2017 Vol. 35, No. 3
Display Method:
2017, 35(3): 425-435.
doi: 10.14027/j.cnki.cjxb.2017.03.001
Abstract:
In the Post-Exxon times of sequence stratigraphy, scientists came up with various sequence models of the complex stratigraphic records as well as its response mechanism, and endowed all models with strong pertinence, which aroused inconsistencies in conceptual system. Therefore, the standardization of sequence stratigraphy aiming at seeking the consistency of terminology has become an important scientific proposition of today's sequence stratigraphy. During the development process of sequence stratigraphy, the identification and distinguishing between normal regression and forced regression has laid an important groundwork for the system description of the sequence development, and has become the first step towards the standardization as these processes are model-independent. The introduction of unconventional system tracts in fluvial sequence models, namely, low and high-accommodation system tract, turned to be another successful attempt of the standardization of sequence stratigraphy because of its model-independent feature. Considering the four particularities of the stratigraphic records—the complexity and the cyclicity in the stratigraphic accumulating process, the non-gradual change and the non-integrity of the stratigraphic records, chasing the variability represented by the diversity of sequence models and the nature of standardization containing variability will provide more clues and approaches for further development of sequence stratigraphy.
In the Post-Exxon times of sequence stratigraphy, scientists came up with various sequence models of the complex stratigraphic records as well as its response mechanism, and endowed all models with strong pertinence, which aroused inconsistencies in conceptual system. Therefore, the standardization of sequence stratigraphy aiming at seeking the consistency of terminology has become an important scientific proposition of today's sequence stratigraphy. During the development process of sequence stratigraphy, the identification and distinguishing between normal regression and forced regression has laid an important groundwork for the system description of the sequence development, and has become the first step towards the standardization as these processes are model-independent. The introduction of unconventional system tracts in fluvial sequence models, namely, low and high-accommodation system tract, turned to be another successful attempt of the standardization of sequence stratigraphy because of its model-independent feature. Considering the four particularities of the stratigraphic records—the complexity and the cyclicity in the stratigraphic accumulating process, the non-gradual change and the non-integrity of the stratigraphic records, chasing the variability represented by the diversity of sequence models and the nature of standardization containing variability will provide more clues and approaches for further development of sequence stratigraphy.
2017, 35(3): 436-448.
doi: 10.14027/j.cnki.cjxb.2017.03.002
Abstract:
It aims to achieve the division and correlation of high-resolution sequences by integrating the Milankovitch cycles with cycles of different scales so as to introduce such a high precision time scale into the high-resolution sequence stratigraphic classification. This work takes the Well Ary301 in Aryskum graben of the South Turgay Basin in Kazakhstan as an example. Based on different sedimentary characteristics, spectral analysis and continuous wavelet transform are used to Intervals I-IV of natural gamma ray data, respectively, which demonstrate that well-preserved Milankovitch cycles are contained in the sedimentary strata. Aryskum graben deposition process is obviously effected by astronomical orbital period, the formation thickness of 31.9~39.5 m is affected by the long eccentricity of 400 kyr, the formations thickness of 11.9~14.2 m and 6.7~8.8 m are affected by the short eccentricity of 125 kyr and 95 kyr, respectively. Cycle curves analyzed by filtering are compared with the astronomical model theory, which helps establish the Karagansky Formation of floating astronomical time scale. Finally, 11.5 middle term cycles and 47 short term cycles are identified, the filtering curves with eccentricity cycles of 400 kyr and 125 kyr are identified as the reference curves to divide middle term and short term cycles to ensure the scientific and unified division scheme in the study area, and a natural standard unaffected by man-made factors is proposed for high-frequency sequence division.
It aims to achieve the division and correlation of high-resolution sequences by integrating the Milankovitch cycles with cycles of different scales so as to introduce such a high precision time scale into the high-resolution sequence stratigraphic classification. This work takes the Well Ary301 in Aryskum graben of the South Turgay Basin in Kazakhstan as an example. Based on different sedimentary characteristics, spectral analysis and continuous wavelet transform are used to Intervals I-IV of natural gamma ray data, respectively, which demonstrate that well-preserved Milankovitch cycles are contained in the sedimentary strata. Aryskum graben deposition process is obviously effected by astronomical orbital period, the formation thickness of 31.9~39.5 m is affected by the long eccentricity of 400 kyr, the formations thickness of 11.9~14.2 m and 6.7~8.8 m are affected by the short eccentricity of 125 kyr and 95 kyr, respectively. Cycle curves analyzed by filtering are compared with the astronomical model theory, which helps establish the Karagansky Formation of floating astronomical time scale. Finally, 11.5 middle term cycles and 47 short term cycles are identified, the filtering curves with eccentricity cycles of 400 kyr and 125 kyr are identified as the reference curves to divide middle term and short term cycles to ensure the scientific and unified division scheme in the study area, and a natural standard unaffected by man-made factors is proposed for high-frequency sequence division.
2017, 35(3): 449-459.
doi: 10.14027/j.cnki.cjxb.2017.03.003
Abstract:
Palaeogeographic reconstruction in small scale is one of the most effective method for discussing tectonic-basin evolution in geological time. Recent progresses in lithofacies paleogeographic study on South China provide new clues on the key geological problems in early Paleozoic. The results of our study show that there is no critical tectonic-basin boundary between the Yangtze and Cathaysia block in early Paleozoic, which has a continuous distribution of sedimentary facies in time and spaces. These lines of evidence deny the presence of Huanan remnant-ocean basin in early Paleozoic, and, with the coupled evolution of paleogeography in successive stages, support the hypothesis of one solid South China Plate. The results also support a mountain-basin coupling process inside of South China Plate, instead of transition from passive continental margin to foreland basin system. This process can be considered as re-cratonization of South China Plate in Early Paleozoic.
Palaeogeographic reconstruction in small scale is one of the most effective method for discussing tectonic-basin evolution in geological time. Recent progresses in lithofacies paleogeographic study on South China provide new clues on the key geological problems in early Paleozoic. The results of our study show that there is no critical tectonic-basin boundary between the Yangtze and Cathaysia block in early Paleozoic, which has a continuous distribution of sedimentary facies in time and spaces. These lines of evidence deny the presence of Huanan remnant-ocean basin in early Paleozoic, and, with the coupled evolution of paleogeography in successive stages, support the hypothesis of one solid South China Plate. The results also support a mountain-basin coupling process inside of South China Plate, instead of transition from passive continental margin to foreland basin system. This process can be considered as re-cratonization of South China Plate in Early Paleozoic.
2017, 35(3): 460-469.
doi: 10.14027/j.cnki.cjxb.2017.03.004
Abstract:
A karst surface is first found at the top of the Upper Triassic Carnian sponge limestone at Hanwang sections in Mianzhu and Jushui section in Anxian, northwestern Sichuan Province, China. Piebald structures and honeycomb dissolved pores are obvious in the karst outcrops, and karst breccia, filling material (e.g., micritic-sparry calcite and terrigenous quartz grains) in the dissolved pores and micritization granules are discovered with microscope. According to the microscopic characteristics and the lithology, the eogenetic karst is determined to be a single layer, overlied yellow and black shale containing abundant marine fossils. The identification of ammonoids in the shales shows that the karst is an important isochronous surface regarded as the boundary of the upper and lower Carnian. The strata above the karst are different between the Hanwang sections and Jushui section, i.e., the overlying rocks above the karst in the Qingyangou section, Hanwang are black silty shale and bioclastic limestone (e.g. lamellated sponge limestone and crinoidal limestone) while in Guanyinya section, Hanwang, the overlying rocks above the karst are shale and moundy sponge limestone. However, karst caves are developed at the top of sponge boulders in the Jushui section. Comprehensive research implies that the formation time of this karst is close to the occurrence of the Longmen Mountain uplift and the Carnian Pluvial Event, it is thus inferred that the karst was caused by the joint effect of uplift of Longmen Mountain and Carnian paleoclimatic event.
A karst surface is first found at the top of the Upper Triassic Carnian sponge limestone at Hanwang sections in Mianzhu and Jushui section in Anxian, northwestern Sichuan Province, China. Piebald structures and honeycomb dissolved pores are obvious in the karst outcrops, and karst breccia, filling material (e.g., micritic-sparry calcite and terrigenous quartz grains) in the dissolved pores and micritization granules are discovered with microscope. According to the microscopic characteristics and the lithology, the eogenetic karst is determined to be a single layer, overlied yellow and black shale containing abundant marine fossils. The identification of ammonoids in the shales shows that the karst is an important isochronous surface regarded as the boundary of the upper and lower Carnian. The strata above the karst are different between the Hanwang sections and Jushui section, i.e., the overlying rocks above the karst in the Qingyangou section, Hanwang are black silty shale and bioclastic limestone (e.g. lamellated sponge limestone and crinoidal limestone) while in Guanyinya section, Hanwang, the overlying rocks above the karst are shale and moundy sponge limestone. However, karst caves are developed at the top of sponge boulders in the Jushui section. Comprehensive research implies that the formation time of this karst is close to the occurrence of the Longmen Mountain uplift and the Carnian Pluvial Event, it is thus inferred that the karst was caused by the joint effect of uplift of Longmen Mountain and Carnian paleoclimatic event.
2017, 35(3): 470-479.
doi: 10.14027/j.cnki.cjxb.2017.03.005
Abstract:
The Beishan orogenic belt is the juncture area of Paleozoic Kazakstan Plate, Tarim Plate and North China Plate. Much remains to be discovered concerning the Late Paleozoic evolution in Beishan area. Therefore, the study on Late Paleozoic stratigraphy is of great importance to reveal the tectonic evolution. Hongliuyuan Formation was studied by isotopic dating,sedimentary facies analysis, grain size analysis and statistical analysis of detrital components in this paper. The LA-ICP-MS zircon U-Pb age of the volcanic rock at the bottom of Hongliuyuan Formation was 359.9±1.4 Ma, refering to regional paleontological data, which belong to the Early Carboniferous. Clastic sediments in the upper developed a large number of turbidite sedimentary structures and typical Bouma sequence, sandstone maturity was much lower, and the results of grain size analysis showed the grain size characteristics of turbidite deposition, which jointly suggest that Hongliuyuan Formation should belong to near provenance turbidite. In addition, statistics of detrital components, Qt-F-L, Qm-F-Lt and Qp-Lv-Ls diagram were used to study sedimentary tectonic background. The results showed that sedimentary provenance of Hongliuyuan Formation in Suanjingzi area are mainly from volcanic arc, and its tectonic setting should be the sedimentary basin adjacent to island arc.
The Beishan orogenic belt is the juncture area of Paleozoic Kazakstan Plate, Tarim Plate and North China Plate. Much remains to be discovered concerning the Late Paleozoic evolution in Beishan area. Therefore, the study on Late Paleozoic stratigraphy is of great importance to reveal the tectonic evolution. Hongliuyuan Formation was studied by isotopic dating,sedimentary facies analysis, grain size analysis and statistical analysis of detrital components in this paper. The LA-ICP-MS zircon U-Pb age of the volcanic rock at the bottom of Hongliuyuan Formation was 359.9±1.4 Ma, refering to regional paleontological data, which belong to the Early Carboniferous. Clastic sediments in the upper developed a large number of turbidite sedimentary structures and typical Bouma sequence, sandstone maturity was much lower, and the results of grain size analysis showed the grain size characteristics of turbidite deposition, which jointly suggest that Hongliuyuan Formation should belong to near provenance turbidite. In addition, statistics of detrital components, Qt-F-L, Qm-F-Lt and Qp-Lv-Ls diagram were used to study sedimentary tectonic background. The results showed that sedimentary provenance of Hongliuyuan Formation in Suanjingzi area are mainly from volcanic arc, and its tectonic setting should be the sedimentary basin adjacent to island arc.
2017, 35(3): 480-488.
doi: 10.14027/j.cnki.cjxb.2017.03.006
Abstract:
The trace fossils Rhizocorallium is abundant in the Upper Devonian Wangguangou Formation in Xichuan, southwestern Henan Province. It consists of U-shape spreite burrows and more or less parallel or slight incline to the bedding of marling limestone. Scanning electron microscope images show that abundant pyrite and iron framboids (iron framboids were mostly oxygenated from pyrite framboids) were found within the Rhizocorallium burrow, including (pyritohedral, octahedron, cube and nearly spherical and irregular shape). No similar framboids were observed outside Rhizocorallium except a few single pyrite crystals. Most of iron framboids were sheathed within the Rhizocorallium burrow. At the same time, the diameter of the submicron crystals in the marginal tube (0.672~1.603 μm, the average diameter of is 1.063 μm ) was bigger than that in the spreite (0.376~0.877 μm, the average diameter is 0.5 μm ). Therefore, it is likely that sulphate-reducing bacteria colonized the Rhizocorallium spreite and marginal tube within a dysoxic environment. The results indicated that Rhizocorallium would represent a burrow for multifunctional purpose, where the trace maker has utilized available conditions (such as substrate type, food supply, dysoxic to oxic environment) for cultivation of microbes.s
The trace fossils Rhizocorallium is abundant in the Upper Devonian Wangguangou Formation in Xichuan, southwestern Henan Province. It consists of U-shape spreite burrows and more or less parallel or slight incline to the bedding of marling limestone. Scanning electron microscope images show that abundant pyrite and iron framboids (iron framboids were mostly oxygenated from pyrite framboids) were found within the Rhizocorallium burrow, including (pyritohedral, octahedron, cube and nearly spherical and irregular shape). No similar framboids were observed outside Rhizocorallium except a few single pyrite crystals. Most of iron framboids were sheathed within the Rhizocorallium burrow. At the same time, the diameter of the submicron crystals in the marginal tube (0.672~1.603 μm, the average diameter of is 1.063 μm ) was bigger than that in the spreite (0.376~0.877 μm, the average diameter is 0.5 μm ). Therefore, it is likely that sulphate-reducing bacteria colonized the Rhizocorallium spreite and marginal tube within a dysoxic environment. The results indicated that Rhizocorallium would represent a burrow for multifunctional purpose, where the trace maker has utilized available conditions (such as substrate type, food supply, dysoxic to oxic environment) for cultivation of microbes.s
2017, 35(3): 489-498.
doi: 10.14027/j.cnki.cjxb.2017.03.007
Abstract:
The plant fossil assemblage from the Jurassic Xishanyao Formation in the north edge of Turpan-Hami Basin, China, is ascribed into Coniopteris-Phoenicopsis flora. The four dominant genera of fossil plants which are Ginkgoites, Phoenicopsis, Cladophlebis, Stenorachis, are chosen to perform stable carbon isotopic analysis. The δ13C values of three fossil leaves of Ginkgoites, Phoenicopsis, Cladophlebis range from -21.66‰ to -23.83‰, which indicates they blong to C3 type. The Stenorachis is one fossil of reproductive organs. Its δ13C value is -20.91‰, more enriched than those of fossil leaves, showing the reliability of carbon isotopic data. According to formula, the δ13C of plants is converted into stable carbon isotopic values of atmospheric CO2 (δ13Ca). It is found that modern and Middle Jurassic δ13Ca values obtained from Ginkgoales leaves are similar to those obtained from other methods, suggesting Ginkgoales leaves are reliable specimens for reconstructing δ13Ca during geological period, which provides a simple and feasible method to obtain δ13Ca from the Mesozoic to Cenozoic. Ci/Ca is an important plant ecophysiological parameter. Thus, δ13C of Ginkgoales leaves is also converted into Ci/Ca. The Ci/Ca value of fossil Ginkgoites is 0.6, similar to 0.63 that is Ci/Ca value of living Ginkgo. It was known that palaeo-CO2 level in the Middle Jurassic is about 4.5 times of nowaday CO2. However, Ci/Ca keeps approximate constant between living and fossil Ginkgoales leaves. It indicates that Ginkgoales plants possess high photosynthetic rate in the Middle Jurassic, as well as favorable sensitivity of stomata to CO2 change. Thereby, stomata of Ginkgoales plants are good indicator of reconstructing palaeo-CO2 level. As a result, variation in Ci/Ca provides effective means to estimate whether one plant can be used as indicator to reconstruct palaeo-CO2 level.
The plant fossil assemblage from the Jurassic Xishanyao Formation in the north edge of Turpan-Hami Basin, China, is ascribed into Coniopteris-Phoenicopsis flora. The four dominant genera of fossil plants which are Ginkgoites, Phoenicopsis, Cladophlebis, Stenorachis, are chosen to perform stable carbon isotopic analysis. The δ13C values of three fossil leaves of Ginkgoites, Phoenicopsis, Cladophlebis range from -21.66‰ to -23.83‰, which indicates they blong to C3 type. The Stenorachis is one fossil of reproductive organs. Its δ13C value is -20.91‰, more enriched than those of fossil leaves, showing the reliability of carbon isotopic data. According to formula, the δ13C of plants is converted into stable carbon isotopic values of atmospheric CO2 (δ13Ca). It is found that modern and Middle Jurassic δ13Ca values obtained from Ginkgoales leaves are similar to those obtained from other methods, suggesting Ginkgoales leaves are reliable specimens for reconstructing δ13Ca during geological period, which provides a simple and feasible method to obtain δ13Ca from the Mesozoic to Cenozoic. Ci/Ca is an important plant ecophysiological parameter. Thus, δ13C of Ginkgoales leaves is also converted into Ci/Ca. The Ci/Ca value of fossil Ginkgoites is 0.6, similar to 0.63 that is Ci/Ca value of living Ginkgo. It was known that palaeo-CO2 level in the Middle Jurassic is about 4.5 times of nowaday CO2. However, Ci/Ca keeps approximate constant between living and fossil Ginkgoales leaves. It indicates that Ginkgoales plants possess high photosynthetic rate in the Middle Jurassic, as well as favorable sensitivity of stomata to CO2 change. Thereby, stomata of Ginkgoales plants are good indicator of reconstructing palaeo-CO2 level. As a result, variation in Ci/Ca provides effective means to estimate whether one plant can be used as indicator to reconstruct palaeo-CO2 level.
2017, 35(3): 499-507.
doi: 10.14027/j.cnki.cjxb.2017.03.008
Abstract:
To investigate the distribution pattern and significance of grain size and provide accurate analogues for grain size records from lake cores, we analyzed surface sediments from 15 lakes of Yunnan Province, China for grain size. Meanwhile, the grain size components of the surface sediments of the 15 lakes were partitioned using the log-normal distribution function method. The results showed that frequency curves of samples indicated polymodal and consisted of two to five grain-size components with the modal size varying within ranges of 0.6~423.0 μm. These components are specified from fine to coarse modes as clay (C1), fine silt (C2), silt (C3), fine to medium sand (C4) and coarse sand (C5). The grain size analysis reveals that the C1 components were the long-term superfine dust and aerosol in the atmosphere which entered the lake water body through the process of gravity and precipitation, and may have represented the background level of atmospheric dust and aerosols in southwest China; C2 and C3 were the main components of surface sediments, the modal size of which reflected the precipitation intensity of the watershed; C4 and C5 components only appeared in minority surface sediments of lakes with the contents were extremely low, and were significantly related to the lake hydrodynamic force. For the large lakes, such as Dianchi and Fuxian Lakes, it requires two processes for the sand components to reach the central part of lakes: process of from drain basin to lakes and from lakeshore to the middle of lakes, and the second one plays a main role, affected by lake current, water depth, gradient of lake basin and so on. Under the background of the drought in southwest China, some small lakes in Yunnan shrinked and even disappeared. However, because of the decrease of precipitation and weakening of general circulation, surface runoff and hydrodynamics of lakes recede, thus the material which transmit to the center of the lakes were primarily fine grain. Small lakes located in the mountainous region, with the limited catchment area and conspicuous terrain slope, can be affected by the surface runoff directly and strongly. Therefore, the increase of coarse grain in the sediments of this kind of lakes reflected the enhancement of precipitation or the precipitation intensity.
To investigate the distribution pattern and significance of grain size and provide accurate analogues for grain size records from lake cores, we analyzed surface sediments from 15 lakes of Yunnan Province, China for grain size. Meanwhile, the grain size components of the surface sediments of the 15 lakes were partitioned using the log-normal distribution function method. The results showed that frequency curves of samples indicated polymodal and consisted of two to five grain-size components with the modal size varying within ranges of 0.6~423.0 μm. These components are specified from fine to coarse modes as clay (C1), fine silt (C2), silt (C3), fine to medium sand (C4) and coarse sand (C5). The grain size analysis reveals that the C1 components were the long-term superfine dust and aerosol in the atmosphere which entered the lake water body through the process of gravity and precipitation, and may have represented the background level of atmospheric dust and aerosols in southwest China; C2 and C3 were the main components of surface sediments, the modal size of which reflected the precipitation intensity of the watershed; C4 and C5 components only appeared in minority surface sediments of lakes with the contents were extremely low, and were significantly related to the lake hydrodynamic force. For the large lakes, such as Dianchi and Fuxian Lakes, it requires two processes for the sand components to reach the central part of lakes: process of from drain basin to lakes and from lakeshore to the middle of lakes, and the second one plays a main role, affected by lake current, water depth, gradient of lake basin and so on. Under the background of the drought in southwest China, some small lakes in Yunnan shrinked and even disappeared. However, because of the decrease of precipitation and weakening of general circulation, surface runoff and hydrodynamics of lakes recede, thus the material which transmit to the center of the lakes were primarily fine grain. Small lakes located in the mountainous region, with the limited catchment area and conspicuous terrain slope, can be affected by the surface runoff directly and strongly. Therefore, the increase of coarse grain in the sediments of this kind of lakes reflected the enhancement of precipitation or the precipitation intensity.
2017, 35(3): 508-515.
doi: 10.14027/j.cnki.cjxb.2017.03.009
Abstract:
The chemical characteristics of major elements and magnetic susceptibility of Tuojiawan profile in the upper Hanjiang River are studied. The change of the indexes revealed that major elements geochemical behavior and the corresponding laws of climate change in the Upper Hanjiang River. With X-Ray fluorescence spectrometer, MS-2 magnetic susceptibility instrument measured element content and magnetic susceptibility values. Results show that: The major elements are SiO2, Al2O3 and Fe2O3. Na,Ca,Mg,Si,K are leached out while Ti,Fe,Al relatively enriched in the paleosol S0. The element mobility and migration ability of the major elements are ranked in the followed order: Na > Ca > Mg > Si > K > Al > Fe. Magnetic susceptibility values showed obvious peak value in 228~260 cm and 294~370 cm depth, the variation in content of Fe and Al elements and chemical alteration index curve and magnetic susceptibility curve showing a high consistency, at this depth are characterized by high value. It was shown that the chemical weathering intensity of this depth was obviously higher than that of Malan loess, close to the palaeosol(S0), belonging to the weak palaeosol(L1~S1 and L1~S2).The age range of L1~S1 and L1~S2 was 27.5~21.5 ka B.P.. The change of the indexes showed the climate and pedogenic environmental changed since Pleistocene. Including the cold and arid glacial and a short time the climate was warm and wet in the glacial period(27.5~21.5 ka B.P.), the gradually intensified southeast monsoon during the early Holocene periods, the strongest monsoon in the mid-Holocene, and the monsoon recession and the climate drying during the late Holocene.
The chemical characteristics of major elements and magnetic susceptibility of Tuojiawan profile in the upper Hanjiang River are studied. The change of the indexes revealed that major elements geochemical behavior and the corresponding laws of climate change in the Upper Hanjiang River. With X-Ray fluorescence spectrometer, MS-2 magnetic susceptibility instrument measured element content and magnetic susceptibility values. Results show that: The major elements are SiO2, Al2O3 and Fe2O3. Na,Ca,Mg,Si,K are leached out while Ti,Fe,Al relatively enriched in the paleosol S0. The element mobility and migration ability of the major elements are ranked in the followed order: Na > Ca > Mg > Si > K > Al > Fe. Magnetic susceptibility values showed obvious peak value in 228~260 cm and 294~370 cm depth, the variation in content of Fe and Al elements and chemical alteration index curve and magnetic susceptibility curve showing a high consistency, at this depth are characterized by high value. It was shown that the chemical weathering intensity of this depth was obviously higher than that of Malan loess, close to the palaeosol(S0), belonging to the weak palaeosol(L1~S1 and L1~S2).The age range of L1~S1 and L1~S2 was 27.5~21.5 ka B.P.. The change of the indexes showed the climate and pedogenic environmental changed since Pleistocene. Including the cold and arid glacial and a short time the climate was warm and wet in the glacial period(27.5~21.5 ka B.P.), the gradually intensified southeast monsoon during the early Holocene periods, the strongest monsoon in the mid-Holocene, and the monsoon recession and the climate drying during the late Holocene.
2017, 35(3): 516-526.
doi: 10.14027/j.cnki.cjxb.2017.03.010
Abstract:
The history and mechanism of aridification in the Asian interior during the late Cenozoic have been an important scientific issue. This study presents the terrigenous deposits from the ~303 m-thick Urumqi River section (URS) in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland. Based on the results of magnetostratigraphic chronology and rock magnetic characteristics, we discussed the magnetic enhancement mechanism of the URS sediments and paleo-climatic implications during the late Cenozoic in this region. The magnetostratigraphic chronology constrains the time spans from about 6.8 Ma to about 3.3 Ma. The results of rock magnetic and diffuse reflection spectrum (DRS) measurements show that the magnetic minerals in the URS sediments are mainly magnetite and hematite, and some magnetic parameters, such as χlf, χARM, SIRM，S-100mT, S-300mT, χARM/SIRM, changed obviously at ~6.3 Ma and ~5.2 Ma. These changes reveal that the measured samples contain coarser magnetic grains with less magnetic grains (after ~6.3 Ma). In contrast, the magnetic grains became finer steadily before ~5.2 Ma, with the content increasing. By the analysis of rare earth elements (REEs), we know that the distribution patterns of rare earth elements (REEs) are consistent obviously. The analysis of rare earth elements (REEs) is likely to indicate a stable source area of the URS deposits. The sediment grain size can also be used to explain variations of terrigenous deposits magnetic characteristics. There are significant correlation relationships between the sediment grain size parameters and χlf，χARM/χlf, the insignificant correlation relationships between the magnetic parameters, such as χARM, SIRM，S-100mT, S-300mT, χARM/SIRM, χfd, and the sediment grain size parameters indicate that the observed variations of magnetic characteristics may not be mainly caused by the sediment grain size parameters. The continuous aridification in the present study area is more likely to be the main cause of the variations of magnetic characteristics. The continuous aridification can contribute to the oxidation of magnetite, which can be used to explain variations of terrigenous deposits magnetic characteristics. In order to verify the results, we make the DRS analysis. The results show that the study region occurred aridification obviously at ~6.3 Ma and ~5.2 Ma. The results of the DRS analysis show the similar paleo-climatic change.
The history and mechanism of aridification in the Asian interior during the late Cenozoic have been an important scientific issue. This study presents the terrigenous deposits from the ~303 m-thick Urumqi River section (URS) in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland. Based on the results of magnetostratigraphic chronology and rock magnetic characteristics, we discussed the magnetic enhancement mechanism of the URS sediments and paleo-climatic implications during the late Cenozoic in this region. The magnetostratigraphic chronology constrains the time spans from about 6.8 Ma to about 3.3 Ma. The results of rock magnetic and diffuse reflection spectrum (DRS) measurements show that the magnetic minerals in the URS sediments are mainly magnetite and hematite, and some magnetic parameters, such as χlf, χARM, SIRM，S-100mT, S-300mT, χARM/SIRM, changed obviously at ~6.3 Ma and ~5.2 Ma. These changes reveal that the measured samples contain coarser magnetic grains with less magnetic grains (after ~6.3 Ma). In contrast, the magnetic grains became finer steadily before ~5.2 Ma, with the content increasing. By the analysis of rare earth elements (REEs), we know that the distribution patterns of rare earth elements (REEs) are consistent obviously. The analysis of rare earth elements (REEs) is likely to indicate a stable source area of the URS deposits. The sediment grain size can also be used to explain variations of terrigenous deposits magnetic characteristics. There are significant correlation relationships between the sediment grain size parameters and χlf，χARM/χlf, the insignificant correlation relationships between the magnetic parameters, such as χARM, SIRM，S-100mT, S-300mT, χARM/SIRM, χfd, and the sediment grain size parameters indicate that the observed variations of magnetic characteristics may not be mainly caused by the sediment grain size parameters. The continuous aridification in the present study area is more likely to be the main cause of the variations of magnetic characteristics. The continuous aridification can contribute to the oxidation of magnetite, which can be used to explain variations of terrigenous deposits magnetic characteristics. In order to verify the results, we make the DRS analysis. The results show that the study region occurred aridification obviously at ~6.3 Ma and ~5.2 Ma. The results of the DRS analysis show the similar paleo-climatic change.
2017, 35(3): 527-539.
doi: 10.14027/j.cnki.cjxb.2017.03.011
Abstract:
The fourth sub-member, the fifth Member, Majiagou Formation (hereinafter referred to as Ma54) of Middle Ordovician is the important gas exploration layer in Ordos Basin, but many lithofacies paleogeographic maps about this layer are based on member or sub-member unit and is with a basin scale, and their resolution is far away from the requirement of gas exploration and development. In this paper, according to paleogeomorphology, anhydrite or gypsum type and its paleoenvironment significance, lithofacies paleogeography will be mapped in the Ma54 divided into Ma543, Ma542 and Ma541 in west Jingbian platform, which fills the gap of lacking high-resolution maps. On the base of sedimentary setting and stratum thickness contour diagram, the thick and slightly steep area in the center is interpreted as depression, and the thin and gentle area around the depression is interpreted as flat. There are massive anhydrite, spherical anhydrite concretion and gypsum crystal in Ma54. Massive anhydrite interbeded with dark muddy algae laminar dolomite represents a shallow and subaqueous evaporative environment which is located in supratidal zone and is sometimes flooded by tide water. Spherical anhydrite concretions, which are dispersed in light yellow micritic and slit-sized crystal dolostone, are formed during penecontemporaneous stage and indicate an evaporative and oxidizing environment with variational salinity. Comparison with the two types of anhydrite, gypsum crystals are not very common, and most of them show a columnar shape. Some crystals associate with spherical anhydrite concretion, so their environment is the same as spherical anhydrite concretion's. Massive anhydrite is distributed in the depression, so the lithofacies paleogeographic name is called anhydrite depression. According to the content of massive anhydrite, anhydrite depression is divided into massive anhydritic dolomite depression, massive anhydrite dolomite depression and dolomitic massive anhydrite depression. Spherical anhydrite concretion and gypsum crystal are mainly distributed in flat. Combined their distribution and sedimentary setting of restricted evaporative supratidal zone, they are called spherical anhydrite concretion dolomite tidal flat. The basic lithofacies paleogeographies of Ma543, Ma542 and Ma541 are almost the same, but from Ma543 to Ma542 and then Ma541, the anhydrite depression becomes smaller and smaller, and the content of massive anhydrite decreases gradually, which shows the process that supratidal evaporative water becomes shallower and shallower. This paper makes some relative high-resolution lithofacies paleogeographic maps, which is very helpful to the gas exploration and development in Lower Paleozoic in Ordos Basin.
The fourth sub-member, the fifth Member, Majiagou Formation (hereinafter referred to as Ma54) of Middle Ordovician is the important gas exploration layer in Ordos Basin, but many lithofacies paleogeographic maps about this layer are based on member or sub-member unit and is with a basin scale, and their resolution is far away from the requirement of gas exploration and development. In this paper, according to paleogeomorphology, anhydrite or gypsum type and its paleoenvironment significance, lithofacies paleogeography will be mapped in the Ma54 divided into Ma543, Ma542 and Ma541 in west Jingbian platform, which fills the gap of lacking high-resolution maps. On the base of sedimentary setting and stratum thickness contour diagram, the thick and slightly steep area in the center is interpreted as depression, and the thin and gentle area around the depression is interpreted as flat. There are massive anhydrite, spherical anhydrite concretion and gypsum crystal in Ma54. Massive anhydrite interbeded with dark muddy algae laminar dolomite represents a shallow and subaqueous evaporative environment which is located in supratidal zone and is sometimes flooded by tide water. Spherical anhydrite concretions, which are dispersed in light yellow micritic and slit-sized crystal dolostone, are formed during penecontemporaneous stage and indicate an evaporative and oxidizing environment with variational salinity. Comparison with the two types of anhydrite, gypsum crystals are not very common, and most of them show a columnar shape. Some crystals associate with spherical anhydrite concretion, so their environment is the same as spherical anhydrite concretion's. Massive anhydrite is distributed in the depression, so the lithofacies paleogeographic name is called anhydrite depression. According to the content of massive anhydrite, anhydrite depression is divided into massive anhydritic dolomite depression, massive anhydrite dolomite depression and dolomitic massive anhydrite depression. Spherical anhydrite concretion and gypsum crystal are mainly distributed in flat. Combined their distribution and sedimentary setting of restricted evaporative supratidal zone, they are called spherical anhydrite concretion dolomite tidal flat. The basic lithofacies paleogeographies of Ma543, Ma542 and Ma541 are almost the same, but from Ma543 to Ma542 and then Ma541, the anhydrite depression becomes smaller and smaller, and the content of massive anhydrite decreases gradually, which shows the process that supratidal evaporative water becomes shallower and shallower. This paper makes some relative high-resolution lithofacies paleogeographic maps, which is very helpful to the gas exploration and development in Lower Paleozoic in Ordos Basin.
2017, 35(3): 540-551.
doi: 10.14027/j.cnki.cjxb.2017.03.012
Abstract:
Shan 2 Member in southeastern Ordos Basin is an important gas bearing stratum. The provenance system is analyzed based on heavy mineral distribution, sandstone composition, rock fragments type and cathodoluminescence characteristics. The sediments of Shan 2 Member mainly comes from the north and south source areas. The sorting of the sediments is moderately to well sorted and rounded. Trough cross bedding, parallel bedding and wave ripples mainly developed in Shan 2 Member, the sedimentary facies of Shan 2 Member is a meandering river delta front based on sedimentary texture and sedimentary structures. The sediments of Shan 2 Member is dominated by saltation and featured by 3 sections and 4 sections while the mouth bar is characterized by well sorted sediments and 2 sections and 3 sections grain size distribution patterns. The sandstone thickness in the south, north and central areas like Zhidan and Ganquan is large. The fluvial sandstone body is characterized by an asymmetric type and stacking pattern. The hydrodynamic condition is moderate to strong. Based on provenance system reconstruction, sedimentary features analysis and identification of thin sections, the sedimentary model of Shan 2 Member which is double sourced meandering river delta is established, which provides a theoretical support for gas exploration and exploitation.
Shan 2 Member in southeastern Ordos Basin is an important gas bearing stratum. The provenance system is analyzed based on heavy mineral distribution, sandstone composition, rock fragments type and cathodoluminescence characteristics. The sediments of Shan 2 Member mainly comes from the north and south source areas. The sorting of the sediments is moderately to well sorted and rounded. Trough cross bedding, parallel bedding and wave ripples mainly developed in Shan 2 Member, the sedimentary facies of Shan 2 Member is a meandering river delta front based on sedimentary texture and sedimentary structures. The sediments of Shan 2 Member is dominated by saltation and featured by 3 sections and 4 sections while the mouth bar is characterized by well sorted sediments and 2 sections and 3 sections grain size distribution patterns. The sandstone thickness in the south, north and central areas like Zhidan and Ganquan is large. The fluvial sandstone body is characterized by an asymmetric type and stacking pattern. The hydrodynamic condition is moderate to strong. Based on provenance system reconstruction, sedimentary features analysis and identification of thin sections, the sedimentary model of Shan 2 Member which is double sourced meandering river delta is established, which provides a theoretical support for gas exploration and exploitation.
2017, 35(3): 552-560.
doi: 10.14027/j.cnki.cjxb.2017.03.013
Abstract:
Qiongdonan Basin is one of China's important hydrocarbon and hydrate-bearing basin. The study of its sedimentary characteristic and deep water deposition system evolution plays a significance role to the future exploration. Based on the high precision 3D seismic data, we analysis the depositional system of the western of Ganquan Uplift in the deep area of Qiongdongnan Basin. Through the method of seismic attribute extraction and recognition, we distinguish the sedimentary characteristics of two different sedimentary bodies, including turbiditic channel and slump. The channel, influenced by the bottom flow, is parallel with the continental slope of South China Sea and combining with the asymmetric levee. Through seismic section interpretation, we can also distinguish the two sets of slide disposition. The bottom slide is a kind of normal disposition with several variable period. The top slide disposition, due to the injection of bottom flow, has a lower density and viscosity. Because of the decrease of the density and viscosity of water, these kinds of slide have wide influence range and significantly layered property. With the help of RMS-attribute slice and sedimentary reconstruction of Yinggehai Formation, we divide the evolution into three stages: the stage of sliding, the stage of erosion by bottom flow channel, and the stage of re-sliding.
Qiongdonan Basin is one of China's important hydrocarbon and hydrate-bearing basin. The study of its sedimentary characteristic and deep water deposition system evolution plays a significance role to the future exploration. Based on the high precision 3D seismic data, we analysis the depositional system of the western of Ganquan Uplift in the deep area of Qiongdongnan Basin. Through the method of seismic attribute extraction and recognition, we distinguish the sedimentary characteristics of two different sedimentary bodies, including turbiditic channel and slump. The channel, influenced by the bottom flow, is parallel with the continental slope of South China Sea and combining with the asymmetric levee. Through seismic section interpretation, we can also distinguish the two sets of slide disposition. The bottom slide is a kind of normal disposition with several variable period. The top slide disposition, due to the injection of bottom flow, has a lower density and viscosity. Because of the decrease of the density and viscosity of water, these kinds of slide have wide influence range and significantly layered property. With the help of RMS-attribute slice and sedimentary reconstruction of Yinggehai Formation, we divide the evolution into three stages: the stage of sliding, the stage of erosion by bottom flow channel, and the stage of re-sliding.
2017, 35(3): 561-576.
doi: 10.14027/j.cnki.cjxb.2017.03.014
Abstract:
The provenance and sedimentary facies of the upper Es4 of Qingnan area, Dongying Depression lack systematic research, especially the distribution and scale of lacustrine beach-bar sediment, which restrict the precise exploration and reserves promotion in this area. This paper determines the types of sedimentary facies through petrological study, clarifies the sedimentary evolution by using logging methods, cleares the provenance direction and influence range using heavy mineral assemblage and the distribution of characteristic element ratio, and thus restricts the distribution of different sedimentary facies controlled by different provenance, especially the precise distribution of each sand-body, which can provide references for precise exploration of the oilfield. According to the research, there are four sedimentary systems(alluvial fan, delta, lake and gravity flow)and five sedimentary facies(coastal subsea apron, delta, fan delta, lake and deep water turbidity fan)in the study area; The boundary of southern and northern provenances lies along the line X7-Wx583-W58-W126-L74-Wx119-L108-L2-L64-Lx63, the southern Guangrao Heave provides a massive provenance to the north and northwest, nevertheless, the northern Qingtuozi Heave provides a limited provenance to the southwest; Delta sand-body exists through the whole Es4 and widely spreads from Guangrao Heave to northwest, deep water turbidity fan sand-body exists at the middle period of Es4 and distributes contiguously at the semi-deep and deep lake evironment in the northwest, fan delta sand-body exists at the late period of Es4 and has a limited distribution from Qingtuozi Heave to the southwest, beach bar sand-body exsits at the whole time of Es4 and has a wide range at the shore-shallow lake evironment, which has a range only smaller than delta sand-body and provides abundant potential reservoirs for lacustrine tight oil and gas.
The provenance and sedimentary facies of the upper Es4 of Qingnan area, Dongying Depression lack systematic research, especially the distribution and scale of lacustrine beach-bar sediment, which restrict the precise exploration and reserves promotion in this area. This paper determines the types of sedimentary facies through petrological study, clarifies the sedimentary evolution by using logging methods, cleares the provenance direction and influence range using heavy mineral assemblage and the distribution of characteristic element ratio, and thus restricts the distribution of different sedimentary facies controlled by different provenance, especially the precise distribution of each sand-body, which can provide references for precise exploration of the oilfield. According to the research, there are four sedimentary systems(alluvial fan, delta, lake and gravity flow)and five sedimentary facies(coastal subsea apron, delta, fan delta, lake and deep water turbidity fan)in the study area; The boundary of southern and northern provenances lies along the line X7-Wx583-W58-W126-L74-Wx119-L108-L2-L64-Lx63, the southern Guangrao Heave provides a massive provenance to the north and northwest, nevertheless, the northern Qingtuozi Heave provides a limited provenance to the southwest; Delta sand-body exists through the whole Es4 and widely spreads from Guangrao Heave to northwest, deep water turbidity fan sand-body exists at the middle period of Es4 and distributes contiguously at the semi-deep and deep lake evironment in the northwest, fan delta sand-body exists at the late period of Es4 and has a limited distribution from Qingtuozi Heave to the southwest, beach bar sand-body exsits at the whole time of Es4 and has a wide range at the shore-shallow lake evironment, which has a range only smaller than delta sand-body and provides abundant potential reservoirs for lacustrine tight oil and gas.
2017, 35(3): 577-591.
doi: 10.14027/j.cnki.cjxb.2017.03.015
Abstract:
Although buried in depth between 3 800~4 600 m, reservoirs of Sangonghe Formation in Mosuowan area have a relatively favorable physical properties, and become one of the key formations in hydrocarbon discoveries in hinterland of Junggar Basin. Thus, for later oil-gas exploration and development, it is of great significance to make clear multi-factor relationships and genetic mechanism of favorable reservoirs which are deeply buried. Through microscopic thin section, scanning electron microscope analysis, physical property analysis, X-ray diffraction of clay mineral, and well drilling- logging data, together with burial history, tectonic evolution, and based on single factors analysis of reservoir property preservation, present paper carries out a detailed multi- factor coupling analysis and discussion in property preservation process of deep buried clastic reservoir of Sangonghe Formation. The results demonstrate that favorable depositional conditions, strata overpressure, changes of diagenetic fluid properties and paleogeotemperature, these four factors respectively make the reservoir properties effectively preserved. Furthermore, the process of property preservation process can be divided into 5 stages, and during different evolution period, the main controlling factor of property preservation is different. During the slow shallow burial period, the main controlling factor were shallow depth and the beginning of strata overpressure; early to mid stage of first quick deep burial period the main factor was strata overpressure; mid to late stage of first quick deep burial and early to mid stage of slow deep burial period the main factor changed from strata overpressure to consolidation of cements; mid to late stage of slow deep burial period the main factor were low geothermal gradient and the dissolution of organic acid; while the second quick deep burial period to nowadays, the main factor are strata overpressure and decrease of geothermal gradient, and finally an oil-gas accumulation and comprehensive diagenetic evolution model of Sanggonghe Formation is proposed.
Although buried in depth between 3 800~4 600 m, reservoirs of Sangonghe Formation in Mosuowan area have a relatively favorable physical properties, and become one of the key formations in hydrocarbon discoveries in hinterland of Junggar Basin. Thus, for later oil-gas exploration and development, it is of great significance to make clear multi-factor relationships and genetic mechanism of favorable reservoirs which are deeply buried. Through microscopic thin section, scanning electron microscope analysis, physical property analysis, X-ray diffraction of clay mineral, and well drilling- logging data, together with burial history, tectonic evolution, and based on single factors analysis of reservoir property preservation, present paper carries out a detailed multi- factor coupling analysis and discussion in property preservation process of deep buried clastic reservoir of Sangonghe Formation. The results demonstrate that favorable depositional conditions, strata overpressure, changes of diagenetic fluid properties and paleogeotemperature, these four factors respectively make the reservoir properties effectively preserved. Furthermore, the process of property preservation process can be divided into 5 stages, and during different evolution period, the main controlling factor of property preservation is different. During the slow shallow burial period, the main controlling factor were shallow depth and the beginning of strata overpressure; early to mid stage of first quick deep burial period the main factor was strata overpressure; mid to late stage of first quick deep burial and early to mid stage of slow deep burial period the main factor changed from strata overpressure to consolidation of cements; mid to late stage of slow deep burial period the main factor were low geothermal gradient and the dissolution of organic acid; while the second quick deep burial period to nowadays, the main factor are strata overpressure and decrease of geothermal gradient, and finally an oil-gas accumulation and comprehensive diagenetic evolution model of Sanggonghe Formation is proposed.
2017, 35(3): 592-599.
doi: 10.14027/j.cnki.cjxb.2017.03.016
Abstract:
To study the play of fault in oil-gas accumulation and distribution, based on the division of fault transporting oil and gas forms, the conditions required for fault transporting oil-gas and the method forecasting distribution are studied. The results show that the fault transporting oil-gas migration forms are different and the required conditions are also different. The conditions required for fault vertically transporting oil-gas upward is that the fault locates in the area where mature source rocks exist. The condition of fault vertically transporting oil-gas downward is the fault located in the maturation zone with ex-high pressure and supply oil ability. The condition of fault laterally transporting petroleum migration is that the fault locates in where cap rocks faulted-contact thickness is greater than or equal to the minimum faulted-contact thickness for oil-gas lateral migration. The condition of fault laterally diameter changing transporting petroleum migration is that the fault locates in the area that cap rocks faulted-contact thickness less than faulted-contact thickness for oil-gas lateral migration. By comparing the matured source rocks distribution or the matured source rocks distribution with anomaly high pressure and supply hydrocarbon ability, oil-gas lateral migration distribution, oil-gas non-lateral migration distribution and fault distribution, a prediction method of different fault transporting distribution area is established. Then it is applied into the study of predicting distribution areas of fault transporting oil-gas migration in Ed2,Ed3 Formation, Jizhong sag of Bohai bay basin, the Fuyang Reservoir in the Sanzhao Depression of Songliao basin, and Ed2 in Wenan slope of Baxian depression, Bohai bay basin. The prediction results are consistent with the discovered distribution of oil and gas, indicating that the prediction method of fault transporting oil and gas migration is feasible.
To study the play of fault in oil-gas accumulation and distribution, based on the division of fault transporting oil and gas forms, the conditions required for fault transporting oil-gas and the method forecasting distribution are studied. The results show that the fault transporting oil-gas migration forms are different and the required conditions are also different. The conditions required for fault vertically transporting oil-gas upward is that the fault locates in the area where mature source rocks exist. The condition of fault vertically transporting oil-gas downward is the fault located in the maturation zone with ex-high pressure and supply oil ability. The condition of fault laterally transporting petroleum migration is that the fault locates in where cap rocks faulted-contact thickness is greater than or equal to the minimum faulted-contact thickness for oil-gas lateral migration. The condition of fault laterally diameter changing transporting petroleum migration is that the fault locates in the area that cap rocks faulted-contact thickness less than faulted-contact thickness for oil-gas lateral migration. By comparing the matured source rocks distribution or the matured source rocks distribution with anomaly high pressure and supply hydrocarbon ability, oil-gas lateral migration distribution, oil-gas non-lateral migration distribution and fault distribution, a prediction method of different fault transporting distribution area is established. Then it is applied into the study of predicting distribution areas of fault transporting oil-gas migration in Ed2,Ed3 Formation, Jizhong sag of Bohai bay basin, the Fuyang Reservoir in the Sanzhao Depression of Songliao basin, and Ed2 in Wenan slope of Baxian depression, Bohai bay basin. The prediction results are consistent with the discovered distribution of oil and gas, indicating that the prediction method of fault transporting oil and gas migration is feasible.
2017, 35(3): 600-610.
doi: 10.14027/j.cnki.cjxb.2017.03.017
Abstract:
Through a comprehensive analysis of drilling, well logging, cores and experimental data, an in-depth study on the Qingshankou Formation's tight oil characteristics and accumulation mode in northern Songliao Basin was described and established. It is found that the unconventional reservoir is a densified reservoir which developed from platelike turbidity current in both deltaic front and lake facies region. The porosity of the reservoir is less than 10% in general, in some part the porosity could reach 15%, and the permeability is less than 0.1×10-3 μm2 in general. Reservoir spaces are intergranular pore, intragranular dissolved pore, mold pore, and microfracture. The diameters of pores range from 5~200 μm and the diameters of pore throat are less than 0.5 μm. The source rock is the lacustrine facies mudstone of the first and second Section in Qingshankou Formation, and that are typical of extensive distribution: kerogens are either type I or type II1, average TOC is 1%~3%, Ro is from 0.9%~1.1% and the rock attributes to mature high-quality source rock. Horizontally, the reservoir has some characteristics of facies belt and regional belt, but there is no obvious entrapment boundary. Vertically, the reservoir and the source rocks piled up alternatively and formed like flaky pastry, reservoir forming type is source-reserve impinge and mutualistic symbiosis. The oil bearing degrees of the reservoir are oil patch and oil stain. Oil immersion and oil-rich rocks do not exist, the crude oil belong to low viscosity and light crude. The reservoir does not have natural production, but a relatively high industrial capacity could be adopted in horizontal well by large-scale segmental bulk fracturing. Therefore, the study on platelike turbidite reservoir develops and accumulation mode develop new space for the tight oil exploration in Songliao Basin, and possess practical significance.
Through a comprehensive analysis of drilling, well logging, cores and experimental data, an in-depth study on the Qingshankou Formation's tight oil characteristics and accumulation mode in northern Songliao Basin was described and established. It is found that the unconventional reservoir is a densified reservoir which developed from platelike turbidity current in both deltaic front and lake facies region. The porosity of the reservoir is less than 10% in general, in some part the porosity could reach 15%, and the permeability is less than 0.1×10-3 μm2 in general. Reservoir spaces are intergranular pore, intragranular dissolved pore, mold pore, and microfracture. The diameters of pores range from 5~200 μm and the diameters of pore throat are less than 0.5 μm. The source rock is the lacustrine facies mudstone of the first and second Section in Qingshankou Formation, and that are typical of extensive distribution: kerogens are either type I or type II1, average TOC is 1%~3%, Ro is from 0.9%~1.1% and the rock attributes to mature high-quality source rock. Horizontally, the reservoir has some characteristics of facies belt and regional belt, but there is no obvious entrapment boundary. Vertically, the reservoir and the source rocks piled up alternatively and formed like flaky pastry, reservoir forming type is source-reserve impinge and mutualistic symbiosis. The oil bearing degrees of the reservoir are oil patch and oil stain. Oil immersion and oil-rich rocks do not exist, the crude oil belong to low viscosity and light crude. The reservoir does not have natural production, but a relatively high industrial capacity could be adopted in horizontal well by large-scale segmental bulk fracturing. Therefore, the study on platelike turbidite reservoir develops and accumulation mode develop new space for the tight oil exploration in Songliao Basin, and possess practical significance.
2017, 35(3): 611-620.
doi: 10.14027/j.cnki.cjxb.2017.03.018
Abstract:
Dolomite oil seepages and hydrocarbon source rocks of Permian Zhanjin Formation were collected systematically from Central uplift belt area in Qiangtang Basin.Based on the analytical data of group component, biomarkers and carbon isotopic compositions of n-alkanes and isopre, the author analyzed the geochemical characteristics of Permian dolomite oil seepages,and the oil-source rock correlation was also studied in the paper. The results indicated that the Permian dolomite oil seepages are high fraction saturated hydrocarbons,followed by non hydrocarbon, aromatics and asphaltene fraction are low. The ratio of saturates/aromatics of dolomite oil seepages are more than 1.0. The alkanes of dolomite oil seepages are composed of nC15 - nC36,with nC17~nC20 as the main peaks,and characteristics of single peak distribution.The nC21-/nC22+ ratios from 1.0 to 4.56,the regular sterans C27-C28-C29 distributed with irregular “V”shape and predominance of C29,homohopane were detected from C31~C35, indicating dolomite oil seepages of hydrocarbon material sources were in algae and other lower aquatic organisms. The Pr/Ph values range of dolomite oil seepages were between 0.91 to 1.30,and gammacerane/C30hopane values were from 0.42 to 0.88, the content of dibenzothiophene were the highest (average 67.39%) and low dibenzofuran content (average 7.89%). 4-MDBT/DBT values of dolomite oil seepages were 0.97 to 4.26, (2+3)-MDBT/DBT values were 0.37 to 1.62, showing dolomite oil seepages hydrocarbon material sources were formed in marine shale with certain salinity reduction environment. The OEP values, C29ααα20S/ααα (20S+ 20R) values,C29αββ/(ααα+αββ) values and C3122S/(22S+22R) values etc., closed to equilibrium values 1, aromatic maturity parameters MPI1,F1 and 4,6/1,4-DMDBT calculated from the equivalent vitrinite reflectance showed that dolomite oil seepages were mature crude oil. The biomarkers of oil seepages are closely correlated to the Zhanjin Formation black mudstone, reflecting that the oil seepages were mainly originated from the Zhanjin Formation. However, carbon isotopic compositions of n-alkanes and isopre exists some differences between oil seepages and Zhanjin Formation black mudstone, indicating a mixture of sources.
Dolomite oil seepages and hydrocarbon source rocks of Permian Zhanjin Formation were collected systematically from Central uplift belt area in Qiangtang Basin.Based on the analytical data of group component, biomarkers and carbon isotopic compositions of n-alkanes and isopre, the author analyzed the geochemical characteristics of Permian dolomite oil seepages,and the oil-source rock correlation was also studied in the paper. The results indicated that the Permian dolomite oil seepages are high fraction saturated hydrocarbons,followed by non hydrocarbon, aromatics and asphaltene fraction are low. The ratio of saturates/aromatics of dolomite oil seepages are more than 1.0. The alkanes of dolomite oil seepages are composed of nC15 - nC36,with nC17~nC20 as the main peaks,and characteristics of single peak distribution.The nC21-/nC22+ ratios from 1.0 to 4.56,the regular sterans C27-C28-C29 distributed with irregular “V”shape and predominance of C29,homohopane were detected from C31~C35, indicating dolomite oil seepages of hydrocarbon material sources were in algae and other lower aquatic organisms. The Pr/Ph values range of dolomite oil seepages were between 0.91 to 1.30,and gammacerane/C30hopane values were from 0.42 to 0.88, the content of dibenzothiophene were the highest (average 67.39%) and low dibenzofuran content (average 7.89%). 4-MDBT/DBT values of dolomite oil seepages were 0.97 to 4.26, (2+3)-MDBT/DBT values were 0.37 to 1.62, showing dolomite oil seepages hydrocarbon material sources were formed in marine shale with certain salinity reduction environment. The OEP values, C29ααα20S/ααα (20S+ 20R) values,C29αββ/(ααα+αββ) values and C3122S/(22S+22R) values etc., closed to equilibrium values 1, aromatic maturity parameters MPI1,F1 and 4,6/1,4-DMDBT calculated from the equivalent vitrinite reflectance showed that dolomite oil seepages were mature crude oil. The biomarkers of oil seepages are closely correlated to the Zhanjin Formation black mudstone, reflecting that the oil seepages were mainly originated from the Zhanjin Formation. However, carbon isotopic compositions of n-alkanes and isopre exists some differences between oil seepages and Zhanjin Formation black mudstone, indicating a mixture of sources.
2017, 35(3): 621-636.
doi: 10.14027/j.cnki.cjxb.2017.03.019
Abstract:
The geochemical characteristics of Jurassic mudstones in the Northern Ordos Basin Hangjinqi Area recorded important geological information at that time. Based on the method of X-ray fluorescence spectrometry of the major element analysis and ICP-MS trace element and rare earth element analysis,the tectonic setting and provenance attribute of Zhiluo Formation and Yan'an Formation have been comprehensively analyzed. Meanwhile, we restored the evolution of sedimentary setting by the vertical variation characteristics of geochemical parameters.The main conclusions can be drawn as follows:The Jurassic sedimentary rocks in the Northern Ordos Basin have affinities to the Precambrian metamorphotic rocks from old basement,such as gneiss,granulite,khondalite and the intrusive rock which formed in different geological time,so the provenance of the study area mainly came from it.The tectonic setting of source area is the active continental margin associated with the continental island arc. The result of paleoenvironment reconstruction is based on the vertical variation characteristics of mudstone geochemical indexes such as Sr/Cu,Rb/Sr,CIA,Sr/Ba,V/(V+Ni)and Ceanom shows that from Yan' an period to early Zhiluo period and then to late Zhiluo period, the paleoclimate was warm and humid at the beginning and tended to become increasingly dry and hot,the palaeosalinity transformed from the brackish water phase of the fresh water environment to the brackish-water phase of the fresh water environment,the redox condition belong to the reducing environment and the water column stratification is not obvious.
The geochemical characteristics of Jurassic mudstones in the Northern Ordos Basin Hangjinqi Area recorded important geological information at that time. Based on the method of X-ray fluorescence spectrometry of the major element analysis and ICP-MS trace element and rare earth element analysis,the tectonic setting and provenance attribute of Zhiluo Formation and Yan'an Formation have been comprehensively analyzed. Meanwhile, we restored the evolution of sedimentary setting by the vertical variation characteristics of geochemical parameters.The main conclusions can be drawn as follows:The Jurassic sedimentary rocks in the Northern Ordos Basin have affinities to the Precambrian metamorphotic rocks from old basement,such as gneiss,granulite,khondalite and the intrusive rock which formed in different geological time,so the provenance of the study area mainly came from it.The tectonic setting of source area is the active continental margin associated with the continental island arc. The result of paleoenvironment reconstruction is based on the vertical variation characteristics of mudstone geochemical indexes such as Sr/Cu,Rb/Sr,CIA,Sr/Ba,V/(V+Ni)and Ceanom shows that from Yan' an period to early Zhiluo period and then to late Zhiluo period, the paleoclimate was warm and humid at the beginning and tended to become increasingly dry and hot,the palaeosalinity transformed from the brackish water phase of the fresh water environment to the brackish-water phase of the fresh water environment,the redox condition belong to the reducing environment and the water column stratification is not obvious.
2017, 35(3): 637-648.
doi: 10.14027/j.cnki.cjxb.2017.03.020
Abstract:
Upper Jurassic marine source rocks in Amu Darya Basin are a set of generally accepted mature source rocks, and the maturity of them show difference against Paleozoic high-over maturity marine source rock in China. Through geochemical analyses of upper Jurassic rock samples in right bank of Amu Darya Basin and contrast among similar source rocks from basins of China Tarim, Huabei, Turpan-Hami, Bohai Gulf, we examine mature marine source rocks in Amu Darya Basin and build evaluation standard and charts of organic matter abundance and types. The results show that there are two types of Jurassic mature marine source rocks in Amu Darya Basin: limestone and mudstone, and the organic matter abundance of limestone is slightly higher than the Paleozoic limestone in Tarim Basin and middle-upper proterozoic limestone in North China Platform, and is close to the Permian limestone in Sichuan, while the organic carbon of mudstone is equal to that of Jurassic mudstone in coal-measures and is much better than the marine mudstone in Tarim Basin and North China Platform; marine mudstone belongs to type Ⅰ2~Ⅱ source rock while marine limestone belongs to type Ⅲ~Ⅱ source rock. Comprehensive analyses show that ①upper Jurassic marine limestone belongs to middle class source rock while marine mudstone belongs to good source rock, and the TOC standard value is 0.5% and 3% respectively; ②parameters like resolvable chloroform asphalt “A” constituents, relation between Pr/Ph and Ph/nC18、polycyclic aromatics "benzfhiore tri-fluorene" of marine carbonate rock or mudstone major in lower eukaryote not only discover the generation environment of source rocks, but also are good parameters to distinguish types of mother matter. The build of evaluation standard and charts of upper Jurassic marine mudstone and limestone in Amu Darya Basin have great significance on overseas marine basins hydrocarbon resources assessment.
Upper Jurassic marine source rocks in Amu Darya Basin are a set of generally accepted mature source rocks, and the maturity of them show difference against Paleozoic high-over maturity marine source rock in China. Through geochemical analyses of upper Jurassic rock samples in right bank of Amu Darya Basin and contrast among similar source rocks from basins of China Tarim, Huabei, Turpan-Hami, Bohai Gulf, we examine mature marine source rocks in Amu Darya Basin and build evaluation standard and charts of organic matter abundance and types. The results show that there are two types of Jurassic mature marine source rocks in Amu Darya Basin: limestone and mudstone, and the organic matter abundance of limestone is slightly higher than the Paleozoic limestone in Tarim Basin and middle-upper proterozoic limestone in North China Platform, and is close to the Permian limestone in Sichuan, while the organic carbon of mudstone is equal to that of Jurassic mudstone in coal-measures and is much better than the marine mudstone in Tarim Basin and North China Platform; marine mudstone belongs to type Ⅰ2~Ⅱ source rock while marine limestone belongs to type Ⅲ~Ⅱ source rock. Comprehensive analyses show that ①upper Jurassic marine limestone belongs to middle class source rock while marine mudstone belongs to good source rock, and the TOC standard value is 0.5% and 3% respectively; ②parameters like resolvable chloroform asphalt “A” constituents, relation between Pr/Ph and Ph/nC18、polycyclic aromatics "benzfhiore tri-fluorene" of marine carbonate rock or mudstone major in lower eukaryote not only discover the generation environment of source rocks, but also are good parameters to distinguish types of mother matter. The build of evaluation standard and charts of upper Jurassic marine mudstone and limestone in Amu Darya Basin have great significance on overseas marine basins hydrocarbon resources assessment.
