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再论华南志留系红层的时代 总被引：2，自引：0，他引：2
牙形刺P.eopennatus带的确立和P.celloni带、P.amorphognathoides带的细分,使华南Llandovery统的划分和对比发生了变化,以往归入P.celloni带的地层,极大多数都要归属到P.eopennatus带,层位变低。依据牙形刺生物地层的分析,溶溪组（下红层）的时代可能为埃隆期晚期,... 相似文献
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陕南川北志留系兰多维列统特列奇阶宁强组的生物礁 总被引：2，自引：0，他引：2
志留纪兰多维列世（Llandovery）扬子地台持续上升。特列奇期（Telychian）griestoniensis笔石带上部至spiralis-grandis带代表的时限内,地处扬子地台西北缘的宁强湾,在温暖浅海的环境中沉积了宁强组巨厚的泥页岩,其中夹含8套碳酸盐岩。在与之对应的8期小型局限碳酸盐岩台地的不同部位建造了生物礁和生物滩。生物礁的类型包括骨架礁、生物层和灰泥丘。生物礁群落由底栖固着的造礁珊瑚、苔藓虫、海百合、藻类、层孔虫,以及非固着的附礁生物腕足类、鹦鹉螺、三叶虫等组成。通过宁强广元地区不同地点和层位的生物礁组合分析,论述它们在生态组合、生长形状和发育过程中的多样性。 相似文献
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CHEN Yang GAI Zhikun LI Qiang WANG Jianhu PENG Lijian WEI Guangbiao ZHU Min 《《地质学报》英文版》2022,96(2):430-439
A new genus and species of agnathan Eugaleaspidiformes (Galeaspida), Yongdongaspis littoralis gen. et sp. nov., is described from the Llandovery (lower Silurian) Huixingshao Formation at Yongdong Town, Xiushan County, Chongqing, southwestern China. This new Telychian taxon morphologically exhibits some transitional states between Sinogaleaspidae and a cluster of higher eugaleaspidiforms containing Tridensaspidae, Eugaleaspidae, Yunnanogaleaspis, and Nochelaspis, which we term here as the ‘eugaleaspid cluster’. Phylogenetic analysis of an extended character matrix of Galeaspida reveals Yongdongaspis, on which Yongdongaspidae fam. nov. is erected, as the sister taxon of this ‘eugaleaspid cluster’, supported by two synapomorphies, the presence of one median transverse canal, and two lateral transverse canals leaving from the infraorbital canal. As the first fish described from the Llandovery Huixingshao Formation in Chongqing, Yongdongaspis provides new fossil evidence for the subdivision and correlation of the Upper Red Beds in South China. 相似文献
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通过对陕西紫阳、岚皋地区多个志留系特列奇阶剖面的研究,根据更为精确的化石定义,奥氏笔石属新种Oktavites ziyangensis sp. nov可以从Oktavites spiralis 居群中识别出来。新种O. ziyangensis 在笔石枝盘旋方式和胞管形态上与O. spiralis 和Oktavites contortus 均存在一定的相似性,三者共生层位为特列奇阶Spirograptus turriculatus 笔石带至Cyrtograptus lapworthi 笔石带。尽管新种O. ziyangensis 地层延限较长,但胞管的快速演化仍使其具备较强的地层对比意义。根据“深水起源、浅水扩散”的笔石演化模式推测,O. contortus-O. ziyangensis-O. spiralis 的演化过程是笔石在纵向上的生态位占据过程,而O. spiralis 居群形态差别则是笔石深度分带的结果。同时,关于O. spiralis 居群差异的研究,也为讨论弓笔石的起源和分类提供更多的参考依据。 相似文献
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论海南岛地区志留系 总被引：5，自引：3，他引：5
海南岛志留系以往被划分为上、中、下三个统。志留系之上是南好组 ,其层位以往被确定为下石炭统岩关阶 ,并认为它与其下的上志留统足赛岭组呈不整合接触。最近在南好组选层型剖面发现早志留世特里奇期晚期(L ate Telychian)的 Xinanospirifer腕足动物群和三叶虫 L atiproetus cf.latilimbatus (Grabau) ,重新论证了以往被确认为中志留统靠亲山组所产的腕足类、三叶虫和珊瑚化石其实都是特里奇期早至中期的分子。现在以无可争辩的事实证明了久归于下石炭统岩关阶南好组 ,以及其下的、以往被确定为上志留统足赛岭组、中志留统靠亲山组等所谓两个构造层的地层都应改归于下志留统 (L landovery Series)。北区下志留统仅有鲁丹期中期至爱隆期早期的黑色碳质页岩相和泥页岩相沉积 ,未发现任何大化石。南区下志留统发育较全 ,为细至中粗粒碎屑岩相夹碳酸盐岩相沉积 ,产丰富介壳相各门类化石 ;当时该区所生存的动物群与扬子区早志留世的关系非常密切 ,并在早志留世末期与扬子区大部分地区一样上升为陆 ,表明海南岛地区在当时属于扬子地台区范畴。 相似文献
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The later Telychian (late Llandovery, Silurian) sea-level highstand was a suitable setting for global carbonate deposition and reef growth in epeiric seas. However, evidence from the northwest margin of Yangtze Platform indicates that small carbonate platforms developed in rapidly-subsiding small basins and were principally controlled by muddy clastic input. In particular, sediments of the Ningqiang Formation, late Telychian, usually more than 2000 m thick, are mostly shales, but eight major units of discontinuous (15 km maximum width) and relatively thin (120 m maximum thickness) reef-bearing carbonates, which developed when the sedimentation rate apparently lessened, occur within a relatively short time interval. This interval is between upper griestonensis to spiralis-grandis graptolite biozones, estimated as a c. 2 Ma duration. More than 30 small- to medium-scale patch reefs occur in several parts of the sequence, but only within the carbonate units. Shelly faunas common throughout the sequence reveal water depth to have been shallow during deposition of the Ningqiang Formation equivalent to BA2–3, which has a depth range from low intertidal to the base of the photic zone. BA3 is interpreted as being no more than 60 m deep (Boucot, 1975), which is above normal wave base, frequently affected by storms (Chen et al., 1996), and is regarded as optimum depth for high diversity of Silurian faunas (Boucot, 1975; Brett, 1991). Thus, the rate of sediment accumulation kept pace with basement subsidence, and was a substantial factor for limiting reef growth. Sharp contacts between carbonate units and shales indicate that carbonate units are constrained by frequent inputs of terrigenous debris, as the major cause for termination of carbonate deposition. Therefore, carbonate platforms, and reefs they contained, formed during times when sediment input to the basin lessened and ended when it increased; present evidence does not allow correlation to modeled dry episodes, and we interpret the control to be principally tectonic. Overall, sedimentation in the region was terminated by the end of Telychian time by tectonic uplift of the Yangtze Platform; the southwestward migration of palaeocoastline shows this progression. Sedimentation ceased until Middle Devonian time. Ludlow marine transgression has been recognized in the offshore area of Ningjiang Bay. 相似文献
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FU Lipu ZHANG ZifuXi ''an Institute of Geology Mineral Resources Xi ''an Shaanxiand GENG LiangyuNanjing Institute of Geology Palaeontology Chinese Academy of Sciences Nanjing Jiangsu 《《地质学报》英文版》2000,74(2):126-131
This paper divides the Telychian into 7 graptolite zones, 12 subzones and 4 chitinoans in the Ziyangregion, China. The zones and subzones of England are almost totally suitable for the case of Ziyang in China, though they are 10000 km apart. All the above-mentioned biozones are found only in a unitary continuous section in Ziyang. It has been proved that the Ziyang section is the one with the most complete sequence of Telychian graptolite biozones in the world. 相似文献