2006 Vol. 24, No. 3
Display Method:
2006, 24(3): 309-320.
Abstract:
Chengdu basin developed ahead of Longmen Shan along eastern margin of Tibetan Plateau, lying between the Longmen Shan and Longquan Shan. The filling in the basin include Dayi conglomerate, Yaan gravel layer and Late Pleistocene and Holocene gravel layer since 3.6Ma，and the sediments in the basin were derived from Longmen Shan with transverse drainage patterns. Based on results by the component analysis of gravel, heavy mineral and geochemistry of major elements in the sediments of Chengdu basin, we draw conclusion that there were two provenances and two paleorivers, one of them was paleoMinjiang, which developed in the northern part of the basin, another was paleoQingyijiang ,which developed in the southern part of the basin. According to the difference between Dayi conglomerate and modern fluvial deposit, we can infer Minjiang and Qinyijiang have changed their course after period of Dayi conglomerate deposition.
Chengdu basin developed ahead of Longmen Shan along eastern margin of Tibetan Plateau, lying between the Longmen Shan and Longquan Shan. The filling in the basin include Dayi conglomerate, Yaan gravel layer and Late Pleistocene and Holocene gravel layer since 3.6Ma，and the sediments in the basin were derived from Longmen Shan with transverse drainage patterns. Based on results by the component analysis of gravel, heavy mineral and geochemistry of major elements in the sediments of Chengdu basin, we draw conclusion that there were two provenances and two paleorivers, one of them was paleoMinjiang, which developed in the northern part of the basin, another was paleoQingyijiang ,which developed in the southern part of the basin. According to the difference between Dayi conglomerate and modern fluvial deposit, we can infer Minjiang and Qinyijiang have changed their course after period of Dayi conglomerate deposition.
2006, 24(3): 333-338.
Abstract:
A catchment's nutrient model SWAT was used in this paper to examine changes in the nutrient sedimentation and transportation in a hundredyear time scale, and Hong Lake Basin, located in the middle reach of Changjiang River was chosen as the study area. Boundary condition in the simulations is prescribed in a preindustrial time mode in order to evaluate a naturalagricultural forced nutrient changes in the Hong Lake Basin one hundred years ago. Total nitrogen (TN) and total phosphorus (TP) in the main channel transported into the lake were simulated in two periods of flood season (summer) and nonflood season (spring, fall and winter) in running 200 model years respectively. Results show the modeling can catch basic features of the basin nutrient transportations and changes. The TN and TP concentrations show significant seasonal changes, and annul mean concentration can be compared well with nutrient concentrations transformed from sediment cores of Hong Lake that records were 137Csdated to ca 100 year ago. Time series in the 200yr simulation shows different trends in TN and TP concentration changes. There are obvious differences spatially in the input and output subbasins. The SWAT model has provided an effective tool to evaluate how nutrient production and changes in natural environmental system of the 200 years in the Hong Lake Basin.
A catchment's nutrient model SWAT was used in this paper to examine changes in the nutrient sedimentation and transportation in a hundredyear time scale, and Hong Lake Basin, located in the middle reach of Changjiang River was chosen as the study area. Boundary condition in the simulations is prescribed in a preindustrial time mode in order to evaluate a naturalagricultural forced nutrient changes in the Hong Lake Basin one hundred years ago. Total nitrogen (TN) and total phosphorus (TP) in the main channel transported into the lake were simulated in two periods of flood season (summer) and nonflood season (spring, fall and winter) in running 200 model years respectively. Results show the modeling can catch basic features of the basin nutrient transportations and changes. The TN and TP concentrations show significant seasonal changes, and annul mean concentration can be compared well with nutrient concentrations transformed from sediment cores of Hong Lake that records were 137Csdated to ca 100 year ago. Time series in the 200yr simulation shows different trends in TN and TP concentration changes. There are obvious differences spatially in the input and output subbasins. The SWAT model has provided an effective tool to evaluate how nutrient production and changes in natural environmental system of the 200 years in the Hong Lake Basin.
2006, 24(3): 349-355.
Abstract:
On the basis of analyzing grainsize proxies, the evolution history of Hongjiannao Lake for the past 80 yrs. is discussed in this article. Grainsize distribution of the samples from the lower part of the sedimentary core is characterized by the “doublepeak” feature, which enables us to distinguish the aeolian materials from the lacustrine sediments. It's revealed that Hongjiannao Lake formed in about 1928 A.D. and in its initial stage sandstorms were prevalent with three extremes took place in 1936 A.D., 1939 A.D. and 1941 A.D.. During 1952~1960 A.D., the lake expanded greatly, due to the sharp increase of inflow waters to the lake as a result of the channelledoff water from the around swamp caused by human beings. Hongjiannao Lake has remained a higher water level since 1960s and the frequency and intensity of sandstorms have reduced a lot with the “doublepeak” feature of the grainsize frequency curve changing into the “singlepeak” feature. The water level of Hongjiannao Lake has been holding a dropping trend since 1950s. The lake evolution history as well as the paleosandstorm characteristics and the anthropogenic activities are perfectly inferred from the study of grainsize proxies.
On the basis of analyzing grainsize proxies, the evolution history of Hongjiannao Lake for the past 80 yrs. is discussed in this article. Grainsize distribution of the samples from the lower part of the sedimentary core is characterized by the “doublepeak” feature, which enables us to distinguish the aeolian materials from the lacustrine sediments. It's revealed that Hongjiannao Lake formed in about 1928 A.D. and in its initial stage sandstorms were prevalent with three extremes took place in 1936 A.D., 1939 A.D. and 1941 A.D.. During 1952~1960 A.D., the lake expanded greatly, due to the sharp increase of inflow waters to the lake as a result of the channelledoff water from the around swamp caused by human beings. Hongjiannao Lake has remained a higher water level since 1960s and the frequency and intensity of sandstorms have reduced a lot with the “doublepeak” feature of the grainsize frequency curve changing into the “singlepeak” feature. The water level of Hongjiannao Lake has been holding a dropping trend since 1950s. The lake evolution history as well as the paleosandstorm characteristics and the anthropogenic activities are perfectly inferred from the study of grainsize proxies.
2006, 24(3): 365-369.
Abstract:
In this work, the late Cenozoic aeolian deposits at Huangshui catchment, the northeastern Tibetan Plateau, is investigated on geochemistry distribution and magnetic property, and, they are compared with that of the aeolian sediment in the Central Loess Plateau.It shows that the dust sources of the aeolian deposit in Huangshui catachment are different from that of the aeolian deposits in the Central Loess Plateau. The arid and/or semiarid region in the middle and west parts of the Tibetan Plateau may be a potential dust source for the aeolian deposit of the northeastern Tibetan Plateau. Therefore, the existence of the late Cenozoic aeolian deposit demonstrates that the middle and west parts of the Tibetan Plateau have been dry since the middle Miocene time.
In this work, the late Cenozoic aeolian deposits at Huangshui catchment, the northeastern Tibetan Plateau, is investigated on geochemistry distribution and magnetic property, and, they are compared with that of the aeolian sediment in the Central Loess Plateau.It shows that the dust sources of the aeolian deposit in Huangshui catachment are different from that of the aeolian deposits in the Central Loess Plateau. The arid and/or semiarid region in the middle and west parts of the Tibetan Plateau may be a potential dust source for the aeolian deposit of the northeastern Tibetan Plateau. Therefore, the existence of the late Cenozoic aeolian deposit demonstrates that the middle and west parts of the Tibetan Plateau have been dry since the middle Miocene time.
2006, 24(3): 370-377.
Abstract:
By studying the sections and cores of Tarim basin, the Tataertage Formation of lower Silurian in Tarim Basin primarily deposited a set of clastic rock composed of sandstone and mudstone. The authors divided Tataertage Formation into onshore sedimentary system and continental shelf sedimentary system by its lithologic, ethologic and geographic character. And the onshore sedimentary system could be further divided into nonbarrier coast sediment and barrier wadd sediment. Its shallow shelf sediment features the continental shelf sedimentary system. The authors also studied the types of rock, grains size distribution and sedimentary tectonic character of these sedimentary facies of Tataertage Formation mentioned above. Based on these studies, the authors analyzed the plane distribution character of Tataertage Formation during sedimentation. The direction of its strike is approximate by south to north, layers distribute nearly parallel from west to east as a whole. The authors established the onshore, wadd, onshorewadd sedimentary model of Tataertage Formation in Tarim Basin, which is primary onshorewadd sedimentary model.
By studying the sections and cores of Tarim basin, the Tataertage Formation of lower Silurian in Tarim Basin primarily deposited a set of clastic rock composed of sandstone and mudstone. The authors divided Tataertage Formation into onshore sedimentary system and continental shelf sedimentary system by its lithologic, ethologic and geographic character. And the onshore sedimentary system could be further divided into nonbarrier coast sediment and barrier wadd sediment. Its shallow shelf sediment features the continental shelf sedimentary system. The authors also studied the types of rock, grains size distribution and sedimentary tectonic character of these sedimentary facies of Tataertage Formation mentioned above. Based on these studies, the authors analyzed the plane distribution character of Tataertage Formation during sedimentation. The direction of its strike is approximate by south to north, layers distribute nearly parallel from west to east as a whole. The authors established the onshore, wadd, onshorewadd sedimentary model of Tataertage Formation in Tarim Basin, which is primary onshorewadd sedimentary model.
2006, 24(3): 387-393.
Abstract:
Ordos basin is only the largest artesian basin in China during Cretaceous. Characteristics of early Cretaceous lithofacies palaeogeographic are significant factors that influence distributing features, aquosity and quality change of three waterbearing Formations, Luohe, HuanheHuachi and Luohandong Formation. Through analyzing palaeotectonic, palaeogeographic, sedimentary environment and lithofeature, sedimentary facies types of mainly waterbearing formation are divided in this article, and relationships between sedimentary facies with aquosity and distributing rule of waterbearing formation have been discussed further.It is considered that waterbearing formations lain in the margin of basin, composed of alluvial fans, rive facies and distributary channel of delta plain, have characteristics of different episode of sedimentary granulite superposition, thicker waterbearing layers, less waterresisting layers of mudstones, optimum circle system of groundwater and low mineralization degree; and there are two types in the inside of basin, windbearing facies sandstones of Luohe Formation and Luohandong Formation are the best of waterbearing formation with charateristics of stabile occurrence, high maturation in component and structure, low solube component and reasonably spatial matching relation of roof and floor lithology and boundary isolated barrier lithology; on the other hand, waterbearing sand boies of HuanheHuachi Formation, composed of feldsparquartz finesand of bar and lakefront, occurs isolated lens and has charateristics of poor aquosity, complex porethroat texture, strong corrosion and high mineralization degree. Asymmetrical lakebasin structure of Ordos basin in EW way, formed in early Cretaceous, not only control development and distribution of main waterbearing bed, but also is the basis of structure forming of artesian basin nowadays.
Ordos basin is only the largest artesian basin in China during Cretaceous. Characteristics of early Cretaceous lithofacies palaeogeographic are significant factors that influence distributing features, aquosity and quality change of three waterbearing Formations, Luohe, HuanheHuachi and Luohandong Formation. Through analyzing palaeotectonic, palaeogeographic, sedimentary environment and lithofeature, sedimentary facies types of mainly waterbearing formation are divided in this article, and relationships between sedimentary facies with aquosity and distributing rule of waterbearing formation have been discussed further.It is considered that waterbearing formations lain in the margin of basin, composed of alluvial fans, rive facies and distributary channel of delta plain, have characteristics of different episode of sedimentary granulite superposition, thicker waterbearing layers, less waterresisting layers of mudstones, optimum circle system of groundwater and low mineralization degree; and there are two types in the inside of basin, windbearing facies sandstones of Luohe Formation and Luohandong Formation are the best of waterbearing formation with charateristics of stabile occurrence, high maturation in component and structure, low solube component and reasonably spatial matching relation of roof and floor lithology and boundary isolated barrier lithology; on the other hand, waterbearing sand boies of HuanheHuachi Formation, composed of feldsparquartz finesand of bar and lakefront, occurs isolated lens and has charateristics of poor aquosity, complex porethroat texture, strong corrosion and high mineralization degree. Asymmetrical lakebasin structure of Ordos basin in EW way, formed in early Cretaceous, not only control development and distribution of main waterbearing bed, but also is the basis of structure forming of artesian basin nowadays.
2006, 24(3): 399-406.
Abstract:
Many oil and gas pools have been found above or below the unconformity in the Junggar Basin, indicating that the unconformity is a good conduit for petroleum migration. Based on the petroleumbearing fluid activities in unconformity zones, we suggested that vertical structure of unconformity is the most key factor controlling the petroleum migration. Two layers of unconformity were divided, i.e. bottom conglomerate (upper layer) and weathered crust (lower layer). In addition, if some mudstone were developed on the top of weathered crust, the unconformity was threelayer structured. The weathered crust could be further divided into weathered fractured crust based on volcanic rocks, and weathered solution crust based on detrital rocks. Then, we defined three types of unconformity according to lithostratigraphic features of the bottom conglomerate and the weathered crust. They include overlapbase type, sandstoneconglomerate type, and sandstonemudstone type, among which the first one is the most favorable for petroleum migration, the second intermediate, and the last could generally not be considered as a conduit.
Many oil and gas pools have been found above or below the unconformity in the Junggar Basin, indicating that the unconformity is a good conduit for petroleum migration. Based on the petroleumbearing fluid activities in unconformity zones, we suggested that vertical structure of unconformity is the most key factor controlling the petroleum migration. Two layers of unconformity were divided, i.e. bottom conglomerate (upper layer) and weathered crust (lower layer). In addition, if some mudstone were developed on the top of weathered crust, the unconformity was threelayer structured. The weathered crust could be further divided into weathered fractured crust based on volcanic rocks, and weathered solution crust based on detrital rocks. Then, we defined three types of unconformity according to lithostratigraphic features of the bottom conglomerate and the weathered crust. They include overlapbase type, sandstoneconglomerate type, and sandstonemudstone type, among which the first one is the most favorable for petroleum migration, the second intermediate, and the last could generally not be considered as a conduit.
2006, 24(3): 414-418.
Abstract:
The granularities of more than 2000 samples from 82 wells in the lowpermeability sandstone reservoirs of Shengli oilfield were tested by the MS2000 laser granulometric analyzer. The experiment showed that the granulometric distributions of sediments in low permeability sandstone reservoir behave as three modes, and each mode has its own characteristics and is related with certain sedimentation process. It is also found that the median distribution of granularity, the shale content of lowpermeability reservoir rock and the classified degree are the three key factors, which influence its permeability, and normal distribution or mixed normal distribution, can preferably describe the granulometric distribution characteristics of sediments in lowpermeability sandstone reservoir.
The granularities of more than 2000 samples from 82 wells in the lowpermeability sandstone reservoirs of Shengli oilfield were tested by the MS2000 laser granulometric analyzer. The experiment showed that the granulometric distributions of sediments in low permeability sandstone reservoir behave as three modes, and each mode has its own characteristics and is related with certain sedimentation process. It is also found that the median distribution of granularity, the shale content of lowpermeability reservoir rock and the classified degree are the three key factors, which influence its permeability, and normal distribution or mixed normal distribution, can preferably describe the granulometric distribution characteristics of sediments in lowpermeability sandstone reservoir.
2006, 24(3): 426-431.
Abstract:
A great number of sporopollen fossils have been discovered in Chang 8 and Chang 7 intervals of Yanchang Formation from drilling cores of Longdong area in the southwestern Ordos Basin, and they were named as AratisporitesPunctatisporites assemblage and AsseretosporaWalchiites assemblage,respectively. Their characteristics are similar to the sporopollen assemblages of Tongchuan Formation and Yanchang Formation discovered in the southeast of the basin, and the geologic times of the assemblages are Ladinian of the late Middle Triassic and Carnian of the early Late Triassic. Based on the environmental distribution of main plant types at present and the analysis of the content of types to recognize the relationship between palynological flora and the characteristics of stratagraphic distribution, we can infer that the climate was warm and moist then, rainfall was plentiful, and the vegetation was luxuriant during Middle Triassic and Late Triassic in Longdong area. The paleoclimate reflected by palynological flora was warmwet or hotwet in temperate to subtropical. The ecological types of palynological flora and the diversity curves of palynoflora indicate that the Chang 8 and Chang 7 phases were suitable period of continuously warm and humid in the area, and the extensive lacustrine transgression occurred in Chang 8 phrase during the development of lake as well as sustaining maximum flooding in Chang 7 phase. It was semihumidity temperate to subtropical climate during Middle Triassic and Late Triassic in northern China. The palynological flora discovered from the Chang 8 and Chang 7 intervals in Longdong area is obviously characteristic of the northern China flora. However, because the area was close to the large-scale lake at that time, and the Chang 7 and Chang 8 phases were the great prosperous period that lake was being expanded, so the characteristics of moister paleoenvironment was indicated. It was just because of longterm stable warm and wet climate and the extended deep lake environment that created conditions for largescale growth of hydrophilous alga, consequently they provided organic matter for the highquality source rocks of Chang 7 section in the area.
A great number of sporopollen fossils have been discovered in Chang 8 and Chang 7 intervals of Yanchang Formation from drilling cores of Longdong area in the southwestern Ordos Basin, and they were named as AratisporitesPunctatisporites assemblage and AsseretosporaWalchiites assemblage,respectively. Their characteristics are similar to the sporopollen assemblages of Tongchuan Formation and Yanchang Formation discovered in the southeast of the basin, and the geologic times of the assemblages are Ladinian of the late Middle Triassic and Carnian of the early Late Triassic. Based on the environmental distribution of main plant types at present and the analysis of the content of types to recognize the relationship between palynological flora and the characteristics of stratagraphic distribution, we can infer that the climate was warm and moist then, rainfall was plentiful, and the vegetation was luxuriant during Middle Triassic and Late Triassic in Longdong area. The paleoclimate reflected by palynological flora was warmwet or hotwet in temperate to subtropical. The ecological types of palynological flora and the diversity curves of palynoflora indicate that the Chang 8 and Chang 7 phases were suitable period of continuously warm and humid in the area, and the extensive lacustrine transgression occurred in Chang 8 phrase during the development of lake as well as sustaining maximum flooding in Chang 7 phase. It was semihumidity temperate to subtropical climate during Middle Triassic and Late Triassic in northern China. The palynological flora discovered from the Chang 8 and Chang 7 intervals in Longdong area is obviously characteristic of the northern China flora. However, because the area was close to the large-scale lake at that time, and the Chang 7 and Chang 8 phases were the great prosperous period that lake was being expanded, so the characteristics of moister paleoenvironment was indicated. It was just because of longterm stable warm and wet climate and the extended deep lake environment that created conditions for largescale growth of hydrophilous alga, consequently they provided organic matter for the highquality source rocks of Chang 7 section in the area.
2006, 24(3): 440-445.
Abstract:
On the basis of the investigation on hydrocarbon source in SongpanAba area, this paper compares the organic thermal evolution with that in Sichuan basin, which has some similarities in structural evolution to SongpanAba area before middle Triassic. It is approach that the thermal evolutional level is higher in SongpanAba area than that in Sichuan basin, and there are several different Bitumen reflectance levels there. Due to the fault and magma activity，the vitrinite reflectance is higher in the margin than that in the center of SongpanAba area. This area centered with Tangke with lower thermal evolution level can be the exploration area at the beginning.
On the basis of the investigation on hydrocarbon source in SongpanAba area, this paper compares the organic thermal evolution with that in Sichuan basin, which has some similarities in structural evolution to SongpanAba area before middle Triassic. It is approach that the thermal evolutional level is higher in SongpanAba area than that in Sichuan basin, and there are several different Bitumen reflectance levels there. Due to the fault and magma activity，the vitrinite reflectance is higher in the margin than that in the center of SongpanAba area. This area centered with Tangke with lower thermal evolution level can be the exploration area at the beginning.
2006, 24(3): 450-460.
Abstract:
To study the biomarker parameters that indicate bacteria activities, fatty acids of three Quaternary mudstone samples from the north of the Sebei area of the Qaidam basin were analyzed by GCMS. A series of unsaturated and abundant xenobioticbranched fatty acids,and isoprenoid acid were identified and discussed in detail. Based on the constitutes of the unsaturated and the xenobiotic branched fatty acids of the two samples, and the geological background of the samples, we think that the unsaturated fatty acids, especially the xenobioticbranched fatty acids and isoprenoid acid were most probably derived from bacteria. The occurrence of these fatty acids in the main biogenic gas production layers indicates that there exist favourable conditions for bacteria upgrowth. The unsaturated and abundant xenobioticbranched fatty acids and isoprenoid acid could be used as indictors that estimate the growth of bacteria in biogenic gas source rocks.
To study the biomarker parameters that indicate bacteria activities, fatty acids of three Quaternary mudstone samples from the north of the Sebei area of the Qaidam basin were analyzed by GCMS. A series of unsaturated and abundant xenobioticbranched fatty acids,and isoprenoid acid were identified and discussed in detail. Based on the constitutes of the unsaturated and the xenobiotic branched fatty acids of the two samples, and the geological background of the samples, we think that the unsaturated fatty acids, especially the xenobioticbranched fatty acids and isoprenoid acid were most probably derived from bacteria. The occurrence of these fatty acids in the main biogenic gas production layers indicates that there exist favourable conditions for bacteria upgrowth. The unsaturated and abundant xenobioticbranched fatty acids and isoprenoid acid could be used as indictors that estimate the growth of bacteria in biogenic gas source rocks.
2006, 24(3): 321-332.
Abstract:
The SongpanGanze basin (Central China) covers a huge triangular area of more than 200,000km2and is bounded by the continental blocks of South China, North China and the Tibetan plateau. The six sandstone samples collected from this belt were analyzed grainbygrain〖KG*2〗using SHRIMP UPb method. The detrital zircons yield a wide range of ages, which〖KG*2〗are focused on Proterozoic with minor contribution from late Archean material. The discordance and Pb loss patterns from low U zircons indicate that they might be resulted from the subsequent magmatism events, including the Sibao to the Indosinian periods.The Caledonian appearance of zircons indicates that the origin of these clastic sediments might originate from the Northern Qinling belt, other zircons originated mainly from the north margin of the Yangtze craton and the south Qinling belt.
The SongpanGanze basin (Central China) covers a huge triangular area of more than 200,000km2and is bounded by the continental blocks of South China, North China and the Tibetan plateau. The six sandstone samples collected from this belt were analyzed grainbygrain〖KG*2〗using SHRIMP UPb method. The detrital zircons yield a wide range of ages, which〖KG*2〗are focused on Proterozoic with minor contribution from late Archean material. The discordance and Pb loss patterns from low U zircons indicate that they might be resulted from the subsequent magmatism events, including the Sibao to the Indosinian periods.The Caledonian appearance of zircons indicates that the origin of these clastic sediments might originate from the Northern Qinling belt, other zircons originated mainly from the north margin of the Yangtze craton and the south Qinling belt.
2006, 24(3): 339-348.
Abstract:
The time sequence of high resolution paleoclimatic change since 2 300 a B.P. has been reconstructed by dating ages of the high precision ICPMS or TIMSU series and the analysis of the carbon and oxygen isotopes from a stalagmite of Dongge cave in the area of Libo, Guizhou. The study showed that the records of the warm and cold events from a stalagmite since 2 300 a B.P. in the area of Libo reflected the paleoclimatic change which can be divided into eight stages: (1) Falling temperature stage from 2 300 a B.P. to 1 800 a B.P. showed that the East Asian summer monsoon became weakly and winter monsoon became strongly, the air temperature gradually fallen, the available rainfall reduced, and they represented the dry and cold climate environment; (2) Rising temperature stage from 1 080 a B.P. indicated that the East Asian winter monsoon slowly weaken 1 800 a B.P. to and summer monsoon slightly strengthened, and they represented the semihumid and warmcool climate environment. (3) Dropping temperature time from 1 080 a B.P. to 680a B.P. showed that the winter monsoon strengthened again, the air temperature reduced again, and the available rainfall relatively increased in winter, and they represented the cold and humid climate environment. This stage was the key transition period of climate change.(4) Warm period from 680 a B.P. to 550 a B.P. revealed that the East Asian summer monsoon strengthened again, the air temperature rose, the available rainfall relatively increased in summer, and they represented the warm and humid climate environment. (5) The cold period from 550 a B.P. to 400 a B.P. indicated that the East Asian winter monsoon rapidly strengthened, the air temperature quickly dropped and the available rainfall increased a lot, and they represented the cold and humid climate environment. This stage was the coldest stage in the last 1000 years. (6)
Warmcool period from 400 a B.P. to 364 a B.P. revealed that the East Asian summer monsoon slightly strengthen, the air temperature slightly increased, and they represented the warmcool and humid climate environment. (7) The coldcool period from 364 a B.P.to 324 a B.P. indicated that the East Asian winter monsoon slightly strengthen, the air temperature slightly dropped, this period was the coldcool and humid climate environment. (8) The relatively fluctuation stage of climate change from 324 a B.P. up to the present revealed that the East Asian monsoon frequently changed, the curve of isotope records submitted the serrated undulations, which included some substages of the coldcool and semihumid, cold and humid climate changes.
Some key centuralscale climate events, for example the drycold period, Suitang warm period, little warm and cold period, and some changes of precipitation and temperture in the ten, century time scale has been revealed since 2 300 years in Libo area according to the continuous record of high resolution paleoclimatic change from a stalagmite. The abrupt events of climatic change in the ten, century time scale from a stalagmite record has an analogy with the events of the ice core records, and reflected that the monsoon climate from stalagmite records in the low latitude region is provided a wonderful relativity with the climate change in the high latitude region and the arctic pole. The above study has the important scientific significance for knowing the change of modern climate system, climatic forecast and driving mechanism of climatic evolution in the future.
The time sequence of high resolution paleoclimatic change since 2 300 a B.P. has been reconstructed by dating ages of the high precision ICPMS or TIMSU series and the analysis of the carbon and oxygen isotopes from a stalagmite of Dongge cave in the area of Libo, Guizhou. The study showed that the records of the warm and cold events from a stalagmite since 2 300 a B.P. in the area of Libo reflected the paleoclimatic change which can be divided into eight stages: (1) Falling temperature stage from 2 300 a B.P. to 1 800 a B.P. showed that the East Asian summer monsoon became weakly and winter monsoon became strongly, the air temperature gradually fallen, the available rainfall reduced, and they represented the dry and cold climate environment; (2) Rising temperature stage from 1 080 a B.P. indicated that the East Asian winter monsoon slowly weaken 1 800 a B.P. to and summer monsoon slightly strengthened, and they represented the semihumid and warmcool climate environment. (3) Dropping temperature time from 1 080 a B.P. to 680a B.P. showed that the winter monsoon strengthened again, the air temperature reduced again, and the available rainfall relatively increased in winter, and they represented the cold and humid climate environment. This stage was the key transition period of climate change.(4) Warm period from 680 a B.P. to 550 a B.P. revealed that the East Asian summer monsoon strengthened again, the air temperature rose, the available rainfall relatively increased in summer, and they represented the warm and humid climate environment. (5) The cold period from 550 a B.P. to 400 a B.P. indicated that the East Asian winter monsoon rapidly strengthened, the air temperature quickly dropped and the available rainfall increased a lot, and they represented the cold and humid climate environment. This stage was the coldest stage in the last 1000 years. (6)
Warmcool period from 400 a B.P. to 364 a B.P. revealed that the East Asian summer monsoon slightly strengthen, the air temperature slightly increased, and they represented the warmcool and humid climate environment. (7) The coldcool period from 364 a B.P.to 324 a B.P. indicated that the East Asian winter monsoon slightly strengthen, the air temperature slightly dropped, this period was the coldcool and humid climate environment. (8) The relatively fluctuation stage of climate change from 324 a B.P. up to the present revealed that the East Asian monsoon frequently changed, the curve of isotope records submitted the serrated undulations, which included some substages of the coldcool and semihumid, cold and humid climate changes.
Some key centuralscale climate events, for example the drycold period, Suitang warm period, little warm and cold period, and some changes of precipitation and temperture in the ten, century time scale has been revealed since 2 300 years in Libo area according to the continuous record of high resolution paleoclimatic change from a stalagmite. The abrupt events of climatic change in the ten, century time scale from a stalagmite record has an analogy with the events of the ice core records, and reflected that the monsoon climate from stalagmite records in the low latitude region is provided a wonderful relativity with the climate change in the high latitude region and the arctic pole. The above study has the important scientific significance for knowing the change of modern climate system, climatic forecast and driving mechanism of climatic evolution in the future.
2006, 24(3): 356-364.
Abstract:
There are only a few long cores drilled and studied on the outer continental shelf of the East China Sea with water depth more than 50m, core EA01〖KG*2〗is one of them with many indexes analyzed. The present study mainly utilizes geochemical data to study the sequence and material source of the core. The down core variation of geochemical data is an important index for the sequence and paleoclimate, 1 cold event and 3 warm events are identified. Many methods including factor analysis, La/Yb—Ni/Co—Cr/V ternary diagram and U/Th—(Zr+Hf)/(Al2O3+TiO2)〖KG*2〗distribution scatter diagram〖KG*2〗are used to determine the material source of core EA01, and it is found that the material of core EA01 mainly come from the Changjiang River, which may vary partly according to different climate and environment.
There are only a few long cores drilled and studied on the outer continental shelf of the East China Sea with water depth more than 50m, core EA01〖KG*2〗is one of them with many indexes analyzed. The present study mainly utilizes geochemical data to study the sequence and material source of the core. The down core variation of geochemical data is an important index for the sequence and paleoclimate, 1 cold event and 3 warm events are identified. Many methods including factor analysis, La/Yb—Ni/Co—Cr/V ternary diagram and U/Th—(Zr+Hf)/(Al2O3+TiO2)〖KG*2〗distribution scatter diagram〖KG*2〗are used to determine the material source of core EA01, and it is found that the material of core EA01 mainly come from the Changjiang River, which may vary partly according to different climate and environment.
2006, 24(3): 378-386.
Abstract:
The eastern Junggar basin located on the northeastern edge of the large down warped lake basin in Jurassic. Mainly three sets of thick coal layers developed in the east of Junggar basin Jurassic strata, respectively lying at the bottom of Xishanyao group, the upper part and the lower of the middle part of Badaowan group. The coal layer of Xishanyao group and the upper part of Badaowan group were formed in the stage of lacustrine regression delta and they are thick and stable regionally. The coal layer of the lower of the middle part of Badaowan group was formed shore swamp in the stage of lacustrine transgression and it is thin and stability in region. The coal accumulation environment and stacking pattern are controled by baselevel and accommodation in the eastern Junggar basin. The accommodation is affected by the structural uplift and basement differential subsidence in the eastern Junggar basin in Jurassic. Accommodation move toward the center of the basin in the process of lacustrine regression and there are bulky accommodation below shoreland where peat are preserved advantageously in the upper section of Badaowan group and the bottom of Xishanyao group. The two sets of coal layers may be acted as the transfer surface of sedimentation. The coal layer of the down of the middle part of Badaowan group may be regard as first flood surface of lacustrine and sequence boundary. Based on accurate correlation of the highresolution sequence stratigraphy, distribution regularity of oil, gas and water of Xishanyao group reservoir can be explained reasonably in the Well CAI 31 area. It has obtained a good effect on the identification of subtle reservoir and precise reservoir description.
The eastern Junggar basin located on the northeastern edge of the large down warped lake basin in Jurassic. Mainly three sets of thick coal layers developed in the east of Junggar basin Jurassic strata, respectively lying at the bottom of Xishanyao group, the upper part and the lower of the middle part of Badaowan group. The coal layer of Xishanyao group and the upper part of Badaowan group were formed in the stage of lacustrine regression delta and they are thick and stable regionally. The coal layer of the lower of the middle part of Badaowan group was formed shore swamp in the stage of lacustrine transgression and it is thin and stability in region. The coal accumulation environment and stacking pattern are controled by baselevel and accommodation in the eastern Junggar basin. The accommodation is affected by the structural uplift and basement differential subsidence in the eastern Junggar basin in Jurassic. Accommodation move toward the center of the basin in the process of lacustrine regression and there are bulky accommodation below shoreland where peat are preserved advantageously in the upper section of Badaowan group and the bottom of Xishanyao group. The two sets of coal layers may be acted as the transfer surface of sedimentation. The coal layer of the down of the middle part of Badaowan group may be regard as first flood surface of lacustrine and sequence boundary. Based on accurate correlation of the highresolution sequence stratigraphy, distribution regularity of oil, gas and water of Xishanyao group reservoir can be explained reasonably in the Well CAI 31 area. It has obtained a good effect on the identification of subtle reservoir and precise reservoir description.
2006, 24(3): 394-398.
Abstract:
By using biological method，microorganisms in the Shihongtan uranium deposit were isolated and identified, and using sulfatereducing bacteria effected on uranium in the deposit underwater. The simulation experiment of the function of microorganisms during the formation of uranium deposit could be done by the waterrockbacteria threephase experiment system. The result showed that the distribution of the main microbe groups in the subzones were different and the geochemical characteristics was obvious to show that uranium could be reduced and precipitated by sulfatereducing bacteria through metabolism function. The result of the reductive reducing experiment indicated that sulfatereducing bacteria could absorb organic carbon as nutrition materials to grow, at the same time, uranium was reduced and precipitated.
By using biological method，microorganisms in the Shihongtan uranium deposit were isolated and identified, and using sulfatereducing bacteria effected on uranium in the deposit underwater. The simulation experiment of the function of microorganisms during the formation of uranium deposit could be done by the waterrockbacteria threephase experiment system. The result showed that the distribution of the main microbe groups in the subzones were different and the geochemical characteristics was obvious to show that uranium could be reduced and precipitated by sulfatereducing bacteria through metabolism function. The result of the reductive reducing experiment indicated that sulfatereducing bacteria could absorb organic carbon as nutrition materials to grow, at the same time, uranium was reduced and precipitated.
2006, 24(3): 407-413.
Abstract:
A set of new equipment has been designed and applied to simulate the diagenetic compaction. Medium quartz sand is selected as material to carry out the experiment. In order to do further research, physical and chemical change have both been detected, and some new conclusion have been reached. During compaction, the porosity and permeability are not varied regularly, and it can be divided into to section, a sudden change section and a uniform change section. In the uniform change section, the porosity decreases with the increase of the pressure, and they have a linear relation. The permeability decreases with the increase of the pressure either, and they have an exponential relation. The porosity and permeability also have semilogarithmic relation. The testing and analysis of solution manifest that compaction is not only a physical change，but also a chemical change, indicating that the dissolution may occurs even at the lower burial depth.
A set of new equipment has been designed and applied to simulate the diagenetic compaction. Medium quartz sand is selected as material to carry out the experiment. In order to do further research, physical and chemical change have both been detected, and some new conclusion have been reached. During compaction, the porosity and permeability are not varied regularly, and it can be divided into to section, a sudden change section and a uniform change section. In the uniform change section, the porosity decreases with the increase of the pressure, and they have a linear relation. The permeability decreases with the increase of the pressure either, and they have an exponential relation. The porosity and permeability also have semilogarithmic relation. The testing and analysis of solution manifest that compaction is not only a physical change，but also a chemical change, indicating that the dissolution may occurs even at the lower burial depth.
2006, 24(3): 419-425.
Abstract:
Abundant molecular biomarkers，including nalkanes，isoprenoid，steranes and terpanes，are detected by GCMS in mudstone and sandstone samples from Tanhai Sanma area in the Huanghua Depression. Some typical biomarkers，such as Gammacerane and Oleanane，which can be used to determine the nature of organic matter，are also been founded in samples. The ratio of Pr/Ph is ranging from 0.54 to 3.03，the Ts/Tm is from 1.1 to 9.11，the O/C30H is from 0.005 to 1.48 and the G/C30H is from 0.03 to 1.03，the parameters of molecular biomarkers in Sanma area have distinct difference which reflected the depositional environment under weak oxidation or deoxidize，and are in close relationship with organic matter import and sedimentary environment. Especially，the parameters of biomarkers distributions in mudstone is different at the same section sequence. The results show that the sequence boundary characteristic between turbidite sediment and the mixed was obvious，and it is easy to see that there exists a close link between them. The whole process of the formation is a complete turbidite depositional sequence and a mixed layer that made up of terrestrial origin and algae import formed in the interval of turbidity event.
Abundant molecular biomarkers，including nalkanes，isoprenoid，steranes and terpanes，are detected by GCMS in mudstone and sandstone samples from Tanhai Sanma area in the Huanghua Depression. Some typical biomarkers，such as Gammacerane and Oleanane，which can be used to determine the nature of organic matter，are also been founded in samples. The ratio of Pr/Ph is ranging from 0.54 to 3.03，the Ts/Tm is from 1.1 to 9.11，the O/C30H is from 0.005 to 1.48 and the G/C30H is from 0.03 to 1.03，the parameters of molecular biomarkers in Sanma area have distinct difference which reflected the depositional environment under weak oxidation or deoxidize，and are in close relationship with organic matter import and sedimentary environment. Especially，the parameters of biomarkers distributions in mudstone is different at the same section sequence. The results show that the sequence boundary characteristic between turbidite sediment and the mixed was obvious，and it is easy to see that there exists a close link between them. The whole process of the formation is a complete turbidite depositional sequence and a mixed layer that made up of terrestrial origin and algae import formed in the interval of turbidity event.
2006, 24(3): 432-439.
Abstract:
Organic matter associated with Dongsheng uranium ore interbedded organic matterrich layers was investigated by gas chromatographicmass spectrometery and carbon isotopic analysis. nAlkanes in organic matterrich strata are characteristic of a higher relative abundance of heavymolecularweight (HMW) homologues and are dominated by the C25, C27 or C29 with distinct oddtoeven carbon number predominance from C23 to C29. nFatty acid methylesters in the organic matterrich layers are characterized by a higher relative abundance of heavymolecularweight (HMW) homologues, maximizing at C24, C26 or C28 with distinct evenoverodd carbon number predominance above C22 homologue range. All of the results indicate that the organic matter in Dongsheng uranium ore interbedded organic matterrich layers are mainly derived from terrestrial high plants, very similar distribution patterns and consistent carbon isotopic variations between nalkanes and nfatty acid methylesters in corresponding samples suggest a productprecursor relationship between these two series of compounds. Thus, we assumed that nfatty acid methylesters could be the diagenetic intermediates for the formation of nalkanes from nfatty acids in the samples studied, or at least, they are derived from the same source precursors. nFatty acid methylesters can be formed and preserved in a strict mildalkali to neuter geological environment. So a geologically mildalkali to neuter environment probably also is a favorable factor for the formation and preservation of the uranium ore deposit in this region.
Organic matter associated with Dongsheng uranium ore interbedded organic matterrich layers was investigated by gas chromatographicmass spectrometery and carbon isotopic analysis. nAlkanes in organic matterrich strata are characteristic of a higher relative abundance of heavymolecularweight (HMW) homologues and are dominated by the C25, C27 or C29 with distinct oddtoeven carbon number predominance from C23 to C29. nFatty acid methylesters in the organic matterrich layers are characterized by a higher relative abundance of heavymolecularweight (HMW) homologues, maximizing at C24, C26 or C28 with distinct evenoverodd carbon number predominance above C22 homologue range. All of the results indicate that the organic matter in Dongsheng uranium ore interbedded organic matterrich layers are mainly derived from terrestrial high plants, very similar distribution patterns and consistent carbon isotopic variations between nalkanes and nfatty acid methylesters in corresponding samples suggest a productprecursor relationship between these two series of compounds. Thus, we assumed that nfatty acid methylesters could be the diagenetic intermediates for the formation of nalkanes from nfatty acids in the samples studied, or at least, they are derived from the same source precursors. nFatty acid methylesters can be formed and preserved in a strict mildalkali to neuter geological environment. So a geologically mildalkali to neuter environment probably also is a favorable factor for the formation and preservation of the uranium ore deposit in this region.
2006, 24(3): 446-455.
Abstract:
The paper systematically studied source rocks of Well Chaican1Ce1, Da1 and Section of Xiaopingcaogou, Dabancheng SubDepression of Chaiwopu Depression. It shows that organic macerals of the source rocks are mainly composed of vitrinite. Source rocks of Well Chaican1Ce1 and Da1 have high maturity, but lower abundance of organic matter, and low potential of oil generation. Source rocks of Section Xiaopingcaogou have higher maturity and higher concentration of organic matter, concentration of TOC amount to 3.87% at most, at the same time, oil generation potential of P2l are much more great than P2h. All the sources of the organic matter are mainly from terrestrial higher plant, and formed in the reductive lake environment of saline or water column stratification environment. The best source rocks of Upper Permian are distributed in the northeast of the Sub-depression. Oil and gas generated in the northeast〖KG*2〗moved to the southwest, the higher part of the slope through fault and permeable carrier layer, and accumulated in the favorable place of strata and structure. As a result, higher place of slope is the favored direction of exploration.
The paper systematically studied source rocks of Well Chaican1Ce1, Da1 and Section of Xiaopingcaogou, Dabancheng SubDepression of Chaiwopu Depression. It shows that organic macerals of the source rocks are mainly composed of vitrinite. Source rocks of Well Chaican1Ce1 and Da1 have high maturity, but lower abundance of organic matter, and low potential of oil generation. Source rocks of Section Xiaopingcaogou have higher maturity and higher concentration of organic matter, concentration of TOC amount to 3.87% at most, at the same time, oil generation potential of P2l are much more great than P2h. All the sources of the organic matter are mainly from terrestrial higher plant, and formed in the reductive lake environment of saline or water column stratification environment. The best source rocks of Upper Permian are distributed in the northeast of the Sub-depression. Oil and gas generated in the northeast〖KG*2〗moved to the southwest, the higher part of the slope through fault and permeable carrier layer, and accumulated in the favorable place of strata and structure. As a result, higher place of slope is the favored direction of exploration.
