1985 Vol. 3, No. 1
column
Display Method:
1985, 3(1): 1-15.
Abstract:
Shidao Island, the highest one among the Xisha Archipelago, is some 15 metersabove sea level.The sequence of the biocalcarenites occurred on the island is cha-racterized by the alternation of that with cross-beddings and parallel beddings.O wing to the misinterpretation of the sedimentary structures, it has caused so m econ troversaries. T he materials of the biocalcarenites are obviously from the destruction of thecontemporaneous reef complex. Most of the grain components range in medium tofine sands with perfect roundness. T hree kinds of boundary surfaces have been found in the sequence.First-orderboundaries are marked with the occurence of paleosols which is nearly horizontal.T he paleosols, w hick indicate a non deposition period and a change of clim ate, arecharacterized by the dece mentation and phosphorization of the rocks, and the occu-rence of continental snail fossils.Wide distributed rhitholiths demonstrate thegrowth of plant during the stage of pedogenesis. The second-order boundaries are those between dune deposits and interdunedeposits.They are formed by the climbing of the dunes and interdunes under theaction of NE-trade wind.The boundaries sli,;htly dip at an angle less than 10.aga-inst the wind direction and comparable with the boundaries found in modern eoliandeposits. T'he third-order boundaries are the boundaries of costs，which inclinc exclusi-vely windward. Based on the principles of comparative se;dimenlology，she first一order and third-order boundaries are isochronous, but the second一order boundories only of facies. At least two first-order boundaries occur in the sequence of biocalcarenites onthe island.The lower one might be traced on the whole island and is 20-30cm inthickness. The upper one is coincident with the modern topographical surface. The dune deposits, usually 3-7m in thickness, have well一preserved cross-beddin-gs on great scale, including trough cross一beddings, convex cross-beddings and planarcross-beddings. The dip argle of the cross-beddings may reach 35 or so. The interdunedeposits show roughly paralled bedding,but in fact, they are all cross-beddings withvery small dip angle. In conclusion, the coexistence of the three boundary surfaces and the dune andinterdune deposits marks the feature of the eolian biocalcarenits. A facies modelshowingin figure 15 is proposed, which may be used elsewhere, Basedon the data of C14 dating collected from the previous works, the authorsbelieve that the biocalcarenites on Shidao Island were formed some 3200 years agowhen the sea level stood at a low level，then the island passed a transgression per-iod with alternation of dry and wet weather. All the controversaries might besolved by the model mentioned in the paper.
Shidao Island, the highest one among the Xisha Archipelago, is some 15 metersabove sea level.The sequence of the biocalcarenites occurred on the island is cha-racterized by the alternation of that with cross-beddings and parallel beddings.O wing to the misinterpretation of the sedimentary structures, it has caused so m econ troversaries. T he materials of the biocalcarenites are obviously from the destruction of thecontemporaneous reef complex. Most of the grain components range in medium tofine sands with perfect roundness. T hree kinds of boundary surfaces have been found in the sequence.First-orderboundaries are marked with the occurence of paleosols which is nearly horizontal.T he paleosols, w hick indicate a non deposition period and a change of clim ate, arecharacterized by the dece mentation and phosphorization of the rocks, and the occu-rence of continental snail fossils.Wide distributed rhitholiths demonstrate thegrowth of plant during the stage of pedogenesis. The second-order boundaries are those between dune deposits and interdunedeposits.They are formed by the climbing of the dunes and interdunes under theaction of NE-trade wind.The boundaries sli,;htly dip at an angle less than 10.aga-inst the wind direction and comparable with the boundaries found in modern eoliandeposits. T'he third-order boundaries are the boundaries of costs，which inclinc exclusi-vely windward. Based on the principles of comparative se;dimenlology，she first一order and third-order boundaries are isochronous, but the second一order boundories only of facies. At least two first-order boundaries occur in the sequence of biocalcarenites onthe island.The lower one might be traced on the whole island and is 20-30cm inthickness. The upper one is coincident with the modern topographical surface. The dune deposits, usually 3-7m in thickness, have well一preserved cross-beddin-gs on great scale, including trough cross一beddings, convex cross-beddings and planarcross-beddings. The dip argle of the cross-beddings may reach 35 or so. The interdunedeposits show roughly paralled bedding,but in fact, they are all cross-beddings withvery small dip angle. In conclusion, the coexistence of the three boundary surfaces and the dune andinterdune deposits marks the feature of the eolian biocalcarenits. A facies modelshowingin figure 15 is proposed, which may be used elsewhere, Basedon the data of C14 dating collected from the previous works, the authorsbelieve that the biocalcarenites on Shidao Island were formed some 3200 years agowhen the sea level stood at a low level，then the island passed a transgression per-iod with alternation of dry and wet weather. All the controversaries might besolved by the model mentioned in the paper.
1985, 3(1): 54-62.
Abstract:
The ore field richin Pb zn ore deposits in the Fengxian-Taibai counties is located in the middle of the Qinling Mts.. The orebearing bed mainly exists in the transitional sedimentary beds between the Gudaoling Group and the xinghongpu Group of the Middle Devonian Series. It can be divided into two ore-bearing beds. The upper bed is the predominant one, forming the huge and the medium-sized ore deposits in this area. This paper briefly deals with the distribution of the sea and the land, the sea floor reliefs, the hydrodynamic conditions and the physico-chemical conditions during the sedimentary period of the main ore-bearing bed of the ore field in the Fengxian-Taibai counties. By the texture analysis section, it describes the evolutionary process of facies from the platform marginal shoal facies to the platform marginal bioherm facies-the localized platform facies-the platform marginal shoal facies-the platform marginal bioherm facies of the Middle Devonian (Lower Givetian) since the ore field is divided into two along the South-north line of Hetaoba, we have found a marked difference of the ore-forming characteristics between the east and the west of the ore field. The geographical distribution of some huge and medium-sized ore deposits clearly shows that the restricted environment forming the barrier island of the bioherms is favorable for the ore-formation. The field work has proved that the distribution of ore deposits is controlled by the barrier island of the bioherms in the neighboring region of the Weiziping. The ore-bearing bed was formed at the end of the two reef-building periods during the Middle Devonian (Lower Givetian), and the formation was closely related to the bioherms. Thus, the advantageous foundation was provided for the ore beds of later concentration under all kinds reconstruction process. In a word, the ore field in the Fengxian-Taibai Counties belongs to a kind of the strata-bound ore deposits, and some promising areas have been indicated in further prospectings.
The ore field richin Pb zn ore deposits in the Fengxian-Taibai counties is located in the middle of the Qinling Mts.. The orebearing bed mainly exists in the transitional sedimentary beds between the Gudaoling Group and the xinghongpu Group of the Middle Devonian Series. It can be divided into two ore-bearing beds. The upper bed is the predominant one, forming the huge and the medium-sized ore deposits in this area. This paper briefly deals with the distribution of the sea and the land, the sea floor reliefs, the hydrodynamic conditions and the physico-chemical conditions during the sedimentary period of the main ore-bearing bed of the ore field in the Fengxian-Taibai counties. By the texture analysis section, it describes the evolutionary process of facies from the platform marginal shoal facies to the platform marginal bioherm facies-the localized platform facies-the platform marginal shoal facies-the platform marginal bioherm facies of the Middle Devonian (Lower Givetian) since the ore field is divided into two along the South-north line of Hetaoba, we have found a marked difference of the ore-forming characteristics between the east and the west of the ore field. The geographical distribution of some huge and medium-sized ore deposits clearly shows that the restricted environment forming the barrier island of the bioherms is favorable for the ore-formation. The field work has proved that the distribution of ore deposits is controlled by the barrier island of the bioherms in the neighboring region of the Weiziping. The ore-bearing bed was formed at the end of the two reef-building periods during the Middle Devonian (Lower Givetian), and the formation was closely related to the bioherms. Thus, the advantageous foundation was provided for the ore beds of later concentration under all kinds reconstruction process. In a word, the ore field in the Fengxian-Taibai Counties belongs to a kind of the strata-bound ore deposits, and some promising areas have been indicated in further prospectings.
1985, 3(1): 63-70.
Abstract:
Epiphyton boundstones are widely distributed in Zhangxia Formation of the Middle Cambrian in the middle of Shandong Province, Fuxian of Liaoning Province, Hunjiang City of Jilin Province and Suxian of Anhui Province. The Epiphyton boundstones exposed in the field are light grey massive limestone. The Epiphyton boundstones are mainly composed of Epiphyton, and the boundstone has not laminated structure. Therefore, the Epiphyton boundstones not only differ from stromatolithic boundstone, but also differ from thrombolitic algal boundstone. The Epiphyton boundstones are pure limestones, containing less than 2% of insoluble residue and less than 0.5% of MgO. The characters of chemical composition in the Epiphyton boundstones have demonstrated that Epiphyton had grown and fliourished in clear water at that geological time. In this area, Epiphyton boundstones occur as three forms: domed bioherm, tabular biostrome and medium to thick-bedded boundstone. The different forms of Epiphyton boundstone and their lithologic type assemblages suggest that Epiphyton boundstone develope in different depositional environments. Domed Epiphyton bioherms are mainly distributed in the upper part of Zhangxia Formation at Xiwangzhuang of Yiyuan County, Shandong Province, Mopan Hill of Fuxian, Liaoning Province and in the middle part of Zhangxia Formation of Changxing Island. The domed Epiphytos bioherm complex interbedded with oosparites in the upper part of Zhangxia Formation indicates that domed bioherm complex was formed in shelf edge shoal. Therefore, the sedimentary assemblages of domed Epiphyton bioherm complex and oosparites probably represented as shelf margin shoal-reef facies passing eastwards into outer shelf. The tabular Epiphyton biostroms are distributed in Jiulong Mountain of Laiwu County, where it spreads laterally over long distances. The tabular Epiphyton biostroms constitute cyclic repetition of beds within the section, each cyclic bed comprising oomicrites at the base, followed by massive Epiphyton boundstone (1-2.5m in thickness) grading upwards into calcareous shales, worm trace micrites, irregular nodular micrites. This sedimentary sequence seems to represent a back shoal environment. The medium to thick-bedded Epiphyton boundstones are distributed in Gushang of Changqing County, where they are interbedded with skeletal micrites, dolomttled micrites containing Epiphyton and Girvanella fragments. This sequence shows that the medium to thick-bedded Epiphyton boundstones was formed in inner shelf lagoon environment. As mentioned-above, the geographical distribution of the Epiphyton boundstones from Changqing County eastward to Juxian County of Shandong Province suggests that a model of depositional facies be divided into four facies belts from west to east: inner shelf lagoon, back shoal, shelf margin shoal-reef and outer shelf during Late Zhangxia time. Whilst depositional environments of the Early to Middle Zhangxia Age are shelf margin shoal and outer shelf at Juxian, Yishui County and Fuxian. From it one might infer that in the eastern reigon to Juxian, Shandong Province and Fuxian, Liaoning Province was not an erosional old land (Jiao-Liao old land) in reality as suggested before, but an open outer continental shelf during the Middle Cambrian Zhangxia Age.
Epiphyton boundstones are widely distributed in Zhangxia Formation of the Middle Cambrian in the middle of Shandong Province, Fuxian of Liaoning Province, Hunjiang City of Jilin Province and Suxian of Anhui Province. The Epiphyton boundstones exposed in the field are light grey massive limestone. The Epiphyton boundstones are mainly composed of Epiphyton, and the boundstone has not laminated structure. Therefore, the Epiphyton boundstones not only differ from stromatolithic boundstone, but also differ from thrombolitic algal boundstone. The Epiphyton boundstones are pure limestones, containing less than 2% of insoluble residue and less than 0.5% of MgO. The characters of chemical composition in the Epiphyton boundstones have demonstrated that Epiphyton had grown and fliourished in clear water at that geological time. In this area, Epiphyton boundstones occur as three forms: domed bioherm, tabular biostrome and medium to thick-bedded boundstone. The different forms of Epiphyton boundstone and their lithologic type assemblages suggest that Epiphyton boundstone develope in different depositional environments. Domed Epiphyton bioherms are mainly distributed in the upper part of Zhangxia Formation at Xiwangzhuang of Yiyuan County, Shandong Province, Mopan Hill of Fuxian, Liaoning Province and in the middle part of Zhangxia Formation of Changxing Island. The domed Epiphytos bioherm complex interbedded with oosparites in the upper part of Zhangxia Formation indicates that domed bioherm complex was formed in shelf edge shoal. Therefore, the sedimentary assemblages of domed Epiphyton bioherm complex and oosparites probably represented as shelf margin shoal-reef facies passing eastwards into outer shelf. The tabular Epiphyton biostroms are distributed in Jiulong Mountain of Laiwu County, where it spreads laterally over long distances. The tabular Epiphyton biostroms constitute cyclic repetition of beds within the section, each cyclic bed comprising oomicrites at the base, followed by massive Epiphyton boundstone (1-2.5m in thickness) grading upwards into calcareous shales, worm trace micrites, irregular nodular micrites. This sedimentary sequence seems to represent a back shoal environment. The medium to thick-bedded Epiphyton boundstones are distributed in Gushang of Changqing County, where they are interbedded with skeletal micrites, dolomttled micrites containing Epiphyton and Girvanella fragments. This sequence shows that the medium to thick-bedded Epiphyton boundstones was formed in inner shelf lagoon environment. As mentioned-above, the geographical distribution of the Epiphyton boundstones from Changqing County eastward to Juxian County of Shandong Province suggests that a model of depositional facies be divided into four facies belts from west to east: inner shelf lagoon, back shoal, shelf margin shoal-reef and outer shelf during Late Zhangxia time. Whilst depositional environments of the Early to Middle Zhangxia Age are shelf margin shoal and outer shelf at Juxian, Yishui County and Fuxian. From it one might infer that in the eastern reigon to Juxian, Shandong Province and Fuxian, Liaoning Province was not an erosional old land (Jiao-Liao old land) in reality as suggested before, but an open outer continental shelf during the Middle Cambrian Zhangxia Age.
1985, 3(1): 81-91.
Abstract:
In this paper the author presents the evolution features of montmorillonite to illite during the diagenetic process of the Cretaceous shales of Songliao Basin and their effects on primary migration of petroleum. 1. During the diagenetic process, the conversion of montmorillonite into illite can be characterized by a high speed at the early stage and a relatively stable one at the late stage. 2. In Songliao Basin, the depth at which the "negative anomaly" occurred well matches with the top depth where montmorillonite transformed into illite, resulting from the diagenetic changes of montmorillonite. The occurrence of the "negative a-nomaly" marked the beginning of the conversion of montmorillonite into illite and the primary migration of petroleum in Songliao Basin. 3. The rapid conversion of montmorillonite into illite provided a favourable condition for hydrocarbon migration. The vertical variations in mudstone porosity, the lower maturation of crude oil and the excellent consistency between the rapid conversion stage of montmorillonite into illite in main source beds and the hydrocarbon migration stage in Songliao Basin have indicated that the rapid conversion stage of montmorillonite into illite is also the most important stage of hydrocarbon migration in Songliao Basin. 4. The study on the porous features of shale and the vertical variations in oil- water properties has shown that the conditions for hydrocarbon expulsion from source beds vary at differant conversion stages of montmorillonite into illite.At the early rapid evolution stage,because of the greater variations in volumes of mineral grains, more rapid dehydration, larger porosity and variations of shales, crude oil could migrate in any status. Thus the rap compaction process of shale was also the resqueezed-out process of oil-gas-water from pores and fractures of shale. At the late relatively stable stage, the source beds were further compacted, the shale porosity decreased and the rigidity increased,the microfractures developed.At this time, specific gravity and viscosity of oil have become lower than those of water, the water within shale existed in the form of irreducible water,while crude oil migrated in the form of oil phase along fractures and faults. 5. Sufficient pressure gradient and favourable path are the key to primary migration of hydrocarbon. However,since the source beds generally have abnormal pressure,the hydrocarbon migration from the source beds mainly depends on the suitable le path for migration.The influence of the hydrocarbon migration by the diagenetic olution of moutmorillonite is shown in the first place in the shale porosity. The rapid conversion of montmorillonite into illite, not only produced large quantity of interstitial water but also provided some suitable path for hydrocarbon migration. In this paper, the author puts emphasis on the study of variation in the relationship between porous features of source rocks and oil-water at different evolution stages,while estimating the influence of conversion of montmorillonite on hydrocarbon migration. And, there are now many obstacles in this study and some problems remain uncertain.
In this paper the author presents the evolution features of montmorillonite to illite during the diagenetic process of the Cretaceous shales of Songliao Basin and their effects on primary migration of petroleum. 1. During the diagenetic process, the conversion of montmorillonite into illite can be characterized by a high speed at the early stage and a relatively stable one at the late stage. 2. In Songliao Basin, the depth at which the "negative anomaly" occurred well matches with the top depth where montmorillonite transformed into illite, resulting from the diagenetic changes of montmorillonite. The occurrence of the "negative a-nomaly" marked the beginning of the conversion of montmorillonite into illite and the primary migration of petroleum in Songliao Basin. 3. The rapid conversion of montmorillonite into illite provided a favourable condition for hydrocarbon migration. The vertical variations in mudstone porosity, the lower maturation of crude oil and the excellent consistency between the rapid conversion stage of montmorillonite into illite in main source beds and the hydrocarbon migration stage in Songliao Basin have indicated that the rapid conversion stage of montmorillonite into illite is also the most important stage of hydrocarbon migration in Songliao Basin. 4. The study on the porous features of shale and the vertical variations in oil- water properties has shown that the conditions for hydrocarbon expulsion from source beds vary at differant conversion stages of montmorillonite into illite.At the early rapid evolution stage,because of the greater variations in volumes of mineral grains, more rapid dehydration, larger porosity and variations of shales, crude oil could migrate in any status. Thus the rap compaction process of shale was also the resqueezed-out process of oil-gas-water from pores and fractures of shale. At the late relatively stable stage, the source beds were further compacted, the shale porosity decreased and the rigidity increased,the microfractures developed.At this time, specific gravity and viscosity of oil have become lower than those of water, the water within shale existed in the form of irreducible water,while crude oil migrated in the form of oil phase along fractures and faults. 5. Sufficient pressure gradient and favourable path are the key to primary migration of hydrocarbon. However,since the source beds generally have abnormal pressure,the hydrocarbon migration from the source beds mainly depends on the suitable le path for migration.The influence of the hydrocarbon migration by the diagenetic olution of moutmorillonite is shown in the first place in the shale porosity. The rapid conversion of montmorillonite into illite, not only produced large quantity of interstitial water but also provided some suitable path for hydrocarbon migration. In this paper, the author puts emphasis on the study of variation in the relationship between porous features of source rocks and oil-water at different evolution stages,while estimating the influence of conversion of montmorillonite on hydrocarbon migration. And, there are now many obstacles in this study and some problems remain uncertain.
1985, 3(1): 99-110.
Abstract:
There is a great deal of siliceous coal balls containing fossil such as Pteridophy-ta in the coal seam of the Upper Permian Lungtan upper series in Fengjiangxi Coal Field of Shaoyang,Hunan Province. There coal balls with the shape of lens or ellipsoid occur in the upper part of the fourth coal seam. In the section there are several layers, and in the plane they are distributed continuously or discontinuous-ly and distinguished clearly from the wall rocks. Authigenic quartz and calcedony are the main coal balls-making substances, and carbonaceous fragmental phytolite conies second. SiO2 content of the coal balls is 85.35%, with 11.4% of burning loss. And the coal balls also contain trace elements, such as Zr, B, Ni, Co, Cu etc.. This coal ball was formed in the diagenetic process. It was related to the pouring of SiO2-rich old river water into the peat bog during the end of the fourth coal seam deposition. In the early period of the diagenetic process, pH of the peat bog decreased, the colloidal solution of SiO2in association with humus hemigel formed better homogeneous embryonic concretion of colloform.After a series of diagenetic changes, the coal balls were formed. The evolution of its formation has three stages: 1. Gel stage in the early period of the diagenetic process. 2. Coal ball-making stage in the middle period of the diagenetic process. 3. Stage of coal ball change in its form, nature and quality in the late period of the diagenetic process. This kind of coal ball was formed in the platform stage,and underwent the formation of all the structures in Diwa (geodepression). The siliceous coal ball is a fine symbol of the coal seam correlation and an im -portant basis for discussing the environment of the incoalation.lt assumes both practical and theoretical significance in the geological exploration of coal field and the development of coal mine.
There is a great deal of siliceous coal balls containing fossil such as Pteridophy-ta in the coal seam of the Upper Permian Lungtan upper series in Fengjiangxi Coal Field of Shaoyang,Hunan Province. There coal balls with the shape of lens or ellipsoid occur in the upper part of the fourth coal seam. In the section there are several layers, and in the plane they are distributed continuously or discontinuous-ly and distinguished clearly from the wall rocks. Authigenic quartz and calcedony are the main coal balls-making substances, and carbonaceous fragmental phytolite conies second. SiO2 content of the coal balls is 85.35%, with 11.4% of burning loss. And the coal balls also contain trace elements, such as Zr, B, Ni, Co, Cu etc.. This coal ball was formed in the diagenetic process. It was related to the pouring of SiO2-rich old river water into the peat bog during the end of the fourth coal seam deposition. In the early period of the diagenetic process, pH of the peat bog decreased, the colloidal solution of SiO2in association with humus hemigel formed better homogeneous embryonic concretion of colloform.After a series of diagenetic changes, the coal balls were formed. The evolution of its formation has three stages: 1. Gel stage in the early period of the diagenetic process. 2. Coal ball-making stage in the middle period of the diagenetic process. 3. Stage of coal ball change in its form, nature and quality in the late period of the diagenetic process. This kind of coal ball was formed in the platform stage,and underwent the formation of all the structures in Diwa (geodepression). The siliceous coal ball is a fine symbol of the coal seam correlation and an im -portant basis for discussing the environment of the incoalation.lt assumes both practical and theoretical significance in the geological exploration of coal field and the development of coal mine.
1985, 3(1): 120-127.
Abstract:
A computer program for the density diagram of boulder fabric has deen designed. This paper discusses the principle, algorithm and characteristics of the program, which is written in BASIC. The efficient and rapid operation need only 17 bytes. This program can be used in ordinary microcomputer. Besides boulder fabric, the density diagrams of joint orientation, P-axes direction of fault plane solution and others can be drawn and calculated by using this program.
A computer program for the density diagram of boulder fabric has deen designed. This paper discusses the principle, algorithm and characteristics of the program, which is written in BASIC. The efficient and rapid operation need only 17 bytes. This program can be used in ordinary microcomputer. Besides boulder fabric, the density diagrams of joint orientation, P-axes direction of fault plane solution and others can be drawn and calculated by using this program.
1985, 3(1): 16-28.
Abstract:
Taking Huolinhe Basin as an example, this paper has discussed, according to the criteria required by basin analysis in sedimentation, tectonics and coal formation, the principles emoloyed in compiling paleoenvironmental map of coal measures of terrestrial facies, the choosing of map unit, classification of sedimentary environment, methodology of map compilation and the application and interpretation of the results. The unit for the paleoenvironmental map is equivalent to a bed deposited during a short time and can be distinguished from the overlying and underlying sedimentary beds by its composition, characteristics and genesis. Included in this paper are 18 paleoenvironmental maps of coal seams and their basal sandstone in the lower coal measures (200-600m in thickness) of Late Mesozoic Huoliuhe Group which consist of 5 coal sets and 9 main coal seams (equal to 9 coal-bearing cycles). The bases for the compilation of these maps are as follows;!) Different sedimentary environments have different macrocosmic environmental features including lithotype (lithof acies),vertical sequence,shape of the sedimentary rock bodies and lithogenetic index.2) Vertical variation of lithofacies results from horizontal shifs of neighboring sedimentary environments in accordance Walther Law. 3) Determination of the genesis of sandstone and/or conglomerate with bodies as a depositional fremework of a basin is the key to the analysis of other sedimentary environments. In compiling paleoenvironmental maps quite a few engineering control points are needed to distribute evenly in the basin. The general procedures for the compilation are: 1) Compilation of sedimentary section maps at certain intervals. 2 ) Analysis bof these maps and determination of map unit. 3) Compilation of lithotype distri-ution maps about successive beds. 4 ) Compilation of paleoenvironmental maps using the distribution maps as base maps and by comprehensive analysis of each bed's paleoenvironment. Determined in Huolinhe Basin are 8 different paleoenvironments the most important of which are shallow lacustrine, alluvial fan and swamp paleoenvironments. The others are lacustrine delta, river, fan delta and deep lacustrine paleoenvironments. The comprehensive analysis of the paleoenvironmental maps shows 1 ) Lithotype distributes and varies regularly during the formation of the lower coal measures.2) There is a distinct spacial zonation of sedimentary facies in the basin and 3 sedimentary facies zones change periodically in width as time goes by. 3) Generally speaking, the area and intensity of coal formation vary vertically from small (weak) to large (strong) and then vice versa. 4)Judging from the changing width of the alluvial fan norihwest of the basin, it can be co ncluded t hat at least 9 relatively intense periodic tectonic movements occurred in the basin in the formation of the lower coal measures.
Taking Huolinhe Basin as an example, this paper has discussed, according to the criteria required by basin analysis in sedimentation, tectonics and coal formation, the principles emoloyed in compiling paleoenvironmental map of coal measures of terrestrial facies, the choosing of map unit, classification of sedimentary environment, methodology of map compilation and the application and interpretation of the results. The unit for the paleoenvironmental map is equivalent to a bed deposited during a short time and can be distinguished from the overlying and underlying sedimentary beds by its composition, characteristics and genesis. Included in this paper are 18 paleoenvironmental maps of coal seams and their basal sandstone in the lower coal measures (200-600m in thickness) of Late Mesozoic Huoliuhe Group which consist of 5 coal sets and 9 main coal seams (equal to 9 coal-bearing cycles). The bases for the compilation of these maps are as follows;!) Different sedimentary environments have different macrocosmic environmental features including lithotype (lithof acies),vertical sequence,shape of the sedimentary rock bodies and lithogenetic index.2) Vertical variation of lithofacies results from horizontal shifs of neighboring sedimentary environments in accordance Walther Law. 3) Determination of the genesis of sandstone and/or conglomerate with bodies as a depositional fremework of a basin is the key to the analysis of other sedimentary environments. In compiling paleoenvironmental maps quite a few engineering control points are needed to distribute evenly in the basin. The general procedures for the compilation are: 1) Compilation of sedimentary section maps at certain intervals. 2 ) Analysis bof these maps and determination of map unit. 3) Compilation of lithotype distri-ution maps about successive beds. 4 ) Compilation of paleoenvironmental maps using the distribution maps as base maps and by comprehensive analysis of each bed's paleoenvironment. Determined in Huolinhe Basin are 8 different paleoenvironments the most important of which are shallow lacustrine, alluvial fan and swamp paleoenvironments. The others are lacustrine delta, river, fan delta and deep lacustrine paleoenvironments. The comprehensive analysis of the paleoenvironmental maps shows 1 ) Lithotype distributes and varies regularly during the formation of the lower coal measures.2) There is a distinct spacial zonation of sedimentary facies in the basin and 3 sedimentary facies zones change periodically in width as time goes by. 3) Generally speaking, the area and intensity of coal formation vary vertically from small (weak) to large (strong) and then vice versa. 4)Judging from the changing width of the alluvial fan norihwest of the basin, it can be co ncluded t hat at least 9 relatively intense periodic tectonic movements occurred in the basin in the formation of the lower coal measures.
1985, 3(1): 29-41.
Abstract:
The classification of sedimentary rocks according to texturegenesis can organically associate the texture tpes with their depositional environments. Therefore, the author classified and described the Chinese phosphorites with this method. In view of the field investigations and the surveys of more than 1400 slices of the phosphorite taken from varied parts of China, the author discussed further the genses of the different kinds of phosphorites and the varied stages of oreforming of phosphorites. According to the differences of the texture types, the Chinese phosphorites can be classified into four groups; 1. The chemical sedimentary texture group Phospholutite is its representative type. It is formed by chemical or colloid-chemical sedimentary process in bottom water enriched with phosphates. 2. The bio-sedimentary texture group It includes pellet, oncolite, stromatolite, guano and boi-clastic phosphorites. They originated from the organism itself or bio-mechanical and bio-chemical processes. 3. The granular texture group. It includes intragranular (i.e.,intraclast, oolite,pisolite) phosphorites and extra-granular (i.e., extraclast) phosphorites .They are formed by the process of physical enrichment, i.e. by mechanical breaking and winnowing process of sea water, being controlled by the energy condition of water basin. 4. The diagenesis texture group It includes nodule, recrystal and replaced phosphorites. They are controlled by diagenetic environment and physicochemical condition in diagenetic process. There are three kinds of cements in phosphorite, i. e, phosphate (with argillaceous at times) cements,carbonate cements and silicate cements. From deep water to shallow water, the changing regularity of the cement kinds is from silicate, phosphate to carbonate. The ore-forming process of phosphorites is very complex, it can be summed up into the following six changing stages: Stage l.The phospates are enriched together in sea basin. It is suggested that phosphorus came from sea-resource, terrestrial resource, and volcanic resource.The phosphates are enriched in sea basin and constituted some local phosphate-rich areas. Stage 2.The chemical sedimentary stage in bottom water.Under the influences of chemical, colloid-chemical and bio-chemical processes, the phosphates in phosphorus-rich sea-water precipited on the interface of sediment/water,forming phospholutites. Stage 3. The phosphate deposited down because of organism or bio-mechanic and bio-chemical processes. With the phosphates constituted biotic cells and tissues and formed biogenetic series phosphorites, organism imbibing phosphorus from sea water. Stage 4.The physical enrichment stage. The nodules and the broken materials of the phosphorites formed early on sea-floor were enriched gradually by scouring, winnowing of sea water, forming intragranular and extraclastic phosphorites. This stage is the most important one among all the stages for industrial phosphorites. Stage 5. The cements precipited from phosphate-rich interstitial water. When the intergranular pore spaces and other pore spaces were filled with phosphate-rich pore water, the phosphate cements would gradually deposit. Stage 6. The changing in diagenetic process. Recrystallization or replacement took place in the diagenesis process of all kinds of phosphorites formed early, forming replaced phosphorite and micrite-medial phosphorites. In the phosphates- rich ooze, the phosphorus removed toward some centres, forming nodule phosphorites. By above-mentioned stages, plentiful types of phosphorite were formed. Surely, the six stages above couldn't develop completely in all deposits, some stages might be absent.
The classification of sedimentary rocks according to texturegenesis can organically associate the texture tpes with their depositional environments. Therefore, the author classified and described the Chinese phosphorites with this method. In view of the field investigations and the surveys of more than 1400 slices of the phosphorite taken from varied parts of China, the author discussed further the genses of the different kinds of phosphorites and the varied stages of oreforming of phosphorites. According to the differences of the texture types, the Chinese phosphorites can be classified into four groups; 1. The chemical sedimentary texture group Phospholutite is its representative type. It is formed by chemical or colloid-chemical sedimentary process in bottom water enriched with phosphates. 2. The bio-sedimentary texture group It includes pellet, oncolite, stromatolite, guano and boi-clastic phosphorites. They originated from the organism itself or bio-mechanical and bio-chemical processes. 3. The granular texture group. It includes intragranular (i.e.,intraclast, oolite,pisolite) phosphorites and extra-granular (i.e., extraclast) phosphorites .They are formed by the process of physical enrichment, i.e. by mechanical breaking and winnowing process of sea water, being controlled by the energy condition of water basin. 4. The diagenesis texture group It includes nodule, recrystal and replaced phosphorites. They are controlled by diagenetic environment and physicochemical condition in diagenetic process. There are three kinds of cements in phosphorite, i. e, phosphate (with argillaceous at times) cements,carbonate cements and silicate cements. From deep water to shallow water, the changing regularity of the cement kinds is from silicate, phosphate to carbonate. The ore-forming process of phosphorites is very complex, it can be summed up into the following six changing stages: Stage l.The phospates are enriched together in sea basin. It is suggested that phosphorus came from sea-resource, terrestrial resource, and volcanic resource.The phosphates are enriched in sea basin and constituted some local phosphate-rich areas. Stage 2.The chemical sedimentary stage in bottom water.Under the influences of chemical, colloid-chemical and bio-chemical processes, the phosphates in phosphorus-rich sea-water precipited on the interface of sediment/water,forming phospholutites. Stage 3. The phosphate deposited down because of organism or bio-mechanic and bio-chemical processes. With the phosphates constituted biotic cells and tissues and formed biogenetic series phosphorites, organism imbibing phosphorus from sea water. Stage 4.The physical enrichment stage. The nodules and the broken materials of the phosphorites formed early on sea-floor were enriched gradually by scouring, winnowing of sea water, forming intragranular and extraclastic phosphorites. This stage is the most important one among all the stages for industrial phosphorites. Stage 5. The cements precipited from phosphate-rich interstitial water. When the intergranular pore spaces and other pore spaces were filled with phosphate-rich pore water, the phosphate cements would gradually deposit. Stage 6. The changing in diagenetic process. Recrystallization or replacement took place in the diagenesis process of all kinds of phosphorites formed early, forming replaced phosphorite and micrite-medial phosphorites. In the phosphates- rich ooze, the phosphorus removed toward some centres, forming nodule phosphorites. By above-mentioned stages, plentiful types of phosphorite were formed. Surely, the six stages above couldn't develop completely in all deposits, some stages might be absent.
1985, 3(1): 42-53.
Abstract:
The migration form in UO2OH+-humic acid complex has been observed innatural water of the coal-bearing detrital rock-type uranium deposits of theEogene period under the wet climate in South China. The relationship betweenuranium and organic substance in natural water is discussed in this paper.We havedetermined both uranium content combined with dissolved humic acid in naturalwater from 68 to 93% and uranium content itt the form of UO2OH+ combined with dissolved humic acid from 62 to 99% How much organic matters contained in water does not fully indicate how muchthey have combined with uranium，but it is neccessary to see in what form the uranium exists. Only when the form of UO2OH+-ion is present, will the dissolved humic acid combine with much uranium. pH and HCO3-ion concentrations play an important controlling role on thetransporting form of uranium in natural water.When the concentration of HCO3-ion in flowing water is high，uranium is transported in the form of uranylcarbonate complexes. Only when the concentration of HCO-3ion is low, willuranium be transported in the form of urano-organic complexes. The transport in the form of UO2OH+-humic acid complexes is carried out inthe weakly acidic (pH<7) medium in the strongly oxidizing environment(Eh:+410- +490mv).The transport in the form of uranyl carbonate complexesis carried out in the weakly alkaline (pH>7.5) mediu m in the m oderate oxidizingenvironmgnt (Eh:+370- +379mv). After natural water in the form of UO2OH+-humic acid complexes flows intothe Eogene bog basin, during the peatification stage the urano-organic complexeswill be deposited tagether with peats, or will be absorbed by clay matter.Hereafter, during the diagenetic process the sediments undergo compressions,consolidations, dehydrations as well as transformations of organic matter, in whichpolymerizations and condensations into macromolecules in the dissolved humic acidgradually take place.As a result, uranium retained and fixed in organic rocks forms ore deposit.
The migration form in UO2OH+-humic acid complex has been observed innatural water of the coal-bearing detrital rock-type uranium deposits of theEogene period under the wet climate in South China. The relationship betweenuranium and organic substance in natural water is discussed in this paper.We havedetermined both uranium content combined with dissolved humic acid in naturalwater from 68 to 93% and uranium content itt the form of UO2OH+ combined with dissolved humic acid from 62 to 99% How much organic matters contained in water does not fully indicate how muchthey have combined with uranium，but it is neccessary to see in what form the uranium exists. Only when the form of UO2OH+-ion is present, will the dissolved humic acid combine with much uranium. pH and HCO3-ion concentrations play an important controlling role on thetransporting form of uranium in natural water.When the concentration of HCO3-ion in flowing water is high，uranium is transported in the form of uranylcarbonate complexes. Only when the concentration of HCO-3ion is low, willuranium be transported in the form of urano-organic complexes. The transport in the form of UO2OH+-humic acid complexes is carried out inthe weakly acidic (pH<7) medium in the strongly oxidizing environment(Eh:+410- +490mv).The transport in the form of uranyl carbonate complexesis carried out in the weakly alkaline (pH>7.5) mediu m in the m oderate oxidizingenvironmgnt (Eh:+370- +379mv). After natural water in the form of UO2OH+-humic acid complexes flows intothe Eogene bog basin, during the peatification stage the urano-organic complexeswill be deposited tagether with peats, or will be absorbed by clay matter.Hereafter, during the diagenetic process the sediments undergo compressions,consolidations, dehydrations as well as transformations of organic matter, in whichpolymerizations and condensations into macromolecules in the dissolved humic acidgradually take place.As a result, uranium retained and fixed in organic rocks forms ore deposit.
1985, 3(1): 71-80.
Abstract:
The Huanglong formation of Mid-Carboniferous in eastern Sichuan is mainly tidal flat deposits, in which have been discovered six gas fields and six gas-bearing .regions since the drilling out of high-productivity natural gas in 1977. Through the exploration practice in recent years,it has been confirmed that, besides the conditions of trapping and preserving, the key in exploration is closely related to the stretch of sedimentary facies zones. The eastern Sichuan was an estuary, Land-bounded on three sides during Mid-Carboniferous age, the transgression area successively enlarged westward from the east,and the tidal channel was situated nearby Zimutang of Jiansi county in western Hubei. Durng Leiyinpu time (C12), the realm of sedimentation was relatively smaller,with sediments of tide-above zone as the main, lithology of which is breccia- limestone, limestone intercalated with dolomites and gypsum rock) during Fuchenzhai time (C22), transgression expanded westwards, with sedimentary facies changed into intertidal zones as the main, lithology of which is mainly breccia-dolomites and dolomites, intercalated with bioclastic breccia-dolomites and bioclastic dolomites of relative abundancejand during the Chuantong (eastern Sichuan) time (C23), transgression broadened continuously, though it was still mainly intertidal zone,yet the tidal channel was not so obvious,the sea-water advanced and retreated fluently, lithology of which had changed into limestone, breccia-limestone and bioclastic limestone as the main, intercalated with dolomites, breccia-dolomites and bioclastic dolomites. The maximum residual thickness is 91m, in which always can be seen such sedimentary characteristics as sun-cracks, laminations, gravels in gravel, bioturbate structure stromatolites, birds-eyes, biogenic burrows, micrite envelope, oncolite, tents, cross-beddings,scouring surfaces, geopetal fabrics, salt-casts ts, gypsum traces, and so on. Organisms are comparatively abundant but broken, always mixed with those of different water realms, such as algae, foraminifera, fusulinids, echinoderms and brachiopods. As the tidal flat sediments are the main,the Carboniferous Huanglong formation in eastern Sichuan has neither oil-generating environment, nor sedimentary facies with ideal conditions of oil accumulation and preservation. Owing to the confinement of the sea basin during sedimentation and the dryness of climate,the calcium carbonate lime which had deposited on tide-above and intertidal zone has beene generally replaced by dolomite so as to form parasyngenetic dolomite; although this kind of dolomite was replaced mainly in volume, and having micro-and silt-crystalline texture,yet their rhombic crystals are fair and the crystalline pores are developed and their mutual communication may be seen under electron canning microscope. And what is still more important is that the intertidal sediments, exposed to the water surface, through successive contraction by dryness, had abundant gravels and grains, and often formed rather developed pores between grains (gravels)and microfractures, thus providing necessary conditions for fresh water to corrode and expand porosities hereafter,and leading to commonly rather better porosities of those which had the developed parasyngenetic dolomites in the Mid-Carboniferous Huanglong formation in eastern Sichuan for example, the intertidal flats both higher and lower etc. during Fuchenzhai time, are such the case, and the gas fields are almost present in the parasyngenetic dolomites of these inter tidal zones. For this reason, the reservoir condition of Carboniferous Huanglong formation in eastern Sichuan, generally speaking, is rather good, but the secondary solution porosities related to sedimentary facies predominate and not the primary porosities formed during sedimentation. In this paper, some problems have been dealt with, such as the especially wide distribution of tidal flat sediments of Carboniferous Huanglong age which surpasses by far the breadth of each tidal region along the sea in the.
The Huanglong formation of Mid-Carboniferous in eastern Sichuan is mainly tidal flat deposits, in which have been discovered six gas fields and six gas-bearing .regions since the drilling out of high-productivity natural gas in 1977. Through the exploration practice in recent years,it has been confirmed that, besides the conditions of trapping and preserving, the key in exploration is closely related to the stretch of sedimentary facies zones. The eastern Sichuan was an estuary, Land-bounded on three sides during Mid-Carboniferous age, the transgression area successively enlarged westward from the east,and the tidal channel was situated nearby Zimutang of Jiansi county in western Hubei. Durng Leiyinpu time (C12), the realm of sedimentation was relatively smaller,with sediments of tide-above zone as the main, lithology of which is breccia- limestone, limestone intercalated with dolomites and gypsum rock) during Fuchenzhai time (C22), transgression expanded westwards, with sedimentary facies changed into intertidal zones as the main, lithology of which is mainly breccia-dolomites and dolomites, intercalated with bioclastic breccia-dolomites and bioclastic dolomites of relative abundancejand during the Chuantong (eastern Sichuan) time (C23), transgression broadened continuously, though it was still mainly intertidal zone,yet the tidal channel was not so obvious,the sea-water advanced and retreated fluently, lithology of which had changed into limestone, breccia-limestone and bioclastic limestone as the main, intercalated with dolomites, breccia-dolomites and bioclastic dolomites. The maximum residual thickness is 91m, in which always can be seen such sedimentary characteristics as sun-cracks, laminations, gravels in gravel, bioturbate structure stromatolites, birds-eyes, biogenic burrows, micrite envelope, oncolite, tents, cross-beddings,scouring surfaces, geopetal fabrics, salt-casts ts, gypsum traces, and so on. Organisms are comparatively abundant but broken, always mixed with those of different water realms, such as algae, foraminifera, fusulinids, echinoderms and brachiopods. As the tidal flat sediments are the main,the Carboniferous Huanglong formation in eastern Sichuan has neither oil-generating environment, nor sedimentary facies with ideal conditions of oil accumulation and preservation. Owing to the confinement of the sea basin during sedimentation and the dryness of climate,the calcium carbonate lime which had deposited on tide-above and intertidal zone has beene generally replaced by dolomite so as to form parasyngenetic dolomite; although this kind of dolomite was replaced mainly in volume, and having micro-and silt-crystalline texture,yet their rhombic crystals are fair and the crystalline pores are developed and their mutual communication may be seen under electron canning microscope. And what is still more important is that the intertidal sediments, exposed to the water surface, through successive contraction by dryness, had abundant gravels and grains, and often formed rather developed pores between grains (gravels)and microfractures, thus providing necessary conditions for fresh water to corrode and expand porosities hereafter,and leading to commonly rather better porosities of those which had the developed parasyngenetic dolomites in the Mid-Carboniferous Huanglong formation in eastern Sichuan for example, the intertidal flats both higher and lower etc. during Fuchenzhai time, are such the case, and the gas fields are almost present in the parasyngenetic dolomites of these inter tidal zones. For this reason, the reservoir condition of Carboniferous Huanglong formation in eastern Sichuan, generally speaking, is rather good, but the secondary solution porosities related to sedimentary facies predominate and not the primary porosities formed during sedimentation. In this paper, some problems have been dealt with, such as the especially wide distribution of tidal flat sediments of Carboniferous Huanglong age which surpasses by far the breadth of each tidal region along the sea in the.
1985, 3(1): 92-98.
Abstract:
This article briefly introduces the method to determine mercury content in source rocks with the model XG-3 determination apparatus, and shows that the linear relationship between organic carbon and mercury content in source rocks in Miyang -Honggang regions is similar to the variation of total hydrocarbons (indicator of organic geochemistry) with burial depth.- Judged from mercury-accumulation of stratigraphic temperature and organic matter, a preliminary explanation has been given to the above-mentioned variation curve. The author deems that after organic matter is converted into oil and gas,the mercury accumulation will be strengthened.
This article briefly introduces the method to determine mercury content in source rocks with the model XG-3 determination apparatus, and shows that the linear relationship between organic carbon and mercury content in source rocks in Miyang -Honggang regions is similar to the variation of total hydrocarbons (indicator of organic geochemistry) with burial depth.- Judged from mercury-accumulation of stratigraphic temperature and organic matter, a preliminary explanation has been given to the above-mentioned variation curve. The author deems that after organic matter is converted into oil and gas,the mercury accumulation will be strengthened.
1985, 3(1): 111-119.
Abstract:
The theory of historical geotectonic geology, stratigraphy and sedimentology are complementary with one another and should be intimately combined. Thus, the development of these theories must have exerted a strong influence on much of the study of geologic history events. No matter how many new discoveries have been made, the progress in the study of plate tectonics will by all means exert a great influence on the sedimentology studies. In the past two decades or so, the sediments and rock samples obtained from beneath the oceans and continents have provided decisive data that have served to revolutionize the earth science. Unexpected features and event courses revealed and comprehensive data built up, the geologic history of the continents and the oceans may be said to have been mastered. Based upon the study of great qualities of data (stratigraphy, lithology, radioactive istope age and paleogeography, etc.) collected and accumulated over so many years, historical geotectonic geology is concerned with the forms and history of the deformation of the earth's crust. To put it briefly, stratigraphy is to study the character, sequence relationship, distribution and origin of sedimentary rocks. Seen from this point of view, every sediment is wholly determined by geotectonic events; but in general, we accept the environmental circumstances which determine the lithofacies of a sediment and palaeogeography and determine its geotectonic control as the variations imposed on it by the ever-changing geotectonic conditions. Much of the lithofacies evidence that is useful in deciphering geotectonic geology-and development is the same as that employed in the reconstruction of palaeogeography. It is mainly distribution and characters of lithofacies and palaeogeogragy phy that is derived from the stratigraphy. It is evident that the primary tectonic environment of Cryptozoic and Phanero-zoic should be related partly with a eugeosyncline or trench, and partly with miog- geosyncline and land block (Craton). They contain a wide variety of rocks. For example,the flysch deposits are widely distributed over the miogeosyncline and eu-geosyncline. Precisely speaking, in the eugeosyncline volcanic rocks may be found underlying the flysch deposits -which in turn were overlain by synorogenic volcanic-rocks. Evidences have been found and have proved the existence of turbiditesin the flysch deposits. It has also become clear that the turbidites consist of material that originated from the land blocks around these geosyclines, and these turbidites were controlled by deep fratures. It is well known that after the Variscian erogenic cycle came the subduction of the Pacific plate that sank lower than the Asia-Europe plate; the collision of the Indian plate with the Asia-Europe plate gave rise to the Tethys-Himalayan geo-synclinal foldbelts, forming such a great variety of rocks. Lithofacies can be reorganized and traced in the subsurface on the basis of drilling records. Among the diagnostic features utilized are: 1. lithologic characters) 2. metamorphic alteration) 3. fossil assembledge) 4. stratigraphic relations) 5 . temporal sequence) 6. structural form) 7. environmental influences) 8. tectonic control) 9. genetic interpretation) 10. geographic occurrence.
The theory of historical geotectonic geology, stratigraphy and sedimentology are complementary with one another and should be intimately combined. Thus, the development of these theories must have exerted a strong influence on much of the study of geologic history events. No matter how many new discoveries have been made, the progress in the study of plate tectonics will by all means exert a great influence on the sedimentology studies. In the past two decades or so, the sediments and rock samples obtained from beneath the oceans and continents have provided decisive data that have served to revolutionize the earth science. Unexpected features and event courses revealed and comprehensive data built up, the geologic history of the continents and the oceans may be said to have been mastered. Based upon the study of great qualities of data (stratigraphy, lithology, radioactive istope age and paleogeography, etc.) collected and accumulated over so many years, historical geotectonic geology is concerned with the forms and history of the deformation of the earth's crust. To put it briefly, stratigraphy is to study the character, sequence relationship, distribution and origin of sedimentary rocks. Seen from this point of view, every sediment is wholly determined by geotectonic events; but in general, we accept the environmental circumstances which determine the lithofacies of a sediment and palaeogeography and determine its geotectonic control as the variations imposed on it by the ever-changing geotectonic conditions. Much of the lithofacies evidence that is useful in deciphering geotectonic geology-and development is the same as that employed in the reconstruction of palaeogeography. It is mainly distribution and characters of lithofacies and palaeogeogragy phy that is derived from the stratigraphy. It is evident that the primary tectonic environment of Cryptozoic and Phanero-zoic should be related partly with a eugeosyncline or trench, and partly with miog- geosyncline and land block (Craton). They contain a wide variety of rocks. For example,the flysch deposits are widely distributed over the miogeosyncline and eu-geosyncline. Precisely speaking, in the eugeosyncline volcanic rocks may be found underlying the flysch deposits -which in turn were overlain by synorogenic volcanic-rocks. Evidences have been found and have proved the existence of turbiditesin the flysch deposits. It has also become clear that the turbidites consist of material that originated from the land blocks around these geosyclines, and these turbidites were controlled by deep fratures. It is well known that after the Variscian erogenic cycle came the subduction of the Pacific plate that sank lower than the Asia-Europe plate; the collision of the Indian plate with the Asia-Europe plate gave rise to the Tethys-Himalayan geo-synclinal foldbelts, forming such a great variety of rocks. Lithofacies can be reorganized and traced in the subsurface on the basis of drilling records. Among the diagnostic features utilized are: 1. lithologic characters) 2. metamorphic alteration) 3. fossil assembledge) 4. stratigraphic relations) 5 . temporal sequence) 6. structural form) 7. environmental influences) 8. tectonic control) 9. genetic interpretation) 10. geographic occurrence.
1985, 3(1): 128-137.
Abstract:
The size analysis of sands in the littoral area of Qinhuangdao shows that the empircal relationships between median diameter, Md, and sorting coefficient,σ, of sands different types and characteristics due to various geneses and hydrodynamic conditions.Therefore,they may be attributed to different depositional environments. A linear σ-Md graph with ascending grade suggests that the sorting of sand particles becomes better as they run way in removal and grow smaller in size, which implies a normal state of depositional differentiation.And down-sloped σ-Md line indicates that when sand particles grow smaller in transportation, their sorting becomes poorer. This means an abnormal depositional differentiation by the disturbance of wash
The size analysis of sands in the littoral area of Qinhuangdao shows that the empircal relationships between median diameter, Md, and sorting coefficient,σ, of sands different types and characteristics due to various geneses and hydrodynamic conditions.Therefore,they may be attributed to different depositional environments. A linear σ-Md graph with ascending grade suggests that the sorting of sand particles becomes better as they run way in removal and grow smaller in size, which implies a normal state of depositional differentiation.And down-sloped σ-Md line indicates that when sand particles grow smaller in transportation, their sorting becomes poorer. This means an abnormal depositional differentiation by the disturbance of wash
