In order to determine the area for oil and gas exploration in China’s north Sichuan basin,we have divided the time during which the Longmenshan foreland basin was formed into five periods,based on the sedimentary res...In order to determine the area for oil and gas exploration in China’s north Sichuan basin,we have divided the time during which the Longmenshan foreland basin was formed into five periods,based on the sedimentary response relationship of the foreland basin to structural evolution: 1) a late Triassic Noric period;2) an early-Middle Jurassic period;3) a late Jurassic to early Cretaceous period;4) a late Cretaceous to Paleogene-Neogene period and 5) the Quaternary period. As well,we analyzed the sedimentary environment and lithologic features of every basin-forming period. The results show that there are several favorable source-reservoir-cap assemblages in our study area,making it a major region for future oil and gas exploration in China’s northern Sichuan basin.展开更多
Longmen Mountain located at the boundary between the Sichuan Basin and Tibetan Plateau,representing the steepest gradient of any edges of the plateau.Three endmember models of uplift process and mechanism have been pr...Longmen Mountain located at the boundary between the Sichuan Basin and Tibetan Plateau,representing the steepest gradient of any edges of the plateau.Three endmember models of uplift process and mechanism have been proposed,including crustal thickening,crustal flow,and crustal isostatic rebound.Here we use coeval sedimentary sequences in the foreland basin to restraint uplift process and mechanism in the Longmen Mountain.The more than 10,000 m thick Late TriassicQuaternary strata filled in this foreland basin and can be divided into six megasequences that are distinguished as two distinct types.The first type is the wedge-shaped megasequences which are sedimentary response of strong active thrust loading events,characterized by a high rate of subsidence and sediment accumulation,coarsening-upward succession and a dual-sourced sediment supply.This type includes Late Triassic,Late Jurassic to Early Cretaceous and Late Cretaceous to Paleogene megasequences.The second type is the tabular megasequences,characterized by the low rate of subsidence and sediment accumulation,finingupward succession,and a single-sourced sediment supply,which is sedimentary response of isostatic rebound and erosion unloading.This type includes the Early to Middle Jurassic,Middle Cretaceous and Neogene to Quaternary megasequences.Basing on sedimentary,active tectonic,geomorphic evidence,we infer that the direction has been reversed from SSWdirected sinistral strike-slip to NNE-directed dextral strike-slip during 40-3.6 Ma,and since 3.6 Ma,the Longmen Mountain thrust belt belong to times of isostatic rebound and erosional unloading with NNEdirected dextral strike-slip.This suggests that crustal isostatic rebound is a primary driver for uplift and topography of the present Longmen Mountain.The Wenchuan(Ms8.0) earthquake,which ruptured a large thrust fault with NNE-directed dextral strikeslip along the range front,is an active manifestation of this crustal isostatic rebound process with dextral strike-slipping and shortening.This process may be the cause for the Wenchuan Earthquake and the apparent paradox of high relief,little shortening,the relative dearth of historical seismicity in the region.展开更多
One-sided ascending or descending Synthetic Aperture Radar（SAR） stereoradargrammetry has limited accuracy of topographic mapping due to the short spatial baseline（-100 km） and small intersection angle. In order to...One-sided ascending or descending Synthetic Aperture Radar（SAR） stereoradargrammetry has limited accuracy of topographic mapping due to the short spatial baseline（-100 km） and small intersection angle. In order to improve the performance and reliability of generating digital elevation model（DEM） from spaceborne SAR radargrammetry, an exploration of two-sided stereoradargrammetry from the combination of ascending and descending orbits with geometric configuration of long spatial baseline（-1000 km） was conducted in this study. The slant-range geometry between SAR sensors to the earth surface and the Doppler positioning equations were employed to establish the stereoscopic intersection model. The measurement uncertainty of two-sided radargrammetric elevation was estimated on the basis of radar parallax of homogeneous points between input SAR images. Two stereo-pairs of ALOS/PALSAR（Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar） acquisitions with the orbital separation almost 1080 km over the west Sichuan foreland basin with rolling topography in southwestern China were employed in the study to obtain the up-to-date terrain data after the 2008 Wenchuan earthquake that hit this area. Thequantitative accuracy assessment of two-sided radargrammetric DEM was performed with reference to field GPS observations. The experimental results show that the elevation accuracy reaches 5.5 m without ground control points（GCPs） used, and the accuracy is further improved to 1.5 m with only one GPS GCP used as the least constraint. The theoretical analysis and testing results demonstrate that the twosided long baseline SAR radargrammetry from the ascending and descending orbits can be a very promising technical alternative for large-area and high accuracy topographic mapping.展开更多
In recent years, studies show that coal formed during marine transigression process is also important in coal accumulation basin. Still, the characteristics of coal formation is more clearly demonstrated by the coal f...In recent years, studies show that coal formed during marine transigression process is also important in coal accumulation basin. Still, the characteristics of coal formation is more clearly demonstrated by the coal formation in TST in the sequence stratigraphic framework. Based on the study of the characteristics of coal formation in epicontinental coal accumulation basin, the viewpoint that coal was formed under marine transgression was put forward by the authors and the mechenism thereof was also analyized. Marine transgression resulted in the forming of swamp and then the peat swamp. And the transgression later on put the peat formed in advance in deep water environment to form coal in the end. The important stratigraphic horrizons, such as coal seams, marine facies layers, formed with marine transgression are of the property of isochronism.展开更多
Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeod...Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeodrainage pattern and the effect of palaeotopography. The sedimentary facies is the most elementary factor controlling the physical property of reservoirs. The layout and spatial combination model of the sand body and faults are the major influential factors on the occurrence of hydrocarbons. Comparative study on Houzhang and Yanglou Braided Deltas as well as Zhangchang and Gucheng Meandering Deltas suggests that the hydrocarbons distribute primarily in the mouth bar subfacies and secondarily in the distal bar subfacies of the braided delta, while the oil-water and aqueous layers are mainly found in the subaquatic distributary channel. Although the sand body of the meandering delta has excellent stratification and high porosity, the thickness is far less than that of the braided delta. Therefore, the yield of hydrocarbon is relatively low. The mudstone of the delta front subfacies is a kind of source rock with a high content of organic matter. The conducting system for oil/gas migration in the North Slope is a composite one comprising faults and sand- stone reservoirs. A large amount of oil/gas from the deep depression first migrated towards the slope along the sand body which stretches and connects with the source rocks, and then redistributed along the faults in the slope. After the movement reached a standstill, the faults formed the occlusion in the up-dip direction of the sand body, generating a great quantity of fault block hydrocarbon reservoirs in the Noah Slope.展开更多
The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North Chi...The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North China blocks. In Upper Priamurie, the collision occurred in the late Early Jurassic as dated by the emplacement of the post-collisional granites （ 191 Ma）. While in Lower Priamurie and West Priokhotie it could take place in the late Middle Jurassic on the basis of fossil evidence from an aceretionary turbidite complex. This event reflected the environmental change from coastal-marine to alluvial plains, often boggy, where coals aecmnulated. The environinental change is in harmony with that of biota. Systematic study of floral and spores/pollen assemblages, particularly in the sections of interbedded marine and non-marine deposits, makes clear the chronostrati-graphic succession of floral associations and shows the possibility of their application for subdivision and correlation of the continental deposits of Priamurie. Tire coastal-marine environment of the residual post-collisional sublatitudinal basins in the uestern part of Priamurie （Upper Amur and Dep basins） was replaced by the continental in the late Middle Jurassic and in the eastern part in the Berriasian-Valanginian （Torom Basin）. Similar environmental change commenced in the submeridional rift basins： the Bureya Basin in the Callovian and the Partizansk Basin in the Hauterivian. Changes in ecosystems ocemTed frequently during the Middle Jurassic-Ne- ocomian, but the most substantial changes took place in the late Middle Jurassic and in the end of Late Jurassie.展开更多
Based on a synthetic geological study of drilling,well logging and seismic data,core observations and geochemical analysis,it is recognized that Triassic sedimentary facies in the Tahe area of Tarim Basin include brai...Based on a synthetic geological study of drilling,well logging and seismic data,core observations and geochemical analysis,it is recognized that Triassic sedimentary facies in the Tahe area of Tarim Basin include braided river deposits filling erosional valleys,and sublacustrine fan,canyon and delta facies.Braided river deposits filling erosional valleys are dominated by coarse-grained lithic quartz sandstone with oblique bedding,and represent the most important sedimentation type of sandstone in the study area.Sublacustrine fan and canyon facies are mainly distributed in the Middle Oil Member.Most delta sediments are deposited in highstand system tract(HST),Because of frequent changes in base level,delta sediments are commonly eroded and rarely preserved.Sedimentary cycles are clearly reflected by lithology,sedimentary structures and well logging data,and are closely related to the changes in lacustrine level.In accordance with the basic principle of sequence subdivision,seven type-I boundaries can be recognized in Triassic strata and six type-I sequences are subdivided correspondingly.In general,lowstand system tract(LST) is well developed within stratigraphic sequences and forms the main body of reservoir sandstone in this area;highstand system tract(HST) and transgressive system tract(TST) are often eroded by upper sequences or missed,Although various factors have different influences on terrestrial sequence stratigraphy,the classical sequence stratigraphy theory proposed by VAIL can be applied to terrestrial strata.展开更多
基金Projects 40772198 and 50678182 supported by the National Natural Science Foundation of China09-3-094 by the Research Fund for Teaching Reform in Institutes of Higher Learning,Chongqing, China
文摘In order to determine the area for oil and gas exploration in China’s north Sichuan basin,we have divided the time during which the Longmenshan foreland basin was formed into five periods,based on the sedimentary response relationship of the foreland basin to structural evolution: 1) a late Triassic Noric period;2) an early-Middle Jurassic period;3) a late Jurassic to early Cretaceous period;4) a late Cretaceous to Paleogene-Neogene period and 5) the Quaternary period. As well,we analyzed the sedimentary environment and lithologic features of every basin-forming period. The results show that there are several favorable source-reservoir-cap assemblages in our study area,making it a major region for future oil and gas exploration in China’s northern Sichuan basin.
基金supported by the China National Natural Science Foundation (Grant No. 40841010,40972083,41172162)CGS Foundation (Grant No.1212011121268)Foundation from State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Grant No. SK-0801)
文摘Longmen Mountain located at the boundary between the Sichuan Basin and Tibetan Plateau,representing the steepest gradient of any edges of the plateau.Three endmember models of uplift process and mechanism have been proposed,including crustal thickening,crustal flow,and crustal isostatic rebound.Here we use coeval sedimentary sequences in the foreland basin to restraint uplift process and mechanism in the Longmen Mountain.The more than 10,000 m thick Late TriassicQuaternary strata filled in this foreland basin and can be divided into six megasequences that are distinguished as two distinct types.The first type is the wedge-shaped megasequences which are sedimentary response of strong active thrust loading events,characterized by a high rate of subsidence and sediment accumulation,coarsening-upward succession and a dual-sourced sediment supply.This type includes Late Triassic,Late Jurassic to Early Cretaceous and Late Cretaceous to Paleogene megasequences.The second type is the tabular megasequences,characterized by the low rate of subsidence and sediment accumulation,finingupward succession,and a single-sourced sediment supply,which is sedimentary response of isostatic rebound and erosion unloading.This type includes the Early to Middle Jurassic,Middle Cretaceous and Neogene to Quaternary megasequences.Basing on sedimentary,active tectonic,geomorphic evidence,we infer that the direction has been reversed from SSWdirected sinistral strike-slip to NNE-directed dextral strike-slip during 40-3.6 Ma,and since 3.6 Ma,the Longmen Mountain thrust belt belong to times of isostatic rebound and erosional unloading with NNEdirected dextral strike-slip.This suggests that crustal isostatic rebound is a primary driver for uplift and topography of the present Longmen Mountain.The Wenchuan(Ms8.0) earthquake,which ruptured a large thrust fault with NNE-directed dextral strikeslip along the range front,is an active manifestation of this crustal isostatic rebound process with dextral strike-slipping and shortening.This process may be the cause for the Wenchuan Earthquake and the apparent paradox of high relief,little shortening,the relative dearth of historical seismicity in the region.
基金supported by the National Natural Science Foundation of China(Grant Nos.41472255,51178404)Open Research Fund by Sichuan Engineering Research Center for Emergency Mapping & Disaster Reduction(Program K2014B006)Fundamental Research Funds for the Central Universities(Grant Nos.SWJTU12ZT07,2682014BR014)
文摘One-sided ascending or descending Synthetic Aperture Radar（SAR） stereoradargrammetry has limited accuracy of topographic mapping due to the short spatial baseline（-100 km） and small intersection angle. In order to improve the performance and reliability of generating digital elevation model（DEM） from spaceborne SAR radargrammetry, an exploration of two-sided stereoradargrammetry from the combination of ascending and descending orbits with geometric configuration of long spatial baseline（-1000 km） was conducted in this study. The slant-range geometry between SAR sensors to the earth surface and the Doppler positioning equations were employed to establish the stereoscopic intersection model. The measurement uncertainty of two-sided radargrammetric elevation was estimated on the basis of radar parallax of homogeneous points between input SAR images. Two stereo-pairs of ALOS/PALSAR（Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar） acquisitions with the orbital separation almost 1080 km over the west Sichuan foreland basin with rolling topography in southwestern China were employed in the study to obtain the up-to-date terrain data after the 2008 Wenchuan earthquake that hit this area. Thequantitative accuracy assessment of two-sided radargrammetric DEM was performed with reference to field GPS observations. The experimental results show that the elevation accuracy reaches 5.5 m without ground control points（GCPs） used, and the accuracy is further improved to 1.5 m with only one GPS GCP used as the least constraint. The theoretical analysis and testing results demonstrate that the twosided long baseline SAR radargrammetry from the ascending and descending orbits can be a very promising technical alternative for large-area and high accuracy topographic mapping.
基金Supported by the 973 Projects under Grant(2002CB211706 and 2003 CB214608)
文摘In recent years, studies show that coal formed during marine transigression process is also important in coal accumulation basin. Still, the characteristics of coal formation is more clearly demonstrated by the coal formation in TST in the sequence stratigraphic framework. Based on the study of the characteristics of coal formation in epicontinental coal accumulation basin, the viewpoint that coal was formed under marine transgression was put forward by the authors and the mechenism thereof was also analyized. Marine transgression resulted in the forming of swamp and then the peat swamp. And the transgression later on put the peat formed in advance in deep water environment to form coal in the end. The important stratigraphic horrizons, such as coal seams, marine facies layers, formed with marine transgression are of the property of isochronism.
文摘Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeodrainage pattern and the effect of palaeotopography. The sedimentary facies is the most elementary factor controlling the physical property of reservoirs. The layout and spatial combination model of the sand body and faults are the major influential factors on the occurrence of hydrocarbons. Comparative study on Houzhang and Yanglou Braided Deltas as well as Zhangchang and Gucheng Meandering Deltas suggests that the hydrocarbons distribute primarily in the mouth bar subfacies and secondarily in the distal bar subfacies of the braided delta, while the oil-water and aqueous layers are mainly found in the subaquatic distributary channel. Although the sand body of the meandering delta has excellent stratification and high porosity, the thickness is far less than that of the braided delta. Therefore, the yield of hydrocarbon is relatively low. The mudstone of the delta front subfacies is a kind of source rock with a high content of organic matter. The conducting system for oil/gas migration in the North Slope is a composite one comprising faults and sand- stone reservoirs. A large amount of oil/gas from the deep depression first migrated towards the slope along the sand body which stretches and connects with the source rocks, and then redistributed along the faults in the slope. After the movement reached a standstill, the faults formed the occlusion in the up-dip direction of the sand body, generating a great quantity of fault block hydrocarbon reservoirs in the Noah Slope.
文摘The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North China blocks. In Upper Priamurie, the collision occurred in the late Early Jurassic as dated by the emplacement of the post-collisional granites （ 191 Ma）. While in Lower Priamurie and West Priokhotie it could take place in the late Middle Jurassic on the basis of fossil evidence from an aceretionary turbidite complex. This event reflected the environmental change from coastal-marine to alluvial plains, often boggy, where coals aecmnulated. The environinental change is in harmony with that of biota. Systematic study of floral and spores/pollen assemblages, particularly in the sections of interbedded marine and non-marine deposits, makes clear the chronostrati-graphic succession of floral associations and shows the possibility of their application for subdivision and correlation of the continental deposits of Priamurie. Tire coastal-marine environment of the residual post-collisional sublatitudinal basins in the uestern part of Priamurie （Upper Amur and Dep basins） was replaced by the continental in the late Middle Jurassic and in the eastern part in the Berriasian-Valanginian （Torom Basin）. Similar environmental change commenced in the submeridional rift basins： the Bureya Basin in the Callovian and the Partizansk Basin in the Hauterivian. Changes in ecosystems ocemTed frequently during the Middle Jurassic-Ne- ocomian, but the most substantial changes took place in the late Middle Jurassic and in the end of Late Jurassie.
基金Project(2008ZX05002-005) supported by the State Major Special Science and Technology Foundation of China
文摘Based on a synthetic geological study of drilling,well logging and seismic data,core observations and geochemical analysis,it is recognized that Triassic sedimentary facies in the Tahe area of Tarim Basin include braided river deposits filling erosional valleys,and sublacustrine fan,canyon and delta facies.Braided river deposits filling erosional valleys are dominated by coarse-grained lithic quartz sandstone with oblique bedding,and represent the most important sedimentation type of sandstone in the study area.Sublacustrine fan and canyon facies are mainly distributed in the Middle Oil Member.Most delta sediments are deposited in highstand system tract(HST),Because of frequent changes in base level,delta sediments are commonly eroded and rarely preserved.Sedimentary cycles are clearly reflected by lithology,sedimentary structures and well logging data,and are closely related to the changes in lacustrine level.In accordance with the basic principle of sequence subdivision,seven type-I boundaries can be recognized in Triassic strata and six type-I sequences are subdivided correspondingly.In general,lowstand system tract(LST) is well developed within stratigraphic sequences and forms the main body of reservoir sandstone in this area;highstand system tract(HST) and transgressive system tract(TST) are often eroded by upper sequences or missed,Although various factors have different influences on terrestrial sequence stratigraphy,the classical sequence stratigraphy theory proposed by VAIL can be applied to terrestrial strata.
