Silurian collisional suturing onto the southern margin of the North China craton: Detrital zircon geochronology constraints from the Qilian Orogen     

Jiang-Hai Yang  Yuan-Sheng Du  Peter A. Cawood  Ya-Jun Xu 《Sedimentary Geology》2009,220(1-2):95-104

The Qilian Orogen of north western China records mid-Paleozoic collisional suturing of arc and continental blocks onto the south western margin of the North China craton. Silurian strata from the retroarc foreland basin mark the transition from ocean closure and northward subduction to the initiation of collision suturing. Detrital zircons were analysed from the western and eastern parts of the basin and show a spectrum of ages from Archean to Paleozoic with major age concentrations at around 2.5 Ga, 1.6 Ga, 1.2 Ga, 0.98 Ga, 0.7 Ga and 0.45 Ga. Archean age grains are derived from the North China craton, whereas the Central Qilian Bloc, which lies to the south provides the likely source for the bulk of the Proterozoic detritus. Paleozoic grains are restricted to Early Silurian samples from the western part of the basin and are considered to have been derived from the magmatic arc related to ocean closure and ultimate collision of the Central Qilian Belt with the North China craton.  相似文献   

湘西地区志留纪沉积体系及典型前陆盆地的形成模式研究   总被引：5，自引：0，他引：5  

李斌  胡博文  石小虎 《地学前缘》2015,22(6):167-176

湘西地区发育志留系中、下志留统碎屑岩地层,缺失上志留统。经沉积学综合研究,可以划分出滞留盆地、浊积扇、三角洲、潮坪滨岸等沉积体系,从下向上海平面逐渐下降,其物源来自于东南部雪峰隆起。湘西地区志留纪沉积盆地构造演化经历了前陆盆地的形成期、发展期及萎缩期、消亡期几个阶段。其沉积构造演化规律为：前陆盆地初始形成期发育深水滞留盆地沉积体系;前陆盆地发展期发育海相浊积扇沉积体系;前陆盆地萎缩期发育三角洲沉积体系,前陆盆地消亡期发育潮坪沙坝滨岸沉积体系。  相似文献   

东昆仑三道湾流纹英安斑岩锆石U-Pb年龄及其地质意义   总被引：2，自引：0，他引：2  

周春景  胡道功  BaroshPJ  吴珍汉  张永清  耿建珍  郝爽  倪晋宇  张耀玲 《地质力学学报》2010,16(1):28-35

东昆仑格尔木河西三道湾流纹英安斑岩构成火山通道侵出相,侵入到纳赤台群哈拉巴依沟组碎屑岩系中,其形成时代对于造山带火山作用的研究和限定哈拉巴依沟组地层时代均具有重要的意义。采用激光烧蚀多接收器电感耦合等离子体质谱(LA-MC-ICP MS)方法,对三道湾流纹英安斑岩进行了锆石U-Pb定年,结果表明,流纹英安斑岩中25个岩浆锆石206Pb/238U加权平均年龄为425.9 ± 2.6 Ma,它被解释为流纹英安斑岩的结晶年龄,说明三道湾次火山岩所代表的火山通道为早古生代造山晚期牦牛山组火山岩形成时的火山喷发中心之一,而非晚侏罗世次火山岩。野外地质关系和次火山岩年龄可以限定哈拉巴依沟组形成于中志留世之前。   相似文献   

塔里木盆地塔中、塔北地区志留系古油藏的油气运移   总被引：18，自引：0，他引：18  

陈元壮刘洛夫  陈利新赵素平  李超霍红 《地球科学》2004,29(4):473-482

运用含氮化合物咔唑类探讨塔中、塔北地区在第一期成藏时志留系油气藏的烃类的运移方向, 为建立古油藏成藏模式, 预测原生油气藏分布提供依据.研究表明, 塔中志留系古油藏的油气主要来源于满加尔凹陷的中、下寒武统烃源岩, 向西南—南的方向首先进入塔中志留系, 然后沿不整合面或顺储层从北西向南东和从北东向南西2个方向向志留系在塔中地区的尖灭线附近运移.塔北志留系古油藏的油气也主要来自满加尔凹陷的中、下寒武统烃源岩, 首先向北西方向进入塔北隆起的志留系, 然后在志留系储层内或不整合面沿上倾方向继续向北西方向运移进入圈闭.   相似文献   

滇东曲靖地区志留纪四射珊瑚的动物群特征及地层时代讨论   总被引：4，自引：0，他引：4  

丁春鸣 《现代地质》1988,2(1):20

本文着重从四射珊瑚动物群的角度讨论了滇东曲靖地区志留系的地层划分及对比问题。并提出曲靖地区的中、晚志留世具有4个珊瑚化石组合。对部分四射珊瑚属种（其中包括9个新种,4个相似种和一个未定属种）进行了描述。  相似文献   

Palaeotopography of the northern portion of the Telychian (Silurian) turbidite basin in central Wales     

D.M.D. James 《Geological Journal》2005,40(5):593-601

New palaeocurrent data from the country northeast and southwest of Corris (central Wales) indicate that Telychian sandstones in the Devil's Bridge Formation hereabouts were transported from both the northeast and northwest, consistent with topographical control by down‐to‐southeast movement on the Bala Lineament. This conclusion is supported by considerations of thickness variation and by evidence for listric detachment faulting in the formation at Bwlch y Groes. Towards Plynlimon, flow is broadly southerly and suggests confinement by the northward extension of the Bronnant Fault. A facies and palaeocurrent map is presented for the utilis sub‐Biozone of the Telychian which links with work by the British Geological Survey between Aberyswyth and Rhayader where, by contrast, palaeoflow is to the NNW. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Upper Ordovician–Lower Silurian transgressive–regressive cycles of the Central Iberian Zone (NE Jaén,Spain)     

J. Rey  M. C. Hidalgo  J. Martínez‐Lpez 《Geological Journal》2005,40(4):477-495

A thick Upper Ordovician shelf sequence was developed in the northern Gondwana margin (southernmost exposures of the Central Iberian Zone). Integrated sedimentologic and stratigraphic studies allow distinction between pedogenetic processes (Facies association C), shoreline deposits (Facies association S), proximal to distal shelf (Facies association L, H₁, H₂, H₃) and outer shelf zone or open marine environments (Facies association M, Mo). The vertical distribution of facies is characterized by the presence of regressive high frequency sequences (partial shelf progradational sequences), affected by the presence of catastrophic phenomena (storms). These sequences, in turn, can be classified into higher‐order transgressive (T)–regressive (R) cycles. Two second‐order T‐R megacycles (MC. Ord‐2 and MC. Sil‐1) limited by a major sequence boundary are identified. Traces of emersion (palaeokarsts and palaeosols) are detected along the sequence boundary, and these are related to the eustatic sea‐level fall that occurred during the Ashgillian. The MC. Ord‐2 and MC. Sil‐1 megacycles extend respectively from the Middle Arenig to the Ashgillian and from Late Ashgillian to the Late Llandovery. Major transgressive peaks occurred at the Llanvirn and at the Middle Llandovery (Aeronian). The vertical distribution of the facies delineates successive genetically related units in relation to relative sea‐level changes. Within the upper part of the first megacycle (MC. Ord‐2) six third‐order cycles are proposed (Lla‐1, Car‐1, Car‐2, Car‐3, Car‐4, Ash‐1), in which a transgressive and a regressive interval can be distinguished. Within the lower part of the second megacycle (MC. Sil‐1) two transgressive–regressive third‐order cycles are proposed (Lly‐1, Lly‐2). Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Japan's earliest ostracods     

David J. Siveter  Gengo Tanaka  Mark Williams  Peep Mnnik 《Island Arc》2019,28(1)

Mesozoic, Cenozoic and especially Holocene ostracod faunas have been documented from Japan. Not surprisingly, considering the plate tectonic factors at play, very few ostracod faunas are known from its early Paleozoic successions. Our pilot studies have recovered new ostracod assemblages from early Paleozoic terranes of Japan. Acid preparation of carbonates has yielded low diversity, poorly preserved yet significant palaeocopid and podocopid ostracod faunas from Wenlock/Ludlow Series Silurian rocks at Gionyama in the Kurosegawa Terrane, Miyazaki Prefecture, Kyushu, and Hitoegane in the Hida‐Gaien Terrane, Gifu Prefecture, Honshu. The ostracod faunas include new eurychilinoid (Pauproles supparata gen. et sp. nov.), hollinoid (Hollinella orienta sp. nov.) and beyrichioid (Clintiella antifrigga sp. nov.) palaeocopid taxa. Conodonts recovered from the same sample as the ostracods from Gionyama confirm a mid‐Silurian age for the part of the Gionyama Formation in question. The ostracod faunas recovered from Gionyama and Hitoegane are the first confirmed, well‐documented record of the group from the Silurian of Japan and are therefore the earliest known ostracods from that country (a previous record of purported Ordovician ostracods from Japan is incorrect). The ostracod taxa display links with the paleocontinents of particularly Laurentia and Baltica and demonstrate a pan‐tropical signature; it appears that climate control was stronger than geographical control in shaping this pattern of ostracod distribution. The material recovered includes adult dimorphic (assumed sexual) pairs of three palaeocopid species, which represent Japan's oldest (423–433 million years) known ‘couples’.  相似文献   

盐源地区古生界页岩气地质条件分析   总被引：6，自引：6，他引：0  

余谦  程锦翔  张海全  王正和  邓敏  赵安坤  刘伟  陆俊泽  杨贵来 《沉积与特提斯地质》2020,40(3):118-128

为了进一步探索我国西南地区的页岩气资源潜力，中国地质调查局成都中心对盐源地区开展公益性页岩气基础地质调查。在系统的地质调查和沉积学、石油地质学研究的基础上，对盐源地区进行页岩气地质条件分析。发现盐源地区早古生代发育志留系龙马溪组和泥盆系坡脚组两套富有机质页岩层系。志留系龙马溪组以碳质硅质泥页岩和碳质粉砂质泥页岩为主，以富有机质、硅质含量高、笔石发育为主要特征，发育于深水陆棚环境中。泥盆系坡脚组以含钙质碳质泥岩和钙质碳质粉砂质泥岩为主，以富有机质、黏土含量高、竹节石发育为主要特征，主要发育于潟湖环境中。两套富有机质页岩层系均具有有机质含量高，沉积厚度大，热演化程度高，脆性指数较高，低孔低渗的特征。盐源地区发育大量宽缓向斜，具备较好的页岩气保存条件。在志留系稗子田组和泥盆系坡脚组的勘探获得了油气显示，表明盐源地区页岩气具备良好的勘探潜力，研究成果为区域油气勘探评价提供借鉴与参考。  相似文献   

Evaluation of 40Ar/39Ar Geochronology of Authigenic Illites in Determining Hydrocarbon Charge Timing: A Case Study from the Silurian Bituminous Sandstone Reservoirs,Tarim Basin,China     

ZHANG Youyu  LIU Keyu  and LUO Xiuquan 《《地质学报》英文版》2016,90(2):684-703

The Silurian bituminous sandstones(SBS) in the Tarim Basin, China are important basinwide reservoirs with an estimated area of approximately 249000 km2. We investigated the ages of authigenic illites in the SBS reservoirs and constrained their formation timing by using the ~(40)Ar/~(39)Ar step wise heating method. The age spectra, ~(39)Ar recoil loss and their controlling factors were investigated systematically. The ~(40)Ar/~(39)Ar ages were compared with the conventional K/Ar ages of identical clay fractions. The clay in the SBS reservoirs is dominated by orderly mixed-layer illite/smectite(I/S) with 5%–30% smectite layers. The I/S minerals morphology comprises primarily honeycomb, short filamentous and curved-lath particles, characteristic of authigenic illites. The unencapsulated ~(40)Ar/~(39)Ar total gas ages(UTGA) of the authigenic illites range from 188.56 ± 6.20 Ma to 491.86 ± 27.68 Ma, which are 7% to 103% older than the corresponding K/Ar ages of 124.87 ± 1.11 Ma to 383.45 ± 2.80 Ma, respectively. The K-Ar ages indicate multistage accumulations with distinct distribution patterns in the Tarim Basin: older(late Caledonian-early Hercynian) around the basin margin, younger(late Hercynian) in the basin centre, and the youngest(middle to late Yanshanian) in the Ha-6 well-block, central area of the North Uplift. The age difference is believed to have been caused by the ~(39)Ar recoil loss during the irradiation process. Compared with the K/Ar ages, the estimated ~(39)Ar recoil losses in this study are in the range from 7% to 51%. The ~(39)Ar recoil loss appears to increase not only with the decreasing particle sizes of the I/S, but also with increasing percentage of smectite layers(IR) of the I/S, and smectite layer content(SLC) of the samples. We conclude that due to significant ~(39)Ar recoil losses, UTGA may not offer any meaningful geological ages of the authigenic illite formation in the SBS and thus can not be used to represent the hydrocarbon charge timing. ~(39)Ar recoil losses during ~(40)Ar/~(39)Ar dating can not be neglected when dating fine authigenic illite, especially when the ordered mixed-layer I/S containing small amount of smectite layers(IR30%) in the reservoir formations. Compared with the unencapsulated Ar-Ar method, the conventional K-Ar method is less complicated, more accurate and reliable in dating authigenic illites in petroleum reservoirs.  相似文献