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981.
华北克拉通东南部蚌埠隆起晚中生代花岗岩类岩体内变形记录与构造意义 总被引:5,自引:0,他引:5
华北克拉通东南部蚌埠隆起上出露了一系列晚中生代花岗岩类岩体,记录了丰富的变形过程。本次与前人锆石定年结果表明,该区经历过两期岩浆活动,分别是中—晚侏罗世(167~148 Ma)和早白垩世(130~112Ma)。区内晚侏罗世蚂蚁山岩体记录了切过该岩体的一条北北东向左行韧性变形带,是北北西—南南东向挤压的产物。该走滑变形带在走滑隆升中又被脆性平移断层所叠加。走滑活动时间可以限定在148~130 Ma之间。研究区在130~112 Ma期间转变为强烈的伸展活动,区域拉张方向为北西西—南东东向,并伴随着岩浆活动与区域隆升。在此伸展过程中,中—晚侏罗世荆山—涂山岩体与早白垩世淮光岩体记录了深部韧性伸展拆离变形带抬升至浅部被脆性正断层所叠加的变形过程,而其它岩体内均记录了地壳浅部的脆性正断层活动。这些岩体的变形记录,指示华北克拉通东部晚中生代由挤压向伸展构造体制转变发生在148~130 Ma期间,提供了在早白垩世克拉通峰期破坏中目前非盆地区构造过程的实例。 相似文献
982.
中国东海和南黄海沿海平原MIS 3晚期海侵层的动力模拟研究 总被引:1,自引:0,他引:1
Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3(MIS 3) and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level(H_S) was defined as the glaciation-climateforced sea levels, and the relative sea level change(H_R) was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±(2.5–4.5) m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions. 相似文献
983.
内蒙古西乌旗地区出露一些石英闪长岩,其LA-ICP-MS锆石U-Pb年龄为(304.64±0.82)Ma和(309.84±0.86)Ma,表明这套岩石形成于晚石炭世。地球化学分析表明,西乌旗地区石英闪长岩属于低Ti O2和高Al2O3钙碱性玄武岩系列;富集Rb、Ba、K大离子亲石元素(LILE),亏损Nb、Ta、Ti、P等高场强元素(HFSE),具有典型弧岩浆岩的特征,显示岩浆源区曾经历过俯冲带流体的交代作用;稀土元素丰度偏低,呈LREE富集HREE亏损的右倾模式;强不相容元素比值(La/Nb、La/Ta等)及判别图解表明晚石炭世石英闪长岩类似大陆边缘弧玄武岩,岩浆来源于浅部岩石圈地幔,系石榴石+尖晶石二辉橄榄岩源区中等程度(10%~20%)部分熔融的结果。综合研究区样品的地球化学特征,结合区域地质资料及对比分析前人成果,认为早石炭世末期西乌旗地区在强烈拉张的裂谷环境下形成了有限洋盆,由于洋盆发育不成熟或边伸展边向两侧俯冲—消减,形成了西乌旗地区类似大陆边缘弧玄武岩特征的晚石炭世石英闪长岩。 相似文献
984.
985.
成岩作用对储层孔隙的影响——以辽河盆地荣37块气田下第三系为例 总被引:13,自引:2,他引:11
通过对岩芯、铸体薄片、阴极发光薄片观察及X-衍射分析,认为辽河盆地下第三系砂岩储层成岩作用中的压实作用和胶结作用减小和破坏储层孔隙,溶蚀作用则增加储层孔隙,且后者仅在一定深度范围内作用,并从沉积相、砂岩的成因及岩屑成份等方面探讨了成岩作用对储层孔隙度的影响。 相似文献
986.
A paleoisthmus linking southern South America with the Antarctic Peninsula during Late Cretaceous and Early Tertiary 总被引:1,自引:0,他引:1
Shen Yanbin 《中国科学D辑(英文版)》1998,41(3):225-229
Paleontological and stratigraphical data indicate that a link between terminal southern South America and the Antarctic Peninsula
probably was an irregularly narrow continuous land from Late Cretaceous (Campanian) through the Eocene period. In paleogeographical
feature it is more like modern Isthmus of Panama. A paleoisthmus called the isthmus of Scotia is hypothesized as a type of
connection between them. It lasted about 35 Ma and extended about 700–900 km long and 100–200 krn wide. This isthmus played
an important role in biotic dispersal and migra-tion among South America, Antarctica, Australia and New Zealand blocks during
this interval.
Project supported by the Science and Technology Con~rnission, the Chinese Academy of Sciences and the National Natural Science
Foundation of China (Grant No. 49572076). 相似文献
987.
Major thrust sheet in the Daqing Shan Mountains Inner Mongolia, China 总被引:13,自引:0,他引:13
Small thrust faults in the Daqing Shan that were previously mapped as separate structures belong to a single Mesozoic thrust,
herein named the Daqing Shan thrust. It extends more than 155 km along the northern margin of the Daqing Shan, obliquely cutting
the Daqing Shan along the western flank of the Jinluandian peak to the southeast and taking its way to Chayouzhongqi to the
east. Kinematic markers indicate tectonic transport of the thrust sheet to the NNW. Minimum displacement, based on the observable
outcrops, is 22 km, and the inferred thrusting distance may be larger than 35 km. The thrust sheet covers the whole eastern
area of the Daqing Shan. The thrust truncates the E-W trending, somewhat older South-directed Panyanshan thrust and, therefore,
the two faults are not as a result of counter thrusting. Such major intraplate tectonic deformation that occurred in the Inner
Mongolia Axis or the Yin Shan latitudinal tectonic belt during late Jurassic time calls for deep thought on its tectonic significance
in dynamics. It is most likely that the Daqing Shan thrust represents major intraplate shortening during Jurassic-Cretaceous
closure of the Mongolo-Okhotsk ocean about 1000 krn away to the north.
Project supported by the National Natural Science Foundation of Chlna (Grant No. 49070135) and by the Natlonal Science Foundation
of the Unlted States (Grant No.EAR-9627909). 相似文献
988.
汤原断陷第三纪地层研究新进展 总被引:12,自引:3,他引:9
主要从生物地层学、年代地层学和地球物理地层学三个方面,对汤原断陷近几年来地层研究的最新成果进行了简要论述,建立了19个化石组合、亚组合,认为本区存在古新统和上新统;获得了11个裂变径迹年龄数据;在地层倾角测井上识别出了4种沉积相变化模式;完善了本区第三系地层层序。 相似文献
989.
990.