塔里木盆地泥盆系——石炭系界线研究

塔里木盆地泥盆系－石炭系东河塘组,甘木里克组和巴楚组产生丰富的孢子,牙形刺和鱼化石,本文依据古生物地层的最新研究成果,论述了东河塘组和甘木里克组（含砾砂岩段）的时代为晚泥盆世,巴楚组（下泥岩段和生屑灰岩段）的时代限于早石炭世早期,论证了泥盆系一石炭系界线应划在含砾砂岩段和下泥岩段之间。     

Dinoflagellate cyst stratigraphy and depositional history of Miocene and Lower Pliocene formations in northern Belgium (southern North Sea Basin)

The occurrence of organic-walled dinoflagellate cysts (dinocysts) in the Diest Formation, a largely decalcified succession with a poor fossil content, and in the adjacent strata of Lower Miocene and Lower Pliocene formations, allowed a biostratigraphic evaluation of these deposits and an assessment of the hiatus between the lithostratigraphic units. The Diest Formation was deposited during Tortonian – Messinian times. Dinocyst biozones defined in the North Sea region and the U.S.A. East Coast are recognised within the Diest Formation, although environmental factors seem to have influenced the presence of some key zonal species in the shallow-marine deposits of northern Belgium. The two members of the Diest Formation studied, i.e., the Dessel Sands and the Diest Sands, appear to be strongly diachronous. The depocentre was located in the Campine area during the early Tortonian and shifted to the area north of Antwerp during late Tortonian to Messinian times. The age assessment provides a correlation of the sequence boundaries of Haq et al. (1987) at the top of the Diest Formation with SB 5.5.     

滇黔桂盆地早二叠世亚丁斯克期的沉积环境分异与䗴有孔虫响应

亚丁斯克期华南滇黔桂地区沉积环境分异明显,主要发育局限或半局限海台地沉积区、开阔海台地沉积区和台地边缘沉积区,不同沉积区䗴有孔虫动物群面貌也有所区别。本文详细研究了黔南地区的猴场打望剖面和惠水竹子冲剖面阿瑟尔期—亚丁斯克期的地层,在打望剖面识别出4个䗴类化石带,由老至新为Pseudoschwagerina beedei-Sphaeroschwagerina constans共存延限带、Staffella xiushuiensis-Eoparafusulina contracta富集带、Pseudofusulina ellipsoidalis富集带和Misellina subcycloidea间隔带。竹子冲剖面识别出3个化石带,由老至新为Pseudoschwagerina uddeni-Sphaeroschwagerina sphaerica组合带、Eoparafusulina certa富集带和Staffella discoides延限带。对滇黔桂地区不同沉积相区剖面䗴类动物群以及沉积相特征的综合研究显示:开阔台地或台地边缘环境的䗴动物群以Pamirina为特征分子,同时还产出丰富的希瓦格䗴亚科(Schwagerininae)分子;局限或半局限台地环境的䗴类以史塔夫䗴亚科分子(Staffellininae)为主。沉积环境对䗴有孔虫的影响可能主要来自水动力、光照和氧气含量。个体较大、隔壁褶皱强烈的纺锤形希瓦格䗴亚科分子更适应水动力强、透光性好、氧气充足的水体;小个体、结构简单的史塔夫䗴亚科分子可在透光性差、含氧量较低的水体中生存。     

黔南上司地区石炭系有孔虫:兼论华南维宪阶有孔虫生物地层序列

石炭纪时期有孔虫具有演化快、分布广、数量丰富、分异度高的特点,对于地层的划分对比具有极为重要的意义。与全球其他重要的石炭纪沉积区相比,华南有孔虫生物地层划分精度相对较低。本文首次较为系统地报道了华南石炭系代表性岩石地层单位旧司组和上司组下部丰富的有孔虫化石及其在剖面上的分布情况,并综合现有关于华南的有孔虫化石资料,将华南维宪阶划分为7个有孔虫化石带,自下而上分别为Eoparastaffella simplex带、Viseidiscus/Planoarchaediscus带、Paraarchaediscus带、Pojarkovella nibelis带、Koskinotextularia带、Bradyina带和Janischewskina带。这些有孔虫带可与全球其他典型的石炭纪沉积区进行很好的对比,从而为相关的研究提供一个较为精细的地层格架。通过对黔南上司地区有孔虫的研究,提议中国石炭系区域性年代地层单位上司阶底界可用有孔虫Bradyina的首现定义,并将上司阶与西欧的Warnantian亚阶中上部和俄罗斯的Aleksinian亚阶—Venevian亚阶对比,对应国际维宪阶上部,为全球石炭系年代地层对比提供了可靠的化石依据。     

Biostratigraphy,sedimentology and sequence stratigraphy of the Tournaisian–Viséan transitional strata in South China (Guangxi)

The biostratigraphy and sedimentological evolution of the Tournaisian–Viséan (T–V) transitional strata in South China (Guangxi) have been investigated. The sediments were deposited on a carbonate platform and in slope and basinal environments. In the T–V transitional strata, six foraminiferal associations have been distinguished which allow correlation between the shallow and deep water deposits. A careful examination of the evolutionary stages of the foraminifer Eoparastaffella provides a more accurate criterion for the definition of the T–V boundary, but does not significantly modify the historical one. The distinction of two morphotypes is based on the elevation of the last whorl and the peripheral outline. Tournaisian specimens of Eoparastaffella have a well rounded periphery (morphotype 1) contrasting with the subangular periphery of younger Viséan specimens (morphotype 2). A coefficient can be deduced from simple biometric measurements for more precisely defining the T–V boundary. The sequence stratigraphy of the T–V strata in South China has been reconstructed by combining biostratigraphical and sedimentological data. It allowed the correlation of the T–V transitional strata between the platform area and the slope and basinal locations. Late Tournaisian strata were deposited during a highstand systems tract. Near the end of the Tournaisian, a major drop in relative sea-level led to the development of an unconformity in the platform area. Lowstand deposits formed during latest Tournaisian time in the basin where a detailed biostratigraphic framework has been devised. Sediments deposited during the ensuing transgressive systems tract overlie the late Tournaisian highstand sediments in the platform area and the latest Tournaisian lowstand deposits in the basin. A major drop in relative sea-level near the end of the Tournaisian has been recognized worldwide. Therefore, the possibility of using the sequence stratigraphy of the T–V strata in South China for worldwide correlations should be investigated. © 1997 John Wiley & Sons, Ltd.     

The paleobiogeographical significance of the Silurian and Devonian trilobites of Japan

Six major groups of trilobites from the Silurian and Devonian of Japan are evaluated for their paleobiogeographical signature. Silurian illaenids and scutelluids show four generic‐level and at least two species‐level links with the Australian segment of the Gondwana paleocontinent; encrinurids also indicate two generic‐level links with Australia and also the South China paleocontinent; whilst Devonian phacopids, and possibly proetids, suggest at least two generic‐level links with the North China paleocontinent. These different patterns may reflect the fragmentary biostratigraphical record of Japanese trilobites, but they also appear to reflect paleoenvironmental parameters associated with lithofacies, and paleoecology. Thus, Japanese assemblages of proetids and phacopids occurring in deep‐water clastic lithofacies have counterparts in similar settings in North China, and Japanese scutelluids and illaenids are strongly associated with shallow marine carbonate lithofacies that are similar to those of their occurrences in Australia. Japanese encrinurids occur in carbonate rocks indicative of shallow marine settings in the Kurosegawa Terrane, and they demonstrate a consistent paleobiogeographical affinity with Australia and South China. Larval ecology cannot be directly assessed for Japanese trilobite groups. However, proetids have consistently been shown to have planktonic protaspides, whereas illaenids, scutelluids, and encrinurids have benthic protaspides. Planktonic protaspides would have a greater propensity for distribution in ocean currents than benthic ones, and therefore may be of more limited paleobiogeographical utility. The combined data from the six different groups indicates that the complex paleobiogeographical patterns of the Japanese trilobite assemblages need to be interpreted with caution, and similarity of taxa does not necessarily denote paleogeographical proximity to other regions.     

Sedimentology,palaeoecology and geochronology of Last Interglacial deposits from Deeping St James,Lincolnshire, England

Pollen, plant macrofossil, molluscan and coleopteran data from organic muds below the low terrace of the River Welland at Deeping St James, Lincolnshire indicate deposition in the mixed oak forest phase of a Late Pleistocene interglacial. Coleopteran and molluscan data suggest summer temperatures up to 4°C warmer than at present in eastern England, and plant macrofossil material suggests a climate more continental than that of Britain in the Holocene. No direct analogue of this biota, however, exists currently in Europe. Biostratigraphical indications from the pollen coleoptera and Mollusca suggest an age in the Ipswichian Interglacial. Thermoluminescence dates between 120 ka and 75 ka and amino-acid ratios with a mean of 0.11 show that deposition of the sediments took place during Oxygen Isotope Stage 5. This accurate dating of a partial Ipswichian succession allows discussion of the ages of a number of other interglacial sites in eastern England of assumed Ipswichian age. Copyright © 1999 John Wiley & Sons, Ltd.     

Radiolarian biostratigraphy in the Southern Bering Sea since Pliocene

Detailed radiolarian biostratigraphy in the Plio-Pleistocene was analyzed by using samples from IODP Site U1340 that was drilled to a core depth of 604 m in the southern Bering Sea. A total of 227 species belonging to 102 genera were identified. Based on the distributions of the radiolarian index species at Site U1340, five radiolarian zones since the Pliocene were established in the southern Bering Sea for the first time, and 25 radiolarian bioevents were recognized. Their ages were estimated on the basis of the age-depth plot that was constructed by the synthetical datum of the effective biostratigraphic and magnetostratigraphic events. The radiolarian zones at Site U1340 were systematically compared with those in its adjacent regions since the late Early Pliocene, which further improved and interpreted the biostratigraphic datum as well as their correlations in the middle-high latitude of the North Pacific. In addition, the comparative results of radiolarian zones show that Botryostrobus aquilonaris Zone emended in this paper is equivalent to the upper part of the same zone defined by Hays, 1970, and Druppatractus irregularis-Dorydruppa bensoni Zone as well as Spongodiscus sp. Zone, newly proposed in this paper, are well correlated with Cycladophora sakaii Zone and Stylatractus universus Zone in the subarctic North Pacific, respectively.     

海南岛含杜内早期腕足动物群层的发现

白沙县金波附近的 Spirifer subgrandis Rotai,Unispirifer extensus Tan,Fusella tornacensis (Koninck) ,Punctospirifer insculptus (Phillips) ,Marginatia huaqiaoensis Tan,Palaeochoristites sp.,Megachonetes sp.,Plicochonetes sp.,Schuchertella sp.,Pustula sp.,Sentisia sp.,Crurithyris sp.,Rhipidomella spp.等是海南岛首次发现的最丰富的杜内早期腕足动物群。据此 ,该地区含化石的南好组第四段确定为下石炭统岩关阶 ,似可与湖南马栏边组、黔南汤耙沟组等层位对比。以石燕贝类最繁盛、长身贝类数量少为特征的该动物群与华南其他地区同期腕足动物群存在诸多相同属种但又有明显差异。