The sedimentary sequences in the Mamfe Basin are generally thought of as continental (fluvio-lacustrine) in origin. But the wide spread occurrence of salt springs and salt accumulations and in places gypsum, often put...The sedimentary sequences in the Mamfe Basin are generally thought of as continental (fluvio-lacustrine) in origin. But the wide spread occurrence of salt springs and salt accumulations and in places gypsum, often puts to question the exclusive continentality throughout this basin’s history. The sequences studied portray a wide range of complex lithologies and lithofacies relationships and include basal and intra-formational conglomerates, sandstones, shales, carbonaceous, carbonate and halite facies respectively. All these are well exposed at several outcrop sections distributed all over the basin with some measuring up to and above 30 m in height.?Sedimentary structures include: parallel aligned imbricated prismatic pebbles, plannar to trough-cross stratifications, fining upward grain size distribution and thin frequently alternating sandstone-shale beds. Palynological data have been obtained for the first time from the shally and carbonate intervals and integrated with five lithofacies associations, permitting the determination of the ages and paleo environmental reconstruction. The palynomorphs are characterized by pteridophytic spores dominated by?Cicatricosisporites?sp.,Cyathidites?sp. and?Deltoidspora?sp., pollen grains include gymnosperms dominated by?Classopollis annulatus?and?Classopollis todosus?and angiosperms represented by?Retitricolpites?sp. and?Retimoncolpites?sp., fungal remains include some hyphae and?Fusiformisporites?sp. Only a few dinoflagellate cysts dominantly?Spiniferites?were encountered at Nfaitok outcrop, suggesting a proximal sea water influence. A fluvial, lacustrine-deltaic and an anoxic deep bottom lake setting sub-environments were reconstructed with no marine strata encountered. The brines are here suggested to have originated from sea water splay over a barrier and complimented by the chemistry of the drained surrounding country rocks. The palynomorph assemblage suggests an Aptian-Turonian age for the studied sequences and a chronostratigraphic sequence in which the Nfaitok and Satom Bridge units are both Late Cenomanian-Turonian (lateral equivalents of each other) are younger and overlie the Aptian-Early-Cenomanian Okoyong sandstone unit.展开更多
Palynological study of the Minato Formation, Noda Group, distributed in the vicinity of Kuji City, Iwate Prefecture, Japan is discussed in this paper. Biostratigraphically important palynomorphs including four angiosp...Palynological study of the Minato Formation, Noda Group, distributed in the vicinity of Kuji City, Iwate Prefecture, Japan is discussed in this paper. Biostratigraphically important palynomorphs including four angiosperm species, Triprojectus subspinulosus(Funkhouser) Braman, Triprojectus cf. spinulosus(Mtchedlishvili) Stanley, Paraalnipollenites confusus Hills et Wallace and Pistillipollenites macgregorii Rouse, and one fungi species, Pesavis tagluensis Elsik et Jansonius are described. Palyno-assembleges from the lower and the middle horizons of the Minato Formation are considered to indicate Danian in age, which corresponds well with the known fission-track dating. Palyno-assembleges from the lower and middle horizons of the Minato Formations are correlative with those from the Wuyun Formation and the Upper Tsagayan Subformation of Heilongjiang(Amur) River area in northeast China and the Russian Far East. Despite the similarity of the palyno-assembleges, differences in the diversity of angiosperms and species composition of some biostratigraphically important species are recognized between the two regions.展开更多
The southern Anhui metamorphic terrane is traditionally regarded as a part of middle-lateProterozoic "Jiangnan Old Land". Based on the occurrence of palynomorphsAsperatopsophosphaera sp., Trachysphaeridium s...The southern Anhui metamorphic terrane is traditionally regarded as a part of middle-lateProterozoic "Jiangnan Old Land". Based on the occurrence of palynomorphsAsperatopsophosphaera sp., Trachysphaeridium sp. and Nucellosphaeridium sp. (late展开更多
We collected, processed, identified, and analyzed the spores and pollen samples from the Zhuanchengzi Bed of the Yixian Formation in the Yingwoshan area of western Liaoning. As a result, we confirm a palynomorph assem...We collected, processed, identified, and analyzed the spores and pollen samples from the Zhuanchengzi Bed of the Yixian Formation in the Yingwoshan area of western Liaoning. As a result, we confirm a palynomorph assemblage of Cicatri- cosisporites-Protoconiferus. The pollen was primarily from gymnosperms, dominated especially by conifer pollen. Pterido- phyte spores were less common and some questionable angiosperm pollen occurred occasionally. The age of the palynomorph assemblage is dated as the late Valanginian or Hauterivian-Barrernian stage, the Early Cretaceous. The study applies the con- cept of Palynological Vegetation based on palynological spectra and the paleoecological characteristics of palynological taxa for the first time. Palynological vegetation type, climatic zone type, and humidity type are divided quantitatively for the Zhuanchengzi Bed in the Yixian Formation of western Liaoning. We then obtained the evolutionary trends. The results showed that the overall climate was warm and humid during the deposition period of the Zhuanchengzi Bed in the Yixian Formation. Palynological vegetation types are various and include coniferous forest, deciduous broadleaf forest, evergreen broad-leaved forest, grass, and shrubs. The local temperature changed from warm to much warmer and from a semi-humid to humid climate. Palynological vegetation types are always dominated by coniferous forest. The coexistence of deciduous broad-leaved forest, evergreen broad-leaved forest, shrubs, grass, and some xerophytic plants indicates vertical zonation and seasonal climate change The vertical vegetation types and the warm humid climate may imply a large geomorphological contrast in the Yixian Formation of western Liaoning.展开更多
Palynological data are used to draw paleoecological inferences for the Dalichai Formation,northeast of Semnan,northeastern Iran.All samples examined yield well-preserved,diverse palynofloras consisting predominantly o...Palynological data are used to draw paleoecological inferences for the Dalichai Formation,northeast of Semnan,northeastern Iran.All samples examined yield well-preserved,diverse palynofloras consisting predominantly of miospores;dinoflagellate cysts,foraminiferal test linings,and fungal spores occur as minor constituents.Fifty-four species of spores(37 genera),18species of pollen(9 genera),and 16 species of dinoflagellate cysts(13 genera)are recognized.Co-occurrence of such miospore species with known vertical ranges as Klukisporites variegatus,Sellaspora asperata,Murospora florida,and Concavissimisporites verrucosus suggests a Middle Jurassic(Bajocian-Callovian)age for the host strata,thus corroborating the available paleozoological evidence.Such spore species as Klukisporites,Cyathidites,and Dictyophyllidites known to have been produced by Pterophyta dominate the palynofloras.Thus the contemporaneous coastal vegetation was characterized by predominance of Pterophyta whereas representatives of Ginkgophyta,Pteridospermophyta,Lycophyta,Coniferophyta,and Bryophyta were rarely represented.This reconstruction implies that a moist,warm climate prevailed in northeastern Iran during the Middle Jurassic(Bajocian-Callovian).This is confirmed by occurrence of fungal spores accompanied by such warm water dinoflagellate cysts as Mendicodinium groenlandicum,Pareodinia ceratophora,and Gonyaulacysta jurassica.Abundance of Amorphous Organic Matter(AOM)signifies a shallow,low-energy,dysoxic-anoxic depositional site for the host strata.Furthermore,the ratio of AOM to marine palynomorphs as well as abundance of blade-shaped to eqiudimensional opaque palynomacerals could indicate low sedimentation rate in a shallow,low-oxygenated marine environment.Additionally,occurrence of chorate dinoflagellate cysts(e.g.,Adnatosphaeridium caulleryi)and acritarchs bearing relatively long processes(e.g.,Micrhystridium)possibly suggests deepening upward in the study section.展开更多
A primary study on palynofacies, which concerns the paleoenvironments from the sight of association of sedimentary organic matter preserved in sedimentary rocks, is conducted for a Late Jurassic-Cretaceous succession ...A primary study on palynofacies, which concerns the paleoenvironments from the sight of association of sedimentary organic matter preserved in sedimentary rocks, is conducted for a Late Jurassic-Cretaceous succession at Gyangze, southern Tibet. Two palynofacies are recognized, which are formed in different sedimentary environments. The one in the pelagic is infertile in organic productivity and monotonous in component and is dominated by AOMA, while the other, being closely bound up with the slope, is characterized by abundant black phytoclasts that are possibly of algal origin and contains much AOM. The influence of terrestrial input is clear in the latter, for particles generated from terrestrial plants are common. A number of fossil spores and pollen together with some dinocysts are discovered, but they are normally in a bad condition of preservation. Nevertheless, this convinces us that the late Jurassic-Cretaceous succession in the Gyangze area has a potential for palynological stratigraphy. We have also proved that the volume of PM can achieve similar results in presenting the productivity of organic matter as the weight of TOC does. This technique is much easier in the laboratory than that we do with TOC.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
Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified...Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified in order to provide relevant, detailed records for paleoclimate research. The early Creta- ceous vegetation and climate of southeastern Songliao basin have been inferred from the analysis of palynomorph genera, algae and Ostracoda of the LSI and SW110 wells. The lower Cretaceous strata include, in ascending stratigraphic order, the Shahezi, Yingcheng and Denglouku formations. Palyno- logical assemblages for each formation, based on biostratigraphic and statistical analyses, provide an assessment of their longitudinal variations. During deposition of the Shahezi Formation, the climate was mid-subtropical. Vegetation consisted of coniferous forest and herbage. During deposition of the Ying- cheng Formation, the climate was south Asian tropical. Vegetation consisted mainly of coniferous forest and herbal shrub. In addition, fresh and saline non-marine water dominated the lacustrine setting during deposition of these formations. Deposition of the Denglouku Formation, however, occurred under a hot and dry tropical climate. The vegetation was mostly coniferous forest and lake waters became saline. Palaeoclimate variation is correlated by the lake level change and the development of sedimentary facies. Palaeoclimate contribute to the formation of hydrocarbon source rocks and reservoir.展开更多
An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for t...An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for the sediments studied, with considerable influx of continental organic matter that were accumulated during the Cenomanian-Turonian age. With reference to the lithostratigraphic profile of the Douala/Kribi-Campo Basin, the age obtained reveals that the sedimentary sections studied belong particularly to the lower section of the Logbadjeck/Mungo River Formation, based on the following benthic foraminifera assemblage: Ammobaculites jessensis, Ammobaculites benuensis, Ammobaculites coprolithiformis, Ammotium cf nkalagum, Ammotium nwalum, Haplophragmoides cf beuchensis, Trochamina taylorana. A particularly very poor palynomorph assemblage was recovered and included no age diagnostic species: Acrostichum aureum, Lycopodiumsporites sp., Fungal spore, Lavigatosporites discordatus, Longapertites sp., Verrucosisporites sp. An organic petrographic analysis performed on these samples revealed Kerogen Type-II and Type-III. The entire data sets obtained from this area is remarkably poor and we suspect poor preservation as the cause viewing the extent of weathering. The paleo-depositional environment of these sediments was suggested both from the foraminifera and palynomorphs present and confirmed from the organic matter types and macrofossil contents. The studied sections are composed generally of dark to dark-gray shale beds. As one of the petroleum producing basins within the Gulf of Guinea in which exploration/exploitation activities are on-going, the current research is aim at providing more data useful in the continuous search for more potential source rocks in this basin.展开更多
Biostratigraphy has remained a tool for basin and environmental reconstruction in sedimentology. This study aims to further delineate and classify the lithology, environment of deposition, and the biozonation of micro...Biostratigraphy has remained a tool for basin and environmental reconstruction in sedimentology. This study aims to further delineate and classify the lithology, environment of deposition, and the biozonation of microorganisms found in the studied well. Thirty-four (34) ditch cutting samples from OMA well, offshore Dahomey Basin, were considered for their textural and palynomorphs/palynofacies characterization. The samples were observed and processed according to the standard palynological procedure for geologic samples using hydrochloric and hydrofluoric acid digestion. The stratigraphic sequence of the well ranges from shale to sandstone to argillaceous sandstone. The shales appear highly fissile and laminated in all shades of grey and black while the sandstone colour ranges from light-grey/brown to brown and very deep brown. The sandstone contains some mica flakes and likely pyrites in fine-medium, sub-angular to rounded grains. A total of 28 diverse palynomorphs were reported from the palynological analysis with low abundance. The low recovery of pollens was likely due to limited terrestrial influence and the reasonable amount of dinoflagellate cysts and microforaminifera wall present indicated a marginal marine to a distal offshore environment. Two zones correlated for this study are Danea mutabilis (Early Paleocene) and Dinogymnium euclaense (Upper Maastrichtian) zones. Palynomaceral classifications through visual, microscopic kerogen assessment resulted in high preservation of organic matter which suggests a reducing environment of deposition. The dominances of 48% amorphous (I), and 36% exinite (II), with a considerable amount of the 5% vitrinite (III), and 11% inertinite (IV) kerogen types, indicate that the organic matter is mainly sapropelic and mixed humic-sapropelic types which are favorable for hydrocarbon generation and primarily of marine origin. The spores/pollen colour ranges from light yellow/brown, brown transitioning into darker brown on a scale of 4/5 transitioning to 5/6. Medium degree of maturation (4/5) to late degree (6/7) of maturation was inferred. The studied interval of the OMA well sediments agrees with the established stratigraphic interval of the offshore, Dahomey basin, within the Upper Maastrichtian to Late Paleocene age range and supports high preservation of organic matter sufficient and mature enough to generate hydrocarbon.展开更多
文摘The sedimentary sequences in the Mamfe Basin are generally thought of as continental (fluvio-lacustrine) in origin. But the wide spread occurrence of salt springs and salt accumulations and in places gypsum, often puts to question the exclusive continentality throughout this basin’s history. The sequences studied portray a wide range of complex lithologies and lithofacies relationships and include basal and intra-formational conglomerates, sandstones, shales, carbonaceous, carbonate and halite facies respectively. All these are well exposed at several outcrop sections distributed all over the basin with some measuring up to and above 30 m in height.?Sedimentary structures include: parallel aligned imbricated prismatic pebbles, plannar to trough-cross stratifications, fining upward grain size distribution and thin frequently alternating sandstone-shale beds. Palynological data have been obtained for the first time from the shally and carbonate intervals and integrated with five lithofacies associations, permitting the determination of the ages and paleo environmental reconstruction. The palynomorphs are characterized by pteridophytic spores dominated by?Cicatricosisporites?sp.,Cyathidites?sp. and?Deltoidspora?sp., pollen grains include gymnosperms dominated by?Classopollis annulatus?and?Classopollis todosus?and angiosperms represented by?Retitricolpites?sp. and?Retimoncolpites?sp., fungal remains include some hyphae and?Fusiformisporites?sp. Only a few dinoflagellate cysts dominantly?Spiniferites?were encountered at Nfaitok outcrop, suggesting a proximal sea water influence. A fluvial, lacustrine-deltaic and an anoxic deep bottom lake setting sub-environments were reconstructed with no marine strata encountered. The brines are here suggested to have originated from sea water splay over a barrier and complimented by the chemistry of the drained surrounding country rocks. The palynomorph assemblage suggests an Aptian-Turonian age for the studied sequences and a chronostratigraphic sequence in which the Nfaitok and Satom Bridge units are both Late Cenomanian-Turonian (lateral equivalents of each other) are younger and overlie the Aptian-Early-Cenomanian Okoyong sandstone unit.
文摘Palynological study of the Minato Formation, Noda Group, distributed in the vicinity of Kuji City, Iwate Prefecture, Japan is discussed in this paper. Biostratigraphically important palynomorphs including four angiosperm species, Triprojectus subspinulosus(Funkhouser) Braman, Triprojectus cf. spinulosus(Mtchedlishvili) Stanley, Paraalnipollenites confusus Hills et Wallace and Pistillipollenites macgregorii Rouse, and one fungi species, Pesavis tagluensis Elsik et Jansonius are described. Palyno-assembleges from the lower and the middle horizons of the Minato Formation are considered to indicate Danian in age, which corresponds well with the known fission-track dating. Palyno-assembleges from the lower and middle horizons of the Minato Formations are correlative with those from the Wuyun Formation and the Upper Tsagayan Subformation of Heilongjiang(Amur) River area in northeast China and the Russian Far East. Despite the similarity of the palyno-assembleges, differences in the diversity of angiosperms and species composition of some biostratigraphically important species are recognized between the two regions.
文摘The southern Anhui metamorphic terrane is traditionally regarded as a part of middle-lateProterozoic "Jiangnan Old Land". Based on the occurrence of palynomorphsAsperatopsophosphaera sp., Trachysphaeridium sp. and Nucellosphaeridium sp. (late
基金supported by National Natural Science Foundation of China(Grant No.41172003)National Basic Research Program of China(Grant No.2012CB821905)Education Department Programs of Liaoning(Grant Nos.L2013105,L2013450)
文摘We collected, processed, identified, and analyzed the spores and pollen samples from the Zhuanchengzi Bed of the Yixian Formation in the Yingwoshan area of western Liaoning. As a result, we confirm a palynomorph assemblage of Cicatri- cosisporites-Protoconiferus. The pollen was primarily from gymnosperms, dominated especially by conifer pollen. Pterido- phyte spores were less common and some questionable angiosperm pollen occurred occasionally. The age of the palynomorph assemblage is dated as the late Valanginian or Hauterivian-Barrernian stage, the Early Cretaceous. The study applies the con- cept of Palynological Vegetation based on palynological spectra and the paleoecological characteristics of palynological taxa for the first time. Palynological vegetation type, climatic zone type, and humidity type are divided quantitatively for the Zhuanchengzi Bed in the Yixian Formation of western Liaoning. We then obtained the evolutionary trends. The results showed that the overall climate was warm and humid during the deposition period of the Zhuanchengzi Bed in the Yixian Formation. Palynological vegetation types are various and include coniferous forest, deciduous broadleaf forest, evergreen broad-leaved forest, grass, and shrubs. The local temperature changed from warm to much warmer and from a semi-humid to humid climate. Palynological vegetation types are always dominated by coniferous forest. The coexistence of deciduous broad-leaved forest, evergreen broad-leaved forest, shrubs, grass, and some xerophytic plants indicates vertical zonation and seasonal climate change The vertical vegetation types and the warm humid climate may imply a large geomorphological contrast in the Yixian Formation of western Liaoning.
文摘Palynological data are used to draw paleoecological inferences for the Dalichai Formation,northeast of Semnan,northeastern Iran.All samples examined yield well-preserved,diverse palynofloras consisting predominantly of miospores;dinoflagellate cysts,foraminiferal test linings,and fungal spores occur as minor constituents.Fifty-four species of spores(37 genera),18species of pollen(9 genera),and 16 species of dinoflagellate cysts(13 genera)are recognized.Co-occurrence of such miospore species with known vertical ranges as Klukisporites variegatus,Sellaspora asperata,Murospora florida,and Concavissimisporites verrucosus suggests a Middle Jurassic(Bajocian-Callovian)age for the host strata,thus corroborating the available paleozoological evidence.Such spore species as Klukisporites,Cyathidites,and Dictyophyllidites known to have been produced by Pterophyta dominate the palynofloras.Thus the contemporaneous coastal vegetation was characterized by predominance of Pterophyta whereas representatives of Ginkgophyta,Pteridospermophyta,Lycophyta,Coniferophyta,and Bryophyta were rarely represented.This reconstruction implies that a moist,warm climate prevailed in northeastern Iran during the Middle Jurassic(Bajocian-Callovian).This is confirmed by occurrence of fungal spores accompanied by such warm water dinoflagellate cysts as Mendicodinium groenlandicum,Pareodinia ceratophora,and Gonyaulacysta jurassica.Abundance of Amorphous Organic Matter(AOM)signifies a shallow,low-energy,dysoxic-anoxic depositional site for the host strata.Furthermore,the ratio of AOM to marine palynomorphs as well as abundance of blade-shaped to eqiudimensional opaque palynomacerals could indicate low sedimentation rate in a shallow,low-oxygenated marine environment.Additionally,occurrence of chorate dinoflagellate cysts(e.g.,Adnatosphaeridium caulleryi)and acritarchs bearing relatively long processes(e.g.,Micrhystridium)possibly suggests deepening upward in the study section.
基金financially supported by the National Basic Research Program of China(2006CB701402)the National Natural Science Foundation of China(40372008).
文摘A primary study on palynofacies, which concerns the paleoenvironments from the sight of association of sedimentary organic matter preserved in sedimentary rocks, is conducted for a Late Jurassic-Cretaceous succession at Gyangze, southern Tibet. Two palynofacies are recognized, which are formed in different sedimentary environments. The one in the pelagic is infertile in organic productivity and monotonous in component and is dominated by AOMA, while the other, being closely bound up with the slope, is characterized by abundant black phytoclasts that are possibly of algal origin and contains much AOM. The influence of terrestrial input is clear in the latter, for particles generated from terrestrial plants are common. A number of fossil spores and pollen together with some dinocysts are discovered, but they are normally in a bad condition of preservation. Nevertheless, this convinces us that the late Jurassic-Cretaceous succession in the Gyangze area has a potential for palynological stratigraphy. We have also proved that the volume of PM can achieve similar results in presenting the productivity of organic matter as the weight of TOC does. This technique is much easier in the laboratory than that we do with TOC.
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.
基金supported by a grant from the Key Project of the National Science and Technology(2011ZX05009-02)
文摘Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified in order to provide relevant, detailed records for paleoclimate research. The early Creta- ceous vegetation and climate of southeastern Songliao basin have been inferred from the analysis of palynomorph genera, algae and Ostracoda of the LSI and SW110 wells. The lower Cretaceous strata include, in ascending stratigraphic order, the Shahezi, Yingcheng and Denglouku formations. Palyno- logical assemblages for each formation, based on biostratigraphic and statistical analyses, provide an assessment of their longitudinal variations. During deposition of the Shahezi Formation, the climate was mid-subtropical. Vegetation consisted of coniferous forest and herbage. During deposition of the Ying- cheng Formation, the climate was south Asian tropical. Vegetation consisted mainly of coniferous forest and herbal shrub. In addition, fresh and saline non-marine water dominated the lacustrine setting during deposition of these formations. Deposition of the Denglouku Formation, however, occurred under a hot and dry tropical climate. The vegetation was mostly coniferous forest and lake waters became saline. Palaeoclimate variation is correlated by the lake level change and the development of sedimentary facies. Palaeoclimate contribute to the formation of hydrocarbon source rocks and reservoir.
文摘An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for the sediments studied, with considerable influx of continental organic matter that were accumulated during the Cenomanian-Turonian age. With reference to the lithostratigraphic profile of the Douala/Kribi-Campo Basin, the age obtained reveals that the sedimentary sections studied belong particularly to the lower section of the Logbadjeck/Mungo River Formation, based on the following benthic foraminifera assemblage: Ammobaculites jessensis, Ammobaculites benuensis, Ammobaculites coprolithiformis, Ammotium cf nkalagum, Ammotium nwalum, Haplophragmoides cf beuchensis, Trochamina taylorana. A particularly very poor palynomorph assemblage was recovered and included no age diagnostic species: Acrostichum aureum, Lycopodiumsporites sp., Fungal spore, Lavigatosporites discordatus, Longapertites sp., Verrucosisporites sp. An organic petrographic analysis performed on these samples revealed Kerogen Type-II and Type-III. The entire data sets obtained from this area is remarkably poor and we suspect poor preservation as the cause viewing the extent of weathering. The paleo-depositional environment of these sediments was suggested both from the foraminifera and palynomorphs present and confirmed from the organic matter types and macrofossil contents. The studied sections are composed generally of dark to dark-gray shale beds. As one of the petroleum producing basins within the Gulf of Guinea in which exploration/exploitation activities are on-going, the current research is aim at providing more data useful in the continuous search for more potential source rocks in this basin.
文摘Biostratigraphy has remained a tool for basin and environmental reconstruction in sedimentology. This study aims to further delineate and classify the lithology, environment of deposition, and the biozonation of microorganisms found in the studied well. Thirty-four (34) ditch cutting samples from OMA well, offshore Dahomey Basin, were considered for their textural and palynomorphs/palynofacies characterization. The samples were observed and processed according to the standard palynological procedure for geologic samples using hydrochloric and hydrofluoric acid digestion. The stratigraphic sequence of the well ranges from shale to sandstone to argillaceous sandstone. The shales appear highly fissile and laminated in all shades of grey and black while the sandstone colour ranges from light-grey/brown to brown and very deep brown. The sandstone contains some mica flakes and likely pyrites in fine-medium, sub-angular to rounded grains. A total of 28 diverse palynomorphs were reported from the palynological analysis with low abundance. The low recovery of pollens was likely due to limited terrestrial influence and the reasonable amount of dinoflagellate cysts and microforaminifera wall present indicated a marginal marine to a distal offshore environment. Two zones correlated for this study are Danea mutabilis (Early Paleocene) and Dinogymnium euclaense (Upper Maastrichtian) zones. Palynomaceral classifications through visual, microscopic kerogen assessment resulted in high preservation of organic matter which suggests a reducing environment of deposition. The dominances of 48% amorphous (I), and 36% exinite (II), with a considerable amount of the 5% vitrinite (III), and 11% inertinite (IV) kerogen types, indicate that the organic matter is mainly sapropelic and mixed humic-sapropelic types which are favorable for hydrocarbon generation and primarily of marine origin. The spores/pollen colour ranges from light yellow/brown, brown transitioning into darker brown on a scale of 4/5 transitioning to 5/6. Medium degree of maturation (4/5) to late degree (6/7) of maturation was inferred. The studied interval of the OMA well sediments agrees with the established stratigraphic interval of the offshore, Dahomey basin, within the Upper Maastrichtian to Late Paleocene age range and supports high preservation of organic matter sufficient and mature enough to generate hydrocarbon.
