华南沿海地区全新世海平面变化特征     

李建生 《海洋科学》1994,18(3):68-71

１海平面变化特征１．１全新世中期海侵根据地层中所含硅藻属种雷州半岛海康南田乡一１５ｍ钻孔岩芯，含有丰富的硅藻，主要属种是①：具槽直链藻（Ｍｅｌｏｓｉｒａ　ｓｕｌｃａｔａ（Ｅｈｒ）Ｋｕｔｚ）、范氏回箱藻（Ｐｙｘｉｃｌｉｃｕｌａ　ｗｅｙｐｒｅｃｈｔｉｉＧｒｕｎ）、条纹小环藻（Ｃｙｃｌｏｔｅｌｌａｓｔｒｉａｔａ（Ｋｕｔｚ）Ｇｒｕｎ）、流水双菱藻（ＳｕｒｉｒｅｌｌａｆｌｕｍｉｎｅｎｓｉｓＧｒｕｎ）。上述硅藻主要是海相生活属种，今日南田乡已距离海岸线５ｋｍ。徐闻海安西侧一１８．５ｍ钻孔岩芯中的硅藻除上述属…  相似文献   

“3S”技术在四川生态环境动态监测中的应用研究   总被引：2，自引：1，他引：1  

郑泽忠  范东明  夏清  邵怀勇  曹云刚 《测绘科学》2008,33(3):165-166

为有效实现四川省生态环境的动态监测,运用RS、GIS和GPS技术,以2004年中巴资源卫星(CBERS-02)遥感影像数据为信息源,2000年TM遥感影像解译的数据为基础,对2004年遥感影像进行解译,修改2000年数据库;手持GPS接收机,在野外对解译成果进行验证,更新数据库;利用GIS技术的空间分析功能,提取出2000～2004年期间土地利用/覆被变化信息,得到2000～2004年期间四川省高精度的土地利用/覆被变化数据库。最后对四川省土地利用/覆被变化信息进行分析,对四川省生态环境的下一步研究指名了方向。  相似文献   

青藏高原甜水海盆地MIS 3阶段湖泊沉积与环境变化   总被引：23，自引：20，他引：3       下载免费PDF全文

李世杰  张宏亮  施雅风  朱照宇 《第四纪研究》2008,28(1):122-131

青藏高原西北部甜水海盆地地处内陆干旱区和喀喇昆仑山的东侧雨影区,气候环境极端干旱。但多次考察结果揭示晚更新世时期存在着大湖和高湖面的地质证据。为了探讨该地区过去气候与环境的演变历史,在甜水海盆地(海拔4840m)进行钻探采得沉积岩芯56.32m(TS95),通过对沉积岩芯其中一段的粒度、生物、同位素及地球化学多指标综合分析,探讨了MIS3时期甜水海地区气候环境演化过程。沉积岩芯显示沉积物岩性变化频繁,记录着湖面多次波动、沉积环境多变的演化过程,分别在59～56kaB.P.,49～47kaB.P.,45～41kaB.P.,35.5～34.0kaB.P.和28～25kaB.P.期间存在高湖面和湖水稀释。在其多环境指标的记录中,Heinrich事件和D-O旋回均有反映,揭示了全球变化信号在研究区的响应。同时,不同高湖面阶段内部环境波动也较明显,差别较大,其产生原因也各有不同,归结为3种情况:1)由于气候变暖导致冰雪融水补给增加而产生的高湖面;2)由于冷湿气候导致的高湖面;和3)由于暖湿气候导致的高湖面。本研究揭示出了MIS3时期气候频繁波动的特征和气候的不稳定性。  相似文献   

黑河流域水环境演变及其驱动机制研究进展   总被引：10，自引：0，他引：10  

肖生春  肖洪浪 《地球科学进展》2008,23(7):748-755

基于近几十年来诸多学者对西北干旱区典型内陆河流域——黑河流域水环境演变诸方面研究成果,综述了上游山区成水环境、中游绿洲用水环境和下游荒漠天然绿洲水成环境在不同时间尺度上的演变过程及其驱动机制。通过对各种古环境代用指标的对比研究表明：在大尺度上,流域上下游表现出阶段性的一致性水环境演变趋势;在小尺度上,则表现水环境演变的时空异质性。驱动机制方面,在空间上,流域上、中、下游水环境演变的气候变化和人类活动影响驱动作用各有侧重;在时间上,表现为不同尺度上气候变化与流域人类活动耦合作用的驱动机制。  相似文献   

Spin rate estimation of sounding rockets using GPS wind-up   总被引：2，自引：1，他引：1  

M. García-Fernández  M. Markgraf  O. Montenbruck 《GPS Solutions》2008,12(3):155-161

Carrier phase wind-up is a well-known effect that arises from the relative rotation between a transmitting and receiving antenna. In GPS measurements at L1 frequency, this effect translates into an error of 19.029 cm per full relative rotation of antennas. Since this effect is independent of the satellite elevation for pure rotation about the antenna boresight axis, it is usually absorbed by the clock estimation in navigation algorithms. Therefore, the impact of wind-up is usually neglected for applications that do not require accuracies to the cm level like RTK. However, in receiving platforms with high rotation rate, the accumulated wind-up value can be important and actually be larger than receiver noise or even ionospheric variations. Therefore, in such scenarios, the wind-up contribution can be isolated and used as a source of information to compute the spin rate of such platforms using an appropriate combination of GPS observables. This work shows some results of a coarse, yet simple, approach to monitor the rotation angle and spin-rate of spin stabilized sounding rockets flown by DLR.  相似文献   

Effect of volatiles erupted from Mesozoic and Cenozoic volcanic activities on paleo-environmental changes in China     

Zhengfu Guo  Xiaoyu Chen  Jiaqi Liu 《Frontiers of Earth Science》2008,2(2):236-239

Based on the determination of composition of volcanic volatiles and petrologic estimation of the total mass of volatiles erupted, we showed important advances in the study of the impact of Mesozoic and Cenozoic volcanic activities on paleo-environmental changes in China. The volcanic activities include western Liaoning and Zhangjiakou Mesozoic intermediate-acidic explosive eruptions, southern Tibet and Shanwang Cenozoic volcanism, and Mt. Changbai volcanic eruption around one thousand years ago. The paper predominantly discusses the earth’s surface temperature changes, ozone depletion, acidic rain formation and mass mortalities of vertebrate induced by the Mesozoic and Cenozoic volcanism in China. __________ Translated from Bulletin of Mineralogy, Petrology and Geochemistry, 2007, 26(4): 319–322 [译自: 矿物岩石地球化学通报]  相似文献   

Group Time Delay in the Reflection of P-Polarized Electromagnetic Plane Waves at a Stratigraphic Interface     

Fu-Ping Liu  Rui-Zhong Li  Jin-yao Li  Hui-Guo Chen  Chang-Chun Yang 《Mathematical Geosciences》2008,40(7):813-829

The group time delay (GTD) formulae of quasi-total reflection of inhomogeneous P-polarized electromagnetic waves (P-PEW, whose electric field parallels to the plane of incidence), caused by the Goos–Hänchen effect, is derived by the phase shift of the wave. A numerical example where the frequency equals to 1 GHz is given. The curves of calculating results show that there are three discontinuous points at the critical angle of phase shift vector, the critical angle of attenuation vector and 90^○. When the angle of incidence is equal to one of these three angles, the GTD will become infinite, and the electromagnetic wave will propagate along the interface. The GTD will be very large, when the angle of incidence is close to one of these three angles. The results indicate that there is an important relationship between the two critical angles and the conductivity and permittivity of the two strata, and that the GTD has an important relationship with the angle of incidence. These results can be used to determine the lithology of the strata and to delimit the interfaces of strata more effectively. It is suggested that this research may prove useful in electromagnetic logging analysis and, perhaps, in the design of logging instruments.  相似文献   

Sea level and diagenesis: a case study on Pleistocene beaches,Whalebone Bay,Bermuda     

R. Vollbrecht  D. Meischner 《International Journal of Earth Sciences》1993,82(2):248-262

Pleistocene fluctuations of sea level have left marine and aeolian limestones intercalated with glacial red soils on the Bermuda Carbonate Platform (Atlantic, 64°50W, 32°20N). Successive eustatic highstands of similar amplitude drowned the tectonically stable platform and piled up similar sets of sediments. Up to three Pleistocene beaches are stacked in shorelines sections. Post-depositional diagenetic histories of these beaches can be linked to repeated changes in sea level and pore waters.This paper presents field evidence and petrographic results (microscope, X-ray, cathodoluminescence, SEMEDAX) for the diagenetic histories of two superimposed Pleistocene beaches in Whalebone Bay, Bermuda North Shore. The younger beach was deposited during isotopic stage 5e, about 120 ka ago. The age of the older beach may be isotopic stage 9 or older.Diagenesis drastically altered the older beach before the stage 5e transgression. Primary high-Mg calcite (HMC) and aragonite were no longer present. Marine skeletal grains were instead leached or recrystallized to low-Mg calcite (LMC). Primary and secondary pore space were largely reduced by LMC cement. Lines of needle relics reminiscent of marine aragonite cement occur as inclusions within syntaxial rim cements around echinoderm grains, indicating that a marine influence had at least once interrupted this period of freshwater alteration. Finally, before the rocks became buried by the sediments of the younger beach, a crust of marine, bladed HMC cement was precipitated throughout the pore space.The younger beach consists of skeletal grains that are, apart from the effects of non-selective dissolution, essentially unaltered. The sediments are only weakly lithified by cryptocrystalline LMC showing an alveolar texture, tangential fibres and other features characteristic of calichification. A younger post-depositional marine influence is not recorded.These results suggest that, under favourable conditions, diagenetic processes can document sea-level fluctuations. The recorded fluctuations, however, are difficult to assess because even major sea-level highstands may not produce a diagenetic imprint. Correspondence to: R. Vollbrecht  相似文献   

相律的应用:蒸发结晶过程自由度          下载免费PDF全文

房春晖  宋彭生 《盐湖研究》1993,(1)

在连续原理和浓度限制条件的基础上,分析了卤水蒸发过程的自由度,提出了“蒸发结晶过程自由度”这一概念。发现蒸发结晶过程自由度在整个过程中不是1便是0,在1和0之间交替变化,与选择的组分数和析出固相数目无关。蒸发结晶过程自由度为1,物理意义是在不引起新相产生旧相不消失的前提下过程连续地变化(水分的连续蒸失),几何意义是指在适当的坐标系中的一条线,一条直线或曲线;0的物理意义是指新相的产生和旧相的即将消失或者前一段的连续变化过渡到后一段的连续变化,几何意义是指一点,两蒸发阶段的交点或者过程的终点。简单地讨论了过程的单向性和连续件。  相似文献   

内蒙古中西部宝音图群石榴角闪岩的地球化学、变质作用及年代学特征     

姜灵  张晋瑞  唐爽  魏春景  初航 《岩石学报》2021,37(12):3759-3780

宝音图群分布于内蒙古中西部狼山、图古日格和达茂旗一带，主要由云母片岩、石英片岩、石英岩、角闪岩和大理岩组成。在狼山格尔敖包沟和图古日格西南地区发育十分典型的石榴角闪岩，均以似层状或透镜状产自云母片岩中，但两地具有不同的矿物组合，前者主要以石榴石+角闪石+斜长石+含钛矿物（金红石和钛铁矿）为特征，后者主要以石榴石+角闪石+绿帘石+含钛矿物（金红石和钛铁矿）为特征。地球化学研究显示两个地区的石榴角闪岩原岩具有相似的化学组成，均为亚碱性玄武岩的拉斑系列。宝音图群的石榴角闪岩具有右倾的稀土配分模式，REE总量为83.31×10^-6~125.9×10^-6，（La/Yb）_N比值为2.17~6.48，δEu=0.87~0.98。Ta、Nb、Ti没有明显的负异常，其配分型式类似E-MORB特点。微量元素构造判别图解表明这些石榴角闪岩的原岩产于板内拉张环境中。本文通过模拟格尔敖包沟样品LS01和图古日格西南地区样品LS35的P-T视剖面图研究其变质作用及矿物演化过程，结果显示这两个样品均经历了早期进变质，峰期以及峰后近等温减压的顺时针型P-T轨迹。样品LS01的峰期温压条件为~11kbar/~735℃，模拟得到的峰期矿物组合可能为石榴石+角闪石+斜长石+黑云母+透辉石+金红石+熔体，P-M（H₂O）视剖面图显示，由于峰后演化过程中存在饱和流体渗透，导致峰期透辉石无法保留。样品LS35的峰期温度压力条件为~8kbar/675℃，其峰期组合为石榴石+角闪石+绿帘石+金红石。两个地区的石榴角闪岩的温度压力条件明显不同，推测宝音图群中呈透镜体或似层状产出的变质基性岩，存在着递增型的变质作用。锆石LA-ICP-MS U-Pb年代学的研究结果显示石榴角闪岩样品LS01的变质锆石年龄为394±8Ma。由此推测这些石榴角闪岩的原岩可能形成于华北北缘在新元古代发育的裂陷盆地，在泥盆纪中期，宝音图群作为华北克拉通的一部分，被卷入到与古亚洲洋闭合有关的造山过程，发育中压型递增变质作用。  相似文献