Understanding the topography in active tectonic areas and assessing the rates and models of active deformation in the upper crust are primary objectives in tectonic geomorphology studies. The drainage pattern of river...Understanding the topography in active tectonic areas and assessing the rates and models of active deformation in the upper crust are primary objectives in tectonic geomorphology studies. The drainage pattern of river systems is highly sensitive to tectonically induced changes, and it often preserves the records of the formation and progression of most tectono-geomorphic processes within its boundaries. Therefore, the evolution of landforms is a consequence of the evolution of individual drainage basins in which they are formed. Assessing the rates of tectonic deformation using geomorphic data is a traditionally adopted method to characterize the nature of active faults. Globally, the Digital Elevation Model(DEM) is widely used as a crucial tool to analyze the morphotectonic features of drainage basins. In this study, some geomorphic indices were applied to investigate the impact of tectonism on landscape along the Karahay?t Fault and its associated drainage areas. These geomorphic indices are mountain front sinuosity(Smf values between 1.17-1.52), valley floor width-to-height ratio(Vf values between 0.25-1.46), basin asymmetry factor(AF values between 15-72), drainage basin shape(Bs values between 3.18-6.01), hypsometric integral and curve(HI values between 0.32-047), channel sinuosity(S values between 1-1.6), normalized steepness index(Ksn values between 1-390) and Chi integral(χ values between 200-4400). The development of drainage areas on the hanging wall and footwall block of the Karahayit Fault differs depending on the uplift. The drainage areas developed on the hanging wall present different patterns depending on the regional uplift caused by the fault. This reveals that the fault contributed significantly to the development of drainage areas and regional uplift in the region. In addition, the maximum earthquake magnitude that may occur in the future on the Karahayit Fault, whose activity is supported by geomorphic indices, is calculated as 6.23. Since an earthquake of this magnitude may cause loss of li展开更多
The present study area,Dadra and Nagar Haveli,contains several lineaments and traces of active faults.The various aspect of the geomo rphic analysis,i.e.,stream length(SL) gradient,hypsometric integral(HI),basin shape...The present study area,Dadra and Nagar Haveli,contains several lineaments and traces of active faults.The various aspect of the geomo rphic analysis,i.e.,stream length(SL) gradient,hypsometric integral(HI),basin shape(BS),valley floor(VF),have been applied to evaluate the relative index of active tectonics(RIAT) of the Damanganga watershed.The high and low zones of tectonic activity have been identified based on the geomorphic analysis of the watershed.After evaluation of all indices,three classes,class IIhigh(1.3 ≤RIAT <1.5),class Ⅲ-moderate(1.5 ≤RIAT <1.8),and class Ⅳ-low(1.8 ≤RIAT),have been obtained to outline the degree/gradation of comparative tectonic activities in the study area.The appraised outcome of the RIAT dispersal is also well reinforced by the geomorphic evidence in the field.The collective outcomes of geomorphic evidence,such as stream deflection and analysis of lineament,deflection of streams,and geomorphic indices,conceal that the Damanganga watershed is affected by tectonic activity.展开更多
Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorph...Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorphic evolution of a basin exerts a key control on riverine sediment input and transport. In this study, the geomorphic characteristics of Buyuan Basin are analyzed using morphological parameters, hydrodynamic parameters and the stream power river incision model. The results show that: 1) The slight north-south difference of channel density is most likely due to lithology and independent of tectonic activity and climate. 2) The weak tectonic activity and the low hypsometric integral(HI) value suggest that the macroscopic landform condition limits erosion and sediment production. 3) The logarithmic longitudinal profile of the main channel defends that the upstream sediments generated by erosion are easily deposited in the downstream channel, rather than being transported directly into the Lancang-Mekong River. 4) Approximately 74% of the reaches have annual average stream power less than 500 W·m^(-1). The narrow variation ranges of stream power in 50% of the river channel indicate relatively stable hydrodynamic environment. 5) Stream erosion and tectonic activity make the longitudinal profiles of the main channel and most tributary channels unstable. The wide range(between 22.01 and 45.58 with θ=0.43) of steepness index(k_(sn)) of longitudinal profiles implies differential uplift in the basin.展开更多
On 05 September 2022,an Ms 6.8(Mw 6.6)earthquake occurred in Luding County,Sichuan Province,China,with the epicenter at 29.59°N,102.08°E and a focal depth of approximately 16.0km.Combining field investigatio...On 05 September 2022,an Ms 6.8(Mw 6.6)earthquake occurred in Luding County,Sichuan Province,China,with the epicenter at 29.59°N,102.08°E and a focal depth of approximately 16.0km.Combining field investigations,high-resolution satellite images and multiple datatpes characterizing the seismogenic structure,topography and geology,this study attempts to discuss the influence of geomorphic and tectonic indexes on landslide distribution.The results show that the 2022 Luding earthquake with seismogenic fault at the Moxi fault,was a sinistral strike-slip event that triggered at least 4528landslides over an area of~2000 km2.These landslides span a total area of 28.1 km^(2),and the western section of the seismogenic fault,which serves as the active wall area,is characterized by a higher landslide concentration,especially in the Wandong Basin.The seismogenic fault and lithology influence the regional distribution of landslides,and more landslides occurred closer to the seismogenic fault and in the controlling lithologies of granite and dolomite.Local topography influences the landslide occurrence position on the slope;the eastern section is prone to form landslides in the lower gorge section,and the western section is prone to form landslides in the upper-top section of the gorge.For coseismic landslides in the eastern Baryan Har block,the eastern boundary(Longmenshan fault),where the earthquakes are characterized by thrusts with slight dextral strike-slip movement,could be the primary landslide-prone area;the southern boundary,the Moxi fault and the southern segment of the Xianshuihe fault,with more intensive strikeslip movement,may be the secondary landsideprone area;and the northern boundary is the tertiary landside-prone area.Additionally,the current landslide inventory may be underestimated although this underestimation has limited influence on the results.展开更多
A recent correlation of stream geomorphic indices to fault activity has revealed that stream geomorphologies in bedrock mountain areas are good records of local fault movements. The Daqingshan piedmont fault is one of...A recent correlation of stream geomorphic indices to fault activity has revealed that stream geomorphologies in bedrock mountain areas are good records of local fault movements. The Daqingshan piedmont fault is one of the main active faults in the fault system on the northern margin of the Hetao Basin and has produced frequent large-scale earthquakes since the Late Pleistocene. In the present study, following the segmentation regime of previous studies, we divide the fault zone into five segments, namely, the Baotou, Tuyouqi West, Tuzuoqi West, Bikeqi, and Hohhot segments, and we discuss the relationship between the drainage basin geomorphology and the piedmont fault activity in the Daqingshan area using 30 m spatial resolution Shuttle Radar Topography Mission(SRTM) digital elevation model(DEM) data. We use a range of geomorphic indices to examine the drainage basins in the Daqingshan area, including the channel steepness index(ksn), slope, hypsometric integral(HI), relief degree of land surface(RDLS), and stream lengthgradient index(SL), extracted with ArcGIS and MATLAB, and we also consider local lithologic and climate aspects. Furthermore, we compare the geomorphic indices with the slip rates of individual segments of the Daqingshan piedmont fault and paleoseismic data. The results show that the geomorphic indices of drainage basins in the Daqingshan area are primarily affected by the piedmont fault activity in the Daqingshan area. The geomorphic indices also demonstrate that piedmont fault activity has been the most intense in the middle segment of this fault system since the Late Quaternary and decreases towards the two sides.展开更多
This paper tests a data mining method for evaluation of the ＂IRTA＂（Index of Relative Tectonic Activity） to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K...This paper tests a data mining method for evaluation of the ＂IRTA＂（Index of Relative Tectonic Activity） to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K-means clustering of six basin-related geomorphic indices（the hypsometric integral, basin asymmetric factor, drainage density, basin shape ratio, mean axial slope of the channel and topographic roughness） that represent the relative strength of active tectonic deformation on topography and morphology, the relative tectonic activity along the Kazerun Fault Zone in the Zagros Mountains of Iran may be classified into low, moderate and high relative tectonic activity zones. The results allow the identification of the clusters of similarly deformed areas related to relative tectonic activity. The utilization of geomorphic parameters as well as IRTA with comparison to the field observations exhibit change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area.展开更多
River capture is of great significance to landform evolution and hominine migration.In the Qinling-Daba Mountains,there is a viewpoint that Jialing River captured Hanjiang River,but this is still controversial.In this...River capture is of great significance to landform evolution and hominine migration.In the Qinling-Daba Mountains,there is a viewpoint that Jialing River captured Hanjiang River,but this is still controversial.In this paper,we discuss the drainage evolution processes in intermountain basins at the Qinling-Daba Mountains based on a combination of detrital zircon UPb geochronology and geomorphic indexes.We suggest that the Hanjiang River gradually captured the Jialing River from east to west,accompanied by the evolution of the ancient Yangtze River.In terms of geomorphic evidences,wide valleys did not match with discharge,and a series of wind gaps developed in the Shiquan-Ankang basin.In addition,the valley shapes and width-toheight ratios(Vf)indicate two possible rapid incisions.The hypsometric integrals(HI)reflect that the landform gradually changes from the old stage to the youth stage from west to east.Theχvalues show that the drainage divide is moving to the side of the Yuehe River,and the Yuehe River is gradually shrinking.According to the sedimentary records,the zircon U-Pb age distributions indicate the provenance change.The high-altitude terraces show three age peaks(200–250,400–505,and 700–900 Ma),with the dominant Indosinian age peak(200–250 Ma),while the modern fluvial sediments only show a single peak of Jinning(700–900 Ma).These data show that there are two major river captures:(1)The ancient Hanjiang River cut through the regional compression ridge,and then captured the Hanzhong Basin river system(a part of the ancient Jialing river system)from east to west,and(2)The southern tributary captured the trunk with the uplift of the divide in the Shiquan-Ankang Basin,forming the modern drainage pattern in the upper Hanjiang River.The activities of the regional strike-slip fault,and the associated compression uplift played a key role in the river captures,the drainage evolution,and related landforms in the Shiquan-Ankang basin.In addition,it is shown that the evolution of the upper tributary basi展开更多
Previous researches had emphasized tectonic impacts on the fluvial system at the tectonically active areas,while the effects of lithology and local base level change have received relatively rare attention.Here we inv...Previous researches had emphasized tectonic impacts on the fluvial system at the tectonically active areas,while the effects of lithology and local base level change have received relatively rare attention.Here we investigated fluvial landforms at different spatial scales,focusing on knickpoints and channel network reorganization from an area affected by the Haiyuan Fault in the northeastern Tibetan Plateau.The geomorphic indices,i.e.,drainage pattern andχanomalies,were calculated and investigated.The results show that two regional radial drainages formed around the Laohu and Hasi Mountains.Within the interior of the radial drainage,tributaries from the southeast side of the Laohu Mountain experienced near 180°direction change.We interpret this as the gradual drainage capture originating from the height difference(~190 m)of the local base level between the two catchments.Some tributaries from the Hasi Mountain show alternating gorges and broad valleys controlled by lithology.Besides,tectonic uplift and the lowering of base level(from the incision of the Yellow River)triggered an autogenic positivefeedback transition from parallel to dendritic drainage patterns.These observations suggest that base level change and lithology play a crucial role in landscape evolution,even in a tectonically active region.展开更多
Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigation...Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigationwithin the area. The study was carried out in the Karra Khola Basin, oneof the prominent basins in the Eastern extreme of the Hetauda Dun Valley,Central Nepal, to investigate geomorphic characteristics of the mainstream of the basin, categorize them into various stream types and studybasin development through drainage basin’s morphometric parameters.Geographical Information System (GIS) and Remote sensing techniquesusing satellite images were used as a tool to make the morphometricanalysis of the basin along with its major 13 sub-basin and delineate streamclassification following the Rosgen’s Level I hierarchical inventory. Themain stream of the Karra Khola is characterized as A-, B- and C-typeand the tributaries segments as B- and F-type. The basin is structurallyunaffected and has the permeable surface area and elongated shape. Thehypsometric analysis indicates that the basin is mostly at the old stage ofgeomorphic development while four out of 13 sub-basin being at maturestage. The Karra Khola sub-basin have higher risk to flash flooding(Lg=0.1-0.16km). Drainage density value reveals that the basin is highlysusceptible to flooding, gully erosion, etc. Similarly, dissection index valueimplies that the north eastern region of the basin is highly vulnerable toerosion as it at the younger stage of geomorphic development. Since thestudy area is highly sensitive to future natural hazards, further study andappropriate measures should be followed for safeguarding against thefuture risk along the Karra Khola basin and its tributaries.展开更多
Landscapes in tectonically active Hindu Kush （NW Pakistan and NE Alghanistanl result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition proces...Landscapes in tectonically active Hindu Kush （NW Pakistan and NE Alghanistanl result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition processes. Active tectonics in this region have greatly influenced the drainage system and geomorphic expressions. The study area is a junction of three important mt^unlain ranges （Hindu Kush-Karakorunl-Himalayas） and is thus an ideal natural laboratory to investigate the relative tectonic activity resulting from the India-Eurasia collision. We evaluate active tectonics using DEM derived drainage network and geomorphic indices hypsometric integral （Hl）. stream-length gradient （SL）, fractal dimension （FD）, basin asymmetry factor （AF）, basin shape index （B,）, valley floor width to wllley height ratio （Vf） and motmtain front sinuosity （Star）. The results obtained from these indices were combined to yield an index of relative active tectonics （IRAT） using GIS. The average of the seven measured geomorphic indices was used to ewfluate the distri- bution of relative tectonic activity in the study area. We defined tour classes to define the degree of rela- tive tectonic activity： class 1 very high （1.0 ≤ IRAT 〈 1.3）; class 2 high （1.3 ≥ IRAT 〈 1.5）： class 3--moderate （1.5 〉 IRAT 〈 1.8）; and class 4--low （1.8 〉 IRAT）. In view of the results, we conclude that this combined approach allows the identification of the highly deformed areas related to active tectonics. Landsat imagery and field observations also evidence the presence of active tectonics based on the deflected streams, deformed landforms, active mountain fronts and triangular facets. The indicative values of IRAT are consistent with the areas of known relative uplift rates, landforms and geology.展开更多
文摘Understanding the topography in active tectonic areas and assessing the rates and models of active deformation in the upper crust are primary objectives in tectonic geomorphology studies. The drainage pattern of river systems is highly sensitive to tectonically induced changes, and it often preserves the records of the formation and progression of most tectono-geomorphic processes within its boundaries. Therefore, the evolution of landforms is a consequence of the evolution of individual drainage basins in which they are formed. Assessing the rates of tectonic deformation using geomorphic data is a traditionally adopted method to characterize the nature of active faults. Globally, the Digital Elevation Model(DEM) is widely used as a crucial tool to analyze the morphotectonic features of drainage basins. In this study, some geomorphic indices were applied to investigate the impact of tectonism on landscape along the Karahay?t Fault and its associated drainage areas. These geomorphic indices are mountain front sinuosity(Smf values between 1.17-1.52), valley floor width-to-height ratio(Vf values between 0.25-1.46), basin asymmetry factor(AF values between 15-72), drainage basin shape(Bs values between 3.18-6.01), hypsometric integral and curve(HI values between 0.32-047), channel sinuosity(S values between 1-1.6), normalized steepness index(Ksn values between 1-390) and Chi integral(χ values between 200-4400). The development of drainage areas on the hanging wall and footwall block of the Karahayit Fault differs depending on the uplift. The drainage areas developed on the hanging wall present different patterns depending on the regional uplift caused by the fault. This reveals that the fault contributed significantly to the development of drainage areas and regional uplift in the region. In addition, the maximum earthquake magnitude that may occur in the future on the Karahayit Fault, whose activity is supported by geomorphic indices, is calculated as 6.23. Since an earthquake of this magnitude may cause loss of li
基金DG ISR and DST (GoG) for providing required supportDMC Dadra and Nagar Haveli (DNH/1255) for providing financial support。
文摘The present study area,Dadra and Nagar Haveli,contains several lineaments and traces of active faults.The various aspect of the geomo rphic analysis,i.e.,stream length(SL) gradient,hypsometric integral(HI),basin shape(BS),valley floor(VF),have been applied to evaluate the relative index of active tectonics(RIAT) of the Damanganga watershed.The high and low zones of tectonic activity have been identified based on the geomorphic analysis of the watershed.After evaluation of all indices,three classes,class IIhigh(1.3 ≤RIAT <1.5),class Ⅲ-moderate(1.5 ≤RIAT <1.8),and class Ⅳ-low(1.8 ≤RIAT),have been obtained to outline the degree/gradation of comparative tectonic activities in the study area.The appraised outcome of the RIAT dispersal is also well reinforced by the geomorphic evidence in the field.The collective outcomes of geomorphic evidence,such as stream deflection and analysis of lineament,deflection of streams,and geomorphic indices,conceal that the Damanganga watershed is affected by tectonic activity.
基金financially supported by the National Key Research and Development Program of China (2016YFA0601601)the National Science and Technology Support Program (2013BAB06B03)+2 种基金the National Natural Science Foundation of China (41472155)Candidates of the Young and MiddleAged Academic Leaders of Yunnan Province (2014HB005)Program for Excellent Young Talents of Yunnan University
文摘Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorphic evolution of a basin exerts a key control on riverine sediment input and transport. In this study, the geomorphic characteristics of Buyuan Basin are analyzed using morphological parameters, hydrodynamic parameters and the stream power river incision model. The results show that: 1) The slight north-south difference of channel density is most likely due to lithology and independent of tectonic activity and climate. 2) The weak tectonic activity and the low hypsometric integral(HI) value suggest that the macroscopic landform condition limits erosion and sediment production. 3) The logarithmic longitudinal profile of the main channel defends that the upstream sediments generated by erosion are easily deposited in the downstream channel, rather than being transported directly into the Lancang-Mekong River. 4) Approximately 74% of the reaches have annual average stream power less than 500 W·m^(-1). The narrow variation ranges of stream power in 50% of the river channel indicate relatively stable hydrodynamic environment. 5) Stream erosion and tectonic activity make the longitudinal profiles of the main channel and most tributary channels unstable. The wide range(between 22.01 and 45.58 with θ=0.43) of steepness index(k_(sn)) of longitudinal profiles implies differential uplift in the basin.
基金supported by National Natural Science Foundation of China(Grant No.U22A20603,U21A2008,42007273)the Special Assistant Researcher Foundation of Chinese Academy of Sciences(Zhao Bo)+1 种基金the China Postdoctoral Science Foundation(2020M673292,and 2021T140650)the IMHE Youth S&T Foundation(SDS-QN-2106)。
文摘On 05 September 2022,an Ms 6.8(Mw 6.6)earthquake occurred in Luding County,Sichuan Province,China,with the epicenter at 29.59°N,102.08°E and a focal depth of approximately 16.0km.Combining field investigations,high-resolution satellite images and multiple datatpes characterizing the seismogenic structure,topography and geology,this study attempts to discuss the influence of geomorphic and tectonic indexes on landslide distribution.The results show that the 2022 Luding earthquake with seismogenic fault at the Moxi fault,was a sinistral strike-slip event that triggered at least 4528landslides over an area of~2000 km2.These landslides span a total area of 28.1 km^(2),and the western section of the seismogenic fault,which serves as the active wall area,is characterized by a higher landslide concentration,especially in the Wandong Basin.The seismogenic fault and lithology influence the regional distribution of landslides,and more landslides occurred closer to the seismogenic fault and in the controlling lithologies of granite and dolomite.Local topography influences the landslide occurrence position on the slope;the eastern section is prone to form landslides in the lower gorge section,and the western section is prone to form landslides in the upper-top section of the gorge.For coseismic landslides in the eastern Baryan Har block,the eastern boundary(Longmenshan fault),where the earthquakes are characterized by thrusts with slight dextral strike-slip movement,could be the primary landslide-prone area;the southern boundary,the Moxi fault and the southern segment of the Xianshuihe fault,with more intensive strikeslip movement,may be the secondary landsideprone area;and the northern boundary is the tertiary landside-prone area.Additionally,the current landslide inventory may be underestimated although this underestimation has limited influence on the results.
基金supported by a research grant from the Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2019-21)the National Natural Science Foundation of China(Nos.41872227,41602221)。
文摘A recent correlation of stream geomorphic indices to fault activity has revealed that stream geomorphologies in bedrock mountain areas are good records of local fault movements. The Daqingshan piedmont fault is one of the main active faults in the fault system on the northern margin of the Hetao Basin and has produced frequent large-scale earthquakes since the Late Pleistocene. In the present study, following the segmentation regime of previous studies, we divide the fault zone into five segments, namely, the Baotou, Tuyouqi West, Tuzuoqi West, Bikeqi, and Hohhot segments, and we discuss the relationship between the drainage basin geomorphology and the piedmont fault activity in the Daqingshan area using 30 m spatial resolution Shuttle Radar Topography Mission(SRTM) digital elevation model(DEM) data. We use a range of geomorphic indices to examine the drainage basins in the Daqingshan area, including the channel steepness index(ksn), slope, hypsometric integral(HI), relief degree of land surface(RDLS), and stream lengthgradient index(SL), extracted with ArcGIS and MATLAB, and we also consider local lithologic and climate aspects. Furthermore, we compare the geomorphic indices with the slip rates of individual segments of the Daqingshan piedmont fault and paleoseismic data. The results show that the geomorphic indices of drainage basins in the Daqingshan area are primarily affected by the piedmont fault activity in the Daqingshan area. The geomorphic indices also demonstrate that piedmont fault activity has been the most intense in the middle segment of this fault system since the Late Quaternary and decreases towards the two sides.
基金the Research Council of Shiraz University which has supported the project
文摘This paper tests a data mining method for evaluation of the ＂IRTA＂（Index of Relative Tectonic Activity） to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K-means clustering of six basin-related geomorphic indices（the hypsometric integral, basin asymmetric factor, drainage density, basin shape ratio, mean axial slope of the channel and topographic roughness） that represent the relative strength of active tectonic deformation on topography and morphology, the relative tectonic activity along the Kazerun Fault Zone in the Zagros Mountains of Iran may be classified into low, moderate and high relative tectonic activity zones. The results allow the identification of the clusters of similarly deformed areas related to relative tectonic activity. The utilization of geomorphic parameters as well as IRTA with comparison to the field observations exhibit change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41971005,41522101,41901004)the Second Tibet Plateau Scientific Research(Grant No.2019QZKK0205)the Major Program of National Social Science Foundation of China(Grant No.19ZDA225).
文摘River capture is of great significance to landform evolution and hominine migration.In the Qinling-Daba Mountains,there is a viewpoint that Jialing River captured Hanjiang River,but this is still controversial.In this paper,we discuss the drainage evolution processes in intermountain basins at the Qinling-Daba Mountains based on a combination of detrital zircon UPb geochronology and geomorphic indexes.We suggest that the Hanjiang River gradually captured the Jialing River from east to west,accompanied by the evolution of the ancient Yangtze River.In terms of geomorphic evidences,wide valleys did not match with discharge,and a series of wind gaps developed in the Shiquan-Ankang basin.In addition,the valley shapes and width-toheight ratios(Vf)indicate two possible rapid incisions.The hypsometric integrals(HI)reflect that the landform gradually changes from the old stage to the youth stage from west to east.Theχvalues show that the drainage divide is moving to the side of the Yuehe River,and the Yuehe River is gradually shrinking.According to the sedimentary records,the zircon U-Pb age distributions indicate the provenance change.The high-altitude terraces show three age peaks(200–250,400–505,and 700–900 Ma),with the dominant Indosinian age peak(200–250 Ma),while the modern fluvial sediments only show a single peak of Jinning(700–900 Ma).These data show that there are two major river captures:(1)The ancient Hanjiang River cut through the regional compression ridge,and then captured the Hanzhong Basin river system(a part of the ancient Jialing river system)from east to west,and(2)The southern tributary captured the trunk with the uplift of the divide in the Shiquan-Ankang Basin,forming the modern drainage pattern in the upper Hanjiang River.The activities of the regional strike-slip fault,and the associated compression uplift played a key role in the river captures,the drainage evolution,and related landforms in the Shiquan-Ankang basin.In addition,it is shown that the evolution of the upper tributary basi
基金supported by the National Natural Science Foundation of China(Grant Nos.41971005,41522101)the Second Tibetan Plateau Scientific Expedition Program(Grant No.2019QZKK0205)the National Key Research and Development Program(Grant No.2016YFA0600500)。
文摘Previous researches had emphasized tectonic impacts on the fluvial system at the tectonically active areas,while the effects of lithology and local base level change have received relatively rare attention.Here we investigated fluvial landforms at different spatial scales,focusing on knickpoints and channel network reorganization from an area affected by the Haiyuan Fault in the northeastern Tibetan Plateau.The geomorphic indices,i.e.,drainage pattern andχanomalies,were calculated and investigated.The results show that two regional radial drainages formed around the Laohu and Hasi Mountains.Within the interior of the radial drainage,tributaries from the southeast side of the Laohu Mountain experienced near 180°direction change.We interpret this as the gradual drainage capture originating from the height difference(~190 m)of the local base level between the two catchments.Some tributaries from the Hasi Mountain show alternating gorges and broad valleys controlled by lithology.Besides,tectonic uplift and the lowering of base level(from the incision of the Yellow River)triggered an autogenic positivefeedback transition from parallel to dendritic drainage patterns.These observations suggest that base level change and lithology play a crucial role in landscape evolution,even in a tectonically active region.
文摘Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigationwithin the area. The study was carried out in the Karra Khola Basin, oneof the prominent basins in the Eastern extreme of the Hetauda Dun Valley,Central Nepal, to investigate geomorphic characteristics of the mainstream of the basin, categorize them into various stream types and studybasin development through drainage basin’s morphometric parameters.Geographical Information System (GIS) and Remote sensing techniquesusing satellite images were used as a tool to make the morphometricanalysis of the basin along with its major 13 sub-basin and delineate streamclassification following the Rosgen’s Level I hierarchical inventory. Themain stream of the Karra Khola is characterized as A-, B- and C-typeand the tributaries segments as B- and F-type. The basin is structurallyunaffected and has the permeable surface area and elongated shape. Thehypsometric analysis indicates that the basin is mostly at the old stage ofgeomorphic development while four out of 13 sub-basin being at maturestage. The Karra Khola sub-basin have higher risk to flash flooding(Lg=0.1-0.16km). Drainage density value reveals that the basin is highlysusceptible to flooding, gully erosion, etc. Similarly, dissection index valueimplies that the north eastern region of the basin is highly vulnerable toerosion as it at the younger stage of geomorphic development. Since thestudy area is highly sensitive to future natural hazards, further study andappropriate measures should be followed for safeguarding against thefuture risk along the Karra Khola basin and its tributaries.
基金Financial support to Syed Amer Mahmood from University of the Punjab,Lahore Government of Pakistan Remote Sensing GroupTU Freiberg,Germanypartial support from German Academic Exchange Association(DAAD)International Association of Mathematical Geosciences(IAMG)
文摘Landscapes in tectonically active Hindu Kush （NW Pakistan and NE Alghanistanl result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition processes. Active tectonics in this region have greatly influenced the drainage system and geomorphic expressions. The study area is a junction of three important mt^unlain ranges （Hindu Kush-Karakorunl-Himalayas） and is thus an ideal natural laboratory to investigate the relative tectonic activity resulting from the India-Eurasia collision. We evaluate active tectonics using DEM derived drainage network and geomorphic indices hypsometric integral （Hl）. stream-length gradient （SL）, fractal dimension （FD）, basin asymmetry factor （AF）, basin shape index （B,）, valley floor width to wllley height ratio （Vf） and motmtain front sinuosity （Star）. The results obtained from these indices were combined to yield an index of relative active tectonics （IRAT） using GIS. The average of the seven measured geomorphic indices was used to ewfluate the distri- bution of relative tectonic activity in the study area. We defined tour classes to define the degree of rela- tive tectonic activity： class 1 very high （1.0 ≤ IRAT 〈 1.3）; class 2 high （1.3 ≥ IRAT 〈 1.5）： class 3--moderate （1.5 〉 IRAT 〈 1.8）; and class 4--low （1.8 〉 IRAT）. In view of the results, we conclude that this combined approach allows the identification of the highly deformed areas related to active tectonics. Landsat imagery and field observations also evidence the presence of active tectonics based on the deflected streams, deformed landforms, active mountain fronts and triangular facets. The indicative values of IRAT are consistent with the areas of known relative uplift rates, landforms and geology.
