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1.
A range of evidence from the Lachlan valley in the southeast Australian highlands is consistent with Neogene isostatic rebound in response to denudational unloading. This evidence is found along the inland edge of the highlands in the transition zone between the highlands proper and the Lachlan's inland alluviated valley and the intracratonic Murray Basin. The amounts and rates of uplift indicated by offsets of suballuvium bedrock profiles and the long profiles of Tertiary valley-filling basalts are consistent with modelling of denudational rebound using known rates of highland denudation and basinal sedimentation, and reasonable crustal properties. The modelling shows that weak to moderately strong strong lithosphere (effective elastic thickness, Te = 1-25 km) and strong lithosphere (Te = 100 km) are all consistent with the observed amounts of rebound. Strong lithosphere must be broken, however, to be consistent with the field data. Even in the Australian setting, which is characterized by very low rates of denudation, isostatic rebound in response to denudational unloading must be a significant factor in maintaining highland elevation and must be incorporated in models of long-term landscape evolution. It would be expected that denudational isostatic rebound would be an even more significant component of long-term landscape evolution in areas of higher denudation rates.  相似文献   

2.
With enhanced rates of sea‐level rise predicted for the next century, the upstream extent of sea‐level influence across coastal plains is a topic of public importance. Australian coastal rivers provide a testing ground for exploring this issue because the area is tectonically stable, was not glaciated, and experienced a Holocene highstand between 7.4 and 2 ka of up to 1.5 m above Australian Height Datum (AHD). In the Shoalhaven River of New South Wales, investigation of a confined bedrock reach at Wogamia, 32 km inland, has identified a unit of dark, cohesive silt and sand with marine diatoms, shell fragments, and enhanced pyrite content, interpreted as estuarine. The unit is up to 13 m thick, thickens downstream, and is overlain by fluvial channel and floodplain deposits. The estuarine unit on‐laps a remnant Pleistocene terrace and extends to approximately +2.2 m AHD. Optically stimulated luminescence (OSL) and radiocarbon ages suggest that estuarine deposition commenced prior to 7.8 ka cal bp , predating the highstand by ~ 500 years, and that marine influence in the area continued to 5.3 ± 0.7 ka. During this period, a delta probably persisted at Wogamia, where a narrow upstream reach opens out, and subsequently advanced to fill the broad Shoalhaven coastal embayment. Although the effect of sea‐level rise depends on many factors, the results suggest that, during a highstand at or above present sea level, a strong marine influence may extend for tens of kilometres inland and penetrate confined bedrock reaches landward of coastal embayments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

3.
The results of palaeomagnetic surveys of Mesozoic and Tertiary rocks from Gondwanaland can be reconciled with the results of modelling the evolution of oceanic floors from analyses of marine magnetic anomalies. Previous inconsistencies were mainly due to errors apparent in the Australian Cenozoic palaeomagnetic data. An alternative Tertiary apparent polar wander path (APWP) has been constructed from an analysis of all published laterite and weathered profile data. Palaeomagnetic results for Africa, Antarctica, Australia, India, Madagascar and South America are compared for rotations corresponding to marine magnetic anomalies 16, 22, 28, 34 and M1 and for “fit”. India has been selected as the reference continent since it provides the most detailed APWP having drifted about 50° of latitude since breakup.  相似文献   

4.
Likangala River catchment in Zomba District of Southern Malawi is important for water resources, agriculture and provides many ecosystem services. Provisioning ecosystem services accrued by the populations within the catchment include water, fish, medicinal plants and timber among others. In spite of its importance, the River catchment is under threat from anthropogenic activities and land use change. This paper studies land uses and land cover change in the catchment and how the changes have impacted on the ecosystem services. Landsat 5 and 8 images (1984, 1994, 2005 and 2013) were used to map land cover change and subsequent inventorying of provisioning ecosystem services. Participatory Geographic Information Systems and Focus group discussions were conducted to identify provisioning ecosystems services that communities benefit from the catchment and indicate these on the map.Post classification comparisons indicate that since 1984, there has been a decline in woodlands from 135.3 km2 in 1984 to 15.5 km2 in 2013 while urban areas increased from 9.8 km2 to 23.8 km2 in 2013. Communities indicated that provisioning ecosystems services such as forest products, wild animals and fruits and medicinal plants have been declining over the years. In addition, evidence of catchment degradation through waste disposal, illegal sand mining, deforestation and farming on marginal lands were observed. Population growth, urbanization and demand for agricultural lands have contributed to this land use and land cover change. The study suggests addressing catchment degradation through integrated method where an ecosystems approach is used. Thus, both the proximate and underlying driving factors of land-use and land cover change need to be addressed in order to sustainably reduce ecosystem degradation.  相似文献   

5.
SWAT模型在斯里兰卡河流径流预测中的运用   总被引：1，自引：0，他引：1  
本文运用SWAT模型和新安江模型对斯里兰卡卡鲁河流域上游地区日径流进行了预测.卡鲁河是斯里兰卡的第二大河,由于流域的降雨量很大,上游地区河流沿峡谷流下,中下游平原地区河床平坦.卡鲁河流域的洪水变的很正常.应用SWAT模型来对卡鲁河的日径流量进行预测,并同应用新安江模型所得到的结果做对比.研究表明,新安江模型要比SWAT (分布式水文模型)模型在卡鲁河日径流量预测上稍微好一些.实际上,或许数据质量不高或不恰当是部分原因,因为SWAT的输出成果严格取决于其输入的数据质量.此外,在斯里兰卡,许多人的日常用水是靠井水.当把流域看作一个整体,通常都是一个很大的范围,那样的话就不可能详尽的记录所有各个小规模的水利用,例如:小灌溉、小规模的家畜管理和工业水利用.这些水利用累积起来或许就很可观.这些数据的缺失对分布式水文模型在水平衡的应用有着独特的影响.但是概念水文模型(如新安江模型)可以根据实际情况在校正中调节它的参数,因为这些参数并没有实质的物理含义.因此,在流域特征和模型输入数据有限或不完整的情况下,概念水文模型比分布式水文模型更具优势.  相似文献   

6.
The Clarence River on Australia's east coast has an anomalous drainage pattern. Its right-bank tributaries are markedly barbed, suggesting reversal, whereas Tertiary volcanism has disrupted its left-bank drainage. The southeast-flowing Clarence is closely aligned with the northwest-flowing Condamine River just across the Continental Divide. The Condamine-Clarence alignment is continued by a large southern tributary, the Orara River, which flows northwest, away from the sea, to meet the southeast-flowing Clarence. A broad river with a quite different character flows east from near the Orara-Clarence junction to the sea. This is essentially an overflow channel. This series of aligned streams, the Condamine-Clarence-Orara, represents the remains of an earlier northwest-flowing stream that extended the full length of the Clarence-Moreton Basin, an eastern extension of the Great Artesian Basin. During the Jurassic, the Clarence-Moreton Basin was filled with sediments from the surrounding highlands, including those to the east of the present coastline. Continental rifting from Late Cretaceous times onwards led to the opening of the Tasman Sea, causing the reversal and beheading of the original northwest-flowing streams and the formation of the Great Escarpment. The evolution of the Clarence River does not fit into most conventional geomorphic paradigms such as cycles, climatic geomorphology or steady-state landforms. It is the result of a succession of unique events on a very long timescale, and as such is a classic example of evolutionary geomorphology.  相似文献   

7.
~~Geomorphologic evidence of phased uplift of the northeastern Qinghai-Tibet Plateau since 14 million years ago~~  相似文献   

8.
福建龙海-漳浦沿海活动断裂与火山活动   总被引：5，自引：0，他引：5       下载免费PDF全文
文中通过福建龙海—漳浦沿海主要断裂的玄武岩喷发,断裂两侧第四纪以来形成的地貌面和海相地层的差异性变化等特点,分析了断裂晚第四纪以来的活动特征及断裂构造的组合特征。研究结果表明:龙海流会-漳浦将军澳断裂在新近纪—第四纪晚更新世早期 (N2—Q3p)有玄武岩多次循其喷发,晚更新世(Q3p)活动明显,属晚更新世活动断裂;龙海港尾 -漳浦湖西断裂亦属晚更新世(Q3p)活动断裂,断裂下盘上升速率为 1. 11mm/a。这 2条断裂将本区切割形成港尾地堑、南太武山地垒、流会-将军澳以东海域地堑  相似文献   

9.
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10.
There is increasing evidence that shore platforms and other elements of rock coasts may be inherited, at least in part, from interglacial stages when sea level was similar to today's. Most of this evidence, which includes ancient beaches and datable terrestrial deposits, has been obtained from areas of resistant, slowly eroding rock, where the platforms often appear to be much too wide to have developed since the sea reached its present level. It is much more dif?cult to demonstrate that inheritance has occurred in areas of weaker rock, which generally lack any datable material. The coast of western Galicia in northwestern Spain has shore platforms in igneous and metamorphic rocks that were deeply weathered during the Tertiary. These platforms are closely associated with ancient beaches from the last interglacial stage, and associated periglacial and ?uvio‐nival deposits that covered and fossilized most of the Eemian platforms and cliffs during the late middle and late Weichselian glacial stage. The sedimentary processes and the thickness and facies of the sediments were determined by the height, aspect and gradient of the coastal mountains, and their distance from the coast. Radiocarbon dating, sedimentary analysis and platform morphology indicate that the shore platforms of Galicia have been inherited from at least the last interglacial stage. They were fossilized in places beneath thick Weichselian deposits and then exhumed during the Holocene transgression. The abundant evidence for inheritance in Galicia has important implications for other coasts in fairly weak rocks where such evidence is generally lacking. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

11.
This paper presents a methodology for hydrograph separation in mountain watersheds, which aims at identifying flow sources among ungauged headwater sub‐catchments through a combination of observed streamflow and data on natural tracers including isotope and dissolved solids. Daily summer and bi‐daily spring season water samples obtained at the outlet of the Juncal River Basin in the Andes of Central Chile were analysed for all major ions as well as stable water isotopes, δ18O and δD. Additionally, various samples from rain, snow, surface streams and exfiltrating subsurface water (springs) were sampled throughout the catchment. A principal component analysis was performed in order to address cross‐correlation in the tracer dataset, reduce the dimensionality of the problem and uncover patterns of variability. Potential sources were identified in a two‐component U‐space that explains 94% of the observed tracer variability at the catchment outlet. Hydrograph separation was performed through an Informative‐Bayesian model. Our results indicate that the Juncal Norte Glacier headwater sub‐catchment contributed at least 50% of summer flows at the Juncal River Basin outlet during the 2011–2012 water year (a hydrologically dry period in the Region), even though it accounts for only 27% of the basin area. Our study confirms the value of combining solute and isotope information for estimating source contributions in complex hydrologic systems, and provides insights regarding experimental design in high‐elevation semi‐arid catchments. The findings of this study can be useful for evaluating modelling studies of the hydrological consequences of the rapid decrease in glacier cover observed in this region, by providing insights into the origin of river water in basins with little hydrometeorological information. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

12.
Stream nitrate levels in a small catchment of mixed land use (the Slapton Wood catchment) have been studied since September 1970; a record of this length is possibly unique in the United Kingdom for such a small basin (94 ha). A sustained increase in nitrate concentration has been observed during the study period. In addition to this long-term trend, short-term changes in nitrate concentrations relate to stream discharge levels and to seasonal variations. Multivariate statistical analysis has been used to quantify these trends and to identify those factors controlling the production and loss of nitrate from the catchment system. The main period of nitrate removal occurs in winter when high concentrations coincide with the main period of throughflow generation. The influence of climatic variability is illustrated by reference to the 1975/76 drought and post-drought period.  相似文献   

13.
Combining field reconstruction and landscape evolution modelling can be useful to investigate the relative role of different drivers on catchment response. The Geren Catchment (~45 km2) in western Turkey is suitable for such a study, as it has been influenced by uplift, climate change and lava damming. Four Middle Pleistocene lava flows (40Ar/39Ar‐ dated from 310 to 175 ka) filled and dammed the Gediz River at the Gediz–Geren confluence, resulting in base‐level fluctuations of the otherwise uplift‐driven incising river. Field reconstruction and luminescence dating suggest fluvial terraces in the Geren Catchment are capped by Middle Pleistocene aggradational fills. This showed that incision of the Geren trunk stream has been delayed until the end of MIS 5. Subsequently, the catchment has responded to base‐level lowering since MIS 4 by 30 m of stepped net incision. Field reconstruction left us with uncertainty on the main drivers of terrace formation. Therefore, we used landscape evolution modelling to investigate catchment response to three scenarios of base‐level change: (i) uplift with climate change (rainfall and vegetation based on arboreal pollen); (ii) uplift, climate change and short‐lived damming events; (iii) uplift, climate and long‐lived damming events. Outputs were evaluated for erosion–aggradation evolution in trunk streams at two different distances from the catchment outlet. Climate influences erosion–aggradation activity in the catchment, although internal feedbacks influence timing and magnitude. Furthermore, lava damming events partly control if and where these climate‐driven aggradations occur. Damming thus leaves a legacy on current landscape evolution. Catchment response to long‐duration damming events corresponds best with field reconstruction and dating. The combination of climate and base level explains a significant part of the landscape evolution history of the Geren Catchment. By combining model results with fieldwork, additional conclusions on landscape evolution could be drawn. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
Quantitative evaluation of the effect of climate variability and human activities on runoff is of great importance for water resources planning and management in terms of maintaining the ecosystem integrity and sustaining the society development. In this paper, hydro‐climatic data from four catchments (i.e. Luanhe River catchment, Chaohe River catchment, Hutuo River catchment and Zhanghe River catchment) in the Haihe River basin from 1957 to 2000 were used to quantitatively attribute the hydrological response (i.e. runoff) to climate change and human activities separately. To separate the attributes, the temporal trends of annual precipitation, potential evapotranspiration (PET) and runoff during 1957–2000 were first explored by the Mann–Kendall test. Despite that only Hutuo River catchment was dominated by a significant negative trend in annual precipitation, all four catchments presented significant negative trend in annual runoff varying from ?0.859 (Chaohe River) to ?1.996 mm a?1 (Zhanghe River). Change points in 1977 and 1979 are detected by precipitation–runoff double cumulative curves method and Pettitt's test for Zhanghe River and the other three rivers, respectively, and are adopted to divide data set into two study periods as the pre‐change period and post‐change period. Three methods including hydrological model method, hydrological sensitivity analysis method and climate elasticity method were calibrated with the hydro‐climatic data during the pre‐change period. Then, hydrological runoff response to climate variability and human activities was quantitatively evaluated with the help of the three methods and based on the assumption that climate and human activities are the only drivers for streamflow and are independent of each other. Similar estimates of anthropogenic and climatic effects on runoff for catchments considered can be obtained from the three methods. We found that human activities were the main driving factors for the decline in annual runoff in Luanhe River catchment, Chaohe River catchment and Zhanghe River catchment, accounting for over 50% of runoff reduction. However, climate variability should be responsible for the decrease in annual runoff in the Hutuo River catchment. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

15.
Continuous wavelet analyses of hourly time series of air temperature, stream discharge, and precipitation are used to compare the seasonal and inter‐annual variability in hydrological regimes of the two principal streams feeding Bow Lake, Banff National Park, Alberta: the glacial stream draining the Wapta Icefields, and the snowmelt‐fed Bow River. The goal is to understand how water sources and flow routing differ between the two catchments. Wavelet spectra and cross‐wavelet spectra were determined for air temperature and discharge from the two streams for summers (June–September) 1997–2000, and for rainfall and discharge for the summers of 1999 and 2000. The diurnal signal of the glacial runoff was orders of magnitude higher in 1998 than in other years, indicating that significant ice exposure and the development of channelized glacial drainage occurred as a result of the 1997–98 El Niño conditions. Early retreat of the snowpack in 1997 and 1998 led to a significant summer‐long input of melt runoff from a small area of ice cover in the Bow River catchment; but such inputs were not apparent in 1999 and 2000, when snow cover was more extensive. Rainfall had a stronger influence on runoff and followed quicker flow paths in the Bow River catchment than in the glacial catchment. Snowpack thickness and catchment size were the primary controls on the phase relationship between temperature and discharge at diurnal time scales. Wavelet analysis is a fast and effective means to characterize runoff, temperature, and precipitation regimes and their interrelationships and inter‐annual variability. The technique is effective at identifying inter‐annual and seasonal changes in the relative contributions of different water sources to runoff, and changes in the time required for routing of diurnal meltwater pulses through a catchment. However, it is less effective at identifying changes/differences in the type of the flow routing (e.g. overland flow versus through flow) between or within catchments. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

16.
Diel fluctuations in discharge not associated with precipitation have been identified in streams around the world and attributed to evapotranspiration of both hillslope and near-stream vegetation. Several mechanisms have been hypothesized to explain the generation of these signals, but a consensus has not been reached. In order to investigate the origin of these daily discharge fluctuations, we measured discharge and groundwater levels in a 43-ha headwater catchment near Cullowhee, NC, USA. The catchment was logged at least twice in the past 120 years, allowing the evergreen invasive Chinese privet (Ligustrum sinense) to become established in near-stream areas. Stream discharge was measured at the outlet, and stream stage and near-stream groundwater level were measured at a second location higher in the catchment. Daily fluctuations in discharge were quantified and found to increase in magnitude with daily mean discharge. Interestingly, daily discharge fluctuations were observed in the dormant season, and our analysis suggests that their magnitude may increase more with discharge than during the growing season. Two previously hypothesized processes may explain our observations. A decrease in signal dampening due to faster transmission of an evapotranspiration signal at elevated flows may explain the increased diel fluctuation magnitude at higher flows. Additionally, because the primary active vegetation in our catchment in the dormant season is in near-stream areas, we suggest that this indicates most of the evapotranspiration signal in stream discharge is derived from near-stream vegetation, not hillslopes.  相似文献   

17.
Identifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho‐structural patterns might plausibly be explained by processes related to late Mesozoic to early Cenozoic rifting and/or differential erosion induced by Cenozoic epeirogenic uplift. The proportional contribution of each process can vary from continent to continent, and potentially even within the same passive margin. In the passive margin setting of the southeast Australian highlands the documented occurrence of neotectonic deformation is rare, and accordingly its role in landscape evolution is difficult to establish. The results of investigations within the Lapstone Structural Complex, which forms the eastern range front of the Blue Mountains Plateau, provide evidence for two periods of Cenozoic neotectonic uplift in this part of the highlands. The first, demonstrated by seismic and structural evidence, is suggested to have occurred in the Paleogene, and is thus unrelated to Cretaceous rifting. The second period, demonstrated by evidence from the Kurrajong Fault (presented herein) suggests that uplift occurred in both the Mio‐Pliocene and the Middle Pleistocene. The cumulative Neogene and younger uplift of ~15 m determined for the Kurrajong Fault is less than 10% of the 130 m of total measured throw across the fault. The apparently minor contribution of neotectonism to the current elevation of the Blue Mountains Plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau's eastern edge. This finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south‐eastern highlands, indicating that present‐day topography cannot be directly related to relief generated by Neogene and younger uplift, even from relatively closely‐spaced (< 150 km) structures within the same passive margin. These findings have implications for understanding the spatio‐temporal variability of post‐rift faulting in continental passive margin settings and the evolution of landscapes therein. © Commonwealth of Australia. Earth Surface Processes and Landforms © 2014 John Wiley & Sons, Ltd.  相似文献   

18.
The 8-km2 Morcille catchment, which is a sub-catchment of the 150-km2 Ardières catchment in the Beaujolais region of France, is one of the first sites in Europe where research has been conducted on surface water contamination by pesticides. A consolidated hydrological and chemical dataset has been set up with data collected since 2002 on the Morcille River and since 2011 on the Ardières River. Additional data on the ecotoxicological and ecological impacts of pesticides on aquatic microbial communities and macroinvertebrates has also been recorded in both rivers since 2005. The ‘Site Atelier Ardières-Morcille Dataset’ described here combines rainfall and stream water height measurements at gauged stations with concentrations of two trace elements and nine pesticides (mainly herbicides, fungicides and some of their metabolites) in both the Ardières and Morcille rivers. All contaminant concentration data showed spatial and temporal variability in water quality associated with pesticide use and rainfall patterns. This long-term monitoring framework made it possible to estimate the persistence of two herbicides (diuron and norflurazon) after legislation banning them. It took 4 years for diuron and more than 10 years for norflurazon concentrations to fall below 0.1 μg/L. Concurrent biological data showed a gradient of impacts consistent with chemical anthropogenic pressure, and rapid recovery of phototrophic microbial communities after the diuron ban. Finally, monitoring data on pesticide transport in a grassed strip set on a slope of the Morcille catchment confirmed that vegetative filter strips can effectively reduce diuron fluxes in surface runoff (>80% abatement) and infiltration water (>70% abatement). The full dataset offers a valuable resource for the validation of hydrological models and the development of global approaches to better understand the pressure–transport–exposure–impact chain and aquatic community resilience at the small catchment scale.  相似文献   

19.
INTRODUCTION TheLonghai ZhangpucoastalareaofFujianProvinceliesonthesouthernsideoftheoutletofthe JiulongjiangRiver.Tectonically,itislocatedonthesouthernsegmentoftheChangle Zhao’anfault zone.Previously,alotofseismogeologicresearchworkhasbeencarriedoutinthi…  相似文献   

20.
Our detailed field investigation, paleoseismic trenching, and airborne light detection and ranging (LiDAR)‐derived topographic data provides the first direct evidence for late Quaternary repetitive surface faulting on the northeast‐striking Isurugi fault along the northwestern margin of the Tonami Plain in the Hokuriku region of north‐central Japan. This fault has been interpreted previously by different researchers as both inactive and active, owing to a lack of geologic evidence and a failure to identify fault‐related geomorphic features. Our mapping of LiDAR topography revealed a series of northeast‐trending warped fluvial terraces, about 1.5 km long and 170 m wide, with an age of ≤ 29 ka. We interpreted these geomorphologic features to represent an active pop‐up structure bounded to the southeast by the northwest‐dipping main thrust of the Isurugi fault and to the northwest by a southeast‐dipping backthrust that splays off the main thrust in the shallow subsurface. Paleoseismic trenching across the northwestern part of an elongate terrace exposed a series of southeast‐dipping backthrusts and associated northwest‐verging monoclines. The deformation and depositional age of the strata provide evidence for repetitive surface rupturing on the backthrusts since the latest Pleistocene; the latest of these events occurred in the Holocene between about 4.0 and 0.9 ka. Despite the poor preservation of the surface expression of the Isurugi fault, repetitive scarp‐forming faulting in the late Quaternary and the proximity of the Oyabe River and its tributaries to the fault trace suggest that there may be an extension of the Isurugi fault to the northeast and southwest beneath the Tonami Plain that makes the fault long enough to generate a large earthquake (Mw ≥ 6.8) accompanied by surface rupture.  相似文献   

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