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Radiocarbon Dating (radiocarbon + dating)
Selected AbstractsOn Radiocarbon Dating of Ground WaterGROUND WATER, Issue 6 2000Chen Zhu No abstract is available for this article. [source] The Sirente crater field, ItalyMETEORITICS & PLANETARY SCIENCE, Issue 11 2002Jens ORMö They are located in the Sirente plain within the mountains of the Abruzzo region, central Italy. The craters are distributed in a field 450 m long and 400 m wide. This field consists of ,17 smaller craters close to a larger main crater. The main crater is located in the southern end of the crater field and is 140 m long and 115 m wide, measured rim-to-rim. It has a well-developed, saddle-shaped rim that rises at a maximum 2.2 m above the surrounding plain. Radiocarbon dating of the target surface preserved below the rim gave a calibrated age of formation at about a.d. 412 (1650 ± 40 radiocarbon years b.p.). This young age is consistent with the apparent little modification of the rim. The morphology of the main crater and its relation to a crater field strongly points to its origin by impact from a projectile that broke up during its passage through the atmosphere. Quartz is very rare in the target and no planar deformation features have been found so far. The rim material and the upper 4 m of the main crater infill are impregnated with ferric oxides, which gives a more reddish colour compared to the other sediments of the plain. Rusty crusts with high Fe and Mn content occur in the rim material, but have not been found in the plain's sediments. Some of these crusts can be separated by magnet, and have sporadic micron-sized Ni-rich granules. The main crater is in the size range of the craters with explosive dispersion of the projectile and has many features comparable to both large experimental and meteoritic impact craters formed in loose sediments. We suggest that this crater represents a rare example of well-preserved, small impact crater formed in unconsolidated target materials. [source] Soil organic carbon pools in a periglacial landscape: a case study from the central Canadian ArcticPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2010Gustaf Hugelius Abstract We investigated total storage and landscape partitioning of soil organic carbon (SOC) in continuous permafrost terrain, central Canadian Arctic. The study is based on soil chemical analyses of pedons sampled to 1-m depth at 35 individual sites along three transects. Radiocarbon dating of cryoturbated soil pockets, basal peat and fossil wood shows that cryoturbation processes have been occurring since the Middle Holocene and that peat deposits started to accumulate in a forest-tundra environment where spruce was present (,6000 cal yrs BP). Detailed partitioning of SOC into surface organic horizons, cryoturbated soil pockets and non-cryoturbated mineral soil horizons is calculated (with storage in active layer and permafrost calculated separately) and explored using principal component analysis. The detailed partitioning and mean storage of SOC in the landscape are estimated from transect vegetation inventories and a land cover classification based on a Landsat satellite image. Mean SOC storage in the 0,100-cm depth interval is 33.8,kg C,m,2, of which 11.8,kg C m,2 is in permafrost. Fifty-six per cent of the total SOC mass is stored in peatlands (mainly bogs), but cryoturbated soil pockets in Turbic Cryosols also contribute significantly (17%). Elemental C/N ratios indicate that this cryoturbated soil organic matter (SOM) decomposes more slowly than SOM in surface O-horizons. Copyright © 2010 John Wiley & Sons, Ltd. [source] Pleistocene Plant Fossils in and near La Selva Biological Station, Costa Rica1BIOTROPICA, Issue 3 2003Sally P. Horn ABSTRACT Radiocarbon dating and 40Ar/39Ar analysis of overlying tephra indicate that plant fossil assemblages exposed by stream erosion and well construction in and near La Selva Biological Station in eastern lowland Costa Rica are Pleistocene in age. We identified plant taxa based on wood, leaves, fruits, seeds, pollen, and spores examined from three sites at ca 30 m elevation. Extrapolating from modern ranges and surface temperature lapse rates suggests paleotemperatures 2.5,3.1°C cooler than at present RESUMEN Dataciones radiocarbónicas y análisis de argon (40Ar/39Ar) de la tefra sobrepuesta indican una edad Pleistocénica para las asociaciones de plantas fósiles expuestas por erosión fluvial y por la construcción de un pozo dentro y cerca de la Estación Biológica La Selva en la bajura oriental de Costa Rica. Se identificaron los táxones vegetales con base en madera, hojas, frutas, semillas, polen, y esporas de tres sitios ubicados a unos 30 m sobre el nivel de mar. Los resultados, basados en la extrapolación de los ámbitos geográficos y del gradiente vertical de la temperatura superficial modernos, sugiere paleotemperaturas 2.5,3.1°C mas frescas que en el presente. [source] Palaeopedological marker horizons in northern central Europe: characteristics of Lateglacial Usselo and Finow soilsBOREAS, Issue 3 2009KNUT KAISER Lateglacial buried soil horizons, which occur widely in sandy aeolian sequences of northern central Europe, were analysed in order to evaluate their regional pedostratigraphical and palaeoenvironmental potential. Data on stratigraphy, sedimentology, pedology, geochronology and palaeobotany from 29 palaeosol-bearing profiles at terrestrial sites are presented. Greyish Ahb and Eb horizons occur, as well as brownish Bwb and BwAhb horizons. They are 5,30 cm thick, showing similar pedological properties except colour, and they frequently bear charcoal typically from pine. Soil classification results in Albic Arenosols (Dystric) and Brunic Arenosols (Dystric) representing palaeosols of the Usselo and Finow types, respectively. Radiocarbon dating of the palaeosols reveals a dominance of Allerød ages followed by Younger Dryas and Preboreal ages. Most luminescence ages on overlying aeolian sands date into the Allerød,Younger Dryas interval. Mapping of all Usselo and Finow soil occurrences (n=96) in northern central Europe known so far reveals a nearly closed Finow soil province between Usselo soil areas in NW Germany and central Poland, mainly situated in NE Germany. Most Usselo soils compiled contain charcoal, indicating widespread and repeated fires. Recent claims that the Usselo soil represents an event layer from rapid aeolian sedimentation caused by an extraterrestrial impact is rejected. Instead, both Usselo and Finow soils can be assumed to be pedostratigraphical marker horizons in northern central Europe and beyond. [source] Diagenesis and Evolution of the Holocene Coquinite from the Haishan Island, Eastern Guangdong, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009Jinlong SUN Abstract: The coastal hard rock with a thickness of over 5 m and a distribution area of nearly 200 ha in the Haishan Island, south China, has long drawn researchers'attention. However, there were controversies over its formation and classification, and these controversies in turn lead to the dispute of sea level changes and coastal uplift-subsidence of this area. To investigate its diagenesis and evolution, petrographic analysis, elemental geochemistry, isotopic analysis, and radiocarbon dating were used in the present study. Radiocarbon dating indicates that the deposition of the Haishan Coquinite commenced in the mid Holocene and lasted to ,600 a B.P. Petrographic analysis shows that the Haishan Coquinite is cemented by low-Mg calcite, indicating that the cementation occurred in a meteoric environment. The elemental geochemistry and isotopic values demonstrate that the coquinite suffered strong leaching, which was thought to be responsible for the meteoric cementation of the coquinite. According to these results, the diagenesis of the coquinite is revealed: deposition of the Haishan Coquinite commenced in the mid Holocene in a shoal environment, initial cementation occurred and cement may be high-Mg calcite or aragonite; latterly the coquinite exposed to meteoric environment as a result of lowering of relative sea level, and the cement altered to low-Mg, which took the morphologies of bladed calcite rim and equant spar. A four-stage evolution model is proposed: (1) deposition stage, (2) initial cementation, (3) exposure to and cementation in meteoric environment, and (4) erosion stage. The published reports indicate that the hard rock should be designated as coquinite. Based on these studies, mid-Holocene sea level in this area was discussed, and the Haishan Island was proposed to uplift with a rate of ,5 mm/a in the last ,600 a. [source] Sediment transmission and storage: the implications for reconstructing landform developmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2010R. C. Chiverrell Abstract The late Holocene (last 3000 years) development of the lower Ribble valley (northwest England) displays evidence for a complex response to a sediment recharge event forced by land-use change induced increases in erosion and sediment delivery. The deposition of fluvial sediments during the late Holocene was restricted to a series of reaches or depocenters separated by zones with no sediment accumulation constrained by older glacial and fluvial terrain. Apparent reach-wide correlations of fluvial terraces break down under the scrutiny applied by comprehensive and extensive radiocarbon control. Bayesian testing of relative order models show that large-scale geomorphological changes, e.g. the progression from one terrace level to another, were time transgressive between different depocenters. The different histories of sediment delivery and storage are probably a function of local- and process-scale variations in these depocenters, and reflect (dis)connectivity relationships within a reach in propagating a basin-scale change (superslug) in the sediment regime. Disconnectivity in the depositional regime through a fluvial reach limits what we can reconstruct in terms of sediment budgets, but radiocarbon dating of multiple palaeochannels offers considerable potential for landform-based research to uncover rates of change within individual depocenters. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2007Thomas C. Pierson Abstract Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes , Mount Rainier, Mount St. Helens and Mount Hood , in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the single largest. A GLT correction of 5 years should be added to the mean ring-count age of the five largest trees growing on the surface being dated, if the trees are cored at ground level. This correction would have an approximate error of ±5 years. If the trees are cored at about 1·4 m above the ground surface (breast height), a CTG correction of 11 years should be added to the mean age of the five sampled trees (with an error of about ±7 years). Published in 2006 by John Wiley & Sons, Ltd. [source] Holocene valley aggradation driven by river mouth progradation: examples from AustraliaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2006Paul Rustomji Abstract Since the end of the post-glacial sea level rise 6800 years ago, progradation of river mouths into estuaries has been a global phenomenon. The responses of upstream alluvial river reaches to this progradation have received little attention. Here, the links between river mouth progradation and Holocene valley aggradation are examined for the Macdonald and Tuross Rivers in south-eastern Australia. Optical and radiocarbon dating of floodplain sediments indicates that since the mid-Holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary. This link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits. Both rivers have abandoned their main Holocene floodplains over the last 2000 years and their channels have contracted. A regional shift to smaller floods is inferred to be responsible for this change, though a greater relative sea level fall experienced by the Macdonald River since the mid-Holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley. Copyright © 2006 John Wiley & Sons, Ltd. [source] Amino acids in Quaternary soil horizons from southwest PolandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2003A. Szponar Summary Aminostratigraphy has proved to be a useful approach for dating fossils from the Quaternary. In these studies the amino acids in Quaternary soil formations were determined in an attempt to establish their stratigraphical relationships and relative ages. The sampling sites are in the southwest of Poland, in the Trzebnickie Hills. Three samples of fossil soils and two of recent soils were analysed. The absolute age of the soil samples was estimated by radiocarbon dating. We found that the total amount of amino acids decreased with the increasing age of soil. The smallest amounts of amino acids were found in the oldest fossil soil of Denekamp (Vistulian) age dated 29 600 ± 760 years bp. A sample of recent loess soil contained the most total amino acids, whereas the fossil soil of Lower Atlantic age, dated 3540 ± 230 years bp, was intermediate in respect of the total amount of amino acids, oxidation state and degree of biochemical transformation. Neutral amino acids formed a majority of all the amino acids studied. The method we describe could be useful in relative chronostratigraphical identification of fossil soils. [source] Advances in optically stimulated luminescence dating of individual grains of quartz from archeological depositsEVOLUTIONARY ANTHROPOLOGY, Issue 6 2007Zenobia Jacobs Abstract Paleoanthropologists and archeologists interested in occupation histories, faunal remains, and objects of material culture have become increasingly reliant on optically stimulated luminescence (OSL) dating to construct Quaternary chronologies. In part, the increased use of OSL dating reflects its capacity to date events beyond the range of radiocarbon dating and in contexts where suitable organic materials are absent. An earlier review in Evolutionary Anthropology by Feathers1 provides a general account of the principles of luminescence dating. Since then, however, important advances have been made in OSL dating of quartz, so that it is now possible to date individual sand-sized grains and thereby resolve issues of postdepositional mixing of archeological sediments. In this review, we discuss the most important of these advances and their implications with regard to improved age control of archeological sites. We cover aspects of instrumental and methodological development that have facilitated the widespread measurement of single grains related to archeological questions and illustrate our review with some examples of where archeological problems have been resolved using single-grain OSL dating. We do not propose single-grain dating as a panacea, because there are instances where it is not straightforward to use or the results may be difficult to interpret; dating in such contexts remains the subject of continuing research. [source] A Reassessment of the holocene stratigraphy of the Wadi Hasa Terrace and Hasa formation, JordanGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2007Joseph Schuldenrein Vita-Finzi's 1960s model for Mediterranean terrace evolution was once the basis for regional valley histories across much of the Levant. A revisit to the Hasa terrace, formerly considered Early to Middle Holocene in age, resulted in a revised chronostratigraphy. Sedimentological and geochemical analyses bolstered by radiocarbon dating indicate that valley floor construction began shortly after the end of the Middle Holocene, at least 2000 years later than initially proposed. An updated model for floodplain evolution proposes three discrete phases of accretion and alluvial plain formation. A weak cambic soil overprints the alluvium and suggests slightly moister climates than at present for much of the Late Holocene. This model is in accord with settlement data. Intensified uplands agropastoralism accelerated the erosion of slope soils that were recycled and deposited as alluvium across the valley floor. The valley floor sequences of the Hasa are analogous to alluvial chronologies for neighboring wadis of the eastern Jordan Rift and can be tied to key Middle and Late Holocene geomorphic events in the Dead Sea and the southwestern Levant. The data strongly indicate that alluvial fill histories after 1800 cal B.C. were anthropogenically driven, whereas Middle Holocene landscape changes were climatically and structurally triggered. © 2007 Wiley Periodicals, Inc. [source] Times of sand: Sedimentary history and archaeology at the Sigatoka Dunes, FijiGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2006Atholl Anderson The orthodox archaeological sequence at the Sigatoka Dunes site (VL 16/1) in Fiji proposes three phases of occupation spanning Fijian prehistory, each associated with a period of dune stability. It has been taken as the standard model of Fijian prehistory for more than 30 years. Recently, however, it has been argued that there is no stratigraphic support for three discrete levels and that the occupation history was fragmented, complex, and continuous within a volatile dune system. We present new data, from optical and radiocarbon dating, to argue that a three-phase model, although somewhat more complex in detail, remains the most robust interpretation of site history. The longest stable phase (Level 2) began 2500,2300 cal yr B.P. and is possibly associated with relatively low ENSO frequency. Substantial sand dune accumulation began after ,1300 cal yr B.P. © 2006 Wiley Periodicals, Inc. [source] Direct luminescence chronology of the Epipaleolithic Kebaran site of Nahal Hadera V, IsraelGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2003D.I. Godfrey-Smith We report direct luminescence ages for the culture-bearing sediments of the Kebaran site of Nahal Hadera V (NHV) in the coastal plain of Israel. Although the site contains, in addition to rich lithic deposits, plentiful mammalian bone, it has proved to be undatable using radiocarbon dating, in spite of the fact that the cultural context places the time of occupation well within the range of radiocarbon dating. In contrast, luminescence dating of the site sediments proved successful. Luminescence ages were determined using the single aliquot additive-dose (SAA) method, applied to sand-sized quartz extracts to determine past equivalent doses (De). Dose rates (R) were calculated using thick source alpha counting for the uranium (U) and thorium (Th) concentrations and x-ray fluorescence analysis for the potassium (K20) concentration. Of the five samples collected at the site, four represent cultural and subcultural deposits and the fifth represents the geological substrate for the archaeological deposit, a quartz-rich, carbonate-cemented dune sand known as aeolianite or kurkar. The luminescence age of the kurkar is 42.7 ± 6.3 ka. Human occupation of the site occurred between 21.3 ka and 14.0 ka ago, during the Last Glacial Maximum. © 2003 Wiley Periodicals, Inc. [source] Medieval big cat remains from the Royal Menagerie at the Tower of LondonINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2006H. O'Regan Abstract Big cats have been regarded as a symbol of power in different cultures throughout history. Here we present a study of the only known big cat remains from the Royal Menagerie at the Tower of London. They were excavated in 1937 but have not previously been published. Our radiocarbon dating has established that they range in date from the 13th,17th centuries, making them the earliest post-Pleistocene big cat remains in Britain. We provide a description of the specimens,two lion skulls, a fragmentary leopard, plus 19 dog crania,and discuss the partially occluded foramen magnum of one of the lions. This anomaly has also been noted in captive and unprovenanced cat skulls from the early 20th century, indicating that it is a condition with a long history. We discuss the remains, the history of the menagerie, and the uses of the animals, in the light of our knowledge of conditions for captive animals at the time. Zooarchaeological studies such as these may also provide insights for modern conservation of zoo animals, and this aspect of the work is also considered. Copyright © 2005 John Wiley & Sons, Ltd. [source] Is thermal oxidation at different temperatures suitable to isolate soil organic carbon fractions with different turnover?JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2010Mirjam Helfrich Abstract Findings of previous studies suggest that there are relations between thermal stability of soil organic matter (SOM), organo-mineral associations, and stability of SOM against microbial decay. We aimed to test whether thermal oxidation at various temperatures (200°C, 225°C, 275°C, 300°C, 400°C, or 500°C) is capable of isolating SOM fractions with increasing stability against microbial degradation. The investigation was carried out on soils (Phaeozem and Luvisol) under different land-use regimes (field, grassland, forest). The stability of the obtained soil organic carbon (SOC) fractions was determined using the natural- 13C approach for continuously maize-cropped soils and radiocarbon dating. In the Luvisol, thermal oxidation with increasing temperatures did not yield residual SOC fractions of increasing microbial stability. Even the SOC fraction resistant to thermal oxidation at 300°C contained considerable amounts of young, maize-derived C. In the Phaeozem, the mean 14C age increased considerably (from 3473 y BP in the mineral-associated SOC fraction to 9116 y BP in the residual SOC fraction after thermal oxidation at 300°C). An increasing proportion of fossil C (calculated based on 14C data) in residual SOC fractions after thermal oxidation with increasing temperatures indicated that this was mainly due to the relative accumulation of thermally stable fossil C. We conclude that thermal oxidation with increasing temperature was not generally suitable to isolate mineral-associated SOC fractions of increasing microbial stability. [source] New evidence for the occurrence of Eurasian lynx (Lynx lynx) in medieval Britain,JOURNAL OF QUATERNARY SCIENCE, Issue 1 2006David A. Hetherington Abstract The presence of Eurasian lynx as a former native species in Britain during the Holocene is known from bones recovered from several sites. AMS radiocarbon dating of lynx bone recovered from two sites in the Craven area of northern England gave 1842,±,35 14C,yr,BP and 1550,±,24 14C,yr,BP, together representing the youngest dates for lynx from England, and in the case of the latter, the youngest for Britain as a whole. These dates support the view that the game animal whose occurrence in the nearby Lake District is described in the early 7th century Cumbric text Pais Dinogad, and whose translation to date has been problematic, is a lynx. The occurrence of lynx in early medieval Britain shows that earlier periods of climate change, previously blamed for the species' extinction in Britain, were not responsible. Instead, anthropogenic factors such as severe deforestation, declining deer populations, and persecution, are likely to have caused the extirpation of lynx in Britain. Consequently, the lynx qualifies as a candidate for reintroduction. Large-scale reafforestation, the growth of deer populations, and more positive attitudes towards carnivores in modern society, could permit the restoration of lynx to Britain, particularly in Scotland. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Holocene shore displacement of Gästrikland, eastern Sweden: a contribution to the knowledge of Scandinavian glacio-isostatic uplift,JOURNAL OF QUATERNARY SCIENCE, Issue 6 2005Mikael Berglund Abstract The shore displacement in Gästrikland, east-central Sweden, has been investigated by means of AMS radiocarbon dating of sediment cores from isolated basins. Twenty dates from 11 sites are presented. Pollen and diatom analyses, and archive material from the Geological Survey of Sweden, have been used to identify isolation intervals in the cores and as chronological support to the 14C dates. An important pollen stratigraphical time-marker is a distinct mid-Holocene increase in Tilia. For the mid-Holocene, pollen stratigraphy is used rather than the 14C dates for the age determination. The deglaciation of Gästrikland, according to the new 14C dates, took place ca. 11,000,cal.,yr,BP (ca. 9500 14C,yr,BP). Through the Holocene the shore displacement is regressive. The regression was initially rapid (on average ca. 3.5,m per 100,yr 11,000,7500,cal.,yr,BP, probably much more rapid at the earliest stage), then slowed down considerably and was from ca. 5000,cal.,yr,BP (probably already from 7000,cal.,yr,BP) relatively constant, ca. 0.8,0.9,m per 100,yr. There are important differences between the shore level curve from Gästrikland and curves from other areas, indicating some irregularities in the regional glacio-isostatic rebound. Copyright © 2005 John Wiley & Sons, Ltd. [source] Dating the introduction of cereal cultivation to the British Isles: early palaeoecological evidence from the Isle of ManJOURNAL OF QUATERNARY SCIENCE, Issue 7 2003James B. Innes Abstract The adoption of cereal cultivation is a key benchmark in the transition from Mesolithic hunter,gatherer foraging to Neolithic farming economies, but the nature, timing and ecological,cultural context of the earliest cereal use in the British Isles and northwest Europe is still uncertain. We present AMS radiocarbon dating and fine-resolution pollen evidence from the Isle of Man for cereal growing in the latter stages of a distinct episode of forest disturbance at almost 6000,yr,BP (uncalibrated). The coherent ecological structure of this phase at the fine resolution level suggests that it records cereal cultivation well before the Ulmus decline, rather than wild grass pollen grains. This example is one of a cluster of early dates for cereal-type pollen near the start of the sixth millenium BP, including several around the Irish Sea, which indicate that the introduction of cereal agriculture probably occurred as early in the central British Isles as in the northern European plain. This early cereal phase is followed later by a probable phase of pre- Ulmus decline pastoral activity. We also report Mesolithic age woodland disturbance around 7000,yr,BP (uncalibrated) and the first radiocarbon dates for mid-Holocene forest history of the Isle of Man. Copyright © 2003 John Wiley & Sons, Ltd. [source] Summary findings of the fourth international radiocarbon intercomparison (FIRI)(1998,2001)JOURNAL OF QUATERNARY SCIENCE, Issue 7 2002Elisabetta Boaretto Abstract Interlaboratory comparisons have been widely used in applied radiocarbon science. These are an important part of ongoing quality assurance (QA) programmes, which are vital to the appropriate interpretation of the evidence provided by the 14C record in Quaternary applications (including climate change and environmental reconstruction). International comparisons of laboratory performance are an essential component of the quality assurance process in radiocarbon dating. If the user community is to have confidence in radiocarbon results, it needs to be assured that laboratories world wide are producing measurements that are reliable and in accordance with ,good practice'. The findings from the most recent (completed in 2001) and extensive (more than 90 participating laboratories) radiocarbon intercomparison (FIRI) are reported here. This study was designed (i) to assess comparability, or otherwise, of the results from different laboratories and (ii) to quantify the extent and possible causes of any interlaboratory variation. The results demonstrate that there are no significant differences amongst the main measurement techniques (gas proportional counting, liquid scintillation counting and accelerator mass spectrometry (AMS)) but there is evidence of small laboratory offsets relative to known age samples for some laboratories. There is also evidence in some cases of underestimation of measurement precision. Approximately 10% of all results were classified as extreme (outliers) and these results were generated by 14% of the laboratories. Overall, the evidence supports the fact that radiocarbon laboratories are generally accurate and precise but that, notwithstanding internal QA procedures, some problems still occur, which can best be detected by participation in independent intercomparisons such as FIRI, where the results allow individual laboratories to assess their performance and to take remedial measures where necessary. The results from FIRI are significant in that they show a broad measure of agreement between measurements made in different laboratories on a wide range of materials and they also demonstrate no statistically significant difference between measurements made by radiometric or AMS techniques. Copyright © 2002 John Wiley & Sons, Ltd. [source] Redating the onset of burning at Lynch's Crater (North Queensland): implications for human settlement in AustraliaJOURNAL OF QUATERNARY SCIENCE, Issue 8 2001C. S. M. Turney Abstract Lynch's Crater preserves a continuous, high-resolution record of environmental changes in north Queensland. This record suggests a marked increase in burning that appears to be independent of any known major climatic boundaries. This increase is accompanied, or closely followed, by the virtually complete replacement of rainforest by sclerophyll vegetation. The absence of any major climatic shift associated with this increase in fire frequency therefore has been interpreted as a result of early human impact in the area. The age for this increase in burning, on the basis of conventional radiocarbon dating, was previously thought to be approximately 38 000 14C yr BP, supporting the traditional model for human arrival in Australia at 40 000 14C yr BP Here we have applied a more rigorous pre-treatment and graphitisation procedure for radiocarbon dating samples from the Lynch's Crater sequence. These new dates suggest that the increase in fire frequency occurred at 45 000 14C yr BP, supporting the alternative view that human occupation of Australia occurred by at least 45 000,55 000 cal. yr BP. Copyright © 2001 John Wiley & Sons, Ltd. [source] Assessment of element distribution and heavy metal contamination in Chilika Lake sediments (India)LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2009D. W. Zachmann Abstract Chilika Lake is situated on the Indian east coast. It is one of the largest lagoons in the world, with a unique assemblage of marine, brackish water and freshwater species. Due to the opening of new connections to the sea in the years 2000 and 2008, an environmental change is expected in the lagoon. The study gives an assessment of sediment contamination by heavy metals on the verge of this change (sampling campaign in 2000). Sediment samples from two surface levels (0,5 and 30,35 cm), and from depth profiles, were analysed for mineralogical composition, main and trace element concentrations, and element bonding forms. Background concentrations from a depth profile were also examined. The profile spans a time of ,13 500 years. Age determinations by radiocarbon dating and the 137Cs- and 210Pb-method were carried out. The composition of the surface sediments is generally uniform. The heavy metals exhibit slightly decreasing concentrations from NE to SW, thus indicating the supply of contaminants from the Mahanadi River. The anthropogenic portion of the heavy metal supply is mainly bound to Fe-oxide-hydroxides. Phosphorus is enriched in the sediments of the southern lake sector. Changes in element concentrations in the last 13 500 years have occurred mainly in two steps. The long-term variations exceed the anthropogenic changes caused by the Mahanadi River inputs. The very sensitive response of coastal area fabrics on climate changes also causes fast geogenic changes in element concentrations in sediments (similar grain sizes). This prevents the use of element concentrations from deep sediment horizons to define contaminations in those areas. [source] Issues and opportunities in accelerator mass spectrometry for stable isotopesMASS SPECTROMETRY REVIEWS, Issue 5 2008Sam Matteson Abstract Accelerator mass spectrometry (AMS) has developed in the last 30 years many notable applications to the spectrometry of radioisotopes, particularly in radiocarbon dating. The instrumentation science of trace element AMS (TEAMS) that analyzes stable isotopes, also called Accelerator SIMS or MegaSIMS, while unique in many features, has also shared in many of these significant advances and has pushed TEAMS sensitivity to concentration levels surpassing many competing mass spectroscopic technologies. This review examines recent instrumentation developments, the capabilities of the new instrumentation and discernable trends for future development. © 2008 Wiley Periodicals, Inc., Mass Spec Rev 27: 470,484, 2008 [source] Evidence of Iberian Bronze Age ,Boquique' Pottery in the Balearic Islands: Trade, Marriage or Culture?OXFORD JOURNAL OF ARCHAEOLOGY, Issue 4 2003W. Waldren Summary. This paper deals with the recent discovery of Iberian ,Boquique' Bronze Age pottery on the Balearic Island of Mallorca. It marks the ,maritime' spread of this distinctive pottery into a geographic area not previously recorded. It should therefore be of particular interest to mainland investigators and others concerned with its geographical distribution as well as those dealing with long-distance trade and possible kinship links during the period. The find is further supported by the ,micaceous' and ,quartz' composition of the pottery clay fabric, since mica is not known on the island as a component of local clays. The presence of Boquique pottery with ,micaceous' clay properties is demonstrated by microphotographic slab and thin sections as well as chemical clay analysis. This suggests that the pottery was imported, either as a trade item or as personal possessions. Along with recent evidence of earlier trade in exotic ,elephant' ivory and other items during Bell Beaker times, where the Boquique pottery appears to be a late intrusive element into local Beaker contexts (Waldren 1998), this new evidence represents the first material sign of cultural maritime interaction (Boquique in the present case), either as demographic extension or commercial exchange of these cultural items into the area. Furthermore, contextual radiocarbon dating surveys strongly indicate a date of 1700,1400 BC for the pottery, in accord both with recent Iberian mainland dates as well as the local archaeological sequence in which it was found. [source] Resistivity structures in alas areas in Central Yakutia, Siberia, and the interpretation of permafrost historyPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2006Koichiro Harada Abstract Deep resistivity structures of permafrost in Siberia were investigated using a transient electromagnetic (TEM) method. The data were compared with temperature profiles. The high and low resistivity layers corresponded to permafrost and a talik, respectively, and the boundary between high and low resistivity was in good agreement with the temperature profile. In TEM surveys conducted from an alas to the taiga forest, the permafrost base was detected at a depth of more than 400,m. This corresponds to the known permafrost depth in this area. A talik was also found to exist at a depth of 100,200,m. Numerical studies indicate that the talik could have been produced by a thermokarst lake. The estimated period after initiation of alas formation agrees with radiocarbon dating results. In combination with the numerical analysis, the geo-electrical information provides a basic model for reconstructing the history of permafrost. Copyright © 2006 John Wiley & Sons, Ltd. [source] Quantitative evaluation of marine protein contribution in ancient diets based on nitrogen isotope ratios of individual amino acids in bone collagen: An investigation at the Kitakogane Jomon siteAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Yuichi I. Naito Abstract Nitrogen stable isotopes analysis of individual bone collagen amino acids was applied to archeological samples as a new tool for assessing the composition of ancient human diets and calibrating radiocarbon dates. We used this technique to investigate human and faunal samples from the Kitakogane shell midden in Hokkaido, Japan (5,300,6,000 cal BP). Using compound-specific nitrogen isotope analysis of individual amino acids, we aimed to estimate i) the quantitative contribution of marine and terrestrial protein to the human diet, and ii) the mean trophic level (TL) from which dietary protein was derived from marine ecosystems. Data were interpreted with reference to the amino acid trophic level (TLAA) model, which uses empirical amino acid ,15N from modern marine fauna to construct mathematical equations that predict the trophic position of organisms. The TLAA model produced realistic TL estimates for the Kitakogane marine animals. However, this model was not appropriate for the interpretation of human amino acid ,15N, as dietary protein is derived from both marine and terrestrial environments. Hence, we developed a series of relevant equations that considered the consumption of dietary resources from both ecosystems. Using these equations, the mean percentage of marine protein in the Kitakogane human diet was estimated to be 74%. Although this study is one of the first systematic investigations of amino acid ,15N in archeological bone collagen, we believe that this technique is extremely useful for TL reconstruction, palaeodietary interpretation, and the correction of marine reservoir effects for radiocarbon dating. Am J Phys Anthropol 143:31,40, 2010. © 2010 Wiley-Liss, Inc. [source] Age of A2 Horizon Charcoal and Forest Structure near Porto Trombetas, Pará, Brazil,BIOTROPICA, Issue 3 2001John K. Francis ABSTRACT To study the structure and composition of old-growth forest in the Saracá-Taquera National Forest near Porto Trombetas, Brazil, we established 36 0.25 ha plots and described the vegetation. We collected charcoal from the A2 soil horizon of each plot for radiocarbon dating. Although fires have been very rare in this forest during historic times, the presence of charcoal in these soils indicates fire at some earlier period. The ages (conventional radiocarbon age adjusted to 1997) of the charcoal ranged from 177 to 1547 years. These ages, however, did not correlate significantly with any of several measures of biodiversity or stand characteristics. The relative uniformity of the current old-growth forest indicates that either the prehistoric fires were of such low intensity that they had little long-term effect on the vegetation or that the present stands have progressed to near steady state. [source] Mangrove Distribution during the Holocene in Tribugí Gulf, Colombia,BIOTROPICA, Issue 1 2000Carlos Jaramillo ABSTRACT Neotropical mangrove ecosystems have undergone drastic changes in terms of extension and floristic composition during Plio,Pleistocene times. It is unclear if the northern Pacific coast of Colombia has been occupied continuously by mangroves during the last 5000 years, or if their presence is a recent phenomenon. Two basic questions were asked: (1) is the establishment of mangroves recent?; and (2) what were the dominant floral taxa during the late Holocene? In the Gulf of Tribugí, northern Colombian Pacific, 22 sediment cores were drilled to a maximum depth of 2 m in a diverse suite of mangrove substrates and positions relative to the shoreline. Data were gathered from sedimentological descriptions, palynological analyses, and radiocarbon dating of these cores. During the last 4500 years, mangroves in the southern area of the Tribugí Gulf have remained floristically stable and dominated by Rhizophora. The abundant presence of Acrostichum aureum is recent, probably related to human activities. In contrast, two areas in the northern part of the Gulf show a different history. In the first area, the establishment of mangrove has been relatively recent (ca 2600 yr), probably a result of local subsidence due to tectonic faulting; this mangrove forest was and is dominated by Pelliciem rhizophorae. In the second area, mangrove pollen was not found in sediments younger than 2500 years, suggesting that the scarce presence of mangrove in the area is a result of recent colonization, and not due to logging as previously thought. RESUMEN Ecosistemas Neotropicales de manglar han sufrido cambios dramáticos tanto en su extensión como en su composición florística asociados con cambios climáticos y variaciories del nivel del mar durante el Plio-Pleistoceno. No es claro si la costa norte del Pacífico Colombiano ha sido ocupada por manglares durante los últimos 5000 años. Quisimos responder dos preguncas básicas: Es el establecimiento del manglar un fenómeno reciente? y Cuales fueron las especies que dominaron el mangle durante el Holoceno? Para responder estas preguntas extrajimos 22 corazones de sedimento cn el Golfo de Tribugá, costa norte del Pacífico Colombiano. Los corazones, de máximo dos metros de profundidad, fueron analizados con méttodos palinológicos, sedimentológicos y dataciones radiométricas. El tipo de sedimento más común fué lodo arenoso verde altamente bioperturbado por actividad infaunal. Los manglares mostraron ser muy estables y doniinados por Rhizophora en la mayoría de los sitios estudiados, con excepción de los manglares en la Chunga (Utría) y El Valle. Allí 10s manglares se establecieron recientemente. En la Chunga, un ascenso relativo del nivel del mar hace aproximadamente 2600 años a.p., probablemente local y asociado con la falla de Utría, posibilitó la colonización del sustrato por Pelliciera rhizophorae; es incierto determinar si este ascenso aún se esta produciendo. En el Valle, el escaso establecimiento del manglar es un proceso reciente de colonización y no una reducción en la cobertura del manglar producto de actividades humanas como previamente se asumía. [source] Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end-moraine zoneBOREAS, Issue 2 2010MARK D. JOHNSON Johnson, M. D. & Ståhl, Y. 2009: Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end-moraine zone. Boreas, 10.1111/j.1502-3885.2009.00124.x. ISSN 0300-9483 Deglaciation of the Middle Swedish end-moraine zone and age of the sediment in and between the moraines have been discussed for about a hundred years. The goal of this project was to determine the stratigraphy and age of the sediment in and between the moraines. Inter-moraine flats are underlain by clay, 10,25 m thick, overlying thin sand and gravel or till on bedrock. The clay is overlain by a few metres of sand and gravel. Much of the clay beneath the flats consists of rhythmites that grade from grey to red and are 2,74 cm thick. Our interpretation of these rhythmites as being varves is supported by grain size and mineralogical and elemental variations. Foraminifera and ostracods show that the clay was deposited in an arctic marine environment, while radiocarbon dating of the microfossils indicates that the clay was deposited 12 150 cal. 14C years ago, during the Younger Dryas chronozone (YD). Most of the optical stimulated luminescence dates on the clay are much older, containing quartz sand that was insufficiently bleached. The stratigraphy indicates that the moraines are composed of YD clay pushed into ridge forms during ice-front oscillations. It is not possible to determine how far north the Scandinavian Ice Sheet retreated prior to the YD advance. We neither support nor reject the suggestion that the ice margin retreated to the northern edge of Mt. Billingen during the Allerød, causing the Baltic Ice Lake to drain. [source] Holocene peat growth and decay dynamics in sub-arctic peat plateaus, west-central CanadaBOREAS, Issue 1 2009A. BRITTA K. SANNEL Peat and net carbon accumulation rates in two sub-arctic peat plateaus of west-central Canada have been studied through geochemical analyses and accelerator mass spectrometry (AMS) radiocarbon dating. The peatland sites started to develop around 6600,5900 cal. yr BP and the peat plateau stages are characterized by Sphagnum fuscum peat alternating with rootlet layers. The long-term peat and net carbon accumulation rates for both profiles are 0.30,0.31 mm/yr and 12.5,12.7 gC/m2yr, respectively. These values reflect very slow peat accumulation (0.04,0.09 mm/yr) and net carbon accumulation (3.7,5.2 gC/m2yr) in the top rootlet layers. Extensive AMS radiocarbon dating of one profile shows that accumulation rates are variable depending on peat plateau stage. Peat accumulation rates are up to six times higher and net carbon accumulation rates up to four times higher in S. fuscum than in rootlet stages. Local fires represented by charcoal remains in some of the rootlet layers result in very low accumulation rates. High C/N ratios throughout most of the peat profiles suggest low degrees of decomposition due to stable permafrost conditions. Hence, original peat accretion has remained largely unaltered, except in the initial stages of peatland development when permafrost was not yet present. [source] | |||||||||||||||||||