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1.
兰州九洲台黄土沉积年代的综合研究 总被引：10，自引：1，他引：10
据上、下粉砂层在剖面上出现的位置、黄土-古土壤地层层序、14C、热释光（TL）和裂变径迹年龄以及古地磁测量结果,兰州九洲台黄土仅仅是距今140-150万年以来才沉积而成的,因而距今220-240万年以来形成的结论不能成立. 相似文献
2.
西藏西部台错湖T1阶地的两个剖面沉积中,除下部10余厘米含碳化植物和50-70 cm处为暗色碳酸盐粘土及粘土外,中、上部全系粘土碳酸盐层,含丰富的介形类和轮藻类。据碳酸盐、介形类、轮藻类的碳、氧稳定同位素值与微体古生物群落生态特征等提供的环境气候变化指标,指示该区距今41.4~4.5 ka BP间气候变化为：在41.4~26.2 ka BP气候较湿润;26.2~25.5 ka BP偏暖稍干;25.5~22.5 ka BP气候暖湿;22.5~21.0 ka BP气候偏冷湿;20.5~17.5 ka BP气候骤冷、偏湿,反映本区处于末次冰期盛冰期;17.5~16.0 ka BP偏冷偏干;16.0~11.8 ka BP气候偏暖湿,为全球间歇性暖事件的响应;11.8~10.4 ka BP气候较冷干,大致相当于新仙女木期,10.4 ka BP气温开始回升;10.4~9.4 ka BP气候偏暖湿;9.4~8.5 ka BP气候呈现短暂暖湿颤动;8.5~7.9 ka BP气候偏干冷,为冰后期强烈降温偏干事件;7.8~6.3 ka BP气候偏暖湿;6.3~4.5 ka BP气候趋向冷干,4.5 ka BP记录到晚更新世晚期以来最大的干燥期。 相似文献
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Yongqin LIU Tandong YAO Nianzhi JIAO Shichang KANG Yonghui ZENG Xiaobo LIU 《Frontiers of Earth Science》2009,3(1):80-90
Snow bacterial abundance and diversity at the Guoqu Glacier and the East Rongbuk Glacier located in the central and southern
Tibetan Plateau were investigated using a 16S rRNA gene clone library and flow cytometry approach. Bacterial abundance was
observed to show seasonal variation, with different patterns, at the two glaciers. High bacterial abundance occurs during
the monsoon season at the East Rongbuk Glacier and during the non-monsoon season at the Guoqu Glacier. Seasonal variation
in abundance is caused by the snow bacterial growth at the East Rongbuk Glacier, but by bacterial input from the dust at the
Guoqu Glacier. Under the influence of various atmospheric circulations and temperature, bacterial diversity varies seasonally
at different degrees. Seasonal variation in bacterial diversity is more distinct at the Guoqu Glacier than at the East Rongbuk
Glacier. Bacterial diversity at the two glaciers exhibits different responses to various environmental conditions. More bacteria
at the Guoqu Glacier are connected with those from a soil environment, while more bacteria affiliated with a marine environment
occur at the East Rongbuk Glacier. 相似文献
4.
Two sedimentary sections were measured at Tai Co (Co means lake in Tibetan) in western Tibet, China. The two sections are almost all composed of clay carbonate beds except in their lower parts where there are carbonized plants at >10 cm depths and dark-colored carbonate clay and clay at 50–70 cm depths, yielding abundant gastropods, ostracods, and charophytes. The carbon and oxygen stable isotope values of carbonate, ostracods, and charophytes and ecological features of microfossil communities indicate the following climatic change in the area from 41.4 to 4.5 ka BP: at 41.4–26.2 ka BP, the climate was relatively wet; at 26.2–25.5 ka BP, it was slightly warm-dry; at 25.5–22.5 ka BP, it was warm-wet; at 22.5–21.0 ka BP, it was slightly cold-wet; at 20.5–17.5 ka BP, it became cold abruptly and slightly wet, implying the climate of the last glacial maximum; at 17.5–16.0 ka BP, it was slightly cold-dry; at 16.0–11.8 ka BP, it was slightly warm-wet; at 11.8–10.4 ka BP, it was relatively cold-dry, roughly equivalent to the climate of the Younger Dryas, and at 10.4 ka BP, the temperatures began to rise again; at 10.4–9.4 ka BP, it was slightly warm-wet; at 9.4–8.5 ka BP, there occurred short warm-wet oscillations; at 8.5–7.9 ka BP, it was slightly dry-cold, representing a strong temperature-lowering and drying event in the postglacial stage; at 7.8–6.3 ka BP, it was slightly warm-wet; at 6.3–4.5 ka BP, the climate tended to be cold-dry. 4.5 ka BP recorded the maximum aridity since the late part of the late Pleistocene. 相似文献
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利用在西藏纳木错流域念青唐古拉山北坡（NQN，海拔5 400 m）和西北保吉乡（BJ，海拔4 730 m）布设的两台带有四层土壤探头自动气象站(AWS)2005—2006年冬季10个月观测数据进行了统计分析。结果表明：观测期间NQN日及月平均气温均低于BJ，但变化幅度均小于BJ，土壤冻结时间比BJ长，两处的气温梯度为0.31℃/100 m。与安多月平均气温比较，推断NQN存在高山多年冻土。NQN大气—土壤及土壤内热传输速度快于BJ；冻结期内土壤中未冻水含量在0～-2.5℃时发生跃变且与土壤温度存在较好的线性关系；相同深度处NQN土未冻水含量较小。土壤温度日变化在0～40 cm深度处较明显，40cm深度以下变化很小，未冻水含量日变化在5 cm深度较明显，20 cm以下变化微弱。利用两观测点冻结深度（Df）与冻结积温（Tg）的良好相关建立模型，NQN为：Df n= 0.0016Tg+ 1.69,R2=0.9958；BJ为：Df b= 0.002 Tg+ 1.13，R2= 0.9424，并由此推断出两观测点最大季节冻结深度分别为1.69 m和1.13 m。 相似文献
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基于青藏铁路沿线P32和P33监测断面连续10年的含融化夹层路基的地温和变形场地实测数据,分析了该两处监测断面左路肩下多年冻土人为上限、季节冻结最大深度、融化夹层厚度及多年冻土人为上限附近地温的年变化过程;同时分析了P32和P33监测断面左右路肩的总沉降年变化过程、P32监测断面左路肩地温场对变形的影响及P33监测断面左右路肩地温场差异对左右路肩差异沉降的影响。结果表明:P32和P33监测断面左路肩下多年冻土人为上限逐年下降、季节冻结最大深度基本不变、融化夹层厚度逐年增厚及多年冻土人为上限附近地温逐年升高;观测期内,P32和P33监测断面左右路肩变形均以沉降为主,且P32监测断面左右路肩的总沉降变形量均小于P33监测断面;其中P32监测断面左路肩暖季沉降变形明显,冷季发生轻微的冻胀变形,且发生沉降和冻胀的时间略滞后于路基下部温度场的变化;P33监测断面左右路肩地温场的差异导致左右路肩存在差异沉降,且其差异沉降值随时间逐年变大。 相似文献
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广东核电站地应力测量及其应用 总被引：3，自引：0，他引：3
基于广东省3个核电站厂址区的水压致裂地应力测量结果,获得了各核电站厂址区现今地应力场分布特征,结果表明,各核电站厂址区以水平应力为主导;大亚湾、阳江核电站水平应力值随深度增加而呈线性增大,台山核电站水平应力随深度线性增加不明显;大亚湾、阳江核电站厂址区最大水平主应力方向为NW-NWW,台山核电站为NNW。根据地应力测量结果、相关理论及判据分析认为,大亚湾核电站拟建隧洞长轴方向较不利于隧洞围岩的稳定,台山和阳江核电站拟建隧洞长轴方向利于围岩的稳定和维护;各核电站拟建隧洞横截面形状以水平长轴、垂向短轴且长、短轴比近似于各隧洞截面上侧压力系数的椭圆形为宜;各隧洞在埋深范围内开挖时均没有发生岩爆的可能性。最后,依据Byerlee滑动摩擦准则,探讨了核电站外围现今活动断层的稳定性。 相似文献
9.
太白山佛爷池剖面的全新世环境变化信息 总被引：5，自引：0，他引：5
太白山佛爷池海拔3410m,是一个发育在古冰斗中的冰蚀湖。自湖中210cm沉积剖面进行沉积物粒度、孢粉和测年采样分析,表明自8200aBP以来的环境经历了明显的冷暖干湿变化。8200~6800aBP温暖湿润,在7200aBP出现明显增温;6800~5900aBP气候开始波动,大约在6300aBP有一次短暂的变冷,在6000aBP前后出现明显暖期;5900~4800aBP气温下降,大约在5200aBP达到最低,然后气温缓慢回升;4800~2600aBP气候较为温暖湿润,大约在3000aBP达到最高;2600~900aBP气候变冷湿,大约1500aBP达到最低;900aBP~现代变好。 相似文献
10.
Structural contribution from the Oman ophiolite to processes of crustal accretion at the East Pacific Rise 总被引：1，自引：0，他引：1 
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下载免费PDF全文 A comprehensive model for the activity of the elementary accretion segment at fast‐spreading ridges relies on integration of structural data from the Oman ophiolite and geophysical results from the East Pacific Rise (EPR) around 9°N, which are of comparable size and spreading rates. The axial melt lens at shallow crustal level provides a link between Deval segmentation at the seafloor and a lower melt sill at Moho level, imaged at the EPR as a crustal melt zone (CMZ) and mapped in Oman as the Moho transition zone (MTZ). Both are attached to a mantle upwelling at the EPR, and to a frozen diapir in Oman. The physical link between diapiric mantle uprising at the Moho and Devals segmentation at the seafloor is the melt being injected from the mantle into the lower MTZ, ponding there, and then being released by powerful injections into the upper melt lens. The magma chamber covers the diapir at a distance of 5 km from the ridge axis. 相似文献
11.
A Mary Selvam A S Ramachandra Murty R Vijayakumar S K Paul G K Manohar R S Reddy B K Mukherjee Bh. V. Ramana Murty 《Journal of Earth System Science》1980,89(2):215-230
The thermodynamical and microphysical characteristics of monsoon clouds in the Poona, Bombay and Rihand regions were investigated using extensive aircraft in-cloud observations. The number of clouds sampled at Poona, Bombay and Rihand is 2199, 169 and 104 respectively. The temperatures inside the cloud are colder than its environment at Poona and Rihand. The maximum difference is about 3°C at the cloud base level and the difference decreased with height. At Bombay the difference is less than 1°C and at some levels the temperatures inside the cloud are warmer than its environment. The lapse rates of temperatures inside the cloud are slightly less than those in the immediate environment of the cloud. The environmental lapse rates are nearly equal to the saturated adiabatic value. The positive increments in liquid water content (LWC) are associated with the increments in temperature inside the cloud. Similarly positive increments in temperatures inside the cloud are associated with the increments in temperature of its immediate environment at the same level or the layer immediately above. The maximum cloud lengths observed at Poona and Bombay respectively are 14 and 3 km. The horizontal cross-section of LWC showed a maximum number of 13 peaks in clouds at Poona while only 7 peaks were observed at Bombay. The location of maximum LWC in the horizontal cross-section is more or less at the centre of the cloud. The LWC profile showed an increase with height from the base of the cloud at Poona and Bombay. There is no marked variation of LWC with height at Rihand. The total droplet concentration at different altitudes at Poona and Bombay is in the range 28–82 cm?3. The size distribution of cloud droplets experienced a broadening effect with increase in height from the cloud base at Poona. The broadening effect at Bombay is not as marked as that at Poona. 相似文献
12.
老挝万象平原钾盐矿床控矿构造研究 总被引：1，自引：0，他引：1
老挝万象平原钾盐矿层赋存于新近系古新统塔贡组中,主要含钾矿物为光卤石,少量钾石盐.成矿期塔贡组及钾盐矿层主要受北西向的边界断裂及塔贡向斜控制;成矿期后钾盐矿层主要受褶皱(盐向斜、盐背斜)控制.在钾盐矿层沉积后,先在水平应力作用下形成宽缓褶皱.由于向斜部位相对沉降,沉积速度较快,钾盐矿层上部的碎屑岩较厚;而背斜部位相对上... 相似文献
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P. Murugavel V. Gopalakrishnan Vimlesh Pant A. K. Kamra 《Journal of Earth System Science》2008,117(1):273-280
Airborne measurements of the number concentration and size distribution of aerosols from 13 to 700 nm diameter have been made at four vertical levels across a coastline at Bhubaneswar (20°25′N, 85°83′E) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) programme conducted in March–April 2006. The measurements made during the constant-level flights at 0.5, 1, 2 and 3 km altitude levels extend ～100 km over land and ～150km over ocean. Aerosol number concentrations vary from 2200 to 4500 cm?3 at 0.5 km level but are almost constant at ～ 6000 cm?3 and ～ 800 cm?3 at 2 and 3 km levels, respectively. At 1km level, aerosol number concentration shows a peak of 18,070 cm?3 around the coastline. Most of the aerosol size distribution curves at 0.5 km and 1 km levels are monomodal with a maxima at 110nm diameter which shifts to 70 nm diameter at 2 and 3 km levels. However, at the peak at 1 km level, number concentration has a bimodal distribution with an additional maximum appearing in nucleation mode. It is proposed that this maxima in nucleation mode at 1 km level may be due to the formation and transport of new particles from coastal regions. 相似文献
14.
Heavy metal contamination of roadside topsoil in Osogbo,Nigeria: its relationship to traffic density and proximity to highways 总被引：12，自引：0，他引：12
The levels of lead, cadmium, copper, nickel and zinc were determined in the roadside topsoil in Osogbo, Nigeria, with the view to determining the effect of traffic density and vehicular contribution to the soil heavy metal burden. The levels of the metals at the high density roads were significantly higher than the corresponding levels at the medium and low traffic density roads. The average levels of Pb, Cd, Cu, Ni, and Zn in all road locations at a distance of 5 m from the roads were 68.74ᆶ.82, 0.60ǂ.31, 21.19ᆟ.34, 8.38DŽ.40, and 42.45ᆥ.68 mg/kg, respectively. Pb, Cd, and Cu were of average levels of 92.07ᆩ.25, 0.76ǂ.35 and 27.69 mg/kg, respectively at a distance of 5 m from the road at high traffic density roads, while the levels of Ni and Zn averaged 9.65DŽ.61 and 56.27ᆟ.58 mg/kg, respectively. There was a rapid decrease in the level of the metals with distance, with the metal levels at a distance of 50 m from the road almost reaching the natural background levels of the metals at the control sites. The levels of the metals were also determined at the four major motor parks and at the seven mechanic workshop settlements. The levels of the metals at the motor parks and mechanic workshops were far above the levels at the control sites. The levels of Pb, Cd, Cu, Ni, and Zn at the motor parks were 519ᇝ.0, 3.6ǂ.8, 37.9ᆠ.5, 17.3dž.6 and 71.9ᆟ.3 mg/kg, respectively, with the levels of Pb, Cd, Cu, Ni, and Zn at the mechanic workshops averaging 729.57뀶.93, 4.59ǃ.01, 116.6ᆮ.8, 30.21Nj.40, and 88.74ᆰ.11 mg/kg, respectively. 相似文献
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采用改造的GDS全自动环境岩土渗透仪,分别以自来水和模拟渗滤液为试验用水,开展不同温度和围压下黏土渗透性能试验。研究表明,当温度从20℃升高至50℃时,渗透系数增大,最大增幅为3.5倍;当围压从50kPa增大至200kPa时,渗透系数从10-6cm/s数量级减小至10-8cm/s数量级。在温度和围压一定时,模拟渗滤液作用下黏土的渗透系数略大于自来水试验结果,二者最大比值为2.8。随着温度的升高,土中吸附结合水膜变薄,且土样体积减小,在两种效应的共同作用下,固有渗透率不是定值,相应条件下50℃与20℃固有渗透率的比值在0.72~2.99之间变化。在本试验条件下,渗透系数随温度的变化主要是由水动力黏滞系数的变化引起,但是在低围压、自来水试验时理论推算渗透系数小于实测值,高围压下理论推算值大于实测值。 相似文献
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静止土压力系数探究 总被引：5，自引：0，他引：5
静止土压力系数是岩土工程领域中一个至关重要的参数,是确定水平场地的应力状态和计算静止土压力的基础。但目前对静止土压力系数的研究还不够。对自然堆积而成处于临界状态的砂堆内应力状态进行分析,推导出自然固结土的静止土压力系数的理论表达式,并与砂性土静止土压力系数表达式k0 =0.95-sin?和黏性土静止土压力系数表达式k0 = 1-sin?进行对比,结果表明,推导的静止土压力公式与砂性土常用表达式非常吻合,与黏性土常用表达式存在一定偏差。文中给出的静止土压力系数公式和推导,较为科学合理地阐述了常用静止土压力系数的由来,有效弥补了当前这块研究的空白,为静止土压力系数的室内、现场试验和经验公式的推导提供了理论支撑,起到了一定的推进作用。 相似文献
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Attila Kilinc 《Engineering Geology》1989,27(1-4):279-299
Shales and graywackes were first metamorphosed at 650°C and then partially melted at 700 and 750°C at 2, 4, 6, and 8 kilobars in the presence of 0.75m NaCl−0.45m KCl and 0.225m CaCl2−0.750m NaCl solutions. In experiments with shales,KK+Na ratio in the decreases with increasing pressure at 650 and 700°C; however, at 750°C this ratio is equal to 0.5 at all pressures investigated. This suggests that melts at 700°C and at 2 to 8 kilobars pressure may be affected metasomatically whereas melts at 700°C and in the same pressure range will not. Melt composition produced in the shale-KClNaCl experiments is granite at 2, 4 and 6 kilobars pressure, whereas the melt compositions in the shale-CaCl2NaCl experiments range from quartz monzonite (2–5 kilobars) to granodiorite (above 5 kilobars). Experiments with graywacke-KClNaCl produced melts of trondhjemite composition at 2, 2.5, 4, 6, and 7.5 kilobars.
These results indicate that partial melting of crustal rocks such as metamorphosed shales and graywackes in the deeper parts of the crust can produce large volumes of granitic magmas ranging in composition from true granite to trondhjemite to quartz monzonite and granodiorite. 相似文献
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贵州兴义大际山地区茅台组砾岩的的发现及其地质意义 总被引：2，自引：2，他引：0
贵州兴义大际山地区的茅台组砾岩系首次发现和圈定,该砾岩及其下伏地层受喜早山期构造变动影响,产生断裂,褶曲及大面积的硅化蚀变带.在硅化黄铁矿化砾岩、角砾岩中,有钼铀矿及汞矿等内生热液矿产出.据此,首次确认我省存在喜山期成矿作用.在今后的工作中,需高度重视喜山期构造活动及其成矿作用,开阔视野,适时调整找矿思路和方向,以扩展找矿远景. 相似文献