SMALL SCALE MORPHODYNAMICAL MODELLING

1 INTRODUCTIONIn the vicinity of smictUres the local velocity of the flow increases, and three-dimensional effects occur,leading to higher shear stresses at the bottom. In case of a movable bed, sediment transport is enhanced.Erosion leads to a scour which can be dangerous for the stability of the strUctUre. The Predichon of a.maximum scour dePth is of vital imPortance for civil engineering. Generally, the maximum scour dePth iseshmated using an emPincal formula (Jolinson, l995). An a…     

Efficiency of Severe Recorded Rainstorms over Maharashtra State

12 severe rainstorms have been experienced by different meteorological sub-divisions of Maharashtra State during the last 100-year period from 1891-1990. For each of the rainstorms efficiency factors (i.e. P/ M ratios) were worked out for maximum one-day duration and for three standard areas of 1000, 5000, and 10,000 km2. Comparison of these ratios with the past has shown that the most efficient rainstorm over Maharashtra was the rainstorm of June, 1908 over the Vidarbha region whose full DAD data as well as isohyetal pattern have been given.     

Iberan黄铁矿带的Tharsis矿山硫化物矿床的沉积构造

Ｔｈａｒｓｉｓ矿区是Ｉｂｅｒｉａｎ黄铁矿带中最大的成矿中心之一。它包括了Ｉｂｅｒｉａｎ半岛西南的广大地区。对Ｔｈａｒｓｉｓ矿山Ｆｉｌｏ Ｎｏｔｖｔｅ硫化物矿床中的沉积构造进行了野外和显微镜下的研究。以内部构造为依据，把硫化矿床分为两类：（１）致密块状黄铁矿矿石；（２）具有沉积构造的黄铁矿石。在后一种类型中，已观察到若干沉积构造，例如：序粒层理、平行纹理、交错纹理及滑塌构造。     

The optimum source－time function for generating finite－difference synthetic seismograms

Ｔｈｅｏｐｔｉｍｕｍｓｏｕｒｃｅ－ｔｉｍｅｆｕｎｃｔｉｏｎｆｏｒｇｅｎｅｒａｔｉｎｇｆｉｎｉｔｅ－ｄｉｆｆｅｒｅｎｃｅｓｙｎｔｈｅｔｉｃｓｅｉｓｍｏｇｒａｍｓＡｂｄｏｌｒａｈｉｍＪＡＶＡＨＥＲＩＡＮ（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ｔｈｅ...     

沉积盆地的动力学模型

对沉积盆地的形成和演化机制进行详细分析,必须最大限度地利用已知信息建立模型。反映岩石圈边界的动学模型提供了最直观的描述。本文阐述了当建立这样的模型时所出现的问题。盆地模拟中的一个重要问题是沉积作用和剥蚀作用的数学模拟。当描述它们时,应当区别两种作用。在所考虑的系统中的侵蚀作用和再沉积作用,以及外部附加物质的供给。     

反射率的人为变化和地球上的气候

人类对地球环境的改变,从地理范围来说是广泛的,而且几乎包括了自然界的各个方面。例如,人们所饮的水、所吃的食物、所呼吸的空气以及所居住的小环境,从全球范围来说,都被人类改变了。在过去二十年中,人们对当前人类对环境的影响表示了关切,认为这种影响可能已经大到足以引起气候变化,而这种变化反过来又会在农业和其它方面产生显著后果。对当今和未来的气候有一种广泛流传的成见,认为只有现代技术才影响环境,这使多数研究     

安大略提敏斯地区金矿床的地质与演化

提敏斯地区金矿床和两个主要层控富碳酸盐岩段在空间与时间上密切共生,且与石英—长石斑岩有关。主要矿化类型为火山同生成因和变质成因两种。火山同生矿体包括层状石英一铁白云石“脉”、黄铁矿化碳酸盐岩、燧石—碳酸盐—凝灰岩及与火山口有关的后成角砾岩和细脉带中的矿体。变质矿体由产于各期区域变形和变质作用阶段发育的膨胀带中的石英—碳酸盐裂隙充填物组成,根据其特征划分为后生的。有证据表明,海底长英质火山作用及喷气热液活动阶段,在洋底及火山口地区,发生了金的初始同生富集作用,以后金又在区域变形,绿片岩相变质阶段进一步富集到石英—碳酸盐网脉中。太古代火山岩区的碳酸盐岩层尽管很薄(几百米),仍可代表能使金搬运和富集的,强烈热液活动期,这类“矿脉”可用以帮助找寻具有经济价值矿化的古火山口和有利构造带的位置。     

Chemical characterization of porewaters in an intertidal mudflat of the Seine estuary: relationship to erosion-deposition cycles

A seasonal field study was carried out in the Seine estuary to determine the chemistry of sediment porewaters using the 'peeper' technique and changes in the elevation of the mudflats using the 'Altus' technique. This approach allowed us to evaluate the release of nutrients and to link these releases to the sediment hydrodynamics. Our results show that nutrient and organic matter cycling in a Seine estuary mudflat exhibits a seasonal behaviour, which is mainly influenced by variations in hydrodynamics. Sediments, rich organic matter, were input during floods and they were mineralized during summer and autumn, releasing nutrients and dissolved organic carbon into the sediment porewaters. The nutrient release, including ammonium, is mainly linked to the mineralization of organic matter, while the release of phosphate is delayed. The delay could be the result of phosphate association with organic matter and/or its co-precipitation with calcium and iron.