Methane consumption in Cariaco Trench waters and sediments

Detailed measurements of CH₄ in the water column and sediments of the Cariaco Trench show that CH₄ is non-conservative in both environments. Concentration differences between the sediments and adjacent overlying water suggest that the sediments are the source of the water column CH₄. Co-metabolism of CH₄ by sulfate reducers appears to be the CH₄ sink in anoxic environments.     

Transfer functions under no-analog conditions: Experiments with Indian Ocean planktonic Foraminifera

This paper documents and investigates an important source of inaccuracy when paleoecological equations calibrated on modern biological data are applied downcore: fossil assemblages for which there are no modern analogs. Algebraic experiments with five calibration techniques are used to evaluate the sensitivity of the methods with respect to no-analog conditions. The five techniques are: species regression; principal-components regression [e.g., Imbrie, J., and Kipp, N. G. (1971). In “The Late Cenozoic Ages,” 71–181]; distance-index regression [Hecht, A. D. (1973). Micropaleontology19, 68–77]; diversity-index regression (Williams, D. F., and Johnson, W. C. (1975). Quaternary Research5, 237–250]; weighted-average method [Jones, J. I. (1964). Unpublished Ph. D. Thesis, Univ. of Wisconsin]. The experiments indicate that the four regression techniques extrapolate under no-analog conditions, yielding erroneous estimates. The weighted-average technique, however, does not extrapolate under no-analog conditions and consequently is more accurate than the other techniques. Methods for recognizing no-analog conditions downcore are discussed, and ways to minimize inaccuracy are suggested. Using several equations based on different calibration techniques is recommended. Divergent estimates suggest that no-analog conditions occur and that estimates are unreliable. The value determined by the weighted-average technique, however, may well be the most accurate.     

Concentrations,physico-chemical states and mean residence times of 210Pb and 210Po in marine and estuarine waters

The concentrations and physico-chemical states of ²¹⁰Pb have been measured in Bikini Atoll and Washington State coastal waters, and ²¹⁰Po in Washington coastal waters. Lead-210 concentrations of 113–133 dpm · m^?3 were found in surface water collections near Bikini Atoll and 29–153 dpm · m^?3 in Bikini Lagoon. The concentrations of ²¹⁰Pb in near Bikini and in Washington State waters increased with depth in the upper 150m at a rate of 0.35–0.45dpm·m^?3 · m^?1. In the North Equatorial Current waters near Bikini Atoll ²¹⁰Pb was found associated predominantly with the soluble (colloidal) fraction, but in Washington coastal waters ²¹⁰Pb and ²¹⁰Po were found associated with the paniculate (> 0.3 μm) fraction. The mean residence times of ²¹⁰Pb, calculated from the atmospheric input to marine waters from precipitation and the concentrations measured in surface water, were consistent with the physico-chemical states of ²¹⁰Pb found in samples collected in deep ocean and coastal waters. Approximate values of the mean residence times were calculated, for the upper 50 m, to be as follows: 58 days in the Strait of Juan de Fuca, 128 days at the 5-mile (8 km) station off Cape Flattery (Washington), 163 days at the 12-mile (19 km) station off Cape Flattery, and 2.6 yr near Bikini Atoll. It appears that ²¹⁰Pb and ²¹⁰Po can be used to trace particle removal rates in the upper layers of marine waters.     

Biostratigraphic usefulness of stromatolitic precambrian microbiotas: A preliminary analysis

Diverse, cellularly preserved microbial communities are now known from stromatolitic sediments of at least twenty-eight Precambrian formations. These fossiliferous deposits, principally cherts and cherty portions of carbonate units, range in age from Early Proterozoic (Transvaal Dolomite, ca. 2250 Ma old) to Vendian (Chichkan Formation, ca. 650 Ma old) and include units from Australia, India, Canada, South Africa, Greenland, the United States and the Soviet Union. More than three-quarters of these microbiotas have been discovered since 1970. Although few, therefore, have as yet been studied in detail, virtually all of the assemblages are known to be dominated by prokaryotic (bacterial and blue-green algal) microorganisms and to contain three major categories of microfossils: spheroidal unicells, cylindrical tube-like sheaths, and cellular trichomic filaments. Analyses of data now available (including measurements of more than 7800 fossil unicells) indicate that each of these three types of microfossils exhibited a gradual, but marked, increase in mean diameter and size range during the Proterozoic and that taxonomic diversity apparently also increased, especially beginning about 1400 Ma ago. Thus, it now seems evident that (i) the microbial components of Proterozoic stomatolitic assemblages have varied systematically as a function of geologic age and that (ii) such communities are both more abundant and more widespread than had previously been recognized. These observations augur well for the future use of such assemblages in Precambrian biostratigraphy. At present, however, data are sufficient to warrant the provisional establishment of only a few microfossil-based subdivisions of the Proterozoic. Such zones, necessarily relatively long-ranging, are here tentatively defined; it is of interest to note that boundaries between certain of these microfossil-based subdivisions appear to coincide, at least approximately, with previously suggested stromatolite-based boundaries. To some extent, therefore, results of this study seem consistent with, and may be supportive of, the concept of stromatolite-based biostratigraphy. At the same time, however, the study seems to indicate that stromatolites of markedly differing age, whether of similar or of dissimilar morphology, were probably formed by distinctly differing microbiotas. Data are as yet insufficient to indicate whether differing types of coetaneous, stratigraphically useful, stromatolites were formed by differing microbial communities and two what extent the “evolution” of stromatolite morphology was a result of the biologic evolution of stromatolite-building microorganisms. There is thus continued need for investigation of the potential biostratigraphic usefulness of stromatolitic microbiotas and, especially, for more effective integration of results of such studies with those available from studies of stromatolites without preserved microbiotas and from studies of the acritarchs preserved in Proterozoic shales.     

Microfracturing and faulting in a limestone

Two fundamentally distinct types of microfractures are present in an experimentally deformed limestone: subaxial microfractures and microfaults. Macroscopic faults are composed of coalesced microfaults and are not related to the subaxial microfractures. A high-temperature mechanical instability occurs at temperatures of 200° C and above when the confining pressure is 600 bars or less.     

A) A. I. H. S. / A) I. A. S. H.

Abstract

In the Southwestern intermountain and high plains areas, precipitation is seasonal, with the major part of the rainfall occurring in the summer. Most winter precipitation occurs as low-intensity rain or snow along slow-moving cold fronts. Most summer precipitation occurs as short-duration, high-intensity thunderstorms from purely convective buildup or from convective cells developing along a weak fast-moving cold front. Almost all runoff occurs from the summer convective storms.

Since runoff-producing precipitation is of primary interest at the Southwest Watershed Research Center, Agricultural Research Service, Tucson, Arizona, the convective storms have been most thoroughly analyzed. Duration, intensity, areal extent, movement, character, and return frequencies for varying volumes and intensities of these convective storms are analyzed from records from dense networks of recording rain gages in four study areas in Arizona and New Mexico. The primary study areas are the 58-square-mile Walnut Gulch Experimental Watershed at Tombstone, Arizona, and the 67-squaremile Alamogordo Creek Watershed near Santa Rosa, New Mexico. Three “record” storms of differing character occurring in 1960 and 1961 on Alamogordo Creek Watershed and one “record” storm in 1961 on the Wlanut Gulch Watershed are analyzed and compared in detail.     

Hanford tank residual waste – Contaminant source terms and release models

Residual waste is expected to be left in 177 underground storage tanks after closure at the US Department of Energy’s Hanford Site in Washington State, USA. In the long term, the residual wastes may represent a potential source of contamination to the subsurface environment. Residual materials that cannot be completely removed during the tank closure process are being studied to identify and characterize the solid phases and estimate the release of contaminants from these solids to water that might enter the closed tanks in the future. As of the end of 2009, residual waste from five tanks has been evaluated. Residual wastes from adjacent tanks C-202 and C-203 have high U concentrations of 24 and 59 wt.%, respectively, while residual wastes from nearby tanks C-103 and C-106 have low U concentrations of 0.4 and 0.03 wt.%, respectively. Aluminum concentrations are high (8.2–29.1 wt.%) in some tanks (C-103, C-106, and S-112) and relatively low (<1.5 wt.%) in other tanks (C-202 and C-203). Gibbsite is a common mineral in tanks with high Al concentrations, while non-crystalline U–Na–C–O–P ± H phases are common in the U-rich residual wastes from tanks C-202 and C-203. Iron oxides/hydroxides have been identified in all residual waste samples studied to date. Contaminant release from the residual wastes was studied by conducting batch leach tests using distilled deionized water, a Ca(OH)₂-saturated solution, or a CaCO₃-saturated water. Uranium release concentrations are highly dependent on waste and leachant compositions with dissolved U concentrations one or two orders of magnitude higher in the tests with high U residual wastes, and also higher when leached with the CaCO₃-saturated solution than with the Ca(OH)₂-saturated solution. Technetium leachability is not as strongly dependent on the concentration of Tc in the waste, and it appears to be slightly more leachable by the Ca(OH)₂-saturated solution than by the CaCO₃-saturated solution. In general, Tc is much less leachable (<10 wt.% of the available mass in the waste) than previously predicted. This may be due to the coprecipitation of trace concentrations of Tc in relatively insoluble phases such as Fe oxide/hydroxide solids.