Tracking denudation and sediment production and transport with cosmogenic 10Be in arid,high-altitude Himalayan half-grabens,Zanskar, northern India     

Craig Dietsch  Kathryn Hedrick  Lewis A. Owen  Marc W. Caffee 《地球表面变化过程与地形》2020,45(13):3103-3119

Understanding the extent to which local factors, including bedrock and structure, govern catchment denudation in mountainous environments as opposed to broader climate or tectonic patterns provides insight into how landscapes evolve as sediment is generated and transported through them, and whether they have approached steady-state equilibrium. We measured beryllium-10 (¹⁰Be) concentrations in 21 sediment samples from glaciated footwall and hanging wall catchments, including a set of nested catchments, and 12 bedrock samples in the Puga and Tso Morari half-grabens located in the high-elevation, arid Zanskar region of northern India. In the Puga half-graben where catchments are underlain by quartzo-feldspathic gneissic bedrock, bedrock along catchment divides is eroding very slowly, about 5 m/Ma, due to extreme aridity and ¹⁰Be concentrations in catchment sediments are the highest (~60–90 × 10⁵ atoms/g SiO₂) as colluvium accumulates on hillslopes, decoupled from their ephemeral streams. At Puga, ¹⁰Be concentrations and the average erosion rates of a set of six nested catchments demonstrate that catchment denudation is transport-limited as sediment stagnates on lower slopes before reaching the catchment outlet. In the Tso Morari half-graben, gneissic bedrock is also eroding very slowly but ¹⁰Be concentrations in sediments in catchments underlain by low grade meta-sedimentary rocks, are significantly lower (~10–35 × 10⁵ atoms/g SiO₂). In these arid, high-elevation environments, ¹⁰Be concentrations in catchment sediments have more to do with bedrock weathering and transport times than steady-state denudation rates. © 2020 John Wiley & Sons, Ltd.  相似文献   

IDENTIFICATION OF PALEO-EARTHQUAKES OF LUOYUNSHAN PIEDMONT FAULT BY QUANTITATIVE MORPHOLOGY OF LIMESTONE FAULT SURFACES          下载免费PDF全文

ZOU Jun-jie  HE Hong-lin  SHI Feng  WEI Zhan-yu  SU Peng  YAN Xiao-bing 《地震地质》2019,41(2):400-418

The quantitative analysis of morphologic characteristics of bedrock fault surface is a useful approach to study faulting history and identify paleo-earthquake. It is an effective complement to trenching technique, specially to identifying paleo-earthquakes in a bedrock area where the trenching technique cannot be applied. This paper focuses on the Luoyunshan piedmont fault, which is an active normal fault extending along the eastern boundary of the Shanxi Graben, China. There are a lot of fault scarps along the fault zone, which supply plentiful samples to be selected to our research, that is, to study faulting history and identify paleo-earthquakes in bedrock area by the quantitative analysis of morphologic characteristics of fault surfaces. In this paper, we calculate the 2D fractal dimension of two bedrock fault surfaces on the Luoyunshan piedmont fault in the Shanxi Graben, China using the isotropic empirical variance function, which is a popular method in fractal geometry. Results indicate that the fractal dimension varies systematically with height above the base of the fault surface exposures, indicating segmentation of the fault surface morphology. The 2D fractal dimension on a fault surface shows a ‘stair-like’ vertical segmentation, which is consistent with the weathering band and suggests that those fault surfaces are outcropped due to periodic faulting earthquakes. However, compared to the results of gneiss obtained by the former researchers, the characteristic fractal value of limestone shows an opposite evolution trend. 1)The paleo-earthquake study of the bedrock fault surface can be used as a supplementary method to study the activity history of faults in specific geomorphological regions. It can be used to fill the gaps in the exploration of the paleo-earthquake method in the bedrock area, and then broaden the study of active faults in space and scope. The quantitative analysis of bedrock fault surface morphology is an effective method to study faulting history and identify paleo-earthquake. The quantitative feature analysis method of the bedrock fault surface is a cost-effective method for the study of paleo-earthquakes in the bedrock fault surface. The number of weathered bands and band height can be identified by the segment number and segment height of the characteristic fractal dimension, and then the paleoearthquake events and the co-seismic displacement can be determined; 2)The exposure of the fault surface of the Luoyunshan bedrock is affected and controlled by both fault activity and erosion. A strong fault activity(ruptured earthquake)forms a segment of fault surface which is equivalent to the vertical co-seismic displacement of the earthquake. After the segment is cropped out, it suffers from the same effect of weathering and erosion, and thus this segment has approximately the same fractal dimension. Multiple severe fault activities(ruptured earthquake)form multiple fault surface topography. The long-term erosion under weak hydrodynamic conditions at the base of the fault cliff between two adjacent fault activities(intermittent period)will form a gradual slow-connect region where the fractal dimension gradually changes with the height of the fault surface. Based on the segmentation of quantitative morphology of the two fault surfaces on the Luoyunshan piedmont fault, we identified four earthquake events. Two sets of co-seismic displacement of about 3m and 1m on the fault are obtained; 3)The relationship between the fault surface morphology parameters and the time is described as follows:The fractal dimension of the limestone area decreases with the increase of the exposure time, which reflects the gradual smoothing characteristics after exposed. The phenomenon is opposite to the evolution of the geological features of gneiss faults acquired by the predecessors on the Huoshan piedmont fault; 4)Lithology plays an important role in morphology evolution of fault surface and the two opposite evolution trends of the characteristic fractal value on limestone and gneiss show that the weathering mechanism of limestone is different from that of the gneiss.  相似文献   

Experiments on the morphological controls of velocity inversions in bedrock canyons          下载免费PDF全文

Brendan Hunt  Jeremy G. Venditti  Eva Kwoll 《地球表面变化过程与地形》2018,43(3):654-668

A better understanding of bedrock incision mechanisms and processes is essential to the study of long‐term landscape evolution. Yet, little is known about flow dynamics in bedrock rivers, limiting our ability to make realistic predictions of local bedrock incision rates. A recent investigation of flow through bedrock canyons of the Fraser River revealed that plunging flows, defined by the downward‐directed movement of near surface flow toward the channel bed, occur in channels that have low width‐to‐depth ratios. Plunging flows occur into deep scour pools, which are often coincident with lateral constrictions and channel spanning submerged ridges (sills). A phenomenological investigation was undertaken to reproduce the flow fields observed in the Fraser canyons and to explore morphological controls on the occurrence and relative strength of plunging flow in bedrock canyons. Our observations show that the plunging flow structure can be produced along a scour pool entrance slope by accelerating the flow at the canyon entrance either over submerged sills or through lateral constrictions. Plunging flow appears to be a function of convective deceleration into a scour pool which can be enhanced by sill height, the amount of the channel width that is constricted, pool entrance slope, discharge, and a reduction in channel width‐to‐depth ratio. Plunging flow greatly enhances the potential for incision to occur along the channel bed and is an extreme departure from the assumptions of steady, uniform flow in bedrock incision models, highlighting the need for improved formulations that account for fluid flow. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Effects of bedrock groundwater discharge on spatial variability of dissolved carbon,nitrogen, and phosphorous concentrations in stream water within a forest headwater catchment     

Tomohiro Egusa  Tomo'omi Kumagai  Tomoki Oda  Nobuhito Ohte 《水文研究》2021,35(1):e13993

The quantitative evaluation of the effects of bedrock groundwater discharge on spatial variability of stream dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP) concentrations has still been insufficient. We examined the relationships between stream DOC, DIN and DIP concentrations and bedrock groundwater contribution to stream water in forest headwater catchments in warm-humid climate zones. We sampled stream water and bedrock springs at multiple points in September and December 2013 in a 5 km² forest headwater catchment in Japan and sampled groundwater in soil layer in small hillslopes. We assumed that stream water consisted of four end members, groundwater in soil layer and three types of bedrock groundwater, and calculated the contributions of each end member to stream water from mineral-derived solute concentrations. DOC, DIN and DIP concentrations in stream water were compared with the calculated bedrock groundwater contribution. The bedrock groundwater contribution had significant negative linear correlation with stream DOC concentration, no significant correlation with stream DIN concentration, and significant positive linear correlation with stream DIP concentration. These results highlighted the importance of bedrock groundwater discharge in establishing stream DOC and DIP concentrations. In addition, stream DOC and DIP concentrations were higher and lower, respectively, than those expected from end member mixing of groundwater in soil layer and bedrock springs. Spatial heterogeneity of DOC and DIP concentrations in groundwater and/or in-stream DOC production and DIP uptake were the probable reasons for these discrepancies. Our results indicate that the relationships between spatial variability of stream DOC, DIN and DIP concentrations and bedrock groundwater contribution are useful for comparing the processes that affect stream DOC, DIN and DIP concentrations among catchments beyond the spatial heterogeneity of hydrological and biogeochemical processes within a catchment.  相似文献   

Adjustment processes of mountainous rivers affected by tilting uplift: Laboratory experiments and a case study of Yakushima Island,Japan     

Reiko Genno  Noritaka Endo 《Island Arc》2019,28(1)

Mountainous river basins are one of the main sources of sediment. Over long time scales, sediment production is sustained by the persistent dissection of river basins, which is promoted by tectonic activity. The response or adjustment of rivers to forcing factors such as uplift is based on the concept of the graded river and a feedback mechanism between the incision and uplift. Although the development of graded rivers under natural circumstances has been discussed for a long time, knowledge about the transition of river basins under heterogeneous uplift is not enough. To understand the development of a river basin with a non‐uniform uplift rate, two simple cases are examined: landward and seaward tilting uplift, where the uplift rate varies linearly in space. For our study, laboratory experiments were conducted and the results were compared with those of natural river basins; two river basins in Yakushima Island were selected for this purpose. In both the laboratory and Yakushima, the longitudinal profile of the river basin under landward‐tilting uplift has a convex‐up zone and a specific knickpoint is formed at the upstream end of this zone. This knickpoint is inactive with respect to migration and incision owing to the insufficient cumulative uplift to the equilibrium state. It was also observed in both the experimental and natural cases that the profile of the river basin under seaward tilting is unlikely to have such a convex‐up zone in the long term, and will instead have a smooth concave profile. Therefore, the spatiotemporal pattern of dissection differs depending on the type of tilting uplift, which suggests that sediment production also varies in time and space according to the type of uplift.  相似文献   

四川省南江县陈家湾滑坡稳定性分析及防治建议          下载免费PDF全文

张涛  石胜伟  谢忠胜  梁炯  熊德清 《探矿工程》2016,43(1):14-19

由于山体的特殊地质背景及人类工程活动,四川省南江县陈家湾滑坡在平面位置上以中间山梁为界分为Ⅰ号、Ⅱ号滑坡及潜在不稳定斜坡。通过地质灾害勘查,研究了滑坡特征及其地质成因机制,并进行了稳定性分析评价。结果表明：仅Ⅰ号滑坡在暴雨工况下处于欠稳定状态。根据滑坡地形特征、稳定性分析结果,结合保护对象,对Ⅰ号滑坡提出了“抗滑桩+截水沟”和“预应力锚索+抗滑短桩+截水沟”两种防治方案。通过对比分析,推荐“抗滑桩+截水沟”为实施方案。  相似文献   

水力压裂技术在豫西基岩地热井增产中的应用研究          下载免费PDF全文

申云飞  卢玮  陈莹  程存平 《探矿工程》2016,43(10):253-256

地热资源是清洁能源,其开发利用主要通过钻井工程来实现。地热资源量（水量）大小决定着开发利用的价值。实际中,因地层等条件的复杂和不确定性,导致地热井出水量和温度不能达到预期的目标。特别是在山区基岩缺水地区地热资源开发,由于水量和温度指标偏低,严重影响了清洁能源的开发利用。本文结合工程实例,首次在豫西基岩严重缺水地区通过压裂车和钻井泵分段水力压裂技术,使低产地热井出水量增加3倍,达到了预期的目的。为今后基岩地区地热和地下水资源开发利用增产提供了借鉴。  相似文献   

浸矿开采对离子型稀土基岩力学特性的影响研究     

钟文  朱文韬  曾鹏  黄震  王晓军  郭钟群  胡凯建 《岩土力学》2022,43(6):1481-1492

为研究原地浸矿母液对离子型稀土矿收液底板的侵蚀影响,以离子型稀土矿基岩（半/弱风化花岗岩）为研究对象,开展了室内浸矿模拟试验。对比分析了不同浸矿时间岩样的应力−应变曲线、峰值应力、峰值应变和弹性模量,获取了不同浸矿历时岩样的孔隙度和细观形貌特征,并运用盒维法对岩样的非线性裂纹特征进行了定量化描述。结果表明：浸矿侵蚀作用对离子型稀土矿底板基岩力学性质的影响主要表现在前150 d,破坏形式由贯穿破坏转变为贯穿破坏与片状剥落并存;浸矿母液侵蚀作用下,基岩力学特性呈现先大幅减小后大幅回升,其后在小范围波动现象,浸矿约60 d对基岩力学特性的影响程度最大;浸矿母液侵蚀造成基岩内小孔隙增长,导致表面出现腐蚀及孔洞现象;浸矿时间不同将造成岩石不同的微观结构变化。  相似文献   

基岩岛屿地下水数值模拟发展研究现状          下载免费PDF全文

王大庆  许颢砾  邓正栋  丁志斌  倪博睿  周泽林  赵小兰 《中国地质调查》2014,6(3):68-74

基岩岛屿占我国岛屿的90%以上,且岛屿上的淡水资源十分珍贵。目前,岛屿上的供水(船运、雨水收集、海水淡化等)存在成本高、设备易坏等缺点。因此,岛屿的地下水资源无疑是优质、可靠、稳定的供水源。为了更好地开发基岩岛屿地下水资源,认为针对基岩岛屿地下水模拟,从地下水理论、地下水模拟的国内外研究现状和模拟模型等方面进行了综述。总结认为: 基岩岛屿的地下水多以“淡水蘑菇体”的形式储存,有别于沙质岛屿; 模拟模型应概化为横向各项同性的达西流或非达西流,或二者的耦合模型,并归纳了相应的地下水流运动方程; 基岩岛屿地下水模拟模型应分为孔隙型、裂隙型和孔隙-裂隙型3种类型; 在岛屿边界设定上,基岩海岸应设为隔水边界,沙质海岸应设为定水头边界。综述研究认为: 基岩岛屿地下水模拟模型应尽可能精细、完整、精准地刻画基岩岛屿的地质地貌,设置完整的岛屿补径排项; 模拟时,应准确对应基岩岛屿的地下水类型,选准模拟方法与模拟软件; 模型验证工作也是十分重要,需多次与岛屿水量均衡,且与实测水量和水位作对照,不断地修善模型。以上综述成果为我国今后开展基岩岛屿地下水数据模拟提供了理论依据。  相似文献   

A REVIEW OF LOW-TEMPERATURE THERMOCHRONOLOGY ON BEDROCK AND DETRITUS FROM RIVERS AROUND THE TIBETAN PLATEAU          下载免费PDF全文

LIN Xu  LIU Jing  PENG Bao-fa  LI Chang-an  WU Quan-yuan 《地震地质》2017,39(6):1091-1110

The large river systems are the major transfer of continental masses to the ocean and basin, playing significant roles in global geochemical cycles. The Tibetan plateau is the birthplace of many huge rivers flowing through eastern and southern Asia, in which the fluvial deposits kept not only closely relate to the geological evolution information from the source areas, but also record the river itself building process. The low-temperature thermochronology method of detrital minerals (zircon and apatite, etc.) can be used to constrain the river's source areas, establishing its source-sink system. It can also combine regional tectonic deformation analysis to determine the potential source region of the river and the formation time of the plateau geomorphology, which is a focused issue in recent years. In this study, we have summarized the research results from the large rivers in the Tibetan plateau in recent years, suggesting that the low-temperature thermochronology analysis of the detrital minerals should be focused on the river's key locations in the upstream, midstream and downstream, respectively, combining the small tributaries analysis which can give a more detailed thermal evolution history in the whole drainage basin. On the conditions of the bedrock, it is shown that in the same river's different place we should use the same low-temperature thermochronology, while in different river's places we should take several low-temperature thermochronology methods (apatite and zircon, etc.)at a same position, so we get a complete time series related to the river incision. Combining the valley bedrock and detrital river minerals with the low-temperature thermalchronology on the Tibetan plateau, together with the chronology, structure analysis and other sedimentary studies, we can obtain detailed structures and river's evolution processes.  相似文献