Quantifying the rate and depth dependence of bioturbation based on optically‐stimulated luminescence (OSL) dates and meteoric 10Be          下载免费PDF全文

Michelle O. Johnson  Simon M. Mudd  Brad Pillans  Nigel A. Spooner  L. Keith Fifield  Mike J. Kirkby  Manuel Gloor 《地球表面变化过程与地形》2014,39(9):1188-1196

Both the rate and the vertical distribution of soil disturbance modify soil properties such as porosity, particle size, chemical composition and age structure; all of which play an important role in a soil's biogeochemical functioning. Whereas rates of mixing have been previously quantified, the nature of bioturbation's depth dependence remains poorly constrained. Here we constrain, for the first time, the relationship between mixing rate and depth in a bioturbated soil in northeast Queensland, Australia using a novel method combining OSL (optically‐stimulated luminescence) ages and meteoric beryllium‐10 (¹⁰Be) inventories. We find that the best fit mixing rate decreases non‐linearly with increasing soil depth in this soil and the characteristic length scale of 0.28 m over which the mixing coefficient decays is comparable to reported rooting depth coefficients. In addition we show that estimates of surface mixing rates from OSL data are highly dependent on erosion rate and that erosion rate must be constrained if accurate mixing rates are to be quantified. We calculate surface diffusion‐like mixing coefficients of 1.8 × 10^?4 and 2.1 × 10^?4 m² yr^?1 for the studied soil for two different estimates of soil erosion. © 2014 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.  相似文献   

Luminescence dating of Weichselian interstadial sediments from the German Baltic Sea coast     

《Quaternary Geochronology》2015

A cliff outcrop called Kluckow, in the Baltic Sea area, with a (glacio-) fluvial to (glacio-) lacustrine succession, provides a unique opportunity to resolve uncertainties in the timing and extent of several poorly constrained Weichselian ice advances. Based on a detailed lithofacies analysis, we selected four sampling horizons for luminescence dating to determine a depositional chronology. We measured both coarse-grain quartz and potassium-rich feldspar for age determination using optically stimulated luminescence (OSL) and post-IR infrared stimulated luminescence (pIRIR). Furthermore we addressed potential problems such as incomplete bleaching and quartz saturation effects. The resulting luminescence-chronology, supported by one radiocarbon age, illustrates a depositional time interval of the investigated sequence between ∼62 and ∼22 ka. Within this sequence a mussel-bearing fluvial sand indicate interstadial climate conditions at approximately 46 ka. The upper part of the section is composed of a 4 m thick glaciolacustrine silty clay and an overlying glaciofluvial sand; the latter yielded an OSL age of ∼22 ka. Shortly after these sequences formed, the subsequent ice advance (indicated by the overlying till sheet) reached the study area. Based on our new chronology and lithofacies analysis, we conclude that the Scandinavian Ice Sheet did not reach the study area between ∼62 and ∼22 ka.  相似文献   

内蒙古扎鲁特旗地区更新世地层划分   总被引：2，自引：2，他引：0       下载免费PDF全文

丁秋红  王杰  李晓海  姚玉来  宗文明  郜晓勇  李文博 《中国地质调查》2015,2(7):24-29

根据孢粉组合特征及光释光测年结果,对分布在内蒙古东南部的第四系更新统做了进一步的划分和研究。研究结果表明,主要分布在内蒙古东南部的中更新统风积物,岩性为黄色亚砂土,含钙质结核,发育柱状节理,区域上称乌尔吉组,含Artemisia-Ephedra-Pinus孢粉组合,光释光测年结果为(40.4±1.9)~(110.0±7.5)ka; 下更新统沉积物,岩性为红褐色亚砂土及亚黏土,含钙质结核、砂砾透镜体,区域上称为赤峰黄土,含Artemisia-Polygonum-Betula孢粉组合,光释光测年结果为（200.9±9.6）~（220.4±13.2）ka。上述2套地层在内蒙古东南部广泛分布,更新世地层的划分为内蒙古东南部地区的第四系地层划分对比研究提供了基础地质资料。  相似文献   

蓬莱黄土剖面光释光年代学及其沉积特征研究   总被引：1，自引：1，他引：0  

徐树建  王涛 《中国沙漠》2011,31(2):295-301

对山东半岛北部蓬莱林格庄黄土剖面进行了系统的野外考察,并进行了光释光测年以及粒度、磁化率指标分析。研究表明,磁化率的变化与不同粒级的百分含量具有一定的相关性,频率磁化率与粗颗粒含量基本呈一定的负相关。结合野外地层划分与光释光年代学测试可以将该剖面划分为3个黄土层和3个古土壤层,该剖面记录了末次间冰期以来该区气候和环境变化的历史。  相似文献   

Confirming geomorphological interpretations based on portable OSL reader data          下载免费PDF全文

Eric W. Portenga  Paul Bishop 《地球表面变化过程与地形》2016,41(3):427-432

Portable optically stimulated luminescence (OSL) readers are increasingly being used in geomorphological and archaeological investigations, but information regarding data reproducibility and the reliability of interpretations based on portable OSL reader data has not yet been presented to the wider geomorphological community. This Letter addresses these two issues by returning to Grabben Gullen Creek in the southeastern Australian Tablelands where we remeasure a sediment profile that was first measured by other researchers 3 years earlier. We also compare portable OSL reader data measured on sediment interpreted to have been deposited in swampy meadow wetlands and flood alluvium settings with data measured on known swampy meadow and flood deposits. Our data show that portable OSL reader data are reproducible. Moreover, we confirm the earlier interpretation that stratigraphies commonly exposed in southeastern Australian Tablelands valley bottoms reflect pre‐European swampy meadow wetlands and flood alluvium. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

脉冲激光抽运铷原子钟研究   总被引：1，自引：0，他引：1  

杜志静  赵文宇  刘杰  张首刚 《武汉大学学报(信息科学版)》2011,36(10):1236-1240

对脉冲激光抽运、微波分立场共振和自由感应微波辐射或者光吸收检测方案（POP）的铷原子钟进行了理论和实验研究。理论研究表明,POP原子钟,可以消除光频移,有效地减小腔牵引频移,从而有利于提高原子钟的稳定度;且微波脉冲面积为π/2时,微波Ramsey条纹的线宽为传统Ramsey条纹的一半,从而提高了原子品质因数。实验获得了...  相似文献   

Growth by extension,and reworking,of a south‐western Kalahari linear dune     

Matt W. Telfer 《地球表面变化过程与地形》2011,36(8):1125-1135

Optically stimulated luminescence (OSL) dating studies of linear (longitudinal) dunes have been used extensively to elucidate late Quaternary environments and climates in arid or formerly arid regions, yet understanding of the development of such dunes is incomplete. In particular, conflicting opinions have been presented regarding the propensity of linear dunes to migrate laterally, the degree to which they rework their own sediment during accumulation and whether they form primarily by extension, as opposed to lateral sand movement from adjacent interdunes. This study focuses on this last point, although the importance of the other controversies is discussed in context. A simple linear dune in the south‐western Kalahari, which has a prominent termination on a pan (playa) surface, provides an opportunity to directly test hypotheses of dune extension. Chronostratigraphy along a ~600 m transect along the crest of the dune, constrained by 42 OSL ages, reveals that the dune grew by extension on occasions in the late Pleistocene and early Holocene, but has also been subject to reworking along its length, which has continued until recent times. Dune development by extensional growth is suggested to operate under environmental conditions more conducive to net accumulation, whereas reworking is largely independent of conditions throughout the last ~18 ka, and may represent seasonal fluctuations in the position of the dune crest. The relative significance of these two modes of development is suggested to be a key control on the efficacy of linear dunes as archives of environmental and climatic change. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

四川盆地南部构造页岩气储层压裂改造技术   总被引：6，自引：0，他引：6  

孙海成  汤达祯 《吉林大学学报(地球科学版)》2011,(Z1):34-39,68

在调研和学习国内外相关页岩气压裂改造技术的基础上,通过室内实验和研究,对四川盆地南部构造S2井页岩储层岩性特征、孔渗特征、天然裂缝发育特征进行了评价。针对S2井极低渗透率(0.000 18×10-3μm2)、天然裂缝和水平层理较发育,天然裂缝内充填有碳酸盐岩,同时吸附气含量较高、脆性程度高,压裂容易形成网络裂缝的特点,进行了压裂工作液体体系优选和压裂工艺优化,采取了大规模、大排量、大砂量、低砂比、减阻水压裂施工工艺,成功实现了页岩气储层大规模减阻水压裂施工;根据微地震显示,压裂改造体积达到了480×104 m3,具有明显的体积改造特征,获得较好的效果,日产10 000 m3。压后分析数据显示,在页岩气储层中,过长的关井时间有可能影响有限支撑剂铺置的裂缝整体导流能力,最终影响到产量。S2井压裂施工成功标志着国内在页岩气压裂施工工艺、压裂工作液体体系、裂缝监测等方面实现突破。  相似文献   

Beryllium-10 terrestrial cosmogenic nuclide surface exposure dating of Quaternary landforms in Death Valley     

Lewis A. Owen  Kurt L. Frankel  Jeffrey R. Knott  Scott Reynhout  Robert C. Finkel  James F. Dolan  Jeffrey Lee 《Geomorphology》2011,125(4):49

  相似文献   

基于年龄测试的黄庄—高丽营断裂活动性研究     

王海刚  贾三满  田芳 《城市地质》2013,8(1):32-34

黄庄—高丽营断裂是北京平原区一条重要的活动断裂,在庙城—高丽营段沿线发生地裂缝,造成大量房屋墙体开裂和道路破坏。在西王路村探槽揭示该断裂错断第四系地层,产生地表地裂缝。探糟断裂孢粉年龄测试,该断裂发生年龄大致在13～22ka,仍处于活动状态。  相似文献