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1.
Planktonic foraminiferal analysis of the Erto section in the Vajont valley (Southern Alps, northern Italy) reveals a relatively complete succession across the Cretaceous–Tertiary (K–T) boundary. The turnover of planktonic foraminiferal fauna was studied for a stratigraphic interval spanning theAbathomphalus mayaroensisZonep.p., Pseudotextularia deformisZone,Guembelitria cretaceaZone,Parvularugoglobigerina eugubinaZone,Eglobigerina eobullioidesSubzone, andParasubbotina pseudobulloidesZonep. p.The extinction of most large, ornate, late Maastrichtian species occurs below a black ‘boundary clay’ (2–4 cm thick); however, part of the Late Cretaceous species, mainly heterohelicidids and hedbergellids, were found over an interval of more than 100 cm above the boundary. Although a relatively high number of species occur for the last time in the main extinction phase, the abundance of these outgoing species is less than 20% of the total population; unkeeled or weakly keeled, simple-shaped forms (heterohelicids, globotruncanellids, hedbergellids) constitute the bulk of the planktonic foraminiferal population both in uppermost Maastrichtian and lowermost Danian beds. The first Tertiary species (‘Globigerina’minutulaand ‘Globigerina’fringa) appear just above the ‘boundary clay’;Parvularuglobigerina eugubinaoccurs a few centimeters above. A marked increase in abundance and diversity in the Tertiary planktonic foraminiferal population occurs at the base of theEoglobigerina eobulloidesSubzone.  相似文献   

2.
The latest Campanian-Middle Palæocene Dakhla Formation has been the subject of few sedimentological studies, despite its great areal distribution. This shale/mudstone unit exhibits marked facies variations in a northwest-southeast direction. The facies distribution patterns, stratal geometries and type, as well as frequency of the associated microfauna, allow a possible subdivision of the Dakhla Formation into ten depositional cycles. These cycles are delineated from each other by a bounding surface, which is defined by an abrupt facies change and/or intensively bioturbated hardground. The sediments of these cycles have been accumulated in a shallow subtidal-upper intertidal-flat environment during Late Cretaceous and in a middle/outer shelf-lower intertidal suite during Palæocene times. Deposition took place in a topographically irregular basin under a constantly high clastic input derived largely from the south and southwest. The cyclic pattern of deposition that characterises the Dakhla Formation, points to repeated relative sea level fluctuations. The submarine palæorelief also plays a significant role on the facies pattern. It is found that the succession was deposited along the marginal part of a palæostructural low. Its deeper area is located around present-day Edmonstone. The study of sedimentary facies characteristics and cyclicity of the Dakhla Formation leads to the recognition of four depositional sequences bounded by five type 2 sequence boundaries. The first and second type 2 depositional sequences correspond to the Late Maastrichtian Mawhoob Shale and lower-middle part of the Beris Mudstone Members, respectively. The third sequence comprises the Beris Mudstone Member ‘upper part’ and the Latest Maastrichtian partition of the Kharga Shale Member. The well-documented Cretaceous-Tertiary boundary marks the type 2 sequence boundary at the top of this sequence. The last depositional sequence coincides with the late Early-Middle Palæocene subdivision of the Kharga Shale Member. These sequences comprise nine systems tracts, mainly of transgressive and highstand systems tract deposits.  相似文献   

3.
This work depends on integrated high-resolution calcareous plankton nannofossil and foraminiferal biostratigraphic analyses for three Upper Cretaceous-Lower Paleogene successions at Farafra-Abu Minqar area, Western Desert, Egypt. These sections are distributed in a north-south geologic profile as follows: El Aqabat, North Gunna, and Abu Minqar. Lithostratigraphically, four formations are recorded in the study area, namely, Khoman (at base), Dakhla, Tarawan, and Esna (at top). In the north at El Aqabat section, Khoman Formation (carbonate facies) is only represented which changes partially toward the south to Dakhla Formation (siliciclastic facies). In the extreme south at Abu Minqar section, it changes completely into siliciclastic facies of Dakhla Formation. Biostratigraphically, seven calcareous nannofossil and eleven planktonic foraminiferal zones represent the Late Cretaceous-Early Paleogene are identified. Based on the occurrence or missing of these zones accompanied with the field criteria resulted in detecting four tectonic events. These tectonic events took place at the Cretaceous/Paleogene (K/Pg), the Danian/Selandian (D/S), the Selandian/Thanetian (S/T), and the Paleocene/Eocene (P/E) boundaries. These tectonic events are related to the impact of the Syrian Arc System. Four sequence boundaries (SB1, SB2, SB3, and SB4) are defined in the Late Cretaceous-Early Paleogene sequence in the Farafra-Abu Minqar area.  相似文献   

4.
Seven planktic foraminiferal zones are distinguished in the Maastrichtian-Paleocene succession at the north Farafra Oasis. These are the Rugoglobigerina hexacamerata (CF8b), Gansserina gansseri, and Contusotruncana contusa zones in the Maastrichtian topped by a well-known unconformity across the Cretaceous/Paleogene (K/Pg) boundary. The Danian is subdivided into two biozones: Globanomalina compressa/Praemurica inconstans-Praemurica uncinata Subzone (P1c) and Praemurica uncinata–Morozovella angulata (P2) Zone. The Late Paleocene is divided into two zones: Morozovella angulata-Globanomalina pseudomenardii (P3) and Globanomalina pseudomenardii (P4). A minor hiatus between the Danian/Selandian and Selandian/Thanetian boundaries are also recorded. These time gaps across the stage boundaries may be related to the tectonic events that affected the sedimentation regime throughout the Upper Cretaceous–Lower Paleogene interval in the Farafra Oasis.  相似文献   

5.
In the Central Anatolia region of Turkey, a mixture of sedimentary and tectonic melanges cover extensive areas, bordering the north, north-west and west of the Kir?ehir Massif. Broadly the age of this melange is Mesozoic; however it includes olistoliths whose ages range from Carboniferous to Cretaceous. A series of interconnected basins existed within the “melange belt” during Late Cretaceous-Early Tertiary times. They have been infilled, throughout the Lower Tertiary, by slump and mass-flow deposits, produced by active tectonic events. These events seem to be a natural continuation of the earlier stronger tectonics which produced the melanges.  相似文献   

6.
藏南定日地区Cenomanian/Turonian界线附近的生物古海洋事件   总被引：4，自引：0，他引：4  
赵文金  万晓樵 《地质科学》2003,38(2):155-164
藏南定日地区在白垩纪中期发育一套浅灰色深灰色的以钙质页岩、泥灰岩及微晶灰岩为主的浅海陆棚相沉积,岩石中除含较高的粘土矿物及陆源石英矿物颗粒以外,还含有十分丰富的有孔虫化石。依据浮游有孔虫Helvetoglobotruncana praehelvetica的首次出现将C/T界线置于样品9922及9923之间,该界线位于Whiteinella archaeocretacea化石带之中。通过定量分析,该区有孔虫的丰度、分异度以及浮游与底栖有孔虫比率、具旋脊与不具旋脊有孔虫的比率等指标在剖面纵向上表现出3个明显的演化阶段,即Rotalipora cushmani带上部、W.archaeocretacea带及H.helvetica带下部,有孔虫动物群的变化特征完整地记录了C/T界线附近古海洋事件的全过程。该次事件中,碳稳定同位素δ13C值存在着明显的异常变化——正向偏移,元素地球化学U、Th及K的丰度也表现出明显的异常变化,其丰度值均比标准平均值偏高。所有这些特征均是在全球洋脊迅速扩张这一背景下海平面发生剧烈变化的结果。  相似文献   

7.
CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894–794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction.  相似文献   

8.
A marine stratigraphic sequence across the Pliocene / Pleistocene boundary has been found in the north-ern continental shelf of the South China Sea. The marine Quaternary deposits in the Yinggehai Basin may ex-ceed 2,000 m in thickness, probably providing the best section for studying the lower boundary of the marinePleistocene in South China. The vertical succession with planktonic foraminifers and nannofossils revealed inboreholes in the basin has been well correlated with that in the international stratotype section of thePliocene / Pleistocene boundary at Vrica, Italy, resulting in the acquirement of a biostratigraphic boundary at1.64 Ma. This boundary, however, does not coincide with any prominent lithological palaeoenvironmentalchanges in the study area and can hardly be used in geological practice. There are, in contrast, significantchanges at the level of LAD of Globorotalia multicamerata sensu lato located below the above-mentionedboundary. The percentage of planktonic foraminifers in the total population and preservation of foraminiferaltests display great changes at this level corresponding to a clear onlap on the seismic profiles and indicating adepositional hiatus at ca. 2.0-2.5 Ma. Since the level can be widely traced in the Pearl River Mouth Basin andthe Beibu Gulf Basin and well corresponds with the marked depositional environmental changes recorded inthe west Pacific and other regions, it is recommended that the Plio / Pleistocene boundary be drawn at the levelof Gr. multicamerata sensu lato LAD, roughly concurrent with the Gauss / Matuyama turn.  相似文献   

9.
西藏岗巴晚白垩世有孔虫动物群与海平面变化   总被引：9，自引：0，他引：9  
西藏南部岗巴地区上白垩统的有孔虫动物群十分丰富，经鉴定共有52属130种。根据岩性，该地区上白垩统可以划分出三个最基本的岩石地层单位：冷青热组、岗巴村口组及宗山组。依据其中有孔虫的形态结构、生态环境、系统演化及地史分布等特征，可以划分出五个主要的有孔虫动物群，Rotalipora动物群，Whiteinella-Helvetoglobotruncana动物群，Dicarinella-Marginotruncana动物群，Globotruncana-Globotuncanita动物群及Orbitoides-Omphalocyclus动物群。这五个有孔虫动物在晚白垩世相继绝灭，其绝灭与古水深有着十分密切的关系，主要是受海平面变化的影响。  相似文献   

10.
The stratigraphy, sedimentology and syn-depositional tectonic events (SdTEs) of the Upper Cretaceous/Paleogene (K–P) succession at four localities in north Eastern Desert (NED) of Egypt have been studied. These localities are distributed from south-southwest to north-northeast at Gebel Millaha, at North Wadi Qena, at Wadi El Dakhal, and at Saint Paul Monastery. Lithostratigraphically, four rock units have been recorded: Sudr Formation (Campanian–Maastrichtian); Dakhla Formation (Danian–Selandian); Tarawan Formation (Selandian–Thanetian) and Esna Formation (Thanetian–Ypresian). These rock units are not completely represented all over the study area because some of them are absent at certain sites and others have variable thicknesses. Biostratigrapgically, 18 planktonic foraminiferal zones have been recorded. These are in stratigraphic order: Globotruncana ventricosa Zone (Campanian); Gansserina gansseri, Contusotruncana contusa, Recimguembelina fructicosa, Pseudohastigerina hariaensis, Pseudohastigerina palpebra and Plummerita hantkenenoides zones (Maastrichtian); Praemurica incostans, Praemurica uncinata, Morozovella angulata and Praemurica carinata/Igorina albeari zones (Danian); Igorina albeari, Globanomanlina pseudomenradii/Parasubbotina variospira, Acarinina subsphaerica, Acarinina soldadoensis/Globanomanlina pseudomenardii and Morozovella velascoensis zones (Selandian/Thantian); and Acarinina sibaiyaensis, Pseudohastigerina wilcoxensis/Morozovella velascoensis zones (earliest Ypresian). Sedimentologically, four sedimentary facies belts forming southwest gently-dipping slope to basin transect have been detected. They include tidal flats, outer shelf, slumped continental slope and open marine hemipelagic facies. This transect can be subdivided into a stable basin plain plus outer shelf in the extreme southwestern parts; and an unstable slope shelf platform in the northeastern parts. The unstable slope shelf platform is characterized by open marine hemipelagic, fine-grained limestones and fine siliciclastic shales (Sudr, Dakhla, Tarawan and Esna formations). The northeastern parts are marked by little contents of planktonic foraminifera and dolomitized, slumped carbonates, intercalated with basinal facies. Tectonically, four remarkable syn-depositional tectonic events (SdTEs) controlled the evolution of the studied succession. These events took place strongly within the Campanian–Ypresian time interval and were still active till Late Eocene. These events took place at: the Santonian/Campanian (S/C) boundary; the Campanian/Maastrichtian (C/M) boundary; the Cretaceous/Paleogene (K/P) boundary; and the Middle Paleocene–Early Eocene interval. These tectonic events are four pronounced phases in the tectonic history of the Syrian Arc System (SAS), the collision of the Afro-Arabian and Eurasian plates as well as the closure of the Tethys Sea.  相似文献   

11.
The foraminiferal fauna from two holes near the coastal section of marls and limestones at Torquay is dominated by inner to mid‐shelf benthic forms, especially the cibicidids, discorbids and miliolids. Planktonic species are rare and rarely age‐diagnostic. A cluster analysis of the species occurrences and relative abundances identified four assemblages, A to D up‐section. These assemblages also closely correspond to lithological changes characterising lithostratigraphic units: Angahook Formation (assemblage A), lower and upper Jan Juc Formation (B, C) and Puebla Clay (D). Biofacies trends based on the relative abundances of inner and outer neritic taxa led to the recognition of third‐order sequences and boundaries equivalent to TB1.1 to TB1.4, confirming a previous identification on sedimentological grounds. They demonstrate that foraminiferal assemblages were directly influenced by third‐order sea‐level fluctuations and can be used to predict third‐order sequences. The long‐uncertain regional Oligocene‐Miocene boundary is placed at the Jan Juc Formation—Puebla Clay contact, across which there was a major faunal change. Several benthic forms disappeared, at least temporarily: Cibicidoides perforatus, Amphistegina lessonii and Pararotalia mackayi. The typical Miocene planktonic taxa Globoquadrina dehiscens and Globoturborotalita brazieri made their first appearance. These events were associated with an increase in inner neritic benthos signalling a low sea‐level, consistent with the contemporaneous global pattern.  相似文献   

12.
Abstract

— The Lhasa Block (s.l.) is bounded to the South by the Tertiary Yarlung Zangbo suture zone and to the North by the terminal Jurassic/earliest Cretaceous Bangong Nu Jiang suture zone. Several tectonostratigraphic units have been recognized in the central-northern part of the Lhasa Block. These are from bottom to top : 1) a thick turbiditic series with a few lenses of allodapic limestones which have yielded an Aalenian — Bajocian foraminiferal assemblage. This series is tectonieally overlain by the Donqiao ophiolite; 2) the continental to shallow marine late Malm to lowermost Cretaceous Zigetang Formation which disconformably overlies the Donqiao ophiolite and 3) continental red detrital rocks or marine Early/Late Aptian boundary to Early Albian foraminifera-rich bedded limestones in which some volcanic rocks are locally interbedded.

We discuss the palaeogeographical distribution and biostratigraphical meaning of some foraminifera (Gutnicella cayeuxi (LUCAS), Palorbitolina fen<ícu/o?(Bl .LMKNBACIl), Praeorbitolina cormyi SCHROEDER and Palor-bilolmoides hedini CHREREHI and ScilKOKDK.lt) and their bearing on the radiometric age of the Aptian-Albian boundary.  相似文献   

13.
This paper presents palaeontological ages based on new nannofossil and foraminiferal studies from a range of sedimentary rocks from the provinces of West and East Kalimantan, Indonesia. The age of sedimentary rocks in Kalimantan, away from the main hydrocarbon exploration areas of the coastal regions, represents a major gap in our basic knowledge of the island of Borneo. The implications of these new results and existing and new correlations are reviewed and suggested. In particular, the base of the Tertiary section in the Kutai Basin is shown to be upper Middle Eocene in age, rather than Late Eocene as originally thought. The limestones of the Batu Belah member of the Ujoh Bilang Formation are dated as NP24–25, Late Oligocene, rather than Early Oligocene as earlier work had suggested. In the western part of the Mangkalihat Peninsula area the base of the Tertiary section is determined to be Late Oligocene. Various basement units from both East and West Kalimantan contained Late Jurassic to Late Cretaceous microfossils.  相似文献   

14.
An integrated magnetobiochronology of the Miyazaki Pliocene–Pleistocene succession in the Miyazaki area, southwest Japan, was established using planktic foraminiferal and calcareous nannofossil biostratigraphy together with paleomagnetic data. The upper Miyazaki succession in the northern Miyazaki region can be divided into the Takanabe, Hisamine (redefined), and Higoyashiki (new) Formations, in ascending order. A depositional hiatus between the Hisamine Formation and the Takanabe and/or older formations was also identified based on integrated magnetobiostratigraphy from five sections including the Nagatani River (NGT) section through the uppermost Miyazaki succession. The hiatus, herein called the Hisamine unconformity, is equivalent to the Kurotaki unconformity between the Miura and Kazusa groups of the Boso Peninsula in central Japan. The depositional hiatus recognised in the lower Pleistocene of Pacific coastal areas in southwestern and central Japan may have resulted from tectonic activity associated with a change in the subduction direction of the Philippine Sea plate, which commenced prior to ca. 2.2 Ma. The youngest unit just below the hiatus is the upper part of the Takanabe Formation in the NGT section. The NGT section represents the continuous Late Pliocene to earliest Pleistocene sequence including the Gauss/Matuyama boundary and is here proposed as the type section for the Pliocene/Pleistocene boundary in Japan, which the IUGS ratified as the base of the Gelasian in 2009.  相似文献   

15.
Studies of calcareous nannofossils and microfossils and their distribution in different intervals of the flysch rhythms in the Kloko ník brook in the Bílé Karpaty Unit of the Magura Group of nappes in the West Carpathians gave the following results. The highest species diversity of calcareous nannofossils was found in the lower parts of the Bouma Te hemipelagic intervals. The Campanian marker species Ceratolithoides aculeus and Aspidolithus parcus were found in practically all layers studied. A stratigraphically important foraminiferal fauna was obtained from the upper parts of the Bouma Te intervals, including the Campanian-Maastrichtian planktic foraminifers Globotruncana arca and Globotruncanita stuartiformis. In the non-calcareous pelagites, agglutinated species with a range from the Late Cretaceous to the Paleogene dominate.  相似文献   

16.
Foraminifers from Middle-Upper Jurassic and Upper Cretaceous sediments of the Kaliningrad basin located in the southwestern part of the East European platform are studied. During the greater part of the Late Mesozoic, the study region represented a northern margin of a spacious epicontinental sea in the Boreal zoogeographic realm. The analyzed composition and quantitative distribution of foraminifers, ratio between planktonic and benthic species, ornamentation degree of tests, and their preservation are used to reconstruct paleogeography and history of eustatic sea-level changes. The upper Callovian through Upper Jurassic zonation based on distribution of Epistomina species is proposed. Defined foraminiferal assemblages are correlated with coeval assemblages from the East to West European platforms and North Atlantic  相似文献   

17.
A method is presented for correlating benthonic foraminiferal communities in Late Quaternary marine sediments on continental shelves and in coastal areas with the planktonic foraminiferal stratigraphy of the North Atlantic and Norwegian Sea deep-sea sediments.  相似文献   

18.
西藏日喀则群昂仁组时代问题新资料   总被引：6，自引：0，他引：6       下载免费PDF全文
昂仁组是一套复理石和类复理石沉积,含晚白垩世土伦期的菊石Mammites[1,2],但因未发现直接的上覆地层和化石稀少而不能肯定是否还包括晚于土伦期或至早第三纪的沉积[1,3]。1980年,笔者在昂仁、萨噶一带的昂仁组中采到瓣鳃、腹足化石;我局区调队在仲巴县错江顶一带,发现连续沉积于昂仁组之上,整合于下第三系之下一套含Masstrichtian期菊石(Sphenodiscus)的杂色地层。本文报道这一发现和对昂仁组时代问题的认识(图1)。  相似文献   

19.
论塔里木盆地西部海相古新统划分   总被引：7，自引：0，他引：7  
郭宪璞 《地质论评》1994,40(4):322-329
塔里木盆地古部海相古新统原来由陈尔塔什组和齐姆根两个组构成，根据在陈尔塔什组下伏地层－吐依洛克组发的有孔虫组合和介形虫的时代，本文将该组厘定为古新统Ｄａｎｉａｎ阶而非上白垩统，本文从生物地层学、事件地层学、稳定同位素地层学，古气候学和地球化学五个方面确定了古新统的底界；提出了古新统划分新方案，即自下而上包括吐依洛克组、阿尔塔什组和刘姆根组三个组；划分出古新统五个有孔虫组合，其中两个为新建；文中还描  相似文献   

20.
An Upper Cretaceous black-gray-red bed sequence was deposited in the Tethys-Himalayan Sea where abundant foraminifera, especially planktons, were yielded. In the shallow shelf to the upper slope on the north margin of Indian plate was recorded an extinction-recovery-radiation cycle of foraminiferal fauna highly sensitive to paleoceanographical changes. The black unit, consisting of the Late Cenomanian-earliest Turonian beds, displays a major extinction, with keeled planktonic and many benthic species as the principal victims at the end of the Cenomanian when existed only low diversity, sin-face water-dwelling foraminifera. The gray unit spans a long-term recovery interval from the Turonian to the early Santonian with keeled planktonic foraminifera returning stepwise to the water colunm. The planktonic biota in the red unit, extremely abundant, indicate a biotic radiation during the Late Santonian and the Early Campanian, implying that the high oxygen levels had returned to all the oceanic depth levels,and that the water stratification disappeared, followed by the radiation of all depth-dwellers. The variation on foraminiferal faunas from the whole sequence refers to the extreme warm climate that appeared in the Middle Cretaceous and to the declined temperature toward the late epoch. Substantial deposits for this warming and cooling zones represent the black shales in the Middle Cretaceous and the red beds in the later period of the southern Tibet. The change in the foraminiferal composition corresponded to the formation of dysaerobic facies and to the development of high-oxidized circumstances.  相似文献   

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