EVOLVING FACTOR ANALYSIS APPLIED TO FLOW INJECTION ANALYSIS DATA

Evolving factor analysis is used to estimate the concentration profiles and spectra of Bi~(3 )and the bismuthchloride complexes BiCl~(2 )through BiCl_6~(3-)formed by injection of bismuth percblorate into a flowingstream of 1.0 mol l~(-1) HCl.The estimated spectra compare favorably with previously published spectraof the complexes.     

Paleo-oceanography of the Norwegian Sea during the past 130,000 years: coccolithophorid and foraminferal data

Faunal, floral and sedimentological properties of Norwegian Sea core V27-86 were examined in order to reconstruct the paleo-oceanographic history of this region. Downcore variations in the relative abundance of three microfossil groups and several sediment properties exhibit three different climate response patterns (CRP). Each pattern is judged to represent the response of a different part of the climate system. The covariance patterns among coccoliths, henthic foraminifera, and other properties suggest that the Norwegian Sea has been ice-free and productive during the present interhlacial. the penultimate interglacial (isotopic-stage se) and at least partially ice-free during an intermediate climatic regime (stages sa-d). A maximum change in these measures occurs at the boundary between isotopic stage 5a (an intermediate climatic regime)and isotopic stage 4 (a glacial climatic regime). In contrast, planktic foraminiferal assemblages and oxygen isotope measurements on planktic foraminifera show a major change at the end of stage 5e (the penultimate interglacial). The contrasting behavior of these two sets of observations is explained by a model which postulates a low-salinity surface layer 115,000 to 75,000 years ago (stages 5a-d).     

The crystalline lunar spherules: Their formation and implications for the origin of meteoritic chondrules

Abstract— Crystalline lunar spherules (CLS) from three thin sections of Apollo 14 regolith breccias (14318,6; 14318,48 and 14315,20) have been examined. The objects have been classified and their abundances, size distributions, bulk compositions, and (where possible) plagioclase compositions determined. By number, 64% consist predominantly of very fine-grained equant plagioclase grains but can also contain larger (～50 μm) feldspar crystals (type X), while 22% contain plagioclase lathes in a fine-grained mafic mesostasis (type Y). Plagioclase in both spherule types displays bright yellow cathodoluminescence that is conspicuous among the blue CL of the normal feldspar of the breccias. Type Z spherules (5%) contain feldspar with blue CL and minor amounts of olivine and pyroxene. Type Q spherules (4%) contain feldspar with yellow CL but in a luminescent mesostasis (of quartz or feldspar?). A few spherules are mixtures of type Y and type X textures. Most type X spherules, and a few type Y spherules, have fine-grained opaque rims. Compound objects were also found and consist of two or more CLS that appear to have collided while still plastic or molten. The CLS are thought to be impact spherules that crystallized in free flight, their coarse textures suggesting fairly slow cooling rates (～ <1 °C/s). The abundance of the CLS resembles that of chondrules in the CM chondrite Murchison, and their cumulative size-frequency distributions are very similar to those of the chondrules in several meteorite classes. The bulk compositions of the CLS do not resemble regoliths at any of the Apollo sites, including Apollo 14, or any of the common impact glasses, but they do resemble the bulk compositions of several lunar meteorites and the impact glasses they contain. The Apollo 14 site is located on a region containing Imbrium ejecta, and we suggest that the CLS derive from the Imbrium impact. Ballistic calculations indicate that only impact events of this size on the Moon are capable of producing melt spherules with the required free flight times and slow cooling rates. Smaller impacts produce glassy spherules and agglutinates. As has been pointed out many times, the CLS have many properties in common with meteoritic chondrules. While much remains unclear, difficulties with a nebular origin and new developments in chondrule chronology, studies of asteroid surfaces and impact ejecta behavior, and the present observations indicate that meteoritic chondrules could have formed by impact.     

WEST AFRICAN ENVIRONMENTAL NARRATIVES AND DEVELOPMENT‐VOLUNTEER PRAXIS*

ABSTRACT. Environmental narratives in Africa have been examined in a flurry of publications since the mid‐1990s. In this article we seek to offer insights into the role and motivations of volunteer development workers in perpetuating environmental narratives. We examine the factors that led to the questioning or nonquestioning of environment‐development discourses and their influence, if any, on the actual work undertaken by volunteers. As former development volunteers, we also explore the role that the development‐volunteer experience subsequently played in shaping our own research as academics. Our analysis is based largely on our tenure as U.S. Peace Corps volunteers in Mali from 1987 until 1989 and our later experiences as academics. We draw on our memories, interviews with former colleagues, and training materials to describe how volunteers were introduced to, and encouraged to act on, environmental problems in the West African Sudano‐Sahel. We adopt a reflexive approach to explore briefly how our experiences as volunteers influenced our research and writing as academics.     

Application of the geographical information systems approach to watershed mass balance studies

This study was undertaken to test the utility of a geographical information systems (GIS) approach to problems of watershed mass balance. This approach proved most useful in exploring the effects that watershed scale, lithology and land use have on chemical weathering rates, and in assessing whether mass balance calculations could be applied to large multilithological watersheds. Water quality data from 52 stations were retrieved from STORET and a complete GIS database consisting of the watershed divide, lithology and land use was compiled for each station. Water quality data were also obtained from 7 experimental watersheds to develop a methodology to estimate annual fluxes from incomplete data sets. The methodology consists of preparing a composite of daily flux data, calculating a best fit sinusoid and integrating the equation to obtain an annual flux. Comparison with annual fluxes calculated from high resolution data sets suggests that this method predicts fluxes within about 10% of the true annual flux. Annual magnesium fluxes (moles km⁻² yr⁻¹) were calculated for all stations and adjusted for fluxes from atmospheric deposition. Magnesium flux was found to be a strong function of the amount of carbonate in the watershed, and silica fluxes were found to increase with the fraction of sandstone present in the watershed. All fluxes were strongly influenced by mining practices, with magnesium fluxes from affected watersheds being 6–10 times higher than fluxes from comparable pristine watersheds. Mining practices enhance chemical weathering by increasing the surface area of unweathered rock to which water has access and by increasing acidity and rate of mineral weathering. Fluxes were also found to increase with watershed size. This scale dependence is most likely caused by the sensitivity of weathering fluxes to even minor quantities of carbonates, which are likely to be found in all lithologies at larger scales. Mass balances were carried out in watersheds where gauged sub-watersheds made up more than 95% of the area. The calculations show large magnesium flux and water balance discrepancies. These errors may be a result of significant groundwater inputs to streams between gauges. The results suggest that improvements in how we measure discharge and estimate fluxes may be required before we can apply mass balance techniques to larger scales. © 1997 John Wiley & Sons, Ltd.     

Applications of grain-pivoting and sliding analyses to selective entrapment of gravel and to flow-competence evaluations

Models of sediment threshold by grain pivoting or sliding over underlying particles are examined in order to explore their application to evaluations of selective entrainment of gravel by flowing water. Of special interest is whether such process-based models provide satisfactory evaluations of flow competence and the movement of large clasts by floods. A detailed derivation is undertaken, focusing first on the fluid flow and forces at the particle level. The resulting threshold equation for the particle-level velocity is then modified to yield the mean entrainment stress for the flow as a whole. This approach is appropriate for considerations of selective entrainment of grains of varying sizes within a deposit, the sorting being due to their relative projection distances above the bed and the dependence of their pivoting angles on grain size and shape. The resulting threshold equations contain a number of coefficients (e.g. drag and lift) whose values are poorly known, but can be constrained by requiring agreement with the Shields curve for the threshold of grains in uniform deposits. If pivoting coefficients based on laboratory measurements with tetrahedral arrangements of particles are used in the models, smaller degrees of selective sorting are predicted than found in the field measurements of gravel entrainment. However, if reasonable modifications of those coefficients are made for expected field conditions, then the models yield good agreement with the data. Sliding models, where sorting is due entirely to projection distances of the grains above the bed, yield somewhat poorer agreement with the field data; however, the sliding models may have support from laboratory experiments on gravel entrainment in that the data and theoretical curves have similar concave trends. The existing measurements lack documentation of the mechanisms of grain movement, so it is not possible to conclusively determine the relative importance of grain pivoting versus sliding. In spite of such uncertainties, the results are encouraging and it is concluded that pivoting and sliding models for grain entrainment do have potential for field computations of selective entrainment and flow competence.     

Hydraulic characteristics of bioclastic deposits: new possibilities for environmental interpretation using settling velocity fractions

This paper examines the hydraulic behaviour of heterogeneous bioclastic sediments using settling velocity fractions. Bioclastic deposits are divided into fractions by splitting hydraulically sorted samples. Compositional analysis of fractions shows that grains exhibit marked variation in composition, shape, size and density which control the hydraulic behaviour of bioclastic deposits. Despite the heterogeneous grain properties of fractions (analogous to sieve fractions) sedimentation analysis shows that they possess a narrow range of settling velocity values. Flume experiments also show that the settling velocity fractions possess a narrow range of threshold velocity values. A threshold relationship is identified in which the velocity required to entrain mixed settling fractions increases from 20.5 to 65-0cm s ^?1 for settling fractions with mean settling values of 5.5 chi (2-2 cm s ^?1) to 1.4 chi (36.0 cm s ^?1), respectively. Heterogeneous settling fractions, due to intergrain effects, were found to possess larger threshold velocities than individual components showing that the composition of bioclastic deposits controls hydraulic behaviour. Thus, caution must be exercised in using the threshold relationship for homogeneous sediments or deposits of markedly different composition. As settling velocity fractions reflect narrow hydraulic (settling and threshold) properties of sediments the mean settling velocity of fractions is considered a good indicator with which to interpret transport and depositional processes. Comparison of settling and sieve-size distributions shows that size distributions do not reflect the hydraulic behaviour of bioclastic deposits and should not be used to interpret environmental processes. The study indicates that examination of settling velocity fractions (for which hydraulic settling and threshold properties are known) coupled with compositional analysis of these fractions will allow much greater environmental interpretation of deposit-forming and energy processes in reef environments.     

Girvanella grabaui sp.nov.aus dem unterpermischen Chuanshan-Kalk Südchinas

Mit 1 Abbildung Nach Abfassung des Manuskriptes meiner Arbeit über"Unterkar-bonische Kalkalgen und Calcisphaeren Deutschlands",die sich u.a.mit