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At least 1,063 records · Page 59Linked to original sources
USGS1974

Water and carbon in rusty lunar rock 66095

Lunar rock 66095 contains a hydrated iron oxide and has an unusual amount of water for a lunar rock (140 to 750 parts per million), 90 percent of which is released below 690°C. The δof water released at these low temperatures varies from -75 to -140 per mil relative to standard mean ocean water (SMOW). The small amount of water released between 690° and 1300°C has a δ of about -175 ±25 per mil SMOW. These δ values are not unusual for terrestrial water. The δ 18 O of water extracted from 110° to 400°C has a value of +5± I per mil SMOW, similar to the value for lunar silicates from rock 66095 and different from the value of -4 to -22 per mil found for samples of terrestrial rust including samples of rusted meteoritic iron. The amount of carbon varies from 11 to 59 parts per million with a δ 13 C from -20 to -30 per mil relative to Pee Dee belemnite. Only very small amounts of reduced species (such as hydrogen, carbon monoxide, and methane) were found, in contrast to the analyses of other lunar rocks. Although it is possible that most of the water in the iron oxide (goethite) may be terrestrial in origin or may have exchanged with terrestrial water during sample return and handling, evidence presented herein suggests that this did not happen and that some lunar water may have a δD that is indistinguishable from that of terrestrial water.

Science↗
USGS1979

Carbon dioxide in the ocean surface: The homogeneous buffer factor

The amount of carbon dioxide that can be dissolved in surface seawater depends at least partially on the homogeneous buffer factor, which is a mathematical function of the chemical equilibrium conditions among the various dissolved inorganic species. Because these equilibria are well known, the homogeneous buffer factor is well known. Natural spatial variations depend very systematically on sea surface temperatures, and do not contribute significantly to uncertainties in the present or future carbon dioxide budget.

Science↗
USGS1979

Submarine seep of carbon dioxide in Norton Sound, Alaska

Earlier workers have described a submarine gas seep in Norton Sound having an unusual mixture of petroleum-like, low-molecular-weight hydrocarbons. Actually, only about 0.04 percent of the seeping gas is hydrocarbons and 98 percent is carbon dioxide. The isotopic compositions of carbon dioxide (δ 13 C PDB = –2.7 per mil) and methane (δ 13 C PDB = –36 per mil) where PDB is the Peedee belemnite standard) indicate that geothermal processes are active here.

Alaska↗
USGS1994

500,000-year stable carbon isotopic record from Devils Hole, Nevada

The record of carbon-13 (δ 13 C) variations in DH-11 vein calcite core from Devils Hole, Nevada, shows four prominent minima near glacial terminations (glacial-interglacial transitions) V to II. The δ 13 C time series is inversely correlated with the DH-11 oxygen isotope ratio time series and leads it by as much as 7000 years. The δ 13 C variations likely record fluctuations in the δ 13 C of dissolved inorganic carbon of water recharging the aquifer. How such variations are transported 80 kilometers to Devils Hole without obliteration by water-rock reaction remains an enigma. The record may reflect (i) global variations in the δ 13 C of atmospheric CO 2 and, hence, the δ 13 C of continental biomass or (ii) variations in extent and density of vegetation in the southern Great Basin. In the latter case, δ 13 C minima at 414, 334, 246, and 133 thousand years ago mark times of maximum vegetation.

Nevada↗
USGS1995

Analysis of factors affecting the accuracy, reproducibility, and interpretation of microbial community carbon source utilization patterns

We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microliter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal- components analysis (PCA), and model communities with different compositions were clearly separated un the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.

Michigan↗
USGS1964

Relation of temperature distribution to ground-water movement in carbonate rocks of central Israel

The Cenomanian-Turonian formations of central Israel constitute a highly permeable dolomite and limestone aquifer. In this area it is on the west limb of an anticlinorium that trends north-northeast, and it contains water under artesian pressure. A graph of water temperatures and well depths suggests that there is a very small vertical temperature gradient in local segments of the aquifer. The small gradient is believed to result from a large vertical component of flow that tends to equalize the vertical temperature distribution . On a regional scale the apparent horizontal temperature distribution indicates a westward increase with increasing depth of the aquifer, suggesting a manifestation of the regional geothermal gradient. The westward increase in temperature also implies that the lateral component of flow may be in the normal range for artesian carbonate - rock aquifers whose pores consist mainly of solution cavities. Locally, pumping appears to have affected the temperature distribution by modifying the natural flow pattern. In parts of the most intensively developed area, the aquifer is hydraulically connected with overlying coastal-plain deposits, and some cooler water has been induced to move into the aquifer from this source. At three other areas, pumping has resulted in an apparent horizontal shift of the isotherms on a temperature - distribution map. The data suggest that the spatial distribution of temperature may be used to determine some of the flow characteristics of carbonate - rock aquifers.

Geological Society of America Bulletin↗
USGS1997

Paleogeographic significance of Clavohamulus hintzei Miller (Conodonta) and other Ibexian conodonts in an early Paleozoic carbonate platform facies of the Argentine Precordillera

Pre-Tremadocian conodonts and trilobites and Tremadocian conodonts are reported from the Cambrian and Ordovician La Silla Formation in the Cerro La Silla section in east-southeast Ja??chal, San Juan Province, Argentina. A shallow marine conodont fauna contains elements of Clavohamulus hintzei Miller, a common species in North America, but reported for the first time from the early Paleozoic platform carbonates of the western Argentine Precordillera. The presence of this species suggests a correlation with the Clavohamulus hintzei conodont subbiozone of the Cordylodus intermedius conodont biozone in North America, considered Early Ordovician (Skullrockian Stage, Ibexian Series) in North America, but by South American and European standards, this biozone would be of latest Cambrian age. C. hintzei and associated conodonts of the La Silla Formation are typical of the tropical faunas of the North American Midcontinent Faunal Province; Late Cambrian trilobites from lower in the formation also are typical North American taxa. The presence of these faunas in the platform carbonates is consistent with plate reconstructions suggesting that the Precordillera was in a tropical or subtropical position close to Laurentia during the late Precambrian and early Paleozoic. These new paleontological data provide one more argument for recent models of the Precordillera as a displaced terrane derived from the Ouachita Embayment at the southern margin of Laurentia.

Geological Society of America Bulletin↗
USGS1985

Origin of caves and other solution openings in the unsaturated (vadose) zone of carbonate rocks: A model for CO2 generation

The enigma that caves and other solution openings form in carbonate rocks at great depths below land surface rather than forming from the surface downward can be explained by the generation of CO2 within the aquifer system. In the proposed model, CO2 is generated by the oxidation of particulate and/or dissolved organic carbon that is transported from the land surface deep into the unsaturated zone by recharging ground water. The organic material is oxidized to CO2 by aerobic bacteria utilizing oxygen that diffuses in from the atmosphere. Because gas transport in the unsaturated zone is controlled largely by diffusion, steady-state generation of even minute amounts of CO2 deep in the unsaturated zone results in the creation of large concentrations of CO2 at depth as it establishes a concentration gradient to the surface or other sink.

Geology↗
USGS1989

Porosity development in coastal carbonate aquifers

Geochemical mixing theory suggests that the mixing of seawater and calcite-saturated fresh ground water can result in a solution that is undersaturated with respect to calcite. Previous studies of the mixing of such waters in carbonate rocks along certain coastlines have indicated that this mixing effect may be responsible for significant amounts of calcite dissolution and porosity development. In this study, potential rates of porosity development by calcite dissolution are assessed by combining geochemical mixing theory with the hydrodynamics of fresh-water-salt-water mixing zones in a coupled reaction- transport model. Results from the reaction-path model PHREEQE are used with a variable-density ground-water flow and solute-transport model to simulate an idealized cross section of a coastal carbonate aquifer. Results of the simulations indicate that the dissolution process is sensitive to fresh-water chemistry, ground-water velocities, and sea-level movement. Dissolution potential was evaluated at three field sites, and evidence from those sites is in general agreement with the simulation results. Dissolution rates indicated by the model show that under the proper conditions this dissolution mechanism can produce significant increases in porosity over relatively short spans of geologic time (tens of thousands of years).

Geology↗
USGS1998

Proxy of monsoon seasonality in carbon isotopes from paleosols of the southern Chinese Loess Plateau

Soil organic matter (SOM) and soil carbonate (SC) are common constituents in soils and are directly related to plant growth. SOM accumulates gradually from the decomposition of plant material over time, whereas SC formation is biased to dry-season soil-dissolved CO 2 that derives from plant respiration during a drying phase of the growing season. In some mixed C 3 -C 4 environments, the peak of C 3 and C 4 plant metabolism differs seasonally, and the carbon source that contributes to the SOM and SC can be different. Consequently, δ 13 SOM values reflect an annual average of the floral biomass, but δ 13 SC values reflect a seasonal aspect of the plant community. The relationship between δ 13 C SC and δ 13 C SOM is mainly controlled by how different the seasonal conditions are. Our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of Indian, East Asian, and Siberian monsoons on the Chinese Loess Plateau during the last interglacial-glacial cycle.

Geology↗
USGS2002

Comment [on 'Are Proterozoic cap carbonates and isotopic excursions a record of gas hydrate destabilization following Earth’s coldest intervals?, Kennedy et al., Geology 29(5), 442-446]

We welcome the evidence noted by Kennedy et al. (2001) for strong methane excursions associated with the cessation of glacial episodes. They identify the carbon in cap carbonates overlying glacial sediments as probably being of biogenic origin and as likely having had a biogenic methane source. These authors suggest that the methane was released from gas hydrate, which we agree is likely. However, we suggest a different mechanism for that release, rather than their suggested warming event. We propose that a dominantly pressure-related mechanism would be more plausible for releasing sufficient methane from the huge gas hydrate reservoir to modify the global greenhouse and drive global warming in a geological instant.

Geology↗
USGS2009

Polar organic compounds in pore waters of the Chesapeake Bay impact structure, Eyreville core hole: Character of the dissolved organic carbon and comparison with drilling fluids

Pore waters from the Chesapeake Bay impact structure cores recovered at Eyreville Farm, Northampton County, Virginia, were analyzed to characterize the dissolved organic carbon. After squeezing or centrifuging, a small volume of pore water, 100 μL, was taken for analysis by electrospray ionization–mass spectrometry. Pore-water samples were analyzed directly without filtration or fractionation, in positive and negative mode, for polar organic compounds. Spectra in both modes were dominated by low-molecular-weight ions. Negative mode had clusters of ions differing by ~60 daltons, possibly due to increasing concentrations of inorganic salts. The number-average molecular weight and weight-average molecular weight values for the pore waters from the Chesapeake Bay impact structure are higher than those reported for other aquatic sources of natural dissolved organic carbon as determined by electrospray ionization–mass spectrometry. In order to address the question of whether drilling mud fluids may have contaminated the pore waters during sample collection, spectra from the pore waters were compared to spectra from drilling mud fluids. Ions indicative of drilling mud fluids were not found in spectra from the pore waters, indicating there was no detectable contamination, and highlighting the usefulness of this analytical technique for detecting potential contamination during sample collection.

Virginia↗
USGS2008

Evolution of Devonian carbonate-shelf margin, Nevada

The north-trending, 550-km-long Nevada segment of the Devonian carbonate-shelf margin, which fringed western North America, evidences the complex interaction of paleotectonics, eustasy, biotic changes, and bolide impact-related influences. Margin reconstruction is complicated by mid-Paleozoic to Paleogene compressional tectonics and younger extensional and strike-slip faulting. Reports published during the past three decades identify 12 important events that influenced development of shelf-margin settings; in chronological order, these are: (1) Early Devonian inheritance of Silurian stable shelf inargin, (2) formation of Early to early Middle 'Devonian shelf-margin basins, (3) propradation of later Middle Devonian shelf margin, (4) late Middle Devonian Taghanic ondap and continuing long-term Frasnian transgression, (5) initiation of latest Middle Devonian to early Frasnian proto-Antler orogenic forebulge, (6) mid-Frasnian Alamo Impact, (7) accelerated development of proto-Antler forebulge and backbulge Pilot basin, (8) global late Frasnian sentichatovae sea-level rise, (9) end-Frasnian sea-level fluctuations and ensuing mass extinction, (10) long-term Famennian regression and continept-wide erosion, (11) late Famennian emergence: of Ahtler orogenic highlands, and (12) end-Devonian eustatic sea-level fall. Although of considerable value for understanding facies relationships and geometries, existing standard carbonate platform-margin models developed for passive settings else-where do not adequately describe the diverse depositional and, structural settings along the Nevada Devonian platform margin. Recent structural and geochemical studies suggest that the Early to Middle Devonian-shelf-margin basins may have been fault-bound and controlled by inherited Precambrian structure. Subsequently, the migrating latest Middle to Late Devonian Antler orogenic forebulge exerted a dominant control on shelf-margin position, morphology, and sedimentation.

Nevada↗
USGS2017

Responses of invasive silver and bighead carp to a carbon dioxide barrier in outdoor ponds

Resource managers need for effective methods to prevent the movement of silver ( Hypophthalmichthys molitrix ) and bighead carp ( H. nobilis ) from the Mississippi River basin into the Laurentian Great Lakes. In this study, we evaluated dissolved carbon dioxide (CO 2 ) as a barrier and deterrent to silver (278 ± 30.5 mm) and bighead (212 ± 7.7 mm) carp movement in continuous-flow outdoor ponds. As a barrier, CO 2 significantly reduced upstream movement but was not 100% effective at blocking fish passage. As a deterrent, we observed a significant shift away from areas of high CO 2 relative to normal movement before and after injection. Carbon dioxide concentrations varied across the pond during injection and reached maximum concentrations of 74.5±1.9 mg/L CO 2 ; 29 532 – 41 393 µatm at the site of injection during three independent trials. We conclude that CO 2 altered silver and bighead carp movement in outdoor ponds and recommend further research to determine barrier effectiveness during field applications.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2019

Lethal and sublethal responses of native mussels (Unionidae: Lampsilis siliquoidea and Lampsilis higginsii) to elevated carbon dioxide

Levels of carbon dioxide (CO 2 ) that have been proposed for aquatic invasive species control (24 000 – 96 000 μatm partial pressure of CO 2 ( P CO 2 ); 1 atm = 101.325 kPa) were tested on two juvenile mussels, the fatmucket ( Lampsilis siliquoidea ) and the US federally endangered Higgins’ eye ( Lampsilis higginsii ). A suite of responses (survival, growth, behavior, and gene expression) were measured after 28 days of exposure to CO 2 and 14 days postexposure. The 28-day LC 20 (concentration lethal to 20% of organisms) was lower for L. higginsii (31 800 μatm P CO 2 , 95% confidence interval (CI) 15 000 – 42 800 μatm) than for L. siliquoidea (58 200 μatm P CO 2 , 95% CI 45 200 – 68 100 μatm). Treatment-related reductions occurred in all measures of growth and condition. Expression of chitin synthase, key for shell formation, was downregulated at 28 days of exposure. Carbon dioxide caused narcotization and movement to the substrate surface of mussels, behaviors that could increase mortality by predation and displacement. We conclude that survival and growth of juvenile mussels could be reduced by continuous exposure to elevated CO 2 , but recovery may be possible with shorter-duration exposure.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2010

The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands

Black spruce (Picea mariana (Mill.) B.S.P.) forest stands range from well drained to poorly drained, typically contain large amounts of soil organic carbon (SOC), and are often underlain by permafrost. To better understand the role of soil drainage class in carbon dioxide (CO2) exchange and decomposition, we measured soil respiration and net CO2 fluxes, litter decomposition and litterfall rates, and SOC stocks above permafrost in three Alaska black spruce forest stands characterized as well drained (WD), moderately drained (MD), and poorly drained (PD). Soil respiration and net CO2 fluxes were not significantly different among sites, although the relation between soil respiration rate and temperature varied with site (Qw: WD > MD > PD). Annual estimated soil respiration, litter decomposition, and groundcover photosynthesis were greatest at PD. These results suggest that soil temperature and moisture conditions in shallow organic horizon soils at PD were more favorable for decomposition compared with the better drained sites. SOC stocks, however, increase from WD to MD to PD such that surface decomposition and C storage are diametric. Greater groundcover vegetation productivity, protection of deep SOC by permafrost and anoxic conditions, and differences in fire return interval and (or) severity at PD counteract the relatively high near-surface decomposition rates, resulting in high net C accumulation.

Canadian Journal of Forest Research↗
USGS1995

Effect of timber harvest on soil carbon storage at Blodgett Experimental Forest, California

Four plots from a mixed conifer forest were similarly cleared, burned, and replanted at various times over 17 years; a plot logged 79 years before sampling was used as a control. The plots had similar slope (2 to 15%, midslope position), aspect (south to southeast), and soil type (Holland series: mesic Haploxeralf; a Gray Brown Luvisol in the Canadian classification system). Twenty sites at each plot were sampled volumetrically by horizon to 20 cm below the organic–mineral soil boundary. Samples were analyzed for bulk density, organic C, and total N. There was an initial loss (15%) of organic C from the soil within 1 to 7 years, likely the result of oxidation (burning and decomposition) and erosion. For 17 years of forest regrowth, the soil continued to lose C (another 15%), probably owing to decomposition of slash material and possibly erosion, despite the slight accumulation of new litter and roots. After 80 years of regrowth, rates of carbon accumulation exceeded rates of loss, but carbon storage had declined and was not likely to recover to preharvest levels. Timber harvest and site preparation dramatically altered soil C and N distribution, in which C/N ratios after site preparation were initially high throughout the upper 20 cm. Subsequently, C/N ratios became lower with depth and with recovery age. Although stocks of C and N varied considerably among the plots and did not change consistently as a function of recovery age, the C/N ratios did vary systematically with recovery age. We hypothesize that the amount of C ultimately stored in the soil at steady state depends largely on N reserves and potentials, which appear to vary with erosion, intensity of burning, and site treatment.

California↗
USGS1984

Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea

The widespread occurrence of organic-carbon-rich strata (‘black shales’) in certain portions of Jurassic, Cretaceous and Cenozoic sequences has been well-documented from Deep Sea Drilling Project sites in the Atlantic and Pacific Oceans and from sequences, now exposed on land, originally deposited in the Tethyan ocean. These ancient black shales usually have been explained by analogy with examples of modern deep-sea sediments in which organic matter locally is preserved by (1) increasing the supply of organic matter, (2) increasing the rate of sedimentation, and/or (3) decreasing the oxygen content of the bottom water. However, detailed examination of many black shales reveals characteristics that cannot be explained by simple local models, including: their approximate coincidence in time globally; their occurrence in a variety of different environments, including open oxygenated oceans, restricted basins, deep and shallow water; their interbedding with organic-carbonpoor strata which often dominate a so-called black shale sequence; their deposition by pelagic, hemipelagic, turbiditic and other processes; and the variations in type and amount of organic matter that occur even within the same sequence. A more complex model for the origin of black shales therefore appears most appropriate, in which the cyclic preservation of organic matter depends on the interplay of the three main variables, namely supply of organic matter, sedimentation rate, and deep-water oxygenation, each of which varies independently to some extent. The variation and relative importance of these parameters in individual basins and widespread black shale deposition in general are linked globally and temporally by changes in global sea-level, climate and related changes in oceanic circulation. An important and often overlooked factor for the supply of organic matter to deep-basin sediments is the frequency and magnitude of redepositional processes. The interplay of these variables is discussed in relation to the middle Cretaceous and Cenozoic organic-carbon-rich strata, in particular, which show marked differences in the relative importance of the different variables.

Geological Society of London Special Publications↗