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1.
Luminescence dating has been applied to volcanogenic outburst flood sediments (Takuma gravel bed) from Aso volcano, Japan, and tephric loess deposits overlying the gravel bed. The poly-mineral fine grains (4–11 μm) from loess deposits were measured with pulsed optically stimulated luminescence (pulsed OSL) and post-IR infrared stimulated luminescence (pIRIR) methods, whereas the Takuma gravel bed containing no quartz, was measured with IRSL and pIRIR methods using sand sized (150–200 μm) plagioclase. The loess deposits date back at least to ~50 ka by consistent IRSL, pIRIR and pulsed OSL ages from the lowermost part of the loess deposits from one section. The ages obtained from the bottom part of the other loess section are not consistent each other. However, we consider that the pIRIR age (72±6 ka) which showed negligible anomalous fading is most reliable, and regard as a preliminary minimum age of the Takuma gravel bed. The equivalent doses (De) for the plagioclase from the Takuma gravel bed have a narrow distribution and the weighted mean of the three samples yield an age of 89±3 ka. This age is in agreement with the last caldera-forming eruption of Aso volcano (~87 ka) and it is likely that the pIRIR signal has not been bleached before the deposition. IRSL dating without applying pIRIR using small aliquots was also conducted, however, the IRSL signal shows no clear evidence of an additional bleaching during the event of outburst flood from the caldera lake.  相似文献   

2.
The musculature of the Recent Australian species, Magadina cumingi (Davidson 1852), is revised and previously unknown dorsal median pedicle muscles are described. The behaviour of M. cumingi is analysed in relation to the physical properties of the bryozoan sands it occupies on the Australian shelf. Functional morphology of a New Zealand Oligocene species, Rhizothyris amygdala Thomson 1920, indicates that this species would also have lived as a free and mobile form in the originally unconsolidated sediments (greensands) in which it is preserved. Shell characters of members of both Magadina and Rhizothyris are incompatible with an attached sedentary existence.  相似文献   

3.
In the last few decades optically stimulated luminescence (OSL) dating has become an important tool in geochronological studies. The great advantage of the method, i.e. dating the depositional age of sediments directly, can be impaired by incomplete bleaching of grains. This can result in a scattered distribution of equivalent doses (DE), leading to incorrect estimation of the depositional age. Thoroughly tested protocols as well as good data analysis with adequate statistical methods are important to overcome this problem. In this study, samples from young fluvial sand and flood plain deposits from the Elbe River in northern Germany were investigated to compare its depositional ages from different age models with well-known historical dates. Coarse grain quartz (100–200 μm and 150–250 μm) and polymineral fine grains (4–11 μm) were dated using the single aliquot regenerative (SAR) dose protocol. The paleodose (DP) was calculated from the DE data set using different approaches. Results were compared with the development of the Elbe River, which is well-documented by historical records and maps covering the last 1,000 years. Depending on the statistical approach it can be demonstrated that depositional ages significantly differ from the most likely depositional age. For the investigated coarse grain quartz samples all ages calculated from the MAM-3UL, including their uncertainties, are within the historical documented age. Results of the polymineral fine grain samples are overestimating the historically documented depositional age, indicating undetectable incomplete bleaching. This study shows the importance of using an adequate statistical approach to calculate reliable OSL ages from fluvial sediments.  相似文献   

4.
Mumba rockshelter is a key archaeological site for the Middle and Later Stone Age occupation of East Africa, but its chronology has remained unresolved. We report the results of a dating study, focussing on the characterisation of the optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) properties of quartz- and potassium-rich feldspar grains. Quartz has previously proven troublesome for dating in East Africa. We identified five general types of quartz grain behaviour, based on the shapes of their OSL decay and dose–response curves. Dose recovery experiments and measurement of the natural samples revealed particular problems with quartz grains that had hyperbolic dose–response curves, low characteristic saturation doses and anomalously large changes in sensitivity between regenerative-dose cycles. The use of pulsed irradiation during measurement and standard and additional quality-assurance criteria during data analysis reduced the number of grains that suffered from these problems. We applied these procedures to individual grains of quartz from eight samples and, using appropriate statistical models, identified post-depositional mixing in three samples. The remaining samples had scattered equivalent-dose distributions typical of quartz grains that had received variable beta dose rates during burial. Stratigraphically consistent OSL ages were obtained for all but the deepest sample. Feldspar ages were estimated for the latter sample and three other samples, using the elevated temperature IRSL signal that exhibited low rates of anomalous fading. Fading-corrected feldspar ages for the latter three samples are consistent with their single-grain quartz ages, but single-grain dating is needed to address problems of post-depositional mixing.  相似文献   

5.
New Zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the North Island. In total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions. Shortly after colonization in the late 13th century AD Polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the Kermadecs and Chatham islands. Although considerable research has been conducted on obsidian sourcing in New Zealand the complexity of geochemical source discrimination and the lack of a practical method of non-destructive geochemical analysis has hindered progress. We present the results of our use of PXRF to provide geochemical data on New Zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources. Our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies. A large case study using an important settlement phase site (S11/20) from the Auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of New Zealand.  相似文献   

6.
Luminescence properties of two samples taken from sand lenses in proglacial outwash de-posits of a piedmont glacier that reached the Swiss midlands during the Last Glacial Maximum are investigated in detail. Deconvolution of CW-OSL decay curves shows that the fast component dominates the OSL signal of quartz. The chemistry of single feldspar grains, in particular the K content in different grains, is determined using wavelength dispersive spectrometry (electron microprobe), revealing an average 12.9 wt.% K of the grains contributing to the IRSL signal. D e distributions are investigated in order to gain insights into partial bleaching, and agreement is found for quartz OSL and feldspar IR50 and pIRIR225 ages for small aliquots and single grains when applying the Minimum Age Model. These ages are also consistent with independent age control. For one sample, ages determined using the Central Age Model result in highly overestimated ages for both feldspar and quartz.  相似文献   

7.
8.
Extraterrestrial events and the extraterrestrial origin of both material and impact forms were recognized in the Morasko, Kaali and Przełazy shallow geological profiles by means of luminescence and radiocarbon dating as well as the frequency of magnetic spherules. The obtained results provide a promising tool for proving theat extraterrestrial events affected characteristic lithological and morphological environmental features.  相似文献   

9.
Archeological research has been trying to provide evidence relevant to understanding both the timing of and processes responsible for human colonization of the Qinghai-Tibetan Plateau (QTP). Hearth is one of the most extensive, important, and typical prehistoric humanity activity evidence on the QTP. However, there are a number of hearths lacking charcoal material because of the wind and water erosion. Fortunately, most of these hearths can be dated by luminescence dating on the remnant sediments around the hearth. In this study, 18 optically stimulated luminescence (OSL) samples from 14 hearths in Yandongtai site (YDT) and Bronze Wire site (BW) in the northeast of Qinghai Lake area were systematically dated. The OSL ages range from 6.8 ± 0.7 to 14.4 ± 1.2 ka. There is a good agreement between OSL dating results and charcoal ages during the last deglaciation period, which indicates that OSL method has great potential in dating hearth on QTP. Combined with the previous dating results from other hearths, the age of hearths concentrates in 11–13 ka BP, i.e., the Younger Dryas (YD) chronozone. The increased number of hearths indicates reinforced colonization in the Qinghai Lake area during YD cold event, implying that the cold climate during YD event was not severe enough to hinder the inhabitation of prehistoric humanity at an elevation of 3.2 km.  相似文献   

10.
Different post-IR Infrared Stimulated Luminescence (IRSL) approaches are applied to sediments from a Holocene coastal foredune sequence on Ruhnu Island in the eastern Baltic Sea. The comparison of D e-values and ages determined by the different approaches is complimented by fading and bleaching experiments. The fading experiments imply strong fading of IRSL (50°C) signals and no fading of any of the post-IR IRSL signals, but this is not confirmed by the determined D e-values. In fact, post-IR IRSL (150°C) D e-values agree within errors with those calculated for IRSL (50°C). From the bleaching experiments it is inferred that the higher values observed for post-IR IRSL at more elevated stimulation temperatures (225°C/290°C) are likely related to either thermal transfer and/or slow-to-bleach components within the signal. For the dating of the Holocene foredune sequence of Ruhnu Island, the post-IR IRSL (150°C) approach is preferred and these agree with the limited independent age control available from radiocarbon dating. Accordingly, the sequence formed between ca. 7.0 ka and 2.5 ka ago.  相似文献   

11.
This study examines preservation of microfossils identified as introduced Ipomoea batatas in soils from northern New Zealand. Starch grains and xylem cells showed highly variable preservation, from good to extremely poor. For starch grains, the latter included brown-staining, expansion and distortion of the grain and vacuole, loss of the Maltese cross, pitting, cracking, fragmentation and disintegration. Degraded xylem showed similar brown-staining, occasional cracking, cross-wise fragmentation, with wall pits becoming progressively less visible or showing distortion, expansion and coalescence.  相似文献   

12.
Among the dating methods in archaeology, thermoluminescence (TL) is widely developed. The present research concerns the construction chronology of the citadel of Termez (Uzbekistan) in the medieval period. On the methodological side along the TL study, we had to take into account two decisive factors that are expected to affect the accuracy: control of anomalous fading on the polymineral fraction (quartz and feldspars) and the effect of thermal treatments on the luminescence properties of the dated material. With regard to the determination of the annual dose, difficulties, associated with the evolution of the radiochemical composition of the dated samples and their environment over time, were overcome.  相似文献   

13.
As the most visible element of the marketing communications mix, advertising has had its critics and, given the choice, developed countries usually select a self-regulatory approach to deal with unacceptable or irresponsible advertising. This article reviews the literature in this area and incorporates thoughtful contributions from research conducted with New Zealand's Advertising Standards Authority. This approach helps bridge the gap between theory and practice and assists advertising practitioners and regulators concerned with advertising control to eliminate undesirable features of such systems in the future. Findings indicate that practice differs from theory in the areas of complaint acceptance procedures and code enforcement. A challenge for future research lies in addressing these two key components of the model in more detail and less breadth.  相似文献   

14.
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 hampered 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.  相似文献   

15.
Changes in the localization of dairy farming in New Zealand are interpreted in terms of environmental advantages, inter-regional competition, transportation costs and policies, and the behaviour of cooperative dairy companies. Since the 1920s dairying has become increasingly localized in environmentally advantaged areas. Competition among dairy companies resulted in o ver-extension of supply areas and disequilibrium between collection costs and economies of scale at the plant. Subsequently, some rationalisation of supply areas has occurred, notably since the adoption of tanker collection from the 1950s with cooperative dairy companies using differential transport pricing policies to discourage suppliers at the spatial margins.  相似文献   

16.
This study aimed to further test the method, reported by St Pierre et al. (2009), to develop robust chronologies of deposits in limestone caves through U/Th (Uranium/Thorium or U-Series) dating of soda straw stalactites. The chronology of fossil bearing deposits at Blanche Cave was further constrained with thermal ionisation mass spectrometry (TIMS) U/Th dating of 17 additional soda straw stalactite samples, and results were compared to recalibrated 14C ages of charcoal. The results support the assertion that soda straw stalactites can provide ages close to the time of sediment deposition and may be used as reliable chronological markers, particularly for periods reaching or beyond the radiocarbon dating limit. The application of an enhanced cleaning technique facilitated the reduction of detrital Th in samples, significantly increasing age accuracy and precision. Additionally U/Th age accuracy and precision was increased through the application of site-specific measured U/Th ratios to correct for the detrital 230Th component in samples.  相似文献   

17.
Pole. M. S., & Raine. J. I., 1994:03:28. Triassic plant fossils from Pollock Road, Southland. New Zealand. Alcheringa 18, 147–159. ISSN 0311-5518.

Sedimentary rocks of the Murihiku Supergroup considered to be latest Triassic (Rhaetian), crop out about 10 m below the Glenham Porphyry, near Glenham, New Zealand. They contain the vegetative macrofossils Marchantites sp. (Hepaticae), Pachydermophyllum praecordillerae (Frenguelli) Retallack and Pachydermophyllum benmorensis Anderson & Anderson (Peltaspermaceae), cf. Dicroidium dubium var. dubium Anderson & Anderson (Corystospermaceae), Desmiophyllum sp. cf. D. indicum Sahni (possible conifer), and Gingkophytopsis sp. (possible progymnosperm).

Reproductive material includes ovulate structures (Peltaspermum cournanei sp. nov.), pollenbearing structures (Antevsia sp.) and probably seeds of the Peltaspermaceae, ? Umkomasia (Corystospermaceae), and a possible progymnosperm microsporophyll.

The palynoflora is dominated by bisaccate gymnospermous pollen, mainly Alisporites spp., consistent with the presence of corystosperm macrofossils. Moderately common pollen of Cycadopites spp. may be of peltasperm origin.  相似文献   

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20.
Pole, M.S., 1994:03:28. Deciduous Nothofagus leaves from the Miocene of Cornish Head, New Zealand. Alcheringa 18, 79–83. ISSN 0311-5518.

Nothofagus leaves with plicate vernation, indicating a deciduous habit, are recorded from the Late Miocene of New Zealand. This is the first unequivocal record in New Zealand of deciduous Nothofagus, deciduous species now being restricted to Tasmania and South America.  相似文献   

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