hominin occupation patterns from ephemeral to more persistent in relation to landscape dynamics during the last interglacial and glacial periods in central Armenia.
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CUB.2015.12.050
Abstract: The fossil record provides tangible, historical evidence for the mode and operation of evolution across deep time. Striking patterns of convergence are some of the strongest ex les of these operations, whereby, over time, similar environmental and/or behavioral pressures precipitate similarity in form and function between disparately related taxa. Here we present fossil evidence for an unexpected convergence between gregarious plant-eating mammals and dinosaurs. Recent excavations of Late Pleistocene deposits on Rusinga Island, Kenya, have uncovered a catastrophic assemblage of the wildebeest-like bovid Rusingoryx atopocranion. Previously known from fragmentary material, these new specimens reveal large, hollow, osseous nasal crests: a craniofacial novelty for mammals that is remarkably comparable to the nasal crests of lambeosaurine hadrosaur dinosaurs. Using adult and juvenile material from this assemblage, as well as computed tomographic imaging, we investigate this convergence from morphological, developmental, functional, and paleoenvironmental perspectives. Our detailed analyses reveal broad parallels between R. atopocranion and basal Lambeosaurinae, suggesting that osseous nasal crests may require a highly specific combination of ontogeny, evolution, and environmental pressures in order to develop.
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
DOI: 10.1038/S41467-020-18996-3
Abstract: The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality.
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 2011
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/FP16035
Abstract: We measured a erse range of foliar characteristics in shrub and tree species in temperate rainforest communities along a soil chronosequence (six sites from 8 to 120 000 years) and used multilevel model analysis to attribute the proportion of variance for each trait into genetic (G, here meaning species-level), environmental (E) and residual error components. We hypothesised that differences in leaf traits would be driven primarily by changes in soil nutrient availability during ecosystem progression and retrogression. Several leaf structural, chemical and gas-exchange traits were more strongly driven by G than E effects. For leaf mass per unit area (MA), foliar [N], net CO2 assimilation and dark respiration rates and foliar carbohydrate concentration, the G component accounted for 60–87% of the total variance, with the variability associated with plot, the E effect, much less important. Other traits, such as foliar [P] and N : P, displayed strong E and residual effects. Analyses revealed significant reductions in the slopes of G-only bivariate relationships when compared with raw relationships, indicating that a large proportion of trait–trait relationships is species based, and not a response to environment per se. This should be accounted for when assessing the mechanistic basis for using such relationships in order to make predictions of responses of plants to short-term environmental change.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 09-2015
Publisher: Cambridge University Press (CUP)
Date: 09-2013
DOI: 10.1016/J.YQRES.2013.06.008
Abstract: Expansion or shrinkage of closed lakes is a natural response to fluctuations in precipitation and evaporation, linked closely to changes in strength or position of atmospheric circulation. In Tibet, there are many such lakes with paleo-shorelines that can be used for reconstructions of climate history. Despite the fact that many paleo-shorelines are well preserved in Tibet, dating them has been seriously hindered by various difficulties. Here we present the first optical dating chronology for a series of paleo-shorelines in Zhari Namco, the third-largest inland lake in central Tibet. Our results indicate that the lake level has dropped 128 m over the past 8.2 ka. Younger shorelines are found at lower altitudes, indicating that the shorelines follow a geomorphic-chronological order and a broadly continuous trend of stepwise shrinkage. The surface area of Zhari Namco has shrunk in size from 4605 km 2 at 8.2 ka ago to 996 km 2 at present 300 km 2 of water has been lost from this lake. Such a loss in water implies a significant reduction in precipitation over the past 8.2 ka, a likely result of a weakening Asian monsoon. Following the decreasing precipitation since the early Holocene, this area has become increasingly arid.
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 02-2202
Publisher: Elsevier BV
Date: 09-2007
Publisher: Elsevier BV
Date: 07-2012
Publisher: Elsevier BV
Date: 07-2012
Publisher: Elsevier BV
Date: 03-2020
Publisher: IOP Publishing
Date: 29-10-2008
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 2007
Publisher: Wiley
Date: 08-11-2018
DOI: 10.1111/GCB.14413
Publisher: Elsevier BV
Date: 02-2006
Publisher: Elsevier BV
Date: 06-2013
Publisher: Walter de Gruyter GmbH
Date: 27-09-2013
DOI: 10.2478/S13386-013-0128-3
Abstract: The residual doses and sensitivity change for potassium-rich feldspar (K-feldspar) have been studied using the post-infrared infrared stimulated luminescence (pIRIR) and multi-elevated-temperature post-IR IRSL (MET-pIRIR) protocols. Laboratory simulated poorly-bleached and well-bleached s les were those K-feldspar grains bleached using a solar simulator for 10 minutes and 8 hours, respectively. The residual doses rise with stimulation temperature and time. The poorly-bleached s le has larger residual doses than the well-bleached s le, especially at high stimulation temperatures. The high-temperature pIRIR signals contain a large amount of hard-to-bleach signals. A decrease of luminescence sensitivity was observed after conducting a high-temperature-treatment in the measurement cycles. The sensitivity decreases significantly between the first and the second cycle. The extent of decrease in sensitivity shows a clear temperature trend. The higher the stimulation temperature of pIRIR signals is, the larger the sensitivity decreases. This decrease is more severe for the poorly-bleached s le than for the well-bleached s le, and could possibly lead to problems in sensitivity correction.
Publisher: Public Library of Science (PLoS)
Date: 09-08-2018
Publisher: MDPI AG
Date: 26-12-2020
DOI: 10.3390/MPS3010002
Abstract: We studied the characteristics of the optically stimulated luminescence (OSL) signal of single-grain quartz from three sites in China, Italy, and Libya, including the brightness, decay curve and dose response curve (DRC) shapes, recuperation, and reproducibility. We demonstrate the large variation in OSL behaviors for in idual quartz grains of different s les from different regions, and show that recuperation, sensitivity change, and reproducibility are independent of the brightness and decay curve shape of the OSL signals. The single-grain DRCs can be ided into at least eight groups with different characteristic saturation doses (D0), and a standardized growth curve (SGC) can be established for each of the DRC groups. There is no distinctive difference in the shape of OSL decay curves among different DRC groups, but s les from different regions have a difference in the OSL sensitivities and decay shapes for different groups. Many of the quartz grains have low D0 values (30–50 Gy), and more than 99% of the grains have D0 values of Gy. Our results raise caution against the dating of s les with equivalent dose values higher than 100 Gy, if there are many low-D0 and ‘saturated’ grains.
Publisher: SAGE Publications
Date: 30-11-2011
Abstract: Luminescence dating of the fluvial and lacustrine sediments from the Sala Us River valley at the south edge of the Mu Us Desert, central Inner Mongolia, is reported. The study region lies in the northwestern marginal zone of the east Asian summer monsoon and is sensitive to climate change. The dating results combined with environmental proxies indicate that the Holocene Climate Optimum period, took place from 8.5 to 5 ka ago and was marked by lake development. After ~5 ka ago, the region became arid, as inferred from lake regression and fluvial activity. Deposition of fluvial sediments lasted from ~5 ka to ~2 ka ago. At about 2 ka ago, incision of the Sala Us River was initiated into the underlying sediments, with a down-cutting rate of ~3–4 cm/yr. Since 2 ka ago, human activities also played an important role in causing environmental change in the region.
Publisher: Springer Science and Business Media LLC
Date: 03-2015
DOI: 10.1038/NATURE14283
Abstract: Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink probably located in the tropics, particularly in the Amazon. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity. The observed decline of the Amazon sink erges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Springer Science and Business Media LLC
Date: 25-07-2014
Publisher: Springer Science and Business Media LLC
Date: 2019
DOI: 10.1038/S41586-018-0843-2
Abstract: The Altai region of Siberia was inhabited for parts of the Pleistocene by at least two groups of archaic hominins-Denisovans and Neanderthals. Denisova Cave, uniquely, contains stratified deposits that preserve skeletal and genetic evidence of both hominins, artefacts made from stone and other materials, and a range of animal and plant remains. The previous site chronology is based largely on radiocarbon ages for fragments of bone and charcoal that are up to 50,000 years old older ages of equivocal reliability have been estimated from thermoluminescence and palaeomagnetic analyses of sediments, and genetic analyses of hominin DNA. Here we describe the stratigraphic sequences in Denisova Cave, establish a chronology for the Pleistocene deposits and associated remains from optical dating of the cave sediments, and reconstruct the environmental context of hominin occupation of the site from around 300,000 to 20,000 years ago.
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 03-2022
Publisher: Springer Science and Business Media LLC
Date: 2019
DOI: 10.1038/S41586-018-0870-Z
Abstract: Denisova Cave in the Siberian Altai (Russia) is a key site for understanding the complex relationships between hominin groups that inhabited Eurasia in the Middle and Late Pleistocene epoch. DNA sequenced from human remains found at this site has revealed the presence of a hitherto unknown hominin group, the Denisovans
Publisher: Wiley
Date: 12-2018
DOI: 10.1002/ECE3.4601
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.JHEVOL.2017.01.008
Abstract: The paper presents the results of optical dating of potassium-rich feldspar grains obtained from the Haua Fteah cave in Cyrenaica, northeast Libya, focussing on the chronology of the Deep Sounding excavated by Charles McBurney in the 1950s and re-excavated recently. S les were also collected from a 1.25 m-deep trench (Trench S) excavated during the present project below the basal level of the Deep Sounding. Optically stimulated luminescence (OSL) data sets for multi-grain, single aliquots of quartz for s les from the Middle Trench were previously published. Re-analyses of these OSL data confirm significant variation in the dose saturation levels of the quartz signal, but allow the most robust OSL ages to be determined for comparison with previous age estimates and with those obtained in this study for potassium-rich feldspars from the Deep Sounding. The latter indicate that humans may have started to visit the cave as early as ∼150 ka ago, but that major use of the cave occurred during MIS 5, with the accumulation of the Deep Sounding sediments. Correlations between optical ages and episodes of "Pre-Aurignacian" artefact discard indicate that human use of the cave during MIS 5 was highly intermittent. The earliest phases of human activity appear to have occurred during interstadial conditions (5e and 5c), with a later phase of lithic discard associated with more stadial conditions, possibly MIS 5b. We argue that the "Pre-Aurignacian" assemblage can probably be linked with modern humans, like the succeeding "Levalloiso-Mousterian" assemblage two modern human mandibles associated with the latter are associated with a modelled age of 73-65 ka. If this attribution is correct, then the new chronology implies that modern humans using "Pre-Aurignacian" technologies were in Cyrenaica as early as modern humans equipped with "Aterian" technologies were in the Maghreb, raising new questions about variability among lithic technologies during the initial phases of modern human dispersals into North Africa.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-10-2020
Abstract: Two archaic lineages overlapped with modern humans outside of Africa: the well-studied Neanderthals and their more mysterious cousins, the Denisovans. Denisovan remains are rare, being limited to Denisovan Cave in Siberia and a putative, undated jaw from Tibet. However, there is evidence for multiple introgressions from Denisovans into modern-day humans, especially in Australasian populations. By examining the sediment of Baishiya Karst Cave located on a high plateau in Tibet, Zhang et al. identified ancient mitochondrial DNA from Denisovans indicating their presence at about 100 thousand, 60 thousand, and possibly 45 thousand years ago. This finding provides insight into the timing and distribution of Denisovans in Asia and extends the time of occupation of the Tibetan plateau by hominins. Science , this issue p. 584
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 10-2011
Publisher: Elsevier BV
Date: 08-2010
Publisher: Wiley
Date: 05-2017
DOI: 10.1002/JQS.2949
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 05-2014
Publisher: Springer Science and Business Media LLC
Date: 25-02-2020
DOI: 10.1038/S41467-020-14668-4
Abstract: India is located at a critical geographic crossroads for understanding the dispersal of Homo sapiens out of Africa and into Asia and Oceania. Here we report evidence for long-term human occupation, spanning the last ~80 thousand years, at the site of Dhaba in the Middle Son River Valley of Central India. An unchanging stone tool industry is found at Dhaba spanning the Toba eruption of ~74 ka (i.e., the Youngest Toba Tuff, YTT) bracketed between ages of 79.6 ± 3.2 and 65.2 ± 3.1 ka, with the introduction of microlithic technology ~48 ka. The lithic industry from Dhaba strongly resembles stone tool assemblages from the African Middle Stone Age (MSA) and Arabia, and the earliest artefacts from Australia, suggesting that it is likely the product of Homo sapiens as they dispersed eastward out of Africa.
Publisher: Elsevier BV
Date: 02-2015
Publisher: IOP Publishing
Date: 30-06-2006
Publisher: Elsevier BV
Date: 10-2020
Publisher: American Association for the Advancement of Science (AAAS)
Date: 12-05-2017
Abstract: Analysis of DNA from archaic hominids has illuminated human evolution. However, sites where thousand-year-old bones and other remains can be found are relatively rare. Slon et al. wanted to exploit any trace remains that our ancestors left behind. They looked for ancient DNA of hominids and other mammals in cave sediments, even those lacking skeletal remains. They identified mitochondrial DNA from Neandertal and Denisovan in iduals in cave sediments at multiple sites. Science , this issue p. 605
Publisher: Elsevier BV
Date: 10-2020
Publisher: Wiley
Date: 02-2019
DOI: 10.1002/JQS.3086
Publisher: Springer Science and Business Media LLC
Date: 23-06-2021
DOI: 10.1038/S41586-021-03675-0
Abstract: Denisova Cave in southern Siberia is the type locality of the Denisovans, an archaic hominin group who were related to Neanderthals 1–4 . The dozen hominin remains recovered from the deposits also include Neanderthals 5,6 and the child of a Neanderthal and a Denisovan 7 , which suggests that Denisova Cave was a contact zone between these archaic hominins. However, uncertainties persist about the order in which these groups appeared at the site, the timing and environmental context of hominin occupation, and the association of particular hominin groups with archaeological assemblages 5,8–11 . Here we report the analysis of DNA from 728 sediment s les that were collected in a grid-like manner from layers dating to the Pleistocene epoch. We retrieved ancient faunal and hominin mitochondrial (mt)DNA from 685 and 175 s les, respectively. The earliest evidence for hominin mtDNA is of Denisovans, and is associated with early Middle Palaeolithic stone tools that were deposited approximately 250,000 to 170,000 years ago Neanderthal mtDNA first appears towards the end of this period. We detect a turnover in the mtDNA of Denisovans that coincides with changes in the composition of faunal mtDNA, and evidence that Denisovans and Neanderthals occupied the site repeatedly—possibly until, or after, the onset of the Initial Upper Palaeolithic at least 45,000 years ago, when modern human mtDNA is first recorded in the sediments.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 06-2020
Publisher: Elsevier BV
Date: 04-2020
Publisher: The Royal Society
Date: 14-12-2016
Abstract: Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high ersity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary ersity, ecosystem function and the response of tropical forests to global change.
Publisher: American Geophysical Union (AGU)
Date: 06-2008
DOI: 10.1029/2007JF000900
Publisher: Wiley
Date: 10-06-2013
DOI: 10.1002/JQS.2639
Publisher: Elsevier BV
Date: 04-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-05-2021
Abstract: Environmental DNA can identify the presence of species, even from the distant past. Surveying three cave sites in western Europe and southern Siberia, Vernot et al. identified nuclear DNA and confirmed that it is from the close relatives of anatomically modern humans—Neanderthal and Denisovan in iduals. A phylogenetic analysis and modeling show that the DNA in sediment s les from several layers corresponds to previously studied skeletal remains. These results demonstrate that environmental data can be applied to study the population genetics of the extinct Neanderthal and Denisovan lineages, identifying a turnover of Neanderthal populations ∼100,000 years ago. Science , this issue p. eabf1667
Publisher: Proceedings of the National Academy of Sciences
Date: 27-01-2020
Abstract: Neanderthals once inhabited Europe and western Asia, spreading as far east as the Altai Mountains in southern Siberia, but the geographical origin and time of arrival of the Altai populations remain unresolved. Excavations at Chagyrskaya Cave in the Altai foothills have yielded 90,000 stone artifacts, numerous bone tools, 74 Neanderthal fossils, and animal and plant remains recovered from 59,000- to 49,000-year-old deposits. The Chagyrskaya Neanderthals made distinctive stone tools that closely resemble Micoquian artifacts from eastern Europe, whereas other Altai sites occupied by earlier Neanderthal populations lack such artifacts. This suggests at least two dispersals of Neanderthals into southern Siberia, with the likely ancestral homeland of the Chagyrskaya toolmakers located 3,000 to 4,000 kilometers to the west, in eastern Europe.
Publisher: Springer Science and Business Media LLC
Date: 13-01-2016
DOI: 10.1038/NATURE16448
Abstract: Sulawesi is the largest and oldest island within Wallacea, a vast zone of oceanic islands separating continental Asia from the Pleistocene landmass of Australia and Papua (Sahul). By one million years ago an unknown hominin lineage had colonized Flores immediately to the south, and by about 50 thousand years ago, modern humans (Homo sapiens) had crossed to Sahul. On the basis of position, oceanic currents and biogeographical context, Sulawesi probably played a pivotal part in these dispersals. Uranium-series dating of speleothem deposits associated with rock art in the limestone karst region of Maros in southwest Sulawesi has revealed that humans were living on the island at least 40 thousand years ago (ref. 5). Here we report new excavations at Talepu in the Walanae Basin northeast of Maros, where in situ stone artefacts associated with fossil remains of megafauna (Bubalus sp., Stegodon and Celebochoerus) have been recovered from stratified deposits that accumulated from before 200 thousand years ago until about 100 thousand years ago. Our findings suggest that Sulawesi, like Flores, was host to a long-established population of archaic hominins, the ancestral origins and taxonomic status of which remain elusive.
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 12-2012
Publisher: Public Library of Science (PLoS)
Date: 11-04-2018
Publisher: Elsevier BV
Date: 08-2022
Publisher: Springer Science and Business Media LLC
Date: 07-04-2013
Publisher: Springer Science and Business Media LLC
Date: 19-11-2019
DOI: 10.1038/S41586-018-0710-1
Abstract: Levallois approaches are one of the best known variants of prepared-core technologies, and are an important hallmark of stone technologies developed around 300,000 years ago in Africa and west Eurasia
Publisher: Cambridge University Press (CUP)
Date: 05-2016
DOI: 10.1016/J.YQRES.2016.03.002
Abstract: The Nihewan Basin is a key region for studying the Palaeolithic archaeology of East Asia. However, because of the lack of suitable dating methods and representative lithic technologies in this region, the ‘Middle Palaeolithic’ sites in this basin have been designated based mainly on stratigraphic correlation, which may be unreliable. In this study, three Palaeolithic sites, Motianling, Queergou and Banjingzi, which have been assigned previously to the ‘Middle Palaeolithic’, are dated based on luminescence dating of K-feldspar grains. Our results show that the cultural layers at Motianling, Queergou and Banjingzi have ages of 315 ± 13, 268 ± 13 and 86 ± 4 ka (corresponding to Marine Isotope Stages 9, 8 and 5), respectively, suggesting that Motianling and Queergou should be assigned to the Lower Palaeolithic, while the age of Banjingzi is consistent with a Middle Palaeolithic attribution. Our results suggest that reassessing the age of ‘Middle Palaeolithic’ sites in the Nihewan Basin, and elsewhere in North China, is crucial for understanding the presence or absence of the Middle Palaeolithic phase in China. Our dating results also indicate that the Sanggan River developed sometime between about 270 and 86 ka ago.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 08-2017
Publisher: Copernicus GmbH
Date: 14-03-2019
Abstract: Abstract. The New Zealand subantarctic islands of Auckland and C bell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap 384 000 ± 26 000 years ago (384±26 ka), most likely during Marine Isotope Stage 10, a period when the subtropical front was reportedly north of its present-day latitude by several degrees, and consistent with hemispheric-wide glacial expansion. Flow line modelling constrained by field evidence suggests a more restricted glacial period prior to the LGM that formed substantial valley glaciers on the C bell and Auckland Islands around 72–62 ka. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM ∼21 ka), our combined approach suggests minimal LGM glaciation across the New Zealand subantarctic islands and that no glaciers were present during the Antarctic Cold Reversal (ACR ∼15–13 ka). Instead, modelling implies that despite a regional mean annual air temperature depression of ∼5 ∘C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the middle to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
Publisher: Elsevier BV
Date: 08-2015
Publisher: Wiley
Date: 10-10-2018
DOI: 10.1111/GEB.12803
Abstract: Large tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan‐tropical model to predict plot‐level forest structure properties and biomass from only the largest trees. Pan‐tropical. Early 21st century. Woody plants. Using a dataset of 867 plots distributed among 118 sites across the tropics, we tested the prediction of the quadratic mean diameter, basal area, Lorey's height, community wood density and aboveground biomass (AGB) from the i th largest trees. Measuring the largest trees in tropical forests enables unbiased predictions of plot‐ and site‐level forest structure. The 20 largest trees per hectare predicted quadratic mean diameter, basal area, Lorey's height, community wood density and AGB with 12, 16, 4, 4 and 17.7% of relative error, respectively. Most of the remaining error in biomass prediction is driven by differences in the proportion of total biomass held in medium‐sized trees (50–70 cm diameter at breast height), which shows some continental dependency, with American tropical forests presenting the highest proportion of total biomass in these intermediate‐diameter classes relative to other continents. Our approach provides new information on tropical forest structure and can be used to generate accurate field estimates of tropical forest carbon stocks to support the calibration and validation of current and forthcoming space missions. It will reduce the cost of field inventories and contribute to scientific understanding of tropical forest ecosystems and response to climate change.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Elsevier BV
Date: 09-2007
Publisher: Walter de Gruyter GmbH
Date: 22-06-2014
DOI: 10.2478/S13386-013-0160-3
Abstract: Quartz has been the main mineral used for optically stimulated luminescence (OSL) dating of sediments over the last decade. The quartz OSL signal, however, has been shown to saturate at relatively low doses of ∼200–400 Gy, making it difficult to be used for dating beyond about 200 thou-sand years (ka), unless the environmental dose rate is low. The infrared stimulated luminescence (IRSL) from feldspars has been shown to continue to grow to higher dose levels than quartz OSL. The application of IRSL dating of feldspars, however, has long been h ered by the anomalous fading effect. Recent progress in understanding anomalous fading of the infrared stimulated luminescence (IRSL) signals in potassium-feldspar has led to the development of post-IR IRSL (pIRIR) protocols and also a multiple elevated temperature (MET) stimulation (MET-pIRIR) protocol. These procedures have raised the prospect of isolating a non-fading IRSL component for dating Quaternary deposits containing feldspars. In this study, we review the recent progress made on (1) overcoming anomalous fading of feldspar, and (2) the development of pIRIR dating techniques for feldspar. The potential and problems associated with these methods are discussed.
Publisher: Elsevier BV
Date: 05-2009
Publisher: Elsevier BV
Date: 05-2006
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 04-2012
Publisher: Elsevier BV
Date: 02-2011
Publisher: Elsevier BV
Date: 07-2012
Publisher: Wiley
Date: 08-07-2016
DOI: 10.1111/NPH.14079
Abstract: We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests ( TMF s) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco ( V cmax ), and the maximum rate of electron transport ( J max )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area ( M a , N a and P a , respectively), and chlorophyll from 210 species at 18 field sites along a 3300‐m elevation gradient. Western blots were used to quantify the abundance of the CO 2 ‐fixing enzyme Rubisco. Area‐ and N‐based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMF s, underpinned by greater investment of N in photosynthesis in high‐elevation trees. Soil [P] and leaf P a were key explanatory factors for models of area‐based V cmax and J max but did not account for variations in photosynthetic N‐use efficiency. At any given N a and P a , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil‐ and leaf‐P in defining the photosynthetic capacity of TMF s, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N‐use efficiency of these critically important forests.
Publisher: Springer Science and Business Media LLC
Date: 13-10-2007
Publisher: Elsevier BV
Date: 07-2006
Publisher: Walter de Gruyter GmbH
Date: 2008
DOI: 10.2478/V10003-008-0003-Z
Abstract: This study investigates lacustrine and fluvial sediments on the Sala Us River in the Mu Us Desert in central north China. Significant changes in environmental dose rate in part of the section could be shown to have occurred from measurements of the present day radioactivity and by the age reversal for some s les that had been dated by optically stimulated luminescence (OSL) measurements on quartz. These changes in dose rate can be attributed to recent uptake of radioactive elements found in the sediments this resulted in significant underestimation of the OSL ages. In this study, the new isochron method using K-feldspar grains has been applied to overcome the effects of changes in dose rate. Calculations are used to show that changes in the environmental dose rate factors, i.e. K, U, Th, water content and cosmic ray flux, and disequilibrium in the U and Th decay chains, e.g. radon escape, have a negligible effect on the isochron age. After applying the new isochron method, the effects of changes in dose rate caused by recent uptake of radioactive elements and changes in past water content were effectively overcome and true ages are obtained this was verified by repeating the luminescence isochron measurements on s les of overlying and underlying sediments.
Publisher: Cambridge University Press (CUP)
Date: 20-12-2020
DOI: 10.1017/QUA.2019.67
Abstract: Tianhuadong is a cave site located in the northwest of Yunnan Province, China. Since 2010, several surveys and one test excavation have yielded more than 1000 stone artifacts. The lithic assemblage shows some features of Levallois and Quina technologies, similar to those found in Middle Paleolithic sites in the Western Hemisphere. In this study, we summarize the lithic industry and propose a reliable chronology for the site using optically stimulated luminescence (OSL) dating of in idual quartz grains extracted from sediments. We applied the standardized growth curve method to deal with the problem associated with the saturation in natural OSL signals in quartz. Our dating results yielded ages of 90–40 ka, suggesting that the associated lithic assemblage could be assigned to Marine Oxygen Isotope Stages 5 and 4 and could potentially represent Middle Paleolithic technologies. Because the number of Middle Paleolithic sites in southwest China is small, this site provides one of the few traces of human occupation in southwest China during the early upper Pleistocene. Thus, it is important for understanding hominin evolution and dispersal in this region.
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 02-2017
Publisher: Research Square Platform LLC
Date: 16-02-2021
DOI: 10.21203/RS.3.RS-226285/V1
Abstract: Early Palaeolithic wooden implements are exceptionally rare. The best known are the spears and throwing sticks from Schöningen, Germany dated to ca. 300–330 thousand years (kyr) ago 1,2 and the 171-kyr old digging sticks from Poggetti Vecchi, Italy 3 . Here, we report a unique assemblage of 35 wooden implements from the site of Gantangqing, southwestern China, which was found associated with stone tools, antler soft hammers and cut-marked bones, and is dated to ca. 361–250 kyr at 95% probability. The wooden implements include digging sticks and complete, small, hand-held pointed tools. The tips of several had starch grains of plants with starch-rich rhizomes. We suggest that most of these tools were used for digging the rhizomes of sub-aquatic plants on the edges of an ancient lake. This discovery provides the earliest tangible evidence for the exploitation of sub-surface plant foods in the Middle Pleistocene. It also highlights the probable role of plant foods (especially underground storage organs [USOs]) in sub-tropical and tropical environments in which a wide variety of edible plants were available, and implies that hominins had a detailed knowledge of which plants, and which parts of plants, were edible. These tools also show that organic materials played an important role in Middle Pleistocene technology, and the sophistication of many of these tools off-sets the seemingly “primitive” design of stone tools in the East Asian Early Palaeolithic.
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 03-2014
Publisher: IAET SB RAS Publishing
Date: 2018
Publisher: Elsevier BV
Date: 10-2015
Publisher: Proceedings of the National Academy of Sciences
Date: 03-04-2017
Abstract: We present evidence from the Late Pleistocene of Sulawesi, Indonesia, where an unusually rich and unique symbolic complex was excavated from archaeological deposits spanning 30,000 to 22,000 y ago. Including previously unknown practices of self-ornamentation, used ochre, pigmented artifacts, and portable art, these findings advance our knowledge of the cultural repertoires of modern humans in Pleistocene Wallacea, including the nonparietal artworks and symbolic material culture of some of the world’s earliest known “cave artists.”
Publisher: Walter de Gruyter GmbH
Date: 26-05-2021
Abstract: Violet stimulation is a new development in optical dating which has been suggested to extend the upper age limit of optically simulated luminescence (OSL) dating of quartz. Despite the reported advantage, few validation tests and applications have been published so far. The present study investigated the violet stimulated luminescence (VSL) using a single aliquot regenerative dose (SAR) protocol and a multiple aliquot additive dose (MAAD) protocol. Sedimentary quartz s les from four archaeological sites in Europe with independent age controls spanning 40–900 ka were used, including Grotte Mandrin (France), Brooksby Quarry (UK), Cueva Negra del Estrecho del Río Quípar (Spain) and Sima de las Palomas del Cabezo Gordo (Spain). The equivalent dose of a relatively young s le (~40 ka) was successfully determined. However, significant underestimations were observed for older s les with higher doses. These findings indicate the need for further development of the measurement protocol to date high-dose natural s les.
Publisher: Elsevier BV
Date: 02-2016
Publisher: Elsevier BV
Date: 06-2013
No related grants have been discovered for Bo Li.