Thick-skinned contractional salt structures are widely developed in the western Kuqa depression, northern Tarim basin. To understand the mechanisms that govern the development of these structures, physical experiments...Thick-skinned contractional salt structures are widely developed in the western Kuqa depression, northern Tarim basin. To understand the mechanisms that govern the development of these structures, physical experiments are conducted and the results show that they are largely governed by the activities of basement faults and the forming of paleo-uplifts and basement slopes. The model materials in this study are dry sand, vaseline and plasticene （or hard foam）, simulating the suprasalt, salt, and subsalt layers respectively. The experiments show that, due to the activities of basement faults and the forming of the paleo-uplifts, salt bodies usually accumulate and thicken significantly on the middle top of the paleo-uplifts which are constrained by the pre-exiting boundary faults. The development of large-scale thrust faults and salt nappes is favored by the basement slops with larger dips. The experiments also conclude that differential structural deformation could occur between the subsalt and suprasalt layers because of the presence of salt layers. Their geometries and the locations of structural highs are different, despite of the great similarities in the uplifted areas. The pierced salt diapir is not observed in the experiments, which indicates that the contractional shortening does not effectively accelerate the development of the salt diapir.展开更多
The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-sc...The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-scale convergence between these units is critical for deciphering the mechanisms driving the northeastward plateau expansion.In this study,we conduct systematic geometric and kinematic analysis of upper-crustal deformation across the northern margin of the North Qilian Shan and the Jiuquan Basin,by integrating multiple datasets including high-resolution seismic reflection data,borehole loggings,surface geology and deformed fluvial terraces.Our results indicated that this region is dominated by NE-directed,thick-skinned,basement-involved reverse faults that root into a gently south-dipping(~10°)décollement at~13-15 km depth,likely within the brittle-ductile transition zone.Wedge-shaped foreland basin deposits in the Middle-Late Miocene Shulehe Formation indicate that uplift of the North Qilian Shan initiated during this time.Palinspastic reconstruction reveals that the upper-crustal shortening is limited to 7.6-11.7 km,with up to 54%-95%accommodated by the frontal thrusts of the North Qilian Shan.These observations indicate that North Qilian Shan has acted as a stable plateau margin since the Middle Miocene,with limited northeastward propagation of deformation into the Jiuquan Basin.Reinterpretation of previously published deep geophysical data identifies a north-dipping lithospheric-scale fault offsetting the Moho by~7.8 km.Collectively,our results support a lithospheric-scale tectonic wedge model along the northeastern margin of the Tibetan Plateau,in which the rigid Jiuquan Basin indents into the weakened North Qilian lower crust under horizontal compression,accommodating limited convergence without large-scale subduction.Our findings suggest that northeastward plateau growth occurs through lithospheric wedging of mechanically distinct tectonic units characterized by distributed deformation,rather than by intracontinental subduction localized along a discrete subduction zone.展开更多
The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the int...The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous. This paper applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. Our work suggests that the pre-defined "Jurassic strata" should be re-dated and sub-divided into three strata units: a Late Triassic to Early Jurassic unit, a Middle Jurassic unit, and a Late Jurassic to early Early Cretaceous unit. Under the control of growth fold-and-thrust structures, five types of growth strata developed in different growth structures: fold-belt foredeep type,thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic,Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in our study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basementinvolved fold-thrust structures and small-scale intramontane broken "axial basins". The westward migration of a "pair" of basement-involved fold-thrust belt and flexure basins might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.展开更多
Nondestructive determination the internal quality of thick-skin fruits has always been a challenge.In order to investigate the prediction ability of full transmittance mode on the soluble solid content(SSC)in thick-sk...Nondestructive determination the internal quality of thick-skin fruits has always been a challenge.In order to investigate the prediction ability of full transmittance mode on the soluble solid content(SSC)in thick-skin fruits,the full transmittance spectra of citrus were collected using a visible/near infrared(Vis/NIR)portable spectrograph(550–1100 nm).Three obvious absorption peakswere found at 710,810 and 915 nmin the original spectra curve.Four spectral preprocessing methods including Smoothing,multiplicative scatter correction(MSC),standard normal variate(SNV)and first derivativewere employed to improve the quality of the original spectra.Subsequently,the effective wavelengths of SSC were selected from the original and pretreated spectra with the algorithms of successive projections algorithm(SPA),competitive adaptive reweighted sampling(CARS)and genetic algorithm(GA).Finally,the prediction models of SSC were established based on the full wavelengths and effectivewavelengths.Results showed that SPA performed the best performance on eliminating the useless information variable and optimizing the number of effective variables.The optimal predictionmodel was established based on 10 characteristic variables selected from the spectra pretreated by SNV with the algorithmof SPA,with the correlation coefficient,root mean square error,and residual predictive deviation for prediction set being 0.9165,0.5684°Brix and 2.5120,respectively.Overall,the full transmittance mode was feasible to predict the internal quality of thick-skin fruits,like citrus.Additionally,the combination of spectral preprocessing with a variable selection algorithmwas effective for developing the reliable predictionmodel.The conclusions of this study also provide an alternative method for fast and real-time detection of the internal quality of thick-skin fruits using Vis/NIR spectroscopy.展开更多
文摘Thick-skinned contractional salt structures are widely developed in the western Kuqa depression, northern Tarim basin. To understand the mechanisms that govern the development of these structures, physical experiments are conducted and the results show that they are largely governed by the activities of basement faults and the forming of paleo-uplifts and basement slopes. The model materials in this study are dry sand, vaseline and plasticene （or hard foam）, simulating the suprasalt, salt, and subsalt layers respectively. The experiments show that, due to the activities of basement faults and the forming of the paleo-uplifts, salt bodies usually accumulate and thicken significantly on the middle top of the paleo-uplifts which are constrained by the pre-exiting boundary faults. The development of large-scale thrust faults and salt nappes is favored by the basement slops with larger dips. The experiments also conclude that differential structural deformation could occur between the subsalt and suprasalt layers because of the presence of salt layers. Their geometries and the locations of structural highs are different, despite of the great similarities in the uplifted areas. The pierced salt diapir is not observed in the experiments, which indicates that the contractional shortening does not effectively accelerate the development of the salt diapir.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22B6002,42272233)。
文摘The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-scale convergence between these units is critical for deciphering the mechanisms driving the northeastward plateau expansion.In this study,we conduct systematic geometric and kinematic analysis of upper-crustal deformation across the northern margin of the North Qilian Shan and the Jiuquan Basin,by integrating multiple datasets including high-resolution seismic reflection data,borehole loggings,surface geology and deformed fluvial terraces.Our results indicated that this region is dominated by NE-directed,thick-skinned,basement-involved reverse faults that root into a gently south-dipping(~10°)décollement at~13-15 km depth,likely within the brittle-ductile transition zone.Wedge-shaped foreland basin deposits in the Middle-Late Miocene Shulehe Formation indicate that uplift of the North Qilian Shan initiated during this time.Palinspastic reconstruction reveals that the upper-crustal shortening is limited to 7.6-11.7 km,with up to 54%-95%accommodated by the frontal thrusts of the North Qilian Shan.These observations indicate that North Qilian Shan has acted as a stable plateau margin since the Middle Miocene,with limited northeastward propagation of deformation into the Jiuquan Basin.Reinterpretation of previously published deep geophysical data identifies a north-dipping lithospheric-scale fault offsetting the Moho by~7.8 km.Collectively,our results support a lithospheric-scale tectonic wedge model along the northeastern margin of the Tibetan Plateau,in which the rigid Jiuquan Basin indents into the weakened North Qilian lower crust under horizontal compression,accommodating limited convergence without large-scale subduction.Our findings suggest that northeastward plateau growth occurs through lithospheric wedging of mechanically distinct tectonic units characterized by distributed deformation,rather than by intracontinental subduction localized along a discrete subduction zone.
基金supported by National Natural Science Foundation of China(Grant Nos.41572189&91114203)National Key R&D Plan(Grant No.2017YFC0601405)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB18000000)
文摘The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous. This paper applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. Our work suggests that the pre-defined "Jurassic strata" should be re-dated and sub-divided into three strata units: a Late Triassic to Early Jurassic unit, a Middle Jurassic unit, and a Late Jurassic to early Early Cretaceous unit. Under the control of growth fold-and-thrust structures, five types of growth strata developed in different growth structures: fold-belt foredeep type,thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic,Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in our study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basementinvolved fold-thrust structures and small-scale intramontane broken "axial basins". The westward migration of a "pair" of basement-involved fold-thrust belt and flexure basins might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.
基金This study was supported by National Key Research and Development Program(2016YFD0200104)Beijing Talents Foundation(2018000021223ZK06)National Natural Science Foundation of China(Grant No.31671927).
文摘Nondestructive determination the internal quality of thick-skin fruits has always been a challenge.In order to investigate the prediction ability of full transmittance mode on the soluble solid content(SSC)in thick-skin fruits,the full transmittance spectra of citrus were collected using a visible/near infrared(Vis/NIR)portable spectrograph(550–1100 nm).Three obvious absorption peakswere found at 710,810 and 915 nmin the original spectra curve.Four spectral preprocessing methods including Smoothing,multiplicative scatter correction(MSC),standard normal variate(SNV)and first derivativewere employed to improve the quality of the original spectra.Subsequently,the effective wavelengths of SSC were selected from the original and pretreated spectra with the algorithms of successive projections algorithm(SPA),competitive adaptive reweighted sampling(CARS)and genetic algorithm(GA).Finally,the prediction models of SSC were established based on the full wavelengths and effectivewavelengths.Results showed that SPA performed the best performance on eliminating the useless information variable and optimizing the number of effective variables.The optimal predictionmodel was established based on 10 characteristic variables selected from the spectra pretreated by SNV with the algorithmof SPA,with the correlation coefficient,root mean square error,and residual predictive deviation for prediction set being 0.9165,0.5684°Brix and 2.5120,respectively.Overall,the full transmittance mode was feasible to predict the internal quality of thick-skin fruits,like citrus.Additionally,the combination of spectral preprocessing with a variable selection algorithmwas effective for developing the reliable predictionmodel.The conclusions of this study also provide an alternative method for fast and real-time detection of the internal quality of thick-skin fruits using Vis/NIR spectroscopy.
