Optically stimulated luminescence dating of loess in South-Eastern China using quartz and polymineral fine grains     

《Quaternary Geochronology》2022

Loess deposits distributed in southeastern China play an important role for paleoclimate reconstruction of the subtropical regions. These loess-paleosol deposits are mainly spread within the middle and lower reaches of the Yangtze River as well as in the drainage area of the Huai River. The ages of loess paleosol sequences that are distributed along the Huai River are not well constrained. In this study, the standard single-aliquot regenerative dose (SAR) optically stimulated luminescence (OSL) protocol and two elevated temperature post infrared-infrared stimulated luminescence SAR protocols (pIRIR₂₂₅ and pIRIR₂₉₀) were applied on 4–11 μm quartz and polymineral fine grains, respectively, in order to obtain the first numerical luminescence chronology for a loess-paleosol sequence in northern Jiangsu Province. Our results show a good agreement between quartz SAR-OSL and polymineral pIRIR ages up to ~70 ka. These findings confirm that Xiashu loess accumulated during the Last Glaciation. For samples older than this, the ages increasingly deviate with depth. Fine quartz ages beyond 70 ka are interpreted as underestimates, as previous studies reported that quartz ages >70 ka from various sedimentary origins worldwide may underestimate even if they pass rejection criteria and dose recovery tests. On the other hand, the pIRIR ages are most likely overestimating the true depositional ages as indicated by the results of dose recovery tests, where a 30–60% overestimation of the recovered dose is reported for values larger than ~400 Gy. The overestimation of pIRIR protocols was also confirmed by the results obtained when large beta doses were added on top of the natural accrued dose. Moreover, our dating results suggest that L1/S1 transition (corresponding to MIS 5/4 boundary) occurred much higher in the stratigraphic sequence than may have been interpreted from the magnetic susceptibility enhancement. This inconsistency can be assigned to invalidity of magnetic susceptibility as a chronostratigraphical proxy due to ferrimagnetic minerals dissolution or transformation during paedogenesis processes in this humid subtropical region in the southeastern China.  相似文献   

胡安·德富卡洋中脊富锌烟囱体流体通道演化特征     

董从芳  周怀阳  彭晓彤  袁远  姚会强 《海洋学报(英文版)》2012,31(4):99-108

对采自Faulty Towers(47°57.447'N,129°6.568'W)硫化物烟囱群一个不再活动的烟囱体硫化物开展了详细的矿物学和地球化学研究。样品从外壁往内壁方向可划分为4个矿物组合带,分别为重晶石-无定形硅-铁氧羟化物带;白铁矿-黄铁矿-无定形硅-重晶石带;白铁矿-黄铁矿-闪锌矿-纤锌矿带;纤锌矿-黄铜矿-白铁矿带。从底部到顶部,样品通道形态主要有3种:不规则、不连续的多通道;椭圆形单通道;封闭的通道。矿物学研究证实,烟囱体以低温矿物组合白铁矿、纤锌矿为主,高温矿物黄铜矿少见,仅局限分布在流体通道附近。²¹⁰Pb定年结果表明,烟囱壁形成经历较短时间(约3 a),而通道的闭合则经历了相对长的过程(约17 a)。结合矿物学研究,最终恢复了整个尖塔结构的生长历史。  相似文献   

Redevelopment of liftoff rates of saltating sand grains based on a simple optimization model     

Hong Cheng  XueYong Zou 《中国科学:地球科学(英文版)》2010,53(4):568-574

This paper is a redevelopment result of liftoff rates of saltating sand grains based on our previous work.Aeolian sand flow is a complex multi-phase flow because of a special two-phase gas-solid flow near ground surface.Despite extensive research on the movement of blowing sand,no model fully characterizes aeolian sand flow,and large differences often exist between simulations of aeolian sand movement and field observations.One key problem is a few of sufficient research on liftoff rates of saltating sand g...  相似文献   

Small aliquot and single grain IRSL and post-IR IRSL dating of fluvial and alluvial sediments from the Pativilca valley,Peru     

《Quaternary Geochronology》2014

Infrared stimulated luminescence (IRSL) and post-IR IRSL are applied to small aliquots and single grains to determine the equivalent dose (D_e) of eleven alluvial and fluvial sediment samples collected in the Pativilca valley, Central Peru at ca. 10°S latitude. Small aliquot D_e distributions are rather symmetric and display over-dispersion values between 15 and 46%. Small aliquot g-values range between 4 and 8% per decade for the IRSL and 1 and 2% per decade for the post-IR IRSL signal. The single grain D_e distributions are highly over-dispersed with some of them skewed to higher doses, implying partial bleaching; this is especially true for the post-IR IRSL. Measurements of a modern analog reveal that residuals due to partial bleaching are present in both the IRSL as well as the post-IR IRSL signal. The g-values of individual grains exhibit a wide range with high individual uncertainties and might contribute significantly to the spread of the single grain D_e values, at least for the IRSL data. Electron Microprobe Analysis performed on single grains reveal that a varying K-content can be excluded as the origin of over-dispersion. Final ages for the different approaches are calculated using the Central Age Model and the Minimum Age Model (MAM). The samples are grouped into well-beached, potentially well-bleached and partially bleached according to the evaluation of the single grain distributions and the agreement of age estimates between methods. The application of the MAM to the single grain data resulted in consistent age estimates for both the fading corrected IRSL and the post-IR IRSL ages, and suggests that both approaches are suitable for dating these samples.  相似文献   

Composition,environment, and economic value of the Permian to Cretaceous coated grains from Zagros and the Persian Gulf     

Mehrangiz Naderi-Khujin  Vahid Tavakoli 《国际泥沙研究》2023,38(3):316-334

Ooid grainstone/packstone carbonate facies of the Dalan, Kangan, and Arab formations are the main hydrocarbon reservoirs in the Persian Gulf. Based on detailed petrographic and petrophysical analyses,sedimentological and mineralogical features of the Permian to Late Cretaceous carbonate and iron-rich coated grains from Zagros and the Persian Gulf were investigated. Frequent ooids in these formations indicate a high-energy environment and a wave-dominated shallow carbonate platform. Because of wi...  相似文献   

Potential of establishing a ‘global standardised growth curve’ (gSGC) for optical dating of quartz from sediments     

《Quaternary Geochronology》2015

We report investigations of the optically stimulated luminescence (OSL) signals of sedimentary quartz from different regions of Asia, Africa, Europe and North America using a single-aliquot regenerative-dose (SAR) procedure. We show that variations in the shape of dose response curves (DRCs), or growth curves, of the test dose sensitivity-corrected OSL signals among single aliquots composed of multiple grains can be greatly reduced by normalising the DRCs using one of the regenerative dose OSL signals. We refer to this regenerative-dose normalisation procedure as ‘re-normalisation’. We find a common re-normalised DRC extends to doses of ∼250 Gy for samples that differ significantly in terms of geological provenance, sedimentary context and depositional age. This feature permits the development of a ‘global standardised growth curve’ (gSGC) for OSL signals from single aliquots of quartz. The equivalent dose (D_e) of an aliquot can be estimated from the natural signal, one regenerative dose signal and their corresponding test dose signals. For the variety of samples investigated, we find that D_e estimates obtained from the gSGC are consistent with those obtained using full SAR procedures for doses of up to ∼250 Gy. Use of the gSGC for single aliquots would greatly reduce the time required to estimate the D_e values of older samples and for a large number of aliquots.  相似文献   

Grains Containing Oil Inclusions in Different Hydrocarbon Production and Show Types of Sandstone Reservoirs from the Central Junggar Basin, Northwest China     

CAO Jian  WANG Xulong  SUN Ping’an  SHI Xinpu  HU Wenxuan  YAO Suping  ZHANG Yueqian  TANG Yong  XIE Xiaomin 《《地质学报》英文版》2011,85(5):1163-1172

The values of grains containing oil inclusions (GOI) in 120 reservoir sandstone samples from the central Junggar Basin of Northwest China were investigated. The sandstones are characterized by different types of hydrocarbon production and shows. The values range from 0.015% to 19.9%, and show a fairly good correlation with the hydrocarbon production/shows, which are qualitatively suggestive of reservoir hydrocarbon abundance and petroleum migration. Thus, it may be implied that the values can reflect hydrocarbon migration, being not controlled mainly by the other influencing factors. Further correlation between the values and the reservoir hydrocarbon production and show types indicates that the GOI method can be used in hydrocarbon migration study when the petroleum type of a reservoir is normal oil or gas alone, but it should be used with caution when light oil charges the reservoirs or a complex hydrocarbon migration event takes place. The case study in the central Junggar Basin using the method presents some new understanding on hydrocarbon migration. Thus, the method may help to solve specific petroleum geological problems, and can be treated as a routine tool in hydrocarbon migration study.  相似文献   

Behavior of the Rayleigh-Taylor mode in a dusty plasma with rotational and shear flows     

Jun Ma  Bao-xia Gan 《Planetary and Space Science》2006,54(8):719-725

The stability of a dusty plasma with sheared rotational flows is investigated. Using the fluid model together with the Bayly nonmodal approach, the inhomogeneous partial differential equations governing short-wavelength perturbations at the center of a rotational flow field or vortex structure are obtained. The effects of flow eccentricity, strength of the flow shear, as well as concentration of dust grains on the stability of the perturbations are investigated numerically. It is found that flow shear can cause secondary Rayleigh-Taylor instability of a rotational flow.  相似文献   

Influence of particle shape and angularity on the behaviour of granular materials: a numerical analysis     

C. Nouguier‐Lehon  B. Cambou  E. Vincens 《国际地质力学数值与分析法杂志》2003,27(14):1207-1226

This paper analyses the influence of grain shape and angularity on the behaviour of granular materials from a two‐dimensional analysis by means of a discrete element method (Contact Dynamics). Different shapes of grains have been studied (circular, isotropic polygonal and elongated polygonal shapes) as well as different initial states (density) and directions of loading with respect to the initial fabric. Simulations of biaxial tests clearly show that the behaviour of samples with isotropic particles can be dissociated from that of samples with anisotropic particles. Indeed, for isotropic particles, angularity just tends to strengthen the behaviour of samples and slow down either local or global phenomena. One of the main results concerns the existence of a critical state for isotropic grains characterized by an angle of friction at the critical state, a critical void ratio and also a critical anisotropy. This critical state seems meaningless for elongated grains and the behaviour of samples generated with such particles is highly dependent on the direction of loading with respect to the initial fabric. The study of local variables related to fabric and particle orientation gives more information. In particular, the coincidence of the principal axes of the fabric tensor with those of the stress tensor is sudden for isotropic particles. On the contrary, this process is gradually initiated for elongated particles. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Influence of crack density on geomechanical behavior of granular composites with porous grains and fluid‐saturated pores     

James G. Berryman 《国际地质力学数值与分析法杂志》2014,38(13):1381-1396

The analysis of geomechanical behavior for granular systems including fluid‐filled pores depends strongly on the crack density present within the system being studied. Effective overall bulk and shear moduli are both significantly influenced by these crack system parameters. Present effort concentrates on the geomechanical analyses needed to treat anisotropic (specifically orthotropic) poroelastic grains jumbled together to form an overall isotropic polycrystalline poroelastic material. As predicted, poroelastic effects induced by fluids in the cracks are observed to be significant for the effective bulk modulus, but simple pore fluids do not affect the magnitude of effective overall shear modulus. These results are also shown to depend in a quantitatively predictable way on crack density values. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献