云南鲁史三合洞组地层时代讨论     

黄晓明  丛峰 《沉积与特提斯地质》2017,37(2):40-45

云南兰坪盆地三合洞组的时代存在争议,有早古生代和中生代两种观点。本文通过对云南鲁史上三叠统三合洞组和挖鲁八组岩石地层、古生物化石、微体化石及碎屑锆石U-Pb年代学研究,认为三合洞组时代为晚三叠世。本区三合洞组生物碎屑灰岩、泥晶灰岩及白云质灰岩与挖鲁八组炭质板岩呈整合接触关系,与歪古村组砂质板岩呈逆断层接触关系,整体表现为倒转地层。挖鲁八组炭质板岩中采获叉皱海燕蛤、虚海燕蛤等晚三叠世化石,而三合洞组灰岩中的小欣德牙形刺、奥泽克刺、滑梯螺、长卵形槽花介等微体化石时代也为晚三叠世。笔者从挖鲁八组粉砂岩中获得碎屑锆石U-Pb年龄,其最小年龄为218 Ma,指示挖鲁八组的最晚沉积时代为晚三叠世。综合生物化石和同位素年代学资料,认为兰坪盆地三合洞组的时代为晚三叠世。  相似文献   

东濮凹陷沙三段正常三角洲沉积中遗迹化石及意义     

常龙  王长征  胡斌  陈传浩 《沉积与特提斯地质》2017,37(3):66-73

通过对钻井岩心的观察和遗迹化石的鉴定,在东濮凹陷古近纪沙河街组沙三段发现遗迹化石10属15种,包括:Skolithos vertivalis,Skolithos linearis,Skolithos isp.,Palaeophycus tubularis,Palaeophycus isp.,Planolites montanus,Planolites beverlegensis,Planolites isp.,Mermoides isp.,Taenidium isp.,Teichichnus isp.,Helminthoidichnites tenuis,Helminthopsis isp.,Beaconites isp.和Thalassinoides isp.。根据岩性特征、沉积构造和遗迹化石的组成、分布特征,研究区沙三段主要发育正常三角洲前缘亚相、前三角洲亚相,并划分了反映不同沉积环境和水体深度的2种遗迹组合,分别为Palaeophycus-Planolites遗迹组合和Planolites-Helminthoidichnites遗迹组合。  相似文献   

Principal aspects of the Ordovician biotic radiation     

ZHANG Yu  ong  ZHAN RenBin  FAN JunXuan  CHENG JunFeng & LIU Xiao LPS  Nanjing Institute of Geology  Palaeontology  Chinese Academy of Sciences  Nanjing  China 《中国科学:地球科学(英文版)》2010,(3)

The Ordovician radiation is among the major bioevents in earth history that have drawn great attention from geologists all over the world, and there have been hundreds of publications treating various aspects of this radiation. The study of the event involves a broad spectrum of research fields and concerns many scientific questions. Many opinions and hypotheses have been proposed on the triggering and controlling factors of the radiation. Herein the authors critically review the study of the Ordovician rad...  相似文献   

Climate variability recorded by n-alkanes of paleolake sediment in Qaidam Basin on the northeast Tibetan Plateau in late MIS3   总被引：1，自引：0，他引：1  

PU Yang    ZHANG HuCai  LEI GuoLiang  CHANG FengQin  YANG MingSheng  ZHANG WenXiang  LEI YanBin  YANG LunQing  & PANG YouZhi  State Key Laboratory of Lake Science  Environment  Nanjing Institute of Geography  Limnology  Chinese Academy of Sciences  Nanjing  China  Graduate University of Chinese Academy of Sciences  Beijing  Key Laboratory of Boyang Lake  MOE  School of Environmental  Chemical Engineering  Nanchang University  Nanchang 《中国科学:地球科学(英文版)》2010,(6)

Here we combine n-alkanes preserved in a shell bar section from Qarhan paleolake, Qaidam Basin with the other sedimentary proxies to elucidate the lake evolution process during the period 39.7 to 17.5 14C ka BP (calibrated age ranges from 43.5 to 22.4 cal. ka BP). In different stages, the n-alkane homologues exhibited different distribution modes indicative of variations in the surrounding vegetation and the hydrologic condition of the lake. The n-alkanes proxies (CPIh, ACLh, Paq) have the same trends as th...  相似文献   

Research on Fossil Heritages Protection in Xingwen World Geopark     

ZHOU Wei  ZHANG Bin  DENG Mao-lin  DING Jie  SHUI Wei  LIU Zu-han  YU Bo 《四川地质学报》2009,(Z1):140-144

There are various Permian fossil heritages in Xingwen World Geopark.However,during constructing Geopark in recent years,the fossil heritages have suffered more serious damages,and thus the protection models of the fossil heritage are worth studying.This paper describes the fossil heritages’ types,abundance and preservation of the current status quo in the geopark.It turns out that natural factors and human factors are the main reasons why lead to the destruction of fossil heritages.At last,it puts forward the corresponding measures in order to protect the integrity of fossil heritages in the world geopark.  相似文献   

河南嵩县南部熊耳群古火山构造与成矿关系研究     

李云  赵玉 《华南地质与矿产》2009,(3):28-36

河南嵩县南部熊耳群古火山构造保存完整,喷发旋回清晰,火山岩相及爆发相主要岩石种类齐全。其主要喷发类型为裂隙式喷发,次为中心式喷发,主要受区域基底断裂控制,且沿区域切壳深大断裂带呈串珠状分布。表明基底断裂一火山喷发带一区域断裂带是一个连续发展的过程。区内金及部分有色金属矿产与熊耳群古火山活动密切关联,古火山口爆发角砾岩产出地段是寻找该类型金矿的最佳地段,受古火山构造控制的古火山口及其周边的中性、酸性次火山岩脉（墙）,是寻找钼、金、铅锌多金属矿产的有利部位。  相似文献   

安徽巢湖地区中二叠统栖霞组的遗迹化石特征及其沉积环境     

王冰  李双应  赵大千  石传军  杜叶龙 《地层学杂志》2012,(1):109-115

在安徽巢湖177高地、无为白牡山等地中二叠统栖霞组顶部灰岩段和臭灰岩段发现大量遗迹化石Zoophycos cf.caudagalli。这些遗迹化石以系统觅食迹为主,指示水动力及波浪作用较弱、贫氧的深水沉积环境。在栖霞组的砾状灰岩中,发现部分Zoophycos穿插于灰岩砾石和基质之中,这揭示栖霞组石灰砾岩中的砾石并非成岩作用成因,而是碎屑流沉积形成,属于异地成因碳酸盐岩。综合巢湖地区栖霞组的地层和岩石地球化学特征以及Zoophycos的生活习性和分布特征,发现表明巢湖地区中二叠统栖霞组臭灰岩段和顶部灰岩段属于贫氧的碳酸盐台缘斜坡沉积。  相似文献   

Subduction of a fossil slow–ultraslow spreading ocean: a petrology-constrained geodynamic model based on the Voltri Massif,Ligurian Alps,Northwest Italy     

《International Geology Review》2012,54(7):787-803

Slow–ultraslow spreading oceans are mostly floored by mantle peridotites and are typified by rifted continental margins, where subcontinental lithospheric mantle is preserved. Structural and petrologic investigations of the high-pressure (HP) Alpine Voltri Massif ophiolites, which were derived from the Late Jurassic Ligurian Tethys fossil slow–ultraslow spreading ocean, reveal the fate of the oceanic peridotites/serpentinites during subduction to depths involving eclogite-facies conditions, followed by exhumation.

The Ligurian Tethys was formed by continental extension within the Europe–Adria lithosphere and consisted of sea-floor exposed mantle peridotites with an uppermost layer of oceanic serpentinites and of subcontinental lithospheric mantle at the rifted continental margins. Plate convergence caused eastward subduction of the oceanic lithosphere of the Europe plate and the uppermost serpentinite layer of the subducting slab formed an antigorite serpentinite-subduction channel. Sectors of the rather unaltered mantle lithosphere of the Adria extended margin underwent ablative subduction and were detached, embedded, and buried to eclogite-facies conditions within the serpentinite-subduction channel. At such P–T conditions, antigorite serpentinites from the oceanic slab underwent partial HP dehydration (antigorite dewatering and growth of new olivine). Water fluxing from partial dehydration of host serpentinites caused partial HP hydration (growth of Ti-clinohumite and antigorite) of the subducted Adria margin peridotites. The serpentinite-subduction channel (future Beigua serpentinites), acting as a low-viscosity carrier for high-density subducted rocks, allowed rapid exhumation of the almost unaltered Adria peridotites (future Erro–Tobbio peridotites) and their emplacement into the Voltri Massif orogenic edifice. Over in the past 35 years, this unique geologic architecture has allowed us to investigate the pristine structural and compositional mantle features of the subcontinental Erro–Tobbio peridotites and to clarify the main steps of the pre-oceanic extensional, tectonic–magmatic history of the Europe–Adria asthenosphere–lithosphere system, which led to the formation of the Ligurian Tethys.

Our present knowledge of the Voltri Massif provides fundamental information for enhanced understanding, from a mantle perspective, of formation, subduction, and exhumation of oceanic and marginal lithosphere of slow–ultraslow spreading oceans.  相似文献   

古大气CO₂浓度重建方法技术研究现状   总被引：1，自引：0，他引：1  

王尹  李祥辉  刘玲 《地质科技情报》2012,31(2):90-98

温室气候引起的全球气候变暖越来越引起人们的关注,大气中不断上升的CO2浓度被认为是导致气候变暖的主要因素.地史时期大气CO2浓度变化与温室气候可能存在类似的关系,可提供参考,因而古大气CO2浓度重建是首要任务.总结近年来古大气CO2浓度重建的进展,重点介绍GEOCARB模型模拟、植物叶片气孔参数和同位素指针的方法和技术.GEOCARB模型是反映全球古大气CO2浓度长期变化的碳相关模型;气孔参数方法是使用气孔比例来估计古大气CO2浓度;同位素指针包括成壤碳酸盐、浮游植物有机质生物标记物、钙质浮游有孔虫、古苔藓植物等,其中成壤碳酸盐碳同位素方法使用最为广泛.国内只是在叶片参数研究方面有一些进展,古大气CO2浓度重建工作任重而道远.  相似文献   

First Description of Fossil Naucoridae (Heteroptera: Nepomorpha) from Late Mesozoic of China     

ZHANG Weiting  YAO Yunzhi  REN Dong  ZHAO Yunyun 《《地质学报》英文版》2011,85(2):490-500

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