Due to the complex dynamic of aeolian and fluvial interacted processes behind the landform development,most of previous works started from classifying the types of landscape characterized by various aeolian and fluvia...Due to the complex dynamic of aeolian and fluvial interacted processes behind the landform development,most of previous works started from classifying the types of landscape characterized by various aeolian and fluvial features.Such classifications are usually generalized based on large geomorphic data set abstracted from satellite images without field verification and dynamic field data.In this study,we identified river banks in deserts as a unique geographical unit dominated by aeolian-fluvial processes.Three distinct locations have been identified as representative study cases,which are in the Keriya River Basin in the west,the Mu Bulag River Basin in the middle and the Xar Moron River Basin in the east of the northern China.The aeolian-fluvial interaction types were quantified based on site observation and measurement,topographic mapping and remote-sensing image analysis.Dimensional morphological relationship between river channel and adjacent sand dunes areas were explored.We concluded that different channels are often associated with different distributions of riparian dunes.The quantitative data enabled us to distinguish statistically four different types of landscape in aeolian-fluvial dominant environment,namely riverside dunes-straight channel,symmetrical interleaving dunes-meandering channel,river-island dunes-braiding channel,and grid-like dunes-anastomosing channel,aiming to provide compensational information to current aeolian-fluvial interaction studies.The angle of interaction between aeolian and fluvial systems,the windward and leeward sites of the bank,vegetation coverage and underlying landform determines the distribution,morphology,scale and direction of extension of the riparian dunes.The results of the work study can provide a reference for study of aeolian-fluvial interactions at different spatial scales in arid region.展开更多
Although neotectonic activity is considered to be the main factor of the terrain evolution of the Qinghai Tibet Plateau and its surrounding high-altitude areas,further geomorphological analysis and literature analysis...Although neotectonic activity is considered to be the main factor of the terrain evolution of the Qinghai Tibet Plateau and its surrounding high-altitude areas,further geomorphological analysis and literature analysis are needed for the understanding of the geomorphic evolution and the Quaternary environment change of the western area of the Alxa Plateau near the northern Tibet Plateau.The purpose of this study is to investigate the distribution of site-specific geomorphic units of the landforms developed in the vast topography of Ejina Basin(Western Alxa),in order to identify the geostructural and climatic causes of the geomorphic landscape and its impact on the change of paleoenvironment.At present,the climate and hydrological conditions in Ejina are relatively monotonous and stable.In addition to tectonic dynamic factors,the most widely distributed landform in the basin is climate landform.There are both geomorphological and sedimentological anomalies of Aeolian landforms occurred in the whole basin,indicating that the underlying surface effect(retention effect)of river(Ejina River)and its related uneven ground and weak wind erosion(deflation)process in the nearby area may be the important factors controlling the formation of Ejina dunes,rather than the arid climate.It is believed that the extensive interaction between the aeolian and fluvial processes is the main mechanism of the regional geomorphic difference in Ejina Basin.According to the comparability of regional geomorphology and sedimentology,the period of the formation of relic geomorphology in the edge of Ejina Basin can be reasonably attributed to the local glacial maximum of the last glacial.The geomorphic transformation from quasi plain and desert valley to desert plain,the appearance of widely moving sand dunes and the presence of large ancient lake geomorphology all indicate that the drought index of Ejina Basin is increasing on the scale of geomorphic formation.Paleogeomorphological and chronological evidences show that the climatic and hydrological conditions of the basin in the last glacial period and the early Holocene are much better than those at present.For example,the average annual precipitation in the area before 39-23ka BP is between 60-350 mm(about 36 mm today),but there are large waves in the Holocene.The coexistence of various climates and landforms in Ejina Basin and the resulting geomorphic diversity should be the composite result of various geomorphic processes and surface processes besides glaciation.The low aridity(relative humidity)in the Ejina Region in the late Pleistocene may be the result of the enhancement of the westerly rain belt and the weakening of the Asian Winter Monsoon in the arid region of Central Asia.展开更多
Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of er...Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion.In this study,based on laboratory rainfall simulation experiments,we analyzed rainfall-induced erosion processes on sand-covered loess slopes(SS)with different sand cover patterns(including length and thickness)and uncovered loess slopes(LS)to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion.The grain-size curves of eroded sediments were fitted using the Weibull function.Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS.The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed.The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS.Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes.The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage.Sand cover on loess slopes aggravates loess erosion,not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess,compared with the loess slopes without sand cover.The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount.Furthermore,given the same sand cover pattern,a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion.This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.展开更多
Complex erosion by wind and water, which is also called aeolian-fluvial interactions, is an important erosion process and landscape in arid and semiarid regions. The effectiveness of links between wind and water proce...Complex erosion by wind and water, which is also called aeolian-fluvial interactions, is an important erosion process and landscape in arid and semiarid regions. The effectiveness of links between wind and water process, spatial environmental transitions and temporal environmental change are the three main driving forces determining the geomorphologic significance of aeolian-fluvial interactions. As a complex interrelating and intercoupling system, complex erosion by wind and water has spatial- temporal variation features. The process of complex erosion by wind and water can be divided into palaeoenvironmental process and contemporary process. Early work in drylands has often been attributed to one of two schools advocating either an ‘aeolianist’ or a ‘fluvialist’ perspective, so it was not until the 1930s that the research on complex erosion by wind and water had been conducted. There are two obstacles restricting the research of complex erosion by wind and water. Firstly, how to transform in different temporal and spatial scales is still unsettled; and secondly, the research methodology is still immature. In the future, the mechanism and control of erosion, the complex soil erodibility in wind and water erosion will be the focus of research on complex erosion by wind and water.展开更多
The Upper Devonian Buchan Formation in the Central North Sea is a typical terrestrial deposit and predominantly comprises fine to medium-grained sandstones with occasional conglomerates and mudstones. The Buchan Forma...The Upper Devonian Buchan Formation in the Central North Sea is a typical terrestrial deposit and predominantly comprises fine to medium-grained sandstones with occasional conglomerates and mudstones. The Buchan Formation has been previously described as being made up mostly of braided fluvial sandstones;however, this study confirms the presence and significance of aeolian sandstones within this fluvial-dominated sequence. Facies architecture is investigated through analogue outcrop study, well log curves and numerical facies modelling, and the results show contrasting differences between fluvial and aeolian facies. The fluvial facies is composed of multiple superimposed and sand-dominated fining-upward cycles in the vertical direction, and laterally an individual cycle has a large width/thickness ratio but is smaller than the field scale. However, the high channel deposition proportion (CDP, average value = 72%) in fluvial-dominated intervals means that it is likely all the sand bodies are interconnected. Aeolian facies comprise superimposed dune and interdune depositions and can be laterally correlated over considerable distances (over 1 km). Although the aeolian sandstones are volumetrically minor (approx. 30%) within the whole Buchan Formation, they have very high porosity and permeability (14.1% - 28%, 27 - 5290 mD) and therefore are excellent potential reservoirs. The fluvial sandstones are significantly cemented by quartz overgrowth and dolomite and by comparison with the aeolian sandstones are poor reservoirs. Aeolian sandstones can be differentiated from fluvial sandstones using several features: pin-stripe lamentation, good sorting, high visible porosity, friable nature and lack of muddy or conglomeratic contents;these characteristics allow aeolian sandstones can be tentatively recognized by low gamma ray values, high sonic transit time and low density in uncored wells. The thin, laterally correlatable and permeable aeolian sandstones within the Buchan Formation are effective reservoirs and could form important exploration targets when the Devonian is targeted elsewhere in the North Sea.展开更多
The interaction between fluvial and aeolian processes can significantly change surface morphology of the Earth. Taking the Horqin Sandy Land as the research area and using Landsat series satellite remote sensing image...The interaction between fluvial and aeolian processes can significantly change surface morphology of the Earth. Taking the Horqin Sandy Land as the research area and using Landsat series satellite remote sensing images, this study utilizes geomorphology and landscape ecology to monitor and analyze the aeolian geomorphology characteristics of the Horqin Sandy Land. Results show that the sand dunes of the Horqin Sandy Land are mainly distributed on alluvial plains along the banks of the mainstream and tributaries of the Western Liao River, and the sand dune types tend to simplify from west to east and from south to north. The aeolian geomorphology coverage tend to be decreasing in the past 40 years, with an average annual change rate of 0.31%. While the area of traveling dunes decreased, the area of fixed and semi-fixed dunes increased. The fractal dimensions of various types of sand dune have all remained relatively constant between 1.07 and 1.10, suggesting that they are experiencing a relatively stable evolutionary process. There is a complex interaction between fluvial and aeolian processes of the Horqin Sandy Land, which plays a central role in surface landscape molding. Sand dunes on both sides of different rivers on the Horqin Sandy Land present certain regularity and different characteristics in terms of morphology, developmental scale, and spatial pattern. There are six fluvial-aeolian interaction modes in this area: supply of sand sources by rivers for sand dune development, complete obstruction of dune migration by rivers, partial obstruction of dune migration by rivers, influence of river valleys on dune developmental types on both sides, influence of river valleys on dune developmental scale on both sides, and river diversion due to obstruction and forcing by sand dunes. This study deepens our understanding of the surface process mechanism of the interaction between fluvial and aeolian processes in semi-arid regions, and provides a basis for researches on regional landscape responses in the context of global environmental change.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.41801004,41871010)the Fundamental Research Funds for the Central Universities(No.GK202001003,GK202003067)+1 种基金China Postdoctoral Science Foundation(No.2020M673334)Natural Science Foundation of Shaanxi Province(No.2021JQ-313)。
文摘Due to the complex dynamic of aeolian and fluvial interacted processes behind the landform development,most of previous works started from classifying the types of landscape characterized by various aeolian and fluvial features.Such classifications are usually generalized based on large geomorphic data set abstracted from satellite images without field verification and dynamic field data.In this study,we identified river banks in deserts as a unique geographical unit dominated by aeolian-fluvial processes.Three distinct locations have been identified as representative study cases,which are in the Keriya River Basin in the west,the Mu Bulag River Basin in the middle and the Xar Moron River Basin in the east of the northern China.The aeolian-fluvial interaction types were quantified based on site observation and measurement,topographic mapping and remote-sensing image analysis.Dimensional morphological relationship between river channel and adjacent sand dunes areas were explored.We concluded that different channels are often associated with different distributions of riparian dunes.The quantitative data enabled us to distinguish statistically four different types of landscape in aeolian-fluvial dominant environment,namely riverside dunes-straight channel,symmetrical interleaving dunes-meandering channel,river-island dunes-braiding channel,and grid-like dunes-anastomosing channel,aiming to provide compensational information to current aeolian-fluvial interaction studies.The angle of interaction between aeolian and fluvial systems,the windward and leeward sites of the bank,vegetation coverage and underlying landform determines the distribution,morphology,scale and direction of extension of the riparian dunes.The results of the work study can provide a reference for study of aeolian-fluvial interactions at different spatial scales in arid region.
基金The study was financially supported by the National Natural Science Foundation of China(grant nos.41930640,41771014)the Project of the Second Comprehensive Scientific Investigation on the Qinghai Tibet Plateau(2019QZKK1003)。
文摘Although neotectonic activity is considered to be the main factor of the terrain evolution of the Qinghai Tibet Plateau and its surrounding high-altitude areas,further geomorphological analysis and literature analysis are needed for the understanding of the geomorphic evolution and the Quaternary environment change of the western area of the Alxa Plateau near the northern Tibet Plateau.The purpose of this study is to investigate the distribution of site-specific geomorphic units of the landforms developed in the vast topography of Ejina Basin(Western Alxa),in order to identify the geostructural and climatic causes of the geomorphic landscape and its impact on the change of paleoenvironment.At present,the climate and hydrological conditions in Ejina are relatively monotonous and stable.In addition to tectonic dynamic factors,the most widely distributed landform in the basin is climate landform.There are both geomorphological and sedimentological anomalies of Aeolian landforms occurred in the whole basin,indicating that the underlying surface effect(retention effect)of river(Ejina River)and its related uneven ground and weak wind erosion(deflation)process in the nearby area may be the important factors controlling the formation of Ejina dunes,rather than the arid climate.It is believed that the extensive interaction between the aeolian and fluvial processes is the main mechanism of the regional geomorphic difference in Ejina Basin.According to the comparability of regional geomorphology and sedimentology,the period of the formation of relic geomorphology in the edge of Ejina Basin can be reasonably attributed to the local glacial maximum of the last glacial.The geomorphic transformation from quasi plain and desert valley to desert plain,the appearance of widely moving sand dunes and the presence of large ancient lake geomorphology all indicate that the drought index of Ejina Basin is increasing on the scale of geomorphic formation.Paleogeomorphological and chronological evidences show that the climatic and hydrological conditions of the basin in the last glacial period and the early Holocene are much better than those at present.For example,the average annual precipitation in the area before 39-23ka BP is between 60-350 mm(about 36 mm today),but there are large waves in the Holocene.The coexistence of various climates and landforms in Ejina Basin and the resulting geomorphic diversity should be the composite result of various geomorphic processes and surface processes besides glaciation.The low aridity(relative humidity)in the Ejina Region in the late Pleistocene may be the result of the enhancement of the westerly rain belt and the weakening of the Asian Winter Monsoon in the arid region of Central Asia.
基金supported by the National Key Research and Development Program of China (2016YFC0402404, 2016YFC0402407)the National Natural Science Foundation of China (L1624052, 41330858, 41471226, and 51509203)the Dr.Innovation Fund of Xi’an University of Technology (310-252071505)
文摘Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion.In this study,based on laboratory rainfall simulation experiments,we analyzed rainfall-induced erosion processes on sand-covered loess slopes(SS)with different sand cover patterns(including length and thickness)and uncovered loess slopes(LS)to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion.The grain-size curves of eroded sediments were fitted using the Weibull function.Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS.The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed.The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS.Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes.The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage.Sand cover on loess slopes aggravates loess erosion,not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess,compared with the loess slopes without sand cover.The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount.Furthermore,given the same sand cover pattern,a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion.This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.
基金National Natural Science Foundation of China, No.30371191 The Ministry of Education of China, No.272008 Program for New Century Excellent Talents in University
文摘Complex erosion by wind and water, which is also called aeolian-fluvial interactions, is an important erosion process and landscape in arid and semiarid regions. The effectiveness of links between wind and water process, spatial environmental transitions and temporal environmental change are the three main driving forces determining the geomorphologic significance of aeolian-fluvial interactions. As a complex interrelating and intercoupling system, complex erosion by wind and water has spatial- temporal variation features. The process of complex erosion by wind and water can be divided into palaeoenvironmental process and contemporary process. Early work in drylands has often been attributed to one of two schools advocating either an ‘aeolianist’ or a ‘fluvialist’ perspective, so it was not until the 1930s that the research on complex erosion by wind and water had been conducted. There are two obstacles restricting the research of complex erosion by wind and water. Firstly, how to transform in different temporal and spatial scales is still unsettled; and secondly, the research methodology is still immature. In the future, the mechanism and control of erosion, the complex soil erodibility in wind and water erosion will be the focus of research on complex erosion by wind and water.
文摘The Upper Devonian Buchan Formation in the Central North Sea is a typical terrestrial deposit and predominantly comprises fine to medium-grained sandstones with occasional conglomerates and mudstones. The Buchan Formation has been previously described as being made up mostly of braided fluvial sandstones;however, this study confirms the presence and significance of aeolian sandstones within this fluvial-dominated sequence. Facies architecture is investigated through analogue outcrop study, well log curves and numerical facies modelling, and the results show contrasting differences between fluvial and aeolian facies. The fluvial facies is composed of multiple superimposed and sand-dominated fining-upward cycles in the vertical direction, and laterally an individual cycle has a large width/thickness ratio but is smaller than the field scale. However, the high channel deposition proportion (CDP, average value = 72%) in fluvial-dominated intervals means that it is likely all the sand bodies are interconnected. Aeolian facies comprise superimposed dune and interdune depositions and can be laterally correlated over considerable distances (over 1 km). Although the aeolian sandstones are volumetrically minor (approx. 30%) within the whole Buchan Formation, they have very high porosity and permeability (14.1% - 28%, 27 - 5290 mD) and therefore are excellent potential reservoirs. The fluvial sandstones are significantly cemented by quartz overgrowth and dolomite and by comparison with the aeolian sandstones are poor reservoirs. Aeolian sandstones can be differentiated from fluvial sandstones using several features: pin-stripe lamentation, good sorting, high visible porosity, friable nature and lack of muddy or conglomeratic contents;these characteristics allow aeolian sandstones can be tentatively recognized by low gamma ray values, high sonic transit time and low density in uncored wells. The thin, laterally correlatable and permeable aeolian sandstones within the Buchan Formation are effective reservoirs and could form important exploration targets when the Devonian is targeted elsewhere in the North Sea.
基金Under the auspices of Natural National Science Foundation of China(No.41671002,41401002)
文摘The interaction between fluvial and aeolian processes can significantly change surface morphology of the Earth. Taking the Horqin Sandy Land as the research area and using Landsat series satellite remote sensing images, this study utilizes geomorphology and landscape ecology to monitor and analyze the aeolian geomorphology characteristics of the Horqin Sandy Land. Results show that the sand dunes of the Horqin Sandy Land are mainly distributed on alluvial plains along the banks of the mainstream and tributaries of the Western Liao River, and the sand dune types tend to simplify from west to east and from south to north. The aeolian geomorphology coverage tend to be decreasing in the past 40 years, with an average annual change rate of 0.31%. While the area of traveling dunes decreased, the area of fixed and semi-fixed dunes increased. The fractal dimensions of various types of sand dune have all remained relatively constant between 1.07 and 1.10, suggesting that they are experiencing a relatively stable evolutionary process. There is a complex interaction between fluvial and aeolian processes of the Horqin Sandy Land, which plays a central role in surface landscape molding. Sand dunes on both sides of different rivers on the Horqin Sandy Land present certain regularity and different characteristics in terms of morphology, developmental scale, and spatial pattern. There are six fluvial-aeolian interaction modes in this area: supply of sand sources by rivers for sand dune development, complete obstruction of dune migration by rivers, partial obstruction of dune migration by rivers, influence of river valleys on dune developmental types on both sides, influence of river valleys on dune developmental scale on both sides, and river diversion due to obstruction and forcing by sand dunes. This study deepens our understanding of the surface process mechanism of the interaction between fluvial and aeolian processes in semi-arid regions, and provides a basis for researches on regional landscape responses in the context of global environmental change.