山东济宁煤田(东区)本溪组和太原组牙形刺生物地层   总被引：2，自引：0，他引：2  

蒋汉朝  张锡麒  王明镇  李增学 《地层学杂志》2002,26(1):27-32,38

通过对山东济宁煤田 (东区 )本溪组和太原组牙形刺动物群的系统研究 ,共鉴定出牙形刺化石 7属 2 0种。根据牙形刺化石在地层中的分布和垂向的变化规律自上而下建立了两个牙形刺组合 : .Streptognathodus isolatus组合和 .Idiognathodus magnificus- I.delicatus组合。通过与邻区及华北部分地区对比 ,本区本溪组和太原组中牙形刺动物群的地质时代应分别为晚石炭世晚期 (组合 )和早二叠世早期 (组合 ) ,本区 C/ P界线应置于第十一层灰岩之底  相似文献   

Early Cambrian palaeogeography and the probable Iberia–Siberia connection     

Alexander P. Gubanov 《Tectonophysics》2002,352(1-2)

The end of the Proterozoic–beginning of the Cambrian is marked by some of the most dramatic events in the history of Earth. The fall of the Ediacaran biota, followed by the Cambrian Explosion of skeletonised bilaterians, a pronounced shift in oceanic and atmospheric chemistry and rapid climatic change from ‘snowball earth’ to ‘greenhouse’ conditions all happened within a rather geologically short period of time. These events took place against a background of the rearrangement of the prevailing supercontinent; some authors view this as a sequence of individual supercontinents such as Mesoproterozoic Midgardia, Neoproterozoic Rodinia and Early Cambrian Pannotia. Assembled in the Mesoproterozoic, this supercontinent appears to have existed through the Neoproterozoic into the Early Cambrian with periodic changes in configuration. The final rearrangement took place during the Precambrian–Cambrian transition with the Cadomian and related phases of the Pan-African orogeny. The distribution of Early Cambrian molluscs and other small shelly fossils (SSF) across all continents indicates a close geographic proximity of all major cratonic basins that is consistent with the continued existence of the supercontinent at that time. Subsequently, Rodinia experienced breakup that led to the amalgamation of Gondwana, separation of Laurentia, Baltica, Siberia and some small terranes and the emergence of oceanic basins between them. Spreading oceanic basins caused a gradual geographic isolation of the faunal assemblages that were united during the Vendian–Early Cambrian.  相似文献   

Past and present state of the ichthyofauna of Lake Lugano     

Rudolf Müller  Hans Jürg Meng 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):338-350

The evolution of the ichthyofauna of Lake Lugano (Lago di Lugano) during the past 120 years is characterized by the introduction of eight new fish species and by the possibly natural addition of the blenny (Blennius fluviatilis) in recent years. Introduced Salmonids such as charr (Salvelinus alpinus) and whitefish (Coregonus sp.) have established strong populations during the first half of this century, but have declined drastically thereafter. Likewise, the population of the native shad (Alosa fallax lacustris) has diminished significantly. A hydroacoustic survey of the pelagic fish stock of Lake Lugano in 1989 revealed the presence of a dense bleak (Alburnus albidus) population at 0 to 14 m depth. No other fish were found to be present in the pelagic zone. Oxygen and temperature distributions seem to confine the bleak to the uppermost layer in summer. In winter, very few fish were located by echosounding. Growth of bleak and roach (Rutilus rubilio) was difficult to interpret since data for comparison are lacking. Growth of perch (Perca fluviatilis) in the littoral zone was found to be slower than in other eutrophic lakes, for no obvious reason. Possible ways of restructuring the pelagic fish community are discussed.  相似文献   

贵州晚二叠世—早三叠世介形虫动物群的演变   总被引：2，自引：0，他引：2  

郝维城 《地质论评》1994,40(1):87-92

贵州有许多二叠系至三叠系的连续剖面，沉积类型多样，生物化石丰富，其中介形虫化石不但类型多，数量也很丰富，保存完好，发展阶段明显。即长兴阶介形虫类型多，数量也多，壳饰复杂，以具瘤刺的为多，早三叠世早期介形虫贫乏，数量及类型都不多，壳饰以光滑或具微细纹饰的为主。根据这些介形虫类型和数量的变化，以及壳饰特征的研究，表明二叠系与三叠系界线附近的介形虫动物群也同其它生物一样发生了重要变化。为二叠－三叠系界线  相似文献   

藏北羌多——查布地区下二叠统划分与早二叠世动物群特征   总被引：1，自引：0，他引：1       下载免费PDF全文

吴瑞忠  杨金全 《地质科学》1991,(1):9-20

下二叠统分角木茶卡组和肖茶卡组。角木茶卡组为碳酸盐岩夹玄武岩,局部夹含砾板岩,厚1000-2500m。含(蜒)类组合Monodiexodina-Parafusulina,珊瑚组合 Lytvolasma Szechuanophyllum,腕足类组合Costiferina-Neospirifer-Spiriferella等。属冷、暖动物群混生类型。肖茶卡组为碳酸盐夹玄武岩,800-2900m。含(蜒)Neoschwagerina,珊瑚组合Iranophyllum-Waagenophyllum,腕足类组合Neospirifer-Spiriferella-Marginifera等,属暖水型动物群。这些反映了早二叠世时冈瓦纳大陆北缘浅海台地深拗陷带碳酸盐和火山岩的沉积特征。  相似文献   

甘肃武都龙家沟三趾马动物群化石的聚集特点   总被引：1，自引：0，他引：1  

张云翔  薛祥煦 《沉积学报》1996,14(3):122-128

龙家沟三趾马动物群中不同类型、不同大小动物的保存量及保存部位相差很大，实际保存量仅为理论保存量的６%左右，其化石材料明显经过水流的搬运作用。搬运过程中的分选作用是造成材料流失的主要原因，其中小型动物的流失最为明显。这是古生态恢复及古环境再造值得注意的问题。  相似文献   

昆明海口早寒武世澄江动物群的新发现及三叶形虫研究          下载免费PDF全文

罗惠麟  张世山 《地质学报》1997,71(2):97-104,T002

本文简要报道了在昆明市海口地下寒武统竹寺阶发现的澄江动物群化石，及其组合面貌和产生层位的地层剖面，重点描述了其中的三叶形虫：ＬｅａｎｃｈｏｉｌｉａａｓｉａｔｉｃａＬｕｏｅｔＨｕ（ｓｐ．ｎｏｖ．），ＹｏｈｏｉａｓｉｎｅｎｓｉｓＬｕｏｅｔＨｕ（ｓｐ．ｎｏｖ），ＺｈｏｎｇｘｉｎｉａｓｐｅｃｉｏｓａＬｕｏｅｔＨｕ（ｇｅｎ．ｅｔｓｐ．ｎｏｖ），ＸａｎｄａｒｅｌｌａｓｐｅｃｔｕｃｕｌｕｍＨｏｕｅｔａｌ．Ｄｉａ  相似文献   

New Quaternary Mammalian Faunas and Cave Deposits in the Zhoukoudian Area,Beijing   总被引：1，自引：1，他引：1  

Cheng Jie  Tian Mingzhong  Cao Boxun  Zhao Zhizhong China University Of Geosciences  Beijing China University of Geosciences  Wuhan  Hubei Institute of Geomechanics  Chinese Academy of Geological Sciences  Beijing Fei Zhenbi 《《地质学报》英文版》1997,71(3):231-243

From 1985 to 1987, four new localities with abundant fossil mammals were dis-covered by Cao, Tian and others in the Zhoukoudian (Choukoutien) area, Beijing. They are theEast, West, Shangdian and Donglingzi caves. The East Cave fauna consists of 28 speices ofmammals and its age is middle Early Pleistocene. The East Cave assemblage shows that a tem-perature-falling event took place at around 1.20 Ma B.P. at Zhoukoudian. Sixteen species ofmammals were collected from the West Cave, which are mainly forms of late Early Pleistoceneage. The West Cave fauna represents a transitional fauna from the East Cave fauna (dry-cold)to the fauna (warm) at locality 9. The Shangdian Cave fauna is composed of four forms, beingMiddle Pleistocene in age. The Donglingzi Cave fauna contains 21 Late Pleistocene forms. Inthe cave two fossil horizons may be distinguished. The age of the lower horizon is early LatePleistocene, which is equivalent to that of the New Cave fauna; while the fauna of the upper ho-rizon may be correlated with the Upper Cave fauna.  相似文献   

青海东昆仑中段早寒武世小壳动物群的发现及其地质意义     

季强 《地质通报》1997,(4)

首次报道青海东昆仑中段早寒武世小壳动物化石，计有Ａｎａｂａｒｉｔｅｓｔｒｉｓｕｌｃａｔｕｓ，Ｈｙｌｉｔｈｅｌｕｓｔｅｎｕｉｓ，Ｈｙｌｉｔｈｅｌｕｓｓｐ．，Ｃｏｎｏｔｈｅｃａｓｐ．，Ｐａｌａｅａｃｍａｅａｓｐ．以及Ｌａｔｏｕｃｈｅｌａｓｐ．。这些化石的发现丰富了该区早古生代古生物资料，对于万宝沟群和纳赤台群的定义、层序和时代归属具有重要意义。  相似文献   

南京湖山地区下二叠统孤峰组放射虫动物群   总被引：2，自引：0，他引：2       下载免费PDF全文

王汝建 《地质科学》1995,(2):139

 南京湖山地区下二叠统孤峰组含有极丰富的放射虫化石,主要由阿尔拜虫类albaillellids.球形多囊虫类sphericalpolycystine和十字多囊虫类stauraxonpolvcystine组成。文章对部分化石进行了描述,并建立1新属新种。根据放射虫在地层中的分布,提出两个组合带,即Pseudoalbaillella fusiformis-P. longtanensis带和Ruzhencevispongus uralicus带,并将这两个组合带与国内外时代大致相当的放射虫组合进行了比较,还讨论了这两个组合的时代。  相似文献