Stratigraphic hiatuses of variable time intervals within the Rhuddanian to early Aeronian （Llandovery, Silurian） are identified in the area bordering East Chongqing, West Hubei and Northwest Hunan in central China. ...Stratigraphic hiatuses of variable time intervals within the Rhuddanian to early Aeronian （Llandovery, Silurian） are identified in the area bordering East Chongqing, West Hubei and Northwest Hunan in central China. Their distribution suggested the existence of a local uplift, traditionally named the Yichang Uplift. The diachronous nature of the basal black shale of the Lungmachi Formation crossing different belts of this Uplift signifies the various developing stages during the uplifting process. The present paper defines the temporal and spatial distribution pattern of the Yichang Uplift, which might be one of the important controlling factors for the preservation and distribution of the shale gas in this region, as it has been demonstrated that the shale gas exploration is generally less promising in the areas where more of the basal part of the Lungmachi Formation is missing. Therefore, better understanding of the circumjacent distribution pattern developed throughout the uplifting process may provide the important guidance for the shale gas exploration. The present work is a sister study to the published paper, ＂Stage-progressive distribution pattern of the Lungrnachian black graplolitic shales from Guizhou to Chongqing, Central China＂. These two studies thus provide a complete Ordovician-Silurian black shale distribution pattern in the Middle and Upper Yangtze, a region with the major shale gas fields in China.展开更多
Chitinozoans collected from upper Tremadocian to lower Floian strata of Chenjiahe section, Yichang, western Hubei, China comprise six species belonging respectively to the genera Euconochitina including a new species,...Chitinozoans collected from upper Tremadocian to lower Floian strata of Chenjiahe section, Yichang, western Hubei, China comprise six species belonging respectively to the genera Euconochitina including a new species, Euconochitina fenxiangensis, Lagenochitina and Bursachitina, together with Desmochitina sp. and Eremochitina sp. The chitinozoan succession across the interval is correlated with relevant conodont and chitinozoan biozones and two new regional chitinozoan biozones, the Lagenochitina destombesi Biozone and the Euconochitina symmetrica Biozone are proposed based on their stratigraphic ranges in the Fenxiang to Honghuayuan formations in the Chenjiahe section.展开更多
Fourteen graptolite species of the Late Tremadoc and Early Floian are described from the Nanba section in the Yiyang area,Hunan Province.Among them,Paradelograptus onubensis, Kiaerograptus bulmani,K.kutchini and Parat...Fourteen graptolite species of the Late Tremadoc and Early Floian are described from the Nanba section in the Yiyang area,Hunan Province.Among them,Paradelograptus onubensis, Kiaerograptus bulmani,K.kutchini and Paratemnograptus isolatus of the Late Tremadoc are first found in China.Based on the current graptolite materials,the correspondingly complete graptolite zones of Upper Tremadocian in China are recognized as follows（in ascending order）：the Adelograptus tenellus Zone,the Aorograptus victoriae Zone,the Araneograptus murrayi Zone and the Hunnegraptus copiosus Zone.In the Nanba section,the Hunnegraptus copiosus Zone is overlain directly by the Tetragraptus approximatus Zone,there is no hiatus below the base of Floian.展开更多
In this study Late Cretaceous stratum in central Iran, Baharestan section in Isfahan area, was evaluated by biozonation and paleobathymetry.?These sediments have 89 meters thick, and strata have been formed of marl an...In this study Late Cretaceous stratum in central Iran, Baharestan section in Isfahan area, was evaluated by biozonation and paleobathymetry.?These sediments have 89 meters thick, and strata have been formed of marl and marl limestone. In order to indicate the ancient depth of Upper Cretaceous at this time, planktonic and benthic foraminifera were studied. The percentage of the total planktonic foraminifera to the whole sample of foraminifera after the removal of indwell benthic foraminifera (%P*) using the formula?D?=?e(3.58718 + (0.03534?×?%P*))?was identified and depth of 200 - 450 meters was achieved for them. In the present investigation, 30 planktonic species of 11 genus have been identified. The Upper Cretaceous deposit was divided to 6 biozones on the basis of planktonic foraminifera which are cosmopolitan and consist of: Biozone 1—Marginotruncana sigali-Dicarinella primitiva?partial range zone;?Biozone 2—Dicarinella concavata?interval zone;?Biozone 3—Dicarinella asymetrica?total range zone;Biozone 4—Globotruncanita elevata?partial range zone;Biozone 5—Globotruncana ventricosa?interval zone;Biozone 6—Radotruncana calcarata?interval zone.?Based on planktonic foraminifera, the Upper Cretaceous sediments in the study area are of the Turonian-Late Campanian ages.展开更多
Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formati...Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formation in Argolis appears,generally,in the form of lensoid bodies of variable sizes,inclination and direction and is always found overlying a formation consisting of keratophyric tuffs.In fact,the contact of the keratophyric tuffs with the overlying limestones,specifically evidenced by an in situ brecciated zone,is stratigraphic and constitutes the base of the Hallstatt Limestones.The contact of the Hallstatt Limestones with the overlying radiolarites is stratigraphic as well.Lithofacies and biostratigraphic research has focused on the lowermost horizons of the Hallstatt Limestones of Anisian age (average thickness about 1.30 m),where a dense sampling has been performed,followed by detailed facies analysis.The lowermost horizons of the Hallstatt Limestones of Theokafta represent typical hiatus beds/concretions sensu Wetzel and Allia (2000),characterized by discontinuous sedimentation and erosion.They consist of red ammonoid-bearing hemipelagic limestones with calcium carbonate nodules floating in an enriched Fe-oxides matrix with dispersed lensoid/prismatic calcium carbonate crystals.This part of the section is characterized by condensed sedimentation,due to significant lowering of the rate of sedimentation and includes omission surfaces,firmgrounds and hardgrounds along certain horizons.Nine lithostratigraphic units have been distinguished in the lowermost horizons of the Hallstatt Limestones,including radiolarian packstones,volcaniclastic facies,packstones/floatstones with ammonoids and lag deposits.Tselepidis (2007) defined nine distinct ammonoid biozones from the Anisian to Ladinian,documenting deposition of the Hallstatt facies during a low depositional rate over nearly 5 million years (using the timescale of Gradstein et al.,2004).The biozones:Japonites/Paracrochordiceras,Hollandites,Procladiscites展开更多
Studies of two wells within the coastal swamp onshore Niger Delta were carried out in order to determine the chronology, biozonation, and establishment of sequence stratigraphic framework for the representative wells....Studies of two wells within the coastal swamp onshore Niger Delta were carried out in order to determine the chronology, biozonation, and establishment of sequence stratigraphic framework for the representative wells. A total of twenty-eight (28) cutting samples were recovered and analysed from Abigboro-1 and Olure-1 exploratory wells for their foraminifera, calcareous nannofossils and palynomorphs’ compositions. The results indicated the presence of diverse species within the wells, which include Lenticulina grandis, Florilus ex. gr. costiferum, Hanzawaia concentrica, Hopkinsina bononiensis, Marginulina costata and pseudonodosaria sp., Bolivina mandoroveensis, Eponides eshira, Lenticulina grandis, Lenticulina grandis, Cibicorbis inflata, Heterolepa floridana, Florilus ex. gr scaphum, Poroeponides lateralis, Uvigerina sparsicostata, Uvigerina subperegrina, Bolivina ex. gr. scalptrata, Valvulineria sp. and Epistominella pacifica. An inner neritic (1694 m - 2161 m), coastal deltaic (1557 m - 1640 m) and shallow inner neritic (1347 m - 1554 m) palaeoenvironment was suggested for Olure-1 well while a broad grouping of the intervals as inner to middle neritic was suggested for Abigboro-1 well. The ratio of species abundance/diversity and integration of log suite data predicted two Maximum Flooding Surfaces (MFS) and one Sequence Boundary (SB) for Olure-1 well. The MFS were encountered at depths 2728 m (MFS 1) and 1797 m (MFS 2), while the SB was predicted at depth 2602 m (SB1). Diverse systems’ tracts were identified and delineated from wireline logs of Olure-1 well and the implication for petroleum exploration was discussed. Late Oligocene - early Miocene age has been assigned for the wells based on the recovered diagnostic species.展开更多
Cenozoic sediments form extensive outcrops in the Niger Delta Basin. Detailed palynostratigraphic study was undertaken across Paleogene sequences exposed in Bende–Umuahia Area in up-dip sectors of the Niger Delta Bas...Cenozoic sediments form extensive outcrops in the Niger Delta Basin. Detailed palynostratigraphic study was undertaken across Paleogene sequences exposed in Bende–Umuahia Area in up-dip sectors of the Niger Delta Basin, southeastern Nigeria, to establish different palynomorphs assemblage zones, with their corresponding ages.Palynological analysis was carried out on 27 selected outcrop samples, using the conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments. Three Cenozoic lithostratigraphic units, including Imo Formation, Ameki Formation, and Ogwashi Formation, are exposed in the study area. Lithologies are sandstone, carbonaceous shale, mudstone, limestone, and the lignite. A total of 65 species of sporomorphs and 51 dinoflagellate cysts were identified. The recovered spores and pollen grains were used to establish six informal palynomorph assemblage zones, labeled as zone A – zone F, based on the first and the last occurrences of two or more species. These palynomorph assemblage zones include:(1) zone A — middle Paleocene Scabratriporites simpliformis–Bombacidites annae zone;(2) zone B — late Paleocene Foveotricolporites crassiexinus–Mauritidiites crassiexinus zone;(3) zone C — early Eocene Striatopollis catatumbus–Momipites africanus zone;(4) zone D — middle Eocene Margocolporites umuahiaensis–Gemmastephanocolporites brevicolpites zone;(5)zone E — late Eocene Cicatricosisporites dorogensis–Perfotricolpites nigerianus zone;and,(6) zone F — Oligocene–early Miocene Verrucatosporites usmensis–Magnastriatites howardii zone. The erected palynozones were correlated and compared with existing biozones in subsurface, down-dip sectors of the Niger Delta Basin, with pantropical palynological zones in tropical areas of Africa, and with palynofloral provinces of northern South America. A comparison of palynozones studied in southeastern Nigeria with other international palynozones, in this study, will assist in establishing the correlation o展开更多
A rich assemblage of planktonic foraminifera has been studied from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the southwest Iran, Deh Dasht area（Kuh-e Siah anticline）. Based on the distributio...A rich assemblage of planktonic foraminifera has been studied from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the southwest Iran, Deh Dasht area（Kuh-e Siah anticline）. Based on the distribution of the planktonic foraminifera, eight biozones have been recognized that included：Dicarinella concavata Interval Zone（Earliest Santonian）, Dicarinella asymetrica Total Range Zone（Santonian to Earliest Campanian）, Globotruncanita elevata Partial Range Zone（Early Campanian）, Globotruncana ventricosa Interval Zone（Middle to Late Campanian）, Radotruncana calcarata Total Range Zone（Late Campanian）, Globotruncanella havanensis Partial Range Zone（Late Campanian）, Globotruncana aegyptiaca Interval Zone（Late to latest Campanian）, Gansserina gansseri Interval Zone（Latest Campanian to Early Maastrichtian）. These biozones indicates that the Gurpi Formation deposited during the Early Santonian- Early Maastrichtian. These biozones are compared to the most standard biozones defined in Tethysian domain. Based on distribution of morphotype groups of planktonic foraminifera, planktonic to benthic ratio（P/B） and content of carbonate, nine third-order sequences are recognized.展开更多
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB26000000)the National Natural Science Foundation of China (Grant Nos. U1562213 and 41502025)the National Science and Technology Major Project of China (Grant No. 2017ZX05035002-001)
文摘Stratigraphic hiatuses of variable time intervals within the Rhuddanian to early Aeronian （Llandovery, Silurian） are identified in the area bordering East Chongqing, West Hubei and Northwest Hunan in central China. Their distribution suggested the existence of a local uplift, traditionally named the Yichang Uplift. The diachronous nature of the basal black shale of the Lungmachi Formation crossing different belts of this Uplift signifies the various developing stages during the uplifting process. The present paper defines the temporal and spatial distribution pattern of the Yichang Uplift, which might be one of the important controlling factors for the preservation and distribution of the shale gas in this region, as it has been demonstrated that the shale gas exploration is generally less promising in the areas where more of the basal part of the Lungmachi Formation is missing. Therefore, better understanding of the circumjacent distribution pattern developed throughout the uplifting process may provide the important guidance for the shale gas exploration. The present work is a sister study to the published paper, ＂Stage-progressive distribution pattern of the Lungrnachian black graplolitic shales from Guizhou to Chongqing, Central China＂. These two studies thus provide a complete Ordovician-Silurian black shale distribution pattern in the Middle and Upper Yangtze, a region with the major shale gas fields in China.
文摘Chitinozoans collected from upper Tremadocian to lower Floian strata of Chenjiahe section, Yichang, western Hubei, China comprise six species belonging respectively to the genera Euconochitina including a new species, Euconochitina fenxiangensis, Lagenochitina and Bursachitina, together with Desmochitina sp. and Eremochitina sp. The chitinozoan succession across the interval is correlated with relevant conodont and chitinozoan biozones and two new regional chitinozoan biozones, the Lagenochitina destombesi Biozone and the Euconochitina symmetrica Biozone are proposed based on their stratigraphic ranges in the Fenxiang to Honghuayuan formations in the Chenjiahe section.
基金supported by the Basic Outlay of Scientific Research Work from Ministry of Science and Technology(No.J0905)
文摘Fourteen graptolite species of the Late Tremadoc and Early Floian are described from the Nanba section in the Yiyang area,Hunan Province.Among them,Paradelograptus onubensis, Kiaerograptus bulmani,K.kutchini and Paratemnograptus isolatus of the Late Tremadoc are first found in China.Based on the current graptolite materials,the correspondingly complete graptolite zones of Upper Tremadocian in China are recognized as follows（in ascending order）：the Adelograptus tenellus Zone,the Aorograptus victoriae Zone,the Araneograptus murrayi Zone and the Hunnegraptus copiosus Zone.In the Nanba section,the Hunnegraptus copiosus Zone is overlain directly by the Tetragraptus approximatus Zone,there is no hiatus below the base of Floian.
文摘In this study Late Cretaceous stratum in central Iran, Baharestan section in Isfahan area, was evaluated by biozonation and paleobathymetry.?These sediments have 89 meters thick, and strata have been formed of marl and marl limestone. In order to indicate the ancient depth of Upper Cretaceous at this time, planktonic and benthic foraminifera were studied. The percentage of the total planktonic foraminifera to the whole sample of foraminifera after the removal of indwell benthic foraminifera (%P*) using the formula?D?=?e(3.58718 + (0.03534?×?%P*))?was identified and depth of 200 - 450 meters was achieved for them. In the present investigation, 30 planktonic species of 11 genus have been identified. The Upper Cretaceous deposit was divided to 6 biozones on the basis of planktonic foraminifera which are cosmopolitan and consist of: Biozone 1—Marginotruncana sigali-Dicarinella primitiva?partial range zone;?Biozone 2—Dicarinella concavata?interval zone;?Biozone 3—Dicarinella asymetrica?total range zone;Biozone 4—Globotruncanita elevata?partial range zone;Biozone 5—Globotruncana ventricosa?interval zone;Biozone 6—Radotruncana calcarata?interval zone.?Based on planktonic foraminifera, the Upper Cretaceous sediments in the study area are of the Turonian-Late Campanian ages.
文摘Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formation in Argolis appears,generally,in the form of lensoid bodies of variable sizes,inclination and direction and is always found overlying a formation consisting of keratophyric tuffs.In fact,the contact of the keratophyric tuffs with the overlying limestones,specifically evidenced by an in situ brecciated zone,is stratigraphic and constitutes the base of the Hallstatt Limestones.The contact of the Hallstatt Limestones with the overlying radiolarites is stratigraphic as well.Lithofacies and biostratigraphic research has focused on the lowermost horizons of the Hallstatt Limestones of Anisian age (average thickness about 1.30 m),where a dense sampling has been performed,followed by detailed facies analysis.The lowermost horizons of the Hallstatt Limestones of Theokafta represent typical hiatus beds/concretions sensu Wetzel and Allia (2000),characterized by discontinuous sedimentation and erosion.They consist of red ammonoid-bearing hemipelagic limestones with calcium carbonate nodules floating in an enriched Fe-oxides matrix with dispersed lensoid/prismatic calcium carbonate crystals.This part of the section is characterized by condensed sedimentation,due to significant lowering of the rate of sedimentation and includes omission surfaces,firmgrounds and hardgrounds along certain horizons.Nine lithostratigraphic units have been distinguished in the lowermost horizons of the Hallstatt Limestones,including radiolarian packstones,volcaniclastic facies,packstones/floatstones with ammonoids and lag deposits.Tselepidis (2007) defined nine distinct ammonoid biozones from the Anisian to Ladinian,documenting deposition of the Hallstatt facies during a low depositional rate over nearly 5 million years (using the timescale of Gradstein et al.,2004).The biozones:Japonites/Paracrochordiceras,Hollandites,Procladiscites
文摘Studies of two wells within the coastal swamp onshore Niger Delta were carried out in order to determine the chronology, biozonation, and establishment of sequence stratigraphic framework for the representative wells. A total of twenty-eight (28) cutting samples were recovered and analysed from Abigboro-1 and Olure-1 exploratory wells for their foraminifera, calcareous nannofossils and palynomorphs’ compositions. The results indicated the presence of diverse species within the wells, which include Lenticulina grandis, Florilus ex. gr. costiferum, Hanzawaia concentrica, Hopkinsina bononiensis, Marginulina costata and pseudonodosaria sp., Bolivina mandoroveensis, Eponides eshira, Lenticulina grandis, Lenticulina grandis, Cibicorbis inflata, Heterolepa floridana, Florilus ex. gr scaphum, Poroeponides lateralis, Uvigerina sparsicostata, Uvigerina subperegrina, Bolivina ex. gr. scalptrata, Valvulineria sp. and Epistominella pacifica. An inner neritic (1694 m - 2161 m), coastal deltaic (1557 m - 1640 m) and shallow inner neritic (1347 m - 1554 m) palaeoenvironment was suggested for Olure-1 well while a broad grouping of the intervals as inner to middle neritic was suggested for Abigboro-1 well. The ratio of species abundance/diversity and integration of log suite data predicted two Maximum Flooding Surfaces (MFS) and one Sequence Boundary (SB) for Olure-1 well. The MFS were encountered at depths 2728 m (MFS 1) and 1797 m (MFS 2), while the SB was predicted at depth 2602 m (SB1). Diverse systems’ tracts were identified and delineated from wireline logs of Olure-1 well and the implication for petroleum exploration was discussed. Late Oligocene - early Miocene age has been assigned for the wells based on the recovered diagnostic species.
文摘Cenozoic sediments form extensive outcrops in the Niger Delta Basin. Detailed palynostratigraphic study was undertaken across Paleogene sequences exposed in Bende–Umuahia Area in up-dip sectors of the Niger Delta Basin, southeastern Nigeria, to establish different palynomorphs assemblage zones, with their corresponding ages.Palynological analysis was carried out on 27 selected outcrop samples, using the conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments. Three Cenozoic lithostratigraphic units, including Imo Formation, Ameki Formation, and Ogwashi Formation, are exposed in the study area. Lithologies are sandstone, carbonaceous shale, mudstone, limestone, and the lignite. A total of 65 species of sporomorphs and 51 dinoflagellate cysts were identified. The recovered spores and pollen grains were used to establish six informal palynomorph assemblage zones, labeled as zone A – zone F, based on the first and the last occurrences of two or more species. These palynomorph assemblage zones include:(1) zone A — middle Paleocene Scabratriporites simpliformis–Bombacidites annae zone;(2) zone B — late Paleocene Foveotricolporites crassiexinus–Mauritidiites crassiexinus zone;(3) zone C — early Eocene Striatopollis catatumbus–Momipites africanus zone;(4) zone D — middle Eocene Margocolporites umuahiaensis–Gemmastephanocolporites brevicolpites zone;(5)zone E — late Eocene Cicatricosisporites dorogensis–Perfotricolpites nigerianus zone;and,(6) zone F — Oligocene–early Miocene Verrucatosporites usmensis–Magnastriatites howardii zone. The erected palynozones were correlated and compared with existing biozones in subsurface, down-dip sectors of the Niger Delta Basin, with pantropical palynological zones in tropical areas of Africa, and with palynofloral provinces of northern South America. A comparison of palynozones studied in southeastern Nigeria with other international palynozones, in this study, will assist in establishing the correlation o
基金the University of Isfahan for providing financial support
文摘A rich assemblage of planktonic foraminifera has been studied from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the southwest Iran, Deh Dasht area（Kuh-e Siah anticline）. Based on the distribution of the planktonic foraminifera, eight biozones have been recognized that included：Dicarinella concavata Interval Zone（Earliest Santonian）, Dicarinella asymetrica Total Range Zone（Santonian to Earliest Campanian）, Globotruncanita elevata Partial Range Zone（Early Campanian）, Globotruncana ventricosa Interval Zone（Middle to Late Campanian）, Radotruncana calcarata Total Range Zone（Late Campanian）, Globotruncanella havanensis Partial Range Zone（Late Campanian）, Globotruncana aegyptiaca Interval Zone（Late to latest Campanian）, Gansserina gansseri Interval Zone（Latest Campanian to Early Maastrichtian）. These biozones indicates that the Gurpi Formation deposited during the Early Santonian- Early Maastrichtian. These biozones are compared to the most standard biozones defined in Tethysian domain. Based on distribution of morphotype groups of planktonic foraminifera, planktonic to benthic ratio（P/B） and content of carbonate, nine third-order sequences are recognized.
