LATE QUATERNARY CRUSTAL SHORTENING RATE OF THE BEILUNTAI FAULT IN SOUTHERN TIAN SHAN,XINJIANG     

YAO Yuan  SONG He-ping  CHEN Jian-bo  LI Shuai  JIA Hai-liang 《地震地质》2018,40(1):71-86

The Beiluntai Fault is a Holocene active fault. It is the boundary between southern Tian Shan and Tarim Basin. Since the late Quaternary, steady activities of the Beiluntai fault have resulted in offsets, folds, and uplift of pluvial terraces. We used the high-resolution RTK topographic surveys to reveal that the fault scarp morphology on the Akeaiken(Ak) segment and Zhuanchang(Zc) segment of the Beiluntai fault. We found that the crustal shortening of Ak and Zc segments are dominated by thrusting and folding-uplift, respectively. We employed th optically stimulated luminescence(OSL) dating method to develop a new chronology for the different pluvial terraces, indicating that they formed at 49.14~58.51, 27±3, 13.72~14.64, 7.13±0.88, (3.32±0.43) ka, respectively. These data permitted to estimate the crustal shortening rate(about 2.4mm/a) remains largely constant on the Ak segment, while the crustal shortening rate of Zc segment was 1.43~1.81mm/a since the Fan4 pluvial terraces was abandoned. Compared with the Ak segment, the crustal shortening rate of the Zc segment declined obviously. This shows that the NS-trending crustal shortening rate of the Beituntai fault decreased gradually from west to east. A comprehensive comparison of the reverse fault-fold belt system in the front of southern Tian Shan also indicates that the crustal shortening rate drops from west to east.  相似文献   

MIS-3晚期以来乌伦古湖古湖相沉积记录的初步研究     

蒋庆丰  钱鹏  周侗  洪佳  范华  刘静峰 《湖泊科学》2016,28(2):444-454

通过对现代乌伦古湖附近出露的古湖相沉积剖面的AMS~(14)C测年,粒度、总有机碳、总有机氮以及碳酸盐等环境代用指标的分析及其与全新世钻孔沉积记录的对比研究,结果发现:乌伦古湖在MIS-3晚期的33600-22500 cal a BP以及冰后期至早中全新世的16500-6500 cal a BP期间,维持着湖相沉积环境,湖面约比现在湖面高40 m.33600-22500 cal a BP的MIS-3晚期,气候相对温暖,乌伦古湖呈现高湖面特征,湖泊沉积物来源以流水搬运为主;22500-16500 cal a BP的末次冰期冰盛期,气候寒冷干燥,湖泊沉积物来源以风力搬运为主;16500-6500 cal a BP的冰后期以及早、中全新世期间,气候回暖,湖泊沉积物主要来源于河流径流作用.6500-5500 cal a BP,受高温干旱事件的影响,湖面收缩、水位剧降,除沉积中心外的其它钻孔位置出现沉积中断.5500 cal a BP后气候转冷变湿,湖泊重新恢复到现在的状态.乌伦古湖MIS-3晚期以来的古湖相沉积环境变化及其反映的古气候万年尺度上的干湿变化与周边区域气候环境变化记录有很好的一致性,响应了区域环境变化和全球气候突变事件.季风和西风的强度消长变化及其引起的环流条件改变以及温度变化引起的蒸发效应可能是区域气候环境变化的主要原因.这一古湖相沉积记录的研究可为MIS-3晚期以来北疆地区的古湖泊演化以及长时间尺度上西风和季风环流相互关系及其影响区的气候环境演化提供地质证据.  相似文献   

临潭—宕昌主干断裂南东段晚第四纪活动的地质地貌证据          下载免费PDF全文

李光涛  程理  吴昊  苏刚 《地震工程学报》2020,42(2):376-383

临潭—宕昌断裂带总体上位于东昆仑断裂和西秦岭北缘断裂之间。作为甘东南构造转换和变形传递过程中的一条重要的断裂,其几何展布\,新活动性和运动特征对讨论地震的孕育有着至关重要的作用。前人对临潭—宕昌断裂进行了大量的调查和研究,尤其在2013年岷县—漳县MS6.6地震发生后,认为该断裂各分支断裂活动差异明显,除主干断裂南东段不活动外,其余次级断裂在晚第四纪以来皆有活动。笔者通过对临潭—宕昌主干断裂1∶5万断裂活动性填图工作,在主干断裂南东段发现了多处晚第四纪活动的地质与地貌证据,这一发现对临潭—宕昌断裂带结构特征及活动性是一个重要补充,有助于完善该地区的区域构造几何图像和运动特征,对认识区域构造活动、构造转换和变形传递有关重要的意义。  相似文献   

昌平-丰南断裂构造浅层地震勘探新证据   总被引：1，自引：1，他引：0       下载免费PDF全文

彭远黔  高武平  冉志杰  朱坤静 《地震工程学报》2020,42(6):1487-1496

昌平-丰南断裂是根据卫星遥感图像解译发现的一条隐伏活动断层,是NWW向张家口-蓬莱断裂带中规模最大的断裂,为进一步调查确认断裂的存在、空间位置、性质和断裂构造特征,并重新厘定其活动性,在卫星遥感影像解译断裂大体空间位置的基础上,布设了2条浅层地震勘探测线,对昌平-丰南断裂进行了高分辨率地震勘探,获得了测线控制范围内地下结构和断裂构造的清晰成像。结果表明,昌平-丰南断是一条倾向S、走向NWW的走滑正断层,浅层地震剖面揭示断层上断点埋深80~100 m,断错了上更新统底界,结合测线附近钻孔资料推测其最新活动时代为晚更新世。  相似文献   

The Liaonan Metamorphic Core Complex： Constitution, Structure and Evolution   总被引：3，自引：0，他引：3  

LIU Junlai  GUAN Huimei  JI Mo  CAO Shuyun  HU Ling State Key Laboratory of Geological Processes  Mineral Resources  and Key Laboratory of Lithosphere Tectonics  Lithoprobing Technology of the Ministry of Education  China University of Geosciences  Bei 《《地质学报》英文版》2006,80(4):502-513

The Liaonan metamorphic core complex (mcc) has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, and highly metamorphosed rocks and intrusive rocks in the lower plate. The allochthonous upper plate is mainly of Neoproterozoic and Paleozoic rocks weakly deformed and metamorphosed in pre-Indosinan stage. Above these rocks is a small-scale supradetachment basin of Cretaceous sedimentary and volcanic rocks. The lower plate is dominated by Archean TTG gneisses with minor amount of supracrustal rocks. The Archean rocks are intruded by late Mesozoic synkinematic monzogranitic and granitic plutons. Different types of fault rocks, providing clues to the evolution of the detachment fault zone, are well-preserved in the fault zone, e.g. mylonitic gneiss, mylonites, brecciated mylonites, microbreccias and pseudotachylites. Lineations in lower plate granitic intrusions have consistent orientation that indicate uniform top-to-NW shearing along the main detachment fault zone. This also provides evidence for the synkinematic characteristics of the granitic plutons in the lower plate. Structural analysis of the different parts in the mcc and isotopic dating of plutonic rocks from the lower plate and mylonitic rocks from detachment fault zone suggest that exhumation of the mcc started with regional crustal extension due to crustal block rotation and tangential shearing. The extension triggered magma formation, upwelling and emplacement. This event ended with appearance of pseudotachylite and fault gauges formed at the uppermost crustal level. U-Pb dating of single zircon grains from granitic rocks in the lower plate gives an age of 130±5 Ma, and biotite grains from the mam detachment fault zone have 40Ar-39Ar ages of 108-119 Ma. Several aspects may provide constraints for the exhumation of the Liaonan mcc. These include regional extensional setting, cover/basement contact, temporal and spatial coupling of extension and magmatism, basin development and evolution of fault tectonites along detachment fault zone. We propose that the exhumation of the Liaonan mcc resulted from regional extension and thinning of crust or lithosphere in eastern North China, and accompanied with synkinematic intrusion of granitic plutons, formation of detachment fault zone, uplifting and exhumation of lower-plate rocks, and appearance of supradetachment basin.  相似文献   

西南天山柯坪推覆构造柯坪塔格山前逆断裂东段晚第四纪的古地震   总被引：4，自引：2，他引：2       下载免费PDF全文

冉勇康  杨晓平  程建武  徐锡伟  陈立春 《地震地质》2006,28(2):245-257

柯坪推覆构造系是西南天山前陆推覆构造的重要组成部分。文中试图通过对柯坪推覆构造区的影像解译和野外观察、断错地貌的实测和探槽开挖,探讨柯坪塔格山前断裂东段晚第四纪以来的古地震活动。在三岔口以西的五道班—三间房一带和三岔口以东的大山口道班一带,除现代洪积扇外,明显可见2期保存较完整的洪积扇被断错。五道班—三间房地段的3个探槽揭露出了晚更新世末期以来该破裂段发生的4次事件,其参考年代为:距今22、14、6·5和4·4ka;重复间隔时间约为:8、7和2ka左右。间隔时间长的事件垂直位移量约1~1·2m,缩短量约1·3~1·4m;间隔时间短的事件,垂直位移量0·20~0·30m,缩短量0·6~0·7m。大山口道班段探槽揭露出了晚更新世末期以来的2次事件,分别发生在稍早于距今13ka和稍晚于距今6ka。重复间隔时间约7ka。同震垂直位移量约50cm,缩短量130cm左右  相似文献   

忻定盆地晚更新世晚期的一次构造运动   总被引：1，自引：1，他引：0       下载免费PDF全文

任俊杰  张世民 《地震地质》2006,28(3):487-496

忻定盆地是山西地堑系北部的一个张性断陷盆地,第四纪构造运动活跃。野外调查表明,盆地内晚更新世晚期经历了一次较强的构造运动,它使得断块山地进一步抬升,中止了末次冰期鼎盛期的一次河流加积过程,位于断裂上升盘的洪积扇扇顶部分也被抬升为洪积台地,山前形成了十几米到几十米的断层陡崖;构造运动还导致断层上升盘河流下切,形成了Ⅱ级阶地。黄土-古土壤时间标尺和多种方式的测年结果表明这次构造运动开始于距今2万年左右  相似文献   

五佛寺断层晚更新世活动段长度及活动方式研究     

张有龙  杨斌  周伶琦  柳煜  刘洪春 《地震研究》2006,29(3):269-275

通过野外地质调查,确定五佛寺、杨窝铺、窑洞水3条断层不构成左阶羽列;五佛寺断层晚更新世活动段展布于石板沟东一大台子北东,长度为8．3km,地质剖面中具有明显的宏观蠕滑特征,室内通过对断层泥进行扫描电镜等显微结构分析发现微观蠕滑特征,因此判断五佛寺断层晚更新世活动段活动方式为蠕滑,断层不会对小观音水库坝址造成影响。  相似文献   

Palaeoenvironmental reconstruction from the last interglacial using phytolith analysis,southeastern North Island,New Zealand     

John A. Carter  Olav B. Lian 《第四纪科学杂志》2000,15(7):733-743

Phytoliths extracted from loess resting conformably on lacustrine sediments in southeastern North Island, New Zealand, provide a nearly continuous vegetation–climate record spanning the time period from the last interglacial (Marine Oxygen Isotope Stage 5) to the present. Phytoliths reveal changes in vegetation patterns following changes in climate. Correlation between tree–shrub phytolith fluctuations and the SPECMAP oxygen isotope curve, between Marine Oxygen Isotope Stages 1 and 5, suggest that changes in the ratio of arboreal to non‐arboreal phytoliths directly result from changes in climate. These data generally support the existing pollen and diatom record. This study confirms the usefulness of phytolith fossils for providing environmental and climate information from the Quaternary sedimentary record, especially in cases where the deposits contain no fossil pollen or diatoms. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

广西钦州湾晚全新世红树林演变及对海平面变化的响应   总被引：2，自引：0，他引：2  

夏鹏  孟宪伟  李珍  支鹏遥  赵蒙维  王恩康 《海洋学报(英文版)》2019,38(11):111-120

Mangroves, widely distributed along the coasts of tropical China, are influenced by Asia monsoon, relative sea level change and enhanced human activity. To predict the impacts of future climate change on mangrove ecosystems, it can be understood by reconstructing past mangrove dynamics using proxies preserved in coastal sediments. In this study, we quantitatively partitioned buried organic matter(OM) sources, collected from a vulnerable mangrove swamp in the Qinzhou Bay of northwestern South China Sea, using a ternary end-member mixing model of δ~(13)C and C:N values. Mangrove-derived OM(MOM) contribution was used as a tracer for mangrove development since 2.34 cal ka BP. This information, together with paleoclimate records(i.e.,speleothem δ~(18)O values, sea level change, grain size parameters) and human activity, was used to divide mangrove development into three stages during the late Holocene: relative flourish(2.34–1.13 cal ka BP), relative degradation(1.13–0.15 cal ka BP) and further degradation(0.15–0 cal ka BP). Before 1.13 cal ka BP, mangroves flourished with a high MOM contribution((88.9±10.6)%), corresponding to stable and high sea level under a warm and humid climate. After 1.13 cal ka BP, rapid fall in relative sea level coupled with the strengthening of the Asian winter monsoon, resulted in mangrove degradation and MOM reduction((62.4±18.9)%). Compared with air temperature and precipitation, the relative sea level fall was the main controlling factor in mangrove development before entering the Anthropocene(the time of the Industrial Revolution). After ～150 cal a BP, reclamation of mangrove swamps to shrimp ponds is the main factor causing mangrove degradation and MOM reduction.  相似文献