Reconstruction of the Yangtze Ramp during Floian to Darriwilian (Ordovician) in South China: Its Morphology, Controlling Factors and Significances     

LUAN Xiaocong  André DESROCHERS  WU Rongchang  LIU Jianbo  WANG Guangxu  LIANG Yan  ZHANG Yuchen  WEI Xin  LI Lixi  ZHAN Renbin 《《地质学报》英文版》2023,97(6):1756-1777

A robust stratigraphic framework and a coherent depositional ramp model for the Zitai, Dawan, Meitan and Ningkuo formations of Floian–Darriwilian age (Early–Middle Ordovician) in the Yangtze (Daoba, Xiangshuidong, Daling, Gudongkou and Honghuayuan sections) and Jiangnan regions (Nanba section) was created based on lithofacies and major element analysis. Three siliciclastic (LF1–3) and six carbonate (LF4–9) lithofacies are recognized representing sediments that were deposited in mixed siliciclastic and carbonate ramp environment. The intensity of mixed sedimentation and terrigenous input were evaluated using the elemental proxies Intensity of Mixed sedimentation (IM) and Aluminum Accumulation Rate (AlAR), as well as their mean values during certain time intervals. Mixed sediments are most well-developed along the marginal Yangtze region, strongly impacted by recurrent influx of westerly derived terrigenous materials in response to global eustatic changes and regional tectonic movements, shaping the gently southeast-dipping morphology. Regular terrigenous influx resulted in periods of enhanced primary productivity on the Yangtze Ramp as evidenced by matching biodiversity peaks in planktonic organisms, i.e., chitinozoans and acritarchs. Brachiopods and other shelly fauna were also able to proliferate as new niches developed along the gently dipping ramp floor with substrate changes. The biodiversification patterns suggest that terrigenous influx controlled in part by regional tectonics played a more important role than previously thought in the development of Great Ordovician Biodiversification Event in South China.  相似文献   

湖南弗拉阶地层的分布特征和页岩气有利区          下载免费PDF全文

王建坡  王传尚  吕嵘  田巍 《中国地质》2021,48(5):1499-1509

湖南上泥盆统弗拉阶佘田桥组泥页岩是重要的页岩气勘探目的层。由于区域上具有岩相分异显著、变化快的特征,佘田桥组存在多个同期地层,容易造成引用和野外识别困难,严重制约其页岩气调查工作进程。通过梳理佘田桥组及其同期地层的历史沿革,明确和圈定了它们的分布区域和使用范围。基于佘田桥组的岩石组合特征、有机碳含量的区域变化和已有调查成果,提出受陆缘碎屑输入影响较强的新化-涟源、邵东地区为页岩气有利勘探区的设想,同时认为找准台盆范围是页岩气调查发现的关键。  相似文献   

The last interglacial sea-level high stand on the southern Cape coastline of South Africa     

Andrew S. Carr  Mark D. Bateman  Colin V. Murray-Wallace  Peter J. Holmes 《Quaternary Research》2010,73(2):351-363

The continental margin of southern South Africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long-term eustatic sea-level changes. We report a suite of optical luminescence ages and supplementary amino acid racemization data, which provide paleosea-level index points for three sites on this coastline. Deposits in the Swartvlei and Groot Brak estuaries display tidal inlet facies overlain by shoreface or eolian facies. Contemporary facies relations suggest a probable high stand 6.0-8.5 m above modern sea level (amsl). At Cape Agulhas, evidence of a past sea-level high stand comprises a gravel beach (ca. 3.8 m amsl) and an overlying sandy shoreface facies (up to 7.5 m amsl). OSL ages between 138 ± 7 ka and 118 ± 7 ka confirm a last interglacial age for all marginal marine facies. The high stand was followed by a sea-level regression that was associated with the accumulation of eolian dunes dating to between 122 ± 7 ka and 113 ± 6 ka. These data provide the first rigorous numerical age constraints for last interglacial sea-level fluctuations in this region, revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far-field locations.  相似文献   

钢锚墩在锦屏一级水电站地下厂房的运用          下载免费PDF全文

黄辉 《探矿工程》2010,37(4):72-74

锦屏一级水电站地下厂房地应力高,分层开挖完成后随着地应力的释放及重新分布,局部岩体出现压碎、层状劈裂破坏,围岩松弛深度及变位不断加深、加大。为了尽快实现锚索锚固支护效应以确保地下厂房洞室群围岩稳定和工程安全,施工时将部分原设计现浇混凝土锚墩调整为钢锚墩进行施工,取得了较好的质量、进度效果。主要介绍了钢锚墩的施工工艺、质量控制要点及其与混凝土锚墩的工效对比分析。  相似文献   

哀牢山造山带构造演化及其两侧盆地耦合   总被引：1，自引：0，他引：1  

邓茂林  张志斌  李长青 《云南地质》2010,29(2):177-181

哀牢山造山带的崛起和盆地耦合,对东西两侧沉降盆地的构造-沉积性质起关键性作用。转换构造性质不仅形成了逆冲推覆与走滑剪切联合作用的构造共生组合,形成两类不同性质的沉积盆地。  相似文献   

早白垩世陆相九佛堂阶的重新厘定及其层型剖面     

田树刚  牛绍武 《地质通报》2010,29(203):173-187

通过实测冀北滦平梁根村-东沟村九佛堂组剖面,并在开展多学科系统研究的基础上,把剖面划分为3个岩性段,建立了系统的叶肢介生物地层6个组合,进行辽西九佛堂组—沙海组与冀北滦平九佛堂组的等时性对比;分析剖面的沉积相叠置特征,证明了剖面的沉积连续性和沉积旋回性变化,识别出剖面的3个浅湖相三级层序,重新厘定九佛堂阶的定义及其单位、界线层型。建议将“沙海阶”并入九佛堂阶,单位和界线层型定在冀北滦平盆地西北部梁根村-东山村之间;底界以叶肢介Eosestheria fuxinensis和E. jiufotangensis 的首现为标志。  相似文献   

皖南龙潭阶与长兴阶界线的一种确定方法──层序地层学应用尝试     

吴基文  陈资平 《地层学杂志》1995,19(2):136-139

以层序地层学理论为指导，通过对皖南地区晚二叠世地层沉积层序特征的综合分析。可知该区晚二叠世存在两次海水进退过程，发育两个层序，两层序之界面即为龙潭阶和长兴阶的分界，该界线在视电阻率测井曲线上有较明显的反映，据此可方便地进行地层划分。  相似文献   

北京西山寒武纪海相红层的分布与时代     

李明  林宝玉 《地质学报》2022,96(6):1895-1921

本文参照北京西山及国内外寒武系相关地层资料，在古生物学和地层学研究的基础上，对北京西山寒武纪海相红层进行了初步研究。在西山寒武纪地层中，共识别出14层(套)海相红层，分别为：早寒武世下苇甸组1层B∈RB1(沧浪铺期)；早—中寒武世早期3层B∈RB2、B∈RB3及B∈RB4(馒头期—毛庄期)；中寒武世中期3层B∈RB5、B∈RB6及B∈RB7(徐庄期)；中寒武世晚期1层B∈RB8(张夏期)；晚寒武世早期2层B∈RB9、B∈RB10(崮山期)；晚寒武世中期3层B∈RB11、B∈RB12、B∈RB13(长山期)：晚寒武世晚期1层B∈RB14(凤山期)。所有14层海相红层形成于陆表海浅水环境，它们均属陆棚红层。红层分布模式说明，它们的形成与其附近的古陆有关。依据海相红层及其上下层位中所含的三叶虫化石，本文初步论述了各海相红层的大致时代，并与其他地区的同期海相红层进行了对比。此外，本文还讨论了山西东部寒武纪海相红层的层序和全球早寒武世沧浪铺期海相红层的广布事件。  相似文献   

INVESTIGATION AND EVALUATION OF EARTHQUAKES IN NUCLEAR POWER PLANT SITING          下载免费PDF全文

Tian Shengqing 《地震地质》1993,15(4):296

On the basis of ten-years major expecrience in investigation and evaluation of earthquakes in nuclear power plant siting in our country, the stage and content associated with investigation and evaluation are outlined in this paper.  相似文献   

模糊聚类分析在有机质演化阶段划分上的应用     

师先进 《上海国土资源》1993,(3):16-21

本文概述了模糊聚类分析的方法,并使用此法对有机质演化阶段的划分进行了初探,这个方法有利于油田的勘探和开采。  相似文献