2016 Vol. 34, No. 1
Display Method:
2016, 34(1): 1-14.
doi: 10.14027/j.cnki.cjxb.2016.01.001
Abstract:
It's difficult to restore and reconstruct the palaeogeographic of the orogenic belt, and there was no research method system to follow. Ordovician in Gansu province was the study target. Combined with the existing study, compiled the sedimentary tectonic map and the sedimentary basin type map of the Lower-Middle-Late Ordovician, the relationship of spatial disposition between them was analyzed. Under the "basin-controlling tectonic, facies-controlling basin" thought, on the basis of the sedimentary lithology, texture-structure and the paleontological, and using the dominant facies principle, littoral-neritic facies, shelf facies, open sea platform facies, platform margin shoals facies, tidal flat facies, bathyal facies (including slope facies) and abyssal facies were figured outin study area. "In the same plate and the same tectonic settings, or in the sedimentary basin which have the space connection configuration, the Walther facies law was used to restore the paleogeographic of the basin. However, restoring paleogeographic of the basin by the real sedimentary environment of the emergence stratums, Palaeogeographic units can't follow the Walther facies law." Under the guidance of the principle, Paleogeography of the study area was restored and rebuilt, also, the corresponding paleogeographic map was established. It provides a mapping train of restoring lithofacies-paleogeographic for orogenic belt, which has the theoretical and practical significance.
It's difficult to restore and reconstruct the palaeogeographic of the orogenic belt, and there was no research method system to follow. Ordovician in Gansu province was the study target. Combined with the existing study, compiled the sedimentary tectonic map and the sedimentary basin type map of the Lower-Middle-Late Ordovician, the relationship of spatial disposition between them was analyzed. Under the "basin-controlling tectonic, facies-controlling basin" thought, on the basis of the sedimentary lithology, texture-structure and the paleontological, and using the dominant facies principle, littoral-neritic facies, shelf facies, open sea platform facies, platform margin shoals facies, tidal flat facies, bathyal facies (including slope facies) and abyssal facies were figured outin study area. "In the same plate and the same tectonic settings, or in the sedimentary basin which have the space connection configuration, the Walther facies law was used to restore the paleogeographic of the basin. However, restoring paleogeographic of the basin by the real sedimentary environment of the emergence stratums, Palaeogeographic units can't follow the Walther facies law." Under the guidance of the principle, Paleogeography of the study area was restored and rebuilt, also, the corresponding paleogeographic map was established. It provides a mapping train of restoring lithofacies-paleogeographic for orogenic belt, which has the theoretical and practical significance.
2016, 34(1): 15-32.
doi: 10.14027/j.cnki.cjxb.2016.01.002
Abstract:
The Linsishan Formation, belonging to the bottom of the middl Early Cretaceous Laiyang Group in Jiaolai basin,Eastern Shandong, consists dominantly of a variety of conglomerates.Based on the petrological compositions, grain sizess and orientation of gravels within conglomerates at least 18 observation localities and a combination of detrital zircon dates of sandstones overlying the Linsishan Formation, this research reports a comprehensive results of the sedimentary facies, provenances,paleocurrents and implications of basin evolution.This study indicates that the Linsishan Formation mainly comprises of alluvial fan conglomerates with a variation of sedimentary microfacies in basin scale.The synsedimentary Jiaolai basin in term of paleogeography was constituted by three individual basins,i.e.,the Laiyang, Haiyang-Jimo and Zhucheng-Wulian basins, separated by the six paleo-uplifts.Provenance of the Laiyang basin are derived from Jiaobei uplift and the northern Sulu Orogenic Belt; source of the Haiyang-Jimu basin provided by northern Sulu Orogenic Belt, Jimo-Mouping uplift and Jiaonan uplift; Provenance of the Zhucheng-Wulian basin are derived from Jiaonan uplift and Mashan-Lijiadang low uplift. Finally,initiation of conglomerates of the Linsishan Formation in Eastern Shandong is a sign of formation of the synsedimentary Jiaolai basin and further,implies a large-scale collapse of the Sulu Orogenic Belt resulted from vast extensional crustal detachment and lithosphere thinning in East China because of destruction of North China Craton.
The Linsishan Formation, belonging to the bottom of the middl Early Cretaceous Laiyang Group in Jiaolai basin,Eastern Shandong, consists dominantly of a variety of conglomerates.Based on the petrological compositions, grain sizess and orientation of gravels within conglomerates at least 18 observation localities and a combination of detrital zircon dates of sandstones overlying the Linsishan Formation, this research reports a comprehensive results of the sedimentary facies, provenances,paleocurrents and implications of basin evolution.This study indicates that the Linsishan Formation mainly comprises of alluvial fan conglomerates with a variation of sedimentary microfacies in basin scale.The synsedimentary Jiaolai basin in term of paleogeography was constituted by three individual basins,i.e.,the Laiyang, Haiyang-Jimo and Zhucheng-Wulian basins, separated by the six paleo-uplifts.Provenance of the Laiyang basin are derived from Jiaobei uplift and the northern Sulu Orogenic Belt; source of the Haiyang-Jimu basin provided by northern Sulu Orogenic Belt, Jimo-Mouping uplift and Jiaonan uplift; Provenance of the Zhucheng-Wulian basin are derived from Jiaonan uplift and Mashan-Lijiadang low uplift. Finally,initiation of conglomerates of the Linsishan Formation in Eastern Shandong is a sign of formation of the synsedimentary Jiaolai basin and further,implies a large-scale collapse of the Sulu Orogenic Belt resulted from vast extensional crustal detachment and lithosphere thinning in East China because of destruction of North China Craton.
2016, 34(1): 33-48.
doi: 10.14027/j.cnki.cjxb.2016.01.003
Abstract:
In order to improve the understanding on the sedimentary characteristics and lithofacies palaeogeography in the Lower Cambrian Longwangmiao Formation of the Sichuan Basin and its adjacent regions, a relative comprehensive analysis on the boreholes and outcrops data were performed. Particularly, by examining the regional geological settings and the thickness distribution pattern within Longwangmiao Fromation, this paper found that the Sichuan Basin and its adjacent areas are bordered by Motianling Micro-oldland and Hannan Oldland in the north, Kangdian Oldland in the west. In the southeast and northeast regions within the study area, were embraced by underwater palaeouplift named Weixin-Qianjiang, Shiqian-Xiushan-Longshan and Zhenba-Wuxi-Badong respectively. Within the present basin, Central Sichuan palaeouplift, and depressins of Langzhong-Tongjiang, Jiangjin-Fengjie constitute of the palaeogeographic pattern of "one uplift and two depressions", while in the south an inherited depression region named "Luzhou-Junlian-Zhaotong" still existed. To the northeast and southwest corner, Qinling ocean and Jiangnan Basin are connected. Strikingly impacted by the palaeogeographic pattern, a land-tied carbonate platform was found to cover the main body of the Sichuan Basin within the platform-ramp-basin sedimentary system, which may further be divided into mixed tidal flat, restricted to evaporate platform, semi-restricted to restricted platform and platform margin. Furtherly, by analyzing the terrigenous clasts content and its direction, the content distribution pattern of limestone, dolostone and gyprock elucidating the waters localization and the relative locations of the platform margin, and the grain-shoal content, it clarifies the distribution pattern of the lithofacies paleogeography during Longwangmiao period, establishing the sedimentary model successively. The results indicate that, the open ocean side of the flat tidal, underwater palaeouplift and the periphery areas of Luzhou-Junlian-Zhaotong are preferable zones for grain shoal development. The filling and joining during the early stage of early Cambrian results in a unified palaeouplift in Leshan and Ziyang, while the north-south staphrogenic Trough in Tongzi-Junlian during the end of Ediacaran and Early Cambrian turned into the Luzhou-Junlian-Zhaotong depression within the platform. Two depression zones in the south have been verified by drilling holes of Well Dengtan 1 and Well Taihe 1. The results may help to guide and broaden the exploration field of karstificated grain-shoal reservoir study.
In order to improve the understanding on the sedimentary characteristics and lithofacies palaeogeography in the Lower Cambrian Longwangmiao Formation of the Sichuan Basin and its adjacent regions, a relative comprehensive analysis on the boreholes and outcrops data were performed. Particularly, by examining the regional geological settings and the thickness distribution pattern within Longwangmiao Fromation, this paper found that the Sichuan Basin and its adjacent areas are bordered by Motianling Micro-oldland and Hannan Oldland in the north, Kangdian Oldland in the west. In the southeast and northeast regions within the study area, were embraced by underwater palaeouplift named Weixin-Qianjiang, Shiqian-Xiushan-Longshan and Zhenba-Wuxi-Badong respectively. Within the present basin, Central Sichuan palaeouplift, and depressins of Langzhong-Tongjiang, Jiangjin-Fengjie constitute of the palaeogeographic pattern of "one uplift and two depressions", while in the south an inherited depression region named "Luzhou-Junlian-Zhaotong" still existed. To the northeast and southwest corner, Qinling ocean and Jiangnan Basin are connected. Strikingly impacted by the palaeogeographic pattern, a land-tied carbonate platform was found to cover the main body of the Sichuan Basin within the platform-ramp-basin sedimentary system, which may further be divided into mixed tidal flat, restricted to evaporate platform, semi-restricted to restricted platform and platform margin. Furtherly, by analyzing the terrigenous clasts content and its direction, the content distribution pattern of limestone, dolostone and gyprock elucidating the waters localization and the relative locations of the platform margin, and the grain-shoal content, it clarifies the distribution pattern of the lithofacies paleogeography during Longwangmiao period, establishing the sedimentary model successively. The results indicate that, the open ocean side of the flat tidal, underwater palaeouplift and the periphery areas of Luzhou-Junlian-Zhaotong are preferable zones for grain shoal development. The filling and joining during the early stage of early Cambrian results in a unified palaeouplift in Leshan and Ziyang, while the north-south staphrogenic Trough in Tongzi-Junlian during the end of Ediacaran and Early Cambrian turned into the Luzhou-Junlian-Zhaotong depression within the platform. Two depression zones in the south have been verified by drilling holes of Well Dengtan 1 and Well Taihe 1. The results may help to guide and broaden the exploration field of karstificated grain-shoal reservoir study.
2016, 34(1): 49-57.
doi: 10.14027/j.cnki.cjxb.2016.01.004
Abstract:
The Jiuxi basin, an inland basin located along the northeastern boundary of Tibetan Plataeu, is rich in thick and consistent Mesozoic-Cenozoic sedimentary strata, which precisely recorded the tectonic evolution of thesturctures and environment of the basin and its adjacent mountains. Based on Cenozoic sediment fluxes study of Huoshaogou, Shiyangjuan, Laojunmiao, Ciyaokou, Hongliuxia, Dahongquan, Wenshushan section of Jiuxi Basin. We founded that: The increase of sediment flux from Huoshaogou(40.5~33.3 Ma) to Baiyanghe(30.9~23.8 Ma) formation under arid climate was caused by acceleration weathering of Qilian Shan and consistent depression of Jiuxi Basin; In the Early Miocene time(Gongxingshan section 23~14 Ma), the sediment flux during the period was low. We attribute this change to the quite tectonic activity, although the climate was relatively warm during this time interval; In the Middle Miocene time(Getanggou section, 14~8.3 Ma), the sediment flux was controlled by the effect of both climate and tectonic activtities of North Qilian Shan; In the Late Miocene time(<8.3 Ma, Niugetao-Yumen Formation), the sediment flux was high and sharply increased. This change was responsible for the quickly uplift of North Qilian Shan, and the following acceleration of weathering and denudation.
The Jiuxi basin, an inland basin located along the northeastern boundary of Tibetan Plataeu, is rich in thick and consistent Mesozoic-Cenozoic sedimentary strata, which precisely recorded the tectonic evolution of thesturctures and environment of the basin and its adjacent mountains. Based on Cenozoic sediment fluxes study of Huoshaogou, Shiyangjuan, Laojunmiao, Ciyaokou, Hongliuxia, Dahongquan, Wenshushan section of Jiuxi Basin. We founded that: The increase of sediment flux from Huoshaogou(40.5~33.3 Ma) to Baiyanghe(30.9~23.8 Ma) formation under arid climate was caused by acceleration weathering of Qilian Shan and consistent depression of Jiuxi Basin; In the Early Miocene time(Gongxingshan section 23~14 Ma), the sediment flux during the period was low. We attribute this change to the quite tectonic activity, although the climate was relatively warm during this time interval; In the Middle Miocene time(Getanggou section, 14~8.3 Ma), the sediment flux was controlled by the effect of both climate and tectonic activtities of North Qilian Shan; In the Late Miocene time(<8.3 Ma, Niugetao-Yumen Formation), the sediment flux was high and sharply increased. This change was responsible for the quickly uplift of North Qilian Shan, and the following acceleration of weathering and denudation.
2016, 34(1): 58-69.
doi: 10.14027/j.cnki.cjxb.2016.01.005
Abstract:
The internal-wave, internal-tide and combined-flow deposit of the ancient deep-water system is a new find in recent twenty years. As the sedimentary records are rare, the sedimentology research on the bottom currents in the deep-water system is restricted. Based on detailed analysis of the geological sections and sedimentary outcrop columns, there exists bottom current deposits in the deep-water deposits of Pingxiang Basin. This paper deeply analyzes the sedimentary structure and paleocurrent of these bottom current deposits. The bottom current deposits consist of internal-wave, internal-tide and combined-flow deposits. The internal-wave and internal-tide deposits are characterized by bidirectional cross lamination, unidirectional cross lamination and lenticular lamination. The combined-flow deposit is characterized by combined-flow ripple lamination, hummocky cross lamination and sharp climbing ripple lamination. Furthermore, it shows the interaction between turbidity and bottom currents. This paper provides a new sample for the research of bottom currents in the ancient deep-water system.
The internal-wave, internal-tide and combined-flow deposit of the ancient deep-water system is a new find in recent twenty years. As the sedimentary records are rare, the sedimentology research on the bottom currents in the deep-water system is restricted. Based on detailed analysis of the geological sections and sedimentary outcrop columns, there exists bottom current deposits in the deep-water deposits of Pingxiang Basin. This paper deeply analyzes the sedimentary structure and paleocurrent of these bottom current deposits. The bottom current deposits consist of internal-wave, internal-tide and combined-flow deposits. The internal-wave and internal-tide deposits are characterized by bidirectional cross lamination, unidirectional cross lamination and lenticular lamination. The combined-flow deposit is characterized by combined-flow ripple lamination, hummocky cross lamination and sharp climbing ripple lamination. Furthermore, it shows the interaction between turbidity and bottom currents. This paper provides a new sample for the research of bottom currents in the ancient deep-water system.
2016, 34(1): 70-78.
doi: 10.14027/j.cnki.cjxb.2016.01.006
Abstract:
The alternating units of dune sands and paleosols are widely distributed acorss arid and semi-arid region of Northern China. To study the possible relationship between sand-paleosol sequences color and paleoclimate, three color parameters, lightness (L*), redness (a*) and yellowness (b*), of seven relict sand-paleosol profiles across Otindag sandy land were measured with a colorimeter. The results show the values of L*, a*, b* are 32.41~65.89, 2.73~7.52 and -1.68~17.16, respectively. Three color parameters have significantly positive relationship, correlation between L* and b* is strongly significant (R2 = 0.90), but that of L* and a* is quite low (R2=0.26). Although lightness, redness and yellowness have similar trend curves along sand-paleosol profiles, their variations are distinctly different. The changes of L* value are significantly larger than that of both a* and b* values. Nonparametric tests of lightness, redness and yellowness on sand-paleosol profiles indicate that lightness and yellowness are significantly different between sand and paleosols layers, with relatively low lightness and yellowness values in the paleosols layers. By contrast, the redness could hardly indicate their differences between sand and paleosols layers. Variations of the lightness are strongly related to the contents of organic matter, clay and silt. Relative effects of these factors on the lightness decrease gradually from organic matter and clay to silt. These changes are founded to be due to variations in the regional patterns of precipitation, which is possibly attributed to cyclic oscillations of East Asian summer monsoon precipitation. Therefore, the lightness (L*) could be used as a proxy indices to reconstruct past summer monsoon variability. Low values of L* possibly indicate a relatively high organic matter and a strengthening signal of East Asian summer monsoon, and vice versa. These results suggest that quantitative color determination of sand-paleosol sequences using a colorimeter could provide a new clue to understand the East Asian summer monsoon changes.
The alternating units of dune sands and paleosols are widely distributed acorss arid and semi-arid region of Northern China. To study the possible relationship between sand-paleosol sequences color and paleoclimate, three color parameters, lightness (L*), redness (a*) and yellowness (b*), of seven relict sand-paleosol profiles across Otindag sandy land were measured with a colorimeter. The results show the values of L*, a*, b* are 32.41~65.89, 2.73~7.52 and -1.68~17.16, respectively. Three color parameters have significantly positive relationship, correlation between L* and b* is strongly significant (R2 = 0.90), but that of L* and a* is quite low (R2=0.26). Although lightness, redness and yellowness have similar trend curves along sand-paleosol profiles, their variations are distinctly different. The changes of L* value are significantly larger than that of both a* and b* values. Nonparametric tests of lightness, redness and yellowness on sand-paleosol profiles indicate that lightness and yellowness are significantly different between sand and paleosols layers, with relatively low lightness and yellowness values in the paleosols layers. By contrast, the redness could hardly indicate their differences between sand and paleosols layers. Variations of the lightness are strongly related to the contents of organic matter, clay and silt. Relative effects of these factors on the lightness decrease gradually from organic matter and clay to silt. These changes are founded to be due to variations in the regional patterns of precipitation, which is possibly attributed to cyclic oscillations of East Asian summer monsoon precipitation. Therefore, the lightness (L*) could be used as a proxy indices to reconstruct past summer monsoon variability. Low values of L* possibly indicate a relatively high organic matter and a strengthening signal of East Asian summer monsoon, and vice versa. These results suggest that quantitative color determination of sand-paleosol sequences using a colorimeter could provide a new clue to understand the East Asian summer monsoon changes.
2016, 34(1): 79-89.
doi: 10.14027/j.cnki.cjxb.2016.01.007
Abstract:
Influenced by transgressions, the shallow strata of Quaternary has a complicated sedimentary evolution in Guangrao area, the inland of Southwest Bohai Sea since Late Pleistocene. Below the surface of 30 meters, it mainly deposits loess in the south of the area, while in the north of the area, it mainly deposits two marine layers, which were respectively named the first transgression layer and the second transgression layer. The first transgression layer is Huanghua transgression layer of 10~4 ka B.P., while the second transgression layer is Xianxian transgression layer of 40~28 ka B.P. According to 4 drilling coring Wells and 88 static sounding wells studied the transgression evolution and loess of the area by using modern test methods (particle size analysis, heavy mineral analysis, 14C dating, geochemical tests) and stratigraphic correlation. The loess layer deposited in late Pleistocene, and can be divided into Dazhan formation and Yanglanhe formation in the south of area on the depth boundary of 17 meters. It had two transgression events (Huanghua transgression and Xianxian transgression) since late Pleistocene and came to the area in the maximum transgression time. Because of the erosion and modification of the two transgressive events, it had formed the transgressive evolution model of "transgression overlap the loess". According to the paleoclimate change which math to transgression and loess deposition evolution, climate change of the area can be divided into six periods since Late Pleistocene, including cold dry climate, warm humid climate, cold dry but slants cool climate, warm climate, moist climate and modern climate. Different type of climate corresponds to different feature of sedimentary evolution.
Influenced by transgressions, the shallow strata of Quaternary has a complicated sedimentary evolution in Guangrao area, the inland of Southwest Bohai Sea since Late Pleistocene. Below the surface of 30 meters, it mainly deposits loess in the south of the area, while in the north of the area, it mainly deposits two marine layers, which were respectively named the first transgression layer and the second transgression layer. The first transgression layer is Huanghua transgression layer of 10~4 ka B.P., while the second transgression layer is Xianxian transgression layer of 40~28 ka B.P. According to 4 drilling coring Wells and 88 static sounding wells studied the transgression evolution and loess of the area by using modern test methods (particle size analysis, heavy mineral analysis, 14C dating, geochemical tests) and stratigraphic correlation. The loess layer deposited in late Pleistocene, and can be divided into Dazhan formation and Yanglanhe formation in the south of area on the depth boundary of 17 meters. It had two transgression events (Huanghua transgression and Xianxian transgression) since late Pleistocene and came to the area in the maximum transgression time. Because of the erosion and modification of the two transgressive events, it had formed the transgressive evolution model of "transgression overlap the loess". According to the paleoclimate change which math to transgression and loess deposition evolution, climate change of the area can be divided into six periods since Late Pleistocene, including cold dry climate, warm humid climate, cold dry but slants cool climate, warm climate, moist climate and modern climate. Different type of climate corresponds to different feature of sedimentary evolution.
2016, 34(1): 90-101.
doi: 10.14027/j.cnki.cjxb.2016.01.008
Abstract:
Based on 54 new drilled holes in shallow layer and a plurality of outcrops, combined with grain size of sediments, thin sections, microfossils, plant pollen, 14C dating, and static cone penetration test, stratigraphic structures and sedimentary types during late Quaternary in Lubei Plain was studied, and sedimentary evolution after terminal late Pleistocene was summarized. The results showed that, from pleniglacial of the last glacial period to the post glacial period, sea transgression and regression and channel migration of the Yellow River affected by topography and climate change were the main factors influencing shallow stratigraphic structures and sedimentary characters. Differences between the southern and northern stratum structure were obviously. Paleochannels, lakes and marshes, loess, deltas, tidal flats, and littoral-neritic sea developed. The distribution area of paleochannels was largest among them, which were divided into three layers. From terminal late Pleistocene to the early stage of early Holocene, influenced by the dry and cold climate, the first period paleochannels developed, and loess deposited to the south of Xiaoqing River. From the late stage of early Holocene to the middle Holocene, transgression layer and deltas developed in the coastal area, while lakes and marshes and the second period paleochannels developed successively in the inland area. After the last stage of middle Holocene or the late Holocene, influenced by flood of Yellow River, the third period paleochannels and the modern Yellow River delta deposited. The studies of stratigraphic structures and sediments distribution have important guide significance to the analysis on the changes of underground water level and selecting the appropriate seismic excitation layer.
Based on 54 new drilled holes in shallow layer and a plurality of outcrops, combined with grain size of sediments, thin sections, microfossils, plant pollen, 14C dating, and static cone penetration test, stratigraphic structures and sedimentary types during late Quaternary in Lubei Plain was studied, and sedimentary evolution after terminal late Pleistocene was summarized. The results showed that, from pleniglacial of the last glacial period to the post glacial period, sea transgression and regression and channel migration of the Yellow River affected by topography and climate change were the main factors influencing shallow stratigraphic structures and sedimentary characters. Differences between the southern and northern stratum structure were obviously. Paleochannels, lakes and marshes, loess, deltas, tidal flats, and littoral-neritic sea developed. The distribution area of paleochannels was largest among them, which were divided into three layers. From terminal late Pleistocene to the early stage of early Holocene, influenced by the dry and cold climate, the first period paleochannels developed, and loess deposited to the south of Xiaoqing River. From the late stage of early Holocene to the middle Holocene, transgression layer and deltas developed in the coastal area, while lakes and marshes and the second period paleochannels developed successively in the inland area. After the last stage of middle Holocene or the late Holocene, influenced by flood of Yellow River, the third period paleochannels and the modern Yellow River delta deposited. The studies of stratigraphic structures and sediments distribution have important guide significance to the analysis on the changes of underground water level and selecting the appropriate seismic excitation layer.
2016, 34(1): 102-110.
doi: 10.14027/j.cnki.cjxb.2016.01.009
Abstract:
The North Yellow Sea is a typical semi-enclosed epicontinental sea and is characterized by strong land-sea interaction and paleoenvironmental changes during the Late Quaternary with sea-level fluctuations. In this study, based upon analysis of lithology, grain-size, micropaleontology and AMS14C dating for Core DLC70-2, located in the central shelf of the North Yellow Sea (NYS), the paleo-environmental evolution can be ascertained. The study suggests that the sedimentary environmental evolution in the central shelf of NYS since mid-MIS3, which was well corresponding to the relative sea level changes, shows prominent multistage characteristics. From 22.89 m to 18.50 m (43 639~42 558 cal yr B.P.), an estuarine facies, developed by sea level rise in the middle of MIS3, and there exists an apparent sedimentary hiatus between the facies and its overlying strata. The seawater arrived at the study area since 14 602 cal yr B.P. and a 18.50 m thick sediment formed from then on, which can be divided into estuarine filling facies (18.50~10.02 m, 14 602~12 602 cal yr B.P.), riverine floodplain facies (10.02~5.10 m, 12 602~10 357 cal yr B.P.)and littoral- neritic facies (5.10~0 m, 10 357~4 913 cal yr B.P.) from the bottom up, corresponding to the process of sea level rising since Last Glacial Maximum, the short stagnated period of sea level during the Younger Dryas event, and the process of sea level rising during the early-middle Holocene, respectively. The section from 10.02 m to 5.10 m (12 602~10 357 cal yr B.P.), a hard clay, the result of the riverine floodplain, may be closely correlated with the global impact of Younger Dryas event and can be regard as a significant evidence of the response of the NYS area to it.
The North Yellow Sea is a typical semi-enclosed epicontinental sea and is characterized by strong land-sea interaction and paleoenvironmental changes during the Late Quaternary with sea-level fluctuations. In this study, based upon analysis of lithology, grain-size, micropaleontology and AMS14C dating for Core DLC70-2, located in the central shelf of the North Yellow Sea (NYS), the paleo-environmental evolution can be ascertained. The study suggests that the sedimentary environmental evolution in the central shelf of NYS since mid-MIS3, which was well corresponding to the relative sea level changes, shows prominent multistage characteristics. From 22.89 m to 18.50 m (43 639~42 558 cal yr B.P.), an estuarine facies, developed by sea level rise in the middle of MIS3, and there exists an apparent sedimentary hiatus between the facies and its overlying strata. The seawater arrived at the study area since 14 602 cal yr B.P. and a 18.50 m thick sediment formed from then on, which can be divided into estuarine filling facies (18.50~10.02 m, 14 602~12 602 cal yr B.P.), riverine floodplain facies (10.02~5.10 m, 12 602~10 357 cal yr B.P.)and littoral- neritic facies (5.10~0 m, 10 357~4 913 cal yr B.P.) from the bottom up, corresponding to the process of sea level rising since Last Glacial Maximum, the short stagnated period of sea level during the Younger Dryas event, and the process of sea level rising during the early-middle Holocene, respectively. The section from 10.02 m to 5.10 m (12 602~10 357 cal yr B.P.), a hard clay, the result of the riverine floodplain, may be closely correlated with the global impact of Younger Dryas event and can be regard as a significant evidence of the response of the NYS area to it.
2016, 34(1): 111-119.
doi: 10.14027/j.cnki.cjxb.2016.01.010
Abstract:
Lying on the northwest of Nihewan Basin, Houjiayao Site (40°06'2.0"N, 113°58'40.7"E) was discovered 40 years ago. But there is still a controversy about the existence age and the living environment of Houjiayao ancient human. Based on the geological investigations, electrical resistivity sounding and altitude measuring, this paper attempts to do a research on stratigraphic structure and the development of the ancient river in Houjiayao Site, and to interpret the above problems. The results are as follows: ①An ancient river, which came from Xionger mountain in the north of the Site, developed in Houjiayao Site, and its width was more than 1 km. The ancient river formed before 240 ka B.P., and disappeared in the early stage of the late Pleistocene, and its developing history ran through the entire living stage of Houjiayao ancient human. ②The Site cultural relics were not buried in the lacustrine facies, but in the oxbow lake sediments of the ancient river and clay layer which lay on the oxbow lake sediments unconformably during the period of 224~161 ka B.P., and it indicates that the Houjiayao ancient people lived here for as long as 60 ka years. ③The Site looks like a wide armchair faced southeast, and it provided a relatively mild and comfortable environment for the ancient. The ancient river provided the ancient human with water, and the superior eco-environment also provided plentiful food for the ancient human. Xionger mountain was not only the source of the ancient river, but also the producing area for high quality stone materials. The old river carried stone materials to the Site, making it easier to make stone implements. Hence, the ancient human, who lived in cold weather, were more likely to choose better habitats such as the Houjiayao Site near the ancient river. ④The old river embedded in the lacustrine facies, so the content of silt was high, and it was feculent. And the water of the oxbow lake near Houjiayao Site was clear and slow. What's more, with plentiful plants, the oxbow lake was a preferred place for all kinds of animals to get food and water. But the geomorphologic features of this oxbow lake made it hard for animals to escape when faced with dangerous situations. So ancient human had a better chance to get food from hunting near the oxbow lake than in other areas.
Lying on the northwest of Nihewan Basin, Houjiayao Site (40°06'2.0"N, 113°58'40.7"E) was discovered 40 years ago. But there is still a controversy about the existence age and the living environment of Houjiayao ancient human. Based on the geological investigations, electrical resistivity sounding and altitude measuring, this paper attempts to do a research on stratigraphic structure and the development of the ancient river in Houjiayao Site, and to interpret the above problems. The results are as follows: ①An ancient river, which came from Xionger mountain in the north of the Site, developed in Houjiayao Site, and its width was more than 1 km. The ancient river formed before 240 ka B.P., and disappeared in the early stage of the late Pleistocene, and its developing history ran through the entire living stage of Houjiayao ancient human. ②The Site cultural relics were not buried in the lacustrine facies, but in the oxbow lake sediments of the ancient river and clay layer which lay on the oxbow lake sediments unconformably during the period of 224~161 ka B.P., and it indicates that the Houjiayao ancient people lived here for as long as 60 ka years. ③The Site looks like a wide armchair faced southeast, and it provided a relatively mild and comfortable environment for the ancient. The ancient river provided the ancient human with water, and the superior eco-environment also provided plentiful food for the ancient human. Xionger mountain was not only the source of the ancient river, but also the producing area for high quality stone materials. The old river carried stone materials to the Site, making it easier to make stone implements. Hence, the ancient human, who lived in cold weather, were more likely to choose better habitats such as the Houjiayao Site near the ancient river. ④The old river embedded in the lacustrine facies, so the content of silt was high, and it was feculent. And the water of the oxbow lake near Houjiayao Site was clear and slow. What's more, with plentiful plants, the oxbow lake was a preferred place for all kinds of animals to get food and water. But the geomorphologic features of this oxbow lake made it hard for animals to escape when faced with dangerous situations. So ancient human had a better chance to get food from hunting near the oxbow lake than in other areas.
2016, 34(1): 120-128.
doi: 10.14027/j.cnki.cjxb.2016.01.011
Abstract:
Based on the core, well log curvies, seismic, sample testing data as well as the basic theory of sedimentology, the distribution law of the Nantun Formation in four mainly depressions in the middle fault zone of Hailaer-Tamt sag is studied. The results show that Nantun Formation developed fan delta, nearshore subaqueous fans,braided river delta and sublacustrine fan, their sedimentary characteristics and identification mark are analysed form depositional setting, development position, sedimentary characteristics, transport mechanism and seismic reflection characteristic. Fan delta mainly developed in the steep slope zone of Wuerxun and Beier sags, nearshore subaqueous fans mainly developed in the steep slope zone of tanan and nanbeier sags.,braided river delta mainly developed in the gentle slope of Wuerxun, Beier and nanbeier sags. Form the edge to the center of the basin, sedimentary facies change form fan delta to nearshore subaqueous fans then to half deep lake-deep subfacies, Sublacustrine fan developed in some part of the half deep -deep lake area,with the whole deposition pattern of" north and south block, east and west belts". Fan delta front subfacies, braided river delta front subfacies and middle fan of nearshore subaqueous fans are the important hydrocarbon accumulation zones. Sublacustrine fan is favorable objects of lithologic reservoir exploration.
Based on the core, well log curvies, seismic, sample testing data as well as the basic theory of sedimentology, the distribution law of the Nantun Formation in four mainly depressions in the middle fault zone of Hailaer-Tamt sag is studied. The results show that Nantun Formation developed fan delta, nearshore subaqueous fans,braided river delta and sublacustrine fan, their sedimentary characteristics and identification mark are analysed form depositional setting, development position, sedimentary characteristics, transport mechanism and seismic reflection characteristic. Fan delta mainly developed in the steep slope zone of Wuerxun and Beier sags, nearshore subaqueous fans mainly developed in the steep slope zone of tanan and nanbeier sags.,braided river delta mainly developed in the gentle slope of Wuerxun, Beier and nanbeier sags. Form the edge to the center of the basin, sedimentary facies change form fan delta to nearshore subaqueous fans then to half deep lake-deep subfacies, Sublacustrine fan developed in some part of the half deep -deep lake area,with the whole deposition pattern of" north and south block, east and west belts". Fan delta front subfacies, braided river delta front subfacies and middle fan of nearshore subaqueous fans are the important hydrocarbon accumulation zones. Sublacustrine fan is favorable objects of lithologic reservoir exploration.
2016, 34(1): 129-136.
doi: 10.14027/j.cnki.cjxb.2016.01.012
Abstract:
The climate was relatively wet, terrain was relatively flat, water power was relatively strong, the source of supply was adequate, lakeshore line relatively frequent changes of the Badaowan Formation sedimentary period of the Mosuowan area in the Central depression of Junggar Basin, which can form shallow-water delta. Sedimentary sandbody that is formed many positive cycle sedimentary sequences vertically mainly fine and medium-fine sandstone, which is the relatively fine grain size. The delta front has a wide distribution, long extension, large area and its planar configurations are major foliaceous, which are consist of compound sandbodies by multi-subaqueous distributary channel sandbody cut and superimposition. Thick, substantial and good connectivity subaqueous distributary channel sandbodies which are vertical superimposition and transverse cut each other are well developed, shale interbeds are relative thin and mouth bar sand body is not developed. The sandbody superimposition modes can be divided into different types, which is the major petroleum reservoir. On the whole, it formed the far-source, widespread, fine-grain shallow-water delta sedimentary system. The deposition and range of delta front and subaqueous distributary channel sandbody that are from two different source direction are different in different period, which is formed shallow-water delta that is mainly composed of wide composite channel sandbody finally.
The climate was relatively wet, terrain was relatively flat, water power was relatively strong, the source of supply was adequate, lakeshore line relatively frequent changes of the Badaowan Formation sedimentary period of the Mosuowan area in the Central depression of Junggar Basin, which can form shallow-water delta. Sedimentary sandbody that is formed many positive cycle sedimentary sequences vertically mainly fine and medium-fine sandstone, which is the relatively fine grain size. The delta front has a wide distribution, long extension, large area and its planar configurations are major foliaceous, which are consist of compound sandbodies by multi-subaqueous distributary channel sandbody cut and superimposition. Thick, substantial and good connectivity subaqueous distributary channel sandbodies which are vertical superimposition and transverse cut each other are well developed, shale interbeds are relative thin and mouth bar sand body is not developed. The sandbody superimposition modes can be divided into different types, which is the major petroleum reservoir. On the whole, it formed the far-source, widespread, fine-grain shallow-water delta sedimentary system. The deposition and range of delta front and subaqueous distributary channel sandbody that are from two different source direction are different in different period, which is formed shallow-water delta that is mainly composed of wide composite channel sandbody finally.
Characteristics and Main Controlling Factor of the Upper Cretaceous Sarvak Reservoir, SouthWest Iran
2016, 34(1): 137-148.
doi: 10.14027/j.cnki.cjxb.2016.01.013
Abstract:
This paper studys on the characteristics and main controlling factors of the upper Cretaceous Sarvak reservoir by the coring, section, SEM, well logging and 3D seismic data. The study area is the Azadegan oilfield of the SouthWest, Iran and which situated in the "hot zone" of the Zagros foreland basin nowadays. The main lithology of the Sarvak is the limestone and chalk limestone which is abundant of the rudist, foraminifer debris. The reservoir is influenced by the multi-stage of the karstification effect and the effect reservoir space is the moldic pore, cavern, vug, and mud matrix dissolved pore. According to the MISC, por-per relationship and lithology, we divided the reservoir into four types that are vug-pore, fracture-pore, matrix pore and non-reservoir. The optimum is the vug-pore and the mainly is the rudist bearing reservoir, and the secondary reservoir is the fracture-pore and the matrix pore reservoir, and mainly is the foraminifer bearing chalk limestone. The reservoir main controlling factor are the 3rd Squence boundary, palaeogeomorphology of the depositional time and rock fracturing by the multi-stage tectonic activities. The Squence boundary control the vertical position of optimum reservoir, the palaeogeomorphology control the lateral reservoir quality distribution, and the rock fracturing control the oiliness property of the chalky limestone. According to these findings, we propose the development suggestions as below: Clearing the 3rd sequence boundary of inner formation and the paleo-high of depositional time is the critical factors to select the favorable vertical develop zone and lateral develop area. The reservoir quality and oiliness of the thick chalk limestone is influenced by the rock fracturing, and is more unstable compare with the reservoir zone near the sequence boundary. So, at the early stage of the field development, we should consider the grading evaluation criteria in the reserves calculation.
This paper studys on the characteristics and main controlling factors of the upper Cretaceous Sarvak reservoir by the coring, section, SEM, well logging and 3D seismic data. The study area is the Azadegan oilfield of the SouthWest, Iran and which situated in the "hot zone" of the Zagros foreland basin nowadays. The main lithology of the Sarvak is the limestone and chalk limestone which is abundant of the rudist, foraminifer debris. The reservoir is influenced by the multi-stage of the karstification effect and the effect reservoir space is the moldic pore, cavern, vug, and mud matrix dissolved pore. According to the MISC, por-per relationship and lithology, we divided the reservoir into four types that are vug-pore, fracture-pore, matrix pore and non-reservoir. The optimum is the vug-pore and the mainly is the rudist bearing reservoir, and the secondary reservoir is the fracture-pore and the matrix pore reservoir, and mainly is the foraminifer bearing chalk limestone. The reservoir main controlling factor are the 3rd Squence boundary, palaeogeomorphology of the depositional time and rock fracturing by the multi-stage tectonic activities. The Squence boundary control the vertical position of optimum reservoir, the palaeogeomorphology control the lateral reservoir quality distribution, and the rock fracturing control the oiliness property of the chalky limestone. According to these findings, we propose the development suggestions as below: Clearing the 3rd sequence boundary of inner formation and the paleo-high of depositional time is the critical factors to select the favorable vertical develop zone and lateral develop area. The reservoir quality and oiliness of the thick chalk limestone is influenced by the rock fracturing, and is more unstable compare with the reservoir zone near the sequence boundary. So, at the early stage of the field development, we should consider the grading evaluation criteria in the reserves calculation.
2016, 34(1): 149-157.
doi: 10.14027/j.cnki.cjxb.2016.01.014
Abstract:
The petroleum exploration of Junggar Basin shows that there exist serious heterogeneity in Bai 2 reservoir of Mabei region, and it is necessary to identify the types of reservoir in consideration of a mass of geological factors that influence reservoir quality. Using core observation, thin section, logging and drilling data, physical property data, CT data, etc., the sedimentary facies, diagenetic facies and fracture facies of the Upper Triassic Baikouquan Formation Member 2 (Bai 2) reservoir in the Ma 131 region were studied. On this basis, the petrophysical faices of Bai 2 layers were examined to evaluate the pore structure by classification and predict zones with high porosity and permeability. The petrophysical facies were divided according to the superposition and combination of sedimentary facies, diagenetic facies. A number of petrophysical facies of Bai 2 layers such as underwater distributary channel, dissolution of unstable components, were identified in this way. Three main categories of petrophysical facies were summed up according to the constructive and destructive impact of sedimentary facies, diagenetic facies on the reservoir property and pore structure of Bai 2 layers. According to three petrophysical facies, the reservoir of Bai 2 can be divided into three categories. Based on mercury injection data, casting thin section, CT data and oil capacity data, reservoir of each categories was characterized and evaluated. At last, the horizontal distribution of different petrophysical facies were mapped, and it can be used to predict the beneficial zones.
The petroleum exploration of Junggar Basin shows that there exist serious heterogeneity in Bai 2 reservoir of Mabei region, and it is necessary to identify the types of reservoir in consideration of a mass of geological factors that influence reservoir quality. Using core observation, thin section, logging and drilling data, physical property data, CT data, etc., the sedimentary facies, diagenetic facies and fracture facies of the Upper Triassic Baikouquan Formation Member 2 (Bai 2) reservoir in the Ma 131 region were studied. On this basis, the petrophysical faices of Bai 2 layers were examined to evaluate the pore structure by classification and predict zones with high porosity and permeability. The petrophysical facies were divided according to the superposition and combination of sedimentary facies, diagenetic facies. A number of petrophysical facies of Bai 2 layers such as underwater distributary channel, dissolution of unstable components, were identified in this way. Three main categories of petrophysical facies were summed up according to the constructive and destructive impact of sedimentary facies, diagenetic facies on the reservoir property and pore structure of Bai 2 layers. According to three petrophysical facies, the reservoir of Bai 2 can be divided into three categories. Based on mercury injection data, casting thin section, CT data and oil capacity data, reservoir of each categories was characterized and evaluated. At last, the horizontal distribution of different petrophysical facies were mapped, and it can be used to predict the beneficial zones.
2016, 34(1): 158-167.
doi: 10.14027/j.cnki.cjxb.2016.01.015
Abstract:
Based on the core, casting thin section, SEM, cathodeluminescence and petrophysical properties analysis data, the characteristics of the Es3x nearshore subaqueous fan reservoir in the steep slope zone of Western Chezhen Sub-sag are discussed. The results show that lithology types are mainly the mud matrix-supported conglomerate, clast-supported conglomerate, pebbly sandstone and so on at macro level, and the microscopic lithology types are showed as lithic sandstone and feldspathic lithic sandstone and their plaster matrix content can be up to 40% for the nearshore subaqueous fan reservoir of Es3X in the steep slope zone of the Western Chezhen sub-sag. The nearshore subaqueous fan reservoir is characterized with extremely low porosity and permeability, and their porosity and permeability are respectively 3.42%, 2.02×10-3 μm2, but there is an abnormal high porosity zone between 3 500 m and 4 000 m in the verticle section, where the porosity can be 10.2% and the reservoir space are mainly dissolved pores and micro-fractures. The reservoir had experienced complex diagenesis in the study area and it is in the B sub-stage of middle diagenesis. The reservoir diagenesis evolution sequence in the study area is as follows: compaction/carbonate cementation→ dissolution of feldspars and carbonate cements→dissolution of quartz/carbonate cementation/plaster recrystallization→quartz overgrowth/carbonate cementation dissolution→carbonate cementation. The different sub-facies of the nearshore subaqueous fan had experienced different diagenesis evolution, because the middle- distal zones of the braided channel of the middle fan and middle fan front had experienced multi-period dissolution, the relative reservoir quality is very good and their average porosity respectively are 4.5% and 7.25%, which can be regarded as the "sweet spot" of the nearshore subaqueous fan glutinite reservoir in the steep slope zone of the Western Chezhen sub-sag.
Based on the core, casting thin section, SEM, cathodeluminescence and petrophysical properties analysis data, the characteristics of the Es3x nearshore subaqueous fan reservoir in the steep slope zone of Western Chezhen Sub-sag are discussed. The results show that lithology types are mainly the mud matrix-supported conglomerate, clast-supported conglomerate, pebbly sandstone and so on at macro level, and the microscopic lithology types are showed as lithic sandstone and feldspathic lithic sandstone and their plaster matrix content can be up to 40% for the nearshore subaqueous fan reservoir of Es3X in the steep slope zone of the Western Chezhen sub-sag. The nearshore subaqueous fan reservoir is characterized with extremely low porosity and permeability, and their porosity and permeability are respectively 3.42%, 2.02×10-3 μm2, but there is an abnormal high porosity zone between 3 500 m and 4 000 m in the verticle section, where the porosity can be 10.2% and the reservoir space are mainly dissolved pores and micro-fractures. The reservoir had experienced complex diagenesis in the study area and it is in the B sub-stage of middle diagenesis. The reservoir diagenesis evolution sequence in the study area is as follows: compaction/carbonate cementation→ dissolution of feldspars and carbonate cements→dissolution of quartz/carbonate cementation/plaster recrystallization→quartz overgrowth/carbonate cementation dissolution→carbonate cementation. The different sub-facies of the nearshore subaqueous fan had experienced different diagenesis evolution, because the middle- distal zones of the braided channel of the middle fan and middle fan front had experienced multi-period dissolution, the relative reservoir quality is very good and their average porosity respectively are 4.5% and 7.25%, which can be regarded as the "sweet spot" of the nearshore subaqueous fan glutinite reservoir in the steep slope zone of the Western Chezhen sub-sag.
2016, 34(1): 168-180.
doi: 10.14027/j.cnki.cjxb.2016.01.016
Abstract:
The third member of Feixianguan Formation (T1f3) is an important gas reservoir in the Jiannan area which consists mainly of tight grainstones and crystalline dolostones. However, the high quality reservoir is limited in the dolostones. Therefore, understanding the distribution mechanism of dolostones is prerequisite to predict the distribution of high-quality reservoir. In this study, the dolomite-content logs were firstly constructed based on the well logs and cores. Secondly, the correlation between dolomite-contents and seismic attributes derived from 3-D seismic volume were defined using the method of multiattribute transforms to predict the distribution of dolomite in the Jiannan area. At last, the predicted dolomite distribution and paleogeography were integrated to explain the source and nature of the dolomitizing fluid.
The dolostone of T1f3 in the Jiannan area consist mainly of fine-grained, planar-e to planar-s crystals, and minor nonplanar crystals. Under CL, dolomite crystals show zoned to uniform dull red luminescence. Five most effective attributes were selected based on the method of multiattribute transforms. These attributes are Amplitude Weighted Frequency, Amplitude Weighted Cosine Phase, Amplitude Envelope, Quadrature Trace and Instantaneous Phase. Integration dolomite distribution and paleogeography indicates that dolomites mainly occur along the opposing margins of a trough. During progressively burial, owing to the increase in pore pressure and different compactability of sediments, Mg-rich, seawater-derived, compaction flow from trough sediments moved laterally and preferentially through less rapidly compacting, trough-margin shoals, which caused extensive dolomitization in shoals. Shoals along margins of the trough can be recognized as important exploration targets.
The third member of Feixianguan Formation (T1f3) is an important gas reservoir in the Jiannan area which consists mainly of tight grainstones and crystalline dolostones. However, the high quality reservoir is limited in the dolostones. Therefore, understanding the distribution mechanism of dolostones is prerequisite to predict the distribution of high-quality reservoir. In this study, the dolomite-content logs were firstly constructed based on the well logs and cores. Secondly, the correlation between dolomite-contents and seismic attributes derived from 3-D seismic volume were defined using the method of multiattribute transforms to predict the distribution of dolomite in the Jiannan area. At last, the predicted dolomite distribution and paleogeography were integrated to explain the source and nature of the dolomitizing fluid.
The dolostone of T1f3 in the Jiannan area consist mainly of fine-grained, planar-e to planar-s crystals, and minor nonplanar crystals. Under CL, dolomite crystals show zoned to uniform dull red luminescence. Five most effective attributes were selected based on the method of multiattribute transforms. These attributes are Amplitude Weighted Frequency, Amplitude Weighted Cosine Phase, Amplitude Envelope, Quadrature Trace and Instantaneous Phase. Integration dolomite distribution and paleogeography indicates that dolomites mainly occur along the opposing margins of a trough. During progressively burial, owing to the increase in pore pressure and different compactability of sediments, Mg-rich, seawater-derived, compaction flow from trough sediments moved laterally and preferentially through less rapidly compacting, trough-margin shoals, which caused extensive dolomitization in shoals. Shoals along margins of the trough can be recognized as important exploration targets.
2016, 34(1): 181-190.
doi: 10.14027/j.cnki.cjxb.2016.01.017
Abstract:
The distributions and compositions of normal alkanes were analyzed in the Precambrian- Lower Paleozoic post-mature marine source rocks from seven outcrop sections and two drilling sections and solid bitumen from Yankong paleo-reservoir in the northern Guizhou depression. It was found that the bimodal distributions of normal alkanes are very common, and nC17 and nC25 is main peak for the former and later peak groups, respectively. However, no odd or even carbon predominance can be observed in every peak group. This phenomenon occurs also in the similar post-mature geological samples from other areas and the products of thermal simulation from the Proterozoic source rocks. Therefore, the bimodal distributions of n-alkanes should be an objective geochemical phenomenon in the related post-mature source rocks. Two parameters such as FCPR and LCPR can be used to describe the distributions of normal alkanes in these source rocks and solid bitumen. When they are more than 1.0, normal alkanes have a bimodal distribution. Considering that these geological samples are very old, in which sedimentary organic matter should be mainly derived from various algae and bacteria rich in hydrogen and long chain aliphatic structures, they are an important sources of long chain alkanes in these related source rocks. In addition, Organic matter in a geological sample exists in very complicate and diverse forms such as free and bound, differential maturation for these different organic matter will occur. At this time, the mixture of normal alkanes derived from different organic matter may happen and result in the bimodal distribution of normal alkanes. Therefore, it may be used as a potential indicator to indicate strongly thermal maturation for organic matter from lower organisms such as algae.
The distributions and compositions of normal alkanes were analyzed in the Precambrian- Lower Paleozoic post-mature marine source rocks from seven outcrop sections and two drilling sections and solid bitumen from Yankong paleo-reservoir in the northern Guizhou depression. It was found that the bimodal distributions of normal alkanes are very common, and nC17 and nC25 is main peak for the former and later peak groups, respectively. However, no odd or even carbon predominance can be observed in every peak group. This phenomenon occurs also in the similar post-mature geological samples from other areas and the products of thermal simulation from the Proterozoic source rocks. Therefore, the bimodal distributions of n-alkanes should be an objective geochemical phenomenon in the related post-mature source rocks. Two parameters such as FCPR and LCPR can be used to describe the distributions of normal alkanes in these source rocks and solid bitumen. When they are more than 1.0, normal alkanes have a bimodal distribution. Considering that these geological samples are very old, in which sedimentary organic matter should be mainly derived from various algae and bacteria rich in hydrogen and long chain aliphatic structures, they are an important sources of long chain alkanes in these related source rocks. In addition, Organic matter in a geological sample exists in very complicate and diverse forms such as free and bound, differential maturation for these different organic matter will occur. At this time, the mixture of normal alkanes derived from different organic matter may happen and result in the bimodal distribution of normal alkanes. Therefore, it may be used as a potential indicator to indicate strongly thermal maturation for organic matter from lower organisms such as algae.
2016, 34(1): 191-199.
doi: 10.14027/j.cnki.cjxb.2016.01.018
Abstract:
Relatively high abundances of the 17α(H)-diahopanes and early-eluting rearranged hopanes were found in coal-bearing source rocks from upper palaeozoic sediments in northeast Ordos Basin. On the basis of the characteristics of rearranged hopanes and their distributions, combined with the compounds of the other biomarkers, aromatic hydrocarbons were applied to discuss the origin of rearranged hopanes. The distribution patterns of saturated hydrocarbons show that rearranged hopanes are related to terrigenous higher plants, and a weak oxidizing environment contributes to their formation. Source rocks, which contain high-abnoraml high abundances of 17α(H)-diahopanes and early-eluting rearranged hopanes (C30*/C30H > 0.2, C30E/C30H > 0.1), are characterized by relatively high concentrations of bicyclic and tricyclic aromatic hydrocarbons (> 50 %) and relatively low concentrations of tetracyclic and pentacyclic aromatic hydrocarbons (< 35%). In addition, aromatic terpenoids and steroids are absent which shows a origin of terrigenous higher plants in source rocks. The characteristics of methylphenanthrenes (MPI1, MPI2 and F1) illustrate that rearranged hopanes in source rocks deposited in a weak oxidizing condition (Pr/Ph>1) mainly form in a mature stage, and their contents increase with the thermal maturity. However, source rocks deposited in a reductive environment (Pr/Ph<1) contain relatively low contents of rearranged hopanes and also increase with the thermal maturity. The parameters of dibenzothiophene, dibenzofuran and fluorine indicate that a weak oxidizing sedimentary environment is important to the formation of 17α(H)-diahopanes and early-eluting rearranged hopanes. A swamp environment is the most helpful to their formation.
Relatively high abundances of the 17α(H)-diahopanes and early-eluting rearranged hopanes were found in coal-bearing source rocks from upper palaeozoic sediments in northeast Ordos Basin. On the basis of the characteristics of rearranged hopanes and their distributions, combined with the compounds of the other biomarkers, aromatic hydrocarbons were applied to discuss the origin of rearranged hopanes. The distribution patterns of saturated hydrocarbons show that rearranged hopanes are related to terrigenous higher plants, and a weak oxidizing environment contributes to their formation. Source rocks, which contain high-abnoraml high abundances of 17α(H)-diahopanes and early-eluting rearranged hopanes (C30*/C30H > 0.2, C30E/C30H > 0.1), are characterized by relatively high concentrations of bicyclic and tricyclic aromatic hydrocarbons (> 50 %) and relatively low concentrations of tetracyclic and pentacyclic aromatic hydrocarbons (< 35%). In addition, aromatic terpenoids and steroids are absent which shows a origin of terrigenous higher plants in source rocks. The characteristics of methylphenanthrenes (MPI1, MPI2 and F1) illustrate that rearranged hopanes in source rocks deposited in a weak oxidizing condition (Pr/Ph>1) mainly form in a mature stage, and their contents increase with the thermal maturity. However, source rocks deposited in a reductive environment (Pr/Ph<1) contain relatively low contents of rearranged hopanes and also increase with the thermal maturity. The parameters of dibenzothiophene, dibenzofuran and fluorine indicate that a weak oxidizing sedimentary environment is important to the formation of 17α(H)-diahopanes and early-eluting rearranged hopanes. A swamp environment is the most helpful to their formation.
2016, 34(1): 200-206.
doi: 10.14027/j.cnki.cjxb.2016.01.019
Abstract:
Considering the organic carbon in the acid solution, a new method is presented for measuring organic carbon in carbonate. It utilizes turface to thicken the residue& acid solution, then the carbon content of sample is analyzed by Elements Analyzer. We prepared standard samples (CaCO3+SiO2+ organic materials) to have common TOC test and new method test. Results showed: The common TOC test of standard samples which added acetic acid, calcium acetate, phenylformic acid and calcium benzoate showed a high relative error in TOC value from 98.50% to 99.66%; The common TOC test of standard samples which added stearic acid, calcium stearate, I-II type kerogen and II-III type kerogen showed a lower relative error in TOC value from 11.90% to 48.12%;The new TOC method test showed a lowest relative error in TOC value from 0.76% to 19.46%. The new TOC method test of standard samples with different TOC Theoretical values showed that the relative error decreased with TOC concentration increasing. Because of mixing and thickening the residue and acid solution after removing the inorganic carbon in initial step, it avoided the organic carbon from loss and could accurately quantify TOC value.
Considering the organic carbon in the acid solution, a new method is presented for measuring organic carbon in carbonate. It utilizes turface to thicken the residue& acid solution, then the carbon content of sample is analyzed by Elements Analyzer. We prepared standard samples (CaCO3+SiO2+ organic materials) to have common TOC test and new method test. Results showed: The common TOC test of standard samples which added acetic acid, calcium acetate, phenylformic acid and calcium benzoate showed a high relative error in TOC value from 98.50% to 99.66%; The common TOC test of standard samples which added stearic acid, calcium stearate, I-II type kerogen and II-III type kerogen showed a lower relative error in TOC value from 11.90% to 48.12%;The new TOC method test showed a lowest relative error in TOC value from 0.76% to 19.46%. The new TOC method test of standard samples with different TOC Theoretical values showed that the relative error decreased with TOC concentration increasing. Because of mixing and thickening the residue and acid solution after removing the inorganic carbon in initial step, it avoided the organic carbon from loss and could accurately quantify TOC value.
