Stable isotopic ratios of lead in surface waters of the Central Pacific

The geographic variation in the isotopic composition of lead in surface waters of the central Pacific provides new evidence of the global anthropogenic perturbation of the element's cycle. Ratios of ²⁰⁶Pb/²⁰⁷Pb decrease from 1.196 in the northern hemisphere (19°N, 158°W) to 1.176 in the southern hemisphere (15°S, 150°W). This decrease parallels the geographic variation in surface concentrations of soluble lead which decrease from 13 ng kg^?1 at the northern station to 4 ng kg^?1 at the southern station. Both the ²⁰⁶Pb/²⁰⁷Pb and the ²⁰⁶Pb/²⁰⁸Pb ratios of those waters fit between the isotopic ratios of Australian (Broken Hill) and North American (Mississippi Valley) leads which are the predominant sources of leads in anthropogenic emissions to the Pacific Ocean basin.     

Partitioning of manganese,iron, copper,zinc, lead,cobalt, and nickel in black coatings on stream boulders in the vicinity of the Magruder mine,Lincoln Co., Georgia

Sequential digestions of Fe-Mn oxide coated boulders collected upstream and downstream from the Magruder mine, Lincoln Co., Georgia, indicate probable partitioning relationships for Zn, Cu, Pb, Co, and Ni with respect to Mn and Fe. Initial digestion with 0.1M hydroxylamine hydrochloride (Hxl) in 0.01M HNO₃ selectively dissolyes Mn oxides, whereas subsequent digestion with 1:4 HCl dissolves remaining Fe oxides.The results indicate that partitioning is not constant, but varies systematically with respect to the location of metal-rich waters derived from sulfide mineralization. Upstream from the mineralized zone Zn and Ni are distinctly partitioned to the Fe oxide component and Co and Cu are partitioned to the Mn oxide component. Immediately downstream from the mineralized zone, Mn oxides become relatively more enriched in Zn, whereas Fe oxides are relatively more enriched in Cu, Co, and Ni. Analytical precision for Pb is poor, but available data suggests it is more closely associated with Fe oxides.For routine geochemical surveys utilizing coated surfaces, a one-step digestion method is probably adequate. Parameters useful for detecting sulfide mineralization are metal concentrations normalized to surface area or various ratios (e.g. Zn/(Mn + Fe), Cu/Mn, Pb/Fe). Ratios can be obtained much faster, and at lower analytical costs than conventional analysis of stream sediment.     

On the solar oblateness: The combined effect of a pole-equator difference in effective temperature and mechanical heating

With the help of a model atmosphere of the Sun we evaluate the pole-equator difference in flux (as measured by Dicke and Goldenberg) assuming the following type of pole-equator temperature difference (T=T _e –T _p ): (a) T 2K for > ₀ (₀ 0.05); (b) T 10K for < ₀.The small T at all optical depths given by (a) could, for example, be due to a pole-equator difference in effective temperatures. At small optical depths a difference in mechanical heating could give rise to the larger temperature difference given by (b). We compare the results of our calculations with Dicke and Goldenberg's observations.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Visual classification of very fine-grained sediments: Evaluation through univariate and multivariate statistics

Classifying very fine-grained rocks through fabric elements provides information about depositional environments, but is subject to the biases of visual taxonomy. To evaluate the statistical significance of an empirical classification of very fine-grained rocks, samples from Devonian shales in four cored wells in West Virginia and Virginia were measured for 15 variables: quartz, illite, pyrite and expandable clays determined by X-ray diffraction; total sulfur, organic content, inorganic carbon, matrix density, bulk density, porosity, silt, as well as density, sonic travel time, resistivity, and -ray response measured from well logs. The four lithologic types comprised: (1) sharply banded shale, (2) thinly laminated shale, (3) lenticularly laminated shale, and (4) nonbanded shale. Univariate and multivariate analyses of variance showed that the lithologic classification reflects significant differences for the variables measured, difference that can be detected independently of stratigraphic effects. Little-known statistical methods found useful in this work included: the multivariate analysis of variance with more than one effect, simultaneous plotting of samples and variables on canonical variates, and the use of parametric ANOVA and MANOVA on ranked data.     

Statistical model of silicate analysis and results of investigation of G-1 and W-1 samples

An analysis of the results of investigation of the G- 1 and W- 1 samples are given and differ from F. Chayes’ point of view. Results of the samples can be evaluated by comparison of frequency-distribution properties of determinations for chemical elements from different laboratories with some standard distribution, which gives the idea of a statistical model. The comparative results indicate that oxides from minerals of the same density have positive correlations and that oxides from minerals of different density have negative correlations. The different results therefore are not from the precision of analysis, but rather from differentiation of sample powder particles by density and shape in the course of preparation.     

The relationship between formation structure and thickness in the Permo-Triassic succession of the Southern Coalfield, Sydney Basin, New South Wales, Australia

Using trend-surface analysis, the patterns of formation structure and thickness variation in the Permo-Triassic succession of the Southern Coalfield, Sydney Basin, are resolved into geologically meaningful large- and small-scale features. The structural trends correspond to the regional syncline of the southern Sydney Basin and the negative and positive residual domains to smaller-scale structures including the South Bulli and Douglas Park Synclines and the Bulli and Kemira Anticlines. The results of trend-surface analysis and simple linear regression reveal an inverse relationship between structural elevation (relative to sea level) and formation thickness on both a regional and a local scale. This relationship is strongest for the Bulli Coal and the Bald Hill Claystone. In the case of the Bulli Coal, the present-day structural trends and formation thickness trends show a strong inverse correlation and the residuals show a moderate inverse correlation; the correlations between the inferred Middle Triassic structure of the Bulli Coal and formation thickness are even stronger than those involving the present-day structure. These results indicate that structures which were active during the Permo-Triassic and which influenced sedimentation have been preserved in the present-day structure. The persistence of the patterns of structure and thickness variation upward through the Permo-Triassic sequence suggests that sedimentation was controlled by contemporaneous basement subsidence, rather than by short-lived compaction-induced subsidence patterns.