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1.
下扬子区海相三叠系层序地层研究 总被引：6，自引：0，他引：6
在详细野外观察、追索和室内多学科手段的交叉和综合地层学研究的基础上,将下扬子区海相下、中三叠统划分出5个三级层序,提出碳酸盐缓坡陆架背景下露头层序地层学研究的一般方法,总结了下扬子区早-中三叠世主体海退背景下的层序发育型式和规律,建立跨越台地边缘不同古地理相带的层序地层和年代地层格架. 相似文献
2.
《中国科学:地球科学》2015,(3)
早期对燕山构造带三叠系不同岩性组时代的确定主要根据植物化石和区域岩性对比,认为刘家沟组与和尚沟组为下三叠统,二马营组为中三叠统.通过对承德下板城盆地和平泉营子盆地三叠系砂岩碎屑锆石年龄分析,本次研究揭示刘家沟组、和尚沟组和二马营组皆为上三叠统.砂岩碎屑锆石年龄还揭示,早期认为属于中-上二叠统石盒子组的上段和上覆孙家沟组实属早三叠世末-中三叠世沉积.本文将石盒子组上段与孙家沟组合并,新命名为营子组;同时用丁家沟组、下板城组和胡杖子组分别替换现在使用的刘家沟组、和尚沟组和二马营组.野外地层和岩相分析证明,石盒子组上部安山岩层的顶面是一个沉积间断面,标记了中二叠统与下-中三叠统之间为平行不整合接触.营子组曲流河沉积指示在早三叠世末-中三叠世构造活动处于相对平静期,而上三叠统丁家沟组和胡杖子组砂质/砾质辫状河、冲积扇、扇三角洲、深湖沉积与火山岩组合代表强烈伸展断陷活动.新的三叠系地层划分、时代限定和沉积过程恢复对深入了解早中生代燕山构造带演化具有重要意义. 相似文献
3.
华南早-中二叠世筳类物种分异度变化过程的统计验证 总被引：1，自引：0，他引：1
用Rarefaction方法对华南早-中二叠世筳类物种表面分异度进行了统计验证, 证明华南筳类动物群物种数在早二叠世初迅速增加, 并在紫松期保持稳定的高分异度状态; 自早二叠世隆林期起, 筳类动物群物种分异度开始下降并呈长期低迷状态; 随着具副隔壁类群的出现, 筳类物种数在早二叠世晚期有所回升; 中二叠世孤峰期筳类动物群物种数再次增加, 但其规模远小于早二叠世初筳类动物群的辐射演化; 中二叠世中、晚期筳类物种分异度持续下降, 至中二叠世末大部分筳类物种消失. 相似文献
4.
用Rarefaction方法对华南早-中二叠世(?)类物种表面分异度进行了统计验证,证明华南(?)类动物群物种数在早二叠世初迅速增加,并在紫松期保持稳定的高分异度状态;自早二叠世隆林期起,(?)类动物群物种分异度开始下降并呈长期低迷状态;随着具副隔壁类群的出现,(?)类物种数在早二叠世晚期有所回升;中二叠世孤峰期(?)类动物群物种数再次增加,但其规模远小于早二叠世初(?)类动物群的辐射演化;中二叠世中、晚期(?)类物种分异度持续下降,至中二叠世末大部分(?)类物种消失. 相似文献
5.
用Rarefaction方法对华南早-中二叠世(蜓)类物种表面分异度进行了统计验证,证明华南(蜓)类动物群物种数在早二叠世初迅速增加,并在紫松期保持稳定的高分异度状态;自早二叠世隆林期起,(蜓)类动物群物种分异度开始下降并呈长期低迷状态;随着具副隔壁类群的出现,(蜓)类物种数在早二叠世晚期有所回升;中二叠世孤峰期(蜓)类动物群物种数再次增加,但其规模远小于早二叠世初(蜓)类动物群的辐射演化;中二叠世中、晚期(蜓)类物种分异度持续下降,至中二叠世末大部分(蜓)类物种消失. 相似文献
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《中国科学:地球科学》2016,(7)
在内蒙林西县及邻区首次观察到大量晚二叠世台缘礁和丘状礁.初步研究证实,兴-蒙地区当时为开放海槽环境.本文首先分析林西官地林西组四、五段沉积相和相序叠置,再造晚二叠世晚期林西-九台裂陷带的稳定沉降-缓慢抬升-迅速闭合过程;并且利用多门类化石的属种延续和丰度分布,确定含生物礁地层的地质时代和划分对比,为生物礁研究奠定基础.然后详细研究多类造礁生物,即海绵、苔藓虫和钙藻等的形态功能和造礁机制,恢复各门类的生态条件和造礁环境,划分出6个造礁生物组合.综合沉积相、地层和生物古生态研究成果,识别出晚二叠世晚期2类陆棚边缘,即丘状礁缓坡陆棚边缘和障壁礁陡坡陆棚边缘.从而论证生物礁的线状分布标志中朝板块北缘及兴蒙-海槽内林西-九台裂陷带在晚二叠世末期闭合. 相似文献
9.
中亚地区晚古生代腕足动物古生物地理与构造古地理的协同演化 总被引：1，自引：0，他引：1
在早泥盆世、早石炭世、晚石炭世、早二叠世、中二叠世等腕足动物古生物地理区划研究基础上,通过对比分析,揭示了中亚地区晚古生代腕足动物古生物地理与构造古地理的协同演化关系,既较为合理解释了此地此时腕足动物古生物地理形成的机制,又为此地此时洋、陆位置及其配置关系研究提供了依据. 相似文献
10.
《中国科学:地球科学》2016,(10)
本文报道唐古拉山北坡开心岭地区的晚石炭-早二叠世地层的古地磁学研究结果.岩石磁学实验研究表明扎日根组灰岩样品中的磁性矿物以磁铁矿为主,诺日巴尕日保组砂岩样品中的磁性矿物以赤铁矿为主或磁铁矿与赤铁矿共存.采用系统热退磁方法对样品进行磁清洗,大部分样品的退磁曲线呈双分量特征,高温分量明显.高温特征分量成功通过了砾石可靠性检验,代表了地层岩石的原生剩磁信息.获得羌北地块晚石炭-早二叠世地层(16个采点127块样品)的原生剩磁分量的平均方向为Ds=30.2°,Is=-40.9°,ks=269.0,a95=2.3°;其对应的古地磁极位置为λ=25.7°N,φ=241.5°E,dp/dm=2.8/1.7,相应的古纬度为23.4°S.表明晚石炭-早二叠世时期羌北地块位于南纬低纬度地区,可能属于冈瓦纳大陆的北缘.结合前人古地磁学研究结果,该地块在其后快速北移,可能与早二叠世-晚三叠世古特提斯洋快速消亡以及新特提斯洋北支班公湖-怒江洋快速扩张相关. 相似文献
11.
Integrated study of rock assemblage, tectonic setting, geochemical feature, fossil contained and isotopic geochronology on
the metamorphic mixed bodies, exposed in the Jinshajiang suture zone, suggests that one informal lithostratigraphic unit,
the Eaqing Complex, and three tectono-stratigraphic units, the Jinshajiang ophiolitic melange, the Gajinxueshan Group and
the Zhongxinrong Group, can be recognized there. It is first pointed out that the redefined Eaqing Complex might represent
the Meso- to Neo-Proterozoic remnant metamorphic basement or mi-crocontinental fragment in the Jinshajiang area. The original
rocks of it should be older than (1627 ±192) Ma based on the geochronological study. The zircon U-Pb age of plagiogranites
within the Jinshajiang ophiolitic assemblage is dated for the first time at (294 ± 3) Ma and (340 ± 3) Ma respectively. The
Jinshajiang ophiolite is approximately equivalent to the Ailaoshan ophiolite in the formation age, covering the interval from
the Late Devonian to the Carboniferous. Dating of U-Pb age from basalt interbeds indicates that the redefined Gajinxueshan
Group and Zhongxinrong Group may be considered Carboniferous to Permian and latest Permian to Middle Triassic in age. In geotectonic
terms the Jinshajiang suture zone is thought to be a back-arc basin in the eastern margin of the Paleo-Tethys. This back-arc
basin started in the Late Devonian, and formed in the Devonian-Carboniferous. The collision event around the Permian/Triassic
boundary to the Middle Triassic led to the closure of the back-arc basin and formation of suture. 相似文献
12.
A mixed mid-Permian marine fauna from the Yanji area, northeastern China: A paleobiogeographical reinterpretation 总被引：4，自引：0，他引：4
Abstract Paleobiogeographically mixed marine faunas have been well recognized from many Permian marine sequences in northeast China. These mixed faunas are normally associated with Monodiexodina fusulinid assemblages. The mixed faunas are characterized by an admixture of both paleo-tropical Cathaysian taxa and cool-temperate elements. In addition, endemic taxa, especially at a specific level, and anti-tropical forms, are also very distinctive.
Previously, the presence of anti-tropical taxa in these mixed faunas has been used to argue that some of the northeast Asian terranes may have originated from northern Gondwana during the Permian, where they may have been m close proximity to Tibet. However, this interpretation is contrasted by the view offered in this paper. It is argued that the anti-tropical distribution of marine taxa is a normal, predictable biogeographical phenomenon that is probably controlled by certain climatic conditions. Permian anti-tropicality seems to have occurred most strongly during the Late Artinskian to Ufimian, probably in association with the presence of distinct mesothermal climatic zones at the time. In the present study we report a mixed mid-Permian marine fauna (fusulinids and brachiopods) from the Dasuangou Formation of the Yanji area in the eastern Jilin Province of northeast China, and discuss its possible origin in the context of Permian paleogeography and the climates of eastern Pangea. 相似文献
Previously, the presence of anti-tropical taxa in these mixed faunas has been used to argue that some of the northeast Asian terranes may have originated from northern Gondwana during the Permian, where they may have been m close proximity to Tibet. However, this interpretation is contrasted by the view offered in this paper. It is argued that the anti-tropical distribution of marine taxa is a normal, predictable biogeographical phenomenon that is probably controlled by certain climatic conditions. Permian anti-tropicality seems to have occurred most strongly during the Late Artinskian to Ufimian, probably in association with the presence of distinct mesothermal climatic zones at the time. In the present study we report a mixed mid-Permian marine fauna (fusulinids and brachiopods) from the Dasuangou Formation of the Yanji area in the eastern Jilin Province of northeast China, and discuss its possible origin in the context of Permian paleogeography and the climates of eastern Pangea. 相似文献
13.
Jonathan D. Phillips 《地球表面变化过程与地形》2017,42(15):2623-2639
Geomorphic and hydraulic units in river channels are closely linked to geodiversity and habitats, and thus to biodiversity. In a ~ 200 km reach of the lower Sabine River, in the northern Gulf of Mexico Coastal Plain, 72 different hydraulic units (HU) were identified in six geomorphic zones or river styles. Richness–area relationships indicate a linear or logarithmic increase of HUs, as opposed to the less steep power functions generally found in biogeographic species–area curves or in soil richness–area analyses. Different results are obtained when starting from the upstream or downstream end of the study area, indicating the importance of directionality in such analyses. These results show that HUs (and related habitats and biotopes) are both richer and more variable than a repeated sequence of units. The number of HUs inundated increases linearly with flow stage categories, indicating the importance of high within‐bank flows in maintaining and activating HUs. Aggregated HUs (AHUs) associated with similar geomorphic units are highly connected, both with respect to patterns of spatial adjacency and potential connectivity at similar flow levels. Spectral graph theory metrics applied to a graph representation of spatial adjacency shows a highly complex network with a high potential for rapid propagation of changes—and even more so for a graph based on flow connectivity. The flow connectivity graph shows far higher synchronization as indicated by algebraic connectivity. Thus suggests more rapid and coherent changes for processes driven by river flow, as opposed to phenomena driven by other factors between flow events. These findings have important implications for understanding relationships between geodiversity and habitat diversity, managing habitat and biodiversity, and linking the latter to instream flows. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
14.
以洛伊地区石油地震、钻井及地化资料为基础,利用镜质体反射率（Ro）进行单井剥蚀厚度恢复,应用平衡剖面恢复的早-中侏罗世古地貌呈"三凹三凸"特征,其中,中条山、熊耳山、嵩山由于隆升无早-中侏罗世沉积,在洛阳-济源、义马-宜阳、伊川形成3个沉降中心。依据盆地充填序列及沉积相带进行分析,认为研究区早-中侏罗世为山间坳陷盆地,其形成与演化受控于印支末期-燕山早期的秦岭-大别造山带陆内造山作用。 相似文献
15.
MASATOSHI GOTO 《Island Arc》1994,3(4):247-254
Abstract In recent years, many fish teeth and scales have been found from the Palaeozoic and Mesozoic age strata of the Japanese Islands. This study is a compilation of the Japanese fish record from the Palaeozoic and early Mesozoic age deposits. Based on the published and unpublished data, the fossil fishes from the Palaeozoic and Early Mesozoic of Japan can be classified into 27 genera and 33 species, that is, one species of Devonian placoderms, 19 species of Permian to Jurassic elasmobranchs, three species of Permian cochliodonts, seven species of Carboniferous to Permian petalodonts, and three species of Triassic to Jurassic osteichthyans. 相似文献
16.
Abstract The chemical Th-U-total Pb isochron method (CHIME) has been applied to determine the ages of monazite grains from metasediments of greenscshist-amphibolite facies in the Altai orogen, northwest China. The area of distribution of these metamorphic rocks is divided into the Permian (261–268 Ma) central-western and Devonian (377–382 Ma) eastern units on the basis of their metamorphic ages. The Devonian CHIME ages are consistent with the Pb–Pb ages of granitoid in the eastern unit, and support the idea that emplacement of the granitoids was synchronous with regional metamorphism at deep levels. The Permian metamorphic ages (the present study) and igneous ages previously reported from the central-western unit can be interpreted in terms of subduction of crustal material and oceanic plate, and rapid exhumation. 相似文献
17.
应用应力调制图像法,对上海地区1970～2007年以来的18次ML≥5．0地震进行了检验。结果显示,有15次地震的震前出现了Se值异常单元,虚报地震9次,漏报3次。 相似文献
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XingFeng Yang Xin Cheng YaNan Zhou Lun Ma XiaoDong Zhang ZhaoSheng Yan XiMing Peng HaiLun Su HanNing Wu 《中国科学:地球科学(英文版)》2017,60(1):124-134
Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains,in the northern Qiangtang terrane(NQT),Tibet,China.Data revealed that magnetic minerals in limestone samples from the Zarigen Formation(CP^z)are primarily composed of magnetite,while those in sandstone samples from the Nuoribagaribao Formation(Pnr)are dominated by hematite alone,or hematite and magnetite in combination.Progressive thermal,or alternating field,demagnetization allowed us to isolate a stable high temperature component(HTC)in 127 specimens from 16 sites which successfully passed the conglomerate test,consistent with primary remnance.The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D_s=30.2°,I_s=-40.9°,k_s=269.0,a_(95)=2.3°,N=16,which yields a corresponding paleomagnetic pole at 25.7°N,241.5°E(dp/dm=2.8°/1.7°),and a paleolatitude of 23.4°S.Our results,together with previously reported paleomagnetic data,indicate that:(1)the NQT in Tibet,China,was located at a low latitude in the southern hemisphere,and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian;(2)the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian,and(3)the NQT subsequently moved rapidly northwards,perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean,the northern branch of the Neo-Tethys Ocean,expanded rapidly during this time. 相似文献
20.
Origin of the Gangdise (Transhimalaya) Permian arc in southern Tibet: Stratigraphic and volcanic geochemical constraints 总被引：2，自引：0，他引：2
The well‐studied Mesozoic and Cenozoic volcanic rocks of the Gangdise Terrane, southern Tibet, are widely interpreted to have resulted from subduction of the Neotethys; however, Late Paleozoic volcanic rocks and their tectonic setting remain poorly studied. Based on new geological data, we carried out stratigraphical and geochemical analyses of Permian volcano‐stratigraphic sequences within an east–west‐trending, fault‐bounded zone of uplift in the central Gangdise Terrane. Sedimentary rocks in this area consist of platform carbonates and terrigenous clastic rocks that represent widespread shallow‐marine sedimentary basins developed around northern Gondwana. A regression or tectonic uplift event is recorded in Permian sedimentary rocks that show the local development of fluvial environments. The sedimentary succession contains evidence of two volcanic stages: a period of basaltic extrusions and younger explosive felsic magmatism. The first volcanic stage is Early and Middle Permian in age. Tholeiitic basaltic lavas are exposed around Maizhokunggar (Tangjia) and Lhunzhub in central Gangdise. The Lower Permian basalts are relatively enriched in MgO (4.58–12.19%), whereas the Middle Permian basalts are characterized by high Al2O3 contents (11.75–21.22%). Rocks of both ages are enriched in large‐ion lithophile elements (LILE) and light rare earth elements (LREE), and show pronounced negative Nb and Ta anomalies. Total REE contents and light (LREE)/heavy (HREE) ratios increased from the Early to Middle Permian. Observed variations in initial Sr, Nd, and Pb isotopes (87Sr/86Sri = 0.7013–0.7066, 207Pb/204Pbi = 15.53–15.63, and 208Pb/204Pbi = 38.04–38.64 for a given 206Pb/204Pbi; εNd = +0.69 to ?11.55) can be explained by crustal interaction with mantle sources, as is characteristic of metasomatism by slab‐derived fluids or assimilation and fractional crystallization (AFC) processes during magmatic evolution. The observed geochemical signatures, coupled with stratigraphic constraints, support the hypothesis that an initial arc formed during the Permian due to southward subduction of the Paleotethys, predating the well‐known Mesozoic arc preserved in the Gangdise Terrane. 相似文献