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1.
Before ESR/U-series models were applied to ungulate teeth, it is generally assumed that calculated ages are close to the “real” ages when they range between the values obtained with the EU and LU models. When the samples show signs of uranium-leaching, a realistic mathematical modelling of the age is not possible. On the other hand, some samples have undergone a very late U-uptake “affecting” directly the U-series ages and rendering the calculated ages younger.

We present results obtained on two open-air sites, which show the limits of such combined models in the case of late uranium incorporation. For the Middle Pleistocene site of Isernia la Pineta (Italy), the ESR dates are expected to fall within the limits imposed by the Ar–Ar results. The other site, the Lower Palaeolithic deposits of Ambrona (Spain), yielded two sets of samples: some at the top of the sequence with uranium uptake ranging between EU and LU limits and thus giving a good idea of the “real” age of the site; others at the base displaying a very late U-uptake, which render an age determination difficult.  相似文献   


2.
The Three Gorges and Western Hubei area in the geographic central part of China was a potential migration corridor for early hominin and mammals linking South and North China during the Pleistocene period. Some key early hominin sites are known in this region where limestone cave and fissure sites are numerous but difficult to date as beyond the dating range of OSL and mass spectrometry U-series method. Here, we report radiometric dating study for such a hominin site, Meipu (Hubei Province), by coupled ESR and U-series dating of nine fossil teeth and cosmogenic 26Al/10Be burial dating of one quartz sediment. The burial age calculated by simple burial model (573 ± 266 ka) gives a minimum age constraint of the sediment. The fossil dating provided two main age groups at 541 ± 48 ka and 849 ± 39 ka, the older age group is in agreement with the U-series age (>630 ka) of the flowstone overlying the fossil layer and the paleomagnetic data which placed the Brunhes-Matuyama boundary in the fossil layer. The reason of this age difference is probably caused by the U-content discrepancy in the enamel of the dated fossil samples. This study exhibits the limitation of ESR/U-series fossil dating and the importance of using multiple dating approach when it is possible in order to identify the problematic ages.  相似文献   

3.
It draws much attention of scientists how early hu- mans occupy and adapt to the rigorous climate and environment at high northern latitudes in East Asia after they stepped out of Africa, passed West Asia and finally arrived in East Asia[1-4]. Reliable age determi- nations of Paleolithic sites from northeastern Asia not only help to find out the earliest occupation of early humans in this region, but also relate to the founda- tion of the overall framework of human origin and migration[1-8]…  相似文献   

4.
The well-developed, late Cenozoic Nihewan Beds in northern China are amongst the most famous and well-preserved Quaternary strata in East Asia. The Nihewan Basin is also well-known for its mammalian fossils and stone artifacts, which document early human settlements in high northern latitudes (around 40°N). It is a key geological place to study palaeoenvironments and ancient human activities due to the excellent age-control of the formation by palaeomagnetism. In the present paper, the sediments of two Paleolithic sites were dated using the ESR signals of the titanium center in quartz. In order to check the reliability of our analytical procedures, a reference sample collected near the Brunhes/Matuyama (B/M) boundary at the Donggutuo site was firstly analyzed, yielding an age of 750 ± 88 ka. Then, three samples collected from the Dongpo site were analyzed by the same procedures. Our ESR results indicate that the age of the Dongpo cultural layer ranges between 304 ± 12 ka and 333 ± 23 ka, with an average of approximately 321 ± 15 ka.  相似文献   

5.
The Paleolithic site of Xibaimaying (XBMY), once considered the youngest flake tool site within the Nihewan Basin, North China, is an ideal archive to study the chronological relationship between flake tool and microblade industries in the Nihewan Basin during the Upper Palaeolithic, but the previous ages obtained for the site remain controversial. From 2015 to 2019, three areas at two archaeological localities (XBMY-I and XBMY-II) of the site were excavated, and well-preserved fossils and flake tools were unearthed. In this study, a total of 26 samples were collected from the three areas for optically stimulated luminescence (OSL) dating using a single-aliquot regenerative-dose (SAR) protocol on fine-grained quartz. A shared ‘Standardized growth curve’ (SGC) for a section was constructed to reduce the time required for De estimation. The long-term weighted average water contents of the samples during their burial period were estimated based on the in-situ water contents of continuous samples from a nearby borehole. All the OSL ages were modelled via Bayesian statistics using the OxCal software, modifying the OSL ages with stratigraphic constraints in each section. The results show that the cultural layer bearing flake tool assemblages falls within the period of 122–36 ka, indicating that the flake tool industry of the Xibaimaying site is comparable to that of the Youfangbei (108–86 ka), Banjingzi (∼86 ka) and Xinmiaozhuang (75–63 ka) sites, rather than the youngest one in the Nihewan basin, which explains why the Xibaimaying site is characterized as pure flake tool culture without any ‘advanced’ trait. The OSL dating results also shed new light on the study of sedimentary processes in the Xibaimaying site area. The different deposition rates (0.01–1.61 mm/a) for the sediments at the three newly excavated areas imply complex geomorphologic processes in the site area.  相似文献   

6.
As one of the most important regions for early human occupation in East Asia, Nihewan Basin in North China is well-known for an abundance of archaeological sites with ages spanning the last 2 Ma. In recent 10 years, more than 27 new archaeological localities have been discovered from the Yuxian (sub-basin of Nihewan), and all of them are with no age control. The lack of reliable ages for these localities affects our understanding for the evolution of the stone-tool technology in the Nihewan Basin. As many localities were founded in the river terrace, the fluvial terrace sequence of the Huliu River (main river of the Yuxian) was investigated. Based on single-grain post-infrared infrared stimulated luminescence (pIRIR) procedure on potassium (K-) feldspar, our results reveal that the formation ages of three Huliu River terraces are 139.6–115.7, 19.7–5.5, and <0.9 ka, respectively. On the basis of these pIRIR ages, the formation of the fluvial terrace sequence may provide informative constraints on the human occupation in the Huliu River terrace in the Nihewan Basin, if a clear stratigraphic correlation is established between the archaeological sites and the dated terrace deposits.  相似文献   

7.
Zircon U–Pb ages of two acidic tuff and two turbidite sandstone samples from the Nakanogawa Group, Hidaka Belt, were measured to estimate its depositional age and the development of the Hokkaido Central Belt, northeast Japan. In the northern unit, homogeneous zircons from pelagic acidic tuff from a basal horizon dated to 58–57 Ma, zircons from sandstone from the upper part of the unit dated to 56–54 Ma, and zircons from acidic tuff from the uppermost part dated to 60–56 Ma and 69–63 Ma. Both of the tuff U–Pb ages are significantly older than the youngest radiolarian fossil age (66–48 Ma). Therefore, the maximum depositional age of the turbidite facies in the northern unit is 58 Ma and the younger age limit, estimated from the fossil age, is 48 Ma. In the southern unit, homogeneous zircons from turbidite sandstone dated to 58–57 Ma. Thus the depositional age of this turbidite facies was interpreted to be 66–56 Ma from the fossil age, probably close to 57 Ma. Most of the zircon U–Pb ages from the Nakanogawa Group are younger than 80 Ma, with a major peak at 60 Ma. This result implies that around Hokkaido volcanic activity occurred mainly after 80 Ma. Older zircon ages (120–80 Ma, 180–140 Ma, 340–220 Ma, 1.9 Ga, 2.2 Ga, and 2.7 Ga) give information about the provenance of other rocks in the Hidaka Belt. It is inferred that the Nakanogawa Group comprises protoliths of the upper sequence of the Hidaka Metamorphic Zone, which therefore has the same depositional age as the Nakanogawa Group (66–48 Ma). The depositional ages of the lower sequence of the Hidaka Metamorphic Zone and the Nakanogawa Group are probably the same.  相似文献   

8.
Although vertebrate fossils are commonly abundant in museum palaeontological collections, they are only rarely accompanied by contextual data (e.g., stratigraphic and taphonomic information) that allow them to be placed independently into reliable temporal frameworks critical for testing significant evolutionary and extinction hypotheses. Moreover, where critical samples do exist in such collections, sampling for direct geochronological analyses becomes a significant concern, especially where such sampling is destructive in nature. Here we apply a direct fossil dating, micro-drilling sampling approach that minimises damage to and destruction of precious museum specimens. We carried out a systematic U–Th dating study (n = 28 ages) of an isolated museum specimen of the extinct Palorchestes azael (megafaunal ‘marsupial tapir’) originally collected in 1977 from Tea Tree Cave, Chillagoe, northeastern Australia. We obtained 21 U–Th ages and constructed 230Th-age profiles across three teeth exposed in cross-section, using micro-drilling and thermal ionisation mass spectrometry. Individual sample masses were as little as 0.18 mg (U concentration 33–82 ppm), meaning that the sampling resulted in only minimal destruction of the specimen. The results show no evidence of U leaching, suggesting that the dates represent reliable minimum ages. For independent age control, we also dated calcite that had encrusted the sample (thus, providing a minimum age; n = 6) and an older calcite clast that had been reworked into the surrounding breccia at the time of burial (thus, providing a maximum age; n = 1). U–Th ages of the teeth are older than the calcite overgrowths and younger than the reworked calcite, consistent with their demonstrable relative age relationships. Collectively, the results unequivocally bracket the age of the fossil between 199.1 ± 8.9 ka and 137.4 ± 1.1 ka (2σ), adding another rare datum to inform the timing and geographic distribution of last occurrences of the species. The benefits of our dating approach of museum fossil specimens are threefold: 1) it is minimally destructive even compared with laser-ablation method; 2) the use of U vs. apparent age approach allows direct testing for potential U leaching as occasionally seen in fossil dating; and 3) the combination of fossil and associated speleothem dating provides the most robust means of securely bracketing the age of fossils that lack firm stratigraphic control.  相似文献   

9.
Xinglong Cave, containing four human teeth, numerous mammalian fossils, stone artifacts and a Stegodon tusk with intentional and seemingly grouped engravings, is one of the most significant archaic Homo sapiens sites in south China, located 95 km south of Fengjie County, in Chongqing. In an attempt to constrain the age of the human relics, calcitic flowstone deposits with a significant detrital component were dated by U–Th methods using a leachate scheme. Total sample digestion MC-ICPMS dating was used to assess the reliability of the leachate technique. Six calcite samples from horizons beneath and above the fossil-bearing layer were dated. We obtained ages of 130 ± 9.1, 124 ± 11, 135 ± 12 and 127 ± 11 ka for the flowstones above the fossil layer with a weighted mean of 128.9 ± 5.2 ka. Two flowstone samples gave MC-ICPMS dates between 128.3 ± 3.3 and 152.4 ± 25.3 ka with an assumed detrital component to correct for the initial 230Th, which are consistent with results obtained using the L/L regression data from layer U-4 within uncertainty. All errors herein quoted at the 2σ level. Ages determined for the flowstone underlying the fossil-bearing layer were 221 ± 29 to 189 ± 19 ka with a weighted mean age of 199 ± 16 ka. These results are stratigraphically consistent within error limits and show that the cave was occupied by Fengjie Man within the time range of ∼200 to ∼130 ka. These new U-series ages of flowstones in association with human teeth and an engraved stegodon tusk at the Xinglong Cave site provide valuable geochronologic information for the study of the origin of modern humans in East Asia and earliest human art.  相似文献   

10.
Geochemical alteration processes in archaeological sites may affect the environmental dose rate during the burial history and cause inaccuracy in age determination by palaeodosimetric dating methods, such as luminescence or ESR. In Arago Cave (Tautavel, France), the original composition of the sandy aeolian sediments of palaeoanthropological level G, where the Homo heidelbergensis Arago XXI skull was found, has been modified by both carbonation and phosphatization processes. Eight fossil teeth were collected from different geochemically affected parts of level G and analyzed by the ESR–U-series method. All the teeth are presumably contemporaneous. The results show that the samples from the phosphated area agree within error with those from the carbonated area. Surprisingly, the samples from the non-altered area show ages 100–150 ka younger. This difference is mainly due to the remarkable changes in the gamma dose rate over time. The measured in situ dose rate accounts for more than 50% of the total dose rate for all the samples. We observed that the samples' equivalent dose (DE) were generally 20% lower in the non-altered area than in the carbonated and phosphated ones. These results show the crucial effect of the geochemical processes affecting the age calculation by ESR–U-series method in comparison with independent chronological data.  相似文献   

11.
Discovered accidently during factory building construction works, the Middle Palaeolithic site of Biache-Saint-Vaast (Pas-de-Calais, France) was excavated from 1976 to 1982 by a team of Lille University directed by Alain Tuffreau. An abundant archaeological and paleontological material, including two human skulls, was there recovered from fossil alluvial deposits of the Scarpe River. In order to determine the ages of these remains, the ESR/U-series method was applied on bone and teeth. As the U-series data obtained of the main part of the analyzed tissues do not allow the use of the classical US-ESR model, the recently proposed AU-ESR model, taking into account if necessary U-leaching from some of the tissues, was used to calculate combined ESR/U-series ages for these samples. The obtained ages suggest a MIS7 attribution to the faunal remains and permit an age of ca 240 ka to be assigned for the human remains and associated archaeological material, in accordance with the stratigraphic data and the large mammal associations.  相似文献   

12.
The applicability of two different approaches in the luminescence dating of old (>70 ka) Chinese loess is investigated. Both SAR-OSL ages obtained on 63–90 μm quartz grains and SAR-IRSL ages obtained on 4–11 μm polymineral grains, for samples collected from two sites in the Chinese Loess Plateau (Luochuan and Dongchuan) are presented. The characteristics of the luminescence signals stimulated by blue and infrared light are investigated in terms of dose response and dose recovery, and as a function of age. Additionally, anomalous fading measurements from the 410 nm IRSL emission in polymineral fine-grains are reported. An average value of g2days amounting to 3% per decade was measured and seems to be independent of site location and age. For the samples from Luochuan, independent age control (pedostratigraphy and palaeomagnetism) is available. At both sites, the SAR-OSL ages are always lower than the SAR-IRSL ages after they have been corrected for anomalous fading. It seems that the quartz-based SAR-OSL ages are accurate for the younger ages, but that they underestimate the true age of deposition for loess that was deposited about 60–70 ka ago. The fading-corrected SAR-IRSL ages are in better agreement with the pedostratigraphic age control (75 and 130 ka) and allow dating beyond the quartz OSL range. Based on our results, we suggest that conventional SAR-OSL and SAR-IRSL protocols at these sites should be restricted to samples of ages not exceeding 40–50  and 100–120 ka, respectively.  相似文献   

13.
The taxonomy of the land-snail genus Cerion, and the relevance of hundreds of shell forms to phylogenetic and evolutionary processes has been the subject of much discussion over the past few decades. Fundamental to understanding evolutionary trends is the independent confirmation of the age, biostratigraphic, and chronostratigraphic order of a comprehensive set of fossil forms. Amino acid racemization (AAR) is a geochronological tool applicable to dating living and fossil Cerion shells. The extent of racemization of aspartic acid (Asp D/L) and glutamic acid (Glu D/L) were determined for 507 Cerion shells dating between the early last interglaciation (marine isotope stage (MIS) 5e, c. 125 ka) and the present from the Bahamas. The AAR data based on Cerion support the established morphostratigraphic succession of deposits younger than MIS 5e and provide greater resolution, particularly for biostratigraphic successions of Holocene age. Age models were constructed for Asp and Glu using D/L values paired with 14C ages and historical collection dates from 23 Cerion shells. In addition to the relative-age time series, the Holocene age models developed from D/L Glu and Asp apply to the last 7 ka and geographically within the central Bahamas. In two case studies, large numbers of AAR-generated ages provide insights into the age structure of accretionary soils and rates and age constraints on evolutionary processes related to Cerion land snails.  相似文献   

14.
The Galería de las Estatuas is a Mousterian site located within the Cueva Mayor-Cueva del Silo karstic system at the Sierra de Atapuerca (Burgos, Spain). This site is characterised by an important Upper Pleistocene stratigraphic sequence in which a large number of lithic artefacts exhibiting clear Mousterian affinities and a rich assemblage of faunal remains have been found.Additionally, this site has yielded a foot phalanx of a clear Neanderthal affinities and its sediment has yielded Neanderthal mitochondrial and nuclear DNA.Two test pits, GE-I and GE-II, have been excavated since 2008 which have been divided in 5 and 2 lithostratigraphical units, respectively. A minimum age of 45 ka cal BP for this site was obtained by radiocarbon dating in GE-II. This chronology was refined using single-grain Optically Stimulated Luminescence (OSL: 80–112 ka in GE-I and 70–79 ka in GE-II) and single-grain thermally transferred OSL (TT-OSL). Although in all case TT-OSL ages were systematically older than their single-grain counterparts. The detrital sequence is sealed by a flowstone whose base is dated to 53.7 ± 3.5 ka cal BP using U-series dating.In order to better constrain the age of this site, nine herbivorous teeth were collected from the whole sedimentary sequence to be dated by the ESR/U-series dating method though only seven provided modelled ages. Six of them were collected from levels 2 to 5 of the GE-I test pit while the last tooth was taken from level 2 of the GE-II test pit. Our results, ranging between 80 and 110 ka, are in agreement with those obtained by single grain TT-OSL and suggest that the sedimentological levels containing Mousterian lithic artefacts and faunal and human remains began to be deposited during the second part of the MIS5. These results fill a temporal gap in the chronology of the Atapuerca sites for which no contemporary MIS5 date was obtained until recently.  相似文献   

15.
Jeju Island, the largest Quaternary volcanic island in Korea, has formed mostly since the early Pleistocene, but its latest chronology of volcanism and sedimentation is still poorly constrained. Here we report optically stimulated luminescence (OSL) ages for two hydromagmatic volcanoes on the southwestern coast of Jeju Island, i.e., the Songaksan and Suwolbong tuff rings. The basaltic tuffs of these volcanoes contain abundant quartz sands from underlying marine sedimentary sequences. Two samples collected from the middle part of the Songaksan Tuff yielded highly reproducible quartz single-aliquot regenerative-dose (SAR) OSL ages of 7.0±0.3 ka, providing the first direct age estimate of Holocene volcanism in Jeju Island. The quartz OSL age estimate of 5.1±0.3 ka for the younger reworked basaltic tuff (the Hamori Formation) is comparable with previous radiocarbon and U-series disequilibrium dating of fossil mollusk shells. Two samples from the Suwolbong Tuff show quartz OSL age estimates of 18.3±0.7 and 18.6±0.9 ka, which are identical within error ranges and younger than the quartz OSL age estimate of 23.2±1.0 ka for the underlying Gosan Formation. This study confirms that volcanism and attendant sedimentation were active in Jeju Island until very recently.  相似文献   

16.
The fluvio-lacustrine sequences in the Nihewan Basin of North China (known as the Nihewan Formation) are rich sources of Early Pleistocene Paleolithic sites and mammalian fossils (known as the Nihewan Fauna sensu lato), which offer an excellent opportunity to investigate the evolution of early humans and land mammals in East Asia. Also abundant mammalian fossils provide clues about the general environmental and climatic setting of early humans. Among the Nihewan Fauna (sensu lato), the Daodi Fauna is one of the most complete and oldest in the eastern Nihewan Basin: seven mammalian fossil-bearing layers in the Nihewan Formation have been described. Except for a biostratigraphy, however, precise age control on the Daodi Fauna has remained unavailable. Here we report a new magnetostratigraphic record that stringently constrains its age. The seven fossil-rich layers span an age range of ca 2.5–1.8 Ma between the Gauss–Matuyama boundary and the termination of the Olduvai polarity subchron. Combining our new and recently published paleomagnetic data, we further establish a Pleistocene magnetochronology of the fauna and Paleolithic sites in the Nihewan Basin. Age ranges of about 2.5–0.5 Ma for the faunas and 1.7–0.3 Ma for the Paleolithic sites are deduced, which span most of the Pleistocene. The chronological framework and calculated proportions of mammals that were adapted to different environments indicate that mixed settings of dominant grasslands and subordinate forests continued at least from 2.5 to 0.5 Ma for early human occupation in the basin, similar to the mixed open savannah and woodland habitats of early humans in Africa. The Nihewan hominins consistently adopted a simple Oldowan-like technology (i.e., Mode 1 core and flake technologies) from at least ca 1.7 to 0.3 Ma. A more advanced Acheulean technology (Mode 2) has not been found in the Nihewan Basin, although it started to emerge in the Bose Basin of South China at ca 0.8 Ma. This implies that multiple groups of hominins distinguished by differential stone-tool-making capabilities may have coexisted in China after 0.8 Ma.  相似文献   

17.
The loess-paleosol sequence on the Chinese Loess Plateau provides a unique archive that records climate change in East Asia in the Quaternary, yet absolute dating of the loess deposits is challenging due to the lack of directly datable materials. Fossil land snail shells, which are made from aragonite, are widely preserved in the loess deposits and have long been used to reconstruct past environmental changes. U-series dating of fossil land snail shells has the potential to provide a route for absolute dating of the loess deposits but remains largely unexplored. In this study, we present the first systematic investigation on the U-series isotope geochemistry as well as the early diagenetic imprints of fossil land snail shells (Cathaica sp.) from the Mangshan loess-paleosol sequence in Henan province, central China. Several geochemical techniques, including Raman microscopy, SEM, LA-ICPMS, LA-MC-ICPMS, solution-MC-ICPMS, and AMS 14C dating, were employed to investigate the mineralogy, chemical and isotopic compositions of both modern and fossil snail shells to micrometer level. Our results show that the fossil Cathaica sp. shells are overall characterized by a higher degree of porosity and elevated contents of organic matter compared to live-collected shells of the same species. The layers with higher porosity and organic matter content in the fossil Cathaica sp. shell are also found to be enriched in Na, Mg, Mn, Ba, and U, indicating diffusion and adsorption of these elements by specific surface binding sites of either aragonitic lattice or organic compounds of the fossil shell. Combining in-situ measurements using LA-MC-ICPMS with solution U-series determination, we further demonstrate that fossil Cathaica sp. shell is relatively homogeneous regrading both [234U/238U] and [230Th/238U] values although the distribution of U in the fossil shell is sample-specific. The comparison of different dating results suggests that the calculated apparent closed system U–Th ages are all systematically younger (∼6000 to 13,000 years) than the corresponding shell 14C ages and quartz SAR (single-aliquot regenerative-dose) ages from the Mangshan section. We suggest that the underestimation of U–Th ages of fossil Cathaica sp. shells is very likely caused by diagenetic uptake of U that started immediately after the burial of the shell and effectively ceased when the fossil shell was isolated from the pore waters due to persistent deposition of eolian dust at the Mangshan section. Our work on both modern and fossil Cathaica sp. shells thus provides detailed morphological and geochemical characterization for the diagenetic alteration of fossil snail shells and suggests that U-series dating of fossil land snail shells may provide age constraints for dust deposits in the semi-arid region although the timing of early diagenetic U-uptake by the fossil shells need to be better quantified for reliable age determination.  相似文献   

18.
Yumidong (Corn Cave) is a newly discovered Paleolithic site in the Three Gorges region of central China. Numerous Paleolithic artifacts have been excavated from the sedimentary deposits of the cave in association with faunal remains attributed to the Middle-Late Pleistocene Ailuropoda-Stegodon fauna of southern China. To establish the chronology of the sedimentary sequence (>5 m thick), 14C dating was applied to bone and charcoal samples (n = 6); the U-series method was used to date in situ precipitated speleothems (n = 12), transported speleothem samples (n = 6) and 18 subsamples of a fossil tooth; and the coupled ESR/U-series method was used to date fossil teeth (n = 6). The derived dates were combined using a hierarchical Bayesian approach to generate a unified chronostratigraphy for the Yumidong sequence. In our Bayesian analyses, the 14C and coupled ESR/U-series dates were considered to provide direct age estimates for the target layers, while the U-series dates of the in situ precipitated speleothems and fossil tooth were used as minimum age constraints and those of the transported speleothem fragments as maximum age constraints. The Bayesian analyses provided robust time intervals for the archeological layers: L2-Upper (14–23 ka), L2-Lower (27–63 ka), L3 (106–171 ka), L4 (140–192 ka), L10 (157–229 ka), L11 (181–256 ka), and L12 (214–274 ka) with a probability of 95%, allowing the establishment of a ∼300 ka long geological and archeological history for the Yumidong site and placing it as a reference site for Paleolithic cultural evolution in the Three Gorges region from the late Middle Pleistocene to Late Pleistocene.  相似文献   

19.
The electron spin resonance (ESR) dating method has been introduced into the Quaternary chronology for nearly 40 years and has been successfully used for dating of fluvial and lacustrine sediments. In order to evaluate the possible effect of the sediment grain size on the dating estimate, the parallel ESR dating testing was carried out on quartz grains of five different size fractions ranging from 50 to 450 μm extracted from the same fluvial and lacustrine sediment collected close to the M/B boundary at the Donggutuo section, Nihewan Basin, China. The results show that equivalent doses and associated ages vary significantly. However the beta irradiation dose rate of the grains with different sizes accounts for only about 6% of the total deviation of the dating results. At the same time, the sensitivity of quartz Ti–Li center was calculated based on the additional irradiation. It shows that the larger grains are more sensitive than the smaller ones, which can leads to higher saturate ESR intensity and less equivalent dose. The variations of the sensitivity of quartz Ti–Li center of the grains with different sizes are responsible for the primary deviation of the dating results. The results also suggest that 100–150 μm grain size fraction would be priority size for the ESR dating of quartz Ti–Li center on fluvial and lacustrine sediments.  相似文献   

20.
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