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
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 marine Tertiary sequence in the north part of the South China Sea may be divided into 18 LateOligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysisof calcareous n...The marine Tertiary sequence in the north part of the South China Sea may be divided into 18 LateOligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysisof calcareous nannofossils from 40 offshore boreholes. The unnamed Eocene assemblage has been found onlyon the northeast margin of the Zhujiangkou basin. The 18 cakareous nannofossil zones of the Late Oligoceneto Pliocene were deposited in succession, but their development degrees are different. Among the 18 calcareousnannofossil zones, those corresponding to Martini's (1971) NN4- NN5 zones, NN11 zone and NN13-NN15zones are well developed, relatively persistent laterally and also widely distributed. They are the importantmarkers for the stratigraphical subdivision and correlation of the Upper Tertiary between the various basins inthe north part of the South China Sea. Based on the calcareous nannofossils and the sedimentsry features coup-led with the foraminifer zonation in certain basins, the present paper discusses the sedimentary characteristicsof the marine Tertiary and as well as the distribution and development of the sedimentary hiatus in the region.The calcareous nannofossil markers for the Upper / Lower Tertiary and the Quaternary / Tertiary boundaries,and the characteristics and geological significance of the reworked calcareous nannofossils are also discussed inthe paper.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
We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/...We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.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
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
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
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
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
The Lower Cretaceous sediments of the Ceahlǎu Nappe （from the bend region of the Romanian Carpathians） were investigated from lithological and micropaleontological （calcareous nannoplankton） points of view. Our i...The Lower Cretaceous sediments of the Ceahlǎu Nappe （from the bend region of the Romanian Carpathians） were investigated from lithological and micropaleontological （calcareous nannoplankton） points of view. Our investigations revealed that the studied deposits were sedimented within the latest Tithonian-Albian interval. The calcareous nannofossil assemblages of the turbidite calcareous successions （the Sinaia Formation） were assigned to the NJK-？NC5 calcareous nannofossil zones, which cover the Late Tithonian-Early Barremian interval. The sandy-shaly turbidites, which followed the calcareous turbidites of the Sinaia Formation, are Early Barremian-Early Albian in age （interval covered by the ？NC5-NC8 calcareous nannofossil zones）. Because the studied deposited are mainly turbidites, many reworked nannofossils from older deposits are present in the calcareous nannofloras. Thus, some biozones （i.e., NC5）, defined based on the last occurrences of nannofossils, could not be identified. The calcareous nannofossil assemblages are composed of Tethyan taxa （which dominate the nannofloras） and cosmopolitan taxa. During two intervals （the Late Valanginian and across the Barremian/Aptian boundary）, Tethyan and cosmopolitan nannofossils, together with Boreal ones, were observed. This type of mixed calcareous nannoplankton assemblage is indicative for sea-level high-stand, which allows the nannofloral exchange between the Tethyan and Boreal realms, within the two-above mentioned intervals.展开更多
A structural-sediment zone of Kopet Dagh is one of the geological units. The southern Kopet Dagh zone is limited to Binalood and the northern limit is with the Turan plateau fault and is created as sediment (Trough) i...A structural-sediment zone of Kopet Dagh is one of the geological units. The southern Kopet Dagh zone is limited to Binalood and the northern limit is with the Turan plateau fault and is created as sediment (Trough) in the late Triassic. The main fault zones are divided into two groups of foundation faults and overthrust. Kopet Dagh is a giant gas field between Turkmenistan, Iran and Afghanistan. Most areas of the region have a temperate climate so cold. From the middle Cambrian to the present, five phases of orogeny have occurred in the region. The geographic location of the study area is 37°43'03"N latitude and 55°35'47"E. In terms of stratigraphic formations in the Cretaceous period, Kopet Dagh area, respectively, is from old to new, including: Shurijeh, Zard, Tiregan, Sar Cheshmeh, Sanganeh, Aitamir, Abderaz, Abtalkh, Neyzar and Kalat. Abtalkh formation is one of the most important rock units in the late Cretaceous in the Kopet Dagh Basin. Abtalkh formation is 489 m and its stratigraphic units are 80 meters of dark grayshale, 20 km dark grayshale with calcareous layers with Inoseramus, 50 m gray marl tend to bluish with Siliceous limestone interlayers, 19 meters of gray-blueshale, 320 meters of light gray shale withthinlayer limestone interlayers. To take pictures of the samples, 100× objective lens and digital camera were used. In the course of this study, the lower part of Abtalkh formation was in Itamir cutting of the study and 9 genera were identified. Recognized calcareous Nannofossil had diversity and abundance. In general, in the greater thickness of the study, samples have moderate preservation. In some cases, the impact of dissolution phenomenon was so great that the main part of the species were corroded. Paying attention to the range of the rise and fall of index species and fossil assemblages, 4 biozones were identified for cutting according to the zones (CC18-CC21) of Sysyngzoning, 1977.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
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.
文摘The marine Tertiary sequence in the north part of the South China Sea may be divided into 18 LateOligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysisof calcareous nannofossils from 40 offshore boreholes. The unnamed Eocene assemblage has been found onlyon the northeast margin of the Zhujiangkou basin. The 18 cakareous nannofossil zones of the Late Oligoceneto Pliocene were deposited in succession, but their development degrees are different. Among the 18 calcareousnannofossil zones, those corresponding to Martini's (1971) NN4- NN5 zones, NN11 zone and NN13-NN15zones are well developed, relatively persistent laterally and also widely distributed. They are the importantmarkers for the stratigraphical subdivision and correlation of the Upper Tertiary between the various basins inthe north part of the South China Sea. Based on the calcareous nannofossils and the sedimentsry features coup-led with the foraminifer zonation in certain basins, the present paper discusses the sedimentary characteristicsof the marine Tertiary and as well as the distribution and development of the sedimentary hiatus in the region.The calcareous nannofossil markers for the Upper / Lower Tertiary and the Quaternary / Tertiary boundaries,and the characteristics and geological significance of the reworked calcareous nannofossils are also discussed inthe paper.
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We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.
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 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 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.
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
文摘The Lower Cretaceous sediments of the Ceahlǎu Nappe （from the bend region of the Romanian Carpathians） were investigated from lithological and micropaleontological （calcareous nannoplankton） points of view. Our investigations revealed that the studied deposits were sedimented within the latest Tithonian-Albian interval. The calcareous nannofossil assemblages of the turbidite calcareous successions （the Sinaia Formation） were assigned to the NJK-？NC5 calcareous nannofossil zones, which cover the Late Tithonian-Early Barremian interval. The sandy-shaly turbidites, which followed the calcareous turbidites of the Sinaia Formation, are Early Barremian-Early Albian in age （interval covered by the ？NC5-NC8 calcareous nannofossil zones）. Because the studied deposited are mainly turbidites, many reworked nannofossils from older deposits are present in the calcareous nannofloras. Thus, some biozones （i.e., NC5）, defined based on the last occurrences of nannofossils, could not be identified. The calcareous nannofossil assemblages are composed of Tethyan taxa （which dominate the nannofloras） and cosmopolitan taxa. During two intervals （the Late Valanginian and across the Barremian/Aptian boundary）, Tethyan and cosmopolitan nannofossils, together with Boreal ones, were observed. This type of mixed calcareous nannoplankton assemblage is indicative for sea-level high-stand, which allows the nannofloral exchange between the Tethyan and Boreal realms, within the two-above mentioned intervals.
文摘A structural-sediment zone of Kopet Dagh is one of the geological units. The southern Kopet Dagh zone is limited to Binalood and the northern limit is with the Turan plateau fault and is created as sediment (Trough) in the late Triassic. The main fault zones are divided into two groups of foundation faults and overthrust. Kopet Dagh is a giant gas field between Turkmenistan, Iran and Afghanistan. Most areas of the region have a temperate climate so cold. From the middle Cambrian to the present, five phases of orogeny have occurred in the region. The geographic location of the study area is 37°43'03"N latitude and 55°35'47"E. In terms of stratigraphic formations in the Cretaceous period, Kopet Dagh area, respectively, is from old to new, including: Shurijeh, Zard, Tiregan, Sar Cheshmeh, Sanganeh, Aitamir, Abderaz, Abtalkh, Neyzar and Kalat. Abtalkh formation is one of the most important rock units in the late Cretaceous in the Kopet Dagh Basin. Abtalkh formation is 489 m and its stratigraphic units are 80 meters of dark grayshale, 20 km dark grayshale with calcareous layers with Inoseramus, 50 m gray marl tend to bluish with Siliceous limestone interlayers, 19 meters of gray-blueshale, 320 meters of light gray shale withthinlayer limestone interlayers. To take pictures of the samples, 100× objective lens and digital camera were used. In the course of this study, the lower part of Abtalkh formation was in Itamir cutting of the study and 9 genera were identified. Recognized calcareous Nannofossil had diversity and abundance. In general, in the greater thickness of the study, samples have moderate preservation. In some cases, the impact of dissolution phenomenon was so great that the main part of the species were corroded. Paying attention to the range of the rise and fall of index species and fossil assemblages, 4 biozones were identified for cutting according to the zones (CC18-CC21) of Sysyngzoning, 1977.
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.
