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
Diversified continental,marginal-marine and marine epicontinental deposits in Poland of Early Jurassic age yielded unusually rich palynomacerals.Numerous parameters,such as the presence of acritarchs and dinoflagellat...Diversified continental,marginal-marine and marine epicontinental deposits in Poland of Early Jurassic age yielded unusually rich palynomacerals.Numerous parameters,such as the presence of acritarchs and dinoflagellate cysts,spore/bisaccate pollen grain ratio,content of terrestrial phytoclasts,degree of oxidation,presence of tetrads and sporangia,degree of palynomorph alteration,presence and character of amorphous organic matter,presence of epibionts on palynomorphs,were collectively found as indicative of certain palynofacies.The ratio of spores and bisaccate pollen grains significantly depends on the climatic conditions where also seasonal changes may influence the local characteristics of palynofacies.However,the ratio also strongly reflects the local depositional environment which may vary regionally and spore/bisaccate pollen grain ratio can be taken as a general indicator of distance from the shore.Early Jurassic palynomacerals from the Polish Basin are strongly dominated by terrestrial elements,marine palynomacerals occur in significant quantities only in Pliensbachian deposits in Pomerania Western Poland.Charcoal is an important component of palynomacerals.Due to its resistance to biogenic degradation and buoyancy,charcoal produced by extensive wildfires was widely re-deposited and concentrated particularly in foreshore to shallow shoreface and delta plain environments.Three types of palynofacies inversions(abnormal palynofacies composition)are discussed.Six main palynofacies types linked to depositional systems previously determined by sedimentological studies have been distinguished providing a robust paleoenvironmental tool for recognition of palynofacies attributed to certain palaeoenvironments.展开更多
Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis...Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T<sub>max</sub>), and Vitrinite Reflectance (VR<sub>o</sub>) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.展开更多
The Permian-Triassic(P/T)transition is marked by the most severe mass-extinction event of the Phanerozoic.Although much is known about this event in the marine realm,there are many open questions regarding what happen...The Permian-Triassic(P/T)transition is marked by the most severe mass-extinction event of the Phanerozoic.Although much is known about this event in the marine realm,there are many open questions regarding what happened during this period to many continental biota.In the case of plants,a drastic mass-extinction event has even been negated by some authors.To add about the knowledge on continental biota in India during this crucial time period,the present study analysed the palynology,palynofacies,organic geochemistry(biomarkers),stable isotopes,and charcoal within the subsurface Gondwana deposits of the Kamthi Formation(late Permian-early Triassic)from core TTB-7 from the Tribida block,located in the Talcher Coalfield of the Mahanadi Basin,India.The primary objectives are to validate the age of the strata,ascertain the palaeodepositional setting of the palaeomire,and propose palaeobotanical evidence regarding the occurrence of wildfires within this stratigraphic succession and changes in floral content across the P/T transition.The palynological study proposes two palynoassemblage zones,Densipollenites magnicorpus and Klausipollenites schaubergeri,suggesting a latest Permian(Lopingian)and early Triassic(Induan?)age for the studied succession,respectively.The age is also inferred based on correlation with coeval assemblages from India and other Gondwana continents.The palynoassemblages reveal the dominance of Glossopteridales and Coniferales along with Filicales,Lycopsidales,Equisetales,Cordaitales and Peltaspermales.The relatively higher values of the carbon preference index and terrigenous/aquatic ratio also suggest higher plant input.However,a bimodal n-alkane distribution pattern suggests the contribution of terrigenous and microbial sources.Although the occurrences of long-chain alkanes indicate input of higher plants,the low Pwax values(<0.26)suggest relatively less contribution.The Paqvalues(≅1)and amorphous organic matter(av.33.24%)suggest a significant macrophyte input in the studied samples,pointing to the occurrence of moderate aquatic conditions in the basin.Furthermore,the distribution of hopanoids and the content of degraded organic matter(av.29.96%)reflect the bacterial degradation of organic matter.Also,the δ^(13)C values of the studied section varied from−31.2‰to−21.8‰.A large carbon isotopic offset of 9.4‰across the P/T transition,Pr/Ph ratio(0.3–1.3)and shift in the distribution pattern of palynofacies components is indicating a significant change in climatic conditions.Moreover,the presence of macroscopic charcoal fragments of gymnospermous affinity with pre-charring colonization by fungi provides evidence for wildfire occurring during the Lopingian(Late Permian)in this basin.展开更多
The sedimentary sequence containing lignite deposits in Gurha quarry of the Bikaner-Nagaur Basin(Rajasthan)has been investigated.The samples from lignite and allied shale horizons were evaluated for petrographical,pal...The sedimentary sequence containing lignite deposits in Gurha quarry of the Bikaner-Nagaur Basin(Rajasthan)has been investigated.The samples from lignite and allied shale horizons were evaluated for petrographical,palynological,palynofacies and organic geochemical inferences,to depict the source flora and to reconstruct the palaeodepositional conditions prevailed during the sedimentation.An assessment for the hydrocarbon generation potential of these deposits has also been made.The results revealed the dominance of huminite macerals and phytoclasts organic matter(OM) indicating the existence of forested vegetation in the vicinity of the depositional site.A relatively high terrigenous/aquatic ratio(TAR) and the carbon preference index(CPI) are also suggesting the contribution of higher plants in the peat formation.However,the n-alkane distributions,maximizing at n-C17 and n-C29,showed inputs from the algal communities along with the higher plant derived organic matters.Recovered palynomorphs of the families Onagraceae,Meliaceae,Arecaceae,Rhizophoraceae,Rubiaceae,Ctenolophonaceae, etc.together with oleanene and ursane types of triterpenoids suggest the contribution from angiosperms source vegetation.Interestingly,the presence of Araucareaceae and Podocarpaceae pollen grains shows the existence of gymnosperms vegetation.Further,the presence of tetracyclic diterpanes;demethylated entbeyerane,sandaracopimarane,pimarane,and Kaurane type of compounds confirms the contribution of conifers.The variation in the values of the coefficient of non-equality(H:0.68%-7.56%),the standard deviation(8:0.04%-0.16%) and the coefficient of variability(V:16.10%-46.47%),also shows the heterogeneity in the source organic matter.The various petrographical indices,palynological entities,and geochemical parameters indicate that the peatforming vegetation was accumulated under a mixed environment and fluctuating hydrological settings.The interpretation of palynofacies data on APP(Amorphous organic matter-Phytoclast-Palynomorphs) diagram suggests that the accumulation of organic matter occurred in a dysoxic-suboxic condition in a proximal(to land)setting with the shift to an anoxic condition in distal setting towards the termination of sedimentation.The huminite(ulminite) reflectance(R_r) values(av.0.28%) showed a good relationship with average T_(max) value(414℃),suggesting the immaturity.The TOC content ranges of 13-59 wt.%,and HI values vary between 101 and 546 mg HC/g TOC in the studied samples.Collectively,the studied lignite and shale samples have the admixed kerogens(Type Ⅲ-Ⅱ) and exhibit the ability to generate the gaseous to oil hydrocarbons upon maturation.展开更多
The mechanisms of lacustrine organic-rich shale formation have attracted attention due to its association with global shale oil and shale gas exploration.Samples of general-quality and excellent-quality source rocks,a...The mechanisms of lacustrine organic-rich shale formation have attracted attention due to its association with global shale oil and shale gas exploration.Samples of general-quality and excellent-quality source rocks,and oil shale from the Beibu Gulf Basin were analyzed to investigate their organic geochemistry,palynofacies,and trace elements.Hydrocarbon potential was higher in the oil shale(29.79 mg/g)than in the general-quality source rock(3.82 mg/g),and its kerogen type wasⅠ-Ⅱ2.Hydrogen-rich liptinite(cutinite and sporinite)components derived from terrigenous higher plants provided most of the hydrocarbon potential of excellent-quality source rock and oil shale.Under the influence of depressioncontrolling fault activity,a deeper subsidence center promotes the deposition of excellent-quality source rock and oil shale in brackish-hypoxic bottom water.A shallower subsidence center,due to subsag-controlling fault activity,promotes the formation of excellent-quality source rock under freshbrackish and weak oxidation-weak reducing conditions.The local uplift and shallow-slope led to the formation of general-quality source rock,under freshwater weak-oxidation conditions.A model was established for organic matter(OM)accumulation in organic-rich shales,accounting for fault activity,terrigenous hydrogen-rich OM,and the preservation conditions,to predict the development of excellent-quality source rock from areas with low levels of exploration.展开更多
The Early Cambrian Niutitang Formation on the Yangtze Block is a set of high-quality marine source rock.However,hydrocarbon-forming organisms of these organic-rich shales was poorly understood.In this paper,the result...The Early Cambrian Niutitang Formation on the Yangtze Block is a set of high-quality marine source rock.However,hydrocarbon-forming organisms of these organic-rich shales was poorly understood.In this paper,the results of palynofacies analysis and hydrocarbon-forming organism characteristics of the Niutitang Formation from the Yangtze Block are reported for the first time,and the sedimentary environment is discussed in combination with geochemical data.Palynofacies analysis show that the organic matter(OM)of the Niutitang Formation is mainly composed of amorphous organic matter(AOM),with a small amount of structural organic matter(STOM)and palynomorphs(PL).The results of CONISS(stratigraphically constrained incremental sum of squares)cluster analysis show that the PL can be divided into three zones in the ascending order:Leiosphaeridia-Micrhystridiumfungal zone,algal bloom zone and fungal development zone,corresponding to three stages:transgression,high-stand and regression,respectively.The principal component analysis(PCA)shows that the main hydrocarbon-forming organisms include planktonic green microalgae or dinoflagellates that are related to Leiosphaeridia and Microcystidium.Palynofacies analysis and geochemical data show that the Niutitang Formation was deposited under anoxic or dysoxic condition which was favorable to the enrichment of organic matter.展开更多
The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the excep...The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the exceptionally high total organic carbon content(TOC,>6%on average)of the tidal sand ridge samples was not compatible with their sedimentary environment,indicating coal-bearing sedimentary debris may have been transferred from the coast to the ocean.In this study,new sights into the origins and supply of organic materials in the coastal environment were proposed in the neritic organic matter of the Eocene Pinghu Formation.A discriminant model was developed using plynofacies analysis data to pinpoint the source of organic materials in marine source rocks.The discrimination results suggested that marine mudstones were associated with tidal flat mudstones rather than deltaic ones.The biomarker characteristics of mudstones deposited in various environments support this assertion,indicating that the supply of plant materials in tidal flats is the primary organic matter source for the marine environment.The organic matter abundance was elevated in tidal flats due to their superior preservation conditions.Additionally,the lithological assemblage of tidal flats suggests that tidal currents can scour marshes and then transport dispersed terrigenous organic materials to neritic areas.These findings indicate that coal-bearing sedimentary debris was likely transferred from the coast to the ocean,and tidal currents are thought to be the dominant mechanism driving organic matter from the tidal to the marine environment.展开更多
The present study deals with the textural characteristics of the sediments from the exposed palaeochannel situated at Dhyangla village near Ladwa, district of Kurukshetra in north-western Haryana. It is a part of vast...The present study deals with the textural characteristics of the sediments from the exposed palaeochannel situated at Dhyangla village near Ladwa, district of Kurukshetra in north-western Haryana. It is a part of vast alluvial plains of India. Samples were taken from a 3 m thick exposed section. Grain size distribution and Palynofacies analyses of these sediments were carried out to study their textural parameters and the organic matter content respectively. Sediments are mostly fine to medium grained sand with silt percentage increasing upwards in the section. These sediments are mostly unimodal showing the grain size population controlled by a single type of grain size, mostly sand. Further the sand samples are moderately well sorted and mesokurtic in nature. Samples with silt are poorly sorted and leptokurtic with positive skewness, denoting those sediments have already sorted elsewhere in the high energy environment and are now transported and modified by the low energy environment. Palynofacies analysis also shows the presence of amorphous particles in the silt samples which indicate low energy environment of the sequence while presence of black debris in the sand samples indicates high energy depositions environment.展开更多
Highly-mature carbonate source rock is essential to the exploration of oil and gas in southern China. In this study, the carbonate strata in the relatively well-developed Lower Permian Chihsia Formation (located in Ch...Highly-mature carbonate source rock is essential to the exploration of oil and gas in southern China. In this study, the carbonate strata in the relatively well-developed Lower Permian Chihsia Formation (located in Chaohu, Lower Yangtze) were targeted, and the formation and influencing factors of source rock were discussed based on paleoenvironment reconstruction using comprehensive sedimentology, palynofacies, and organic geochemistry data. The results demonstrate that the Chihsia Formation is oxygen-deficient biogenic carbonate sediments, with marked variations in the organic and inorganic components, formed during a period of Permian transgression. The formation of source rock is the combined result of high bioproductivity and oxygen-deficient environment generated by transgression and oxygenation events which frequently occurred during transgression periods. Source rock was affected by self-dilution effects and diagenesis, causing its heterogeneous distribution in many intervals. Source rock is over 40 m thick, and can be identified based on its different organic, biological, and mineral composition characteristics. The carbonate rock appears to require no specific clay content in order to become a source rock. The combination of sedimentology, palynofacies, and organic geochemistry has provided an effective means for evaluating and predicting high-maturity carbonate source rock in the region.展开更多
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.
基金financed by the Polish scientific funds 2006/2007 as the project N30701131/0941from the scientific funds of the Polish Geological Institute,project no.6.10.0003.00.0This is a contribution to IGCP project 506“Marine and Non-marine Jurassic:Global Correlation and Major Geological Events”.
文摘Diversified continental,marginal-marine and marine epicontinental deposits in Poland of Early Jurassic age yielded unusually rich palynomacerals.Numerous parameters,such as the presence of acritarchs and dinoflagellate cysts,spore/bisaccate pollen grain ratio,content of terrestrial phytoclasts,degree of oxidation,presence of tetrads and sporangia,degree of palynomorph alteration,presence and character of amorphous organic matter,presence of epibionts on palynomorphs,were collectively found as indicative of certain palynofacies.The ratio of spores and bisaccate pollen grains significantly depends on the climatic conditions where also seasonal changes may influence the local characteristics of palynofacies.However,the ratio also strongly reflects the local depositional environment which may vary regionally and spore/bisaccate pollen grain ratio can be taken as a general indicator of distance from the shore.Early Jurassic palynomacerals from the Polish Basin are strongly dominated by terrestrial elements,marine palynomacerals occur in significant quantities only in Pliensbachian deposits in Pomerania Western Poland.Charcoal is an important component of palynomacerals.Due to its resistance to biogenic degradation and buoyancy,charcoal produced by extensive wildfires was widely re-deposited and concentrated particularly in foreshore to shallow shoreface and delta plain environments.Three types of palynofacies inversions(abnormal palynofacies composition)are discussed.Six main palynofacies types linked to depositional systems previously determined by sedimentological studies have been distinguished providing a robust paleoenvironmental tool for recognition of palynofacies attributed to certain palaeoenvironments.
文摘Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T<sub>max</sub>), and Vitrinite Reflectance (VR<sub>o</sub>) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.
基金The authors are thankful to the Director(Prof.Mahesh G.Thakkar),Birbal Sahni Institute of Palaeosciences,Lucknow for providing the necessary permission and laboratory facilities to carry out this work(BSIP/RDCC/Publication no.73/2024-25)Author(SM)expresses sincere thanks to DST(Govt.of India)project no.EEQ/2018/000303 for the financial support.
文摘The Permian-Triassic(P/T)transition is marked by the most severe mass-extinction event of the Phanerozoic.Although much is known about this event in the marine realm,there are many open questions regarding what happened during this period to many continental biota.In the case of plants,a drastic mass-extinction event has even been negated by some authors.To add about the knowledge on continental biota in India during this crucial time period,the present study analysed the palynology,palynofacies,organic geochemistry(biomarkers),stable isotopes,and charcoal within the subsurface Gondwana deposits of the Kamthi Formation(late Permian-early Triassic)from core TTB-7 from the Tribida block,located in the Talcher Coalfield of the Mahanadi Basin,India.The primary objectives are to validate the age of the strata,ascertain the palaeodepositional setting of the palaeomire,and propose palaeobotanical evidence regarding the occurrence of wildfires within this stratigraphic succession and changes in floral content across the P/T transition.The palynological study proposes two palynoassemblage zones,Densipollenites magnicorpus and Klausipollenites schaubergeri,suggesting a latest Permian(Lopingian)and early Triassic(Induan?)age for the studied succession,respectively.The age is also inferred based on correlation with coeval assemblages from India and other Gondwana continents.The palynoassemblages reveal the dominance of Glossopteridales and Coniferales along with Filicales,Lycopsidales,Equisetales,Cordaitales and Peltaspermales.The relatively higher values of the carbon preference index and terrigenous/aquatic ratio also suggest higher plant input.However,a bimodal n-alkane distribution pattern suggests the contribution of terrigenous and microbial sources.Although the occurrences of long-chain alkanes indicate input of higher plants,the low Pwax values(<0.26)suggest relatively less contribution.The Paqvalues(≅1)and amorphous organic matter(av.33.24%)suggest a significant macrophyte input in the studied samples,pointing to the occurrence of moderate aquatic conditions in the basin.Furthermore,the distribution of hopanoids and the content of degraded organic matter(av.29.96%)reflect the bacterial degradation of organic matter.Also,the δ^(13)C values of the studied section varied from−31.2‰to−21.8‰.A large carbon isotopic offset of 9.4‰across the P/T transition,Pr/Ph ratio(0.3–1.3)and shift in the distribution pattern of palynofacies components is indicating a significant change in climatic conditions.Moreover,the presence of macroscopic charcoal fragments of gymnospermous affinity with pre-charring colonization by fungi provides evidence for wildfire occurring during the Lopingian(Late Permian)in this basin.
基金DST-SERB for providing the post-doctoral fellowship(PDF/2018/000883)。
文摘The sedimentary sequence containing lignite deposits in Gurha quarry of the Bikaner-Nagaur Basin(Rajasthan)has been investigated.The samples from lignite and allied shale horizons were evaluated for petrographical,palynological,palynofacies and organic geochemical inferences,to depict the source flora and to reconstruct the palaeodepositional conditions prevailed during the sedimentation.An assessment for the hydrocarbon generation potential of these deposits has also been made.The results revealed the dominance of huminite macerals and phytoclasts organic matter(OM) indicating the existence of forested vegetation in the vicinity of the depositional site.A relatively high terrigenous/aquatic ratio(TAR) and the carbon preference index(CPI) are also suggesting the contribution of higher plants in the peat formation.However,the n-alkane distributions,maximizing at n-C17 and n-C29,showed inputs from the algal communities along with the higher plant derived organic matters.Recovered palynomorphs of the families Onagraceae,Meliaceae,Arecaceae,Rhizophoraceae,Rubiaceae,Ctenolophonaceae, etc.together with oleanene and ursane types of triterpenoids suggest the contribution from angiosperms source vegetation.Interestingly,the presence of Araucareaceae and Podocarpaceae pollen grains shows the existence of gymnosperms vegetation.Further,the presence of tetracyclic diterpanes;demethylated entbeyerane,sandaracopimarane,pimarane,and Kaurane type of compounds confirms the contribution of conifers.The variation in the values of the coefficient of non-equality(H:0.68%-7.56%),the standard deviation(8:0.04%-0.16%) and the coefficient of variability(V:16.10%-46.47%),also shows the heterogeneity in the source organic matter.The various petrographical indices,palynological entities,and geochemical parameters indicate that the peatforming vegetation was accumulated under a mixed environment and fluctuating hydrological settings.The interpretation of palynofacies data on APP(Amorphous organic matter-Phytoclast-Palynomorphs) diagram suggests that the accumulation of organic matter occurred in a dysoxic-suboxic condition in a proximal(to land)setting with the shift to an anoxic condition in distal setting towards the termination of sedimentation.The huminite(ulminite) reflectance(R_r) values(av.0.28%) showed a good relationship with average T_(max) value(414℃),suggesting the immaturity.The TOC content ranges of 13-59 wt.%,and HI values vary between 101 and 546 mg HC/g TOC in the studied samples.Collectively,the studied lignite and shale samples have the admixed kerogens(Type Ⅲ-Ⅱ) and exhibit the ability to generate the gaseous to oil hydrocarbons upon maturation.
基金supported by the Certificate of National Science and Technology Major Project of the Ministry of Science and Technology of China(2016ZX05006-007-004)National Natural Science Foundation of China(41702139,41772138,41602142,42072130)the Fundamental Research Funds for the Central Universities(18CX02008A)。
文摘The mechanisms of lacustrine organic-rich shale formation have attracted attention due to its association with global shale oil and shale gas exploration.Samples of general-quality and excellent-quality source rocks,and oil shale from the Beibu Gulf Basin were analyzed to investigate their organic geochemistry,palynofacies,and trace elements.Hydrocarbon potential was higher in the oil shale(29.79 mg/g)than in the general-quality source rock(3.82 mg/g),and its kerogen type wasⅠ-Ⅱ2.Hydrogen-rich liptinite(cutinite and sporinite)components derived from terrigenous higher plants provided most of the hydrocarbon potential of excellent-quality source rock and oil shale.Under the influence of depressioncontrolling fault activity,a deeper subsidence center promotes the deposition of excellent-quality source rock and oil shale in brackish-hypoxic bottom water.A shallower subsidence center,due to subsag-controlling fault activity,promotes the formation of excellent-quality source rock under freshbrackish and weak oxidation-weak reducing conditions.The local uplift and shallow-slope led to the formation of general-quality source rock,under freshwater weak-oxidation conditions.A model was established for organic matter(OM)accumulation in organic-rich shales,accounting for fault activity,terrigenous hydrogen-rich OM,and the preservation conditions,to predict the development of excellent-quality source rock from areas with low levels of exploration.
基金supported by the National Natural Science Foundation of China(No.41430101)the State Special Fund from Ministry of Science and Technology(No.2017ZX05036002)。
文摘The Early Cambrian Niutitang Formation on the Yangtze Block is a set of high-quality marine source rock.However,hydrocarbon-forming organisms of these organic-rich shales was poorly understood.In this paper,the results of palynofacies analysis and hydrocarbon-forming organism characteristics of the Niutitang Formation from the Yangtze Block are reported for the first time,and the sedimentary environment is discussed in combination with geochemical data.Palynofacies analysis show that the organic matter(OM)of the Niutitang Formation is mainly composed of amorphous organic matter(AOM),with a small amount of structural organic matter(STOM)and palynomorphs(PL).The results of CONISS(stratigraphically constrained incremental sum of squares)cluster analysis show that the PL can be divided into three zones in the ascending order:Leiosphaeridia-Micrhystridiumfungal zone,algal bloom zone and fungal development zone,corresponding to three stages:transgression,high-stand and regression,respectively.The principal component analysis(PCA)shows that the main hydrocarbon-forming organisms include planktonic green microalgae or dinoflagellates that are related to Leiosphaeridia and Microcystidium.Palynofacies analysis and geochemical data show that the Niutitang Formation was deposited under anoxic or dysoxic condition which was favorable to the enrichment of organic matter.
基金China Postdoctoral Science Foundation under contract No.2021M703619。
文摘The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin.However,the exceptionally high total organic carbon content(TOC,>6%on average)of the tidal sand ridge samples was not compatible with their sedimentary environment,indicating coal-bearing sedimentary debris may have been transferred from the coast to the ocean.In this study,new sights into the origins and supply of organic materials in the coastal environment were proposed in the neritic organic matter of the Eocene Pinghu Formation.A discriminant model was developed using plynofacies analysis data to pinpoint the source of organic materials in marine source rocks.The discrimination results suggested that marine mudstones were associated with tidal flat mudstones rather than deltaic ones.The biomarker characteristics of mudstones deposited in various environments support this assertion,indicating that the supply of plant materials in tidal flats is the primary organic matter source for the marine environment.The organic matter abundance was elevated in tidal flats due to their superior preservation conditions.Additionally,the lithological assemblage of tidal flats suggests that tidal currents can scour marshes and then transport dispersed terrigenous organic materials to neritic areas.These findings indicate that coal-bearing sedimentary debris was likely transferred from the coast to the ocean,and tidal currents are thought to be the dominant mechanism driving organic matter from the tidal to the marine environment.
文摘The present study deals with the textural characteristics of the sediments from the exposed palaeochannel situated at Dhyangla village near Ladwa, district of Kurukshetra in north-western Haryana. It is a part of vast alluvial plains of India. Samples were taken from a 3 m thick exposed section. Grain size distribution and Palynofacies analyses of these sediments were carried out to study their textural parameters and the organic matter content respectively. Sediments are mostly fine to medium grained sand with silt percentage increasing upwards in the section. These sediments are mostly unimodal showing the grain size population controlled by a single type of grain size, mostly sand. Further the sand samples are moderately well sorted and mesokurtic in nature. Samples with silt are poorly sorted and leptokurtic with positive skewness, denoting those sediments have already sorted elsewhere in the high energy environment and are now transported and modified by the low energy environment. Palynofacies analysis also shows the presence of amorphous particles in the silt samples which indicate low energy environment of the sequence while presence of black debris in the sand samples indicates high energy depositions environment.
基金supported by the National Natural Science Foundation of China (Grant No. 40872089)Science and Technology Office Fund of China Petroleum & Chemical Co., Ltd. (Grant No. G080007ZS188)the National Oil and Gas Special Fund (Grant No. 2008ZX05023-003)
文摘Highly-mature carbonate source rock is essential to the exploration of oil and gas in southern China. In this study, the carbonate strata in the relatively well-developed Lower Permian Chihsia Formation (located in Chaohu, Lower Yangtze) were targeted, and the formation and influencing factors of source rock were discussed based on paleoenvironment reconstruction using comprehensive sedimentology, palynofacies, and organic geochemistry data. The results demonstrate that the Chihsia Formation is oxygen-deficient biogenic carbonate sediments, with marked variations in the organic and inorganic components, formed during a period of Permian transgression. The formation of source rock is the combined result of high bioproductivity and oxygen-deficient environment generated by transgression and oxygenation events which frequently occurred during transgression periods. Source rock was affected by self-dilution effects and diagenesis, causing its heterogeneous distribution in many intervals. Source rock is over 40 m thick, and can be identified based on its different organic, biological, and mineral composition characteristics. The carbonate rock appears to require no specific clay content in order to become a source rock. The combination of sedimentology, palynofacies, and organic geochemistry has provided an effective means for evaluating and predicting high-maturity carbonate source rock in the region.
