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1.
The genus Arthricocephalus Bergeron, 1899 is revised, and Halipanktos Balker & Peel, 1997 is suggested here as a senior synonym. The subgenus Arthricocephalus (Arthricocephalites) Chien & Lin in Lu et al., 1974 is considered as a separate genus. Of the 20 previously assigned species of Arthricocephalus (Arthricocephalus) Bergeron, 1899, Arthricocephalus (Arthricocephalites) Chien & Lin in Lu et al., 1974, Arthricocephalus (Euarthricocephalus) Ju, 1983 are lumped into eight species. The speciation trend of Arthricocephalus and Arthricocephalites is demonstrated based on their stratigraphic occurrences. It not only enhances the resolution of the biostatigraphic zonation in the uppermost Lower Cambrian, but also represents a potential candidate to define the Duyunian stage. The base of the stage is suggested at the first appearance datum (FAD) of Arthricocephalus chauveaui Bergeron, 1899 within the evolutionary lineage from Ar. jiangkouensis Yin in Yin & Li,1978 to Ar. chauveaui in a global scale. 相似文献
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The genus Arthricocephalus Bergeron, 1899 is revised, and Halipanktos Balker & Peel, 1997 is suggested here as a senior synonym. The subgenus Arthricocephalus (Arthricocephalites) Chien & Lin in Lu et al., 1974 is considered as a separate genus. Of the 20 previously assigned species of Arthricocephalus (Arthricocephalus) Bergeron, 1899, Arthricocephalus (Arthricocephalites) Chien & Lin in Lu et al., 1974, Arthricocephalus (Euarthricocephalus) Ju, 1983 are lumped into eight species. The speciation trend of Arthricocephalus and Arthricocephalites is demonstrated based on their stratigraphic occurrences. It not only enhances the resolution of the biostatigraphic zonation in the uppermost Lower Cambrian, but also represents a potential candidate to define the Duyunian stage. The base of the stage is suggested at the first appearance datum (FAD) of Arthricocephalus chauveaui Bergeron, 1899 within the evolutionary lineage from Ar. jiangkouensis Yin in Yin & Li,1978 to Ar. chauveaui in a global scale. 相似文献
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δ13Ccarb and Ceanom excursions in the post-glacial Neoproterozoic and Early Cambrian interval in Guizhou,South China 总被引:2,自引:0,他引:2
Secular δ 13Ccarb and Ceanom profiles in the post-glacial Neoproterozoic and Early Cambrian interval are reported from Guizhou on the southeasten border of the Yangtze platform, South China. Overall, the δ 13Ccarb profile drifts to negative values in the post-glacial Nantuo and lower to middle Doushantuo Formations, and then to positive values in the upper Doushantuo and Dengying Formations of Neoproterozoic, followed by negative values in the Lower Cambrian Gezhongwu and Niutitang Formations. A detailed investigation of the relationship between the δ 13Ccarb and Ceanom profiles reveals that the main anoxic and oxic episodes are coupled with negative and positive δ 13Ccarb values, respectively. This may suggest a control of alternation between ocean stratification and mixing on variations in 13C abundance in the ancient ocean of the investigated areas. 相似文献
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Plankton from Early Cambrian black shale series on the Yangtze Platform, and its influences on lithologies 总被引:2,自引:0,他引:2
Blackshalesandcherts ,containingnodularphosphoritesandorelayers[1] arecommonintheEar lyCambriandeeperwaterfaciesoftheYangtzePlat form[2 ] andoffera goodchanceformicropaleonto logicalresearchusingtechniquesofchemicaldissolu tion ,peelingandsectioning .Wetriedtoseparateandinvestigateoceanicplanktoncommunitiesfrombitu minous,“deeperwater”chert ,blackshale andphosphoritelithologies ,andtodocumenttheirpreser vationandinfluencesonthecompositionofthesedi ments .Thepresentpaperaimsatgivingareportof… 相似文献
6.
HANJian SHUDegan ZHANGZhifei LIUJianni 《科学通报(英文版)》2004,49(17):1860-1868
The taxonomy of an early ancestor of Recent Priapulidae, Xiaoheiqingella peculiaris (= Yunnanpriapulus halteroformis Huang et al., 2004) from the Early Cambrian Chengjiang fossil Lagerstaette, is revised. Morphological characters comprise a pair of caudal appendages rather than a single appendage flanking the trunk end and a possible urogenital duct found inside the preanal region. An additional extremely rare fossil priapulid worm, Paratubiluchus bicaudatus gen. nov., sp. nov. is also described herein. Its diagnostic characters are: an introvert bearing 25 longitudinal rows of scalids, a distinct neck region, no annulus on the oval trunk, and a pair of caudal appendages. The proportion of body parts is similar in size to that of loricate larvae of Recent priapulids and larva-formed Palaeopriapulitidae. Taking account of the features of Xiaoheiqingella, bicaudal appendages are considered to be a synapomorphy of Priapulidae and Tubiluchidae. Paratubiluchus gen. nov. is most likely a candidate for the ancestor of the Tubiluchidae; it probably originated from a larva-formed priapulid with 25 rows of scalids, thus representing an intermediate link between the priapulids in mature-form and the priapulids with lorica. 相似文献
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A new Chengjiang-type fossil assemblage is reported herein from the lower part of the Hongjingshao Formation at Xiazhuang village of Chenggong,Kunming,Yunnan.The fossil assemblage,named as Xiazhuang fossil assemblage,yields predominantly soft-bodied fossils,including arthropods,brachiopods,priapulids,lobopods and some problematic taxa,with arthropods being the most dominant group.Preservation and composition of the fossil assemblage are very similar to the typical Chengjiang biota,which is preserved in the middle Yu’anshan Formation in the large area of eastern Yunnan.The associated trilobites demonstrate that the soft-bodied fossil assemblage belongs to the late Qiongzhusian in age(Stage 3,Cambrian),suggesting that the Hongjingshao Formation is probably a diachronous lithostratigraphic unit ranging from the upper Qiongzhusian to the lower Canglangpuan stages in eastern Yunnan.The fossil assemblage from the Xiazhuang area fills up the missing link between the typical older Chengjiang biota and the younger Malong and Guanshan biotas,making eastern Yunnan a unique area in the world to reveal the early evolutionary history of animals and palaeocommunity dynamics during the‘‘Cambrian explosion’’. 相似文献
8.
Stable isotopic geochemistry of organic carbon and pyrite sulfur from the Early Cambrian black shales in Northwestern Hunan, China 总被引:4,自引:0,他引:4
The early Cambrian black shale sequence in Northwestern Hunan Province has been investigated for its stable isotopic geochemistry of organic carbon and pyrite sulfur. The relatively low δ 13C values of organic matter, -29.7‰~-34.2‰, are interpreted as caused by the high CO2 concentration in atmosphere/ocean and an anoxic depositional environment in early Cambrian. Variable, but significantly positive δ 34S values, 10.2‰~ 28.2‰, for sedimentary pyrite reveals bacterial sulfate reduction as the pyrite-forming process but under sulfate-limited conditions. A protected anoxic basin, which had very limited access to open ocean, and its sediments, where metabolizable organic matter was rich and bioturbation was absent, are supposed to be the sulfate-limited environments and might have existed in South China in the early Cambrian. 相似文献
9.
YANG Jinghong JIANG Shaoyong* LING Hongfei FENG Hongzhen CHEN Yongquan CHEN Jianhua 《自然科学进展(英文版)》2004,14(2)
TheLowerCambrianblackshalesequenceoccursinSouthChinaalonganarc parallellinearbeltex tendingmorethan 16 0 0km .Theseorganic richblackshalesformedinvariousmarineenvironmentsandtypicallycontainhigheramountsofmolybdenum ,nickel,vanadium ,andanumberofothereconomical lyimportantmetalsthandoanyothersedimentaryrocks[1,2 ] .Therefore ,thestudyoftheseblackshaleshasnotonlypaleoceangraphicimplicationbutalsoe conomicsignificance .Marinesedimentssuchasblackshalearecom plexmixturesofdetritalphasesandseawat… 相似文献
10.
清末民初是中国政治近代化进程中的一个重要阶段。以往学界过多关注留日生对这一进程的推动作用,事实上留美生的作用也不容忽视。留美生在清末民初的政坛上占据了重要地位,他们在推进官僚政治的革新及资产阶级民主共和政体的建立方面发挥了重要作用。由于中国近代政治环境的恶劣及其自身的"美国化"倾向,留美生对中国政治近代化的推动又带有很大的局限性。 相似文献
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预测四川盆地覆盖区的中下寒武统优质膏质岩盖层的分布,为油气勘探提供依据.通过石膏露头细测、野外剖面实测与钻录井分析的方法,发现四川盆地南部的雷波县沙坪子西王庙组((C)2x)、火草坪龙王庙组((C)l)2个中下寒武统石膏露头点,膏质岩层出露6层,厚度>21.5 m.描述了甘洛县黑马中寒武统大鼻山组((C)2d)石膏露头共5层,厚度>18.5 m.同时,窝深1井也揭示中下寒武统膏质岩层,在抓抓岩与乐山范店实测剖面上发现了可与石膏露头、钻井类比的膏溶角砾岩.研究表明,雷波—甘洛石膏露头区发育内缓坡相、蒸发岩台地(或塞卜哈)、局限台地相湖间坪亚相与潟湖亚相的石膏岩与膏溶角砾岩沉积,它们与泥晶白云岩或 相似文献
12.
江西修武盆地下寒武统黑色页岩矿物成分特征及意义 总被引:3,自引:0,他引:3
以江西修武盆地下寒武统王音铺组、观音堂组黑色页岩为研究对象,通过对野外剖面样品和钻井取心样品定性和定量分析,研究修武盆地下寒武统页岩气储层矿物成分特征,结果表明,王音铺组、观音堂组黑色页岩矿物成分以黏土矿物和石英为主,石英的平均质量分数为58.63%,黏土矿物平均为25.4%。其次为方解石,平均为51.46%,另外还含有较高的长石和黄铁矿,平均质量分数分别为2.5%和4.68%。其余矿物如方解石、白云石、(硬)石膏等含量较少,平均质量分数5%。这种矿物成分组成与Barnett页岩及龙马溪组页岩既有相似性,又有差异性。修武盆地下寒武统页岩矿物组分所反映的沉积环境、有机质演化及黑色页岩储集意义表明,该套页岩石英的质量分数50%的泥(页)岩厚度接近50m,是理想的页岩气勘探开发层位。 相似文献
13.
剑河八郎松山寒武系黔东统都匀阶清虚洞组主要由泥岩、灰岩组成,下部以灰岩为主,上部为泥岩、灰岩互层,顶部为中层白云岩.上部含有大量的莱德利基虫类、耸棒头虫类和褶颊虫类三叶虫及带软躯体动物多门类化石.本文报道的拜如尼亚虫Byronia Mathew,1899产于清虚洞组中部及中上部,分异度低,仅1属1相似种,即原生拜如尼亚虫(相似种)Byronia cf.annulata Liu,1986.原生拜如尼亚虫(相似种)Byronia cf.annulata化石保存较好,管壁保存有横脊.剑河八郎松山清虚洞组的拜如尼亚虫是贵州杷榔组和凯里组之后另一个产出层位,它的发现不仅丰富了清虚洞组生物群的组成,同时亦为贵州乃至全球寒武系拜如尼亚虫Byronia的演化、埋藏特征等研究提供了新的素材. 相似文献
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青藏高原西部燕山晚期花岗岩地球化学特征及其大地构造意义 总被引:1,自引:0,他引:1
对青藏高原西部燕山晚期花岗岩进行了地质、地球化学综合研究。结果表明 ,燕山晚期早白垩世花岗岩为 I型 ,形成于火山弧环境 ,岩石组合为石英二长闪长岩 -花岗闪长岩 -二长花岗岩 ,岩石系列为高钾钙碱性系列 ,A/ CNK<1,稀土元素含量中等 ,并且属轻稀土富集型 ,铕亏损不明显 ,L IL E有选择地得到富集 ,HFSE相对亏损 ;晚白垩世花岗岩为 S型 ,形成于同碰撞环境 ,岩石组合为二云母二长花岗岩 -二云母花岗岩 ,岩石系列为高钾钙碱性系列 ,但 A/CNK>1.1,稀土元素含量较低 ,铕亏损明显 ,微量元素中以 Rb和 F含量高为显著特征。为研究喀喇昆仑山构造演化提供了限定条件 相似文献
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Yuanlong Zhao Jinliang Yuan Shanchi Peng Loren E. Babcock Jin Peng Qingjun Guo Jihpai Lin Tongshu Tai Ruidong Yang Yuxian Wang 《自然科学进展(英文版)》2008,18(12)
A trilobite biostratigraphic study of a new section of the Kaili Formation at Jianshan,Chuandong Village,Jianhe County,Guizhou is reported.Additional occurrences of key species associated with the Ovatoryctocara granulata-Bathynotus holopygus Zone and the overlying Oryctocephalus indicus Zone that were originally defined from the trilobite assemblages at the Wuliu-Zengjiayan section of the Kaili are reported from this new section.The first appearance datum (FAD) of Oryctocephalus indicus occurs at the 44.52 m above the base of the unit.Based on study of abundant specimens (n = 800) from the Kaili Formation,we argue that Oryctocephalus indicus is a widespread taxon with a global distribution.O.Reticulatus (Lermontova,1940) from the middle part of the Kounamkites Zone of the Amganian Stage in the Molodo River region of Siberia and O.Americanus (Sundberg and McCollum,2003) from Nevada,North America are similar to representatives of O.Indicus which occur in the O.Indicus Zone of the Kaili Formation.O.Reticulatus and O.Americanus are here synonymized with O.Indicus (Reed,1910).This study strengthens the Wuliu-Zengjiayan section of the Kaili Formation as a candidate section for a Global Stratotype for the base of the unnamed Cambrian Series 3. 相似文献
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页岩气成藏体系研究——以四川盆地及其周缘下寒武统为例 总被引:1,自引:1,他引:1
页岩气是非常规天然气藏的一种,属于"单源一位"成藏体系,在成藏特征上不同于常规油气,集烃源体、输导体和圈闭体等所有关键的成藏体系各要素于同一套页岩层.在成藏体系的划分上,页岩气藏不同于常规成藏体系的划分.综合考虑页岩层系发育时代、沉积特征、演化历史、所处现今大地构造位置、构造特征、页岩残留状况、分布特点、埋深和含气量等因素,提出了页岩气成藏体系划分的一般性原则.将四川盆地及其周缘下寒武统页岩气成藏体系划分为川南—川东南、黔北—黔中、渝东、湘鄂西、龙门山、米仓山—大巴山和川中7个成藏体系,并按战略展开区、战略突破区、战略准备区和战略远景区4个层次对成藏体系进行了评价,明确了勘探层次. 相似文献
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分布在博格达山东段北缘的花岗岩类,侵入于早石炭世玄武岩及酸性火山碎屑岩中,具较高的Si(w(SiO_2)=69.50%~71.40%),低Mg(w(MgO)=0.82%~1.10%)和Al(w(Al_2O_3)=13.89%~14.30%),w(K_2O)/w(Na_2O)=0.73~0.83,w(Al_2O_3)/(w(K_2O)+w(Na_2O)+w(CaO))=0.98~1.10,显示花岗岩为准铝质Ⅰ型花岗岩.岩石富集K,Rb,Ba,Th,U及LREE(w(La)/w(Yb))_N=5.69~7.72,亏损高场强元素(Nb,Ta,P,Ti)和Sr,具弱Eu负异常(δEu=0.81)和较低的占δ~(18)O(6.08‰),以及低w(Sr)(158×10~(-6)~169×10~(-6)),w(Yb)(2.09×10~(-6)~2.85×10~(-6)),w(Y)(17.00×10~(-6)~23.60×10~(-6))和MREE略亏损(Ho_NYb_N)的地球化学特征.推断研究区花岗岩源于先前形成的底侵玄武质岩石(新生地壳)受热发生重熔作用,源区存在有限的角闪石+斜长石+辉石残留,形成于陆内裂谷环境,其动力学机制应与石炭纪克拉麦里蛇绿岩带或康古尔塔格碰撞带所代表的古大洋消减引起的陆内拉张作用有关. 相似文献
19.
LIU Jianni SHU Degan HAN Jian ZHANG Zhifei Early Life Institute & The Key Laboratory of Continental Dynamics Northwest University Xi''''an China School of Earth Sciences Resources China University of Geosciences Beijing China Correspondence should be addressed to Shu Degan 《科学通报(英文版)》2004,(10)
The origin of arthropods has long been one ofthe most hotly-debated subjects. Arthropods used to bethought closely related with annelids, but the two groups arenow believed to be separated into two major realms withinProtostomia on the basis of new molecular data. Although itis generally held by paleontologists that arthropods should berooted in the early lobopods--a kind of worm-like creaturewith non-segmented legs, no intermediate forms have beenfound to bridge them. Here we report an organism with amixture of characters, including features characteristic ofarthropods (e.g., primary cephalization with paired eyes,paired antennae, and preliminary tagmosis) and of lobopods(e.g., worm-like body design, the dorsal spines, andnon-segmented Iimbs or lobe-like legs). The discovery of therare transitional form may throw new light on the origin ofarthropods and suggests that the most primitive arthropodsbegan with paired uniramous legs and the biramous onesevolved later. 相似文献
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贵阳乌当地区湄潭组下段化石丰富,笔石、腕足类最为常见.腕足类计有10属10种,分属于4目5超科6科,具明显的多样性,其中Sinorthis数量最多,乌当湄潭组下段的腕足动物组合属于Sinorthis动物群.该段地层腕足动物的研究提供了黔中地区早奥陶世腕足动物辐射演化的新信息,也为整个奥陶纪生物辐射演化的研究积累了资料. 相似文献