珠江口盆地荔湾凹陷W22井渐新世生物地层研究

通过对珠江口盆地荔湾凹陷超深水井W22井3 266～3 991 m井段72个样品开展有孔虫和钙质超微化石分析,讨论了该层段的地层划分并确定了其年代。研究层位含有丰富的有孔虫和钙质超微化石,详细的生物地层学分析显示其属于渐新世。其中,有孔虫分析发现3 390 m以下为早渐新世P18-P21a带沉积、3 380 m以上为晚渐新世P21b-P22带至N4带下部沉积,显示其地层年代为33-23 Ma;而钙质超微化石分析则揭示出该层位包含了自NP25带底部到NP21带的地层,下渐新统/上渐新统的沉积界限在3 390 m左右, Coccolithus formosus的末现面出现在3 841 m表明钻井3 841 m以深地层年代大于32.92 Ma,但更深地层未发现始新世钙质超微化石,表明底部年龄仍为早渐新世,但推测已经接近渐新世/始新世界限(33.89 Ma)。荔湾凹陷渐新世经历了从陆架浅海到上陆坡半深海环境的演变。     

珠江口盆地新近系钙质超微化石研究综述

根据珠江口盆地新近系钙质超微化石研究文献,综述了研究内容及发展过程。纵观二十多年来珠江口盆地新近系钙质超微化石的研究历史,大致可分成两个阶段(1)上世纪80年代初至90年代初,侧重于化石带的报道及主要化石属种的描述;(2)上世纪90年代中后期至今,主要为高分辨率钙质超微生物地层研究阶段。评述了以往研究中存在的问题,明确了今后研究的方向与任务。     

珠江口盆地西部古近系与新近系生物地层界线研究

古近系与新近系的界线在浮游生物地层分带中的具体位置长期存在争议,笔者依据珠江口盆地西部50余口钻井微体古生物资料中的浮游有孔虫和钙质超微化石记录,辅以沟鞭藻和主要孢粉事件对研究区古近系与新近系的生物地层界线展开研究,探讨了浮游有孔虫Globigerina ciperoensis,Globoquadrina dehiscens,Globigeri-noidestrilobus以及钙质超微浮游生物Sphenolithus ciperoensis,Zygrhablithus bijugatus和Reticulofenestra bisec-ta等标志性化石的地层意义,并重新厘定了珠江口盆地西部古近系与新近系的生物地层界线标准。     

南海北部珠江口盆地PY30井早中新世-更新世钙质超微化石生物地层及沉积环境

本文对南海北部珠江口盆地PY30井早中新世―更新世地层中的钙质超微化石进行了系统研究,发现490-690m和1 040-1 170m井段化石丰度和分异度均较高,700-1 035m和1 179-1 809m化石丰度中等,井段下部1 818-3 478m化石稀少,种类单调。根据钙质超微化石标志种的存在,对该井的生物地层进行了划分。在490—3 478m地层中识别出12个钙质超微化石带或联合化石带,地层时代为早中新世―更新世,据此建立了该井的钙质超微化石生物地层框架,探讨了下中新统与中中新统、中中新统与上中新统、上中新统与上新统以及上新统与更新统界线划分的钙质超微化石标志。根据钙质超微化石总丰度、分异度及特征性环境指示种丰度的变化,划分了8个沉积环境演化阶段,从而讨论了早中新世至更新世沉积环境演化特征。     

珠江口盆地揭阳凹陷早渐新世-中新世古生物地层及沉积环境

位于珠江口盆地揭阳凹陷的S1井是盆地东南部唯一钻井,其地层和沉积环境分析意义重大。本研究通过对S1井孢粉、有孔虫和钙质超微化石地层对比分析,确定了所钻地层时代。井段(3 326.5～2 950 m)共鉴定孢粉40属62种,孢粉组合无明显变化,以桤木粉-双束松粉为主,组合与盆地内渐新统珠海组相同。整个分析段3 326.5～2 059.5 m共鉴定浮游有孔虫11属41种,依据标准种首末现事件共划分出P19-N6 5个带或联合化石带。钙质超微化石共鉴定8属24种,划分NP23-NN4共5个钙质超微化石带。综合判定:地层时代为早渐新世-早中新世(～31-18 Ma),渐新统与中新统的界限在2 876.5 m附近。利用浮游有孔虫的丰度和底栖有孔虫的组合来判别该地层的沉积环境,认为揭阳凹陷S1井在早渐新世-早中新世均为陆坡深水环境,水深1 000 m。     

南海北部琼东南盆地崖北凹陷Y-8-X井晚渐新世—更新世钙质超微化石

对南海北部琼东南盆地崖北凹陷Y-8-X井1 338.1～3 086.1 m井段内的110块样品进行了钙质超微化石分析,发现上部1 338.1～2 075.7 m地层含较丰富的钙质超微化石,而下部2 091.0～3 086.1 m井段化石丰度低或未见。根据钙质超微化石标志种的存在,识别出NN17带、NN15带、NN11带、NN6带、NN4带和NP25带等6个钙质超微化石末现面事件,由此对该井的生物地层进行了划分,认为研究井段的地层时代为晚渐新世—更新世,推测本井缺失了部分中新统沉积。依据钙质超微化石总丰度、分异度及特征性环境指示属或种的丰度变化,探讨了1 338.1～3086.1 m井段的沉积环境演化过程,可分为6个演化阶段。从晚渐新世至更新世,经历了海水由浅变深再变浅的过程,其中早中新世早期水深最浅,中中新世—早上新世水体温暖且水深最大。     

微古生物在高分辨层序地层学中的应用——以珠江口盆地惠州凹陷层序地层分析为例

以南海珠江口盆地惠州凹陷第三纪某井段的层序地层分析为例,说明微古生物（钙质超微化石和有孔虫）在层序地层分析中的作用。浮游有孔虫和钙质超微化石的ＬＯＤ能为层序地层提供精确可靠的年代地层格架,它们的丰度、分异度的峰值能指示沉积层序中不同的界面特征。通常浮游有孔虫和钙质超微化石的丰度、分异度的最大峰值与层序中最大海泛面凝缩段对应,而层序界面附近井段出现丰度、分异度峰值的低谷。     

南海北部莺琼盆地钙质超微化石年代地层研究

本文依据南海北部大陆架莺琼盆地67口钻井的钙质超微化石资料,结合ODP184航次、2004年国际地质年代表等国内外几十年以来的研究成果,探讨了研究区渐新统以来31个钙质超微化石属种的地质年代意义,厘定了18个化石带及3个联合化石带。讨论了乐东组、莺歌海组、黄流组、梅山组、三亚组、陵水组和崖城组的时代归属以及更新统与上新统、上新统与中新统、上中新统与中中新统、中中新统与下中新统、中新统与渐新统界线的钙质超微化石划分标志,建立起可与全球对比的莺琼盆地高精度年代地层格架。     

伊朗卡尚地区古近纪介形类的发现

本文简要报道了发现于伊朗卡尚地区古近系的介形类,计16属6种、8比较种、9未定种及1亲近种。根据介形类化石组合面貌,并结合钙质超微、沟鞭藻和有孔虫化石组合,认为含介形类化石的地层时代为始新世至渐新世,推测其沉积环境为正常浅海大陆架环境,而且为温暖浅海内陆架。     

赤道几内亚里奥姆尼盆地K-1井白垩纪生物地层

赤道几内亚境内西部里奥姆尼(Rio Muni)盆地K-1井白垩纪地层含丰富的沟鞭藻类,孢粉,钙质超微和介形类等化石,自下而上可以划分出3个生物组合带,A带含孢粉Classopollis-Cicatricosisporites-Inaperturopollenites-Afropollis组合和介形类Hourcqia,Petrobrasia等,时代属于Aptian—Albian期。B带含孢粉Schizaeoisporites-Ephedripites-Jugella-Tricolpites组合,沟鞭藻类Dinogymnium,Oligosphaeridium,Impletosphaeridium,Florentinia,以及钙质超微化石Eiffelithus eximius,Lithastrinus grillii,Eprolithus moratus等,时代为Cenomanian—Santonian期。C带含孢粉Polypodiaceae-Psophosphaera-Proteacidites-Tricolpopollenites组合,沟鞭藻类Peridiniaceae,Dinogymnium,Tenua,Spiniferites,和钙质超微化石Micula concave,Arkangelskiella cymbiformis等,时代为Campanian—Maastrichtian期。     

Reproducibility and reliability of the Pliensbachian calcareous nannofossil biohorizons from the Basque-Cantabrian Basin (Northern Spain)

Based on calcareous nannofossil assemblages identified in four expanded and well-dated sections from the Basque-Cantabrian Basin, the main objective of this paper is to improve the knowledge of the Pliensbachian calcareous nannofossil events, and to calibrate these events to the ammonite zones established for this area. The semiquantitative analysis of more than 140 smear slides from the Tudanca and Santotis sections, and the re-analysis of more than 200 smear slides from the Camino and San Andrés sections, have been carried out in order to describe the succession of calcareous nannofossil assemblages. Related to their composition changes, we have recognized and calibrated to the ammonite zones two main events: the first occurrences (FOs) of Similiscutum cruciulus and Lotharingius hauffii, and six secondary events: the FOs of Biscutum novum, Biscutum grande, Biscutum finchii, Lotharingius barozii and the FCOs (first common occurrences) of Calcivascularis jansae and L. hauffii. In the Camino and San Andrés sections, we also identify the FOs of Biscutum dubium, Bussonius prinsii and Lotharingius sigillatus. The obtained data allow us to assess the degree of reproducibility of the Pliensbachian calcareous nannofossil events in the studied area. The biohorizon succession recognized in the Basque-Cantabrian Basin are compared to those proposed for NW Europe, Lusitanian Basin, Italy and Southern France.     

High resolution calcareous nannofossil biostratigraphy and paleoecology across the Latest Danian Event (LDE) in central Eastern Desert,Egypt

A detailed study of the calcareous nannofossil assemblages of latest Danian to early Selandian age from Wadi Qena (the Qreiya-1, Qreiya-2, and Araas sections) in the central Eastern Desert and the Gebel Duwi section at the Red Sea Coast has been carried out to understand the local phytoplankton paleocommunities. For the first time in Egypt four calcareous nannofossil zones (NTp6, NTp7, NTp8, NTp9) and five subzones (NTp7A, NTp7B, NTp8A, NTp8B and NTp8C) were distinguished subdividing the standard NP4 and NP5 zones. The calcareous nannofossil zones were correlated with nannofossil zonations from the Tethyan region (e.g. Tunisia and the Zumaia section, the GSSP for the Danian/Selandian boundary). The calcareous nannofossil assemblages are moderately to well preserved. The event beds are characterized by a dark-brown shaley-marl bed rich in organic carbon and coprolites. Three main assemblages are distinguished: a pre-event assemblage, a transitional assemblage and a post-event assemblage. The paleoenvironments vary from cool eutrophic water below and above the event to warm oligotrophic conditions during the event. The result of this study concludes that the “Latest Danian Event” (LDE) may represent an early Paleocene hyperthermal.     

从微体化石群看我国沿海早第三纪含油盆地的差异

对我国沿海3个含油盆地－珠江口、北部湾和渤海湾盆地下第三系湖相生油岩中的微体化石群进行比较分析。3个盆地中以渤海湾盆地下第三系湖相化石群最为丰富,数量多,分异度高,而且化石群以地方性属种比例高、咸水类型多,存在“海源陆生生物化石”为特征;北部湾盆地,在涠洲组和流沙港组发现较多的介形类化石及个别腹足类和轮藻化石;而珠江口下经三系湖相地层中,微体化石罕见,只在个别层位发现贝壳碎片。据化石群特征,推测渤海湾盆地早第三纪是封闭型的咸水湖泊,而且部分沉积时期,可能是以Cl^-和Na^ 为主的咸水湖泊;珠江口盆地早第三纪是湖水矿化度低、硬度、pH值也低的淡水湖泊;而北部湾盆地早第三纪可能仍属淡水湖泊,但有一定的矿化度。     

西藏南部岗巴地区白垩纪中期钙质超微化石带和Cenomanian-Turonian界线

我国西藏南部海相白垩系含有较丰富的钙质超微化石。文中着重研究岗巴地区两个剖面 (即剖面A ,B)Albian Santonian钙质超微化石的分布。根据标志种的存在 ,识别出 5个初现面事件 ,相应地建立 6个钙质超微化石带 ,自下至上是Prediscosphaeracretacea带 ,Eiffellithusturriseiffeli带 ,Lithraphiditesacutum带 ,Gartneragoobliquum带 ,Quadrumgartneri带 ,Lucianorhabduscayeuxii带。同时 ,通过洲际对比 ,建议以G .obliquum初现面作为划分本区Cenomanian和Turonian界线的标志。此外 ,Q .gartneri带和I .cayeuxii带之间缺失多个化石带 ,据此推测Turonian至Santonian期间本区可能存在沉积间断。     

Calcareous nannofossil productivity and carbonate production across the Middle-Late Jurassic transition in the French Subalpine Basin

The distribution pattern of calcareous nannofossils was analysed across the Middle-Late Jurassic transition in the French Subalpine Basin (south-eastern France). This basin is characterized in the hemipelagic-pelagic domain by a continuous sedimentary succession, allowing a good biostratigraphic resolution for this time interval. The nannofossil assemblages are consistently dominated by Watznaueria britannica. However, major changes in trophic and paleoenvironmental conditions are recorded across the Middle-Late Jurassic transition. An increase in marine primary productivity and cooling of surface waters is recorded across the Callovian-Oxfordian boundary, as already shown in the higher latitude setting of the eastern Paris Basin. Increased precipitation and runoff under contrasting seasonal climatic conditions (monsoon-type) has led to eutrophication of marine surface waters in the French Subalpine Basin at this period. Then, decreased runoff and associated nutrients certainly linked to drier climatic conditions lead to a decrease in calcareous nannofossil productivity during the middle part of the Early Oxfordian (mariae-cordatum ammonite Zone transition). At the Early-Middle Oxfordian transition, more favourable conditions for the nannofossil community (warmer and mesotrophic surface waters) prevailed. The pelagic (nannofossil) carbonate contribution is limited, and the carbonate fraction is predominantly of nektonic/benthic origin at the Callovian-Oxfordian transition and of allochthonous origin from carbonate platforms at the Early Oxfordian-Middle Oxfordian transition.     

长江三角洲DY03孔颗石藻及沉积环境浅析

本文研究了上海奉贤DY03孔的颗石藻化石。钻孔60.8-2m深度产颗石藻化石,涵盖上更新统的川沙组、南汇组,全新统的娄塘组、上海组和青浦组。颗石藻化石赋存于灰色泥、泥质粉砂或粉细砂中,但化石种类贫乏。群落面貌以Gephyrocapsa oceanica占绝对数量,Braarudosphaera bigelowii,Helicosphaera hyalina和Heli-cosphaera wallichii等偶现,属典型的单种类组合。研究依据颗石藻定量统计,划分出两个海相层:第一海相层,孔深61-40m,属上更新统川沙组和南汇组,颗石藻丰度低,属种单一,代表了海侵过程中的潮上带环境;第二海相层,孔深24.8-2.0m,属全新统娄塘组、上海组和青浦组,颗石藻化石丰度较高,并有数个属种共生,反映当时的滨岸潮上带-河口滨海-浅海近岸海湾的环境演化过程。综合前人的研究成果,认为长江三角洲全新世海侵之强度和范围都超过晚更新世发生的海侵。此外,本文仔细讨论了Gephyrocapsa oceanica的生态特征,显示其为一个盐度适应能力较强、分布广泛的暖水种。     

Contribution of calcareous nannoplankton to carbonate deposition: a new approach applied to the Lower Jurassic of central Italy

The Upper Pliensbachian–Lower Toarcian Somma section (Central Italy), which displays alternation of limestone–marl lithotypes, was investigated for its calcareous nannofossil and CaCO₃ contents. In order to evaluate the contribution of calcareous phytoplankton to the carbonate fraction of rocks a new method was applied combining a recently developed technique for nannofossil absolute quantification and measurements of nannofossil size. Our study suggests that nannofossils did not produce the bulk of carbonate mud in the studied section, although they contribute to different extents to the pelagic carbonate fraction. The contribution of both coccoliths and (mainly) the Incertae sedis Schizosphaerella to the carbonate fraction was important only in periods of reduced accumulation rates and/or during clay deposition. The highest estimated carbonate production by nannofossils in the studied section is around 83% of the total carbonate content, but in a sample containing only 12.8 wt% CaCO₃. The observed limestone–marl alternations therefore result from cyclical export of carbonate mud from the shallow Latium–Abruzzi carbonate platform to the Umbria–Marche Basin and, only subordinately, from changes in nannoplankton productivity.     

Pliensbachian (Early Jurassic) calcareous nannofossils from the Peniche section (Lusitanian Basin,Portugal): A clue for palaeoenvironmental reconstructions

Quantitative analysis of Early Jurassic calcareous nannofossil assemblages from the Peniche section in Portugal have been performed in order to interpret palaeoenvironmental changes occurring in the Lusitanian Basin during the Late Pliensbachian Davoei, Margaritatus and Spinatum Ammonite Zones. Nannofossil data are compared to already published carbon and oxygen stable isotope data, organic matter content (wt.%Total Organic Carbon, TOC), and biomarker analysis. A significant change in calcareous nannofossil assemblages and species diversity at the transition between the Margaritatus and Spinatum Ammonite Zones matches with the pattern shown by geochemical data. This suggests that a profound change in environmental conditions occurred at that time. In the Davoei and Margaritatus Ammonite Zones, in a context of general sea-level rise, the Lusitanian Basin was characterized by water column stratification that favoured the sedimentation and preservation of organic matter. Biomarkers and oxygen isotope trends suggest that stratification of water masses occurred because of low salinity in surface waters. The shallowest part of the water column, characterized by oligotrophic conditions, was inhabited by the (probable) calcareous dinocyst Schizosphaerella spp., while the deep-dweller Crepidolithus crassus flourished in the lower photic-zone layers. In the Spinatum Ammonite Zone, a regressive trend occurred and a salinity increase is inferred on the basis of oxygen isotope values. Water masses were probably less stratified at that time. The upper photic-zone nannofossil assemblages were still dominated by Schizosphaerella spp. whilst, in the deep photic-zone, Mitrolithus jansae (a Mediterranean taxon) replaced C. crassus (a taxon with NW-European affinity). This pattern may indicate a change in palaeoceanographic conditions related to surface current circulation. The sea-level fall occurring during the Spinatum Ammonite Zone may have resulted in the partial isolation of the Lusitanian Basin from the NW-Europe basins because of the creation of a threshold. Alternatively, tectonic drowning of North African carbonate platforms in the Late Pliensbachian may have promoted better exchanges of nannoplankton between the Lusitanian Basin and the Mediterranean Tethys via the creation of new seaway connections.     

Palaeogene marine stratigraphy in China

Palaeogene deposits are widespread in China and are potential sequences for locating stage boundaries. Most strata are non‐marine origin, but marine sediments are well exposed in Tibet, the Tarim Basin of Xinjiang, and the continental margin of East China Sea. Among them, the Tibetan Tethys can be recognized as a dominant marine area, including the Indian‐margin strata of the northern Tethys Himalaya and Asian‐margin strata of the Gangdese forearc basin. Continuous sequences are preserved in the Gamba–Tingri Basin of the north margin of the Indian Plate, where the Palaeogene sequence is divided into the Jidula, Zongpu, Zhepure and Zongpubei formations. Here, the marine sequence ranges from Danian to middle Priabonian (66–35 ma), and the stage boundaries are identified mostly by larger foraminiferal assemblages. The Paleocene/Eocene boundary is found between the Zongpu and Zhepure formations. The uppermost marine beds are from the top of the Zongpubei Formation (~35 ma), marking the end of Indian and Asian collision. In addition, the marine beds crop out along both sides of the Yarlong Zangbo Suture, where they show a deeper marine facies, yielding rich radiolarian fossils of Paleocene and Eocene. The Tarim Basin of Xinjiang is another important area of marine deposition. Here, marine Palaeogene strata are well exposed in the Southwest Tarim Depression and Kuqa Depression. They comprise mostly neritic and coastal lagoon facies of the Tethyan realm. Palaeontological evidence suggests that the Paleocene/Eocene boundary here is in middle of the Qimugen Formation. The Tarim Basin was largely drained by Late Oligocene. To the east, the marine offshore Palaeogene strata are widespread in the North Taiwan and East Zhejiang depressions of the continental shelf basin of East China Sea. Abundant fossils including foraminifera, calcareous nannofossils, ostracods, pollen and bivalves occur in the marine environment. Biostratigraphically, the sequence is well correlated with the international planktonic foraminiferal and nannofossil zonations.