1991 Vol. 9, No. 3
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Display Method:
1991, 9(3): 1-10.
Abstract:
The Huainan Coalfield, covering an area of more than 8000 km2. is concealed by the Quaternary system and the main coal-bearing strata are Permian Members C-D. By the investigation of more than 5000 bores and surveying of undergroud tunnels of the coal mines in the research district, many characteristics of the paleodrainage have been acquired as follows: 1. By undergroud surveying of the main channel sandstones of the members C-D, it is shown that during their deposition the paleocurrent direction is southward. 2.The paleodrainage of the Permian members C-D have two forms, the branched channel system (in member C) and the anastomosing channel system (in member D). The channels composed the drainages are very stable and fail to lateral migration. 3. The results of grainsize analysis and the C-M pattern of the same genetic increment demonstrates that the paleostream flown from north to south, and the south side is more near to the sea. 4. The characteristics of sedimentology and sedimentary geochemistry indicate that the t;ne sediments of member C which deposited in the branched channel system contain much more of the tidal sediments, bur- rows, and Lingula sp. etc. The content of the trace element B. B; Ga and Ca (Fe+Ca) are higher than that of member D To sum up the characteristics discussed above and analyze by means of Walther's Law of correlation of fades. and compare with the drainage on the modern Pearl River, the authers propose that the paleodrainage of the members C-D is more similar to that on the modern Pearl River Delta, that is to say, it can be divided into two parts, the anastomosing fluvial system near the continent and the branched fluvial system close to the sea. It is recognized that the paleodrainage discussed m this paper is different from that on the Mississippi River Delta and’or on the Yangtze River Delta. that could he account for which discussed' in this p:ner is a complex delta formed together by several continental streams, the low-medium thal range and the Coriolis Force exist in the history of the Earth.
The Huainan Coalfield, covering an area of more than 8000 km2. is concealed by the Quaternary system and the main coal-bearing strata are Permian Members C-D. By the investigation of more than 5000 bores and surveying of undergroud tunnels of the coal mines in the research district, many characteristics of the paleodrainage have been acquired as follows: 1. By undergroud surveying of the main channel sandstones of the members C-D, it is shown that during their deposition the paleocurrent direction is southward. 2.The paleodrainage of the Permian members C-D have two forms, the branched channel system (in member C) and the anastomosing channel system (in member D). The channels composed the drainages are very stable and fail to lateral migration. 3. The results of grainsize analysis and the C-M pattern of the same genetic increment demonstrates that the paleostream flown from north to south, and the south side is more near to the sea. 4. The characteristics of sedimentology and sedimentary geochemistry indicate that the t;ne sediments of member C which deposited in the branched channel system contain much more of the tidal sediments, bur- rows, and Lingula sp. etc. The content of the trace element B. B; Ga and Ca (Fe+Ca) are higher than that of member D To sum up the characteristics discussed above and analyze by means of Walther's Law of correlation of fades. and compare with the drainage on the modern Pearl River, the authers propose that the paleodrainage of the members C-D is more similar to that on the modern Pearl River Delta, that is to say, it can be divided into two parts, the anastomosing fluvial system near the continent and the branched fluvial system close to the sea. It is recognized that the paleodrainage discussed m this paper is different from that on the Mississippi River Delta and’or on the Yangtze River Delta. that could he account for which discussed' in this p:ner is a complex delta formed together by several continental streams, the low-medium thal range and the Coriolis Force exist in the history of the Earth.
1991, 9(3): 22-30.
Abstract:
The Xicheng Pb-Zn orefield is one of the most famous orefields in China. Xihanshui Group of Devonian is the main Pb-Zn ore bearing stratum, which was divided into three formation. In this paper, stratigraphic correlation of Givetian-Frasnian (Honglingshan Formation) is made through analysing conodonts in this area and its sedimentary facies and paleogeography. Honglingshan Fomation in this area consists of 12 types of microfacies and 6 macro facies which are: open shelf, open platform, restricted platform, reef and bioherm, forereef slope and lagoon facies. Honglingshan Formation in Xicheng aera is suggested being a rim carbonate platform, on the northern and southern edges of which are rim reefs or bioherms. Thus, there were five sedimentary areas and belts of facies in Givetian and Frasnian, which are: 1) northern open shelf area, 2) Dongshan-Changba reefs belts (windward), 3) Shepu-Xiangyangshan lagoon area, 4) Yeshuihe-Bijiashan reefs belts (leeward), and 5) southern open shelf area. The most of Pb-Zn ore deposits in Xicheng orefield are in the lagoon area between the north and the south reefs belts, showing the lagoon basin is a favourable area to form Pb-Zn ore, which is an important area to explore Pb-Zn ore in the future.
The Xicheng Pb-Zn orefield is one of the most famous orefields in China. Xihanshui Group of Devonian is the main Pb-Zn ore bearing stratum, which was divided into three formation. In this paper, stratigraphic correlation of Givetian-Frasnian (Honglingshan Formation) is made through analysing conodonts in this area and its sedimentary facies and paleogeography. Honglingshan Fomation in this area consists of 12 types of microfacies and 6 macro facies which are: open shelf, open platform, restricted platform, reef and bioherm, forereef slope and lagoon facies. Honglingshan Formation in Xicheng aera is suggested being a rim carbonate platform, on the northern and southern edges of which are rim reefs or bioherms. Thus, there were five sedimentary areas and belts of facies in Givetian and Frasnian, which are: 1) northern open shelf area, 2) Dongshan-Changba reefs belts (windward), 3) Shepu-Xiangyangshan lagoon area, 4) Yeshuihe-Bijiashan reefs belts (leeward), and 5) southern open shelf area. The most of Pb-Zn ore deposits in Xicheng orefield are in the lagoon area between the north and the south reefs belts, showing the lagoon basin is a favourable area to form Pb-Zn ore, which is an important area to explore Pb-Zn ore in the future.
1991, 9(3): 40-49.
Abstract:
Taranaki Basin is located in the northwest of the North Island in New Zealand. It was formed in the Late Cretaceous The maximum thickness of the sediments reaches to 11,000m. Taranaki Basin is one of the most prospective areas for petroleum in New Zealand, up to date, four oil (gas) fields have been drilled out, the crude oil show general features of terristrial oil. On the base of present investigation results, it is suggested that Pakawau and Kapuni Croup, which were deposited respectively in Late Cretaceous and Paleoecene-Eocene Epoch, are the possible source rocks. Pakawau and Kapuni groups are mainly composed of the deposits of continental facies and of marine and continental interactive facies. Biogenic sedimentary structures are very developed in the drilled cores of these two groups. Their types of causes of formation and developing degree may be regarded as the mark of oxygen content in sediments. The results of investigation show that the oxygen content is lower than 0.1-0.2ml/1 in coal bed and carbonaceous mudstone with high content of organic matter and has not distroyed by boiturbation; and medium in muddy siltstone and silty mudstone with very developed biogenic structures and intergrowth of bioturbation and small scale borrows, while abundant in coarse clastic rocks with large scale vertical burrows. According to the results of the above investigation and combining sedimentary sequence and primary sedimentary structure sequence, we carry on a comprehensive explanation of sedimentary environment to the partial cores of wells Tane-1 and Kapuni-8. Well Tane1 is taken as an example. This core section belongs to Pakawau Group, the lithologic character is fine-coarse sandstone at the bottom and turns gradually into siltstone, silty mudstone, carbonaceous mudstone and coal bed upwards. The relevant primary sedimentary structures are massive bedding , medium scale cross bedding, compound bedding of lenticular and wavy bedding, small scale cross bedding, horizontal laminated bedding, homogeneous bedding upwards. The regular change of primary sedimentary structure and the grain size character fining upwards are commonly composed of the typical normal fining upwards sedimentary sequence. This kind of sequence is just the product of hydrodynamic change of fluvial sedimentary system. Based on the characters of lacking of fluvial lag deposits at the bottom of sequence and thick over-bank fine sediments in the upper sequence, this core section should belong to the product of later- al migration of meandering stream point bar and of accretion of over-bank fine sediments upwards. Biogenic sedimentary structures change regularly from weak to strong from bottom to top. However, biogenic sedimentary structures are not developed in coal bed and carbonaceous mudstone in the upper of the sequence and in coarse sandstoin in the lower of the sequence. The former is because of the oxygen-popr environment, although the latter is oxygen-rich, the strong bottom washing made organisms difficult to survive. Large amounts of biogenic sedimentary structures are formed in muddy siltstone with medium oxygen content. Therefore, the change process of oxygen content is from strong to weak in vertical direction in the sediments of sedimentary sequence of meandering stream point bar. The oxygen content in coal bed and carbonaceous mudstone may be lower than 0.lml/1.
Taranaki Basin is located in the northwest of the North Island in New Zealand. It was formed in the Late Cretaceous The maximum thickness of the sediments reaches to 11,000m. Taranaki Basin is one of the most prospective areas for petroleum in New Zealand, up to date, four oil (gas) fields have been drilled out, the crude oil show general features of terristrial oil. On the base of present investigation results, it is suggested that Pakawau and Kapuni Croup, which were deposited respectively in Late Cretaceous and Paleoecene-Eocene Epoch, are the possible source rocks. Pakawau and Kapuni groups are mainly composed of the deposits of continental facies and of marine and continental interactive facies. Biogenic sedimentary structures are very developed in the drilled cores of these two groups. Their types of causes of formation and developing degree may be regarded as the mark of oxygen content in sediments. The results of investigation show that the oxygen content is lower than 0.1-0.2ml/1 in coal bed and carbonaceous mudstone with high content of organic matter and has not distroyed by boiturbation; and medium in muddy siltstone and silty mudstone with very developed biogenic structures and intergrowth of bioturbation and small scale borrows, while abundant in coarse clastic rocks with large scale vertical burrows. According to the results of the above investigation and combining sedimentary sequence and primary sedimentary structure sequence, we carry on a comprehensive explanation of sedimentary environment to the partial cores of wells Tane-1 and Kapuni-8. Well Tane1 is taken as an example. This core section belongs to Pakawau Group, the lithologic character is fine-coarse sandstone at the bottom and turns gradually into siltstone, silty mudstone, carbonaceous mudstone and coal bed upwards. The relevant primary sedimentary structures are massive bedding , medium scale cross bedding, compound bedding of lenticular and wavy bedding, small scale cross bedding, horizontal laminated bedding, homogeneous bedding upwards. The regular change of primary sedimentary structure and the grain size character fining upwards are commonly composed of the typical normal fining upwards sedimentary sequence. This kind of sequence is just the product of hydrodynamic change of fluvial sedimentary system. Based on the characters of lacking of fluvial lag deposits at the bottom of sequence and thick over-bank fine sediments in the upper sequence, this core section should belong to the product of later- al migration of meandering stream point bar and of accretion of over-bank fine sediments upwards. Biogenic sedimentary structures change regularly from weak to strong from bottom to top. However, biogenic sedimentary structures are not developed in coal bed and carbonaceous mudstone in the upper of the sequence and in coarse sandstoin in the lower of the sequence. The former is because of the oxygen-popr environment, although the latter is oxygen-rich, the strong bottom washing made organisms difficult to survive. Large amounts of biogenic sedimentary structures are formed in muddy siltstone with medium oxygen content. Therefore, the change process of oxygen content is from strong to weak in vertical direction in the sediments of sedimentary sequence of meandering stream point bar. The oxygen content in coal bed and carbonaceous mudstone may be lower than 0.lml/1.
1991, 9(3): 59-64.
Abstract:
Sinian tempestites is proved for the first time in the northwestern margin of the Tarim Platform, which occur in the upper sub-formation of the Sugiterblack Formation of Upper Sinian System (simply called "upper sub-formation" land can be divided into two types: l.Calcarenaceous tempestites which lie in the nearshore-deposited clastic rocks in the middle and lower parts of the upper sub-formation. 2.Sandy tempestites lie in the shallow-shelf-deposited carbonate at the top of the upper sub-formation. The calcarenaceous tempestites consist of calcirudites. calcisiltites. calcarenites. oolitic limestones and residual oolitic limestones, calcarenaceous sandstones, calcilutites and mudstones. The calcirutes are abundant with sharp eroded boundarys at the bottom and many multi-orientation marks. Scour and fill structures, graded beds and a variety of hummocky cross-stratifications are usually found in the typical tempestites. The synthetic idealized tempestite sequence is composed of seven divisions above the erosional base. They are coarse-grained calcirudite division A (winnowed lag), graded division A. massive dividion B. hummocky cross-stratification division C. planar parallel lamination division D. ripple cross-lamination division E and pelitic division F from the bottom to the top. In comparison with the synthetic idealized tempestite sequence, the sectional structures may be divded into 12 types of quasi-complete, incomplete and complex sections and 9 of which occur in the calcarenaceous tempestites. They represent different stages of storm development controlled by storm intensity, the way of storm moving and current effect, duration of storm and depth of sea water.
Sinian tempestites is proved for the first time in the northwestern margin of the Tarim Platform, which occur in the upper sub-formation of the Sugiterblack Formation of Upper Sinian System (simply called "upper sub-formation" land can be divided into two types: l.Calcarenaceous tempestites which lie in the nearshore-deposited clastic rocks in the middle and lower parts of the upper sub-formation. 2.Sandy tempestites lie in the shallow-shelf-deposited carbonate at the top of the upper sub-formation. The calcarenaceous tempestites consist of calcirudites. calcisiltites. calcarenites. oolitic limestones and residual oolitic limestones, calcarenaceous sandstones, calcilutites and mudstones. The calcirutes are abundant with sharp eroded boundarys at the bottom and many multi-orientation marks. Scour and fill structures, graded beds and a variety of hummocky cross-stratifications are usually found in the typical tempestites. The synthetic idealized tempestite sequence is composed of seven divisions above the erosional base. They are coarse-grained calcirudite division A (winnowed lag), graded division A. massive dividion B. hummocky cross-stratification division C. planar parallel lamination division D. ripple cross-lamination division E and pelitic division F from the bottom to the top. In comparison with the synthetic idealized tempestite sequence, the sectional structures may be divded into 12 types of quasi-complete, incomplete and complex sections and 9 of which occur in the calcarenaceous tempestites. They represent different stages of storm development controlled by storm intensity, the way of storm moving and current effect, duration of storm and depth of sea water.
1991, 9(3): 74-79.
Abstract:
By means of the study on the blasto-sedimentary structures in metamorphosed sedimentary rocks of the upper member of Danfeng Group in Lantian area, Shaanxi Province, the auhtors found and determined some sedimentary structures of storm origion, such as hummocky cross stratification, erosion surfaces, graded bed.ect. The sectional textures of the storm deposits are classified into three types: ABC type. EBCD type. and ABCD type. The tuff at the bottom of the upper member of Danfeng Group deposited on the basic pillow lava at the top of the middle member. Upwards, come the normal marine deposits, which is mainly composed of clay, silty clay, and calcilutite. This phenomenon means that the volcanic activity decreased obviously. The lack of the cross bedding, ripples, which reflect stronger current acting, indicates that the deposition took place below the normal wave base. In the middle part of the upper member of Danfeng Group, there is obvious rhythmic sedimentation which shows the character of flysch. At the top of the upper member, there are thin bedded quartz sandstones, conglomeratic sandstones and dolomites(marbles), additionally, cross bedding, erosion surface can also be seen, therefore, the flow energy is higher and the corresponding sedimentation took place approximately over the normal wave base. Small scale erosion troughes, quasi-flate-gentle wavelike erosion surfaces, and the pebbles with the conponent different from that of the underlying rocks; indicate that it belongs to the distal source type; according to the characters of the storm-formed turbidity current. As a whole, the sedimentary formation of the upper member of Danfeng Group is a shoaling-upwards sequence, which formed approximately at the upper part of the slop to the shelf facies. According to the previous researchers' studies on the geotectonic environment of Danfeng Group, the most of geochemical components of the basic volcanic rocks of Danfeng Group drop into the area of island arc basalt. To the north of Danfeng Group, located Xieyuguan Group of Lower Palaeozoic; while Qinling Group(Pti qn) located between them two. Danfeng Group, the authors propose, to be formed in a Palaeoz forearc basin; and Xieyuguan Group in the backarc basin, while the arc between these two basins was posed of Qinling Group which undergone Proterozoic structural deformation.
By means of the study on the blasto-sedimentary structures in metamorphosed sedimentary rocks of the upper member of Danfeng Group in Lantian area, Shaanxi Province, the auhtors found and determined some sedimentary structures of storm origion, such as hummocky cross stratification, erosion surfaces, graded bed.ect. The sectional textures of the storm deposits are classified into three types: ABC type. EBCD type. and ABCD type. The tuff at the bottom of the upper member of Danfeng Group deposited on the basic pillow lava at the top of the middle member. Upwards, come the normal marine deposits, which is mainly composed of clay, silty clay, and calcilutite. This phenomenon means that the volcanic activity decreased obviously. The lack of the cross bedding, ripples, which reflect stronger current acting, indicates that the deposition took place below the normal wave base. In the middle part of the upper member of Danfeng Group, there is obvious rhythmic sedimentation which shows the character of flysch. At the top of the upper member, there are thin bedded quartz sandstones, conglomeratic sandstones and dolomites(marbles), additionally, cross bedding, erosion surface can also be seen, therefore, the flow energy is higher and the corresponding sedimentation took place approximately over the normal wave base. Small scale erosion troughes, quasi-flate-gentle wavelike erosion surfaces, and the pebbles with the conponent different from that of the underlying rocks; indicate that it belongs to the distal source type; according to the characters of the storm-formed turbidity current. As a whole, the sedimentary formation of the upper member of Danfeng Group is a shoaling-upwards sequence, which formed approximately at the upper part of the slop to the shelf facies. According to the previous researchers' studies on the geotectonic environment of Danfeng Group, the most of geochemical components of the basic volcanic rocks of Danfeng Group drop into the area of island arc basalt. To the north of Danfeng Group, located Xieyuguan Group of Lower Palaeozoic; while Qinling Group(Pti qn) located between them two. Danfeng Group, the authors propose, to be formed in a Palaeoz forearc basin; and Xieyuguan Group in the backarc basin, while the arc between these two basins was posed of Qinling Group which undergone Proterozoic structural deformation.
1991, 9(3): 90-97.
Abstract:
Based on Rhoads-Morse-Byers Model of biofacies in an anoxic basin with consideration of the depth of water, the anoxic basin deposits can be downwards divided into oxygen-rich zone (oxygenate zone), oxygen-weak zone and oxygen-free zone. Corresponded with them are the three biozones as aerobic zone, dysaerobic zone and anaerobic zone. According to the model, this paper deals with the characteristics of the Devonian deposits and biotas in Nandan, Guangxi Province. The Devonian deposits in this region are supposed to be the anoxic basin rocks accummulated in a rifted trough environment. As the result of the increase of separating of earth crust in the end of Early Devonian, the oxygen-weak deposits were presented at Luofu, the central zone of the basin, and lasted into Middle Devonian. At the margin of the basin, such as in Mangchang, delta deposit were occurred in Nabiao age (D21) At the begining of Late Devonian, the oxygen-free sediments with volcanic tuff were deposited in the basin, then the basin began to inversion in the late stage. Summarily, there are four stages that can be divided during the evolution of Devonian sediments and biotas in Nandan anoxic basin: (1) oxygen-rich (oxygenate)-aerobic (D11), (2)oxygen-weak-dysaerobic (D12D2), (3)oxygen-free naerobic (D31), and (4) oxygen-weak -Hiysaerobic(D32).
Based on Rhoads-Morse-Byers Model of biofacies in an anoxic basin with consideration of the depth of water, the anoxic basin deposits can be downwards divided into oxygen-rich zone (oxygenate zone), oxygen-weak zone and oxygen-free zone. Corresponded with them are the three biozones as aerobic zone, dysaerobic zone and anaerobic zone. According to the model, this paper deals with the characteristics of the Devonian deposits and biotas in Nandan, Guangxi Province. The Devonian deposits in this region are supposed to be the anoxic basin rocks accummulated in a rifted trough environment. As the result of the increase of separating of earth crust in the end of Early Devonian, the oxygen-weak deposits were presented at Luofu, the central zone of the basin, and lasted into Middle Devonian. At the margin of the basin, such as in Mangchang, delta deposit were occurred in Nabiao age (D21) At the begining of Late Devonian, the oxygen-free sediments with volcanic tuff were deposited in the basin, then the basin began to inversion in the late stage. Summarily, there are four stages that can be divided during the evolution of Devonian sediments and biotas in Nandan anoxic basin: (1) oxygen-rich (oxygenate)-aerobic (D11), (2)oxygen-weak-dysaerobic (D12D2), (3)oxygen-free naerobic (D31), and (4) oxygen-weak -Hiysaerobic(D32).
1991, 9(3): 106-115.
Abstract:
The measurement results of homogenization temperature and salinity of gas-liquid inclusions inauthigenic quartz of deep sectional sandstone in eastern Songliao Basin are presented, and the mechanism ofthe authiqenic quartz forming, the application of the mentioned results are discussed in this paper. Authigenic quartz is one of the main diagenitic minerals in sandstone, the homogenization temperatureand salinity of gas-liquid inclusions in which may approximatly stand for the diagenitic temperature andsalinity of pore fluid. The index of secondary growth, which is one of the main forms of authigenic quartzforming, reaches to 4-6 in Songliao Basin. It is shown by electronic probe that the enlarged quartz werefromed in different stages and controlled by buried diagenese. The inclusions in the secondary enlargedquartz may represent partially the changing of temperature (76℃-173 ℃)and salinity (0-4 g/100m1) o'f po;e-uid during the forming of the secondary enlarged quartz. The normal relation between homogenizationtemperature (135=150'C ) and salinity has been set up according to Well Chao N0.2. Temperature(℃)=128.85+5.04 x Salinity, with the coofficient of 0..5932. Based on the comparition of homogenization temperature in different depth of several wells, thepalaeothermal gradient of eastern Songliao Basin can be estimated as 4.66"C/100m which is a little higherthan the average thermal gradient 4.2'}/100m of present, this kind of differences may be caused by the dif-ference between palaeo-burial depth and the modern depth. The relative risen height of Chaoyanggou area iscalculated as about 400-SOOm when compared with Sanzhao aera. The functional relation between depth and palaeotemperature in Sanzhao area can be deduced accordineto the data of palaeothermal qradiend and the present thermal gradient: Hb=21.46Tb-137 it can be calculated based on this formula that: The large amount of authigenic quartz formed in 1494.0m(Tb= 76℃);the threshold of oil generation is at I150.Om(Tb60℃);the initial hydrocarbon expelling atdepth of 1365.2-1794.4m (Tb=70-90℃)and the limit depth of petroleum exploration is 2459.7m (Tb=121℃) Salinity of inclusions, carbon and oxygen isotopic compositions of calcite cement in sandstone indicatethat the sedimentary environment was most likely be large fresh-brackish lacustriae rather than marine dur-ing the Early Cretaceous Epoch. The authors are sure that the data of homogenization temperature is quantitatively believable and thatof salinity is semi-quantitative.
The measurement results of homogenization temperature and salinity of gas-liquid inclusions inauthigenic quartz of deep sectional sandstone in eastern Songliao Basin are presented, and the mechanism ofthe authiqenic quartz forming, the application of the mentioned results are discussed in this paper. Authigenic quartz is one of the main diagenitic minerals in sandstone, the homogenization temperatureand salinity of gas-liquid inclusions in which may approximatly stand for the diagenitic temperature andsalinity of pore fluid. The index of secondary growth, which is one of the main forms of authigenic quartzforming, reaches to 4-6 in Songliao Basin. It is shown by electronic probe that the enlarged quartz werefromed in different stages and controlled by buried diagenese. The inclusions in the secondary enlargedquartz may represent partially the changing of temperature (76℃-173 ℃)and salinity (0-4 g/100m1) o'f po;e-uid during the forming of the secondary enlarged quartz. The normal relation between homogenizationtemperature (135=150'C ) and salinity has been set up according to Well Chao N0.2. Temperature(℃)=128.85+5.04 x Salinity, with the coofficient of 0..5932. Based on the comparition of homogenization temperature in different depth of several wells, thepalaeothermal gradient of eastern Songliao Basin can be estimated as 4.66"C/100m which is a little higherthan the average thermal gradient 4.2'}/100m of present, this kind of differences may be caused by the dif-ference between palaeo-burial depth and the modern depth. The relative risen height of Chaoyanggou area iscalculated as about 400-SOOm when compared with Sanzhao aera. The functional relation between depth and palaeotemperature in Sanzhao area can be deduced accordineto the data of palaeothermal qradiend and the present thermal gradient: Hb=21.46Tb-137 it can be calculated based on this formula that: The large amount of authigenic quartz formed in 1494.0m(Tb= 76℃);the threshold of oil generation is at I150.Om(Tb60℃);the initial hydrocarbon expelling atdepth of 1365.2-1794.4m (Tb=70-90℃)and the limit depth of petroleum exploration is 2459.7m (Tb=121℃) Salinity of inclusions, carbon and oxygen isotopic compositions of calcite cement in sandstone indicatethat the sedimentary environment was most likely be large fresh-brackish lacustriae rather than marine dur-ing the Early Cretaceous Epoch. The authors are sure that the data of homogenization temperature is quantitatively believable and thatof salinity is semi-quantitative.
1991, 9(3): 123-129.
Abstract:
As one of the important and precious non-metallic minerals, placer oriental sapphire within basalt of Cenozoic in the eastern coastal China is disscused on its mineralization, geology of deposits and its relationship with geotectonics, in order to provide some messages of exploration. Distribution and the chemical composition of basalt are studied, morever, some potential mineral belts are put out. Occunence, mineral assemblage and principles of mineralization are discussed, similarities and differences in different regions are pointed out. Oriental sapphire, acorite in Hainan and Fujian and ciannamon garnet are analysed. It is revealed by the author that the forming of placer oriental sapphire is controlled by tectonic-magma and weathering. It worth to pay attention to the aluminium hupersaturated basalt, especially for the developed region of washed and drifted deposits.
As one of the important and precious non-metallic minerals, placer oriental sapphire within basalt of Cenozoic in the eastern coastal China is disscused on its mineralization, geology of deposits and its relationship with geotectonics, in order to provide some messages of exploration. Distribution and the chemical composition of basalt are studied, morever, some potential mineral belts are put out. Occunence, mineral assemblage and principles of mineralization are discussed, similarities and differences in different regions are pointed out. Oriental sapphire, acorite in Hainan and Fujian and ciannamon garnet are analysed. It is revealed by the author that the forming of placer oriental sapphire is controlled by tectonic-magma and weathering. It worth to pay attention to the aluminium hupersaturated basalt, especially for the developed region of washed and drifted deposits.
1991, 9(3): 11-21.
Abstract:
The alluvial fans on the western margin of Late Triassic Ordos Basin can be divided into three parts; upper, middle and lower. Upper fans mainly consist of conglomerates which genetically include debris flow, grain flow, sheetflood flow, mud flow and braided stream deposits. Debris flow deposits are mainly composed of clasts. Most of the conglomerates are matrix supported and poorly sorted. With the increase of distance from source area to depositional sites, maximum clast size are reduced, differences among clast size are minimized, ratio of clast to matrix are increased and the rocks are changed gradually from matrix supported to clast supported. Grain flow deposits are identified by their matrix lacking of features. Clasts in these deposits were cemented by iron-oxides, clay minerals or other materials which had precipitated around clasts as thin film through the processes of diagenesis. Sheetflood flow deposits occur as thinly bedded sandstones or gravelly sandstones. And most of their thickness are about tens of centimeters. Braided stream conglomerates are typical for cross beddings and scours on their bases. Mud flow deposits are characterized by a small percentage of clasts and a large percentage of mud. Long axes of some clasts in mud flow deposits may be perpendicular to beddings. Distribution frequency curves of clast size of the conglomerates mentioned above can be classified obviously into three groups, which are correspondent to debris or grain flow, braided stream and sheedflood flow deposits respectively. Curves for debris or grain flow deposits are characterized by multiple peaks showing lack of sorting. Curves of braided stream conglomerates possess a peak near the finest end and gently wave in coarse part, showing poor sorting. Curves of sheetflood flow deposits rise from coarsest end to finest end monotonously, representing quick waning down of the flood. In addition to the shape differences of the curves, the Maximum Distribution Frequency (Mdf) and the Respondent Gravel Size (Rgs) for each of the three deposits are also different. For debris or grain flow deposits, mean Mdf, Rgs and Mdf/ Rgs are 20. 1.5 and 13 respectively, for braided steam ones, they are 30. 1.2 and 23 and for sheetflood flow ones 38. 0.7 and 54. These parameters have their genetic significance. The lower of the values of Mds / Rgs, the higher cohesiveness or transportation energy the flow would have. The authors believe that it is very hopeful to use these curve patterns and parameters as tools in identifying environments of gravelly alluvial fan deposits.
The alluvial fans on the western margin of Late Triassic Ordos Basin can be divided into three parts; upper, middle and lower. Upper fans mainly consist of conglomerates which genetically include debris flow, grain flow, sheetflood flow, mud flow and braided stream deposits. Debris flow deposits are mainly composed of clasts. Most of the conglomerates are matrix supported and poorly sorted. With the increase of distance from source area to depositional sites, maximum clast size are reduced, differences among clast size are minimized, ratio of clast to matrix are increased and the rocks are changed gradually from matrix supported to clast supported. Grain flow deposits are identified by their matrix lacking of features. Clasts in these deposits were cemented by iron-oxides, clay minerals or other materials which had precipitated around clasts as thin film through the processes of diagenesis. Sheetflood flow deposits occur as thinly bedded sandstones or gravelly sandstones. And most of their thickness are about tens of centimeters. Braided stream conglomerates are typical for cross beddings and scours on their bases. Mud flow deposits are characterized by a small percentage of clasts and a large percentage of mud. Long axes of some clasts in mud flow deposits may be perpendicular to beddings. Distribution frequency curves of clast size of the conglomerates mentioned above can be classified obviously into three groups, which are correspondent to debris or grain flow, braided stream and sheedflood flow deposits respectively. Curves for debris or grain flow deposits are characterized by multiple peaks showing lack of sorting. Curves of braided stream conglomerates possess a peak near the finest end and gently wave in coarse part, showing poor sorting. Curves of sheetflood flow deposits rise from coarsest end to finest end monotonously, representing quick waning down of the flood. In addition to the shape differences of the curves, the Maximum Distribution Frequency (Mdf) and the Respondent Gravel Size (Rgs) for each of the three deposits are also different. For debris or grain flow deposits, mean Mdf, Rgs and Mdf/ Rgs are 20. 1.5 and 13 respectively, for braided steam ones, they are 30. 1.2 and 23 and for sheetflood flow ones 38. 0.7 and 54. These parameters have their genetic significance. The lower of the values of Mds / Rgs, the higher cohesiveness or transportation energy the flow would have. The authors believe that it is very hopeful to use these curve patterns and parameters as tools in identifying environments of gravelly alluvial fan deposits.
1991, 9(3): 31-39.
Abstract:
This paper describes the application of element geochemistry- statistics method to sedimentary basin analysis.Over 300 samples of mudstone were systematically collected from the two fully cored wells (W3 and SN15 wells) of southern Songliao Basin, 11 main elemens and 16 trace elements were analyzed for each sample. After the geochemical data are computerized with the models of group analysis, relation analysis, regression analysis and Markov transition matrix, the authors applied these results to stratigraphic division, sedimentary cycle analysis and the study of sedimentary fades, the following are the conclusions: 1 .The green mudstone sequence, which is generally considered to be the upper unit of the fourth member of Quantou Group, should belong to the lower Qingshankou Group. 2.The interbeded red-green mudstones of Yaojia middle member should be interpreted as the sequence deposited in shallow lacustrine flat environment. 3.The results of stratigraphic division and sedimentary cycle analysis obtained from this method should be more reliable than those from well logging for the unique thick mudstone sequence. 4. Element geochemistry is a good way to study sedimentary facies, but some cares should be taken, such as the consideration of sedimentary derivation in the working area, the choice of multi-sedimentary facies only depending on a few elemental geochemical data. 5.The element geochemistry-statistics method can well enlarge the application scope of well debris.
This paper describes the application of element geochemistry- statistics method to sedimentary basin analysis.Over 300 samples of mudstone were systematically collected from the two fully cored wells (W3 and SN15 wells) of southern Songliao Basin, 11 main elemens and 16 trace elements were analyzed for each sample. After the geochemical data are computerized with the models of group analysis, relation analysis, regression analysis and Markov transition matrix, the authors applied these results to stratigraphic division, sedimentary cycle analysis and the study of sedimentary fades, the following are the conclusions: 1 .The green mudstone sequence, which is generally considered to be the upper unit of the fourth member of Quantou Group, should belong to the lower Qingshankou Group. 2.The interbeded red-green mudstones of Yaojia middle member should be interpreted as the sequence deposited in shallow lacustrine flat environment. 3.The results of stratigraphic division and sedimentary cycle analysis obtained from this method should be more reliable than those from well logging for the unique thick mudstone sequence. 4. Element geochemistry is a good way to study sedimentary facies, but some cares should be taken, such as the consideration of sedimentary derivation in the working area, the choice of multi-sedimentary facies only depending on a few elemental geochemical data. 5.The element geochemistry-statistics method can well enlarge the application scope of well debris.
1991, 9(3): 50-58.
Abstract:
Southern Sichuan in this paper refers an area south of Yongchuan City, or is limited in the south of Sichuan Basin, there are a series of gentle foldings, the major structure is named as Luzhou Palaeoupwarping which develeped since Early Permian and reached its peak stage in Early Triassic. As a result of subqeous rising of eastern Sichuan and northen Guizhou, the water flow was restricted and a set of shallow sea and lagoon carbonate-gypsum interdeposits were formed during Jialingjiang Period. By the end of Jialingjiang Period, erogenic activity (corressponding to the initial episodo of Indo-China movement) led to the rising and upwraping of the study area and accompany with volcanic eruptions. The member 4 and 5 of Jialingjiang Formation on the top of Luzhou paleaoupwarping eroded entirely and the member 3 eroded in different scale. Then the Jurassic and Cretaceous sedimented continuously. The first and the second member of Jialingjiang Formation are a set of shallow sea carbonate mudstone, the lower part of which contain much of marine fossils but there are no longer in the upper part, it indicates that by the end of Jialingjiang Age, the study area was a near shore tidal to above tidal environment. Fossils and geochemical parameters change abruptly at the stratigraphic boundary. According to the δC13 value and other parameters, the T1 J12 should be re-calasified to T1 J51. The metacontemporaneous dolomite maintain the initial istopic composition more persistently than its calcite precursor, the calculated sedimentary temperature based on δ18O of metacomporaneous dolomite is 28.5-37.5℃ and it shows clearly that the difference of δ18O between paragenetic dolomite and calcite is less than 2% , which suggests that most dolomite is not formed by dolomization. In the case of constant CO3= and solid state, Mg++ replaced Ca++ and the increase of porosity because of the diffrence between the radius of Mg++ and Ca++. The preservence of porosity depends mainly on the process of dolomization and the genetic type of dolomite. There are some dolomitic cements formed in later diagenesis and the δ13C and δ18O values are slightly lighter than that of calcite. The equilibrium temperature of dolomite-calcite is 150-260℃ with the average of 210℃ , associated with palaeogeothermal gradient, it can be predicted that the burial depth of the first and second memeber of Jialingjiang Formation is 3700-4000m. compare with 1600-1700m of the present, it indicates that the strata may have been upwarped and eroded about 2000m. A sedimentary diagenesis model of lower Triassic in southern Sichuan is set up based on the isotopic, petrologic and palaeontologic data.
Southern Sichuan in this paper refers an area south of Yongchuan City, or is limited in the south of Sichuan Basin, there are a series of gentle foldings, the major structure is named as Luzhou Palaeoupwarping which develeped since Early Permian and reached its peak stage in Early Triassic. As a result of subqeous rising of eastern Sichuan and northen Guizhou, the water flow was restricted and a set of shallow sea and lagoon carbonate-gypsum interdeposits were formed during Jialingjiang Period. By the end of Jialingjiang Period, erogenic activity (corressponding to the initial episodo of Indo-China movement) led to the rising and upwraping of the study area and accompany with volcanic eruptions. The member 4 and 5 of Jialingjiang Formation on the top of Luzhou paleaoupwarping eroded entirely and the member 3 eroded in different scale. Then the Jurassic and Cretaceous sedimented continuously. The first and the second member of Jialingjiang Formation are a set of shallow sea carbonate mudstone, the lower part of which contain much of marine fossils but there are no longer in the upper part, it indicates that by the end of Jialingjiang Age, the study area was a near shore tidal to above tidal environment. Fossils and geochemical parameters change abruptly at the stratigraphic boundary. According to the δC13 value and other parameters, the T1 J12 should be re-calasified to T1 J51. The metacontemporaneous dolomite maintain the initial istopic composition more persistently than its calcite precursor, the calculated sedimentary temperature based on δ18O of metacomporaneous dolomite is 28.5-37.5℃ and it shows clearly that the difference of δ18O between paragenetic dolomite and calcite is less than 2% , which suggests that most dolomite is not formed by dolomization. In the case of constant CO3= and solid state, Mg++ replaced Ca++ and the increase of porosity because of the diffrence between the radius of Mg++ and Ca++. The preservence of porosity depends mainly on the process of dolomization and the genetic type of dolomite. There are some dolomitic cements formed in later diagenesis and the δ13C and δ18O values are slightly lighter than that of calcite. The equilibrium temperature of dolomite-calcite is 150-260℃ with the average of 210℃ , associated with palaeogeothermal gradient, it can be predicted that the burial depth of the first and second memeber of Jialingjiang Formation is 3700-4000m. compare with 1600-1700m of the present, it indicates that the strata may have been upwarped and eroded about 2000m. A sedimentary diagenesis model of lower Triassic in southern Sichuan is set up based on the isotopic, petrologic and palaeontologic data.
1991, 9(3): 65-73.
Abstract:
The palaeomorphologic feature is one of the primary geological parameters in basin analysis. This paper demonstrates the palaeomorphologic features of the basement of the Jurassic coal measures, the depositional characteristics of Fuxian Formation and the relationships between them in Yulin district. Ordos Basin. It has been revealed that there is a buried-valley Shenyu Buried-Valley) in the eastern study area, and a buried-hill (Wushenqi Buried-Hill) in the western. Fuxian Formation, which directly overlies on the basement with 0-131.11 mthick, consists of conglomerate, sandstone, mudstonc. claystone and coal line. The principal components recognized in outcrops and drill cores are alluvial fan. lacustrine beach, small delta, lacustrine, fluvial and swamp deposits. Controlled by the palaeomorphologic relief, the lacustrine environment dominated the eastern study area, the alluvial fan and fluvial environment developed in the northeastern and western parts, and in the transition part, the lacustrine beach and samll delta were deposited. As a whole, the general depositional features of the Shenyu Buried -Valley are determined by the associations between buried-hills and buried-valleys in Ordos Basin.
The palaeomorphologic feature is one of the primary geological parameters in basin analysis. This paper demonstrates the palaeomorphologic features of the basement of the Jurassic coal measures, the depositional characteristics of Fuxian Formation and the relationships between them in Yulin district. Ordos Basin. It has been revealed that there is a buried-valley Shenyu Buried-Valley) in the eastern study area, and a buried-hill (Wushenqi Buried-Hill) in the western. Fuxian Formation, which directly overlies on the basement with 0-131.11 mthick, consists of conglomerate, sandstone, mudstonc. claystone and coal line. The principal components recognized in outcrops and drill cores are alluvial fan. lacustrine beach, small delta, lacustrine, fluvial and swamp deposits. Controlled by the palaeomorphologic relief, the lacustrine environment dominated the eastern study area, the alluvial fan and fluvial environment developed in the northeastern and western parts, and in the transition part, the lacustrine beach and samll delta were deposited. As a whole, the general depositional features of the Shenyu Buried -Valley are determined by the associations between buried-hills and buried-valleys in Ordos Basin.
1991, 9(3): 80-89.
Abstract:
The reef of the Honghuayuanian Age in Zhangzhai of Yuping County. Guizhou Province is a baffling buildup reef, which scatters in marginal platform facies. The association of fossils is characterized by sponge such as "calathium" sp., Anchaoscyphia chiliense, A. sp. and algae. The o'thers are Crinoil. Trilobite, Braichiopodaetc. The sedimentary rocks, th refore. are divided mainly into four types as algal limestone, sponge limestone, bioclastic limestone, oncolites and clotted limestone. In the reef core facies. there are algal limestone (A), sponge limestone (B). bioclastic limestone (C). and oncelites and clotted limestone (D). These types of rocks make up a practical sequence of stratum that consists of 41 layers: Top-DCDCDCDABADCDCBDBCDABABDC ABACBABDBDCBDCBD-bottom In which there are 7 As. 11 Bs. 11Cs and 12 Ds. In term of the Markov chain analysis, it was found that the depositional sequence of each cycle is composed of: →B→A→B→D→C→D→C→ Fore reef facies is characterized by micrite. pelmicrite and bioclastic limestone. These rocks are dolomitized locally. Joints are very developed, bitumens contaminated and stuffed in the joints as leticulars. There are much collapse breccia. This facies belong to the quiet environment which is much deep lower than the wave base. The buildup of reef core is washed by wave and collapsed, the breccia then is formed. The association of fossils and rocks in back reef facies. are similar to that of the reef core, but different in their thickness. This facies. actually, belongs to the carbonate platform biostrom facies. The base of reef are stratum of Tongzian Age which is composed of sparry pellet limstone and oncolites - clotted limestone, this stratum belongs to the carbonate platform marginal allochcm bank facies. The algal and other crust organisms arc very develeped. Similar to the strata of the same ages, this stratum form a buildup too. The depositional materials of this platform marginal facies formed a solid sedimentary base where is favour for reef forming.
The reef of the Honghuayuanian Age in Zhangzhai of Yuping County. Guizhou Province is a baffling buildup reef, which scatters in marginal platform facies. The association of fossils is characterized by sponge such as "calathium" sp., Anchaoscyphia chiliense, A. sp. and algae. The o'thers are Crinoil. Trilobite, Braichiopodaetc. The sedimentary rocks, th refore. are divided mainly into four types as algal limestone, sponge limestone, bioclastic limestone, oncolites and clotted limestone. In the reef core facies. there are algal limestone (A), sponge limestone (B). bioclastic limestone (C). and oncelites and clotted limestone (D). These types of rocks make up a practical sequence of stratum that consists of 41 layers: Top-DCDCDCDABADCDCBDBCDABABDC ABACBABDBDCBDCBD-bottom In which there are 7 As. 11 Bs. 11Cs and 12 Ds. In term of the Markov chain analysis, it was found that the depositional sequence of each cycle is composed of: →B→A→B→D→C→D→C→ Fore reef facies is characterized by micrite. pelmicrite and bioclastic limestone. These rocks are dolomitized locally. Joints are very developed, bitumens contaminated and stuffed in the joints as leticulars. There are much collapse breccia. This facies belong to the quiet environment which is much deep lower than the wave base. The buildup of reef core is washed by wave and collapsed, the breccia then is formed. The association of fossils and rocks in back reef facies. are similar to that of the reef core, but different in their thickness. This facies. actually, belongs to the carbonate platform biostrom facies. The base of reef are stratum of Tongzian Age which is composed of sparry pellet limstone and oncolites - clotted limestone, this stratum belongs to the carbonate platform marginal allochcm bank facies. The algal and other crust organisms arc very develeped. Similar to the strata of the same ages, this stratum form a buildup too. The depositional materials of this platform marginal facies formed a solid sedimentary base where is favour for reef forming.
1991, 9(3): 98-105.
Abstract:
The strata of Gaoshanhe Group lies in Long County to Luonan County of Shaanxi Province in the Southern Margin of the North China Platform. The total thickness of the deposits reaches to 3989.9 metres, and the clasolite tidal flat deposits are well developed, conglomerate, sandstone, siltstone and argillaceous rock (slate) occupy an important proportion, while a little dolomite. Some typical sedimentary features which reflect their envioronment have been preserved in the tidal flat deposits. The predominant ones are double mud beds, B-C sequence, tidal bedding, herringbone cross-bedding, reactivated surface structure, various shapes of ripples, drying cracks, flattened mud gravels, wormes and their trace fossils and so on. The clasolite tidal flat sedimentary envioronment of the Gaoshanhe Group can be farther divided into three subfacieses, low tidal flat, middle tidal flat and high tidal flat. When sedimentation moved forward to sea, the tidal flats piled up successively, and formed a progradational sequence in which the grain size of sediments diminishes uppwards. In the low tidal flat, the medium-bedded, medium-fine grained quartatic sandstone which have higher maturity and small-scale current cross bedding is deposited in the thick-bedded, medium-grained quartzitic sandstone in tidal under flat which have large scale cross bedding. The flattened mud gravels, herringbone cross-bedding, reactionary surface structure and various ripple shapes can be seen and they are intorgrown. In the midc tidal flat, the dominant kinds of rock are brown-grey thin-medium bedded, fine-grained quartzose sandstone, quartz graywacke, dark grey slate and sand-contained slate. They are thin-interbedded, the flaser beddings, wavy beddings and lenticular beddings are developed. In the high tidal flat, the dominant kinds of rocks are thick-bedded slate, sand-contained slate with a little thin梑edded siltstone and thin-grained quartzose sandstone, the horizontal beddings are developed and drying cracks are very usual. The thickness of a complete tidal flat sedimentary sequence in the region is 2 to 5 metres in general with the average of 3.5 metres. Based on the theory of G. deV. Klein (1970). it can be infered that the old tidal range of the Gaoshanhe stage is maybe about 3.5 metres which is similar to the modern tidal range of the gulf. The region has been considered as a very important sedimentary centre of the North China Platform during the Gaoshanhe stage of Changcheng Period. Under the tectonic setting which descended steadily for long period and was compensated correspondingly, a suit of deposits in which the predominant kinds of rock are clasolite tidal flat ones is developed. We can infer that these kinds of sediments formed basically in the tidal epicontinental sea of the old continental margin.
The strata of Gaoshanhe Group lies in Long County to Luonan County of Shaanxi Province in the Southern Margin of the North China Platform. The total thickness of the deposits reaches to 3989.9 metres, and the clasolite tidal flat deposits are well developed, conglomerate, sandstone, siltstone and argillaceous rock (slate) occupy an important proportion, while a little dolomite. Some typical sedimentary features which reflect their envioronment have been preserved in the tidal flat deposits. The predominant ones are double mud beds, B-C sequence, tidal bedding, herringbone cross-bedding, reactivated surface structure, various shapes of ripples, drying cracks, flattened mud gravels, wormes and their trace fossils and so on. The clasolite tidal flat sedimentary envioronment of the Gaoshanhe Group can be farther divided into three subfacieses, low tidal flat, middle tidal flat and high tidal flat. When sedimentation moved forward to sea, the tidal flats piled up successively, and formed a progradational sequence in which the grain size of sediments diminishes uppwards. In the low tidal flat, the medium-bedded, medium-fine grained quartatic sandstone which have higher maturity and small-scale current cross bedding is deposited in the thick-bedded, medium-grained quartzitic sandstone in tidal under flat which have large scale cross bedding. The flattened mud gravels, herringbone cross-bedding, reactionary surface structure and various ripple shapes can be seen and they are intorgrown. In the midc tidal flat, the dominant kinds of rock are brown-grey thin-medium bedded, fine-grained quartzose sandstone, quartz graywacke, dark grey slate and sand-contained slate. They are thin-interbedded, the flaser beddings, wavy beddings and lenticular beddings are developed. In the high tidal flat, the dominant kinds of rocks are thick-bedded slate, sand-contained slate with a little thin梑edded siltstone and thin-grained quartzose sandstone, the horizontal beddings are developed and drying cracks are very usual. The thickness of a complete tidal flat sedimentary sequence in the region is 2 to 5 metres in general with the average of 3.5 metres. Based on the theory of G. deV. Klein (1970). it can be infered that the old tidal range of the Gaoshanhe stage is maybe about 3.5 metres which is similar to the modern tidal range of the gulf. The region has been considered as a very important sedimentary centre of the North China Platform during the Gaoshanhe stage of Changcheng Period. Under the tectonic setting which descended steadily for long period and was compensated correspondingly, a suit of deposits in which the predominant kinds of rock are clasolite tidal flat ones is developed. We can infer that these kinds of sediments formed basically in the tidal epicontinental sea of the old continental margin.
1991, 9(3): 116-122.
Abstract:
Xingyun Lake is a faulted trough lake which measures 10.5 by 3.8 km. The formation of vivianite nodule in which has been systematically researched by field observation and the using of the techniques of x-ray diffraction and x-ray photograph, infrared spectrogram, stable isotope analysis, chemical composition analysis and electron microprobe analysis, etc. The vivianite which is first discovered in Xingyun Lake has been determined and its physical properties, chemical composition, mineralogical parameters have been described in detail. A typical x-ray peaks (7.8899? 6.691 ?, 4.896?, 4.062?, 2.917?, 2.702?,) and infrared spectrograms (3137-1cm. 1600-1cm. 1090-1cm. 940-1cm. 540-1cm. and 470-1cm.), x-ray photograph data (a= 10.096A, b= 13.50?, c = 4.70?, 0= 104°34 ' ) of vivianite have been supplied. The origion model of vivianite in Xingyun Lake has been put forward based on the discussion of the sources of phosphorus and ferric matter and the formation of reducing environment. The ferric matter was carried by river and the phosphorus matter by animal, vegetation and bacterial reduction, and then deposit in low enery areas. The organic matter and organisms are buried by sediments, and pore water is enclosed in it. The organic matter is decomposed and carbon dioxide is produced by the bacteria action and fermentation. Under the reducing environment, ferrous (Fe3+) is reducd to ferric (Fe:2+). Vivianite is supersaturated and precipitated from sediments as the contents of ferric and phosphated ion of pore water increase. The chemical reaction equation is as folio ws. 3Fe2++2HPO42-+2OH-1+6H-2O=Fe3(PO4)2 · 8H2O (vivianite) The condition of the formation of vivianite itself, diagenesis of sediments, trace elements, stable isotopes, rock properties and sedimentary structures as well as clay mineral assemblages of welling core burying in vivianite have been studied. It can be deduced that the vivianite nodules may stand for the primary edimentary environment, i. e., a sedimentary symbol of inland fresh lake ,and it is only discovered in sediments of fresh shallow lake and lake bay. That is ,it formed in a low energy environment of fresh shallow lake or lake bay.
Xingyun Lake is a faulted trough lake which measures 10.5 by 3.8 km. The formation of vivianite nodule in which has been systematically researched by field observation and the using of the techniques of x-ray diffraction and x-ray photograph, infrared spectrogram, stable isotope analysis, chemical composition analysis and electron microprobe analysis, etc. The vivianite which is first discovered in Xingyun Lake has been determined and its physical properties, chemical composition, mineralogical parameters have been described in detail. A typical x-ray peaks (7.8899? 6.691 ?, 4.896?, 4.062?, 2.917?, 2.702?,) and infrared spectrograms (3137-1cm. 1600-1cm. 1090-1cm. 940-1cm. 540-1cm. and 470-1cm.), x-ray photograph data (a= 10.096A, b= 13.50?, c = 4.70?, 0= 104°34 ' ) of vivianite have been supplied. The origion model of vivianite in Xingyun Lake has been put forward based on the discussion of the sources of phosphorus and ferric matter and the formation of reducing environment. The ferric matter was carried by river and the phosphorus matter by animal, vegetation and bacterial reduction, and then deposit in low enery areas. The organic matter and organisms are buried by sediments, and pore water is enclosed in it. The organic matter is decomposed and carbon dioxide is produced by the bacteria action and fermentation. Under the reducing environment, ferrous (Fe3+) is reducd to ferric (Fe:2+). Vivianite is supersaturated and precipitated from sediments as the contents of ferric and phosphated ion of pore water increase. The chemical reaction equation is as folio ws. 3Fe2++2HPO42-+2OH-1+6H-2O=Fe3(PO4)2 · 8H2O (vivianite) The condition of the formation of vivianite itself, diagenesis of sediments, trace elements, stable isotopes, rock properties and sedimentary structures as well as clay mineral assemblages of welling core burying in vivianite have been studied. It can be deduced that the vivianite nodules may stand for the primary edimentary environment, i. e., a sedimentary symbol of inland fresh lake ,and it is only discovered in sediments of fresh shallow lake and lake bay. That is ,it formed in a low energy environment of fresh shallow lake or lake bay.
1991, 9(3): 130-138.
Abstract:
The purplish-red diamicton of Nantuo Formation in eastern Sichuan is considered by the author as the origin of debris flows which has four featurs as follows. (l)The mixed and washed gravel layers are shown by the contents of gravels, the washed layers contain 25-30 percent of gravels while the mixed ones 5-20% percent. The mixed layer was formed by debris flow and then some of the matrix and granules on the top of it were washed away by mountain streams, so the washed layer was formed.(2)There are a lot of lenticular sandstones in the purple diamicton, as the mineral composition, texture and structure of the lenticulars are astonishingly similar to those of the sandstones in alluvial fans of Chengjiang Formation, the origins of them should be the same.(3)Boulders are more rich in the upper part of the diamicton and (4).there are a great many of collisional pots on the gravel surface, it might be caused by the colliding and floating inter gravels during the flowing of debris flow . At least 7 or 8 actions of debris flow can be recognized based on the depositibnal features of the diamicton. Two subfacies can be divided of the diamicton which are debris flow channels in the west of Xiaojiang fault and debris fans in the east of the fault. The palaeocurrent direction of debris flow is in accordance with the alluvial facies of Chengjiang Formation, i. e. from west to east. In Nantuo Period, the palaeolatitude of eastern Yunnan Province was 16.9° N, Combined with palaeoclimatical data, the palaeoclimate then should be hot rather than cold. So the being of Nantuo Ice Age is doubtful.
The purplish-red diamicton of Nantuo Formation in eastern Sichuan is considered by the author as the origin of debris flows which has four featurs as follows. (l)The mixed and washed gravel layers are shown by the contents of gravels, the washed layers contain 25-30 percent of gravels while the mixed ones 5-20% percent. The mixed layer was formed by debris flow and then some of the matrix and granules on the top of it were washed away by mountain streams, so the washed layer was formed.(2)There are a lot of lenticular sandstones in the purple diamicton, as the mineral composition, texture and structure of the lenticulars are astonishingly similar to those of the sandstones in alluvial fans of Chengjiang Formation, the origins of them should be the same.(3)Boulders are more rich in the upper part of the diamicton and (4).there are a great many of collisional pots on the gravel surface, it might be caused by the colliding and floating inter gravels during the flowing of debris flow . At least 7 or 8 actions of debris flow can be recognized based on the depositibnal features of the diamicton. Two subfacies can be divided of the diamicton which are debris flow channels in the west of Xiaojiang fault and debris fans in the east of the fault. The palaeocurrent direction of debris flow is in accordance with the alluvial facies of Chengjiang Formation, i. e. from west to east. In Nantuo Period, the palaeolatitude of eastern Yunnan Province was 16.9° N, Combined with palaeoclimatical data, the palaeoclimate then should be hot rather than cold. So the being of Nantuo Ice Age is doubtful.
