A biostratigraphic study on calcareous nannofossils from the CM3D06 Co-rich ferromanganese crust from the Magellan seamounts in the northwestern Pacific enabled estimation of depositional age. The bio-imprinting of ca...A biostratigraphic study on calcareous nannofossils from the CM3D06 Co-rich ferromanganese crust from the Magellan seamounts in the northwestern Pacific enabled estimation of depositional age. The bio-imprinting of calcareous nannofossils and other fossil species suggests six age ranges for the nannofossils： late Cretaceous, late Paleocene, （early, middle, late） Eocene, middle Miocene, late Pliocene, and Pleistocene. Gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS） were used to test the Co-rich crusts, and a variety of molecular fossils were detected, such as chloroform bituminous ＂A＂ , n-alkane, isoprenoid and sterol. Peak carbon and molecular indices （such as C23-/C24＋, CPI, Pr/Ph, Pr/nC17, Ph/nCxs and j13C） indicate that the parent organic matter is dominated by marine phytoplankton and thallogen whereas there is little input of terrestrial organic matter. Researches on calcareous nannofossils, molecular fossils and molecular organic geochemistry data reveal that the Paleocene/Eocene （P/E） global event is recorded in the cobalt- rich crusts from the northwestern Pacific Ocean. A succession of biomes can be observed near the 85 mm boundary （about 55 Ma）, i.e., the disappearance of the late Cretaceous Watznaueria barnesae and Zigodicus spiralis, and Broisonia parka microbiotas above the P/E boundary, and the bloom of Coccolithus formosus, Discoaster multiradiatus, Discoaster mohleri and Discoaster sp. below the boundary. Typical parameters of molecular fossils, such as saturated hydrocarbon components and carbon-number maxima, Pr/Ph, Pr/C17, Ph/C18, distribution types of sterols, Ts/Tm ratios and bacterial hopane, also exhibit dramatic changes near the P/E boundary. These integrated results illustrate that the biome succession of calcareous nannofossils, relative content of molecular fossils and molecular indices in the cobalt-rich crusts near the 85 mm boundary faithfully record the P/E global event.展开更多
Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interv...Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interval was identified and traced across different parts of the North Dezful zone and partly Abadan Plain.In order to characterize the OM quality and richness of the studied intervals,Rock-Eval pyrolysis and nannofossils evaluation were performed,and the geochemical data collected along selected wells were correlated to capture the variations of thickness and source potential of the OM-rich interval.Accordingly,remarkable variations were identified within the depth ranges of 2480–2552 m and also 2200–2210 m,which were attributed to the maximum increase in the rate of growth R-selected species.This increase in the productivity rate was found to be well correlated to high Rock-Eval total organic carbon(TOC)and hydrogen index(HI)values.Given that the maturity of Pabdeh Formation in the studied area was found to have reached the oil window,we expect significant hydrocarbon generation(Type II kerogen),making the play economically highly promising.展开更多
We describe in detail the Miocene to Quaternary paleoceanography of the western equatorial Pacific Ocean based on calcareous nannofossils of Hole 805B. The relative abundance of Discoaster which lived in the lower pho...We describe in detail the Miocene to Quaternary paleoceanography of the western equatorial Pacific Ocean based on calcareous nannofossils of Hole 805B. The relative abundance of Discoaster which lived in the lower photic zone under the stable sea with nutricline and thermocline, decreased step by step at NN5/NN6 and NN10/NN11 boundaries. Al- though the size of Reticulofenestra which is strongly influenced by nutrient, increased five times throughout the section, it drastically decreased in NN4-5 zone, NN10, NN12, and in NN15/NN16 boundary. On the basis of the relationship between Discoaster abundance and Reticulofenestra size change, collapse of the stability of the sea surface in the west- ern equatorial Pacific Ocean progressed step by step throughout the Miocene to Quaternary.展开更多
This study investigates the Gurpi Formation in the northeast of Izeh,southwestern Iran.In this study,59 species and 34 genera were determined.Biostratigraphy allows the identification of zones CC21 to CC26,which is eq...This study investigates the Gurpi Formation in the northeast of Izeh,southwestern Iran.In this study,59 species and 34 genera were determined.Biostratigraphy allows the identification of zones CC21 to CC26,which is equivalent to the UC15c^(TP)-UC20d^(TP) that spans the Late Campanian to Late Maastrichtian.Subsequently,the presence of NP1 to NP6,equivalent to CNP1 to CNP8,indicates that the sequence extends to Selandian.Then the Pabdeh Formation,which dates back to Thanetian,covers the sequence.Several major changes were recorded here in order of importance.The first change is the Campanian-Maastrichtian transition,which was identified based on the last occurrence of the Aspidolithus parcus constrictus.Subsequently,the Early/Late Maastrichtian boundary was determined based on the last occurrence of Reinhardtites levis.In addition,another change in the Late Maastrichtian–Early Danian is associated with an abrupt decrease in the richness of nannofossils,although a significant increase in the abundance of Early Paleocene new species has been observed along with the abundance of Thoracosphaera spp.blooms.Eventually,the final change coincides with an increase in Iridium throughout NP1.These changes may indicate changes in environmental conditions in this part of Iran during the Late Cretaceous–Paleogene transition in the eastern Neo-Tethys domain.展开更多
In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early...In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early Miocene diagnostic species thus obtained. The nannofossil zonation of this interval was subdivided and the Oligocene-Miocene boundary was further determined. Several last Late Oligocene events were recognized, indicating a long-term sedimentary hiatus in the uppermost Upper Oligocene. The time span of the hiatus was estimated for about 2.2 Ma, at least from 23.9 to 26.1 Ma. The lithological and geophysical data from Site 1148 indicate some abrupt sedimentary changes that occurred below and above the hiatus. This hiatus at Site 1148 was probably related to the tectonic change, a major ridge jump during the seafloor spreading in the Late Oligocene South China Sea.展开更多
The biostratigraphy of calcareous nannofossils of the Cretaceous is investigated in the boundary between Abderaz and Kalat Formations through the record of species richness, diversity and distribution patterns in the ...The biostratigraphy of calcareous nannofossils of the Cretaceous is investigated in the boundary between Abderaz and Kalat Formations through the record of species richness, diversity and distribution patterns in the west Kopet-Dagh region. The Kalat Formation comprising of coarse-grained detritus limestone with subordinate sandstone intercalations and the Abderaz Formation mainly consists of limestone, Shale and Limy marl. Nannofossils of this boundary in each of studied sections are listed and figured. 21 species in?Ghalehzoo section, 29 species in Sheikh section and 19 species in Jozak section have been determined. Boistratigraphy based on calcareous nannofossil allow the identification of nannofossil standard zones CC21 and CC26 in all of sections, According to these zones in all of sections, the age of the studied thickness is Early Late Campanian-Late Late Maastrichtian in these sections.展开更多
Forty four (44) different forms of nannofossils recovered from the middle-Miocene to late-Miocene sediments of a section ((8900 - 11,000) ft (2713 - 3353 m)) of a well in the prolific oil producing Niger delta, Nigeri...Forty four (44) different forms of nannofossils recovered from the middle-Miocene to late-Miocene sediments of a section ((8900 - 11,000) ft (2713 - 3353 m)) of a well in the prolific oil producing Niger delta, Nigeria were described and grouped into twelve, though not on phylogenetic relationship, for documentation purpose. The standard strewn-slide technique was used to recover the fossils. The aim is to present the distinguishing morphological features of each of the nannofossils group. Of the recovered forms Genus, Discoaster, was found prominent and divisible into six sub-groups: 6-rayed discoaster with bifurcations, 6-rayed discoasters without bifurcation, 5-rayed discoasters, 5-rayed discoaster with acute bifurcations, 5-rayed nannolith and the indeterminate forms. Genus Sphenolithus recovered is also divisible into two: species without prominent apical spines and species with prominent, monocrystalline apical spines. Other genera found and described are Catinaster, Cyclicargolithus, Coccolithu, Minylitha, Syracosphaera, Helicosphaera, Pontosphaera, Calcidiscus and Reticulofenestra. All the nannofossils fall within NN11, NN10, NN9, NN8 and NN5 zones belonging to the Middle-Late Miocene age.展开更多
Abstract Based upon the features of nannofossil composition, distribution, abundance and diversity, the fossil-bearing sediments exposed by five drill holes in the offshore area of southern Hongkong can be divided int...Abstract Based upon the features of nannofossil composition, distribution, abundance and diversity, the fossil-bearing sediments exposed by five drill holes in the offshore area of southern Hongkong can be divided into the upper Middle Pleistocene, the Upper Pleistocene and Holocene. There were two palaeoclimatic stages in the Holocene in this area according to fossil palaeoecologic and sedimentation analyses: the temperature-rising stage and the warm stage. The latter involves two temperature-falling periods, which could be the major factor causing sea-level fall during that time.展开更多
The distributional trends and their controlling factors of dominant species and nannofossil abundance in sur face sediments of marginal and coastal seas in low to middle latitudes and high latitudes are discussed on t...The distributional trends and their controlling factors of dominant species and nannofossil abundance in sur face sediments of marginal and coastal seas in low to middle latitudes and high latitudes are discussed on the basis of theanalysis of 146 samples from the nothern and central parts of the South China Sea and of comparison between the resultsof current work and data from other seas.Despite significant variations in taxonomic composition between seas or between areas within one sea, there are somegeneral trends in nannofossil distribution of marginal and coastal seas. All those nannofossil assemblages in middle and lowlatitudes are dominated by two species: Gephyrocapsa oceanica and Emiliania huxleyi. Although the relative abundanceof these species may vary greatly from area to area, Gephyrocapsa oceanica in general prevails in nearshore or semiclosedenvironments, increasing in number towards the shoreline, while Emiliania huxleyi increases in relative abundance to wards continental slope and open ocean environments, decreasing in abundance again only in very deep-water, i. e., nearthe CCD. Similarly, the abundance of calcareous nannofossils, as a whole, is lower nearshore, increasing with water depthtowards the continental slope, and then decreasing again towards and near the CCD. In high latitudes, the dominantspecies are Emiliania huxleyi and Coccolithus pelagicus.There are two groups of factors controlling the nannofossil distribution in surface sediments: ecological factors, in cluding particularly water temperature, supply of nutrients; and sedimentological factors, including influx of terrigenousmaterials and deep-water carbonate dissolution.展开更多
Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation(Priabonian–Rupelian) and the lower part of the Asmari Formation(Chattian) in the Bid-Zard section, were used to in...Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation(Priabonian–Rupelian) and the lower part of the Asmari Formation(Chattian) in the Bid-Zard section, were used to investigate the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran(eastern Tethys). The upper part of the Pabdeh Formation was composed of shale, thin-bedded pelagic limestone and dolostone, which is disconformably overlain by the Asmari Formation. For the first time, 29 species of calcareous nannofossils belonging to 13 genera were identified in the studied section. The calcareous nannofossils in the upper part of the Pabdeh Formation indicate the Isthmolithus recurvus Zone/Sphenolithus pseudoradians Zone(combined zone), Ericsonia subdisticha Zone, Helicosphaera reticulata Zone and Sphenolithus praedistentus Zone,from the Priabonian to the Rupelian. The Sphenolithus ciperoensis Zone of the Chattian was identified in the lower part of the Asmari Formation. Calcareous nannofossil stratigraphy across the upper Eocene–Oligocene interval also reveals a disconformity at the Rupelian/Chattian transition due to a bio-event. Shallowing of the basin and environmental changes in this part of the Tethyan domain could have led to the lithostratigraphic and biostratigraphic changes. In fact, during the late Eocene to late Oligocene, marine phytoplankton was sensitive to climate changes such as decreasing temperature, as well as possibly to a nutrient increase and changes in basin depth.展开更多
A certain number of calcareous nannofos-sils were recovered in samples from the Qua-ternary deposits of interior saline lakes ofmore than ten localities in provinces of Qing-hai, Gansu and Xinjiang of China. They arem...A certain number of calcareous nannofos-sils were recovered in samples from the Qua-ternary deposits of interior saline lakes ofmore than ten localities in provinces of Qing-hai, Gansu and Xinjiang of China. They aremainly the Quaternary taxa, such展开更多
A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1143 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5&...A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1143 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5×106 up to almost 53×106 coccoliths/g sediment, with an average of 16×106 coccoliths/g sediment. The accumulation rate of total coccoliths varies from 1×106 to 278×106 coccoliths/cm2 ka. The nannofossil assemblages are usually dominated by a lower-photic species-Florisphaera profunda, of which the average percentage is about 70% in all samples. The absolute abundance and the accumulation rate of nannofossils as well as the percentage ofF. profunda display significant oscillations on two different time scales. One is the fluctuation coincident with the glacial-interglacial cycle, and the other is the long-term changes on a time scale longer than 100 ka. Six evolutionary stages of calcareous nannofossils could be divided for the last 2.32 Ma, from which we can reconstruct the changes in the depth of nutricline of the Nansha area. In this paper, the possible mechanism resulting in these variations is also discussed.展开更多
Two records of the crust laminae from the Marcus-Wake Seamounts and the Magellan Seamount were biostratigraphically studied. Based on biological imprints of the calcareous nannofossils, the geological ages of the two ...Two records of the crust laminae from the Marcus-Wake Seamounts and the Magellan Seamount were biostratigraphically studied. Based on biological imprints of the calcareous nannofossils, the geological ages of the two records were determined, with CM1D03 from the Marcus-Wake Seamounts being of late Paleocene to Pleistocene and CM3D06 from the Magellan Seamount of Late Cretaceous （more than 70.0 Ma）. There are the obvious temporal-spatial differences in the initial formation period and enrichment characteristics of the cobalt-rich crusts of the two seamount chains and differences in the combination and distribution of microfossils in the inner crust layers between the seamounts. These differences are due to the adaptabilities of oceanic species in different environments. Ecological research was carried out in terms of population size of the calcareous nannofossi｜s preserved in the crustal layers to discern the relation of the geological events at the Eocene-Oligocene （E/O） tran- sition. The results show the transitions and recombination of species in the biotic community during the E/O transition obvi- ously corresponded to 25 mm depth in the CM1D03 crust and 58 mm depth in the CM3D06 crust. The changes in biological species and the formation of particular ecological structures indicate the adaptive response of the paleo-biological community in the western Pacific Ocean to the global cold-climate events and the close correlation between the formation of the crust and the global climate change.展开更多
Precise taxonomy and the chronostratigraphic calibration of the Middle Eocene Alveolina from Central Iran is here undertaken from the Chah-Talkh section of the southern Sabzevar region(Central Iran). We have identifie...Precise taxonomy and the chronostratigraphic calibration of the Middle Eocene Alveolina from Central Iran is here undertaken from the Chah-Talkh section of the southern Sabzevar region(Central Iran). We have identified Alveolina kieli, Alveolina stercusmuris and Alveolina nuttalli along with the new species Alveolina ozcani n. sp. that we include into the Alveolina elliptica group. We have also found Nummulites uroniensis, Nummulites obesus and Nummulites cf. verneuili and associated calcareous nannofossils that look reliable to make thoughtful correlations with the Shallow Benthic Zones(SBZ). The foraminiferal biostratigraphy suggests an assignment to the upper part of the lower Lutetian-lower part of the middle Lutetian,SBZ13(Middle Eocene), further strengthened through the identification of the calcareous nannofossil NP14b-NP15b or CNE8-CNE10 biozones, providing a solid correlation with the global stratigraphic standards.展开更多
During the last decades,several integrated studies of Tethyan Jurassic/Cretaceous boundary sections from different countries were published with the objective to indicate problems for the selection of biological,chemi...During the last decades,several integrated studies of Tethyan Jurassic/Cretaceous boundary sections from different countries were published with the objective to indicate problems for the selection of biological,chemical or physical markers suitable for identification of the Jurassic/Cretaceous boundary-the only system boundary within the Phanerozoic still not fixed by GSSP.Drawing the boundary between the Jurassic and Cretaceous systems is a matter of global scale discussions.The problem of proposing possible J/K boundary stratotypes results from lack of a global index fossils, global sea level drop,paleogeographic changes causing development of isolated facies areas,as well as from the effect of Late Cimmerian Orogeny.This contribution summarizes and comments data on J/K boundary interval obtained from several important Tethyan sections and shows still existing problems and discrepancies in its determination.展开更多
A biostratigraphic study of calcareous nannofossils of sediments from Lingfeng No.1 well in the East China Sea was carried out to provide more detailed nannofossil data and a stratigraphic correlation among offshore ...A biostratigraphic study of calcareous nannofossils of sediments from Lingfeng No.1 well in the East China Sea was carried out to provide more detailed nannofossil data and a stratigraphic correlation among offshore wells located in the East China Sea.14 Paleocene to Pleistocene calcareous nannofossil zones were recognized based on a detailed examination. According to these nannofossil data, the Paleocene/Eocene and Pliocene/Pleistocene boundaries, as well as the Miocene base were determined.Oligocene NP23 and Miocene NN1 zones are firstly recognized by this study. The existence of Miocene NN1 at this well suggests that the Miocene transgression began in the Early Miocene in this area. The records of NP23 indicate that the marine Oligocene sediments exist in the series of Lingfeng wells, but probably as very thin layers.展开更多
The oldest Asian record of alpheid shrimps,assigned to genus Alpheus,based on snapping claw fingertips from the Miocene Khari Nadi Formation in the Kutch Basin,western India reported herein,extends the fossil record o...The oldest Asian record of alpheid shrimps,assigned to genus Alpheus,based on snapping claw fingertips from the Miocene Khari Nadi Formation in the Kutch Basin,western India reported herein,extends the fossil record of the family Alpheidae from Asia by~22 million years.An early Miocene(Aquitanian)age is estimated based on the associated assemblage of calcareous nannofossils,Sphenolithus disbelemnos,Cyclicargolithus floridanus,and Reticulofenestra haqii.The co-occurring microbiota includes bony fish otolith remains,identified as“genus Gobiidarum”,isolated teeth of Dasyatis rays,Sphyrna sharks,and teleosts,ctenoid and placoid scales,ostracods,belonging to the genera Paractinocythereis,Alocopocythere,Ruggieria,Aglaiocypris,Bairdoppilata,and echinoid spines.Taken together,the microfossil assemblage and data from chemical analyses using Energy Dispersive Spectroscopy,X-Ray Diffraction and Wavelength Dispersive X-Ray Fluorescence of host and associated lithologies suggests prevalence of a shallow(neritic)to coastal marine(intertidal)depositional paleoenvironment.The present investigation also provides the oldest fossil evidence on the co-occurrence of Alpheus and gobiids(based on otoliths)that strongly advocates that the mutualistic association between these animal groups had developed by the Aquitanian.展开更多
Carbonate rocks contain prolific hydrocarbon reserves all over the world,particularly in the Middle East.For exploration and production strategies,it is essential to understand carbonate reservoirs in terms of their i...Carbonate rocks contain prolific hydrocarbon reserves all over the world,particularly in the Middle East.For exploration and production strategies,it is essential to understand carbonate reservoirs in terms of their internal characteristics,depositional environment,relative age,diagenetic processes and impact on petrophysical properties.This study has been performed on exposed Cretaceous,Paleocene and Miocene marine carbonate sedimentary sequences in two localities(Maghdoucheh and Qennarit)near the city of Sidon(Southern Lebanon).It represents the first comprehensive study that takes into consideration the carbonate reservoir facies,diagenetic history and reservoir quality in the area.Rocks at Maghdoucheh are mainly dominated by limestone beds showing sedimentary structures and erosive bases alternating with microfossil-rich silty marls,related to a shallowing upward sequence in a restricted marine platform environment.Shells of benthic foraminifera and mollusks dominate the fossil assemblage extracted from the studied rocks.The microfossil and nannofossil assemblage detected in the Maghdoucheh sections indicates a middle Miocene age.Rocks at Qennarit are composed of mudstone/wackestone limestone beds rich in planktonic foraminifera and nannofossils related to open marine conditions.Based on the nannofossil content,rocks from Qennarit 1 and 2 are Paleocene and Cretaceous in age,respectively.Four main types of microfacies have been identified,i.e.(1)microbioclastic peloidal calcisiltite,(2)pelagic lime mudstone and wackestone with planktonic microfossils,(3)grainstone/packstone with abundant foraminifera and(4)fenestral bindstones,mudstones and packstones with porostromate microstructures.The porosity-permeability(poro-perm)analysis of representative samples reveals moderate to good porosity but very low permeability.This is mainly due to the presence of large moldic pores that are isolated in nature.The diagenetic features are dominated by micritization and dissolution(both fabric selective and non-fabric selective).Among all diagenetic features,dissolution in both localities contributes to porosity enhancement,while micritization,cementation,compaction and the filled fractures have negative impacts on permeability;hence the overall reservoir quality.展开更多
The Eocene Kuldana Formation(KF)in the Yadgar area of Pakistan,comprises a diverse range of sedimentary facies,including variegated red beds of shales,mudstones,and sandstones,as well as interbedded limestone and marl...The Eocene Kuldana Formation(KF)in the Yadgar area of Pakistan,comprises a diverse range of sedimentary facies,including variegated red beds of shales,mudstones,and sandstones,as well as interbedded limestone and marl.In this study,we conducted an integrated micropaleontological,sedimentological,mineralogical,and geochemical investigation to determine the depositional setting,biochronology,provenance,and paleoclimate of the KF.The study identified six lithofacies and six microfacies,which indicate a variety of environments ranging from floodplains and channels to the margins and shallow marine settings.The nannofossil biostratigraphy places the KF in the Early Eocene,more precisely the NP10 zone(Ypresian),and the fossil zone of benthic foraminifera classifies the study section as the Shallow Benthic Zone SBZ-8(Middle Ilerdian 2).In terms of petrography,the KF sandstone was classified as litharenite and feldspathic litharenite,while the QtFL diagram suggests a recycled orogen.Geochemical proxies indicate an oxidizing environment,a high-to-low regular sedimentation rate,moderate-to-intense chemical weathering in the source region,and a warm-humid to dry climate during the deposition of KF.Overall,the findings suggest that the deposition of KF marks the end of Neo-Tethys due to the Early Eocene Indian–Kohistan collision and that the uplifting of the Himalayas provided the source for the deposition of KF in the foreland basin.The study provides new insights into the depositional environment,biochronology,provenance,and paleoclimate of KF,and highlights the potential for red beds as reliable indicators of oxygenation levels in proximity to mineral deposits.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 41076072 and 40676025)
文摘A biostratigraphic study on calcareous nannofossils from the CM3D06 Co-rich ferromanganese crust from the Magellan seamounts in the northwestern Pacific enabled estimation of depositional age. The bio-imprinting of calcareous nannofossils and other fossil species suggests six age ranges for the nannofossils： late Cretaceous, late Paleocene, （early, middle, late） Eocene, middle Miocene, late Pliocene, and Pleistocene. Gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS） were used to test the Co-rich crusts, and a variety of molecular fossils were detected, such as chloroform bituminous ＂A＂ , n-alkane, isoprenoid and sterol. Peak carbon and molecular indices （such as C23-/C24＋, CPI, Pr/Ph, Pr/nC17, Ph/nCxs and j13C） indicate that the parent organic matter is dominated by marine phytoplankton and thallogen whereas there is little input of terrestrial organic matter. Researches on calcareous nannofossils, molecular fossils and molecular organic geochemistry data reveal that the Paleocene/Eocene （P/E） global event is recorded in the cobalt- rich crusts from the northwestern Pacific Ocean. A succession of biomes can be observed near the 85 mm boundary （about 55 Ma）, i.e., the disappearance of the late Cretaceous Watznaueria barnesae and Zigodicus spiralis, and Broisonia parka microbiotas above the P/E boundary, and the bloom of Coccolithus formosus, Discoaster multiradiatus, Discoaster mohleri and Discoaster sp. below the boundary. Typical parameters of molecular fossils, such as saturated hydrocarbon components and carbon-number maxima, Pr/Ph, Pr/C17, Ph/C18, distribution types of sterols, Ts/Tm ratios and bacterial hopane, also exhibit dramatic changes near the P/E boundary. These integrated results illustrate that the biome succession of calcareous nannofossils, relative content of molecular fossils and molecular indices in the cobalt-rich crusts near the 85 mm boundary faithfully record the P/E global event.
基金supported by the Exploration Directorate of National Iranian Oil Company(NIOC)。
文摘Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interval was identified and traced across different parts of the North Dezful zone and partly Abadan Plain.In order to characterize the OM quality and richness of the studied intervals,Rock-Eval pyrolysis and nannofossils evaluation were performed,and the geochemical data collected along selected wells were correlated to capture the variations of thickness and source potential of the OM-rich interval.Accordingly,remarkable variations were identified within the depth ranges of 2480–2552 m and also 2200–2210 m,which were attributed to the maximum increase in the rate of growth R-selected species.This increase in the productivity rate was found to be well correlated to high Rock-Eval total organic carbon(TOC)and hydrogen index(HI)values.Given that the maturity of Pabdeh Formation in the studied area was found to have reached the oil window,we expect significant hydrocarbon generation(Type II kerogen),making the play economically highly promising.
文摘We describe in detail the Miocene to Quaternary paleoceanography of the western equatorial Pacific Ocean based on calcareous nannofossils of Hole 805B. The relative abundance of Discoaster which lived in the lower photic zone under the stable sea with nutricline and thermocline, decreased step by step at NN5/NN6 and NN10/NN11 boundaries. Al- though the size of Reticulofenestra which is strongly influenced by nutrient, increased five times throughout the section, it drastically decreased in NN4-5 zone, NN10, NN12, and in NN15/NN16 boundary. On the basis of the relationship between Discoaster abundance and Reticulofenestra size change, collapse of the stability of the sea surface in the west- ern equatorial Pacific Ocean progressed step by step throughout the Miocene to Quaternary.
基金Imam Khomeini International University for all its support。
文摘This study investigates the Gurpi Formation in the northeast of Izeh,southwestern Iran.In this study,59 species and 34 genera were determined.Biostratigraphy allows the identification of zones CC21 to CC26,which is equivalent to the UC15c^(TP)-UC20d^(TP) that spans the Late Campanian to Late Maastrichtian.Subsequently,the presence of NP1 to NP6,equivalent to CNP1 to CNP8,indicates that the sequence extends to Selandian.Then the Pabdeh Formation,which dates back to Thanetian,covers the sequence.Several major changes were recorded here in order of importance.The first change is the Campanian-Maastrichtian transition,which was identified based on the last occurrence of the Aspidolithus parcus constrictus.Subsequently,the Early/Late Maastrichtian boundary was determined based on the last occurrence of Reinhardtites levis.In addition,another change in the Late Maastrichtian–Early Danian is associated with an abrupt decrease in the richness of nannofossils,although a significant increase in the abundance of Early Paleocene new species has been observed along with the abundance of Thoracosphaera spp.blooms.Eventually,the final change coincides with an increase in Iridium throughout NP1.These changes may indicate changes in environmental conditions in this part of Iran during the Late Cretaceous–Paleogene transition in the eastern Neo-Tethys domain.
文摘In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early Miocene diagnostic species thus obtained. The nannofossil zonation of this interval was subdivided and the Oligocene-Miocene boundary was further determined. Several last Late Oligocene events were recognized, indicating a long-term sedimentary hiatus in the uppermost Upper Oligocene. The time span of the hiatus was estimated for about 2.2 Ma, at least from 23.9 to 26.1 Ma. The lithological and geophysical data from Site 1148 indicate some abrupt sedimentary changes that occurred below and above the hiatus. This hiatus at Site 1148 was probably related to the tectonic change, a major ridge jump during the seafloor spreading in the Late Oligocene South China Sea.
文摘The biostratigraphy of calcareous nannofossils of the Cretaceous is investigated in the boundary between Abderaz and Kalat Formations through the record of species richness, diversity and distribution patterns in the west Kopet-Dagh region. The Kalat Formation comprising of coarse-grained detritus limestone with subordinate sandstone intercalations and the Abderaz Formation mainly consists of limestone, Shale and Limy marl. Nannofossils of this boundary in each of studied sections are listed and figured. 21 species in?Ghalehzoo section, 29 species in Sheikh section and 19 species in Jozak section have been determined. Boistratigraphy based on calcareous nannofossil allow the identification of nannofossil standard zones CC21 and CC26 in all of sections, According to these zones in all of sections, the age of the studied thickness is Early Late Campanian-Late Late Maastrichtian in these sections.
文摘Forty four (44) different forms of nannofossils recovered from the middle-Miocene to late-Miocene sediments of a section ((8900 - 11,000) ft (2713 - 3353 m)) of a well in the prolific oil producing Niger delta, Nigeria were described and grouped into twelve, though not on phylogenetic relationship, for documentation purpose. The standard strewn-slide technique was used to recover the fossils. The aim is to present the distinguishing morphological features of each of the nannofossils group. Of the recovered forms Genus, Discoaster, was found prominent and divisible into six sub-groups: 6-rayed discoaster with bifurcations, 6-rayed discoasters without bifurcation, 5-rayed discoasters, 5-rayed discoaster with acute bifurcations, 5-rayed nannolith and the indeterminate forms. Genus Sphenolithus recovered is also divisible into two: species without prominent apical spines and species with prominent, monocrystalline apical spines. Other genera found and described are Catinaster, Cyclicargolithus, Coccolithu, Minylitha, Syracosphaera, Helicosphaera, Pontosphaera, Calcidiscus and Reticulofenestra. All the nannofossils fall within NN11, NN10, NN9, NN8 and NN5 zones belonging to the Middle-Late Miocene age.
文摘Abstract Based upon the features of nannofossil composition, distribution, abundance and diversity, the fossil-bearing sediments exposed by five drill holes in the offshore area of southern Hongkong can be divided into the upper Middle Pleistocene, the Upper Pleistocene and Holocene. There were two palaeoclimatic stages in the Holocene in this area according to fossil palaeoecologic and sedimentation analyses: the temperature-rising stage and the warm stage. The latter involves two temperature-falling periods, which could be the major factor causing sea-level fall during that time.
文摘The distributional trends and their controlling factors of dominant species and nannofossil abundance in sur face sediments of marginal and coastal seas in low to middle latitudes and high latitudes are discussed on the basis of theanalysis of 146 samples from the nothern and central parts of the South China Sea and of comparison between the resultsof current work and data from other seas.Despite significant variations in taxonomic composition between seas or between areas within one sea, there are somegeneral trends in nannofossil distribution of marginal and coastal seas. All those nannofossil assemblages in middle and lowlatitudes are dominated by two species: Gephyrocapsa oceanica and Emiliania huxleyi. Although the relative abundanceof these species may vary greatly from area to area, Gephyrocapsa oceanica in general prevails in nearshore or semiclosedenvironments, increasing in number towards the shoreline, while Emiliania huxleyi increases in relative abundance to wards continental slope and open ocean environments, decreasing in abundance again only in very deep-water, i. e., nearthe CCD. Similarly, the abundance of calcareous nannofossils, as a whole, is lower nearshore, increasing with water depthtowards the continental slope, and then decreasing again towards and near the CCD. In high latitudes, the dominantspecies are Emiliania huxleyi and Coccolithus pelagicus.There are two groups of factors controlling the nannofossil distribution in surface sediments: ecological factors, in cluding particularly water temperature, supply of nutrients; and sedimentological factors, including influx of terrigenousmaterials and deep-water carbonate dissolution.
基金supported by Grant 751541 of the Imam Khomeini International University。
文摘Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation(Priabonian–Rupelian) and the lower part of the Asmari Formation(Chattian) in the Bid-Zard section, were used to investigate the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran(eastern Tethys). The upper part of the Pabdeh Formation was composed of shale, thin-bedded pelagic limestone and dolostone, which is disconformably overlain by the Asmari Formation. For the first time, 29 species of calcareous nannofossils belonging to 13 genera were identified in the studied section. The calcareous nannofossils in the upper part of the Pabdeh Formation indicate the Isthmolithus recurvus Zone/Sphenolithus pseudoradians Zone(combined zone), Ericsonia subdisticha Zone, Helicosphaera reticulata Zone and Sphenolithus praedistentus Zone,from the Priabonian to the Rupelian. The Sphenolithus ciperoensis Zone of the Chattian was identified in the lower part of the Asmari Formation. Calcareous nannofossil stratigraphy across the upper Eocene–Oligocene interval also reveals a disconformity at the Rupelian/Chattian transition due to a bio-event. Shallowing of the basin and environmental changes in this part of the Tethyan domain could have led to the lithostratigraphic and biostratigraphic changes. In fact, during the late Eocene to late Oligocene, marine phytoplankton was sensitive to climate changes such as decreasing temperature, as well as possibly to a nutrient increase and changes in basin depth.
文摘A certain number of calcareous nannofos-sils were recovered in samples from the Qua-ternary deposits of interior saline lakes ofmore than ten localities in provinces of Qing-hai, Gansu and Xinjiang of China. They aremainly the Quaternary taxa, such
基金the National Natural Science Foundation of China (Grant No. 49999560) and NKBRSF (Grant Nos. G1999043409 and G2000078500).
文摘A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1143 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5×106 up to almost 53×106 coccoliths/g sediment, with an average of 16×106 coccoliths/g sediment. The accumulation rate of total coccoliths varies from 1×106 to 278×106 coccoliths/cm2 ka. The nannofossil assemblages are usually dominated by a lower-photic species-Florisphaera profunda, of which the average percentage is about 70% in all samples. The absolute abundance and the accumulation rate of nannofossils as well as the percentage ofF. profunda display significant oscillations on two different time scales. One is the fluctuation coincident with the glacial-interglacial cycle, and the other is the long-term changes on a time scale longer than 100 ka. Six evolutionary stages of calcareous nannofossils could be divided for the last 2.32 Ma, from which we can reconstruct the changes in the depth of nutricline of the Nansha area. In this paper, the possible mechanism resulting in these variations is also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.41076072 and 40676025)
文摘Two records of the crust laminae from the Marcus-Wake Seamounts and the Magellan Seamount were biostratigraphically studied. Based on biological imprints of the calcareous nannofossils, the geological ages of the two records were determined, with CM1D03 from the Marcus-Wake Seamounts being of late Paleocene to Pleistocene and CM3D06 from the Magellan Seamount of Late Cretaceous （more than 70.0 Ma）. There are the obvious temporal-spatial differences in the initial formation period and enrichment characteristics of the cobalt-rich crusts of the two seamount chains and differences in the combination and distribution of microfossils in the inner crust layers between the seamounts. These differences are due to the adaptabilities of oceanic species in different environments. Ecological research was carried out in terms of population size of the calcareous nannofossi｜s preserved in the crustal layers to discern the relation of the geological events at the Eocene-Oligocene （E/O） tran- sition. The results show the transitions and recombination of species in the biotic community during the E/O transition obvi- ously corresponded to 25 mm depth in the CM1D03 crust and 58 mm depth in the CM3D06 crust. The changes in biological species and the formation of particular ecological structures indicate the adaptive response of the paleo-biological community in the western Pacific Ocean to the global cold-climate events and the close correlation between the formation of the crust and the global climate change.
基金supported financially by the Vice Chancellor for Research and Technology at University of Isfahan。
文摘Precise taxonomy and the chronostratigraphic calibration of the Middle Eocene Alveolina from Central Iran is here undertaken from the Chah-Talkh section of the southern Sabzevar region(Central Iran). We have identified Alveolina kieli, Alveolina stercusmuris and Alveolina nuttalli along with the new species Alveolina ozcani n. sp. that we include into the Alveolina elliptica group. We have also found Nummulites uroniensis, Nummulites obesus and Nummulites cf. verneuili and associated calcareous nannofossils that look reliable to make thoughtful correlations with the Shallow Benthic Zones(SBZ). The foraminiferal biostratigraphy suggests an assignment to the upper part of the lower Lutetian-lower part of the middle Lutetian,SBZ13(Middle Eocene), further strengthened through the identification of the calcareous nannofossil NP14b-NP15b or CNE8-CNE10 biozones, providing a solid correlation with the global stratigraphic standards.
基金the APVV-0280-07,APVV-0248-07APVV- 0465-06+1 种基金APVT 51-011305VEGA 0196 and 0065
文摘During the last decades,several integrated studies of Tethyan Jurassic/Cretaceous boundary sections from different countries were published with the objective to indicate problems for the selection of biological,chemical or physical markers suitable for identification of the Jurassic/Cretaceous boundary-the only system boundary within the Phanerozoic still not fixed by GSSP.Drawing the boundary between the Jurassic and Cretaceous systems is a matter of global scale discussions.The problem of proposing possible J/K boundary stratotypes results from lack of a global index fossils, global sea level drop,paleogeographic changes causing development of isolated facies areas,as well as from the effect of Late Cimmerian Orogeny.This contribution summarizes and comments data on J/K boundary interval obtained from several important Tethyan sections and shows still existing problems and discrepancies in its determination.
基金This study is supported by the National Natural Science Foundation of China( No.49772 12 3 )
文摘A biostratigraphic study of calcareous nannofossils of sediments from Lingfeng No.1 well in the East China Sea was carried out to provide more detailed nannofossil data and a stratigraphic correlation among offshore wells located in the East China Sea.14 Paleocene to Pleistocene calcareous nannofossil zones were recognized based on a detailed examination. According to these nannofossil data, the Paleocene/Eocene and Pliocene/Pleistocene boundaries, as well as the Miocene base were determined.Oligocene NP23 and Miocene NN1 zones are firstly recognized by this study. The existence of Miocene NN1 at this well suggests that the Miocene transgression began in the Early Miocene in this area. The records of NP23 indicate that the marine Oligocene sediments exist in the series of Lingfeng wells, but probably as very thin layers.
基金granted by the BSIP LucknowIndia in the form of an In-house Project No. 3 (2021–2025)
文摘The oldest Asian record of alpheid shrimps,assigned to genus Alpheus,based on snapping claw fingertips from the Miocene Khari Nadi Formation in the Kutch Basin,western India reported herein,extends the fossil record of the family Alpheidae from Asia by~22 million years.An early Miocene(Aquitanian)age is estimated based on the associated assemblage of calcareous nannofossils,Sphenolithus disbelemnos,Cyclicargolithus floridanus,and Reticulofenestra haqii.The co-occurring microbiota includes bony fish otolith remains,identified as“genus Gobiidarum”,isolated teeth of Dasyatis rays,Sphyrna sharks,and teleosts,ctenoid and placoid scales,ostracods,belonging to the genera Paractinocythereis,Alocopocythere,Ruggieria,Aglaiocypris,Bairdoppilata,and echinoid spines.Taken together,the microfossil assemblage and data from chemical analyses using Energy Dispersive Spectroscopy,X-Ray Diffraction and Wavelength Dispersive X-Ray Fluorescence of host and associated lithologies suggests prevalence of a shallow(neritic)to coastal marine(intertidal)depositional paleoenvironment.The present investigation also provides the oldest fossil evidence on the co-occurrence of Alpheus and gobiids(based on otoliths)that strongly advocates that the mutualistic association between these animal groups had developed by the Aquitanian.
基金funded by the URB of the American University of Beirut(Award#103603,Project#24687)。
文摘Carbonate rocks contain prolific hydrocarbon reserves all over the world,particularly in the Middle East.For exploration and production strategies,it is essential to understand carbonate reservoirs in terms of their internal characteristics,depositional environment,relative age,diagenetic processes and impact on petrophysical properties.This study has been performed on exposed Cretaceous,Paleocene and Miocene marine carbonate sedimentary sequences in two localities(Maghdoucheh and Qennarit)near the city of Sidon(Southern Lebanon).It represents the first comprehensive study that takes into consideration the carbonate reservoir facies,diagenetic history and reservoir quality in the area.Rocks at Maghdoucheh are mainly dominated by limestone beds showing sedimentary structures and erosive bases alternating with microfossil-rich silty marls,related to a shallowing upward sequence in a restricted marine platform environment.Shells of benthic foraminifera and mollusks dominate the fossil assemblage extracted from the studied rocks.The microfossil and nannofossil assemblage detected in the Maghdoucheh sections indicates a middle Miocene age.Rocks at Qennarit are composed of mudstone/wackestone limestone beds rich in planktonic foraminifera and nannofossils related to open marine conditions.Based on the nannofossil content,rocks from Qennarit 1 and 2 are Paleocene and Cretaceous in age,respectively.Four main types of microfacies have been identified,i.e.(1)microbioclastic peloidal calcisiltite,(2)pelagic lime mudstone and wackestone with planktonic microfossils,(3)grainstone/packstone with abundant foraminifera and(4)fenestral bindstones,mudstones and packstones with porostromate microstructures.The porosity-permeability(poro-perm)analysis of representative samples reveals moderate to good porosity but very low permeability.This is mainly due to the presence of large moldic pores that are isolated in nature.The diagenetic features are dominated by micritization and dissolution(both fabric selective and non-fabric selective).Among all diagenetic features,dissolution in both localities contributes to porosity enhancement,while micritization,cementation,compaction and the filled fractures have negative impacts on permeability;hence the overall reservoir quality.
文摘The Eocene Kuldana Formation(KF)in the Yadgar area of Pakistan,comprises a diverse range of sedimentary facies,including variegated red beds of shales,mudstones,and sandstones,as well as interbedded limestone and marl.In this study,we conducted an integrated micropaleontological,sedimentological,mineralogical,and geochemical investigation to determine the depositional setting,biochronology,provenance,and paleoclimate of the KF.The study identified six lithofacies and six microfacies,which indicate a variety of environments ranging from floodplains and channels to the margins and shallow marine settings.The nannofossil biostratigraphy places the KF in the Early Eocene,more precisely the NP10 zone(Ypresian),and the fossil zone of benthic foraminifera classifies the study section as the Shallow Benthic Zone SBZ-8(Middle Ilerdian 2).In terms of petrography,the KF sandstone was classified as litharenite and feldspathic litharenite,while the QtFL diagram suggests a recycled orogen.Geochemical proxies indicate an oxidizing environment,a high-to-low regular sedimentation rate,moderate-to-intense chemical weathering in the source region,and a warm-humid to dry climate during the deposition of KF.Overall,the findings suggest that the deposition of KF marks the end of Neo-Tethys due to the Early Eocene Indian–Kohistan collision and that the uplifting of the Himalayas provided the source for the deposition of KF in the foreland basin.The study provides new insights into the depositional environment,biochronology,provenance,and paleoclimate of KF,and highlights the potential for red beds as reliable indicators of oxygenation levels in proximity to mineral deposits.
