中国黄土剖面蓝田正极性亚带之确认

中国黄土广泛分布于中国北方,是典型的更新世沉积。巨厚的黄土地层较完整地记录了200多万年来地球磁场变化信息,使我们得以通过黄土进行古地磁研究。作者先后对20多个黄土剖面进行了古地磁测量。结果表明:黄土剖面清楚地反映出布容正极性带与松山负极性带的界限(B/M)位于第八层黄土(L_8)中部。松山负极性带与高斯正极性带的界限(M/Ga)恰是更新世黄土与第三纪红粘土的界限。在松山负极性带中清楚地反映出哈拉米洛正极性亚带(J),奥尔都维正极性亚带(O)与留尼汪正极性亚带(R).     

世界最厚的黄土地层——靖远黄土剖面研究进展

靖远曹岘黄土剖面位于甘肃靖远盆地中部,它座落在黄河六级阶地上,黄土厚505m,地层连续完整。出露清楚,是目前已知世界上最厚的黄土剖面。它为研究黄土高原黄土,特别是高原西部黄土的地层、岩性、成因及形成环境等提供了十分有意义的资料。古地磁测试结果表明,曹岘黄土剖面含布容正极性时和松山反极性时,B/M界线位于L_8中部,年龄为0.73Ma B·P·;加拉米洛正极性亚时位于L_(10)—L_(13)位置,年龄为0.97～     

陕县张汴塬黄土剖面的古地磁研究

本文通过交变退磁后的古地磁测定结果,着重讨论了张汴塬黄土古地磁特征及黄土地层划分。古地磁测定结果表明:早更新世与中更新世黄土界线和布容与松山之间界线吻合,在剖面的下粉砂层顶部。中更新世黄土始于73万年。在布容正极性世中,第二层古土壤中出现反极性标本,有可能是反极性事件。早更新世沉积物中显示出哈拉米洛与奥尔都维两个事件。最底部出现的正极性标本可能是留尼昂事件的反映,因此陕县黄土可能形成于240万年左右。在中国黄土中发现留尼昂事件的剖面还不多。为进一步搞清这几个事件,目前正在进一步工作。此外本文还研究了标本的虚磁极位置,以及强度与岩性的关系。     

西安黄土台塬区全新世黄土磁化率古气候环境演变

通过对西安神禾塬鱼包头村和泾阳县新庄村典型剖面全新世黄土—古土壤地层的岩性描述、地层划分和对比,结合泾阳县新庄村AMS~(14)C的年代测定和其他学者的测年数据,建立了该地区全新世以来黄土沉积年代序列.根据磁化率气候替代指标在剖面上的变化规律以及该黄土剖面反映的东亚冬、夏季风强弱变化特点,详细分析了西安地区全新世以来环境变化的特征和规律,进而将该剖面磁化率曲线特征与其他学者的孢粉谱建立的温度曲线进行对比.对西安地区全新世以来古气候的阶段进行了划分,将西安地区10 000 a以来的气候演变划分为6个气候阶段:10.0~9.0 kaBP,冷温转换阶段;9.0~7.0 kaBP,暖冷波动阶段;7.0~5.0 kaBP,温暖阶段;5.0~3.4 kaBP,暖冷剧烈波动阶段;3.4~2.0 kaBP,气温先降后升阶段;2.0 kaBP至现在,温暖半湿润、半干旱阶段.     

山西临猗杨范第四纪沉积剖面初步研究

通过对杨范剖面黄土地层岩性特征、沉积结构、质量磁化率和频率磁化率的分析及与深海氧同位素曲线的对比,划分了剖面地层,初步确定了黄土沉积始于1.20 Ma B P,黄土沉积以来该区发生了13次大的干冷-暖湿气候变化;沉积转型指示河流强烈加积转变为河流侵蚀,代表约在1.20 Ma B P发生过一次强烈的构造抬升事件。     

深海氧同位素第5阶段的气候记录:武都黄土剖面与极地冰心、深海沉积同位素记录的对比

武都地区晚更新世以来堆积了厚约１７ｍ的黄土地层，其间夹有多层厚度不一、发育程度不同的古土壤层．在剖面１３．２～１７ｍ黄土中，野外可清晰的观察到６层古土壤．通过剖面磁化率、粒度、稳定同位素、元素地球化学、ＴＬ年代、ＣａＣＯ３、有机质含量的综合分析，认为它敏感而详尽地记录了深海氧同位素第５阶段的气候变化历史．对比研究结果显示：除总体模型与中国中西部黄土高原、深海氧同位素及南极冰心记录一致外，还可以与格陵兰Ｓｕｍｍｉｔ冰心记录进行良好的细节对比，揭示了全球气候变化地质记录的统一性．     

南京下蜀土剖面磁化率测量及其与深海沉积的对比

本文通过对典型样品的低温磁行为分析探讨了磁化率反映古气候的机制,并尝试把下蜀土剖面磁化率古气候记录与华北黄土及深海沉积的记录相对比。     

兰州九洲台黄土剖面古地磁研究

兰州黄土剖面厚约335m。含有28层淡红褐色古土壤,该剖面共采集古地磁样品约10块。进行了岩石磁学和古土壤学方面的研究。结果表明:该剖面所含磁性矿物主要为磁铁矿,并含极少量赤铁矿、钛铁矿。天然剩磁强度平均为5×10~(-5)emμ/cm~3,磁化率为60-20×10~(-6)emμ/oc、B/M界限位于L_8中,哈拉米洛(J)亚带位于S_(10)至S_(11),在B/M界限与J亚带之间有一正极性地层段,为松山负极性时最末期的一次正极性倒转,兰州黄土最早形成于14×10~5年。     

萧县黄土剖面的磁化率测量及意义

新近发现的萧县黄土剖面是关于淮河北部地区黄土堆积的初次报导．野外观察表明，该剖面可划分为４层古土壤和４层黄土．对该剖面磁化率测量表明，该剖面的磁化率曲线与古土壤一黄土系列有着高度的一致性．９个磁化率阶段的划分，说明磁化率测量比野外观察更能反映物质组成和古气候的细微变化．磁化率曲线峰谷变化的特征暗示该剖面堆积过程中气候转型事件的存在，这一剖面的的发现，填补了淮河中下游地区缺少黄土堆积的空白．     

西安狄寨塬全新世的古气候环境

对西安地区全新世以来的环境演变特征进行系统研究,建立该地区全新世以来黄土—古土壤沉积年代序列,揭示其反映的东亚冬、夏季风变迁规律,为预测西安地区乃至中国和全球未来环境的发展趋势提供依据.通过对西安白鹿塬刘家坡典型剖面全新世黄土—古土壤地层的岩性描述、地层划分和对比,结合泾阳县新庄村AMS14 C的年代测定和其他学者的测年数据,建立了该地区全新世以来黄土沉积年代序列.根据磁化率气候替代指标显示的曲线特征,阐述了这一替代指标在剖面上的变化规律,探讨了该黄土剖面所反映的东亚冬、夏季风强弱变化特点,论证和详细分析了西安地区全新世以来环境变化的特征和规律,进而对该剖面磁化率曲线特征与其他学者的孢粉谱建立的温度曲线对比,对西安地区全新世以来古气候的阶段性进行了详细分析和论证.将西安地区10 000年以来的气候演变划分为7个气候阶段.     

Age estimation of the mid-Pleistocene microtektite event in the South China Sea: A case showing the complexity of the sea-land correlation

The present study confirms the stratigraphical position of microtektite layer being clearly located below the Brunhes/Matuyama (BIM) boundary. Based on the sedimentation rate derived from the stable isotopic and magnetic data of ODP Site 772A, cores 17957 and 17959 in the South China Sea, the age of the mid-Pleistocene impact event was estimated at 1–12 ka earlier than the Brunhes-Matuyama polarity reversal. However, the microtektites were found above the measured BIM boundary in the loess profile due to the downward deviation of the measured B/M boundary from its true position^[1]. This demonstrates the complexity of paleo-magnetic records in the loess profiles which, in turn, causes the confusion in the sea-land stratigraphic correlation.     

The elemental carbon record in Weinan loess section since the last 21 ka

We studied the records of elemental carbon (EC) of the last 21 ka in the Weinan loess section, Shanxi Province. The variations of EC abundance and δ¹³C_EC value along with depth (or age) were presented. There are four large peaks of EC abundance around the following years: 20.16 ka, 17.76 ka, 11.97 ka and 4.49 ka. Climatic situation was changed rapidly during these periods. The peaks around 11.97 ka and 20.16 ka are particularly sharp, occurring over intervals of tens to hundreds of years, which could represent short-duration intense events. δ¹³C_EC values in the upper 4 m of the Weinan loess section vary between −11.71‰ and −21.34‰, which suggests that the vegetation pattern of the last 21 ka on the Loess Plateau is C₄-dominated grasses.     

A recording phase lag between ocean and continent climate changes: Constrained by the Matuyama/Brunhes polarity boundary

The Matuyama/Brunhes polarity boundary (MBPB) is recorded in Chinese loess L8, which is associated with the glacial period. It is proved that loess L8 is capable of recording earth’s secular variation, and the lock-in depth in Chinese loess is no more than that of marine sediments. Comparison with the location of MBPB in Chinese loess and marine sediments, it is put forward that there is a recording phase lag between ocean and continent climate changes.     

Vegetation evolution on the central Chinese Loess Plateau since late Quaternary evidenced by elemental carbon isotopic composition

There are many controversial issues in loess studies such as natural vegetation types on the Chinese Loess Plateau during the historical periods and the spatial and temporal evolution of C3/C4 plants. Elemental carbon isotopic composition （δ^13Cec） in the loess section may offer new evidence for these problems. Elemental carbon （EC） is produced by incomplete combustion of vegetation, and its carbon isotopic composition has a very small difference from that of the formal vegetation, then δ^13Cec can be used as a record to recover the changes of vegetation. Elemental carbon was extracted by applying the oxidation method from the Ioess-paleosol sequence in the central Chinese Loess Plateau, and its car- bon isotope composition was analyzed by the isotope mass spectrometer. The results showed that the vegetation in this region was a mixed type of C3 and C4 plants, dominated with C3 plants in most of the time. Since late Quaternary, C3/C4 plants may not follow a simple glacial-interglacial cycle mode on the Chinese Loess Plateau, but showing fluctuations. C3 plants increased gradually in L4 period, and more C3 plants occurred during $3 period, and C4 plants increased again during L3-- L2 periods, after that, Cs plants dominated again during S1 --S0 periods. During periods of paleosol development, C3 plants were abundant in S3 and S1, and there were more Ca plants in S2 and SO. During periods of loess sedimen- tation, there were more C3 plants in L4 and L1, and there were more C4 plants in L3 and L2. On the orbital timescale, the vegetation variations revealed by δ^13Cec record are consistent with the results of pollen data and also similar to the results obtained by organic carbon isotopic composition since the last glacial period.     

Features of major greenhouse gases in loess, Shanxi Province, China

According to the investigations of five loess sections in Shanxi Province, China, it was found that the concentrations of the major greenhouse gases CO₂, CH₄ and N₂O in loess-paleosol sequences are generally high, even sometimes may be several times or scores of times higher than their atmospheric concentrations respectively. Although the CO₂ concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH₄ concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ¹³C values of CO₂ in loess are -11.14‰—15.48‰ (relative to PDB standard). Analysis of carbon isotopic compositions of CO₂ indicates that the main source of CO₂ in loess section is decomposition of ‘stable’ organic matters by microbes. The δ¹³C_g of CO₂ is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not only makes the loess a huge carbon reservior but also adjusts     

A climatic reversal at the last interglacial-last glacial transition recorded in the loess section at Zhaitang, Beijing

A weakly developed paleosol was identified at S1-L1 transition of the loess section of Zhaitang, Beijing. This paleosol may represent a climatic reversal which is associated with the strengthening in summer monsoon and correlated well with the climatic regression event documented in the paleoclimate records from Greenland ice, marine sediments and European pollen at the last interglacial-last glacial transition.     

Effect of fatty acids on polyamine contents and Na+/H+ antiport activity in PM vesicles isolated from roots of barley under salt stress

With 200 mmol/L NaCl treatment on barley cultivar “Jian 4” (Hordeum vulgare L. cv. J4) seedlings for 6 d, the contents of covalently and noncovalently conjugated polyamines (PAs) and activities of H⁺-ATPase in plasma membrane (PM) vesicles isolated from the roots decreased remarkably. Moreover, the activity of Na⁺/H⁺ antiport was detected first in PM vesicles. The results showed that the decrease in the contents of membrane phospholipid, noncovalently conjugated PAs and activity of H⁺-ATPase caused by NaCl could be restored partially by application of 1 mmol/L stearie acid (C_16:0) and linoleic acid (C_18:2), and C_18:2 was more effective than C_16:0 In addition, a reduction in the contents of covalently conjugated PAs was only reversed partially in the presence of C_18:2 Furthermore, Na⁺/H⁺ antiport activity was strengthened by exogenous C_16:0 and C_18:2 and C_18:2 was more effective than C_16:0. The correlative analysis suggested that, after application of C_16:0 and C_18:2 under salt stress, there was a significant positive correlation existing among phospholipid content, noncovalently conjugated PA levels, H⁺-ATPase activities and Na⁺/H⁺ antiport activities, indicating that one of the mitigative mechanisms of exogenous fatty acids on salt injury was to improve membrane phospholipid and PA contents, leading to an enhance in membrane integrity and a change in charge status of PM vesicles, so the activity of membrane-associated enzyme H⁺-ATPase was increased and synthesis of Na⁺/H⁺ antiport protein was activated.     

10Be/7Be implies the contribution of stratosphere-troposphere transport to the winter-spring surface O3 variation observed on the Tibetan Plateau

10Be/7Be is a stratospheric sensitive tracer.In this paper,measurements of 10Be/7Be and surface O3 from October 2005 to May 2006 at Mt.Waliguan (hereafter WLG,100.898°E,39.287°N,3810 m,a.s.l.),China global atmospheric watch (GAW) observatory,are introduced and used to investigate the stratosphere-troposphere transport (STT) and its impact on surface O3 on the Tibetan Plateau.The results show that the magnitude of STT is weak in winter,followed by strengthening from the end of winter to the middle of spring (from mid February to mid April) with large increases in 10Be,7Be,10Be/7Be and surface O3.At the end of spring (from the end of April to mid May in this paper),the STT weakened,and the continuous increase of surface O3 at WLG is produced by tropospheric photochemistry reactions.     

BLim1/2+(m=6、7)团簇的结构及储氢性能的研究

为开发新型储氢材料提供更为丰富的理论基础,采用B3LYP泛函在6-311++G(d,p)基组水平上对BLi₆⁺超碱团簇和BLi₇²⁺超碱土团簇的稳定性结构、电荷分布等方面进行理论研究,进而研究团簇的储氢性能。结果表明：两个离子团簇均比它们所对应的中性团簇均具有较高的动力学稳定性。两个离子团簇中的每个Li原子同时有效吸附2个氢分子,BLi₆⁺团簇中氢分子在团簇表面平均吸附能为0.969~2.162kCal/mol,储氢质量分数达31.56wt%。而BLi₇⁺团簇中氢分子在团簇表面平均吸附能为1.764~3.714kCal/mol,储氢质量分数达32.21wt%。它们的储氢性能表明BLi₆⁺团簇和BLi₇²⁺团簇均有望成为良好的储氢媒介。     

Magnetic characteristics and their paleoclimatic significance of Fengzhou loess in the Qinling Mountains of China

The Fengzhou loess section is very typical in the Qinling Mountains. The section, about 82 m thick and underlain by the Neogene red clay, consists of 33 layers of loess and 33 layers of paleosol. The section covers Brunnes normal polarity zone and Matuyama reversed polarity zone, and the B/M boundary is located in the middle of L₈. Matuyama reversed polarity zone records Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between Matuyama reversed polarity zone and Gauss normal polarity zone (M/Ga) appears in the lithological boundary between loess and the Neogene red clay. Loess accumulation in Fengzhou started before 2.48 Ma. The magnetic susceptibility curve indicates 33 cold-dry and humid-warm cycles of paleoclimatic variation in the Qinling Mountains during the last 2.48 Ma. The above climatic fluctuation may be well compared with that of the oxygen isotopic records from deep-sea deposits.