淮北地区寒武系／新元古界办线讨论

淮北地区寒武系与新元古界的界线，长期以来存在争议，主要有5种划分意见，猴家山组／沟后组，沟后组／金山寨组，沟后组上段／沟后组下段，金山寨组／望山组及猴家山组／金山寨组之间，通过近年来的实地考察和室内研究，从叠层石，宏体碳质压膜化石及小壳动物化石组合合考虑，认为该区新元古界最上面的岩组应是沟后组，而超覆于区内新元古界不同层位上的长期被描述为猴家山组“豹斑状”灰岩，白云岩，实为昌平组，属下寒武统。     

安徽淮南下寒武统沉积环境以及碳酸盐岩微相分析

华北地台南缘安徽淮南老鹰山剖面下寒武统猴家山组和馒头组的沉积环境和碳酸盐岩微相指示了３期地区性海进沉积旋回序列。假整合于前寒武系凤台组冰积砾岩层之上的猴家山组蒸发相白云岩和馒头组下段的深褐色页岩、钙质页岩和深灰色、灰色中厚层至薄层灰岩构成第１个海进序列;馒头组中段的页岩和薄层灰岩及馒头组上部的深褐色页岩构成第２个海进序列;第３次海进以近馒头组顶部的页岩出现为标志,至老鹰山组下段局部地区的剥蚀面作为中下寒武统的界限和第二次海退的终结。     

华北地层大区东南区寒武纪早期地层对比与统一划分

华北地层大区东南区的寒武纪早期地层 ,宜统一划分为6个三叶虫化石带(Shantungaspis,Yaojiayuella ,Qiaotouaspis,Redlichia(Pteroredlichia) ,Megapalaeolenus和Hsuaspis)和3个组(毛庄组、馒头组和猴家山组)。毛庄组包含Shantungaspis带 ,Yaojiayuella带和Qiaotouaspis带一部分 ,馒头组包含Qiaotouaspis带大部分、Redlichia(Pteroredlichia)带和Megapaeolenus带 ,猴家山组仅含Hsuapis带。前2带属毛庄阶 ,第3、4带属龙王庙阶 ,后2带属沧浪铺阶。中、下寒武统界线划在毛庄阶与龙王庙阶即Yaojiayuella带与Qiaotouaspis带之间。毛庄组属下—中寒武统 ,其它2组属下寒武统。按各组的岩层组合特征 ,统一划分为15个岩性段     

安徽凤阳考城许氏盾壳虫的发现

<正> 安徽北部寒武系的猴家山组,原称“猴家山统”,由徐嘉炜(1956)创立,标准地点在凤台之东的猴家山,自上而下包括③白鹤山层,②雨台山页岩,①凤台砾岩。在皖西霍丘雨台山页岩之上的砂灰岩中,采到了Hsuaspis sp., 下部采到了Obolus sp.和Obolopsis sp.。     

中国南北方元古代地层之衔接部位─—小秦岭元古界剖面特征

小秦岭地区元古代地层发育良好，顶、底界线清楚，下伏地层为太古界太华群，其上被寒武系平行不整合覆盖；元古界自下而上分为中元古界铁铜沟组、熊耳群、高山河组、龙家园组、巡检司组、杜关组、冯家湾组和上元古界石北沟组、罗圈组，其构造简单、层序清楚，含有丰富的叠层石、核形石及微古植物化石，各类沉积相标志十分发育。1982年已被列为陕西省自然保护点。     

江苏徐州及邻近地区的猴家山组

<正> 猴家山组是由“猴家山统”演变而来,“猴家山统”系徐嘉炜1956年创建,作为馒头组以下的一个地层单元,并与滇东沧浪铺组和筇竹寺组相对比。苏、鲁、皖交界地区有无猴家山组的存在?徐嘉炜认为有相当淮南的白鹤山层存在;潘江等认为徐州一带缺失沉积;毕德昌等认为淮北有猴家山组的存在,但都缺少化石依据。 1974年,我们在本区的馒头组肝紫色页岩之下的灰色中厚层豹皮灰岩中,首次发现了Megapalaeoenus,从而肯定了猴家山组的存在,并从生物地层上提供了对比依据。     

中国北部寒武纪介形虫地层分布时代

中国北部寒武纪介形虫分布于早晚寒武世.其所在地层的确切时代(期或亚期)以往多未完全确定下来或者还在争论之中.通过分析有关介形虫、三叶虫及小壳化石的组合面貌,并结合岩石地层学特征,文章认为:(1)新疆下寒武统肖尔布拉克组与玉尔吐斯组应合为一组,仍称肖尔布拉克组,时代大致为梅树村期最晚期至沧浪铺期红井哨亚期.其中所见的介形虫基本上均属筇竹寺期.(2)河南淅川等地包括整个下寒武统的水沟口组,自下而上宜分成水沟口组、上集组、小泉沟组和脑子寨组.目前发现的介形虫产于上集组下部(Ichangia-Neocobboldia带),时代为沧浪铺期红井哨亚期晚期,上集组上部可建立Palaeolenus带,时代为沧浪铺期乌龙箐亚期早期.(3)辛集组和雨台山组及其相当地层应统称猴家山组,但应用系指原"猴家山组"下部的一套含磷岩系,原组上部含Megapalaeolenus的一套灰岩及白云岩则应称昌平组.修订后的猴家山组时代为沧浪铺期红井哨亚期晚期.陕西、安徽迄今所见的介形虫即分布于这一时期.(4)辽宁金县所谓"三十里堡阶"实为馒头组的同物异名,其中所产的介形虫Alutella nakamurai的时代因此应为龙王庙期.(5)辽宁本溪的Aluta chiusbueusis瓦房店的A.paiensis和A.paiensis tenuis曾被认为产于奥陶系底部,实际上其时代前者为晚寒武世凤山期晚期,后两者为凤山期早期.另外,后两者实为Mononotella的同种个体.     

中国北部寒武纪介形虫地层分布时代

中国北部寒武纪介形虫分布于早晚寒武世。其所在地层的确切时代(期或亚期)以往多未完全确定下来或者还在争论之中。通过分析有关介形虫、三叶虫及小壳化石的组合面貌,并结合岩石地层学特征,文章认为:(1)新疆下寒武统肖尔布拉克组与玉尔吐斯组应合为一组,仍称肖尔布拉克组,时代大致为梅树村期最晚期至沧浪铺期红井哨亚期。其中所见的介形虫基本上均属筇竹寺期。(2)河南淅川等地包括整个下寒武统的水沟口组,自下而上宜分成水沟口组、上集组、小泉沟组和脑子寨组。目前发现的介形虫产子上集组下部(Ichangia—Neocobboldia带),时代为沧浪铺期红井哨亚期晚期;上集组上部可建立Palaeolenus带,时代为沧浪铺期乌龙箐亚期早期。(3)辛集组和雨台山组及其相当地层应统称猴家山组,但应用系指原“猴家山组”下部的一套含磷岩系,原组上部含Megapalaeolenus的一套灰岩及白云岩则应称昌平组。修订后的猴家山组时代为沧浪铺期红井哨亚期晚期。陕西、安徽迄今所见的介形虫即分布于这一时期。(4)辽宁金县所谓“三十里堡阶”实为馒头组的同物异名,其中所产的介形虫Alutella nakamurai的时代因此应为龙王庙期。(5)辽宁本溪的Aluta chiushuensis与瓦房店的A.paiensis和A.paiensis te-nuis曾被认为产于奥陶系底部,实际上其时代前者为晚寒武世凤山期晚期,后两者为凤山期早期。另外,后两者实为Mononotella的同种个体。     

苏皖北部晚前寒武纪地层层序的厘定

<正> 苏皖北部晚前寒武纪地层是指凤阳群不整合面之上,寒武系下统猴家山组平行不整合面之下的一套地层。这套地层在没有进行1:20万区域地质调查之前,前人的地质工作主要是在淮南,所建立起来的晚前寒武纪地层层序是正确的,如徐嘉炜(1959)所确定的晚前寒武纪地层层序及其划分(自下而上为下震旦统八公山统下部石英岩,它不整合在前震旦纪角闪片岩为主变质岩系上,其上为刘老碑页岩,再上为上部石英岩和上震旦统四顶山统泥质灰岩及泥灰岩层,其上是矽质灰岩,并被寒武系下统猴家山组平行不整合覆盖)是比较完善的。     

吉林省南部复兴村寒武系碱厂组Redlichia的确定及其意义

复兴村下古生界盆地的寒武系,主要分布在集安县的复兴村—治安村一带。前人对该地寒武系研究较差,仅在一比二十万区域地质调查过程中建立了较完整的层序,但因缺少化石依据,地层单元只划分到统。一九八四年六月我们在踏勘一比五万复兴村幅上元古界及下古生界剖面时,在三道沟、下吊子沟、上吊子沟等地,前人划分为上元古界钓鱼台组、南芬组石英砂岩所夹结晶灰岩透镜体中,发现有三叶虫化石(图1),经我所古生物室朱乃文鉴定为Redlichia     

Protoconodont fossils for refining the Cambrian bottom and the contribution to shale gas formation along the southwest margin of Yangtze Block

It has been an intense debate on the exact boundary between Ediacaran and Cambrian in the southwest Yangtze Block. The calibration of this critical boundary has a remarkable influence on the further investigation of the break-up of the Rodinia Supercontinent, the early life evolution, and the mechanism of the phosphorite deposit. Ediacaran and Cambrian strata and fossils are widely distributed in Anning, Yunnan Province in China. In recent years, the Xiaowaitoushan Member from the Lower Yuhucun Formation has been studied. Through this interval with continuous collections, the first appearance datums (FADs) of the protoconodont (Fomitchella cf. inchoate Yang et He, Protohertzina cf. anabarica Missarzhevsky) and globular embryos fossil (Olivooides sp.) earlier than these in the Lower Cambrian strata of the Meishucun Formation were discovered. This discovery indicates that the Xiaowaitoushan Member has included more FADs than the previously discovered single FAD of Anabarites primitivus Qian et Jiang, and the Ediacaran–Cambrian boundary in southwest China should be replaced below the Point “A” of the Meishucun Formation in Yunnan Province. The Point “B” of the Meishucun Formation is younger than the suggested age 541 Ma of the Ediacaran–Cambrian boundary and can no longer reference the Global Boundary Stratotype Section and Point (GSSP) correlation in southwest China. It can be suggested based on the previous stratigraphy and palaeontology studies from northern Sichuan and southern Shaanxi and the FAD of the globular embryos fossils that the Ediacaran−Cambrian boundary in the southwest Yangtze Block should be placed at the base of the Xiaowaitoushan Member; other phosphorite strata refer to Xiaowaitoushan Member. The discovery of the FADs of the shelly fossils in the Xiaowaitoushan Member provides new evidence for the global correlation of the Ediacaran –Cambrian boundary in the southwest Yangtze Block. The conodont discoloration index (CAI) of the specimens in Anning is between 2 and 3, which indicates that the organic matter in Xiaowaitoushan Member is matured and has high potential to form a shale gas reservoir.     

陕西新元古代末期奇异骨骼化石新发现及其意义

陕西宁强新元古代末期灯影组高家山段上部发现与Cloudina,Sinotubulites等管状动物骨骼化石共生的大量微体奇异骨骼化石，其中的一些似与寒武纪早期的小壳化石有一定的亲缘，如形态奇特的铆钉状化石、腹足类化石等，证实寒武纪与前寒武纪生物界之间存在明显的连续性；奇异骨骼与陡山沱期生物也存在一定的相似性，如一些分枝的管状化石，这一化石组合具有承前启后的作用。该组合包含了可能的矿化后生藻类（具各种分枝类型）、矿化的蓝绿藻类化石等。种种迹象表明，在新元古代末期整个生物界发生了一次强烈的生物矿化事件，这一发现弥补了国内外新元古代末期矿化后生植物资料的空缺；磷酸盐化球状化石的研究已成为国内外研究的热点，本文所展示的球状化石由于形态多样，数量众多，内部结构各异，对其进行深入研究，可望在后生动物起源和早期演化研究方面取得突破。     

Pb-Pb dating of black shales from the Lower Cambrian and Neoproterozoic strata, South China

Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng’an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique. The ²⁰⁶Pb/²⁰⁴Pb ratios in both sections show large variations, from 18.906 to 43.737 in the Weng’an section and from 24.811 to 38.110 in the Xiuning section. In contrast, the ranges for ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values in both sections are relatively smaller from 15.649 to 17.126 and 37.744-38.199 in the Weng’an section, and from 16.034 to 16.783 and 38.602-39.391 in the Xiuning section, respectively. These data yielded two Pb isotope isochron ages of 536±39 and 572±36 Ma, respectively. These ages well accord with other published data and we suggest that they represent the depositional ages for the Lower Cambrian Hetang Formation and the upper Neoproterozoic Doushantuo Formation in South China.     

Furongian (upper Cambrian) Guole Konservat-Lagerst?tte from South China

The Guole biota contains common shelly fossils and some exceptionally well-preserved soft-bodied fossils. Stratigraphically, it is located in the mudstones and siltstones of the Sandu Formation near Guole Town, Jingxi County, Guangxi, South China. It is the first Furongian (late Cambrian) Burgess Shale-type biota found in the world, thereby filling the gap between middle Cambrian and Lower Ordovician Burgess Shale-type Lagerst?tten. Preliminary studies suggest that the Guole biota includes approximately seven metazoan groups as well as algae. These will provide important new evolutionary and ecological information.     

Vase-shaped microfossils from the Ediacaran Weng'an biota, Guizhou, South China

Vase-shaped microfossils (VSMs) are described from the Ediacaran Doushantuo phosphorites (ca. 599–584 Ma) of Guizhou Province, South China. They are morphologically attributed to two genera and three species, and thus expand our knowledge of the Neoproterozoic protozoans in the Weng'an biota. They resemble to the VSMs from the Lower Cambrian pre-trilobitic Kuanchuanpu Formation of southern Shaanxi Province in terms of the microstructures and chemical composition of the fossil walls. Microscopic observations indicate that the VSMs from both the Weng'an biota and the Kuanchuanpu Formation are preserved in either single-layered or multi-layered walls, and composed of calcium phosphate in chemical composition. The present fossils also share similarities, in size and general contour, to the VSMs previously described from the Gaojiashan Member, middle part of the Dengying Formation (ca. 551–542 Ma) in southern Shaanxi. The discovery of the VSMs from the Doushantuo phosphorite is an important contribution to the Weng'an biota, and may throw much light on the early evolution and diversification of protozoans during Precambrian–Cambrian interval.     

峡东寒武纪三叶虫化石新材料

三峡东部中寒武统化石稀少。本文对在宜昌三斗坪中寒武世覃家庙组二段下部含鲕粒灰岩、细晶灰岩中所采获的三叶虫Xingrenaspis sp.进行了研究和描述,并对含化石地层时代进行了讨论。此次发现,丰富了峡东中寒武世的化石资料,也为本区中寒武世地层划分对比提供了新的依据。     

北京西山寒武系下苇甸组——一个新建议的组

下苇甸组系从北京西山下寒武统底部独立出来 ,新建立的一个组。它虽然厚度不大 ,但岩性与昌平组有别 ,顶、底界面清楚 ,分布稳定 ,在北京西山地区可广泛追踪 ,符合建组条件     

浙西下寒武统大陈岭组沉积异常及其海啸成因初探

前人对浙西下寒武统大陈岭组沉积相分析一直存在半深水相和浅水相两种观点。大陈岭组化石极少,仅中上部产营漂浮或游泳生活的节头虫类Arthicocephalus, Arthricocephalites和Changaspis,不见底栖类化石。对大陈岭组碳酸盐岩碳氧同位素分析显示,对应于产半深水相生物化石的层位存在碳同位素正漂移,表明此处水体较深;但该组大量发育碳酸盐岩台坪相的沉积标志-鸟眼构造,与较深水相生物和碳同位素正漂移的解释结果相悖。作者在对浙西开化、常山、江山寒武系野外调查时发现大陈岭组存在一套地震-海啸沉积岩系,且海啸岩的产出层位与江山较深水相化石、碳同位素正漂移层位相当。研究认为,海啸作用可以使不同环境的沉积物相互混合,造成沉积异常,浙西下寒武统大陈岭期沉积异常是海啸事件的反映,海啸作用把较深水生物和沉积物带到浅水区沉积下来,并造成碳氧同位素短暂、急剧的正漂移。     

论淮南生物群

淮南生物群 (Huainan Biota)产于安徽淮南地区新元古代淮南群中 ,由宏观藻类 Chuaria- Tawuia组合和蠕形动物 Pararenicola- Paleolina组合组成 ,可与加拿大西北麦肯齐山新元古代小达尔群 (L ittle Dal Group)小达尔生物群 (L ittle Dal Biota)对比 ,为新元古代大冰期前的一个特有生物群落 ,地质时代为前震旦纪 (本文的震旦纪即目前的南华纪至震旦纪 ) ,时限约为 85 0— 75 0 Ma,从而将前人所定淮南生物群为青白口纪至震旦纪的时代结论修订为前震旦纪。这对我国乃至国际上新元古代地层层序的重新划分与对比 ,以及新元古代早期生命演化研究等都具有重大的理论意义和实际价值。文中还着重论述了淮南生物群的组合特征和特定的生物发展阶段 ,而区别于青白口纪和震旦纪的生物群落 ,并通过洲际对比 ,讨论了淮南生物群的地层学意义     

河南灵宝朱阳下寒武统辛集组软体动物群的发现

河南灵宝朱阳地区下寒武统辛集组中新发现的小壳动物化石包括软体动物群的软舌螺、单板类、双壳类和腹足类以及海绵骨针和齿形类。该动物群可与安徽淮南雨台山组、河南确山、叶县、宝丰及陕西洛南辛集组动物群对比，时代属早寒武世中期，与澳大利亚新南威尔士早寒武世中期软体动物群属同一生物地理区。软体动物有可能在中国云南开始出现，并迅速迁移至扬子浅海各地，后经某种渠道迁移到华北地台南缘，演化成新的动物群。