新西兰韦恩加瓦河砾石的沉积环境、阶地断错和8级地震重复率          下载免费PDF全文

程绍平 《地震地质》1988,10(1):39

新西兰北岛南部韦恩加瓦河地区在晚更新世冰缘气候控制下,由沉积和侵蚀的交替作用形成较高较老的阶地。较低较新的阶地是在全新世中期以来的现代正常气候条件下形成的。这些阶地分别被怀拉拉帕断层水平错动297米、100米,57米和28米。距今10000年以来,怀拉拉帕断层的平均水平滑动速度为10毫米/年。1855年8级地震的重复率为1500年  相似文献   

Measurement of bedload gravel transport: The calibration of a self-generated noise system     

H. L. Rouse 《地球表面变化过程与地形》1994,19(9):789-800

Self-generated noise (SGN) is a passive acoustic technique for the measurement of bedload transport through the acoustic detection of intergranular collisions using a submerged hydrophone system. SGN is of interest because of the possibilities it offers to the measurement of transport parameters at the frequencies of turbulent or oscillating current scales. This paper describes the background of the technique, and reports the results from laboratory experiments on the relationship between SGN and the absolute transport rate.  相似文献   

论潜蚀和块体运动在河流袭夺中的主导作用─—河流袭夺作用机制与实例剖析     

许仲路 《地理研究》1995,14(2):41-48

区域地壳隆升或地槽回返褶皱成山后,斜坡上出现平行状水系.随着河流的溯源侵蚀,分水岭后退,水系适应内外力条件演变成不同型式,并发生河流袭夺.导致河流发生袭夺的决定性原因,一是袭夺河的快速溯源侵蚀,二是位于分水岭反面的高位被袭夺河的河床下与古分水岭下潜蚀作用和块体运动.湔江支流之一海子河在早更新世末依次袭夺了古花园沟河(已消失)和古银厂沟河(原石亭江右支流)等河.  相似文献   

Photo-sieving: A method for grain-size analysis of coarse-grained,unconsolidated bedding surfaces     

Hillert Ibbeken  Ruprecht Schleyer 《地球表面变化过程与地形》1986,11(1):59-77

The photo-sieving method enables the grain-size analysis of particles > 10 mm from unconsolidated openwork bedding surfaces. The accuracy is equal to the machine-sieving method. The sediment surface is photographed in the field using a camera stand. The enlarged print is digitized for computer processing by tracing the outlines of the pebbles. From the size and shape of the projection area of the individual pebble images the computer determines the ellipsoids of revolution, classifies these ellipsoids, and establishes their grain-size distribution in percentage by weight. Thus photo-sieving differs distinctly from point-counting techniques. With the aid of photo-sieving, the surface grain-size distributions of larger sedimentary systems may be regularly mapped. Alluvial fans, braided rivers, both onshore and offshore coasts or areas of relict sediments and manganese nodules are suitable for this method.  相似文献   

The occurrence on carboniferous coal of anthropogenic origin in the contemporaneous Vistula river sediments near Cracow (Southern Poland)     

J. Rutkowski 《地球表面变化过程与地形》1986,11(3):321-326

Carboniferous pit coal is the most important anthropogenic component of the contemporaneous Vistula river gravels and sands with individual fractions containing from 10 to 98 per cent coal fragments. Coal concentration is connected with differences in the bulk density between coal and other gravel components. The lower sediments date from the first half of the nineteenth century when the coal began to appear in large quantities in the Vistula channel. The presence of coal is also an indicator of the depth of channel sediment reworking during floods in the nineteenth and twentieth centuries.  相似文献   

Typology of segregated (armoured/paved) surfaces: Some comments     

Basil Gomez 《地球表面变化过程与地形》1984,9(1):19-24

A review of the characteristics of segregated surfaces and consideration of the origins of the terms armoured and paved suggests that the two terms are interchangeable, and that neither term is specifically associated with a particular segregation process. The dichotomy between segregated surfaces which are formed in channels in which the entire range of bed material is mobile under the prevailing hydrologic regime, and segregated surfaces which are intrinsically stable, forms the basis of an elementary distinction between different types of segregated surface. It is suggested that the term stable armour or stable pavement be applied to those cases where the segregated surface is considered to be inactive under the prevailing hydrologic regime, and that the term unstable armour or unstable pavement be applied to cases where the segregated surface experiences periodic mobilization.  相似文献   

Characteristics of diamondiferous Plio-Pleistocene littoral deposits within the palaeo-Orange River mouth, Namibia     

R.I. Spaggiari  B.J. Bluck  J.D. Ward 《Ore Geology Reviews》2006,28(4):475

The Orange River, the principal conduit transporting diamonds from hinterland sources to the Namibian coast in post-Cretaceous times, is characterised by an extreme wave dominated delta that has given rise to a progression of coarse rudaceous littoral deposits preserved onshore for > 150 km north of the mouth. Under the long-lived, prevailing vigorous wave, wind and northward longshore drift regimes, the Orange River outfall has been reworked into, amongst others, a series of economically viable, diamondiferous Plio-Pleistocene onshore gravel beach deposits. These placers comprise spits and barrier beaches in the proximal reach within the palaeo-Orange River mouth that, after ca. 5 km northwards, merge into extensive but narrow linear beaches that, in turn after ca. 70 km, give way to pocket beaches. Gravel and diamond size decreases northwards away from the ancestral Orange River mouth. The linear and pocket beach types have considerably higher diamond content but lower average diamond stone size than the two proximal units that are characterised by low diamond grade but comparatively large average diamond size. Given the risk of delineating low grade alluvial diamond deposits accurately, we present here sedimentological reconstructions of the subtidal, intertidal and supra-tidal facies that constitute the spit and barrier beach sequences, based largely on face mapping of exploration trenches and open-cast, mine cuts, as well as the results of large tonnage, sampling campaigns. Diamond distribution is also linked convincingly to basic littoral processes that were operational within the palaeo-Orange River mouth during the complex transgression that gave rise to the + 30 m package in Plio-Pleistocene times. In both the spit and barrier beach settings, the intertidal deposits prove to be the most promising targets whereas the subtidal sediments are the least economic. The constant raking associated with coarse, cobble–boulder-sized gravel foreshore deposits in an energetic micro-tidal wave regime increased the average diamond stone size in the intertidal deposits to 1 to 2 carats per stone (cts/stn), but the lack of fixed trapsites (no competent footwall within the palaeo-Orange River mouth at that level) prohibited the accumulation of substantially enriched diamondiferous gravels. Consequently, grades of only 1.5 to 6 carats per 100 tons (cpht) are realised. The highest grades (2 to 6 cpht) are found in the landward-facing, intertidal beach deposits on the spits where gentle reworking in that sheltered environment had somewhat enriched and preserved the diamond content. Significantly, the low average stone size of ca. 0.5 cts/stn in this lower energy setting probably reflects that of the general diamond population available at that time. In contrast, the sand-rich subtidal deposits in the spit sequence return the lowest grades (0.1 to 0.5 cpht), similar to those in the slightly younger, subtidal transgressive boulder lags of the barrier beaches. However, the stone size in the spit subtidal sediments is also low (0.1 to 0.5 cts/stn) due to the highly mobile, fine-grained character of those deposits, whereas that in the subtidal transgressive lag is large (2 to 3 cts/stn) as a result of the local, semi-permanent turbulence associated with the boulder-sized clasts in these gravel sheets. Diamond distribution is therefore also influenced by littoral facies and associated beach types, in addition to the spatial and temporal parameters that have already been documented for the onshore marine placers of the southern Namibian coast.  相似文献   

印度尼西亚苏拉威西岛砾岩型红土镍矿床地质特征及成因     

程立群  刘剑波  任学义  吴国学 《世界地质》2015,34(1):120-126

红土型镍矿是基性、超基性岩在热带、亚热带地区常年高温、多雨的环境下,经过风化--淋滤--沉积富集而成。基性、超基性岩是此类矿床的成矿母岩。因此,以往针对红土型镍矿的找矿勘探首先是寻找基性、超基性岩。笔者近期在印度尼西亚苏拉威西省Kolaka县发现了一种新型红土镍矿床,该矿床成矿母岩并非是基性、超基性岩,而是砾石成分以超基性岩为主的一套砾岩。为了区分传统意义上由基性、超基性岩风化淋滤形成的红土型镍矿,笔者将其称为砾岩型红土镍矿。该矿床的结构分带由上往下可分为:腐植土层、红土层、强风化砾岩层、半风化砾岩层、砾岩层,镍矿体主要分布于半风化砾岩层中。初步认为矿床是由砾岩经过风化--水解-淋滤-沉淀富集等作用形成的。  相似文献   

Gravel excavation and geomorphic evolution of the mining affected river in the upstream reach of the Yangtze River,China     

Yi Xiao  Wenjie Li  Shengfa Yang 《国际泥沙研究》2022,37(2):272-286

As economic development upstream in the Yangtze River basin has progressed in recent decades,the demand for sediment has rapidly increased and contributed to an expansion in sediment excavation that may affect the river’s stability and navigation safety.In the current study,the distribution of gravel mining in the upstream reach of the Yangtze River was investigated using field measurements obtained from2008 to 2017.An experimental investigation was then done to analyze the bed load behavior in ...  相似文献   

The Middle Pleistocene terraces of the central Waveney valley,Earsham, south Norfolk,UK     

Philippa Holmes  James Rose  Jonathan R. Lee  Rene Barendregt  Ian Candy  James B. Riding  Mark Lewis 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(1):70-88

Although substantial work has been done on the pre-glacial terraces of East Anglia, very little systematic work has been done to understand the origin of river terraces in East Anglia that have formed since ice last covered the region. This paper records the results of studies of exposures and borehole records in ‘classical’ Quaternary terrace landforms that are considered to have formed since the Anglian (MIS 12) Glaciation, in the middle Waveney Valley. These features have been examined in terms of their morphological and sedimentological properties, in order to provide a detailed record of their form and composition, understand their processes of formation, and identify their stratigraphical status. The results show that the main body of the highest terrace (Homersfield Terrace, Terrace 3) is not composed of river sediments, but of shallow marine sediments, and is a remnant of early Middle Pleistocene Wroxham Crag. River sediments, in the form of Anglian age (MIS 12) glaciofluvial Aldeby Sands and Gravels also exist in the area as a channel fill, cut through the Wroxham Crag, and reflect outwash erosion and sedimentation from a relatively proximal ice margin to the west. The results mean that the interpretations previously presented for the terrace landforms of the middle Waveney valley are not applicable. The issue of why the terrace stratigraphy, hitherto identified in East Anglia cannot be related to that for the River Thames to the south and the rivers of Midland England to the west, still requires further research.  相似文献