1990 Vol. 8, No. 2
column
Display Method:
1990, 8(2): 1-8.
Abstract:
The orogenic belt that rises straight up in relief is easy to recognize. However, some fossil orogenicbelt, having been strongly eroded, now are absent from surfac of the earth and covered by later sediments,Of course it, is very difficult to identify this kind of orogenic belt, but studying molasse-deposited closelyrelated to the orogenic belt-can provide a good method for identifying the orogenic beltz.Different orogenicbelt may produce different kind of molassed.The authors concluded the characteristics of molasse related tothe colliding orogenic belt, such as: 1.The sedimentary body is a very thick wedge which is thicker close to the orogenic belt and pinches outin the direckion of the craton. 2.The clastic sediments are coarse, and thick strata of kconglomerates may occur near by the orogenicbelt. 3. The sediments of the molasse are of recyclic character, and the chemical composition is rich mSiO2 and so the ratio of AL203 SiO2 is iow. 4. The molasse is deposited mainly on land where the proximal portion of molasse mainly exists or inneritic environments where the distal portion of molasse often occurs. 5. Abundant sedimentary structures show that paleocurrent direction is perpendicular to the orogenicbelt. 6.Sedimentary sequences are rhythmic ones in which the thickness of one rhythmic unit is about severalcm to several m 7.The molasse is unconformable with underlying strata which is often flysch in the proximal region, andis disconformable or conformable whith underlying strata which is platform formation in the distal area. The authors analyzed the Silurian molasse formation in the Northwest of Zhejiang, Southeast ofAnhui, and South of Jiangsu Provinces, and deduced that there was a Later Caledonianfossil orogenic beltin the east edge of Yangzi plate.Comparing the molasse with the underlying strata-the Upper Ordovicianflysch formation in sedimentological characteristics and tectonic settings, the authors found many impor-tant facts, some of them are listed here: l.The underlying Ordovician flysch deposited in an aulacogen, and it‘s elastic materials were suppliedfrom both (southeast and northwest) sides of the basin and transported mainly along the basin axis in thenortheast direction; but the sediments of the molasse came from east side and were transported mainlywestward. 2.The; thickness of sedimentary body of the molasse may be up to (i000m in the east area, and decreasesrapidly in the west of the molasse basin.3.The mineral composition of the molasse apparently differs from that of the underlying flysch, c.imefrom a recyclic orogemc belt On the basis of above-mentioned study, the authors made a careful study of the sedtmentologtcal characteristics of Maoshan formation(Upper Silurian) in the Southern Jiangsu and Southern :Anhw Thesults show tht the Maoshan formation is the uppermost and sthe westpart of the molasse.The sediments comefrom easternside, and the bottom of the sedimentary basin sloped to in the west at that time.So the source aream the east is the orogenic belt uplifted since the end of Ordovician. Because the deeper part of the orogcnticbelt were eroded, the slightly metamorphosed debris are more abundant and the igneous, sedunentary debris are fewer in the Maoshan Group than those in the lower part of the molasse.The Maoshan Group car, betreated as fresh water deposited upper molasse and the other strata (including Middle, Lower Stlunan ,tndthe uppermost part of Ordovician) can be ;:onsidered as the lower molasse deposited in nerittc zone. C'mm-paring the western boundary of the lomr molasse with that of the upper molasse, O is clear that thesedimentary axis of the molasse basin migrued westward for at least 90km in the period from the em? ofOrdovician to the end of Silurian.The spcee, migration is about 3mm per year.The study on Maoshan Group further proved that there existed a colliding orogenic belt(almost loomsouth to north in the east side of the basin，m the area nearby the outfall of Yangzi River The area adjacentto Jiangsu, Zhejiang and Anhui Provinces was , the foreland basin of the orogenic belt, and m such a basmdeposited the molasse fot}nation again from the end tit Ordovician to the end of Silurian.Such a ctinclusiun isbeneficial to reconsidering the evolution of ptleozolc geotectonics in Southern China and to exploring oil andgas in the Paleozoic strata.
The orogenic belt that rises straight up in relief is easy to recognize. However, some fossil orogenicbelt, having been strongly eroded, now are absent from surfac of the earth and covered by later sediments,Of course it, is very difficult to identify this kind of orogenic belt, but studying molasse-deposited closelyrelated to the orogenic belt-can provide a good method for identifying the orogenic beltz.Different orogenicbelt may produce different kind of molassed.The authors concluded the characteristics of molasse related tothe colliding orogenic belt, such as: 1.The sedimentary body is a very thick wedge which is thicker close to the orogenic belt and pinches outin the direckion of the craton. 2.The clastic sediments are coarse, and thick strata of kconglomerates may occur near by the orogenicbelt. 3. The sediments of the molasse are of recyclic character, and the chemical composition is rich mSiO2 and so the ratio of AL203 SiO2 is iow. 4. The molasse is deposited mainly on land where the proximal portion of molasse mainly exists or inneritic environments where the distal portion of molasse often occurs. 5. Abundant sedimentary structures show that paleocurrent direction is perpendicular to the orogenicbelt. 6.Sedimentary sequences are rhythmic ones in which the thickness of one rhythmic unit is about severalcm to several m 7.The molasse is unconformable with underlying strata which is often flysch in the proximal region, andis disconformable or conformable whith underlying strata which is platform formation in the distal area. The authors analyzed the Silurian molasse formation in the Northwest of Zhejiang, Southeast ofAnhui, and South of Jiangsu Provinces, and deduced that there was a Later Caledonianfossil orogenic beltin the east edge of Yangzi plate.Comparing the molasse with the underlying strata-the Upper Ordovicianflysch formation in sedimentological characteristics and tectonic settings, the authors found many impor-tant facts, some of them are listed here: l.The underlying Ordovician flysch deposited in an aulacogen, and it‘s elastic materials were suppliedfrom both (southeast and northwest) sides of the basin and transported mainly along the basin axis in thenortheast direction; but the sediments of the molasse came from east side and were transported mainlywestward. 2.The; thickness of sedimentary body of the molasse may be up to (i000m in the east area, and decreasesrapidly in the west of the molasse basin.3.The mineral composition of the molasse apparently differs from that of the underlying flysch, c.imefrom a recyclic orogemc belt On the basis of above-mentioned study, the authors made a careful study of the sedtmentologtcal characteristics of Maoshan formation(Upper Silurian) in the Southern Jiangsu and Southern :Anhw Thesults show tht the Maoshan formation is the uppermost and sthe westpart of the molasse.The sediments comefrom easternside, and the bottom of the sedimentary basin sloped to in the west at that time.So the source aream the east is the orogenic belt uplifted since the end of Ordovician. Because the deeper part of the orogcnticbelt were eroded, the slightly metamorphosed debris are more abundant and the igneous, sedunentary debris are fewer in the Maoshan Group than those in the lower part of the molasse.The Maoshan Group car, betreated as fresh water deposited upper molasse and the other strata (including Middle, Lower Stlunan ,tndthe uppermost part of Ordovician) can be ;:onsidered as the lower molasse deposited in nerittc zone. C'mm-paring the western boundary of the lomr molasse with that of the upper molasse, O is clear that thesedimentary axis of the molasse basin migrued westward for at least 90km in the period from the em? ofOrdovician to the end of Silurian.The spcee, migration is about 3mm per year.The study on Maoshan Group further proved that there existed a colliding orogenic belt(almost loomsouth to north in the east side of the basin，m the area nearby the outfall of Yangzi River The area adjacentto Jiangsu, Zhejiang and Anhui Provinces was , the foreland basin of the orogenic belt, and m such a basmdeposited the molasse fot}nation again from the end tit Ordovician to the end of Silurian.Such a ctinclusiun isbeneficial to reconsidering the evolution of ptleozolc geotectonics in Southern China and to exploring oil andgas in the Paleozoic strata.
1990, 8(2): 23-31.
Abstract:
The Upper Carboniferous Huanglung Formation in the eastern Sichuan may be divided into three members, which can be correlated with the previously established three fusulinid zones-Pseudostaffella,profusulinella, and Fusulinella- Fusulina-of the Upper Carboniferous Weining Formation in westGuizhou.In this paper on the base of correlation with equivalents in Yangtze region, sedimentary facies are divided chronologically.It is thought that the Huanglongqi transgression began from south to north and during Ijthe stage it obviously came from the north.During the early and middle stages the yangtze Sea is substantically a narrow-elongated gulf in an east-west direction, with ""Daba Mountain-North Hubei old land and Huaiyang old land in the north, Upper Yangtze old land in the west and southwest, low plain Jiangnan old land in the south, and Cathaysian old land in the southeast. Upper Yangtze old land and Jiangnan old land are joined by slight saddle at Jingjiang.The gulf is topographically higher in the west and lower in the east and its lower tidal line lies roughly between Tongling and Chao Xian in southern Anhui.The sea water flew into the middle Yangtre gulf in a form of tide or through the Jingjiang tidal mouth and then westward into the Upper Yangtze gulf. The sea water of Upper Yangtre gulf arrived only during special storm. That: is why the tidal flat sediments are extraordinaryly widely distributed during the early and middle stages.Thus it is explained that how sea water far from a thousand kilometer entered and retreated the tidal flood area of Yangtze gulf.During the late stage when the Jiangnan old land subsided, the sea water transgressed from both south and north, expanding the limited sea to a normal shallow sea, where the sediments were simple in nature but great in thickness with organisms rather flourishing.Each stage lacked oil- producing enviroments and coarse clastic sediments formed in high energy enviroment. For lack of high porosity sedimentary facies, primary reservoir conditions are not good.In the middle and upper Yangtze region parasyngenetic dolomites were developed in the intertidal zone during the early and middle stages, which is easy to be dissolved by fresh water and favorable for the formation of reservoir space for oil and gas. The gas produced in East Sichuan derived essentially from them On the edge of Jiangnan old land in lower Yangtre area and its northeast extended zone, although there txsisls dolomite facies favorable for reservoir of oil and gas, concidering the other factors, the testervoir condition is reia tively poor.
The Upper Carboniferous Huanglung Formation in the eastern Sichuan may be divided into three members, which can be correlated with the previously established three fusulinid zones-Pseudostaffella,profusulinella, and Fusulinella- Fusulina-of the Upper Carboniferous Weining Formation in westGuizhou.In this paper on the base of correlation with equivalents in Yangtze region, sedimentary facies are divided chronologically.It is thought that the Huanglongqi transgression began from south to north and during Ijthe stage it obviously came from the north.During the early and middle stages the yangtze Sea is substantically a narrow-elongated gulf in an east-west direction, with ""Daba Mountain-North Hubei old land and Huaiyang old land in the north, Upper Yangtze old land in the west and southwest, low plain Jiangnan old land in the south, and Cathaysian old land in the southeast. Upper Yangtze old land and Jiangnan old land are joined by slight saddle at Jingjiang.The gulf is topographically higher in the west and lower in the east and its lower tidal line lies roughly between Tongling and Chao Xian in southern Anhui.The sea water flew into the middle Yangtre gulf in a form of tide or through the Jingjiang tidal mouth and then westward into the Upper Yangtze gulf. The sea water of Upper Yangtre gulf arrived only during special storm. That: is why the tidal flat sediments are extraordinaryly widely distributed during the early and middle stages.Thus it is explained that how sea water far from a thousand kilometer entered and retreated the tidal flood area of Yangtze gulf.During the late stage when the Jiangnan old land subsided, the sea water transgressed from both south and north, expanding the limited sea to a normal shallow sea, where the sediments were simple in nature but great in thickness with organisms rather flourishing.Each stage lacked oil- producing enviroments and coarse clastic sediments formed in high energy enviroment. For lack of high porosity sedimentary facies, primary reservoir conditions are not good.In the middle and upper Yangtze region parasyngenetic dolomites were developed in the intertidal zone during the early and middle stages, which is easy to be dissolved by fresh water and favorable for the formation of reservoir space for oil and gas. The gas produced in East Sichuan derived essentially from them On the edge of Jiangnan old land in lower Yangtre area and its northeast extended zone, although there txsisls dolomite facies favorable for reservoir of oil and gas, concidering the other factors, the testervoir condition is reia tively poor.
1990, 8(2): 33-42.
Abstract:
Siliceous rock-carbonate rock-mudrock" type stratabound uranium deposits refer to those occured in special lithologic formations consisting mainly of siliceous rocks, carbonate rocks and mudrocks. Presently, this kind of ore deposits is one of the unique types of uranium deposits in China.The Silurian in this area is also called Bailongjiang Group which is a suit of fine-grained terrigenou. clastic rocks such as siltstone, mudstone and sandstone, interbedded with siliceous rocks, and carbonaterocks.The Middle Silurian series of orefield in the area can be fallen into three: Yangchanggou Formation Taer Formation, and Lalong Formation. The lower part of each formation consists of fine- grained terrigenous clastic rocks, the upper part of each formation consists of siliceous rocks, carbonate rocks and mudrocks. Almost all of the uranium deposits are occured in the strata of siliceous rocks, carbonat rocks ami mudrocks, upper part of each formation of Middle Silurian.According to the comprehensive reserch of sedimentary facies of Silurian, two facies areas have beet recognized: the restricted shelf facies area in western region, and the open shelf facies in eastern region.The former can be subdivided into: restricted inner shelf facies, gulf facies, and the comples of orgam reef/ shoal facies and tidal flat/ lagoon facies (isolated platform facies) . The latter can be subdivides into: inner-outer shelf facies, and the neritic shoal facies. As a result of discovering of Stromatopora organ ic reef and other shallow-water criteria, a entirely new view of lithofacies arid paleogeography of Silurian in this area has been obtained. In Silurian, it should belong to a marginal neritic environment in north of deep sea environment believed by earlier authors. Because of the existence of Baiyi subaqueous uplift, a isolated platform was developed in the restricted inner shelf environment during the reef- forming period of Middle Silurian, and formed the special complex of organic reef/ shoal facies and tidal flat/ lagoon facies.Eastwardly, it was a open shelf to sub-deep marine environment in this period.The uranium deposits are obviously controlled by the strata and lithofacies. Both the uranium sources and mineralizer came from the strata of siliceous rocks, carbonate rocks and mudrocks.It can be concluded that the uranium deposits in this area are typical stratabound deposits reformed by midium-lower temperature hydrothermal solutions based on the nature of ore-forming solutions, the physico-chemical conditions and the metallogtenic epoch.The ore-controlling factors for the uranium deposits are mainly as follows:(1) The strata of "siliceous rock-carbonate rock-mudrock" of Middle Silurian.(2) The complex of organic reef/ shoal facies and tidal flat/ lagoon facies, the main roles include: I. the lagoon facies is favourable for forming of uranium sourcebeds, Ⅱ the lithologic formations in the complex is favourable for enrichment of uranium during the metallogeic processes.(3) The uranium deposits in the orefield are almot dstributed along the nearly EW faulting structures.(4) The preserval conditions of uranium deposits.
Siliceous rock-carbonate rock-mudrock" type stratabound uranium deposits refer to those occured in special lithologic formations consisting mainly of siliceous rocks, carbonate rocks and mudrocks. Presently, this kind of ore deposits is one of the unique types of uranium deposits in China.The Silurian in this area is also called Bailongjiang Group which is a suit of fine-grained terrigenou. clastic rocks such as siltstone, mudstone and sandstone, interbedded with siliceous rocks, and carbonaterocks.The Middle Silurian series of orefield in the area can be fallen into three: Yangchanggou Formation Taer Formation, and Lalong Formation. The lower part of each formation consists of fine- grained terrigenous clastic rocks, the upper part of each formation consists of siliceous rocks, carbonate rocks and mudrocks. Almost all of the uranium deposits are occured in the strata of siliceous rocks, carbonat rocks ami mudrocks, upper part of each formation of Middle Silurian.According to the comprehensive reserch of sedimentary facies of Silurian, two facies areas have beet recognized: the restricted shelf facies area in western region, and the open shelf facies in eastern region.The former can be subdivided into: restricted inner shelf facies, gulf facies, and the comples of orgam reef/ shoal facies and tidal flat/ lagoon facies (isolated platform facies) . The latter can be subdivides into: inner-outer shelf facies, and the neritic shoal facies. As a result of discovering of Stromatopora organ ic reef and other shallow-water criteria, a entirely new view of lithofacies arid paleogeography of Silurian in this area has been obtained. In Silurian, it should belong to a marginal neritic environment in north of deep sea environment believed by earlier authors. Because of the existence of Baiyi subaqueous uplift, a isolated platform was developed in the restricted inner shelf environment during the reef- forming period of Middle Silurian, and formed the special complex of organic reef/ shoal facies and tidal flat/ lagoon facies.Eastwardly, it was a open shelf to sub-deep marine environment in this period.The uranium deposits are obviously controlled by the strata and lithofacies. Both the uranium sources and mineralizer came from the strata of siliceous rocks, carbonate rocks and mudrocks.It can be concluded that the uranium deposits in this area are typical stratabound deposits reformed by midium-lower temperature hydrothermal solutions based on the nature of ore-forming solutions, the physico-chemical conditions and the metallogtenic epoch.The ore-controlling factors for the uranium deposits are mainly as follows:(1) The strata of "siliceous rock-carbonate rock-mudrock" of Middle Silurian.(2) The complex of organic reef/ shoal facies and tidal flat/ lagoon facies, the main roles include: I. the lagoon facies is favourable for forming of uranium sourcebeds, Ⅱ the lithologic formations in the complex is favourable for enrichment of uranium during the metallogeic processes.(3) The uranium deposits in the orefield are almot dstributed along the nearly EW faulting structures.(4) The preserval conditions of uranium deposits.
1990, 8(2): 51-58.
Abstract:
The; Devonian in Ninglang- Lijiang region of western Chuxiong Basin, Yunnan, is dommanted by a series of carbonate sediments. The dolomitic rocks is one of the major rock types and has largely a forming mechanism of mixed dolomitization. Under microscopy, the fabrics of dolomitic rocks are floating-romb, contact- romb, hypidiotopic mosaic and sutured mosaic fabrics. It is suggested with the results of cathodoluminescence and electronic probe analysis that: the dolomite formed through mixed dolomitization has a tendancey of Fe++, Mn++becoming rich but K+poor fron center to margin. Dolomite grains are characterized by fogged center with clear margin, which display nuclei and girdles under cathodoluminescence microscopy. The very coarsely crystalline dolomite in subsruface and deep burial diagenesis environments display brown girdles under microscopy but lumines dark- red to non- luminescence under .cathodoluminescence microscopy.
The; Devonian in Ninglang- Lijiang region of western Chuxiong Basin, Yunnan, is dommanted by a series of carbonate sediments. The dolomitic rocks is one of the major rock types and has largely a forming mechanism of mixed dolomitization. Under microscopy, the fabrics of dolomitic rocks are floating-romb, contact- romb, hypidiotopic mosaic and sutured mosaic fabrics. It is suggested with the results of cathodoluminescence and electronic probe analysis that: the dolomite formed through mixed dolomitization has a tendancey of Fe++, Mn++becoming rich but K+poor fron center to margin. Dolomite grains are characterized by fogged center with clear margin, which display nuclei and girdles under cathodoluminescence microscopy. The very coarsely crystalline dolomite in subsruface and deep burial diagenesis environments display brown girdles under microscopy but lumines dark- red to non- luminescence under .cathodoluminescence microscopy.
1990, 8(2): 67-73.
Abstract:
On the basis of analyzing clay minerals of more than 8, 000 shale samples collected from 20 oil-bearing basins, we summarize six transformation types of smectite in Chinese oil-bearing basins: I .Continual conversion type from smectite to illite; H .Noncontinous conversion type from smectite to illite; Ⅲ.Conversion type from smectite to chlorite; Ⅳ. Conversion type from minor smectite to illite; V . Nonconversion type of smectite and Ⅵ.Smectite-absent type.We discuss different effects of these types on the primary migration of petroleum in this paper.First of all in the basin of continual conversion type, the mineral transformation does obvious effect to the primary migration.For in this kind of basin.the dehydration stage in the conversion from smectite to illite corresponds to the stage of the primary migration of petroleum. When organism transform into petroleum, the mineral smectite coexisted with organism transforms into interstratified illite / smectite-and furthur illite.The shale microfractures emerged in the process of transformation provides channel for the primary migration of petroleum. The dehydrated water in this process contributes as a carrier and the unusual high presure produces power to the primary migration. Whearas, the second, in the basins of noncontinous conversion or non-conversion type, the effect is not obvious, since mineral tranformation does not match with the stage of petroleum generation or there is not enough transformative smectite. And the third, if there isn't smectite's transformation or smectite itself in the basins, the trans formation and dehydration of smectite seldom occur.Conseouently.there is no effect of clay minerals on the primary migration.
On the basis of analyzing clay minerals of more than 8, 000 shale samples collected from 20 oil-bearing basins, we summarize six transformation types of smectite in Chinese oil-bearing basins: I .Continual conversion type from smectite to illite; H .Noncontinous conversion type from smectite to illite; Ⅲ.Conversion type from smectite to chlorite; Ⅳ. Conversion type from minor smectite to illite; V . Nonconversion type of smectite and Ⅵ.Smectite-absent type.We discuss different effects of these types on the primary migration of petroleum in this paper.First of all in the basin of continual conversion type, the mineral transformation does obvious effect to the primary migration.For in this kind of basin.the dehydration stage in the conversion from smectite to illite corresponds to the stage of the primary migration of petroleum. When organism transform into petroleum, the mineral smectite coexisted with organism transforms into interstratified illite / smectite-and furthur illite.The shale microfractures emerged in the process of transformation provides channel for the primary migration of petroleum. The dehydrated water in this process contributes as a carrier and the unusual high presure produces power to the primary migration. Whearas, the second, in the basins of noncontinous conversion or non-conversion type, the effect is not obvious, since mineral tranformation does not match with the stage of petroleum generation or there is not enough transformative smectite. And the third, if there isn't smectite's transformation or smectite itself in the basins, the trans formation and dehydration of smectite seldom occur.Conseouently.there is no effect of clay minerals on the primary migration.
1990, 8(2): 87-96.
Abstract:
Crest Basin, lies in the middle Rhone valley in France. The tectonic position is situated at foreland depression of the late Alpine orogeny. A series of non-volcanic molassic fades-assemblage of Miocene is deposited in this basin, among which the Burdigalian is composed of sandstone, sandy mudstone, sandy limestone and sandy bioclastic limestone. Mainly by the analysis of facies distribution, fossil association, sedimentary characteristics of continental clasts, light and heavy sand minerals, clay mineral composition, and facies indicator elements as well as petrographic characteristics etc, the author approches the sedimentary environment, material origin of each facies in the series, and the paleogeographic feature of the basin.The results of the analysis show that Burdigalian deposits contain delta, beach, transitional zone, and offshore (central basin) sedimentary facies. Silican clastic sedimentation is predominant with short period of or partial calcareous sedimentation. Orientation of paleochnnel is NE- SW. The coastal coarse- grained clastic sediments are exposed between Autichamp to Moutier, and Rochette to Barcelonne, but the fine-graned sediments are well developed in central-west of the basin. The deposits show a complicated vertical and lateral facies change controlled by particular and complicated topography of basin, and by the inflences of importation of continental runoff. There are two principal sources of the continental clasts in Burdigalian sediments, they are Alpine erogenic zone containing typic metamorphic minerals of high pressure and low temperature, and Mesozoic overlay in adjacent areas containing typic minerals of contact metamorphism. They are transported respectively by sea current and river current. Fossil assemblages in sediments reflect a warm climate and normal salinity coastal environment. This inference is also sopported by the early diagenetic cementation developed in some carbonate facies with intertidal sedimentary characteristics
Crest Basin, lies in the middle Rhone valley in France. The tectonic position is situated at foreland depression of the late Alpine orogeny. A series of non-volcanic molassic fades-assemblage of Miocene is deposited in this basin, among which the Burdigalian is composed of sandstone, sandy mudstone, sandy limestone and sandy bioclastic limestone. Mainly by the analysis of facies distribution, fossil association, sedimentary characteristics of continental clasts, light and heavy sand minerals, clay mineral composition, and facies indicator elements as well as petrographic characteristics etc, the author approches the sedimentary environment, material origin of each facies in the series, and the paleogeographic feature of the basin.The results of the analysis show that Burdigalian deposits contain delta, beach, transitional zone, and offshore (central basin) sedimentary facies. Silican clastic sedimentation is predominant with short period of or partial calcareous sedimentation. Orientation of paleochnnel is NE- SW. The coastal coarse- grained clastic sediments are exposed between Autichamp to Moutier, and Rochette to Barcelonne, but the fine-graned sediments are well developed in central-west of the basin. The deposits show a complicated vertical and lateral facies change controlled by particular and complicated topography of basin, and by the inflences of importation of continental runoff. There are two principal sources of the continental clasts in Burdigalian sediments, they are Alpine erogenic zone containing typic metamorphic minerals of high pressure and low temperature, and Mesozoic overlay in adjacent areas containing typic minerals of contact metamorphism. They are transported respectively by sea current and river current. Fossil assemblages in sediments reflect a warm climate and normal salinity coastal environment. This inference is also sopported by the early diagenetic cementation developed in some carbonate facies with intertidal sedimentary characteristics
1990, 8(2): 105-112.
Abstract:
Based on the analogical method on studying Paleotemperature and Palecoclimate with foraminiferal isotope in marine sediments, the features of carbon and oxygen isotopic compositon in lacustrine shell fossils from (he wells of Kunming Basin, Taihu lake and Chaidamu Basin with their climatic and enrironmental signiticance have been reported for the first time in this paper.By arialysising isotopic compositions of about one hundred shell fossils in different terrestrial environments, some regularities are found by comparing them with as follows:(1) Change of oxygen isotopic light and heavy composition in marine and terrestrial shell fossils is similar and show a period over 100, 000years.This that global climatic change is synchronows.(2) Change of oxygen isotopic composition of marine shell, utmost of which is 3‰ , if not considering evolution of sea water and seasonal temperature change, is cheifly controlled by annually average temperature. As temperature has a change of 4.2℃ , isotope has a change of 1‰, However oxygen isotopic composition of terrestrial shell, is not only influenced by temperature, but mainly by oxygen isotopic composition of pricipitation and evaportion. That is, temperature, change of 1℃ causes isotopic change of 1‰.(3) In the same section, isotopic compositions of terrestral shells with different age change quite. δ18O difference of total shell is more than 7‰, and δ13C is about 5‰.For Kunming Basin, authors set up a climatic curve of oxygen isotope, chiefly based on data of this experiment and referencing paleomagntic dating, uranrum dating and ，14C dating measuredl by others. This curve coincides with oxygen isotopic curve of deep sea foraminifera and paleoclimatic curve of loess paleosoil sesimentary system. Late Wurm glacial epoch (200, 000-100, 000 YBP) is period to accumulate most violently heavy isotopic composition (δ18O = -3.5‰-7.5‰, δ13C = -3.5‰) which implies that this period was the coldest and driest in Kunming basin. This result has been suppoted by data of sedimentary rock and palaeontology. The Period of the most violent accumulation of light isotopic composition was 500, 000- 600, 000 YBP (δ18O=-14.6‰, δ13C=-8.3‰) and it is deduced that preicipiation of this period was 150mm-200mm / Y more than that of moder time. Isotope of shell fossils distributed in 10 meters thickness of lacustrine silt clay under the base of Taihu lake is abundant with lighter compositim (δ18O = 7. 1‰-8.4‰) .and it is suggested that sediment was deposited during Wurm subinterglacial epoch (400, 000-200, 000 YBP) and was in estuary environment of restricted marine.Isotopic composition of Holcence shell show that the transgression did not reach Taihu lake.
Based on the analogical method on studying Paleotemperature and Palecoclimate with foraminiferal isotope in marine sediments, the features of carbon and oxygen isotopic compositon in lacustrine shell fossils from (he wells of Kunming Basin, Taihu lake and Chaidamu Basin with their climatic and enrironmental signiticance have been reported for the first time in this paper.By arialysising isotopic compositions of about one hundred shell fossils in different terrestrial environments, some regularities are found by comparing them with as follows:(1) Change of oxygen isotopic light and heavy composition in marine and terrestrial shell fossils is similar and show a period over 100, 000years.This that global climatic change is synchronows.(2) Change of oxygen isotopic composition of marine shell, utmost of which is 3‰ , if not considering evolution of sea water and seasonal temperature change, is cheifly controlled by annually average temperature. As temperature has a change of 4.2℃ , isotope has a change of 1‰, However oxygen isotopic composition of terrestrial shell, is not only influenced by temperature, but mainly by oxygen isotopic composition of pricipitation and evaportion. That is, temperature, change of 1℃ causes isotopic change of 1‰.(3) In the same section, isotopic compositions of terrestral shells with different age change quite. δ18O difference of total shell is more than 7‰, and δ13C is about 5‰.For Kunming Basin, authors set up a climatic curve of oxygen isotope, chiefly based on data of this experiment and referencing paleomagntic dating, uranrum dating and ，14C dating measuredl by others. This curve coincides with oxygen isotopic curve of deep sea foraminifera and paleoclimatic curve of loess paleosoil sesimentary system. Late Wurm glacial epoch (200, 000-100, 000 YBP) is period to accumulate most violently heavy isotopic composition (δ18O = -3.5‰-7.5‰, δ13C = -3.5‰) which implies that this period was the coldest and driest in Kunming basin. This result has been suppoted by data of sedimentary rock and palaeontology. The Period of the most violent accumulation of light isotopic composition was 500, 000- 600, 000 YBP (δ18O=-14.6‰, δ13C=-8.3‰) and it is deduced that preicipiation of this period was 150mm-200mm / Y more than that of moder time. Isotope of shell fossils distributed in 10 meters thickness of lacustrine silt clay under the base of Taihu lake is abundant with lighter compositim (δ18O = 7. 1‰-8.4‰) .and it is suggested that sediment was deposited during Wurm subinterglacial epoch (400, 000-200, 000 YBP) and was in estuary environment of restricted marine.Isotopic composition of Holcence shell show that the transgression did not reach Taihu lake.
1990, 8(2): 120-126.
Abstract:
Influenced by bath the coustal movement and the climatie fluctuation, the sedimentary environment has occured alternately as fluvial and lake within the area of West chifeng Plateau since Quaternary.With the uplift of crust, it can be divided into five sedimentary stages under cold climate, in which fluvial deposits formed dominantly (not include the 5th stage) .The so and δi of the sediments in the first stage are higher than other stages. It shows strong hydrodynamic and the bad sorting. Because of the inrich of unstable mineral in eaeh cold stage, the associate section of unstable nrineral is easly seen (K K) except a part of K K, which causeel by climatie fluetuation.Most of the traee elemeuts are dispersed and a few are concentrated in every stage.This phenomenon is related to source of materials besides the influence of climate in our opinion.The temperature in the third stage is higher than the fourth. Similarily, it can be divided 5 sedimentary stages under Warm climate, when the crust descents or. stable relatively.The lacustrine seelimentation played a leading role in evey warm stage with the exception in the first one.Because of the inrich of stable minerals in each warm stage, the association seetions of stable minerals exist in the mineral content curve (K K) except a part of K K which coused by climatie fluctuation. The most of the trace elements are concentrateed and only a few are scattered as a result of the warm-humid climate and rapid deposition. Aceording to the materials on hand, the fourth and fifth warm stages helong to fresh-water or light salt-water environment.
Influenced by bath the coustal movement and the climatie fluctuation, the sedimentary environment has occured alternately as fluvial and lake within the area of West chifeng Plateau since Quaternary.With the uplift of crust, it can be divided into five sedimentary stages under cold climate, in which fluvial deposits formed dominantly (not include the 5th stage) .The so and δi of the sediments in the first stage are higher than other stages. It shows strong hydrodynamic and the bad sorting. Because of the inrich of unstable mineral in eaeh cold stage, the associate section of unstable nrineral is easly seen (K K) except a part of K K, which causeel by climatie fluetuation.Most of the traee elemeuts are dispersed and a few are concentrated in every stage.This phenomenon is related to source of materials besides the influence of climate in our opinion.The temperature in the third stage is higher than the fourth. Similarily, it can be divided 5 sedimentary stages under Warm climate, when the crust descents or. stable relatively.The lacustrine seelimentation played a leading role in evey warm stage with the exception in the first one.Because of the inrich of stable minerals in each warm stage, the association seetions of stable minerals exist in the mineral content curve (K K) except a part of K K which coused by climatie fluctuation. The most of the trace elements are concentrateed and only a few are scattered as a result of the warm-humid climate and rapid deposition. Aceording to the materials on hand, the fourth and fifth warm stages helong to fresh-water or light salt-water environment.
1990, 8(2): 135-139.
Abstract:
Currently there are some argument to the data by line measurement and to the treatment of matxices.It have concerned that the method of grain size analysis have been used rightly and data have been reality and reliability.Therefore we must discuss the dissertation"T" about the questions of theory.This paper that has taken throught the analysis of the treatment of matxices and the grain size data of the dissertation "T" has proved that the grain size of 4.5φ have been absent and probability curve have been Variation, result from testing rather than by line measurment.Thus the methed has not used on the treatment of matxices of article "T". If only grain size analysis have been systematized and regulatized in sampling, chip, granulometry, tests have been Confirmed that the result by line measuremet is valid and reliable.
Currently there are some argument to the data by line measurement and to the treatment of matxices.It have concerned that the method of grain size analysis have been used rightly and data have been reality and reliability.Therefore we must discuss the dissertation"T" about the questions of theory.This paper that has taken throught the analysis of the treatment of matxices and the grain size data of the dissertation "T" has proved that the grain size of 4.5φ have been absent and probability curve have been Variation, result from testing rather than by line measurment.Thus the methed has not used on the treatment of matxices of article "T". If only grain size analysis have been systematized and regulatized in sampling, chip, granulometry, tests have been Confirmed that the result by line measuremet is valid and reliable.
1990, 8(2): 9-21.
Abstract:
A spectrum of gravity-displaced deposits from isolated rock blocks through slides and slumps to various kinds of gravity flow sediments can be recognized through anatomizing deepwater deposits in many marine basins of South China.Their different association reflects the different types of sedimentary system to which they belong and their different distribution in each given system.Based on major sources those systems related lo gravity-displacement are divided into three categories: (1) gravity-displaced clastic system: (2) grivi-ty-displaced carbonate system; and (3) gravity displaced mixing sediment system.Category 1 includes two subdivisions of submerine fan and axial-transported system. In terms of the slope gradient of carbonate platform margin category 2 provides three kinds of the models or systems. 1) Ramp-type: besides some thin turbidites and small slumps, its sedimentary characteristics are the dominant fine deposits from sediment rain and the lack of gravity flow deposits containing the materials derived from shallow platform although reefs or mounds and shoals or ooids bands can exist in upper slope or outer shelf. 2) Middle slope gradient- type: it consists of four parts: a) a steeper bypass zone- upper slope which is indicated by periplatform fine sediments deposited in areas between numerous small channels that are perpendicular to the trend of the slope arid are filled with coarse gravity-displaced deposits; b) a gentle middle and lower siope which is the most important site for almost all kinds of gravity-displaced deposits; c) a slope toe in which channelized deposits disappear obviously but are replaced mainly by finer and thiner sheet beds of gravity flow depostits, and the combination of these beds constitutes a banded zone parallel to the trend of the slope along the slope toe; and d) a flat basin floor in which only fine deposits from sediment rain are developed and occasionally interlayered with thin turbidites. 3) Steep slope-type: it includes a very steep slope and a very adjacent fiat basin floor, and is characterized by the lack of channelized deposits and the development of gravity flow calcirudite sheets in large scale. In category 3 the framework of sedimentary systeem is the most complex and commonly is a combination of several subsystems, including: 1) carbonate slope system and clastic submarine fan; and 2) carbonate slope system and pyroclastic gravity flow axial-transported system.
A spectrum of gravity-displaced deposits from isolated rock blocks through slides and slumps to various kinds of gravity flow sediments can be recognized through anatomizing deepwater deposits in many marine basins of South China.Their different association reflects the different types of sedimentary system to which they belong and their different distribution in each given system.Based on major sources those systems related lo gravity-displacement are divided into three categories: (1) gravity-displaced clastic system: (2) grivi-ty-displaced carbonate system; and (3) gravity displaced mixing sediment system.Category 1 includes two subdivisions of submerine fan and axial-transported system. In terms of the slope gradient of carbonate platform margin category 2 provides three kinds of the models or systems. 1) Ramp-type: besides some thin turbidites and small slumps, its sedimentary characteristics are the dominant fine deposits from sediment rain and the lack of gravity flow deposits containing the materials derived from shallow platform although reefs or mounds and shoals or ooids bands can exist in upper slope or outer shelf. 2) Middle slope gradient- type: it consists of four parts: a) a steeper bypass zone- upper slope which is indicated by periplatform fine sediments deposited in areas between numerous small channels that are perpendicular to the trend of the slope arid are filled with coarse gravity-displaced deposits; b) a gentle middle and lower siope which is the most important site for almost all kinds of gravity-displaced deposits; c) a slope toe in which channelized deposits disappear obviously but are replaced mainly by finer and thiner sheet beds of gravity flow depostits, and the combination of these beds constitutes a banded zone parallel to the trend of the slope along the slope toe; and d) a flat basin floor in which only fine deposits from sediment rain are developed and occasionally interlayered with thin turbidites. 3) Steep slope-type: it includes a very steep slope and a very adjacent fiat basin floor, and is characterized by the lack of channelized deposits and the development of gravity flow calcirudite sheets in large scale. In category 3 the framework of sedimentary systeem is the most complex and commonly is a combination of several subsystems, including: 1) carbonate slope system and clastic submarine fan; and 2) carbonate slope system and pyroclastic gravity flow axial-transported system.
1990, 8(2): 43-50.
Abstract:
The writer collected 769 data on bulk analysis of carbonate rock and carbonatite from more than 20 country in the world and 21 provinces of china.Results of statistics and calculation indicated that content ranges of main elements between sedimentary carbonate rock and carbonatite are similar.The carbonatite can be distinguished from sedimentary carbonate rock by discriminant anaalysis.The carbonatite is P2O5-rich and usually content of P2O5 is more than0.2% .The number of data, P2O5 0.2% , is 86% of all carbonatite data. But sedimentary carbonate rock is P2O5-poor.The number of data, P2O50.2% only makes up 12% in all this rock s data.Therefor, content of P2O5 is one important standard for discriminanting genetic type of carbonate rock. When eleven variables are adopted in two set discriminant analysis, discriminanting efficiency of various genetic type of calcareous carbonate rocks, dolomitic carbonate rocks and ferruginous carbonate rock is 93.5%, 90.7% and 89.8% separetaly. When P2O5, Na2O, A12O3, MnO, CaO, K2O and Fe2O3 are used as discriminating variables in discriminant analysis of step by step, discriminanting effect of calcareous carbonate rock is the best and discriminanting efficiency is 94. 5%. While FeO, Fe2O3, Al2O3 and P2O5 are adopted in discriminant analysis for dolomitic carbonate fock, process of calculation is more simple and discriminanting efficiency reached 96% . Using CaO. P2O5 MgO, SiO2, Fe2O3 and Al2O3 for discriminant analysis of ferruginous carbonate rocks, discriminanting efficiency comes up 98. 5% . Generally, discriminanting effect of sedimentary carbonate rocks (near 100%) is better than carbonatite (more than 85% ) , i.e. sedimentary carbonate rock generally isn ' t distinguished.Results of discriminant analysis of limestone and dolomitite from Baiyinobo region indicat that 17 samples of limestone are all distinguished sedimentary carbonate rock, but 3 samples in 57 samples of dolomitite are distinguished sedimentary carbonate rock, making up 5.3% of collecting data, other samples are distinguished carbonatite.The conclusion is in accord with its geological occurrence, geochemical and isotopic composition characteristics
The writer collected 769 data on bulk analysis of carbonate rock and carbonatite from more than 20 country in the world and 21 provinces of china.Results of statistics and calculation indicated that content ranges of main elements between sedimentary carbonate rock and carbonatite are similar.The carbonatite can be distinguished from sedimentary carbonate rock by discriminant anaalysis.The carbonatite is P2O5-rich and usually content of P2O5 is more than0.2% .The number of data, P2O5 0.2% , is 86% of all carbonatite data. But sedimentary carbonate rock is P2O5-poor.The number of data, P2O50.2% only makes up 12% in all this rock s data.Therefor, content of P2O5 is one important standard for discriminanting genetic type of carbonate rock. When eleven variables are adopted in two set discriminant analysis, discriminanting efficiency of various genetic type of calcareous carbonate rocks, dolomitic carbonate rocks and ferruginous carbonate rock is 93.5%, 90.7% and 89.8% separetaly. When P2O5, Na2O, A12O3, MnO, CaO, K2O and Fe2O3 are used as discriminating variables in discriminant analysis of step by step, discriminanting effect of calcareous carbonate rock is the best and discriminanting efficiency is 94. 5%. While FeO, Fe2O3, Al2O3 and P2O5 are adopted in discriminant analysis for dolomitic carbonate fock, process of calculation is more simple and discriminanting efficiency reached 96% . Using CaO. P2O5 MgO, SiO2, Fe2O3 and Al2O3 for discriminant analysis of ferruginous carbonate rocks, discriminanting efficiency comes up 98. 5% . Generally, discriminanting effect of sedimentary carbonate rocks (near 100%) is better than carbonatite (more than 85% ) , i.e. sedimentary carbonate rock generally isn ' t distinguished.Results of discriminant analysis of limestone and dolomitite from Baiyinobo region indicat that 17 samples of limestone are all distinguished sedimentary carbonate rock, but 3 samples in 57 samples of dolomitite are distinguished sedimentary carbonate rock, making up 5.3% of collecting data, other samples are distinguished carbonatite.The conclusion is in accord with its geological occurrence, geochemical and isotopic composition characteristics
1990, 8(2): 59-66.
Abstract:
The Middle Devonian Qujing Formation, situated in Qujing, Yunan, provides an opportunity for thestudy of mixing sedimentation. In the study area, the Qupng Formation is characterized by the rocks composed of the mrxed sedrmentsof siliciclastics and carbonate and the interbedding of terrigenous elastic rock and carbonate rokc w rthterrigenous mudstone. The rocks composed of the mixed terrigenous elastic and carbonate sed}menls are vroyeye-catching.Here we name this kind of rocks MIXOSEDIMENTITE.The mixosedimentites are the typmalproducts of mixing sedimentation.The mixosedimentites of the Qujing Formation have the follewmg char;rc-teristics: 1) The rocks are composed of terrigenous sand> silt and mud and marine lime mud andbioclastics: 2) The remains of trees and fish from the land area coexist mth the marine bioclastrcs: 3 ) T hesorting of the mixed sediments is very poor: 4) The rocks are of massive of graded bedding;3 ) There aretrace fossils such as Zoophycos. Rhizocorallium. ChondrUes or Phycodes in the rocks. 60 Themixosedimentites have no vertical or lateral transition with carbonate rocks. The depositronal environment of the Qujing Formation in the study area was mainly representrtivc of gulf, reef--bank and shallow shelf.Rivers flow into the gulf somewhere, carrying terrigenous sediments andthe remains of trees and fish into the sea.The terrigenous mud was the background sediment of the gulf in thenormal condition. But the terrigeneous mud deposition in the gulf was freqently interrupted by the input ofterrigenous elastics and marine carbonate.In the margin of the gulf lay the reef-bank complex, which is themain source of carbonate material.0utside the reef-bank was the shallow shelf characterized by the interbed-ded nodular limestones with mudstones. The mixing sedimentation occurred in the gulf behind reef-bank complex.It is considered that the mix-ing of sediments was most likely caused by storms. Flowing toward the shore, the storm-surge currentseroded the reef-bank and transported lime mud and bioclastics into the gulf. When flowing back from theshore, the storm-surge currents could also transport the terrigenous material into the gulf.The terrigeneouselastics and carbonate could be mixed and rapidly deposited probably out of the suspension to form themixosedimentites or only interbedded with the background mud.
The Middle Devonian Qujing Formation, situated in Qujing, Yunan, provides an opportunity for thestudy of mixing sedimentation. In the study area, the Qupng Formation is characterized by the rocks composed of the mrxed sedrmentsof siliciclastics and carbonate and the interbedding of terrigenous elastic rock and carbonate rokc w rthterrigenous mudstone. The rocks composed of the mixed terrigenous elastic and carbonate sed}menls are vroyeye-catching.Here we name this kind of rocks MIXOSEDIMENTITE.The mixosedimentites are the typmalproducts of mixing sedimentation.The mixosedimentites of the Qujing Formation have the follewmg char;rc-teristics: 1) The rocks are composed of terrigenous sand> silt and mud and marine lime mud andbioclastics: 2) The remains of trees and fish from the land area coexist mth the marine bioclastrcs: 3 ) T hesorting of the mixed sediments is very poor: 4) The rocks are of massive of graded bedding;3 ) There aretrace fossils such as Zoophycos. Rhizocorallium. ChondrUes or Phycodes in the rocks. 60 Themixosedimentites have no vertical or lateral transition with carbonate rocks. The depositronal environment of the Qujing Formation in the study area was mainly representrtivc of gulf, reef--bank and shallow shelf.Rivers flow into the gulf somewhere, carrying terrigenous sediments andthe remains of trees and fish into the sea.The terrigenous mud was the background sediment of the gulf in thenormal condition. But the terrigeneous mud deposition in the gulf was freqently interrupted by the input ofterrigenous elastics and marine carbonate.In the margin of the gulf lay the reef-bank complex, which is themain source of carbonate material.0utside the reef-bank was the shallow shelf characterized by the interbed-ded nodular limestones with mudstones. The mixing sedimentation occurred in the gulf behind reef-bank complex.It is considered that the mix-ing of sediments was most likely caused by storms. Flowing toward the shore, the storm-surge currentseroded the reef-bank and transported lime mud and bioclastics into the gulf. When flowing back from theshore, the storm-surge currents could also transport the terrigenous material into the gulf.The terrigeneouselastics and carbonate could be mixed and rapidly deposited probably out of the suspension to form themixosedimentites or only interbedded with the background mud.
1990, 8(2): 75-86.
Abstract:
The strata of Lower Crataceous Xiagou Formation, Jiuxi basin, were deposited in the fault subsidence of nomarine.The sedimentation of gravity-now-submerged-fan is studied in this paper.The authors defined the fan-shaped bodies of sand conglomerates interlayer with lacustrine mudstone and not changed to the river deposits, as Igravity-flow-submerged-fan according to the investigating more than one hundred layers of sandy gravel rock and eighty-four pieces of thin section.The submerged-fan consist of four lithofacies ( conglomerate facies, conglomeratic mudstone facies, sandstone facies and silt / mudstone), including fifteen sublithofacies.The analysis of lithofacies show that conglomerate facies were mainly deposited by subaqueous debris flow, sandston facies by high-density turbidite and silt/ mudstone by low-density turbidity currents and lacustrine sedimentation.Conglomeratic mudstone facies is polygenetic, that is , a genetic spectrum was not formed by them. Having analyzed spacial relationship of lithofacies for the genesis, it is proposed thai the events of catasstrophic flood (subaqueous llandslip) , high-density turbidity currents and low-density turbidity currents are the genetic sequence of hydraulic development in the little sized fault-sidence basin it is discussed that the spacial relationship of lithofacies, control factor of tectonic and the environment evolution in the sedimentary context model of the gravity-flow-submerged-fan at last.To make the sedimentological study of suberged-fan is favourable for developing auto-genetic tnd auto-stored oil-reservoir.
The strata of Lower Crataceous Xiagou Formation, Jiuxi basin, were deposited in the fault subsidence of nomarine.The sedimentation of gravity-now-submerged-fan is studied in this paper.The authors defined the fan-shaped bodies of sand conglomerates interlayer with lacustrine mudstone and not changed to the river deposits, as Igravity-flow-submerged-fan according to the investigating more than one hundred layers of sandy gravel rock and eighty-four pieces of thin section.The submerged-fan consist of four lithofacies ( conglomerate facies, conglomeratic mudstone facies, sandstone facies and silt / mudstone), including fifteen sublithofacies.The analysis of lithofacies show that conglomerate facies were mainly deposited by subaqueous debris flow, sandston facies by high-density turbidite and silt/ mudstone by low-density turbidity currents and lacustrine sedimentation.Conglomeratic mudstone facies is polygenetic, that is , a genetic spectrum was not formed by them. Having analyzed spacial relationship of lithofacies for the genesis, it is proposed thai the events of catasstrophic flood (subaqueous llandslip) , high-density turbidity currents and low-density turbidity currents are the genetic sequence of hydraulic development in the little sized fault-sidence basin it is discussed that the spacial relationship of lithofacies, control factor of tectonic and the environment evolution in the sedimentary context model of the gravity-flow-submerged-fan at last.To make the sedimentological study of suberged-fan is favourable for developing auto-genetic tnd auto-stored oil-reservoir.
1990, 8(2): 97-104.
Abstract:
By contrasting the data of elemental analysis to that of water depth, it may be found that most of the contents of metallic elements gradually increase with the increasing depth, excep for the contents of Ca and Sr, which decrease inversely, and that changes in types of sediments take place, as well as the abundance of manganes nodules differs from one to another.By means of analysis of companion sediments in the following items such as contents of metallic elements, constituents of clay, and contents of organic matters, it can also be found that the content of metallic elements is in direct proportion to either the constituents of clay or the contents of organic matters.It can be seen from the analysis of samples each with the same sedimentary grain size that contents of most metallic elements from the clay grade are higher than that in raw samples, and at the same time, the work in comparison of ratio of abundance for manganese nodules with the above mentioned results has been carried out.It can b seen from analysis of samples treated by different methods that contents of metallic elements in clay, of which the organic matters had been extracted, generally reduce. The phenomena, as stated earlier, show that the clay material is not noly an important carrier for the envionmnt of some metallic ele-ments in ocean sediments, but also the carrier for the organic matters enrichment and that since a part of metallic elements is closely bonding with the organic matters so that the conditions for formation of those manganese nodules have beencreeted.
By contrasting the data of elemental analysis to that of water depth, it may be found that most of the contents of metallic elements gradually increase with the increasing depth, excep for the contents of Ca and Sr, which decrease inversely, and that changes in types of sediments take place, as well as the abundance of manganes nodules differs from one to another.By means of analysis of companion sediments in the following items such as contents of metallic elements, constituents of clay, and contents of organic matters, it can also be found that the content of metallic elements is in direct proportion to either the constituents of clay or the contents of organic matters.It can be seen from the analysis of samples each with the same sedimentary grain size that contents of most metallic elements from the clay grade are higher than that in raw samples, and at the same time, the work in comparison of ratio of abundance for manganese nodules with the above mentioned results has been carried out.It can b seen from analysis of samples treated by different methods that contents of metallic elements in clay, of which the organic matters had been extracted, generally reduce. The phenomena, as stated earlier, show that the clay material is not noly an important carrier for the envionmnt of some metallic ele-ments in ocean sediments, but also the carrier for the organic matters enrichment and that since a part of metallic elements is closely bonding with the organic matters so that the conditions for formation of those manganese nodules have beencreeted.
1990, 8(2): 113-119.
Abstract:
In this paper the authors studied characteristics of distribution and evolution of in- and tetracyclic diterpenoid compounds and their significance of organic geochemistry in modern marsh sediments from southern Gansu and Dianchi lake, Yunnan by means of GC-MBTricyclic diterpenoids detected in modern marsh sediments are pimarane, dehydroabietane, dehydroabietin, nine kindes of pimaradiene and long chain tricyciic terpane ( C19- C27) . In this paper, mass spectra of △8, 9- Sandaracopimaradiene, 13-Isopimaradiene, Isopimara-7, 15-diene compounds are first reported in China.Tricyclic diterpenoids with pimarane and abietane skeletons come from diterpenoidacrd in higher plant resins, therefore they reflect organic matter types in modern marsh sediments.Distributional types of long chain tricyciic terpanes in modern marsh sediments are similar to those in modern lake and sea water sediments. They all have reverse" V" type that C23 compound is apex in C21,. = C23 and C24 compounds, therefore distributiona characteristics of long chain tricyciic terpanes almost have not significance of indicating sedimentary environments.Tetracyclic terpanes in modern marsh sediments are composed mainly of normal tetracyclic terpanes (C23-C26), kaurane and de-A-lupane.Normal tetracyclic terpanes ha\ e distributional characteristics of step type with major peak of C26compound.This type of dis- tribution may reflect sedimentary environment of higher plant input. Kaurane come from diterpene in higher plants; de-A-lupane may is the products formed from lupenoid precursors by photochemical degradation or biochemical degradation, therefore they all are biomarker compounds of indicating higher plant input.In the early stage of diagenesis, evolution of tricyclic terpenoids is obvious.Diterpenoids of pimarane type are mainly composed of pimanthrenes and the ratio of pimanthrenes to pimarane decreases with increasing depth. These show that diagenetic products of pimarane- type diterpenoids mainly are pimanthenes formed by decarboxylation But the main type of diagenetic reaction of abietane-type diterpenoids is aromatization.That major peak of long chain tricyclic terpane remove forwards with increasing depth probably reflects that long chain tricyclic terpanes of low carbon number is the products formed from long chain tricyclic terpanes of high carbon number by biochemical degradation.
In this paper the authors studied characteristics of distribution and evolution of in- and tetracyclic diterpenoid compounds and their significance of organic geochemistry in modern marsh sediments from southern Gansu and Dianchi lake, Yunnan by means of GC-MBTricyclic diterpenoids detected in modern marsh sediments are pimarane, dehydroabietane, dehydroabietin, nine kindes of pimaradiene and long chain tricyciic terpane ( C19- C27) . In this paper, mass spectra of △8, 9- Sandaracopimaradiene, 13-Isopimaradiene, Isopimara-7, 15-diene compounds are first reported in China.Tricyclic diterpenoids with pimarane and abietane skeletons come from diterpenoidacrd in higher plant resins, therefore they reflect organic matter types in modern marsh sediments.Distributional types of long chain tricyciic terpanes in modern marsh sediments are similar to those in modern lake and sea water sediments. They all have reverse" V" type that C23 compound is apex in C21,. = C23 and C24 compounds, therefore distributiona characteristics of long chain tricyciic terpanes almost have not significance of indicating sedimentary environments.Tetracyclic terpanes in modern marsh sediments are composed mainly of normal tetracyclic terpanes (C23-C26), kaurane and de-A-lupane.Normal tetracyclic terpanes ha\ e distributional characteristics of step type with major peak of C26compound.This type of dis- tribution may reflect sedimentary environment of higher plant input. Kaurane come from diterpene in higher plants; de-A-lupane may is the products formed from lupenoid precursors by photochemical degradation or biochemical degradation, therefore they all are biomarker compounds of indicating higher plant input.In the early stage of diagenesis, evolution of tricyclic terpenoids is obvious.Diterpenoids of pimarane type are mainly composed of pimanthrenes and the ratio of pimanthrenes to pimarane decreases with increasing depth. These show that diagenetic products of pimarane- type diterpenoids mainly are pimanthenes formed by decarboxylation But the main type of diagenetic reaction of abietane-type diterpenoids is aromatization.That major peak of long chain tricyclic terpane remove forwards with increasing depth probably reflects that long chain tricyclic terpanes of low carbon number is the products formed from long chain tricyclic terpanes of high carbon number by biochemical degradation.
1990, 8(2): 127-134.
Abstract:
Analysis of grain grade is widely used in geology for studying sedimeust transimition and sedimental environments. Besides the conventioned sieve analysis, there occure some new methods, such as computer-controled IAS-FLUS image analysis instrument and the microscope combined with WDJ.But wich one is the most economically benificial method and how to improver the analytical speed and precision.In this study, some different samples have been analysed with the three methods and the results fiave been coprnared.Some conclusions obtained as follow:1. Sieve analysis is suitable for cohesionless sandestone especially for wind, river, lake-formed sandstone after Cenozic and Mesozoic,2. TAS-PLUS image aualysis instrument is beter for quartz-sandstone, fundamentally cemented saudstone, striped sandstone and differently lighted sandstone. 3, The microscope combined with WDJ is suitable for most kinds of sandstone.Even though it could be widely used. the oberservating is very difficult under microscope and influnced by some manal factions.So, using a suitable method is important for benified sample analysis.
Analysis of grain grade is widely used in geology for studying sedimeust transimition and sedimental environments. Besides the conventioned sieve analysis, there occure some new methods, such as computer-controled IAS-FLUS image analysis instrument and the microscope combined with WDJ.But wich one is the most economically benificial method and how to improver the analytical speed and precision.In this study, some different samples have been analysed with the three methods and the results fiave been coprnared.Some conclusions obtained as follow:1. Sieve analysis is suitable for cohesionless sandestone especially for wind, river, lake-formed sandstone after Cenozic and Mesozoic,2. TAS-PLUS image aualysis instrument is beter for quartz-sandstone, fundamentally cemented saudstone, striped sandstone and differently lighted sandstone. 3, The microscope combined with WDJ is suitable for most kinds of sandstone.Even though it could be widely used. the oberservating is very difficult under microscope and influnced by some manal factions.So, using a suitable method is important for benified sample analysis.
