中国古生代放射虫研究世纪回顾—为庆贺盛金章院士80华诞而作

20世纪中国古生代放射虫研究取得三方面成绩：1.研究地域涉及全国大部分省区。除东北三省、河北、山西、山东、海南、台湾外,古生代放射虫巳在我国19个省区发现。时代从晚寒武世至晚二叠世长兴期;2.研究领域逐步扩大,确立了三种不同的放射虫岩相类型,洋盆相区以广西钦州板城最为典型,从晚泥盆世弗拉斯期-晚二叠世长兴早期共建立18个化石带;岛孤相区以云南西部昌宁-孟连地体作代表,从中泥盆世吉维持期-晚二叠世长兴期发育12个化石带;台盆相区以苏皖地区中二叠世孤峰组放射虫研究得较好,建立3个化石带,这些放射虫化石带,与洋盆相区,岛弧相区同时代的带基本上相似和相同;3.中国4条主要蛇绿岩带都发现了放射虫硅质岩和放射虫动物群。这对蛇绿岩带的形成时代和板块碰撞时间和确定提供了有力的证据。最后,文中还提出了新世纪里我国古生代放射虫研究的方向。     

横断山地区石炭纪和二叠纪有孔虫

横断山地区石炭纪和二叠纪海相沉积分布非常广泛,在早石炭世杜内期至晚二叠世各沉积中均含有大量有孔虫化石,其中尤以维宪期和长兴期沉积中的有孔虫化石最为丰富和保存极佳。本文描述了较为常见和特征的分子共11科30属65种,其中8个为新种,根据分析和比较,横断山地区石炭纪和二叠纪有孔虫动物群的组合面貌和特征与我国华南地区同期地层中所见有孔虫动物基本一致,同属“南方型”生物群,同时也与特提斯海域同期地层中有孔虫动物群非常近似,因此可以说明横断山地区当时的海水不仅与我国华南海域及特提斯海域都是相通的,同时都繁衍着大致相同的有孔虫动物群,它们均生活在温暖和盐度较为正常的浅海水域中。     

广西南部二叠纪长兴期放射虫动物群

广西南宁南部柳桥区的长兴组上部硅质岩中存着精美的长兴期晚期放射虫动物群,共有24属39例,其中3个新种,其中以Latentifistularia最为常见,其次是Albaillllidae和Entactiniidae,属于二叠纪晚期的Neoalbaillella optima组合。半生生物有有孔虫、海绵骨针、腕足动物等。多数属在接近二叠纪－三叠世界线附近消失,但生物群中已出现少量三叠纪分子。     

黔南紫云四大寨长兴期小有孔虫

首次报道了产自贵州紫云四大寨剖面长兴期的有孔虫动物群,共计有9属22种,将此动物群与华南长兴期其它地区的有孔虫动物群进行了对比。     

江苏仑山地区和湖北宜昌地区上奥陶统五峰组放射虫动物群

本文报道了江苏仑山岗岗山剖面和湖北宜昌黄花场宜黄-1井岩芯中晚奥陶世五峰组灰色、灰黑色硅质页岩和硅质岩中的放射虫动物群。通过对仑山和宜昌五峰组放射虫动物群的再研究,发现该放射虫动物群以空滴虫科(Inaniguttidae)放射虫发育为特点,丰度高,但分异度低、属种单调,仑山地区仅有一科、一属、两种,包括Inani-gutta webbyi和Inanigutta jiangsuensis。宜昌地区同样发现空滴虫科放射虫,但难以鉴定到属种。两个地区的化石整体保存状况较差。根据伴生的笔石化石判断该放射虫动物群时代为凯迪晚期至赫南特早期。动物群特征与凯迪早、中期放射虫动物群有一定差异。同时,在两地五峰组中还新发现一类分类位置待定的锥形疑似放射虫化石,具有一定的地层对比意义。     

湖南桑植早三叠世放射虫化石

上二叠统深海相地层中放射虫化石十分常见,浅海相灰岩中也时有发现。然而,格里斯巴赫阶至今未找到放射虫化石,迪纳尔期和史密斯期的放射虫化石仅有土耳其西北部,泰国南部、湖南桑植和美国俄勒冈州中部四个化石点。这些放射虫化石普遍产自灰岩中,并以极低的分层度为特征,仅由1到4个种组成,均为古生代型分子。根据牙形石化石,湖南桑植放射虫化石产物迪尔阶和史密斯阶的结核状灰岩中,鉴定有两个种,即Entactinia nikorni和？Polyentactinia phatthalungesnsis。它们与泰国南部迪纳尔期的放射虫可以对比,但与土耳其西北部迪纳尔斯至史密斯期的放射虫动物群略有不同。     

桂西南柳桥地区二叠纪末期浅水相小有孔虫动物群

本文研究了广西扶绥县柳桥地区二叠纪末期的浅水相小有孔虫动物群。该动物群赋存于硅质岩相地层中的灰岩夹层里。动物群丰度和分异度均较高,共发现12属25种。其中包括长兴期的常见分子如Glomospira,No-dosaria,Colaniella等。此有孔虫组合与Colaniella组合大致相当,可以与类Paleofusulina带和Gallowayiella带相对比。     

贵州紫云猫场剖面二叠纪-三叠纪之交有孔虫的灭绝过程

本研究通过对贵州紫云地区猫场剖面长兴组上部及二叠系-三叠系界线附近地层进行高密度采样和系统切片,获得有孔虫化石标本1 178枚,共鉴定出有孔虫37属65种,包括类有孔虫4属7种。其中35属63种有孔虫消失在生物碎屑灰岩与微生物岩界线之下,包括所有的类有孔虫,其种级和属级灭绝率分别为96.9%和94.6%。这与华南其它微生物岩剖面类似,进一步表明浅水相有孔虫的灭绝发生在长兴期末期。猫场剖面长兴组生物碎屑灰岩中Dagmarita和Cribrogenerina两属非常丰富,其个体数量分别为209枚和126枚,占总数量的28.4%,是该动物群的优势分子,称为Dagmarita-Cribrogenerina组合。猫场组微生物岩中仅发现有孔虫Earlandia和Postcladella两个属,称为Earlandia-Postcladella组合。     

西藏南部早白垩世贝里阿斯期放射虫化石组合

白垩纪放射虫硅质岩广泛分布于藏南雅鲁藏布蛇绿岩带两侧,形成于多种沉积-构造背景,为藏南特提斯演化研究提供了丰富信息。为确定硅质岩的时代,需要建立藏南白垩纪放射虫分带系统。作为第一步,本文重新研究了江孜地区宗卓组含白垩纪早期放射虫(吴浩若和李红生,1982)的滑塌岩块标本(80-R1),描述了放射虫化石29种,包括6个新种。有13种见于阿曼同期的放射虫动物群(Dumitrica et al.,1997),其中Loopus yangi和Stichocapsa labyrinthica限于白垩纪初贝里阿斯期。藏南和阿曼的动物群中都富含Godia Wu和Becus Wu两属,前者始现于贝里阿斯期(O'Dogherty et al.,2009)。此外,Obesacapsula polyedra是加利福尼亚贝里阿斯期放射虫动物群的重要分子。宗卓组化石组合与藏南下鲁硅岩的Pseudodictyomitra carpatica带(KR1)(Matsuoka et al.,2002)比较,仅有很少共同分子。下鲁硅岩中该带的时代被归于提塘期-瓦兰今期。然而,其所含Eucyrtidiellum pyramis以及与含Loopus primitivus的西太平洋P.carpatica带底部化石群的密切关系,指示其时代可能限于晚侏罗世提塘期。     

黔桂皖二叠纪末期硅泥质岩相地层中的介形类

对广西柳桥剖面、贵州晒瓦剖面和安徽平顶山西剖面晚二叠世末期硅泥质岩相地层中产出的介形类化石进行了系统分类学研究,共鉴定介形类化石30属86种,其中包括1个新属Denticupachydomella Yuan gen.nov.和2个新种Pseudobythocypris guiqianensis Yuan sp.nov.和Denticupachydomella spinosa Yuan sp.nov..该动物群主要由薄壳和个体较小的介形类组成,呈现出以古生代分子为主,同时含有少量典型中生代先驱分子(如:Abrobairdia,Lobobairdia)的混合动物群面貌.通过这些剖面之间的对比以及与前人研究资料对比,发现各剖面产出的介形类动物群具有强烈的地方性,三个剖面之间无相同分子,亦仅有20种曾报道于欧洲和东南亚等地区晚石炭世-晚二叠世地层.     

Biostratigraphy and paleoecology of the Oligo-Miocene succession in Fars and Khuzestan areas (Zagros Basin,SW Iran)

Paleontological and biostratigraphical studies on carbonate platform succession from southwest Iran documented a great diversity of shallow-water benthic foraminifera during the Oligocene–Miocene. Larger foraminifera are the main means for the stratigraphic zonation of carbonate sediments. The distributions of larger benthic foraminifera in two outcrop sections (Abolhayat and Lali) in the Zagros Basin, Iran, are used to determine the age of the Asmari Formation. Four assemblage zones have been recognized by distribution of the larger benthic foraminifera in the study areas. Assemblage 3 (Aquitanian age) and 4 (Burdigalian age) have not been recognized in the Abolhayat section (Fars area), due to sea-level fall. The end Chattian sea-level fall restricted marine deposition in the Abolhayat section and Asmari Formation replaced laterally by the Gachsaran Formation. This suggests that the Miocene part of the formation as recognized in the Lali section (Khuzestan area) of the Zagros foreland basin is not present in the Abolhayat outcrop. The distribution of the Oligocene larger benthic foraminifera indicates that shallow marine carbonate sediments of the Asmari Formation at the study areas have been deposited in the photic zone of tropical to subtropical oceans. Based on analysis of larger benthic foraminiferal assemblages and microfacies features, three major depositional environments are identified. These include inner shelf, middle shelf and outer shelf. The inner shelf facies is characterized by wackestone–packstone, dominated by various taxa of imperforate foraminifera. The middle shelf is represented by packstone–grainstone to floatstone with a diverse assemblage of larger foraminifera with perforate wall. Basinwards is dominated by argillaceous wackestone characterized by planktonic foraminifera and large and flat nummulitidae and lepidocyclinidae. Planktonic foraminifera wackestone is the dominant facies in the outer shelf.     

Facies,paleoenvironment, carbonate platform and facies changes across Paleocene Eocene of the Taleh Zang Formation in the Zagros Basin,SW-Iran

The Paleocene–Eocene Taleh Zang Formation of the Zagros Basin is a sequence of shallow-water carbonates. We have studied carbonate platform, sedimentary environments and its changes based on the facies analysis with particular emphasis on the biogenic assemblages of the Late Paleocene Sarkan and Early Eocene Maleh kuh sections. In the Late Paleocene, nine microfacies types were distinguished, dominated by algal taxa and corals at the lower part and larger foraminifera at the upper part. The Lower Eocene section is characterised by 10 microfacies types, which are dominated by diverse larger foraminifera such as alveolinids, orbitolitids and nummulitids. The Taleh Zang Formation at the Sarkan and Maleh kuh sections represents sedimentation on a carbonate ramp.

The deepening trends show a gradual increase in perforate foraminifera, the deepest environment is marked by the maximum occurrence of perforate foraminifers (Nummulites), while the shallowing trends are composed mainly of imperforate foraminifera and also characterised by lack of fossils in tidal flat facies.

Based on the facies changes and platform evolution, three stages are assumed in platform development: I; algal and coralgal colonies (coralgal platform), II; coralgal reefs giving way to larger foraminifera, III; dominance of diverse and newly developing larger foraminifera lineages in oligotrophic conditions.     

Changhsingian brachiopod communities along a marine depth gradient in South China and their ecological significance in the end-Permian mass extinction

Diversity indices (dominance and evenness) and ecological spatial structure (lifestyles and relative abundances) are important features of Changhsingian brachiopod communities prior to the end-Permian mass extinction (EPME) and could predict temporal and spatial extinction patterns during the EPME. In South China, Changhsingian brachiopod communities show higher diversity than other contemporaneous brachiopod communities in the world and have been reported from a variety of sedimentary environments. In this paper, brachiopods from 18 sections in South China were selected to divide communities and compare their ecological structure. Based on the results of network analysis, cluster analysis and quantitative data from the selected sections, we show that Changhsingian brachiopod communities in South China can be categorized into three assemblages along a marine depth gradient: the Neochonetes–Fusichonetes–Paryphella Assemblage from the shallow-water clastic-rock facies, Spinomarginifera–Peltichia–Oldhamina Assemblage from the shallow-water carbonate platform facies and Fusichonetes–Crurithyris Assemblage from the deep-water siliciclastic intracontinental basin facies. Compared with communities from carbonate platform facies, the communities from siliciclastic facies were characterized by high dominance, low evenness and low lifestyle diversity, which might be important biotic factors leading to earlier extinctions. After the extinction began in all environments, the whole earliest Triassic brachiopod community was first dominated by Fusichonetes and then by Crurithyris. These patterns of domination and replacement could be explained by morphological and ecological advantages. The domination of these two genera, which were already adapted to the oxygen and food-limited deep-water habitat, indicates that the cooler deep-water environment might have been a relatively less stressed habitat after the beginning of the EPME. This suggests that global warming might be the main trigger among the previously proposed synergistic environmental stresses, while anoxia might not, at least for the beginning of EPME.     

山东新汶煤田太原组小有孔虫动物群及石炭-二叠系界线的探讨

通过对山东新汶煤田太原组小有孔虫动物群的系统研究,共鉴定出小有孔虫化石24属66种,根据小有孔虫在太原组中的垂向分布和含量的变化,自下而上分为3个小有孔虫组合：1．Brad yina samarica- Palaeotextularia angusta elongata组合,2．Nodosaria sinensis- Tetrataxis组合,3．Geinitzina postacarbonica组合。通过与邻区及华北部分地区的对比,本区太原组小有孔虫动物群的地质时代应归属于早二叠世,其层位大致相当于华北各地太原组(ting)类的Pseudoschwagerina带。     

Discovery of the Late Changhsingian Bivalve Complex and Two Fauna Extinction Episodes in Northeastern Asia at the End of the Permian

A late Changhsingian bivalve complex including species from the genera Palaeonucula, Dacryomya, Malletia ?, Sarepta ?, Myalina, Pteria, Maitaia, and Unionites is discovered in northeastern Asia for the first time. The transition from the Permian to the Triassic in high-boreal basins has been shown to include two extinction episodes similar to those observed in the low-boreal basins and apparently evoked by trap volcanism activation in Siberia. Changes in benthic foraminifera diversity and vertical distribution of ammonoidea of the genus Otoceras in transitional Permian–Triassic deposits also are considered. Images of bivalves from the most typical taxa are presented.     

Paléoécologie des foraminifères benthiques de nouvelles coupes de basse latitude du passage Crétacé-Paléogène : Coupes de l’Oued Es Smara et de l’Oued Abiod (région de Téjerouine,NW Tunisie)

Due to an impact of a bolide at the K/Pg boundary, the planktonic foraminifera have suffered sever mass extinction. However, no small Benthic Foraminifera species have documented mass extinction at the K/Pg boundary. Nevertheless, many species showed disturbance. The Maastrichtian assemblages may be different from those of the lower Paleogene by their species content, diversity and frequencies. At Oued Es Smara and Oued Abiod sections, the small benthic foraminifera indicate lower bathyal environment, and manifest significant faunal turnover. Until the uppermost Maastrichtian, their assemblages are highly diversified, with 77 species and 76 species respectively at Oued Es Smara and Oued Abiod sections. These are dominated by endobenthic morphotypes. At the K/Pg boundary, although 33 species (42,85%) (Oued Es Smara section) and 27 species (35,52%) (Oued Abiod section) of them seem to disappear, but only few species have really extinct such as Arenobulimina obesa. Nevertheless, the majority of species persist elsewhere at the Danian (e.g., Pseudoglandulina manifesta, Cibicioides proprius, Clavulinoides amorpha, Coryphostoma plaitum, Pullenia coryelli). At the lower Danian, the survivor Maastrichtian species are of 58% (Oued Es Smara) and 65% (Oued Abiod). Throughout the Parasubbotina pseudobulloides subzone, 4 others species were progressively disappeared. They are oligotrophic and low oxygen tolerant. About the Masstrichtian species, at the two studied sections (e.g. Gaudryina inflata and Tritaxia midwayensis) they seem to be more trophic exigent. Consequently, the benthic Foraminifera did not suffer massive extinction at the K/Pg boundary, but their assemblages underwent a significant faunal turnover which reflects important environmental changes. These changes are compatible with the catastrophic scenario induced by the large asteroid impact.     

Palaeogeographic and stratigraphic distribution of mid-late Oxfordian foraminiferal assemblages in the Prebetic Zone (Betic Cordillera, Southern Spain)

Middle-Upper Oxfordian assemblages of foraminifera in the Prebetic Zone (Betic Cordillera, SE Spain) were analysed at the genus level to determine their composition, relative abundance, diversity, and dominance, as well as the size of the specimens. A relationship has been established between lithofacies, palaeogeography and composition of foraminiferal assemblages, the former two also determining the stratigraphic record of these microfossil assemblages. Two assemblages of foraminifera serve to identify relatively distal and proximal areas in the Prebetic shelf. The distal assemblage is characterized by higher diversity, specimens of greater size, and more abundant planktic and agglutinated forms. Benthic forms include Ophthalmidium, Epistomina and colonies of encrusting foraminifera. The proximal assemblage shows lower diversity, lower abundance of planktic forms, Epistomina and encrusting nubeculariids, and a greater abundance of spirillinids and Reofax. On the whole, planktic foraminifera decrease upwards in the studied succession, which, together with decreasing nodularity, could be related to system tract conditions previously proposed for Oxfordian deposits in the southern palaeomargin of Iberia.     

羌塘盆地北部乌兰乌拉湖地区晚二叠世古生物新资料

首次在北羌塘盆地北部乌兰乌拉湖地区测制了多条晚二叠世地层剖面,并采获丰富的古生物化石。将区内二叠系划分为那益雄组和拉卜查日组两个正式组级地层单位。描述了新发现的一个类新种和四个海绵类新种,建立了两个类生物带,即Codonofusiella-Gallowayinellalaxa组合带及Palaeofusulinasinensis延限带,一个非有孔虫组合带,即Colaniellanana-Robuloidesacutus组合带。其地质年代为晚二叠世长兴期。     

Biodiversity and community structure of Late Pleistocene foraminifera from Kish Island, Persian Gulf (Iran)

The raised coral reef sequences at Kish Island provide a rare window into the depositional setting and paleoenvironment of a high-latitude, shallow-water coral reef that developed under turbid conditions in the Persian Gulf during Marine Isotope Stage 7 (~200 to 250?ka). Six sedimentary facies and eight foraminiferal assemblages can be identified throughout the sequence. A ninth assemblage can be defined for the modern subtidal realm. At the base of the sequence is a marl rich in hyaline foraminifera (Elphidium, Ammonia, Asterorotalia, Bulimina, Nonion, and Quinqueloculina) and ostracods, which was deposited in about 30–40?m water depth in a turbid deltaic setting. Shallowing resulted in the marl becoming sandy, and changing to a mollusc-rich facies with rare foraminifera (mostly smaller miliolid taxa) that formed the substrate for coral recruitment. The coral marl layer contains many large corals embedded in situ in an aggregate and coralline algae-rich marl. Two abundance peaks in the foraminifera occur at the base and mid-way through this layer, which also correspond to a change from Murrayinella-dominated to Placopsilina-dominated assemblages, indicating deepening and more open-marine conditions, but elevated turbidity. Towards the top of the layer, abundance of foraminifera decreases and miliolid foraminifera become dominant. The top-most layer is dominated by coral and mollusc fragments and has an Amphistegina-rich reef-related assemblage. Of the Late Pleistocene foraminiferal assemblages, the Murrayinella-, Pararotalia-, and Placopsilina-dominated assemblages are no longer present in the modern gulf for unknown reasons. Of the other five assemblages, only the Amphistegina assemblage is found within proximity to the modern Kish Island. The Elphidium and Asterorotalia-Bulimina assemblages are from deeper areas of the gulf. The Ammonia and Quinqueloculina assemblages occur in lagoonal sediments on the Arabian side of the gulf. Like the modern Persian Gulf, the diversity of foraminifera was low (~80 common species) during the Pleistocene and does not correlate with foraminiferal abundance.