云南东部震旦系—寒武系边界层的遗迹化石和遗迹相

本文介绍了国际前寒武系-寒武系界线层型候选剖面所在地的滇东地区震旦系-寒武系边界层中新发现的遗迹化石娄型及新的化石层位,根据生物相和沉积相的综合分析将本区划分为3个沉积相区和Skolithos,Cruziaua,Cuziaua-Zoophycus 3个遗迹相带,最后讨论了遗迹化石在划分震旦系-寒武系界线上的意义。     

四川峨眉高桥震旦系——寒武系界线

四川峨眉高桥震旦系—寒武系界线剖面构造简单,沉积连续,化石丰富,是我国研究震旦系与寒武系界线重要剖面之一。本文系统地介绍了峨眉山地区震旦系—寒武系的研究历史,剖面详细分层及岩性和生物特征。论述了本区晚震旦世至早寒武世初期沉积环境的变迁、生物演化及震旦系—寒武系界线划分。本文以首次多门类带壳动物的大量出现作为划分震旦系与寒武系界线的主要依据。寒武系的下界划分在麦地坪组下部以小壳动物Anabarites—Circotheca为代表的化石组合的底界上,并与国内外相当时代的地层及界线进行了对比。     

下寒武统宽背虫(Bathynotus)的灭绝过程——以贵州剑河八郎凯里组的Bathynotus kueichouensis为例

宽背虫(Bathynotus)这一传统早寒武世或寒武纪第2世晚期最重要的三叶虫属,广泛分布于全球寒武纪3个生物大区,为区域地层对比的标准化石.Bathynotus在贵州剑河八郎乌溜-曾家崖剖面凯里组下部极为丰富.该剖面已成为全球寒武系第2统和第3统界线层型候选剖面,表明凯里组是一个穿时的地层单元,其3个三叶虫带最下部一个带为Bathynotus holopygus-Ovatoryctocara granulata.经过逐层大量的化石标本采集统计证实,乌溜-曾家崖剖面宽背虫(Bathynotus)在距凯里组底部51.60 m处骤然绝灭,距寒武系第2统的顶界(距凯里组底52.80 m)只有1.20 m.本文就乌溜-曾家崖剖面凯里组下部宽背虫(Bathynotus)的数量分布变化认为其灭绝过程是逐步的.     

四川西部峨眉、甘洛等地震旦纪晚期——寒武纪早期的遗迹化石

四川西部峨眉、甘洛等地是我国研究震旦系与寒武系界线重要地区之一。近年来,通过在本区开展系统的界线研究工作,在寒武系最低三叶虫层位以下,至寒武系底界附近,不仅发现了门类多、数量丰富的小壳动物化石,而且在不同地区相当的层位中发现了多种多样的遗迹化石(见表1)。二者从寒武系底部向上平行发展,为地层的划分对比和沉积相的分析提供了可靠依据,同时为该时期后生动物的发展和演化提供了丰富的资料。     

陕西南郑、西乡一带的寒武纪地层

该文叙述了陕西南郑、西乡一带寒武系四条剖面的岩性及三叶虫动物群,根据岩性及三叶虫动物群的性质,将这两个地区的寒武系划分为两个统五个组:即中寒武统的陡坡寺组,下寒武统的孔明洞组、阎王碥组、仙女洞组及郭家坝组。并分别相当于滇东中寒武统的陡坡寺组和川北下寒武统的孔明洞组、阎王碥组、仙女洞组及郭家坝组。     

江苏省句容县崙山地层新知

崙山是我国研究地层最早的地区之一,是长江下游下奥陶统崙山组的命名地,也是宁镇地区重要的下古生界出露地区。我们到崙山工作(1976)之前,已知最老的地层为上寒武统观音台组。通过两年的工作,地质系师生发现了重要的三叶虫等化石及葡萄状等牛物沉积结构,证实崙山还有更老的下寒武统和上震旦统存在,并且作了如下划分:     

湖南花垣中寒武世晚期开腔骨类化石

记述了湖南花垣县排碧剖面寒武系花桥组上部灰岩中的开腔骨类化石。40余块形态多样的化石标本,包括具6-7+1型的Chancelloria altaica;4＋0型Archiasterella sp.;和3＋0型Allonnia sp.;以及形态奇特的开腔骨针Chancelloria sp.,与三叶虫、牙形石、腕足动物、软舌螺类等共生,时代属中寒武世晚期。与其他研究比较证明,这是迄今我国中寒武世晚期开腔骨类最高产出层位,也是世界上少数几个开腔骨类较高的产出层位之一。通过对开腔骨类骨片构造、保存环境及其地史地理分布的分析,认为开腔骨类是一类与海绵类有密切关系、已绝灭的后生动物,是一类生活于浅海环境的底栖固着型生物。     

苏皖北部晚前寒武纪倪园组微体化石的新发现

苏皖北部上前寒武系发育良好,生物化石比较丰富,加之在大地构造上又处于中朝地台的东南缘,目前已成为解决我国南北上前寒武系对比和衔接的关键地区之一。为了进一步对苏皖北部上前寒武系进行深入研究,1981年夏我们和江苏省区测队、南京地质矿产研究所共同对徐淮地区上前寒武系剖面,进行了详细考察和系统采样。在徐淮地区,上前寒武系厚达4200米,以不整合覆于泰山群片麻岩之上,与含三虫叶的猴家山组(下寒武统)则呈平行不整合接触。根据苏皖两省地质局的工作成果,该区上前寒武系由下而上可划分为13个组,即兰陵组(八公山组)、新兴组(刘老碑组)、岠山组(寿县组)、贾园组、赵圩组、倪园组、九顶山组、张渠组、魏集组、史家组、望山组、金山寨组     

我国是全球地层“金钉子”最多的国家

2011年7月9日,国际地质科学联合会(下称"国际地科联")执行委员会通过了国际地层委员会提交的我国寒武系江山阶底界为全球标准层型剖面点位(俗称"金钉子")的议案,并由国际地科联主席李卡迪(Riccardi)教授签署批准。这是位于中国的第10枚"金钉子",它的确立使我国成为拥有全球地层"金钉子"最多的国家。这枚"金钉子"位于浙江省江山县礁边村附近,层型剖面(礁边村B剖面)点位就在晚寒武世晚期江山阶底界,即以三叶虫化石——东方拟球接子     

内蒙古自治区向阳盆地地球化学异常晕解析

1．区域地质 1．1地层 向阳盆地位于内蒙古自治区额右旗,本区地层区划属天山-兴安岭地层区伊勒呼里分区额尔古纳小区。出露地层从老到新有古生界寒武系、奥陶系、志留系、石炭系,中生界侏罗系,新生界第四系。古生界地层分布于额尔纳河东侧一带,出露面积较小,其中以寒武系出露为主．这套地层应属滨河-浅海相沉积,为中浅变质的区域变质岩。奥陶系应届浅海相沉积,为连续的海进层序。志留系的浅海相碎屑岩、     

Skara hunanensis a new species of Skaracarida (Crustacea) from Upper Cambrian (Furongian) of Hunan, south China

The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world, but it was not until 2005 that the Orsten-type fossils represented by Skaracarida and Phosphatocopida were first reported to be found in western Hunan, South China. Here, we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaracarida. They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section, western Hunan, south China, assigned to a new species Skara hunanensis herein. Skara hunanensis is characterized by small, soft-integumented, marine forms with slender, annulate body; labrum large and ventrocaudally directed; uniramous antennulae; biramous antennae and mandibulae; maxillas and maxillipeds of the same shape; all postantennular limbs join a short cephalic filter apparatus. The body has two tagmata: a cephalon with five pairs of well developed appendages and a trunk composed of 11 ring-shaped conical segments.     

Skara hunanensis a new species of Skaracarida (Crustacea) from Upper Cambrian (Furongian) of Hunan,south China

The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world,but it was not until 2005 that the Orsten-type fossils represented by Skaraearida and Phosphatocopida were first reported to be found in western Hunan,South China. Here,we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaraearida.They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section,western Hunan,south China,assigned to a new species Skara huna- nensis herein.Skara hunanensis is characterized by small,soft-integumented,marine forms with slender,annulate body;labrum large and ventrocaudally directed;uniramous antennulae;biramous antennae and mandibulae;maxillas and maxillipeds of the same shape;all postantennular limbs join a short cephalic filter apparatus.The body has two tagmata:a cephalon with five pairs of well developed ap- pendages and a trunk composed of 11 ring-shaped conical segments.     

Discovery of hydrothermal venting community at the base of Cambrian barite in Guizhou Province, Western China: Implication for the Cambrian biological explosion

The barite deposit in the Niutitang Formation of Lower Cambrian, in Tianzhu County, Guizhou Province, western China, is a superlarge barite deposit with about 2 × 10^9 tons of reserves. Mineral, petrological and geochemical studies reveal that this barite deposit belongs to a hydrothermal sedimentary deposit. Microscopic observations indicate that a lot of algae, sponge spicules and tube-type fossils are well-preserved in this barite section, and moreover, those fossils share most characteristics of the deep-sea hydrothermal venting community in the modern Pacific. We suggest that the hydrothermal venting community was thriving in hydrothermal vent in early Cambrian, and it is of great significance for elucidating the geological background of the ＂Cambrian explosion＂.     

湘西花垣中寒武统具表面装饰的管状微体化石

对采自湘西花垣县排碧剖面中寒武统花桥组灰岩中具表面装饰的磷灰石质管状化石（Ornamented tubes）进行了研究,依据化石的壳面装饰特征,建立了3形态类型：Ornamented Tube Form Ⅰ,Ornamented Tube Form Ⅱ 和 Ornamented Tube Form Ⅲ。其中Ⅰ型壳体表面装饰有尖细的小刺,多数标本壳刺成行排列,行间存在宽约0.01～0.05 mm的间隔;Ⅱ 型管体表面具有零散稀疏而不规则分布的斑疹状壳饰,壳体微微向外弯曲的一侧具有一列粗壮的呈锯齿状排列的脊刺;Ⅲ型整个壳体表面布满圆形、卵圆形瘤状壳饰,壳饰中空,与壳体内腔相通,壳体微微向外弯曲的一侧具有一列粗壮的呈羽状排列的脊刺。从壳体形态、表面装饰特征分析,这类管状化石可能是节肢动物(如高肌虫类)生物体壳瓣上的前刺或背部的刺等管状硬体构造。     

Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan, China

Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the upper Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan, China. Two morphological patterns, including Ornamented Tube Form I and Ornamented Tube Form II are described. Based on the analysis of the preservation, wall structure and composition of the fossils, it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthropods with phosphatic carapaces, such as bradoriid crustaceans. Analysis of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.     

Proposal and prospects for the global Lower-Middle Cambrian boundary

In recent years paleontologists have been working on the global stratotype section and standard point (GSSP) for the Lower-Middle Cambrian boundary in North America, China, Morocco, Spain and Russia. Continually, they suggest the potential first appearance datum (FAD) of the Middle Cambrian, such as Oryctocephalus indicus, Ovatoryctocara granulata, Acadoparadoxides mureroensis, Hupeolenus and Arthricocephalus chauveaui as being relevant to the potential stratotype section for the Lower-Middle Cambrian boundary. There are only a few trilobites distributed widely enough in the Early to Middle Cambrian connection, so virtually no trilobite(s) can act as the FAD for the global Middle Cambrian. The easily identified Oryctocephalus indicus is widely distributed in three realms of the global Cambrian. Its first appearance position is linked to the extinction of old species coevolution of new ones. It appears to be a comparatively good FAD of Middle Cambrian. The continuous and unbroken Wuliu section (Balang, Taijiang County, Guizhou Province, China) includes O. indicus and co-occurs with many benthic and nektonic trilobites. The evolution of acritarchs in the section, the changed characteristics of trace elements (REE and C isotopes) are generally consistent with the evolution of trilobites both above and below the boundary. Strata above the boundary yield the famous Kaili Biota. The Wuliu section is easily accessible from a main highway.     

An Early Cambrian tunicate from China

Like the Burgess Shales of Canada, the Chengjiang Lagerst?tte from the Lower Cambrian of China is renowned for the detailed preservation as fossils of delicate, soft-bodied creatures, providing an insight into the Cambrian explosion. The fossils of possible hemichordate chordates and vertebrates have attracted particular attention. Tunicates, or urochordates, comprise the most basal chordate clade, and details of their evolution could be important in understanding the sequence of character acquisition that led to the emergence of chordates and vertebrates. However, definitive fossils of tunicates from the Cambrian are scarce or debatable. Here we report a probable tunicate Cheungkongella ancestralis from the Chengjiang fauna. It resembles the extant ascidian tunicate genus Styela whose morphology could be useful in understanding the origin of the vertebrates.     

贵州金沙寒武系牛蹄塘组古盘虫类三叶虫的地层意义

通过对贵州金沙岩孔剖面牛蹄塘组的逐层化石采集,发现了大量古盘虫类三叶虫,包括Tsunyidiscus armatus和Tsunyidiscus niutitangensis,同时确定了T.armatus的顶界,将T.armatus顶峰带修订为T.armatus延限带。T.armatus是贵州最早出现的三叶虫,其对于寒武系第3阶底界的确定具有重要意义,此次修订的T.armatus延限带体现了生物的演化阶段,为区域地层的精细划分与对比提供重要的基础资料。本文也对Tsunyidiscidae做了初步讨论,认为该科包括Tsunyidiscus,Hupeidiscus和Badiscus3个有效属。