Isotopic ratios, concentration of noble gases and mineral and bulk composition of extraterrestrial dust particles in Dome Fuji ice core, East Antarctica

Two silicate-rich dust layers were found in the Dome Fuji ice core in East Antarctica, at Marine Isotope Stages 12 and 13. Morphologies, textures, and chemical compositions of constituent particles reveal that they are high-temperature melting products and are of extraterrestrial origin. Because similar layers were found ~2000 km east of Dome Fuji, at EPICA (European Project for Ice Coring in Antarctica)-Dome C, particles must have rained down over a wide area 434 and 481 ka. The strewn fields occurred over an area of at least 3 × 10**6 km**2. Chemical compositions of constituent phases and oxygen isotopic composition of olivines suggest that the upper dust layer was produced by a high-temperature interaction between silicate-rich melt and water vapor due to an impact explosion or an aerial burst of a chondritic meteoroid on the inland East Antarctic ice sheet. An estimated total mass of the impactor, on the basis of particle flux and distribution area, is at least 3 × 10**9 kg. A possible parent material of the lower dust layer is a fragment of friable primitive asteroid or comet. A hypervelocity impact of asteroidal/cometary material on the upper atmosphere and an explosion might have produced aggregates of sub-µm to µm-sized spherules. Total mass of the parent material of the lower layer must exceed 1 × 10**9 kg. The two extraterrestrial horizons, each a few millimeters in thickness, represent regional or global meteoritic events not identified previously in the Southern Hemisphere.

Isotopic composition of ground ice, ebullition gases and thermokarst lake water, North America

Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of dD-CH4 emissions from Siberian and North American lakes. dD CH4 reflects regionally varying dD values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes. We found that Alaskan thermokarst lake dD-CH4 was higher (-334 ± 17 per mil) than Siberian lake dD-CH4 (-381 ± 18 per mil). Weighted mean dD CH4 values for Beringian lakes ranged from -385 per mil to -382 per mil over the deglacial period. Bottom-up estimates suggest that Beringian thermokarst lakes contributed 15 ± 4 Tg CH4 /yr to the atmosphere during the Younger Dryas and 25 ± 5 Tg CH4 /yr during the Preboreal period. These estimates are supported by independent, top-down isotope mass balance calculations based on ice core dD-CH4 and d13C-CH4 records. Both approaches suggest that thermokarst lakes and boreal wetlands together were important sources of deglacial CH4.

isotopic composition of gases and interstitial fluides of ODP Site 104-644

Pleistocene- to middle Miocene-age sediment was drilled at Site 341 (67? 20.1'N, 6? 06.6'E) on the inner Voring Plateau during Leg 38 of the Deep Sea Drilling Project (DSDP). In 1985, the Ocean Drilling Program (ODP) returned to the inner Wring Plateau near Site 341 and drilled a new hole at Site 644 (66° 40.7'N, 4° 34.6'E) as part of a transect to study Norwegian Sea paleoenvironments. In Hole 341, gas expansion pockets formed in cores which were recovered from depths below 50 m. This gas was characterized as predominantly methane with delta13C values in the range of -87 to -77 per mil (Morris, 1976, doi:10.2973/dsdp.proc.38.124.1976). At Site 644, sediment gas and pore-water samples were obtained to study the geochemistry of methanogenesis. Of particular interest is the possibility that methane hydrate might be present in these sediments.

Geochemical data from pore water and solids from cores GS08-153-91GC12 and GS08-153-53-GC6, Arctic Mid-Ocean Ridge

Microbial communities and their associated metabolic activity in marine sediments have a profound impact on global biogeochemical cycles. Their composition and structure are attributed to geochemical and physical factors, but finding direct correlations has remained a challenge. Here we show a significant statistical relationship between variation in geochemical composition and prokaryotic community structure within deep-sea sediments. We obtained comprehensive geochemical data from two gravity cores near the hydrothermal vent field Loki's Castle at the Arctic Mid-Ocean Ridge, in the Norwegian-Greenland Sea. Geochemical properties in the rift valley sediments exhibited strong centimeter-scale stratigraphic variability. Microbial populations were profiled by pyrosequencing from 15 sediment horizons (59,364 16S rRNA gene tags), quantitatively assessed by qPCR, and phylogenetically analyzed. Although the same taxa were generally present in all samples, their relative abundances varied substantially among horizons and fluctuated between Bacteria- and Archaea-dominated communities. By independently summarizing covariance structures of the relative abundance data and geochemical data, using principal components analysis, we found a significant correlation between changes in geochemical composition and changes in community structure. Differences in organic carbon and mineralogy shaped the relative abundance of microbial taxa. We used correlations to build hypotheses about energy metabolisms, particularly of the Deep Sea Archaeal Group, specific Deltaproteobacteria, and sediment lineages of potentially anaerobic Marine Group I Archaea. We demonstrate that total prokaryotic community structure can be directly correlated to geochemistry within these sediments, thus enhancing our understanding of biogeochemical cycling and our ability to predict metabolisms of uncultured microbes in deep-sea sediments.

The compleat measurer or, The whole art of measuring : In two parts. The first part teaching decimal arithmetick ... The second part teaching to measure all sorts of superficies and solids ... /

Mode of access: Internet.

Odors, gases and particulate matter from high density poultry management systems as they relate to air pollution : final report /

"April 15, 1969."

Liquefied petroleum gases; laws, rules and regulations relating to the storage, transportation, sale and use of liquefied petroleum gases, and the use of liquefied petroleum gas containers.

Mode of access: Internet.

Key to the Complete system of mensuration of superfices and solids : containing solutions to all the problems and questions therein contained : calculated for the use of schools, academies, and private learners /

Mode of access: Internet.

A complete system of mensuration of superfices and solids, of all regular figures : calculated for the use of schools, academies, and private learners /

On cover: Published 1834.

Elementary and practical arithmetic on the inductive system, by analysis and synthesis : containing lucid demonstrations of the rules, arithmetical improvements, and curiosities, mensuration of planes and solids, philosophical problems ... /

Mode of access: Internet.