2013 Vol. 31, No. 1
Display Method:
2013, 31(1): 1-9.
Abstract:
Oncoids are well preserved in the Chuanshan Formation in Majiaoba, Jiangyou County. Five types of core and lamina and three types of structures could be divided according to their microstructures. Five types of core are composed of bioclasts, intraclast, recrystallized bioclasts, pelletoid or early period oncoids and organic shell carbonate. Five types of lamina are commomly composed of sparry laminae, micritic laminae, clotlike laminae, micritic laminae including or alternating with layers of recognizable encrusting microfossils and porostromate laminae. Three types of structures are birdseye structure, micritization, layered structure and so on. At the same time, the relationship of the cores and laminas are discussed in the paper. The types of lamina are easy dominated by the type of core, especially the original shape of the core.Six oncoid types are distinguished by their cores, laminas and shapes, such as big ball oncoids(diameter>4mm), small ball oncoids(diameter 0.5~4 mm), longshaped oncoids(long axis and minor axis ratio>2), gibbous oncoids, irregular oncoids and combined oncoids. They are deposited in winnowed platform edge sands, open platforms or restricted platforms separately. Both the distribution of the oncoids and their forming and depositional environments are discussed in this paper. (1) Forming environments and depositional environments are inconsistent. Oncoids contents have big sizes and are cemented by sparites in the strata, laminas are more complex and thicker than cores, and constituents of core and matrix are different. The cores, which are deposited nearby open platforms with weak water power, suspended nearby winnowed platform edge sands with strong water power capturing and adhering carbonate particles. Additionally, biological clastics are seriously brokem in such samples. (2) Forming environments are not similar with depositional environments, at the same time the cores and the matrix are both composed by complete biological clasts. Medium spreaded oncoids contents have medium diameters and simple laminas and were cemented by sparites. Some biological clasts in their original places capture and adhere to carbonate particles during suspended in open platforms state. （3）Forming environments are exactly same with depositional environments. The oncoids are deposited in restricted platforms, with low contents，anomalistic diameters, polytropical edges, simple laminas, low biological clastic and thin laminas.
Oncoids are well preserved in the Chuanshan Formation in Majiaoba, Jiangyou County. Five types of core and lamina and three types of structures could be divided according to their microstructures. Five types of core are composed of bioclasts, intraclast, recrystallized bioclasts, pelletoid or early period oncoids and organic shell carbonate. Five types of lamina are commomly composed of sparry laminae, micritic laminae, clotlike laminae, micritic laminae including or alternating with layers of recognizable encrusting microfossils and porostromate laminae. Three types of structures are birdseye structure, micritization, layered structure and so on. At the same time, the relationship of the cores and laminas are discussed in the paper. The types of lamina are easy dominated by the type of core, especially the original shape of the core.Six oncoid types are distinguished by their cores, laminas and shapes, such as big ball oncoids(diameter>4mm), small ball oncoids(diameter 0.5~4 mm), longshaped oncoids(long axis and minor axis ratio>2), gibbous oncoids, irregular oncoids and combined oncoids. They are deposited in winnowed platform edge sands, open platforms or restricted platforms separately. Both the distribution of the oncoids and their forming and depositional environments are discussed in this paper. (1) Forming environments and depositional environments are inconsistent. Oncoids contents have big sizes and are cemented by sparites in the strata, laminas are more complex and thicker than cores, and constituents of core and matrix are different. The cores, which are deposited nearby open platforms with weak water power, suspended nearby winnowed platform edge sands with strong water power capturing and adhering carbonate particles. Additionally, biological clastics are seriously brokem in such samples. (2) Forming environments are not similar with depositional environments, at the same time the cores and the matrix are both composed by complete biological clasts. Medium spreaded oncoids contents have medium diameters and simple laminas and were cemented by sparites. Some biological clasts in their original places capture and adhere to carbonate particles during suspended in open platforms state. （3）Forming environments are exactly same with depositional environments. The oncoids are deposited in restricted platforms, with low contents，anomalistic diameters, polytropical edges, simple laminas, low biological clastic and thin laminas.
2013, 31(1): 20-31.
Abstract:
In order to discuss depositional setting and its tectonic background of the black shale and on the base of the researched 20 profiles, we chose 20 samples collected from bottom of lower Cambrian in the north of Guizhou Province to test and analyze clay minerals, Xray diffraction of the rock minerals and trace elements (including REE). Current study shows that the main minerals are quartz whose average content are 55.75%, and clay minerals whose average content are 28.35%, Among which, the average content of illite is 59%,and the main aeceasory mineral is pyrite in the bottom of lower Cambrian in the north of Guizhou Province; ΣREE is very high and the differentiation between LREE and HREE is distinct which LREE is enriched and Eu is postive anomaly and Ce is negative anomaly; the average ratio of WV/(WNi+WV)and U/Th is respectively 0.78 and 3.76 and the depleted Ce together reflect that Black shale in the north of Guizhou Province forms in reduction environment with stable crust, transgression sea climax and open sea area；the enrichment of trace elements Mo,Sb,U,Cd, V,Ba,Tl,Ni,W,Cr,Cs,Cu,Zn,Bi，strongly depleted Sr,Re , positive Eu anomaly and the lower Co/Zn ratio of the Black shale in the north of Guizhou Province are most likely due to a hydrothermal input;. By the contrast of major elements, trace elements and REE parameters , a conclusion can drawn that in research areas source rocks are mainly sedimentary rocks and granitic rocks with a few locallyinvolved basalt components , the tectonic setting is mainly passive continental margin and partly continental island arc because of hydrothermal input.
In order to discuss depositional setting and its tectonic background of the black shale and on the base of the researched 20 profiles, we chose 20 samples collected from bottom of lower Cambrian in the north of Guizhou Province to test and analyze clay minerals, Xray diffraction of the rock minerals and trace elements (including REE). Current study shows that the main minerals are quartz whose average content are 55.75%, and clay minerals whose average content are 28.35%, Among which, the average content of illite is 59%,and the main aeceasory mineral is pyrite in the bottom of lower Cambrian in the north of Guizhou Province; ΣREE is very high and the differentiation between LREE and HREE is distinct which LREE is enriched and Eu is postive anomaly and Ce is negative anomaly; the average ratio of WV/(WNi+WV)and U/Th is respectively 0.78 and 3.76 and the depleted Ce together reflect that Black shale in the north of Guizhou Province forms in reduction environment with stable crust, transgression sea climax and open sea area；the enrichment of trace elements Mo,Sb,U,Cd, V,Ba,Tl,Ni,W,Cr,Cs,Cu,Zn,Bi，strongly depleted Sr,Re , positive Eu anomaly and the lower Co/Zn ratio of the Black shale in the north of Guizhou Province are most likely due to a hydrothermal input;. By the contrast of major elements, trace elements and REE parameters , a conclusion can drawn that in research areas source rocks are mainly sedimentary rocks and granitic rocks with a few locallyinvolved basalt components , the tectonic setting is mainly passive continental margin and partly continental island arc because of hydrothermal input.
2013, 31(1): 38-49.
Abstract:
This paper discusses the growth stages, spatial structures, quantitative fitting relationships among various parameters, growth patterns and influencing factors of mud cracks by field survey, core observation and SEM analysis. The study shows that: (1) Mud crack growth can go through three stages, i.e. syndiagenetic stage, burial diagenetic stage (including early diagenetic stage, middlelate diagenetic stage) and epidiagenetic stage in turn. The number of mud cracks in different stages is represented as Σ syndiagenesis > Σ epidiagenesis > Σ burial diagenesis. (2) Mud crack growth has three models, such as unilateral growth model including linear growth pattern, curvilineal growth pattern and bifurcation growth pattern, multilateral growth model including intersectional growth pattern, join growth pattern and dispersed growth pattern, and mixed growth model including the combination of any patterns listed above. (3) Modern mud crack growth usually undergoes four stages, among which, sand beds in sandmud rhythmic strata can play a lubricative role on crack growth, and provide enough sandy sediments for filling cracks. (4) Mud crack growth usually produces bifurcation and bifurcation angle is mostly 120, then 90, mainly related to sediment heterogeneity and released energy. (5) Factors affecting mud crack growth cover many aspects, that is to say, clay content and salinity can control the number of mud cracks in different areas, terrain can control mud crack morphology, and different sedimentary cycle can control the growth patterns and filling models of mud cracks. (6) Structure fractures can contribute to the growth and preservation of mud cracks, and they affect each other at different diagenetic stages.
This paper discusses the growth stages, spatial structures, quantitative fitting relationships among various parameters, growth patterns and influencing factors of mud cracks by field survey, core observation and SEM analysis. The study shows that: (1) Mud crack growth can go through three stages, i.e. syndiagenetic stage, burial diagenetic stage (including early diagenetic stage, middlelate diagenetic stage) and epidiagenetic stage in turn. The number of mud cracks in different stages is represented as Σ syndiagenesis > Σ epidiagenesis > Σ burial diagenesis. (2) Mud crack growth has three models, such as unilateral growth model including linear growth pattern, curvilineal growth pattern and bifurcation growth pattern, multilateral growth model including intersectional growth pattern, join growth pattern and dispersed growth pattern, and mixed growth model including the combination of any patterns listed above. (3) Modern mud crack growth usually undergoes four stages, among which, sand beds in sandmud rhythmic strata can play a lubricative role on crack growth, and provide enough sandy sediments for filling cracks. (4) Mud crack growth usually produces bifurcation and bifurcation angle is mostly 120, then 90, mainly related to sediment heterogeneity and released energy. (5) Factors affecting mud crack growth cover many aspects, that is to say, clay content and salinity can control the number of mud cracks in different areas, terrain can control mud crack morphology, and different sedimentary cycle can control the growth patterns and filling models of mud cracks. (6) Structure fractures can contribute to the growth and preservation of mud cracks, and they affect each other at different diagenetic stages.
2013, 31(1): 56-66.
Abstract:
Large scale glutenite was developed in the sedimentary period of the lower submember of first Member of Liushagang Formation of Paleogene in A well field of Weixinan Depression. Core and analysis and test data l suggest that the sandbody developed abundant sedimentary structure of Bouma cycle, erosion and loading, and the deformation structure and has the type of grain size accumulation curve of uphill arched "1 segment" pattern and line "1 segment" pattern. In vertical section, characterized by superposition of several positive cycles with the sedimentary structure of erosion and loading in the bottom, phase sequence displays the positive sequence as a whole. Sedimentary characteristics showed that the glutenite was sublacustrine fan. 3 stages of sublacustrine fan deposits have been recognized according to the seismic reflection characteristics and the patterns of superposition of verstical formation. In each stage the thickness of sand body of sublacustrine fan is well related to the seismic attribution of average peak amplitude, energy half time and instantaneous frequency. Under the constraint of high resolution sequence stratigraphic framework, combined with well drilling, logging and analysis of seismic attribution, each stage of sublacustrine fan is characterized by contstant migration and wiggle in twodimensional system, and superimposed development in the vertical evolution. The episodic activity of No.5 fault as a result of the influence of No. 0 fault and No.3 fault, led to the transformation of accommatation space. So, the unbalanced transformation of accommatation space constrainted by structure activity is the main factor controlling the distribution of sand body of sublacustrine fan of the first Member of Liushagang Formation.
Large scale glutenite was developed in the sedimentary period of the lower submember of first Member of Liushagang Formation of Paleogene in A well field of Weixinan Depression. Core and analysis and test data l suggest that the sandbody developed abundant sedimentary structure of Bouma cycle, erosion and loading, and the deformation structure and has the type of grain size accumulation curve of uphill arched "1 segment" pattern and line "1 segment" pattern. In vertical section, characterized by superposition of several positive cycles with the sedimentary structure of erosion and loading in the bottom, phase sequence displays the positive sequence as a whole. Sedimentary characteristics showed that the glutenite was sublacustrine fan. 3 stages of sublacustrine fan deposits have been recognized according to the seismic reflection characteristics and the patterns of superposition of verstical formation. In each stage the thickness of sand body of sublacustrine fan is well related to the seismic attribution of average peak amplitude, energy half time and instantaneous frequency. Under the constraint of high resolution sequence stratigraphic framework, combined with well drilling, logging and analysis of seismic attribution, each stage of sublacustrine fan is characterized by contstant migration and wiggle in twodimensional system, and superimposed development in the vertical evolution. The episodic activity of No.5 fault as a result of the influence of No. 0 fault and No.3 fault, led to the transformation of accommatation space. So, the unbalanced transformation of accommatation space constrainted by structure activity is the main factor controlling the distribution of sand body of sublacustrine fan of the first Member of Liushagang Formation.
Vertical Structure and Dominating Factors of Chang 9 Sandbody from Yanchang Formation in Ordos Basin
2013, 31(1): 77-88.
Abstract:
With the reunderstanding of hydrocarbon geological conditions in Ordos Basin, a new discovery and breakthrough have been found in Chang 9 Reservoir Group form the lower part of Upper Triassic Yanchang Formation in recent years, and it has become the important succeed layer of strategic exploration. Through comprehensive study of outcrop section, drilling, core, well logging and tests, combining with the background analysis of sedimentary paleogeography, based on sedimentary characteristics and facies marker, it is considered that the genetic types of Chang 9 sandbody within the basin mainly include onshore and underwater distributary channel, natural levee, crevasse splay, sheet sand and other sandbodies associated with traction current effect in delta environment, the rivermouth bar, distal bar, sheet sand and other sand bodies in delta front, and the sandy shoal and bar, sheet sand and other sand bodies related to lakewave and lakeflow reworking in shore to shallow lake environment. According to the detailed description of core sections and the analysis of sedimentary microfacies, combined with logging interpretation, it is pointed out that Chang 9 single sand body mainly develops B, C, I, F and D basic vertical structure types and multistory sandbodies have complicated and variable vertical stacking patterns, with BB, CC, CB, II, CI, BC, BI and FF as the common types. It is indicated that sedimentary environment, depositional facies and baselevel fluctuating cycle are main geologic factors controlled on vertical structure of individual sandbody, vertical stacking pattern and distribution of multistory sandbodies from the analysis of dominating factors of vertical structure of Chang 9 sandbodies.
With the reunderstanding of hydrocarbon geological conditions in Ordos Basin, a new discovery and breakthrough have been found in Chang 9 Reservoir Group form the lower part of Upper Triassic Yanchang Formation in recent years, and it has become the important succeed layer of strategic exploration. Through comprehensive study of outcrop section, drilling, core, well logging and tests, combining with the background analysis of sedimentary paleogeography, based on sedimentary characteristics and facies marker, it is considered that the genetic types of Chang 9 sandbody within the basin mainly include onshore and underwater distributary channel, natural levee, crevasse splay, sheet sand and other sandbodies associated with traction current effect in delta environment, the rivermouth bar, distal bar, sheet sand and other sand bodies in delta front, and the sandy shoal and bar, sheet sand and other sand bodies related to lakewave and lakeflow reworking in shore to shallow lake environment. According to the detailed description of core sections and the analysis of sedimentary microfacies, combined with logging interpretation, it is pointed out that Chang 9 single sand body mainly develops B, C, I, F and D basic vertical structure types and multistory sandbodies have complicated and variable vertical stacking patterns, with BB, CC, CB, II, CI, BC, BI and FF as the common types. It is indicated that sedimentary environment, depositional facies and baselevel fluctuating cycle are main geologic factors controlled on vertical structure of individual sandbody, vertical stacking pattern and distribution of multistory sandbodies from the analysis of dominating factors of vertical structure of Chang 9 sandbodies.
2013, 31(1): 99-107.
Abstract:
Provenance analysis on terrigenous sedimentary rocks is significant for all of palaeogeomorphology remolding, palaeogeography reconstruction, palaeoenvironment and palaeoclimate recovering, original basin resuming, sedimentary basin reappearing, depositional system analysis, sedimentary deposits forecasting, petroleum reservoir predicting, parent rock property tracing, geotectonics settings analysis, crust and geotectonics evolvement resume, and study on coupling of basin and moutains. We summarized traditional provenance analysis methods and research progress of sedimentological method, petrographic method, heavy mineral method, element geochemistry method, geochronology method, clay mineral method, fossil and biomarker method, and geophysics method. We also introduced new methods on provenance analysis of magnetic mineralogy method, mineral microtexture method upraise in recent years. Herewith, we prospect development tendency of provenance analysis: with constantly upraising of new technique and new method, provenance analysis transferring from traditional methods to modern testing technics, from single technique to colligation of multiple methods, from one subject to alliance and overlap of multiple disciplines, from qualitative analysis to quantitative analysis.
Provenance analysis on terrigenous sedimentary rocks is significant for all of palaeogeomorphology remolding, palaeogeography reconstruction, palaeoenvironment and palaeoclimate recovering, original basin resuming, sedimentary basin reappearing, depositional system analysis, sedimentary deposits forecasting, petroleum reservoir predicting, parent rock property tracing, geotectonics settings analysis, crust and geotectonics evolvement resume, and study on coupling of basin and moutains. We summarized traditional provenance analysis methods and research progress of sedimentological method, petrographic method, heavy mineral method, element geochemistry method, geochronology method, clay mineral method, fossil and biomarker method, and geophysics method. We also introduced new methods on provenance analysis of magnetic mineralogy method, mineral microtexture method upraise in recent years. Herewith, we prospect development tendency of provenance analysis: with constantly upraising of new technique and new method, provenance analysis transferring from traditional methods to modern testing technics, from single technique to colligation of multiple methods, from one subject to alliance and overlap of multiple disciplines, from qualitative analysis to quantitative analysis.
2013, 31(1): 108-119.
Abstract:
The vertical variation, composition and sources of sedimentary organic matter and aliphatic hydrocarbons of the core sediments from the south Yellow Sea were exactly evaluated and characterized in terms of the molecular composition of the hydrocarbon compounds and its implication for the sedimentary environment. The results show that there exited a good positive correlation between the total organic carbon and total nitrogen, while the occurrence inorganic nitrogen and its potential influence on the SOM identification is poor, which could be related with the low riverine input of the terrigenous materials in the study area. The long chain nalkanes show a high abundance in the 0～10 cm section with eventoodd predominance of the C2535 nalkanes and a higher Pr/Ph ratio (>1.0), indicating a relatively oxidative sedimentary environment. This condition is unfavorable for the preservation of marine organic matter, and in turn, exhibiting a more contribution from the terrigenous organic matter at this interval, while the compositional patterns of hopanes and steranes suggested the presence of a more mature constituents in the upper sections. The sedimentary setting exchanged from the oxidative condition to the anoxic ones with the increasing depth at the 10～20 cm section. Below the 20 cm layer, the sedimentary environment is more characterized of anoxic condition with a low maturation of the buried organic matter. The alkanes in those downsections showed a bimodal with the even carbon preference of the C1222 nalkanes, which could be derived from marine bacteria, fungi and yeast species. By comparing with the sedimentary records in Bohai Sea which were more related to the variation of the historical fluvial input and human actions, while for the Yellow Sea, the molecular compositional patterns of the typical hydrocarbon compounds indicate the important role of the sedimentary condition and microbial biodegradation for the burial and preservation of organic matter in the core sediments.
The vertical variation, composition and sources of sedimentary organic matter and aliphatic hydrocarbons of the core sediments from the south Yellow Sea were exactly evaluated and characterized in terms of the molecular composition of the hydrocarbon compounds and its implication for the sedimentary environment. The results show that there exited a good positive correlation between the total organic carbon and total nitrogen, while the occurrence inorganic nitrogen and its potential influence on the SOM identification is poor, which could be related with the low riverine input of the terrigenous materials in the study area. The long chain nalkanes show a high abundance in the 0～10 cm section with eventoodd predominance of the C2535 nalkanes and a higher Pr/Ph ratio (>1.0), indicating a relatively oxidative sedimentary environment. This condition is unfavorable for the preservation of marine organic matter, and in turn, exhibiting a more contribution from the terrigenous organic matter at this interval, while the compositional patterns of hopanes and steranes suggested the presence of a more mature constituents in the upper sections. The sedimentary setting exchanged from the oxidative condition to the anoxic ones with the increasing depth at the 10～20 cm section. Below the 20 cm layer, the sedimentary environment is more characterized of anoxic condition with a low maturation of the buried organic matter. The alkanes in those downsections showed a bimodal with the even carbon preference of the C1222 nalkanes, which could be derived from marine bacteria, fungi and yeast species. By comparing with the sedimentary records in Bohai Sea which were more related to the variation of the historical fluvial input and human actions, while for the Yellow Sea, the molecular compositional patterns of the typical hydrocarbon compounds indicate the important role of the sedimentary condition and microbial biodegradation for the burial and preservation of organic matter in the core sediments.
2013, 31(1): 130-138.
Abstract:
About 3 500 surface sediment samples were got by grab and box sampler in the north of South China sea, for the sample intervals are 3 km、5 km & 10 km, all the samples grain size were tested by Mastersizer 2000 which produced by Malvern company, and more than 700 samples were tested for Major Elements by Magix—pro 2440. From the test, we found that most of the sediment are Silty sand, the mean grain size are mostly between 3 and 8, the sediment were mainly composed of SiO2、Al2O3、Fe2O3、CaO、K2O、MgO and Na2O, which occupied more than 90% in the sediment for the average value. Relativity analyse were used for the value of the major elements and mean grain size(), the result is that SiO2 and CaO have a negative correlation with mean grain size(), the other major elements have a positive correlation with mean grain size(), Al2O3、P2O5、K2O and TiO2 are related to each other, which mostly came from the continent, CaO has a negative correlation with most major elements, and the correlationship is low, which indicate that CaO mostly formed by calcareous. The sediment were divided by quick clustering method, and 3 different areas were plot out at last, they were Pearl River Estuary and the west of Guangdong area（Ⅰ）、the east of Qiongzhou strait area（Ⅱ）、the east of Hainan area（Ⅲ）,at the same time we also got the sediment transport trends and routes. For the area Ⅰ, which is very wide, the sediment mainly came from Pearl River which spread radially to the open sea, and much suspended matter from Pearl River was transported to the west of Guangdong sea by the coast current, the transport route is close to the coast until arrived at Dianbai sea area, than turn to the south, this route is very long and many major elements have the same indication. For the area Ⅱ, which is located in Qiongzhou Strait and its east, most of the sediments are medium and coarse sand that is very different from other areas, the sediments are mainly from the side and bottom of the Qiongzhou Strait, the transport route is from inner to out of the strait, and the route is short. For the area Ⅲ, which is located in northeast of Hainan, the obvious characters of the sediments in this area is that the content of CaO is much higher than other places, which indicate that the biological activities are extensive in this area, we also can figure out that the sediments mainly come from the continent after the comparison with the content of major elements in the middle of South China sea, Chinese continent and Pacific, as we known there were many residual sediments which formed in late Pleiocene, so in this area the sediments mainly deposit in early stage, and also were reformed obviously by the biological activities, the transport route is not clear in this area.
About 3 500 surface sediment samples were got by grab and box sampler in the north of South China sea, for the sample intervals are 3 km、5 km & 10 km, all the samples grain size were tested by Mastersizer 2000 which produced by Malvern company, and more than 700 samples were tested for Major Elements by Magix—pro 2440. From the test, we found that most of the sediment are Silty sand, the mean grain size are mostly between 3 and 8, the sediment were mainly composed of SiO2、Al2O3、Fe2O3、CaO、K2O、MgO and Na2O, which occupied more than 90% in the sediment for the average value. Relativity analyse were used for the value of the major elements and mean grain size(), the result is that SiO2 and CaO have a negative correlation with mean grain size(), the other major elements have a positive correlation with mean grain size(), Al2O3、P2O5、K2O and TiO2 are related to each other, which mostly came from the continent, CaO has a negative correlation with most major elements, and the correlationship is low, which indicate that CaO mostly formed by calcareous. The sediment were divided by quick clustering method, and 3 different areas were plot out at last, they were Pearl River Estuary and the west of Guangdong area（Ⅰ）、the east of Qiongzhou strait area（Ⅱ）、the east of Hainan area（Ⅲ）,at the same time we also got the sediment transport trends and routes. For the area Ⅰ, which is very wide, the sediment mainly came from Pearl River which spread radially to the open sea, and much suspended matter from Pearl River was transported to the west of Guangdong sea by the coast current, the transport route is close to the coast until arrived at Dianbai sea area, than turn to the south, this route is very long and many major elements have the same indication. For the area Ⅱ, which is located in Qiongzhou Strait and its east, most of the sediments are medium and coarse sand that is very different from other areas, the sediments are mainly from the side and bottom of the Qiongzhou Strait, the transport route is from inner to out of the strait, and the route is short. For the area Ⅲ, which is located in northeast of Hainan, the obvious characters of the sediments in this area is that the content of CaO is much higher than other places, which indicate that the biological activities are extensive in this area, we also can figure out that the sediments mainly come from the continent after the comparison with the content of major elements in the middle of South China sea, Chinese continent and Pacific, as we known there were many residual sediments which formed in late Pleiocene, so in this area the sediments mainly deposit in early stage, and also were reformed obviously by the biological activities, the transport route is not clear in this area.
2013, 31(1): 149-156.
Abstract:
Sand layers are commonly embedded in lacustrine sediments from Zhuye Lake. Surface textures of quartz sands of samples from the QTH01 and QTH02 sections in Zhuye Lake were analysized and compared with samples from paleoshorelines and modern sand dunes in the study area. The results showed that samples from the QTH01 and QTH02 sections have characteristics of both typical aeolian and aqueous environments. The characteristics of aqueous environment covered on the features of aeolian environment on the samples of the Zhuye Lake sediments, while the distribution frequency of Vshaped impact pits was not common. The psephicity of samples from the QTH01 and QTH02 sections was similar to samples from modern dunes samples, and the surface textures were similar to paleoshorelines samples. These results suggested that the sand layers of Zhuye Lake had experienced aeolian environment before aqueous environment. The formation of sand layers in Zhuye Lake was similar to sands from paleoshorelines. During the period of sand layer formation, the dust activity was strong; the hydrodynamic conditions of Zhuye lake were stable; and rivers had few impacts to it.
Sand layers are commonly embedded in lacustrine sediments from Zhuye Lake. Surface textures of quartz sands of samples from the QTH01 and QTH02 sections in Zhuye Lake were analysized and compared with samples from paleoshorelines and modern sand dunes in the study area. The results showed that samples from the QTH01 and QTH02 sections have characteristics of both typical aeolian and aqueous environments. The characteristics of aqueous environment covered on the features of aeolian environment on the samples of the Zhuye Lake sediments, while the distribution frequency of Vshaped impact pits was not common. The psephicity of samples from the QTH01 and QTH02 sections was similar to samples from modern dunes samples, and the surface textures were similar to paleoshorelines samples. These results suggested that the sand layers of Zhuye Lake had experienced aeolian environment before aqueous environment. The formation of sand layers in Zhuye Lake was similar to sands from paleoshorelines. During the period of sand layer formation, the dust activity was strong; the hydrodynamic conditions of Zhuye lake were stable; and rivers had few impacts to it.
2013, 31(1): 157-166.
Abstract:
The lithology of Neogene reservoirs in the northwest part of Qaidam Basin is very complex. The rock minerals contain terrigenous materials such as quartz and feldspar as well as lacustrine materials such as carbonate and clay minerals. In addition, the grain size of the sediment is very fine. As a result, the rocks can not be denominated easily by means of thin section examination. This paper mainly discusses four oil structures of the area, including Nanyishan, Youquanzi, Xiaoliangshan and Xianshuiquan. Based on core observation and thin section examination, with the help of Xray diffraction analysis, the sediments of the reservoirs are considered to be mixed deposition which is composed of terrigenous clastic materials and biochemical carbonate minerals. A triangular graph is drawn according to the contents of clay minerals, carbonate minerals, and quartz and feldspar. So，a lithology classification is put forwards and the rocks can be classified as mudstone, sandstone，carbonatite, and mixing deposited rocks. The physical properties of the reservoirs are poor, and the pore types include intergranular solution pores, microfractures and micropores. Compaction，corrosion and cementation are main factors controlling the characteristic of the reservoir.
The lithology of Neogene reservoirs in the northwest part of Qaidam Basin is very complex. The rock minerals contain terrigenous materials such as quartz and feldspar as well as lacustrine materials such as carbonate and clay minerals. In addition, the grain size of the sediment is very fine. As a result, the rocks can not be denominated easily by means of thin section examination. This paper mainly discusses four oil structures of the area, including Nanyishan, Youquanzi, Xiaoliangshan and Xianshuiquan. Based on core observation and thin section examination, with the help of Xray diffraction analysis, the sediments of the reservoirs are considered to be mixed deposition which is composed of terrigenous clastic materials and biochemical carbonate minerals. A triangular graph is drawn according to the contents of clay minerals, carbonate minerals, and quartz and feldspar. So，a lithology classification is put forwards and the rocks can be classified as mudstone, sandstone，carbonatite, and mixing deposited rocks. The physical properties of the reservoirs are poor, and the pore types include intergranular solution pores, microfractures and micropores. Compaction，corrosion and cementation are main factors controlling the characteristic of the reservoir.
2013, 31(1): 176-183.
Abstract:
A series of kerogen pyrolysis in gold tube reactors were conducted at two heating rates of 20 ℃/h (from 373.5 to 526 ℃) and 2 ℃/h (from 343 to 489.2 ℃) under a constant pressure of 24.1 MPa. The kerogen (PY) concentrated from Enping Formations immature carboniferous mudstone in the Panyu Low Massif and North Slope of Baiyun Sag in Pearl River Mouth Basin, China was used in this study. For comparison purpose, the isolated kerogens from Green River shale (GR) and Woodford mudstone(WF) representing typical type I and II kerogens were employed as well. The yields of C15, C614 and C14+ were quantified, and the carbon isotopic compositions of residual kerogens and asphalts were measured. The results show the total yield of hydrocarbons are low from PY kerogen pyrolysis, and the yield of gaseous hydrocarbons is 1.5 times to liquid hydrocarbons. In contrast, the total yields of hydrocarbons from GR and WF kerogen pyrolysis are apparently great, and are dominated by liquid hydrocarbons. This indicates PY kerogen thermal decomposition mainly forms natural gas. During kerogen thermal decomposition, the oil to gas ratio is controlled by both of organic matter thermal maturity and kerogentypes, yet the ratio of gas and light hydrocarbons is mainly affected by thermal maturation. The carbon isotopic compositions of residual kerogens and alsphalt fraction are almost identical, and less than 0.3‰ 13C enrichment to original value of kerogen is observed from 0.7% to 2.7% Ro during thermal maturation. This suggests that δ13C of residual kerogens or alsphaltane could be used as a indicator to the reconstruction of organic matter type for highmature source rock.
A series of kerogen pyrolysis in gold tube reactors were conducted at two heating rates of 20 ℃/h (from 373.5 to 526 ℃) and 2 ℃/h (from 343 to 489.2 ℃) under a constant pressure of 24.1 MPa. The kerogen (PY) concentrated from Enping Formations immature carboniferous mudstone in the Panyu Low Massif and North Slope of Baiyun Sag in Pearl River Mouth Basin, China was used in this study. For comparison purpose, the isolated kerogens from Green River shale (GR) and Woodford mudstone(WF) representing typical type I and II kerogens were employed as well. The yields of C15, C614 and C14+ were quantified, and the carbon isotopic compositions of residual kerogens and asphalts were measured. The results show the total yield of hydrocarbons are low from PY kerogen pyrolysis, and the yield of gaseous hydrocarbons is 1.5 times to liquid hydrocarbons. In contrast, the total yields of hydrocarbons from GR and WF kerogen pyrolysis are apparently great, and are dominated by liquid hydrocarbons. This indicates PY kerogen thermal decomposition mainly forms natural gas. During kerogen thermal decomposition, the oil to gas ratio is controlled by both of organic matter thermal maturity and kerogentypes, yet the ratio of gas and light hydrocarbons is mainly affected by thermal maturation. The carbon isotopic compositions of residual kerogens and alsphalt fraction are almost identical, and less than 0.3‰ 13C enrichment to original value of kerogen is observed from 0.7% to 2.7% Ro during thermal maturation. This suggests that δ13C of residual kerogens or alsphaltane could be used as a indicator to the reconstruction of organic matter type for highmature source rock.
2013, 31(1): 10-19.
Abstract:
From Cambrian in the first and second Member of Mantou Formation, 9 layers stromatolites are exposed, half of the 18 layers' in Cambrian in the western Henan province, China. The morphological characteristics are rich and notable, mainly columnshaped, wavyshaped, hemisphereshaped and surrounding flatpebble conglomerate limestones shaped, and it can be divided into 4 big and 8 small categories. On the basis of analyzing the characteristics of sedimentary facies of every beds of the first and second Member, Mantou Formation in Cambrian, western Henan Province, the distribution model of sedimentary environments has been established as 8 small categories and 11 types stromatolites in Mantou Formation through detailed description on the macro, meso morphological characteristics of different types of stromatolites and accompanying sedimentary structure. At the same time, the paper proved the distribution model of sedimentary environments with the growth environment of modern marine stromatolites and the sedimentary environment of Precambrian. The gently wavyshaped stromatolites are dominated by supratidal, with subordinate wavyshaped, small columnar and having horizontal thin bedded mud stromatolites. The wavyshaped, small columnar and having horizontal thin bedded mud stromatolites are dominated by upper intertidal, with subordinate conicalshaped stromatolites. The teretifolious stramatolites are dominated of middle intertidal having elliptical oncolites and flatpebble conglomerate, with subordinate conicalshaped and surrounding flatpebble conglomerate limestones shaped stromatolites. The teretifolious stramatolites having rounded oncolites and hemisphere shaped stromatolites are dominated of bottom intertidal to subtidal, with subordinate inverted conicalshaped stromatolites having oncolites. Sea level change i.e. hydrodynamic condition is the decisive factor of the stromatolites growth categories.
From Cambrian in the first and second Member of Mantou Formation, 9 layers stromatolites are exposed, half of the 18 layers' in Cambrian in the western Henan province, China. The morphological characteristics are rich and notable, mainly columnshaped, wavyshaped, hemisphereshaped and surrounding flatpebble conglomerate limestones shaped, and it can be divided into 4 big and 8 small categories. On the basis of analyzing the characteristics of sedimentary facies of every beds of the first and second Member, Mantou Formation in Cambrian, western Henan Province, the distribution model of sedimentary environments has been established as 8 small categories and 11 types stromatolites in Mantou Formation through detailed description on the macro, meso morphological characteristics of different types of stromatolites and accompanying sedimentary structure. At the same time, the paper proved the distribution model of sedimentary environments with the growth environment of modern marine stromatolites and the sedimentary environment of Precambrian. The gently wavyshaped stromatolites are dominated by supratidal, with subordinate wavyshaped, small columnar and having horizontal thin bedded mud stromatolites. The wavyshaped, small columnar and having horizontal thin bedded mud stromatolites are dominated by upper intertidal, with subordinate conicalshaped stromatolites. The teretifolious stramatolites are dominated of middle intertidal having elliptical oncolites and flatpebble conglomerate, with subordinate conicalshaped and surrounding flatpebble conglomerate limestones shaped stromatolites. The teretifolious stramatolites having rounded oncolites and hemisphere shaped stromatolites are dominated of bottom intertidal to subtidal, with subordinate inverted conicalshaped stromatolites having oncolites. Sea level change i.e. hydrodynamic condition is the decisive factor of the stromatolites growth categories.
2013, 31(1): 32-37.
Abstract:
In the northwest of South China Sea, a huge far source Sedimentary System which is called Red River Sedimentary System has been discovered recently. The Red River depositional system refers to "a genetically related combination of a series of deltas, submarine canyon infillings, submarine fans and finegrained suspension deposits deriving from the terrestrial clastics of the Red River in Neocene". The main body of this depositional system comprises the Red River delta, the Red River submarine fan and the Central Canyon. In order to understand the identify standard and distributing in the plan view, a great deal of 2D seismic profiles has been used. The paper mainly focuses on the system which is developed during late Miocene to Pliocene. Base on the distributing in the plan view, the development history of the Red River Sedimentary system can be understood. The results show that deltas, channels, submarine canyon, channellevee complex and lobes can be identified in the Red River Sedimentary system based on the seismic reflection characteristics. According to the combination and spatial distribution features of the Red River sedimentary system, the development history of the system can be subdivided into three stages: SQ1SQ2, the formation period of Red River submarine fan, which is characterized by huge submarine fan; SQ3SQ4, the development period of the confined submarine fanCentral Canyon, which is characterized by a confined submarine fan developed before the central Canyon; and SQ5SQ6,the weakening period of the Red River depositional system, which is characterized by Red River Sedimentary System fading out in the research area, instead of Hainan slope's growing. Red River Sedimentary System derives from QinghaiTibetan Plateau uplift. The research is not only beneficial for ascertaining Oil and gas prospecting, but also helpful for rebuilding uplift history of QinghaiTibetan Plateau, and answering the question whether Red River capture occurred or not.
In the northwest of South China Sea, a huge far source Sedimentary System which is called Red River Sedimentary System has been discovered recently. The Red River depositional system refers to "a genetically related combination of a series of deltas, submarine canyon infillings, submarine fans and finegrained suspension deposits deriving from the terrestrial clastics of the Red River in Neocene". The main body of this depositional system comprises the Red River delta, the Red River submarine fan and the Central Canyon. In order to understand the identify standard and distributing in the plan view, a great deal of 2D seismic profiles has been used. The paper mainly focuses on the system which is developed during late Miocene to Pliocene. Base on the distributing in the plan view, the development history of the Red River Sedimentary system can be understood. The results show that deltas, channels, submarine canyon, channellevee complex and lobes can be identified in the Red River Sedimentary system based on the seismic reflection characteristics. According to the combination and spatial distribution features of the Red River sedimentary system, the development history of the system can be subdivided into three stages: SQ1SQ2, the formation period of Red River submarine fan, which is characterized by huge submarine fan; SQ3SQ4, the development period of the confined submarine fanCentral Canyon, which is characterized by a confined submarine fan developed before the central Canyon; and SQ5SQ6,the weakening period of the Red River depositional system, which is characterized by Red River Sedimentary System fading out in the research area, instead of Hainan slope's growing. Red River Sedimentary System derives from QinghaiTibetan Plateau uplift. The research is not only beneficial for ascertaining Oil and gas prospecting, but also helpful for rebuilding uplift history of QinghaiTibetan Plateau, and answering the question whether Red River capture occurred or not.
2013, 31(1): 50-55.
Abstract:
This chimney(TVG14C11) was collected by SO177 cruise in 2004 from the northeastern Dongsha, South China Sea. It is composed of Mgcalcite. Author did high resolution sampling on a cross section of the chimney to analyze their Cand Oisotope compositions. Based on their mineral composition, we used carbonatewater fractionation equation to calculate the δ18O of the precipitating fluid and discussed the fluid sources. We showed that the δ13C of the chimney varied from -50.14‰ to -43.92‰, and δ18O from 2.76‰ to 4.85‰. From the inner to the outer, the δ13C increased gradually while δ18O was decreaseing. The equilibrium δ18O of the precipitating fluid were in the range of 1.2‰-2.3‰VSMOW, which were significantly heavier than the modern seawater or glacial water. It is suggested that the water released from gas hydrate dissociation were responsible for the 18O enrichment. According to the two end-member mixing model, it was calculated that the precipitating fluid consisted of 53.6% gas hydrate water and 46.4% seawater during the precipitation stage of the inner layer. It got diluted gradually when it diffused into the sediments to form the outer layer, where the contribution of gas hydrate water decreased to 6.1%. Based on the growth structure and the variation of carbon and oxygen isotope composition, a growth model of the seep carbonate chimney was proposed.
This chimney(TVG14C11) was collected by SO177 cruise in 2004 from the northeastern Dongsha, South China Sea. It is composed of Mgcalcite. Author did high resolution sampling on a cross section of the chimney to analyze their Cand Oisotope compositions. Based on their mineral composition, we used carbonatewater fractionation equation to calculate the δ18O of the precipitating fluid and discussed the fluid sources. We showed that the δ13C of the chimney varied from -50.14‰ to -43.92‰, and δ18O from 2.76‰ to 4.85‰. From the inner to the outer, the δ13C increased gradually while δ18O was decreaseing. The equilibrium δ18O of the precipitating fluid were in the range of 1.2‰-2.3‰VSMOW, which were significantly heavier than the modern seawater or glacial water. It is suggested that the water released from gas hydrate dissociation were responsible for the 18O enrichment. According to the two end-member mixing model, it was calculated that the precipitating fluid consisted of 53.6% gas hydrate water and 46.4% seawater during the precipitation stage of the inner layer. It got diluted gradually when it diffused into the sediments to form the outer layer, where the contribution of gas hydrate water decreased to 6.1%. Based on the growth structure and the variation of carbon and oxygen isotope composition, a growth model of the seep carbonate chimney was proposed.
2013, 31(1): 67-76.
Abstract:
This paper focuses on the sequence stratigraphy and sedimentary facies of Yingcheng formation in the southeastern margin of the Songliao Basin. The degree of previous studies in this area is lower, based on seismic，logging and core analysis, the sequence stratigraphy and sedimentary facies are studied. Rift basin is characterized by deposition which is significantly controlled by tectonic movements and episodic tectonic cycles, sedimentary and tectonic evolution of the Songliao Basin experienced the initial rift period, strongly faulted period, faulted the peak late, the conversion period of faulted and depression and depression period amounting to five stages of evolution. Northwest of Lishu depression is the most promising oil and gas rich region. The block Shahezi 2nd member & Ying 1st member deposition period are extended strong faulted period of the rapid subsidence and deep water, provided the preconditions condition for gravity flow deposits development, especially in the braided river delta front near the deep water, easily turbidite sandstone develops, turbidite sand embedded in thick dark mudstone which creates a unique condition for lithologic reservoir formation. With the gradual indepth exploration and geological theory oil and gas exploration gradually to the west of the central belt with a particular deep extensions to the northwest, and achieved encouraging preliminary exploration results. The study area is located in the transition belt of northern slope and southern deep depression zone, and the structure superimposed over the same period as a background, is favorable area to find the structure and construction of reservoirscomplex reservoir lithology. However, the deposition type ,evolution of sedimentary facies, reservoir characteristics etc. is with little facility in the northwest of the studied area. So it is necessary to conduct a detailed study of sedimentary features of northwest. Use of geological and geophysical data for the Yingcheng formation strata from Northwest Lishu fault depression to identify sequence boundaries, the Yingcheng formation was studied, and which was divided into two thirdorder sequences, respectively, from bottom to top with SQ5 and SQ6, corresponding to the three sequence boundaries are SB5, SB6 and SB7. The thirdorder sequences were further subdivided into lowstand system tract, transgressive systems tract and highstand system tract. Lowstand system tract mainly is composed of the composition of parasequence sets, transgressive systems tract mainly is composed of the retrogradation parasequence set, and highstand system tract is made of the accretion type parasequence set. Sediment types are composed of nearshore subaqueous fan, fan delta, braid delta and lakes, and the lakes and braided river delta are the most developed type. Nearshore subaqueous fan and fan delta depositional systems develop in the downthrow side of fault for each sequence unit, which is controlled by the tectonic movements significantly, and always developed in the steep belt; braided delta sedimentary system are often associated with abundant long axis of the material source, which often developed in the gentle slope. The evolution and tectonic with deposition system configured are controlled by the ancient tectonic and landscape. Concluded that the most favorable reservoir area is located in the gentle belt of northwest Lishu fault depression.
This paper focuses on the sequence stratigraphy and sedimentary facies of Yingcheng formation in the southeastern margin of the Songliao Basin. The degree of previous studies in this area is lower, based on seismic，logging and core analysis, the sequence stratigraphy and sedimentary facies are studied. Rift basin is characterized by deposition which is significantly controlled by tectonic movements and episodic tectonic cycles, sedimentary and tectonic evolution of the Songliao Basin experienced the initial rift period, strongly faulted period, faulted the peak late, the conversion period of faulted and depression and depression period amounting to five stages of evolution. Northwest of Lishu depression is the most promising oil and gas rich region. The block Shahezi 2nd member & Ying 1st member deposition period are extended strong faulted period of the rapid subsidence and deep water, provided the preconditions condition for gravity flow deposits development, especially in the braided river delta front near the deep water, easily turbidite sandstone develops, turbidite sand embedded in thick dark mudstone which creates a unique condition for lithologic reservoir formation. With the gradual indepth exploration and geological theory oil and gas exploration gradually to the west of the central belt with a particular deep extensions to the northwest, and achieved encouraging preliminary exploration results. The study area is located in the transition belt of northern slope and southern deep depression zone, and the structure superimposed over the same period as a background, is favorable area to find the structure and construction of reservoirscomplex reservoir lithology. However, the deposition type ,evolution of sedimentary facies, reservoir characteristics etc. is with little facility in the northwest of the studied area. So it is necessary to conduct a detailed study of sedimentary features of northwest. Use of geological and geophysical data for the Yingcheng formation strata from Northwest Lishu fault depression to identify sequence boundaries, the Yingcheng formation was studied, and which was divided into two thirdorder sequences, respectively, from bottom to top with SQ5 and SQ6, corresponding to the three sequence boundaries are SB5, SB6 and SB7. The thirdorder sequences were further subdivided into lowstand system tract, transgressive systems tract and highstand system tract. Lowstand system tract mainly is composed of the composition of parasequence sets, transgressive systems tract mainly is composed of the retrogradation parasequence set, and highstand system tract is made of the accretion type parasequence set. Sediment types are composed of nearshore subaqueous fan, fan delta, braid delta and lakes, and the lakes and braided river delta are the most developed type. Nearshore subaqueous fan and fan delta depositional systems develop in the downthrow side of fault for each sequence unit, which is controlled by the tectonic movements significantly, and always developed in the steep belt; braided delta sedimentary system are often associated with abundant long axis of the material source, which often developed in the gentle slope. The evolution and tectonic with deposition system configured are controlled by the ancient tectonic and landscape. Concluded that the most favorable reservoir area is located in the gentle belt of northwest Lishu fault depression.
2013, 31(1): 89-98.
Abstract:
Massive dolomites are widely distributed in the Cambrian System of Tarim basin, and in Middle Cambrian with thick evaporite, evaporite and dolomite can be good reservoirseal assemblage, so the dolomite strata is a new exploration field of Tarim Basin in the future. Sabkha dolomite and seepage reflux dolomite are the two kinds of dolomite related to evaporite, and the main controlling factors of reservoir are also associated with evaporite directly or indirectly. This article summarized the petrologic and geochemical characteristics of sabkha dolomite and seepage reflux dolomite by analyzing a lot of cores, thin sections, major element, REE and stable isotope (carbon, oxygen and strontium) data. The lithology of sabkha dolomite reservoir characterized by the deposits of gypsodolomicrite, gypsum mould pores and intergravel pores of solutioncollapse breccia are the two kinds of porosity, sabkha dolomitization, gypsum precipitation and dissolution of meteoric freshwater are the main controlling factors of this reservoir; The lithology of seepage reflux dolomite reservoir featured by crystal powder dolomite which has reserved the original grainstone or algae mound structure, intergranular pores, mould pore, framework pores and organism pores are the main kinds of porosity, seepage reflux dolomitization and meteoric freshwater dissolution are the main controlling factors of this reservoir; The distribution law of these tow dolomite reservoirs are controlled by sedimentary facies, and chiefly developed in arid climate background of middle Cambrian, Tarim basin.
Massive dolomites are widely distributed in the Cambrian System of Tarim basin, and in Middle Cambrian with thick evaporite, evaporite and dolomite can be good reservoirseal assemblage, so the dolomite strata is a new exploration field of Tarim Basin in the future. Sabkha dolomite and seepage reflux dolomite are the two kinds of dolomite related to evaporite, and the main controlling factors of reservoir are also associated with evaporite directly or indirectly. This article summarized the petrologic and geochemical characteristics of sabkha dolomite and seepage reflux dolomite by analyzing a lot of cores, thin sections, major element, REE and stable isotope (carbon, oxygen and strontium) data. The lithology of sabkha dolomite reservoir characterized by the deposits of gypsodolomicrite, gypsum mould pores and intergravel pores of solutioncollapse breccia are the two kinds of porosity, sabkha dolomitization, gypsum precipitation and dissolution of meteoric freshwater are the main controlling factors of this reservoir; The lithology of seepage reflux dolomite reservoir featured by crystal powder dolomite which has reserved the original grainstone or algae mound structure, intergranular pores, mould pore, framework pores and organism pores are the main kinds of porosity, seepage reflux dolomitization and meteoric freshwater dissolution are the main controlling factors of this reservoir; The distribution law of these tow dolomite reservoirs are controlled by sedimentary facies, and chiefly developed in arid climate background of middle Cambrian, Tarim basin.
2013, 31(1): 120-129.
Abstract:
The Taiwan Strait connects the East China Sea and the South China Sea, which are two major marginal seas of west Pacific Ocean. This region serves as a canonical area for investigating the terrigenous detrital materials that are transported into the sea, including the provenance and flux, as well as the modelling of the distribution, transport and dispersion in continental shelf areas. Under the combined influence of the southbound Zhemin Coastal Current (ZCC) and northbound Taiwan Warm Current, the sediments in the Taiwan Strait exhibit the characteristics of multiple origins.Clay minerals in surface sediments from the Taiwan Strait and adjacent area were analyzed by XRay Diffraction (XRD) method to constrain the possible provenances including the Yangtze, Fujian and Taiwanese rivers. Clay mineral assemblage in the Min River (one of the largest Fujian rivers) consists dominantly of kaolinite (>40%) with minor amounts of illite and chlorite but without smectite, indicating that clay minerals in Min River drainage basin is originated from upriver granites by weathering under warm and humid conditions. Yangtzedominated clays have relatively high illite (61%～66%), with small amounts of chlorite (16%～17%) and kaolinite (10%～13%), low smectite (6%～9%) and poor illite crystallinity. Taiwandominated clays (Zhoshui River), in contrast, have the highest illite contents (>70%), and no smectite. The clay mineral assemblages from both sides of the Taiwan Strait are different, because of the source rocks and weathering condition factors. In the Taiwan Strait, kaolinite contents of the sediments decrease gradually from west to east, indicating that they are mostly originated from Fujian rivers. In the east region of the 50 m isobath in the Taiwan Strait, the clay mineral assemblage is dominated by illite and chorite with scarce smectite and kaolinite (both generally<5%), different from those of the Yangtze and Fujian rivers. Moreover, both chemistry index and crystallinity of illite are lower than those of the Yangtze and Fujian rivers, but similar to those of the Taiwanese rivers. Our data suggest that most of illite and chlorite in the northern Taiwan Strait were provided by Taiwanese rivers through the Taiwan Warm Current. However, clay minerals in offshore areas of Fujian Province were mainly provided by Fujian rivers, and locally possible mixed by the Yangtze river, such as the neighbor oceanic area of Pingtan island.
The Taiwan Strait connects the East China Sea and the South China Sea, which are two major marginal seas of west Pacific Ocean. This region serves as a canonical area for investigating the terrigenous detrital materials that are transported into the sea, including the provenance and flux, as well as the modelling of the distribution, transport and dispersion in continental shelf areas. Under the combined influence of the southbound Zhemin Coastal Current (ZCC) and northbound Taiwan Warm Current, the sediments in the Taiwan Strait exhibit the characteristics of multiple origins.Clay minerals in surface sediments from the Taiwan Strait and adjacent area were analyzed by XRay Diffraction (XRD) method to constrain the possible provenances including the Yangtze, Fujian and Taiwanese rivers. Clay mineral assemblage in the Min River (one of the largest Fujian rivers) consists dominantly of kaolinite (>40%) with minor amounts of illite and chlorite but without smectite, indicating that clay minerals in Min River drainage basin is originated from upriver granites by weathering under warm and humid conditions. Yangtzedominated clays have relatively high illite (61%～66%), with small amounts of chlorite (16%～17%) and kaolinite (10%～13%), low smectite (6%～9%) and poor illite crystallinity. Taiwandominated clays (Zhoshui River), in contrast, have the highest illite contents (>70%), and no smectite. The clay mineral assemblages from both sides of the Taiwan Strait are different, because of the source rocks and weathering condition factors. In the Taiwan Strait, kaolinite contents of the sediments decrease gradually from west to east, indicating that they are mostly originated from Fujian rivers. In the east region of the 50 m isobath in the Taiwan Strait, the clay mineral assemblage is dominated by illite and chorite with scarce smectite and kaolinite (both generally<5%), different from those of the Yangtze and Fujian rivers. Moreover, both chemistry index and crystallinity of illite are lower than those of the Yangtze and Fujian rivers, but similar to those of the Taiwanese rivers. Our data suggest that most of illite and chlorite in the northern Taiwan Strait were provided by Taiwanese rivers through the Taiwan Warm Current. However, clay minerals in offshore areas of Fujian Province were mainly provided by Fujian rivers, and locally possible mixed by the Yangtze river, such as the neighbor oceanic area of Pingtan island.
2013, 31(1): 139-148.
Abstract:
The Cenozoic sediments of the XiningGuide basin, locates in the northeastern margin of the Tibetan plateau, recorded the uplift and deformation history of northeastern plateau. The detrital heavy mineral analysis is a sensitive tool to deciphering these records. Five heavy mineral stages of sedimentary evolution along this region have been revealed by the heavy minerals and tectonicsedimentary analysis: ① the earliest tectonic uplift phase between Paleocene and Early Eocene, ②steady stage of middle EoceneLate Oligocene, ③ late OligoceneEarly Miocene tectonic activity again, ④middle Miocene tectonic clam stage, ⑤stronger activity phases since Late Miocene. With the chlorite characteristics and the paleocurrent analysis，we suggest that the GuideXining was an uniform weakly flexural or rejuvenated Paleozoic foreland basin of the eastern Kunlun Mountain. The onset of deformation and rock uplift along the eastern part of the Laji Mountain, which was possibly effected by the surface uplift of the Tibetan plateau, divided the Guide and Xining basins. At about Late Miocene, the Laji Mountain began strongly deformation and surface uplift, and the Guide and Xining basins gradually recessed. These results provide a significant evidence to thoroughly understand the formation and evolution of the NE margin of Tibet.
The Cenozoic sediments of the XiningGuide basin, locates in the northeastern margin of the Tibetan plateau, recorded the uplift and deformation history of northeastern plateau. The detrital heavy mineral analysis is a sensitive tool to deciphering these records. Five heavy mineral stages of sedimentary evolution along this region have been revealed by the heavy minerals and tectonicsedimentary analysis: ① the earliest tectonic uplift phase between Paleocene and Early Eocene, ②steady stage of middle EoceneLate Oligocene, ③ late OligoceneEarly Miocene tectonic activity again, ④middle Miocene tectonic clam stage, ⑤stronger activity phases since Late Miocene. With the chlorite characteristics and the paleocurrent analysis，we suggest that the GuideXining was an uniform weakly flexural or rejuvenated Paleozoic foreland basin of the eastern Kunlun Mountain. The onset of deformation and rock uplift along the eastern part of the Laji Mountain, which was possibly effected by the surface uplift of the Tibetan plateau, divided the Guide and Xining basins. At about Late Miocene, the Laji Mountain began strongly deformation and surface uplift, and the Guide and Xining basins gradually recessed. These results provide a significant evidence to thoroughly understand the formation and evolution of the NE margin of Tibet.
2013, 31(1): 167-175.
Abstract:
Xujiahe Formation in southern Sichuan Basin deposited in distributary channel of braided river delta plain and is dominated by lithic arenite, lithic quartz arenite. The Upper Triassic tight reservoirs with average porosity of 4.04% and average permeability of 0.147×103μm2 are in a current depth of 02 673 m (mostly 800 ~ 2 000 m). The causes of low porosity and permeability include four aspects. (1) The relative short transportation distance from provenance to deposition area resulted in large quantities of shale, phyllite and other plastic debris as well as poorly sorted grain pattern. (2) The early mudstone was easily eroded and mixed with sand grains because of the hydropower instability and quickly lateral diversion of braided river during the deposition process. (3) During the burial process, strong deformation of plastic particles caused by mechanical compaction combined with quartz cementation during the afterwards chemical compaction resulted in significant reduction of primary porosity. (4) The deficiency of acid fluid from the source rocks because the long distance from deposition center of basin resulting in weak dissolution after densification of sandstone. Hence, limited amount of secondary pores generated.
Xujiahe Formation in southern Sichuan Basin deposited in distributary channel of braided river delta plain and is dominated by lithic arenite, lithic quartz arenite. The Upper Triassic tight reservoirs with average porosity of 4.04% and average permeability of 0.147×103μm2 are in a current depth of 02 673 m (mostly 800 ~ 2 000 m). The causes of low porosity and permeability include four aspects. (1) The relative short transportation distance from provenance to deposition area resulted in large quantities of shale, phyllite and other plastic debris as well as poorly sorted grain pattern. (2) The early mudstone was easily eroded and mixed with sand grains because of the hydropower instability and quickly lateral diversion of braided river during the deposition process. (3) During the burial process, strong deformation of plastic particles caused by mechanical compaction combined with quartz cementation during the afterwards chemical compaction resulted in significant reduction of primary porosity. (4) The deficiency of acid fluid from the source rocks because the long distance from deposition center of basin resulting in weak dissolution after densification of sandstone. Hence, limited amount of secondary pores generated.
2013, 31(1): 184-192.
Abstract:
Well Taishen 1 of three lake is a new exploratory well of Qaidam basin, by studying geochemical characteristics of hydrocarbon source rock of this well, the scientific basis are provided for the further exploration. Based on the information about hydrocarbon source rock, such as total organic carbon (TOC), rockeval, group composition，the characteristic of saturated hydrocarbon and biomarkers, the characteristic of aromatic hydrocarbon, the characteristic of nonhydrocarbon, the wholerock organic carbon isotope, as well as the gas isotope, this paper thoroughly analyze the geochemical characteristic of Source rocks and gas in Well Taishen 1 and its possible cause of formation. It is concluded that the 8, 14secohopanes and isofatty acids and transisofatty acids, which are relevant to the microorganism, are discovered form the chloroform bitumen "A" of hydrocarbon source rock. At the same time the existence of microorganism in the hydrocarbongenerating environment of hydrocarbon source rock are confirmed by the discrepancy between OEP1 and OEP2 and the asynchrony between C29ββ/(ββ+αα) of sterane and C31αβ22S/22(S+R) of hopance and δ13C1 of natural gas. The degree of methylation of organic matter has been reinforced by the degradation of microorganism, which are beneficial to the generating of natural gas in Well Taishen 1. It is found that the organic matter of hydrocarbon source rock in Well Taishen 1 are in the low evolution stage by OEP2 of the nalkane and pregnane and rearranged steranen and C29ααα20S/20(S+R) of sterane and the isopotal natrual gas. Some characteristic (OEP1 of the nalkane and C31αβ22S/22(S+R) of hopane) of the hydrocarbon source rock show the mature characteristics of organic matter for the degradation of microorganism. The kerogen type of hydrocarbon source rock in Well Taishen 1 is dominated by the terrigenous higher plants, but which have the contribution of the aquatic organisms from some characteristics, such as the high abundance C20tricyclic diterpane and C20tetracycoloterpane, lupcune, perylene, retene, and the distribution of nalkane, ∑C27+C29/∑C31+ of hopance, the relative abundance of C27 and C29ααα20R in sterane, δ13C of hydrocarbon source rock and isopotal of natural gas. So the hydrocarbon source rock of Taishen 1 well are of the basis of the parent material for the generating of natural gas in the low evolution stage. The hydrocarbongenerating environment of hydrocarbon source rock in Well Taishen 1 have revealed shallow lake faciessulfsalineweak reducingweak oxidizing environment reducing environment by the elemental eight sulfur ring and the biomarker characteristics.
Well Taishen 1 of three lake is a new exploratory well of Qaidam basin, by studying geochemical characteristics of hydrocarbon source rock of this well, the scientific basis are provided for the further exploration. Based on the information about hydrocarbon source rock, such as total organic carbon (TOC), rockeval, group composition，the characteristic of saturated hydrocarbon and biomarkers, the characteristic of aromatic hydrocarbon, the characteristic of nonhydrocarbon, the wholerock organic carbon isotope, as well as the gas isotope, this paper thoroughly analyze the geochemical characteristic of Source rocks and gas in Well Taishen 1 and its possible cause of formation. It is concluded that the 8, 14secohopanes and isofatty acids and transisofatty acids, which are relevant to the microorganism, are discovered form the chloroform bitumen "A" of hydrocarbon source rock. At the same time the existence of microorganism in the hydrocarbongenerating environment of hydrocarbon source rock are confirmed by the discrepancy between OEP1 and OEP2 and the asynchrony between C29ββ/(ββ+αα) of sterane and C31αβ22S/22(S+R) of hopance and δ13C1 of natural gas. The degree of methylation of organic matter has been reinforced by the degradation of microorganism, which are beneficial to the generating of natural gas in Well Taishen 1. It is found that the organic matter of hydrocarbon source rock in Well Taishen 1 are in the low evolution stage by OEP2 of the nalkane and pregnane and rearranged steranen and C29ααα20S/20(S+R) of sterane and the isopotal natrual gas. Some characteristic (OEP1 of the nalkane and C31αβ22S/22(S+R) of hopane) of the hydrocarbon source rock show the mature characteristics of organic matter for the degradation of microorganism. The kerogen type of hydrocarbon source rock in Well Taishen 1 is dominated by the terrigenous higher plants, but which have the contribution of the aquatic organisms from some characteristics, such as the high abundance C20tricyclic diterpane and C20tetracycoloterpane, lupcune, perylene, retene, and the distribution of nalkane, ∑C27+C29/∑C31+ of hopance, the relative abundance of C27 and C29ααα20R in sterane, δ13C of hydrocarbon source rock and isopotal of natural gas. So the hydrocarbon source rock of Taishen 1 well are of the basis of the parent material for the generating of natural gas in the low evolution stage. The hydrocarbongenerating environment of hydrocarbon source rock in Well Taishen 1 have revealed shallow lake faciessulfsalineweak reducingweak oxidizing environment reducing environment by the elemental eight sulfur ring and the biomarker characteristics.
