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1.
塔里木盆地塔北隆起发育两组呈小角度相交(40°)的透入性X型走滑断裂,分别沿着NNE走向和NNW延伸。在对塔北哈拉哈塘地区三维地震资料解释的基础上,对走滑断层的几何展布特征以及断层的剖面变形特征进行研究;同时重点解析了RP6断裂和HA13断裂,分析比较NNW向与NNE向断层的变形及发育特征差异;结合盆地重磁资料以及周缘造山带的活动特征,对塔北隆起小角度的X型走滑断层的发育机制以及演化进行了分析。研究表明,塔北隆起走滑断层在垂向上具有明显的分层变形特征,分为三个构造层:震旦系-中寒武统下构造层(TH3界面以下)、上寒武统-中奥陶统中构造层(TH3-TO3t界面)和上奥陶统-石炭系上构造层(TO3t-TP界面)。断层在下构造层和中构造层中整体处于压扭环境,多发育正花状构造;上构造层中断层主要发育负花状构造或正断层,整体处于张扭环境。两组断裂比较,NNW向断裂活动性强,在各构造层中均有显著的断裂特征发育,垂向连通性强,发育先存基底断裂,而NE向断层主要发育在中构造层,在下构造层和上构造层中断层发育不明显。活动性分析表明,断层的形成与演化具有多期性,走滑断层的形成经历了三期主要活动:中寒武世末、中晚奥陶世和志留纪-石炭纪。塔北隆起X型走滑断裂的形成受到了NNW向基底断裂和薄弱带的控制,NNW向先存基底断裂带或薄弱带优先发育走滑断裂,基底断裂与主挤压应力方向的夹角小于45°-Φ/2,NNE断层的发育受NNW向先存断裂限制,最终形成小角度相交的X型断裂。 相似文献
2.
A synthesis of Holocene pollen records from the Tibetan Plateau shows the history of vegetation and climatic changes during the Holocene. Palynological evidences from 24 cores/sections have been compiled and show that the vegetation shifted from subalpine/alpine conifer forest to subalpine/alpine evergreen sclerophyllous forest in the southeastern part of the plateau; from alpine steppe to alpine desert in the central, western and northern part; and from alpine meadow to alpine steppe in the eastern and southern plateau regions during the Holocene. These records show that increases in precipitation began about 9 ka from the southeast, and a wide ranging level of increased humidity developed over the entire of the plateau around 8-7 ka, followed by aridity from 6 ka and a continuous drying over the plateau after 4-3 ka. The changes in Holocene climates of the plateau can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Indian Monsoon which expanded northwards 相似文献
3.
Houyuan Lu Naiqin Wu Kam-biu Liu Liping Zhu Xiangdong Yang Tandong Yao Luo Wang Quan Li Xingqi Liu Caiming Shen Xiaoqiang Li Guobang Tong Hui Jiang 《Quaternary Science Reviews》2011,30(7-8):947-966
This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1202 sites along an altitudinal gradient of 10–5500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1840 mm and mean annual temperature (MAT) from ?7 to 21.5 °C. A total of 153 pollen taxa were found with relative abundances greater than 1% in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters.Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R2-boot = 0.89, RMSEP = 109 mm), MAT (R2-boot = 0.78, RMSEP = 2.3 °C), ALT (R2-boot = 0.73, RMSEP = 597 m), HHH (R2-boot = 0.82, RMSEP = 4.5%), and July mean precipitation (MP7) (R2-boot = 0.87, RMSEP = 23 mm). Overall, our results confirm that pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environmental reconstruction based on pollen data in the regions. 相似文献
4.
Gang Zeng Wei-Chyung Wang Caiming Shen Zhixin Hao 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(3):355-364
We present a study of summer precipitation changes over the Yangtze River Valley (YRV) and North China (NC) simulated from 20 models of the CMIP3 (phase 3 of the Coupled Model Intercomparison Project). It is found that the LASG-FGOALS-g1.0 (fgoals) model has the highest ability in simulating both the interannual variability of individual regions and the seesaw pattern of the two regions observed during the past few decades. Analyses of atmospheric circulations indicate that the variability in precipitation is closely associated with the 850 hPa meridional winds over the two regions. Wetness in the YRV and dryness in NC are corresponding to strong meridional wind gradient and weak meridional wind over these two regions, respectively. The ability of a coupled general circulation model (CGCM) to simulate precipitation changes in the YRV and NC depends on how well the model reproduces both observed associations of precipitation with overlying meridional winds and observed meridional wind features in summer. Analysis of future precipitation changes over the two regions projected by the fgoals model under the IPCC scenarios B1 and A1B suggests a significant increase of 7–15% for NC after 2040s due to the strengthened meridional winds, and a slight increase over the YRV due to less significant intensification of the Mei-yu front. 相似文献
5.
油页岩原位转化开采加热的最终温度、加热时间和最终油气转化率与原位开采的经济成本息息相关。利用Rock-Eval 6型岩石热解分析仪分别获取不同升温速率下的油页岩烃产率-转化率和烃产率-活化能之间的关系,以烃产率为桥梁,建立活化能与转化率的对应关系;在此基础上,依据化学动力学反应原理,将油页岩有机质（干酪根）演化生成油气的过程近似为具一级反应特征的热裂解反应,获取不同转化率条件下温度倒数（1/T）与时间对数（ln t）的关系式,建立油页岩原位转化温度-时间-转化率关系图。以广东茂名盆地油柑窝组油页岩为例,通过上述方法建立了油页岩原位转化开采温度-时间-转化率关系图。由判识关系图可知：加热至350℃开采该区油页岩,转化率达90%需要98 a;加热至200℃开采该区油页岩,在不采取其他措施的情况下即使转化10%也需要147 a。实际情况下,地下油页岩原位受热具有非均质性,加热开采能耗大,通过添加催化剂降低油页岩原位油气转化所需的温度、改善油气产物品质可能是油页岩原位开采技术的一种发展方向。 相似文献
6.
塔中隆起位于塔里木盆地中央隆起带中部,是塔里木盆地油气勘探的重点区块之一。塔中地区奥陶系碳酸盐岩走滑断裂发育,控储控藏作用明显,走滑断裂成因机制的研究对于油气勘探开发十分重要。塔里木盆地塔中隆起走滑断裂具有典型的分层变形特点,为了明确塔中隆起走滑断裂分层变形机制的主控因素设计了4组物理模拟实验模型。实验结果表明:走滑断裂分层变形特征的形成主要与垂向上地层性质变化(分层)和多期活动(分期)有关,分层与分期都能造成走滑断裂产生分层变形的特征,塔中走滑断裂分层差异变形特征,是由垂向上地层岩性差异性和构造活动多期性共同造成的。 相似文献
7.
定量重建贵州梵净山一万年以来的植被与气候 总被引：8，自引：0，他引：8
在孢粉分析和＾１４Ｃ测定年龄资料的基础上，以现代梵净山植被带及其气候状况为类比系统，应用主成分分析方法，定量重建贵州梵净山１万年以来的古植被和古气候演化历史，将其分为三个阶段：１０－７．８ｋａＢ．Ｐ．，７．８－２．７ｋａＢ．Ｐ．和２．７ｋａ Ｂ．Ｐ到现在，依次为升温期，高温期和降温期、其中高温期年平均温度比现代年平均温度高出１．６－３．３℃。１万年以来的年降水量比较稳定，使本地区一直处于较湿润状态 相似文献
8.
青藏高原南部第四纪花粉植物群及古气候 总被引：3，自引：0，他引：3
本文选择了青藏高原南部具有代表性的６个花粉剖面，应用主成分分析处理这些剖面的花粉数据，重建了这些地区的古植被和古气候。研究表明，在青藏高原南部，早、中更新世的植被类型主要是松林、云杉林、铁杉林、桦林、桤木林和栎林，晚更新世和全新世的植被类型主要是高山灌丛草原、小半灌木草原、杂类草草甸、亚高山灌丛和落叶阔叶灌丛；在早、中更新世气候条件良好，有森林生长，晚更新世以后气候明显恶化，基本无森林生长。 相似文献
9.
我国西南地区湖泊众多,利用湖泊沉积物已开展了大量全新世植被、降水、温度和水位等的重建工作.然而,代用指标的季节性差异和气候演变的区域差异使得不同代用指标和地区重建的古气候结果存在较大差异,需要更多可靠记录来相互佐证和构建我国西南地区气候变化的详细图景.本文以云南抚仙湖FXH-6钻孔沉积物为研究对象,对正构烷烃和色度指标作了分析,在厘清其来源及环境指示意义的基础上,重建过去近5000年抚仙湖有机质的来源和湖泊水位的变化,探讨了湖泊环境变化与区域气候变化的关系.结果表明,抚仙湖沉积物中正构烷烃n-C23和n-C31可有效指示内源沉水植物和外源陆生植物.近5000年抚仙湖湖泊环境经历了3个阶段:在5000—2300 cal a BP阶段,沉水植物广泛分布,湖泊水位处于高位;在2300—2000 cal a BP阶段,抚仙湖沉积环境快速变化,内源沉水植物生物量锐减,水位快速下降;2000 cal a BP至今,沉水植物生物量持续减少,湖泊水位保持低水位;同时,人类活动也影响了该阶段(2000 cal a BP至今)陆源植物的输入.本研究重建的抚仙湖持续降低的水位变化和湖泊生产力趋势与过去5000年西南地区的年平均温逐渐降低、年平均降水量逐渐减小的总体趋势相对应,表明区域气候变化是湖泊沉积环境变化的主要驱动力. 相似文献
10.
以云南阳宗海1020 cm长的湖泊沉积物岩芯为研究对象,由7个木屑和树叶残体样的AMS14C测年建立岩芯年代框架,以18~19 cm间隔获取52个样品作花粉/炭屑分析,重建了阳宗海流域过去13000年的植被、气候以及森林火灾历史。研究结果表明,过去13000年植被演替、气候变化和森林火灾可分为5个阶段:1)13200~11000 cal.a B.P.,植被以常绿、落叶阔叶混交林为主,气候温凉湿润,森林火灾多发,后期(12300~11000 cal.a B.P.)随着温度和湿度的降低,森林火灾发生愈加频繁;2)11000~8000 cal.a B.P.,松林扩张,阔叶林缩小,气候较上阶段温暖偏干,森林火灾发生次数明显降低;3)8000~5000 cal.a B.P.,松林和常绿阔叶林占优势,且出现暖热性的枫香林,流域内气温升至13000 cal.a B.P.以来的最高值,湿度进一步降低,但森林火灾发生频率低;4)5000~800 cal.a B.P.,松林扩张至最盛,常绿阔叶林收缩,落叶阔叶林成分增加,气温和湿度均明显下降,森林火灾发生频率有所增加;5)800 cal.a B.P.至今,松林和常绿阔叶林收缩,落叶阔叶成分增加,草本植物中禾本科迅速上升,可能与人类活动有关,森林火灾发生频率低。阳宗海花粉/炭屑记录重建的植被、气候和森林火灾史表明,在滇中地区,落叶阔叶成分易引起森林火灾,冷气候导致多发的森林火灾,冷干气候是宜森林火灾发生的气候条件。 相似文献