二叠-三叠纪转折期放射虫动物群的变化

综述了二叠 -三叠纪转折期放射虫动物群的研究进展 ,长兴阶晚期放射虫动物群 90 %以上的种在二叠纪末期灭绝 ,只有少数在浅海灰岩和远洋硅质岩中均能够发现的属种才成功残存到三叠纪 ;三叠纪放射虫的复苏和辐射经历了较长的过程 ,Griesbachian至 Smithian为放射虫残存期 ,Spathian 为放射虫的复苏期 ,Anisian是放射虫的辐射期。Anisian放射虫的辐射受到强缺氧事件的影响。     

Turonian Radiolarians from Karnezeika,Argolis Peninsula,Peloponnesus (Greece)

Near Karnezeika a roughly 140 m thick Upper Cretaceous section consists of interbedded pelagic limestones, cherts and coarse polymict breccias including ophiolites and shallow water limestones. At the base, pink pelagic limestones rest on deeply altered and fractured Lower Jurassic Pantokrator Limestone. This first pelagic facies is dated as middle Turonian, based on planktonic Foraminifera. Over 100 m of coarse ophiolite-carbonate breccias, interpreted as a channel or canyon fill in a pelagic environment, document the erosion of the Late Jurassic nappe edifice along the Cretaceous Pelagonian margin. Above these breccias, we mesured 16 m of principally pink and red pelagic limestones and radiolarian cherts, in which we recovered well-preserved radiolarians discussed here. In this interval, the presence of planktonic Foraminfera allows to state a late Turonian to Coniacian age. More than 40 radiolarian species are described and figured in this work. The radiolarian chronostratigraphy established by 10 different authors in 11 publications was compared for this study and used to establish radiolarian ranges. This exercise shows major discrepancies between authors for the radiolarian ranges of the studied assemblage. Nevertheless, a Turonian age can be stated based on a synthesis of cited radiolarian ranges. This age is consistent with the age based on planktonic foraminifera. In combining the ages of both Radiolaria and planktonic Foraminifera, the studied samples can be restricted to the late Turonian. However, the discrepancies of published radiolarian ranges call for an urgent, major revision of the Late Cretaceous radiolarian biochronology. The integration of planktonic foraminifera with radiolarians may greatly enhance biochronologic resolution in sections where both groups occur.     

North Pacific Radiolarian assemblages and their relationship to oceanographic parameters

A quantitative study of the distribution of Radiolaria in surface sediments of the North Pacific has demonstrated the feasibility of utilizing complete radiolarian thanatocoenoses as indicators of past oceanographic conditions.In samples from 36 core tops from the region 33° N-54° N, 148° E-140° W, 87–96% of all radiolarians encountered could be assigned to one of 120 taxa recognized. Q-mode factor analysis of distributional data for the 57 most abundant species yields four independent assemblages. Three of these reflect near-surface oceanographic conditions, and the fourth responds to bottom conditions. Regression-developed transfer functions describe the relationship between the assemblages and oceanographic parameters.     

放射虫现代生态学的研究进展及其应用前景--利用放射虫化石揭示古海洋、古环境的基础研究

放射虫以其不易溶解的硅质壳体在古海洋、古环境研究中起着不可替代的作用,其种类组合与海洋物理、水文环境有着很好的对应关系。随着放射虫在古海洋环境研究中的广泛应用以及研究手段的改进,放射虫现代生态学研究在世界各大洋得到了广泛开展。中国加入综合大洋钻探计划,势必会加快[JP2]我国古海洋学的研究步伐,放射虫作为海洋微体古生物中的一个重要类群,其生态学知识是重建古海洋、古环境的基础。因此,有必要向我国学术界提供放射虫现代生态学的研究成果及最新发展趋势,促使我国放射虫的研究与国际接轨,以提供更多的古海洋、古环境替代性指标。     

Uneven Distribution of Pseudotormentus De Wever et Caridroit (Radiolaria, Protozoa): Provincialism of a Permian Planktonic Microorganism

The Permian planktonic distribution is not well known, in contrast to other fossil distributions of nekton and benthos. Radiolaria are representative microfossils of plankton in the Permian palaeocean. This study compares both correlated radiolarian occurrences (Pseudotormentus De Wever et Caridroit and Quadriremis Nazarov et Ormiston) in literature data from the Pacific Rim and quantitative data from the Liuhuang and Gujingling sections in South China. Pseudotormentus distributions are concentrated in the Panthalassa, whereas Quadriremis occurrences are distributed over both the Panthalassa and the Palaeotethys. The uneven distribution of Pseudotormentus seems to have been controlled by a difference in the oceanic basins, indicating the presence of faunal differences in Permian planktonic microorganisms between the Panthalassa and the Palaeotethys. In other words, this study infers the provincialism of Permian planktonic microorganisms. The uneven distribution is explainable by a hypothesis that Pseudotormentus was strongly affected by a Panthalassan equatorial current.     

Paleoceanography of the Santa Barbara Basin during the last 8000 years

The varved sediments of the Santa Barbara Basin off southern California, offer a unique opportunity to study the changes in oceanographic conditions of this nearshore area during the last 8000 yr. Quantitative analysis of Radiolaria found in recent surface sediment samples from the eastern North Pacific allows the identification of four “assemblages” which can be related to the physical oceanography of the California Current. Two assemblages are associated with the southerly flowing California Current, one with the main stream of the current (California Current Assemblage) and the other with the offshore flow along northern California (Central Assemblage). The two other assemblages are associated with the subtropical region of the eastern North Pacific (Subtropical Assemblage) and one found mostly off the coast of Baja California (Baja Assemblage). Analysis of the Radiolaria found in the varved sediments of a core from the Santa Barbara Basin give an 8000-yr continuous record of these four assemblages. The California and Baja Assemblages show only minor fluctuations in their importance in the sediments of the Santa Barbara Basin. The California Assemblage, however, shows a steady increase during this time period. Prior to 5400 yr B.P. the Radiolaria were predominately subtropical in character, whereas after 5400 yr B.P. the Central Assemblage becomes more important. Since 5400 yr B.P. most of the changes in the radiolarian fauna consist of fluctuations in the importance of these two assemblages. Past sea-surface temperatures for the month of February were calculated using the transfer function technique of J. Imbrie and N. G. Kipp (1971, In “The Late Cenozore Glacial Ages” L. K. Turekian, Ed.), (Chap. 5, Yale Univ. Press, New Haven, Conn.). The time series of paleotemperature estimates show major changes in the average February temperature of Santa Barbara Basin waters. The range of estimated temperatures (12°C) exceeds that of the historical observations of February temperatures in the Santa Barbara Basin but does not exceed the observed range for the California Current region. The intervals from 800 to 1800 yr B.P. 3600 to 3800 yr B.P. and 5400 to the end of the record appear to have been generally warmer than today. Comparison of the Holocene record of alpine glacial advances with the radiolarian assemblage and paleotemperature time series shows that the initiations of advances was coincident with a decrease in sea-surface temperatures and an increase in the importance of the Central Assemblage in the Santa Barbara Basin. The terminations of these advances were not marked by any consistent characteristic in the Santa Barbara Basin time series.     

冲绳海槽表层沉积物放射虫属种空间分布特征及其影响因素

为探究冲绳海槽放射虫属种的空间分布特征及其海洋学意义,对采自冲绳海槽北部、中部和南部3个海域的34个表层沉积物中的放射虫群落组成特征进行了系统研究。总体看来,冲绳海槽表层沉积物放射虫丰度较高,群落组成以热带-亚热带暖水放射虫属种为主,其中优势种为Tetrapyle octacantha group、Spongodiscus resurgens和Euchitonia furcata。结果表明冲绳海槽放射虫属种存在明显的区域差异性,除T.octacantha group以外,其余暖水指示种含量总体上均呈现南高北低的变化趋势。冲绳海槽北部陆架-陆坡区受长江冲淡水的影响,温度和盐度变化较为剧烈,因此可能不利于大多数放射虫暖水指示种的发育,但T.octacantha group却因自身适宜生存的温度范围较大,进而得以在冲绳海槽北部陆坡区呈现出高值。较高的中层水温度可能是抑制亚北极中层水指示种Cycladophora davisiana在冲绳海槽分布的主要因素,而冲绳海槽的高海槛则限制了太平洋深层水种Carpocanistrum papillosum和Cornutella profunda的入侵。冲绳海槽放射虫的空间分布对区域海洋环境特征有着很好的响应,因此可以为古环境重建研究提供重要依据。     

Pleistocene radiolarians from the Leg 119 Site 745, sections (1H to 4H) in the southern ocean region

This paper presents a detailed record of radiolarian species from the Leg 119 Site 745 (sections 1H to 4H) in the southern ocean region. Forty five species were identified and illustrated from forty six samples. The taxonomy, two radiolarian zones namely NR1 and NR2, morphological variations and distribution of taxa have been made from these sections. Twelve new species are identified but they are not formally named. The study provides the detailed Antarctic Pleistocene radiolarian data, proposed the placement of NR1 and NR2 zonal boundary at a shallow depth of 6.63 mbsf and data is used for comparative studies with other parts of the Antarctic region.     

Preservation of Radiolarian Diversity and Abundance in Surface Sediments of the South China Sea and Its Environmental Implication

Quantitative analysis of radiolarian preservation in surface sediments from different regional environments of the South China Sea (SCS) is discussed in this article for illustrating their relationship. The results show that species diversity and abundance of radiolarian in the surfacese diment increase with water depth, indicating no obvious dissolution of radiolarian shell in the deep SCS. Upwelling activity and volcanic eruption are both in favor of radiolarian propagation, and cause the settlement enrichment of radiolarian shell. Whereas, an abnormal reduced radiolarian fauna in deeper slope sediment may result from the remain of turbid flow that brings sediments from shallow area, such as shelf and upper slope. Radiolartan species are mainly composed of tropic-subtropic types,and include some cold or polar species, which indicates that a mistake in paleoceanographic analysis should arise from the monospecific index. However, synthesis radiolarian indexes in sediments may well respond to the ecologic and depositional environments in the SCS.     

Albian—Cenomanian Radiolarian Assemblage from the Smaginsk Formation,the Kamchatskii Mys Peninsula of Eastern Kamchatka

The Albian—Cenomanian sediments belong to the oldest deposits bearing fossils in the Eastern Kamchatka. Described in this work is one carbonate-cherty section of the Smaginsk Complex in the Kamchatskii Mys Peninsula. Two interlayers enriched in sapropelic organic matter represent a peculiar feature of the studied section. The interlayers originated most likely under the influence of Cretaceous anoxic events. All radiolarian taxa identified formerly and now in rocks of the Smaginsk Complex are considered. New data clarify the taxonomic composition of radiolarian assemblages, characterizing the Smaginsk Complex. Some of the currently defined radiolarian species were known before only from the DSDP Sites in the Pacific Ocean. According to data of radiolarian analysis, the section part sandwiched between two interlayers enriched in organic matter is attributed to the Cenomanian. The early Cenomanian age is suggested for one of the studied samples.     

南海表层沉积物中放射虫的组合特征与海洋环境

南海拥有较齐全的边缘海地理地貌与生态环境, 沉积物中保存的放射虫种类繁多, 个体丰富.本文采用数理统计与聚类分析方法, 对表层沉积物中放射虫的组合特征进行了较为详细的定量分析, 以期获得可靠的放射虫组合与分布的特征.聚类分析结果显示, 放射虫组合在南海表层沉积物中的分布大致可区分为5种类型: 陆架浅水区型、陆坡珊瑚礁区型、中央海盆区型、南部富营养区型和夏季上升流区型, 它们分别对应于特有的海洋环境, 并由含有某些优势种类的放射虫群落所组成.进一步分析还表明, 南海的北部、中部和南部分别表现为3个不同生态环境的海区: 北部海区受陆源影响较为明显; 中部海区被中央水团、海底火山活动和夏季上升流活动所控制; 南部海区总体上属于典型的珊瑚礁海洋环境, 生态与沉积环境明显优越于北部海区.南海表层沉积物中放射虫的组合分布特征较好地响应和反映了所在海区的生态环境与沉积条件, 是探讨古海洋环境的重要依据.      

新疆南天山库尔干一带泥盆纪—早石炭世放射虫组合的发现

新疆南天山库尔干南阿尔腾柯斯组硅质岩地层中发现了丰富的保存良好的放射虫化石，共计21属34种，11个未定种，1个未定种属。研究表明，两个样品的放射虫组合时代分别为中-晚泥盆世和早石炭世。中-晚泥盆世放射虫组合的发现，丰富了库车地区泥盆纪放射虫生物群组合，为确定阿尔腾柯斯组的时代奠定了生物化石依据。结合前人对该组生物化石的研究，该组为跨时代岩石地层单元，应予解体。而具有早泥盆世-晚石炭世放射虫硅质岩的深水海相沉积地层为古南天山洋盆的演化过程提供了地层学证据。     

南海表层沉积物中放射虫多样性与丰度的分布与环境

采用定量分析方法, 较系统地探讨了整个南海不同环境表层沉积物中放射虫的分布特征及其环境指示意义.结果显示: 南海表层沉积物中放射虫的种类多样性和个体丰度随着水深而增加, 表明南海较深水处的放射虫壳体溶解现象不明显; 上升流活动和海底火山喷发有利于放射虫的大量繁殖, 产生区域性的沉积富集; 反之, 较深水的陆坡区沉积物中出现放射虫种类与丰度异常减少, 可能属浊流搬运再沉积的结果, 物源来自陆架或上陆坡; 种类组成以热带-亚热带特征为主, 还包含了一定数量的冷水种或极区种, 表明在特定海区的古环境分析中采用单一指标判断可能会造成误解.沉积物中放射虫的综合指标较好地反映了南海的生态与沉积环境特征.      

Radiolaria,planktonic foraminifera,and stratigraphy of Turonian-lower Coniacian in the Biyuk-Karasu section,Crimea

The first data on the distribution of Radiolaria and planktonic Foraminifera in the section at Biyuk-Karasu River in central part of the Crimean Mountains, are presented. Based on the study of radiolarian findings, the upper Cretaceous deposits of Biyuk-Karasu section are subdivided into the following biostratigraphic units: Alievium superbum-Phaseliforma turovi (middle Turonian), Dactylodiscus longispinus-Patulibracchium (?) quadroastrum (upper Turonian), and Orbiculiforma quadrata-Patellula sp. B (Turonian-Coniacian boundary deposits). The stratigraphic interval of Alievium superbum-Phaseliforma turovi has been previously characterized by the complex of Alievium superbum-Phaseliforma sp. A (middle Turonian, Mt. Chuku section, SW of the Crimean Mountains, and middle Turonian, Mt. Ak, central part of the Crimean Mountains). Based on the study of Foraminifera findings, the following biostratigraphic subdivisions were identified: Whiteinella paradubia (lower-lower part of the middle Turonian), Marginotruncana pseudolinneiana (uppermost middle Turonian), and Marginotruncana coronata (upper Turonian). The complex of beds with Marginotruncana pseudolinneiana and Marginotruncana coronata are comparable to the deposits of zones of same name in the Crimean-Caucasian region.     

Radiolarites et sédiments hypersiliceux océaniques: une comparaison

The mineralogical and chemical composition of Jurassic radiolarian cherts has been studied in Morocco (Rif), Italy (Lombardy basin and Apennines), Greece (Pindus zone and Vourinos Massif), some in close association with ophiolites. We have compared these samples with Cretaceous cherts from the NW Pacific (Leg 32) and with Cenozoic diatomaceous oozes from the Sea of Japan (Leg 31). The silica in the radiolarian cherts is quartz or chalcedony. Most of these rocks also contain feldspars and hematite while the clay fraction is composed of illite and/or chlorite generally associated with swelling clays and, locally, with kaolinite. In oceanic sediments all mineralogical species of silica have been detected (from opal to quartz), the clays generally being the same as those of the radiolarian cherts, the feldspars also being present. Based on the chemical composition of the radiolarian cherts, three facies can be distinguished: massive cherts, pelitic radiolarites and ferruginous radiolarites, the latter occurring only near the contact with volcanic basement. The chemical composition of cherts and diatom oozes from the Pacific is very close to the composition of radiolarian cherts. Although the mineralogy of radiolarian cherts can be related to several models (detrital, diagenesis of pelagic clays etc.) the detrital origin of part of the clay fraction seems certain. The origin of silica and its relation to the palaeolatitudes and the relatively confined nature of the Tethys oceans as well as the influence of volcanic inputs are evaluated, Chemical and mineralogical composition of radiolarian cherts shows that the diagenesis of the clay fraction is not a significant source of silica. Accumulation of diatom oozes in the Sea of Japan and in other areas, shows that the distance from continents and very deep seas are not essential to the development of siliceous sedimentation.     

新疆南天山库尔干一带泥盆纪-早石炭世放射虫组合的发现

新疆南天山库尔干南阿尔腾柯斯组硅质岩地层中发现了丰富的保存良好的放射虫化石,共计21属34种,11个未定种,1个未定种属。研究表明,两个样品的放射虫组合时代分别为中—晚泥盆世和早石炭世。中—晚泥盆世放射虫组合的发现,丰富了库车地区泥盆纪放射虫生物群组合,为确定阿尔腾柯斯组的时代奠定了生物化石依据。结合前人对该组生物化石的研究,该组为跨时代岩石地层单元,应予解体。而具有早泥盆世—晚石炭世放射虫硅质岩的深水海相沉积地层为古南天山洋盆的演化过程提供了地层学证据。     

Integrated Radiolarian and Conodont Biostratigraphy of the Middle to Late Permian Linghao Formation in Northwestern Guangxi, South China

The Permian radiolarian zones and their correlations with conodont zones or other chronostratigraphic schemes are still under debate. In this study, four genera, 21 species and two subspecies of radiolarians together with one genus and six species of conodonts were recovered from the Linghao Formation cropping out at the Longwangpo (LWP) section, northwestern Guangxi, South China. Six radiolarian interval zones and one abundance zone are recognized in the section, namely in ascending order, the Follicucullus scholasticus, Albaillella cavitata, A. protolevis, A. levis, A. excelsa, A. triangularis Interval zones and A. yaoi Abundance Zone. They are correlated with the Clarkina dukouensis, C. guangyuanensis and C. orientalis conodont zones recognized at the same section. Based on our data, the F. scholasticus Interval Zone and the lowermost part of A. cavitata Interval Zone are recognized to be upper Capitanian age, whereas the four Albaillella Interval zones are of Lopingian age (Wuchiapingian to the late Changhsingian). Two previously known Changhsingian radiolarian zones, namely the A. triangularis and A. yaoi Interval zones, should be extended down to the uppermost Wuchiapingian in this studied section.     

Early Eocene Radiolarian Fauna from the Sangdanlin, Southern Tibet: Constraints on the Timing of Initial India-Asia Collision

This is a new report on the early Eocene radiolarian fauna from the Sangdanlin section in the Gyirong region, along the southern margin of the Yarlung Zangbo Suture Zone. The Sangdanlin section measured in this study is divided into three lithostratigraphic units from bottom to top: the Zongzhuo, Sangdanlin, and Zheya formations. Abundant radiolarian fossils were obtained from the Sangdanlin section and 54 species of 30 genera were identified and assigned as follows: Cryptamphorella conara-C. macropora the late Cretaceous Zone and Amphisphaera coronate, Buryella tetradica-Bekoma campechensis, and B.bidartensis-B. divaricata the Paleocene-early Eocene Interval Zones. The Paleocene–early Eocene radiolarian zones are comparable to the radiolarian zones RP4-RP8 in New Zealand. Based on the data of radiolaria and lithofacies, it is suggested that the Zongzhuo Formation should be deposited along the base of the north-facing, continental slope of the Greater Indian continental margin, and the Sangdanlin Formation should be a deep marine, sedimentary sequence located in a foreland basin. The early Eocene radiolarian fauna in the Sangdanlin Formation constrains the initial age of the India-Asia collision to no later than 53.6 Ma.     

The radiolarian assemblages of the Bonarelli Horizon in the Umbria-Marche Apennines and Southern Alps, Italy

The Bonarelli Horizon is an important regional marker level in the Umbria-Marche Apennines. It is characterized by consisting of black bituminous shales that yield a distinctive radiolarian fauna. Black shales referable to the Bonarelli Horizon are also present in the Southern Alps. The horizon is of uniform lithology and contains radiolarian assemblages of late Cenomanian-early Turonian age throughout both the Umbria-Marche Apennines and Southern Alps. Several new radiolarian taxa have been recognised and described from the Bonarelli Horizon of both areas. Two new species are defined in this paper, namelySethocapsa bossoensisandXitus picenus.     

Late Olenekian Radiolarians from Bedded Chert of Ashio Terrane, Northeast Japan,and Faunal Turnovers in Western Panthalassa during Early Triassic

Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria, with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Asisian faunas, respectively, and is herein named the Minowa fauna. Study of the literaure indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore, 121 of 143 species disappeared during late Olenekian time, and in turn 118 new species appeared in the western Panthalassa around the Olenekian-Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic.The first turnover is the Poalaozoie-type radiolarian extinction at the Permain-Triassic boundary,the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time, and the third is a faunal turnover from the Minowa fauna to the true Mesozoic-type radiolarian famas that are characterized by mulit0segmented Nassellaria.