Origin of palaeofluids in a normal fault setting in the Aegean region

The province of Burdur (SW Turkey) is seismically an active region. A structural, geochronological, petrographical, geochemical and fluid inclusion study of extension veins and fault‐related calcite precipitates has been undertaken to reconstruct the palaeofluid flow pattern in this normal fault setting in the Aegean region. A palaeostress analysis and U/Th dating of the precipitates reveals the neotectonic significance of the sampled calcites. Fluid inclusion microthermometry of calcites‐filling extension veins shows final melting temperatures (T_m ice) of 0°C. This indicates pure water, most likely of meteoric origin. The oxygen isotope values (?9.8‰ to ?6.5‰ VPDB) and the carbon isotopic composition (?10.4‰ to ?2.9‰ VPDB) of these calcites also show a near‐surface meteoric origin of the fluid responsible for precipitation. The microstructural characteristics of fault‐related calcites indicate that calcite precipitation was linked with fault activity. Final melting temperature of fault‐related calcites ranges between 0 and ?1.9°C. The oxygen isotope values show a broad range between ?15.0‰ and ?2.2‰ VPDB. Several of these calcites have a δ¹⁸O composition that is higher or lower than the oxygen isotopic composition of meteoric calcites in the area (i.e. between ?10‰ and ?6‰ VPDB). The δ¹³C composition largely falls within the range of the host limestones and reflects a rock‐buffered system. Microthermometry and stable isotopic study indicate a meteoric origin of the fluids with some degree of water–rock interaction or mixing with another fluid. Temperatures deduced from microthermometry and stable isotope analyses indicate precipitation temperatures around 50°C. These higher temperatures and the evidence for water–rock interaction indicate a flow path long enough to equilibrate with the host–rock limestone and to increase the temperature. The combined study of extension vein‐ and fault‐related calcite precipitates enables determining the origin of the fluids responsible for precipitation in a normal fault setting. Meteoric water infiltrated in the limestones to a depth of at least 1 km and underwent water–rock interaction or mixing with a residual fluid. This fluid was, moreover, tapped during fault activity. The extension veins, on the contrary, were passively filled with calcites precipitating from the downwards‐migrating meteoric water.     

Palaeoenvironmental and chronological investigations of the Magdalenian sites of Goyet Cave and Trou de Chaleux (Belgium), via stable isotope and radiocarbon analyses of horse skeletal remains

Trou de Chaleux and Goyet are caves situated less than 30 km apart in Belgium that contain stratified Magdalenian artefacts and butchered faunal remains. Published radiocarbon dates suggest that both sites were contemporaneously occupied during to the Late-glacial interstadial. It has previously been suggested that the Trou de Chaleux Late-glacial faunal remains might be slightly older than those at Goyet Cave, and that Trou de Chaleux has two phases of occupation during the Late-glacial interstadial. However, the limited number of radiocarbon dates currently available makes it impossible to determine whether the sites are truly contemporaneous, and the assessment of their absolute chronologies is complicated by a plateau in the calibration curve. In this paper, bone collagen δ¹³C and δ¹⁵N signatures of horse bones from the two sites are used to reconstruct local palaeoenvironments. We hypothesise that if occupations at the two sites were contemporaneous, the horse collagen δ¹³C and δ¹⁵N isotope signatures from both sites will be similar, since comparable carbon and nitrogen isotopic values would reflect similar diets, ecologies and environments. To provide clear dating parameters, new AMS radiocarbon determinations are also presented. Results show that horse collagen δ¹³C and δ¹⁵N isotope signatures at the two sites are different, indicating that the populations were not subject to similar diets, ecologies and environments. The new radiocarbon dates confirm that the horse bones from Trou de Chaleux date to the Late-glacial interstadial, but they also show that in Goyet Cave Horizons 1 and 2, older horse remains dating to ca. 32?000–27?000 ¹⁴C yr BP are mixed with Late-glacial horse remains. The δ¹⁵N values of the Goyet Cave horse bones radiocarbon dated to the Pleniglacial are substantially higher than those that have Late-glacial radiocarbon dates. Therefore, we now hypothesise that the majority of the horse bones isotopically analysed from Goyet Cave Horizon 1 are Pleniglacial in age. Statistical analysis of the radiocarbon dates indicates that the Late-glacial occupation at the two sites was contemporaneous, and that while there may appear to be two phases of occupation at Trou de Chaleux, this may be an artefact of the radiocarbon calibration curve.     

放射性碳素测定年代报告(三四)

本报告发表的是中国社会科学院考古研究所考古科技实验研究中心碳十四实验室在2006年到2007年期间测定的30个考古数据。数据表示方式同此前所发报告。为方便应用另做几点说明如下。1.碳十四年代半衰期按5568年计算。2.校正年代所用程序为OxCal,校正曲线为1998年公布版本。3.与以往报告相同,所给年代误差范围均为±16,年代范围的概率分布为68.2%。4.由于树轮年代校正曲线各区段形状不同,校     

Restrictions on fluorine depth profiling for exposure age dating in archaeological bones

Archaeological fragments of bone and teeth that are exposed to a humid environment take up fluorine from the surrounding soil. The fluorine ion replaces the hydroxyl group in the mineral phase of the bone, forming chemically more stable fluorapatite. In cortical parts of the long bone diaphysis a fluorine concentration profile can be observed, which decreases from the outer surface and the marrow cavity towards the inner parts of the bone matrix. Geological time spans are needed for this process to reach equilibrium and for the distribution to become uniform. As the shape of the profile, which can be described by a diffusion model, contains information on the exposure duration of the fossil object, several attempts to use fluorine profiling as a dating method have been undertaken. The distribution of fluorine in an archaeological sample however is strongly influenced by environmentally induced processes of bone diagenesis, i.e. alteration in the structure and composition of the mineral phase and degradation of organic components that may make the time information indistinct. The primary chemical composition of bones can thus be obscured by diagenesis within tens, hundreds or thousands of years. This depends more on the diagenetic environment than on the geological age. To observe the impact of environmental influence on the profile shape, samples from several burial sites featuring various soil conditions have been analyzed for their fluorine distribution and preservation state. This paper provides an overview on the restrictions that have to be considered when attempts are undertaken to relate a fluorine diffusion pattern to the archaeological age of a bone specimen.     

Obsidian hydration dating: accuracy and resolution limitations imposed by intrinsic water variability

Obsidian hydration dating typically yields a range of ages for a single chronometric measurement, even after controlling for source chemistry and effective hydration temperature. Previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water, and specifically hydroxyl ions, in the obsidian. Such variability exists within any given obsidian source, and even within any particular specimen. This paper analyzes the effect on age estimates of intrinsic water variability and concludes that if a controlled sample of obsidian yields a range of ages, there is no way to tell whether the range is due to long site use or to variations in hydroxyl concentration. At present there is no robust and cost-effective protocol for measuring hydroxyl concentration. Suggested guidelines for obsidian hydration dating are developed using a case study. These findings do not invalidate obsidian hydration as a chronometric technique, but they do suggest limits to the temporal resolution achievable.     

Rodent-based age appraisal of the Lower Siwalik Subgroup of Kalaunta,Ramnagar, Jammu,India

Parmar, V., Magotra, R., Norboo, R. & Prasad, G.V.R., July 2016. Rodent-based age appraisal of the Lower Siwalik Subgroup of Kalaunta, Ramnagar, Jammu, India. Alcheringa 41, xx-xx. ISSN 0311-5518.

Rocks of the Lower Siwalik Subgroup exposed around Ramnagar town in Jammu, India, have been known for more than 90 years to yield Chinji-equivalent (14.2–11.2 Ma) hominoid fossils. In 1997, the fossil ape Sivapithecus reported near Kalaunta village in the vicinity of Ramnagar was argued to be about 18 Ma old by its discoverers. This had implications for hominoid evolutionary studies, as molecular clock calibrations are commonly based on Sivapithecus first appearance datum (FAD). In a paper published in 2010, the identification of this hominoid tooth was questioned and reassigned to a suid. Recently, based upon the discovery of an indeterminate fossil bovid from the supposedly hominoid-yielding site near Kalaunta, an age estimate between ca 13.9 and 10.8 Ma was provided. As rodent biochronology has proven to be useful in age assignment of upper Cenozoic terrestrial sequences, the age of the fossil-bearing Lower Siwalik Subgroup of Kalaunta is re-assessed based upon newly recovered cricetid taxa. The cricetid rodents from this site comprise Punjabemys downsi and P. mikros. These two species are known to exist in the well-dated Potwar Siwalik Group succession between 14.3 and 12.6 Ma and between 16.3 and 13.0 Ma, respectively. Based on the overlapping temporal ranges of the cricetid taxa and an indeterminate Bovidae (ca 13.9–10.8 Ma) reported previously from this area, an age of 13.9–13.0 Ma is inferred for rocks occurring in the vicinity of Kalaunta. The new finds refute earlier claims of rocks in the area extending back to ca 18 Ma or as young as 10.8 Ma.

Varun Parmar [varunparmarvp@gmail.com], Rahul Magotra [rahulmagotra01@gmail.com] and Rigzin Norboo [norboo04@gmail.com], Post Graduate Department of Geology, University of Jammu, Jammu, 180 006, India; Guntupalli Veera Raghavendra Prasad [guntupalli.vrprasad@gmail.com], Department of Geology, Centre for Advanced Studies, University of Delhi, Delhi, 110 007, India.     

耀州窑瓷器的热释光特性研究及年代测定

耀州窑是中国古代北方青瓷的代表,在青瓷发展史上占有重要位置。为了深入研究耀州窑青瓷的热释光特性,提高热释光测定耀州窑瓷器年代的准确性,本研究测试了16件耀州窑瓷片。前剂量饱和指数法被应用于测定耀州窑青瓷的古剂量。运用厚源计数法测量瓷胎与埋藏环境土壤样品的α计数、X射线荧光光谱仪测量K含量等方法进行年剂量测定;得到了针对测量耀州窑瓷器样品的热释光特性参数,优化了测量程序,获得了更适用于耀州窑地理环境的年剂量数据,减小了未来样品的取样量,为更好地研究与鉴别其真伪提供了有效的科学依据与方法。     

用于碳十四年代测定的古代灰浆样品分析与前处理方法述评

自新石器时代以来,灰浆常被用作建筑的建造和装饰材料,如房址白灰面、砖墙缝隙胶凝材料、壁画灰质地仗层等。灰浆是研究古代建筑建造、修葺和壁画制作年代的重要样品,因其固化过程与建筑的建造、修葺和壁画制作行为直接相关。灰浆受原料、制作工艺和保存状态影响,其组分复杂,其中无机质组分中可能含有不同年代生成的干扰组分,因此准确测定灰浆样品碳十四年代的难度较大。本研究梳理了国内外对灰浆样品碳十四年代测定的前处理和制备方法,以及近年来无机质组分形成机理的研究成果,归纳现有灰浆样品分析检测与前处理方法的优势与不足,并提出利用计算机模拟计算干扰组分影响、有机残留物提取测年等可能的未来研究方向。     

Induced hydration of obsidian: a simulation study of accuracy requirements

Determination of the hydration rate constant of obsidian is basic to the use of obsidian for establishing chronologies. The constant can, in principle, be determined in either of two ways: by correlations with archaeological sequences, or by laboratory experiments using induced hydration. Induced hydration holds promise of great accuracy, but results reported to date have been disappointing. This paper is based on the hypothesis that the outcomes are the result of error build-up in the induced hydration protocol, and describes an analysis based on a Monte Carlo simulation of the measurement and analysis process. Data are presented which show that the poor results are due to errors inherent in optical measurement of hydration rim thickness. It is concluded that successful use of induced hydration requires an order of magnitude improvement in accuracy of hydration rim measurement over the accuracies currently claimed for optical microscopy. The results do not affect the validity of hydration dating based on archaeological correlations.     

Professor Andrew Charles O'Dell,M.Sc., F.R.S.E.

Regional

The Economic Geography of France. By J. N. Tuppen. 22 × 14, 383pp. 66 tables, 40 figures, bibliography, index. Croom Helm, Beckenham, 1983. £16.95.

Urban France. Ian Scargill, 22 × 14, 186pp. Croom Helm, Beckenham, 1983. £14.95.

Transport Geography

Transport Geography. By H. P. White &; M. L. Senior. 28 × 15.5, 224pp., figures, tables, bibliography, index. Longman, Harlow, 1983. £6.95.

Transport for Recreation. Ed. D. A. Halsall. 22 × 14, 231pp. Inst. Brit. Geogrs., 1983.

Mobile Services in Rural Areas. By M. J. Moseley and J. Packman. 225pp. University of East Anglia, 1983. £8.

Educational

The Fabric of Geography. By W. Farleigh Rice. 24 × 18.5, 288pp. plus worksheets. Longman Harlow, 1983, £4.95.