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Recent tectonic activity in Central Alborz Mountain,Iran:morphometric analysis and knickpoint identification

Journal of Mountain Science 2020年第12期17卷 3137-3161页

作者： Parisa SHOKRI Maryam DEHBOZORGI Saeid HAKIMI ASIABAR Department of Earth Science Kharazmi UniversityTehran15719-14911Iran Department of Geology Lahijan BranchAzad UniversityGilan1616Iran

Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late *** study area located in Central Alborz encompasses different Quaternary ***,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central *** this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the ***,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS *** on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study ***,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian ***,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.

关键词： Morphotectonic Bedrock rivers knickpoint Quaternary Fault Uplift Central Alborz

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Application of River Longitudinal Profile Morphometrics to Reveal the Uplift of Lushan Mountain

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Acta Geologica Sinica(English Edition) 2017年第5期91卷 1644-1652页

作者： HAN Zhiyong LI Xusheng WANG Nairui CHEN Gang WANG Xianyan LU Huayu School of Geographic and Oceanographic Sciences Nanjing University Nanjing 210023 China Nanjing Hydraulic Research Institute Nanjing 210029 China

The stream power model was applied to Lushan Mt. in South China in order to verify its capability of interpreting the uplift of a small block mountain. On a log-log plot, the longitudinal profiles of 9 rivers derived from a 30 m DEM exhibit primary characteristics similar to those derived from a 5 m DEM; however, the 5 m DEM clearly reveals more minor knickpoints, and the positions of knickpoints are pinpointed more accurately. All of the studied rivers on the block mountain are in a transient state due to geological perturbations. Some of them exhibit two segments in steady state separated by a slopebreak knickpoint. Such rivers generally develop in a longitudinal valley, which are less perturbed by substrate inhomogeneities. The similar heights of the slope-break knickpoints and the similar uplift rate indicated by the k_（sn） values demonstrate an almost simultaneous headward erosion induced by the fall in base level. This modelling result is consistent with the mode of formation of this particular block mountain. Our study demonstrates that the stream power model is applicable to a small tectonicallyactive massif only if the channel segments are in a steady state.

关键词： knickpoint river longitudinal profile normalized steepness index uplift rate

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Regional- to local-scale controls on waterfalls in Rocky Mountain National Park,Colorado

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Journal of Mountain Science 2020年第8期17卷 1874-1890页

作者： Jose A.ORTEGA-BECERRIL Bridget LIVERS Ellen WOHL Department of Geology and Geochemistry Autonomous University of MadridMadrid.28049Spain Department of Natural Resource Ecology and Management Iowa State UniversityAmesLA 50011 USA Department of Geosciences Colorado State UniversityFort CollinsCO 80523-1482USA

Previous work on the eastern side of Rocky Mountain National Park(RMNP),Colorado indicated correlations among waterfall location,waterfall morphology,and the characteristics of bedrock *** of waterfalls on the western side of the national park do not correlate as strongly with joint *** river profiles on the western side are less concave and waterfalls account for a greater proportion of the total elevation *** interpret these differences to result from more widely spaced joints,lithological differences,and complex glacial *** results demonstrate that waterfall shape and typology may change due to both local and regional controls operating in a mountain *** regions had alpine valley glaciers,but continued landscape evolution via fluvial erosion has developed waterfalls with diverse locations and morphologies that reflect the influences of glacial deposits,bedrock erosional resistance,and joint geometry.

关键词： Waterfall Rocky Mountain National Park knickpoint Bedrock Mountain stream regional-scale controls

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Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

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International Journal of Geosciences 2013年第6期4卷 8-16页

作者： Yuichi S. Hayakawa Center for Spatial Information Science The University of Tokyo Chiba Japan

A waterfall highlights the locus of active fluvial erosion of bedrock, and its mechanism has been the subject of several studies;however, erosional processes remain to be clarified for specific rock structures composing a waterfall. Herein, the detailed morphology of cliffs around a waterfall is examined by a terrestrial laser scanning (TLS) approach to analyze erosional processes occurring in the cliffs. The study site is Kegon Falls in Japan, which has a vertical drop of surface water from the top of its cliff and groundwater outflows from its lower portion. The entire cliff is mostly overhanging and minor rockfalls are often observed. The latest major rockfall occurred in 1986, causing an approximate 8-m upstream shift of the waterfall lip. From the point cloud obtained by TLS measurement, a digital elevation model on a vertical plane was generated, and cross-sectional profiles were extracted. A distinct 5- to 10-m depression was found at the bottom of the upper andesite layer of the waterfall cliff, which appears to have been formed by freeze-thaw and wet-dry weathering following the upstream shift of the surface water drop. Stability analysis of the waterfall cliff with an undercutting notch indicates that the igneous rock composing the cliff is sufficiently strong to maintain its current overhanging shape and that catastrophic collapse of the entire waterfall face rarely occurs. Following the formation of the depression, the upper cliff face appears to have been gradually eroded by gravitational collapses of relatively small blocks bounded by columnar and platy joints.

关键词： Bedrock Erosion knickpoint Waterfall Recession Terrestrial Laser Scanning

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RETROGRESSIVE EROSION AND LONGITUDINAL PROFILE EVOLUTION IN NONCOHESIVE MATERIAL

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International Journal of Sediment Research 2006年第2期21卷 113-122页

作者： Lien-Kuang CHEN Su-Chin CHEN Department of Soil and Water Conservation National Chung Hsing University Taichung Taiwan 402 China Dr. Department of Soil and Water Conservation National Chung Hsing University Taichung Taiwan 402 China Prof.

Retrogressive erosion plays a significant role in soil erosion and in channel morphology evolution. Retrogressive erosion occurs and migrates when the flow conditions and/or channel bed slope change. This study investigates through a series of experiments, the migration behavior of retrogressive erosion and the longitudinal profile evolution of a channel consisting of noncohesive sediment. Experimental results indicate that retrogressive erosion can be categorized into two types, stepped and rotating. In stepped erosion a nearly parallel erosion surface migrates upstream at a constant speed. The migration speed in rotating erosion is a function of the square root of time. The experimental results reveal that the discharge does not affect the migration speed of stepped erosion. However, the migration speed of rotating erosion increases with rising discharge. The crucial difference between rotating and stepped erosion, i.e. the threshold value separating the two forms of erosion is a function of the initial channel bed lowering and critical water depth. A model of retrogressive erosion in a noncohessive channel is developed based on the experimental results.

关键词： Headcuts Retrogressive erosion knickpoint Stepped and rotating

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