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1.
The first thermoluminescence (TL) dates of pottery from aRamayana associated site are reported. The TL dates for pre-NBPW Black-Slipped Ware levels are 730 and 765 B.C., while radiocarbon date takes the earliest Black Slipped Ware level (for which no TL dates are available) to 905 B.C. (uncorrected). For the OCW level, three TL dates are available which range from 1035 B.C. to 875 B.C. The early NBPW period believed to be associated with theRamayana episode will thus be post-750 B.C.  相似文献   

2.
西藏拉萨昌果沟遗址位于雅鲁藏布江中游支流的阶地上,是重要的新石器时代遗址.为探讨昌果沟遗址附近的古环境,对遗址附近开展地貌调查,在遗址北面约1 km处选取1个全新世风成沉积剖面进行光释光测年和环境指标分析,在雅鲁藏布江中游选2个阶地剖面进行光释光测年分析;此外,还总结了雅鲁藏布江中游23个全新世古土壤/泥炭的测年数据,进行概率密度分析,试图揭示区域的环境演化特征.研究表明:全新世古土壤/泥炭年代的概率密度可以较好地反映区域气候变化,9.0~6.0 ka古土壤/泥炭发育在波动中增强,气候由冷干向暖湿转换;6.0~2.9 ka古土壤/泥炭发育最强,气候相对温干;2.9 ka后鲜有古土壤/泥炭发育,气候变得冷干,史前人类活动受限.4.5 ka之后雅鲁藏布江中游及其支流一级阶地的形成为新石器时期先民提供农业耕作的场所,古土壤的发育为农作物提供了丰富的营养.1.4~1.1 ka期间(吐蕃王朝时期)局部地区有古土壤发育,气候好转.  相似文献   

3.
Although the carbon-reservoir problem with bulk-sediment radiocarbon dates from lakes has long been recognized, many synoptic studies continue to use chronologies derived from such dates. For four sites in central North America, we evaluate chronologies based on conventional radiocarbon dates from bulk sediment versus chronologies based on accelerator mass spectrometry (AMS) radiocarbon dates from terrestrial plant macrofossils. The carbon-reservoir error varies among sites and temporally at individual sites from 0 to 8000 yr. An error of 500–2000 yr is common. This error has important implications for the resolution of precise event chronologies.  相似文献   

4.
Peak activities of radiocaesium (137Cs) in lake sediments have frequently been used to infer the ages of sediments deposited in the 1960s (137Cs derived from nuclear bomb testing) or in 1986 (Chernobyl derived 137Cs). Records of the vertical distribution of 137Cs in sediments can thus be used to provide accurate dates for a critical period in which palaeoecological reconstructions often overlap contemporary monitoring data. However, knowledge regarding how the distribution of 137Cs in sediments is affected by post‐depositional processes is limited to interpretations based on the 137Cs distribution in sediments sampled at a single given date. This study assesses the extent to which the 137Cs record in annually laminated (varved) lake sediments is affected by post‐depositional diffusion, using 11 archived sediment cores sampled between 1986 and 2007. The sediment record reveals how Chernobyl 137Cs incorporated into the 1986 varve diffused downwards in the core at a decreasing rate over time, whereas the surface sediments continued to receive inputs of 137Cs mobilized from the catchment soils or lake margin. In spite of these processes, all cores post‐dating the Chernobyl accident had a clear and well‐resolved peak in the 1986 varve, justifying the use of this feature as a fixed chronostratigraphic feature. Because of the very high levels of Chernobyl fallout at this site, downwards migration of Chernobyl 137Cs has, however, completely masked the nuclear weapons 137Cs fallout peak that had been clearly preserved in the 1964 varve of a pre‐Chernobyl core sampled just three weeks before the Chernobyl accident. In consequence, the weapons fallout marker is likely to be of little use for determining 137Cs dates in areas strongly affected by high levels of Chernobyl fallout.  相似文献   

5.
Excavations at the Wenas Creek Mammoth Site yielded mammoth, bison, and two possible artifacts in a single colluvial stratum, with radiocarbon bone dates ∼17 ka. Eight infrared‐stimulated luminescence (IRSL) samples were collected to establish general ages of site strata, returning multi‐grain estimates consistent with stratigraphic integrity and the radiocarbon dates. Four additional IRSL samples were collected to estimate the depositional age of one artifact found in place. These produced a pooled total of 94 single‐grain estimates from near the artifact, 80% averaging 16.8 ± 0.9 ka, and 20% averaging 5.1 ± 0.5 ka. These results could be interpreted to demonstrate pre‐Clovis age artifact deposition consistent with the bone dates, or a mid to late Holocene intrusion into older deposits, possibly by bioturbation. The single‐grain IRSL dates do not provide proof of pre‐Clovis presence beyond reasonable doubt at this site, but do show that this technique is valuable in assessing the stratigraphic integrity needed for any such claim.  相似文献   

6.
A high-resolution 14C chronology for the Teopancazco archaeological site in the Teotihuacan urban center of Mesoamerica was generated by Bayesian analysis of 33 radiocarbon dates and detailed archaeological information related to occupation stratigraphy, pottery and archaeomagnetic dates. The calibrated intervals obtained using the Bayesian model are up to ca. 70% shorter than those obtained with individual calibrations. For some samples, this is a consequence of plateaus in the part of the calibration curve covered by the sample dates (2500 to 1450 14C yr BP). Effects of outliers are explored by comparing the results from a Bayesian model that incorporates radiocarbon data for two outlier samples with the same model excluding them. The effect of outliers was more significant than expected. Inclusion of radiocarbon dates from two altered contexts, 500 14C yr earlier than those for the first occupational phase, results in ages calculated by the model earlier than the archaeological records. The Bayesian chronology excluding these outliers separates the first two Teopancazco occupational phases and suggests that ending of the Xolalpan phase was around cal AD 550, 100 yr earlier than previously estimated and in accordance with previously reported archaeomagnetic dates from lime plasters for the same site.  相似文献   

7.
海水入侵导致地下水变咸对青岛李哥庄地区经济发展产生了不利影响,急需开展治理该地区咸水体的工作。根据研究区已有的降雨、蒸发及水文地质等资料,结合现场调查和监测,利用地下水模拟软件Visual-MODFLOW中的SEAWAT模块建立了该地区的数值模型,并利用实测资料识别和验证了该模型参数,表明所建模型能反映李哥庄地区的实际水文地质条件。为了模拟研究区地下咸水体的恢复治理情况,提出了连续抽水、间歇式抽水和抽注水结合三种咸水恢复方案,并利用该模型对三种恢复方案进行了模拟优化。结果表明,抽取地下咸水只是咸水恢复的一个因素,周边淡水的驱替作用则是咸水恢复另一个的因素,抽注水结合恢复方案为三种方案中最优的方案。  相似文献   

8.
Using the classic thermoluminescence (TL) dating technique for fired ceramic materials, we have obtained the first direct ages for five ceramic artifacts recovered from BfDa-1, a prehistoric archaeological site located in St. Croix, southcentral Nova Scotia. BfDa-1 is the only archaeological site in Nova Scotia to produce the full range of ceramic styles associated with the Woodland or Ceramic Period (c. 1050 B.C. to A.D. 1500); thus our new chronology can be used to revise the current local and regional ceramic chronologies. The five sherds from the St. Croix site yielded absolute gas of 1.15 ± 0.15 ka to 2.62 ± 0.29 ka (1 ka = 1000 years). The oldest of these TL ages was obtained on a sherd decorated with a pseudoscallop shell design and is in excellent agreement with a 14C date of 2500 ± 120 B.P. associated with Early Ceramic artifacts at this site. The other TL ages are in agreement with the relative ceramic chronology deduced from their decorative attributes. All five TL dates are in the correct depth-age order. This demonstrates that the recent excavations explored a part of the site which remained undisturbed in spite of extensive agricultural and horticultural activities in the vicinity in recent centuries. The dates also indicate a high degree of compression for the cultural remains at the site. They suggest a sediment deposition rate of 1.3 cm/100 yr during the early stages of the occupation period (2000–2600 yr B.P.), and a decrease in the deposition rate to 0.5 cm/100 yr during the last 2000 years. These dates provide the first successful application of TL dating to ceramics of the Minas Basin area. They confirm an initial hypothesis based on the stylistic attributes of ceramics recovered from BfDa-1, that human occupation at the site must have been of long duration. The excellent quality of the analytical data indicates that the TL dating technique should be well suited to the study of ceramic technology in other parts of the province, and that local mineralogy is suitable for optical dating of sediments at the site and elsewhere in Nova Scotia. © 1997 John Wiley & Sons, Inc.  相似文献   

9.
Recent excavations at Nahal Neqarot Rockshelter in the Central Negev, Israel, revealed 60 cm of in situ sediments. The associated lithic industry is mostly attributable to the Middle Epipalaeolithic Ramonian industry, though there is also evidence for sporadic earlier and later Epipalaeolithic use of the site. This is confirmed by three accelerator 14C dates, which contribute to a better understanding of the chronological framework for the Epipalaeolithic in the region. Microscopic examination of charred wood remains uncovered with the lithics, revealed the dominance of juniper, which is presently extinct in the nearby contemporaneous vegetation, otherwise composed of still extant taxa. © 1998 John Wiley & Sons, Inc.  相似文献   

10.
Silcretes on the N.S.W. coast near Ulladulla have long been attributed to. a sub‐basaltic origin, but field evidence is at odds with all variations of the sub‐basaltic hypothesis, and one site shows good evidence that the basalt post‐dates the silcrete. K‐Ar ages averaging 29.7 ± 0.5 Ma from the basalts provide a minimum age for silcrete development in this area. Furthermore, the K‐Ar dates, together with evidence for an erosional rather than tectonic origin of the coastal lowland, demonstrate that the adjacent tablelands reached their present elevation prior to the mid‐Oligocene.  相似文献   

11.
Weckström, J., Seppä, H. & Korhola, A. 2010: Climatic influence on peatland formation and lateral expansion in sub‐arctic Fennoscandia. Boreas, Vol. 39, pp. 761–769. 10.1111/j.1502‐3885.2010.00168.x. ISSN 0300‐9843. The initiation and lateral expansion patterns of five small sub‐arctic peatlands in the Fennoscandian tree‐line region were studied by 21 accelerator mass spectrometry (AMS) 14C‐dated basal‐peat samples representing three to six dates per site. The radiocarbon dates were converted to calendar years and are based on the median probability. When combined with earlier basal‐peat dates from the region, four distinctive periods can be observed in the cumulative record of the dates. The early Holocene, from c. 10 000 to 8000 cal. yr BP, was characterized by the fast initiation and rapid expansion of peatlands, whereas at 8000–4000 cal. yr BP lateral expansion was modest. The most intensive period of peatland expansion occurred at the beginning of the late Holocene at c. 4000 to 3000 cal. yr BP, after which it slowed down towards the present. All these periods are in rough agreement with the main Holocene climatic periods in the area, namely the relatively warm and moist early Holocene, the warm and dry Holocene thermal maximum (HTM) at 8000–4000 cal. yr BP, and the start of the cooler and moister trend (neoglacial cooling) from c. 4000 cal. yr BP to the present, indicating a broad‐scale climatic control on the lateral growth of sub‐arctic peatlands in Fennoscandia. In order to study the lateral expansion of peatlands and to evaluate their Holocene succession patterns, more studies based on multiple dates from the same peatland are needed.  相似文献   

12.
The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.  相似文献   

13.
Central Switzerland shows comparatively high seismic activity by Swiss standards. Many historical earthquakes are known and several of them caused damage. The last major event dates back to 1964 and has the characteristics of an earthquake swarm. Among dozens of felt shocks were two main shocks (Mw = 5 and 5.7) that moderately damaged a limited area with hundreds of buildings suffering loss. Our aim here was to reconstruct the damage field and to analyze whether it was influenced by site effects. Given the existence of a contemporary damage assessment and other historical sources, we could describe the damage field in detail. For about 95% of the affected buildings, we could reconstruct the location and extent of loss, using assessments from the European Macroseismic Scale (EMS 98). Spatial analysis of the resulting data showed that most losses were concentrated in the villages of Sarnen and Kerns. Damage to residential houses and barns was by far most frequent (90%), but expensive losses to the relatively few sacral buildings were responsible for almost 50% of the repair costs. We compared the damage data with deposit thickness and soil composition and carried out field experiments using H/V spectral ratios to measure the fundamental frequency of ground resonance at 75 sites to estimate the frequency band in which amplification occurs. Our results show that locations on both thick fluviatile sediments and large alluvial cones showed higher intensities than did other ground types. Moreover, at some sites, intensity was probably increased by a layer of weathered rock below thin deposits.  相似文献   

14.
A summary of previous and new research on the Schaefer mammoth site is presented. The Schaefer site in extreme southeastern Wisconsin, USA was excavated in 1992 and 1993. Seventy-five percent of a mammoth ?Mammuthus primigenius, the woolly mammoth (but comparable as well with M. jeffersonii, the Jefferson mammoth) was recovered. Drifted wood specimens and plant macro fossils were also recovered from the site.Twenty-five specimens of wood have been identified as Picea sp., Picea/Larix sp., or unidentified hardwood. Macro fossils in the form of cones have been identified as black spruce (Picea mariana). These preliminary data do not appear to support the traditional environment inferred for the woolly mammoth and points to a need for study of the animal's attribution to species. The animal was a male, 36 years of age at death.Thirteen AMS 14C assays on bone cluster between 12,290 and 12,570 BP. Sixteen dates on wood specimens intimately associated with bone yield a range of dates from 11,980 to 12,940 BP.The remains exhibit multiple cut and wedge marks interpreted as cultural. Non-diagnostic cultural lithics were recovered. A disarticulated bone pile deposited in a low energy environment is consistent with human interaction.  相似文献   

15.
The210Pb dates from a salt-marsh sediment sequence at Tites Point, Severn Estuary, southwest England, were compared with the results of three other independent dating techniques. These methods are inspection of dated topographic maps for the presence of absence of the salt marsh, dating of artifacts in a well-defined horizon within the sequence, and counting annual bands. All four sets of dates showed good agreement to about 30 cm depth from the present marsh surface; thereafter, dates from the210Pb method are earlier than those from the other methods, which are themselves in agreement. It is concluded that a wide range of methods can be successfully used for dating salt-marsh sediments (e.g., radiometric techniques, topographic maps, archaeological evidence, annual banding). Where possible, it is important to confirm dates using at least two independent techniques.  相似文献   

16.
The geoarchaeological study of the Palaeoeskimo Tayara site on Qikirtaq Island (Nunavik) has led to a better understanding of archaeological site formation in the arctic periglacial environment. The surrounding geomorphology (extra‐site) is characterized by fine‐grained, low plastic and leached postglacial glaciomarine sediments that have been reworked by sheet‐like solifluction. This process buried the northern part of the Tayara site with mean annual rates between 1.68 and 2.86 cm/yr over approximately 350 years (1330–980 yr B.P.). The physicochemical and mineralogical properties of the frost‐susceptible glaciomarine sediments may explain their susceptibility to solifluction. This process was probably enhanced by longer thawing periods or warmer/moister summer months that induced active layer thickening or rapid soil thawing. The dates we obtained in the downstream valley show that solifluction occurred during short warm periods in the Late Holocene between ca. 1500 and 1000 yr B.P., after 1000 yr B.P. (or after 500 yr B.P.) and recently (90–60 yr B.P.). Our data provide insights on the site factors and climate factors that govern site burial by solifluction. Solifluction promoted the preservation of the three superposed archaeological levels in the Tayara site; however, the waterlogging of the site related to solifluction also likely caused the subsequent abandonment of the site by the Palaeoeskimo people. © 2008 Wiley Periodicals, Inc.  相似文献   

17.
The near-surface layer of the dominant microhabitat types on a peatland in the Rainy River area, northwestern Ontario, Canada was dated using a number of previously published methods. No single method was found to be appropriate in all microhabitat types, and discrepancies of up to 15 yr over a time-scale of 80 yr were encountered. The results suggested that the post-depositional mobility of 210Pb, and possibly its atmospheric supply, are affected by microhabitat type. 210Pb dates consistently underestimated independently derived dates in the uppermost sections of the cores. Ages derived by measuring the length of annual increments on moss stems were in general agreement with the 210Pb dates, but were subject to bias where the moss remains were poorly preserved. 14C analyses on material from the base to the near-surface horizon confirmed the modern (post-AD 1950) origin suggested by the 210Pb and moss increment dates. Increased ash content at the base of the near-surface layer was correlated with the dustbowl of the 1930s, but assignment of dates to other stratigraphic markers (charcoal, Ambrosia pollen, and Larix needles) was less certain. The ash peak (55 yr before AD 1990) was used as datum for relative dating methods based on assumptions of a constant rate of peat accumulation (constant bulk density method) and constant rate of pollen accumulation (pollen density method). The constant bulk density method provided quick, inexpensive estimates of maximum age, but could not be extrapolated beyond datum, nor applied to cores showing marked stratigraphic changes. The pollen density method was a valuable but time-consuming alternative for dating peatland depressions, which lack annual moss increments and are subject to 210Pb leaching.  相似文献   

18.
Variations in Alpine white mica 40Ar/39Ar dates from the cover units of the Siviez-Mischabel Nappe relate to regional variations in the thermal history of the nappe. We focus on three regions within the nappe: the central Siviez-Mischabel (CSM), the southern Siviez-Mischabel (SSM), and the eastern Siviez-Mischabel (ESM). Our approach weaves together observations of quartz and mica textures in thin section, the variation of 40Ar/39Ar date with grain size, considerations of the effective diffusion dimension (EDD) of argon in white mica, and a comparison of dates with diffusion model results. In the CSM, pressure solution of quartz and dislocation glide in mica accommodated Alpine deformation. Dates record mica growth during nappe emplacement from 40 to 36 Ma and do not vary with grain size. In the SSM and ESM, both mica and quartz show textures associated with dynamic recrystallization, and dates decrease with grain size. In the SSM, dates also agree with the timing of nappe emplacement, but in the ESM, dates significantly post-date the timing of nappe emplacement. A comparison of dates with diffusion model results supports inferences from rock fabrics that the SSM experienced higher peak temperatures than the CSM, even though dates from both units approximate the timing of mica growth. Dates obtained from the ESM, however, do not compare well with simple models, and the thermal evolution of this region of the nappe, in the neighborhood of the Simplon Fault Zone, is not well understood.  相似文献   

19.
Caseldine & Edwards ( Boreas , Vol. 11, pp. 119–122) have misrepresented assessments of published evidence in the paper by Sissons 1981 ( Boreas , Vol. 10, No. 1). They have not used radiocarbon dates objectively and argue illogically. A different interpretation for the Teindland site is suggested.  相似文献   

20.
Abstract

Fourteen bone samples are analysed to test the usefulness of equivalent dose (ED) determinations by electron spin resonance (ESR) as a rapid method of determining relative age and making an estimate of absolute age. ED values are compared with eight aspartic acid dates and two C14 dates. The latter are dates on charcoal found in close association with bone at archaeological sites. For samples less than 25 000 years old an excellent correlation is obtained when ED values are compared with dates obtained by the other two methods. The relationship suggests that ED values can be converted to estimates of bone age by assuming a mean annual dose rate of 0.1 rad/yr. Age determinations provide little evidence to support earlier suggestions that elements of the Late Pleistocene megafauna survived until the end of the Pleistocene. Bone material at some sites in the‐Florentine Valley and near Montagu appears to be much older than had previously been believed. Only one site (Main Cave, Montagu) containing megafaunal elements appears to be terminal Pleistocene in age but the possibility of reworking of megafauna material from nearby older sites cannot be excluded. ESR dating has considerable potential as an exploratory dating tool but can only be applied to dense, unaltered bone samples. Attempts to analyse five samples from Kutikina Cave in Western Tasmania were unsuccessful because of post‐depositional contamination of the bone.  相似文献   

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