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Introduction A set of reddish clay-silt-sized sediments named red clay underlying the Quaternary loess-paleosol sequence widely distribute in the Chinese Loess Plateau. The thickness of the red clay sediments ranges from decades of meters to over 100 m (Evan et al.1991,Mo and Derbyshire 1991, SUN et al. 1997&1998, DING et al. 1999, GUO et al. 2001, QIANG et al. 2001). Previous studies show that not only loess-paleosol (e.g.LIU et al.1985,AN et al.1990,DING et al.1992),but also red … 相似文献
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关中盆地属于断陷盆地,地质构造复杂,活动断裂发育,地震活动频繁,城市建设中面临一系列重大基础地质问题。在搜集分析关中盆地1 000多个各类钻孔数据的基础上,对关中盆地城市群1∶5万综合地质调查中实施的主要钻井和剖面进行研究,探讨了城市群发展中面临盆地形成演化与活动断裂规避、第四系下限与关中盆地三维地质结构重建、水系演化与城市发展、历史时期古洪水事件与海绵城市建设等基础地质问题。研究表明:①关中裂陷形成于中晚白垩纪,始新世开始成湖,经过多次断陷与隆起,形成2个沉积中心,到上新世时湖泊扩展达到最大范围,盆地第四纪以来仍处于持续、缓慢的下降接受沉积过程,受秦岭持续构造隆升的影响,沉积中心由南向北迁移,这将对城市群布局产生重要影响。关中盆地城市群建设要回避断裂交汇处、端点和断层运动的枢纽部位。②建议将绿三门组划为上新统,不宜划分到第四系,三门组的形成时代是穿时的,在关中盆地第四系与地下空间规划的时候需要进行关注和纠正。③城市规划建设要遵循河湖演化的自然规律和区域地质地貌特征,千年、百年一遇的洪水水位分别高于河漫滩7m和2.2m,最大年降水量超过900mm,但季节分布不均,可作为城市防洪水和海绵城市建设的设计依据。 相似文献
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环境地质学已成为当今地学中引人注目的学科,对其研究内容众说纷纭,莫衷一是。本文提出环境地质学是指研究自然地质作用(条件、因素)及人类活动引起地质条件发生变化对人类生存环境造成影响的科学。其研究内容主要是自然物理地质作用、自然化学作用(地球化学环境)以及人为因素对环境的影响。 相似文献
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1 Introduction The Lanping Basin, western Yunnan Province,Southwest China, is situated at the juncture of the Eurasian and Indian plates, and it is part of eastern Tethys, located in between the Lancangjiang and Jinshajiang-Ailaoshan faults, is a part of… 相似文献
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Earthworm calcite granules (ECG), generally produced in Morren's glands of the earthworm Lumbricus terrestris and Lumbricus rubellus, are commonly preserved in Quaternary soils and sediments well. These granules can not only provide radio-carbon dating (Carbon-14) with the efficacious materials, but accurately record a wealth of climatic and environmental information on temperature and precipitation. For instance, researchers from France reconstructed the paleotemperature and paleoprecipitation during the last glacial in west part of Europe by taking advantage of δ18O and δ13C signal contained in ECG. Additionally, scientists from Germany and France carried out radiocarbon dating of ECG from two different loess-paleosol sequences, and the results showed consistency with the dating results of other materials (such as charcoal, bone, plant calcified root cells, etc.). Therefore, this new bio-indicator has been confirmed as a proxy for paleoenvironmental and paleoclimatic reconstruction, hopefully becoming the golden key to understanding the paleoclimate change. This paper, based on the previous literatures, reviewed the present research status of ECG in paleoclimatology, mainly consisting of five aspects: (i) ECGs' production mechanism and their characteristics; (ii) The theoretical foundation of stable carbon and oxygen isotopes in terrestrial fossil earthworm calcite granules for paleoclimatic reconstruction; (iii) The pre-treatment of ECG samples; (iv) Current applications in chronology and paleoclimatology of earthworm calcite granules;(v) Major problems at present regarding paleoclimatic explanation and radiocarbon-14 dating of ECG. Finally, we proposed the future research and development direction in this field, which is expected to make a reference to the future researches. 相似文献
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The Lüliang Mountains, located in the North China Craton, is a relatively stable block, but it has experienced uplift and denudation since the late Mesozoic. We hence aim to explore its time and rate of the exhumation by the fission-track method. The results show that, no matter what type rocks are, the pooled ages of zircon and apatite fission-track range from 60.0 to 93.7 Ma and 28.6 to 43.3 Ma, respectively; all of the apatite fission-track length distributions are unimodal and yield a mean length of ~13?μm; and the thermal history modeling results based on apatite fission-track data indicate that the time-temperature paths exhibit similar patterns and the cooling has been accelerated for each sample since the Pliocene (c.5 Ma). Therefore, we can conclude that a successive cooling, probably involving two slow (during c.75-35 Ma and 35-5 Ma) and one rapid (during c.5 Ma-0 Ma) cooling, has occurred through the exhumation of the Lüliang Mountains since the late Cretaceous. The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35°C/km. Combined with the tectonic setting, this exhumation may be the resultant effect from the surrounding plate interactions, and it has been accelerated since c.5 Ma predominantly due to the India-Eurasia collision. 相似文献
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碳酸盐矿物是黄土的重要组成部分,是古环境重建的重要指标之一.通过对地处西风区的新疆伊犁盆地昭苏黄土剖面的全岩样品和分粒级样品的X射线衍射测试,分析了其碳酸盐矿物组成,利用麦夸特算法计算了碳酸盐矿物的含量.综合碳酸盐矿物的含量、粒径分布及风化特征等因素,对其古环境意义进行了辨识,从而建立了该剖面末次冰期以来碳酸盐矿物记录的古气候环境变化序列.结果表明:昭苏剖面中原生碳酸盐矿物(方解石和白云石)含量占主导地位,次生方解石对样品中总方解石含量的贡献较少;白云石含量可能与亚轨道尺度冷暖交替导致的西风环流强度变化有关;方解石含量的变化可能指示了西风区降水量的变化;碳酸盐矿物含量揭示了昭苏地区在末次冰期时气候冷湿,在全新世时气候暖干. 相似文献