Genesis of Silica-phosphatic Nodules with Small Shelly Fossils Preserved in the Lowermost Cambrian of South China

Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China, which is correlated to the Fortunian Stage, Terreneuvian Series, Cambrian System. The nodules are rich in small shelly fossils and hence attract the attention of numerous paleontologists and sedimentary geologists. However, the genesis of the nodules and the preservation of the small shelly fossils are poorly understood. Here we analyze morphological, structural, mineralogical and chemical features of the nodules in multiscale using a combination of micro-X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy and confocal laser Raman spectroscopy. Results reveal that nodules are concentric in chemical and mineralogical compositions, comprising a silica-phosphatic core encrusted sequentially by a phosphatic zone, a siliceous zone and a very thin pyrite outer rim. The black shales hosting the nodules demonstrate a laminated texture of alternating clayey and silty laminae, which were respectively deposited in sulfidic/less sulfidic, high/low production, intense/weak chemical weathering conditions. The phosphogenesis of the nodules resulted in the phosphatization of small shelly fossils, which prevented the fossils from being dissolved during diagenesis, whereas the silica encrustation sealed the fossils within the nodules and thus protected the fossils from alteration by deep burial and surface weathering.     

双峰县下寒武统小壳动物化石群

双峰具下寒武统灰绿色板岩、硅质板岩中产大量小壳动物化石,为研究湘中南地区震旦一寒武系界面划分提供了古生物资料。     

Stratigraphic Implications of Skeletal Microfossils from the Cambrian of Korea: A Preliminary Report

Diverse small shelly fossils and other associated fossils were recently recovered from the Cambrian Hanaeri section, southwestern Mungyeong, Korea. The fauna includes conoidal problematica, poriferans (sponge spicules), coeloscleritophorans (chancelloriids), brachiopods, monoplacophorans, trilobite (?) fragments, echinoderms, and conodonts. A preliminary assessment of faunal associations, stratigraphic implications, and the correlation of these skeletal fossils is given, based on occurrences of Actinotheca cf. mira (He), Microcornus sp., Torellela laevigata (Linnarsson), Torellela sp., Archiasterella quadratina Lee, Chancelloria sp., Lingulella sp., Prototreta sp., Phakelodus tenuis (Müller), Phakelodus elongates (An), Hertzina sp., and Furnishina sp.     

Stratigraphic Implications of Skeletal Microfossils from the Cambrian of Korea: A Preliminary Report

Diverse small shelly fossils and other associated fossils were recently recovered from the Cambrian Hanaeri section, southwestern Mungyeong, Korea. The fauna includes conoidal problematica, poriferans (sponge spicules), coeloscleritophorans (chancelloriids), brachiopods, monoplacophorans, trilobite (?) fragments, echinoderms, and conodonts. A preliminary assessment of faunal associations, stratigraphic implications, and the correlation of these skeletal fossils is given, based on occurrences of Actinotheca cf. mira (He), Microcornus sp., Torellela laevigata (Linnarsson), Torellela sp., Archiasterella quadratina Lee, Chancelloria sp., Lingulella sp., Prototreta sp., Phakelodus tenuis (Müller), Phakelodus elongates (An), Hertzina sp., and Furnishina sp.     

湖北宜昌滚子坳剖面寒武系幸运阶顶底界线

对湖北宜昌地区滚子坳剖面寒武系纽芬兰统幸运阶顶底界线的位置进行较为细致的研究.通过切片法及酸蚀法对61个样品进行系统处理,获得了大量的小壳化石、疑源类化石及其他分类位置未定化石.系统鉴定和描述了23属44种.根据具刺疑源类化石Asteridium和小壳化石Protohertzina sp.的首现位置以及无机碳同位素BA...     

新疆阿克苏地区寒武纪幸运期早期小壳化石

本文报道新疆阿克苏地区寒武纪幸运期最早期的小壳化石组合。化石产自玉尔吐斯组底部,包括：Protohertzina anabarica Missarzhevsky, 1973、Protohertzina unguliformis Missarzhevsky, 1973、Anabarites trisulcatus Voronova and Missarzhevsky, 1969、Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Cambrotubulus decurvatus Missarzhevsky in Rozanov et al., 1969、Olivooides sp.、Kaiyangites novilis Qian and Yin, 1984以及海绵骨针化石。据此可以在新疆阿克苏地区玉尔吐斯组下部建立Anabarites trisulcatus-Protohertzina unguliformis组合带。该组合带下界以Anabarites trisulcatus、Protohertzina ungulifo...     

黔中寒武纪梅树村期磷块岩中小壳动物化石结构和成分：对生物成磷的制约

小壳动物化石微结构及壳体成分的认知对于揭露寒武纪早期小壳动物群的演化具有重要意义,黔中地区早寒武世梅树村期磷块岩中保存了大量的小壳化石,为了获取该时期小壳化石微结构及成分的关键信息,本文利用电子显微镜、扫描电镜对岩石薄片小壳化石个体进行观察、分析,获得了贵州织金熊家场和清镇落夯地区的寒武纪梅树村期磷块岩中小壳动物化石微结构、壳体成分特征。结果显示,织金、清镇地区的磷块岩中小壳化石多样性与其壳体成分表现一致,主要为软舌螺类,其成分为P、Ca、F、O等氟磷灰石组成元素;小壳化石壳体保存有明显的纳米级磷灰石矿化颗粒骨架、多圈层结构、溶蚀多孔隙和管体嵌套的现象。另外,通过电子探针对小壳化石进行原位微区元素面扫描,发现主要元素P、Ca分布在小壳化石及小壳化石碎片中,胶结物几乎不含P元素。综合判断,两个研究区域的寒武纪梅树村期磷块岩小壳动物化石多为异地埋藏保存,且保存过程中,成岩作用等后期磷酸盐化、搬运沉积对小壳化石微结构及其壳体成分产生一定改造影响;基于薄片全玻面扫描推断全岩小壳动物化石(含化石碎片)含量,与磷块岩中磷含量呈正相关关系,认为寒武纪梅树村期小壳动物的繁盛对同期磷块岩的形成具有重要贡献。     

Trace Fossils from Lower Cambrian Wusongger Formation in Xiaoerbulake Outcrop,Kalpin Area,Xinjiang

Based on the analysis of trace fossils collected from the typical outcrop of the Lower Cambrian Wusongger Formation in the Kalpin area, ten ichnospecies of six ichnogenus were identified in the upper member of the Wusongger Formation, with most of them being found for the first time. The trace fossils are described seriatim. The ichnospecies are mainly represented by such common trace fossils as Ophiomorpha nodosa, Helminthopsis hieroglyphica, Helminthopsis ichnosp., Planolites beverleyensis, Planolites vulgaris, Planolites montanus, Palaeophycus striatus, Palaeophycus curvatus?, Cochlichnus anguineus and Rituichnus elongatum. The trace fossils are of high diversity and low abundance, and can be diagnosed as the Cruziana ichnofacies. They can be interpreted as having formed in a shallow water environment.     

贵州台江早—中寒武世凯里组的宏观藻类化石

本文描述了贵州寒武纪凯里组中的宏观藻类化石７属１２种,其中有６个新属１０个新种;Ｂｏｓｗｏｒｔｈｉａ ｓｉｍｕｌａｎｓ,Ｂ．ｇｙｇｅｓ,Ｅｏｌａｍｉｎａｒｉａ ｇｒａｎｄｉｓ ｇｅｎ。ｅｔ ｓｐ．ｎｏｖ。,Ｅ．ｐｅｒｅｌｅｇａｎｓ ｇｅｎ。ｅｔ ｓｐ。ｎｏｖ．,Ｆ．ｖｅｉｎ ｇｅｎ．ｅｔ ｓｐ．ｎｏｖ．,Ｋａｉｌｉｐｈｙｔｏｎ ｓｉｍｕｌａｎｓ ｇｅｎ．ｅｔ ｓｐ．ｎｏｖ．,Ｐａｌａｅｏｓｐｉｎｅ     

贵州遵义寒武系底部硅质岩中细菌状化石的发现

通过扫描电镜精细观测,在贵州遵义松林地区早寒武世黑色岩系剖面,于其底部的硅质页岩中发现了可能的细菌状化石,直径200～500 nm,形态不一,具有细菌的大小和形状,有机碳含量丰富,大部分细菌含磷.通过与已有报道中具相似形态生物体的对比,认为其可能是原生的、具有细菌生物结构的微生物小球体(Microbioids),本文称之为细菌状化石.这类细菌状化石可以赋存于石英颗粒表面、石英颗粒间,甚至嵌入石英颗粒中.据前人的模拟实验推测,细菌在石英颗粒沉淀过程中可能起到过重要促进作用,这从微观上为硅质岩的形成提供了新信息.     

The Brine Origin of Cambrian in Tianba County,Chongqing City,China

正1 Introduction Tinba salt factory in Wuxi county was founded in the early seventies,under the background of salt demand being in shortage in Sichuan mountain aera,which were     

Early Cambrian radiation of brachiopods: A perspective from South China

Brachiopods, a group of benthic suspension-feeding marine invertebrates, made their first appearance in the Lower Cambrian. In the Yangtze Platform (South China), well-exposed Lower Cambrian stratigraphic succession represents shallow to deeper water environments. Strata from eastern Yunnan, southern Shaanxi and the Yangtze gorges areas of western Hubei Province, deposited in muddy-siltstone and carbonate lithofacies, contained an abundant variety of brachiopods, including all the representatives of the subphylum Linguliformea and the calcareous-shelled genera of Kutorgina and Nisusia from the subphylum Rhynchonelliformea. Thus the fossil assemblage bears witness to the first major phase of evolutionary radiation of brachiopods during the ‘Cambrian explosion’ interval of metazoans. Brachiopods from the celebrated Chengjiang fauna have exquisitely preserved soft-tissues, which reveal the body plans and evolutionary acquisition of morphological novelties of the early stocks, and also provide a good opportunity for testing the analogies with the stem groups from the extant representatives. These fossils have corroborated the view that brachiopods developed complex organization of tissues, and achieved considerable evolutionary success already by the onset of ‘Cambrian Explosion’. Thus it is not improbable that a large part of this radiation occurred within, or only just before early Cambrian time. Studies of Chengjiang brachiopods suggest that attachment by a pedicle to the substrate was probably the most common relationship of Cambrian brachiopods with the substrate where they inhabited.     

Tommotian (Lower Cambrian) stratigraphy and fossil fauna communities in the Kiya River section (Kuznetsk Alatau)

The lower Ust’-Kundat Formation has been studied in detail in a section along the Kiya River (Kuznetsk Alatau, Altai-Sayan folded area). The section was deposited during the Tommotian stage and is a stratotype for the Lower Cambrian Ust’-Kundat sequence comprising several members of the Ust’-Kundat Formation. Member 2 contains newly discovered and previously known species of archaeocyathids near its top found stratigraphically lower than the oldest known archaeocyathan assemblage of the Nochoroicyathus mariinskii biozone. The found archaeocyaths cannot be dated precisely and may have either Tommotian or Atdabanian ages. Small shelly fossils from the same section cover a large stratigraphic range as well. The findings call for updating the age of the upper Ust’-Kundat sequence and the Tommotian upper boundary in the regional stratigraphy of the Altai-Sayan folded area.     

A New Arthropod, Guangweicaris Luo, Fu et Hu gen. nov. from the Early Cambrian Guanshan Fauna, Kunming, China

The Guanshan Fauna is a soft-bodied fauna dominated by arthropods （including trilobites, trilobitoides, Tuzoia, Isoxys, and bradorids） in association with priapulids, brachiopods, anomalocaridids, vetulicoliids, sponges, chancellorids, and echinoderms. This paper reports and describes a new arthropod from the yellowish green mudstone at the lower part of the Wulongqing Formation, Canglangpuan Stage, Lower Cambrian in Kunming, Yunnan, China. The stratigraphic and geographic distribution, classification, fossil preservation, life style of this new arthropod and comparisons with other fossil arthropods are also discussed in details. The discovery and research of the non-mineralized arthropod, Guangweicaris Luo, Fu et Hu gen. nov. from the Guanshan Fauna adds new members to the taxonomic list and provides new information to the evolution of early arthropods. Furthermore, this study would shed new light into the ＂Cambrian Explosion＂ and the evolution of early life.     

三峡地区寒武系纽芬兰统岩家河组小壳化石研究进展

埃迪卡拉纪—寒武纪转换时期小壳化石的突然出现是世人瞩目的重要演化事件之一,它见证了动物的爆发式快速演化过程,标志着以两侧对称动物为特征的寒武纪生态系统的开始。湖北三峡地区寒武系纽芬兰统岩家河组处于幸运阶—第二阶这一关键层段,是研究上述问题的理想地区之一。岩家河组小壳化石研究最近取得的进展,为寒武系纽芬兰统幸运阶/第二阶界线的标定,和寒武纪早期软体动物和刺胞动物的演化及个体发育提供了重要的化石依据,本文对其进行了总结。全球界线层型剖面和点位(GSSP)寒武系第二阶底界划分标志的Watsonella crosbyi和Aldanella attleborensis在岩家河组第5段底部的同时出现,意味着岩家河组第5段已归属寒武系第二阶。这两类软体动物化石均广泛分布于华南、蒙古、西伯利亚和北美等大陆碳酸盐岩相寒武系第二阶地层中,它们均是定义寒武系第二阶底界的有力竞争者。另外,W.crosbyi壳顶下方一对肌肉附着结构的发现提供了重要的软组织结构信息,证实了W.crosbyi为内腹型壳,归属为未扭曲的软体动物太阳女神螺类。新发现六方锥石类Septuconularia yanjiaheensis具侧向压扁、两辐射对称的、14个等大锥面的围鞘,是迄今所描述的六方锥石类中锥面数最多的类型。根据横肋疏密程度,围鞘由下向上可分为三部分,可能代表胚胎期、幼年期和成年期不同的生长阶段。Septuconularia显然由寒武系幸运阶Hexaconularia通过扇面扩增演变而来,证明Hexaconularia可能是Arthrochites和Septuconularia之间的中间过渡类型。新发现的橄榄蛋类Octapyrgites elongatus与幸运阶Olivooides和Quadrapyrgites十分相似,围鞘由方形的壳顶区和波纹状倒宝塔形的远顶区组成。然而Octapyrgites只有8个口折叶,有别于具12个口折叶的Quadrapyrgites。通过与幸运期水母类多种对称方式对比,发现在寒武系第二阶橄榄蛋类数量减少和五辐射对称骨状壳类缺失,表明在幸运期/第二期转换时期,底栖固着型的刺胞动物水母类多样性发生了明显衰落,甚至部分绝灭,而同期的两侧对称动物则迅速辐射演化。     

豫西登封地区寒武系张夏组中部生物扰动构造及其地质意义

掘穴生物作为生态系统工程的建造者,其对沉积物进行的改造直接影响了沉积物的物理化学性质,进而影响了底栖生态系统。豫西登封地区寒武系苗岭统张夏组中部薄层微晶灰岩中发育大量的生物扰动构造,利用地球生物学、古生物学和生物扰动指数等方法,探讨了生物扰动构造的形成环境及其对沉积物的影响。研究表明,研究区张夏组中部生物扰动构造特征多为扰动边界模糊不清,生物扰动指数（BI）为2 ~ 5,说明该沉积期食物充足,氧气含量高。此外,在生物扰动中识别出3种遗迹化石：Thalassinoides bacae,Planolites isp.和Rhizocorallium isp.,说明生物扰动构造为多种生物造迹形成的。依据寒武系苗岭统张夏组中部的遗迹化石以及沉积特征,可知其整体处于偶尔受到风暴影响的滩间局限台地环境。     

Pediculate Brachiopod Diandongia pista from the Lower Cambrian of South China

The Chengjiang Lagerstatte has been celebrated for prolific soft-bodied fossils. Based on specimens recently excavated in the Chengjiang Lagerstatte by the Early Life Institute, Northwest University, Diandongia pista Rong, 1974, is directly revealed to be a pediculate brachiopod, assigned to the Family Botsfordiidae, as is further confirmed by the exceptionally preserved vascular system including dorsal and ventral mantle canals. These specimens described herein exhibit some peculiarities, notably the extremely thin and long pedicles, which suggest that Diandongia is epifaunal rather than burrowing brachiopod. A study of this group of animals indicates that they may be vital to understand the relationship between the lingulids and the remaining brachiopods, and the character evolution of the early Cambrian brachiopods.     

一个典型的寒武系油藏:塔里木盆地塔中62井油藏成因分析

塔里木盆地志留系沥青砂岩广泛发育,主要原因是来源于寒武系的原油在进入志留系储层后区域性的抬升剥蚀使油藏遭到严重破坏,但到目前为止,究竟是寒武系烃源岩还是中上奥陶统烃源岩或是两者都对现今的志留系沥青砂岩中的有机质有贡献还不清楚.对塔中62井原油的化学组成和油源的分析表明,其甾萜类组成具有寒武系烃源岩的组成特征,反映该油藏原油主要来源于寒武系.另一方面,塔中62井砂岩透镜体被泥岩圈闭,油藏具有较好的保存条件,且后期中上奥陶统生成的烃类难以充注进入油藏.塔中62井志留系油藏破坏作用较弱、保存较好,是塔里木盆地在志留系发现的第一例来源于寒武系的油藏.