The downstream gradation of particle sizes in the Squamish river,British Columbia

The exponential downstream decline in particle size predicted by Sternberg (1875) is examined within a highly active alpine fluvial environment, the gravel-bed Squamish River in southwestern British Columbia. Transect survey procedures for sampling within the coarse alluvial gravels are described in detail. Downstream trends for various particle size statistics, plotted with distance from a major sediment source, are considered according to two scenarios. Evaluation of overall trends indicates that the downstream expression derived by Sternberg (1875) is not the most appropriate; rather, curves are better described by power functions. This reflects a very rapid decline in particle size immediately downstream of the major sediment source. Secondly, evaluation of downstream trends in relation to channel planform determines that exponential functions with different coefficients describe adequately relations within individual planform reaches. There is insufficient evidence to suggest which of these two scenarios may be appropriate. Several lines of evidence suggest that the trends found are more the result of selective sediment transport phenomena than of abrasion, a condition attributed to channel competence within a system dominated by sediment-supply conditions.     

Unequilibrated ordinary chondrites: A tentative subclassification based on volatile-element content

For unequilibrated ordinary chondrites (= UOC), two measures of primitiveness are available: volatile content, in principle reflecting accretion conditions from the solar nebula, and metamorphism, reflecting reheating in the parent bodies. These two measures do not always correlate, and we have therefore developed a tentative classification scheme based on volatile content that complements the Searset al. (1980) scheme based on metamorphism. Like the latter, it subdivides type 3 chondrites on a scale of 3.0 to 3.9; the notation 3.4/0 indicates a meteorite that is subtype 3.4 according to metamorphism and 3.0 according to volatile content.The classification is based mainly on C and Xe—two elements that are little affected by shock-induced reheating—and to a lesser extent on Ar³⁶,Bi,In, and Tl. Of 22 meteorites considered, the majority have concordant classifications (±0.2) on the two scales. However, 5 meteorites are richer in volatiles than their metamorphic grade indicates: Sharps 3.4/0, ALHA 77011 3.5/0, Ngawi 3.6/3, ALHA 77299 3.7/4, and Mezö-Madaras 3.7/3. It remains to be seen whether these differences indeed denote a more primitive nature.Some new clues to the formation of chondrites may eventually come from Xe and C. Their concentrations in UOC's vary by more than 5×, but the $\text{Xe}\text{C}$ ratio remains nearly constant at 3.4 × 10^?3 of the solar-system ratio. Even the ratios for other chondrite classes differ only slightly from that for UOC's, e.g., C3O (1.5×) and E3,4 (0.4×). Either the 4 factors determining this ratio (T, t, P, and internal surface area of the carbon) varied in complementary fashion, or—more probably—they varied only slightly in the entire source region of chondrites.     

The DH ratios of sap in trees: Implications for water sources and tree ring DH ratios

Measurements of $\text{D}\text{H}$ ratios of tree sap can be used to determine the source water for a tree. Based on these measurements, trees can be separated into three categories: those which rely solely on summertime rainfalls, those which rely solely on groundwaters and those which utilize both water sources. For trees in the last category, $\text{D}\text{H}$ ratios of sap can be used to quantify the relative contributions to the tree's source water of summertime rainfalls and groundwaters. These measurements can be used to select trees for tree ring isotope studies. Single source trees, those which rely solely on summertime rain or groundwaters, appear to be the best choices for measuring long records of tree ring $\text{D}\text{H}$ ratios.     

The thermodynamic properties of radium

The enthalpy, Gibbs free energy, and entropies of aqueous radium species and radium solids have been evaluated from empirical data, or estimated when necessary for 25°C and 1 bar. Estimates were based on such approaches as extrapolation of the thermodynamic properties of Ca, Sr, and Ba complexes and solids plotted against cationic radii and charge to radius functions, and the use of the Fuoss or electrostatic mathematical models of ion pair formation (Langmuir, 1979). Resultant log K (assoc) and ΔH⁰ (assoc) (kcal/mol) values are: for RaOH⁺ 0.5 and 1.1; RaCl⁺ ?0.10 and 0.50; RaCO⁰₃ 2.5 and 1.07; and RaSO⁰₄ 2.75 and 1.3. Log Ksp and ΔH⁰ (dissoc) (kcal/mol) values for RaCO₃(c) and RaSO₄(c) are ?8.3 and ?2.8, and ?10.26 and ?9.4, respectively.Trace Ra solid solution in salts of Pb and of the lighter alkaline earths, has been appraised based on published distribution coefficient (D) data, where D ～- (mM²⁺)(N_RaX)/(mRa²⁺)(N_MX) (m and N are the aqueous molality and mole fraction of Ra and cation M in salt X, respectively. The empirical solid solution data have been used to derive both enthalpies and Gibbs free energies of solid solution of trace Ra in sulfate and carbonate minerals up to 100°C. Results show that in every case D values decrease with increasing temperature. Among the sulfate and carbonate minerals, D values decrease for the following minerals in the order: anhydrite > celestite > anglesite > barite > aragonite > strontianite > witherite > cerussite.     

Effect of monochloramine on isolated fulvic acid

Monochloramine is interesting both as a selective oxidant of fulvic acid and as a drinking water disinfectant. In this study, the controlled reaction of aquatic fulvic acid with monochloramine did not result in products detectable by ether extraction-gas chromatography-flame ionization detection techniques. Evidence of a reaction was shown by bleaching of the fulvic acid solution (decreased absorbance at 465 nm) and chlorine substitution. Chlorine-containing products were quantified by the total carbon adsorbable organic halide (TOX) parameter. Bleaching and organic chlorine formation were much less extensive than in the reaction of free chlorine with fulvic acid. Monochloramine was shown to produce an organic chlorine fraction more hydrophilic and with higher molecular size than that produced by chlorine and fulvic acid. Results suggest that monochloramine may be useful tool for the investigation of certain humic functionalities because it reacts rather selectively and to a small extent with aquatic fulvic acid.     

Organic geochemical characterization of the New Albany Shale group in the Illinois Basin

Benzene extractable aliphatic hydrocarbons from the New Albany Shale in the Illinois Basin were characterized by gas chromatography and mass spectrometry, and the total organic matter of the shale was characterized by solid state carbon-13 cross polarization magic angle spinning nuclear magnetic resonance. Core samples from a northwest-trending cross-section of the Illinois Basin were studied. Gas chromatography (GC) and gas chromatography-mass spectrometric analysis (GC/MS) data indicate a regional variation of the aliphatic composition of the shale extracts. A positive, linear relationship between the two ratios, pristane/n-C₁₇ and phytane/n-C₁₈, is indicated. The NMR results indicated that organic matter deposited in northwestern Illinois shale is relatively high in aliphatic hydrocarbon content while, in contrast, organic matter found in southeastern Illinois shale is relatively low in aliphatic hydrocarbon content. Our findings suggest that the organic variation of the shale is mainly due to the differences in thermal maturity of the shale organic matter and the use of pristane/n-C₁₇ ratio as a thermal parameter in the study of oil may be extended to the study of the ancient sediments.     

Origin of discontinuities in coal-bearing strata at roaring creek (basal Pennsylvanian of Indiana)

Basal Pennsylvanian coal-bearing strata exposed along Roaring Creek, west-central Indiana, exhibit extreme lateral discontinuity. Coal seams abruptly change in thickness and elevation; they split, grade into shale, are cut out by channels and disrupted by soft-sediment deformational structures. Initial sediments were laid down by a network of southwest-flowing streams that traversed a deeply channelized upland surface of Mississippian carbonate rocks. Channels aggraded rapidly as uplands were worn down, so the region changed through time from uplands to upper deltaic plain. Local environments included channels, localized point bars, small natural levees and crevasse splays, overbank deposits, and swamps. Differential compaction and subsidence, slumping stream banks, and possibly collapsing sinkholes influenced sedimentation. As a consequence, coals are too discontinuous for economical mining, although they are locally thick and high in quality.     

Helium isotopic variability within single diamonds from the Orapa kimberlite pipe

The distribution and isotopic composition of helium has been measured in a suite of well-characterized one-carat diamonds from the Orapa kimberlite, Botswana. Crushing of the diamonds in vacuo indicates that most of the helium is contained by the matrix (generally greater than 90%), rather than by the inclusions. Step-heating experiments, performed on inclusion-free fragments remaining after crushing, indicate that the³He/⁴He ratio is variablewithin individual diamonds. The fragments, as small as 10 mg, were heated in two timed steps, both at 2000°C. In every case, lower³He/⁴He ratios are observed in the first graphitization step (0.05–3 × atmospheric), while the last heating step releases helium with systematically higher³He/⁴He ratio (30–80 × atmospheric). We suggest that this internal isotopic variability is the result of stepwise graphitization: the first heating step initiates graphitization, which nucleates around defects, and the second heating step graphitizes the relatively defect-free regions of the diamond. The³He/⁴He ratio measured, using the partial graphitization technique, differs by up to a factor of 100 within a single specimen. The inclusion-free fragments release small quantities of helium below 2000°C, which suggests that helium release is obtained only by graphitization. The³He contents of the monocrystalline diamonds are relatively constant (at 3 × 10⁻¹³ cm³ STP/gram) and indicate that most of the isotopic variability is due to radiogenic⁴He. The variations in⁴He content are either related to zoning of Th and U in the diamonds (i.e., in-situ decay), to zoning of inherited⁴He, or to implantation of α-particles from a Th and U rich environment (i.e., kimberlite). Because the Orapa diamonds were mined from roughly 40 m depth in the kimberlite, spallation reactions from cosmic ray interactions are not a significant source of³He. However, calculations based on the age of the kimberlite (90 m.y.) and reasonable Th and U abundances suggest that most of the³He in the Orapa diamonds could be produced by⁶Li(n, α)T in the diamond. Although this may not be true of all diamonds, nuclear reactions in the crust and mantle (including spallation reactions at the surface) can explain many of the high³He/⁴He ratios previously reported for diamonds.