The Dabashan orocline is situated in the northwestern margin of the central Yangtze block,central China.Previous studies have defined the orthogonal superposed folds growing in its central-western segment thereby conf...The Dabashan orocline is situated in the northwestern margin of the central Yangtze block,central China.Previous studies have defined the orthogonal superposed folds growing in its central-western segment thereby confirming its two-stage tectonic evolution history.Geological mapping has revealed that more types of superposed folds have developed in the eastern segment of the orocline,which probably provides more clues for probing the structure and tectonic history of the Dabashan orocline.In this paper,based on geological mapping,structural measurements and analyses of deformation,we have identified three groups of folds with different trends （e.g.NW-,NE-and nearly E-trending folds） and three types of structural patterns of superposed folds in the eastern Dabashan foreland （e.g.syn-axial,oblique,and conjunctional superposed folds）.In combination with geochronological data,we propose that the synaxial superposed folds are due to two stages of ～N-S shortening in the west and north of the Shennongjia massif,and that oblique superposed folds have been resulted from the superposition of the NW-and NE-trending folds onto the early ～ E-W folds in the east of the Shennongjia massif in the late Jurassic to early Cretaceous.The conjunctional folds are composed of the NW-and NE-trending folds,corresponding to the regional-scale dual-orocline in the eastern Sichuan as a result of the southwestward expansion of the Dabashan foreland during late Jurassic to early Cretaceous,coeval with the northwestward propagation of the Xuefengshan foreland.Integration of the structure and geochronology of the belt shows that the Dabashan orocline is a combined deformation belt primarily experiencing a twostage tectonic evolution history in Mesozoic,initiation of the Dabashan orocline as a foreland basin along the front of the Qinling orogen in late Triassic to early Jurassic due to collisional orogeny,and the final formation of the Dabashan orocline owing to the southwestward propagation of the Qinling orogen during late Jurassi展开更多
The Kalpin nappe structure is a strongest thrust and fold deformation belt in front of the Tianshan Mountains since the Cenozoic time. The tectonic deformation occurred in 5―6 striking Meso-zoic-Cenozoic fold zones, ...The Kalpin nappe structure is a strongest thrust and fold deformation belt in front of the Tianshan Mountains since the Cenozoic time. The tectonic deformation occurred in 5―6 striking Meso-zoic-Cenozoic fold zones, and some renascent folds formed on the recent alluvial-proluvial fans in front of the folded mountains. We used the total station to measure gully terraces along the longitudinal to-pographic profile in the renascent fold zones and collected samples from terrace deposits for age de-termination. Using the obtained formation time and shortening amount of the deformed terraces, we calculated the shortening rate of 4 renascent folds to be 0.1±0.03 mm/a, 0.12±0.04 mm/a, 0.59±0.18 mm/a, and 0.26±0.08 mm/a, respectively. The formation time of the renascent folds is some later than the major tectonic uplift event of the Qinghai-Tibet Plateau 0.14 Ma ago. It may be the long-distance effect of this tectonic event on the Tianshan piedmont fold belt.展开更多
Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault-fold remnant basin. The basin’s shape is generally consisten...Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault-fold remnant basin. The basin’s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks’ dis- placement features rusulted from by the movement of the edge faults and the main basement faults.展开更多
The geology, sediment and soil studies are important due to its significant impacts on agriculture, mining, constructions materials, industries, environment, ground water percolation, air pollution, surface and ground...The geology, sediment and soil studies are important due to its significant impacts on agriculture, mining, constructions materials, industries, environment, ground water percolation, air pollution, surface and ground water pollutions, earthquakes and geo-hazards in Afghanistan. In this research, we studied petrography, Sediment, tectonic structures, soil fraction selection by using hydrometer, sieving analysis, and geological mapping. Results show different kinds of metamorphic rocks of low grade and medium grade metamorphisms, Garnete mica Schist, Garnete Schist, Quarsite, different types of minerals among rocks. Further, type of sediment consisting residual angular (Autochthonous) and rounded (Allochthonous) transported by water, among sediments consisting Garnete, Gneiss, Schist, Quarsite, Biotite and consisting different type of sizes boulders, Cobble, Granule, Sand, Silt. Hydrometer analysis shows different types of soil clayey loam, sandy loam, silty loam. Moreover, Geological mapping shows complex tectonic structures like joints, cracks, faults, folds, anticline and syncline. The obtained<i> </i><span style="font-family:Verdana;">results suggest that the petrography, sediments and soil researches can be used efficiently for catchments of the Kabul Basin and other basins in Afghanistan.</span>展开更多
基金supported by National Natural Foundation of China(No.41172184)SINOPROBE-08-01SNOPEC(China)
文摘The Dabashan orocline is situated in the northwestern margin of the central Yangtze block,central China.Previous studies have defined the orthogonal superposed folds growing in its central-western segment thereby confirming its two-stage tectonic evolution history.Geological mapping has revealed that more types of superposed folds have developed in the eastern segment of the orocline,which probably provides more clues for probing the structure and tectonic history of the Dabashan orocline.In this paper,based on geological mapping,structural measurements and analyses of deformation,we have identified three groups of folds with different trends （e.g.NW-,NE-and nearly E-trending folds） and three types of structural patterns of superposed folds in the eastern Dabashan foreland （e.g.syn-axial,oblique,and conjunctional superposed folds）.In combination with geochronological data,we propose that the synaxial superposed folds are due to two stages of ～N-S shortening in the west and north of the Shennongjia massif,and that oblique superposed folds have been resulted from the superposition of the NW-and NE-trending folds onto the early ～ E-W folds in the east of the Shennongjia massif in the late Jurassic to early Cretaceous.The conjunctional folds are composed of the NW-and NE-trending folds,corresponding to the regional-scale dual-orocline in the eastern Sichuan as a result of the southwestward expansion of the Dabashan foreland during late Jurassic to early Cretaceous,coeval with the northwestward propagation of the Xuefengshan foreland.Integration of the structure and geochronology of the belt shows that the Dabashan orocline is a combined deformation belt primarily experiencing a twostage tectonic evolution history in Mesozoic,initiation of the Dabashan orocline as a foreland basin along the front of the Qinling orogen in late Triassic to early Jurassic due to collisional orogeny,and the final formation of the Dabashan orocline owing to the southwestward propagation of the Qinling orogen during late Jurassi
基金Supported by the National Natural Science Foundation of China (Grant No. 40572126)China Earthquake Administration under project Integrated Investiga-tion of Seismogenic Structures for Intermediate-Strong Earthquakes in Jiashi-Bachu of Xinjiang Uygur Autonomous Region.
文摘The Kalpin nappe structure is a strongest thrust and fold deformation belt in front of the Tianshan Mountains since the Cenozoic time. The tectonic deformation occurred in 5―6 striking Meso-zoic-Cenozoic fold zones, and some renascent folds formed on the recent alluvial-proluvial fans in front of the folded mountains. We used the total station to measure gully terraces along the longitudinal to-pographic profile in the renascent fold zones and collected samples from terrace deposits for age de-termination. Using the obtained formation time and shortening amount of the deformed terraces, we calculated the shortening rate of 4 renascent folds to be 0.1±0.03 mm/a, 0.12±0.04 mm/a, 0.59±0.18 mm/a, and 0.26±0.08 mm/a, respectively. The formation time of the renascent folds is some later than the major tectonic uplift event of the Qinghai-Tibet Plateau 0.14 Ma ago. It may be the long-distance effect of this tectonic event on the Tianshan piedmont fold belt.
文摘Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault-fold remnant basin. The basin’s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks’ dis- placement features rusulted from by the movement of the edge faults and the main basement faults.
文摘The geology, sediment and soil studies are important due to its significant impacts on agriculture, mining, constructions materials, industries, environment, ground water percolation, air pollution, surface and ground water pollutions, earthquakes and geo-hazards in Afghanistan. In this research, we studied petrography, Sediment, tectonic structures, soil fraction selection by using hydrometer, sieving analysis, and geological mapping. Results show different kinds of metamorphic rocks of low grade and medium grade metamorphisms, Garnete mica Schist, Garnete Schist, Quarsite, different types of minerals among rocks. Further, type of sediment consisting residual angular (Autochthonous) and rounded (Allochthonous) transported by water, among sediments consisting Garnete, Gneiss, Schist, Quarsite, Biotite and consisting different type of sizes boulders, Cobble, Granule, Sand, Silt. Hydrometer analysis shows different types of soil clayey loam, sandy loam, silty loam. Moreover, Geological mapping shows complex tectonic structures like joints, cracks, faults, folds, anticline and syncline. The obtained<i> </i><span style="font-family:Verdana;">results suggest that the petrography, sediments and soil researches can be used efficiently for catchments of the Kabul Basin and other basins in Afghanistan.</span>
