Raindrop‐impact‐induced erosion processes and prediction: a review

Raindrop‐impact‐induced erosion is initiated when detachment of soil particles from the surface of the soil results from an expenditure of raindrop energy. Once detachment by raindrop impact has taken place, particles are transported away from the site of the impact by one or more of the following transport processes: drop splash, raindrop‐induced flow transport, or transport by flow without stimulation by drop impact. These transport processes exhibit varying efficiencies. Particles that fall back to the surface as a result of gravity produce a layer of pre‐detached particles that provides a degree of protection against the detachment of particles from the underlying soil. This, in turn, influences the erodibility of the eroding surface. Good understanding of rainfall erosion processes is necessary if the results of erosion experiments are to be properly interpreted. Current process‐based erosion prediction models do not deal with the issue of temporal variations in erodibility during a rainfall event or variabilities in erodibility associated with spatial changes in dominance of the transport processes that follow detachment by drop impact. Although more complex erosion models may deal with issues like this, their complexity and high data requirement may make them unsuitable for use as general prediction tools. Copyright © 2005 John Wiley & Sons, Ltd.     

Epithermal base-metal vein mineralization in the southern uplands of scotland: Nature and origin of the fluids

The sedimentary sequences of the Southern Uplands of Scotland host numerous lead-zinc-copper-silver vein deposits, the genesis of which has never been adequately explained. Fluid inclusion and stable isotope analysis of vein minerals from these deposits indicate that, for the vein stages studied, the mineralizing fluids were low temperature (< 150°C), high salinity (19 to 30 equiv. wt. % NaCl + CaCl₂) modified meteoric waters. A consideration of the availability of such fluids throughout the geological history of the Southern Uplands suggests a Lower Carboniferous (Dinantian) age for the mineralization.     

Algorithmic techniques of identifying discriminative ocean areas in oceanology problems

A problem of locating and comprehensively investigating ocean areas that exercise a significant influence over the migration dynamics of fishing ranks among important problems of fisheries oceanology. Among all the environment factors affecting various fishery situations, factors should be chosen that are constantly logged on large water areas for a long time comparable with fishery observation time. As described in a number of works, the most suitable information for these purposes is data on the distribution of surface temperature fields. The problem of locating discriminative areas can then be stated as follows. For a particular fishery situation (e.g., for the period of maximum catch in fishing season), temperature values or thermostructural features should be singled out that are suitable to define the situation, using hydrological charts of surface temperature fields. Correlating the feature with the areas where they were observed, we will obtain discriminative areas. The important problem is then to develop techniques and means for algorithmically identifying areas. This relates to a vast volume of information and complex structure. Logical-mathematical models of locating discriminative areas are being developed at the Pacific Oceanological Institute for some years. These models are to be for forecasting fishery situations in the NW Pacific. Techniques for representing isotherm fields in a computer have been developed. Formal operations of comparing the fields have been proposed which aid in distinguishing significant differences in their structure. A software for analyzing isotherm fields has been developed based on threshold logic models. This approach allows one not only to identify discriminative areas for relatively stable fishery situations but also to trace their dynamics. This has been achieved due to multiple-alternative computations and the presentations of data obtained in the form suitable for their interpretation. Some components of proposed models have been used in the system of short-term forecasting saira and sardine fishery in the South-Kuril area.     

Diagenetic alunite in clastic sequences, Kuwait, Arabian Gulf

Diagenetic alunite occurs with calcrete, gypcrete and silcrete deposits in a Mio-Pleistocene clastic sequence at several locations in southern Kuwait, Arabian Gulf. Based on their physical properties and textural characteristics the alunite deposits were divided into (1) chalky quartzitic alunite, (2) chalky quartz-free alunite, (3) hard pink alunitic sandstone. The chalky alunite is composed mainly of hydronium-alunite (H₃O)Al₃(SO₄)₂(OH)₆, while the hard pink alunite is composed solely of well developed potassium alunite KAl₃(SO₄)₂(OH)₆. These minerals resulted from the action of sulphuric acid on clays and K-feldspars in the muddy sandstone and mudstone host sediments. The sulphuric acid is most probably produced by the oxidation of hydrogen sulphide that might have seeped in from the oil fields of this area. Four diagenetic stages are suggested for the genesis of the studied alunites: gypsification, sulphuratization, silicification and alunitization. In oil field areas, the occurrences of alunite would serve as an indicator for the presence at depth of hydrocarbons.     

A surface instability detection apparatus

Summary A surface instability detection apparatus for investigating axial splitting and spalling phenomena in rocks and rock-like materials is described. The apparatus simulates the conditions under which these phenomena occur and allows one to accurately measure them. Experimental results from tests on Berea sandstone are presented where the successive formation of spalling fractures was monitored with an acoustic emission system and the location of the seismic events was mapped. The test results show the potential for benchmark tests in determining the spalling tendency and characteristics of different rocks.     

Pollen representation,source area,and basin size: Toward a unified theory of pollen analysis

The concepts of pollen source area and of production and dispersal biases in pollen representation are quantified by means of a simple theoretical model. Source areas and relative pollen representation are shown to depend on basin size according to functions that describe the amount of pollen remaining airborne at increasing distances from single pollen sources. The form of these functions is determined by physical processes. Standard formulas for elevated sources do not apply, but the integrated form of Sutton's equation for particle dispersal from a ground-level source gives useful approximations applicable to pollen transport over a forest canopy. Simulations using this equation yielded source areas that increased realistically with basin size, showed substantial differences between source areas for pollen grains with different deposition velocities, and predicted that lighter pollen grains should become better represented with increasing basin size. All of these predictions are qualitatively consistent with present knowledge of the characteristics of pollen assemblages in different depositional environments. The model further allows parameters that can be estimated by statistical calibration methods to be predicted from underlying physical quantities. This extension suggests procedures for testing the theory with quantitative data on surface pollen and forest composition. Preliminary results showed reasonable agreement between estimated and predicted values of dispersal indices for the most abundant taxa in pollen spectra from the northern midwestern United States.