Science.gov

Sample records for archean weathering profiles

  1. REE chemistry and Sm-Nd systematics of late Archean weathering profiles in the Fortescue Group, Western Australia

    NASA Technical Reports Server (NTRS)

    MacFarlane, A. W.; Danielson, A.; Holland, H. D.; Jacobsen, S. B.

    1994-01-01

    Two weathering profiles, each consisting of an upper, sericite-rich zone and a lower, chlorite-rich zone, are preserved between flows of the Mt. Roe Basalt in the Fortescue Group, Hamersley Basin, Western Australia. REE concentrations in samples from these two profiles, which originally developed ca 2,760 Ma, show large variations depending on stratigraphic position. LREE abundances and (La/Yb)N are greatest at depths of 3-6 m below the paleosurface of the Mt. Roe #1 profile and are somewhat lower in samples above this level. The LREEs reach concentrations 6-9 times greater than in the underlying basalt, and thus appear to have been mobilized downward in the paleosol and concentrated in its middle part. LREE concentrations in the #2 profile show a similar distribution but with a sharp increase in all REE concentrations within 50 cm of the paleosurface. The distinction between the REE profiles in the two paleosols may be related to the difference in the overlying material. The #1 paleosol is overlain by a few meters of sediments and then by basalt, whereas the #2 paleosol is directly overlain by basalt. The LREEs appear to have been mobilized both during chemical weathering of the parental basalt and during later lower-greenschist-facies metamorphism and metasomatism of the paleosols. Remobilization of the REEs during the regional metamorphism of the Fortescue Group is confirmed by a whole-rock Sm-Nd reference isochron of Mt. Roe #1 samples with an age of 2,151 +/- 360 Ma. Variable initial 143Nd/144Nd values of unweathered basalt samples which may represent the paleosol protolith prevents a confident determination of the magnitude of LREE mobility. Both the initial mobilization of the REEs during weathering and the metasomatic remobilization appear to have taken place under redox conditions where Ce was present dominantly as Ce3+, because Ce anomalies are not developed within the sericite zone samples regardless of concentration. Europium anomalies in the

  2. REE chemistry and Sm-Nd systematics of late Archean weathering profiles in the Fortescue Group, Western Australia.

    PubMed

    MacFarlane, A W; Danielson, A; Holland, H D; Jacobsen, S B

    1994-04-01

    Two weathering profiles, each consisting of an upper, sericite-rich zone and a lower, chlorite-rich zone, are preserved between flows of the Mt. Roe Basalt in the Fortescue Group, Hamersley Basin, Western Australia. REE concentrations in samples from these two profiles, which originally developed ca 2,760 Ma, show large variations depending on stratigraphic position. LREE abundances and (La/Yb)N are greatest at depths of 3-6 m below the paleosurface of the Mt. Roe #1 profile and are somewhat lower in samples above this level. The LREEs reach concentrations 6-9 times greater than in the underlying basalt, and thus appear to have been mobilized downward in the paleosol and concentrated in its middle part. LREE concentrations in the #2 profile show a similar distribution but with a sharp increase in all REE concentrations within 50 cm of the paleosurface. The distinction between the REE profiles in the two paleosols may be related to the difference in the overlying material. The #1 paleosol is overlain by a few meters of sediments and then by basalt, whereas the #2 paleosol is directly overlain by basalt. The LREEs appear to have been mobilized both during chemical weathering of the parental basalt and during later lower-greenschist-facies metamorphism and metasomatism of the paleosols. Remobilization of the REEs during the regional metamorphism of the Fortescue Group is confirmed by a whole-rock Sm-Nd reference isochron of Mt. Roe #1 samples with an age of 2,151 +/- 360 Ma. Variable initial 143Nd/144Nd values of unweathered basalt samples which may represent the paleosol protolith prevents a confident determination of the magnitude of LREE mobility. Both the initial mobilization of the REEs during weathering and the metasomatic remobilization appear to have taken place under redox conditions where Ce was present dominantly as Ce3+, because Ce anomalies are not developed within the sericite zone samples regardless of concentration. Europium anomalies in the

  3. A model for late Archean chemical weathering and world average river water

    NASA Astrophysics Data System (ADS)

    Hao, Jihua; Sverjensky, Dimitri A.; Hazen, Robert M.

    2017-01-01

    Interpretations of the geologic record of late Archean near-surface environments depend very strongly on an understanding of weathering and resultant riverine transport to the oceans. The late Archean atmosphere is widely recognized to be anoxic (pO2,g =10-5 to 10-13 bars; pH2,g =10-3 to 10-5 bars). Detrital siderite (FeCO3), pyrite (FeS2), and uraninite (UO2) in late Archean sedimentary rocks also suggest anoxic conditions. However, whether the observed detrital minerals could have been thermodynamically stable during weathering and riverine transport under such an atmosphere remains untested. Similarly, interpretations of fluctuations recorded by trace metals and isotopes are hampered by a lack of knowledge of the chemical linkages between the atmosphere, weathering, riverine transport, and the mineralogical record. In this study, we used theoretical reaction path models to simulate the chemistry involved in rainwater and weathering processes under present-day and hypothetical Archean atmospheric boundary conditions. We included new estimates of the thermodynamic properties of Fe(II)-smectites as well as smectite and calcite solid solutions. Simulation of present-day weathering of basalt + calcite by world-average rainwater produced hematite, kaolinite, Na-Mg-saponite, and chalcedony after 10-4 moles of reactant minerals kg-1 H2O were destroyed. Combination of the resultant water chemistry with results for granitic weathering produced a water composition comparable to present-day world average river water (WARW). In contrast, under late Archean atmospheric conditions (pCO2,g =10-1.5 and pH2,g =10-5.0 bars), weathering of olivine basalt + calcite to the same degree of reaction produced kaolinite, chalcedony, and Na-Fe(II)-rich-saponite. Late Archean weathering of tonalite-trondhjemite-granodiorite (TTG) formed Fe(II)-rich beidellite and chalcedony. Combining the waters from olivine basalt and TTG weathering resulted in a model for late Archean WARW with the

  4. Oxidative Weathering of Archean Sulfides: Implications for the Great Oxidation Event

    NASA Astrophysics Data System (ADS)

    Johnson, A.; Romaniello, S. J.; Reinhard, C.; Garcia-Robledo, E.; Revsbech, N. P.; Canfield, D. E.; Lyons, T. W.; Anbar, A. D.

    2015-12-01

    The first widely accepted evidence for oxidation of Earth's atmosphere and oceans occurs ~2.45 Ga immediately prior to the Great Oxidation Event (GOE). A major line of evidence for this transition includes the abundances and isotopic variations of redox-sensitive transition metals in marine sediments (e.g., Fe, Mo, Re, Cr, and U). It is often assumed that oxidative weathering is required to liberate these redox-sensitive elements from sulfide minerals in the crust, and hence that their presence in early Archean marine sediments signifies that oxidative weathering was stimulated by small and/or transient "whiffs" of O2 in the environment.1 However, studies of crustal sulfide reactivity have not been conducted at O2 concentrations as low as those that would have prevailed when O2 began its rise during the late Archean (estimated at <10-5 present atmospheric O2).2 As a result, it is difficult to quantify O2 concentrations implied by observed trace metal variations. As a first step toward providing more quantitative constraints on late Archean pO2, we conducted laboratory studies of pyrite and molybdenite oxidation kinetics at the nanomolar O2 concentrations that are relevant to late Archean environments. These measurements were made using recently developed, highly sensitive optical O2 sensors to monitor the rates at which the powdered minerals consumed dissolved O2 in a range of pH-buffered solutions.3Our data extend the range of experimental pyrite oxidation rates in the literature by three orders of magnitude from ~10-3 present atmospheric O2 to ~10-6. We find that molybdenite and pyrite oxidation continues to <1 nM O2 (4 x 10-6 present atmospheric O2). This implies that oxidative weathering of sulfides could occur under conditions which preserve MIF S fractionation. Furthermore, our results indicate that the rate law and reaction order of pyrite oxidation kinetics change significantly at nanomolar concentrations of O2 when compared to previous compilations.2 Our

  5. Deciphering post-Deccan weathering and erosion history of South Indian Archean rocks from cryptomelane 40Ar-39Ar dating

    NASA Astrophysics Data System (ADS)

    Bonnet, Nicolas; Arnaud, Nicolas; Beauvais, Anicet; Chardon, Dominique

    2015-04-01

    Since the extrusion of Deccan traps ~ 63 Ma ago, weathering and erosion processes have shaped the landscapes of this Peninsula India. This resulted in pervasive bauxitic weathering on traps and deep lateritic weathering of their basement on either side of the Western Ghats Escarpment, which separates a coastal lowland from an East-dipping highland plateau. Mn-rich lateritic profiles formed by supergene weathering of Late Archean manganiferous protores in the different greenstone belts are exposed on relict paleosurfaces, which are preserved at different elevations on the highland plateau and in the coastal lowland, allowing for direct comparison of paleosurfaces and geomorphological processes across one of the most prominent relief in the Indian peninsula. Detailed petrological and geochemical investigations of samples collected in the different Mn-rich lateritic profiles allowed for precise characterization of cryptomelane [Kx Mn8-xIV MnxIII O16, nH2O], a Mn-oxide suitable for 40Ar-39Ar dating. The ages obtained document major weathering periods at ~ 53-50 Ma, ~ 40-32 Ma, and ~ 30-23 Ma in the highland profiles, and ~ 47-45 Ma, ~ 24-19 Ma and a younger age at ~ 9 Ma in the coastal lowland profiles. The age clusters are in good agreement with major regional and global Cenozoic paleoclimatic events, e.g., the Eocene climatic optimum and the early beginnings of Asian monsoons at ~ 40 Ma. The old ages obtained both in the coastal lowland and high plateau indicate synchronous lateritic (mostly bauxitic) weathering on both sides of the escarpment. The ages also indicate that most of the incision and dissection of plateau landsurfaces must have taken place during successive periods after 45, 32 and 23 Ma, while the coastal lowland surface was only weakly incised after 19 Ma. Our results thus document post-Eocene divergent erosion and weathering histories across the escarpment since it was formed at least 47 Ma ago, suggesting installation of a dual climatic regime on

  6. Weathering in the late Archean and perturbations by oxygenic photosynthesis (Invited)

    NASA Astrophysics Data System (ADS)

    Sverjensky, D. A.; Lee, N.; Hazen, R. M.

    2009-12-01

    Low values for logfO2 in the near-surface late Archean environment have long been suggested based on upper limits deduced from the preservation of detrital siderite, pyrite and uraninite, paleosols, atmospheric models, and models of sulfur isotope data. Reducing conditions could presumably be maintained by an adequate supply of reductants such as H2 and CO supplied from volcanic sources, although these must have reacted with exposed rocks via aqueous solutions during weathering processes. In addition, once oxygenic photosynthesis arose, there would probably be a period of time during which weathering and atmospheric reductants would compete with the O2 released by photosynthesis. What has not been sufficiently explored quantitatively are the implications of such processes for the evolution of the aqueous solution chemistry and weathering products. In the present study, irreversible chemical mass transfer models were used to investigate the chemical reaction of rainwater from an Archean atmosphere with volcanic gases and continental crust to gain insight into the types of minerals that may result, and the evolution of the water chemistry and oxidation state of the near-surface environment. The minerals enstatite, ferrosilite, diopside, anorthite and albite were permitted to react irreversibly with a model rainwater with a starting composition similar to that of the present-day, but with logfO2 = -70 and logfCO2 = -1.5. Simultaneously, the rainwater was reacted with a model mixture of volcanic gases including H2, H2S, SO2, CO2 and CO. The reactions produced a Na-Mg-Ca-HCO3 water and minerals such as pyrite, kaolinite, chalcedony, siderite and calcite. Dissolved ferrous iron reached a maximum of about 3 ppm indicating that ferrous iron could be transported in Archean riverine systems to the oceans. The oxidation state of the system stayed roughly constant (about ±2 units of logfO2) in or near the pyrite and siderite stability fields consistent with the preservation

  7. Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean

    PubMed Central

    Kendall, Brian; Creaser, Robert A.; Reinhard, Christopher T.; Lyons, Timothy W.; Anbar, Ariel D.

    2015-01-01

    It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event. A depositional age of 2495 ± 14 million years and an initial 187Os/188Os of 0.34 ± 0.19 were obtained for rhenium- and molybdenum-rich black shales. The initial 187Os/188Os is higher than the mantle/extraterrestrial value of 0.11, pointing to mild environmental oxygenation and oxidative mobilization of rhenium, molybdenum, and radiogenic osmium from the upper continental crust and to contemporaneous transport of these metals to seawater. By contrast, stratigraphically overlying black shales are rhenium- and molybdenum-poor and have a mantle-like initial 187Os/188Os of 0.06 ± 0.09, indicating a reduced continental flux of rhenium, molybdenum, and osmium to seawater because of a drop in environmental O2 levels. Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean. PMID:26702438

  8. Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean.

    PubMed

    Kendall, Brian; Creaser, Robert A; Reinhard, Christopher T; Lyons, Timothy W; Anbar, Ariel D

    2015-11-01

    It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event. A depositional age of 2495 ± 14 million years and an initial (187)Os/(188)Os of 0.34 ± 0.19 were obtained for rhenium- and molybdenum-rich black shales. The initial (187)Os/(188)Os is higher than the mantle/extraterrestrial value of 0.11, pointing to mild environmental oxygenation and oxidative mobilization of rhenium, molybdenum, and radiogenic osmium from the upper continental crust and to contemporaneous transport of these metals to seawater. By contrast, stratigraphically overlying black shales are rhenium- and molybdenum-poor and have a mantle-like initial (187)Os/(188)Os of 0.06 ± 0.09, indicating a reduced continental flux of rhenium, molybdenum, and osmium to seawater because of a drop in environmental O2 levels. Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean.

  9. Geochemistry of archean shales from the Witwatersrand Supergroup, South Africa: source-area weathering and provenance

    SciTech Connect

    Wronkiewicz, D.J.; Condie, K.C.

    1987-09-01

    With a few exceptions, shales from the Archean Witwatersrand Supergroup in South Africa are depleted in Na, Ca, Large ion lithophile elements (LILE, rare earth elements (REE) and half field strength elements ((HFSE) compared to Phanerozoic shales. Cr, Co and Ni are enriched in all Witwatersrand shales and Fe and Mg are high in shales from the West Rand Groups (WRG) and lower Central Rand Group (CRG). Shales from the CRG and uppermost WRG are enriched in Na, Al, LILE, REE, HFSE and transition metals relative to shales from the lower WRG. Chondrite-normalized REE patterns for all Witwatersrand shales are enriched in light-REE and exhibit small to moderate negative Eu anomalies. Relative to shales from the CRG, shales from the WRG exhibit depletions of Na, Ca and Sr, a feature probably reflecting intense chemical weathering of their source rocks. CIA indices in Witwatersrand shales are variable, even within the same shale unit. Such variations reflect chiefly variable climatic zones or rates of tectonic uplift in source areas with perhaps some contribution from provenance and element remobilization during metamorphism. Compared to present-day upper continental crust, all but the Orange Grove, Roodepoort, and K8 shales appear to have been derived from continental sources depleted in LILE, REE, and HFSE and enriched in transition metals. Computer mixing models abased on six relatively immobile elements (Th, Hf, Yb, La, Sc, Co) and four source rocks indicate that the relative proportions of granite, basalt and komatiite increased with time in sediment source areas at the expense of tonalite.

  10. The Archean kerogen paradox

    NASA Astrophysics Data System (ADS)

    Ohmoto, H.

    2012-12-01

    The constituents of organic matter buried in sediments (kerogen) are classified into three types: (1) liable components that may be decomposed by aerobic and anaerobic microbes during the early diagenesis of sediments, and by thermal decomposition during the burial at ~3-5 km depths (T = 100 ~150°C) to generate bitumen (oil); (2) refractory components that may decompose into gaseous components at greater depths (T = 150-230°C); and (iii) inert components that may be converted to graphite during high temperature metamorphism. Laboratory experiments and field observations indicate that matured kerogen (i.e., refractory and inert components) is decomposed during the weathering under an oxygenated atmosphere by reaction C + O2 → CO2, promoted by aerobic organisms. This has resulted in the general absence of old detrital kerogen (except debris of vascular plants) in Phanerozoic-aged sedimentary rocks. In contrast, matured kerogen would not be decomposed during the weathering under a reducing atmosphere, because the reactions C + 2H2 → CH4, C + 2H2O → CO2 + 2H2 and 2C + 2H2O → CO2 + CH4 would not proceed at low temperatures even with the aid of anaerobic organisms. If such reactions could occur at low temperatures, sedimentary rocks, regardless of their age, would have lost all their kerogen before being buried to depths ~3 km. If the Archean atmosphere had been reducing, as postulated by the dominant paradigm of the early Earth, detrital kerogen should be ubiquitously present in Archean-aged sedimentary rocks. We should also find general increasing trends in both the ratio of detrital/syngenetic kerogens and the total amount of reduced C (syngenetic and detrital kerogens) in sedimentary rocks from ~3.8 Ga to ~2.5 Ga in age. Because the detrital kerogen had been subjected to metamorphism and weathering before being transported to the oceans, detrital kerogen would have different structures, textures, and elemental and isotopic ratios compared to the syngenetic

  11. Weathering profiles in granites, Sierra Norte (Córdoba, Argentina)

    NASA Astrophysics Data System (ADS)

    Kirschbaum, Alicia; Martínez, Estela; Pettinari, Gisela; Herrero, Silvana

    2005-09-01

    Two weathering profiles evolved on peneplain-related granites in Sierra Norte, Córdoba province, were examined. Several weathering levels, of no more than 2 m thickness, were studied in these profiles. They had developed from similar parent rock, which had been exposed to hydrothermal processes of varying intensity. Fracturing is the most notable feature produced by weathering; iron oxides and silica subsequently filled these fractures, conferring a breccia-like character to the rock. The clay minerals are predominantly illitic, reflecting the mineral composition of the protolith. Smaller amounts of interstratified I/S RO type are also present, as well as scarce caolinite+chlorite that originated from the weathering of feldspar and biotite, respectively. The geochemical parameters define the weathering as incipient, in contrast to the geomorphological characteristics of Sierra Norte, which point to a long weathering history. This apparent incompatibility could be due to the probable erosion of the more weathered levels of the ancient peneplains, of which only a few relicts remain. Similar processes have been described at different sites in the Sierras Pampeanas. Reconstruction and dating of the paleosurfaces will make it possible to set time boundaries on the weathering processes studied and adjust the paleographic and paleoclimatic interpretations of this great South American region.

  12. Impact of AIRS Thermodynamic Profile on Regional Weather Forecast

    NASA Technical Reports Server (NTRS)

    Chou, Shih-Hung; Zavodsky, Brad; Jedlovee, Gary

    2010-01-01

    Prudent assimilation of AIRS thermodynamic profiles and quality indicators can improve initial conditions for regional weather models. AIRS-enhanced analysis has warmer and moister PBL. Forecasts with AIRS profiles are generally closer to NAM analyses than CNTL. Assimilation of AIRS leads to an overall QPF improvement in 6-h accumulated precipitation forecasts. Including AIRS profiles in assimilation process enhances the moist instability and produces stronger updrafts and a better precipitation forecast than the CNTL run.

  13. Sulfate-rich Archean Oceans

    NASA Astrophysics Data System (ADS)

    Brainard, J. L.; Choney, A. P.; Ohmoto, H.

    2012-12-01

    deposits, except for the lower d34S values for the seawater SO4. The abundance of pyrite in Archean black shales is also evidence of sulfate rich seawater. Pyrites in Archean-aged black shales were most likely the products of either bacterial or thermochemical sulfate reduction during diagenesis of the sediments. Their abundance in sedimentary rocks is determined by: (a) the availability of reactive carbon; (b) the availability of reactive Fe (Fe3+ hydroxides and Fe2+-rich pore fluid); (c) the sedimentation rate; and (d) the flux of SO42- in the sediments, which depends on the seawater SO42- contents. Contrary to a widely held belief, pyrite- and organic C rich black Archean shales are quite common, such as the 2.7 Ga Jeerinah and the 2.5 Ga McRae Shales in WA. Our modeling suggests that the formation of such pyrite-rich shales requires seawater SO4 contents greater than ~1 mM. As for the main source of SO4 in the Archean oceans, the current paradigm, based on mass independent fractionation of sulfur isotopes (MIF-S) in some pyrite and barite samples from some pre-2.4 Ga sedimentary rocks, postulates that the seawater SO4 was produced by UV photolysis of volcanic SO2 gas in an O2-poor atmosphere. However, the recent findings of the absence of MIF-S in many Archean sedimentary rocks, as well as those of oxidized paleosols of Archean ages, suggest that the abundant SO4 in the Archean oceans were generated by the oxidative weathering of sulfides.

  14. Clay mineralogy of weathering profiles from the Carolina Piedmont.

    USGS Publications Warehouse

    Loferski, P.J.

    1981-01-01

    Saprolite profiles (12) that formed over various crystalline rocks from the Charlotte 1o X 2o quadrangle showed overall similarity in their clay mineralogy to depths of 6 to 45 m indicating control by weathering processes rather than by rock type. Most saprolite contained 10-25% clay, and ranged 3 to 70%. Kaolinite and halloysite composed = or >75% of the clay fraction of most samples. The ratio kaolinite:halloysite ranged widely, from 95% kaolinite to 90% halloysite, independent of depth. Clay-size mica was present in all profiles, and ranged 5-75% over a sericite schist. Mixed-layer mica-smectite and mica-vermiculite were subordinate; discrete smectite and vermiculite were rare. The abundance of halloysite indicates a continuously humid environment since the time of profile formation, because of the rapidity with which halloysite dehydrates irreversibly. -R.S.M.

  15. Chemical depth profiling of photovoltaic backsheets after accelerated laboratory weathering

    NASA Astrophysics Data System (ADS)

    Lin, Chiao-Chi; Krommenhoek, Peter J.; Watson, Stephanie S.; Gu, Xiaohong

    2014-10-01

    Polymeric multilayer backsheets provide protection for the backside of photovoltaic (PV) module from the damage of moisture and ultraviolet (UV). Due to the nature of multilayer films, certain material property characterization of a backsheet could only be studied by examining its cross-section parallel to the thickness direction of the film. In this study, commercial PPE (polyethylene terephthalate (PET)/PET/ethylene vinyl acetate (EVA)) backsheet films were aged on the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) with UV irradiance at 170 W/m2 (300 nm to 400 nm) under accelerated weathering conditions of 85°C and two relative humidity (R.H.) levels of 5% (low) and 60% (high). Cryo-microtomy was used to obtain cross-sectional PPE samples with a flat surface parallel to the thickness direction, and chemical depth profiling of multilayers was conducted by Raman microscopic mapping. Atomic force microscopy with peak force tapping mode was used complementarily for cross-sectional imaging. The results revealed that the PPE backsheet films were comprised of five main layers, including pigmented-PET, core PET, inner EVA, pigmented-EVA and outer EVA, along with their interfacial regions and two adhesive layers. UV and moisture degradation on the outer pigmented PET layer was clearly observed; while the damage on the core PET layer was less significance, indicating that the outer pigmented PET layer effectively reduced the damage from UV. In high R.H. exposure, both adhesive layers were severely deteriorated. It was found that the EVA layers were susceptible to moisture at elevated temperature, especially for the pigmented-EVA. Based on the results of accelerated weathering, this depth profiling study brings new understanding to the mechanisms of failure observed in polymeric multilayer backsheets during field exposure.

  16. Chemical and Mineralogical Patterns Along a Late-Archean Crustal Profile in Southern India: Signatures of a High Temperature Brine?

    NASA Astrophysics Data System (ADS)

    Hansen, E. C.; Harlov, D. E.

    2004-12-01

    Several features are present in a regional dehydration zone in Tamil Nadu, Southern India that have been attributed to the action of high temperature brines in smaller scale more localized dehydration zoneselsewhere (Harlov and Forster, 2002. J Pet. 43: 769-824). Many of these same features can also be explained by a model in which dehydration is the result of partial melting during high-grade metamorphism. An 8-km thick section of late Archean, mid to lower crust was studied along a 100 km traverse from Krishnagiri to Salem. Intermediate to felsic orthognesises make up the bulk of the terrane. In the northern amphibolite-facies zone these contain hornblende and biotite. First clinopyroxene and then orthopyroxene appear in the central transitional zone and become more abundant southwards as biotite and hornblende abundances decrease. Orthopyroxene is the dominant ferromagnesian silicate in the southern zone and garnet is widespread. Among the features of this traverse that can be explained by the migration of a high temperature brine upwards through the crust are: 1) the presence of K-feldspar grain boundary veins that increase in abundance with increasing metamorphic grade , 2) monazite grains within and on the rim of apatites in orthopyroxene-bearing gneisses, 3) increases in F concentrations in apatite and biotite and increases in the calculated HF-fugacity/H2O-fugacity ratios with increasing metamorphic grade, 4) depletion in whole rock Th and U, 5) depletion in both whole rock Rb and Rb in biotite southwards with increasing grade, 6) relatively high oxygen fugacities (2.5 log units above QFM) in orthopyroxene-bearing rocks, 7) increases in the abundance of hematite-rich hemo-ilmenites southwards with increasing grade, and 8) redistribution of REE from titanite in amphibolite-facies gneisses to apatite in granulite-facies gneisses. Monazite rims on apatite and K-feldspar grain boundary veins are also consistent with a model of metamorphism involving dehydration

  17. Weather.

    ERIC Educational Resources Information Center

    Ruth, Amy, Ed.

    1996-01-01

    This theme issue of "The Goldfinch" focuses on weather in Iowa and weather lore. The bulletin contains historical articles, fiction, activities, and maps. The table of contents lists: (1) "Wild Rosie's Map"; (2) "History Mystery"; (3) "Iowa's Weather History"; (4) "Weather Wonders"; (6)…

  18. Depth-related changes in community structure of culturable mineral weathering bacteria and in weathering patterns caused by them along two contrasting soil profiles.

    PubMed

    Huang, Jing; Sheng, Xia-Fang; Xi, Jun; He, Lin-Yan; Huang, Zhi; Wang, Qi; Zhang, Zhen-Dong

    2014-01-01

    Bacteria play important roles in mineral weathering and soil formation. However, few reports of mineral weathering bacteria inhabiting subsurfaces of soil profiles have been published, raising the question of whether the subsurface weathering bacteria are fundamentally distinct from those in surface communities. To address this question, we isolated and characterized mineral weathering bacteria from two contrasting soil profiles with respect to their role in the weathering pattern evolution, their place in the community structure, and their depth-related changes in these two soil profiles. The effectiveness and pattern of bacterial mineral weathering were different in the two profiles and among the horizons within the respective profiles. The abundance of highly effective mineral weathering bacteria in the Changshu profile was significantly greater in the deepest horizon than in the upper horizons, whereas in the Yanting profile it was significantly greater in the upper horizons than in the deeper horizons. Most of the mineral weathering bacteria from the upper horizons of the Changshu profile and from the deeper horizons of the Yanting profile significantly acidified the culture media in the mineral weathering process. The proportion of siderophore-producing bacteria in the Changshu profile was similar in all horizons except in the Bg2 horizon, whereas the proportion of siderophore-producing bacteria in the Yanting profile was higher in the upper horizons than in the deeper horizons. Both profiles existed in different highly depth-specific culturable mineral weathering community structures. The depth-related changes in culturable weathering communities were primarily attributable to minor bacterial groups rather than to a change in the major population structure.

  19. Depth-Related Changes in Community Structure of Culturable Mineral Weathering Bacteria and in Weathering Patterns Caused by Them along Two Contrasting Soil Profiles

    PubMed Central

    Huang, Jing; Xi, Jun; Huang, Zhi; Wang, Qi; Zhang, Zhen-Dong

    2014-01-01

    Bacteria play important roles in mineral weathering and soil formation. However, few reports of mineral weathering bacteria inhabiting subsurfaces of soil profiles have been published, raising the question of whether the subsurface weathering bacteria are fundamentally distinct from those in surface communities. To address this question, we isolated and characterized mineral weathering bacteria from two contrasting soil profiles with respect to their role in the weathering pattern evolution, their place in the community structure, and their depth-related changes in these two soil profiles. The effectiveness and pattern of bacterial mineral weathering were different in the two profiles and among the horizons within the respective profiles. The abundance of highly effective mineral weathering bacteria in the Changshu profile was significantly greater in the deepest horizon than in the upper horizons, whereas in the Yanting profile it was significantly greater in the upper horizons than in the deeper horizons. Most of the mineral weathering bacteria from the upper horizons of the Changshu profile and from the deeper horizons of the Yanting profile significantly acidified the culture media in the mineral weathering process. The proportion of siderophore-producing bacteria in the Changshu profile was similar in all horizons except in the Bg2 horizon, whereas the proportion of siderophore-producing bacteria in the Yanting profile was higher in the upper horizons than in the deeper horizons. Both profiles existed in different highly depth-specific culturable mineral weathering community structures. The depth-related changes in culturable weathering communities were primarily attributable to minor bacterial groups rather than to a change in the major population structure. PMID:24077700

  20. Non-systematic weathering profile in the Blue Ridge Mountains, N. C. : Role of geochemical variables

    SciTech Connect

    Ciampone, M.A.; McVey, D.E.; Gerke, T.L.; Briggs, W.D.; Zhang, Yangsheng; Maynard, J.B.; Huff, W.D. . Dept. of Geology)

    1992-01-01

    Weathering profiles from representative cores of the Coweeta Group, schist, and Tallulah Falls Fm, gneiss, in the Blue Ridge Mountains of North Carolina were examined. The predominant alteration minerals, which formed from the partial alteration of biotite and plagioclase, include kaolinite, chlorite, vermiculite interstratified with biotite, gibbsite. These mineral phases were identified using petrographic observation, SEM, X-ray diffraction, and selected electron microprobe analysis. These minerals commonly represent a weathering profile (developed from surface to depth on a single source rock) ranging from mature (gibbsite), to intermediate (kaolinite + interlayered biotite/vermiculite), to immature (plagioclase + biotite) at depth. In this study, however, there is no clear vertical zonation of the weathering profile. This indicates a more selective weathering process than would typically be assumed. This nonsystematic weathering profile may reflect variations in bulk composition of the parent rock and/or variations in the composition of ground water. The presence and abundance of gibbsite in these weathering profiles is unusual because it is normally associated with bauxite in which the Al[sub 2]O[sub 3] content is > 80 wt.%. In this study the Al[sub 2]O[sub 3] content of the regolith is approximately 20 wt.%. The presence of gibbsite emphasizes the importance of solution-reprecipitation of Al-rich phases as an independent process in temperature climates, and suggests the activity of silica is more critical than regional climatological effects in controlling regolith formation.

  1. Fossil Microorganisms and Formation of Early Precambrian Weathering Profiles

    NASA Technical Reports Server (NTRS)

    Rozanov, A. Yu; Astafieva, M. M.; Vrevsky, A. B.; Alfimova, N. A.; Matrenichev, V. A.; Hoover, R. B.

    2009-01-01

    Weathering crusts are the only reliable evidences of the existence of continental conditions. Often they are the only source of information about exogenous processes and subsequently about conditions under which the development of the biosphere occurred. A complex of diverse fossil microorganisms was discovered as a result of Scanning Electron Microscope investigations. The chemical composition of the discovered fossils is identical to that of the host rocks and is represented by Si, Al, Fe, Ca and Mg. Probably, the microorganisms fixed in rocks played the role of catalyst. The decomposition of minerals comprising the rocks and their transformation into clayey (argillaceous) minerals, most likely occurred under the influence of microorganisms. And may be unique weathering crusts of Early Precambrian were formed due to interaction between specific composition of microorganism assemblage and conditions of hypergene transformations. So it is possible to speak about colonization of land by microbes already at that time and about existence of single raw from weathering crusts (Primitive soils) to real soils.

  2. The Impact of Atmospheric InfraRed Sounder (AIRS) Profiles on Short-term Weather Forecasts

    NASA Technical Reports Server (NTRS)

    Chou, Shih-Hung; Zavodsky, Brad; Jedlovec, Gary J.; Lapenta, William

    2007-01-01

    The Atmospheric Infrared Sounder (AIRS), together with the Advanced Microwave Sounding Unit (AMSU), represents one of the most advanced spacebased atmospheric sounding systems. The combined AlRS/AMSU system provides radiance measurements used to retrieve temperature profiles with an accuracy of 1 K over 1 km layers under both clear and partly cloudy conditions, while the accuracy of the derived humidity profiles is 15% in 2 km layers. Critical to the successful use of AIRS profiles for weather and climate studies is the use of profile quality indicators and error estimates provided with each profile Aside form monitoring changes in Earth's climate, one of the objectives of AIRS is to provide sounding information of sufficient accuracy such that the assimilation of the new observations, especially in data sparse region, will lead to an improvement in weather forecasts. The purpose of this paper is to describe a procedure to optimally assimilate highresolution AIRS profile data in a regional analysis/forecast model. The paper will focus on the impact of AIRS profiles on a rapidly developing east coast storm and will also discuss preliminary results for a 30-day forecast period, simulating a quasi-operation environment. Temperature and moisture profiles were obtained from the prototype version 5.0 EOS science team retrieval algorithm which includes explicit error information for each profile. The error profile information was used to select the highest quality temperature and moisture data for every profile location and pressure level for assimilation into the ARPS Data Analysis System (ADAS). The AIRS-enhanced analyses were used as initial fields for the Weather Research and Forecast (WRF) system used by the SPORT project for regional weather forecast studies. The ADASWRF system will be run on CONUS domain with an emphasis on the east coast. The preliminary assessment of the impact of the AIRS profiles will focus on quality control issues associated with AIRS

  3. 10Be analysis of a Quaternary weathering profile in the Virginia Piedmont.

    USGS Publications Warehouse

    Pavich, M.J.; Brown, Louis; Valette-Silver, J. Nathalie; Klein, Jeffrey; Middleton, Roy

    1985-01-01

    Samples from a residual weathering profile in the Virginia Piedmont have been analyzed for cosmogenic 10Be. Concentrations are highest in clay-rich soil and decrease exponentially to a depth of about 15 m. Despite uncertainties about the processes by which 10Be may be intercepted before entering the solum and eroded after incorporation, a minimum age may be calculated for the regolith. This calculation is based on the delivery rate of 10Be and its decay rate and suggests that this residual profile developed during a period no shorter than 8 × 105 yr. The calculated minimum age may be within a factor of 2 of maximum-age estimates based on surface lowering by erosion and on the rate of rock weathering to saprolite. The vertical distribution of 10Be in the profile could result from a steady-state balance of deposition, weathering, radioactive decay, and erosion.

  4. The scope of the Weatherization Assistance Program: Profile of the population in need

    SciTech Connect

    Eisenberg, J.F.; Michels, E.; Carroll, D.; Berdux, N.

    1994-03-01

    The U.S. Department of Energy (DOE) is conducting a national evaluation of its Weatherization Assistance Program, an energy efficiency program that provides financial assistance to qualifying low-income households for the {open_quotes}weatherization{close_quotes} of their housing units. The evaluation, being conducted for the Department by Oak Ridge National Laboratory (ORNL), is comprised of five studies. One of the five is a two-part analysis of the scope of the Weatherization Assistance Program and other resources devoted to low-income energy efficiency, including the number of dwellings weatherized to date and the population remaining to be served. This study is referred to here as the {open_quotes}Scope{close_quotes} study. This report presents the results of the second part of the {open_quotes}Scope{close_quotes} study, which investigates the characteristics of the population eligible for and in need of the DOE Weatherization Assistance Program - The Profile of the Population in Need. The {open_quotes}Profile{close_quotes} study is an attempt to use the Energy Information Administration`s Residential Energy Consumption Survey (RECS) for 1990 to define the weatherization-related characteristics of the low-income population. The RECS, a national survey with a sample size of 5,095 households, is the most reliable source for information regarding residential energy-use and housing characteristics because data is collected from fuel vendors on actual household energy bills and consumption for a large and representative sample of households.

  5. The Scope of the Weatherization Assistance Program: Profile of the Population in Need

    SciTech Connect

    Eisenberg, J.F.

    1994-01-01

    The U.S. Department of Energy (DOE) is conducting a national evaluation of its Weatherization Assistance Program, an energy efficiency program that provides financial assistance to qualifying low-income households for the ''weatherization'' of their housing units. The evaluation, being conducted for the Department by Oak Ridge National Laboratory (ORNL), is comprised of five studies. One of the five is a two-part analysis of the scope of the Weatherization Assistance Program and other resources devoted to low-income energy efficiency, including the number of dwellings weatherized to date and the population remaining to be served. This study is referred to here as the ''Scope'' study. This report presents the results of the second part of the ''Scope'' study, which investigates the characteristics of the population eligible for and in need of the DOE Weatherization Assistance Program--The Profile of the Population in Need. The ''Profile'' study is an attempt to use the Energy Information Administration's Residential Energy Consumption Survey (RECS) for 1990 to define the weatherization-related characteristics of the low-income population. The RECS, a national survey with a sample size of 5,095 households, is the most reliable source for information regarding residential energy-use and housing characteristics because data is collected from fuel vendors on actual household energy bills and consumption for a large and representative sample of households.

  6. Determining rates of chemical weathering in soils - Solute transport versus profile evolution

    USGS Publications Warehouse

    Stonestrom, D.A.; White, A.F.; Akstin, K.C.

    1998-01-01

    SiO2 fluxes associated with contemporary solute transport in three deeply weathered granitoid profiles are compared to bulk SiO2 losses that have occurred during regolith development. Climates at the three profiles range from Mediterranean to humid to tropical. Due to shallow impeding alluvial layers at two of the profiles, and seasonally uniform rainfall at the third, temporal variations in hydraulic and chemical state variables are largely attenuated below depths of 1-2 m. This allows current SiO2 fluxes below the zone of seasonal variations to be estimated from pore-water concentrations and average hydraulic flux densities. Mean-annual SiO2 concentrations were 0.1-1.5 mM. Hydraulic conductivities for the investigated range of soil-moisture saturations ranged from 10-6 m s-1. Estimated hydraulic flux densities for quasi-steady portions of the profiles varied from 6 x 10-9 to 14 x 10-9 m s-1 based on Darcy's law and field measurements of moisture saturations and pressure heads. Corresponding fluid-residence times in the profiles ranged from 10 to 44 years. Total SiO2 losses, based on chemical and volumetric changes in the respective profiles, ranged from 19 to 110 kmoles SiO2 m-2 of land surface as a result of 0.2-0.4 Ma of chemical weathering. Extrapolation of contemporary solute fluxes to comparable time periods reproduced these SiO2 losses to about an order of magnitude. Despite the large range and non-linearity of measured hydraulic conductivities, solute transport rates in weathering regoliths can be estimated from characterization of hydrologic conditions at sufficiently large depths. The agreement suggests that current weathering rates are representative of long-term average weathering rates in the regoliths.SiO2 fluxes associated with contemporary solute transport in three deeply weathered granitoid profiles are compared to bulk SiO2 losses during regolith development. Due to shallow impeding alluvial layers at two of the profiles, and seasonally uniform

  7. Water-rock interaction on the development of granite gneissic weathered profiles in Garhwal Lesser Himalaya, India

    NASA Astrophysics Data System (ADS)

    Vyshnavi, S.; Islam, R.

    2015-07-01

    The development and sustainability of weathered profiles are very difficult in the Himalaya due to its complex lithology, tectonic history and fast erosion. Despite this, two weathered profiles namely WPa (weathered profile a) and WPb (weathered profile b) which have sustained erosion are developed on porphyry granite gneiss and granite gneissic lithology in Alaknanda valley of the Garhwal Lesser Himalaya. Systematic sampling of these two weathered profiles was done from bottom to top and they were chemically analysed to understand the elemental mobility in each profile. Major, trace and rare earth element studies show dissimilar behaviour with the advancement of weathering. In WPa profile, the CIA value of LAR (LAR) is 50 which reveals that the rock has not suffered any alteration but in WPb profile, the CIA value of LAR is 64 which indicates significant amount of chemical alteration. A-CN-K projection also exhibits similar behaviour. Further, the relative mobility of all the major and trace elements show variable elemental distribution in both the profiles. Enrichment of Mg, Fe, Ti, Al, Co, Ni, Zr, LREE and depletion of Na, K, P, Ca, Si, LILE and HFSE are observed in WPa profile; while the depletion of Na, K, Ca, P, Si, HREE and enhancement of Fe, Mn, Ti, Sc, Co, Zr, LREE are noticed in WPb profile. The rare earth elements also show a dissimilar mobilization pattern in both the profiles due to their strong dependency on lithology, and corresponding climate and tectonic interaction. Contrasting elemental mobility in both the profiles depict the major role in disparity of lithological characters and subsequent development of fractures produced by the major thrust system (Ramgarh thrust) which made an easy passage for rain water, thus causing the development of a chemically altered profile in the Lesser Himalayan region. Further, the present study infers the climate and tectonic milieu which is responsible for the development of such weathered profiles in Himalayan

  8. Archean geotherms and supracrustal assemblages

    NASA Astrophysics Data System (ADS)

    Condie, Kent C.

    1984-06-01

    Metamorphic mineral assemblages suggest the existence of variable geotherms and lithospheric thicknesses beneath late Archean continental crust. Archean granite-greenstone terranes reflect steep geotherms (50-70°C/km) while high-grade terranes reflect moderate geotherms similar to present continental crust with high heat flow (25-40°C/km). Corresponding lithosphere thicknesses for each terrane during the late Archean are 35-50 km and 50-75 km, respectively. Early Archean (⩾ 3.0 b.y.) greenstones differ from late Archean (˜ 2.7 b.y.) greenstones by the rarity or absence of andesite and graywacke and the relative abundance of pelite, quartzite, and komatiite. Mature clastic sediments in early greenstones reflect shallow-water, stable-basin deposition. Such rocks, together with granite-bearing conglomerate and felsic volcanics imply the existence of still older granitic source terranes. The absence or rarity of andesite in early greenstones reflects the absence of tectonic conditions in which basaltic and tonalitic magmas are modified to produce andesite. A model is presented in which early Archean greenstones form at the interface between tonalite islands and oceanic lithosphere, over convective downcurrents; high-grade supracrustals form on stable continental edges or interiors; and late Archean greenstones form in intracontinental rifts over mantle plumes.

  9. The use of mineralogic techniques as relative age indicators for weathering profiles on the Atlantic Coastal Plain, USA

    USGS Publications Warehouse

    Soller, D.R.; Owens, J.P.

    1991-01-01

    Textural, geochemical, and mineralogic study of soils and weathering profiles has led to the practice of applying varioys weathering parameters as relative age indicators. In our studies examined the entire thickness of weathered sediment (i.e., the weathering profile) for evidence of weathering-induced changes in both sand- and clay-sized mineralogy, and used two techniques for relative age determinations. These techniques were developed as tools to support geologic mapping. One of our techniques for determining relative ages is based on the depth of weathering as recorded by progressive loss of denrital sand-sized minerals upward in the weathering profile. This is our preferred tool, especially in areas where weathering profiles have been truncated. We have found a gradual trend of increasing loss of labile sand-sized minerals (e.g., hornblendes, feldspars) and increasing depth of weathering with increasing age of the deposit. Of significance to many research programs, this technique does not require expensive instruments such as an X-ray diffractometer. Our other technique depends on accumulation of stable, secondary clay-sized minerals in the upper part of the weathering profile. In our study area on the Atlantic Coastal Plain of the United States, the stable assemblage consists of vermiculite, kaolinite, gibbsite, and iron oxides and hydroxides. This technique can be effective for relative age determinations where profiles have not been truncated, and can provide useful information on depositional and erosional history. However, in areas of widespread erosion and profile truncation, such as the Carolinas, the utility of this technique for relative age determinations is limited. There, soils were partially or completely removed in many localities in relatively recent times. ?? 1991.

  10. Thickness of Weathering Profiles:Relaying Tectonic Signal to Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Yoo, K.; Weinman, B. A.; Hurst, M. D.; Mudd, S. M.; Gabet, E. J.; Attal, M.; Maher, K.

    2011-12-01

    Generation and transport of sediment across hillslopes and rivers are closely tied to mechanisms that produce and remove weathered material; in uplands this production and transport controls the thicknesses of weathering profiles. These processes, by controlling the residence time of minerals in the weathering profiles, further regulate the interactions between these minerals and largely biologically cycled elements like carbon and calcium. Here, we present and discuss the thicknesses of colluvial soils and underlying saprolites along three hillslopes that are subject to different rates of basal channel incision. Our field site is within a tributary basin to the Middle Folk Feather River in the Northern Sierra Nevada of California where the river has been down cutting through an uplifting granitic batholith over the past five to ten million years. Conventional modeling predicts that colluvial soil thickness declines with increasing denudation rates. Contrary to this expectation, intensive measurements of colluvial soil thickness show largely consistent values across the three hillslopes examined. This finding, in combination with the abrupt transitions to partial or full bare-rock landscapes with further increase in slope curvature or greater proximity to the Middle Folk Feather River, suggests that the mechanisms of soil production are capable of keeping pace with physical erosion rate until a certain threshold erosion rate is reached. We observe, however, that thicknesses of the underlying saprolite and the morphology (eg., color and texture) and geochemistry (eg., elemental concentration and extraction chemistry of iron) of both colluvial soil and saprolite materials vary systematically with the total denudation rates. This finding further allows us to build a simple relationship to describe and predict how the changes in erosion rates translate to the soils' capacity to store biologically cycled elements within rooting depths. Therefore, geomorphic and

  11. Chemical models for martian weathering profiles: Insights into formation of layered phyllosilicate and sulfate deposits

    NASA Astrophysics Data System (ADS)

    Zolotov, Mikhail Yu.; Mironenko, Mikhail V.

    2016-09-01

    Numerical chemical models for water-basalt interaction have been used to constrain the formation of stratified mineralogical sequences of Noachian clay-bearing rocks exposed in the Mawrth Vallis region and in other places on cratered martian highlands. The numerical approaches are based on calculations of water-rock type chemical equilibria and models which include rates of mineral dissolution. Results show that the observed clay-bearing sequences could have formed through downward percolation and neutralization of acidic H2SO4-HCl solutions. A formation of weathering profiles by slightly acidic fluids equilibrated with current atmospheric CO2 requires large volumes of water and is inconsistent with observations. Weathering by solutions equilibrated with putative dense CO2 atmospheres leads to consumption of CO2 to abundant carbonates which are not observed in clay stratigraphies. Weathering by H2SO4-HCl solutions leads to formation of amorphous silica, Al-rich clays, ferric oxides/oxyhydroxides, and minor titanium oxide and alunite at the top of weathering profiles. Mg-Fe phyllosilicates, Ca sulfates, zeolites, and minor carbonates precipitate from neutral and alkaline solutions at depth. Acidic weathering causes leaching of Na, Mg, and Ca from upper layers and accumulation of Mg-Na-Ca sulfate-chloride solutions at depth. Neutral MgSO4 type solutions dominate in middle parts of weathering profiles and could occur in deeper layers owing to incomplete alteration of Ca minerals and a limited trapping of Ca to sulfates. Although salts are not abundant in the Noachian geological formations, the results suggest the formation of Noachian salty solutions and their accumulation at depth. A partial freezing and migration of alteration solutions could have separated sulfate-rich compositions from low-temperature chloride brines and contributed to the observed diversity of salt deposits. A Hesperian remobilization and release of subsurface MgSO4 type solutions into newly

  12. An Archean Biosphere Initiative

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Boyd, E. S.; Buick, R.; Claire, M.; DesMarais, D.; Domagal-Goldman, D.; Eigenbrode, J.; Erwin, D.; Freeman, K.; Hazen, R.; Johnson, C.; Lyons, T.; Meadows, V.; Ohmoto, H.; Ono, S.; Peters, J. W.; Shapiro, B.; Summons, R.; Walter, M.

    2011-01-01

    The search for life on extrasolar planets will necessarily focus on the imprints of biolgy on the composition of planetary atmospheres. The most notable biological imprint on the modern terrestrial atmosphere is the presence of 21 % O2, However, during most of the past 4 billion years, life and the surface environments on Earth were profoundly different than they are today. It is therefore a major goal of the astrobiology community to ascertain how the O2 content of the atmosphere has varied with time. and to understand the causes of these variations. The NAI and NASA Exobiology program have played critical roles in developing our current understanding of the ancient Earth's atmosphere, supporting diverse observational, analytical, and computational research in geoscience, life science, and related fields. In the present incarnation of the NAI, ongoing work is investigating (i) variations in atmospheric O2 in the Archean to the Cambrian, (ii) characterization of the redox state of the oceans shortly before, during and after the Great Oxidation Event (GOE), and (iii) unraveling the complex connections between environmental oxygenation, global climate, and the evolution of life.

  13. Characterization of weathering profile in granites and volcanosedimentary rocks in West Africa under humid tropical climate conditions. Case of the Dimbokro Catchment (Ivory Coast)

    NASA Astrophysics Data System (ADS)

    Koita, M.; Jourde, H.; Koffi, K. J. P.; da Silveira, K. S.; Biaou, A.

    2013-06-01

    In granitic rocks, various models of weathering profile have been proposed, but never for the hard rocks of West Africa. Besides, in the literature there is no description of the weathering profile in volcanosedimentrary rocks. Therefore, we propose three models describing the weathering profiles in granites, metasediments, and volcanic rocks for hard rock formations located in West Africa. For each of these models proposed for granitic and volcanosedimentary rocks of the Dimbokro catchment, vertical layered weathering profiles are described, according to the various weathering and erosion cycles (specific to West Africa) that the geological formations of the Dimbokro catchment experienced from the Eocene to the recent Quaternary period. The characterization of weathering profiles is based on: i) bedrocks and weathering profile observations at outcrop, and ii) interpretation and synthesis of geophysical data and lithologs from different boreholes. For each of the geological formations (granites, metasediments, and volcanic rocks), their related weathering profile model depicted from top to bottom comprises four separate layers: alloterite, isalterite, fissured layer, and fractured fresh basement. These weathering profiles are systematically covered by a soil layer. Though granites, metasediments and volcanic rocks of the Dimbokro catchment experience the same weathering and erosion cycles during the palaeoclimatic fluctuations from Eocene to recent Quaternary period, they exhibit differences in thickness. In granites, the weathering profile is relatively thin due to the absence of iron crust which protects weathering products against dismantling. In metasediments and volcanic rocks iron crusts develop better than in granites; in these rocks the alterite are more resistant to dismantling.

  14. Reconciling atmospheric temperatures in the early Archean

    NASA Astrophysics Data System (ADS)

    Pope, E. C.; Rosing, M.; Bird, D. K.; Albarede, F.

    2012-12-01

    Average surface temperatures of Earth in the Archean remain unresolved despite decades of diverse approaches to the problem. As in the present, early Earth climates were complex systems dependent on many variables. With few constraints on such variables, climate models must be relatively simplistic, and consider only one or two factors that drive Archean climate (e.g. a fainter young sun, a low albedo, the extent and effect of cloud cover, or the presence and abundance of a wide array of greenhouse and icehouse gasses). Compounded on the limitations of modeling is the sparse and often ambiguous Archean rock record. The goal of this study is to compile and reconcile Archean geologic and geochemical features that are in some way controlled by surface temperature and/or atmospheric composition, so that at the very least paleoclimate models can be checked by physical limits. Data used to this end include the oxygen isotope record of chemical sediments and ancient ocean crust, chemical equilibria amongst primary phases in banded iron formations (BIFs), sedimentary features indicative of temperate or glacial environments, and paleosol indicators of atmospheric CO2. Further, we explore the extent to which hydrogen isotopes contribute to the geologic record as a signal for glaciations, continental growth and atmospheric methane levels. Oceanic serpentinites and subduction-related volcanic and hydrothermal environments obtain their hydrogen isotope signature from seawater, and thus may be used to calculate secular variation in δDSEAWATER which may fluctuate significantly due to hydrogen escape, continental growth and large-scale glaciation events. Further, ancient records of low-δD meteoric fluids signal both cooler temperatures and the emergence of large continents (increasing the effects of continental weathering on climate). Selective alteration of δD in Isua rocks to values of -130 to -100‰ post-dates ca. 3.55Ga Ameralik dikes, but may be associated with a poorly

  15. Uranium isotope composition of a laterite profile during extreme weathering of basalt in Guangdong, South China

    NASA Astrophysics Data System (ADS)

    Huang, J.; Zhou, Z.; Gong, Y.; Lundstrom, C.; Huang, F.

    2015-12-01

    Rock weathering and soil formation in the critical zone are important for material cycle from the solid Earth to superficial system. Laterite is a major type of soil in South China forming at hot-humid climate, which has strong effect on the global uranium cycle. Uranium is closely related to the environmental redox condition because U is stable at U(Ⅳ) in anoxic condition and U(Ⅵ) as soluble uranyl ion (UO22+) under oxic circumstance. In order to understand the behavior of U isotopes during crust weathering, here we report uranium isotopic compositions of soil and base rock samples from a laterite profile originated from extreme weathering of basalt in Guangdong, South China. The uranium isotopic data were measured on a Nu Plasma MC-ICP-MS at the University of Illinois at Urbana-Champaign using the double spike method. The δ238U of BCR-1 is -0.29±0.03‰ (relative to the international standard CRM-112A), corresponding to a 238U/235U ratio of 137.911±0.004. Our result of BCR-1 agrees with previous analyses (e.g., -0.28‰ in Weyer et al. 2008) [1]. U contents of the laterite profile decrease from 1.9 ppm to 0.9 ppm with depth, and peak at 160 - 170 cm (2.3 ppm), much higher than the U content of base rocks (~0.5 ppm). In contrary, U/Th of laterites is lower than that of base rock (0.27) except the peak at the depth of 160-170 cm (0.38), indicating significant U loss during weathering. Notably, U isotope compositions of soils show a small variation from -0.38 to -0.28‰, consistent with the base rock within analytical error (0.05‰ to 0.08‰, 2sd). Such small variation can be explained by a "rind effect" (Wang et al., 2015) [2], by which U(Ⅳ) can be completely oxidized to U(VI) layer by layer during basalt weathering by dissolved oxygen. Therefore, our study indicates that U loss during basalt weathering at the hot-humid climate does not change U isotope composition of superficial water system. [1] Weyer S. et al. (2008) Natural fractionation of 238U/235

  16. Impact of Atmospheric Infrared Sounder (AIRS) Thermodynamic Profiles on Regional Weather Forecasting

    NASA Technical Reports Server (NTRS)

    Chou, Shih-Hung; Zavodsky, Bradley T.; Jedlovee, Gary J.

    2010-01-01

    In data sparse regions, remotely-sensed observations can be used to improve analyses and lead to better forecasts. One such source comes from the Atmospheric Infrared Sounder (AIRS), which together with the Advanced Microwave Sounding Unit (AMSU), provides temperature and moisture profiles with accuracy comparable to that of radiosondes. The purpose of this paper is to describe a procedure to assimilate AIRS thermodynamic profile data into a regional configuration of the Advanced Research Weather Research and Forecasting (WRF-ARW) model using its three-dimension variational (3DVAR) analysis component (WRF-Var). Quality indicators are used to select only the highest quality temperature and moisture profiles for assimilation in both clear and partly cloudy regions. Separate error characteristics for land and water profiles are also used in the assimilation process. Assimilation results indicate that AIRS profiles produce an analysis closer to in situ observations than the background field. Forecasts from a 37-day case study period in the winter of 2007 show that AIRS profile data can lead to improvements in 6-h cumulative precipitation forecasts due to instability added in the forecast soundings by the AIRS profiles. Additionally, in a convective heavy rainfall event from February 2007, assimilation of AIRS profiles produces a more unstable boundary layer resulting in enhanced updrafts in the model. These updrafts produce a squall line and precipitation totals that more closely reflect ground-based observations than a no AIRS control forecast. The location of available high-quality AIRS profiles ahead of approaching storm systems is found to be of paramount importance to the amount of impact the observations will have on the resulting forecasts.

  17. Lidar Wind Profiler Comparison to Weather Balloon for Support of Orion Crew Exploration Vehicle Landings

    NASA Technical Reports Server (NTRS)

    Houtas, Franzeska F.; Teets, Edward H.

    2010-01-01

    A comparison study by the National Aeronautics and Space Administration Dryden Flight Research Center (Edwards, California) and the Naval Post Graduate School Center for Interdisciplinary Remotely-Piloted Aircraft Studies (Marina, California) was conducted to show the advantages of an airborne wind profiling light detection and ranging (lidar) system in reducing drift uncertainty along a reentry vehicle descent trajectory. This effort was in support of the once planned Orion Crew Exploration Vehicle ground landing. A Twin Otter Doppler Wind Lidar was flown on multiple flights along the approximate ground track of each ascending weather balloon launched from the Marina Municipal Airport (Marina, California). The airborne lidar used was a 5-mJ, 2-micron infrared laser with a 10-cm telescope and a two-axis scanner. Each lidar wind profile contains data for an altitude range between the surface and flight altitude of 2.7 km, processed on board every 20 s. In comparison, a typical weather balloon would traverse that same altitude range with a similar data set available in approximately 15 to 20 min. These tests were conducted on November 15 and 16, 2007. Results show a best-case absolute difference of 0.18 m/s (0.35 knots) in speed and 1 degree in direct

  18. Archean upper crust transition from mafic to felsic marks the onset of plate tectonics.

    PubMed

    Tang, Ming; Chen, Kang; Rudnick, Roberta L

    2016-01-22

    The Archean Eon witnessed the production of early continental crust, the emergence of life, and fundamental changes to the atmosphere. The nature of the first continental crust, which was the interface between the surface and deep Earth, has been obscured by the weathering, erosion, and tectonism that followed its formation. We used Ni/Co and Cr/Zn ratios in Archean terrigenous sedimentary rocks and Archean igneous/metaigneous rocks to track the bulk MgO composition of the Archean upper continental crust. This crust evolved from a highly mafic bulk composition before 3.0 billion years ago to a felsic bulk composition by 2.5 billion years ago. This compositional change was attended by a fivefold increase in the mass of the upper continental crust due to addition of granitic rocks, suggesting the onset of global plate tectonics at ~3.0 billion years ago.

  19. Archean upper crust transition from mafic to felsic marks the onset of plate tectonics

    NASA Astrophysics Data System (ADS)

    Tang, Ming; Chen, Kang; Rudnick, Roberta L.

    2016-01-01

    The Archean Eon witnessed the production of early continental crust, the emergence of life, and fundamental changes to the atmosphere. The nature of the first continental crust, which was the interface between the surface and deep Earth, has been obscured by the weathering, erosion, and tectonism that followed its formation. We used Ni/Co and Cr/Zn ratios in Archean terrigenous sedimentary rocks and Archean igneous/metaigneous rocks to track the bulk MgO composition of the Archean upper continental crust. This crust evolved from a highly mafic bulk composition before 3.0 billion years ago to a felsic bulk composition by 2.5 billion years ago. This compositional change was attended by a fivefold increase in the mass of the upper continental crust due to addition of granitic rocks, suggesting the onset of global plate tectonics at ~3.0 billion years ago.

  20. Geochemical balance of lateritization processes and climatic signatures in weathering profiles overlain by ferricretes in Central Africa

    NASA Astrophysics Data System (ADS)

    Beauvais, Anicet

    1999-12-01

    A simple geochemical balance of lateritization processes governing the development of several tens of meters of weathering profiles overlain by ferricretes is estimated on the basis of detailed mineralogical and geochemical data. The lateritic weathering mantle of the "Haut-Mbomou" area in Central Africa is composed of different weathering layers described from the base to the top of vertical profiles as a saprolite, a mottled clay layer, a soft nodular layer, a soft ferricrete, and a ferricrete in which kaolinite, gibbsite, goethite, and hematite occur in various quantities. Incongruent dissolution of kaolinite leads to the formation of gibbsite in the upper saprolite, whereas the hematite does not clearly replace the kaolinite according to an epigene process in the upper ferruginous layers of the profiles. Instead, that kaolinite is also transformed into gibbsite according to an incongruent dissolution under hydrated and reducing conditions induced by a relatively humid climatic pattern. The respective relations of the silica, iron, and aluminum balances and the Al substitution rate of the hematite on the one hand, and of RHG [RHG = 100 (hematite/hematite + goethite)] and the kaolinite on the other hand, to the consumption or the release of protons H + permit differentiation of aggrading ferruginization and degradation processes operating in the different lateritic weathering profiles. The Al substitution rate of the Fe-oxyhydroxides varies according to the nature of lateritization processes, e.g., saprolitic weathering and aggrading ferruginization vs. degradation. The observations and results indicate that the ferruginization process of the weathering materials of parent rocks is not a simple ongoing process as often thought. This suggests that the actual lateritic weathering mantle of the Haut-Mbomou area may result from different stages of weathering and erosion during climatic changes.

  1. Spectral Characterization of a Deeply Weathered Laterite Profile, Koraput, Orissa, Eastern India

    NASA Astrophysics Data System (ADS)

    Amrutkar, R. P.; Aranha, M.; Prakash, N.; Porwal, A.

    2015-12-01

    This contribution reports the spectral characterization of a 30-m long lateritic regolith profile over khondalite near Koraput, Eastern India. The area forms a part of the Archaean Eastern Ghats Mobile Belt, comprising high grade metamorphic rocks such as khondalites, charnockites, migmatites and granite gneisses. The area has been deeply weathered under tropical conditions leading to the development of thick laterite horizon. Samples were collected from the lateritic profile at intervals of 1-2 m. Fresh or slightly altered khondalite are exposed at the bottom and grade into laterite upwards. Reflectance spectra were collected using FieldSpec3 spectroradiometer in the VNIR-SWIR region. An Al-OH absorption feature at 2208 nm occurs throughout the profile. A blue shift of this feature related to the progressive leaching of Al and enrichment of Fe is observed in the top 5 m of the profile. An absorption feature at 2165 nm occurs throughout revealing a mixture of kaolinite, illite and smectite. Several Fe absorption features, possibly because of crystal field splitting, are observed at shorter wavelengths, particularly, 482-495 nm and 675-685 nm. Another Fe absorption feature due to intervalence charge transfer is observed around 416-428 nm. Absorption features at 2250 nm and 2263 nm suggest the presence of jarosite in the top 5 m of the profile. An absorption feature at 936 nm is observed in the top 12 m of the profile, which indicates progressive Fe enrichment. Fourier Transform Infra-Red (FTIR) spectroscopy in the TIR - MIR region support the above interpretations of the VNIR-SWIR spectra. Goethite shows distinct absorption features at 3000 nm and 6800-7000 nm. An absorption feature at 13000 nm reveals the presence of kaolinite and 15600 nm absorption feature confirms jarosite. Further, X-Ray diffraction (XRD) helped in identification and quantification of major mineral phases present in each sample. XRD results showed gradual decrease in kaolinitic content and

  2. Development of weathering profile of a forest hillslope in clay-rich sedimentary system

    NASA Astrophysics Data System (ADS)

    Nicklas, R. W.; Kim, H.; Bishop, J. K.; Rempe, D. M.

    2012-12-01

    Hillslopes are an essential element to the understanding of landscape evolution, storm flow generation and biogeochemical processes. Since 2008, extensive studies of climate variables, vegetation, soil moisture, subsurface hydrology, and water chemistry have taken place at a small forested hillslope, "Rivendell", at the Angelo Coast Range Reserve located at the headwaters of the Eel River, California. Here we report on the signature of weathering processes through analysis of core and soil samples collected during well drilling campaigns. Core samples from multiple depths at four wells (at creek edge, mid-slope, up-slope, and ridge-top) were selected and include 1) soil; 2) unsaturated fractured/ weathered zone; 3) zone of seasonal water table fluctuation within weathered bedrock; and 4) chronically saturated fresh bedrock zone. We also include soil samples from a groundwater seep located at the toe of the slope. The mineralogy of these samples was identified using X-ray diffraction. Samples were analyzed for salt and Ca(Mg)CO3 concentrations, and cation exchange capacity using Milli-Q water and acetic acid extraction and BaCl2-NH4Cl treatments, respectively. To further quantify the mineral dissolution and secondary mineral precipitation, a sequential extraction of trace metals were conducted - 1) exchangeable using MgCl2; 2) bound to carbonates using NaOAc; 3) bound to Fe-Mn oxides using NH2OH HCl; and 4) bound to organic matters using H2O2 and HNO3. The total elemental contents were determined using HF-HNO3-HClO4 dissolution. The mineralogy of the fresh bedrock zone showed similar patterns throughout the site -for clay minerals, chlorite, illite, interstratified illite/smectite were dominant; K-feldspar dominated the primary minerals. Shallow (<30 cm) soils had kaolinite, and chlorite was absent in some samples. CaCO3 was also predominantly found in the fresh bedrock zone and progressively increased with depth. The depletion profile of major cations (Ca, Na, Mg

  3. The New Weather Radar for America's Space Program in Florida: A Temperature Profile Adaptive Scan Strategy

    NASA Technical Reports Server (NTRS)

    Carey, L. D.; Petersen, W. A.; Deierling, W.; Roeder, W. P.

    2009-01-01

    A new weather radar is being acquired for use in support of America s space program at Cape Canaveral Air Force Station, NASA Kennedy Space Center, and Patrick AFB on the east coast of central Florida. This new radar replaces the modified WSR-74C at Patrick AFB that has been in use since 1984. The new radar is a Radtec TDR 43-250, which has Doppler and dual polarization capability. A new fixed scan strategy was designed to best support the space program. The fixed scan strategy represents a complex compromise between many competing factors and relies on climatological heights of various temperatures that are important for improved lightning forecasting and evaluation of Lightning Launch Commit Criteria (LCC), which are the weather rules to avoid lightning strikes to in-flight rockets. The 0 C to -20 C layer is vital since most generation of electric charge occurs within it and so it is critical in evaluating Lightning LCC and in forecasting lightning. These are two of the most important duties of 45 WS. While the fixed scan strategy that covers most of the climatological variation of the 0 C to -20 C levels with high resolution ensures that these critical temperatures are well covered most of the time, it also means that on any particular day the radar is spending precious time scanning at angles covering less important heights. The goal of this project is to develop a user-friendly, Interactive Data Language (IDL) computer program that will automatically generate optimized radar scan strategies that adapt to user input of the temperature profile and other important parameters. By using only the required scan angles output by the temperature profile adaptive scan strategy program, faster update times for volume scans and/or collection of more samples per gate for better data quality is possible, while maintaining high resolution at the critical temperature levels. The temperature profile adaptive technique will also take into account earth curvature and refraction

  4. Application of wind-profiling radar data to the analysis of dust weather in the Taklimakan Desert.

    PubMed

    Wang, Minzhong; Wei, Wenshou; Ruan, Zheng; He, Qing; Ge, Runsheng

    2013-06-01

    The Urumqi Institute of Desert Meteorology of the China Meteorological Administration carried out an atmospheric scientific experiment to detect dust weather using a wind-profiling radar in the hinterland of the Taklimakan Desert in April 2010. Based on the wind-profiling data obtained from this experiment, this paper seeks to (a) analyze the characteristics of the horizontal wind field and vertical velocity of a breaking dust weather in a desert hinterland; (b) calculate and give the radar echo intensity and vertical distribution of a dust storm, blowing sand, and floating dust weather; and (c) discuss the atmosphere dust counts/concentration derived from the wind-profiling radar data. Studies show that: (a) A wind-profiling radar is an upper-air atmospheric remote sensing system that effectively detects and monitors dust. It captures the beginning and ending of a dust weather process as well as monitors the sand and dust being transported in the air in terms of height, thickness, and vertical intensity. (b) The echo intensity of a blowing sand and dust storm weather episode in Taklimakan is about -1~10 dBZ while that of floating dust -1~-15 dBZ, indicating that the dust echo intensity is significantly weaker than that of precipitation but stronger than that of clear air. (c) The vertical shear of horizontal wind and the maintenance of low-level east wind are usually dynamic factors causing a dust weather process in Taklimakan. The moment that the low-level horizontal wind field finds a shear over time, it often coincides with the onset of a sand blowing and dust storm weather process. (d) When a blowing sand or dust storm weather event occurs, the atmospheric vertical velocity tends to be of upward motion. This vertical upward movement of the atmosphere supported with a fast horizontal wind and a dry underlying surface carries dust particles from the ground up to the air to form blown sand or a dust storm.

  5. Uranium and thorium in weathering and pedogenetic profiles developed on granitic rocks from NW Spain.

    PubMed

    Taboada, Teresa; Martínez Cortizas, Antonio; García, Carlota; García-Rodeja, Eduardo

    2006-03-01

    Uranium and thorium were analyzed in seven weathering and pedogenetic soil profiles developed on granitic rocks from NW Spain. Concentrations were measured by X-ray fluorescence spectrometry (XRF) and the U- and Th-bearing minerals were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Both elements were determined in rock, bulk soil and in different grain-size fractions (sand: 2000-50 microm, silt: 50-2 microm, and clay: <2 microm). U concentrations in the rock varied between 5.3 and 27.7 mg kg(-1) and Th concentrations from 5.5 to 50.7 mg kg(-1). The most alkalic rocks can be considered as U-rich granites. Bulk soil U and Th concentrations are similar to those of the rocks (4.8-29.2 and 7.4-56.7 mg kg(-1), respectively), but in the grain-size fractions both elements show the lowest concentrations in the sand and the highest in the clay. In the latter, concentrations are always higher than those of the rocks, particularly in the C horizons with enrichments up to 4 times for U and 5 times for Th. The concentration profiles and the ratios to the parent rock suggest that U and Th are leached from the surface soil and accumulate in the deeper horizons. Mass balance calculations, using Ti as a reference immobile element, also support U and Th leaching in the solum and supergene enrichment in bottom horizons. Leaching seems to be more intense on horizons with gravel content higher than 20%. The leaching of U and Th in the topmost horizons and the accumulation in the bottom soil horizons can be considered as a natural attenuation of the impact of these radiogenic elements in the environment. But their enrichment in the potentially airborne fraction poses some risk of redistribution in the ecosystems.

  6. Tertiary weathering profiles in central Nigeria as indicators of paleoenvironmental conditions

    NASA Astrophysics Data System (ADS)

    Zeese, Reinhard

    1996-05-01

    In central Nigeria the Fluviovolcanic Series of the Jos Plateau are composed by deeply weathered volcanic rocks and sediments. The sequence is often capped by ferricretes. Ferricretes, remains of former soils, are also intercalated in the series. Profile sections between two ferricretes are deep (> 10 m). The repeated saprolite/solum sequence sometimes exceeds 100 m. It can be separated into a lower section without bauxitisation, but often with total bleaching of the saprolite, a middle section with bauxite and hematite in the saprolite and an upper kaolinitic section with hematite and goethite. Bleaching by total removal of Fe 2+ and bauxitisation by total desilification are both indicators of wet and hot climates with a high biomass production. In the first case the groundwater was permanently high, in the latter a well drained fluctuating groundwater can be assumed. Changing groundwater conditions may be the result of plateau uplift. Paleoenvironmental changes are, thus, reflected in relatively datable paleosols. Undatable paleosoils with comparable characteristics on the planation surfaces of Central and Northeast Nigeria also result from paleoenvironmental conditions. Consequently, concepts of landscape evolution must take into account changing environments.

  7. [Advance in the study of the powdered weathering profile of sandstone on China Yungang Grottoes based on VIS/NIR hyperspectral imaging].

    PubMed

    Zhou, Xiao; Gao, Feng; Zhang, Ai-wu; Zhou, Ke-chao

    2012-03-01

    Yungang Grottoes were built in the mid-5th century A. D., and named as a UNESCO World Heritage site in 2001. Most of the grottoes were built on the feldspathic quartz sandstones. They were seriously damaged due to the environmental impact. The main form of the weathering is the powdered weathering. The weathering conditions are generally characterized by electrical sounding, penetration resistance, molecular spectroscopy, etc. However, although these methods can give good results about the weathering conditions for a specified sample or site, they are not suitable for providing a global profile of the weathering conditions. The present paper provides a method for effectively and roundly assessing the overall powdered weathering conditions of the Yungang Grottoes based on hyperspectral imaging. Powdered weathering could change the structure and granularity of the sandstone, and thus change the spectral reflectance of the sandstone surface. Based on the hyperspectral data collected from 400 nm to 1 000 nm and normalized by log residuals method, the powdered weathering conditions of the sandstones were classified into strong weathering and weak weathering. The weathering profile was also mapped in the Envi platform. The mapping images were verified using the measured hyperspectal data of the columns in front of the 9th and 10th grottoes as the examples. The mapping images were substantially fitted to the real observations, showing that hyperspectral imaging can be used to estimate the overall powdered weathering of the sandstones.

  8. A Quantitative Geochemical, Mineralogical and Physical Study of Some Selected Rock Weathering Profiles from Brazil

    DTIC Science & Technology

    1977-08-17

    weather to gibbsite (plus or minus iron oxides) in well-drained, and smectite in poorly-drained, environments. Kaolinite found in the vicinity of quartz...rock and completely weathered saprolite. Quartz-rich rock types exhibit wide, gradational weathered zones and usually form kaolinite or halloysite in...free rocks is either formed by re-silication of gibbsite , or is of secondary origin (transported). Texture of the rock (aphanitic vs. phaneric) has

  9. Weathering and denudation rates determined by the combined analysis of Uranium series nuclides and in situ Beryllium in a weathering profile (Vosges massif, Strengbach catchment, France)

    NASA Astrophysics Data System (ADS)

    Ackerer, Julien; Chabaux, François; Van der Woerd, Jerome; Pelt, Eric; Kali, Elise; Pierret, Marie Claire; Viville, Daniel; Wyns, Robert; Negrel, Philippe

    2015-04-01

    The determination of soil sustainability is a major issue for societies. It is crucial to estimate the soil formation and denudation rates to evaluate the landscapes stability and their response to natural or anthropological forcings. In this work, we propose to combine the analysis of Uranium-Thorium-Radium isotopes with the cosmogenic in situ Beryllium in a weathering profile located in the Strengbach catchment to estimate both production rate of regolith and denudation rate of soil and to establish a soil mass balance at millennial timescales. The weathering profile is located on the summit of the watershed and extending from the top soil to the granitic fractured bedrock at 2 m depth. Whole rock data shows different trends of variation of major and trace element concentrations and also of U-Th-Ra disequilibria in the upper part of the regolith (0-80 cm) and the deeper part of the fractured saprolith and/or bedrock (100cm-200cm). Modeling of the U-Th-Ra data in this deeper part of the profile, using a particle swarm optimization model dedicated to isotopic ratios leads to a regolith production rate at the summit of the watershed of 35 ± 9 T/km²/year. In addition, a numerical optimization for nonlinear inverse problem has been performed to estimate the regolith residence time and the mean denudation rate at the summit from the Beryllium data. The results show that the regolith residence time is about 14 000 years and the mean denudation rate is 32 ± 8 T/km²/year. The consistency between the regolith production rate and the soil denudation rate suggests therefore that in such a temperate context, the long-term mass balance of soil developed on granitic bedrock would be close to a steady state. The data also highlights that the determination of a weathering production rate from analysis of Uranium series nuclides in whole rock samples cannot be easily obtained by analyzing only surficial soil samples, and requires the analysis of the deeper fractured saprolith

  10. Chemical weathering of a marine terrace chronosequence, Santa Cruz, California. Part II: Solute profiles, gradients and the comparisons of contemporary and long-term weathering rates

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Stonestrom, D.A.; Vivit, D.V.; Fitzpatrick, J.; Bullen, T.D.; Maher, K.; Blum, A.E.

    2009-01-01

    changes and/or climate. Pore waters approach thermodynamic saturation with respect to albite at depth in the younger terraces, indicating that weathering rates ultimately become transport-limited and dependent on hydrologic flux. Contemporary rates Rsolute are estimated from linear Na and Si pore weathering gradients bsolute such that Rsolute = frac(qh, bsolute ?? Sv) where Sv is the volumetric surface area and ?? is the stoichiometric coefficient. Plagioclase weathering rates (0.38-2.8 ?? 10-15 mol m-2 s-1) are comparable to those based on 87Sr/86Sr mass balances and solid-state Na and Ca gradients using analogous gradient approximations. In addition, contemporary solute gradients, under transport-limited conditions, approximate long-term solid-state gradients when normalized against the mass of protolith plagioclase and its corresponding aqueous solubility. The multi-faceted weathering analysis presented in this paper is perhaps the most comprehensive yet applied to a single field study. Within uncertainties of the methods used, present day weathering rates, based on solute characterizations, are comparable to average long-term past rates as evidenced by soil profiles.

  11. Chemical weathering of a marine terrace chronosequence, Santa Cruz, California. Part II: Solute profiles, gradients and the comparisons of contemporary and long-term weathering rates

    NASA Astrophysics Data System (ADS)

    White, Art F.; Schulz, Marjorie S.; Stonestrom, David A.; Vivit, Davison V.; Fitzpatrick, John; Bullen, Tom D.; Maher, Kate; Blum, Alex E.

    2009-05-01

    vegetational changes and/or climate. Pore waters approach thermodynamic saturation with respect to albite at depth in the younger terraces, indicating that weathering rates ultimately become transport-limited and dependent on hydrologic flux. Contemporary rates R solute are estimated from linear Na and Si pore weathering gradients b solute such that Rsolute={qh}/{bsoluteβSv} where S v is the volumetric surface area and β is the stoichiometric coefficient. Plagioclase weathering rates (0.38-2.8 × 10 -15 mol m -2 s -1) are comparable to those based on 87Sr/ 86Sr mass balances and solid-state Na and Ca gradients using analogous gradient approximations. In addition, contemporary solute gradients, under transport-limited conditions, approximate long-term solid-state gradients when normalized against the mass of protolith plagioclase and its corresponding aqueous solubility. The multi-faceted weathering analysis presented in this paper is perhaps the most comprehensive yet applied to a single field study. Within uncertainties of the methods used, present day weathering rates, based on solute characterizations, are comparable to average long-term past rates as evidenced by soil profiles.

  12. Sink or Swim? the Role of Intracrustal Differentiation in the Generation of Compositional Diversity and Crustal Delamination in the Archean

    NASA Astrophysics Data System (ADS)

    VanTongeren, J. A.; Herzberg, C. T.; Kaus, B.; Johnson, T. E.; Brown, M.

    2014-12-01

    Significant debate exists regarding the processes of crustal formation and stabilization in the Archean, with some researchers advocating for continuous subduction-like processes throughout earth history, and others advocating crustal recycling by lithospheric delamination or 'drip tectonics'. Much of the debate hinges on whether Archean mantle potential temperatures (Tp) were significantly hotter than the present day. The rock record of non-arc Archean primary magma compositions (Herzberg et al., 2010) has been used to infer higher ambient Tp (Tp = 1500-1650C) during the Archean, causing high melt fractions during decompression melting, and leading to extreme primary (oceanic) crustal thicknesses of 30-40 km (Herzberg and Rudnick, 2012). Such crustal thicknesses might inhibit subduction, in which case an alternative mechanism of crustal recycling would be required. In their recent paper, Johnson et al. (2014) showed that at Tp > 1500C, the lower portions of a thick homogenous Archean primary crust generated would be density unstable with respect to the ambient mantle. Additionally, they showed that given realistic rheological constraints, large-scale lower crustal delamination is a very efficient crustal recycling mechanism at Tp >1600C. The Archean crust, however, is likely to be internally differentiated. Here we present pMELTS and Perple_X modeling results on the intracrustal differentiation of Archean primary crust, resulting in the formation of TTG-like granitoids in the upper crust and a lower crust dominated by clinopyroxenite. Using the composition and density profiles generated by intracrustal differentiation, our geodynamic modeling extends the Tp over which efficient crustal delamination will occur to lower values, consistent with those likely throughout the Archean. Efficient crustal differentiation and delamination of dense mafic residues throughout the Archean may explain the apparent paucity of mafic lithologies relative to TTGs that characterize

  13. Using GC × GC-FID profiles to estimate the age of weathered gasoline samples.

    PubMed

    Zorzetti, Brianne M; Harynuk, James J

    2011-11-01

    Predicting the amount of time that a petroleum mixture has been exposed to weathering effects has applications in areas of environmental and other forensic investigations, such as aiding in determining the cause and intent of a fire. Historically, research on the evaporation rates of hydrocarbon mixtures has focused on forensic oil spill identification and predicting if a fresh sample could be weathered to give an observed composition in an aged sample. Relatively little attention has focused on approaching the problem from the other direction: estimating exposure time based on the observed composition of a weathered sample at a given time and assuming a prior composition. Here, we build upon our previous research into the weathering of model mixtures by extending our work to gasoline. Samples of gasoline with varying octane ratings and from several vendors were weathered under controlled conditions and their composition monitored over time by two-dimensional gas chromatography (GC × GC). A variety of chemometric models were explored, including partial least squares (PLS), nonlinear PLS (PolyPLS) and locally weighted regression (LWR). A hierarchical application of multivariate techniques was able to predict the time for which a sample had been exposed to evaporative weathering. Partial least squares discriminant analysis could predict whether a sample was relatively fresh (<12 h exposure time) or highly weathered (>20 h exposure time). Subsequent regression models for these classes were evaluated for accuracy using the root mean square error of prediction. LWR was the most successful, whereby fresh and highly weathered samples were predicted to within 30 min and 5 h of exposure, respectively.

  14. Solute profiles in soils, weathering gradients and exchange equilibrium/disequilibrium

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Stonestrom, D.A.; Vivit, D.V.; Fitzpatrick, J.; Bullen, T.

    2008-01-01

    The spatial and temporal changes in hydrology and pore water elemental and 87/86Sr compositions were used to determine contemporary weathering rates in a 65 to 226 ky old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Cl-corrected Na, K and Si increased with depth denoting inputs from the weathering of plagioclase and K-feldspar. Solute 87/86Sr exhibited progressive mixing of sea water-dominated precipitation with inputs from less radiogenic plagioclase. Linear approximations to these weathering gradients were used to determine plagioclase weathering rates of between 0.38 and 8.9 ?? 10-15 moles m-2 s-1. The lack of corresponding weathering gradients for Ca and Sr indicated short-term equilibrium with the clay ion exchange pool which requires periodic resetting by natural perturbations to maintain continuity, in spite of soil composition changes reflecting the effects of long-term weathering. ?? 2008 The Mineralogical Society.

  15. Chemical weathering of a marine terrace chronosequence, Santa Cruz, California I: Interpreting rates and controls based on soil concentration-depth profiles

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Vivit, D.V.; Blum, A.E.; Stonestrom, D.A.; Anderson, S.P.

    2008-01-01

    The spatial and temporal changes in element and mineral concentrations in regolith profiles in a chronosequence developed on marine terraces along coastal California are interpreted in terms of chemical weathering rates and processes. In regoliths up to 15 m deep and 226 kyrs old, quartz-normalized mass transfer coefficients indicate non-stoichiometric preferential release of Sr > Ca > Na from plagioclase along with lesser amounts of K, Rb and Ba derived from K-feldspar. Smectite weathering results in the loss of Mg and concurrent incorporation of Al and Fe into secondary kaolinite and Fe-oxides in shallow argillic horizons. Elemental losses from weathering of the Santa Cruz terraces fall within the range of those for other marine terraces along the Pacific Coast of North America. Residual amounts of plagioclase and K-feldspar decrease with terrace depth and increasing age. The gradient of the weathering profile bs is defined by the ratio of the weathering rate, R to the velocity at which the profile penetrates into the protolith. A spreadsheet calculator further refines profile geometries, demonstrating that the non-linear regions at low residual feldspar concentrations at shallow depth are dominated by exponential changes in mineral surface-to-volume ratios and at high residual feldspar concentrations, at greater depth, by the approach to thermodynamic saturation. These parameters are of secondary importance to the fluid flux qh, which in thermodynamically saturated pore water, controls the weathering velocity and mineral losses from the profiles. Long-term fluid fluxes required to reproduce the feldspar weathering profiles are in agreement with contemporary values based on solute Cl balances (qh = 0.025-0.17 m yr-1). During saturation-controlled and solute-limited weathering, the greater loss of plagioclase relative to K-feldspar is dependent on the large difference in their respective solubilities instead of the small difference between their respective

  16. Magnetotelluric survey to locate the Archean/Proterozoic suture zone north of Wells, Nevada

    USGS Publications Warehouse

    Williams, Jackie M.; Rodriguez, Brian D.

    2006-01-01

    It is important to know whether major mining districts in the Northern Nevada Gold Province are underlain by rocks of the Archean Wyoming craton, which are known to contain orogenic gold deposits, or by accreted rocks of the Paleoproterozoic Mojave province. It is also important to know the location and orientation of the Archean/Proterozoic suture zone between these provinces as well as major basement structures within these terranes because they may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. The Archean was the main gold-mineralization period, and Archean lode-gold deposits were formed at mid-crustal depths along major shear zones. The nature of the crystalline basement below the Northern Nevada Gold Province and the location of major faults within it are relevant to Rodinian reconstructions, crustal development, and ore deposit models (e.g., Hofstra and Cline, 2000; Grauch and others, 2003). According to Whitmeyer and Karlstrom (2004), the Archean cratons of the northwestern United States and Canada had stabilized as continental lithosphere by 2.5 Ga, and were rifted and assembled into a large continental mass by 1.8 Ga, to which the 1.73-1.68 Ga Mohave province was accreted by 1.65 Ga. The Archean/Proterozoic suture zone has a west-southwest strike where it is exposed (Reed, 1993) at the eastern Utah and southwestern Wyoming border (Cheyenne Belt) where it is characterized by an up to 7-km-thick mylonite zone (Smithson and Boyd, 1998). In the Great Basin, the strike of the Archean/Proterozoic suture zone is poorly constrained because it is largely concealed below a Neoproterozoic-Paleozoic miogeocline and basin fill. East-west and southwest-northeast strikes for the Archean/Proterozoic suture zone have been inferred based on Sr, Nd, and Pb isotopic compositions of granitoid intrusions (Tosdal and others, 2000). To better constrain the location and strike of the Archean/Proterozoic suture zone below cover

  17. Chemistry of sands from the modern Indus River and the Archean Witwatersrand basin: Implications for the composition of the Archean atmosphere

    SciTech Connect

    Maynard, J.B.; Ritger, S.D. ); Sutton, S.J. )

    1991-03-01

    Both the Indus River and the Witwatersrand basin contain sand with grains of detrital uraninite. Because this mineral is easily oxidized, its presence in Archean strata as a detrital particle has been used as evidence for a low-oxygen atmosphere before 2.5 Ga. However, its presence in modern sand from the Indus River system has been used to argue that detrital uraninite does not provide information about the oxygen concentration of Earth's early atmosphere. Petrographic and chemical study of sand from these two sources reveals differences that suggest the modern Indus sand cannot be used as an analog for the Archean Witwatersrand occurrences. The Witwatersrand quartzites are depleted in Ca, Mg, and Na, indicating that the original sand from which they formed had been subjected to intense weathering. The chemical index of alteration (CIA), a commonly used indicator of degree of weathering, yields an average value of about 0.80 for Witwatersrand quartzites, comparable to modern tropical streams such as the Orinoco that drain deeply weathered terrains under tropical conditions (CIA=0.75). In contrast, the CIA for Indus sand is 0.45, indicating virtually no chemical weathering. The significance of Archean quartz-pebble conglomerates is not just that they contain unstable detrital phases like uraninite and pyrite, but that these particles are associated with rocks whose compositions suggest intense weathering. These conglomerates must have been subjected to intense weathering under tropical conditions, either in their source area or at the site of deposition, and the preservation of minerals like uraninite such conditions is indeed strong evidence for a low-oxygen atmosphere.

  18. Extreme weather events: Should drinking water quality management systems adapt to changing risk profiles?

    PubMed

    Khan, Stuart J; Deere, Daniel; Leusch, Frederic D L; Humpage, Andrew; Jenkins, Madeleine; Cunliffe, David

    2015-11-15

    Among the most widely predicted and accepted consequences of global climate change are increases in both the frequency and severity of a variety of extreme weather events. Such weather events include heavy rainfall and floods, cyclones, droughts, heatwaves, extreme cold, and wildfires, each of which can potentially impact drinking water quality by affecting water catchments, storage reservoirs, the performance of water treatment processes or the integrity of distribution systems. Drinking water guidelines, such as the Australian Drinking Water Guidelines and the World Health Organization Guidelines for Drinking-water Quality, provide guidance for the safe management of drinking water. These documents present principles and strategies for managing risks that may be posed to drinking water quality. While these principles and strategies are applicable to all types of water quality risks, very little specific attention has been paid to the management of extreme weather events. We present a review of recent literature on water quality impacts of extreme weather events and consider practical opportunities for improved guidance for water managers. We conclude that there is a case for an enhanced focus on the management of water quality impacts from extreme weather events in future revisions of water quality guidance documents.

  19. Constraining the location of the Archean--Proterozoic suture in the Great Basin based on magnetotelluric soundings

    USGS Publications Warehouse

    Rodriguez, Brian D.; Sampson, Jay A.

    2012-01-01

    It is important to understand whether major mining districts in north-central Nevada are underlain by Archean crust, known to contain major orogenic gold deposits, or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between the Archean crust and Mojave province is also critical because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. In the Great Basin, the attitude of the suture zone is unknown because it is concealed below cover. A regional magnetotelluric sounding profile along the Utah-Nevada State line reveals a deeply penetrating, broad electrical conductor that may be the Archean-Proterozoic suture zone in the northwest corner of Utah. This major crustal conductor's strike direction is northwest, where it broadens to about 80 km wide below about 3-km depth. These results suggest that the southwestern limit of intact Archean crust in this part of the Great Basin is farther north than previously reported. These results also suggest that the major gold belts in north-central Nevada are located over the Paleoproterozoic Mojave province, and the Archean terrain lies northeast in the northwest corner of Utah. Rifted Archean crust segments south and west of the suture suggest that future mineral exploration northeast of current mineral trends may yield additional gold deposits.

  20. Atmospheric profiling via satellite to satellite occultations near water and ozone absorption lines for weather and climate

    NASA Astrophysics Data System (ADS)

    Kursinski, E. R.; Ward, D.; Otarola, A. C.; McGhee, J.; Stovern, M.; Sammler, K.; Reed, H.; Erickson, D.; McCormick, C.; Griggs, E.

    2016-05-01

    Significantly reducing weather and climate prediction uncertainty requires global observations with substantially higher information content than present observations provide. While GPS occultations have provided a major advance, GPS observations of the atmosphere are limited by wavelengths chosen specifically to minimize interaction with the atmosphere. Significantly more information can be obtained via satellite to satellite occultations made at wavelengths chosen specifically to characterize the atmosphere. Here we describe such a system that will probe cm- and mmwavelength water vapor absorption lines called the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS). Profiling both the speed and absorption of light enables ATOMMS to profile temperature, pressure and humidity simultaneously, which GPS occultations cannot do, as well as profile clouds and turbulence. We summarize the ATOMMS concept and its theoretical performance. We describe field measurements made with a prototype ATOMMS instrument and several important capabilities demonstrated with those ground based measurements including retrieving temporal variations in path-averaged water vapor to 1%, in clear, cloudy and rainy conditions, up to optical depths of 17, remotely sensing turbulence and determining rain rates. We conclude with a vision of a future ATOMMS low Earth orbiting satellite constellation designed to take advantage of synergies between observational needs for weather and climate, ATOMMS unprecedented orbital remote sensing capabilities and recent cubesat technological innovations that enable a constellation of dozens of very small spacecraft to achieve many critical, but as yet unfulfilled, monitoring and forecasting needs.

  1. The Archean Nickel Famine Revisited.

    PubMed

    Konhauser, Kurt O; Robbins, Leslie J; Pecoits, Ernesto; Peacock, Caroline; Kappler, Andreas; Lalonde, Stefan V

    2015-10-01

    Iron formations (IF) preserve a history of Precambrian oceanic elemental abundance that can be exploited to examine nutrient limitations on early biological productivity. However, in order for IF to be employed as paleomarine proxies, lumped-process distribution coefficients for the element of interest must be experimentally determined or assumed. This necessitates consideration of bulk ocean chemistry and which authigenic ferric iron minerals controlled the sorption reactions. It also requires an assessment of metal mobilization reactions that might have occurred in the water column during particle descent and during post-depositional burial. Here, we summarize recent developments pertaining to the interpretation and fidelity of the IF record in reconstructions of oceanic trace element evolution. Using an updated compilation, we reexamine and validate temporal trends previously reported for the nickel content in IF (see Konhauser et al., 2009 ). Finally, we reevaluate the consequences of methanogen Ni starvation in the context of evolving views of the Archean ocean-climate system and how the Ni famine may have ultimately facilitated the rise in atmospheric oxygen.

  2. The formation and deposition of primary silica granules - A new model of early Archean silica deposition

    NASA Astrophysics Data System (ADS)

    Stefurak, E. J.; Lowe, D. R.; Zentner, D.; Fischer, W. W.

    2013-12-01

    In the modern silica cycle, biologically-mediated silica precipitation provides the dominant sink for dissolved silica in seawater, with additional smaller sinks in the form of authigenic phyllosilicates and silica cements. Fundamental questions remain about the mechanics of the processes responsible for removing silica from seawater prior to the evolution of silica biomineralization in late Proterozoic time, with important implications for the chemistry of seawater on the early Earth, including alkalinity budgets and the efficiency of the silicate weathering feedback. The degree to which dissolved silica leaves seawater as authigenic phyllosilicates instead of amorphous silica is important because these 'reverse weathering' reactions do not consume CO2. The abundant presence of siliceous sedimentary rocks in Archean sequences, mainly in the form of chert, reinforces the inference that abiotic silica precipitation played a more significant role during Archean time. Previous authors hypothesized that these cherts formed as primary marine precipitates, but were unable to identify a specific mode of sedimentation. Here we present sedimentologic, petrographic, and geochemical evidence that some and perhaps many Archean cherts were deposited exclusively or in large part as primary, sub-spherical, structureless, sand-sized silica grains, here termed silica granules, which precipitated within marine waters. This mode of silica deposition appears to be unique to Archean time and provides evidence that primary abiotic silica precipitation indeed occurred in Archean oceans. Furthermore, the apparent early cementation of some granules indicates that the rate of silica precipitation was rapid under certain environmental conditions, which could provide insight into microfossil preservation via early silicification.

  3. Major, trace and REE geochemistry in contrasted chlorite schist weathering profiles from southern Cameroon: Influence of the Nyong and Dja Rivers water table fluctuations in geochemical evolution processes

    NASA Astrophysics Data System (ADS)

    Onana, Vincent Laurent; Ntouala, Roger Firmin Donald; Tang, Sylvie Noa; Effoudou, Estelle Ndome; Kamgang, Veronique Kabeyene; Ekodeck, Georges Emmanuel

    2016-12-01

    Three weathering profiles developed on chlorite schists, formations on which little studies have been conducted, were chosen to understand the weathering processes prevailing downslope in Southern Cameroon. The materials nearest to Nyong River at Ayos weather under the influence of the fluctuations of groundwater table and acid rain, while those from Bengbis and Mbalmayo weather under the influence of acid rain. The result is the thickening of materials and weathering profiles, without formation of a nodular ferruginous horizon at Ayos. The Ayos weathered materials (CIA ∼ 92) are the most altered and the least lateritised (IOL ∼ 32). The most stable systems are Hf - U - Nb - Ti - Zr - Mo - W (Bengbis), Yb - U - Nb - Ti - Zr - Hf - Mo - W - Th (Mbalmayo) and Th - Nb - Zr - Hf - Mo - Ta (Ayos). Molybdenum accumulations are important in the studied materials. Uranium accumulations are found only in Mbalmayo. Coarse saprolitic materials at Ayos are the most depleted and fractionated in REE ((La/Yb)N = 0.07, Ce/Ce* = 2.24), while superficial clayey materials are less fractionated. This process is reversed at Bengbis and Mbalmayo. By contrast, weathered materials at Ayos do not show any Eu anomalies (as in Bengbis and Mbalmayo). Weathered materials from Bengbis, nearest to the Dja River, have (La/Yb)N < 1 ratios, indicating the relative immobility of HREE relative to LREE due to xenotime abnormally rich in HREE (HREE-PO4). Weak Ce anomalies (1.05-2.24) are ubiquitous in all the studied materials.

  4. Archean sedimentary styles and early crustal evolution

    NASA Technical Reports Server (NTRS)

    Lowe, D. R.

    1986-01-01

    The distinctions between and implications of early and late Archean sedimentary styles are presented. Early Archean greenstone belts, such as the Barberton of South Africa and those in the eastern Pilbar Block of Australia are characterized by fresh or slightly reworked pyroclastic debris, orthochemical sediments such as carbonates, evaporites, and silica, and biogenic deposits including cherts and stromatolitic units. Terrigenous deposits are rare, and it is suggested that early Archean sediments were deposited on shallow simatic platforms, with little or no components derived from sialic sources. In contrast, late Archean greenstone belts in the Canadian Shield and the Yilgarn Block of Australia contain coarse terrigenous clastic rocks including conglomerate, sandstone, and shale derived largely from sialic basement. Deposition appears to have taken place in deepwater, tectonically unstable environments. These observations are interpreted to indicate that the early Archean greenstone belts formed as anorogenic, shallow water, simatic platforms, with little or no underlying or adjacent continental crust, an environment similar to modern oceanic islands formed over hot spots.

  5. Weathering profiles in granitoid rocks of the Sila Massif uplands, Calabria, southern Italy: New insights into their formation processes and rates

    NASA Astrophysics Data System (ADS)

    Scarciglia, Fabio; Critelli, Salvatore; Borrelli, Luigi; Coniglio, Sabrina; Muto, Francesco; Perri, Francesco

    2016-05-01

    In this paper we characterized several weathering profiles developed on granitoid rocks in the Sila Massif upland (Calabria, southern Italy), integrating detailed macro- and micromorphological observations with physico-mechanical field tests and petrographic, mineralogical and geochemical analyses. We focused our attention on the main weathering and pedogenetic processes, trying to understand apparent discrepancies between weathering grade classes based on field description and geomechanical properties, and two common weathering indices, such as the micropetrographic index (Ip) and the chemical index of alteration (CIA). Our results showed that sericite on plagioclase and biotite chloritization, that represent inherited features formed during late-stage hydrothermal alteration of granitoid rocks, may cause an overestimation of the real degree of weathering of primary mineral grains under meteoric conditions, especially in lower weathering grade classes. Moreover, the frequent identification of Fe-Mn oxides and clay coatings of illuvial origin (rather than or in addition to those formed in situ), both at the macro- and microscale, may also explain an overestimation of the weathering degree with respect to field-based classifications. Finally, some apparent inconsistencies between field geomechanical responses and chemical weathering were interpreted as related to physical weathering processes (cryoclastism and thermoclastism), that lead to rock breakdown even when chemical weathering is not well developed. Hence, our study showed that particular caution is needed for evaluating weathering grades, because traditional field and geochemical-petrographic tools may be biased by inherited hydrothermal alteration, physical weathering and illuvial processes. On the basis of chronological constraints to soil formation obtained from a 42 ka-old volcanic input (mixed to granite parent materials) detected in the soil cover of the Sila Massif upland, a first attempt to estimate

  6. Late Archean Euxinia as a Window into Early Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Scott, C.; Bekker, A.; Reinhard, C.; Lyons, T. W.

    2009-12-01

    A number of transition metals present in seawater in trace amounts (10-10 to 10-7 moles/L) are nevertheless bioessential micronutrients, utilized in a wide range of cellular activities. Because their abundances in seawater are largely a reflection of redox-controlled sources and sinks, Precambrian biogeochemists increasingly focus on the interrelated nature of major redox transitions, the chemical composition of the oceans, and the evolution of life on Earth. Of particular interest are temporal trends in seawater inventories of elements utilized in the nitrogen cycle, both nitrogen fixation (Fe, V, Mo) and denitrification (Cu). Recent work on the link between trace metal abundance and the biologically mediated nitrogen cycle has focused on the Proterozoic Eon, when oxidative weathering was well established and sulfidic conditions were common in the deep ocean. However, we know little about trace metal availability during the Archean Eon, when oxygenic photosynthesis first appeared on Earth and began to alter the chemical composition of the oceans and atmosphere. The development of euxinic conditions, or anoxic and sulfidic bottom waters, provides important information regarding the cycling of major elements such as C, S and Fe. However, euxinic black shales can also provide a record of trace metal abundance. Mo is highly enriched in these shales and displays a conspicuous covariation with the concentration of total organic carbon (TOC). Furthermore, it has been demonstrated that the ratio Mo/TOC is proportional to the concentration of Mo in seawater. Cu and V are also enriched in euxinic black shales, and both correlate with TOC. By analogy with Mo, it is likely that the ratios Cu/TOC and V/TOC also contain information on the concentration of these transition metals in seawater. Here we present C-S-Fe systematics as well as trace metal concentrations from black shales of the Roy Hill Member of the late Archean Jeerinah Formation. Fe speciation indicates that the

  7. Photochemistry and climate on the Archean earth

    NASA Astrophysics Data System (ADS)

    Pavlov, Alexander Anatolevich

    The purpose of my thesis was to explore the consequences of reduced levels of oxygen and reduced solar luminosity, both of which should have affected atmospheric composition and climate. Recent studies of Archean sediments discovered evidence of mass-independent sulfur isotope fractionation in sulfides and sulfates. This type of fractionation pattern cannot be produced by aqueous-phase chemical or biochemical reactions. Mass independent fractionation (MIF) is observed, however, in atmospheric photochemical reactions (photolysis of SO2, H2S). Using laboratory data on SO2 photolysis, I calculated how sulfur isotopic fractionation propagates to other sulfur-bearing species (HA S, SO, H 2SO4) by means of atmospheric chemical reactions. I have been able to estimate what types of isotopic separation must have occurred in order to produce the observed fractionation pattern in Archean sediments. Although mass-independent fractionation continued to occur in the post-Archean atmosphere, its signature was lost before being preserved in sediments because all sulfur-bearing species were re-homogenized as oceanic sulfate. To transfer the mass-independent fractionation pattern from the atmosphere into sediments, the Archean atmosphere must have contained virtually no free oxygen (<10 -5 PAL [times the Present Atmospheric Level]). High concentrations of greenhouse gases would have been required to offset low solar luminosity early in Earth's history. Enhanced CO2 levels are probably at least part of the solution, but CH4 (in an anoxic Archean atmosphere) may have played a significant role as well, particularly during the Late Archean era, 2.5--3.0 Ga, when methanogenic bacteria were almost certainly present. Moreover, biological CH4 production should have led to CO 2 drawdown by way of a negative feedback loop involving the carbonate-silicate geochemical cycle. I suggest here that the atmospheric CH4/CO 2 ratio approached the value of ˜1 needed to trigger the formation of Titan

  8. Weathering processes and dating of soil profiles from São Paulo State, Brazil, by U-isotopes disequilibria.

    PubMed

    Bonotto, Daniel Marcos; Jiménez-Rueda, Jairo Roberto; Fagundes, Isabella Cruz; Filho, Carlos Roberto Alves Fonseca

    2017-01-01

    This study reports the use of the U-series radionuclides (238)U and (234)U for dating two soil profiles. The soil horizons developed over sandstones from Tatuí and Pirambóia formations at the Paraná sedimentary basin, São Paulo State, Brazil. Chemical data in conjunction with the (234)U/(238)U activity ratios (AR's) of the soil horizons allowed investigating the U-isotopes mobility in the shallow oxidizing environment. Kaolinization and laterization processes are taking place in the profiles sampled, as they are especially common in regions characterized by a wet and dry tropical climate and a water table that is close to the surface. These processes are implied by inverse significant correlations between silica and iron in both soil profiles. Iron oxides were also very important to retain uranium in the two sites investigated, helping on the understanding of the weathering processes acting there. (238)U and its progeny (234)U permitted evaluating the processes of physical and chemical alteration, allowing the suggestion of a possible timescale corresponding to the Middle Pleistocene for the development of the more superficial soil horizons.

  9. Identification and uncertainty estimation of vertical reflectivity profiles using a Lagrangian approach to support quantitative precipitation measurements by weather radar

    NASA Astrophysics Data System (ADS)

    Hazenberg, P.; Torfs, P. J. J. F.; Leijnse, H.; Delrieu, G.; Uijlenhoet, R.

    2013-09-01

    This paper presents a novel approach to estimate the vertical profile of reflectivity (VPR) from volumetric weather radar data using both a traditional Eulerian as well as a newly proposed Lagrangian implementation. For this latter implementation, the recently developed Rotational Carpenter Square Cluster Algorithm (RoCaSCA) is used to delineate precipitation regions at different reflectivity levels. A piecewise linear VPR is estimated for either stratiform or neither stratiform/convective precipitation. As a second aspect of this paper, a novel approach is presented which is able to account for the impact of VPR uncertainty on the estimated radar rainfall variability. Results show that implementation of the VPR identification and correction procedure has a positive impact on quantitative precipitation estimates from radar. Unfortunately, visibility problems severely limit the impact of the Lagrangian implementation beyond distances of 100 km. However, by combining this procedure with the global Eulerian VPR estimation procedure for a given rainfall type (stratiform and neither stratiform/convective), the quality of the quantitative precipitation estimates increases up to a distance of 150 km. Analyses of the impact of VPR uncertainty shows that this aspect accounts for a large fraction of the differences between weather radar rainfall estimates and rain gauge measurements.

  10. Influence of chemical weathering on the composition of the continental crust: Insights from Li and Nd isotopes in bauxite profiles developed on Columbia River Basalts

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Ming; Rudnick, Roberta L.; McDonough, William F.; Cummings, Michael L.

    2013-08-01

    Mineralogical, chemical, and Li and Nd isotopic compositions of two drill cores (8-9 m deep) through bauxites developed on the Miocene Columbia River Basalts document the changes associated with basalt weathering, provide insights into the processes involved, and allow us to examine the overall influence of chemical weathering on juvenile (basaltic) crust. Gibbsite, hematite, ±kaolinite, halloysite, goethite, and maghemite are the weathering products in the bauxites. Quartz is observed near the tops of the cores and its abundance decreases progressively with depth; no quartz is observed below five meters depth in either core. Most major and trace elements, including "mobile" and some "immobile" elements are severely depleted in the bauxites. Niobium is less mobile relative to the rare earth elements, thus chemical weathering attenuates the negative Nb anomaly in the continental crust. Li and Nd are strongly depleted relative to fresh basalt, and both increase systematically towards the surface in the quartz-bearing samples while δ7Li and ɛNd values decrease systematically towards the surface in these same samples. Both Li and Nd were likely lost from the bauxites through leaching. The systematic enrichment of Li, Nd, and quartz, as well as the less radiogenic Nd isotopic composition at the tops of both profiles reflects 20-60 wt.% addition of an eolian component to the soils. The eolian dust is unlikely to have experienced significant post-depositional weathering due to the relatively high Li contents near the tops of the profiles, and, therefore, the low δ7Li and ɛNd values suggest that the dust came from an old, weathered region of the continent. Our results demonstrate that lithium isotopes are sensitive tracers of chemical weathering, particularly in extreme weathering settings, and support the hypothesis that chemical weathering influences the mass and composition of the continental crust.

  11. Venus and the Archean Earth: Thermal considerations

    NASA Technical Reports Server (NTRS)

    Sleep, N. H.

    1989-01-01

    The Archean Era of the Earth is not a direct analog of the present tectonics of Venus. In this regard, it is useful to review the state of the Archean Earth. Most significantly, the temperature of the adiabatic interior of the Earth was 200 to 300 C hotter than the current temperature. Preservation biases limit what can be learned from the Archean record. Archean oceanic crust, most of the planetary surface at any one time, has been nearly all subducted. More speculatively, the core of the Earth has probably cooled more slowly than the mantle. Thus the temperature contrast above the core-mantle boundary and the vigor of mantle plumes has increased with time on the Earth. The most obvious difference between Venus and the present Earth is the high surface temperature and hence a low effective viscosity of the lithosphere. In addition, the temperature contrast between the adiabatic interior and the surface, which drives convection, is less on Venus than on the Earth. It appears that the hot lithosphere enhanced tectonics on the early Venus significantly enough that its interior cooled faster than the Earth's. The best evidence for a cool interior of Venus comes from long wavelength gravity anomalies. The low interior temperatures retard seafloor spreading on Venus. The high surface temperatures on Venus enhance crustal deformation. That is, the lower crust may become ductile enough to permit significant flow between the upper crust and the mantle. There is thus some analogy to modern and ancient areas of high heat flow on the Earth. Archean crustal blocks typically remained stable for long intervals and thus overall are not good analogies to the deformation style on Venus.

  12. Production of mineral surface area within deep weathering profiles at eroding vs. depositional hillslope locations: Christina River Basin Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Fisher, B.; Yoo, K.; Aufdenkampe, A. K.; Nater, E.

    2014-12-01

    Geomorphic and biogeochemical processes and hillslope morphology are partly controlled by the extent and degree of chemical weathering between soil and bedrock. The production of mineral specific surface area (SSA) via chemical weathering is a critical variable for mechanistic understanding of weathering and provides an interface between minerals and the soil carbon cycle. We examined two 21-meter deep drill cores in the Laurels Schist at 141 MASL (summit) and 130 MASL (interfluve) in a 900 ha first order watershed in the Laurels Preserve, a forested land use end member in the Christina River Basin CZO. In addition to mineral SSA, we report elemental and mineralogical changes through both weathering profiles. Despite highly variable bedrock composition, mobile elements (Ca & Na) are depleted within 3-5 m below the ground surface, which is consistent with the removal of Ca-Na-plagioclase ((Na,Ca)Al(Si,Al)3O8) at this interval; we consider this depth as a weathering front. The water table in both boreholes was ~123 MASL (5/2014), which is well below the weathering front, suggesting that weathering processes are not coupled with groundwater interactions in this system. Clay XRD reveals the presence of secondary phyllosilicates including vermiculite, illite, and kaolinite in the upper 3 m of the summit weathering profile, which are weathering products of primary plagioclase, muscovite, and chlorite. The currently available clay mineralogy results are consistent with the decrease in total SSA from up to 20 m2g-1 at the surface to <5 m2g-1 below 3 m depth. Within the first 3 m from the surface, citrate-dithionate extractable iron contributed 30-60% of the total surface area. Therefore transformation of primary minerals to secondary phyllosilicate minerals, involving leaching loss of cations, was partly responsible for SSA production, but iron oxides play a significant role in production of SSA above the weathering front. This observation did not differ between

  13. Snow temperature profiles and heat fluxes measured on the Greenland crest by an automatic weather station

    SciTech Connect

    Stearns, C.R.; Weidner, G A.

    1992-03-01

    In June 1989 three automatic weather station (AWS) units were installed on the Greenland crest at the GISP2 (78.58 N, 38.46 W, 3265 m) and GRIP (78.57 N, 37.62 W, 3230 m) ice coring sites and at Kenton (72.28 N, 38.80 W, 3185 m), the air sampling site. The purpose of the AWS units is to measure the local meteorological variables, including snow temperatures at various depths, in support of ice coring studies. The AWS units measure wind speed and direction, air temperature, and relative humidity at a nominal height of 3.6 meters, air pressure at the electronics enclosure, and air temperature difference between 3.6 m and 0.5 m. The AWS units at GISP2 and GRIP also measure solar radiation, and seven snow temperatures from the surface to a depth of approximately 4 m in the snow. The data are updated at 10-minute intervals and transmitted to the ARGOS data collection system on board the NOAA series of polar-orbiting satellites. The air temperature and snow temperatures are presented as a function of time for the period from June 8, 1989 to August 31, 1990 and as tautochrones at 30-day intervals. The heat flux into the snow is determined from the daily mean snow temperature between the day after and the day before using the volumetric heat capacity of the snow assuming a snow density of 300 kg m-3. The daily mean heat flux into the snow between the highest and the lowest levels of snow temperature is presented as a function of time.

  14. Tracking the Archean-Proterozoic suture zone in the northeastern Great Basin, Nevada and Utah

    USGS Publications Warehouse

    Rodriguez, B.D.; Williams, J.M.

    2008-01-01

    It is important to know whether major mining districts in north-central Nevada are underlain by crust of the Archean Wyoming craton, known to contain major orogenic gold deposits or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between these provinces is also important because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. The suture zone is exposed in northeastern Utah and south-western Wyoming and exhibits a southwest strike. In the Great Basin, the suture zone strike is poorly constrained because it is largely concealed below a Neoproterozoic-Paleozoic miogeocline and Cenozoic basin fill. Two-dimensional resistivity modeling of three regional north-south magnetotelluric sounding profiles in western Utah, north-central Nevada, and northeastern Nevada, and one east-west profile in northeastern Nevada, reveals a deeply penetrating (>10 km depth), broad (tens of kilometers) conductor (1-20 ohm-meters) that may be the Archean-Proterozoic suture zone, which formed during Early Proterozoic rifting of the continent and subsequent Proterozoic accretion. This major crustal conductor changes strike direction from southwest in Utah to northwest in eastern Nevada, where it broadens to ???100 km width that correlates with early Paleozoic rifting of the continent. Our results suggest that the major gold belts may be over-isolated blocks of Archean crust, so Phanerozoic mineral deposits in this region may be produced, at least in part, from recycled Archean gold. Future mineral exploration to the east may yield large gold tonnages. ?? 2008 Geological Society of America.

  15. Emergent relation between surface vapor conductance and relative humidity profiles yields evaporation rates from weather data.

    PubMed

    Salvucci, Guido D; Gentine, Pierre

    2013-04-16

    The ability to predict terrestrial evapotranspiration (E) is limited by the complexity of rate-limiting pathways as water moves through the soil, vegetation (roots, xylem, stomata), canopy air space, and the atmospheric boundary layer. The impossibility of specifying the numerous parameters required to model this process in full spatial detail has necessitated spatially upscaled models that depend on effective parameters such as the surface vapor conductance (C(surf)). C(surf) accounts for the biophysical and hydrological effects on diffusion through the soil and vegetation substrate. This approach, however, requires either site-specific calibration of C(surf) to measured E, or further parameterization based on metrics such as leaf area, senescence state, stomatal conductance, soil texture, soil moisture, and water table depth. Here, we show that this key, rate-limiting, parameter can be estimated from an emergent relationship between the diurnal cycle of the relative humidity profile and E. The relation is that the vertical variance of the relative humidity profile is less than would occur for increased or decreased evaporation rates, suggesting that land-atmosphere feedback processes minimize this variance. It is found to hold over a wide range of climate conditions (arid-humid) and limiting factors (soil moisture, leaf area, energy). With this relation, estimates of E and C(surf) can be obtained globally from widely available meteorological measurements, many of which have been archived since the early 1900s. In conjunction with precipitation and stream flow, long-term E estimates provide insights and empirical constraints on projected accelerations of the hydrologic cycle.

  16. Implication of Land Use and Belowground Weather on Nitrous Oxide Soil Depth Profiles and Denitrification Potential

    NASA Astrophysics Data System (ADS)

    Phillips, R. L.; Song, B.; Saliendra, N.; Liebig, M. A.

    2013-12-01

    oxygen profiles followed similar patterns for cropland and prairie, ranging from 12 to 21%, with median values of 19 and 20% at both depths. We did not observe linear concentration gradients between 15 and 90 cm depths, likely due to differences in rates of production and consumption throughout the soil profile. Potential rates of denitrification at 0-15 cm were over two times higher in the cropland, as compared to prairie. We conclude that N2O production occurs not only close to the surface but also nearly a meter beneath both undisturbed prairie and cropland. Greater surface fluxes and N2O concentrations at all depths in the cropland under variable conditions point to enhanced N2O production in the absence of synthetic N addition from 2009-2013. While denitrification potential in the laboratory was greater beneath this alfalfa field, the soil oxygen profile measurements indicated conditions favorable for complete denitrification of N to N2 were rare at near-surface and sub-surface soil depths. Microbial N2O production and consumption processes vary with soil depth and land use in the absence of synthetic N inputs, and further investigation is warranted.

  17. Building Archean cratons from Hadean mafic crust.

    PubMed

    O'Neil, Jonathan; Carlson, Richard W

    2017-03-17

    Geologic processing of Earth's surface has removed most of the evidence concerning the nature of Earth's first crust. One region of ancient crust is the Hudson Bay terrane of northeastern Canada, which is mainly composed of Neoarchean felsic crust and forms the nucleus of the Northeastern Superior Province. New data show these ~2.7-billion-year-old rocks to be the youngest to yield variability in neodymium-142 ((142)Nd), the decay product of short-lived samarium-146 ((146)Sm). Combined (146-147)Sm-(142-143)Nd data reveal that this large block of Archean crust formed by reworking of much older (>4.2 billion-year-old) mafic crust over a 1.5-billion-year interval of early Earth history. Thus, unlike on modern Earth, mafic crust apparently could survive for more than 1 billion years to form an important source rock for Archean crustal genesis.

  18. [Attenuated Total Reflection Infrared Spectroscopy for Degradation Profile of High Density Polyethylene after Weathering Aging].

    PubMed

    Guo, Jun-jun; Yan, Hua; Bao, He-bin; Wang, Xue-mei; Hu, Zhi-de; Yang, Jian-jian

    2015-06-01

    High density polyethylene (HDPE) was widely used as rotational packaging case in the material reserve field. The chemical changes of HDPE, exposed to particular climatic conditions of tropic marine atmosphere for one year-long in Wanning Hainan, were elucidated by the attenuated total reflection infrared spectroscopy (ATR-FTIR). The structural changes were studied qualitatively, mainly from the polymeric chain breaking, branching and oxidation to distinguish the degradation profile. The variations of crystallinity & carbonyl index were also studied quantitatively according to the characteristic peaks intensity & area ratio. Finally, the relationships between structural changes and mechanical properties were investigated. The results showed that the polymeric chain breaking & branching play a leading role before 3 months in the aging progress. Then oxidation phenomena gradually takes place during 3-6 months. The chain branching & oxidation were predominant factors after 6 months. Nine months later, the oxidation was saturated gradually. Furthermore, the aging process is positively correlated to the temperature and irradiation. After 12 months aging, the carbonyl index increased by 112 times and crystallinity was 10% higher than before. The tensile/bending modulus deceased faster than tensile/bending strength of HDPE. The linear degree of tensile modulus and carbonyl index was 0.97. The degree of linearity of tensile strength and crystallinity calculated by feature bands (720-730 cm(-1)) was 0.96. It showed that the mechanical properties of HDPE can be speculated from the structural changes by ATR-FTIR.

  19. Reappraisal of hydrocarbon biomarkers in Archean rocks.

    PubMed

    French, Katherine L; Hallmann, Christian; Hope, Janet M; Schoon, Petra L; Zumberge, J Alex; Hoshino, Yosuke; Peters, Carl A; George, Simon C; Love, Gordon D; Brocks, Jochen J; Buick, Roger; Summons, Roger E

    2015-05-12

    Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial. To resolve this debate, we performed a multilaboratory study of new cores from the Pilbara Craton, Australia, that were drilled and sampled using unprecedented hydrocarbon-clean protocols. Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit, but when they were detectable, they had total hopane (<37.9 pg per gram of rock) and total sterane (<32.9 pg per gram of rock) concentrations comparable to those measured in blanks and negative control samples. In contrast, hopanes and steranes measured in the exteriors of conventionally drilled and curated rocks of stratigraphic equivalence reach concentrations of 389.5 pg per gram of rock and 1,039 pg per gram of rock, respectively. Polycyclic aromatic hydrocarbons and diamondoids, which exceed blank concentrations, exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores. These results demonstrate that previously studied Archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons. Therefore, existing lipid biomarker evidence cannot be invoked to support the emergence of oxygenic photosynthesis and eukaryotes by ∼ 2.7 billion years ago. Although suitable Proterozoic rocks exist, no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration for Archean biomarkers should screen for rocks with milder thermal histories.

  20. Reappraisal of hydrocarbon biomarkers in Archean rocks

    PubMed Central

    French, Katherine L.; Hallmann, Christian; Hope, Janet M.; Schoon, Petra L.; Zumberge, J. Alex; Hoshino, Yosuke; Peters, Carl A.; George, Simon C.; Love, Gordon D.; Brocks, Jochen J.; Buick, Roger; Summons, Roger E.

    2015-01-01

    Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial. To resolve this debate, we performed a multilaboratory study of new cores from the Pilbara Craton, Australia, that were drilled and sampled using unprecedented hydrocarbon-clean protocols. Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit, but when they were detectable, they had total hopane (<37.9 pg per gram of rock) and total sterane (<32.9 pg per gram of rock) concentrations comparable to those measured in blanks and negative control samples. In contrast, hopanes and steranes measured in the exteriors of conventionally drilled and curated rocks of stratigraphic equivalence reach concentrations of 389.5 pg per gram of rock and 1,039 pg per gram of rock, respectively. Polycyclic aromatic hydrocarbons and diamondoids, which exceed blank concentrations, exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores. These results demonstrate that previously studied Archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons. Therefore, existing lipid biomarker evidence cannot be invoked to support the emergence of oxygenic photosynthesis and eukaryotes by ∼2.7 billion years ago. Although suitable Proterozoic rocks exist, no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration for Archean biomarkers should screen for rocks with milder thermal histories. PMID:25918387

  1. Reappraisal of hydrocarbon biomarkers in Archean rocks

    NASA Astrophysics Data System (ADS)

    French, Katherine L.; Hallmann, Christian; Hope, Janet M.; Schoon, Petra L.; Zumberge, J. Alex; Hoshino, Yosuke; Peters, Carl A.; George, Simon C.; Love, Gordon D.; Brocks, Jochen J.; Buick, Roger; Summons, Roger E.

    2015-05-01

    Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial. To resolve this debate, we performed a multilaboratory study of new cores from the Pilbara Craton, Australia, that were drilled and sampled using unprecedented hydrocarbon-clean protocols. Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit, but when they were detectable, they had total hopane (<37.9 pg per gram of rock) and total sterane (<32.9 pg per gram of rock) concentrations comparable to those measured in blanks and negative control samples. In contrast, hopanes and steranes measured in the exteriors of conventionally drilled and curated rocks of stratigraphic equivalence reach concentrations of 389.5 pg per gram of rock and 1,039 pg per gram of rock, respectively. Polycyclic aromatic hydrocarbons and diamondoids, which exceed blank concentrations, exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1,000 ng per gram of rock in hydropyrolysates from the ultraclean cores. These results demonstrate that previously studied Archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons. Therefore, existing lipid biomarker evidence cannot be invoked to support the emergence of oxygenic photosynthesis and eukaryotes by ∼2.7 billion years ago. Although suitable Proterozoic rocks exist, no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration for Archean biomarkers should screen for rocks with milder thermal histories.

  2. Was there a late Archean biospheric explosion?

    PubMed

    Lindsay, John F

    2008-08-01

    There is a growing body of evidence which suggests that the evolution of the planet drives the evolution of the biosphere. There have been 2 significant stages in Earth history when atmospheric oxygen levels rose rapidly, and both appear to be associated with supercontinent cycles. The earlier biospheric event, which extends across the Archean-Proterozoic boundary (ca. 3.0-2.2 Ga), has received little attention and is the focus of this study. Recent work on the Pilbara Craton of Western Australia has shown that concretion formed by microbial activity during the diagenesis of these sediments are absent from early Archean sediments but abundant in late Archean and early Paleoproterozoic successions of the Hamersley Basin, appearing abruptly in sedimentary rocks younger than 2.7 Ga. This study suggests that their internal architecture may have been defined by the diffusion of humic acids and the formation of polymer gels during diagenesis. The data imply that the biosphere expanded suddenly shortly after 3.0 Ga and may have begun to raise the oxygen levels of the oceanic water column earlier than thought-possibly as much as 300 my earlier.

  3. Identification of an Archean marine oxygen oasis

    SciTech Connect

    Riding, Dr Robert E; Fralick, Dr Philip; Liang, Liyuan

    2014-01-01

    The early Earth was essentially anoxic. A number of indicators suggest the presence of oxygenic photosynthesis 2700 3000 million years (Ma) ago, but direct evidence for molecular oxygen (O2) in seawater has remained elusive. Here we report rare earth element (REE) analyses of 2800 million year old shallowmarine limestones and deep-water iron-rich sediments at Steep Rock Lake, Canada. These show that the seawater from which extensive shallow-water limestones precipitated was oxygenated, whereas the adjacent deeper waters where iron-rich sediments formed were not. We propose that oxygen promoted limestone precipitation by oxidative removal of dissolved ferrous iron species, Fe(II), to insoluble Fe(III) oxyhydroxide, and estimate that at least 10.25 M oxygen concentration in seawater was required to accomplish this at Steep Rock. This agrees with the hypothesis that an ample supply of dissolved Fe(II) in Archean oceans would have hindered limestone formation. There is no direct evidence for the oxygen source at Steep Rock, but organic carbon isotope values and diverse stromatolites in the limestones suggest the presence of cyanobacteria. Our findings support the view that during the Archean significant oxygen levels first developed in protected nutrient-rich shallow marine habitats. They indicate that these environments were spatially restricted, transient, and promoted limestone precipitation. If Archean marine limestones in general reflect localized oxygenic removal of dissolved iron at the margins of otherwise anoxic iron-rich seas, then early oxygen oases are less elusive than has been assumed.

  4. Insights into chemical weathering of the upper continental crust from the geochemistry of ancient glacial diamictites

    NASA Astrophysics Data System (ADS)

    Li, Su; Gaschnig, Richard M.; Rudnick, Roberta L.

    2016-03-01

    Glacial diamictites, with ages ranging from ∼2900 to 0.01 Ma, record the changing composition of the upper continental crust through time (Gaschnig et al., 2014). Li concentrations and isotopic compositions, combined with Pb isotopic compositions, chemical index of alteration (CIA) values and relative Sr concentrations are used here to assess the degree of chemical weathering recorded in these deposits and the origin of this signature. The δ7Li values of most of the diamictites (ranging from -3.9 to +3.5) are lower than those of mantle-derived basalts (+3.7 ± 2, 2σ), and the low δ7Li values are generally accompanied by high CIA and low Sr/Sr∗ values (or Sr depletion factor, Sr/Sr∗ = Sr/(Ce∗Nd)0.5), reflecting a weathering signature that may have derived from pre-depositional, syn-depositional, and/or post-depositional weathering processes. Profiles through three glacial diamictites with relatively high CIA (a fresh road cut of the Neoproterozoic Nantuo Formation (CIA = 62-69), and drill cores through the Paleoproterozoic Timeball Hill (CIA = 66-75) and Duitschland Formations (CIA = 84-91)) do not show evidence of significant post-depositional weathering. High Th/U, reflecting loss of uranium during oxidative weathering, is seen in all Paleozoic and Neoproterozoic diamictites and a few Paleoproterozoic deposits. Pb isotopic systematics suggest that this signature was largely inherited from preexisting crust, although a subset of samples (the Neoproterozoic Konnarock, Paleozoic Dwyka, and several of the Paleoproterozoic Duitschland samples) appears to have experienced post-depositional U loss. Modern glaciomarine sediments record little weathering (CIA = 47, Sr/Sr∗ = 0.7, δ7Li = +1.8), consistent with the cold temperatures accompanying glacial periods, and suggesting that limited syn-depositional weathering has occurred. Thus, the chemical weathering signature observed in ancient glacial diamictites appears to be largely inherited from the upper

  5. Regolith evolution on the millennial timescale from combined U-Th-Ra isotopes and in situ cosmogenic 10Be analysis in a weathering profile (Strengbach catchment, France)

    NASA Astrophysics Data System (ADS)

    Ackerer, J.; Chabaux, F.; Van der Woerd, J.; Viville, D.; Pelt, E.; Kali, E.; Lerouge, C.; Ackerer, P.; di Chiara Roupert, R.; Négrel, P.

    2016-11-01

    U-Th-Ra disequilibria, cosmogenic in situ 10Be concentrations and major and trace element concentrations have been analyzed in a 2 m-deep weathering profile sampled at the summit of the granitic Strengbach catchment (France). The data have been used to independently estimate both the long-term regolith production and denudation rates and the weathering and erosion rates. Modeling of the 238U-234U-230Th-226Ra disequilibrium variations in the lower part of the profile yields a regolith production rate of 12 ± 4 mm/kyr (30 ± 10 T/km2/yr), while modeling of the high-resolution 10Be concentration profile leads to an exposure age of 19.7 ± 2.2 kyr, an inherited concentration of 15,000 ± 1,000 at/g in quartz and a mean denudation rate of 22 ± 10 mm/kyr (37 ± 15 T/km2/yr). The consistency between production and denudation rates suggests that, on a millennial timescale, the regolith mass balance at the summit of the catchment is close to a steady state, even if the watershed may have been impacted by Quaternary climatic changes and by recent anthropogenic perturbations (e.g., 20th century acid rain and recent afforestation efforts). The results also indicate that physical erosion is likely the dominant long-term process of regolith denudation in the catchment. Furthermore, the comparison of the long-term production and denudation rates and of weathering and erosion rates determined from the depth profile analyses with the current weathering and erosion rates estimated at the outlet of the watershed based on monitoring of the water chemistry and sediment fluxes suggests that physical erosion may have varied more than the chemical weathering flux during the last 150 kyr. Although very few other sites with U-series, in situ 10Be and stream monitoring data are available for comparison, the current data suggest that (1) the mass balance steady state of regolith might be commonly achieved in soil mantled landscapes, and (2) physical erosion has varied much more than

  6. Late-Archean continental emergence: consequences for the rise of atmospheric oxygen

    NASA Astrophysics Data System (ADS)

    Flament, N. E.; Coltice, N.; Rey, P. F.

    2008-12-01

    The balance between the secular cooling of the Earth's mantle and the growth of the continental crust implies changes in the isostatic equilibrium between continents and oceans, in the oceanic bathymetry, and in the area of emerged continental crust. The evolution of the latter is of fundamental importance to the geochemical coupling between the continental crust, the atmosphere and the oceans. The area of emerged land can be estimated from models that depend on mantle temperature, continental area and continental hypsometry. In the Archean, the mantle was probably 150-200°C hotter than present and the continental area could have increased from 20% of present at ~~3.5Ga to 80% of present by ~~2.5Ga. Using these values, and comparing different thermal evolution models for the Earth, we calculate that the area of emerged continental crust would be reduced to 1-12% of the Earth's area during the Archean (compared to 27.5% for present-day Earth). As for the continental hypsometry, a greater radiogenic crustal heat production and a greater mantle heat flow would have reduced the strength of the continental lithosphere in the Archean, thus limiting the crustal thickening due to mountain building processes and the maximum elevation in the Earth's topography [Rey and Coltice, Geology 36, 635-638 (2008)]. Taking this into account, we show that the continents were mostly flooded until the end of the Archean and that less than 3% of the Earth's area (which is roughly the superficy of South America) consisted of emerged continental crust by ~~2.5~Ga. These results are consistent with widespread Archean submarine continental flood basalts, and with the emergence of a sialic geochemical reservoir recorded from ~~2.5~Ga in (a) the composition of shales, (b) the isotopic ratio 87Sr/86Sr of marine carbonates and (c) the δ18O signature of igneous zircons. The progressive emergence of the continents as shown by our models from the late-Archean

  7. Ground-based remote sensing profiling and numerical weather prediction model to manage nuclear power plants meteorological surveillance in Switzerland

    NASA Astrophysics Data System (ADS)

    Calpini, B.; Ruffieux, D.; Bettems, J.-M.; Hug, C.; Huguenin, P.; Isaak, H.-P.; Kaufmann, P.; Maier, O.; Steiner, P.

    2011-08-01

    The meteorological surveillance of the four nuclear power plants in Switzerland is of first importance in a densely populated area such as the Swiss Plateau. The project "Centrales Nucléaires et Météorologie" CN-MET aimed at providing a new security tool based on one hand on the development of a high resolution numerical weather prediction (NWP) model. The latter is providing essential nowcasting information in case of a radioactive release from a nuclear power plant in Switzerland. On the other hand, the model input over the Swiss Plateau is generated by a dedicated network of surface and upper air observations including remote sensing instruments (wind profilers and temperature/humidity passive microwave radiometers). This network is built upon three main sites ideally located for measuring the inflow/outflow and central conditions of the main wind field in the planetary boundary layer over the Swiss Plateau, as well as a number of surface automatic weather stations (AWS). The network data are assimilated in real-time into the fine grid NWP model using a rapid update cycle of eight runs per day (one forecast every three hours). This high resolution NWP model has replaced the former security tool based on in situ observations (in particular one meteorological mast at each of the power plants) and a local dispersion model. It is used to forecast the dynamics of the atmosphere in the planetary boundary layer (typically the first 4 km above ground layer) and over a time scale of 24 h. This tool provides at any time (e.g. starting at the initial time of a nuclear power plant release) the best picture of the 24-h evolution of the air mass over the Swiss Plateau and furthermore generates the input data (in the form of simulated values substituting in situ observations) required for the local dispersion model used at each of the nuclear power plants locations. This paper is presenting the concept and two validation studies as well as the results of an emergency

  8. Ground-based remote sensing profiling and numerical weather prediction model to manage nuclear power plants meteorological surveillance in Switzerland

    NASA Astrophysics Data System (ADS)

    Calpini, B.; Ruffieux, D.; Bettems, J.-M.; Hug, C.; Huguenin, P.; Isaak, H.-P.; Kaufmann, P.; Maier, O.; Steiner, P.

    2011-01-01

    The meteorological surveillance of the four nuclear power plants in Switzerland is of first importance in a densely populated area such as the Swiss Plateau. The project "Centrales Nucléaires et Météorologie" CN-MET aimed at providing a new security tool based on one hand on the development of a high resolution numerical weather prediction (NWP) model. The latter is providing essential nowcasting information in case of a radioactive release from a nuclear power plant in Switzerland. On the other hand, the model input over the Swiss Plateau is generated by a dedicated network of surface and upper air observations including remote sensing instruments (wind profilers and temperature/humidity passive microwave radiometers). This network is built upon three main sites ideally located for measuring the inflow/outflow and central conditions of the main wind field in the planetary boundary layer over the Swiss Plateau, as well as a number of surface automatic weather stations (AWS). The network data are assimilated in real-time into the fine grid NWP model using a rapid update cycle of eight runs per day (one forecast every 3 h). This high resolution NWP model has replaced the former security tool based on in situ observations (in particular one meteorological mast at each of the power plant) and a local dispersion model. It is used to forecast the dynamics of the atmosphere in the planetary boundary layer (typically the first 4 km above ground layer) and over a time scale of 24 h. This tool provides at any time (e.g. starting at the initial time of a nuclear power plant release) the best picture of the 24-h evolution of air mass over the Swiss Plateau and furthermore generates the input data (in the form of simulated values substituting in situ observations) required for the local dispersion model used at each of the nuclear power plants locations. This paper is presenting the concept and two validation studies as well as the results of an emergency response exercise

  9. Biomarker evidence for Archean oxygen fluxes (Invited)

    NASA Astrophysics Data System (ADS)

    Hallmann, C.; Waldbauer, J.; Sherman, L. S.; Summons, R. E.

    2010-12-01

    Knowledge of deep-time organismic diversity may be gained from the study of preserved sedimentary lipids with taxonomic specificity, i.e. biomarker hydrocarbons (e.g. Brocks and Summons, 2003; Waldbauer et al., 2009). As a consequence of long residence times and high thermal maturities however, biomarker concentrations are extremely low in most ancient (Precambrian) sediment samples, making them exceptionally prone to contamination during drilling, sampling and laboratory workup (e.g. Brocks et al., 2008). Outcrop samples most always carry a modern overprint and deep-time biogeochemistry thus relies on drilling operations to retrieve ‘clean’ sediment cores. One such effort was initiated by NASA’s Astrobiology Institute (NAI): the Archean biosphere drilling project (ABDP). We here report on the lipids retrieved from sediment samples in drill hole ABDP-9. Strong heterogeneities of extractable organic matter - both on a spatial scale and in free- vs. mineral-occluded bitumen - provide us with an opportunity to distinguish indigenous lipids from contaminants introduced during drilling. Stratigraphic trends in biomarker data for mineral-occluded bitumens are complementary to previously reported data (e.g. S- and N-isotopes, molybdenum enrichments) from ABDP-9 sediments (Anbar et al., 2007; Kaufman et al., 2007; Garvin et al., 2009) and suggest periodic fluxes of oxygen before the great oxidation event. Anbar et al. A whiff of oxygen before the great oxidation event. Science 317 (2007), 1903-1906. Brocks & Summons. Sedimentary hydrocarbons, biomarkers for early life. In: Schlesinger (Ed.) Treatise on Geochemistry, Vol. 8 (2003), 63-115. Brocks et al. Assessing biomarker syngeneity using branched alkanes with quaternary carbon (BAQCs) and other plastic contaminants. Geochimica et Cosmochimica Acta 72 (2008), 871-888. Garvin et al. Isotopic evidence for a aerobic nitrogen cycle in the latest Archean. Science 323 (2009), 1045-1048. Kaufman et al. Late Archean

  10. Sulphur tales from the early Archean world

    NASA Astrophysics Data System (ADS)

    Montinaro, A.; Strauss, H.

    2016-07-01

    Sedimentary and magmatic rocks and their distinct sulphur isotopic signatures indicate the sources and processes of sulphur cycling, in particular through the analysis of all four stable sulphur isotopes (32S, 33S, 34S and 36S). Research over the past 15 years has substantially advanced our understanding of sulphur cycling on the early Earth, most notably through the discovery of mass-independently fractionated sulphur isotopic signatures. A strong atmospheric influence on the early Archean global sulphur cycle is apparent, much in contrast to the modern world. Diverse microbially driven sulphur cycling is clearly discernible, but its importance for Earth surface environments remains to be quantified.

  11. Archean collisional tectonics in SW Montana

    SciTech Connect

    Mogk, D.; Rickmond, D.; Salt, K.; Clark, M.; Mueller, P.; Lafrenze, D.; Wooden, J.; Henry, D.

    1985-01-01

    The Archean continental crust of SW Montana evolved through alternating cycles of stable platform sedimentation followed by crustal thickening through collisional tectonics. The ancient sialic crust in the Beartooth Mountains served as the nucleus for accretion of younger terranes to the west. The oldest orogenic cycle recognized in the Beartooth Mountains involves a 3.4 Ga old supracrustal sequence which was metamorphosed in the granulite facies (T=700-800/sup 0/C, P=6Kb, 35/sup 0/C/Km); deep burial is interpreted as the result of collisional tectonic thickening. The second orogenic cycle is subduction related and has produced 2.8 Ga old andesites, 2.75 Ga old calc-alkaline intrusives, upper amphibolite grade metamorphism, transcurrent faulting (in the North Snowy Block and Yankee Jim canyon at 2.8 Ga) and nappe emplacement. In the central Beartooths post-orogenic granites intrude pelitic schists (T=600/sup 0/C, P=8Kb, 25/sup 0/C/Km). West of the Beartooths the basement consists of 2.75-2.70 Ga old, tectonically telescoped coarse clastics (Gallatin, Madison Ranges) and stable platform sequences (Gravelly, Tobacco Root, Ruby Ranges). Nappe formation and granulite-migmatite (700-750/sup 0/C) associations are common, suggesting deep burial through tectonic thickening. A later-kinematic mesozonal (8Kb) qtz diorite-granodiorite batholithic complex is present in the northern Madison Range. Quartzofeldspathic paragneisses in the westernmost Archean basement are derived from either a continental or island arc source.

  12. Biomarkers Indigenous to Late Archean Rocks

    NASA Astrophysics Data System (ADS)

    Eigenbrode, J. L.; Freeman, K. H.; Summons, R. E.; Love, G. D.; Snape, C. E.

    2003-12-01

    Two new lines of evidence support the authenticity of molecular fossils in late Archean rocks of the Hamersley Province, Western Australia. Specifically, they support 1) a syngenetic relationship between the kerogen and extractable biomarkers, and 2) a indigenous relationship between extractable compounds and the host rocks. Carbon skeletons released from kerogen via high-pressure hydropyrolysis match those found in associated extracted bitumen. Biomarker ratios indicate less mature steranes and terpanes (i.e. hopanes and tricyclic terpanes) are embedded in the kerogen matrix as compared to the highly mature steranes and terpanes in the extracts, which is similar to findings in other hydropyrolysis experiments. Lithology-associated variations in biomarker distributions are noteworthy and suggest environmental settings are associated with differing biotic ecosystems. The evidence reported here confirms the 2.7 Ga antiquity of diverse biosynthetic pathways. Molecular data, together with isotopic data, indicate aerobic and anaerobic respiration pathways were fundamental to the complex microbial biogeochemistry of the late Archean. The biomarkers in these rocks support an early radiation of the three domains of life and radiation within the bacteria, such that clades of cyanobacteria, green sulfur bacteria, and proteobacteria had been established.

  13. The Rise of Continents and the Transition Archean to Proterozoic

    NASA Astrophysics Data System (ADS)

    Rey, P. F.; Flament, N.; Coltice, N.

    2011-12-01

    Terrestrial planets evolve in part via partial melting and gravitational differentiation, and in part via fluid/rock interactions at the surface. Mass and energy transfers across their various envelopes depend on the mode of convective motion, which may involve stagnant or mobile lid systems, for which plate tectonics is a possible mode; one promoting the coupling between exogenic and endogenic envelopes. In the other hand, fluid/rock interaction at the surface depends on the planet hypsometry and availability of weathering agents such as liquid water. It also depends on fluid/rock interaction at mid-oceanic ridge and therefore on the mode of convection. Hence, from 4.54 to 2.5 Ga the interplay between deep and surface processes under the forcing of secular cooling was such that the Earth differentiation was non-linear with sudden crises that punctuated periods of relative quietness. The Earth secular cooling impacted on deep and surface processes through the modulation of the Earth's hypsometry. This modulation occurred via cooling and strengthening of the lithosphere (Rey and Coltice, Geology, 2008), and via the deepening of oceanic basin, which lowered the mean sea level forcing the continents to emerge (Flament et al., EPSL, 2008). Stronger lithospheres are able to sustain higher orogenic belts and orogenic plateaux, the erosion of which lead to stronger fluxes towards the ocean. Secular strengthening and emergence conspired to enhance weathering and erosion of the continents and therefore to enhance the geochemical coupling between the endogenic and exogenic Earth's envelopes (Rey and Coltice, Geology, 2008). The shift to the aerobic world, at the Archean to Proterozic transition, took place at a time when exogenic envelopes recorded major shifts in composition (eg. Taylor and McLennan, Rev. of Geophys., 1995; Veizer and Compston, Geochem. Cosmochem Acta, 1976; Valley et al., Contrib. to Mineral. Petrol., 2005) that are consistent with the progressive exposure

  14. Geostable molecules and the Late Archean 'Whiff of Oxygen'

    NASA Astrophysics Data System (ADS)

    Summons, R. E.; Illing, C. J.; Oduro, H. D.; French, K. L.; Ono, S.; Hallmann, C.; Strauss, H.

    2012-12-01

    Geoscientists continue to debate the course of oxygenation of Earth's surface environment. The prevailing scenarios include the one articulated by Cloud, Holland and Walker which proposes an initially anoxic or very low O2 atmosphere but one where oxygen-releasing Photosystem II appeared early. A strong imbalance between sources & sinks kept the atmospheric pO2 low until the 'Great Oxidation Event' or GOE at c. 2.45 Ga. An alternative scenario is that the GOE marks the first appearance of oxygen-releasing photosynthesis (Kopp et al., 2005). However, there is a wealth of geochemical and paleontological data that is consistent with the presence of both cyanobacteria (e.g. Bosak et al., 2009) and traces of environmental oxygen (e.g. Anbar et al., 2007) several hundred million years prior to the GOE. Here we report new studies of 2.7-2.5 Ga sedimentary rocks from the Transvaal Supergroup of the Kaapvaal Craton and from the Mt. Bruce Supergroup of the Pilbara Craton. We used improved analytical techniques which identified and excluded minor sources of contaminating hydrocarbons. We also focused on mineral-occluded hydrocarbons that show distribution patterns that co-vary with lithology and replicated earlier identifications of molecular fossils that require oxygen for their biosynthesis (Waldbauer et al., 2008, 2011). Some sediment horizons in the studied sections contain diagenetic products of pigments characteristic of phototrophic green sulfur bacteria and their co-variance with inorganic proxies, each leading to similar paleoenvironmental reconstructions and confirming the authenticity of this signal. The carotenoid-derived biomarkers, although diagnostic for anoxygenic phototrophs, indicate that the seas of the Hamersley and Transvaal Basins provided an intermittent supply of hydrogen sulfide to the photic zone. Indirectly, this suggests replenishment of the marine sulfate pool from the oxidative weathering of metal sulfides. Organic sulfur in these same sediments

  15. Dating brittle deformation in the Archean Yilgarn Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Thebaud, N.; Zwingmann, H.

    2012-12-01

    Major deformation throughout the Archean Yilgarn Craton has mostly been interpreted to be Neoarchean (Blewett and Czarnota, 2007). The timing of the deformation events of the brittle/ductile deformation generally relies on dating of cross-cutting intrusions or unconformities. Proterozoic overprinting and reactivation of Archean structures in the north-western part of the Yilgarn Craton has previously been dated from direct dating of the structures and fabrics from the Narryer Terrane(Spaggiari et al., 2008). However, the brittle deformation that postdates Neoarchean brittle-ductile structures in the Yilgarn Craton have received little attention to date. In the centre of the Yilgarn Craton, the Eastern Goldfields present a well developed network of E-W trending of normal brittle faults and fractures. Typically these structures are interpreted to have developed in result of a late Neoarchean tectonic relaxation following the main Yilgarn wide E-W contraction (Blewett and Czarnota, 2007). Poorly preserved and weathered faulted rocks in the subsurface environment preclude direct dating of fault gouge. However, exposure from the underground Agnew mine, in the Agnew Wiluna greenstone belt, recently provided access to fresh fault gouge material suitable for analysis. The clay gouge was characterized by SEM, TEM and XRD methods prior to age dating indicating an authigenic origin (Zwingmann et al., 2010). K-Ar illite age data of a whole rock sample split yielded an age of 1148 ± 23 Ma, which is within error close to the <2 micron clay fraction yielding an age of 1094 ± 22 Ma (Mesoproterozoic-Stenian). Our result is the first documentation of the age of the brittle deformation that affects the Yilgarn Craton. This age is within error of the Gilles event which is an extension event that affected the whole Australian continent and is responsible for the emplacement of the Warakurna Large Igneous Province and related dolerite dykes in the Yilgarn Craton (Evins et al., 2010

  16. Comparison of Archean and Phanerozoic granulites: Southern India and North American Appalachians

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Kittleson, Roger C.

    1988-01-01

    Archean granulites at the southern end of the Dharwar craton of India and Phanerozoic granulites in the southern Appalachians of North America share an important characteristic: both show continuous transitions from amphibolite facies rocks to higher grade. This property is highly unusual for granulite terranes, which commonly are bounded by major shears or thrusts. These two terranes thus offer an ideal opportunity to compare petrogenetic models for deep crustal rocks formed in different time periods, which conventional wisdom suggests may have had different thermal profiles. The salient features of the Archean amphibolite-to-granulite transition in southern India have been recently summarized. The observed metamorphic progression reflects increasing temperature and pressure. Conditions for the Phanerozoic amphibolite-to-granulite transition in the southern Appalachians were documented. The following sequence of prograde reactions was observed: kyanite = sillimanite, muscovite = sillimanite + K-feldspar, partial melting of pelites, and hornblende = orthopyroxene + clinopyroxene + garnet. The mineral compositions of low-variance assemblages in mafic and intermediate rocks are almost identical for the two granulite facies assemblages. In light of their different fluid regimes and possible mechanisms for heat flow augmentation, it seems surprising that these Archean and Phanerozoic granulite terranes were apparently metamorphosed under such similar conditions of pressure and temperature. Comparison with other terrains containing continuous amphibolite-to-granulite facies transitions will be necessary before this problem can be addressed.

  17. Middle Archean continent formation by crustal delamination

    NASA Astrophysics Data System (ADS)

    Zegers, Tanja E.; van Keken, Peter E.

    2001-12-01

    The processes that created the first large cratonic areas such as the Pilbara and the Kaapvaal remain poorly understood. Models based on the uniformitarian extrapolation of present-day arc volcanic processes to a hotter early Earth have not adequately explained the observations in these terranes. Here we propose an alternative mechanism for the formation of the earliest continental crust. The formation of continental crust may be achieved by delamination of the lower eclogitic part of an oceanic plateau like protocrust. Such delamination results in uplift, extension, and the production of tonalite, trondhjemite, and granodiorite (TTG) suites as recorded in Middle Archean cratons. The available geologic and geophysical observations in combination with model calculations permit this scenario as an alternative to subduction-based hypotheses.

  18. Phosphate microaggregates in Archean sediments. [Abstract only

    NASA Technical Reports Server (NTRS)

    Mojzsis, S.; Fan, G. Y.; Arrhenius, G.

    1994-01-01

    Light microscopy conducted on samples of Archean sediments reveals phosphate microaggregates which are suggestive of a biotic origin (Arrhenius et al., 1993). These aggregates, typically 15 micrometers wide and 50 micrometers long, are thought to be the mineral remains of colonies of microorganisms that lived during the late Archean Eon (greater than or equal to 2.5 Ga). Confocal microscopy was used to study the structures of these microaggregates in three dimensions. Samples used in this study are from the lowermost section of drill core taken from the Dales Gorge Member of the Brockman Iron-Formation (Hamersley Basin) in Western Australia. These sediments are well-preserved and escaped extensive metamorphism typically experienced by older rocks of this type. Two types of samples were prepared for study under the microscope: thin sections (30 micrometers) for transmitted light microscopy to study the general rock texture and to locate the grains of interest, and thick sections (3mm) for confocal microscopy to determine the 3-D structure of the aggregates in situ. The samples have been carefully polished so that they may be directly placed on the oil-immersion lens without the use of a cover slip. No chemical treatments of the surfaces have been performed. The aggregates often form clusters, although isolated aggregates have also been found. The clusters tend to distribute along microbands in the rocks. Electron microprobe analyses show that the phosphate grains and their inclusions, besides calcium and phosphorus, contain no major elements heavier than sodium. The proportions of calcium to phosphorus, the absence of stoichiometric amounts of other cations such as magnesium and iron, as well as optical properties suggest apatite as the mineral form.

  19. Rain cell-based identification of the vertical profile of reflectivity as observed by weather radar and its use for precipitation uncertainty estimation

    NASA Astrophysics Data System (ADS)

    Hazenberg, P.; Torfs, P. J. J. F.; Leijnse, H.; Uijlenhoet, R.

    2012-04-01

    The wide scale implementation of weather radar systems over the last couple of decades has increased our understanding concerning spatio-temporal precipitation dynamics. However, the quantitative estimation of precipitation by these devices is affected by many sources of error. A very dominant source of error results from vertical variations in the hydrometeor size distribution known as the vertical profile of reflectivity (VPR). Since the height of the measurement as well as the beam volume increases with distance from the radar, for stratiform precipitation this results in a serious underestimation (overestimation) of the surface reflectivity while sampling within the snow (bright band) region. This research presents a precipitation cell-based implementation to correct volumetric weather radar measurements for VPR effects. Using the properties of a flipping carpenter square, a contour-based identification technique was developed, which is able to identify and track precipitation cells in real time, distinguishing between convective, stratiform and undefined precipitation. For the latter two types of systems, for each individual cell, a physically plausible vertical profile of reflectivity is estimated using a Monte Carlo optimization method. Since it can be expected that the VPR will vary within a given precipitation cell, a method was developed to take the uncertainty of the VPR estimate into account. As a result, we are able to estimate the amount of precipitation uncertainty as observed by weather radar due to VPR for a given precipitation type and storm cell. We demonstrate the possibilities of this technique for a number of winter precipitation systems observed within the Belgian Ardennes. For these systems, in general, the precipitation uncertainty estimate due to vertical reflectivity profile variations varies between 10-40%.

  20. Mantle differentiation and chemical cycling in the Archean (Invited)

    NASA Astrophysics Data System (ADS)

    Lee, C.

    2010-12-01

    Differentiation of Earth’s silicate mantle is largely controlled by solid-state convection. Today, upwelling mantle leads to decompression melting. Melts, being of low density, rise to form the continental and oceanic crusts. Because many trace elements, such as heat-producing U, Th and K, as well as the noble gases, preferentially partition into melts, melt extraction concentrates these elements into the crust or atmosphere. However, one by-product of whole-mantle convection is that melting during the Earth’s first billion years was likely deep and hot. Such high pressure melts may have been dense, allowing them to stall, crystallize and later founder back into the lower mantle. These sunken lithologies would have ‘primordial’ chemical signatures despite a non-primordial origin. As the Earth cools, the proportion of upwards melt segregation relative to downwards melt segregation increases, removing volatiles and other incompatible elements to the surface. Recycling of these elements back into the Earth’s interior occurs by subduction, but because of chemical weathering, hydrothermal alteration and photosynthetic reactions occurring in the Earth’s exosphere, these recycled materials may re-enter the mantle already chemically transformed. In particular, photosynthetic production of oxygen and, especially, the progressive oxygenation of the Earth’s atmosphere require removal of reduced carbon from the Earth’s surface. If such removal occurred by subduction, the mantle would have become progressively reduced. During the Archean and early Proterozoic, much of this material may have contributed to making cratonic mantle, and if so, cratonic mantle may have been assembled by reduced building blocks, perhaps explaining the origin of diamonds with organic carbon isotopic signatures. The origin of peridotitic diamonds in cratonic mantle could then be explained if the underlying convecting mantle was in fact more oxidizing such that carbonatitic liquids

  1. On the photosynthetic potential in the very Early Archean oceans.

    PubMed

    Avila, Daile; Cardenas, Rolando; Martin, Osmel

    2013-02-01

    In this work we apply a mathematical model of photosynthesis to quantify the potential for photosynthetic life in the very Early Archean oceans. We assume the presence of oceanic blockers of ultraviolet radiation, specifically ferrous ions. For this scenario, our results suggest a potential for photosynthetic life greater than or similar to that in later eras/eons, such as the Late Archean and the current Phanerozoic eon.

  2. Weather Watch

    ERIC Educational Resources Information Center

    Bratt, Herschell Marvin

    1973-01-01

    Suggests a number of ways in which Federal Aviation Agency weather report printouts can be used in teaching the weather section of meteorology. These weather sequence reports can be obtained free of charge at most major airports. (JR)

  3. An archean suture zone in the Tobacco Root Mountains? (1984) Evolution of Archean Continental Crust, SW Montana (1985)

    NASA Technical Reports Server (NTRS)

    Mogk, D. W.; Kain, L.

    1985-01-01

    The Lake Plateau area of the Beartooth Mountains, Montana were mapped and geochemically sampled. The allochthonous nature of the Stillwater Complex was interpreted as a Cordilleran-style continental margin. The metamorphic and tectonic history of the Beartooth Mountains was addressed. The Archean geology of the Spanish Peaks area, northern Madison Range was addressed. A voluminous granulite terrain of supracrustal origin was identified, as well as a heretofore unknown Archean batholithic complex. Mapping, petrologic, and geochemical investigations of the Blacktail Mountains, on the western margin of the Wyoming Province, are completed. Mapping at a scale of 1:24000 in the Archean rocks of the Gravelly Range is near completion. This sequence is dominantly of stable-platform origin. Samples were collected for geothermometric/barometric analysis and for U-Pb zircon age dating. The analyses provide the basis for additional geochemical and geochronologic studies. A model for the tectonic and geochemical evolution of the Archean basement of SW Montana is presented.

  4. The origin of jarosite associated with a gossan on Archean gneiss in Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Peng, Y.; Pratt, L. M.; Young, S. A.; Cadieux, S. B.; White, J. R.

    2013-12-01

    The mineral Jarosite [KFe3(SO4)2(OH)6] since its discovery, by Opportunity rover at Meridiani Planum on Mars, has been the subject of intense geochemical and environmental study over the last 5-10 years. Jarosite requires highly acidic, K-enriched, and oxidizing aqueous conditions for formation. Stable isotopes of O, H, and S of jarosite have the ability to record the temperatures of formation, environments of deposition, fluids, and fluid/atmospheric interactions. Therefore, the origin of jarosite is important for understanding present and past environmental conditions on Mars. Unfortunately, the origin of jarosite on Mars remains unclear. Jarosite is commonly found on Earth in the weathering zones of pyrite-bearing ore deposits, near-surface playa sediments in acid-saline lakes, or epithermal environments and hot springs. Here, we report the occurrence of jarosite in association with a gossan overlying weathered Archean gneiss and Paleoproterozoic mafic dikes at the ice-free margin of southwestern Greenland. In our 2012 field campaign, we excavated soil pits to a depth of 40 cm with a high vertical sampling resolution. No visible pyrite was found in the nearby outcroppings of gneiss in the field. XRD data show that all samples were composed of anorthite, quartz, albite, jarosite, muscovite, and microcline. Jarosite was the only sulfur-bearing mineral identified by XRD, with abundance of jarosite increasing with depth (up to 8.4 wt. %) in the soil pits. Water soluble and acid soluble sulfate were sequentially extracted using 10% NaCl and 2N HCl solutions, respectively. Pyrite was then subsequently extracted from insoluble residues by a chromium reduction method. The average abundance of water soluble sulfate, acid soluble sulfate, and pyrite were 100 ppm, 7 wt. %, and 10 ppm, respectively. The δ34S values of water soluble sulfate, acid soluble sulfate, and pyrite range from -0.7‰ to 3.1‰ (average= 1.5‰), -1.2 to 1.5‰ (average= 0.7‰), and 0.3‰ to 6.7

  5. Geochemistry of precambrian carbonates. II. Archean greenstone belts and Archean sea water

    SciTech Connect

    Veizer, J. ); Hoefs, J. ); Lowe, D.R. ); Thurston, P.C. )

    1989-04-01

    Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans. The greenstones containing such carbonates appear to cluster at {approximately}2.8 {plus minus} 0.2 and {approximately}3.5 {plus minus} 0.1 Ga ago. The samples for the younger group are from the Abitibi, Yellowknife, Wabigoon, Michipicoten and Uchi greenstone belts of Canada and the Upper Greenstones of Zimbabwe. The older group includes the Swaziland Supergroup of South Africa, Warrawoona Group of Australia and the Sargur marbles of India. Mineralogically, the carbonates of the younger greenstones are mostly limestones and of the older ones, ferroan dolomites (ankerites); the latter with some affinities to hydrothermal carbonates. In mineralized areas with iron ores, the carbonate minerals are siderite {plus minus} ankerite, irrespective of the age of the greenstones. Iron-poor dolomites represent a later phase of carbonate generation, related to post-depositional tectonic faulting. The original mineralogy of limestone sequences appears to have been an Sr-rich aragonite. The Archean carbonates yield near-mantle Sr isotopic values, with ({sup 87}Sr/{sup 86}Sr){sub o} of 0.7025 {plus minus} 0.0015 and 0.7031 {plus minus} 0.0008 for younger and older greenstones, respectively. The mineralogical and chemical attributes of Archean carbonates are consistent with the proposition that the composition of the coeval oceans may have been buffered by a pervasive interaction with the mantle, that is, with the oceanic crust and the coeval ubiquitous volcanosedimentary piles derived from mantle sources.

  6. Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water.

    PubMed

    Veizer, J; Hoefs, J; Lowe, D R; Thurston, P C

    1989-01-01

    Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans. The greenstones containing such carbonates appear to cluster at approximately 2.8 +/- 0.2 and approximately 3.5 +/- 0.1 Ga ago. The samples for the younger group are from the Abitibi, Yellowknife, Wabigoon (Steep Rock Lake), Michipicoten and Uchi greenstone belts of Canada and the "Upper Greenstones" of Zimbabwe. The older group includes the Swaziland Supergroup of South Africa, Warrawoona Group of Australia and the Sargur marbles of India. Mineralogically, the carbonates of the younger greenstones are mostly limestones and of the older ones, ferroan dolomites (ankerites); the latter with some affinities to hydrothermal carbonates. In mineralized areas with iron ores, the carbonate minerals are siderite +/- ankerite, irrespective of the age of the greenstones. Iron-poor dolomites represent a later phase of carbonate generation, related to post-depositional tectonic faulting. The original mineralogy of limestone sequences appears to have been an Sr-rich aragonite. The Archean carbonates yield near-mantle Sr isotopic values, with (87Sr/86Sr)o of 0.7025 +/- 0.0015 and 0.7031 +/- 0.0008 for younger and older greenstones, respectively. The best preserved samples give delta 13C of +1.5 +/- 1.5% PDB, comparable to their Phanerozoic counterparts. In contrast, the best estimate for delta 18O is -7% PDB. Archean limestones, compared to Phanerozoic examples, are enriched in 16O as well as in Mn2+ and Fe2+, and these differences are not a consequence of post-depositional alteration phenomena. The mineralogical and chemical attributes of Archean carbonates (hence sea water) are consistent with the proposition that the composition of the coeval oceans may have been buffered by a pervasive interaction with the "mantle", that is, with

  7. Tectonic implications of Archean anorthosite occurrences

    NASA Technical Reports Server (NTRS)

    Phinney, W. C.; Morrison, D. A.; Maczuga, D. E.

    1988-01-01

    The occurrences of megacrystic anorthosite and basalt in a variety of geologic settings were reviewed and it was found that these rock types occur in a variety of tectonic settings. Anorthosites and megacrystic basalts are petrogenetically related and are found in oceanic volcanic crust, cratons, and shelf environments. Although megacrystic basalts are most common in Archean terranes, similar occurrences are observed in rocks of early Proterozoic age, and even in young terranes such as the Galapagos hotspot. Based on inferences from experimental petrology, all of the occurrences are apparently associated with similar parental melts that are relatively Fe-rich tholeiites. The megacrystic rocks exhibit a two- (or more)-stage development of plagioclase, with the megacrysts having relatively uniform composition produced under nearly isothermal and isochemical conditions over substantial periods of time. The anorthosites appear to have intruded various crustal levels from very deep to very shallow. The petrogenetic indicators, however, suggest that conditions of formation of the Precambrian examples were different from Phanerozoic occurrences.

  8. Low Temperature Weathering vs. Hydrothermal Alteration of Radiation-damaged Zircon in a Lateritic Profile From Nsimi (Cameroon)

    NASA Astrophysics Data System (ADS)

    Delattre, S.; Utsunomiya, S.; Ewing, R. C.; Balan, E.; Calas, G.

    2006-05-01

    Zircon has an exceptional chemical durability. Hence, zirconium is used as a reference for mass balance calculations of chemical weathering. However, radiation damage from the alpha-decay of U and Th increases its chemical reactivity. The impact of radiation-induced amorphization on the mobility of zirconium is still debated. Previous results obtained on zircons from sediments and soils of the Amazon basin (Brazil) have shown that highly metamict zircons do not survive to the intense weathering and erosion processes under tropical conditions, suggesting that metamict zircon could be a significant source of Zr at the Earth's surface. Here we report new results about the relations between zircon alteration and accumulated radiation damage in a laterite developed in situ from granitic rocks, ruling out any preferential mechanical abrasion of metamict zircon. SEM images of the zircons, combined with Raman microprobe measurements of the degree of cristallinity, revealed preferential alteration of damaged grains. Based on TEM analysis, there is no evidence of a reprecipitation of baddeleyite (ZrO2) or incongruent dissolution of zircon. However, the damaged areas display higher amounts of Al, Fe (up to 1 wt. %) and Ca, with significant Pb loss. TEM observations reveal the presence of abundant nano-vesicles containing some chlorine (> 5 wt. %) and to a lesser extent Na and Ca. These features are most likely related to hydrothermal alteration. This event has lead to significant chemical exchanges and partial recrystallization of metamict zircon grains, which might occur at relatively low temperature in wet environments. This study illustrates the need to establish quantitative criteria to distinguish between the hydrothermal alteration and low-temperature weathering of zircon.

  9. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This month's insert, Severe Weather, has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in this poster are hurricanes,…

  10. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This article deals with a poster entitled, "Severe Weather," that has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in…

  11. Archean Subduction or Not? The Archean Volcanic Record Re-assessed.

    NASA Astrophysics Data System (ADS)

    Pearce, Julian; Peate, David; Smithies, Hugh

    2013-04-01

    Methods of identification of volcanic arc lavas may utilize: (1) the selective enrichment of the mantle wedge by 'subduction-mobile' elements; (2) the distinctive preconditioning of mantle along its flow path to the arc front; (3) the distinctive combination of fluid-flux and decompression melting; and (4) the effects of fluids on crystallization of the resulting magma. It should then be a simple matter uniquely to recognise volcanic arc lavas in the Geological Record and so document past subduction zones. Essentially, this is generally true in the oceans, but generally not on the continents. Even in recent, fresh lavas and with a full battery of element and isotope tools at our disposal, there can be debate over whether an arc-like geochemical signature results from active subduction, an older, inherited subduction component in the lithosphere, or crustal contamination. In the Archean, metamorphism, deformation, a different thermal regime and potential non-uniformitarian tectonic scenarios make the fingerprinting of arc lavas particularly problematic. Not least, the complicating factor of crustal contamination is likely to be much greater given the higher magma and crustal temperatures and higher magma fluxes prevailing. Here, we apply new, high-resolution immobile element fingerprinting methods, based primarily on Th-Nb fractionation, to Archean lavas. In the Pilbara, for example, where there is a volcanic record extending for over >500 m.y., we note that lavas with high Th/Nb (negative Nb anomalies) are common throughout the lava sequence. Many older formations also follow a basalt-andesite-dacite-rhyolite (BADR) sequence resembling present-day arcs. However, back-extrapolation of their compositions to their primitive magmas demonstrates that these were almost certainly crustally-contaminated plume-derived lavas. By contrast, this is not the case in the uppermst part of the sequence where even the most primitive magmas have significant Nb anomalies. The

  12. Geochemistry of Archean metasedimentary rocks of the Aravalli craton, NW India: Implications for provenance, paleoweathering and supercontinent reconstruction

    NASA Astrophysics Data System (ADS)

    Ahmad, Iftikhar; Mondal, M. E. A.; Satyanarayanan, M.

    2016-08-01

    Basement complex of the Aravalli craton (NW India) known as the Banded Gneissic Complex (BGC) is classified into two domains viz. Archean BGC-I and Proterozoic BGC-II. We present first comprehensive geochemical study of the Archean metasedimentary rocks occurring within the BGC-I. These rocks occur associated with intrusive amphibolites in a linear belt within the basement gneisses. The association is only concentrated on the western margin of the BGC-I. The samples are highly mature (MSm) to very immature (MSi), along with highly variable geochemistry. Their major (SiO2/Al2O3, Na2O/K2O and Al2O3/TiO2) and trace (Th/Sc, Cr/Th, Th/Co, La/Sc, Zr/Sc) element ratios, and rare earth element (REE) patterns are consistent with derivation of detritus from the basement gneisses and its mafic enclaves, with major contribution from the former. Variable mixing between the two end members and closed system recycling (cannibalism) resulted in the compositional heterogeneity. Chemical index of alteration (CIA) of the samples indicate low to moderate weathering of the source terrain in a sub-tropical environment. In A-CN-K ternary diagram, some samples deceptively appear to have undergone post-depositional K-metasomatism. Nevertheless, their petrography and geochemistry (low K2O and Rb) preclude the post-depositional alteration. We propose non-preferential leaching of elements during cannibalism as the cause of the deceptive K-metasomatism as well as enigmatic low CIA values of some highly mature samples. The Archean metasedimentary rocks were deposited on stable basement gneisses, making the BGC-I a plausible participant in the Archean Ur supercontinent.

  13. Some examples of deep structure of the Archean from geophysics

    NASA Technical Reports Server (NTRS)

    Smithson, S. B.; Johnson, R. A.; Pierson, W. R.

    1986-01-01

    The development of Archean crust remains as one of the significant problems in earth science, and a major unknown concerning Archean terrains is the nature of the deep crust. The character of crust beneath granulite terrains is especially fascinating because granulites are generally interpreted to represent a deep crustal section. Magnetic data from this area can be best modeled with a magnetized wedge of older Archean rocks (granulitic gneisses) underlying the younger Archean greenstone terrain. The dip of the boundary based on magnetic modeling is the same as the dip of the postulated thrust-fault reflection. Thus several lines of evidence indicate that the younger Archean greenstone belt terrain is thrust above the ancient Minnesota Valley gneiss terrain, presumably as the greenstone belt was accreted to the gneiss terrain, so that the dipping reflection represents a suture zone. Seismic data from underneath the granulite-facies Minnesota gneiss terrain shows abundant reflections between 3 and 6 s, or about 9 to 20 km. These are arcuate or dipping multicyclic events indicative of layering.

  14. Differences in volatile profiles of Cabernet Sauvignon grapes grown in two distinct regions of China and their responses to weather conditions.

    PubMed

    Xu, Xiao-Qing; Liu, Bin; Zhu, Bao-Qing; Lan, Yi-Bin; Gao, Yuan; Wang, Dong; Reeves, Malcolm J; Duan, Chang-Qing

    2015-04-01

    Volatile compounds are considered important for plants to communicate with each other and interact with their environments. Most wine-producing regions in China feature a continental monsoon climate with hot-wet summers and dry-cold winters, giving grapes markedly different growing environments compared to the Mediterranean or oceanic climates described in previous reports. This study focused on comparing the volatile profiles of Vitis vinifera L. cv. Cabernet Sauvignon berries from two regions with distinct climate characteristics: Changli has a warm and semi-humid summer, and Gaotai has a cool-arid summer and a cold winter. The relationship between meteorological metrics and the concentrations of grape volatiles were also examined. In harvested grapes, benzyl alcohol, phenylethyl alcohol, 1-hexanol and 1-octen-3-ol were more abundant in the Changli berries, while hexanal, heptanal, 2-methoxy-3-isobutylpyrazine, and (E)-β-damascenone presented higher levels in the Gaotai berries. The fluctuation in the accumulation of volatile compounds observed during berry development was closely correlated with variations in short-term weather (weather in a week), especially rainfall. The concentration of some volatiles, notably aliphatic aldehydes, was significantly related to diurnal temperature differences. The variability during berry development of concentrations for compounds such as C6 volatile compounds, 2-methoxy-3-isobutylpyrazine and (E)-β-damascenone strongly depended upon weather conditions. This work expands our knowledge about the influence of continental monsoon climates on volatile compounds in developing grape berries. It will also improve the comprehension of the plant response to their surrounding environments through the accumulation of volatiles. The results will help growers to alter viticultural practices according to local conditions to improve the aromatic quality of grapes.

  15. Weather & Weather Maps. Teacher's Manual.

    ERIC Educational Resources Information Center

    Metro, Peter M.; Green, Rachel E.

    This guide is intended to provide an opportunity for students to work with weather symbols used for reporting weather. Also included are exercises in location of United States cities by latitude and longitude, measurement of distances in miles and kilometers, and prediction of weather associated with various types of weather fronts. (RE)

  16. Interaction of Komatiitic Liquids With Archean Arcs

    NASA Astrophysics Data System (ADS)

    Kerrich, R.

    2006-12-01

    New, and compilations of, high precision data for 3.0 to 2.7 Ga komatiites of the Superior province show positive normalized anomalies of Nb relative to Th-La, and Nb/Th>8. These features are present in Al- undepleted (AUK) and Al-depleted komatiites(ADK) screened for minimal alteration and absence of crustal contamination. AUK possess positive Zr(Hf)/Sm anomalies, whereas ADK counterparts have negative anomalies. For AUK, positive (Nb,Zr)/REE anomalies are interpreted as oceanic lithosphere processed through a dehydration-dominated subduction zone and recycled into the mantle source of plumes. For ADK, HFSE/REE anomalies may reflect recycled oceanic lithosphere processed through a melt(TTG)-dominated subduction zone, melting of a plume with residual majorite garnet at >400 km, or some combination. Both AUK and ADK are associated with anhydrous intraplate plume-related magmas, based on field associations and Ti/V. A new compositional type of Neoarchean intraoceanic low-K (Ce) tholeiitic arc basalt has been identified. These are characterized by a spectrum of negative to positive (Nb,Ta,Zr,Hf)/REE anomalies, but systematic negative Ti/REE anomalies, where Nb antivaries with Zr/Nb, and Ni>300ppm. This type differs from low-K arc tholeiites of Archean and Phanerozoic age variably associated with andesites, dacites, rhyolites, and characterized by systematic negative anomalies of (Nb,Ta,P,Ti)/REE, with Ni<250ppm. The new type tholeiites are consistent with a model of earlier komatiitic liquids that stalled in, and fertilized, upper mantle. As an arc migrated through composite upper mantle, hydrous melting generated a basalt compositional spectrum from subdued AUK-like to classic arc-like HFSE/REE anomalies. Alternatively, contemporaneous AUK liquids leaked through a slab into the sub-arc mantle wedge, hybridizing with wedge peridotite melts.

  17. Paleomagnetic measurements of Archean and Hadean zircons

    NASA Astrophysics Data System (ADS)

    Cottrell, R. D.; Tarduno, J. A.; Bono, R. K.

    2014-12-01

    The long-term history of the geodynamo can provide important constraints on core and mantle evolution. The oldest paleointensity records on extant rocks suggest a relatively strong magnetic field at 3.45 Ga (Tarduno et al., 2010). Examining an even older magnetic field, however, must rely on igneous components (e.g. zircons hosting magnetic inclusions) now found in younger sedimentary rocks. Here we focus on methods developed to address the challenges posed by the paleointensity measurement of crystals having weak natural remanent magnetizations (NRMs). We use a small bore (6.3 mm) 2G SQUID magnetometer that currently has the highest 3-component moment resolution for measurements, and CO2 laser heating for demagnetization. Use of this 3-component system allows for the direct measurement of full vector natural remanent magnetizations and avoids the non-uniqueness inherent in scanning magnetometer approaches. To reduce sample blank size, we use 0.5 mm fused quartz sample holders. We find that some Archean to Hadean zircons of the Jack Hills (Yilgarn Craton, Western Australia) have NRMs of ca. 1-3 x 10-9 emu, within the resolution of the ultra-high moment resolution SQUID magnetometer. Thermal demagnetization data indicate most the magnetization unblocks between 550 and 580 °C, consistent with a magnetite carrier. Magnetic force microscopy suggests the presence of sub-micron single domain-like magnetic inclusions in the zircon. Thellier-Coe paleointensity data suggest the presence of a magnetic field at 3.55 Ga. We will discuss measurements and criteria to evaluate the presence/absence of an even older Paleoarchean and Hadean magnetic field, and opportunities provided by further increases in moment resolution provided by a new spin exchange relaxation-free magnetometer.

  18. Moho offsets beneath the Western Ghat and the contact of Archean crusts of Dharwar Craton, India

    NASA Astrophysics Data System (ADS)

    Saikia, Utpal; Rai, S. S.; Meena, Rishikesh; Prasad, B. N. V.; Borah, Kajaljyoti

    2016-03-01

    We present the Moho depth variation along a 600 km long profile from the west to the east coast of South India covering the passive continental margin, and the Western Ghat escarpment created during India-Madagascar separation at ~ 85 Ma; Archean western and eastern Dharwar Craton, and Proterozoic basin. The image is generated through three different approaches: H - vP/vS stacking, common conversion point (CCP) migration and inversion of teleseismic receiver functions at 38 locations. The Moho depth along the profile varies smoothly between 34 and 41 km, except beneath the Western Ghat and at the contact of east and west Dharwar Craton, where it is offset by up to ~ 8 km. The study suggests (i) the possible differential uplift of the Western Ghat, as a consequence of India-Madagascar separation and the prominent role of deep crustal structure in the location of the escarpment, compared to the surface process and (ii) presence of long-lived steeply dipping fault separating the two distinct Archean crustal blocks indicative of mechanically strong continental lithosphere beneath the Dharwar Craton.

  19. Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: Occurrence of Archean oceanic plateau

    NASA Astrophysics Data System (ADS)

    El Atrassi, Fatima; Debaille, Vinciane; Mattielli, Nadine; Berger, Julien

    2015-04-01

    While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African craton in Mauritania (Amsaga area). The Amsaga Archean crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. We report the results of a combined petrologic, Sm-Nd isotopic, major element and rare earth element (REE) study of the Archean amphibolites in the West African craton. This study was conducted in order to characterize these rocks, to constrain the time of their formation and to evaluate their tectonic setting and their possible mantle source. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. They are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. These amphibolites have tholeiitic basalt composition. On a primitive mantle-normalized diagram, they display fairly flat patterns without negative anomalies for either Eu or Nb-Ta. We have shown using Sm-Nd whole rock isotopic data that these amphibolites formed at 3.3 ±0.075 Ga. They have positive ɛNdi values (+5.2 ± 1.6). These samples show isotopically juvenile features, which rule out the possibility of significant contamination of the protolith magmas by ancient continental crust. Based on these geochemical data we propose that the tholeiitic basalts were formed in an oceanic plateau tectonic setting from a mantle plume source and that they have a

  20. Respective roles of the weathering profile and the tectonic fractures in the structure and functioning of crystalline thermo-mineral carbo-gaseous aquifers

    NASA Astrophysics Data System (ADS)

    Dewandel, B.; Alazard, M.; Lachassagne, P.; Bailly-Comte, V.; Couëffé, R.; Grataloup, S.; Ladouche, B.; Lanini, S.; Maréchal, J.-C.; Wyns, R.

    2017-04-01

    Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMCG hydrosystem associated with a peri-alpine graben. A multidisciplinary approach with a very large set of data and methods - geological modelling with geophysics and geological data from outcrops and several boreholes, hydrodynamic data, hydrochemistry, hydrogeological and geochemical modelling - reveals very novel results and allows a robust conceptual model to be constructed. The aquifer at the origin of the carbo-gaseous natural mineral water is the 100-125 m-thick fractured stratiform layer of the weathering profile of the crystalline rock (granite). It forms a rather large and thick inertial aquifer that can be numerically modelled, in a similar fashion to a porous medium. The majority of tectonic faults length act as impervious boundaries that divide this aquifer into around ten elongated compartments that were precisely delineated. These tectonic faults are permeable only along two small areas that were also precisely located. These permeable zones feed some aquifer compartments with deep, highly mineralised carbo-gaseous water, which mixes with ;fresher; water and forms the exploited NMW. These results can be generalised and in particular show a strong opposition between low-inertia CTMCG hydrosystems without a subsurface reservoir, as the weathering profile was eroded, and high-inertia hydrosystems such as the one studied.

  1. Partition coefficients for calcic plagioclase - Implications for Archean anorthosites

    NASA Technical Reports Server (NTRS)

    Phinney, W. C.; Morrison, D. A.

    1990-01-01

    In most Archean cratons, cumulates of equant plagioclase megacrysts form anorthositic complexes, including those at Bad Vermilion Lake (Ontario). In this paper, partition coefficients (Ds) of REEs between natural high-Ca plagioclase megacrysts and their basaltic matrices were determined, using a multiple aliquot techique, and megacrystic plagioclases occurring in anorthosites were analyzed for the same components which, in conjunction with their Ds, were applied to calculations of melts in equilibrium with anorthosites. The REE's Ds were found to agree well with experimentally determined values and to predict equilibrium melts for Archean anorthosites that agree well with coeval basaltic flows and dikes. The Ds also appear to be valid for both the tholeiitic and alkali basalts over a wide range of mg numbers and REE concentrations. It is suggested that the moderately Fe-rich tholeiites that are hosts to plagioclase megacrysts in greenstone belts form the parental melts for megacrysts which make up the Bad Vermilion Lake Archean anorthositic complex.

  2. Nitrogen isotopic composition and density of the Archean atmosphere.

    PubMed

    Marty, Bernard; Zimmermann, Laurent; Pujol, Magali; Burgess, Ray; Philippot, Pascal

    2013-10-04

    Understanding the atmosphere's composition during the Archean eon is fundamental to unraveling ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0- to 3.5-billion-year-old hydrothermal quartz that the partial pressure of N2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean partial pressure of CO2 was probably lower than 0.7 bar.

  3. Geology and tectonics of the Archean Superior Province, Canadian Shield

    NASA Technical Reports Server (NTRS)

    Card, K. D.

    1986-01-01

    Superior Province consists mainly of Late Archean rocks with Middle Archean gneisses in the south, and possibly in the north. The Late Archean supracrustal sequences are of island arc and interarc affinity and are cut by abundant plutonic rocks, including early arc-related intrusions, late synorogenic intrusions, and post-orogenic plutons that are possibly the product of crustal melting caused by thermal blanketing of newly-thickened continental crust combined with high mantle heat flux. The contemporaneity of magmatic and deformational events along the lengths of the belts is consistent with a subduction-dominated tectonic regime for assembly of the Kenoran Orogen. Successive addition of volcanic arcs accompanied and followed by voluminous plutonism resulted in crustal thickening and stabilization of the Superior craton prior to uplift of Kapuskasing granulites, emplacement of the Matachewan diabase dykes, and Early Proterozoic marginal rifting.

  4. The early Earth -- A perspective on the Archean

    SciTech Connect

    Hamilton, W.B. )

    1993-04-01

    Dominant models of Archean tectonics and magmatism involve plate-tectonic mechanisms. Common tenets of geochemistry (e.g., model ages) and petrology visualize a cold-accreted Earth in which primitive mantle gradually fractionated to produce crust during and since Archean time. These popular assumptions appear to be incompatible with cosmologic and planetologic evidence and with Archean geology. All current quantitative and semiquantitative theories agree that the Earth was largely or entirely melted (likely superheated) by giant impacts, including the Mars-size impact which splashed out the Moon, and by separation of the core. The Earth at [approximately]4.5 Ga was a violently convecting anhydrous molten ball. Both this history and solar-system position indicate the bulk Earth to be more refractory than chondrite. The outer part of whatever sold shell developed was repeatedly recycled by impacts before 3.9 Ga. Water and CO[sub 2] were added by impactors after the Moon-forming event; the mantle is not a source of primordial volatiles, but rather is a sink that has depleted the hydrosphere. Voluminous liquidus ultramafic lava (komatiite) indicates that much Archean upper mantle was above its solidus. Only komatiitic and basaltic magma entered Archean crust from the mantle. Variably hydrous contamination, secondary melting, and fractionation in the crust produced intermediate and felsic melts. Magmatism was concurrent over vast tracts. Within at least the small sample of Archean crust that has not been recycled into the mantle, heat loss was primarily by voluminous, dispersed magmatism, not, as in the modern Earth, primarily through spreading windows through the crust. Only in Proterozoic time did plate-tectonic mechanisms become prevalent.

  5. Archean crustal evolution of the northern North China Craton

    NASA Technical Reports Server (NTRS)

    Qian, Xianglin; Chen, Yaping; Liu, Jinzhong

    1988-01-01

    The Archean granultie facies rocks of the North China (Sino-Korean) Craton mostly occur inside the northern boundary forming a unique and spectacular granulite belt trending roughly E-W from eastern Hebei, North China in the east to Mt. Daqinchan, western Inner Mongolia in the west, ranging about 1,000 km long. Over the years in the middle portion of this Archean high-grade metamorphic belt a stratigraphic unconformity between the khondalite rock assemblage and the medium in composition granulite assemblage in Datong-Xinghe area is determined. The geological structural properties of the North China Craton are discussed.

  6. Observing System Simulation Experiments to Determine the Potential Impact of Space-Based Lidar Wind Profiles on Weather Prediction

    NASA Technical Reports Server (NTRS)

    Atlas, Robert

    2003-01-01

    Observing system simulation experiments (OSSE's) provide an effective means to evaluate the potential impact of a proposed observing system, as well as to determine tradeoffs in their design, and to evaluate data assimilation methodology. Great care must be taken to ensure realism of the OSSE's, and in the interpretation of OSSE results. All of the OSSE's that have been conducted to date have demonstrated tremendous potential for space-based wind profile data to improve atmospheric analyses, forecasts, and research. This has been true for differing data assimilation systems, analysis methodology, and model resolutions. OSSE's clearly show much greater potential for observations of the complete wind profile than for single-level wind data or observations of the boundary layer alone.

  7. Mineral artefacts mimicking microfossils in Archean rocks

    NASA Astrophysics Data System (ADS)

    Lepot, K.; Philippot, P.; Benzerara, K.

    2009-04-01

    Because prokaryotes populating the early Earth were structurally and morphologically very simple, it is difficult to obtain taxonomic information from microfossils, and even more problematic, to distinguish true fossils from abiotic objects. For example, many self-assembly processes associated with the precipitation of nanoscale minerals in the presence of organic compounds generate cell-like structures. Based on high resolution microscopy observations on natural samples, we describe three types of features common to Archean rocks and suggest that they represent microfossil-like artefacts. Using Scanning Electron Microscopy we have observed carbon-free silica inclusions in carbonate sediments that are very similar in size and shape (rods and spheres) to microorganisms. The common distribution of organic carbon at grain boundaries in those rocks indicate that such cell-like minerals, when coated by secondarily-migrated carbonaceous mater, could easily be mistaken for microfossils. The organisation and the micro- to nano-structure of bacteriomorphs might be even more confusing. We have observed chains of spheres that match in size and arrangement with some coccoid bacteria such as streptococci. Transmission Electron Microscopy (TEM) observation of Focused Ion Beam (FIB) sections cut through these spheres shows that they are composed of TiO2nanocrystallites partly rimmed or linked by nanoscale chlorite films. This assemblage creates smooth cell-like structures at the micron-scale. However, the absence of organic carbon in those structures as well as the observation of many similar TiO2 chains of spheres dispersed in volcanic glass shards argue against a biologic origin. Ambient inclusions trails also generate filamentous structures that can be mistaken for microfossils. (Knoll and Barghoorn, 1974) suggested that such pseudofossils could have formed by the displacement of a crystal (e.g. pyrite) in its mineral matrix owing to pressure solution processes linked to gas

  8. Archean Arctic continental crust fingerprints revealing by zircons from Alpha Ridge bottom rocks

    NASA Astrophysics Data System (ADS)

    Sergeev, Sergey; Petrov, Oleg; Morozov, Andrey; Shevchenko, Sergey; Presnyakov, Sergey; Antonov, Anton; Belyatsky, Boris

    2015-04-01

    Whereas thick Cenozoic sedimentary cover overlapping bedrock of the Arctic Ocean, some tectonic windows were sampled by scientific submarine manipulator, as well as by grabbing, dredging and drilling during «Arctic-2012» Russian High-Arctic expedition (21 thousands samples in total, from 400-km profile along Alpha-Mendeleev Ridges). Among others, on the western slope of Alpha Ridge one 10x10 cm fragment without any tracks of glacial transportation of fine-layered migmatitic-gneiss with prominent quartz veinlets was studied. Its mineral (47.5 vol.% plagioclase + 29.6% quartz + 16.6% biotite + 6.1% orthoclase) and chemical composition (SiO2:68.2, Al2O3:14.9, Fe2O3:4.44, TiO2:0.54, MgO:2.03, CaO:3.13, Na2O:3.23, K2O:2.16%) corresponds to trachydacite vulcanite, deformed and metamorphozed under amphibolite facies. Most zircon grains (>80%) from this sample has an concordant U-Pb age 3450 Ma with Th/U 0.8-1.4 and U content of 100-400 ppm, epsilon Hf from -4 up to 0, and ca 20% - ca 3.3 Ga with Th/U 0.7-1.4 and 90-190 ppm U, epsilon Hf -6.5 to -4.5, while only 2% of the grains show Proterozoic age of ca 1.9 Ga (Th/U: 0.02-0.07, U~500 ppm, epsilon Hf about 0). No younger zircons were revealed at all. We suppose that magmatic zircon crystallized as early as 3450 Ma ago during acid volcanism, the second phase zircon crystallization from partial melt (or by volcanics remelting) under amphibolite facies metamorphism was at 3.3 Ga ago with formation of migmatitie gneisses. Last zircon formation from crustal fluids under low-grade metamorphic conditions was 1.9 Ga ago. There are two principal possibilities for the provenance of this metavolcanic rock. The first one - this is ice-rafted debris deposited by melted glacial iceberg. However, presently there are no temporal and compositional analogues of such rocks in basement geology of peri-oceanic regions, including Archean Itsaq Gneiss Complex, Lewisian Complex and Baltic Shield but these regions are far from the places of

  9. A revised, hazy methane greenhouse for the Archean Earth.

    PubMed

    Haqq-Misra, Jacob D; Domagal-Goldman, Shawn D; Kasting, Patrick J; Kasting, James F

    2008-12-01

    Geological and biological evidence suggests that Earth was warm during most of its early history, despite the fainter young Sun. Upper bounds on the atmospheric CO2 concentration in the Late Archean/Paleoproterozoic (2.8-2.2 Ga) from paleosol data suggest that additional greenhouse gases must have been present. Methanogenic bacteria, which were arguably extant at that time, may have contributed to a high concentration of atmospheric CH4, and previous calculations had indicated that a CH4-CO2-H2O greenhouse could have produced warm Late Archean surface temperatures while still satisfying the paleosol constraints on pCO2. Here, we revisit this conclusion. Correction of an error in the CH4 absorption coefficients, combined with the predicted early onset of climatically cooling organic haze, suggest that the amount of greenhouse warming by CH4 was more limited and that pCO2 must therefore have been 0.03 bar, at or above the upper bound of the value obtained from paleosols. Enough warming from CH4 remained in the Archean, however, to explain why Earth's climate cooled and became glacial when atmospheric O2 levels rose in the Paleoproterozoic. Our new model also shows that greenhouse warming by higher hydrocarbon gases, especially ethane (C2H6), may have helped to keep the Late Archean Earth warm.

  10. Archean komatiite volcanism controlled by the evolution of early continents.

    PubMed

    Mole, David R; Fiorentini, Marco L; Thebaud, Nicolas; Cassidy, Kevin F; McCuaig, T Campbell; Kirkland, Christopher L; Romano, Sandra S; Doublier, Michael P; Belousova, Elena A; Barnes, Stephen J; Miller, John

    2014-07-15

    The generation and evolution of Earth's continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50-30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean-Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits.

  11. Petrogenesis of calcic plagioclase megacrysts in Archean rocks

    NASA Technical Reports Server (NTRS)

    Phinney, W. C.; Morrison, D. A.

    1986-01-01

    Anorthositic complexes with large equidimensional plagioclase grains of highly calcic composition occur in nearly all Archean cratons. Similar plagioclase occur as megacrysts in many Archean sills, dikes, and volcanic flows. In the Canadian Shield these units occur throughout the Archean portions of the entire shield and are particularly common as dikes over an area of a few 100,000 sq km in Ontario and Manitoba during a period of at least 100 m.y. in many different rock types and metamorphic grades. The plagioclase generally occurs in three modes: as inclusions in mafic intrusions at various stages of fractionation, as crystal segregations in anorthosite complexes, or as megacrysts in fractionated sills, dikes, and flows. Most occurrences suggest that the plagioclase was formed elsewhere before being transported to its present location. The evidence seems to be quite clear that occurrences of these types of calcic plagioclase require: (1) ponding of a relatively undifferentiated Archean tholeiitic melt at some depth; (2) isothermal crystallization of large, equidimensional homogeneous plagioclase crystals; (3) separation of the plagioclase crystals from any other crystalline phases; (4) further fractionation of melt; (5)transport of various combinations of individual plagioclase crystals and clusters of crystals by variously fractionated melts; and (6) emplacement as various types of igneous intrusions or flows.

  12. Archean metamorphic sequence and surfaces, Kangerdlugssuaq Fjord, East Greenland

    NASA Technical Reports Server (NTRS)

    Kays, M. A.

    1986-01-01

    The characteristics of Archean metamorphic surfaces and fabrics of a mapped sequence of rocks older than about 3000 Ma provide information basic to an understanding of the structural evolution and metamorphic history in Kangerdlugssuaq Fjord, east Greenland. This information and the additional results of petrologic and geochemical studies have culminated in an extended chronology of Archean plutonic, metamorphic, and tectonic events. The basis for the chronology is considered, especially the nature of the metamorphic fabrics and surfaces in the Archean sequence. The surfaces, which are planar mineral parageneses, may prove to be mappable outside Kangerdlugssuaq Fjord, and if so, will be helpful in extending the events that they represent to other Archean sequences in east Greenland. The surfaces will become especially important reference planes if the absolute ages of their metamorphic assemblages can be determined in at least one location where strain was low subsequent to their recrystallization. Once an isochron is obtained, the dynamothermal age of the regionally identifiable metamorphic surface is determined everywhere it can be mapped.

  13. Possible magmatic underplating beneath the west coast of India and adjoining Dharwar craton: Imprint from Archean crustal evolution to breakup of India and Madagascar

    NASA Astrophysics Data System (ADS)

    Saikia, Utpal; Das, Ritima; Rai, S. S.

    2017-03-01

    The shear wave velocity of the crust along a ∼660 km profile from the west to the east coast of South India is mapped through the joint inversion of receiver functions and Rayleigh wave group velocity. The profile, consisting of 38 broadband seismic stations, covers the Archean Dharwar craton, Proterozoic Cuddapah basin, and rifted margin and escarpment. The Moho is mapped at a depth of ∼40 km beneath the mid-Archean Western Dharwar Craton (WDC), Cuddapah Basin (CB), and the west and east coasts formed through the rifting process. This is in contrast with a thin (∼35 km) crust beneath the late-Archean Eastern Dharwar Craton (EDC). Along the profile, the average thickness of the upper, middle and lower crust is ∼4 km, 12 ± 4 km and 24 ± 4 km respectively. Above the Moho, we observe a high-velocity layer (HVL, Vs > 4 km/s) of variable thickness increasing from 3 ± 1 km beneath the EDC to 11 ± 3 km beneath the WDC and the CB, and 18 ± 2 km beneath the west coast of India. The seismic wave velocity in this layer is greater than typical oceanic lower crust. We interpret the high-velocity layer as a signature of magmatic underplating due to past tectonic processes. Its significant thinning beneath the EDC may be attributed to crustal delamination or relamination at 2.5 Ga. These results demonstrate the dual signature of the Archean Dharwar crust. The change in the geochemical character of the crust possibly occurred at the end of Archean when Komatiite volcanism ceased. The unusually thick HVL beneath the west coast of India and the adjoining region may represent underplated material formed due to India-Madagascar rifting, which is supported by the presence of seaward dipping reflectors and a 85-90 Ma mafic dyke in the adjoining island.

  14. Intercomparison of snowfall estimates derived from the CloudSat Cloud Profiling Radar and the ground based weather radar network over Sweden

    NASA Astrophysics Data System (ADS)

    Norin, L.; Devasthale, A.; L'Ecuyer, T. S.; Wood, N. B.; Smalley, M.

    2015-08-01

    To be able to estimate snowfall accurately is important for both weather and climate applications. Ground-based weather radars and space-based satellite sensors are often used as viable alternatives to rain-gauges to estimate precipitation in this context. The Cloud Profiling Radar (CPR) onboard CloudSat is especially proving to be a useful tool to map snowfall globally, in part due to its high sensitivity to light precipitation and ability to provide near-global vertical structure. The importance of having snowfall estimates from CloudSat/CPR further increases in the high latitude regions as other ground-based observations become sparse and passive satellite sensors suffer from inherent limitations. Here we intercompared snowfall estimates from two observing systems, CloudSat and Swerad, the Swedish national weather radar network. Swerad offers one of the best calibrated data sets of precipitation amount at very high latitudes that are anchored to rain-gauges and that can be exploited to evaluate usefulness of CloudSat/CPR snowfall estimates in the polar regions. In total 7.2×105 matchups of CloudSat and Swerad over Sweden were inter-compared covering all but summer months (October to May) from 2008 to 2010. The intercomparison shows encouraging agreement between these two observing systems despite their different sensitivities and user applications. The best agreement is observed when CloudSat passes close to a Swerad station (46-82 km), when the observational conditions for both systems are comparable. Larger disagreements outside this range suggest that both platforms have difficulty with shallow snow but for different reasons. The correlation between Swerad and CloudSat degrades with increasing distance from the nearest Swerad station as Swerad's sensitivity decreases as a function of distance and Swerad also tends to overshoots low level precipitating systems further away from the station, leading to underestimation of snowfall rate and occasionally missing

  15. Composition and Origin of Archean Migmatites from Iisalmi, Central Finland

    NASA Astrophysics Data System (ADS)

    Brueckner, S. M.; Foley, S. F.; Nehring, F.; Hölttä, P.; von der Handt, A.

    2008-12-01

    Besides greenstone belts, the most known prominent rock type of the Archean is tonalite-trondhjemite- granodiorite (TTG) representing continental crust. Changes in the geochemical behavior of TTG during the Archean are explained by increasingly deep melting of the subducted slab towards the end of the Archean, resulting in increasing interaction of slab melts with the overlying mantle wedge [1]. We present major and trace element data for migmatized, late-Archean TTGs and associated amphibolites from three different locations in Central Finland. We investigated in particular the content of the transition trace elements Cr, Ni, Co and Zn within mesosome and neosome (leucosome + melanosome) of metatexitic TTGs to ascertain whether they developed by metamorphic segregation and partial melting or by another process. Our data show that some melanosomes have elevated Cr (> 70 ppm) and Ni (> 40 ppm) contents, and cannot be produced by simple partial melting of unmodified TTG with subsequent metamorphic segregation and fractional crystallization of the neosome. Rather, these 'melanosomes' represent basaltic melts, now amphibolites, which intruded syn- to early post-tectonically into the TTGs, and were subsequently deformed, giving the appearance of strongly banded metatexitic migmatites. In contrast to these 'contaminated' TTGs, most of the investigated samples show typical TTG characteristics, but no particular geochemical evidence for an increasing interaction with an overlying mantle wedge. Contamination by basaltic dyking may be an alternative explanation for the increase in MgO and decrease in SiO2 of migmatitic TTG with time during the Archean. [1] Martin, H. and Moyen, J.-F., 2002: Geology 30: 319-322.

  16. Venus and the Earth's Archean: Geological mapping and process comparisons

    NASA Astrophysics Data System (ADS)

    Head, J. W.; Hurwitz, D. M.; Ivanov, M. A.; Basilevsky, A. T.; Senthil Kumar, P.

    2008-09-01

    Introduction. The geological features, structures, thermal conditions, interpreted processes, and outstanding questions related to both the Earth's Archean and Venus share many similarities [1-3] and we are using a problem-oriented approach to Venus mapping, guided by insight from the Archean record of the Earth, to gain new perspectives on the evolution of Venus and Earth's Archean. The Earth's preserved and well-documented Archean record [4] provides important insight into high heat-flux tectonic and magmatic environments and structures [5] and the surface of Venus reveals the current configuration and recent geological record of analogous high-temperature environments unmodified by subsequent several billion years of segmentation and overprinting, as on Earth. Here we address the nature of the Earth's Archean, the similarities to and differences from Venus, and the specific Venus and Earth-Archean problems on which progress might be made through comparison. The Earth's Archean and its Relation to Venus. The Archean period of Earth's history extends from accretion/initial crust formation (sometimes called the Hadean) to 2.5 Ga and is thought of by most workers as being a transitional period between the earliest Earth and later periods largely dominated by plate tectonics (Proterozoic and Phanerozoic) [2, 4]. Thus the Archean is viewed as recording a critical period in Earth's history in which a transition took place from the types of primary and early secondary crusts seen on the Moon, Mars and Mercury [6] (and largely missing in the record of the Earth), to the style of crustal accretion and plate tectonics characterizing later Earth history. The Archean is also characterized by enhanced crustal and mantle temperatures leading to differences in deformation style and volcanism (e.g., komatiites) [2]. The preserved Archean crust is exposed in ~36 different cratons [4], forming the cores of most continental regions, and is composed of gneisses, plutons and

  17. Empirical Records of Environmental Change across the Archean-Proterozoic Transition

    NASA Astrophysics Data System (ADS)

    Kaufman, A. J.

    2011-12-01

    Time-series geochemical analyses of scientific drill cores intersecting the Archean-Proterozoic transition suggest a coupling of environmental and biological change that culminated in the pervasive oxygenation of Earth's atmosphere and oceans. Elemental and multiple isotope measurements of sedimentary archives, including carbonate, shale, and banded iron-formation from Western Australia, South Africa, Brazil, and southern Canada, indicate important changes in the carbon, sulfur, and nitrogen cycles that monitor the redox state of the oceans and the cyanobacterial buildup of atmospheric oxygen and ozone. In response, continental weathering would have increased, resulting in the enhanced delivery of sulfate and nutrients to seawater, further stimulating photoautotrophic fluxes of oxygen to surface environments. The positive feedback may additionally be responsible for the decline of atmospheric methane and surface refrigeration, represented by a series of discrete ice ages beginning around 2.4 billion years ago, due to the loss of greenhouse capacity during a time of lower solar luminosity. While speculative, the linkage of surface oxidation with enhanced nutrient supply and development of stratospheric sunscreen soon after the Archean-Proterozoic boundary suggests that the earliest perturbation in the carbon cycle may be associated with the rapid expansion of single-celled eukaryotes. Both sterol synthesis in eukaryotes and aerobic respiration require significant levels of oxygen in the ambient environment. Hence, Earth's earliest ice age(s) and onset of a modern and far more energetic carbon cycle may have been directly related to the global expansion of cyanobacteria that released oxygen to the environment, and of eukaryotes that respired it.

  18. Weather Instruments.

    ERIC Educational Resources Information Center

    Brantley, L. Reed, Sr.; Demanche, Edna L.; Klemm, E. Barbara; Kyselka, Will; Phillips, Edwin A.; Pottenger, Francis M.; Yamamoto, Karen N.; Young, Donald B.

    This booklet presents some activities to measure various weather phenomena. Directions for constructing a weather station are included. Instruments including rain gauges, thermometers, wind vanes, wind speed devices, humidity devices, barometers, atmospheric observations, a dustfall jar, sticky-tape can, detection of gases in the air, and pH of…

  19. Wacky Weather

    ERIC Educational Resources Information Center

    Sabarre, Amy; Gulino, Jacqueline

    2013-01-01

    What do a leaf blower, water hose, fan, and ice cubes have in common? Ask the students who participated in an integrative science, technology, engineering, and mathematics (I-STEM) education unit, "Wacky Weather," and they will tell say "fun and severe weather"--words one might not have expected! The purpose of the unit…

  20. Archean microfossils: a reappraisal of early life on Earth.

    PubMed

    Altermann, Wladyslaw; Kazmierczak, Józef

    2003-11-01

    The oldest fossils found thus far on Earth are c. 3.49- and 3.46-billion-year-old filamentous and coccoidal microbial remains in rocks of the Pilbara craton, Western Australia, and c. 3.4-billion-year-old rocks from the Barberton region, South Africa. Their biogenicity was recently questioned and they were reinterpreted as contaminants, mineral artefacts or inorganic carbon aggregates. Morphological, geochemical and isotopic data imply, however, that life was relatively widespread and advanced in the Archean, between 3.5 and 2.5 billion years ago, with metabolic pathways analogous to those of recent prokaryotic organisms, including cyanobacteria, and probably even eukaryotes at the terminal Archean.

  1. Development of Archean crust in the Wind River Mountains, Wyoming

    NASA Technical Reports Server (NTRS)

    Frost, C. D.; Koesterer, M. E.; Koesterer, M. E.; Koesterer, M. E.; Koesterer, M. E.

    1986-01-01

    The Wind River Mountains are a NW-SE trending range composed almost entirely of high-grade Archean gneiss and granites which were thrust to the west over Phanerozoic sediments during the Laramide orogeny. Late Archean granites make up over 50% of the exposed crust and dominates the southern half of the range, while older orthogneisses and magnatites form most of the northen half of the range. Locally these gneisses contain enclaves of supracrustal rocks, which appear to be the oldest preserved rocks in the range. Detailed work in the Medina Mountain area of the central Wind River Mountains and reconnaissance work throughout much of the northern part of the range has allowed definition of the sequence of events which marked crustal development in this area. The sequence of events are described.

  2. Origin of microbial biomineralization and magnetotaxis during the Archean.

    PubMed

    Lin, Wei; Paterson, Greig A; Zhu, Qiyun; Wang, Yinzhao; Kopylova, Evguenia; Li, Ying; Knight, Rob; Bazylinski, Dennis A; Zhu, Rixiang; Kirschvink, Joseph L; Pan, Yongxin

    2017-02-28

    Microbes that synthesize minerals, a process known as microbial biomineralization, contributed substantially to the evolution of current planetary environments through numerous important geochemical processes. Despite its geological significance, the origin and evolution of microbial biomineralization remain poorly understood. Through combined metagenomic and phylogenetic analyses of deep-branching magnetotactic bacteria from the Nitrospirae phylum, and using a Bayesian molecular clock-dating method, we show here that the gene cluster responsible for biomineralization of magnetosomes, and the arrangement of magnetosome chain(s) within cells, both originated before or near the Archean divergence between the Nitrospirae and Proteobacteria This phylogenetic divergence occurred well before the Great Oxygenation Event. Magnetotaxis likely evolved due to environmental pressures conferring an evolutionary advantage to navigation via the geomagnetic field. Earth's dynamo must therefore have been sufficiently strong to sustain microbial magnetotaxis in the Archean, suggesting that magnetotaxis coevolved with the geodynamo over geological time.

  3. Origin of microbial biomineralization and magnetotaxis during the Archean

    PubMed Central

    Paterson, Greig A.; Wang, Yinzhao; Kopylova, Evguenia; Li, Ying; Knight, Rob; Bazylinski, Dennis A.; Zhu, Rixiang; Kirschvink, Joseph L.; Pan, Yongxin

    2017-01-01

    Microbes that synthesize minerals, a process known as microbial biomineralization, contributed substantially to the evolution of current planetary environments through numerous important geochemical processes. Despite its geological significance, the origin and evolution of microbial biomineralization remain poorly understood. Through combined metagenomic and phylogenetic analyses of deep-branching magnetotactic bacteria from the Nitrospirae phylum, and using a Bayesian molecular clock-dating method, we show here that the gene cluster responsible for biomineralization of magnetosomes, and the arrangement of magnetosome chain(s) within cells, both originated before or near the Archean divergence between the Nitrospirae and Proteobacteria. This phylogenetic divergence occurred well before the Great Oxygenation Event. Magnetotaxis likely evolved due to environmental pressures conferring an evolutionary advantage to navigation via the geomagnetic field. Earth’s dynamo must therefore have been sufficiently strong to sustain microbial magnetotaxis in the Archean, suggesting that magnetotaxis coevolved with the geodynamo over geological time. PMID:28193877

  4. The production of Barberton komatiites in an Archean Subduction Zone

    NASA Astrophysics Data System (ADS)

    Parman, S. W.; Grove, T. L.; Dann, J. C.

    Based upon their geochemical similarity, we propose that the 3.5 Ga Barberton basaltic komatiites (BK) are the Archean equivalents of modern boninites, and were produced by the same melting processes (i.e. hydrous melting in a subduction zone). The Barberton komatiites also share some geochemical characteristics with boninites, including petrologic evidence for high magmatic H2O contents. Experimental data indicates that the Archean sub-arc mantle need only be 1500-1600°C to produce hydrous komatiitic melts. This is considerably cooler than estimates of mantle temperatures assuming an anhydrous, plume origin for komatiites (up to 1900°C). The depleted mantle residue that generates the Barberton komatiites and BK will be cooled and metasomatised as it resides beneath the fore-arc, and may represent part of the material that formed the Kaapvaal cratonic keel.

  5. Workshop on a Cross Section of Archean Crust

    NASA Technical Reports Server (NTRS)

    Ashwal, L. D. (Editor); Card, K. D. (Editor)

    1983-01-01

    Various topics relevant to crustal genesis, especially the relationship between Archean low - and high-grade terrains, were discussed. The central Superior Province of the Canadian Shield was studied. Here a 120 km-wide transition from subgreenschist facies rocks of the Michipicoten greenstone belt to granulite facies rocks of the Kapuskasing structural zone represents an oblique cross section through some 20 km of crust, uplifted along a northwest-dipping thrust fault.

  6. Hospitable archean climates simulated by a general circulation model.

    PubMed

    Wolf, E T; Toon, O B

    2013-07-01

    Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model.

  7. Dating carbonaceous matter in archean cherts by electron paramagnetic resonance.

    PubMed

    Bourbin, M; Gourier, D; Derenne, S; Binet, L; Le Du, Y; Westall, F; Kremer, B; Gautret, P

    2013-02-01

    Ancient geological materials are likely to be contaminated through geological times. Thus, establishing the syngeneity of the organic matter embedded in a mineral matrix is a crucial step in the study of very ancient rocks. This is particularly the case for Archean siliceous sedimentary rocks (cherts), which record the earliest traces of life. We used electron paramagnetic resonance (EPR) for assessing the syngeneity of organic matter in cherts that have a metamorphic grade no higher than greenschist. A correlation between the age of Precambrian samples and the shape of their EPR signal was established and statistically tested. As thermal treatments impact organic matter maturity, the effect of temperature on this syngeneity proxy was studied; cyanobacteria were submitted to cumulative short thermal treatment at high temperatures followed by an analysis of their EPR parameters. The resulting carbonaceous matter showed an evolution similar to that of a thermally treated young chert. Furthermore, the possible effect of metamorphism, which is a longer thermal event at lower temperatures, was ruled out for cherts older than 2 Gyr, based on the study of Silurian cherts of the same age and same precursors but various metamorphic grades. We determined that even the most metamorphosed sample did not exhibit the lineshape of an Archean sample. In the hope of detecting organic contamination in Archean cherts, a "contamination-like" mixture was prepared and studied by EPR. It resulted that the lineshape analysis alone does not allow contamination detection and that it must be performed along with cumulative thermal treatments. Such treatments were applied to three Archean chert samples, making dating of their carbonaceous matter possible. We concluded that EPR is a powerful tool to study primitive organic matter and could be used in further exobiology studies on low-metamorphic grade samples (from Mars for example).

  8. Nitrogen isotope evidence for alkaline lakes on late Archean continents

    NASA Astrophysics Data System (ADS)

    Stüeken, E. E.; Buick, R.; Schauer, A. J.

    2015-02-01

    Nitrogen isotope ratios in ancient sedimentary rocks are generally interpreted as a proxy for metabolic nitrogen pathways and the redox state of the water column. Fractionation processes occurring under anoxic, alkaline conditions during the dissociation of NH4+ to H+ and volatile NH3 are frequently overlooked, although this mechanism imparts large isotopic fractionations. Here we propose that NH3 volatilization is largely responsible for δ15N values of up to + 50 ‰ at high C/N ratios in the late Archean Tumbiana Formation. This sequence of sedimentary rocks represents a system of lakes that formed on subaerial flood basalts and were partly filled by basaltic volcanic ash. Aqueous alteration of volcanic glass followed by evaporative concentration of ions should have led to the development of high alkalinity with a pH of 9 or higher, as in modern analogues. In this sedimentologically unusual setting, nitrogen isotope ratios thus provide indirect evidence for the oldest alkaline lake system in the rock record. These very heavy lacustrine δ15N values contrast markedly with those of Archean marine sedimentary rocks, making a Precambrian "soda ocean" unlikely. Today, alkaline lakes are among the most productive ecosystems on Earth. Some nutrients, in particular molybdenum, are more soluble at high pH, and certain prebiotic reactions would likely have been favored under alkaline conditions in similar settings earlier in Earth's history. Hence alkaline lakes in the Archean could have been significant for the origin and early evolution of life.

  9. Chemical constraints on the evolution of Archean continental crust

    NASA Technical Reports Server (NTRS)

    Weaver, B. L.; Tarney, J.

    1985-01-01

    One of the challenges of Archean geochronology is to find isotopic systems that preserve an indication of a rock's primary age in spite of the effects of later metamorphism. Zircon dating has been used widely with considerable success but not without difficulty, especially in polymetamorphic terrains. Zircons in such cases commonly are found to have lost radiogenic Pb, and despite fractionizing the zircons or abrading them to remove disturbed portions; it often is not possible to define a pattern of Pb loss from which the original age can confidently be inferred. The refinement of techniques to enable extremely small samples, or even single crystals, to be analyzed has contributed greatly to solving the problem but even those techniques cannot resolve the micron scale isotopic heterogeneities within single zircons in which much of their history is recorded. That can only be done by ion microprobe. Progress reports on studies of four Archean rocks, each of which illustrates the power and potential of ion microprobe analysis in solving problems of Archean geochronology are discussed.

  10. Archean komatiite volcanism controlled by the evolution of early continents

    PubMed Central

    Mole, David R.; Fiorentini, Marco L.; Thebaud, Nicolas; Cassidy, Kevin F.; McCuaig, T. Campbell; Kirkland, Christopher L.; Romano, Sandra S.; Doublier, Michael P.; Belousova, Elena A.; Barnes, Stephen J.; Miller, John

    2014-01-01

    The generation and evolution of Earth’s continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50–30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean–Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits. PMID:24958873

  11. Bridging Two Worlds: From the Archean to the Proterozoic

    NASA Technical Reports Server (NTRS)

    Schopf, J. William

    2000-01-01

    As now known, the Archean and Proterozoic appear to have been different worlds: the geology (tectonic style, basinal distribution, dominant rock types), atmospheric composition (O2, CO21, CH4), and surface environment (day-length, solar luminosity, ambient temperature) all appear to have changed over time. And virtually all paleobiologic indicators can be interpreted as suggesting there were significant biotic differences as well: (1) Stromatolites older than 2.5 Ga are rare relative to those of the Proterozoic; their biotic components are largely unknown; and the biogenicity of those older than approx. 3.2 Ga has been questioned. (2) Bona fide microfossils older than approx. 2.4 Ga are rare, poorly preserved, and of uncertain biological relations. Gaps of hundreds of millions of years in the known record make it impossible to show that Archean microorganisms are definitely part of the 2.4 Ga-to-present evolutionary continuum. and (3) In rocks older than approx. 2.2 Ga, the sulfur isotopic record is subject to controversy; phylogenetically distinctive bio-markers are unknown; and nearly a score of geologic units contain organic carbon anomalously light isotopically (relative to that of the Proterozoic and Phanerozoic) that may reflect the presence of Archaeans ("Archaebacteria of earlier classifications) but may not (since cellularly preserved Archean-age Archaeans have never been identified).

  12. How widely is the Andean type of continental margin represented in the Archean

    NASA Technical Reports Server (NTRS)

    Burke, Kevin

    1988-01-01

    Application of the principle of uniformitarianism to the Archean was discussed in a search for evidence of Archean-type continental margins in Archean rocks. The author cautioned that Archean rocks represent only 2 percent of the current exposure of the continents, half of which is in the North American Superior Province. Care must be taken in interpreting the global tectonic significance of relatively small exposures of Archean rocks, such as South India. Andean margins were characterized by their elongate shape, magmatic associations, and isotopic signatures. Although the compositional evidence alone will always be ambiguous, it was suggested that supporting structural evidence may aid in the identification of Archean Andean margins. Andean margin remains have been recognized in the Superior Province of Canada by these criteria, and the author suggested that the Closepet granite of South India may represent another example.

  13. How to draw down CO2 from severe Hadean to habitable Archean?

    NASA Astrophysics Data System (ADS)

    Zhelezinskaia, I.; Ding, S.; Mulyukova, E.; Martirosyan, N.; Johnson, A.; West, J. D.; Kolesnichenko, M.; Saloor, N.; Moucha, R.

    2015-12-01

    It has been hypothesized that as the magma ocean crystallized in the Hadean, volatiles such as CO2 and H2O were released to the surface culminating with the formation of a liquid ocean by about 4.4 Ga [1] and hot CO2-rich atmosphere [2]. The resulting late Hadean atmospheric pCO2 may have been as high as 100 bars [3] with corresponding surface temperatures ~500 K [4]. Geological evidence suggests that by the early-to-mid Archean, atmospheric pCO2 became less than 1 bar [5]. However, the mechanisms responsible for the great amount of CO2 drawdown in a relatively short period of time remain enigmatic. To identify these possible mechanisms, we have developed a box model during the CIDER 2015 Summer Program that takes into account geological constraints on basalt alteration [6, 7] and possible rate of new oceanic crust formation [8] for the Archean. Our model integrates geodynamic and geochemical approaches of interaction between the Hadean atmosphere, hydrosphere, oceanic crust, and mantle to drawdown CO2. Our primary assumption for the Hadean is the absence of the continental crust and thus continental weathering. Therefore in the model we present, the level of CO2 in the atmosphere is regulated by the formation of oceanic crust (OC), rate of the interaction between the ocean and OC, and carbonate subduction/CO2 degassing. Preliminary results suggest that it would take about 1 billion years for the atmospheric CO2 to decrease to 1 bar if the production of oceanic crust was 10 times more than today and the pH of the ocean was less than 7, making the basalt alteration more efficient. However, there is evidence that some continental crust began to form as early as 4.4 Ga [9] and therefore the role of continental weathering and its rate of CO2 drawdown will need to be further explored. References: [1] Wilde et al. (2001). Nature 409(6817), 175-178. [2] Walker (1985). Origins of Life and Evolution of the Biosphere 16(2), 117-127. [3] Elkins-Tanton (2008). EPSL, 271, 181

  14. Hazy Archean Earth as an Analog for Hazy Earthlike Exoplanets

    NASA Astrophysics Data System (ADS)

    Arney, Giada; Meadows, Victoria; Domagal-Goldman, Shawn; Claire, Mark; Schwieterman, Edward

    2015-01-01

    Hazy exoplanets may be common (Bean et al. 2010, Sing et al. 2011, Kreidberg et al 2014), and in our solar system, Venus and Titan have photochemically-produced hazes. There is evidence that Earth itself had a hydrocarbon haze in the Archean (Zerkle et al. 2012, Domagal-Goldman et al. 2008) with important climatic effects (Pavlov et al. 2001, Trainer et al. 2006, Haqq-Misra et al. 2008, Wolf and Toon 2012). We use a 1D coupled photochemical-climate model and a line-by-line radiative transfer model to investigate the climactic and spectral impacts of a fractal hydrocarbon haze on Archean Earth. The haze absorbs significantly at shorter wavelengths and can strongly suppress the Rayleigh scattering tail, a broadband effect that would be remotely detectable at low spectral resolution at wavelengths less than 0.5 μm. Hazes may have a more significant impact on transit transmission spectra. Using the transit transmission radiative transfer model developed by Misra et al. (2014) to generate hazy Archean spectra, we find that even a thin hydrocarbon haze masks the lower atmosphere from the visible into the near infrared where the haze optical depth exceeds unity. The transit transmission spectra we generate for hazy Archean Earth are steeply sloped like the Titan solar occultation spectrum observed by Robinson et al. (2014). Thick hazes can also cool the planet significantly: for example, the thick fractal haze generated around Archean Earth with 0.3% CH4, 1% CO2 and 1 ppm C2H6 cools the planet from roughly 290 K without the haze to below freezing with the haze. Finally, we investigate the impact of host star spectral type on haze formation, comparing the hazes generated around a solar-type star to those generated at an Earth analog planet around the M dwarf AD Leo. Our results indicate hazes around M dwarfs for the same initial atmospheric composition may be thinner due to decreased UV photolysis of methane and other hydrocarbons needed for haze formation. Earthlike

  15. Constraining Archean Earth's Atmosphere with the Geological Record

    NASA Astrophysics Data System (ADS)

    Horan, A. M.; Domagal-Goldman, S. D.; Claire, M.

    2014-12-01

    A warm, water-bearing Archean Earth, when the Sun was young and faint, remains a paradox to the scientific world. Abundant geological data suggests that Archean Earth had standing water at the surface, despite the fainter Sun. An explanation of this paradox is vital to the understanding of Earth's history and coevolution with life. If the surface of the planet was not being kept warm by the Sun, which was 25% less luminous than now, it must have been kept warm a different way—by an atmospheric composition high in greenhouse gases. Constraints on these gases come from the geological record, which have provided proxies for the redox state of the atmosphere (limiting H2 and O2), the total atmospheric pressure, and the partial pressure of certain gases such as carbon dioxide (CO2) and methane (CH4). Previous attempts at solutions to the paradox are consistent with some, but not all, of the geological proxies. The constraints are used as inputs for a 1-D photochemical code, which calculates atmospheric composition and predicts the abundances of atmospheric gases that affect climate, particularly methane (CH4) and gaseous hydrogen (H2). A coupled 1-D radiative-convective climate code is then used to calculate the corresponding surface temperature. Critically, the improved photochemical code maintains strict redox boundary conditions, and is being further updated to ensure that the redox fluxes from volcanoes and mid-ocean ridge vents are consistent with both each other and the redox state of the mantle. These code improvements will lead to changes in both the inputs to the atmosphere from volcanoes and the sink for oxidants at mid-ocean ridges, in turn affecting the abundance of redox-sensitive greenhouse gases such as CH4 and H2. The main purpose of this project is to extend simulations of the Archean surface environment down into the mantle, and to search for a solution to the faint young sun paradox that is consistent with the geological proxies. Beyond having

  16. Large S-33 Anomalies in Late Archean Carbonacous Shales

    NASA Astrophysics Data System (ADS)

    Ono, S.; Rumble, D.; Pavlov, A.; Kharecha, P.; Kasting, J. F.

    2002-12-01

    Multi-sulfur isotope ratios (34S/33S/32S) were determined on sulfides extracted from two late Archean carbonaceous shale units, the Mt. McRae shale (~2.5 Ga) and the Jeerinah formation (~2.7 Ga), from the Hamersley Basin, Western Australia by using the CO2-laser fluorination line at the Geophisical Laboratory. We have measured the largest Δ33S anomaly yet reported for a terrestrial sample on sulfides from 22 m core section of the Mt McRae shale. The large positive Δ33S, up to +6.9 ‰ , is found in the lower part of the core section; the Δ33S shifts to negative upward in the section to as low as -1.9 ‰ . The age of the Mt. McRae shale is bracketed by 2470 and 2561 Ma. Therefore, the observed isotopic shift represents the maximum duration of 91 million years, but most likely less than 30 million years by assuming a constant sedimentation rate for the Mt. McRae shale that has average thickness of 60 m in the area. Sulfide sulfur from the Jeerinah formation also yield large Δ33S anomalies ranging from -0.1 to +4.4 ‰ . Our model fundamentally follows the one proposing a strong atmospheric influence in the Archean sulfur cycle by Farquhar et al. (2000). Our new data show the large and systematic variation between Δ33S and δ34S. This allows us to further speculate the isotopic compositions of Archean sulfur reservoirs and the manner in which the atmospheric signature was transferred to sediments. Our data are consistent with the late Archean seawater sulfate reservoir that has a negative Δ33S of ~ -2 ‰ . Thus, pyrite formed via microbial sulfate reduction shows variable δ34S and negative Δ33S. The large positive Δ33S of + 6.9 ‰ is likely to be a signature of deposition of sulfur aerosol, probably elemental sulfur. Our sulfur isotope data is best explained by mixing of those two components. Atmospheric deposition of elemental sulfur requires an anoxic atmosphere, and subsequent burial and preservation of the signature into pelagic sediments would have

  17. Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

    NASA Technical Reports Server (NTRS)

    Berndt, E. B.; Zavodsky, B. T.; Folmer, M. J.; Jedlovec, G. J.

    2014-01-01

    Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), 32-km North American Regional Reanalysis (NARR) interpolated to a 12-km grid, and 13-km Rapid Refresh analyses.

  18. Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

    NASA Technical Reports Server (NTRS)

    Berndt, E. B.; Zavodsky, B. T.; Jedlovec, G. J.

    2014-01-01

    Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and Rapid Refresh analyses.

  19. The Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

    NASA Technical Reports Server (NTRS)

    Berndt, Emily; Zavodsky, Bradley; Jedlovec, Gary; Elmer, Nicholas

    2013-01-01

    Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and Rapid Refresh analyses.

  20. Impact of the Assimilation of Hyperspectral Infrared Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

    NASA Technical Reports Server (NTRS)

    Berndt, Emily B.; Zavodsky, Bradley T; Jedlovec, Gary J.; Elmer, Nicholas J.

    2013-01-01

    Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), North American Regional Reanalysis (NARR) reanalysis, and Rapid Refresh analyses.

  1. Direct dating of weathering phenomena by [sup 40]Ar/[sup 39]Ar and K-Ar analysis of supergene K-Mn oxides

    SciTech Connect

    Vasconcelos, P.M.; Brimhall, G.H. ); Renne, P.R.; Becker, T.A. )

    1994-03-01

    Potassium-bearing manganese oxides, cryptomelane, K[sub 1-2](Mn[sup 3+]Mn[sup 4+])[sub 8] O[sub 16] [center dot] xH[sub 2]O, and hollandite, (K,Ba)[sub 1-2](Mn[sup 3+],Mn[sup 4+])[sub 8] O[sub 16] [center dot] xH[sub 2]O, are often authigenically precipitated in weathering profiles. Dating of these phases allows timing of the progression of oxidation fronts during weathering and pedogenic processes. Potential problems in manganese oxide dating, such as Ar and/or K losses, excess argon, [sup 39]Ar loss by recoil during neutron irradiation, etc. are addressed. The K-Ar and [sup 40]Ar/[sup 39]Ar analytical results indicate that Ar and/or K losses, excess [sup 40]Ar, and [sup 39]Ar recoil seem not to pose problems in manganese oxide dating. This investigation suggests that the fine scale, laser-probe [sup 40]Ar/[sup 39]Ar technique is most appropriate for dating of weathering phenomena because this technique permits identification of contaminating phases and the presence of multiple generations of weathering minerals in the inherently complex mineral assemblage characteristic of weathering profiles. K-Ar and [sup 40]Ar/[sup 39]Ar dating of supergene K-bearing manganese oxides formed during lateritization of Archean and Proterozoic bedrocks in the Carajas Region, Amazonia, Brazil, indicates that weathering started before 72 [+-] 6 Ma. Petrographic, electron microscope, and electron microprobe investigation reveal multiple generations of manganese oxide precipitation. Age clusters at 65-69, 51-56, 40-43, 33-35, 20, 24, 12-17 Ma, and zero-age (0.2 [+-] 0.2 Ma) suggest episodic precipitation of K-Mn oxides resulting form changing weathering conditions in the Amazon throughout the Cenozoic. K-Ar and [sup 40]Ar/[sup 39]Ar dating of supergene cryptomelane from weathering profiles in eastern Minas Gerais, southeastern Brazil, suggests continuous weathering from 10 to 5.6 Ma ago, possibly reflecting local climatic conditions due to the proximity with the Atlantic Ocean.

  2. Weatherizing America

    SciTech Connect

    Stewart, Zachary; Bergeron, T.J.; Barth, Dale; Qualis, Xavier; Sewall, Travis; Fransen, Richard; Gill, Tony

    2009-01-01

    As Recovery Act money arrives to expand home weatherization programs across the country, Zachary Stewart of Phoenix, Ariz., and others have found an exciting opportunity not only to start working again, but also to find a calling.

  3. Weatherizing America

    ScienceCinema

    Stewart, Zachary; Bergeron, T.J.; Barth, Dale; Qualis, Xavier; Sewall, Travis; Fransen, Richard; Gill, Tony

    2016-07-12

    As Recovery Act money arrives to expand home weatherization programs across the country, Zachary Stewart of Phoenix, Ariz., and others have found an exciting opportunity not only to start working again, but also to find a calling.

  4. A high continental weathering flux into Paleoarchean seawater revealed by strontium isotope analysis of 3.26 Ga barite

    NASA Astrophysics Data System (ADS)

    Satkoski, Aaron M.; Lowe, Donald R.; Beard, Brian L.; Coleman, Max L.; Johnson, Clark M.

    2016-11-01

    Controls on Archean seawater chemistry remain controversial. Many studies have suggested that it was largely controlled by oceanic hydrothermal fluid circulation. Recent work, however, from clastic sequences, Hf-O isotope data from detrital zircons, and models for the Rb/Sr evolution of the continental crust suggest that intense continental weathering and low-temperature surface alteration were more important than previously thought during the early Archean. This is consistent with biogeochemical studies that suggest the Archean had a diverse microbial ecology, which would, in part, need to be sustained by nutrients (e.g., phosphorus) that were derived from continental weathering. To further quantify continental weathering during the early Archean, we analyzed 3.26 Ga barite from the Fig Tree Group, South Africa for strontium, oxygen, and sulfur isotope compositions. We propose that the seawater component of the barite is characterized by 87Sr/86Sr ratios >0.701, which is significantly more radiogenic than contemporaneous mantle (∼0.7007-0.7008). The radiogenic nature of seawater at this time suggests that the continental weathering flux at 3.26 Ga had a large impact on ocean chemistry 400 million years earlier than previously suggested.

  5. Seafloor weathering buffering climate: numerical experiments

    NASA Astrophysics Data System (ADS)

    Farahat, N. X.; Archer, D. E.; Abbot, D. S.

    2013-12-01

    Continental silicate weathering is widely held to consume atmospheric CO2 at a rate controlled in part by temperature, resulting in a climate-weathering feedback [Walker et al., 1981]. It has been suggested that weathering of oceanic crust of warm mid-ocean ridge flanks also has a CO2 uptake rate that is controlled by climate [Sleep and Zahnle, 2001; Brady and Gislason, 1997]. Although this effect might not be significant on present-day Earth [Caldeira, 1995], seafloor weathering may be more pronounced during snowball states [Le Hir et al., 2008], during the Archean when seafloor spreading rates were faster [Sleep and Zahnle, 2001], and on waterworld planets [Abbot et al., 2012]. Previous studies of seafloor weathering have made significant contributions using qualitative, generally one-box, models, and the logical next step is to extend this work using a spatially resolved model. For example, experiments demonstrate that seafloor weathering reactions are temperature dependent, but it is not clear whether the deep ocean temperature affects the temperature at which the reactions occur, or if instead this temperature is set only by geothermal processes. Our goal is to develop a 2-D numerical model that can simulate hydrothermal circulation and resulting alteration of oceanic basalts, and can therefore address such questions. A model of diffusive and convective heat transfer in fluid-saturated porous media simulates hydrothermal circulation through porous oceanic basalt. Unsteady natural convection is solved for using a Darcy model of porous media flow that has been extensively benchmarked. Background hydrothermal circulation is coupled to mineral reaction kinetics of basaltic alteration and hydrothermal mineral precipitation. In order to quantify seafloor weathering as a climate-weathering feedback process, this model focuses on hydrothermal reactions that influence carbon uptake as well as ocean alkalinity: silicate rock dissolution, calcium and magnesium leaching

  6. Microaerobic steroid biosynthesis and the molecular fossil record of Archean life.

    PubMed

    Waldbauer, Jacob R; Newman, Dianne K; Summons, Roger E

    2011-08-16

    The power of molecular oxygen to drive many crucial biogeochemical processes, from cellular respiration to rock weathering, makes reconstructing the history of its production and accumulation a first-order question for understanding Earth's evolution. Among the various geochemical proxies for the presence of O(2) in the environment, molecular fossils offer a unique record of O(2) where it was first produced and consumed by biology: in sunlit aquatic habitats. As steroid biosynthesis requires molecular oxygen, fossil steranes have been used to draw inferences about aerobiosis in the early Precambrian. However, better quantitative constraints on the O(2) requirement of this biochemistry would clarify the implications of these molecular fossils for environmental conditions at the time of their production. Here we demonstrate that steroid biosynthesis is a microaerobic process, enabled by dissolved O(2) concentrations in the nanomolar range. We present evidence that microaerobic marine environments (where steroid biosynthesis was possible) could have been widespread and persistent for long periods of time prior to the earliest geologic and isotopic evidence for atmospheric O(2). In the late Archean, molecular oxygen likely cycled as a biogenic trace gas, much as compounds such as dimethylsulfide do today.

  7. Microaerobic steroid biosynthesis and the molecular fossil record of Archean life

    PubMed Central

    Waldbauer, Jacob R.; Newman, Dianne K.; Summons, Roger E.

    2011-01-01

    The power of molecular oxygen to drive many crucial biogeochemical processes, from cellular respiration to rock weathering, makes reconstructing the history of its production and accumulation a first-order question for understanding Earth’s evolution. Among the various geochemical proxies for the presence of O2 in the environment, molecular fossils offer a unique record of O2 where it was first produced and consumed by biology: in sunlit aquatic habitats. As steroid biosynthesis requires molecular oxygen, fossil steranes have been used to draw inferences about aerobiosis in the early Precambrian. However, better quantitative constraints on the O2 requirement of this biochemistry would clarify the implications of these molecular fossils for environmental conditions at the time of their production. Here we demonstrate that steroid biosynthesis is a microaerobic process, enabled by dissolved O2 concentrations in the nanomolar range. We present evidence that microaerobic marine environments (where steroid biosynthesis was possible) could have been widespread and persistent for long periods of time prior to the earliest geologic and isotopic evidence for atmospheric O2. In the late Archean, molecular oxygen likely cycled as a biogenic trace gas, much as compounds such as dimethylsulfide do today. PMID:21825157

  8. Triple sulfur isotope composition of Late Archean seawater sulfate

    NASA Astrophysics Data System (ADS)

    Paris, G.; Fischer, W. W.; Sessions, A. L.; Adkins, J. F.

    2013-12-01

    Multiple sulfur isotope ratios in Archean sedimentary rocks have provided powerful insights into the behavior of the ancient sulfur cycle, the redox state of fluid Earth, and the timing of the rise of atmospheric oxygen [1]. Most processes fractionate sulfur isotopes in proportion to their mass differences, but the Archean sulfur isotope record is marked by pronounced mass-independent fractionation (MIF, Δ33S≠0). The origin of these signatures has been traditionally interpreted as the result of photolysis of SO2 from short wavelength UV light, with positive Δ33S values recorded in pyrite and negative Δ33S values in sulfate-bearing phases [2]. This long-held hypothesis rests on observations of negative Δ33S from enigmatic barite occurrences from mixed volcanic sedimentary strata in Mesoarchean greenstone terrains. Despite forming the framework for understanding Archean sulfur cycle processes [3], it is largely untested [3]. It is largely untested. Consequently, the biggest challenge to our current understanding of the early sulfur cycle is a poor understanding of the isotopic composition of seawater sulfate. Sulfate evaporite minerals are absent from Archean strata and the sulfur isotope record is written entirely by measurements of pyrite. Carbonate associated sulfate (CAS) provides an important archive for assaying the isotopic composition of ancient seawater sulfate It has been exploited in many studies of Phanerozoic and Proterozoic sulfate but have been only marginally used thus far for Archean samples because of the extremely low concentration of CAS in limestones and dolomites from this era. We have developed a novel MC-ICP-MS approach to solve this problem [4]. This new method lowers the detection limit by up to three orders of magnitude for δ34S and Δ33S measurements, enabling to work on a few nmols of sulfate which represent only tens of mg of sample powders micromilled from specific carbonate textures. Two stratigraphic sections from the 2

  9. Diamondiferous eclogites from Siberia: Remnants of Archean oceanic crust

    NASA Astrophysics Data System (ADS)

    Jacob, D.; Jagoutz, E.; Lowry, D.; Mattey, D.; Kudrjavtseva, G.

    1994-12-01

    We have investigated eight diamond-bearing bimineralic eclogite xenoliths from the Udachnaya Mine, Yakutia, Siberia, in terms of major elements, 87Sr /86Sr- , 143Nd /144Nd and oxygen isotopic ratios. The β18O-values, measured with the new laser-fluorination technique, are different from mantle values and range between 5.19 and 7.38%. with an average error of 0.08%.. Strontium and neodymium initial isotopic ratios for cpx are between 0.70226 and 0.70699 and 0.51170 and 0.51257, respectively. Chemically and petrographically, the Siberian eclogites are very similar to the South African eclogite suite from Roberts Victor or Bellsbank, the most important similarities being the late Archean age (2.76 Ga) and the δ18O values that deviate from mantle values. However, differences exist in detail, as no samples with δ18O values lower than mantle values have yet been reported from Siberia and the cesium concentrations of the Siberian eclogites are generally lower than those of the Roberts Victor eclogite suite. The data obtained from the studied sample suite are best explained by a model proposing an origin from Archean oceanic crust that was intensely altered prior to subduction to mantle depths. Using oxygen isotopic values, the effects of seawater alteration can be shown and the composition of the unaltered protolith qualitatively estimated. We propose that mantle eclogites from kimberlites were generated by a globally operating subduction process during the late Archean and that differences between samples from different cratons are small compared to their similarities.

  10. Accretionary origin for the late Archean Ashuanipi Complex of Canada

    NASA Technical Reports Server (NTRS)

    Percival, J. A.

    1988-01-01

    The Ashuanipi complex is one of the largest massif granulite terrains of the Canadian Shield. It makes up the eastern end of the 2000 km long, lower-grade, east-west belts of the Archean Superior Province, permitting lithological, age and tectonic correlation. Numerous lithological, geochemical and metamorphic similarities to south Indian granulites suggest common processes and invite comparison of tectonic evolution. The Ashuanipi granulite terrain of the Cannadian Superior Province was studied in detail, and an origin through self-melting of a 55 km thick accretionary wedge seems possible.

  11. Geological Mapping of Fortuna Tessera (V-2): Venus and Earth's Archean Process Comparisons

    NASA Technical Reports Server (NTRS)

    Head, James W.; Hurwitz,D. M.; Ivanov, M. A.; Basilevsky, A. T.; Kumar, P. Senthil

    2008-01-01

    The geological features, structures, thermal conditions, interpreted processes, and outstanding questions related to both the Earth's Archean and Venus share many similarities and we are using a problem-oriented approach to Venus mapping, guided by insight from the Archean record of the Earth, to gain new insight into the evolution of Venus and Earth's Archean. The Earth's preserved and well-documented Archean record provides important insight into high heat-flux tectonic and magmatic environments and structures and the surface of Venus reveals the current configuration and recent geological record of analogous high-temperature environments unmodified by subsequent several billion years of segmentation and overprinting, as on Earth. Elsewhere we have addressed the nature of the Earth's Archean, the similarities to and differences from Venus, and the specific Venus and Earth-Archean problems on which progress might be made through comparison. Here we present the major goals of the Venus-Archean comparison and show how preliminary mapping of the geology of the V-2 Fortuna Tessera quadrangle is providing insight on these problems. We have identified five key themes and questions common to both the Archean and Venus, the assessment of which could provide important new insights into the history and processes of both planets.

  12. Archean plate tectonics geodynamics: example from the Belomorian province, Fennoscandian Shield

    NASA Astrophysics Data System (ADS)

    Slabunov, Alexander

    2014-05-01

    A fragment of the Archean collisional Belomorian orogen has been identified as the Belomorian province (BP) of the Fennoscandian Shield (Slabunov, 2008; Holtta et al., 2014). The province consists dominantly of Archean rocks, Early Paleoproterozoic rocks being less abundant. Rock of BP exhumed from middle crustal depths in Paleoproterozoic time (1.94-1.8 Ga). Seismic (CDP) profiling data (Sharov et al., 2010) show that the internal structure of BP reflects nappe tectonics: in Archean time, a collage of numerous slides was formed, and in Paleoproterozoic time the BP was thrusted on the Karelian craton and, in turn, was thrusted by rocks of the Kola province. The BP consists dominantly of Meso- and Neoarchean rock association (Slabunov et al. 2006). Neoarchean granitoids predominate, but eclogite-bearing metam?lange (Volodichev et al., 2004; Mints et al., 2010; Shchipansky et al., 2012), island-arc volcanics, front-arc basin sediments, ophiolite-type oceanic plateau-type rocks, collisional S-granites, kyanite-facies metamorphic rocks, molassa-type rocks, subalkaline granitoids and leucogabbro have been revealed among supracrustal rock associations. Rocks of the Belomorian province were subjected to multiple metamorphism in Archean and Paleoproterozoic time at moderately high to high pressures and were considerably deformed. High-grade supracrustal complexes make up not more than 20 % of the BP, but as they probably host ore and are crucial for the understanding of the formation and evolution of the structure, they are given close attention. Five generations of greenstone complexes of different ages: 2.88-2.82 Ga, 2.8-2.78 Ga, ca. 2.75 Ga , ca. 2.72 Ga and not later than 2.66 Ga, and two paragneiss complex in which sediments were formed 2.89-2.82 and 2.78 Ga ago, are distinguished. The main stages of crustal evolution in the BP: ca 2.88-2.82 Ga - the first subduction-accretion event marked by the following complexes: island-arc volcanics of the Keret GB; metagraywacke

  13. Profiles.

    ERIC Educational Resources Information Center

    School Arts, 1979

    1979-01-01

    Profiles seven Black, Native American, and Chicano artists and art teachers: Hale A. Woodruff, Allan Houser, Luis Jimenez, Betrand D. Phillips, James E. Pate, I, and Fernando Navarro. This article is part of a theme issue on multicultural art. (SJL)

  14. Mineralogy and composition of Archean Crust, Greenland: A pilot study

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Curtiss, Brian

    1989-01-01

    The Portable Instant Display and Analysis Spectrometer (PIDAS) was taken to southwestern Greenland to investigate in situ the potential application of AVIRIS to estimate the mineralogy and composition of rocks exposed in Archean terranes. The goal was to determine the feasibility of using a high spectral resolution scanner to find and study pristine rocks, those that have not been altered by subsequent deformation and metamorphism. The application of AVIRIS data to the problems in Greenland is logical. However, before a costly deployment of the U-2 aircraft to Greenland is proposed, this study was undertaken to acquire the spectral data necessary to verify that mineralogical mapping in the environmental conditions found there is possible. Although field conditions were far from favorable, all of the major objectives of the study were addressed. One of the major concerns was that lichens would obscure the rock surfaces. It was found that the spectral signature of the lichens was distinct from the underlying rocks. Thus, a spectrum of a rock outcrop, with its partial cover of lichens, can be un-mixed into rock and lichen components. The data acquired during the course of this study supports the conclusion that areas of pristine Archean crust can be differentiated from that which has experienced low grade alteration associated with Proterizoic faulting.

  15. Early Archean tonalite gneiss in the upper peninsula of Michigan

    NASA Technical Reports Server (NTRS)

    Peterman, Z. E.; Zartman, R. E.; Sims, P. K.

    1986-01-01

    Geochronological results on tonalite gneiss of northern Michigan that is 3.56 Ga or slightly older is presented. Tonalitic augen gneiss and structurally overlying biotite gneiss and schist are exposed in a dome near Watersmeet. They are part of an extensive gneiss terrane of southern Minnesota, Wisconsin and Michigan that includes rocks of early to late Archean ages and lies south of the Wawa volcanic subprovince. Two samples of the augen gneiss and one of the biotite gneiss show zircon grains of similar shape, zoning, color, and development of crystal faces. These zircons give Pb/U isotopic ratios that plot on a chord of 3,560 + or - 40 m.y. upper intersect and of 1,250 + or m.y. lower intersect. The 3,560 m.y. number is believed to be a minimum age because analysis of one of the least discordant zircon fractions by ion microprobe that gave a nearly concordant age of 3,650 m.y. The 1,250 m.y. lower intersect is without geological significance: it is interpreted to be a result of multiple lead loss at 2.7, 1.8, and 0.5 Ga by U/Pb in zircon. Archean rocks 10 to 25 km northwest of the Watersmeet dome give a 2.75 Ga age on zircons. Quartz monzonite here is dated at 2.65 Ga.

  16. Post-orogenic thermal evolution of newborn Archean continents

    NASA Astrophysics Data System (ADS)

    Jaupart, C.; Mareschal, J.-C.

    2015-12-01

    The post-orogenic thermal evolution of newborn cratons in the Archean is marked by high-temperature metamorphism and plutonic activity that lag accretion by several tens of million years. The source of the heat that is required remains controversial. Here, we show that such late activity is consistent with the thermal evolution of new continental crust that adjusts to heat released by radioactive decay. Quantitative results depend on the total amount of radioactive elements in the newborn crust. Using heat flow and heat production data from the Archean Superior Province of the Canadian Shield, we show that temperatures ≈800-900 °C were reached in the lower crust a few tens of million years after the final accretion event. The timing of post-orogenic metamorphism is sensitive to the thermal structure acquired at the end of accretion. For the Superior Province, the relatively short time-lag between the end of accretion and metamorphism suggests that the lithosphere was thin or had been heated up by sustained magma percolation.

  17. Stored mafic/ultramafic crust and early Archean mantle depletion

    NASA Technical Reports Server (NTRS)

    Chase, Clement G.; Patchett, P. J.

    1990-01-01

    Both early and late Archean rocks from greenstone belts and felsic gneiss complexes exhibit positive epsilon(Nd) values of +1 to +5 by 3.5 Ga, demonstrating that a depleted mantle reservoir existed very early. The amount of preserved pre-3.0 Ga continental crust cannot explain such high epsilon values in the depleted residue unless the volume of residual mantle was very small: a layer less than 70 km thick by 3.0 Ga. Repeated and exclusive sampling of such a thin layer, especially in forming the felsic gneiss complexes, is implausible. Extraction of enough continental crust to deplete the early mantle and its destructive recycling before 3.0 Ga ago requires another implausibility, that the sites of crustal generation of recycling were substantially distinct. In contrast, formation of mafic or ultramafic crust analogous to present-day oceanic crust was continuous from very early times. Recycled subducted oceanic lithosphere is a likely contributor to present-day hotspot magmas, and forms a reservoir at least comparable in volume to continental crust. Subduction of an early mafic/ultramafic oceanic crust and temporary storage rather than immediate mixing back into undifferentiated mantle may be responsible for the depletion and high epsilon(Nd) values of the Archean upper mantle.

  18. Manganese carbonates as possible biogenic relics in Archean settings

    NASA Astrophysics Data System (ADS)

    Rincón-Tomás, Blanca; Khonsari, Bahar; Mühlen, Dominik; Wickbold, Christian; Schäfer, Nadine; Hause-Reitner, Dorothea; Hoppert, Michael; Reitner, Joachim

    2016-07-01

    Carbonate minerals such as dolomite, kutnahorite or rhodochrosite are frequently, but not exclusively generated by microbial processes. In recent anoxic sediments, Mn(II)carbonate minerals (e.g. rhodochrosite, kutnahorite) derive mainly from the reduction of Mn(IV) compounds by anaerobic respiration. The formation of huge manganese-rich (carbonate) deposits requires effective manganese redox cycling in an oxygenated atmosphere. However, putative anaerobic pathways such as microbial nitrate-dependent manganese oxidation, anoxygenic photosynthesis and oxidation in ultraviolet light may facilitate manganese cycling even in an early Archean environment, without the availability of oxygen. In addition, manganese carbonates precipitate by microbially induced processes without change of the oxidation state, e.g. by pH shift. Hence, there are several ways how these minerals could have been formed biogenically and deposited in Precambrian sediments. We will summarize microbially induced manganese carbonate deposition in the presence and absence of atmospheric oxygen and we will make some considerations about the biogenic deposition of manganese carbonates in early Archean settings.

  19. THE COSMIC-RAY INTENSITY NEAR THE ARCHEAN EARTH

    SciTech Connect

    Cohen, O.; Drake, J. J.; Kota, J.

    2012-11-20

    We employ three-dimensional state-of-the-art magnetohydrodynamic models of the early solar wind and heliosphere and a two-dimensional model for cosmic-ray transport to investigate the cosmic-ray spectrum and flux near the Archean Earth. We assess how sensitive the cosmic-ray spectrum is to changes in the sunspot placement and magnetic field strength, the large-scale dipole magnetic field strength, the wind ram pressure, and the Sun's rotation period. Overall, our results confirm earlier work that suggested the Archean Earth would have experienced a greatly reduced cosmic-ray flux than is the case today. The cosmic-ray reduction for the early Sun is mainly due to the shorter solar rotation period and tighter winding of the Parker spiral, and to the different surface distribution of the more active solar magnetic field. These effects lead to a global reduction of the cosmic-ray flux at 1 AU by up to two orders of magnitude or more. Variations in the sunspot magnetic field have more effect on the flux than variations in the dipole field component. The wind ram pressure affects the cosmic-ray flux through its influence on the size of the heliosphere via the pressure balance with the ambient interstellar medium. Variations in the interstellar medium pressure experienced by the solar system in orbit through the Galaxy could lead to order of magnitude changes in the cosmic-ray flux at Earth on timescales of a few million years.

  20. Louisiana High School Weathers the Storm to Become a Leader in Student Achievement and High Graduation Rates. "High Schools That Work" Profile

    ERIC Educational Resources Information Center

    Southern Regional Education Board (SREB), 2011

    2011-01-01

    Warren Easton Charter High School in New Orleans, Louisiana, has weathered changes of many types, including Hurricane Katrina in 2005. After having to close for the 2005-2006 school year, the school reopened as a charter school with a board and stepped up its efforts to raise student achievement. Now the school is receiving attention for the…

  1. The Raman-Derived Carbonization Continuum: A Tool to Select the Best Preserved Molecular Structures in Archean Kerogens

    NASA Astrophysics Data System (ADS)

    Delarue, Frédéric; Rouzaud, Jean-Noël; Derenne, Sylvie; Bourbin, Mathilde; Westall, Frances; Kremer, Barbara; Sugitani, Kenichiro; Deldicque, Damien; Robert, François

    2016-06-01

    The search for indisputable traces of life in Archean cherts is of prime importance. However, their great age and metamorphic history pose constraints on the study of molecular biomarkers. We propose a quantitative criterion to document the thermal maturity of organic matter in rocks in general, and Archean rocks in particular. This is definitively required to select the best candidates for seeking non-altered sample remnants of life. Analysis of chemical (Raman spectroscopy, 13C NMR, elemental analysis) and structural (HRTEM) features of Archean and non-Archean carbonaceous matter (CM) that was submitted to metamorphic grades lower than, or equal to, that of greenschist facies showed that these features had all undergone carbonization but not graphitization. Raman-derived quantitative parameters from the present study and from literature spectra, namely, R1 ratio and FWHM-D1, were used to draw a carbonization continuum diagram showing two carbonization stages. While non-Archean samples can be seen to dominate the first stage, the second stage mostly consists of the Archean samples. In this diagram, some Archean samples fall at the boundary with non-Archean samples, which thus demonstrates a low degree of carbonization when compared to most Archean CM. As a result, these samples constitute candidates that may contain preserved molecular signatures of Archean CM. Therefore, with regard to the search for the oldest molecular traces of life on Earth, we propose the use of this carbonization continuum diagram to select the Archean CM samples.

  2. Activities in Teaching Weather

    ERIC Educational Resources Information Center

    Tonn, Martin

    1977-01-01

    Presented is a unit composed of activities for teaching weather. Topics include cloud types and formation, simple weather instruments, and the weather station. Illustrations include a weather chart and instruments. A bibliography is given. (MA)

  3. Early Archean Spherule Beds-Confirmation of Impact Origin

    NASA Technical Reports Server (NTRS)

    Shukolyukov, A.; Kyte, F. T.; Lugmair, G. W.; Lowe, D. R.; Byerly, G. R.

    2000-01-01

    The oldest record of major impact events on Earth may be a number of early Archean (3.5 to 3.2 Ga) spherule beds that have been identified in the Barberton Greenstone Belt, South Africa. Several field, petrographic, and geochemical criteria distinguish these beds from typical volcanic and clastic sediments. These criteria include the wide geographic distribution of two beds in a variety of depositional environments, the presence of relict quench textures, absence of juvenile volcaniclastic debris within the beds, and extreme enrichment of Ir and other platinum group elements (PGE) as compared to surrounding sediments. Some researchers, however, argued for a terrestrial origin for spherule bed formation, possibly related to volcanism and gold mineralization.

  4. Methane Greenhouses and Anti-Greenhouses During the Archean Era

    NASA Astrophysics Data System (ADS)

    Kasting, J. F.; Pavlov, A. A.

    2002-12-01

    Climate and life are coupled today through the biogeochemical carbon cycle, but they may have been even more tightly coupled in the distant past when atmospheric O2 levels were lower. The finding of mass-independently fractionated S isotopes in Archean rocks confirms that pO2 was very low, probably <10-13 times the present level, prior to 2.3 Ga (1). The Sun was also some 20 percent less luminous at this time (2). High CO2 levels were initially proposed to solve this `faint young Sun problem' (3); however, these levels are in conflict in data from paleosols (4). CH4 is an alternative greenhouse gas which could have kept the Archean climate warm if present at concentrations of 0.01-0.1 percent by volume (5). The primary source of methane is biological. CH4 is produced by methanogenic bacteria that today live in anaerobic environments such as the intestines of ruminants and the water-logged soils underlying rice paddies. During the Archean, however, methanogens should have been widespread, and the methane they produced would have had a long photochemical lifetimes, around 10,000 years (6). Most methanogens are thermophiles or hyperthermophiles, and those which are more thermophilic have shorter doubling times than those that prefer cooler temperatures. This suggests that a positive feedback loop may have existed, whereby methanogens warmed the climate by releasing CH4, which in turn promoted the proliferation of faster-growing methanogens. This positive feedback would have been halted, however, once the ratio of CH4 to CO2 in the atmosphere exceeded unity. At this point, polymerization of CH4 by solar UV radiation would have caused the formation of an organic haze layer similar to that observed today on Titan. Such a haze layer would have cooled the climate by creating an `anti-greenhouse effect.' This creates an overall negative feedback loop that may have been responsible for maintaining a stable Archean climate. The rise of O2 at 2.3 Ga disrupted this equilibrium

  5. Archean evolution of the Leo Rise and its Eburnean reworking

    NASA Astrophysics Data System (ADS)

    Thiéblemont, Denis; Goujou, Jean Christian; Egal, Emmanuel; Cocherie, Alain; Delor, Claude; Lafon, Jean Michel; Fanning, C. Mark

    2004-06-01

    Recent geological mapping in southeastern Guinea, supported by zircon dating, has called into question traditional understanding concerning the evolution of the Leo Rise. Gneiss dated at about 3540 Ma appears to constitute the earliest evidence for continental accretion within the Leo Rise. The existence of a Leonian depositional cycle at about 3000 Ma is confirmed, marked by volcanic and sedimentary rocks that can be correlated with the Loko Group in Sierra Leone. The span of ages (3244-3050 Ma) suggests that the Leonian cycle comprises different episodes whose respective chronology is as yet uncertain. Clearly distinct from the Leonian cycle, the Liberian cycle (˜2900-2800 Ma) is represented in Guinea by granite and migmatite (˜2910-2800 Ma), reflecting remobilization of the ancient Archean basement and deformation of the Leonian rocks; no deposition is associated with this cycle. After the Liberian, the Nimba and Simandou successions, containing Liberian detrital zircons, are assigned to the Birimian (˜2200-2000 Ma). Finally, Eburnean tectonism caused intense deformation of the Archean craton, accompanied by high-grade metamorphism and the intrusion of granite and syenite with ages between 2080 and 2020 Ma. The evolution of the Kénéma-Man domain, attributed to the cumulated effect of the Leonian and Liberian cycles, is thus in part Eburnean. We can suppose, therefore, that the NNE-SSW-trending structures attributed to the Liberian in Sierra Leone are, in fact, Eburnean. The Kambui Supergroup, also affected by this tectonism, should thus be assigned to the Birimian rather than the Liberian, which would explain its similarities with the Nimba and Simandou successions.

  6. Late Archean mafic volcanism in the Rainy Lake area, Minnesota

    SciTech Connect

    Day, W.C.

    1985-01-01

    The Late Archean greenstone-granite terrane of the Rainy Lake area of Minnesota contains a bimodal suite of mafic and felsic volcanic and coeval intrusive rocks. New geochemical data show that the mafic rocks occur in three distinct suites: (1) low-Ti olivine- and quartz-tholeiite, (2) high-Ti quartz-tholeiite and basaltic andesite, and (3) calc-alkaline lamprophyric monzodiorite and quartz diorite. The low-Ti tholeiites have only slightly evolved Mg-numbers from 53-63, Ni=125-300 ppm, and MORB-like REE. In contrast, the high-Ti tholeiites are more evolved, with Mg*=26-48, Ni=43-135 ppm, and higher total REE. Compared to the tholeiitic suites, the monzodiorite suite has more primitive Mg-numbers, with Mg*=70-78, Ni<410 ppm, and anomalously high LREE. The two tholeiitic suites cannot be genetically related by simple fractionation from a single parent magma; however, lower degrees of partial melting (<8 percent) of a mantle source (spinel periodotite) with REE=2-4 times chondrites could have produced the high-Ti tholeiites, and higher degrees of melting (20-30 percent) of a similar source could have generated the low-Ti tholeiites. In contrast, the monzodiorite suite must have been generated from either a LREE-rich or (and) a garnet-bearing source (garnet periodotite). The authors conclude that shallow melting (<40-50 km) within the Archean mantle in the Rainy Lake area produced the tholeiitic rocks, and that deep melting (>40-50 km) generated the lamprophyric monzodiorites.

  7. PGE Chemistry and Systematics of Some Archean Spherule Layers in the Barberton Mountain Land

    NASA Astrophysics Data System (ADS)

    Mohr-Westheide, T.; Reimold, W. U.; Greshake, A.; Hoehnel, D.; Fritz, J.; Schmitt, R. T.; Salge, T.; Hofmann, A.; Oezdemir, S.; Schulz, T.; Koeberl, C.

    2015-07-01

    Comprehensive study of petrographic, mineralogical, and geochemical characteristics from a set of new samples of Archean spherule layers in the ICDP drill core BARB5 and drill core CT3 from the Barberton Greenstone Belt (BGB), South Africa.

  8. Rare earth element patterns in Archean high-grade metasediments and their tectonic significance

    NASA Technical Reports Server (NTRS)

    Taylor, Stuart Ross; Rudnick, Roberta L.; Mclennan, Scott M.; Eriksson, Kenneth A.

    1986-01-01

    REE data on metasedimentary rocks from two different types of high-grade Archean terrains are presented and analyzed. The value of REEs as indicators of crustal evolution is explained; the three geologic settings (in North America, Southern Africa, and Australia) from which the samples were obtained are described; and the data are presented in extensive tables and graphs and discussed in terms of metamorphic effects, the role of accessory phases, provenance, and tectonic implications (recycling, the previous extent of high-grade terrains, and a model of Archean crustal growth). The diversity of REE patterns in shallow-shelf metasediments is attributed to local provenance, while the Eu-depleted post-Archean patterns are associated with K-rich plutons from small, stable early Archean terrains.

  9. Dating Archean zircon by ion microprobe: New light on an old problem

    NASA Technical Reports Server (NTRS)

    Williams, I. S.; Kinny, P. D.; Black, L. P.; Compston, W.; Froude, D. O.; Ireland, T. R.

    1985-01-01

    Ion microprobe analysis of zircons from three sites (Watersmeet Dome in northern Michigan, Mount Sones in eastern Antarctica, and Mount Narryer in western Australia) is discussed. Implications of the results to Archean geochronology and early Earth crust composition are addressed.

  10. Nature of the Coast Batholith, Southeastern Alaska: Are there Archean analogs

    NASA Technical Reports Server (NTRS)

    Barker, Fred; Arth, J. G.

    1988-01-01

    The comparison of Phanerozoic Andean margins and their possible Archean analogs was made. Geochemical and isotopic data was presented for the episodic intrusion of the elongate, continental margin Coast batholith of southeastern Alaska and British Columbia. The batholith was characterized as having been formed in direct response to subduction in accreted terranes of oceanic or slope origin. It was concluded that there were good analogs of the Coast batholith in Archean plutonic suites.

  11. Magnetotelluric survey to locate the Archean-Proterozoic suture zone in the northeastern Great Basin, Nevada, Utah, and Idaho

    USGS Publications Warehouse

    Sampson, Jay A.; Rodriguez, Brian D.

    2013-01-01

    North-central Nevada contains a large amount of gold in linear belts, the origin of which is not fully understood. During July 2008, September 2009, and August 2010, the U.S. Geological Survey, as part of the Assessment Techniques for Concealed Mineral Resources project, collected twenty-three magnetotelluric soundings along two profiles in Box Elder County, Utah; Elko County, Nevada; and Cassia, Minidoka, and Blaine Counties, Idaho. The main twenty-sounding north-south magnetotelluric profile begins south of Wendover, Nev., but north of the Deep Creek Range. It continues north of Wendover and crosses into Utah, with the north profile terminus in the Snake River Plain, Idaho. A short, three-sounding east-west segment crosses the main north-south profile near the northern terminus of the profile. The magnetotelluric data collected in this study will be used to better constrain the location and strike of the concealed suture zone between the Archean crust and the Paleoproterozoic Mojave province. This report releases the magnetotelluric sounding data that was collected. No interpretation of the data is included.

  12. Continental emergence in the Late Archean reconciles early and late continental growth models

    NASA Astrophysics Data System (ADS)

    Flament, Nicolas; Coltice, Nicolas; Rey, Patrice

    2014-05-01

    The analysis of ancient sediments (Rare Earth Element composition of black shales, isotopic strontium composition of marine carbonates, isotopic oxygen composition of zircons) suggests that continental growth culminated around the Archean-Proterozoic transition. In stark contrast, the geochemical analysis of ancient basalts suggests that depletion of the mantle occurred in the Hadean and Eoarchean. This paradox may be solved if continents were extracted from the mantle early in Earth's history, but remained mostly below sea level throughout the Archean. We present a model to estimate the area of emerged land and associated isotopic strontium composition of the mantle and oceans as a function of the coupled evolution of mantle temperature, continental growth and distribution of surface elevations (hypsometry). For constant continental hypsometry and four distinct continental growth models, we show that sea level was between 500 and 2000 m higher in the Archean than at present, resulting in < 12% of emerged land, compared to ~ 28% at present. If in addition the hot Archean lithosphere could not sustain high relief, as little as 2-3% of Earth's surface would have been emerged in the Archean. Using a geochemical box model for the strontium isotopic composition of the mantle and oceans, we show that a reduced area of emerged continental crust can explain why the geochemical fingerprint of continents extracted early in Earth's history was not recorded at the surface of the Earth until the late Archean.

  13. Investigation of Archean microfossil preservation for defining science objectives for Mars sample return missions

    NASA Astrophysics Data System (ADS)

    Lorber, K.; Czaja, A. D.

    2014-12-01

    Recent studies suggest that Mars contains more potentially life-supporting habitats (either in the present or past), than once thought. The key to finding life on Mars, whether extinct or extant, is to first understand which biomarkers and biosignatures are strictly biogenic in origin. Studying ancient habitats and fossil organisms of the early Earth can help to characterize potential Martian habitats and preserved life. This study, which focuses on the preservation of fossil microorganisms from the Archean Eon, aims to help define in part the science methods needed for a Mars sample return mission, of which, the Mars 2020 rover mission is the first step.Here is reported variations in the geochemical and morphological preservation of filamentous fossil microorganisms (microfossils) collected from the 2.5-billion-year-old Gamohaan Formation of the Kaapvaal Craton of South Africa. Samples of carbonaceous chert were collected from outcrop and drill core within ~1 km of each other. Specimens from each location were located within thin sections and their biologic morphologies were confirmed using confocal laser scanning microscopy. Raman spectroscopic analyses documented the carbonaceous nature of the specimens and also revealed variations in the level of geochemical preservation of the kerogen that comprises the fossils. The geochemical preservation of kerogen is principally thought to be a function of thermal alteration, but the regional geology indicates all of the specimens experienced the same thermal history. It is hypothesized that the fossils contained within the outcrop samples were altered by surface weathering, whereas the drill core samples, buried to a depth of ~250 m, were not. This differential weathering is unusual for cherts that have extremely low porosities. Through morphological and geochemical characterization of the earliest known forms of fossilized life on the earth, a greater understanding of the origin of evolution of life on Earth is gained

  14. Building early Archean cratons from recycled Hadean crust

    NASA Astrophysics Data System (ADS)

    O'Neil, J.; Carlson, R. W.; Boyet, M.

    2013-12-01

    The formation of Earth's early crust and the geological processes leading to creation and preservation of stable Archean cratons are still poorly understood. Archean terrains are dominated by felsic Tonalite-Trondhjemite-Granodiorite (TTG) rocks. These felsic rocks however, cannot be directly produced from melting of the mantle but must instead be derived from the melting of an older mafic precursor. Despite growing evidence for a basaltic >4.3 Ga primordial crust on Earth, there are only a few occurrences of zircons older than 4.0 Ga; in the Jack Hills conglomerates and in the Acasta gneisses. Only after ~3.8 Ga does the zircon record become more prominent. The zircon age distribution in itself suggests a long quiescence period of over half a billion years before the mafic primitive crust was extensively recycled to produce a significant amount of felsic magma. The Nuvvuagittuq greenstone belt (NGB) provides a glimpse at the nature of the mafic primitive crust. The mafic rocks from the Nuvvuagittuq greenstone belt (NGB), called the Ujaraaluk unit, have 146Sm-142Nd systematics consistent with them being formed in the Hadean, between 4.3 and 4.4 Ga. The NGB also comprises multiple generations of TTG ranging from 3.75 Ga to 3.35 Ga. Despite the fact that the mafic and felsic lithologies of the NGB show strong evidence of disturbance in the 147Sm-143Nd and 176Lu-177Hf long-lived isotopic systems, the NGB TTGs yield 142Nd and 182W anomalies that can be only generated in the Hadean. Moreover, zircons from the 3.35 to 3.65 TTGs have strongly subchondritic initial ɛHf values and display an ɛHf vs. age array consistent with their derivation from a Hadean mafic precursor. The NGB TTGs appear to have been formed primarily from melting of a source compositionally similar to the 4.4 Ga Ujaraaluk unit. The crustal history recorded in the NGB seems to be similar to the early crustal evolution recorded in the Jack Hills Hadean zircons where reworking of a >4.3 Ga enriched

  15. Dating of Archean basement in northeastern Wyoming and southern Montana.

    USGS Publications Warehouse

    Peterman, Z.E.

    1981-01-01

    Rb-Sr whole-rock and U-Pb zircon ages of granite and gneiss cores from three deep drill holes extend known occurrences of Archean rocks in the subsurface of NE Wyoming and S Montanta. Rb-Sr and K- Ar mineral ages are discordant and reflect early or middle Proterozoic disturbance. Highly altered rocks occur in a thin zone immediately below the sub-Cambrian unconformity. Samples from a few metres deeper in the basement are much fresher but show the effects of this alteration in filled fractures and thin adjacent alteration haloes. Whole-rock Rb-Sr systems have retaioned a fair degree of integrity in spite of increased susceptibility to modification because of the disturbed mineral systems. Interaction of the rocks with water a few metres below the sub-Cambrian unconformity probably occurred for only a relatively short time. Fractures filled rapidly with secondary minerals such as chlorite, anhydrite, and carbonate to maintain a relatively impermeable crystalline basement in which the silicates and their contained isotopic systems were preserved.- Author

  16. A Coupled General Circulation Model of the Archean Earth

    NASA Astrophysics Data System (ADS)

    Wolf, E. T.; Toon, O. B.

    2011-12-01

    We present results from a new coupled general circulation model suitable for deep paleoclimate studies. Particular interest is given to the faint young Sun paradox. The model is based on the Community Earth System Model maintained by the National Center for Atmospheric Research [1]. Prognostic atmosphere, ocean, land, ice, and hydrological cycle models are coupled. A new correlated-k radiative transfer model has been implemented allowing accurate flux calculations for anoxic atmospheres containing high concentrations of CO2 and CH4 [2, 3]. This model represents a significant improvement upon one-dimensional radiative-convective climate models used previously to study ancient climate [4]. Cloud and ice albedo feedbacks will be accurately quantified and new constraints on Archean surface temperatures will be revealed. References [1] Collins W.D. et al. "Description of the NCAR Community Atmosphere Model (CAM 3.0)." NCAR Technical Note, 2004. [2] Toon O.B., McKay, C.P., Ackerman, T.P. "Rapid Calculation of Radiative Heating Rates and Photodissociation Rates in Inhomogeneous Multiple Scattering Atmospheres." J. Geo. Res., 94(D13), 16287 - 16301, 1989. [3] Mlawer, E.J., et al. "Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave." J. Geo. Res., 102(D14), 16663 - 16682, 1997. [4] Kasting J.F., Pollack, J.B., Crisp, D. "Effects of High CO2 Levels on Surface Temperature and Atmospheric Oxidation State of the Early Earth." J. Atm. Chem., 1, 403-428, 1984.

  17. Lithopsheric anisotropy in the Archean Slave craton, Canada

    NASA Astrophysics Data System (ADS)

    Snyder, D. B.; Bostock, M.; Lockhart, G. D.

    2003-12-01

    Shear wave anisotropy and discontinuity studies of teleseismic earthquakes recorded at single seismic stations help to define vertical mantle stratigraphic columns. Beneath the Archean outcrops of the central Slave craton seismic discontinuities at 38, 115, 140, and 190 km appear to bound two distinct anisotropic layers. The discontinuity at 38 km is the Moho; discontinuities at 110-120 and 140-150 km depths observed at multiple nearby stations indicate that a layer of low velocity or distinct anisotropy exists between these depths. The coherent pulses at about 13 seconds on the radial component indicates a strong decrease in velocity at 110 km depth north and west of the Ekati diamond mine, but not to the south. The response on the transverse component indicates a rotation of anisotropic fabric at 117 km depth, a reversal at 140 km, and another rotation at 190 km. A flip in polarity at a back azimuth of about 280° occurs in the 117 km discontinuity and apparently marks an axis of symmetry of anisotropy, here probably the dip direction of steep layering or planar fabric. SKS anisotropy studies at this station indicate that the upper of two anisotopic layers has a fast-axis direction of 010° . Geochemical studies of xenolith samples from nearby kimberlites suggest that the boundaries at 115 and 140 bound a layer of ultra-depleted harzburgite, almost pure olivine, that formed as oceanic crust.

  18. Archean foreland basin tectonics from the Witwatersrand, South Africa

    SciTech Connect

    Burke, K.; Kidd, W.S.F.; Kusky, T.M.

    1985-01-01

    The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These and other features indicate that the Witwatersrand strata were deposited in a foreland basin. A regional geologic synthesis suggests that his basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. We suggest that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Striking similarities are seen between this phase of Witwatersrand Basin evolution and active basins located north of the Tibetan Plateau. The geologic evidence is not so compatible with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben.

  19. Archean foreland basin tectonics in the Witwatersrand, South Africa

    SciTech Connect

    Burke, K.; Kidd, W.S.F.; Kusky, T.M.

    1986-06-01

    The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These features indicate that the Witwatersrand strata may have been deposited in a foreland basin and a regional geologic synthesis suggests that this basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. It is suggested that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Similarities are seen between this Phase of Witywatersrand Basin evolution and that of active basins north of the Tibetan Plateau. The geologic evidence does not agree with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben. 64 references.

  20. Archean foreland basin tectonics in the Witwatersrand, South Africa

    NASA Technical Reports Server (NTRS)

    Burke, K.; Kidd, W. S. F.; Kusky, T. M.

    1986-01-01

    The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These features indicate that the Witwatersrand strata may have been deposited in a foreland basin and a regional geologic synthesis suggests that this basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. It is suggested that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Similarities are seen between this phase of Witwatersrand Basin evolution and that of active basins north of the Tibetan Plateau. The geologic evidence does not agree with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben.

  1. Archean foreland basin tectonics in the Witwatersrand, South Africa

    NASA Technical Reports Server (NTRS)

    Burke, K.; Kidd, W. S. F.; Kusky, T. M.

    1986-01-01

    The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These features indicate that the Witwatersrand strata may have been deposited in a foreland basin and a regional geologic synthesis suggests that this basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. It is suggested that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Similarities are seen between this Phase of Witywatersrand Basin evolution and that of active basins north of the Tibetan Plateau. The geologic evidence does not agree with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben.

  2. Archean regional transpression and paleomagnetism in northwestern Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Werner, T.; Dehls, J. F.; Spark, R. N.

    1993-04-01

    The Archean metamorphic rocks of the Superior province of the Canadian Shield occur in lithologically defined belts or subprovinces. The tectonically more stable interiors of belts possess consistent primary components of magnetic remanence. In the case of the Quetico belt, these stable directions are tightly grouped about 005°/55° with some minor dispersion and most were acquired during the cooling that followed syntectonic recrystallisation. This study examines the directions of primary remanence components for rocks along the margins of the Quetico belt, within 4 km of the strongly deformed vertical, ENE-trending boundaries. The boundaries are known to have experienced dextral transpression involving penetrative single-phase deformation which out-lasted metamorphism. Within a few kilometres of the belt boundaries, the primary remanence components are re-distributed along a vertical ENE-trending, great-circle girdle which is nearly parallel to the plane of transpressive shear and regional schistosity. It is suggested that the effects of transpression have mechanically deflected the components of primary remanence toward this plane.

  3. Forecasting the Weather.

    ERIC Educational Resources Information Center

    Bollinger, Richard

    1984-01-01

    Presents a computer program which predicts the weather based on student input of such weather data as wind direction and barometric pressure. Also provides procedures for several hands-on, weather-related activities. (JN)

  4. Weather in the News.

    ERIC Educational Resources Information Center

    Markle, Sandra

    1989-01-01

    A discussion of TV weather forecasting introduces this article which features several hands-on science activities involving observing, researching, and experimenting with the weather. A reproducible worksheet on the reliability of weather forecasts is included. (IAH)

  5. The Archean crust in the Wawa-Chapleau-Timmins region. A field guidebook prepared for the 1983 Archean Geochemistry-Early Crustal Genesis Field Conference

    NASA Technical Reports Server (NTRS)

    Percival, J. A.; Card, K. D.; Sage, R. P.; Jensen, L. S.; Luhta, L. E.

    1983-01-01

    This guidebook describes the characteristics and interrelationships of Archean greenstone-granite and high-grade gneiss terrains of the Superior Province. A 300-km long west to east transect between Wawa and Timmins, Ontario will be used to illustrate regional-scale relationships. The major geological features of the Superior Province are described.

  6. Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere.

    PubMed

    Pavlov, A A; Kasting, J F

    2002-01-01

    Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.

  7. Archean orthogneiss lithologies of Northern Yellowstone National Park and their geochemical contribution to the younger rhyolites

    NASA Astrophysics Data System (ADS)

    Tarbert, K.; Larson, P. B.

    2010-12-01

    The Archean rocks within the northern section of Yellowstone National Park have yet to be thoroughly analyzed so that their role in the genesis of the young rhyolite magmas that erupted from calderas in the Park can be evaluated. Major and trace element concentrations and stable and radiogenic isotope ratios have been measured for three separate orthogneiss units that are representative of the Park's dominant Archean units. Preliminary major element analyses indicate that partial melting of more primitive Archean lithologies may have produced the more evolved Archean igneous units. This is illustrated by a large gap in the silica compositions (between 54 and 64 wt. percent) of exposed plutonic rocks. REE data indicate enrichment of the HREE to variable degrees and both positive and negative Eu anomalies. Aside from one unit that displays a negative Eu anomaly, these lithologies are not readily distinguishable by REE compositions alone. The young Lava Creek and Canyon Flow Tuff rhyolites have similar HREE patterns and slightly enriched LREE when compared to the orthogneiss samples. Partial melting or assimilation of the Archean granites can produce the observed increase in the young rhyolites LREE. Primary feldspar O isotope ratios range from 6.8 to 8.9 per mil, which are significantly higher than the low O ratios found in some of the young rhyolites. Epsilon Nd values for the Archean rocks are very low and range from -35.8 to -41.5. The young rhyolites have low epsilon Nd values but not as low as the range of the Archean rocks. We can now begin to assess the role that these units have as components in the younger rhyolitic magmas. Preliminary models show that partial melting or assimilation of the Archean rocks can reasonably contribute a significant part to the young rhyolites. In addition to identifying a major contributor to the Yellowstone rhyolites, these data provide insight to the main facies that constitute the basement rocks buried beneath the younger

  8. Generation of felsic crust in the Archean: a geodynamic modeling perspective

    NASA Astrophysics Data System (ADS)

    Sizova, Elena; Gerya, Taras; Stüwe, Kurt; Brown, Michael

    2015-04-01

    The relevance of contemporary tectonics to the formation of the Archean terrains is a matter of vigorous debate. Higher mantle temperatures and higher radiogenic heat production in the past would have impacted on the thickness and composition of the oceanic and continental crust. As a consequence of secular cooling, there is generally no modern analog to assist in understanding the tectonic style that may have operated in the Archean. For this reason, well-constrained numerical modeling, based on the fragmentary evidence preserved in the geological record, is the most appropriate tool to evaluate hypotheses of Archean crust formation. The main lithology of Archean terrains is the sodic tonalite-trondhjemite-granodiorite (TTG) suite. Melting of hydrated basalt at garnet-amphibolite to eclogite facies conditions is considered to be the dominant process for the generation of the Archean TTG crust. Taking into account geochemical signatures of possible mantle contributions to some TTGs, models proposed for the formation of Archean crust include subduction, melting at the bottom of thickened continental crust and fractional crystallization of mantle-derived melts under water-saturated conditions. We evaluated these hypotheses using a 2D coupled petrological-thermomechanical numerical model with initial conditions appropriate to the Eoarchean-Mesoarchean. As a result, we identified three tectonic settings in which intermediate to felsic melts are generated by melting of hydrated primitive basaltic crust: 1) delamination and dripping of the lower primitive basaltic crust into the mantle; 2) local thickening of the primitive basaltic crust; and, 3) small-scale crustal overturns. In addition, we consider remelting of the fractionated products derived from underplated dry basalts as an alternative mechanism for the formation of some Archean granitoids. In the context of a stagnant lid tectonic regime which is intermittently terminated by short-lived subduction, we identified

  9. The Raman-Derived Carbonization Continuum: A Tool to Select the Best Preserved Molecular Structures in Archean Kerogens

    PubMed Central

    Rouzaud, Jean-Noël; Derenne, Sylvie; Bourbin, Mathilde; Westall, Frances; Kremer, Barbara; Sugitani, Kenichiro; Deldicque, Damien; Robert, François

    2016-01-01

    Abstract The search for indisputable traces of life in Archean cherts is of prime importance. However, their great age and metamorphic history pose constraints on the study of molecular biomarkers. We propose a quantitative criterion to document the thermal maturity of organic matter in rocks in general, and Archean rocks in particular. This is definitively required to select the best candidates for seeking non-altered sample remnants of life. Analysis of chemical (Raman spectroscopy, 13C NMR, elemental analysis) and structural (HRTEM) features of Archean and non-Archean carbonaceous matter (CM) that was submitted to metamorphic grades lower than, or equal to, that of greenschist facies showed that these features had all undergone carbonization but not graphitization. Raman-derived quantitative parameters from the present study and from literature spectra, namely, R1 ratio and FWHM-D1, were used to draw a carbonization continuum diagram showing two carbonization stages. While non-Archean samples can be seen to dominate the first stage, the second stage mostly consists of the Archean samples. In this diagram, some Archean samples fall at the boundary with non-Archean samples, which thus demonstrates a low degree of carbonization when compared to most Archean CM. As a result, these samples constitute candidates that may contain preserved molecular signatures of Archean CM. Therefore, with regard to the search for the oldest molecular traces of life on Earth, we propose the use of this carbonization continuum diagram to select the Archean CM samples. Key Words: Archean—Early life—Kerogen—Raman spectroscopy—Carbonization. Astrobiology 16, 407–417. PMID:27186810

  10. Reconstructing Earth's Surface Oxidation Across The Archean- Proterozoic Transition

    NASA Astrophysics Data System (ADS)

    Kaufman, A. J.; Guo, Q.; Strauss, H.; Schröder, S.; Gutzmer, J.; Wing, B. A.; Baker, M.; Bekker, A.; Jin, Q.; Kim, S.; Farquhar, J.

    2010-12-01

    The Archean-Proterozoic transition is characterized by the widespread deposition of organic-rich shale, sedimentary iron formation, glacial diamictite, and marine carbonates recording profound carbon isotope anomalies, but notably lacks bedded evaporites. All deposits reflect environmental changes in oceanic and atmospheric redox states, in part associated with Earth’s earliest ice ages. Time-series data for multiple sulfur isotopes from carbonate associated sulfate as well as sulfides in the glaciogenic Duitschland Formation of the Transvaal Supergroup, South Africa, capture the concomitant buildup of sulfate in the ocean and the loss of mass independent sulfur isotope fractionation. This is arguably associated with the atmospheric rise of oxygen (as well as the protective ozone layer) coincident with profound changes in ocean chemistry and biology. The loss of the MIF signal within the Duitschland succession is in phase with the earliest recorded positive carbon isotope anomaly, convincingly linking these environmental perturbations to the Great Oxidation Event (ca. 2.3 Ga). The emergence of cyanobacteria and oxygenic photosynthesis may be associated with a geochemical “whiff of oxygen” recorded in 2.5 Ga sediments. If true, the delay in the GOE can then be understood in terms of a finite sink for molecular oxygen - ferrous iron, which was abundant in deep Neoarchean seawater and sequestered in a worldwide episode of iron formation deposition ending shortly before accumulation of the Duitschland Formation. Insofar as early Paleoproterozoic glaciation is associated with oxygenation of a methane-rich atmosphere, we conclude that Earth’s earliest ice age(s) and the onset of a modern and far more energetic carbon cycle are directly related to the global expansion of cyanobacteria that released oxygen to the environment, and of eukaryotes that respired it.

  11. The Building of the Archean Superior Craton: Thermal Perspective

    NASA Astrophysics Data System (ADS)

    Jaupart, C. P.; Mareschal, J. C.

    2014-12-01

    The building of a craton involves the extraction of continental crust from the Earth's mantle and the lateral accretion of juvenile volcanic terranes. Ascertaining which conditions allow a newborn continental assemblage to survive requires information on its mechanical strength, which depends on the amount and vertical distribution of radioactive elements in the crust. There is thus a connection between crust formation mechanisms and a successful amalgamation process. To address outstanding questions concerning Archean cratons, the Superior province in Canada is the perfect region because it contains a well preserved geological record of accretion that provides compelling evidence for plate tectonic processes at 2.7 Ga. At almost the same time, the rate of continental growth decreased significantly, which may result from either slower crust formation or enhanced destruction through erosion and subduction. These issues are linked to the strength of the newborn continent. The extensive heat flow data set now available in the Superior Province reveals a clear demarcation between a chemically depleted and differentiated craton core and weakly differentiated enriched juvenile accreted terranes. The Superior craton was thus made of a strong core surrounded by weak terranes. This dichotomy implies that the accretion process could not involve complex imbrication of the accreted belts into the craton core. Subsequently, the craton may have been protected from convective disruption or delamination by its weak margins. Differences between the craton core and accreted terranes may be due to different crustal extraction processes, such as melting in a mantle plume or magmatism in a subduction zone. If subduction started at about 3 Ga, as advocated by several authors, the assembly and survival of large cratons may well be a consequence of this key shift in mantle activity. Alternatively, the chemical depletion of the craton core may be due to a prolonged history of internal

  12. Natural Weathering Rates of Silicate Minerals

    NASA Astrophysics Data System (ADS)

    White, A. F.

    2003-12-01

    mechanisms between climate and chemical weathering. On timescales longer than a million years, atmospheric CO2 levels have been primarily controlled by the balance between the rate of volcanic inputs from the Earth's interior and the rate of uptake through chemical weathering of silicates at the Earth's surface (Ruddiman, 1997). Weathering is proposed as the principal moderator in controlling large increases and decreases in global temperature and precipitation through the greenhouse effects of CO2 over geologic time (R. A. Berner and E. K. Berner, 1997). Weathering processes observed in paleosols, discussed elsewhere in this volume (see Chapter 5.18), have also been proposed as indicating changes in Archean atmospheric CO2 and O2 levels (Ohmoto, 1996; Rye and Holland, 1998).

  13. Imaging the Moho and V(p)/V(s) ratio in the western Superior Archean craton with wide angle reflections

    USGS Publications Warehouse

    Kay, I.; Musacchio, G.; White, D.; Asudeh, I.; Roberts, B.; Forsyth, D.; Hajnal, Z.; Koperwhats, B.; Farrell, D.

    1999-01-01

    A refraction/wide-angle reflection survey in northwestern Ontario investigated the Archean Superior Province of the Canadian Shield. Images of apparent Moho topography were produced from both the PmP and SmS Moho wide angle reflections. The average Moho depth is 41 km, and average P- and S-wave velocities 6.6 and 3.8 (??0.05) km/s respectively. The Moho dips southward from 39.5 to 42 km depth over roughly 400 km. From ratios of S and P travel times to the Moho, profiles of V(p)/V(s) were constructed. The average V(p)/V(s) ratios are 1.74 and 1.76 for on the E-W and N-S lines (Poisson's ratio ?? = 0.253 and 0.262 respectively). V(p)/V(s) profiles show a sharp increase from west to east and a gradual increase from north to south, correlating with the distribution of more felsic continental crust and composite crust in the Western Superior.A refraction/wide-angle reflection survey in northwestern Ontario investigated the Archean Superior Province of the Canadian Shield. Images of apparent Moho topography were produced from both the PmP and SmS Moho wide angle reflections. The average Moho depth is 41 km, and average P- and S-wave velocities 6.6 and 3.8 (?? 0.05) km/s respectively. The Moho dips southward from 39.5 to 42 km depth over roughly 400 km. From ratios of S and P travel times to the Moho, profiles of Vp/Vs were constructed. The average Vp/Vs ratios are 1.74 and 1.76 for on the E-W and N-S lines (Poisson's ratio ?? = 0.253 and 0.262 respectively). Vp/Vs profiles show a sharp increase from west to east and a gradual increase from north to south, correlating with the distribution of more felsic continental crust and composite crust in the Western Superior.

  14. Teaching Weather Concepts.

    ERIC Educational Resources Information Center

    Sebastian, Glenn R.

    Ten exercises based on the weather map provided in the national newspaper "U.S.A. Today" are used to teach intermediate grade students about weather. An overview describes the history of "U.S.A. Today," the format of the newspaper's weather map, and the map's suitability for teaching weather concepts. Specific exercises, which are briefly…

  15. Fun with Weather

    ERIC Educational Resources Information Center

    Yildirim, Rana

    2007-01-01

    This three-part weather-themed lesson for young learners connects weather, clothing, and feelings vocabulary. The target structures covered are: asking about the weather; comparing weather; using the modal auxiliary, should; and the question word, when. The lessons utilize all four skills and include such activities as going outside, singing,…

  16. Weather in Your Life.

    ERIC Educational Resources Information Center

    Kannegieter, Sandy; Wirkler, Linda

    Facts and activities related to weather and meteorology are presented in this unit. Separate sections cover the following topics: (1) the water cycle; (2) clouds; (3) the Beaufort Scale for rating the speed and force of wind; (4) the barometer; (5) weather prediction; (6) fall weather in Iowa (sleet, frost, and fog); (7) winter weather in Iowa…

  17. The Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

    NASA Technical Reports Server (NTRS)

    Brendt. Emily; Zavodsky, Bradley; Jedlovec, Gary; Elmer, Nicholas

    2014-01-01

    Tropopause folds are identified by warm, dry, high-potential vorticity, ozone-rich air and are one explanation for damaging non-convective wind events. Could improved model representation of stratospheric air and associated tropopause folding improve non-convective wind forecasts and high wind warnings? The goal of this study is to assess the impact of assimilating Hyperspectral Infrared (IR) profiles on forecasting stratospheric air, tropopause folds, and associated non-convective winds: (1) AIRS: Atmospheric Infrared Sounder (2) IASI: Infrared Atmospheric Sounding Interferometer (3) CrIMSS: Cross-track Infrared and Microwave Sounding Suite

  18. The nature of Archean terrane boundaries: an example from the northern Wyoming Province

    USGS Publications Warehouse

    Mogk, D.W.; Mueller, P.A.; Wooden, J.L.

    1992-01-01

    The Archean northern Wyoming Province can be subdivided into two geologically distinct terranes, the Beartooth-Bighorn magmatic terrane (BBMT) and the Montana metasedimentary terrane (MMT). The BBMT is characterized by voluminous Late Archean (2.90-2.74 Ga) magmatic rocks (primarily tonalite, trondhjemite, and granite); metasedimentary rocks are preserved only as small, rare enclaves in this magmatic terrane. The magmatic rocks typically have geochemical and isotopic signatures that suggest petrogenesis in a continental magmatic arc environment. The MMT, as exposed in the northern Gallatin and Madison Ranges, is dominated by Middle Archean trondhjemitic gneisses (3.2-3.0 Ga); metasedimentary rocks, however, are significantly more abundant than in the BBMT. Each terrane has experienced a separate and distinct geologic history since at least 3.6 Ga ago based on differences in metamorphic and structural styles, composition of magmatic and metasupracrustal rocks, and isotopic ages; consequently, these may be described as discrete terranes in the Cordilleran sense. Nonetheless, highly radiogenic and distinctive Pb-Pb isotopic signatures in rocks of all ages in both terranes indicate that the two terranes share a significant aspect of their history. This suggests that these two Early to Middle Archean crustal blocks, that initially evolved as part of a larger crustal province, experienced different geologic histories from at least 3.6 Ga until their juxtaposition in the Late Archean (between 2.75 to 2.55 Ga ago). Consequently, the boundary between the BBMT and MMT appears to separate terranes that are not likely to be exotic in the sense of their Phanerozoic counterparts. Other Archean provinces do appear to contain crustal blocks with different isotopic signatures (e.g. West Greenland, India, South Africa). The use of the term exotic, therefore, must be cautious in situations where geographic indicators such as paleontologic and/or paleomagnetic data are not available

  19. Apparent polar wander paths and the close of late Archean crustal transpression, northern Ontario

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Lemmetty, T. J.; Werner, T.

    2003-08-01

    Lamprophyre dikes of the southern Superior Province of the Canadian Shield crosscut Archean structures, including a late Archean unconformity and its overlying younger Archean Timiskaming sedimentary and volcanic rocks. The dikes also cut the single schistosity that formed in these rocks. Nevertheless, the lamprophyre dikes show a weak internal tectonic fabric that is approximately parallel to the schistosity in the bedrock and oblique to dike walls. The consistent orientation of this internal tectonic fabric has been recognized in every lamprophyre dike using anisotropy of magnetic susceptibility (AMS). Thus the lamprophyre dikes provide a useful chronological marker, trapping the last pulse of Archean tectonism. Unfortunately, our previous attempts to compare the lamprophyre paleopoles with those of the age-calibrated apparent polar wander path (APWP) failed because it was not possible to isolate separate young and old components of magnetization. That failure occurred due to the overlap of blocking temperatures or coercivities for the different characteristic vector components [, 1994a]. Using new cores from the same specimens, here we distinguish successfully between consistently oriented vector components by using low-temperature demagnetization (LTD) before thermal demagnetization. Although the paleopoles appear well defined, comparisons with published APWPs for the Superior Province from late Archean [, 1979; , 1983; , 1994] to early Proterozoic [, 2000] are difficult. Moreover, the earlier parts of the paths are progressively less precise and complete. Nevertheless, A component remanences for the dikes give a paleopole near the path at ˜2650 Ma. For a Timiskaming volcanic breccia with a U-Pb age of 2696 Ma the A component paleopole may lie between 2600 and 2650 Ma. B component remanences yield paleopoles in the NW Pacific region, incompatible with any proposed Archean path but perhaps representing some much younger Proterozoic remagnetization event (e

  20. Micro Weather Station

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E.

    1999-01-01

    Improved in situ meteorological measurements in the troposphere and stratosphere are needed for studies of weather and climate, both as a primary data source and as validation for remote sensing instruments. Following the initial development and successful flight validation of the surface acoustic wave (SAW) hygrometer, the micro weather station program was directed toward the development of an integrated instrument, capable of accurate, in situ profiling of the troposphere, and small enough to fly on a radiosonde balloon for direct comparison with standard radiosondes. On April 23, 1998, working with Frank Schmidlin and Bob Olson of Wallops Island Flight Facility, we flew our instrument in a dual payload experiment, for validation and direct comparison with a Vaisala radiosonde. During that flight, the SAW dewpoint hygrometer measured frostpoint down to -76T at 44,000 feet. Using a laptop computer in radio contact with the balloon, we monitored data in real time, issued the cutdown command, and recovered the payload less than an hour after landing in White Sands Missile Range, 50 miles from the launch site in Hatch, New Mexico. Future flights will extend the intercomparison, and attempt to obtain in situ meteorological profiles from the surface through the tropopause. The SAW hygrometer was successfully deployed on the NASA DC8 as part of NASA's Third Convection and Moisture Experiment (CAMEX-3) during August and September, 1998. This field campaign was devoted to the study of hurricane tracking and intensification using NASA-funded aircraft. In situ humidity data from the SAW hygrometer are currently being analyzed and compared with data from other instruments on the DC8 and ER2 aircraft. Additional information is contained in the original.

  1. Variations in the magnitude of non mass dependent sulfur fractionation in the Archean atmosphere

    NASA Astrophysics Data System (ADS)

    Claire, M.; Kasting, J. F.

    2010-12-01

    Recent experimental data have enabled quantitatively meaningful computations of the non-mass dependent fractionation of sulfur’s isotopes (Δ33S) that exemplify the Archean rock record. The Δ33S signal originates as a result of fine structure in the absorption cross-section of SO2 isotopologues [1], which only undergo significant photolysis in reducing atmospheres [2]. The Δ33S signal produced by SO2 photolysis varies significantly between 190 and 220 nm, and thus is strongly dependent on any other atmospheric gases which absorb photons in this range [3], as well as the height at which photolysis occurs. A model that is capable of resolving the altitude-dependent radiative transfer through a realistic self-consistent reducing atmosphere is therefore essential when making direct comparisons between atmospheric Δ33S production and the rock record. In this work, we investigate how the magnitude of Δ33S might vary as function of atmospheric composition, which in turn allows the rock record to constrain the Archean atmosphere. Other recent work on this topic using simplied atmospheric models has implicated large concentrations of SO2 [5], OCS [3], and CO2 [6] as being responsible for the variations in Archean Δ33S. We present results from an altitude-dependent photochemical model of Archean photochemistry [4] of necessary complexity to resolve the complicated redox structure of the Archean atmosphere. We show that while increased concentrations of these gases all affect Δ33S in an unconstrained model, the atmospheric conditions required for OCS or SO2 shielding are unlikely to occur in an Archean atmosphere constrained by reasonable expectations of volcanic and biogenic fluxes. Within the context of plausible Archean atmospheres, we investigate how shielding due to changing amounts of CO2, biogenic sulfur gases, and fractal organic haze [7] affect the magnitude of Δ33S produced by the Archean atmosphere, and show why simplified atmospheric modeling may lead to

  2. An Archean Terrestrial Fractionation Line for Oxygen Isotopes

    NASA Astrophysics Data System (ADS)

    Rumble, D.; Blake, R. E.; Bao, H.; Bowring, S.; Komiya, T.; Rosing, M.; Ueno, Y.

    2008-12-01

    The Terrestrial Fractionation Line (TFL) for oxygen isotopes is defined by 17O/16O and 18O/16O analyses of meteoric waters, seawater, sedimentary, metamorphic, and igneous rocks and constituent minerals. Interlaboratory measurements of the slope of the TFL on a plot of d18O vs. d17O revealed eclogitic garnets with a slope of 0.526 and hydrothermal quartz of 0.524 from rocks younger than 0.8 Ga (Giga years before present). New measurements show Archean metamorphic rocks and minerals from Barberton, (3.2 Ga, S. Africa), Isua (3.8 Ga, Greenland), and Acasta (4.0 Ga, Canada) have a slope of 0.524 +/- 0.002 (95% confidence, MSWD = 0.66). Analysis of Ag3PO4 prepared from apatite mineral separates from Isua meta-sediments gives a slope of 0.509 +/- 0.022 (95% confidence, MSWD = 0.59). Taken at face value, steeper slopes on a d17O vs. d18O diagram indicate an approach towards isotope exchange equilibrium. Lower slopes are expected when isotope fractionation is kinetically controlled. The lower slope of 0.509 for Isua apatite suggests that the formation of orthophosphate was kinetically controlled. Kinetic fractionations are known to occur during catalysis of reactions by enzymes secreted by microbes. Enzymatic catalysis confers an advantage on organisms because energy-producing reactions may be induced to occur at lower temperature conditions more accessible to the organism. May it be definitively concluded that enzymatic catalysis was responsible for the measured 0.509 slope? No, abiotic kinetic fractionation cannot be disproven with existing data. The preparation of Ag3PO4 from apatite may have introduced kinetic fractionation as an analytical artifact. Conclusions fully supported by the data suggest: (1) Mixing accompanying the violent birth of the Earth- Moon system had already succeeded in establishing Earth's current oxygen isotope composition by 4.0 Ga; and (2) No trace of an episode of late heavy meteorite bombardment remains in the oxygen isotope compositions of

  3. Paleoproterozoic magmatism across the Archean-Proterozoic boundary in central Fennoscandia: Geochronology, geochemistry and isotopic data (Sm-Nd, Lu-Hf, O)

    NASA Astrophysics Data System (ADS)

    Lahtinen, Raimo; Huhma, Hannu; Lahaye, Yann; Lode, Stefanie; Heinonen, Suvi; Sayab, Mohammad; Whitehouse, Martin J.

    2016-10-01

    The central Fennoscandia is characterized by the Archean-Proterozoic (AP) boundary and the Central Finland Granitoid Complex (CFGC), a roundish area of approximately 40,000 km2 surrounded by supracrustal belts. Deep seismic reflection profile FIRE 3A runs across these units, and we have re-interpreted the profile and crustal evolution along the profile using 1.92-1.85 Ga plutonic rocks as lithospheric probes. The surface part of the profile has been divided into five subareas: Archean continent (AC) in the east, AP, CFGC, boundary zone (BZ) and the Bothnian Belt (BB) in the west. There are 12 key samples from which zircons were studied for inclusions and analyzed (core-rim) by ion probe for U-Pb dating and oxygen isotopes, followed by analyzes for Lu-Hf by LA-MC-ICP-MS. The AC plutonic rocks (1.87-1.85 Ga) form a bimodal suite, where the proposed mantle source for the mafic rocks is 2.1-2.0 Ga metasomatized lower part of the Archean subcontinental lithospheric mantle (SCLM) and the source for the felsic melts is related plume-derived underplated mafic material in the lower crust. Variable degrees of contamination of the Archean lower crust have produced "subduction-like" Nb-Ta anomalies in spidergrams and negative εNd (T) values in the mafic-intermediate rocks. The felsic AC granitoids originate from a low degree melting of eclogitic or garnet-bearing amphibolites with titanite ± rutile partly prevailing in the residue (Nb-Ta fractionation) followed by variable degree of assimilation/melting of the Archean lower crust. The AP plutonic rocks (ca. 1.88 Ga) can be divided into I-type and A-type granitoids (AP/A), where the latter follow the sediment assimilation trend in ASI diagram, have high δ18O values (up to 8‰) in zircons and exhibit negative Ba anomalies (Rb-Ba-Th in spidergram), as found in sedimentary rocks. A mixing/assimilation of enriched mantle-derived melts with melts from already migmatized sedimentary rocks ± amphibolites is proposed. The CFGC is

  4. What Solutions Caused Noachian Weathering on Mars?

    NASA Astrophysics Data System (ADS)

    Zolotov, M. Y.

    2015-12-01

    The stratified sequence of Al-rich and Fe/Mg phyllosilicates in Noachian formations indicates widespread chemical weathering of mafic materials [1]. The composition of alteration solutions could be inferred from the mineralogy of weathering profiles and models for water-rock interaction. We have developed numerical models for basalt weathering by acidic solutions with different concentrations of weak (H2CO3) and strong (H2SO4, HCl) acids equilibrated with low- and high-pressure CO2 atmospheres. The results show that the observed clay stratigraphies could be produced by neutral to strongly acidic solutions. Weathering by solutions equilibrated with dense CO2 atmospheres produces abundant carbonates at depth, which are not observed in clay stratigraphies. The development of weathering profiles by S-, Cl-free solutions equilibrated with 6 mbar CO2 requires large volumes of water. These volumes are inconsistent with density and orientation of Noachian valley networks and climate models [3-5]. Weathering by sulfate-free fluids does not produce abundant Ca sulfates reported in the Mawrth Valley region [2]. Weathering by low-pH H2SO4-bearing solutions does not require elevated water/rock ratios, a warm climate, or a dense CO2 atmosphere. It leads to formation of Ca sulfates in middle parts of weathering profiles together with neutralized Mg-rich sulfate solutions at depth. The weathering could have occurred through transient volcanism- and impact-generated supply of strong acids, and volcanism-, impact-, obliquity-related warming and partial ice melting, consistent with climate models [3-5]. Refs: [1] Carter, J. et al. (2015), Icarus 248, 373-382. [2] Wray, J. J. et al. (2010), Icarus 209, 416-421. [3] Wordsworth, R. et al. (2013), Icarus 222, 1-19. [4] Mischna, M. A. et al. (2013), J. Geophys. Res. Planets 118, 518-576. [5] Halevy, I., Head, J.W. (2014), Nature Geosci. 7, 865-868.

  5. Pilot weather advisor

    NASA Technical Reports Server (NTRS)

    Kilgore, W. A.; Seth, S.; Crabill, N. L.; Shipley, S. T.; Graffman, I.; Oneill, J.

    1992-01-01

    The results of the work performed by ViGYAN, Inc., to demonstrate the Pilot Weather Advisor cockpit weather data system using a broadcast satellite communication system are presented. The Pilot Weather Advisor demonstrated that the technical problems involved with transmitting significant amount of weather data to an aircraft in-flight or on-the-ground via satellite are solvable with today's technology. The Pilot Weather Advisor appears to be a viable solution for providing accurate and timely weather information for general aviation aircraft.

  6. Texture-specific Si isotope variations in Barberton Greenstone Belt cherts record low temperature fractionations in early Archean seawater

    NASA Astrophysics Data System (ADS)

    Stefurak, Elizabeth J. T.; Fischer, Woodward W.; Lowe, Donald R.

    2015-02-01

    diagenesis and metamorphism, although fractionations during diagenetic phase transformations may have affected certain textures. We interpret these systematic variations to reflect fractionation during silica precipitation as well as isotopically distinct fluids from which later phases originated. SIMS δ18O values fall in a range from 16.39‰ to 23.39‰ (n = 381), similar to previously published data from bulk gas source mass spectrometry of Onverwacht cherts. We observed only limited examples of texture-related variation in δ18O and did not observe correlation of δ18O with δ30Si trends. This is consistent with hypotheses that Si isotope ratios are more resistant to alteration under conditions of rock-buffered diagenesis (Marin-Carbonne et al., 2011). Our results indicate that low temperature processes fractionated silicon isotopes in early Archean marine basins, a behavior that probably precludes the application of chert δ30Si as a robust paleothermometer. The values we observe for facies that sedimentological and petrographic observations indicate formed as primary and earliest diagenetic silica precipitates from seawater are more 30Si-rich than that expected for bulk silicate Earth. This is consistent with the hypothesis that the silicon isotope budget is balanced by the coeval deposition of 30Si-enriched cherts and 30Si-depleted iron formation lithologies. Precipitation of authigenic clay minerals in both terrestrial and marine settings may have also comprised a large 30Si-depleted sink, with the corollary of an important non-carbonate alkalinity sink consuming cations released by silicate weathering.

  7. Post-Archean formation of the lithospheric mantle in the central Siberian craton: Re-Os and PGE study of peridotite xenoliths from the Udachnaya kimberlite

    NASA Astrophysics Data System (ADS)

    Ionov, Dmitri A.; Doucet, Luc S.; Carlson, Richard W.; Golovin, Alexander V.; Korsakov, Andrey V.

    2015-09-01

    The formation age of the Siberian cratonic mantle is not well established. Re-Os data on various mantle-derived materials brought up by kimberlite magmas have shown that it contains Archean components, but the reported ages range broadly (3.4 to <1 Ga). We report Re-Os isotope and PGE concentration data for a suite of 29 fresh, well-characterized xenoliths from the Udachnaya-East kimberlite representing all major peridotite rock types and a large part of the cratonic mantle profile. Several xenoliths with very low Os contents (<0.3 ppb) and/or high Re/Os ratios are not suitable for age estimates. The Os (and Ir) depletions are common in cpx-bearing spinel harzburgites and coarse garnet harzburgites, but are not found in deformed, high-T peridotites. Twenty refractory (Al2O3 0.1-1.6%) peridotites yield TRD ages from 0.9 to 2.2 Ga. TRD for a subset of six high-Mg# (0.92-0.93), low-T (⩽930 °C) spinel harzburgites and a single garnet harzburgite yield a narrow range from 2.0 to 2.2 Ga with an average of 2.1 ± 0.1 Ga, which we consider the best estimate for the age of the melting event that initially formed the lithospheric mantle beneath Udachnaya. The TRD estimates for less refractory (Mg# 0.907-0.919) deformed garnet peridotites show a greater range and are generally lower (0.9-2.0 Ga; average 1.54 ± 0.28 Ga) apparently due to the effects of melt metasomatism on the initial melting residues. The predominant part of the mantle in the central Siberian craton formed in the Paleoproterozoic and not in the Archean, unlike cratons in southern Africa and North America. Minor older components reported earlier from Udachnaya may be fragments of pre-existing lithosphere trapped during stacking of melting residues formed about 2 Ga ago. We argue that the formation of cratonic lithospheric mantle, with common high-Mg# (⩾0.92) and opx-enriched peridotites, was not limited to the Archean as previously thought, but continued in the Paleoproterozoic, i.e. that asthenospheric

  8. Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere

    PubMed Central

    Ventura, Gregory T.; Kenig, Fabien; Reddy, Christopher M.; Schieber, Juergen; Frysinger, Glenn S.; Nelson, Robert K.; Dinel, Etienne; Gaines, Richard B.; Schaeffer, Philippe

    2007-01-01

    Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed by thermal stress, are present in solvent extracts of 2,707- to 2,685-million-year-old (Ma) metasedimentary rocks from Timmins, ON, Canada. These lipids appear in conventional gas chromatograms as unresolved complex mixtures and include cyclic and acyclic biphytanes, C36–C39 derivatives of the biphytanes, and C31–C35 extended hopanes. Biphytane and extended hopanes are also found in high-pressure catalytic hydrogenation products released from solvent-extracted sediments, indicating that archaea and bacteria were present in Late Archean sedimentary environments. Postdepositional, hydrothermal gold mineralization and graphite precipitation occurred before metamorphism (≈2,665 Ma). Late Archean metamorphism significantly reduced the kerogen's adsorptive capacity and severely restricted sediment porosity, limiting the potential for post-Archean additions of organic matter to the samples. Argillites exposed to hydrothermal gold mineralization have disproportionately high concentrations of extractable archaeal and bacterial lipids relative to what is releasable from their respective high-pressure catalytic hydrogenation product and what is observed for argillites deposited away from these hydrothermal settings. The addition of these lipids to the sediments likely results from a Late Archean subsurface hydrothermal biosphere of archaea and bacteria. PMID:17726114

  9. Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere.

    PubMed

    Ventura, Gregory T; Kenig, Fabien; Reddy, Christopher M; Schieber, Juergen; Frysinger, Glenn S; Nelson, Robert K; Dinel, Etienne; Gaines, Richard B; Schaeffer, Philippe

    2007-09-04

    Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed by thermal stress, are present in solvent extracts of 2,707- to 2,685-million-year-old (Ma) metasedimentary rocks from Timmins, ON, Canada. These lipids appear in conventional gas chromatograms as unresolved complex mixtures and include cyclic and acyclic biphytanes, C36-C39 derivatives of the biphytanes, and C31-C35 extended hopanes. Biphytane and extended hopanes are also found in high-pressure catalytic hydrogenation products released from solvent-extracted sediments, indicating that archaea and bacteria were present in Late Archean sedimentary environments. Postdepositional, hydrothermal gold mineralization and graphite precipitation occurred before metamorphism (approximately 2,665 Ma). Late Archean metamorphism significantly reduced the kerogen's adsorptive capacity and severely restricted sediment porosity, limiting the potential for post-Archean additions of organic matter to the samples. Argillites exposed to hydrothermal gold mineralization have disproportionately high concentrations of extractable archaeal and bacterial lipids relative to what is releasable from their respective high-pressure catalytic hydrogenation product and what is observed for argillites deposited away from these hydrothermal settings. The addition of these lipids to the sediments likely results from a Late Archean subsurface hydrothermal biosphere of archaea and bacteria.

  10. Deformation coupling between the Archean Pukaskwa intrusive complex and the Hemlo shear zone, Superior Province, Canada

    NASA Astrophysics Data System (ADS)

    Liodas, Nathaniel T.; Gébelin, Aude; Ferré, Eric C.; Misgna, Girmay M.

    2013-11-01

    Archean greenstone belts typically form narrow sheared basins separating bulbous tonalo-trondjhemo-granodioritic (TTG) intrusive complexes. The role played by gravity in the development of such dome-and-keel structures constitutes a key question in Archean tectonics. The Pukaskwa intrusive complex (PIC)-Hemlo greenstone belt system stands as a remarkable example of the dome-and-keel architecture that commonly occurs in Archean terrains. Abundant strain markers in the greenstone belt and in the Hemlo shear zone (HSZ) attest of late sinistral strike-slip kinematics (D2) whereas, in general, the quartzofeldspathic coarse-grained rocks of the Pukaskwa intrusive complex bear little macroscopically visible kinematic indicators, most likely due to pervasive recrystallization. The PIC consists dominantly of a heterogeneous assemblage of TTG plutonic rocks and gneisses, which overall are less dense than the greenstone rocks. The study of anisotropy of magnetic susceptibility (AMS), based on 120 stations and 1947 specimens from the PIC, reveals east-west trending prolate and plano-linear fabrics across the northern margin of the complex, i.e., along the HSZ. Since geotherms were higher in the Archean than in the present, the effective viscosity of the TTG units would have been sufficiently low to allow their diapiric ascent through denser greenstone rocks. Here we propose an alternative model where thrust tectonics is responsible for the early structuration of the PIC. Later transpressive tectonics causes strain localization along internal strike-slip shear zones and along lithological boundaries.

  11. Non-enzymatic glycolysis and pentose phosphate pathway-like reactions in a plausible Archean ocean.

    PubMed

    Keller, Markus A; Turchyn, Alexandra V; Ralser, Markus

    2014-04-25

    The reaction sequences of central metabolism, glycolysis and the pentose phosphate pathway provide essential precursors for nucleic acids, amino acids and lipids. However, their evolutionary origins are not yet understood. Here, we provide evidence that their structure could have been fundamentally shaped by the general chemical environments in earth's earliest oceans. We reconstructed potential scenarios for oceans of the prebiotic Archean based on the composition of early sediments. We report that the resultant reaction milieu catalyses the interconversion of metabolites that in modern organisms constitute glycolysis and the pentose phosphate pathway. The 29 observed reactions include the formation and/or interconversion of glucose, pyruvate, the nucleic acid precursor ribose-5-phosphate and the amino acid precursor erythrose-4-phosphate, antedating reactions sequences similar to that used by the metabolic pathways. Moreover, the Archean ocean mimetic increased the stability of the phosphorylated intermediates and accelerated the rate of intermediate reactions and pyruvate production. The catalytic capacity of the reconstructed ocean milieu was attributable to its metal content. The reactions were particularly sensitive to ferrous iron Fe(II), which is understood to have had high concentrations in the Archean oceans. These observations reveal that reaction sequences that constitute central carbon metabolism could have been constrained by the iron-rich oceanic environment of the early Archean. The origin of metabolism could thus date back to the prebiotic world.

  12. Winter Weather Checklists

    MedlinePlus

    ... About CDC.gov . Natural Disasters and Severe Weather Earthquakes Being Prepared Emergency Supplies Home Hazards Indoor Safety ... Matters What's New Preparation & Planning Disasters & Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis Volcanoes ...

  13. Winter Weather: Frostbite

    MedlinePlus

    ... About CDC.gov . Natural Disasters and Severe Weather Earthquakes Being Prepared Emergency Supplies Home Hazards Indoor Safety ... Matters What's New Preparation & Planning Disasters & Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis Volcanoes ...

  14. Winter Weather: Outdoor Safety

    MedlinePlus

    ... About CDC.gov . Natural Disasters and Severe Weather Earthquakes Being Prepared Emergency Supplies Home Hazards Indoor Safety ... Matters What's New Preparation & Planning Disasters & Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis Volcanoes ...

  15. Winter Weather Emergencies

    MedlinePlus

    Severe winter weather can lead to health and safety challenges. You may have to cope with Cold related health problems, including ... there are no guarantees of safety during winter weather emergencies, you can take actions to protect yourself. ...

  16. Exploring Archean seawater sulfate via triple S isotopes in carbonate associated sulfate.

    NASA Astrophysics Data System (ADS)

    Paris, G.; Fischer, W. W.; Sessions, A. L.; Adkins, J. F.

    2015-12-01

    Multiple sulfur isotope ratios in Archean sedimentary rocks provide powerful insights into the behavior of the ancient sulfur cycle, the redox state of fluid Earth, and the timing of the rise of atmospheric oxygen [1]. The Archean sulfur isotope record is marked by pronounced mass-independent fractionation (Δ33S≠0)—signatures widely interpreted as the result of SO2 photolysis from "short-wavelength" UV light resulting in a reduced phase carrying positive Δ33S values (ultimately recorded in pyrite) and an oxidized phase carrying negative Δ33S values carried by sulfate [2]. Support for this hypothesis rests on early laboratory experiments and observations of negative Δ33S from barite occurrences in mixed volcanic sedimentary strata in Mesoarchean greenstone terrains. Despite forming the framework for understanding Archean sulfur cycle processes, this hypothesis is still largely untested, notably due to the lack of sulfate minerals in Archean strata. Using a new MC-ICP-MS approach combined with petrography and X-ray spectroscopy we have generated a growing S isotope dataset from CAS extracted from Archean carbonates from a range of sedimentary successions, including: the 2.6 to 2.521 Ga Campbellrand-Malmani carbonate platform (Transvaal Supergroup, South Africa), 2.7 Ga Cheshire Formation (Zimbabwe), and 2.9 Ga Steep Rock Formation (Canada). Importantly, we observe positive δ34S and Δ33S values across a range of different lithologies and depositional environments. These results demonstrate that dissolved sulfate in seawater was characterized by positive Δ33S values—a result that receives additional support from recent laboratory and theoretical experiments [e.g. 4, 5]. [1] Farquhar et al., 2000, Science [2] Farquhar et al., 2001, Journal of Geophysical Research: Planets [3] Paris et al., 2014, Science. [4] Whitehill et al., 2013, Proceedings of the National Academy of Sciences. [5] Claire et al., 2014 Geochimica et Cosmochimica Acta

  17. The Archean geology of the Godthabsfjord Region, southern west Greenland (includes excursion guide)

    NASA Technical Reports Server (NTRS)

    Mcgregor, V. R.; Nutman, A. P.; Friend, C. R. L.

    1986-01-01

    The part of the West Greenland Archean gneiss complex centered around Godthabsfjord and extending from Isukasia in the north to south Faeringehavn is studied. Extensive outcrops of 3800 to 3400 Ma rocks can provide some direct evidence of conditions and processes that operated on the Earth in the early Archean. However, the ways in which primary characteristics have been modified by later deformation, metamorphism, and chemical changes are first taken into account. The rocks exposed are the products of two major phases of accretion of continental crust, at 3800 to 3700 Ma and 3100 to 29 Ma. The main features of these two accretion phases are similar, but careful study of the least modified rocks may reveal differences related to changes in the Earth in the intervening period. The combination of excellent exposure over an extensive area, relatively detailed geological mapping of much of the region, and a considerable volume of isotopic and other geochemical data gives special insights into processes that operated at moderately deep levels of the crust in the Archean. Of particular interest is the effect of late Archean granulite facies metamorphism on early Archean rocks, especially the extent to which isotope systems were disturbed. Similar processes may well have partly or wholly destroyed evidence of more ancient components of other high grade terrains. This account does not attempt to be an exhaustive review of all work carried out on the geology of the region. Rather, it attempts to summarize aspects of the geology and some interest in the context of early crustal genesis.

  18. Diversity in the Archean biosphere: new insights from NanoSIMS.

    PubMed

    Oehler, Dorothy Z; Robert, François; Walter, Malcolm R; Sugitani, Kenichiro; Meibom, Anders; Mostefaoui, Smail; Gibson, Everett K

    2010-05-01

    The origin of organic microstructures in the approximately 3 Ga Farrel Quartzite is controversial due to their relatively poor state of preservation, the Archean age of the cherts in which they occur, and the unusual spindle-like morphology of some of the forms. To provide more insight into the significance of these microstructures, nano-scale secondary ion mass spectrometry (NanoSIMS) maps of carbon, nitrogen, sulfur, silicon, and oxygen were obtained for spheroidal and spindle-shaped constituents of the Farrel Quartzite assemblage. Results suggest that the structures are all bona fide approximately 3 Ga microfossils. The spindles demonstrate an architecture that is remarkable for 3 Ga organisms. They are relatively large, robust, and morphologically complex. The NanoSIMS element maps corroborate their complexity by demonstrating an intricate, internal network of organic material that fills many of the spindles and extends continuously from the body of these structures into their spearlike appendages. Results from this study combine with previous morphological and chemical analyses to argue that the microstructures in the Farrel Quartzite comprise a diverse assemblage of Archean microfossils. This conclusion adds to a growing body of geochemical, stromatolitic, and morphological evidence that indicates the Archean biosphere was varied and well established by at least approximately 3 Ga. Together, the data paint a picture of Archean evolution that is one of early development of morphological and chemical complexity. The evidence for Archean evolutionary innovation may augur well for the possibility that primitive life on other planets could adapt to adverse conditions by ready development of diversity in form and biochemistry.

  19. American Weather Stories.

    ERIC Educational Resources Information Center

    Hughes, Patrick

    Weather has shaped United States' culture, national character and folklore; at times it has changed the course of history. The seven accounts compiled in this publication highlight some of the nation's weather experiences from the hurricanes that threatened Christopher Columbus to the peculiar run of bad weather that has plagued American…

  20. Aviation weather services

    NASA Technical Reports Server (NTRS)

    Sprinkle, C. H.

    1983-01-01

    The primary responsibilities of the National Weather Service (NWS) are to: provide warnings of severe weather and flooding for the protection of life and property; provide public forecasts for land and adjacent ocean areas for planning and operation; and provide weather support for: production of food and fiber; management of water resources; production, distribution and use of energy; and efficient and safe air operations.

  1. Weather Fundamentals: Meteorology. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series, for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes) looks at how meteorologists gather and interpret current weather data collected from sources…

  2. Cold-Weather Sports

    MedlinePlus

    ... Surgery? A Week of Healthy Breakfasts Shyness Cold-Weather Sports KidsHealth > For Teens > Cold-Weather Sports Print A A A What's in this ... Equipment Ahh, winter! Shorter days. Frigid temperatures. Foul weather. What better time to be outdoors? Winter sports ...

  3. Hot Weather Tips

    MedlinePlus

    ... FCA - A A + A You are here Home HOT Weather Tips Printer-friendly version We all suffer in hot weather. However, for elderly and disabled people and ... stress and following these tips for dealing with hot weather. Wear cool clothing: See that the person ...

  4. Weatherization and Intergovernmental Program - Weatherization Assistance Program

    SciTech Connect

    2010-06-01

    The U.S. Department of Energy’s (DOE) Weatherization Assistance Program reduces energy costs for low-income households by increasing the energy efficiency of their homes, while ensuring their health and safety.

  5. Structural development of an Archean Orogen, Western Point Lake, Northwest Territories

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy M.

    1991-08-01

    The Point Lake orogen in the central Archean Slave Province of northwestern Canada preserves more than 10 km of structural relief through an eroded antiformal thrust stack and deeper anastomosing midcrustal mylonites. Fault restoration along a 25 km long transect requires a minimum of 69 km slip and 53 km horizontal shortening. In the western part of the orogen the basal decollement places mafic plutonic/volcanic rocks over an ancient tonalitic gneiss complex. Ten kilometers to the east in the Keskarrah Bay area, slices of gneiss unroofed on brittle thrusts shed molasse into several submerged basins. Conglomerates and associated thinly bedded sedimentary rocks are interpreted as channel, levee, and overbank facies of this thrust-related sedimentary fan system. The synorogenic erosion surface at the base of the conglomerate truncates premetamorphic or early metamorphic thrust faults formed during foreland propagation, while other thrusts related to hinterland-progressing imbrication displace this unconformity. Tightening of synorogenic depositional troughs resulted in the conglomerates' present localization in synclines to the west of associated thrust faults and steepening of structural dips. Eastern parts of the orogen consist of isoclinally folded graywackes composed largely of Mutti and Ricci-Lucchi turbidite facies B, C, and D, interpreted as submarine fan deposits eroded from a distant volcanic arc. Thrust faults in the metasedimentary terrane include highly disrupted slate horizons with meter-scale duplex structures, and recrystallized calcmylonites exhibiting sheath folds and boudin trains with very large interboudin distances. The sequence of fabric development and the overall geometry of this metasedimentary terrane strongly resembles younger forearc accretionary prisms. Conditions of deformation along the thrusts parallel the regional metamorphic zonation: amphibolite facies in the basal decollement through greenschist facies shear zones to cataclastic

  6. Speculations on the Archean mantle: Missing link between komatiite and depleted garnet peridotite

    NASA Astrophysics Data System (ADS)

    Takahashi, Eiichi

    1990-09-01

    Like in the modern Earth, thermal and tectonic regime of the planet in the Archean (>=2.5 Ga) may have been dominated by those activities on the ocean floor. Because of the continuous operation of plate tectonics, however, the geologic record of the Archean ocean floor has been eliminated a long time ago. Using high-pressure melting experiment data on a mantle peridotite and some key observations on Archean rocks (DGPs and PKs), a model for mid-oceanic ridge in the Archean (AMOR) is constructed. High magnesian peridotitic komatiites (PKs, MgO>=33 wt%) which are limited only on the oldest cratons (>=3.3 Ga) are considered to have been produced by partial melting of mantle peridotite at >=7 GPa and >=1800°C. Less magnesian PKs (MgO>=25 wt%) which are characteristic of the latest Archean (>=2.5 Ga) may have been produced at >=4 GPa and >=1650°C. Potential mantle temperatures (PMTs) of the Earth were estimated from the above two constraints on PKs and that for the genesis of mid-ocean ridge basalts (MORBs) in the modern Earth; PMT=1750°C at 3.5 Ga, 1600°C at 2.5 Ga, and 1280°C at present. If estimated cooling rate of the Earth's mantle (1.3°C/ 107 years) is valid for another 5×108 years or so, PMT will become lower than mantle solidus, and then plate tectonics would cease. Very depleted garnet peridotites (DGPs) found as xenoliths in south African kimberlites show distinct chemical trends compared with spinel and garnet peridotites found in young orogenic terrains and oceanic regions. Re-Os isotopic analyses on bulk xenoliths and Sm-Nd model ages of garnets in diamonds in them indicate that DGPs have undergone extensive partial melting and melt extraction in the early Archean. The bulk chemical trends of DGPs can be explained by extraction of PK magma from primitive mantle peridotite. A 40-60 wt% extraction of PK magma ranging from 25 to 35 wt% MgO would suffice to yield entire spectrum of DGPs. A hypothesis for their origin by global melting (magma ocean) of

  7. A much warmer Earth surface for most of geologic time: implications to biotic weathering

    NASA Technical Reports Server (NTRS)

    Schwartzman, D. W.; McMenamin, M.

    1993-01-01

    The authors present two scenarios for the temperature history of Earth. One scenario is conventional, the other relies on a warmer history. Both scenarios include surface cooling determined by the evolution of the biosphere and are similar until the Proterozoic period. The warmer scenario requires a higher plant/lichen terrestrial biota to increase weathering intensity. Justification for a warmer surface includes period temperatures from the oxygen isotope record of coexisting phosphates and cherts, an upper limit of 58 degrees C from primary gypsum precipitation, and the lack of fractionation of sulfur isotopes between sulfide and sulfates in Archean sediments.

  8. Characterization of the Weatherization Assistance Program network. Weatherization Assistance Program

    SciTech Connect

    Mihlmester, P.E.; Koehler, W.C. Jr.; Beyer, M.A.; Brown, M.A.; Beschen, D.A. Jr.

    1992-02-01

    The Characterization of the Weatherization Assistance Program (WAP) Network was designed to describe the national network of State and local agencies that provide WAP services to qualifying low-income households. The objective of this study was to profile the current WAP network. To achieve the objective, two national surveys were conducted: one survey collected data from 49 State WAP agencies (including the coterminous 48 States and the District of Columbia), and the second survey collected data from 920 (or 81 percent) of the local WAP agencies.

  9. Discovering the Carrier Phase of the Extraterrestrial Component in Archean Spherule Layers, Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Mohr-Westheide, T.; Fritz, J.; Reimold, W. U.; Schmitt, R. T.; Hofmann, A.; Koeberl, C.; Luais, B.; Tagle, R.; Salge, T.; Hoehnel, D.

    2014-09-01

    Comprehensive study of sedimentary, petrographic, mineralogical, and geochemical characteristics from a set of new samples of Archean spherule layers in the ICDP Drill Core BARB5 from the Barite Valley.

  10. The weathering of municipal solid waste incineration bottom ash evaluated by some weathering indices for natural rock.

    PubMed

    Takahashi, Fumitake; Shimaoka, Takayuki

    2012-12-01

    The weathering of municipal solid waste incineration (MSWI) residues consists of complicated phenomena. This makes it difficult to describe leaching behaviors of major and trace elements in fresh/weathered MSWI bottom ash, which was relevant interactively to pH neutralization and formation of secondary minerals. In this study, mineralogical weathering indices for natural rock profiles were applied to fresh/landfilled MSWI bottom ash to investigate the relation of these weathering indices to landfill time and leaching concentrations of component elements. Tested mineralogical weathering indices were Weathering Potential Index (WPI), Ruxton ratio (R), Weathering Index of Parker (WIP), Vogt's Residual Index (V), Chemical Index of Alternation (CIA), Chemical Index of Weathering (CIW), Plagioclase Index of Alternation (PIA), Silica-Titania Index (STI), Weathering Index of Miura (Wm), and Weatherability index of Hodder (Ks). Welch's t-test accepted at 0.2% of significance level that all weathering indices could distinguish fresh and landfilled MSWI bottom ash. However, R and STI showed contrasted results for landfilled bottom ash to theoretical expectation. WPI, WIP, Wm, and Ks had good linearity with reclamation time of landfilled MSWI bottom ash. Therefore, these four indices might be applicable as an indicator to identify fresh/weathered MSWI bottom ash and to estimate weathering time. Although WPI had weak correlation with leachate pH, other weathering indices had no significant correlation. In addition, all weathering indices could not explain leaching concentration of Al, Ca, Cu, and Zn quantitatively. Large difficulty to modify weathering indices correctly suggests that geochemical simulation including surface sorption, complexation with DOM, and other mechanisms seems to be the only way to describe leaching behaviors of major and trace elements in fresh/weathered MSWI bottom ash.

  11. Space Weathering of Rocks

    NASA Technical Reports Server (NTRS)

    Noble, Sarah

    2011-01-01

    Space weathering discussions have generally centered around soils but exposed rocks will also incur the effects of weathering. On the Moon, rocks make up only a very small percentage of the exposed surface and areas where rocks are exposed, like central peaks, are often among the least space weathered regions we find in remote sensing data. However, our studies of weathered Ap 17 rocks 76015 and 76237 show that significant amounts of weathering products can build up on rock surfaces. Because rocks have much longer surface lifetimes than an individual soil grain, and thus record a longer history of exposure, we can study these products to gain a deeper perspective on the weathering process and better assess the relative impo!1ance of various weathering components on the Moon. In contrast to the lunar case, on small asteroids, like Itokowa, rocks make up a large fraction of the exposed surface. Results from the Hayabusa spacecraft at Itokowa suggest that while the low gravity does not allow for the development of a mature regolith, weathering patinas can and do develop on rock surfaces, in fact, the rocky surfaces were seen to be darker and appear spectrally more weathered than regions with finer materials. To explore how weathering of asteroidal rocks may differ from lunar, a set of ordinary chondrite meteorites (H, L, and LL) which have been subjected to artificial space weathering by nanopulse laser were examined by TEM. NpFe(sup 0) bearing glasses were ubiquitous in both the naturally-weathered lunar and the artificially-weathered meteorite samples.

  12. Establishing Denudation Chronology through Weathering Geochronology

    NASA Astrophysics Data System (ADS)

    Riffel, S. B.; Vasconcelos, P. M.; Farley, K. A.; Carmo, I. O.

    2011-12-01

    Planar landforms - erosion surfaces - are used as temporal markers in denudation chronology. These surfaces are interpreted as the result of long-term weathering and denudation controlled by a specific base level within a given time-interval characterized by long-term tectonic stability. The presence of several planar landforms at distinct elevations is interpreted as evidence for distinct denudation events, separated by periods of tectonic reactivation and crustal uplift. We selected an area in the Paraná-La Plata basin, southern Brazil (25°S lat.) to investigate if the application of weathering geochronology by the 40Ar/39Ar and (U-Th)/He methods could permit differentiating different elevation landsurfaces. We dated supergene Mn oxyhydroxides by 40Ar/39Ar geochronology and coexisting supergene Fe oxyhydroxides by the (U-Th)/He method from one of the three regional landsurfaces - The First, Second, and Third Paraná plateaus - previously identified in this area. Two sites were sampled from the Second Paraná Plateau: a ferricrust at Serra das Almas (7 hand specimens of goethite at 1080 m of altitude) and deeply weathered ferricretes and saprolites at Vila Velha (11 hand specimens of cryptomelane and 14 of goethite at 910 m of altitude). The Serra das Almas sites hosts a stratified weathering profile with ferricrust, and mottle zone. The Vila Velha site results from intense weathering that led to the precipitation of well-crystallized supergene minerals precipitated within fractures in the saprolites. The geochronological results are correlatable between the two sites and the two distinct methods (40Ar/39Ar and (U-Th)/He), and they reveal three generations of weathering and mineral precipitation: Late Eocene-Oligocene, Early Miocene, and Pleistocene. The geochronological results suggested that the Second Paraná Plateau formed by regional erosion during the Oligocene, and that this landsurface has been continuously exposed to weathering and erosion since then

  13. Returning from the deep: Archean atmospheric fingerprints in modern hotspot lavas (Invited)

    NASA Astrophysics Data System (ADS)

    Jackson, M. G.; Cabral, R. A.; Rose-Koga, E. F.; Koga, K. T.; Whitehouse, M. J.; Antonelli, M. A.; Farquhar, J.; Day, J. M.; Hauri, E. H.

    2013-12-01

    Ocean plates transport surface materials, including oceanic crust and sediment, into the mantle at subduction zones. However, the fate of the subducted package--oceanic crust and sediment--in the mantle is poorly understood. A long-standing hypothesis maintains that subducted materials reside in the mantle for an extended, but unknown, period of time and are then recycled back to the Earth's surface in regions of buoyantly upwelling mantle and melted beneath hotspots. Sulfur isotopes provide an important new tool to evaluate the presence of ancient recycled materials in hotspot lavas. Widespread terrestrial mass independently fractionated sulfur (MIF-S) isotope signatures were generated exclusively through atmospheric photochemical reactions until ~2.45 Ga. In fact, the only significant reservoirs of MIF-S containing rocks documented so far are sediments and hydrothermal rocks older than ~2.45 Ga. Armed with this insight, we examined sulfur isotopes in olivine phenocrysts and olivine-hosted sulfides in lavas from the island of Mangaia, Cook Islands. Lavas from this location host unusually radiogenic Pb-isotopic compositions--referred to as a HIMU (high U/Pb) component--and this has been attributed to ancient recycled oceanic crust in the mantle source. In Cabral et al. (2013), we report MIF-S in olivine phenocrysts and olivine-hosted sulfides. The discovery of MIF-S isotopic signatures in young hotspot lavas appears to provide a "timestamp" and "signature" for preservation of subducted Archean surface materials in the mantle sourcing Mangaia lavas. We report new sulfur isotope data on olivine-hosted sulfides from the Mangaia lavas that reinforce our discovery of MIF-S anomalies reported in Cabral et al. (2013). We also report new sulfur isotopic data on Mangaia whole rock powders, and we find no evidence of MIF-S signatures. It is not yet clear why the individual Mangaia sulfides and the olivine separates have more extreme MIF-S than the whole rocks. We consider it

  14. NASA Connect: 'Plane Weather'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Excerpt from the NASA Connect show 'Plane Weather' This clip explains what high and low pressure weather systems are, and how these affect weather patterns. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.

  15. Tales of future weather

    NASA Astrophysics Data System (ADS)

    Hazeleger, W.; van den Hurk, B. J. J. M.; Min, E.; van Oldenborgh, G. J.; Petersen, A. C.; Stainforth, D. A.; Vasileiadou, E.; Smith, L. A.

    2015-02-01

    Society is vulnerable to extreme weather events and, by extension, to human impacts on future events. As climate changes weather patterns will change. The search is on for more effective methodologies to aid decision-makers both in mitigation to avoid climate change and in adaptation to changes. The traditional approach uses ensembles of climate model simulations, statistical bias correction, downscaling to the spatial and temporal scales relevant to decision-makers, and then translation into quantities of interest. The veracity of this approach cannot be tested, and it faces in-principle challenges. Alternatively, numerical weather prediction models in a hypothetical climate setting can provide tailored narratives for high-resolution simulations of high-impact weather in a future climate. This 'tales of future weather' approach will aid in the interpretation of lower-resolution simulations. Arguably, it potentially provides complementary, more realistic and more physically consistent pictures of what future weather might look like.

  16. Explaining the structure of the Archean mass-independent sulfur isotope record.

    PubMed

    Halevy, Itay; Johnston, David T; Schrag, Daniel P

    2010-07-09

    Sulfur isotopes in ancient sediments provide a record of past environmental conditions. The long-time-scale variability and apparent asymmetry in the magnitude of minor sulfur isotope fractionation in Archean sediments remain unexplained. Using an integrated biogeochemical model of the Archean sulfur cycle, we find that the preservation of mass-independent sulfur is influenced by a variety of extra-atmospheric mechanisms, including biological activity and continental crust formation. Preservation of atmospherically produced mass-independent sulfur implies limited metabolic sulfur cycling before approximately 2500 million years ago; the asymmetry in the record indicates that bacterial sulfate reduction was geochemically unimportant at this time. Our results suggest that the large-scale structure of the record reflects variability in the oxidation state of volcanic sulfur volatiles.

  17. The rock components and structures of Archean greenstone belts: An overview

    NASA Technical Reports Server (NTRS)

    Lowe, D. R.; Byerly, G. R.

    1986-01-01

    Knowledge of the character and evolution of the Earth's early crust is derived from the studies of the rocks and structures in Archean greenstone belts. Ability to resolve the petrologic, sedimentological and structural histories of greenstone belts, however, hinges first on an ability to apply the concepts and procedures of classical stratigraphy. Unfortunately, early Precambrian greenstone terrains present particular problems to stratigraphic analysis. Many current controversies of greenstone belt petrogenesis, sedimentology, tectonics and evolution arise more from an inability to develop a clear stratigraphic picture of the belts than from ambiguities in interpretation. Four particular stratigraphic problems that afflict studies of Archean greenstone belts are considered: determination of facing directions, correlation of lithologic units, identification of primary lithologies and discrimination of stratigraphic versus structural contacts.

  18. Fiskenaesset Anorthosite Complex: Stable isotope evidence for shallow emplacement into Archean ocean crust

    SciTech Connect

    Peck, W.H.; Valley, J.W.

    1996-06-01

    Oxygen and hydrogen isotope ratios indicate that unusual rocks at the upper contact of the Archean Fiskenaesset Anorthosite Complex at Fiskenaesset Harbor (southwest Greenland) are the products of hydrothermal alteration by seawater at the time of anorthosite intrusion. Subsequent granulite-facies metamorphism of these Ca-poor and Al- and Mg-rich rocks produced sapphirine- and kornerupine-bearing assemblages. Because large amounts of surface waters cannot penetrate to depths of 30 km during granulite-facies metamorphism, the isotopic signature of the contact rocks must have been obtained prior to regional metamorphism. The stable isotope and geochemical characteristics of the contact rocks support a model of shallow emplacement into Archean ocean crust for the Fiskenaesset Anorthosite Complex. 45 refs., 3 figs., 2 tabs.

  19. Clues from Fe isotope variations on the origin of early Archean BIFs from Greenland.

    PubMed

    Dauphas, Nicolas; van Zuilen, Mark; Wadhwa, Meenakshi; Davis, Andrew M; Marty, Bernard; Janney, Philip E

    2004-12-17

    Archean rocks may provide a record of early Earth environments. However, such rocks have often been metamorphosed by high pressure and temperature, which can overprint the signatures of their original formation. Here, we show that the early Archean banded rocks from Isua, Akilia, and Innersuartuut, Greenland, are enriched in heavy iron isotopes by 0.1 to 0.5 per mil per atomic mass unit relative to igneous rocks worldwide. The observed enrichments are compatible with the transport, oxidation, and subsequent precipitation of ferrous iron emanating from hydrothermal vents and thus suggest that the original rocks were banded iron formations (BIFs). These variations therefore support a sedimentary origin for the Akilia banded rocks, which represent one of the oldest known occurrences of water-laid deposits on Earth.

  20. Geochemical investigation of weathering processes in a forested headwater catchment: Mass-balance weathering fluxes

    USGS Publications Warehouse

    Jones, B.F.; Herman, J.S.

    2008-01-01

    Geochemical research on natural weathering has often been directed towards explanations of the chemical composition of surface water and ground water resulting from subsurface water-rock interactions. These interactions are often defined as the incongruent dissolution of primary silicates, such as feldspar, producing secondary weathering products, such as clay minerals and oxyhydroxides, and solute fluxes (Meunier and Velde, 1979). The chemical composition of the clay-mineral product is often ignored. However, in earlier investigations, the saprolitic weathering profile at the South Fork Brokenback Run (SFBR) watershed, Shenandoah National Park, Virginia, was characterized extensively in terms of its mineralogical and chemical composition (Piccoli, 1987; Pochatila et al., 2006; Jones et al., 2007) and its basic hydrology. O'Brien et al. (1997) attempted to determine the contribution of primary mineral weathering to observed stream chemistry at SFBR. Mass-balance model results, however, could provide only a rough estimate of the weathering reactions because idealized mineral compositions were utilized in the calculations. Making use of detailed information on the mineral occurrence in the regolith, the objective of the present study was to evaluate the effects of compositional variation on mineral-solute mass-balance modelling and to generate plausible quantitative weathering reactions that support both the chemical evolution of the surface water and ground water in the catchment, as well as the mineralogical evolution of the weathering profile. ?? 2008 The Mineralogical Society.

  1. Weather and climate

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Recommendations for using space observations of weather and climate to aid in solving earth based problems are given. Special attention was given to: (1) extending useful forecasting capability of space systems, (2) reducing social, economic, and human losses caused by weather, (3) development of space system capability to manage and control air pollutant concentrations, and (4) establish mechanisms for the national examination of deliberate and inadvertent means for modifying weather and climate.

  2. Hydrogeologic and water-quality characteristics of the crystalline-rock aquifers of Archean and Proterozoic age, Minnesota

    USGS Publications Warehouse

    Anderson, H.W.

    1986-01-01

    Five aquifers in crystalline rocks of Archean and Proterozoic age in Minnesota include in descending order the North Shore Volcanic, Sioux Quartzite, Proterozoic metasedimentary, Biwabik Iron formation and undifferentiated Precambrian aquifers. The North Shore Volcanic aquifer generally yields < 15 gal/min to wells from interflow sediments and fractures in the basaltic lava flows along the northern shore of Lake Superior and along the upper St. Croix River. Dissolved solids concentrations range from 91 to 74,300 mg/L, and the water is of several chemical types. The Sioux Quartzite aquifer yields from 1 to 450 gal/min to wells open to joints and fractures and loose sand zones in the predominantly pink orthoquartzite in southwestern Minnesota. Dissolved solids concentrations range from 237 mg/L in water from wells in outcrop areas to 2,300 mg/L from wells where the Sioux Quartzite aquifer underlies Cretaceous rocks or thick Des Moines drift. The water generally is a calcium sulfate type. The Proterozoic metasedimentary aquifer generally yields < 20 gal/min to wells in weathered regolith and fractures in thin-bedded gray to black argillite in north-central Minnesota. Dissolved solids concentrations generally range from 126 to 340 mg/L, and the water is a calcium magnesium bicarbonate type. The Biwabik Iron formation aquifer yields 1,000 gal/min to wells in leached zones in the ferruginous chert and interbedded hematite and magnitite iron ore in north-central Minnesota. Dissolved solids range from 157 to 388 mg/L in water that is a calcium magnesium bicarbonate type. The undifferentiated Precambrian aquifer generally yields < 25 gal/min to wells from fractures and the weathered regolith developed on a variety of crystalline-rock types. Wells have been developed in parts of the aquifer throughout the State except in the southeast where it is too deeply buried. Dissolved solids concentrations average < 400 mg/L in central and northeastern Minnesota, but average about 700

  3. The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth.

    PubMed

    Arney, Giada; Domagal-Goldman, Shawn D; Meadows, Victoria S; Wolf, Eric T; Schwieterman, Edward; Charnay, Benjamin; Claire, Mark; Hébrard, Eric; Trainer, Melissa G

    2016-11-01

    Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7-2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets. Key Words: Haze-Archean Earth-Exoplanets-Spectra-Biosignatures-Planetary habitability

  4. The sensitivity of the EMAC model to spectrally resolved irradiances during the Archean.

    NASA Astrophysics Data System (ADS)

    Kunze, Markus; Godolt, Mareike; Hamann-Reinus, Anke; Langematz, Ulrike; Rauer, Heike; Jöckel, Patrick

    The contradiction of a reduced solar luminosity by 15-25% during the Archean and the geo-logic evidence for relative high surface temperatures that allowed the presence of liquid water is known as the faint young sun problem. It is supposed that the cooling induced by a fainter sun was offset by higher levels of greenhouse gases during the Archean. We present a study in which we investigate this problem using the Chemistry Climate model EMAC (ECHAM/MESSy At-mospheric Chemistry) with a constructed, spectrally resolved irradiance dataset valid for the Archean. As proxy for the irradiance of our young sun we use the G0V-dwarf star β com. We test differently scaled spectrally resolved irradiances in an offline version of the FUBrad radiation scheme, to analyse the sensitivity of the input data on the heating rates in the middle atmo-sphere. We then use the EMAC model to analyse the sensitivity of the model dynamics to the spectrally resolved irradiances and other parameters valid for the late Archean Earth, such as the composition of the atmosphere and the land sea mask. Our experimental setup includes a control run, which has a zero land fraction, a slab ocean, the present day atmospheric composition, and the present day solar luminosity. Three sensitivity experiments are performed for: (1) 20% reduced solar irradiance, (2) 15% reduced solar irra-diance, and (3) increased CO2 concentration. We concentrate on the thermal and dynamical state of the atmosphere with emphasis on the middle atmosphere.

  5. Modeling the signature of sulfur mass-independent fractionation produced in the Archean atmosphere

    NASA Astrophysics Data System (ADS)

    Claire, Mark W.; Kasting, James F.; Domagal-Goldman, Shawn D.; Stüeken, Eva E.; Buick, Roger; Meadows, Victoria S.

    2014-09-01

    Minor sulfur isotope anomalies indicate the absence of O2 from the Archean atmosphere. A rich dataset showing large variations in magnitude and sign of Δ33S and Δ36S, preserved in both sulfates and sulfides, suggests that further constraints on Archean atmospheric chemistry are possible. We review previous quantitative constraints on atmospheric Δ33S production, and suggest that a new approach is needed. We added sulfur species containing 33S and 34S to a 1-D photochemical model and describe the numerical methodology needed to ensure accurate prediction of the magnitude and sign of Δ33S produced by and deposited from the Archean atmosphere. This methodology can test multiple MIF-S formation mechanisms subject to a variety of proposed atmospheric compositions, yielding Δ33S predictions that can be compared to the rock record. We systematically test SO2 isotopologue absorption effects in SO2 photolysis (Danielache et al., 2008), one of the primary proposed mechanisms for Δ33S formation. We find that differential absorption through the Danielache et al. (2008) cross sections is capable of altering predicted Δ33S as a function of multiple atmospheric variables, including trace O2 concentration, total sulfur flux, CO2 content, and the presence of hydrocarbons, but find a limited role for OCS and H2S. Under all realistic conditions, the Danielache et al. (2008) cross sections yield Δ33S predictions at odds with the geologic record, implying that additional pathways for sulfur MIF formation exist and/or the cross sections have significant errors. The methodology presented here will allow for quantitative constraints on the Archean atmosphere beyond the absence of O2, as soon as additional experimental measurements of MIF-S producing processes become available.

  6. The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth

    PubMed Central

    Domagal-Goldman, Shawn D.; Meadows, Victoria S.; Wolf, Eric T.; Schwieterman, Edward; Charnay, Benjamin; Claire, Mark; Hébrard, Eric; Trainer, Melissa G.

    2016-01-01

    Abstract Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8–2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets. Key Words: Haze—Archean Earth

  7. Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life

    NASA Astrophysics Data System (ADS)

    Schopf, J. William

    1993-04-01

    Eleven taxa (including eight heretofore undescribed species) of cellularly preserved filamentous microbes, among the oldest fossils known, have been discovered in a bedded chert unit of the Early Archean Apex Basalt of northwestern Western Australia. This prokaryotic assemblage establishes that trichomic cyanobacterium-like microorganisms were extant and morphologically diverse at least as early as ~3465 million years ago and suggests that oxygen-producing photoautotrophy may have already evolved by this early stage in biotic history.

  8. The transition from an Archean granite-greenstone terrain into a charnockite terrain in southern India

    NASA Technical Reports Server (NTRS)

    Condie, K. C.; Allen, P.

    1983-01-01

    In southern India, it is possible to study the transition from an Archean granite-greenstone terrain (the Karnataka province) into high grade charnockites. The transition occurs over an outcrop width of 20-35 km and appears to represent burial depths ranging from 15 to 20 km. Field and geochemical studies indicate that the charnockites developed at the expense of tonalites, granites, and greenstones. South of the transition zone, geobarometer studies indicate burial depths of 7-9 kb.

  9. Weather assessment and forecasting

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Data management program activities centered around the analyses of selected far-term Office of Applications (OA) objectives, with the intent of determining if significant data-related problems would be encountered and if so what alternative solutions would be possible. Three far-term (1985 and beyond) OA objectives selected for analyses as having potential significant data problems were large-scale weather forecasting, local weather and severe storms forecasting, and global marine weather forecasting. An overview of general weather forecasting activities and their implications upon the ground based data system is provided. Selected topics were specifically oriented to the use of satellites.

  10. Cockpit weather information needs

    NASA Technical Reports Server (NTRS)

    Scanlon, Charles H.

    1992-01-01

    The primary objective is to develop an advanced pilot weather interface for the flight deck and to measure its utilization and effectiveness in pilot reroute decision processes, weather situation awareness, and weather monitoring. Identical graphical weather displays for the dispatcher, air traffic control (ATC), and pilot crew should also enhance the dialogue capabilities for reroute decisions. By utilizing a broadcast data link for surface observations, forecasts, radar summaries, lightning strikes, and weather alerts, onboard weather computing facilities construct graphical displays, historical weather displays, color textual displays, and other tools to assist the pilot crew. Since the weather data is continually being received and stored by the airborne system, the pilot crew has instantaneous access to the latest information. This information is color coded to distinguish degrees of category for surface observations, ceiling and visibilities, and ground radar summaries. Automatic weather monitoring and pilot crew alerting is accomplished by the airborne computing facilities. When a new weather information is received, the displays are instantaneously changed to reflect the new information. Also, when a new surface or special observation for the intended destination is received, the pilot crew is informed so that information can be studied at the pilot's discretion. The pilot crew is also immediately alerted when a severe weather notice, AIRMET or SIGMET, is received. The cockpit weather display shares a multicolor eight inch cathode ray tube and overlaid touch panel with a pilot crew data link interface. Touch sensitive buttons and areas are used for pilot selection of graphical and data link displays. Time critical ATC messages are presented in a small window that overlays other displays so that immediate pilot alerting and action can be taken. Predeparture and reroute clearances are displayed on the graphical weather system so pilot review of weather along

  11. Pilot Weather Advisor System

    NASA Technical Reports Server (NTRS)

    Lindamood, Glenn; Martzaklis, Konstantinos Gus; Hoffler, Keith; Hill, Damon; Mehrotra, Sudhir C.; White, E. Richard; Fisher, Bruce D.; Crabill, Norman L.; Tucholski, Allen D.

    2006-01-01

    The Pilot Weather Advisor (PWA) system is an automated satellite radio-broadcasting system that provides nearly real-time weather data to pilots of aircraft in flight anywhere in the continental United States. The system was designed to enhance safety in two distinct ways: First, the automated receipt of information would relieve the pilot of the time-consuming and distracting task of obtaining weather information via voice communication with ground stations. Second, the presentation of the information would be centered around a map format, thereby making the spatial and temporal relationships in the surrounding weather situation much easier to understand

  12. Evaluation of early Archean volcaniclastic and volcanic flow rocks as possible sites for carbonaceous fossil microbes.

    PubMed

    Walsh, Maud M

    2004-01-01

    Sedimentary rocks have traditionally been the focus of the search for Archean microfossils; the Earth's oldest fossil bacteria are associated with carbonaceous matter in sedimentary cherts in greenstone belts in the eastern Pilbara block of Western Australia and Barberton greenstone belt of South Africa. Reports of possible fossils in a martian meteorite composed of igneous rock and the discovery of modern bacteria associated with basalts have stimulated a new look at Archean volcanic rocks as possible sites for fossil microbes. This study examines silicified volcaniclastic rocks, near-surface altered volcanic flow rocks, and associated stromatolite- like structures from the Archean Barberton greenstone belt to evaluate their potential for the preservation of carbonaceous fossils. Detrital carbonaceous particles are widely admixed with current-deposited debris. Carbonaceous matter is also present in altered volcanic flow rocks as sparse particles in silica veins that appear to be fed by overlying carbonaceous chert layers. Neither microfossils nor mat-like material was identified in the altered volcanic rocks or adjacent stromatolite-like structures. Ancient volcanic flow and volcaniclastic rocks are not promising sites for carbonaceous fossil preservation.

  13. Earth's early atmosphere as seen from carbon and nitrogen isotopic analysis of Archean sediments

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Carr, L. P.; Gilmour, I.; Pillinger, C. T.

    1986-01-01

    The origin and evolution of the Earth's early atmosphere has long been a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of stromatolite deposits (Precambrian Paleobiology Research Group) has extended our knowledge of Archean ecosystems. It has been shown that many stromatolite deposits have undergone negligible alteration since their time of formation. The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archiean sediments and the observation that the 3.3 b.y. old Barberton cherts have remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of the volatile constituents present at their time of formation. Of primary interest to this study was the possibility that the stromatolites and other Archean sediments might retain a vestige of the atmosphere and thus afford an indication of the variations in carbon dioxide and nitrogen isotopic compositions with time. A suite of essentially unaltered Archean stromatolites and the cherts of different ages and geologic sites have been analyzed for their trapped carbon dioxide and nitrogen compositions by the stepped combustion extraction tech nique utilizing static mass spectrometers for the isotope measurements.

  14. Controls on the Archean climate system investigated with a global climate model.

    PubMed

    Wolf, E T; Toon, O B

    2014-03-01

    The most obvious means of resolving the faint young Sun paradox is to invoke large quantities of greenhouse gases, namely, CO2 and CH4. However, numerous changes to the Archean climate system have been suggested that may have yielded additional warming, thus easing the required greenhouse gas burden. Here, we use a three-dimensional climate model to examine some of the factors that controlled Archean climate. We examine changes to Earth's rotation rate, surface albedo, cloud properties, and total atmospheric pressure following proposals from the recent literature. While the effects of increased planetary rotation rate on surface temperature are insignificant, plausible changes to the surface albedo, cloud droplet number concentrations, and atmospheric nitrogen inventory may each impart global mean warming of 3-7 K. While none of these changes present a singular solution to the faint young Sun paradox, a combination can have a large impact on climate. Global mean surface temperatures at or above 288 K could easily have been maintained throughout the entirety of the Archean if plausible changes to clouds, surface albedo, and nitrogen content occurred.

  15. Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

    PubMed Central

    Delavault, Hélène; Thomassot, Emilie; Devey, Colin W.; Dazas, Baptiste

    2016-01-01

    The isotopic diversity of oceanic island basalts (OIB) is usually attributed to the influence, in their sources, of ancient material recycled into the mantle, although the nature, age, and quantities of this material remain controversial. The unradiogenic Pb isotope signature of the enriched mantle I (EM I) source of basalts from, for example, Pitcairn or Walvis Ridge has been variously attributed to recycled pelagic sediments, lower continental crust, or recycled subcontinental lithosphere. Our study helps resolve this debate by showing that Pitcairn lavas contain sulfides whose sulfur isotopic compositions are affected by mass-independent fractionation (S-MIF down to Δ33S = −0.8), something which is thought to have occurred on Earth only before 2.45 Ga, constraining the youngest possible age of the EM I source component. With this independent age constraint and a Monte Carlo refinement modeling of lead isotopes, we place the likely Pitcairn source age at 2.5 Ga to 2.6 Ga. The Pb, Sr, Nd, and Hf isotopic mixing arrays show that the Archean EM I material was poor in trace elements, resembling Archean sediment. After subduction, this Archean sediment apparently remained stored in the deep Earth for billions of years before returning to the surface as Pitcairn´s characteristic EM I signature. The presence of negative S-MIF in the deep mantle may also help resolve the problem of an apparent deficit of negative Δ33S anomalies so far found in surface reservoirs. PMID:27791057

  16. Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

    NASA Astrophysics Data System (ADS)

    Delavault, Hélène; Chauvel, Catherine; Thomassot, Emilie; Devey, Colin W.; Dazas, Baptiste

    2016-11-01

    The isotopic diversity of oceanic island basalts (OIB) is usually attributed to the influence, in their sources, of ancient material recycled into the mantle, although the nature, age, and quantities of this material remain controversial. The unradiogenic Pb isotope signature of the enriched mantle I (EM I) source of basalts from, for example, Pitcairn or Walvis Ridge has been variously attributed to recycled pelagic sediments, lower continental crust, or recycled subcontinental lithosphere. Our study helps resolve this debate by showing that Pitcairn lavas contain sulfides whose sulfur isotopic compositions are affected by mass-independent fractionation (S-MIF down to Δ33S = -0.8), something which is thought to have occurred on Earth only before 2.45 Ga, constraining the youngest possible age of the EM I source component. With this independent age constraint and a Monte Carlo refinement modeling of lead isotopes, we place the likely Pitcairn source age at 2.5 Ga to 2.6 Ga. The Pb, Sr, Nd, and Hf isotopic mixing arrays show that the Archean EM I material was poor in trace elements, resembling Archean sediment. After subduction, this Archean sediment apparently remained stored in the deep Earth for billions of years before returning to the surface as Pitcairńs characteristic EM I signature. The presence of negative S-MIF in the deep mantle may also help resolve the problem of an apparent deficit of negative Δ33S anomalies so far found in surface reservoirs.

  17. Geochemistry of Precambrian carbonates: 3-shelf seas and non-marine environments of the Archean

    SciTech Connect

    Veizer, J. Ruhr Universitaet, Bochum ); Clayton, R.N. ); Hinton, R.W. Grant Institute of Geology, Edinburgh ); von Brunn, V. ); Mason, T.R. ); Buck, S.G. ); Hoefs, J. )

    1990-10-01

    A comprehensive whole-rock study of mineralogical, chemical, and isotopic attributes of Archean carbonates suggests that their lithologies and facies have been controlled by tectonic setting. In the first two papers of this series they have shown that the dominant lithology of sedimentary carbonates in greenstone belt settings is limestone. In this paper the authors suggest that the Archean shelf sequences are mostly dolostone, and the contemporaneous lacustrine playa lakes are characterized by limestone facies. The present study is of the shelf environments of the Archean, represented by the Pongola Supergroup of South Africa and the Hamersley Group of Australia. The lacustrine playa examples have been sampled from the Ventersdorp Supergroup of South Africa and the Fortescue Group of Australia. Geological, trace element, and oxygen isotope considerations of the shelf carbonates suggest that their original mineralogy may have been aragonite and that the Pongola dolostones probably represent a direct dolomitization product of this precursor. In contrast, the stabilization of the Hamersley carbonates may have involved an additional step of transformation of a metastable precursor into limestone prior to dolomitization.

  18. Magnesium isotope fractionation during continental weathering

    NASA Astrophysics Data System (ADS)

    Teng, F. Z.; Huang, K. J.; Li, W.; Liu, X. M.; Ma, L.

    2014-12-01

    Continental weathering links the atmosphere, hydrosphere and continents as it regulates the CO2 content of the atmosphere, shifts the composition of the continental crust from basaltic to andesitic, and ultimately controls the chemical composition of river waters and seawater. Magnesium is a water-soluble major element in the hydrosphere, continental crust and the mantle, and has three stable isotopes (24Mg, 25Mg and 26Mg). Studies of Mg isotopes during continental weathering may help to document the interactions between hydrosphere, crust and mantle. Previous studies have shown that the continental crust has a heterogeneous but on average heavier Mg isotopic composition than the mantle, whereas the hydrosphere is isotopically light. The complementary characteristics of Mg isotopic compositions between continental and hydrosphere have been attributed to continental weathering, with light Mg isotopes partitioned into water, leaving heavy Mg isotopes behind in the crustal residue. Here we summarize our studies of Mg isotope fractionation in four weathering profiles under various climate conditions. We show that large Mg isotope fractionation can occur during continental weathering. Although the weathered residue is usually enriched in heavier Mg isotopes than unaltered parent rocks, some heavily weathered products can be quite light in Mg isotopic composition. The complicated behaviors of Mg isotopes reflect different control factors during weathering such as parent rock lithology, primary mineral dissolution, secondary mineral formation, ion exchange, vegetation uptake etc. Though studies of natural samples can provide direct evidence on isotope fractionation, more well-controlled laboratory experiments on Mg isotope fractionation between fluids and minerals are needed in order to fully understand the behaviors of Mg isotopes during weathering, which ultimately lays the foundation for making Mg isotope geochemistry an important tool for studying different geological

  19. Preferential Weathering of Carbonatite Lava at Ol Doinyo Lengai, Tanzania

    NASA Astrophysics Data System (ADS)

    Robertson, C. H.; Harpp, K. S.; Geist, D.; Bosselait, M.

    2014-12-01

    Although carbonatites have been produced since the Archean and are preserved in the geologic record, the East African Rift is home to the only active carbonatite volcano, at Ol Doinyo Lengai. It has long been known that the natrocarbonatites become strongly weathered the first time they are exposed to rain. We studied the weathering patterns in the field and have determined the mineralogical transformations via petrography and XRD. Mass transport is assessed by XRF and ICP-MS analyses. Water preferentially dissolves specific minerals in the pristine lava, permeating through earlier layers of flow to form stalactites, which have differing mineralogical composition. These hang both from the host flow and from the bottom of underlying earlier flows. The weathering product is characterized by trona, a hydrated carbonate mineral, as well as the sodium sulfate mineral aphthitalite. Data from XRD analysis of the carbonatite lava confirm transformation of its original minerals, nyerereite and gregoryite, into secondary hydrated carbonate minerals gaylussite and pirssonite (e.g., Zaitsev and Keller, 2006). This transformation is attributed to the instability of the erupted minerals at atmospheric conditions. Data from XRF analysis indicate a 4-fold increase in the amount of sodium present in the stalactite as well as a 8-fold increase in potassium. Trace element analysis by ICP-MS indicates significantly elevated levels of vanadium, copper, and rubidium in the weathering product, whereas strontium, barium, lanthanum, and cesium are left behind in high concentrations in the carbonatite lava. Our results provide further evidence supporting the proposal by Dawson et al. (1987) that calcium carbonate dominated lava flows result from extensive weathering of sodic carbonatite flows.

  20. Weather and emotional state

    NASA Astrophysics Data System (ADS)

    Spasova, Z.

    2010-09-01

    Introduction Given the proven effects of weather on the human organism, an attempt to examine its effects on a psychic and emotional level has been made. Emotions affect the bio-tonus, working ability and concentration, hence their significance in various domains of economic life, such as health care, education, transportation, tourism, etc. Data and methods The research has been made in Sofia City within a period of 8 months, using 5 psychological methods (Eysenck Personality Questionnaire (EPQ), State-Trait Anxiety Inventory (STAI), Test for Self-assessment of the emotional state (developed by Wessman and Ricks), Test for evaluation of moods and Test "Self-confidence - Activity - Mood" (developed by the specialists from the Military Academy in Saint Petersburg). The Fiodorov-Chubukov's complex-climatic method was used to characterize meteorological conditions because of the purpose to include in the analysis a maximal number of meteorological elements. 16 weather types are defined in dependence of the meteorological elements values according to this method. Abrupt weather changes from one day to another, defined by the same method, were considered as well. Results and discussions The results obtained by t-test show that the different categories of weather lead to changes in the emotional status, which indicates a character either positive or negative for the organism. The abrupt weather changes, according to expectations, have negative effect on human emotions but only when a transition to the cloudy weather or weather type, classified as "unfavourable" has been realized. The relationship between weather and human emotions is rather complicated since it depends on individual characteristics of people. One of these individual psychological characteristics, marked by the dimension "neuroticism", has a strong effect on emotional reactions in different weather conditions. Emotionally stable individuals are more "protected" to the weather influence on their emotions

  1. Weathering Database Technology

    ERIC Educational Resources Information Center

    Snyder, Robert

    2005-01-01

    Collecting weather data is a traditional part of a meteorology unit at the middle level. However, making connections between the data and weather conditions can be a challenge. One way to make these connections clearer is to enter the data into a database. This allows students to quickly compare different fields of data and recognize which…

  2. Designing a Weather Station

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2012-01-01

    The collection and analysis of weather data is crucial to the location of alternate energy systems like solar and wind. This article presents a design challenge that gives students a chance to design a weather station to collect data in advance of a large wind turbine installation. Data analysis is a crucial part of any science or engineering…

  3. KSC Weather and Research

    NASA Technical Reports Server (NTRS)

    Maier, Launa; Huddleston, Lisa; Smith, Kristin

    2016-01-01

    This briefing outlines the history of Kennedy Space Center (KSC) Weather organization, past research sponsored or performed, current organization, responsibilities, and activities, the evolution of weather support, future technologies, and an update on the status of the buoys located offshore of Cape Canaveral Air Force Station and KSC.

  4. Weather Fundamentals: Clouds. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series, for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes) discusses how clouds form, the different types of clouds, and the important role they play in…

  5. Home Weatherization Visit

    ScienceCinema

    Chu, Steven

    2016-07-12

    Secretary Steven Chu visits a home that is in the process of being weatherized in Columbus, OH, along with Ohio Governor Ted Strickland and Columbus Mayor Michael Coleman. They discuss the benefits of weatherization and how funding from the recovery act is having a direct impact in communities across America.

  6. On Observing the Weather

    ERIC Educational Resources Information Center

    Crane, Peter

    2004-01-01

    Rain, sun, snow, sleet, wind... the weather affects everyone in some way every day, and observing weather is a terrific activity to attune children to the natural world. It is also a great way for children to practice skills in gathering and recording information and to learn how to use simple tools in a standardized fashion. What better way to…

  7. Weather Cardboard Carpentry

    ERIC Educational Resources Information Center

    DeBruin, Jerome E.

    1977-01-01

    Included are instructions and diagrams for building weather instruments (wind vane, Celsius temperature scale, and anemometer) from simple tools and Tri-Wall, a triple-thick corrugated cardboard. Ordering sources for Tri-Wall are listed. Additional weather instruments that can be constructed are suggested. (CS)

  8. Tracking Weather Satellites.

    ERIC Educational Resources Information Center

    Martin, Helen E.

    1996-01-01

    Describes the use of weather satellites in providing an exciting, cohesive framework for students learning Earth and space science and in providing a hands-on approach to technology in the classroom. Discusses the history of weather satellites and classroom satellite tracking. (JRH)

  9. Weatherizing a Structure.

    ERIC Educational Resources Information Center

    Metz, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with weatherizing a structure. Its objective is for the student to be able to analyze factors related to specific structures that indicate need for weatherizing activities and to determine steps to correct defects in structures that…

  10. Teacher's Weather Sourcebook.

    ERIC Educational Resources Information Center

    Konvicka, Tom

    This book is a teaching resource for the study of weather-related phenomena. A "weather unit" is often incorporated into school study because of its importance to our daily lives and because of its potential to cut across disciplinary content. This book consists of two parts. Part I covers the major topics of atmospheric science such as the modern…

  11. Mild and Wild Weather.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Presents background information and six activities that focus on clouds, precipitation, and stormy weather. Each activity includes an objective, recommended age level(s), subject area(s), and instructional strategies. Also provided are two ready-to-copy pages (a coloring page on lightning and a list of weather riddles to solve). (JN)

  12. Weather Fundamentals: Wind. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series, for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes) describes the roles of the sun, temperature, and air pressure in creating the incredible power…

  13. World weather program

    NASA Technical Reports Server (NTRS)

    1980-01-01

    A brief description of the Global Weather Experiment is presented. The world weather watch program plan is described and includes a global observing system, a global data processing system, a global telecommunication system, and a voluntary cooperation program. A summary of Federal Agency plans and programs to meet the challenges of international meteorology for the two year period, FY 1980-1981, is presented.

  14. The Home Weather Station.

    ERIC Educational Resources Information Center

    Steinke, Steven D.

    1991-01-01

    Described is how an amateur weather observer measures and records temperature and precipitation at a well-equipped, backyard weather station. Directions for building an instrument shelter and a description of the instruments needed for measuring temperature and precipitation are included. (KR)

  15. Fabulous Weather Day

    ERIC Educational Resources Information Center

    Marshall, Candice; Mogil, H. Michael

    2007-01-01

    Each year, first graders at Kensington Parkwood Elementary School in Kensington, Maryland, look forward to Fabulous Weather Day. Students learn how meteorologists collect data about the weather, how they study wind, temperature, precipitation, basic types/characteristics of clouds, and how they forecast. The project helps the students grow in…

  16. NASA Connect: 'Plane Weather'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Excerpt from the NASA Connect show 'Plane Weather' This clip explains what high and low pressure weather systems are, and how they form. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.

  17. Weather in Mountainous Terrain (Overcoming Scientific Barriers to Weather Support)

    DTIC Science & Technology

    2011-02-15

    Weather in Mountainous Terrain (Overcoming Scientific Barriers to Weather Support) Fiesta Resort & Conference Center Tempe, AZ February 1...Meteorology Overcoming Scientific Barriers to Weather Support Fiesta Resort & Conference Center Tempe, AZ February 1 & 2, 2010 Hosted by University

  18. Geology and geochronology of granitoid and metamorphic rocks of late Archean age in northwestern Wisconsin

    USGS Publications Warehouse

    Sims, P.K.; Peterman, Z.E.; Zartman, R.E.; Benedict, F.C.

    1985-01-01

    Granitoid rocks of the Puritan Quartz Monzonite and associated biotite gneiss and amphibolite in northwestern Wisconsin compose the southwestern part of the Puritan batholith of Late Archean age. They differ from rocks in the Michigan segment of the batholith in having been deformed by brittle-ductile deformation and partly recrystallized during shearing accompanying development of the midcontinent rift system of Keweenawan (Middle Proterozoic) age. Granitoid rocks ranging in composition from granite to tonalite are dominant in the Wisconsin part of the batholith. To the north of the Mineral Lake fault zone, they are massive to weakly foliated and dominantly of granite composition, whereas south of the fault zone they are more strongly foliated and mainly of tonalite composition. Massive granite, leucogranite, and granite pegmatite cut the dominant granitoid rocks. Intercalated with the granitoid rocks in small to large conformable bodies are biotite gneiss, amphibolite, and local tonalite gneiss. Metagabbro dikes of probable Early Proterozoic age as much as 15 m thick cut the Archean rocks. Rubidium-strontium whole-rock data indicate a Late Archean age for the granitoids and gneisses, but data points are scattered and do not define a single isochron. Zircon from two samples of tonalitic gneiss for uranium-thorium-Iead dating define a single chord on a concordia diagram, establishing an age of 2,735?16 m.y. The lower intercept age of 1,052?70 m.y. is in close agreement with rubidium-strontium and potassium-argon biotite ages from the gneisses. Two episodes of deformation and metamorphism are recorded in the Archean rocks. Deformation during the Late Archean produced a steep west-northwest-oriented foliation and gently plunging fold axes and was accompanied by low amphibolite-facies metamorphism of the bedded rocks. A younger deformation resulting from largely brittle fracture was accompanied by retrogressive metamorphism; this deformation is most evident adjacent

  19. Late Archean mineralised cyanobacterial mats and their modern analogs

    NASA Astrophysics Data System (ADS)

    Kazmierczak, J.; Altermann, W.; Kremer, B.; Kempe, S.; Eriksson, P. G.

    2008-09-01

    Abstract Reported are findings of Neoarchean benthic colonial coccoid cyanobacteria preserved as abundant remnants of mineralized capsules and sheaths visible in SEM images as characteristic patterns after etching highly polished carbonate rock platelets. The samples described herein were collected from the Nauga Formation at Prieska (Kaapvaal craton, South Africa). The stratigraphic position of the sampling horizon (Fig. 1) is bracketed by single zircon ages from intercalated tuffs, of 2588±6 Ma and 2549±7Ma [1]. The cyanobacteria-bearing samples are located within sedimentary sequence which begins with Peritidal Member displaying increasingly transgressive character, passing upward into the Chert Member and followed by the Proto-BIF Member and by the Naute Shale Member of the Nauga Formation successively. All three latter members were deposited below the fair weather wave base. As in our previous report [2], the samples are taken from lenses of massive micritic flat pebble conglomerate occurring in otherwise finely laminated siliceous shales intercalating with thin bedded platy limestone. This part of the Nauga Formation is about 30 m thick. The calcareous, cyanobacteria-bearing flat pebble conglomerate and thin intercalations of fine-grained detrital limestones embedded in the clayey sapropel-rich deposits are interpreted as carbonate sediments winnowed during stormy weather from the nearby located peritidal carbonate platform. The mass occurrence and exceptional preservation of mineralised cyanobacterial remains in the micritic carbonate (Mg-calcite) of the redeposited flat pebbles can be explained by their sudden burial in deeper, probably anoxic clay- and sapropel-rich sediments. When examined with standard petrographic optical microscopic technique, the micritic carbonates show rather obscure structure (Fig. 2a), whereas under the SEM, polished and slightly etched platelets of the same samples reveal surprisingly well preserved patterns (Fig. 2b

  20. Environmental Education Tips: Weather Activities.

    ERIC Educational Resources Information Center

    Brainard, Audrey H.

    1989-01-01

    Provides weather activities including questions, on weather, heating the earth's surface, air, tools of the meteorologist, clouds, humidity, wind, and evaporation. Shows an example of a weather chart activity. (RT)

  1. Weather--An Integrated Unit

    ERIC Educational Resources Information Center

    McConnell, Vivian

    1976-01-01

    Outlined is a two week unit on weather offered as independent study for sixth- and seventh-year students in Vancouver, Canada, schools. Included is a section on weather lore and a chart of weather symbols. (SL)

  2. Key findings of the national weatherization evaluation

    SciTech Connect

    Brown, M.A.; Berry, L.G.

    1994-10-01

    In 1990, the U.S. Department of Energy sponsored a comprehensive evaluation of its Weatherization Assistance Program, the nation`s largest residential energy conservation program. The primary goal of the evaluation was to establish whether the Program meets the objectives of its enabling legislation and fulfills its mission statement, to reduce the heating and cooling costs for low-income families-particularly the elderly, persons with disabilities, and children by improving the energy-efficiency of their homes and ensuring their health and safety. Oak Ridge National Laboratory managed a five-part study which produced a series of documents evaluating the Program. The objective of this document is to summarize the findings of the five-part National Weatherization Evaluation. The five studies were as follows: (1) Network Study-this study characterized the weatherization network`s leveraging, capabilities, procedures, staff, technologies, and innovations; (2) Resources and Population Study-this study profiled low-income weatherization resources, the weatherized population, and the population remaining to be served; (3) Multifamily Study-this study described the nature and extent of weatherization activities in larger multifamily buildings; (4) Single-family Study-this study estimated the national savings and cost- effectiveness of weatherizing single-family and small multifamily dwellings that use natural gas or electricity for space heating; (5) Fuel-Oil Study-this study estimated the savings and cost-effectiveness of weatherizing single-family homes, located in nine northeastern states, that use fuel oil for space heating. This paper provides a brief overview of each study`s purposes, research methods and most important findings.

  3. Strontium and neodymium isotopic variations in early Archean gneisses affected by middle to late Archean high-grade metamorphic processes: West Greenland and Labrador

    NASA Technical Reports Server (NTRS)

    Collerson, K. D.; Mcculloch, M. T.; Bridgwater, D.; Mcgregor, V. R.; Nutman, A. P.

    1986-01-01

    Relicts of continental crust formed more than 3400 Ma ago are preserved fortuitously in most cratons. The cratons provide the most direct information about crust and mantle evolutionary processes during the first billion years of Earth history. In view of their polymetamorphic character, these terrains are commonly affected by subsequent tectonothermal events. Hence, their isotope systematics may be severely disturbed as a result of bulk chemical change or local isotopic homogenization. This leads to equivocal age and source information for different components within these terrains. The Sr and Nd isotopic data are presented for early Archean gneisses from the North Atlantic Craton in west Greenland and northern Labrador which were affected by younger metamorphic events.

  4. EPR study of thermally treated Archean microbial mats analogues and comparison with Archean cherts: towards a possible marker of oxygenic photosynthesis?

    NASA Astrophysics Data System (ADS)

    Bourbin, M.; Derenne, S.; Westall, F.; Gourier, D.; Gautret, P.; Rouzaud, J.-N.; Robert, F.

    2012-04-01

    The datation of photosynthesis apparition remains an open question nowadays: did oxygenic photosynthesis appear just before the Great Oxidation Event (GOE) of the atmosphere, 2.3 to 2.4 Gyr ago, or does it originate much earlier? It is therefore of uttermost interest to find markers of oxygenic photosynthesis, applicable to samples of archean age. In order to handle this problem, Microcoleus Chtonoplastes cyanobacteria and Chloroflexus-like non-oxygenic photosynthetic bacteria, were studied using Electron Paramagnetic Resonance (EPR) spectroscopy, a high sensitivity technique for the study of organic radicals in mature geological samples (coals, cherts, meteorites...). M. chtonoplastes and Chloroflexus-like bacteria were sampled in mats from the hypersaline lake "La Salada de Chiprana" (Spain), an analogue to an Archean environment, and were submitted to accelerated ageing through cumulative thermal treatments. For thermal treatment temperatures higher than 620° C, a drastic increase in the EPR linewidth of the oxygenic photosynthetic bacteria (M. chtonoplastes) occurred, as compared with the anoxygenic photosynthetic one (Chloroflexus-like). The EPR study of a thermally treated mixture of the two bacteria evidences that this linewidth increase is driven by catalytic reaction at high temperatures on an element selectively fixed by M. chtonoplastes. Based on comparative EDS analyses, Mg is a potential candidate for this catalytic activity but its precise role and the nature of the reaction are still to be determined. The EPR study of organic radicals in chert rocks of ages ranging from 0.42 to 3.5 Gyr, from various localities and that underwent various metamorphisms, revealed a dispersion of the signal width for the most mature samples. This comparative approach between modern bacterial samples and Precambrian cherts leads to propose the EPR linewidth of mature organic matter in cherts as a potential marker of oxygenic photosynthesis. If confirmed, this marker

  5. The world turns over: Hadean-Archean crust-mantle evolution

    NASA Astrophysics Data System (ADS)

    Griffin, W. L.; Belousova, E. A.; O'Neill, C.; O'Reilly, Suzanne Y.; Malkovets, V.; Pearson, N. J.; Spetsius, S.; Wilde, S. A.

    2014-02-01

    We integrate an updated worldwide compilation of U/Pb, Hf-isotope and trace-element data on zircon, and Re-Os model ages on sulfides and alloys in mantle-derived rocks and xenocrysts, to examine patterns of crustal evolution and crust-mantle interaction from 4.5 Ga to 2.4 Ga ago. The data suggest that during the period from 4.5 Ga to ca 3.4 Ga, Earth's crust was essentially stagnant and dominantly mafic in composition. Zircon crystallized mainly from intermediate melts, probably generated both by magmatic differentiation and by impact melting. This quiescent state was broken by pulses of juvenile magmatic activity at ca 4.2 Ga, 3.8 Ga and 3.3-3.4 Ga, which may represent mantle overturns or plume episodes. Between these pulses, there is evidence of reworking and resetting of U-Pb ages (by impact?) but no further generation of new juvenile crust. There is no evidence of plate-tectonic activity, as described for the Phanerozoic Earth, before ca 3.4 Ga, and previous modelling studies indicate that the early Earth may have been characterised by an episodic-overturn, or even stagnant-lid, regime. New thermodynamic modelling confirms that an initially hot Earth could have a stagnant lid for ca 300 Ma, and then would experience a series of massive overturns at intervals on the order of 150 Ma until the end of the EoArchean. The subcontinental lithospheric mantle (SCLM) sampled on Earth today did not exist before ca 3.5 Ga. A lull in crustal production around 3.0 Ga coincides with the rapid buildup of a highly depleted, buoyant SCLM, which peaked around 2.7-2.8 Ga; this pattern is consistent with one or more major mantle overturns. The generation of continental crust peaked later in two main pulses at ca 2.75 Ga and 2.5 Ga; the latter episode was larger and had a greater juvenile component. The age/Hf-isotope patterns of the crust generated from 3.0 to 2.4 Ga are similar to those in the internal orogens of the Gondwana supercontinent, and imply the existence of plate

  6. Weathering in a Cup.

    ERIC Educational Resources Information Center

    Stadum, Carol J.

    1991-01-01

    Two easy student activities that demonstrate physical weathering by expansion are described. The first demonstrates ice wedging and the second root wedging. A list of the needed materials, procedure, and observations are included. (KR)

  7. National Weather Service

    MedlinePlus

    ... SAFETY Floods Tsunami Beach Hazards Wildfire Cold Tornadoes Air Quality Fog Heat Hurricanes Lightning Safe Boating Rip Currents ... ACTIVE ALERTS FORECAST MAPS RADAR RIVERS, LAKES, RAINFALL AIR QUALITY SATELLITE PAST WEATHER " ); }); American Samoa Guam Puerto Rico/ ...

  8. Weather Information Processing

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Science Communications International (SCI), formerly General Science Corporation, has developed several commercial products based upon experience acquired as a NASA Contractor. Among them are METPRO, a meteorological data acquisition and processing system, which has been widely used, RISKPRO, an environmental assessment system, and MAPPRO, a geographic information system. METPRO software is used to collect weather data from satellites, ground-based observation systems and radio weather broadcasts to generate weather maps, enabling potential disaster areas to receive advance warning. GSC's initial work for NASA Goddard Space Flight Center resulted in METPAK, a weather satellite data analysis system. METPAK led to the commercial METPRO system. The company also provides data to other government agencies, U.S. embassies and foreign countries.

  9. Weathering of Martian Evaporites

    NASA Technical Reports Server (NTRS)

    Wentworth, S. J.; Velbel, M. A.; Thomas-Keprta, K. L.; Longazo, T. G.; McKay, D. S.

    2001-01-01

    Evaporites in martian meteorites contain weathering or alteration features that may provide clues about the martian near-surface environment over time. Additional information is contained in the original extended abstract.

  10. Directable weathering of concave rock using curvature estimation.

    PubMed

    Jones, Michael D; Farley, McKay; Butler, Joseph; Beardall, Matthew

    2010-01-01

    We address the problem of directable weathering of exposed concave rock for use in computer-generated animation or games. Previous weathering models that admit concave surfaces are computationally inefficient and difficult to control. In nature, the spheroidal and cavernous weathering rates depend on the surface curvature. Spheroidal weathering is fastest in areas with large positive mean curvature and cavernous weathering is fastest in areas with large negative mean curvature. We simulate both processes using an approximation of mean curvature on a voxel grid. Both weathering rates are also influenced by rock durability. The user controls rock durability by editing a durability graph before and during weathering simulation. Simulations of rockfall and colluvium deposition further improve realism. The profile of the final weathered rock matches the shape of the durability graph up to the effects of weathering and colluvium deposition. We demonstrate the top-down directability and visual plausibility of the resulting model through a series of screenshots and rendered images. The results include the weathering of a cube into a sphere and of a sheltered inside corner into a cavern as predicted by the underlying geomorphological models.

  11. Weather Radar Studies.

    DTIC Science & Technology

    1985-03-31

    National Center for Atmospheric Research JAWS program and the National Severe Storms Laboratory are being analyzed to develop low-altitude wind shear...public through low-altitude wind shear aviation weather products the National Technical Information Service, NEXR I turbulence., Springfield, VA 22161. 19...were analyzed preliminarily to determine wind shear characteristics in the Memphis area. Doppler weather radar data from the National Center for

  12. The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth

    NASA Astrophysics Data System (ADS)

    Arney, Giada; Domagal-Goldman, Shawn D.; Meadows, Victoria S.; Wolf, Eric T.; Schwieterman, Edward; Charnay, Benjamin; Claire, Mark; Hébrard, Eric; Trainer, Melissa G.

    2016-11-01

    Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ˜ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7-2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets.

  13. SQUID-SIMS is a useful approach to uncover primary signals in the Archean sulfur cycle.

    PubMed

    Fischer, Woodward W; Fike, David A; Johnson, Jena E; Raub, Timothy D; Guan, Yunbin; Kirschvink, Joseph L; Eiler, John M

    2014-04-15

    Many aspects of Earth's early sulfur cycle, from the origin of mass-anomalous fractionations to the degree of biological participation, remain poorly understood--in part due to complications from postdepositional diagenetic and metamorphic processes. Using a combination of scanning high-resolution magnetic superconducting quantum interference device (SQUID) microscopy and secondary ion mass spectrometry (SIMS) of sulfur isotopes ((32)S, (33)S, and (34)S), we examined drill core samples from slope and basinal environments adjacent to a major Late Archean (∼2.6-2.5 Ga) marine carbonate platform from South Africa. Coupled with petrography, these techniques can untangle the complex history of mineralization in samples containing diverse sulfur-bearing phases. We focused on pyrite nodules, precipitated in shallow sediments. These textures record systematic spatial differences in both mass-dependent and mass-anomalous sulfur-isotopic composition over length scales of even a few hundred microns. Petrography and magnetic imaging demonstrate that mass-anomalous fractionations were acquired before burial and compaction, but also show evidence of postdepositional alteration 500 million y after deposition. Using magnetic imaging to screen for primary phases, we observed large spatial gradients in Δ(33)S (>4‰) in nodules, pointing to substantial environmental heterogeneity and dynamic mixing of sulfur pools on geologically rapid timescales. In other nodules, large systematic radial δ(34)S gradients (>20‰) were observed, from low values near their centers increasing to high values near their rims. These fractionations support hypotheses that microbial sulfate reduction was an important metabolism in organic-rich Archean environments--even in an Archean ocean basin dominated by iron chemistry.

  14. Leucogranites of the Teton Range, Wyoming: A record of Archean collisional orogeny

    NASA Astrophysics Data System (ADS)

    Frost, Carol D.; Swapp, Susan M.; Frost, B. Ronald; Finley-Blasi, Lee; Fitz-Gerald, D. Braden

    2016-07-01

    Leucogranitic rocks formed by crustal melting are a prominent feature of collisional orogens of all ages. This study describes leucogranitic gneisses associated with an Archean collisional orogeny preserved in the Teton Range of northwestern Wyoming, USA. These leucogneisses formed at 2.68 Ga, and initial Nd isotopic compositions suggest they are derived from relatively juvenile sources. Two distinct groups of leucogneisses, both trondhjemitic, are identified on the basis of field relations, petrology, and geochemistry. The Webb Canyon gneiss forms large, sheet-like bodies of hornblende biotite trondhjemite and granodiorite. This gneiss is silica-rich (SiO2 = 70-80%), strongly ferroan, comparatively low in alumina, and is characterized by high Zr and Y, low Sr, and high REE contents that define "seagull"-shaped REE patterns. The Bitch Creek gneiss forms small sills, dikes, and plutons of biotite trondhjemite. Silica, Zr, Y, and REE are lower and alumina and Sr are higher than in the Webb Canyon gneiss. These differences reflect different melting conditions: the Webb Canyon gneiss formed by dehydration melting in which amphibole and quartz breaks down, accounting for the low alumina, high FeO, high silica content and observed trace element characteristics. The Bitch Creek gneiss formed by H2O-excess melting in which plagioclase breaks down leaving an amphibole-rich restite, producing magmas higher in alumina and Sr and lower in FeO and HREE. Both melt mechanisms are expected in collisional environments: dehydration melting accompanies gravitational collapse and tectonic extension of dramatically thickened crust, and water-excess melting may occur when collision places a relatively cool, hydrous lower plate beneath a hotter upper plate. The Archean leucogranitic gneisses of the Teton Range are calcic trondhjemites and granodiorites whereas younger collisional leucogranites typically are true granites. The difference in leucogranite composition reflects the

  15. SQUID–SIMS is a useful approach to uncover primary signals in the Archean sulfur cycle

    PubMed Central

    Fischer, Woodward W.; Fike, David A.; Johnson, Jena E.; Raub, Timothy D.; Guan, Yunbin; Kirschvink, Joseph L.; Eiler, John M.

    2014-01-01

    Many aspects of Earth’s early sulfur cycle, from the origin of mass-anomalous fractionations to the degree of biological participation, remain poorly understood—in part due to complications from postdepositional diagenetic and metamorphic processes. Using a combination of scanning high-resolution magnetic superconducting quantum interference device (SQUID) microscopy and secondary ion mass spectrometry (SIMS) of sulfur isotopes (32S, 33S, and 34S), we examined drill core samples from slope and basinal environments adjacent to a major Late Archean (∼2.6–2.5 Ga) marine carbonate platform from South Africa. Coupled with petrography, these techniques can untangle the complex history of mineralization in samples containing diverse sulfur-bearing phases. We focused on pyrite nodules, precipitated in shallow sediments. These textures record systematic spatial differences in both mass-dependent and mass-anomalous sulfur-isotopic composition over length scales of even a few hundred microns. Petrography and magnetic imaging demonstrate that mass-anomalous fractionations were acquired before burial and compaction, but also show evidence of postdepositional alteration 500 million y after deposition. Using magnetic imaging to screen for primary phases, we observed large spatial gradients in Δ33S (>4‰) in nodules, pointing to substantial environmental heterogeneity and dynamic mixing of sulfur pools on geologically rapid timescales. In other nodules, large systematic radial δ34S gradients (>20‰) were observed, from low values near their centers increasing to high values near their rims. These fractionations support hypotheses that microbial sulfate reduction was an important metabolism in organic-rich Archean environments—even in an Archean ocean basin dominated by iron chemistry. PMID:24706767

  16. Mass independently fractionated sulfur isotopes reveal recycling of Archean lithosphere in modern oceanic hotspot lavas

    NASA Astrophysics Data System (ADS)

    Jackson, Matthew; Cabral, Rita; Rose-Koga, Estelle; Koga, Ken; Whitehouse, Martin; Antonelli, Michael; Farquhar, James; Day, James; Hauri, Erik

    2013-04-01

    Oceanic crust and sediments are introduced to the mantle at subduction zones, but the fate of this subducted material within the mantle, as well as the antiquity of this process, is unknown. The mantle is compositionally and isotopically heterogeneous, and it is thought that much of this heterogeneity derives from incorporation of diverse subducted components—both crustal and oceanic lithosphere—over geologic time. Basaltic lavas erupted at some oceanic hotspot volcanoes have long been considered to be melts of ancient subducted lithosphere. However, compelling evidence for the return of subducted materials in mantle plumes is lacking. We report mass independently fractionated (MIF) S-isotope signatures in olivine-hosted sulfides from 20-million-year-old ocean island basalts (OIBs) from Mangaia, Cook Islands (Polynesia). Terrestrial MIF S-isotope signatures were generated exclusively through atmospheric photochemical reactions until ~2.45 billion years ago. Therefore, the discovery of MIF-S in young OIBs indicates that sulfur—likely derived from hydrothermally-altered oceanic crust—was subducted into the mantle before 2.45 Ga and recycled into the mantle source of Mangaia lavas. These new data provide evidence for ancient materials, with MIF 33S depletions, in the mantle source for Mangaia lavas. An Archean age for recycled oceanic crust provides key constraints on the length of time that subducted crustal material can survive in the mantle and on the timescales of mantle convection from subduction to melting and eruption at plume-fed hotspots. The new S-isotope measurements confirm inferences about the cycling of sulfur between the major reservoirs from the Archean to the Phanerozoic, extending from the atmosphere and oceans to the crust and mantle, and ultimately through a return cycle to the surface that, here, is completed in Mangaia lavas. It remains to be seen whether hotspots lavas sampling different compositional mantle endmembers (e.g., EM1, EM2

  17. Genetically optimizing weather predictions

    NASA Astrophysics Data System (ADS)

    Potter, S. B.; Staats, Kai; Romero-Colmenero, Encarni

    2016-07-01

    humidity, air pressure, wind speed and wind direction) into a database. Built upon this database, we have developed a remarkably simple approach to derive a functional weather predictor. The aim is provide up to the minute local weather predictions in order to e.g. prepare dome environment conditions ready for night time operations or plan, prioritize and update weather dependent observing queues. In order to predict the weather for the next 24 hours, we take the current live weather readings and search the entire archive for similar conditions. Predictions are made against an averaged, subsequent 24 hours of the closest matches for the current readings. We use an Evolutionary Algorithm to optimize our formula through weighted parameters. The accuracy of the predictor is routinely tested and tuned against the full, updated archive to account for seasonal trends and total, climate shifts. The live (updated every 5 minutes) SALT weather predictor can be viewed here: http://www.saao.ac.za/ sbp/suthweather_predict.html

  18. Cockpit weather information system

    NASA Technical Reports Server (NTRS)

    Tu, Jeffrey Chen-Yu (Inventor)

    2000-01-01

    Weather information, periodically collected from throughout a global region, is periodically assimilated and compiled at a central source and sent via a high speed data link to a satellite communication service, such as COMSAT. That communication service converts the compiled weather information to GSDB format, and transmits the GSDB encoded information to an orbiting broadcast satellite, INMARSAT, transmitting the information at a data rate of no less than 10.5 kilobits per second. The INMARSAT satellite receives that data over its P-channel and rebroadcasts the GDSB encoded weather information, in the microwave L-band, throughout the global region at a rate of no less than 10.5 KB/S. The transmission is received aboard an aircraft by means of an onboard SATCOM receiver and the output is furnished to a weather information processor. A touch sensitive liquid crystal panel display allows the pilot to select the weather function by touching a predefined icon overlain on the display's surface and in response a color graphic display of the weather is displayed for the pilot.

  19. Pale Orange Dots: Hazy Archean Earth as an Analog for Hazy Earthlike Exoplanets

    NASA Astrophysics Data System (ADS)

    Arney, Giada; Domagal-Goldman, Shawn; Meadows, Victoria S.; Claire, Mark; Schwieterman, Edward

    2014-11-01

    Of the four terrestrial worlds with significant atmospheres in our solar system - Venus, Earth, Mars, and Titan - two of these worlds are presently enshrouded by hazes, and observations suggest that hazy exoplanets are also common (Bean et al. 2010, Sing et al. 2011, Kreidberg et al 2014, Knutson et al. 2014). The early (Archean) Earth may have had a photochemical hydrocarbon haze similar to Titan's (Zerkle et al. 2012), with important climactic effects (Pavlov et al. 2001, Trainer et al. 2006, Haqq-Misra et al. 2008, Domagal-Goldman et al. 2008, Wolf and Toon 2012). Here, we considered Archean Earth as an analog for hazy Earthlike exoplanets and used a modified version of the 1-D photochemical code developed originally by Kasting et al. (1979) to generate model Archean atmospheres with fractal hydrocarbon haze particles. A 1-D line-by-line fully multiple scattering radiative transfer model (Meadows and Crisp 1996) was then used to generate synthetic spectra of early Earth with haze. We have used the resulting synthetic spectra to examine the effect of haze on the detectability of putative biosignatures and the Rayleigh scattering slope, which has been suggested as a means for constraining atmospheric pressure (Benneke and Seager 2012). We also examined haze's impact on the spectral energy distribution reaching the planetary surface. Because the atmospheric pressure and haze particle composition of the Archean Earth are poorly constrained, and because exoplanets will occupy a range of parameter space, we tested the influence of atmospheric pressure and particle density on haze formation, and explored how various particle size distributions affect the spectrum. We find that haze strongly affects the spectral region of the Rayleigh slope, a change detectable at low spectral resolution that impacts the ability to constrain pressure with Rayleigh scattering. The spectral energy distribution at the surface is modulated by haze thickness and the assumed particle size

  20. Climatic impact of spectrally resolved irradiances during the late Archean as modeled with EMAC-FUB

    NASA Astrophysics Data System (ADS)

    Kunze, M.; Langematz, U.; Godolt, M.; Hamann-Reinus, A.; Rauer, H.; Joeckel, P.

    2011-12-01

    During the Archean eon the surface temperatures of the Earth are assumed to have been high enough to support liquid water, despite a lower luminosity of the young Sun. This fact, known as the faint young Sun paradox, can be explained by assuming higher concentrations of greenhouse gases during the early stages of the Earth. But there is still an ongoing debate about the possible range of greenhouse gas concentrations that are consistent with the geologic evidence. We present a study in which we investigate this problem using the Chemistry Climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) in a resolution of T42/L39 with the high-resolution shortwave radiation scheme FUBRad (EMAC-FUB). We are using a constructed, spectrally resolved irradiance dataset valid for the Archean Sun, and analyze the climatic impact of the reduced solar luminosity, an anoxic environment, an increased CO2 concentration, and the different land mass. In total six simulations have been performed, where two simulations only differ by the O2 and O3 content and otherwise have present day conditions. Four simulations use a global ocean, as the distribution and fraction of the continents are highly uncertain during the Archean, and anoxic conditions. Three simulations use a reduced solar luminosity, where two CO2 scenarios are tested (3 ± PAL and 10 ± PAL). As proxy for the early Sun during the late Archean at 2.5 Ga (109 years ago) we take the dwarf star β Com. The spectrally resolved irradiances are compiled from measurements and modeled data, and scaled to a total solar irradiance (TSI) of 82 % the present TSI (i.e. 1121 W m-2). We show that in an anoxic environment with reduced solar luminosity at 2.5 Ga, a global ocean, and present day greenhouse gases, it is still possible to have liquid water in tropical latitudes, even though the global, annual mean surface temperature is below the freezing point of water. When the CO2 concentration is increased, the region of open water widens. The

  1. The western Wabigoon Subprovince, Superior Province, Canada: Archean greenstone succession in rifted basement complex

    NASA Technical Reports Server (NTRS)

    Edwards, G. R.; Davis, D. W.

    1986-01-01

    The Wabigoon Subprovince, interposed between the predominantly metasedimentary-plutonic and gneissic English River and Quetico Subprovinces to the north and south respectively, exposed Archean greenstone and granitoid rocks for a strike length of greater than 700 km. Based on predominating rock types, the western part of the subprovince is divided into two terrains: the northern Wabigoon volcano-sedimentary and pluonic terrain (NWW) and the Wabigoon Diapiric Axis terrain (WDA). Both the NWW and WDA are described according to volcanic sequence, geological faults, chemical composition and evolutionary history.

  2. Fragments of the Archean Mantle in Ultramafic Dykes From Wawa, Ontario

    NASA Astrophysics Data System (ADS)

    Morissette, C. L.; Francis, D.

    2004-05-01

    The Wawa area of the Superior Province possesses numerous ultramafic dykes of Archean age that contain ultramafic nodules potentially representing samples of Archean mantle. Three different types of dykes can be distinguished, each of which hosts its own suite of xenoliths. The Sandor and BandOre dykes, located north of Wawa, exhibit overall compositional similarities with Phanerozoic shoshonite / minette suites. They are characterised by high Al2O3 and K2O contents, and are rich in biotite and chlorite. These two dykes contain rounded nodules, ranging in size from about 5 to 60 cm, composed mostly of actinolite and tremolite, which are interpreted to have been pyroxenites. They are ultrabasic to basic in composition, ranging in SiO2 from 43 to 55 wt%, have orthopyroxene / clinopyroxene ratios of approximately 1:1, and MgOs ranging from 80 to 88. Some xenoliths, however, have significantly high Al content (>11 wt%), and could very well represent recrystallized fragments of the host minette, or other gabbroic protolith. The second type of Archean dykes, located east of Wawa near Dalton, is more similar in composition to Group-II kimberlites. They are characterised by low Al2O3, but high SiO2 contents, and are composed of chlorite, serpentine and feldspar as the dominant mineral phases. This matrix hosts olivine pyroxenite xenoliths with orthopyroxene / clinopyroxene proportions of 2:1. The presence of a poikilitic texture and the vestiges of zoning in pseudomorphs after clinopyroxene indicates they were cumulates. Another nearby dyke is also similar in composition to type II kimberlites, but richer in SiO2. This dyke has feldspar, amphibole and serpentine as its dominant minerals and hosts ultramafic xenoliths that have almost completely been altered to serpentine, though some fresh olivine relicts remain. These xenoliths have the normative mineralogy of highly depleted harzburgite (<1.5 wt.% Al2O3) with MgOs between 88 and 93. A small variation in Ni compared to

  3. Vanadium in peridotites, mantle redox and tectonic environments: Archean to present

    NASA Astrophysics Data System (ADS)

    Canil, Dante

    2002-01-01

    New measurements of partition of vanadium (V) between spinel, garnet and a pigeonite-like high pressure ( P) pyroxene and magnesian liquids on the mantle solidus as a function of oxygen fugacity (fO 2) are presented. The spinel-liquid experiments show an effect of Cr/Al in spinel on partitioning, and further suggest that V exists as V 3+, V 4+ and V 5+ in melts at terrestrial fO 2. Vanadium is mildly incompatible in both 'pigeonitic' pyroxene and garnet between 4.5 and 6.5 GPa on the mantle solidus. Analysis of the fO 2-sensitive partitioning for V between mantle minerals and melts are combined with compositional data from peridotite melting experiments to model the covariation of V and Al in peridotite residues produced by non-modal, fractional melting under different fO 2 from 1.0 to 7.0 GPa. The partial melting models at 1.0 to 3.0 GPa fit the covariation of V and Al in abyssal peridotites quite well at fO 2s similar to those of mid-ocean ridge basalt. Many orogenic massifs and spinel lherzolite xenoliths represent mantle that formed at fO 2 higher than that produced at mid-ocean ridges in a range of tectonic environments. A large proportion of spinel-facies Archean cratonic lithosphere formed at fO 2s significantly higher than those of abyssal peridotites possibly linking its formation to a convergent margin (arc) tectonic setting. The case for garnet-facies cratonic mantle is equivocal; it may have formed at significantly higher pressures (7.0 GPa), or within the spinel-facies at lower pressures but at significantly higher fO 2 than is observed for abyssal peridotites. The imbrication of both oceanic garnet-facies mantle with spinel-facies arc mantle may explain the datasets for some Archean cratons. Overall, the data for Archean mantle melts and residues make clear that models cannot look to reduced, mantle-derived volcanic gases containing H 2 and CO to engender early life synthesis, or to promote hydrogen escape and gradual oxygenation of the Archean earth

  4. The Preservation of Meso- Archean Refractory Lithospheric Mantle Underneath the Eastern Margin of the Tanzania Craton

    NASA Astrophysics Data System (ADS)

    Shu, Q.; Liu, J.; Pearson, G. D.; Gibson, S. A.

    2014-12-01

    Numerous studies on the petrology and geochemistry of peridotite xenoliths from the Tanzanian Craton and its rifted margins have investigated the origin, chemical change and thermal state of the cratonic roots from its core area (Nzega and Mwadui), its Northern (Marsabit) and Eastern margin Labait and Lashaine area (e.g. Dawson, 1964; Henjes-Kunst and Altherr, 1991; Lee & Rudnick, 1999; Chesley et al., 1999; Gibson et al., 2013). These studies suggest that the Tanzanian cratonic mantle formed via high degrees of melt extraction in the Archean (oldest Re-depletion age TRD = 3.4 Ga, Burton et al., 2000) and sev­eral episodes of refertilization. In order to gain further temporal and chemical understanding on the effects of tectonic processes on cratonic roots, we carried out a Re-Os isotopic study on peridotites (n = 11) from Lashaine, which will be followed by Lu-Hf, Sm-Nd and Sr isotope investigations of the constituent minerals of the same samples. The preliminary whole-rock Os isotope data from Lashaine peridotites show a large range of 187Os/188Os (0.1061 - 0.1261), with TRD ages from Meso-Archean to very young (3.1 Ga to 0.3 Ga). There is a negative correlation between TRD and bulk alumina contents. One sample with the lowest Al2O3 yields the oldest age of 3.1 Ga. Five samples range from 2.5 to 2.8 Ga, three give ages close to 2 Ga, and one sample with a high Al2O3 has a TRD at 0.3 Ga. The positive Al2O3-187Os/188Os correlation trend passes above the PM composition may reflect ancient metasomatism by high Re/Os melts or recent metasomatism by very radiogenic Os plume-derived melts. These processes could be related to the evolution of the peripheral Proterozoic mobile belts, or Cenozoic rifting on the Eastern margin. Collectively, our new Os isotope data demonstrate that Meso-Archean (at least 3.1 Ga old) mantle portions are still retained underneath the rifted Eastern margin of the Craton. This is in line with previous results indicating that Archean cratonic

  5. Multiple sulfur isotope geochemistry of Dharwar Supergroup, Southern India: Late Archean record of changing atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    Mishima, Kaoru; Yamazaki, Rie; Satish-Kumar, Madhusoodhan; Ueno, Yuichiro; Hokada, Tomokazu; Toyoshima, Tsuyoshi

    2017-04-01

    Earth's tectonic and climatic systems may have changed fundamentally before the Great Oxidation Event (GOE) at about 2.3 Ga. Sulfur Mass Independent Fractionation (S-MIF) has demonstrated that Earth's atmosphere was virtually oxygen-free before the GOE. During 3.0 to 2.4 Ga, the change in Δ33S and Δ36S signals may reflect the perturbation of atmospheric chemistry, though the mechanisms of the change are uncertain. Here, we reported multiple sulfur isotopic studies of Archean volcano-sedimentary sequences of the Dharwar Supergroup, distributed in the Chitradurga Schist Belt (CSB), Southern India. New field mapping and zircon U-Pb dating allows us to reconstruct detailed lithostratigraphy of the Dharwar Supergroup. The lower unit consists of post-3.0 Ga conglomerate, stromatolitic carbonate, siliciclastics with diamictite, chert/BIF and pillowed basalt in ascending order, all of which are older than the 2676 Ma dacite dyke that had intruded into the lower unit. The upper unit unconformably overlies the pillow basalts at the top of the lower unit, and consists of conglomerate/sandstone with ∼2600 Ma detrital zircons, komatiitic basalt, BIF and siliciclastic sequence with mafic volcanics. Sulfur isotope analysis of extracted sulfides shows MIF signals (Δ33S > + 1 ‰) with clear Δ33S- Δ36S correlations. The lower group of the Dharwar Supergroup shows a Δ36S / Δ33S slope of -1.48, the middle group shows -1.16 and -1.07, and the upper group shows -0.94. Reassessment of all the Archean S-MIF records from sedimentary rocks indicates that the Δ36S / Δ33S slope systematically changed during the Archean period. The observed trend in the Indian section is similar to those of its Pilbara-Kaapvaal equivalents, thus it could reflect a global atmospheric signature. Moreover, the isotopic trend seems to correlate with mid-Archean glaciation. Thus, the Δ36S / Δ33S slope could be a useful tracer for atmospheric chemistry and its link with climate change before the GOE.

  6. Controls on Atmospheric O2: The Anoxic Archean and the Suboxic Proterozoic

    NASA Astrophysics Data System (ADS)

    Kasting, J. F.

    2015-12-01

    Geochemists have now reached consensus that the Archean atmosphere was mostly anoxic, that a Great Oxidation Event (GOE) occurred at around 2.5 Ga, and that the ensuing Proterozoic atmosphere was consistently oxidized [1,2]. Evidence for this broad-scale change in atmospheric composition comes from a variety of sources, most importantly from multiple sulfur isotopes [3,4]. The details of both the Archean and Proterozoic environments remain controversial, however, as does the underlying cause of the GOE. Evidence of 'whiffs' of oxygen during the Archean [5] now extend back as far as 3.0 Ga, based on Cr isotopes [6]. This suggests that O2 was being produced by cyanobacteria well before the GOE and that the timing of this event may have been determined by secular changes in O2 sinks. Catling et al. [7] emphasized escape of hydrogen to space, coupled with progressive oxidation of the continents and a concomitant decrease in the flux of reduced gases from metamorphism. But hydrogen produced by serpentinization of seafloor could also have been a controlling factor [8]. Higher mantle temperatures during the Archean should have resulted in thicker, more mafic seafloor and higher H2 production; decreasing mantle temperatures during the Proterozoic should have led to seafloor more like that of today and a corresponding decrease in H2 production, perhaps by enough to trigger the GOE. Once the atmosphere became generally oxidizing, it apparently remained that way during the rest of Earth's history. But O2 levels in the mid-Proterozoic could have been as low at 10-3 times the Present Atmospheric Level (PAL) [9]. The evidence, once again, is based on Cr isotopes. Possible mechanisms for maintaining such a 'suboxic' Proterozoic atmosphere will be discussed. Refs: 1. H. D. Holland, Geochim. Cosmochim. Acta 66, 3811 (2002). 2. H. D. Holland, Philosophical Transactions of the Royal Society B-Biological Sciences 361, 903 (Jun 29, 2006). 3. J. Farquhar, H. Bao, M. Thiemans, Science

  7. A model of weathering intensity for the Australian continent

    NASA Astrophysics Data System (ADS)

    Wilford, J.

    2013-12-01

    Regolith encompasses all weathered materials in the zone between the Earth's surface and fresh bedrock at depth. This weathered zone includes the soil, which may constitute the whole of the regolith profile or represent only its upper part. Important hydrological and biogeochemical processes operate within the regolith, including the infiltration and storage of near-surface water and nutrients, which sustain agricultural productivity. The degree to which the regolith is weathered (or its weathering intensity) is intrinsically linked to the factors involved in soil formation including parent material, climate, topography, biota and time. The degree to which the bedrock or sediments are weathered has a significant effect on the nature and distribution of regolith materials. There is commonly a strong correlation between weathering intensity and the degree of soil development as well as the depth of the weathering front. Changes in weathering intensity correspond to changes in the geochemical and physical properties of bedrock, ranging from essentially unweathered parent materials through to intensely weathered and leached regolith where all traits of the original protolith (original unweathered rock) are overprinted or lost altogether. With increasing weathering intensity we see mineral and geochemical convergence to more resistant secondary weathered materials including clay, silica, and various oxides. A weathering intensity index (WII) over the Australian continent has been developed at a 100 m resolution using two regression models based on airborne gamma-ray spectrometry imagery and the Shuttle Radar Topography Mission (SRTM) elevation data. Airborne gamma-ray spectrometry measures the concentration of three radioelements -- potassium (K), thorium (Th) and uranium (U) at the Earth's surface. The total gamma-ray flux (dose) is also calculated based on the weighted additions of the three radioelements. In general K is leached with increasing weathering whereas Th

  8. New Constraints on the Extent of Paleoproterozoic and Archean Basement in the Northwest U.S. Cordillera

    NASA Astrophysics Data System (ADS)

    Brewer, R. A.; Vervoort, J.; Lewis, R. S.; Gaschnig, R. M.; Hart, G.

    2008-12-01

    The Laurentian basement west of the Wyoming craton in southwest Montana and northern Idaho has been interpreted as a collage of Archean and Proterozoic terranes which accreted to the North American craton and incorporated into Laurentia at ~ 1.86 Ga [1]. This basement and the geometry of the Archean and Proterozoic crust are poorly understood due to coverage by metasediments of the Belt-Purcell Supergroup and are further obscured by Mesozoic magmatism (Idaho Batholith, sensu lato). Exposures of the basement are rare but have been documented in a few regions including the Priest River Complex in northern Idaho and the Sevier fold and thrust belt just northwest of the Wyoming craton in the Great Falls tectonic zone (Foster et al. 2006). New ages and isotopic data from orthogneisses in north-central Idaho provide evidence for previously undocumented exposures of both Paleoproterozoic and Archean basement that may place important constraints on the reconstruction of Laurentia and its tectonic setting. The orthogneisses analyzed in this study (all previously mapped as deformed Cretaceous plutons) fall into two distinct age groups of 1.86 Ga and 2.67 Ga. The zircons from both the Archean and Proterozoic rocks have simple systematics. The zircons from three Archean samples have ɛHf(i) values of 2.4 ± 2.1, 3.8 ± 1.8, and 5.2 ± 3.5 (average values based on 6 individual zircon Hf analyses per sample). Zircons from the Paleoproterozoic gneisses have different but internally consistent ɛHf(i) values of -8.0 ± 0.9 and -0.6 ± 1.4. In contrast, both Hf and Nd whole rock data are highly scattered in these samples especially in the Archean samples in which ɛHf(i) varies from -25 to +21 and ɛNd(i) varies from -8 to +11. These extreme values are implausible for initial compositions and indicate open system behavior in both Lu-Hf and Sm-Nd in the whole rocks. The zircons, in contrast, appear to be closed to significant Hf mobility on the scale of the laser analyses. The data

  9. Niobium-enriched basalts from the Wabigoon subprovince, Canada: evidence for adakitic metasomatism above an Archean subduction zone

    NASA Astrophysics Data System (ADS)

    Wyman, D. A.; Ayer, J. A.; Devaney, J. R.

    2000-06-01

    Late Archean niobium-enriched basalts from the Central Sturgeon Lake assemblage and Neepawa group of the western Wabigoon subprovince have mantle-normalized Nb/La between 0.8 and 1.3 and Zr/Y between 4 and 7. They are compositionally similar to basalts attributed to adakite metasomatism of mantle wedge regions in Cenozoic subduction zones [Sajona et al., J. Petrol. 37 (1996) 693-726]. In detail, their Sc-REE systematics suggest the Archean basalts were generated above the garnet stability field. An association with adakite-like volcanic rocks, an absence of komatiites and the arc-like attributes of their host sequences suggest a subduction-related origin for the basalts. If current models of adakite and Niobium-enriched basalt genesis are valid, then additional examples of these rocks should be relatively common in other Archean greenstone belts.

  10. Did the character of subduction change at the end of the Archean? Constraints from convergent-margin granitoids

    NASA Astrophysics Data System (ADS)

    Condie, Kent C.

    2008-08-01

    Large ion lithophile and high field strength element distributionsin juvenile upper continental crust are controlled chiefly bythe abundance of tonalite-trondhjemite-granodiorite (TTG) inthe Archean shifting to a combination of TTG, calc-alkalinegranitoid, and graywacke control thereafter. Geochemical differencesbetween TTG and high-silica adakites do not require productionof most TTG magmas in descending slabs. Changes in the ratioof TTG to calc-alkaline granitoids after 2.5 Ga indicate thatArchean subduction zones must have differed from younger subductionzones in two very important ways: (1) a deep mafic crust servedas a TTG magma source (either as thickened crust or in descendingslabs), and (2) they did not give rise to significant volumesof calc-alkaline magma. Thickened mafic crust in the Late Archeanmay have resulted from plate jams in subduction zones causedby thicker oceanic crust and oceanic plateaus produced duringLate Archean mantle thermal events.

  11. Recombination reactions as a possible mechanism of mass-independent fractionation of sulfur isotopes in the Archean atmosphere of Earth.

    PubMed

    Babikov, Dmitri

    2017-03-21

    A hierarchy of isotopically substituted recombination reactions is formulated for production of sulfur allotropes in the anoxic atmosphere of Archean Earth. The corresponding system of kinetics equations is solved analytically to obtain concise expressions for isotopic enrichments, with focus on mass-independent isotope effects due to symmetry, ignoring smaller mass-dependent effects. Proper inclusion of atom-exchange processes is shown to be important. This model predicts significant and equal depletions driven by reaction stoichiometry for all rare isotopes: (33)S, (34)S, and (36)S. Interestingly, the ratio of capital [Formula: see text] values obtained within this model for (33)S and (36)S is -1.16, very close to the mass-independent fractionation line of the Archean rock record. This model may finally offer a mechanistic explanation for the striking mass-independent fractionation of sulfur isotopes that took place in the Archean atmosphere of Earth.

  12. Archean inheritance in zircon from late Paleozoic granites from the Avalon zone of southeastern New England: an African connection

    USGS Publications Warehouse

    Zartman, R.E.; Don, Hermes O.

    1987-01-01

    In southeastern New England the Narragansett Pier Granite locally intrudes Carboniferous metasedimentary rocks of the Narragansett basin, and yields a monazite UPb Permian emplacement age of 273 ?? 2 Ma. Zircon from the Narragansett Pier Granite contains a minor but detectable amount of an older, inherited component, and shows modern loss of lead. Zircon from the late-stage, aplitic Westerly Granite exhibits a more pronounced lead inheritance -permitting the inherited component to be identified as Late Archean. Such old relict zircon has not been previously recognized in Proterozoic to Paleozoic igneous rocks in New England, and may be restricted to late Paleozoic rocks of the Avalon zone. We suggest that the Archean crustal component reflects an African connection, in which old Archean crust was underplated to the Avalon zone microplate in the late Paleozoic during collision of Gondwanaland with Avalonia. ?? 1987.

  13. Archean Age Fossils from Northwestern Australia (Approximately 3.3 to 3.5 GA, Warrawoona Group, Towers Formation)

    NASA Technical Reports Server (NTRS)

    Smith, Penny A. Morris

    1999-01-01

    Archean aged rocks from the Pilbara Block area of western Australia (Warrawoona Group, Towers Formation, -3.3-3.5 Ga) contain microfossils that are composed of various sizes of spheres and filaments. The first descriptions of these microfossils were published in the late 1970's (Dunlop, 1978; Dunlop, et. al., 1978). The authenticity of the microfossils is well established. The small size of the microfossils prevents isotope dating, at least with the present technology. Microbiologists, however, have established guidelines to determine the authenticity of the Archean aged organic remains (Schopf, Walter, 1992).

  14. DOPPLER WEATHER SYSTEM

    SciTech Connect

    Berlin, Gary J.

    2002-08-05

    The SRS Doppler Weather System consists of a Doppler Server, A Master Server (also known as the Weather Server), several Doppler Slave Servers, and client-side software program called the Doppler Radar Client. This system is used to display near rel-time images taken from the SRS Weather Center's Doppler Radar computer. The Doppler Server is software that resides on the SRS Doppler Computer. It gathers raw data, 24-bit color weather images via screen scraping ever five minutes as requested by the Master Server. The Doppler Server then reduces the 24-bit color images to 8-bit color using a fixed color table for analysis and compression. This preserves the fidelity of the image color and arranges the colors in specific order for display. At the time of color reduction, the white color used for the city names on the background images are remapped to a different index (color) of white that the white on the weather scale. The Weather Server places a time stamp on the image, then compresses the image and passes it to all Doppler Slave servers. Each of the Doppler Slave servers mainitain a circular buffer of the eight most current images representing the last 40 minutes of weather data. As a new image is added, the oldest drops off. The Doppler Radar Client is an optional install program for any site-wide workstation. When a Client session is started, the Client requests Doppler Slave server assignment from the Master Server. Upon its initial request to the Slave Server, the Client obtains all eight current images and maintains its own circular buffer, updating its images every five minutes as the Doppler Slave is updated. Three background reference images are stored as part of the Client. The Client brings up the appropriate background image, decompresses the doppler data, and displays the doppler data on the background image.

  15. Monitoring moisture dynamics in weathered, fractured bedrock

    NASA Astrophysics Data System (ADS)

    Rempe, D. M.; Salve, R.; Oshun, J.; Dietrich, W. E.

    2013-12-01

    response, using the timing of the response and manufacturer or site specific calibration, allowed us to effectively quantify moisture storage and transport rates in the weathered bedrock. We found that in response to rainfall, all water passes through the soil and weathered bedrock at the site and perches above the fresh bedrock before it travels laterally downslope. The rapid water table response to the first storm events of the season often occurs before the wetting front progresses through the first few meters of the weathered profile. Though shallower weathered bedrock wets and dries annually, deeper portions of the weathered bedrock zone do not show significant seasonal changes in moisture content. As investigations of the critical zone extend deeper, robust techniques for monitoring moisture in weathered bedrock are needed to quantify the significance of rock moisture in hydrologic and geomorphic processes.

  16. The chemical conditions of the late Archean Hamersley basin inferred from whole rock and pyrite geochemistry with Δ33S and δ34S isotope analyses

    NASA Astrophysics Data System (ADS)

    Gregory, Daniel D.; Large, Ross R.; Halpin, Jacqueline A.; Steadman, Jeffery A.; Hickman, Arthur H.; Ireland, Trevor R.; Holden, Peter

    2015-01-01

    The well-preserved late Archean sedimentary rocks of the Fortescue and Hamersley Basins in Western Australia offer fascinating insights into early earth ocean chemistry prior to the Great Oxidation Event (GOE). In this study, we use a combination of whole rock geochemistry, LA-ICPMS trace element analysis of sedimentary pyrite and pyrrhotite and SHRIMP-SI sulfur isotope analyses to elucidate the chemical changes in these sedimentary rocks. These proxies are used to examine chemical conditions of the ocean during the late Archean. Two to three periods of oxygen enrichment prior to the deposition of banded iron formations (BIF) can be identified. One minor stage of general increase in whole rock enrichment factors and trace element content of pyrite is observed up stratigraphy in the Jeerinah Formation, Fortescue Basin and a more substantial stage is present in the Paraburdoo and Bee Gorge Members of the Wittenoom Formation, Hamersley Basin. Some of the trace element enrichments indicate organic matter burial flux (Ni, Cr, Zn, Co and Cu) which suggests an increase in biological productivity. If the increased biological activity reflects an increase in cyanobacteria activity then an associated increase in oxygen is likely to have occurred during the deposition of the Bee Gorge Member. An increase in atmospheric oxygen would result in continental weathering of sulfide and other minerals, increasing the trace element content of the water column via erosion and avoiding excessive depletion of trace elements due to drawdown in seawater. Since some of these trace elements may also be limiting nutrients (such as Mo and Se) for the cyanobacteria, the degree of biological productivity may have further increased due to the increasing amount of trace elements introduced by oxygenation in a positive feedback loop. These periods of increased productivity and oxygen rise stopped prior to the onset of BIF deposition in the Hamersley Basin. This may be due to the ocean reaching an

  17. Evidence for a complex archean deformational history; southwestern Michipicoten Greenstone Belt, Ontario

    NASA Technical Reports Server (NTRS)

    Mcgill, George E.; Shrady, Catherine H.

    1986-01-01

    The Michipicoten Greenstone Belt extends for about 150 km ENE from the northeastern angle of Lake Superior. In common with many other Archean greenstone belts, it is characterized by generally steep bedding dips and a distribution of major lithologic types suggesting a crudely synclinal structure for the belt as a whole. Detailed mapping and determination of structural sequence demonstrates that the structure is much more complex. The Archean history of the belt includes formation of at least three regionally significant cleavages, kilometer-scale overturning, extensive shearing, and diabase intrusion. Most well defined, mappable 'packages' of sedimentary rocks appear to be bounded by faults. These faults were active relatively early in the structural history of the belt, when extensive overturning also occurred. Steepening of dips, NW-SE shortening, development of steep NE cleavage, and pervasive shearing all postdate the early faulting and the regional overturning, obscuring much of the detail needed to define the geometry of the earlier structures. The results obtained so far suggest, however, that the Michipicoten Greenstone Belt underwent an early stage of thrusting and associated isoclinal folding, probably in a convergent tectonic environment.

  18. Geochemical consequences of the metasomatic conversion of an Early Archean komatiite sequence into chert

    SciTech Connect

    Hanor, J.S.; Duchac, K.C.

    1985-01-01

    Duchac and Hanor (1985) have demonstrated from field and petrographic evidence that the stratiform, muscovite-bearing cherts of Skokhola Ridge, Barberton Mountain Land, South Africa, represent a pervasively silicified sequence of komatiites and komatiitic basalts of Early Archean age. Most alteration took place early, prior to any significant tectonic deformation. The isovolumetric nature of the alteration, as confirmed by excellent preservation of igneous textures, and the immobility of Al make it possible to quantify elemental gains and losses during metasomatism. The sequence was strongly depleted in Na, Mg, Ca, Sr, Fe, and Mn, and enriched in K, Rb, and Ba, Al, Y, Zr, Ti, and P were immobile. It is most likely that the sequence was altered by large volumes of ascending hydrothermal solutions, with the decrease in T upward favoring precipitation of silica and muscovite. The net effect was to convert an ultramafic igneous rock into a rock having a composition approaching that of the average sandstone. Such alteration, if regionally extensive, undoubtedly affected the geochemical evolution of both the Early Archean crust and hydrosphere in the Barberton greenstone belt.

  19. Electron Paramagnetic Resonance Study of a Photosynthetic Microbial Mat and Comparison with Archean Cherts

    NASA Astrophysics Data System (ADS)

    Bourbin, M.; Derenne, S.; Gourier, D.; Rouzaud, J.-N.; Gautret, P.; Westall, F.

    2012-12-01

    Organic radicals in artificially carbonized biomass dominated by oxygenic and non-oxygenic photosynthetic bacteria, Microcoleus chthonoplastes-like and Chloroflexus-like bacteria respectively, were studied by Electron Paramagnetic Resonance (EPR) spectroscopy. The two bacteria species were sampled in mats from a hypersaline lake. They underwent accelerated ageing by cumulative thermal treatments to induce progressive carbonization of the biological material, mimicking the natural maturation of carbonaceous material of Archean age. For thermal treatments at temperatures higher than 620 °C, a drastic increase in the EPR linewidth is observed in the carbonaceous matter from oxygenic photosynthetic bacteria and not anoxygenic photosynthetic bacteria. This selective EPR linewidth broadening reflects the presence of a catalytic element inducing formation of radical aggregates, without affecting the molecular structure or the microstructure of the organic matter, as shown by Raman spectroscopy and Transmission Electron Microscopy. For comparison, we carried out an EPR study of organic radicals in silicified carbonaceous rocks (cherts) from various localities, of different ages (0.42 to 3.5 Gyr) and having undergone various degrees of metamorphism, i.e. various degrees of natural carbonization. EPR linewidth dispersion for the most primitive samples was quite significant, pointing to a selective dipolar broadening similar to that observed for carbonized bacteria. This surprising result merits further evaluation in the light of its potential use as a marker of past bacterial metabolisms, in particular oxygenic photosynthesis, in Archean cherts.

  20. Prebiotic Synthesis of Glycine from Ethanolamine in Simulated Archean Alkaline Hydrothermal Vents.

    PubMed

    Zhang, Xianlong; Tian, Ge; Gao, Jing; Han, Mei; Su, Rui; Wang, Yanxiang; Feng, Shouhua

    2016-09-23

    Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. In recent years, a novel hydrothermal system in Archean subseafloor has been proposed. In this model, highly alkaline and high temperature hydrothermal fluids were generated in basalt-hosted hydrothermal vents, where H2 and CO2 could be abundantly provided. These extreme conditions could have played an irreplaceable role in the early evolution of life. Nevertheless, sufficient information has not yet been obtained for the abiotic synthesis of amino acids, which are indispensable components of life, at high temperature and alkaline condition. This study aims to propose a new method for the synthesis of glycine in simulated Archean submarine alkaline vent systems. We investigated the formation of glycine from ethanolamine under conditions of high temperature (80-160 °C) and highly alkaline solutions (pH = 9.70). Experiments were performed in an anaerobic environment under mild pressure (0.1-8.0 MPa) at the same time. The results suggested that the formation of glycine from ethanolamine occurred rapidly and efficiently in the presence of metal powders, and was favored by high temperatures and high pressures. The experiment provides a new pathway for prebiotic glycine formation and points out the phenomenal influence of high-temperature alkaline hydrothermal vents in origin of life in the early ocean.

  1. Prebiotic Synthesis of Glycine from Ethanolamine in Simulated Archean Alkaline Hydrothermal Vents

    NASA Astrophysics Data System (ADS)

    Zhang, Xianlong; Tian, Ge; Gao, Jing; Han, Mei; Su, Rui; Wang, Yanxiang; Feng, Shouhua

    2016-09-01

    Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. In recent years, a novel hydrothermal system in Archean subseafloor has been proposed. In this model, highly alkaline and high temperature hydrothermal fluids were generated in basalt-hosted hydrothermal vents, where H2 and CO2 could be abundantly provided. These extreme conditions could have played an irreplaceable role in the early evolution of life. Nevertheless, sufficient information has not yet been obtained for the abiotic synthesis of amino acids, which are indispensable components of life, at high temperature and alkaline condition. This study aims to propose a new method for the synthesis of glycine in simulated Archean submarine alkaline vent systems. We investigated the formation of glycine from ethanolamine under conditions of high temperature (80-160 °C) and highly alkaline solutions (pH = 9.70). Experiments were performed in an anaerobic environment under mild pressure (0.1-8.0 MPa) at the same time. The results suggested that the formation of glycine from ethanolamine occurred rapidly and efficiently in the presence of metal powders, and was favored by high temperatures and high pressures. The experiment provides a new pathway for prebiotic glycine formation and points out the phenomenal influence of high-temperature alkaline hydrothermal vents in origin of life in the early ocean.

  2. Electron paramagnetic resonance study of a photosynthetic microbial mat and comparison with Archean cherts.

    PubMed

    Bourbin, M; Derenne, S; Gourier, D; Rouzaud, J-N; Gautret, P; Westall, F

    2012-12-01

    Organic radicals in artificially carbonized biomass dominated by oxygenic and non-oxygenic photosynthetic bacteria, Microcoleus chthonoplastes-like and Chloroflexus-like bacteria respectively, were studied by Electron Paramagnetic Resonance (EPR) spectroscopy. The two bacteria species were sampled in mats from a hypersaline lake. They underwent accelerated ageing by cumulative thermal treatments to induce progressive carbonization of the biological material, mimicking the natural maturation of carbonaceous material of Archean age. For thermal treatments at temperatures higher than 620 °C, a drastic increase in the EPR linewidth is observed in the carbonaceous matter from oxygenic photosynthetic bacteria and not anoxygenic photosynthetic bacteria. This selective EPR linewidth broadening reflects the presence of a catalytic element inducing formation of radical aggregates, without affecting the molecular structure or the microstructure of the organic matter, as shown by Raman spectroscopy and Transmission Electron Microscopy. For comparison, we carried out an EPR study of organic radicals in silicified carbonaceous rocks (cherts) from various localities, of different ages (0.42 to 3.5 Gyr) and having undergone various degrees of metamorphism, i.e. various degrees of natural carbonization. EPR linewidth dispersion for the most primitive samples was quite significant, pointing to a selective dipolar broadening similar to that observed for carbonized bacteria. This surprising result merits further evaluation in the light of its potential use as a marker of past bacterial metabolisms, in particular oxygenic photosynthesis, in Archean cherts.

  3. Early Archean serpentine mud volcanoes at Isua, Greenland, as a niche for early life.

    PubMed

    Pons, Marie-Laure; Quitté, Ghylaine; Fujii, Toshiyuki; Rosing, Minik T; Reynard, Bruno; Moynier, Frederic; Douchet, Chantal; Albarède, Francis

    2011-10-25

    The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal sequence and on serpentinites from modern ophiolites, midocean ridges, and the Mariana forearc. In stark contrast to modern midocean ridge and ophiolite serpentinites, Zn in Isua and Mariana serpentinites is markedly depleted in heavy isotopes with respect to the igneous average. Based on recent results of Zn isotope fractionation between coexisting species in solution, the Isua serpentinites were permeated by carbonate-rich, high-pH hydrothermal solutions at medium temperature (100-300 °C). Zinc isotopes therefore stand out as a pH meter for fossil hydrothermal solutions. The geochemical features of the Isua fluids resemble the interstitial fluids sampled in the mud volcano serpentinites of the Mariana forearc. The reduced character and the high pH inferred for these fluids make Archean serpentine mud volcanoes a particularly favorable setting for the early stabilization of amino acids.

  4. Evidence for reactive reduced phosphorus species in the early Archean ocean

    PubMed Central

    Pasek, Matthew A.; Harnmeijer, Jelte P.; Buick, Roger; Gull, Maheen; Atlas, Zachary

    2013-01-01

    It has been hypothesized that before the emergence of modern DNA–RNA–protein life, biology evolved from an “RNA world.” However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive. Recently, it has been proposed that during the Hadean–Archean heavy bombardment by extraterrestrial impactors, meteorites would have provided reactive P in the form of the iron–nickel phosphide mineral schreibersite. This reacts in water, releasing soluble and reactive reduced P species, such as phosphite, that could then be readily incorporated into prebiotic molecules. Here, we report the occurrence of phosphite in early Archean marine carbonates at levels indicating that this was an abundant dissolved species in the ocean before 3.5 Ga. Additionally, we show that schreibersite readily reacts with an aqueous solution of glycerol to generate phosphite and the membrane biomolecule glycerol–phosphate under mild thermal conditions, with this synthesis using a mineral source of P. Phosphite derived from schreibersite was, hence, a plausible reagent in the prebiotic synthesis of phosphorylated biomolecules and was also present on the early Earth in quantities large enough to have affected the redox state of P in the ocean. Phosphorylated biomolecules like RNA may, thus, have first formed from the reaction of reduced P species with the prebiotic organic milieu on the early Earth. PMID:23733935

  5. Earth's earliest biosphere-a proposal to develop a collection of curated archean geologic reference materials

    NASA Technical Reports Server (NTRS)

    Lindsay, John F.; McKay, David S.; Allen, Carlton C.

    2003-01-01

    The discovery of evidence indicative of life in a Martian meteorite has led to an increase in interest in astrobiology. As a result of this discovery, and the ensuing controversy, it has become apparent that our knowledge of the early development of life on Earth is limited. Archean stratigraphic successions containing evidence of Earth's early biosphere are well preserved in the Pilbara Craton of Western Australia. The craton includes part of a protocontinent consisting of granitoid complexes that were emplaced into, and overlain by, a 3.51-2.94 Ga volcanigenic carapace - the Pilbara Supergroup. The craton is overlain by younger supracrustal basins that form a time series recording Earth history from approximately 2.8 Ga to approximately 1.9 Ga. It is proposed that a well-documented suite of these ancient rocks be collected as reference material for Archean and astrobiological research. All samples would be collected in a well-defined geological context in order to build a framework to test models for the early evolution of life on Earth and to develop protocols for the search for life on other planets.

  6. Evidence for reactive reduced phosphorus species in the early Archean ocean.

    PubMed

    Pasek, Matthew A; Harnmeijer, Jelte P; Buick, Roger; Gull, Maheen; Atlas, Zachary

    2013-06-18

    It has been hypothesized that before the emergence of modern DNA-RNA-protein life, biology evolved from an "RNA world." However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive. Recently, it has been proposed that during the Hadean-Archean heavy bombardment by extraterrestrial impactors, meteorites would have provided reactive P in the form of the iron-nickel phosphide mineral schreibersite. This reacts in water, releasing soluble and reactive reduced P species, such as phosphite, that could then be readily incorporated into prebiotic molecules. Here, we report the occurrence of phosphite in early Archean marine carbonates at levels indicating that this was an abundant dissolved species in the ocean before 3.5 Ga. Additionally, we show that schreibersite readily reacts with an aqueous solution of glycerol to generate phosphite and the membrane biomolecule glycerol-phosphate under mild thermal conditions, with this synthesis using a mineral source of P. Phosphite derived from schreibersite was, hence, a plausible reagent in the prebiotic synthesis of phosphorylated biomolecules and was also present on the early Earth in quantities large enough to have affected the redox state of P in the ocean. Phosphorylated biomolecules like RNA may, thus, have first formed from the reaction of reduced P species with the prebiotic organic milieu on the early Earth.

  7. Earth's earliest biosphere-a proposal to develop a collection of curated archean geologic reference materials.

    PubMed

    Lindsay, John F; McKay, David S; Allen, Carlton C

    2003-01-01

    The discovery of evidence indicative of life in a Martian meteorite has led to an increase in interest in astrobiology. As a result of this discovery, and the ensuing controversy, it has become apparent that our knowledge of the early development of life on Earth is limited. Archean stratigraphic successions containing evidence of Earth's early biosphere are well preserved in the Pilbara Craton of Western Australia. The craton includes part of a protocontinent consisting of granitoid complexes that were emplaced into, and overlain by, a 3.51-2.94 Ga volcanigenic carapace - the Pilbara Supergroup. The craton is overlain by younger supracrustal basins that form a time series recording Earth history from approximately 2.8 Ga to approximately 1.9 Ga. It is proposed that a well-documented suite of these ancient rocks be collected as reference material for Archean and astrobiological research. All samples would be collected in a well-defined geological context in order to build a framework to test models for the early evolution of life on Earth and to develop protocols for the search for life on other planets.

  8. New weather index

    NASA Astrophysics Data System (ADS)

    Scientists at the National Oceanic and Atmospheric Administration (NOAA) and the University of Delaware have refined the wind-chill factor, a common measurement of weather discomfort, into a new misery register called the weather stress index. In addition to the mix of temperature and wind speed data used to calculate wind chill, the recipe for the index adds two new ingredients—humidity and a dash of benchmark statistics—to estimate human reaction to weather conditions. NOAA says that the weather stress index estimates human reaction to weather conditions and that the reaction depends on variations from the ‘normal’ conditions in the locality involved.Discomfort criteria for New Orleans, La., and Bismarck, N.D., for example, differ drastically. According to NOAA, when it's the middle of winter and it's -10°C with a relative humidity of 80% and 24 km/h winds, persons in New Orleans would be highly stressed while those in Bismarck wouldn't bat an eye.

  9. Weather from the Stratosphere?

    NASA Technical Reports Server (NTRS)

    Baldwin, Mark P.; Thompson, David W. J.; Shuckburgh, Emily F.; Norton, Warwick A.; Gillett, Nathan P.

    2006-01-01

    Is the stratosphere, the atmospheric layer between about 10 and 50 km, important for predicting changes in weather and climate? The traditional view is that the stratosphere is a passive recipient of energy and waves from weather systems in the underlying troposphere, but recent evidence suggests otherwise. At a workshop in Whistler, British Columbia (1), scientists met to discuss how the stratosphere responds to forcing from below, initiating feedback processes that in turn alter weather patterns in the troposphere. The lowest layer of the atmosphere, the troposphere, is highly dynamic and rich in water vapor, clouds, and weather. The stratosphere above it is less dense and less turbulent (see the figure). Variability in the stratosphere is dominated by hemispheric-scale changes in airflow on time scales of a week to several months. Occasionally, however, stratospheric air flow changes dramatically within just a day or two, with large-scale jumps in temperature of 20 K or more. The troposphere influences the stratosphere mainly through atmospheric waves that propagate upward. Recent evidence shows that the stratosphere organizes this chaotic wave forcing from below to create long-lived changes in the stratospheric circulation. These stratospheric changes can feed back to affect weather and climate in the troposphere.

  10. Archean to Paleoproterozoic polymetamorphic history of the Salma eclogite in Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Imayama, Takeshi; Oh, Chang-Whan; Park, Chan-Soo; Yi, Keewook; Jung, Haemyeong

    2015-04-01

    One of the most important questions in the Earth Science is when and how plate tectonics operate in the Precambrian time. The tectonic and thermal evolution of the Precambrian eclogite is significant key for understanding the Precambrian geodynamic mechanisms. Eclogites in Kola Peninsula, Russia are some of the oldest eclogites of the world, but there has been much debate about the timing of eclogite-facies metamorphism: Archean (e.g. Volodichev et al. 2004; Mints et al., 2010) or Paleoproterozoic (e.g. Skublob et al., 2011, 2012). The controversy is mainly because of the lack of zircon dating coupled with the formation of garnet and omphacite. In this study, we present geochronological, petrographic, and geochemical data from the Salma eclogites in the Kola Peninsula, Russia to characterize subduction and collision processes in the Precambrian. Microstructural observations, P-T analyses, zircon inclusion analyses, and U-Pb zircon dating revealed multiple metamorphic stages that the Salma eclogite underwent. The amphibolite facies metamorphic event firstly occurred at 2.73-2.72 Ga during Archean. In the Paleoproterozoic period, the Salma eclogites underwent prograde stage of epidote-amphibolite facies metamorphism. The eclogite facies metamorphic event took place under the P-T condition of 16-18 kbar and 740-770 °C at 1.89-1.88 Ga, with a subsequent granulite facies metamorphism during decompression stage from 18 kbar to 9-12 kbar. Finally, later amphibolite facies metamorphism occurred at 8-10 kbar and 590-610 °C on cooling. The Archean metamorphic zircons that contain inclusions of Grt + Am + Bt + Pl + Qtz + Rt are unzoned grains with dark CL, and they are relatively enriched in HREE. In contrast, the 1.89-1.88 Ga sector or concentric zoned zircons with pale-grey CL include inclusions of Grt + Omp + Ca-Cpx + Am + Bt + Qtz + Rt, and they have the flat pattern of HREE due to the amounts of abundant garnet during the eclogite-facies metamorphism. Whole rock

  11. Evaluating the earliest traces of Archean sub-seafloor life by NanoSIMS

    NASA Astrophysics Data System (ADS)

    Mcloughlin, N.; Grosch, E. G.; Kilburn, M.; Wacey, D.

    2012-12-01

    The Paleoarchean sub-seafloor has been proposed as an environment for the emergence of life with titanite microtextures in pillow lavas argued to be the earliest traces of microbial micro-tunneling (Furnes et al. 2004). Here we use a nano-scale ion microprobe (NanoSIMS) to evaluate possible geochemical traces of life in 3.45 Ga pillow lavas of the Barberton Greenstone Belt, South Africa. We investigated both surface and drill core samples from the original "Biomarker" outcrop in the Hooggenoeg Fm. Pillow lava metavolcanic glass contain clusters of segmented microcrystalline titanite filaments, ~4μm across and <200μm in length. Their size, shape and distribution have been directly compared to those found in recent oceanic crust. Thus it has been argued that they are the mineralized remains of tunnels formed by microbes that etched volcanic glass in the Archean sub-seafloor (Furnes et al 2004; Banerjee et al. 2006). Elemental mapping by NanoSIMS was undertaken to investigate reports of enrichments in carbon (possibly also nitrogen) along the margins of the microtextures previously interpreted as decayed cellular remains. We mapped for 12C-, 26CN-, 32S- along with 16O-, 28Si-, 24Mg+,27Al+, 40Ca+, 48Ti+ and 56Fe+ in chlorite and quartz hosted examples. The 12C- or 26CN- linings were not found along the margins of the microtextures in neither the original, nor the drill core samples, despite NanoSIMS being a more sensitive and higher-spatial-resolution technique than earlier microprobe X-ray maps. The absence of organic linings in these samples excludes a key line of evidence previously used to support the biogenicity of the microtextures. Sulfur isotopes 32S and 34S were measured by NanoSIMS on two types of sulfide: i) small sulfides (1-15μm) intimately associated with the microtextures and; ii) larger sulfides (10-60μm) that cross-cut the microtextures and are disseminated near a quartz-carbonate vein. The sulfide inclusions in the microtextures have strongly

  12. Spaceborne weather radar

    NASA Technical Reports Server (NTRS)

    Meneghini, Robert; Kozu, Toshiaki

    1990-01-01

    The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

  13. Planetary Space Weather

    NASA Astrophysics Data System (ADS)

    Grande, M.

    2012-04-01

    Invited Talk - Space weather at other planets While discussion of space weather effects has so far largely been confined to the near-Earth environment, there are significant present and future applications to the locations beyond, and to other planets. Most obviously, perhaps, are the radiation hazards experienced by astronauts on the way to, and on the surface of, the Moon and Mars. Indeed, the environment experienced by planetary spacecraft in transit and at their destinations is of course critical to their design and successful operation. The case of forthcoming missions to Jupiter and Europa is an exreme example. Moreover, such craft can provide information which in turn increases our understanding of geospace. Indeed, space weather may be a significant factor in the habitability of other solar system and extrasolar planets, and the ability of life to travel between them.

  14. Space Weather Workshop

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.

    2004-01-01

    This workshop will focus on what space weather is about and its impact on society. An overall picture will be "painted" describing the Sun's influence through the solar wind on the near-Earth space environment, including the aurora, killer electrons at geosynchronous orbit, million ampere electric currents through the ionosphere and along magnetic field lines, and the generation of giga-Watts of natural radio waves. Reference material in the form of Internet sites will be provided so that teachers can discuss space weather in the classroom and enable students to learn more about this topic.

  15. Impact of Probabilistic Weather on Flight Routing Decisions

    NASA Technical Reports Server (NTRS)

    Sheth, Kapil; Sridhar, Banavar; Mulfinger, Daniel

    2006-01-01

    probabilistic description of weather (Ref. 9). This paper focuses on. specified probability in a local region for flight intrusion/deviation decision-making. The process uses a probabilistic weather description, implements that in a air traffic assessment system to study trajectories of aircraft crossing a cut-off probability contour. This value would be useful for meteorologists in creating optimum distribution profiles for severe weather, Once available, the expected values of flight path and aggregate delays are calculated for efficient operations. The current research, however, does not deal with the issue of multiple cell encounters, as well as echo tops, and will be a topic of future work.

  16. No coincidence? Exploring the connection between the Great Oxidation Event and craton stabilization during the Archean-Proterozoic transition

    NASA Astrophysics Data System (ADS)

    Kump, L. R.

    2014-12-01

    As geochronological constraints on the timing of the Great Oxidation Event (here defined as the passage of atmospheric oxygen levels through the proposed upper limit of 10-5 of present) have improved, it has become increasingly clear that this event is somehow tied to the tectonic factors that have defined the Archean-Proterozoic boundary for decades, namely the stabilization of continental cratons allowing for the growth of large continents. We have proposed two connections in the past: 1) elevated late Archean mantle plume activity brought oxidized material from the lithospheric graveyard to the upper mantle, reducing the oxygen fugacity of post-Archean volcanism, and 2) that the stabilization of the cratons allowed for a proportional increase in less-reducing, subaerial volcanism at the expense of more reducing, submarine volcanism. Critiques of these two proposals will be addressed in the context of subsequent work by the geosciences community on the geodynamics and geochemistry of the Archean-Proterozoic transition, and a synthetic hypothesis for a tectonic driver for atmospheric oxygenation will be presented.

  17. Diversification in the Archean Biosphere: Insight from NanoSIMS of Microstructures in the Farrel Quartzite of Australia

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Robert, F.; Walter, M. R.; Sugitani, K.; Meibom, A.; Mostefaoui, S.; Gibson, E. K.

    2010-01-01

    The nature of early life on Earth is difficult to assess because potential Early Archean biosignatures are commonly poorly preserved. Interpretations of such materials have been contested, and abiotic or epigenetic derivations have been proposed (summarized in [1]). Yet, an understanding of Archean life is of astrobiological importance, as knowledge of early evolutionary processes on Earth could provide insight to development of life on other planets. A recently-discovered assemblage of organic microstructures in approx.3 Ga charts of the Farrel Quartzite (FQ) of Australia [2-4] includes unusual spindle-like forms and a variety of spheroids. If biogenicity and syngeneity of these forms could be substantiated, the FQ assemblage would provide a new view of Archean life. Our work uses NanoSIMS to further assess the biogenicity and syngeneity of FQ microstructures. In prior NanoSIMS studies [5-6], we gained an understanding of nano-scale elemental distributions in undisputed microfossils from the Neoproterozoic Bitter Springs Formation of Australia. Those results provide a new tool with which to evaluate poorly preserved materials that we might find in Archean sediments and possibly in extraterrestrial materials. We have applied this tool to the FQ forms.

  18. Weathering the Double Whammy.

    ERIC Educational Resources Information Center

    Wellman, Jane V.

    2002-01-01

    Discusses how governing boards can help their institutions weather the "double-whammy" of doing more with less: identify the institution's short-term and long-term challenges; refocus the institution's mission, planning, and programming; assess and integrate the institution's tuition, aid, and outreach strategies; redouble the…

  19. Weather Specialist (AFSC 25120).

    ERIC Educational Resources Information Center

    Air Univ., Gunter AFS, Ala. Extension Course Inst.

    This correspondence course is designed for self-study to help military personnel to attain the rating of weather specialist. The course is organized in three volumes. The first volume, containing seven chapters, covers background knowledge, meteorology, and climatology. In the second volume, which also contains seven chapters, surface…

  20. Microbial Weathering of Olivine

    NASA Technical Reports Server (NTRS)

    McKay, D. S.; Longazo, T. G.; Wentworth, S. J.; Southam, G.

    2002-01-01

    Controlled microbial weathering of olivine experiments displays a unique style of nanoetching caused by biofilm attachment to mineral surfaces. We are investigating whether the morphology of biotic nanoetching can be used as a biosignature. Additional information is contained in the original extended abstract.

  1. Weather and Flight Testing

    NASA Technical Reports Server (NTRS)

    Wiley, Scott

    2007-01-01

    This viewgraph document reviews some of the weather hazards involved with flight testing. Some of the hazards reviewed are: turbulence, icing, thunderstorms and winds and windshear. Maps, pictures, satellite pictures of the meteorological phenomena and graphs are included. Also included are pictures of damaged aircraft.

  2. Worldwide Marine Weather Broadcasts.

    ERIC Educational Resources Information Center

    Department of the Navy, Washington, DC.

    This publication is a source of marine weather broadcast information in all areas of the world where such service is provided. This publication was designed for the use of U.S. naval and merchant ships. Sections 1 through 4 contain details of radio telegraph, radio telephone, radio facsimile, and radio teleprinter transmissions, respectively. The…

  3. Weather at LANL

    SciTech Connect

    Bruggeman, David Alan

    2016-04-19

    This report gives general information about how to become a meteorologist and what kinds of jobs exist in that field. Then it goes into detail about why weather is monitored at LANL, how it is done, and where the data can be accessed online.

  4. Weather, Climate, and You.

    ERIC Educational Resources Information Center

    Blai, Boris, Jr.

    Information from the American Institute of Medical Climatologists on human responses to weather and climatic conditions, including clouds, winds, humidity, barometric pressure, heat, cold, and other variables that may exert a pervasive impact on health, behavior, disposition, and the level of efficiency with which individuals function is reviewed.…

  5. Dress for the Weather

    ERIC Educational Resources Information Center

    Glen, Nicole J.; Smetana, Lara K.

    2010-01-01

    "If someone were traveling to our area for the first time during this time of year, what would you tell them to bring to wear? Why?" This question was used to engage students in a guided-inquiry unit about how climate differs from weather. In this lesson, students explored local and national data sets to give "travelers" advice…

  6. Shipboard Weather Observation.

    ERIC Educational Resources Information Center

    Palmaccio, Richard J.

    1983-01-01

    Details of how observers on a moving ship can furnish an accurate report of wind velocity are provided. A method employing vector addition and some trigonometry is covered. Wind velocity is initially indicated through an anemometer and a wind vane. Ships are urged to radio weather data. (MP)

  7. Rainy Weather Science.

    ERIC Educational Resources Information Center

    Reynolds, Karen

    1996-01-01

    Presents ideas on the use of rainy weather for activities in the earth, life, and physical sciences. Topics include formation and collision of raindrops, amount and distribution of rain, shedding of water by plants, mapping puddles and potholes, rainbow formation, stalking storms online, lightning, and comparing particles in the air before and…

  8. Weather in Motion.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    The ATS-111 weather satellite, launched on November 18, 1967, in a synchronous earth orbit 22,000 miles above the equator, is described in this folder. The description is divided into these topics: the satellite, the camera, the display, the picture information, and the beneficial use of the satellite. Photographs from the satellite are included.…

  9. Satellite Weather Watch.

    ERIC Educational Resources Information Center

    Summers, R. Joe

    1982-01-01

    Describes an inexpensive (about $1,500) direct-readout ground station for use in secondary school science/mathematics programs. Includes suggested activities including, among others, developing map overlays, operating station equipment, interpreting satellite data, developing weather forecasts, and using microcomputers for data storage, orbit…

  10. Sulfur MIF, Organic Haze, and the Gaia Hypothesis in the Archean

    NASA Astrophysics Data System (ADS)

    Domagal-Goldman, S.; James, K. F.

    2006-05-01

    The presence of mass-independent fractionation (MIF) of sulfur isotopes in Archean sedimentary rocks provides evidence for a low-O2 atmosphere prior to 2.4 Ga. Recent data suggest that S-MIF vanished transiently between ~3.2 Ga and 2.8 Ga. The absence of S-MIF after 2.4 Ga is commonly attributed to the rise of O2 in the atmosphere, as the presence of free O2 would have oxidized all sulfur species, thereby erasing any MIF created by atmospheric photochemistry. However, if free O2 did not appear in the atmosphere until 2.4 Ga, then why did S-MIF disappear transiently much earlier? Could S-MIF have been eliminated from the rock record without the presence of free atmospheric O2? We used a 1-dimensional photochemical model to demonstrate how this might have happened. Increasing the CH4/CO2 ratio in the model atmosphere results in the formation of organic haze. If the haze was sufficiently thick, it would have blocked out much of the solar UV radiation shortward of 220 nm that dissociates SO2 and SO, and thereby causes MIF. The haze should also have caused anti-greenhouse cooling and may have triggered the (putative) 2.8-Ga glaciations. Speculatively, an increase in CH4 at 3.0 Ga could have been caused by the evolution of methanogens, while a CH4 decrease at 2.7 Ga could correspond to the evolution of cyanobacteria. The presence of an optically thin organic haze between 2.4 and 2.7 Ga may explain the larger S-MIF values seen at this time, as compared to the early Archean. If such an organic haze existed, it could have resulted in a biologically-mediated negative feedback loop that stabilized the Archean climate. This feedback loop would have operated as follows: an increase in the biological CH4 flux would have led to an increase in haze thickness and a stronger anti-greenhouse effect, cooling the surface. The surface cooling would have caused a reduction of methanogen productivity, thus offsetting the original increase in the CH4 flux. Such stabilizing feedbacks

  11. Lithospheric thinning in the Eastern Indian Craton: Evidence for lithospheric delamination below the Archean Singhbhum Craton?

    NASA Astrophysics Data System (ADS)

    Mandal, Prantik

    2017-02-01

    We herein present shear velocity structure extending down to 300 km depth below the Archean Singhbhum-Odisha Craton (SOC) and Proterozoic Chotanagpur granitic-gneissic terrain (CGGT), which has been obtained through the inversion modeling of P-receiver functions. We use three-component broadband recordings of 200 teleseismic earthquakes (30° ≤ ∆ ≤ 90°) from a 15 station seismic network that has been operational in the Eastern Indian shield since February 2013. We obtain the thinnest crust of 35 km overlying a thin lithosphere of 78 km, below the region near south Singhbhum shear zone, which could be attributed to the 1.6 Ga plume activity associated with Dalma volcanic. However, the thickest crust of 47 km overlying a thin lithosphere of 81 km is noticed below the region near the Singhbhum granite of 3.6 Ga. This thinning of lithosphere could be attributed to the delamination of lithospheric root due to the Himalayan orogeny with a shortening rate of 2 cm/year. This delamination model in SOC gets further support from the densification of the lower crust, which could result from repeated episodes of basaltic underplating associated with episodes related to Dalma ( 1.6 Ga) and Rajmahal ( 117 Ma) volcanisms. This led to relatively more mafic, heterogeneous and deformed crustal structure in SOC as well as EGMB (with an average crustal Vs of 4.0 km/s) in comparison to that in CGGT (with an average crustal Vs of 3.9 km/s), as seen through our modeling results. The thickest lithosphere of 100 km is observed in the southwestern SOC as well as northeastern CGGT. We also notice that a sharp and flat Moho in CGGT, which could be attributed to thermal reactivation and large volume melting of the mafic cratonic crust during the late Archean subduction process and associated volcanism episodes. This model gets further support from the estimated 169 km thick lower Vs zone in the upper mantle below CGGT. Our modeling results also support a northward subduction of Archean

  12. Ophiolitic Chromitites from the Andriamena Greenstone Belt, Madagascar: Possible Evidence for mid-Archean Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Reisberg, L. C.; Ohnenstetter, M.; Zimmermann, C.; Ratefiarimino, A.; Levy, D.

    2015-12-01

    Determining the time of the onset of plate tectonics is critical to understanding the geodynamic processes that controlled the evolution of the early Earth. The near absence of Archean ophiolites, as defined by the presence of a residual ultramafic section, has been considered to be one of the primary arguments against Archean plate tectonics. The Andriamena greenstone belt of Madagascar contains massive chromitite bodies consisting of about 90% chromite and about 10% gangue minerals, mostly secondary (talc, green amphibole, orthopyroxene, Ca and Mg carbonate). Numerous observations argue in favor of an ophiolitic origin for these chromitites, including the high Cr# (0.67-0.74), coupled with relatively high Mg# (0.6-0.78) of the constituent chromite. In addition, these phases display extremely low TiO2 contents (<0.25%), which are also characteristic of ophiolites and possibly suggestive of an arc environment. Though in many places the chromitite is in tectonic contact with a variety of unrelated igneous lithologies, remnants of apparently cogenetic ultramafic rock types, including dunites, harzburgites, and some pyroxenites are sometimes immediately juxtaposed with the chromitite. The very high Fo content of the olivine in the associated dunite, as high as 0.95, also attests to an ophiolitic provenance. Platinum group element (PGE) and 187Os/188Os analyses were performed on several chromitite samples. Chondrite normalized PGE spectra display marked depletions in PPGE relative to IPGE, with (Pt/Ir)N ranging from ~0 to 0.09, though Pd contents are somewhat less depleted than those of Pt. The observed PPGE depletion is another feature characteristic of ophiolitic chromitites. The IPGE enrichment is consistent with the presence of laurite microinclusions in the chromite revealed by SEM. Os isotopic compositions are tightly clustered, with 187Os/188Os ranging from 0.1057 to 0.1059, corresponding to TRD model ages of ~ 3.2 Ga, assuming primitive upper mantle parameters

  13. Weatherization Works: An interim report of the National Weatherization Evaluation

    SciTech Connect

    Brown, M.A.; Berry, L.G.; Kinney, L.F.

    1993-11-01

    The National Weatherization Evaluation is the first comprehensive evaluation of the Weatherization Assistance Program since 1984. The evaluation was designed to accomplish the following goals: Estimate energy savings and cost effectiveness; Assess nonenergy impacts; Describe the weatherization network; Characterize the eligible population and resources; and Identify factors influencing outcomes and opportunities for the future. As a national program, weatherization incorporates considerable diversity due to regional differences. Therefore, evaluation results are presented both in aggregate and for three climate regions: cold, moderate and hot.

  14. Onset of oxidative weathering of continents recorded in the geochemistry of ancient glacial diamictites

    NASA Astrophysics Data System (ADS)

    Gaschnig, Richard M.; Rudnick, Roberta L.; McDonough, William F.; Kaufman, Alan J.; Hu, Zhaochu; Gao, Shan

    2014-12-01

    Glacial diamictites deposited in the Mesoarchean, Paleoproterozoic, Neoproterozoic, and Paleozoic eras record temporal variations in their average compositions that reflect the changing composition of the upper continental crust (UCC). Twenty six of the 27 units studied show elevated chemical index of alternation (CIA) and low Sr abundances, regardless of their age, documenting pervasive weathering of the average UCC. Lower abundances of transition metals reflect a shift towards more felsic crustal compositions after the Archean. Superimposed on this chemical difference is the signal of the rise of oxidative weathering of the continents, recorded by changes in the absolute and relative abundances of the redox sensitive elements Mo and V. Neoproterozoic and Paleozoic diamictites show pervasive depletion in Mo and V, reflecting their loss from the continents due to increasing intensity of oxidative weathering, as also recorded in some of the Paleoproterozoic diamictites. A few of the Paleoproterozoic diamictites deposited after the Great Oxidation Event show no depletion in Mo and V (e.g., Gowganda), but such signatures could be inherited from their provenance. In contrast, the pre-GOE Duitschland diamictite (ca. 2.3-2.5 Ga) from South Africa reveals evidence of intense oxidative weathering (i.e., large depletions in Mo), supporting a growing body of observations showing the presence of measurable atmospheric oxygen prior to permanent loss of the mass independent fractionation signal in sulfur isotopes.

  15. Bringing Weather into Your Classroom.

    ERIC Educational Resources Information Center

    Mogil, H. Michael

    1979-01-01

    Discusses meteorological resources available to classroom teachers. Describes in detail the National Oceanic and Atmospheric Administration (NOAA) Weather Radio and the A.M. Weather Show on Public Broadcasting Service (PBS). Includes addresses where teachers can get more information. (MA)

  16. Geography and Weather: Mountain Meterology.

    ERIC Educational Resources Information Center

    Mogil, H. Michael; Collins, H. Thomas

    1990-01-01

    Provided are 26 ideas to help children explore the effects of mountains on the weather. Weather conditions in Nepal and Colorado are considered separately. Nine additional sources of information are listed. (CW)

  17. Origin of Archean anorthosites - Evidence from the Bad Vermilion Lake anorthosite complex, Ontario

    NASA Technical Reports Server (NTRS)

    Ashwal, L. D.; Morrison, D. A.; Phinney, W. C.; Wood, J.

    1983-01-01

    Studies of the petrology and geochemistry of the anorthosite complex at Bad Vermillion Lake, Canada, based on 400 samples collected in summer, 1979, are presented. Petrographic, microprobe, X-ray-fluorescence, and instrumental-neutron-activation analyses were performed. Major and trace-element abundances of the anorthositic rocks and surrounding mafic and felsic rocks are reported in tables, chondrite-normalized rare-earth-element patterns are shown, and the anorthositic, intrusive, and metavolcanic formations are characterized in detail. The anothrositic plagioclases are found to have a coarse porphyritic texture and calcic composition (80 normative mol percent An) similar to those of other Archean anorthosite complexes. Chemical similarities indicate that the gabbro and mafic to felsic metavolcanic formations associated with the anorthosite complex may be comagmatic with it, while the absence of ultramafic material and the bulk composition of the comagmatic basalt (about 20 wt percent Al2O3) suggest that much of the original comagmatic material has been separated.

  18. In situ carbon isotope analysis of Archean organic matter with SIMS

    NASA Astrophysics Data System (ADS)

    Williford, K. H.; Ushikubo, T.; Lepot, K.; Hallmann, C.; Spicuzza, M. J.; Eigenbrode, J. L.; Summons, R. E.; Valley, J. W.

    2011-12-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to μm). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 μm using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 μm spot size with two Faraday cup detectors was 0.4%, and 0.8% for analyses using 1 μm and 3 μm spot sizes with a Faraday cup (for 12C) and an electron multiplier (for 13C). Eight coals, two ambers, a shungite, and a graphite were evaluated for μm-scale isotopic heterogeneity, and LCNN anthracite (δ13C = -23.56 ± 0.1%, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a 13CH/13C measurement included in every analysis and a 12CH measurement made immediately after every analysis. The total range of the H/C effect observed for the Archean samples analyzed was < 3%. Analyses of Archean OM domains for which 12C count rate varies with the proportions of organic carbon, carbonate carbon, and quartz suggest that instrumental bias is consistent for 12C count

  19. Crustal anisotropy in the Archean Minnesota River Valley Subprovince and its significance

    NASA Astrophysics Data System (ADS)

    Gebelin, A.; Ferre, E. C.; Teyssier, C.

    2007-12-01

    The origin and evolution of the American continental lithosphere is a key question addressed by EarthScope. The Superior Province formed as an amalgamation of Archean/ Proterozoic terranes that subsequently acted as a stabilizing nucleus. This province is characterized by a strong seismic anisotropy (SWS = 1.3 s) of unknown origin. As suggested for the Archean Kaapvaal Craton (South Africa), this could be attributed (1) to current asthenospheric flow, or (2) to fossil lithospheric anisotropy, or (3) to the role of lithospheric keels on modern asthenospheric flow. The first hypothesis is not favored because SWS data for the Superior Province do not fit global mantle flow models. The second hypothesis would be compatible with obliquity between lithospheric mantle and crustal seismic anisotropies, possibly due to oblique docking. The third hypothesis would require asthenospheric flow to be controlled by lithospheric block geometry. The origin of seismic anisotropy and its spatial variations need to be determined to test these hypotheses. The deployment of USArray in the Superior Province in FY10, along with the prospect of deployment of a Flexible Array and the GeoFrame Superior focus area should provide a wealth of seismic data. Yet, the contribution of the Archean-early Proterozoic continental crust to seismic anisotropy is unknown. This study focusses on the Minnesota River Valley (MRV) Subprovince, part of the Superior Province. The MRV Subprovince consists of four juxtaposed blocks (Benson, Montevideo, Morton and Jeffers) of amphibolite to granulite grade migmatites, tonalites, granodiorites, diorites and pelitic rocks interlayered into each other. These blocks are separated by EW-dipping shear zones broadly parallel to SWS observations. In other parts of the world, the crustal seismic anisotropy is generally considered to be modest (SWS = 0.1-0.2 s), although experiments specifically designed to constrain it are scarce. The MRV represents a 200 km-wide, tilted

  20. A major Archean, gold- and crust-forming event in the Kaapvaal craton, South Africa.

    PubMed

    Kirk, Jason; Ruiz, Joaquin; Chesley, John; Walshe, John; England, Gavin

    2002-09-13

    The 2.89- to 2.76-gigayear-old conglomerates of the Central Rand Group of South Africa host an immense concentration of gold. The gold and rounded pyrites from the conglomerates yield a rhenium-osmium isochron age of 3.03 +/- 0.02 gigayears and an initial 187Os/188Os ratio of 0.1079 +/- 0.0001. This age is older than that of the conglomerates. Thus, the gold is detrital and was not deposited by later hydrothermal fluids. This Middle Archean gold mineralization event corresponds to a period of rapid crustal growth in which much of the Kaapvaal craton was formed and is evidence for a significant noble metal flux from the mantle.

  1. Accretionary history of the Archean Barberton Greenstone Belt (3.55-3.22 Ga), southern Africa.

    PubMed

    Lowe, D R

    1994-12-01

    The 3.55-3.22 Ga Barberton Greenstone Belt, South Africa and Swaziland, and surrounding coeval plutons can be divided into four tectono-stratigraphic blocks that become younger toward the northwest. Each block formed through early mafic to ultramafic volcanism (Onverwacht Group), probably in oceanic extensional, island, or plateau settings. Volcanism was followed by magmatic quiescence and deposition of fine-grained sediments, possibly in an intraplate setting. Late evolution involved underplating of the mafic crust by tonalitic intrusions along a subduction-related magmatic arc, yielding a thickened, buoyant protocontinental block. The growth of larger continental domains occurred both through magmatic accretion, as new protocontinental blocks developed along the margins of older blocks, and when previously separate blocks were amalgamated through tectonic accretion. Evolution of the Barberton Belt may reflect an Early Archean plate tectonic cycle that characterized a world with few or no large, stabilized blocks of sialic crust.

  2. River Valley pluton, Ontario - A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D.; Wooden, Joseph L.

    1989-01-01

    This paper presents Nd, Sr, and Pb isotopic data indicating a late-Archean/early-Proterozoic age for the River Valley anorthositic pluton of the southwestern Grenville Province of Sudbury, Ontario. Pb-Pb isotopic data on 10 whole-rock samples ranging in composition from anorthosite to gabbro yield an age of 2560 + or - 155 Ma. The River Valley pluton is thus the oldest anorthositic intrusive yet recognized within the Grenville Province. The Sm-Nd isotopic system records an age of 2377 + or - 68 Ma. High Pb-208/Pb-204 of deformed samples relative to igneous-textured rocks implies Th introduction and/or U loss during metamorphism in the River Valley area. Rb-Sr data from igneous-textured and deformed samples and from mineral separates give an age of 2185 + or - 105 Ma, indicating substantial disturbance of the Rb-Sr isotopic system.

  3. Geophysical consequences of phanerozoic and Archean crustal evolution: Evidence from crustal cross-sections

    NASA Technical Reports Server (NTRS)

    Fountain, D. M.

    1983-01-01

    Geophysical properties of continental crust depend on the nature of crustal evolution. This is well illustrated by examination of two crustal cross-sections (1), the combined Ivrea-Verbano zone (IVZ) and Strona-Ceneri zone (SCZ) of northern Italy and the Pikwitonei granulite belt (PGB) and Cross Lake subprovince (CLS) of Manitoba. These two cross-sections are of particular interest because the IVZ and SCZ developed during Phanerozoic time whereas the PGB-CLS is an example of Archean crustal evolution. Consequently, each cross-section is geologically distinctive and, thus, exhibits very different geophysical properties such as density, seismic velocity, heat production, and magnetism. Results of geological investigations of each area are given.

  4. Fluid-deposited graphite and its geobiological implications in early Archean gneiss from Akilia, Greenland.

    PubMed

    Lepland, A; van Zuilen, M A; Philippot, P

    2011-01-01

    Graphite, interpreted as altered bioorganic matter in an early Archean, ca. 3.83-Ga-old quartz-amphibole-pyroxene gneiss on Akilia Island, Greenland, has previously been claimed to be the earliest trace of life on Earth. Our petrographic and Raman spectroscopy data from this gneiss reveal the occurrence of graphitic material with the structure of nano-crystalline to crystalline graphite in trails and clusters of CO₂, CH₄ and H₂O bearing fluid inclusions. Irregular particles of graphitic material without a fluid phase, representing decrepitated fluid inclusions are common in such trails too, but occur also as dispersed individual or clustered particles. The occurrence of graphitic material associated with carbonic fluid inclusions is consistent with an abiologic, fluid deposited origin during a poly-metamorphic history. The evidence for fluid-deposited graphitic material greatly complicates any claim about remnants of early life in the Akilia rock.

  5. Evidence for crustal recycling during the Archean: The parental magmas of the stillwater complex

    NASA Technical Reports Server (NTRS)

    Mccallum, I. S.

    1988-01-01

    The petrology and geochemistry of the Stillwater Complex, an Archean (2.7 Ga) layered mafic intrusion in the Beartooth Mountains of Montana is discussed. Efforts to reconstruct the compositions of possible parental magmas and thereby place some constraints on the composition and history of their mantle source regions was studied. A high-Mg andesite or boninite magma best matches the crystallization sequences and mineral compositions of Stillwater cumulates, and represents either a primary magma composition or a secondary magma formed, for example, by assimilation of crustal material by a very Mg-rich melt such as komatiite. Isotopic data do not support the extensive amounts of assimilation required by the komatiite parent hypothesis, and it is argued that the Stillwater magma was generated from a mantle source that had been enriched by recycling and homogenization of older crustal material over a large area.

  6. Isotopic evidence for an aerobic nitrogen cycle in the latest Archean.

    PubMed

    Garvin, Jessica; Buick, Roger; Anbar, Ariel D; Arnold, Gail L; Kaufman, Alan J

    2009-02-20

    The nitrogen cycle provides essential nutrients to the biosphere, but its antiquity in modern form is unclear. In a drill core though homogeneous organic-rich shale in the 2.5-billion-year-old Mount McRae Shale, Australia, nitrogen isotope values vary from +1.0 to +7.5 per mil (per thousand) and back to +2.5 per thousand over approximately 30 meters. These changes evidently record a transient departure from a largely anaerobic to an aerobic nitrogen cycle complete with nitrification and denitrification. Complementary molybdenum abundance and sulfur isotopic values suggest that nitrification occurred in response to a small increase in surface-ocean oxygenation. These data imply that nitrifying and denitrifying microbes had already evolved by the late Archean and were present before oxygen first began to accumulate in the atmosphere.

  7. Advanced Weather Awareness and Reporting Enhancements

    NASA Technical Reports Server (NTRS)

    Busquets, Anthony M. (Technical Monitor); Ruokangas, Corinne Clinton; Kelly, Wallace E., III

    2005-01-01

    AWARE (Aviation Weather Awareness and Reporting Enhancements) was a NASA Cooperative Research and Development program conducted jointly by Rockwell Scientific, Rockwell Collins, and NASA. The effort culminated in an enhanced weather briefing and reporting tool prototype designed to integrate graphical and text-based aviation weather data to provide clear situational awareness in the context of a specific pilot, flight and equipment profile. The initial implementation of AWARE was as a web-based preflight planning tool, specifically for general aviation pilots, who do not have access to support such as the dispatchers available for commercial airlines. Initial usability tests showed that for VFR (Visual Flight Rules) pilots, AWARE provided faster and more effective weather evaluation. In a subsequent formal usability test for IFR (Instrument Flight Rules) pilots, all users finished the AWARE tests faster than the parallel DUAT tests, and all subjects graded AWARE higher for effectiveness, efficiency, and usability. The decision analysis basis of AWARE differentiates it from other aviation safety programs, providing analysis of context-sensitive data in a personalized graphical format to aid pilots/dispatchers in their complex flight requirements.

  8. Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

    DOE PAGES

    Kochanov, R. V.; Gordon, I. E.; Rothman, L. S.; ...

    2015-08-25

    In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm-1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist largemore » or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 (dimer)+ NO2 was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra.« less

  9. Characterizing the Purple Earth: Modeling the Globally Integrated Spectral Variability of the Archean Earth

    NASA Astrophysics Data System (ADS)

    Sanromá, E.; Pallé, E.; Parenteau, M. N.; Kiang, N. Y.; Gutiérrez-Navarro, A. M.; López, R.; Montañés-Rodríguez, P.

    2014-01-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. However, the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3.0 Gyr ago. At that time, one of the more widespread life forms on the planet was purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and purple bacteria concentration/distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  10. Modeling the globally-integrated spectral variability of the Archean Earth: The purple planet

    NASA Astrophysics Data System (ADS)

    Palle, E.; Sanroma, E.; Parenteau, M. N.; Kiang, N. Y.; Gutierrez-Navarro, A. M.; Lopez, R.; Montañes-Rodríguez, P.

    2014-03-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. But the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3 Gyr ago. At that time, one of the more widespread life forms on the planet were purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and bacteria concentration/ distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  11. The Photochemical Oxidation of Siderite That Drove Hydrogen Based Microbial Redox Reactions in The Archean Biosphere

    NASA Astrophysics Data System (ADS)

    Kim, J. D.; Yee, N.; Falkowski, P. G.

    2012-12-01

    Hydrogen is the most abundant element in the universe and molecular hydrogen (H2) is a rich source of electron in a mildly reducing environment for microbial redox reactions, such as anoxygenic photosynthesis and methanogenesis. Subaerial volcanoes, ocean crust serpentinization and mid-ocean ridge volcanoes have been believed to be the major source of the hydrogen flux to the atmosphere. Although ferrous ion (Fe2+) photooxidation has been proposed as an alternative mechanism by which hydrogen gas was produced, ferruginous water in contact with a CO2-bearing atmosphere is supersaturated with respect to FeCO3 (siderite), thus the precipitation of siderite would have been thermodynamically favored in the Archean environment. Siderite is the critical mineral component of the oldest fossilized microbial mat. It has also been inferred as a component of chemical sedimentary protolith in the >3750 Ma Nuvvuagittuq supracrustal belt, Canada and the presence of siderite in the protolith suggests the occurrence of siderite extends to Hadean time. Analyses of photooxidation of siderite suggest a significant flux of hydrogen in the early atmosphere. Our estimate of the hydrogen production rate under Archean solar flux is approximately 50 times greater than the estimated hydrogen production rate by the volcanic activity based on a previous report (Tian et al. Science 2005). Our analyses on siderite photooxidation also suggest a mechanism by which banded iron formation (BIF) was formed. The photooxidation transforms siderite to magnetite/maghemite (spinnel iron oxide), while oxygenic oxidation of siderite leads to goethite, and subsequently to hematite (Fe3+2O3) upon dehydration. We will discuss the photochemical reaction, which was once one of the most ubiquitous photochemical reactions before the rise of oxygen in the atmosphere. Photooxidation of siderite over time by UV light From left to right: UV oxidized siderite, pristine siderite, oxidized siderite by oxygen

  12. Extreme Hf and light Fe isotopes in Archean komatiites - a remnant of very early mantle depletion?

    NASA Astrophysics Data System (ADS)

    Nebel, O.; Sossi, P.; Campbell, I. H.; Van Kranendonk, M. J.

    2014-12-01

    Hafnium isotope signatures in some Archean komatiites (ca. 3.5-3.0 billion years old) require a mantle source with a time-integrated Lu/Hf that exceeds average modern depleted mantle. Investigation of the timing and locus of parent-daughter fractionation in their mantle sources potentially constrains differentiation processes in the early Earth and their subsequent distribution and storage. In addition, they may help to constrain the Hf isotope evolution of the greater depleted mantle. In order to shed light on these processes, we discuss radiogenic Hf isotopes in conjunction with stable Fe isotope systematics in Archean komatiites from the Pilbara craton in Western Australia. Our findings indicate that, after careful evaluation of the effects of alteration, pristine samples are characterised by initial 176Hf/177Hf, which lie above the age-corrected depleted mantle, as a consequence of ancient melt extraction. Iron isotope systematics for these samples further point to a mantle source that is isotopically lighter than average modern depleted mantle, which is also consistent with melt-depletion. Taken together, these observations require a component of an old, super-depleted reservoir in the komatiite mantle source(s) that survived in the mantle for possibly hundreds of millions of years. The Lu/Hf of this refractory mantle appears to be complementary to, and therefore contemporaneous with, the first terrestrial crust, as preserved in Hadean (i.e., > 4 Ga) detrital zircon cores, which may indicate a causal relationship between them. We will discuss implications for very early mantle dynamics and the formation of very early mantle reservoirs.

  13. Release of bound aromatic hydrocarbons from late Archean and Mesoproterozoic kerogens via hydropyrolysis

    NASA Astrophysics Data System (ADS)

    Brocks, Jochen J.; Love, Gordon D.; Snape, Colin E.; Logan, Graham A.; Summons, Roger E.; Buick, Roger

    2003-04-01

    Hydrogen-lean kerogens (atomic H/C<0.4) isolated from the 2.5-billion-year-old (Ga) Mt. McRae Shale, Hamersley Group, at Tom Price, Western Australia, were studied via hydropyrolysis, a continuous-flow technique that degrades organic matter in a stream of high-pressure hydrogen assisted by a dispersed Mo catalyst. The hydropyrolysates yielded predominantly phenanthrene and pyrene, and higher polyaromatic hydrocarbons and alkylated homologues were generated in low relative concentrations. Saturated hydrocarbons were not detected. The molecular and carbon isotopic compositions of the hydropyrolysates are very similar to aromatic hydrocarbons obtained by solvent extraction of the host rocks. Because molecular structures covalently attached to kerogen are unaffected by contamination, this indicates that both the bound and extractable aromatic fractions are syngenetic with the host rocks. Therefore, the results of the hydropyrolysis experiments provide compelling evidence for preserved bitumen of Archean age. The very high proportion of nonalkylated polyaromatic hydrocarbons in the hydropyrolysates is consistent with hydrothermal dehydrogenation of the kerogen, and a marked concentration difference of pyrene in rock extracts and hydropyrolysates might be explained by hydrothermal redistribution of the bitumen. The kerogen and bitumen composition is therefore consistent with models suggesting a hydrothermal origin for the giant iron ore deposits at Mt. Tom Price. Comparison of the Archean samples with hydropyrolysates from immature Mesoproterozoic kerogens from the Roper Group, McArthur Basin, Northern Territory, and with pyrolysis experiments on Proterozoic kerogens in the literature suggests that Precambrian kerogens are frequently highly aromatic and lipid-poor regardless of their degree of thermal preservation.

  14. Towards Definition of Early Proterozoic/Archean Paleomagnetic Dipole Moments from Karelia (Russia)

    NASA Astrophysics Data System (ADS)

    Smirnov, A. V.; Tarduno, J. A.

    2001-05-01

    The onset of the geomagnetic dynamo may be related to the formation of the Earth's inner core. The timing of this event during the Precambrian differs in a number of theoretical models and the paleointensity database needs to be significantly extended to test various model predictions. We determine paleointensity from single plagioclase crystals derived from border dikes of the Early Proterozoic/Archean ( ~2.45 Ga) Burakovka layered intrusion (North Karelia, Russia). The use of these single crystals can result in data less affected by alteration. Magnetic hysteresis properties of plagioclases suggest that they contain single-domain to pseudo-single-domain magnetic inclusions. A study of low-temperature magnetic properties of single plagioclase crystals shows a sharp Verwey transition at 120 K, indicating the presence of stoichiometric, non-stressed magnetite. A significant magnetic anisotropy was not observed in the crystals, implying that magnetite exsolution was minor, consistent with fast cooling of the border dikes. We investigated four dikes using a modified Thellier technique. Of the twenty-two samples studied thus far, eight paleointensity determinations meet our reliability criteria (success rate is 36%). Based on these eight determinations, the average paleointensity is 36.5 +/- 1.2 μ T which corresponds to a virtual dipole moment of 6.49 +/- 0.21 x 1022 Am2. The latter value is consistent with the existence of a fully developed geomagnetic dynamo by the Early Proterozoic. Our results suggest that border dikes of the Burakovka layered intrusion can be used to obtain additional Early Proterozoic/Archean paleointensity values. Because of their fast cooling rates relative to the interiors of layered intrusions, border dikes also offer the opportunity to obtain secular variation data which, together with paleointensity values, could be used to define paleomagnetic dipole moments.

  15. Characterizing the Purple Earth: Modeling the globally integrated spectral variability of the Archean Earth

    SciTech Connect

    Sanromá, E.; Pallé, E.; López, R.; Montañés-Rodríguez, P.; Kiang, N. Y.; Gutiérrez-Navarro, A. M.

    2014-01-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. However, the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3.0 Gyr ago. At that time, one of the more widespread life forms on the planet was purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and purple bacteria concentration/distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  16. Weather Folklore: Fact or Fiction?

    ERIC Educational Resources Information Center

    Jones, Gail; Carter, Glenda

    1995-01-01

    Integrating children's weather-related family folklore with scientific investigation can be an effective way to involve elementary and middle level students in lessons spanning the disciplines of science, geography, history, anthropology, and language arts. Describes weather folklore studies and examples of weather investigations performed with…

  17. Weather Specialist/Aerographer's Mate.

    ERIC Educational Resources Information Center

    Chanute AFB Technical Training Center, IL.

    This course trains Air Force personnel to perform duties prescribed for weather specialists and aerographer's mates. Training includes meteorology, surface and ship observation, weather radar, operation of standard weather instruments and communications equipment, and decoding and plotting of surface and upper air codes upon standard maps and…

  18. Severe Weather Planning for Schools

    ERIC Educational Resources Information Center

    Watson, Barbara McNaught; Strong, Christopher; Bunting, Bill

    2008-01-01

    Flash floods, severe thunderstorms, and tornadoes occur with rapid onset and often no warning. Decisions must be made quickly and actions taken immediately. This paper provides tips for schools on: (1) Preparing for Severe Weather Emergencies; (2) Activating a Severe Weather Plan; (3) Severe Weather Plan Checklist; and (4) Periodic Drills and…

  19. Weather Fundamentals: Climate & Seasons. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes), describes weather patterns and cycles around the globe. The various types of climates around…

  20. Improved weather information and aviation

    NASA Technical Reports Server (NTRS)

    Hallahan, K.; Zdanys, V.

    1973-01-01

    The major impacts of weather forecasts on aviation are reviewed. Topics discussed include: (1) present and projected structure of American aviation, (2) weather problems considered particularly important for aviation, (3) projected needs for improved weather information by aviators, (4) safety and economics, and (5) future studies utilizing satellite meteorology.

  1. Whether weather affects music

    NASA Astrophysics Data System (ADS)

    Aplin, Karen L.; Williams, Paul D.

    2012-09-01

    The creative output of composers, writers, and artists is often influenced by their surroundings. To give a literary example, it has been claimed recently that some of the characters in Oliver Twist and A Christmas Carol were based on real-life people who lived near Charles Dickens in London [Richardson, 2012]. Of course, an important part of what we see and hear is not only the people with whom we interact but also our geophysical surroundings. Of all the geophysical phenomena to influence us, the weather is arguably the most significant because we are exposed to it directly and daily. The weather was a great source of inspiration for artists Claude Monet, John Constable, and William Turner, who are known for their scientifically accurate paintings of the skies [e.g., Baker and Thornes, 2006].

  2. Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Strati, Virginia; Mantovani, Fabio; Shirey, Steven B.; McDonough, William F.

    2014-10-01

    SNO+ detector that is currently under construction in Ontario, Canada, will be a new kiloton-scale liquid scintillation detector with the capability of recording geoneutrino events that can be used to constrain the strength of the Earth's radiogenic power, and in turn, to test compositional models of the bulk silicate Earth (BSE). We constructed a detailed 3-D model of the regional crust centered at SNO+ from compiled geological, geophysical, and geochemical information. Crustal cross sections obtained from refraction and reflection seismic surveys were used to characterize the crust and assign uncertainties to its structure. The average Moho depth in the study area is 42.3 ± 2.6 km. The upper crust was divided into seven dominant lithologic units on the basis of regional geology. The abundances of U and Th and their uncertainties in each upper crustal lithologic unit were determined from analyses of representative outcrop samples. The average chemical compositions of the middle and lower crust beneath the SNO+ region were determined by coupling local seismic velocity profiles with a global compilation of the chemical compositions of amphibolite and granulite facies rocks. Monte Carlo simulations were used to predict the geoneutrino signal originating from the regional crust at SNO+ and to track asymmetrical uncertainties of U and Th abundances. The total regional crust contribution of the geoneutrino signal at SNO+ is predicted to be 15.6-3.4+5.3 TNU (a Terrestrial Neutrino Unit is one geoneutrino event per 1032 target protons per year), with the Huronian Supergroup near SNO+ dominantly contributing 7.3-3.0+5.0 TNU to this total. Future systematically sampling of this regional unit and denser seismic surveys will better model its composition and structure, and thus reduce the uncertainty on geoneutrino signal at SNO+. The bulk crustal geoneutrino signal at SNO+ is estimated to be 30.7-4.2+6.0 TNU, which is lower than that predicted in a global-scale reference

  3. Chemical and isotopic studies of granitic Archean rocks, Owl Creek Mountains, Wyoming: Geochronology of an Archean granite, Owl Creek Mountains, Wyoming

    SciTech Connect

    Hedge, C.E.; Simmons, K.R.; Stuckless, J.S.

    1986-01-01

    Rubidium-strontium analyses of whole-rock samples of an Archean granite from the Owl Creek Mountains, Wyo., indicate an intrusive age of 2640 {plus minus} 125 Ma. Muscovite-bearing samples give results suggesting that these samples were altered about 2300 Ma. This event may have caused extensive strontium loss from the rocks as potassium feldspar was altered to muscovite. Alteration was highly localized in nature as evidence by unaffected rubidium-strontium mineral ages in the Owl Creek Mountains area. Furthermore, the event probably involved a small volume of fluid relative to the volume of rock because whole-rock {delta}{sup 18}O values of altered rocks are not distinct from those of unaltered rocks. In contrast to the rubidium-strontium whole-rock system, zircons from the granite have been so severely affected by the alteration event, and possibly by a late-Precambrian uplift event, that the zircon system yields little usable age information. The average initial {sup 87}Sr/{sup 86}Sr (0.7033 {plus minus} 0.0042) calculated from the isochron intercept varies significantly. Calculated initial {sup 87}Sr/{sup 86}Sr ratios for nine apparently unaltered samples yield a range of 0.7025 to 0.7047. These calculated initial ratios correlate positively with whole-rock {delta}{sup 18}O values; and, therefore, the granite was probably derived from an isotopically heterogeneous source. The highest initial {sup 87}Sr/{sup 86}Sr ratio is lower than the lowest reported for the metamorphic rocks intruded by the granite as it would have existed at 2640 Ma. Thus, the metamorphic sequence, at its current level of exposure, can represent no more than a part of the protolith for the granite.

  4. Thermospheric Space Weather Modeling

    DTIC Science & Technology

    2007-06-01

    atmospheric temperature V = satellite velocity relative to the ambient gas ’ Senior physicist, Space Weather Center of Excellence, Mail Stop: VSBXT; Member...where temperature rises drastically to -600 - 2000 K. The density and hence drag in this region is driven mainly by two solar influences: directly by EUV...bulge that drives winds to transport heat away from the hot dayside toward the Earth’s cold nightside. Temperatures on the dayside are typically 30

  5. Weather Radar Studies.

    DTIC Science & Technology

    2014-09-26

    and Doppler weather radar data from the National Center for Atmospheric Research JAWS program and the National .Severe Storms Laboratory, are being...Atmospheric Research JAWS program and the National Severe Storms Laboratory, are being analyzed to develop low-altitude wind-shear detection algorithms...pictures, and dusted for fingerprints. The wind sensors, rain gauge, and antenna were destroyed but the DCP, solar panel, and other site components

  6. Space Weather Ballooning

    NASA Astrophysics Data System (ADS)

    Phillips, Tony; Johnson, Sam; Koske-Phillips, Amelia; White, Michael; Yarborough, Amelia; Lamb, Aaron; Herbst, Anna; Molina, Ferris; Gilpin, Justin; Grah, Olivia; Perez, Ginger; Reid, Carson; Harvey, Joey; Schultz, Jamie

    2016-10-01

    We have developed a "Space Weather Buoy" for measuring upper atmospheric radiation from cosmic rays and solar storms. The Buoy, which is carried to the stratosphere by helium balloons, is relatively inexpensive and uses off-the-shelf technology accessible to small colleges and high schools. Using this device, we have measured two Forbush Decreases and a small surge in atmospheric radiation during the St. Patrick's Day geomagnetic storm of March 2015.

  7. Salt Weathering on Mars

    NASA Astrophysics Data System (ADS)

    Jagoutz, E.

    2006-12-01

    Large well rounded boulders and angular rock fragments characterizes the Martian landscape as seen on the recent excellent quality photos. Analyzing the different rock-shapes indicates a time sequence of emplacement, fragmentation and transport of different rocks on Mars, which might give interesting insight into transport and weathering processes. Larger commonly well rounded boulders were emplaced onto gravel plains. After emplacement, these rocks were fragmented and disassembled. Nests of angular rock fragments are marking the locations of preexisting larger rocks. Frequently it is possible to reconstruct larger rounded rocks from smaller angular fragments. In other cases transport after fragmentation obscured the relationship of the fragments. However, a strewn field of fragments is still reminiscent of the preexisting rock. Mechanical salt weathering could be a plausible explanation for the insitu fragmentation of larger rounded blocks into angular fragments. Impact or secondary air fall induced fragmentation produces very different patterns, as observed around impact crates on Earth. Salt weathering of rocks is a common process in terrestrial environments. Salt crystallization in capillaries causes fragmentation of rocks, irrespective of the process of salt transportation and concentration. On Earth significant salt weathering can be observed in different climatic environments: in the transition zone of alluvial aprons and salt playas in desserts and in dry valleys of Antarctica. In terrestrial semi-arid areas the salt is transported by salt solution, which is progressively concentrated by evaporation. In Antarctic dry valleys freeze-thaw cycles causes salt transportation and crystallization resulting in rock fragmentation. This salt induced process can lead to complete destruction of rocks and converts rocks to fine sand. The efficient breakdown of rocks is dominating the landscape in some dry valleys of the Earth but possibly also on Mars. (Malin, 1974

  8. Weather Radar Technology Development

    DTIC Science & Technology

    1990-08-15

    uelocitV WMs ) data processing systems such as NEXRAD to have a reliable technique for removing ambiguities due to velocity aliasing. Performance of many...intended for automated implementation on radar systems such as the NEXt generation weather RADar ( NEXRAD ) system. Several research areas were addressed...with Doppler radar will soon be realized with the deployment of the NEXRAD radar systems. Some of these large scale storms can have devastating wind

  9. Benign Weather Modification

    DTIC Science & Technology

    2007-11-02

    The first Combat Search and Rescue (CSAR) attempt, scheduled for 6 September 1995, was canceled due to unsatisfactory launch site weather for the ...Such an RPV could clear the fog and search for the downed airman at the same time. To increase the odds of finding the airmen, several RPVs could fly...COBLE A THESIS PRESENTED TO THE FACULTY OF THE SCHOOL OF ADVANCED AIRPOWER STUDIES FOR COMPLETION OF GRADUATION

  10. Areosynchronous weather imager

    NASA Astrophysics Data System (ADS)

    Puschell, Jeffery J.; Lock, Robert

    2016-09-01

    Mars is characterized by rapidly changing, poorly understood weather that is a concern for future human missions. Future Areosynchronous Mars Orbit (AMO) communication satellites offer possible platforms for Mars weather imagers similar to the geosynchronous Earth orbit (GEO) weather imagers that have been observing Earth since 1966. This paper describes an AReosynchronous Environmental Suite (ARES) that includes two imagers: one with two emissive infrared bands (10.8 μm and 12.0 μm) at 4 km resolution and the other with three VNIR bands (500 nm, 700 nm, 900 nm) at 1 km resolution. ARES stares at Mars and provides full disk coverage as fast as every 40 sec in the VNIR bands and every 2 min in the emissive bands with good sensitivity (SNR 200 in the VNIR for typical radiances and NEDT 0.2K at 180 K scene temperature in the emissive infrared). ARES size, mass, power and data rate characteristics are compatible with expectations for hosted payloads onboard future AMO communication satellites. Nevertheless, more work is needed to optimize ARES for future missions, especially in terms of trades between data rate, full disk coverage rate, sensitivity, number of spectral bands and spatial resolution and in study of approaches for maintaining accurate line of sight knowledge during data collection.

  11. Kazakhstan Space Weather Initiative

    NASA Astrophysics Data System (ADS)

    Kryakunova, Olga

    2012-07-01

    Kazakhstan experimental complex is a center of experimental study of space weather. This complex is situated near Almaty, Kazakhstan and includes experimental setup for registration of cosmic ray intensity (neutron monitor) at altitude of 3340 m above sea level, geomagnetic observatory and setup for registration of solar flux density with frequency of 1 and 3 GHz with 1 second time resolution. Results of space environment monitoring in real time are accessible via Internet. This experimental information is used for space weather investigations and different cosmic ray effects. Almaty mountain cosmic ray station is one of the most suitable and sensitive stations for investigation and forecasting of the dangerous situations for satellites; for this reason Almaty cosmic ray station is included in the world-wide neutron monitor network for the real-time monitoring of the space weather conditions and European Database NMDB (www.nmdb.eu). All data are represented on the web-site of the Institute of Ionosphere (www.ionos.kz) in real time. Since July, 2006 the space environment prediction laboratory represents the forecast of geomagnetic activity every day on the same site (www.ionos.kz/?q=en/node/21).

  12. Activities of NICT space weather project

    NASA Astrophysics Data System (ADS)

    Murata, Ken T.; Nagatsuma, Tsutomu; Watari, Shinichi; Shinagawa, Hiroyuki; Ishii, Mamoru

    NICT (National Institute of Information and Communications Technology) has been in charge of space weather forecast service in Japan for more than 20 years. The main target region of the space weather is the geo-space in the vicinity of the Earth where human activities are dominant. In the geo-space, serious damages of satellites, international space stations and astronauts take place caused by energetic particles or electromagnetic disturbances: the origin of the causes is dynamically changing of solar activities. Positioning systems via GPS satellites are also im-portant recently. Since the most significant effect of positioning error comes from disturbances of the ionosphere, it is crucial to estimate time-dependent modulation of the electron density profiles in the ionosphere. NICT is one of the 13 members of the ISES (International Space Environment Service), which is an international assembly of space weather forecast centers under the UNESCO. With help of geo-space environment data exchanging among the member nations, NICT operates daily space weather forecast service every day to provide informa-tion on forecasts of solar flare, geomagnetic disturbances, solar proton event, and radio-wave propagation conditions in the ionosphere. The space weather forecast at NICT is conducted based on the three methodologies: observations, simulations and informatics (OSI model). For real-time or quasi real-time reporting of space weather, we conduct our original observations: Hiraiso solar observatory to monitor the solar activity (solar flare, coronal mass ejection, and so on), domestic ionosonde network, magnetometer HF radar observations in far-east Siberia, and south-east Asia low-latitude ionosonde network (SEALION). Real-time observation data to monitor solar and solar-wind activities are obtained through antennae at NICT from ACE and STEREO satellites. We have a middle-class super-computer (NEC SX-8R) to maintain real-time computer simulations for solar and solar

  13. Space Weathering of Lunar Rocks

    NASA Technical Reports Server (NTRS)

    Noble, S. K.; Keller, L. P.; Christoffersen, R.; Rahman, Z.

    2012-01-01

    All materials exposed at the lunar surface undergo space weathering processes. On the Moon, boulders make up only a small percentage of the exposed surface, and areas where such rocks are exposed, like central peaks, are often among the least space weathered regions identified from remote sensing data. Yet space weathered surfaces (patina) are relatively common on returned rock samples, some of which directly sample the surface of larger boulders. Because, as witness plates to lunar space weathering, rocks and boulders experience longer exposure times compared to lunar soil grains, they allow us to develop a deeper perspective on the relative importance of various weathering processes as a function of time.

  14. Salt weathering on Mars

    NASA Astrophysics Data System (ADS)

    Jagoutz, E.

    Large well rounded boulders and angular rock fragments characterizes the Martian landscape as seen on the recent excellent quality photos. Analyzing the different rock-shapes indicates a time sequence of emplacement, fragmentation and transport of different rocks on Mars, which might give interesting insight into transport and weathering processes. Larger commonly well rounded boulders were emplaced onto gravel plains. After emplacement, these rocks were fragmented and disassembled. Nests of angular rock fragments are marking the locations of preexisting larger rocks. Frequently it is possible to reconstruct larger rounded rocks from smaller angular fragments. In other cases transport after fragmentation obscured the relationship of the fragments. However, a strewn field of fragments is still reminiscent of the preexisting rock. Mechanical salt weathering could be a plausible explanation for the insitu fragmentation of larger rounded blocks into angular fragments. Impact or secondary air fall induced fragmentation produces very different patterns, as observed around impact crates on Earth. Salt weathering of rocks is a common process in terrestrial environments. Salt crystallization in capillaries causes fragmentation of rocks, irrespective of the process of salt transportation and concentration. On Earth significant salt weathering can be observed in different climatic environments: in the transition zone of alluvial aprons and salt playas in desserts and in dry valleys of Antarctica. In terrestrial semi-arid areas the salt is transported by salt solution, which is progressively concentrated by evaporation. In Antarctic dry valleys freeze-thaw cycles causes salt transportation and crystallization resulting in rock fragmentation. This salt induced process can lead to complete destruction of rocks and converts rocks to fine sand. The efficient breakdown of rocks is dominating the landscape in some dry valleys of the Earth but possibly also on Mars. (Malin, 1974

  15. Weather dissemination and public usage

    NASA Technical Reports Server (NTRS)

    Stacey, M. S.

    1973-01-01

    The existing public usage of weather information was examined. A survey was conducted to substantiate the general public's needs for dissemination of current (0-12 hours) weather information, needs which, in a previous study, were found to be extensive and urgent. The goal of the study was to discover how the general public obtains weather information, what information they seek and why they seek it, to what use this information is put, and to further ascertain the public's attitudes and beliefs regarding weather reporting and the diffusion of weather information. Major findings from the study include: 1. The public has a real need for weather information in the 0-6 hour bracket. 2. The visual medium is preferred but due to the lack of frequent (0-6 hours) forecasts, the audio media only, i.e., telephone recordings and radio weathercasts, were more frequently used. 3. Weather information usage is sporadic.

  16. Space Weather Services of Korea

    NASA Astrophysics Data System (ADS)

    Yoon, KiChang; Kim, Jae-Hun; Kim, Young Yun; Kwon, Yongki; Wi, Gwan-sik

    2016-07-01

    The Korean Space Weather Center (KSWC) of the National Radio Research Agency (RRA) is a government agency which is the official source of space weather information for Korean Government and the primary action agency of emergency measure to severe space weather condition. KSWC's main role is providing alerts, watches, and forecasts in order to minimize the space weather impacts on both of public and commercial sectors of satellites, aviation, communications, navigations, power grids, and etc. KSWC is also in charge of monitoring the space weather condition and conducting research and development for its main role of space weather operation in Korea. In this study, we will present KSWC's recent efforts on development of application-oriented space weather research products and services on user needs, and introduce new international collaborative projects, such as IPS-Driven Enlil model, DREAM model estimating electron in satellite orbit, global network of DSCOVR and STEREO satellites tracking, and ARMAS (Automated Radiation Measurement for Aviation Safety).

  17. Space Weather Services of Korea

    NASA Astrophysics Data System (ADS)

    Yoon, K.; Hong, S.; Park, S.; Kim, Y. Y.; Wi, G.

    2015-12-01

    The Korean Space Weather Center (KSWC) of the National Radio Research Agency (RRA) is a government agency which is the official source of space weather information for Korean Government and the primary action agency of emergency measure to severe space weather condition. KSWC's main role is providing alerts, watches, and forecasts in order to minimize the space weather impacts on both of public and commercial sectors of satellites, aviation, communications, navigations, power grids, and etc. KSWC is also in charge of monitoring the space weather condition and conducting research and development for its main role of space weather operation in Korea. In this study, we will present KSWC's recent efforts on development of application-oriented space weather research products and services on user needs, and introduce new international collaborative projects, such as IPS-Driven Enlil model, global network of DSCOVR and STEREO satellites tracking, and ARMAS (Automated Radiation Measurement for Aviation Safety).

  18. Complex Molybdenum Isotope Behavior During Weathering and Erosional Transport

    NASA Astrophysics Data System (ADS)

    Siebert, C.; Pett-Ridge, J. C.; Burton, K.; Halliday, A. N.

    2009-12-01

    The oceans play a major role in regulating global climate because they both react and drive changes in other geochemical reservoirs. Non-traditional stable isotope systems have become important proxies for changes in ocean chemistry making the quantification of these changes possible. Molybdenum isotopes have great potential as tracers of changes in the oxygenation of the oceans over geological time scales. Although significant progress has been made and the amount of data on the biogeochemical behaviour of Mo in the marine environment has been increasing rapidly over the last few years, some important aspects of Mo geochemistry remain poorly understood. These include diagenetic processes at continental margins and continental weathering. Mo isotope behaviour in these settings has a potentially large impact on the interpretation of the geological record. A recent study of Archer and Vance (2008) has shown that dissolved Mo in many of Earths major rivers has a heavy isotope composition relative to most magmatic rocks. A potential cause for this isotope composition in modern rivers is isotope fractionation during weathering and erosion processes. We investigated Mo isotope behaviour in weathering profiles from Hawaii and Puerto Rico. Results clearly show significant Mo isotope fractionation during chemical weathering. Mo retained in saprolithe samples from Hawaii has light isotope compositions of up to -0.5 permill. The extent of fractionation is dependent on redox-conditions in the investigated profiles. The particular setting of these profiles keeps other factors that might influence the Mo isotope composition to a minimum. The results also indicate the possible use of Mo isotope signals as paleoredox-proxy of weathering processes. However, a weathering profile with intermittent changes in redox, pH and porewater saturation show more variable Mo isotope signals with partly positive isotope values. Sequential extractions of saphrolite samples show a clear

  19. Municipalities' Preparedness for Weather Hazards and Response to Weather Warnings

    PubMed Central

    Mehiriz, Kaddour; Gosselin, Pierre

    2016-01-01

    The study of the management of weather-related disaster risks by municipalities has attracted little attention even though these organizations play a key role in protecting the population from extreme meteorological conditions. This article contributes to filling this gap with new evidence on the level and determinants of Quebec municipalities’ preparedness for weather hazards and response to related weather warnings. Using survey data from municipal emergency management coordinators and secondary data on the financial and demographic characteristics of municipalities, the study shows that most Quebec municipalities are sufficiently prepared for weather hazards and undertake measures to protect the population when informed of imminent extreme weather events. Significant differences between municipalities were noted though. Specifically, the level of preparedness was positively correlated with the municipalities’ capacity and population support for weather-related disaster management policies. In addition, the risk of weather-related disasters increases the preparedness level through its effect on population support. We also found that the response to weather warnings depended on the risk of weather-related disasters, the preparedness level and the quality of weather warnings. These results highlight areas for improvement in the context of increasing frequency and/or severity of such events with current climate change. PMID:27649547

  20. The Archean Dongwanzi ophiolite complex, North China craton: 2.505-billion-year-old oceanic crust and mantle.

    PubMed

    Kusky, T M; Li, J H; Tucker, R D

    2001-05-11

    We report a thick, laterally extensive 2505 +/- 2.2-million-year-old (uranium-lead ratio in zircon) Archean ophiolite complex in the North China craton. Basal harzburgite tectonite is overlain by cumulate ultramafic rocks, a mafic-ultramafic transition zone of interlayered gabbro and ultramafic cumulates, compositionally layered olivine-gabbro and pyroxenite, and isotropic gabbro. A sheeted dike complex is rooted in the gabbro and overlain by a mixed dike-pillow lava section, chert, and banded iron formation. The documentation of a complete Archean ophiolite implies that mechanisms of oceanic crustal accretion similar to those of today were in operation by 2.5 billion years ago at divergent plate margins and that the temperature of the early mantle was not extremely elevated, as compared to the present-day temperature. Plate tectonic processes similar to those of the present must also have emplaced the ophiolite in a convergent margin setting.

  1. Severe Weather Forecast Decision Aid

    NASA Technical Reports Server (NTRS)

    Bauman, William H., III; Wheeler, Mark M.; Short, David A.

    2005-01-01

    This report presents a 15-year climatological study of severe weather events and related severe weather atmospheric parameters. Data sources included local forecast rules, archived sounding data, Cloud-to-Ground Lightning Surveillance System (CGLSS) data, surface and upper air maps, and two severe weather event databases covering east-central Florida. The local forecast rules were used to set threat assessment thresholds for stability parameters that were derived from the sounding data. The severe weather events databases were used to identify days with reported severe weather and the CGLSS data was used to differentiate between lightning and non-lightning days. These data sets provided the foundation for analyzing the stability parameters and synoptic patterns that were used to develop an objective tool to aid in forecasting severe weather events. The period of record for the analysis was May - September, 1989 - 2003. The results indicate that there are certain synoptic patterns more prevalent on days with severe weather and some of the stability parameters are better predictors of severe weather days based on locally tuned threat values. The results also revealed the stability parameters that did not display any skill related to severe weather days. An interactive web-based Severe Weather Decision Aid was developed to assist the duty forecaster by providing a level of objective guidance based on the analysis of the stability parameters, CGLSS data, and synoptic-scale dynamics. The tool will be tested and evaluated during the 2005 warm season.

  2. Weather Forecasting Aid

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Weather forecasters are usually very precise in reporting such conditions as temperature, wind velocity and humidity. They also provide exact information on barometric pressure at a given moment, and whether the barometer is "rising" or "falling"- but not how rapidly or how slowly it is rising or falling. Until now, there has not been available an instrument which measures precisely the current rate of change of barometric pressure. A meteorological instrument called a barograph traces the historical ups and downs of barometric pressure and plots a rising or falling curve, but, updated every three hours, it is only momentarily accurate at each updating.

  3. Weather Radar Studies

    DTIC Science & Technology

    1988-03-31

    Reflectivity Core Recognition 68 IV-10 Middle-Level Precursor Recognition 69 IV-l I Early Microburst Hazard Declaration 70 IV-12 Example of Results from...Denver Test Bed 106 V-I Selected Product Types 14 V-2 Encoded Map Size (in ELMs ) for Terminal Map Data Set 119 V-3 Encoded Map Size (in ELMs ) for En...Route Data Sets 119 V-4 Encoded Map Size (in ELMs ) for Terminal Map Data Set 125 xiii WEATHER RADAR STUDIES 1. INTRODUCTION The principal areas of

  4. A stability analysis of AVE-4 severe weather soundings

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1982-01-01

    The stability and vertical structure of an average severe storm sounding, consisting of both thermodynamic and wind vertical profiles, were investigated to determine if they could be distinguished from an average lag sounding taken 3 to 6 hours prior to severe weather occurrence. The term average is defined here to indicate the arithmetic mean of a parameter, as a function of altitude, determined from a large number of available observations taken either close to severe weather occurrence, or else more than 3 hours before it occurs. The investigative computations were also done to help determine if a severe storm forecast or index could possibly be used or developed. These mean vertical profiles of thermodynamic and wind parameters as a function of severity of the weather, determined from manually digitized radar (MDR) categories are presented. Profile differences and stability index differences are presented along with the development of the Johnson Lag Index (JLI) which is determined entirely upon environmental vertical parameter differences between conditions 3 hours prior to severe weather, and severe weather itself.

  5. The Bombardment of the Earth During the Hadean and Early Archean Eras

    NASA Astrophysics Data System (ADS)

    Marchi, S.; Bottke, W. F.; Elkins-Tanton, L. T.; Morbidelli, A.; Wuennemann, K.; Kring, D. A.; Bierhaus, M.

    2013-12-01

    Our knowledge of the Earth during the Hadean and early Archean eons (ca 4.5-3.5 Ga) is very limited, mainly because few rocks older than 3.8 Ga have been found (e.g. Harrison 2009). Hadean-era zircons have allowed us to glean important insights into this era, but their data has led to considerably different evolution models for the evolution of the early Earth; some predict a hellish world dominated by a molten surface with a sporadic steam atmosphere (e.g. Pollack 1997), while others have predicted a tranquil, cool surface with stable oceans (e.g. Wilde et al 2001; Valley et al 2002). To understand whether either model (or both) could be right, we believe it is useful to quantitatively examine the post Moon-forming impact bombardment of the early Earth. Over the last several years, through a combination of observations (e.g., Marchi et al 2012), theoretical models (e.g., Bottke et al 2012), and geochemical constraints from lunar rock (e.g. highly siderophile elements -HSE- abundances delivered to the Moon by impactors; the global number of lunar basins; the record of Archean-era impact spherule beds on Earth; Walker 2009; Neumann et al 2012), we have constructed a calibrated model of the early lunar impactor flux (Morbidelli et al 2012). Our results have now been extrapolated to the Earth, where they can make predictions about its early bombardment. Using a Monte Carlo code to account for the stochastic nature of major impacts, and constraining our results by the estimated HSE abundances of Earth's mantle (that were presumably delivered by impactors; Walker 2009; Bottke et al. 2010), we find the following trends. In the first ~100-200 Myr after the formation of the Moon, which we assume was created ~4.5 Ga, the Earth was almost entirely resurfaced by impacts. This bombardment, which included numerous D > 1000 km diameter impactors, should have vigorously mixed the crust and upper mantle. Between ~4.1-4.3 Ga, the impactor flux steadily decreased; though an uptick

  6. Spatially Resolved, In Situ Carbon Isotope Analysis of Archean Organic Matter

    NASA Technical Reports Server (NTRS)

    Williford, Kenneth H.; Ushikubo, Takayuki; Lepot, Kevin; Hallmann, Christian; Spicuzza, Michael J.; Eigenbrode, Jennifer L.; Summons, Roger E.; Valley, John W.

    2011-01-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to micron). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 micron using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 micron spot size with two Faraday cup detectors was 0.4 %, and 0.8 % for analyses using 1 micron and 3 micron spot sizes with a Faraday cup (for C-12) and an electron multiplier (for C-13). Eight coals, two ambers, a shungite, and a graphite were evaluated for micron-scale isotopic heterogeneity, and LCNN anthracite (delta C-13 = -23.56 +/- 0.1 %, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a C-13H/C-13 measurement included in every analysis. Matrix effects of variable C/SiO2 were evaluated by measuring mm to sub-micron graphite domains in quartzite from Bogala mine, Sri Lanka. Apparent instrumental bias and C-12 count rate are correlated in this case, but this may be related to a crystal orientation effect in graphite. Analyses of amorphous

  7. Deep-Time drilling in the Australian Archean: the Agouron Institute geobiological drilling project. (Invited)

    NASA Astrophysics Data System (ADS)

    Buick, R.

    2010-12-01

    The Agouron Institute has sponsored deep-time drilling across the South African Archean-Proterozoic boundary, investigating the rise of oxygen over an onshore-offshore environmental transect. It is now supporting a drilling program in the Australian Archean of the Pilbara Craton, addressing a similar theme but with the added goal of resolving controversy over the age and origin of hydrocarbon biomarker molecules in ancient kerogenous shales. As these have been claimed to provide evidence for the evolution of oxygenic photosynthesis long before the rise of atmospheric oxygen to persistently high levels during the ~2.3 Ga “Great Oxidation Event”, their syngenesis with their host shales is thus of critical importance for the interpretation of Earth’s early oxygenation history. During the first drilling season, 3 holes were drilled using techniques and equipment to minimize organic geochemical contamination (new drill-string components cleaned before drilling potentially biomarker-bearing rocks, pre-contamination of drilling fluid with a synthetic organic compound of similar geochemical characteristics to biomarkers, sterile cutting and storage of samples immediately upon retrieval from the core-barrel). The initial hole was a blank control for organic geochemistry, drilled into rocks too metamorphosed to retain biomarker molecules. These rocks, cherts, carbonates and pelites of the 3.52 Ga Coucal Formation, Coonterunah Group, have been metamorphosed to upper greenschist facies at temperatures near 500°C and so should have had any ancient soluble hydrocarbons destroyed. However, because they contain both carbonate and organic carbon, these rocks can instead provide isotopic information about the earliest evolution of biological metabolism as they possess residues of both the reactant and product sides of the carbon-fixation reaction. The second hole sampled an on-shore section of carbonates and kerogenous shales in the ~2.65 Ga Carawine Dolomite and Lewin Shale

  8. Diamonds in an Archean greenstone belt: Diamond suites in unconventional rocks of Wawa, Northern Ontario (Canada)

    NASA Astrophysics Data System (ADS)

    Kopylova, Maya; Bruce, Loryn; Ryder, John

    2010-05-01

    Diamonds typically are found on Archean cratons entrained by younger Phanerozoic kimberlites. In contrast, Wawa diamonds are hosted in "unconventional", non-kimberlitic rocks that formed contemporaneously with the mafic and sedimentary rocks of the Archean Michipicoten Greenstone Belt (MGB). We studied two diamond suites that occur within the 2.9-2.7 Ga greenschist facies rocks of MGB located in the southwest portion of the Superior Craton (E. Canada). The first diamond suite henceforth referred to as the Wawa breccia diamonds (384 stones), are hosted in the 2618-2744 Ma calc-alkaline lamprophyres and volcaniclastic breccias, contemporaneous with pillow basalts and felsic volcanics of MGB. The second suite, the Wawa conglomerate diamonds (80 crystals), are hosted in the 2697-2700 Ma poorly sorted sedimentary polymictic conglomerate which is interpreted as a proximal alluvial fan debris flow in a fan-delta environment. The majority of the diamonds was found within the matrix of the conglomerate. The diamondiferous breccia occurs 20 km north of the town of Wawa, whereas the conglomerate is found 12 km northeast of Wawa. Diamonds from the 2 occurrences were characterized and described for provenance studies. Both the breccia and conglomerate diamonds show similar crystal habits, with the predominance of octahedral single crystals and ~ 10% of cubes. The conglomerate diamonds are significantly less resorbed (no resorbtion in 43% of the stones) than the breccia diamonds (8% non-resorbed stones). In both suites, only 21-24% show high degrees of resorption. The majority of crystals in both suites are colourless, with some yellow, brown and grey stones. Conglomerate diamonds had a wider variety of colours that were not seen in the breccia diamonds, including green and pink. The breccia diamonds contain 0-740 ppm N and show two modes of N aggregation at 0-30 and 60-95%. Among the breccia diamonds, Type IaA stones comprise 17%, whereas IaAB stones make up 49% of the

  9. Evolution of the Archean Mohorovičić discontinuity from a synaccretionary 4.5 Ga protocrust

    NASA Astrophysics Data System (ADS)

    Hamilton, Warren B.

    2013-12-01

    This review evaluates and rejects the currently dominant dogmas of geodynamics and geochemistry, which are based on 1950s-1970s assumptions of a slowly differentiating Earth. Evidence is presented for evolution of mantle, crust, and early Moho that began with fractionation of most crustal components, synchronously with planetary accretion, into mafic protocrust by ~ 4.5 Ga. We know little about Hadean crustal geology (> 3.9 Ga) except that felsic rocks were then forming, but analogy with Venus, and dating from the Moon, indicate great shallow disruption by large and small impact structures, including huge fractionated impact-melt constructs, throughout that era. The mantle sample and Archean (< 3.9 Ga) crustal geology integrate well. The shallow mantle was extremely depleted by early removal of thick mafic protocrust, which was the primary source of the tonalite, trondhjemite, and granodiorite (TTG) that dominate preserved Archean crust to its base, and of the thick mafic volcanic rocks erupted on that crust. Lower TTG crust, kept mobile by its high radioactivity and by insulating upper crust, rose diapirically into the upper crust as dense volcanic rocks sagged synformally. The mobile lower crust simultaneously flowed laterally to maintain subhorizontal base and surface, and dragged overlying brittler granite-and-greenstone upper crust. Petrologically required garnet-rich residual protocrust incrementally delaminated, sank through low-density high-mantle magnesian dunite, and progressively re-enriched upper mantle, mostly metasomatically. Archean and earliest Proterozoic craton stabilization and development of final Mohos followed regionally complete early delamination of residual protocrust, variously between ~ 2.9 and 2.2 Ga. Where some protocrust remained, Proterozoic basins, filled thickly by sedimentary and volcanic rocks, developed on Archean crust, beneath which delamination of later residual protocrust continued top-down enrichment of upper mantle. That

  10. Multiple sulfur-isotope signatures in Archean sulfates and their implications for the chemistry and dynamics of the early atmosphere

    PubMed Central

    Muller, Élodie; Philippot, Pascal; Rollion-Bard, Claire; Cartigny, Pierre

    2016-01-01

    Sulfur isotopic anomalies (∆33S and ∆36S) have been used to trace the redox evolution of the Precambrian atmosphere and to document the photochemistry and transport properties of the modern atmosphere. Recently, it was shown that modern sulfate aerosols formed in an oxidizing atmosphere can display important isotopic anomalies, thus questioning the significance of Archean sulfate deposits. Here, we performed in situ 4S-isotope measurements of 3.2- and 3.5-billion-year (Ga)-old sulfates. This in situ approach allows us to investigate the diversity of Archean sulfate texture and mineralogy with unprecedented resolution and from then on to deconvolute the ocean and atmosphere Archean sulfur cycle. A striking feature of our data is a bimodal distribution of δ34S values at ∼+5‰ and +9‰, which is matched by modern sulfate aerosols. The peak at +5‰ represents barite of different ages and host-rock lithology showing a wide range of ∆33S between −1.77‰ and +0.24‰. These barites are interpreted as primary volcanic emissions formed by SO2 photochemical processes with variable contribution of carbonyl sulfide (OCS) shielding in an evolving volcanic plume. The δ34S peak at +9‰ is associated with non–33S-anomalous barites displaying negative ∆36S values, which are best interpreted as volcanic sulfate aerosols formed from OCS photolysis. Our findings confirm the occurrence of a volcanic photochemical pathway specific to the early reduced atmosphere but identify variability within the Archean sulfate isotope record that suggests persistence throughout Earth history of photochemical reactions characteristic of the present-day stratosphere. PMID:27330111

  11. Magnetic Properties through the Archean/Paleoproterozoic Transition from the Pilbara Craton, Western Australia: Bio-environmental Implications

    NASA Astrophysics Data System (ADS)

    Isambert, A.; Carlut, J. H.; Bouquerel, H.; Pecoits, E.; Philippot, P.; Vennin, E.; Ader, M.; Thomazo, C.; Buoncristiani, J. F.; Baton, F.; Le Huen, A. L.; Muller, E.; Deldicque, D.; Sforna, M. C.

    2015-12-01

    The origin of iron oxides in Archean and Paleoproterozoic Banded Iron Formations is still a matter of debate. We report here low and high temperature magnetic properties, susceptibility and saturation magnetization results coupled with scanning microscope, transmission electron microscopy, Raman observations and microprobe analyses along a 60 meters section, which encompasses the uppermost Archean Boolgeeda Iron Formation and its transition into the lower Paleoproterozoic Kungarra Formation in the Pilbara Craton, Western Australia. With the exception of two volcanoclastic intervals characterized by low susceptibility and magnetization, nearly pure magnetite is identified as the main magnetic carrier in all iron-rich layers including hematite-bearing jasper beds. The relative magnetic contribution of magnetite and hematite throughout the section is evidenced by IRM acquisition curves. We observed a sharp decrease in magnetization at the Archean-Proterozoic transition and a general trend in the Verwey temperature. Two populations of magnetically distinct magnetites are reported from a 2 meter-thick interval lying within the late Archean section of the core. Each population shows a specific Verwey transition temperature: one around 120-124K and the other in the range of 105-110K. The two Verwey transitions are interpreted to reflect two distinct stoichiometry and likely two stages of magnetite crystallization. The 120-124K transition is attributed to nearly pure stoichiometric magnetite, whereas SEM, TEM and microprobe observations suggest that the lower temperature transition is related to chemically impure silician magnetite. Microbial-induced partial substitution of iron by silicon is suggested here. This is supported by an increase in Total Organic Carbon (TOC) in the same interval and Raman spectroscopy data showing a close association of organic carbon with magnetite.

  12. U Pb zircon age constraints on the Dongwanzi ultramafic mafic body, North China, confirm it is not an Archean ophiolite

    NASA Astrophysics Data System (ADS)

    Zhao, Guochun; Wilde, Simon A.; Li, Sanzhong; Sun, Min; Grant, Matthew L.; Li, Xuping

    2007-03-01

    In Science May 11 2001 (p.1142-1145), Kusky et al. reported an ophiolite complex of late Archean age in the Dongwanzi area of the North China Craton, which has subsequently been considered a hallmark for Archean plate tectonics. However, this interpretation has been questioned because no convincing pillow lavas or sheeted dikes have been found in the Dongwanzi complex and, more importantly, as a major part of the ophiolite complex, the Dongwanzi ultramafic-mafic body has not previously been dated and it therefore remains unknown whether it is of Archean age. In this study, we carried out detailed field investigations and SHRIMP U-Pb zircon dating on the rocks of the Dongwanzi ultramafic-mafic body, as recognized by Kusky et al. Our field observations reveal that in several places along the boundaries of the Dongwanzi body, mafic dikes emanating from the main body intrude the country rocks of the unmetamorphosed Mesoproterozoic sedimentary successions of the Changcheng-Jixian 'System'. One of these dikes yielded a SHRIMP U-Pb zircon age of 306 ± 6 Ma, similar to the SHRIMP U-Pb zircon age of 308 ± 4 Ma obtained from a plagioclase-bearing pyroxenite from the Dongwanzi ultramafic-mafic body. Four other samples collected from various parts of the ultramafic-mafic body (gabbro, leucogabbro or pyroxenite) record similar SHRIMP U-Pb zircon ages around ˜ 300 Ma. Therefore, both field relationships and SHRIMP U-Pb zircon dating results unequivocally demonstrate that the Dongwanzi ultramafic-mafic body is not part of an Archean ophiolite.

  13. Multiple sulfur-isotope signatures in Archean sulfates and their implications for the chemistry and dynamics of the early atmosphere

    NASA Astrophysics Data System (ADS)

    Muller, Élodie; Philippot, Pascal; Rollion-Bard, Claire; Cartigny, Pierre

    2016-07-01

    Sulfur isotopic anomalies (∆33S and ∆36S) have been used to trace the redox evolution of the Precambrian atmosphere and to document the photochemistry and transport properties of the modern atmosphere. Recently, it was shown that modern sulfate aerosols formed in an oxidizing atmosphere can display important isotopic anomalies, thus questioning the significance of Archean sulfate deposits. Here, we performed in situ 4S-isotope measurements of 3.2- and 3.5-billion-year (Ga)-old sulfates. This in situ approach allows us to investigate the diversity of Archean sulfate texture and mineralogy with unprecedented resolution and from then on to deconvolute the ocean and atmosphere Archean sulfur cycle. A striking feature of our data is a bimodal distribution of δ34S values at ˜+5‰ and +9‰, which is matched by modern sulfate aerosols. The peak at +5‰ represents barite of different ages and host-rock lithology showing a wide range of ∆33S between -1.77‰ and +0.24‰. These barites are interpreted as primary volcanic emissions formed by SO2 photochemical processes with variable contribution of carbonyl sulfide (OCS) shielding in an evolving volcanic plume. The δ34S peak at +9‰ is associated with non-33S-anomalous barites displaying negative ∆36S values, which are best interpreted as volcanic sulfate aerosols formed from OCS photolysis. Our findings confirm the occurrence of a volcanic photochemical pathway specific to the early reduced atmosphere but identify variability within the Archean sulfate isotope record that suggests persistence throughout Earth history of photochemical reactions characteristic of the present-day stratosphere.

  14. NASA Space Weather Center Services: Potential for Space Weather Research

    NASA Technical Reports Server (NTRS)

    Zheng, Yihua; Kuznetsova, Masha; Pulkkinen, Antti; Taktakishvili, A.; Mays, M. L.; Chulaki, A.; Lee, H.; Hesse, M.

    2012-01-01

    The NASA Space Weather Center's primary objective is to provide the latest space weather information and forecasting for NASA's robotic missions and its partners and to bring space weather knowledge to the public. At the same time, the tools and services it possesses can be invaluable for research purposes. Here we show how our archive and real-time modeling of space weather events can aid research in a variety of ways, with different classification criteria. We will list and discuss major CME events, major geomagnetic storms, and major SEP events that occurred during the years 2010 - 2012. Highlights of major tools/resources will be provided.

  15. Road Weather and Connected Vehicles

    NASA Astrophysics Data System (ADS)

    Pisano, P.; Boyce, B. C.

    2015-12-01

    On average, there are over 5.8 M vehicle crashes each year of which 23% are weather-related. Weather-related crashes are defined as those crashes that occur in adverse weather or on slick pavement. The vast majority of weather-related crashes happen on wet pavement (74%) and during rainfall (46%). Connected vehicle technologies hold the promise to transform road-weather management by providing improved road weather data in real time with greater temporal and geographic accuracy. This will dramatically expand the amount of data that can be used to assess, forecast, and address the impacts that weather has on roads, vehicles, and travelers. The use of vehicle-based measurements of the road and surrounding atmosphere with other, more traditional weather data sources, and create road and atmospheric hazard products for a variety of users. The broad availability of road weather data from mobile sources will vastly improve the ability to detect and forecast weather and road conditions, and will provide the capability to manage road-weather response on specific roadway links. The RWMP is currently demonstrating how weather, road conditions, and related vehicle data can be used for decision making through an innovative Integrated Mobile Observations project. FHWA is partnering with 3 DOTs (MN, MI, & NV) to pilot these applications. One is a mobile alerts application called the Motorists Advisories and Warnings (MAW) and a maintenance decision support application. These applications blend traditional weather information (e.g., radar, surface stations) with mobile vehicle data (e.g., temperature, brake status, wiper status) to determine current weather conditions. These weather conditions, and other road-travel-relevant information, are provided to users via web and phone applications. The MAW provides nowcasts and short-term forecasts out to 24 hours while the EMDSS application can provide forecasts up to 72 hours in advance. The three DOTs have placed readers and external

  16. Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

    SciTech Connect

    Kochanov, R. V.; Gordon, I. E.; Rothman, L. S.; Sharpe, S. W.; Johnson, T. J.; Sams, R. L.

    2015-08-25

    In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm-1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 (dimer)+ NO2 was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra.

  17. In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers

    NASA Astrophysics Data System (ADS)

    Peters, Carl A.; Piazolo, Sandra; Webb, Gregory E.; Dutkiewicz, Adriana; George, Simon C.

    2016-11-01

    The detection of early life signatures using hydrocarbon biomarkers in Precambrian rocks struggles with contamination issues, unspecific biomarkers and the lack of suitable sedimentary rocks due to extensive thermal overprints. Importantly, host rocks must not have been exposed to temperatures above 250 °C as at these temperatures biomarkers are destroyed. Here we show that Archean sedimentary rocks from the Jeerinah Formation (2.63 billion yrs) and Carawine Dolomite (2.55 billion yrs) of the Pilbara Craton (Western Australia) drilled by the Agouron Institute in 2012, which previously were suggested to be suitable for biomarker studies, were metamorphosed to the greenschist facies. This is higher than previously reported. Both the mineral assemblages (carbonate, quartz, Fe-chlorite, muscovite, microcline, rutile, and pyrite with absence of illite) and chlorite geothermometry suggest that the rocks were exposed to temperatures higher than 300 °C and probably ∼400 °C, consistent with greenschist-facies metamorphism. This facies leads to the destruction of any biomarkers and explains why the extraction of hydrocarbon biomarkers from pristine drill cores has not been successful. However, we show that the rocks are cut by younger formation-specific carbonate veins containing primary oil-bearing fluid inclusions and solid bitumens. Type 1 veins in the Carawine Dolomite consist of dolomite, quartz and solid bitumen, whereas type 2 veins in the Jeerinah Formation consist of calcite. Within the veins fluid inclusion homogenisation temperatures and calcite twinning geothermometry indicate maximum temperatures of ∼200 °C for type 1 veins and ∼180 °C for type 2 veins. Type 1 veins have typical isotopic values for reprecipitated Archean sea-water carbonates, with δ13CVPDB ranging from - 3 ‰ to 0‰ and δ18OVPDB ranging from - 13 ‰ to - 7 ‰, while type 2 veins have isotopic values that are similar to hydrothermal carbonates, with δ13CVPDB ranging from - 18

  18. Weatherization Apprenticeship Program

    SciTech Connect

    Watson, Eric J

    2012-12-18

    Weatherization improvement services will be provided to Native people by Native people. The proposed project will recruit, train and hire two full-time weatherization technicians who will improve the energy efficiency of homes of Alaska Natives/American Indians residing in the Indian areas, within the Cook Inlet Region of Alaska. The Region includes Anchorage as well as 8 small tribal villages: The Native Villages of Eklutna, Knik, Chickaloon, Seldovia, Ninilchik, Kenaitze, Salamatof, and Tyonek. This project will be a partnership between three entities, with Cook Inlet Tribal Council (CITC) as the lead agency: CITCA's Employment and Training Services Department, Cook Inlet Housing Authority and Alaska Works Partnership. Additionally, six of the eight tribal villages within the Cook Inlet Region of Alaska have agreed to work with the project in order to improve the energy efficiency of their tribally owned buildings and homes. The remaining three villages will be invited to participate in the establishment of an intertribal consortium through this project. Tribal homes and buildings within Anchorage fall under Cook Inlet Region, Inc. (CIRI) tribal authority.

  19. Weathering of rock 'Ginger'

    NASA Technical Reports Server (NTRS)

    1997-01-01

    One of the more unusual rocks at the site is Ginger, located southeast of the lander. Parts of it have the reddest color of any material in view, whereas its rounded lobes are gray and relatively unweathered. These color differences are brought out in the inset, enhanced at the upper right. In the false color image at the lower right, the shape of the visible-wavelength spectrum (related to the abundance of weathered ferric iron minerals) is indicated by the hue of the rocks. Blue indicates relatively unweathered rocks. Typical soils and drift, which are heavily weathered, are shown in green and flesh tones. The very red color in the creases in the rock surface correspond to a crust of ferric minerals. The origin of the rock is uncertain; the ferric crust may have grown underneath the rock, or it may cement pebbles together into a conglomerate. Ginger will be a target of future super-resolution studies to better constrain its origin.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator. JPL is an operating division of the California Institute of Technology (Caltech).

  20. Space Weather Effects on Range Operations

    DTIC Science & Technology

    2013-02-01

    galaxy for some ten million years before intersecting the earth. They are partly kept out by the earth’s magnetic field and have easier access at the...prediction based on AP- 8 & 1970 magnetic field model. Double-peak pass at orbit 23 is not predicted. Figure 5 show count-rate profiles for a typical day in...space that affect Earth and its technological systems. Space Weather is a consequence of the behavior of the Sun, the nature of Earth’s magnetic field

  1. Characterization of the Weatherization Assistance Program network

    SciTech Connect

    Mihlmester, P.E.; Koehler, W.C. Jr.; Beyer, M.A. . Applied Management Sciences Div.); Brown, M.A. ); Beschen, D.A. Jr. . Office of Weatherization Assistance Programs)

    1992-02-01

    The Characterization of the Weatherization Assistance Program (WAP) Network was designed to describe the national network of State and local agencies that provide WAP services to qualifying low-income households. The objective of this study was to profile the current WAP network. To achieve the objective, two national surveys were conducted: one survey collected data from 49 State WAP agencies (including the coterminous 48 States and the District of Columbia), and the second survey collected data from 920 (or 81 percent) of the local WAP agencies.

  2. Weather Forecasting Systems and Methods

    NASA Technical Reports Server (NTRS)

    Mecikalski, John (Inventor); MacKenzie, Wayne M., Jr. (Inventor); Walker, John Robert (Inventor)

    2014-01-01

    A weather forecasting system has weather forecasting logic that receives raw image data from a satellite. The raw image data has values indicative of light and radiance data from the Earth as measured by the satellite, and the weather forecasting logic processes such data to identify cumulus clouds within the satellite images. For each identified cumulus cloud, the weather forecasting logic applies interest field tests to determine a score indicating the likelihood of the cumulus cloud forming precipitation and/or lightning in the future within a certain time period. Based on such scores, the weather forecasting logic predicts in which geographic regions the identified cumulus clouds will produce precipitation and/or lighting within during the time period. Such predictions may then be used to provide a weather map thereby providing users with a graphical illustration of the areas predicted to be affected by precipitation within the time period.

  3. Weather forecasting expert system study

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Weather forecasting is critical to both the Space Transportation System (STS) ground operations and the launch/landing activities at NASA Kennedy Space Center (KSC). The current launch frequency places significant demands on the USAF weather forecasters at the Cape Canaveral Forecasting Facility (CCFF), who currently provide the weather forecasting for all STS operations. As launch frequency increases, KSC's weather forecasting problems will be great magnified. The single most important problem is the shortage of highly skilled forecasting personnel. The development of forecasting expertise is difficult and requires several years of experience. Frequent personnel changes within the forecasting staff jeopardize the accumulation and retention of experience-based weather forecasting expertise. The primary purpose of this project was to assess the feasibility of using Artificial Intelligence (AI) techniques to ameliorate this shortage of experts by capturing aria incorporating the forecasting knowledge of current expert forecasters into a Weather Forecasting Expert System (WFES) which would then be made available to less experienced duty forecasters.

  4. Contrasting lithium and magnesium isotope fractionation during continental weathering

    NASA Astrophysics Data System (ADS)

    Teng, F.; Li, W.; Rudnick, R. L.; Gardner, R. L.

    2010-12-01

    Magnesium isotopic compositions of a profile through saprolites developed on a diabase dike from South Carolina have been measured in order to study the behavior of Mg isotopes during continental weathering. As weathering progresses, Mg isotopes are strongly fractionated and are correlated with Mg concentration, clay mineral proportions and density of the saprolites. δ26Mg values increase from -0.22 in the unweathered diabase to +0.65 in the most weathered saprolite. These observations are consistent with release of light Mg to the hydrosphere and formation of isotopically heavy Mg in the weathered products. The process can be modeled by Rayleigh distillation with an apparent fractionation factor between the saprolite and fluid (α) of 1.00005 to 1.00043, i.e., up to 0.43‰ fractionation in the 26Mg/24Mg ratio between the rocks and fluid during weathering. Like Mg isotopes, Li isotopes in the saprolite profile are also greatly fractionated, with δ7Li values as low as -20. The large Li isotope fractionation and variation in Li concentration, as well as irregularities in the δ7Li profile with depth, however, cannot be explained by Rayleigh distillation alone. Instead, Li can be modeled by a two-step process: (1) equilibrium isotope fractionation during weathering, which lowered δ7Li and Li concentrations and produced a Li concentration gradient in the saprolites like that seen in Mg isotopes, 2) subsequent kinetic isotope fractionation produced by diffusion of Li in the saprolites, possibly across a paleo water table. The results presented here suggest that continental weathering will shift the Mg isotopic composition of the continental crust to values higher than the mantle value, whereas crustal recycling over the history of the Earth will have no discernible effect on the Mg isotopic composition of the mantle.

  5. Weathering Intensity on Laurentia in the Mesoproterozoic: Evidence From CIA of the Lower Belt Supergroup

    NASA Astrophysics Data System (ADS)

    Kerrich, R.; Gonzalez-Alvarez, I.

    2004-05-01

    The Belt Supergroup siliciclastic sequence was deposited between 1.47 to 1.40 Ga in a passive rift on the margin of Laurentia associated with the opening of the Grenville Ocean. Nominal CIA values of the Appekunny and Grinnell siltstones are 49 to 68. Given pervasive secondary enrichment of K due to basinal brines, corrected values are 66 to 85 using the procedure of Fedo et al., (1995). Red and green colored siltstones from the Appekunny and Grinnell formations in the lower Belt Supergroup, have abundances of CaO, Na(2)O, and Sr depleted up to 6 times relative to PA-UCC, stemming from intense weathering of the provenance. In contrast, there are pronounced additions of K (x 1.5) as well as high Li, Rb, and Cs, hence high Rb/Sr ratios, and negative anomalies of Eu/Eu* relative to PA-UCC. Red siltstones have an average K/Cs ratio of 1600. This post-depositional potassic alteration is a common feature of siliciclastic sedimentary sequences, and has been documented in several Precambrian sedimentary basins. Interpretation of corrected CIA values is complex, as CIA reflects some combination of contemporaneous weathering and recycled sediments in the source area. Low Sr contents in conjunction with high Rb/Sr ratios, relative to Archean or post-Archean UCC, have been reported in other studies of several Archean and Proterozoic metasedimentary sequences as a proxy for deeply weathered cratonic rocks. Low Sr contents coupled with high Rb/Sr, with an average of 5.5 for red siltstones in the Appekunny and Grinnell formations, whereas the Aldridge and Fort Steele formations in the lower Belt Supergroup have Rb/Sr averages of 2.0 and 2.2 respectively. This stratigraphic trend is interpreted as a secular enlargement in the area of the drainage basin to erode more recycled sedimentary rocks, and/or an increase in weathering intensity. A mantle plume associated with the opening of the Grenville Ocean ~1.5 Ga ago may have degassed massive quantities of CO(2), resulting in intense

  6. The Origin of "Space Weather"

    NASA Astrophysics Data System (ADS)

    Cade, William B.; Chan-Park, Christina

    2015-02-01

    Although "space weather" is a fairly recent term, there is a rich history of similar terms being used beginning in the middle to late 1800s. "Solar meteorology," "magnetic weather," and "cosmic meteorology" all appeared during that time frame. The actual first appearance of space weather can be attributed to the publication Science News Letter in 1957 (with the first modern usage in 1959) and was possibly coined by the editor at the time, Watson Davis.

  7. Climate signal and weather noise

    SciTech Connect

    Leith, C.E.

    1995-04-01

    A signal of small climate change in either the real atmosphere or numerical simulation of it tends to be obscured by chaotic weather fluctuations. Time-lagged covariances of such weather processes are used to estimate the sampling errors of time average estimates of climate parameters. Climate sensitivity to changing external influences may also be estimated using the fluctuation dissipation relation of statistical mechanics. Answers to many climate questions could be provided by a realistic stochastic model of weather and climate.

  8. On the potential use of radar-derived information in operational numerical weather prediction

    NASA Technical Reports Server (NTRS)

    Mcpherson, R. D.

    1986-01-01

    Estimates of requirements likely to be levied on a new observing system for mesoscale meteonology are given. Potential observing systems for mesoscale numerical weather prediction are discussed. Thermodynamic profiler radiometers, infrared radiometer atmospheric sounders, Doppler radar wind profilers and surveillance radar, and moisture profilers are among the instruments described.

  9. Space Weathering: An Ultraviolet Indicator

    NASA Technical Reports Server (NTRS)

    Hendrix, A. R.; Vilas, F.

    2003-01-01

    We present evidence suggesting that the spectral slope of airless bodies in the UV-visible wavelength range can be used as an indicator of exposure to space weathering. While space weathering generally produces a reddening of spectra in the visible-NIR spectral regions, it tends to result in a bluing of the UV-visible portion of the spectrum, and may in some cases produce a spectral reversal. The bluing effect may be detectable with smaller amounts of weathering than are necessary to detect the longer-wavelength weathering effects.

  10. Space Weathering: An Ultraviolet Indicator

    NASA Technical Reports Server (NTRS)

    Hendrix, A. R.; Vilas, F.

    2004-01-01

    We present evidence suggesting that the spectral slope of airless bodies in the UV-visible wavelength range can be used as an indicator of exposure to space weathering. While space weathering generally produces a reddening of spectra in the visible-NIR spectral regions, it tends to result in a bluing of the UV-visible portion of the spectrum, and may in some cases produce a spectral reversal. The bluing effect may be detectable with smaller amounts of weathering than are necessary to detect the longer-wavelength weathering effects.

  11. AWE: Aviation Weather Data Visualization

    NASA Technical Reports Server (NTRS)

    Spirkovska, Lilly; Lodha, Suresh K.

    2001-01-01

    The two official sources for aviation weather reports both require the pilot to mentally visualize the provided information. In contrast, our system, Aviation Weather Environment (AWE) presents aviation specific weather available to pilots in an easy to visualize form. We start with a computer-generated textual briefing for a specific area. We map this briefing onto a grid specific to the pilot's route that includes only information relevant to his flight route that includes only information relevant to his flight as defined by route, altitude, true airspeed, and proposed departure time. By modifying various parameters, the pilot can use AWE as a planning tool as well as a weather briefing tool.

  12. Solar weather/climate predictions

    NASA Technical Reports Server (NTRS)

    Schatten, K. H.; Goldberg, R. A.; Mitchell, J. M.; Olson, R.; Schaefer, J.; Silverman, S.; Wilcox, J.; Williams, G.

    1979-01-01

    Solar variability influences upon terrestrial weather and climate are addressed. Both the positive and negative findings are included and specific predictions, areas of further study, and recommendations listed.

  13. Small Sensors for Space Weather

    NASA Astrophysics Data System (ADS)

    Nicholas, A. C.

    2015-12-01

    The Naval Research Laboratory is actively pursuing enhancing the nation's space weather sensing capability. One aspect of this plan is the concept of flying Space Weather sensor suites on host spacecraft as secondary payloads. The emergence and advancement of the CubeSat spacecraft architecture has produced a viable platform for scientifically and operationally relevant Space Weather sensing. This talk will provide an overview of NRL's low size weight and power sensor technologies targeting Space Weather measurements. A summary of on-orbit results of past and current missions will be presented, as well as an overview of future flights that are manifested and potential constellation missions.

  14. Bishop Paiute Weatherization Training Program

    SciTech Connect

    Carlos Hernandez

    2010-01-28

    The DOE Weatherization Training Grant assisted Native American trainees in developing weatherization competencies, creating employment opportunities for Bishop Paiute tribal members in a growing field. The trainees completed all the necessary training and certification requirements and delivered high-quality weatherization services on the Bishop Paiute Reservation. Six tribal members received all three certifications for weatherization; four of the trainees are currently employed. The public benefit includes (1) development of marketable skills by low-income Native individuals, (2) employment for low-income Native individuals in a growing industry, and (3) economic development opportunities that were previously not available to these individuals or the Tribe.

  15. New Constraints on Archean-Paleoproterozoic Carbonate Chemistry and pCO2

    NASA Astrophysics Data System (ADS)

    Blättler, C. L.; Higgins, J. A.

    2015-12-01

    Very few constraints exist on Archean and Proterozoic seawater chemistry, leaving huge uncertainties on the boundary conditions for the evolution of life and a habitable environment. Ancient carbonate chemistry, which is intimately related to oceanic pH and atmospheric pCO2, remains particularly uncertain, despite its importance for understanding environments and temperatures on early Earth. Using a new application of high-precision calcium isotope measurements, we present data from the Tumbiana Formation (2.7 Ga, Western Australia), the Campbellrand Platform (2.6 Ga, South Africa) and the Pethei Group (1.9 Ga, Northwest Territories, Canada) that allow us to place constraints on carbonate chemistry both before and after the Great Oxidation Event. By analogy with calcium isotope behavior in sulfate minerals (Blättler and Higgins, 2014) and Mono Lake (Nielsen and DePaolo, 2013), we infer a lower limit on the ratio of calcium ions to carbonate alkalinity during deposition of these three sedimentary sequences. These data rule out the soda ocean hypothesis (Kempe and Degens, 1985) and make further predictions about the role of CO2 in solving the faint young Sun problem.

  16. Trace element differences between Archean, Proterozoic and Phanerozoic crustal components: Implications for crustal growth processes

    NASA Technical Reports Server (NTRS)

    Tarney, J.; Wyborn, L. E. A.; Sheraton, J. W.; Wyborn, D.

    1988-01-01

    Critical to models for continental crust growth and recycling are the processes through which crustal growth takes place. In particular, it is important to know whether these processes have changed fundamentally with time in response to the earth's thermal evolution, and whether the crustal compositions generated are compatible with crustal remobilization, crustal recycling, or represent primary additions. There are some significant and consistent differences in the major and trace element compositions of crustal components with time which have important implications for crustal growth processes. These will be illustrated with reference to Archean rocks from a number of shield areas, Proterozoic granitoids from Australia and elsewhere, Palaeozoic granitoids from Australia and Scotland, and Mesozoic - recent granitoids from present continental margin belts. Surprisingly some rather simple and consistent patterns energy using this technique. There are then significant differences in compositions of granitoid crustal additions throughout geological time, with a particular type of granitoid apparently dominating a particular time period. This implies that the tectonic processes giving rise to granite generation have changed in response to the earth's thermal evolution.

  17. Large sulfur-isotope anomaly in nonvolcanic sulfate aerosol and its implications for the Archean atmosphere

    PubMed Central

    Shaheen, Robina; Abaunza, Mariana M.; Jackson, Teresa L.; McCabe, Justin; Savarino, Joël; Thiemens, Mark H.

    2014-01-01

    Sulfur-isotopic anomalies have been used to trace the evolution of oxygen in the Precambrian atmosphere and to document past volcanic eruptions. High-precision sulfur quadruple isotope measurements of sulfate aerosols extracted from a snow pit at the South Pole (1984–2001) showed the highest S-isotopic anomalies (Δ33S = +1.66‰ and Δ36S = +2‰) in a nonvolcanic (1998–1999) period, similar in magnitude to Pinatubo and Agung, the largest volcanic eruptions of the 20th century. The highest isotopic anomaly may be produced from a combination of different stratospheric sources (sulfur dioxide and carbonyl sulfide) via SOx photochemistry, including photoexcitation and photodissociation. The source of anomaly is linked to super El Niño Southern Oscillation (ENSO) (1997–1998)-induced changes in troposphere–stratosphere chemistry and dynamics. The data possess recurring negative S-isotope anomalies (Δ36S = −0.6 ± 0.2‰) in nonvolcanic and non-ENSO years, thus requiring a second source that may be tropospheric. The generation of nonvolcanic S-isotopic anomalies in an oxidizing atmosphere has implications for interpreting Archean sulfur deposits used to determine the redox state of the paleoatmosphere. PMID:25092338

  18. Relationship between high- and low-grade Archean terranes: Implications for early Earth paleogeography

    NASA Technical Reports Server (NTRS)

    Eriksson, K. A.

    1986-01-01

    The Western Gneiss Terrain (WGT) of the Yilgarn Block, Western Australia was studied. The WGT forms an arcuate belt of Archean gneisses that flank the western margin of the Yilgarn Block. In general the WGT is composed of high-grade orthogneisses and paragneisses which contain supracrustal belts composed largely of siliciclastic metasediments and subordinate iron formation. The platformal nature of the metasedimentary belts and lack of obvious metavolcanic lithologies contrasts with the composition of typical Yilgarn greenstones to the east. Radiometric data from WGT rocks indicates that these rocks are significantly older than Yilgarn rocks to the east (less than 3.3 Ga) and this has led to the suggestion that the WGT represents sialic basement to Yilgarn granite-greenstone belts. The Mount Narryer region exposes the northernmost occurrence of high-grade metasediments within the WGT and consists of quartz-rich clastic metasediments at upper amphibolite to granulite grade. Most occurrences of supracrustal rocks in this region comprise isolated lenses within the gneissic basement. However, at Mount Narryer a unique sequence of metaclastics with preserved bedding provide an unusual window into the parentage of similar supracrustal bodies in this region.

  19. Archean Earth Atmosphere Fractal Haze Aggregates: Light Scattering Calculations and the Faint Young Sun Paradox

    NASA Astrophysics Data System (ADS)

    Boness, D. A.; Terrell-Martinez, B.

    2010-12-01

    As part of an ongoing undergraduate research project of light scattering calculations involving fractal carbonaceous soot aggregates relevant to current anthropogenic and natural sources in Earth's atmosphere, we have read with interest a recent paper [E.T. Wolf and O.B Toon,Science 328, 1266 (2010)] claiming that the Faint Young Sun paradox discussed four decades ago by Carl Sagan and others can be resolved without invoking heavy CO2 concentrations as a greenhouse gas warming the early Earth enough to sustain liquid water and hence allow the origin of life. Wolf and Toon report that a Titan-like Archean Earth haze, with a fractal haze aggregate nature due to nitrogen-methane photochemistry at high altitudes, should block enough UV light to protect the warming greenhouse gas NH3 while allowing enough visible light to reach the surface of the Earth. To test this hypothesis, we have employed a rigorous T-Matrix arbitrary-particle light scattering technique, to avoid the simplifications inherent in Mie-sphere scattering, on haze fractal aggregates at UV and visible wavelenths of incident light. We generate these model aggregates using diffusion-limited cluster aggregation (DLCA) algorithms, which much more closely fit actual haze fractal aggregates than do diffusion-limited aggregation (DLA) algorithms.

  20. Archean geochemistry of formaldehyde and cyanide and the oligomerization of cyanohydrin

    NASA Astrophysics Data System (ADS)

    Arrhenius, T.; Arrhenius, G.; Paplawsky, W.

    1994-02-01

    The sources and speciation of reduced carbon and nitrogen inferred for the early Archean are reviewed in terms of current observations and models, and known chemical reactions. Within this framework hydrogen cyanide and cyanide ion in significant concentration would have been eliminated by reaction with excess formaldehyde to form cyanohydrin (glycolonitrile), and with ferrous ion to formferrocyanide. Natural reactions of these molecules would under such conditions deserve special consideration in modeling of primordial organochemical processes. As a step in this direction, transformation reactions have been investigated involving glycolonitrile in the presence of water. We find that glycolonitrile, formed from formaldehyde and hydrogen cyanide or cyanide ion, spontaneously cyclodimerizes to 4-amino-2-hydroxymethyloxazole. The crystalline dimer is the major product at low temperatue (approximately 0 C); the yield diminishes with increasing temperature at the expense of polymerization and hydrolysis products. Hydrolysis of glycolamide and of oxazole yields a number of simpler organic molecules, including ammonia and glycolamide. The spontaneous polymerization of glycolonitrile and its dimer gives rise to soluble, cationic oligomers of as yet unknown structure, and, unless arrested, to a viscous liquid, insoluble in water. A loss of cyanide by reaction with formaldehyde, inferred for the early terrestrial hydrosphere and cryosphere would present a dilemma for hypotheses invoking cyanide and related compounds as concentrated reactants capable of forming biomolecular precursor species. Attempts to escape from its horns may take advantage of the efficient concentration and separation of cyanide as solid ferriferrocyanide, and most directly of reactions of glycolonitrile and its derivatives.

  1. Archean geochemistry of formaldehyde and cyanide and the oligomerization of cyanohydrin

    NASA Technical Reports Server (NTRS)

    Arrhenius, T.; Arrhenius, G.; Paplawsky, W.

    1994-01-01

    The sources and speciation of reduced carbon and nitrogen inferred for the early Archean are reviewed in terms of current observations and models, and known chemical reactions. Within this framework hydrogen cyanide and cyanide ion in significant concentration would have been eliminated by reaction with excess formaldehyde to form cyanohydrin (glycolonitrile), and with ferrous ion to formferrocyanide. Natural reactions of these molecules would under such conditions deserve special consideration in modeling of primordial organochemical processes. As a step in this direction, transformation reactions have been investigated involving glycolonitrile in the presence of water. We find that glycolonitrile, formed from formaldehyde and hydrogen cyanide or cyanide ion, spontaneously cyclodimerizes to 4-amino-2-hydroxymethyloxazole. The crystalline dimer is the major product at low temperatue (approximately 0 C); the yield diminishes with increasing temperature at the expense of polymerization and hydrolysis products. Hydrolysis of glycolamide and of oxazole yields a number of simpler organic molecules, including ammonia and glycolamide. The spontaneous polymerization of glycolonitrile and its dimer gives rise to soluble, cationic oligomers of as yet unknown structure, and, unless arrested, to a viscous liquid, insoluble in water. A loss of cyanide by reaction with formaldehyde, inferred for the early terrestrial hydrosphere and cryosphere would present a dilemma for hypotheses invoking cyanide and related compounds as concentrated reactants capable of forming biomolecular precursor species. Attempts to escape from its horns may take advantage of the efficient concentration and separation of cyanide as solid ferriferrocyanide, and most directly of reactions of glycolonitrile and its derivatives.

  2. Paleoremanence dispersal across a transpressed Archean terrain: Deflection by anisotropy or by late compression?

    NASA Astrophysics Data System (ADS)

    Werner, Tomasz; Borradaile, Graham J.

    1996-03-01

    The Quetico Belt is an Archean metasedimentary terrain sandwiched between greenstone subprovinces. A single regional schistosity is subparallel to magnetic foliation defined by anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence (AARM). Aligned micas are the primary cause of AMS. Aligned pyrrhotite is the sole cause of AARM. Each magnetic subfabric is due to minerals that grew in overlapping intervals in the strain history. Their slight obliquity may be due to crystallization during noncoaxial strain. Magnetic fabric ellipsoids suggest varying severity of flattening: very strong flattening on the northern boundary, less severe on the southern boundary, and least severe in the interior. The interior and the southern boundary of the belt stretched horizontally and the shortening direction varies gradually, from NS in the north to NNW in the south. The paleomagnetic record carried by pyrrhotite shows characteristic remanences dispersed around a great circle subparallel to the regional schistosity and magnetic foliations. Late stress effects rotated paleoremanences into this pattern; we discount deflection of the paleofield by anisotropy. The pattern of dispersal indicates uniaxial oblate flattening of the region with NNW-SSE shortening, late in the metamorphic cooling history (<300°C). This postdates schistosity, AMS and AARM fabrics but it is controlled by the same kinematic pattern.

  3. Realtime Space Weather Forecasts Via Android Phone App

    NASA Astrophysics Data System (ADS)

    Crowley, G.; Haacke, B.; Reynolds, A.

    2010-12-01

    For the past several years, ASTRA has run a first-principles global 3-D fully coupled thermosphere-ionosphere model in real-time for space weather applications. The model is the Thermosphere-Ionosphere Mesosphere Electrodynamics General Circulation Model (TIMEGCM). ASTRA also runs the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) in real-time. Using AMIE to drive the high latitude inputs to the TIMEGCM produces high fidelity simulations of the global thermosphere and ionosphere. These simulations can be viewed on the Android Phone App developed by ASTRA. The SpaceWeather app for the Android operating system is free and can be downloaded from the Google Marketplace. We present the current status of realtime thermosphere-ionosphere space-weather forcasting and discuss the way forward. We explore some of the issues in maintaining real-time simulations with assimilative data feeds in a quasi-operational setting. We also discuss some of the challenges of presenting large amounts of data on a smartphone. The ASTRA SpaceWeather app includes the broadest and most unique range of space weather data yet to be found on a single smartphone app. This is a one-stop-shop for space weather and the only app where you can get access to ASTRA’s real-time predictions of the global thermosphere and ionosphere, high latitude convection and geomagnetic activity. Because of the phone's GPS capability, users can obtain location specific vertical profiles of electron density, temperature, and time-histories of various parameters from the models. The SpaceWeather app has over 9000 downloads, 30 reviews, and a following of active users. It is clear that real-time space weather on smartphones is here to stay, and must be included in planning for any transition to operational space-weather use.

  4. Archean high δ18O Mg-diorite: crustal-derived melt hybridized with enriched mafic accumulated rocks

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Guo, Jing-Hui

    2016-04-01

    The genesis of Mg-diorite or sanukitoids has significances to understand the crustal growth and tectonic style in Archean. The chemical compositions of minerals and rocks, whole-rock Sm-Nd isotope, zircon SIMS U-Pb ages and Hf-O isotopes of Zhulagou (ZLG) Mg-diorite and their mafic enclaves (Yinshan Block, North China Craton) were studied to place constraints on their sources and genesis, and therefore provide information about dynamic processes. The ~2520 Ma ZLG diorites have intermediate SiO2 (59.4-65.5 wt.%), high Mg# (49-52), Cr (90.4-438 ppm), Ni (15.0-95.9 ppm), Sr (436-882 ppm) and Ba (237-1206 ppm) contents with fractionated rare earth elements (REE, LaN/YbN = 9.1-40.5) and depleted high field-strength element (HFSE, e.g. Nb, Ta and Ti). These geochemical signatures are similar to those Archean high-Mg diorites and sanukitoids. However, they are sodic with low K2O/Na2O (0.14-0.49) ratios, exhibiting an affinity with Archean trondhjemite-tonalite-granodiorite (TTG). Abundant coeval amphibole-bearing mafic enclaves (~2525 Ma) are enclosed within the ZLG diorites. They display low SiO2 (46.5-50.3 wt.%) contents but high concentrations of MgO (9.0-14.5 wt.%), Cr (647-1946 ppm) and Ni (197-280 ppm). They are enriched in K2O (0.64-3.43 wt.%) and large ion lithophile element (LILE), depleted in Nb, Ta and Ti. Combined with their concave REE patterns and prominent negative Eu anomaly, we suggest that they are cumulates of the melt which probably derived from subduction-related Archean metasomatized mantle source. Mineral trace element modelling results, similar ɛNd(t) (+0.6 to +2.3) and δ18O(Zrc) values (~8.6-9.0 ‰) of the diorites and mafic enclaves, strongly reflect that they had experienced intense interaction and hybridization. Evolved whole-rock Nd isotopes (TDM = 2.80-2.70 Ga), variable zircon ɛHf (t) (-1.6 to +6.0) and high δ18O (~9.0 ‰) values of the diorites indicate that they most likely originated from melting of an older continental crust (≥ 2

  5. Intelligent Weather Agent

    NASA Technical Reports Server (NTRS)

    Spirkovska, Liljana (Inventor)

    2006-01-01

    Method and system for automatically displaying, visually and/or audibly and/or by an audible alarm signal, relevant weather data for an identified aircraft pilot, when each of a selected subset of measured or estimated aviation situation parameters, corresponding to a given aviation situation, has a value lying in a selected range. Each range for a particular pilot may be a default range, may be entered by the pilot and/or may be automatically determined from experience and may be subsequently edited by the pilot to change a range and to add or delete parameters describing a situation for which a display should be provided. The pilot can also verbally activate an audible display or visual display of selected information by verbal entry of a first command or a second command, respectively, that specifies the information required.

  6. Global weather research

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Modeling, prediction, and analysis of global meteorological phenomena influencing the large scale behavior of the atmosphere are summarized. Prediction of global weather phenomena based on satellite data is discussed and models of global phenomena developed. The atmospheric general circulation model (AGCE) is reviewed, axisymmetric flow calculated, and axisymmetric states in cylindrical, spherical, three dimensional, and spin up numerical models for AGCE described. The role of latent heat release in baroclinic waves, latent heat and cyclonic systems, and a theoretical study of baroclinic flow related to the AGCE and the flow regime were studied with a simplified general circulation model. AGCE and the geophysical fluid flow cell (GFFC) instrumentation are discussed. Investigation of solar and planetary convection for GFFC is described. The utilization of satellite cloud observations to diagnose the energy state and transformations in extratropical cyclones is reviewed.

  7. Geophysical and Chemical Weathering Signatures Across the Deep Weathered-Unweathered Granite Boundary of the Calhoun Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Richter, D., Jr.; Bacon, A. R.; Brantley, S. L.; Holbrook, W. S.

    2015-12-01

    To understand the relationship between geophysical measurements and chemical weathering at Earth's surface, we combine comprehensive chemical and physical analyses of a 70-m granite weathering profile in the Southern Piedmont in the southeastern United States. The research site is in the uplands of the Calhoun Critical Zone Observatory and is similar to many geomorphically stable, ancient, and highly-weathered Ultisol soils of the region. Surface and downhole geophysical analyses suggest significant physical changes to depths of about 40 m, where geophysical properties are consistent with competent and unweathered granite. At this depth, surface refraction velocities increase to >4.5 km/s; variations in downhole sonic velocities decrease by more than two-fold; and deviations in the downhole caliper log sharply decrease as well. Forty meters depth is also the depth of initiation of plagioclase feldspar weathering, as inferred from bulk geochemical measurement of the full 70-m deep core. Specifically, element-depth profiles, cast as mass transfer coefficient profiles using Ti and Zr as immobile elements, document inferred loss of plagioclase in the depth interval between 15 and 40-m depth. Plagioclase feldspar is the most abundant of the highly reactive minerals in the granite. Such a wide reaction front is characteristic of weathering granites. Some loss of K is observed at these depths but most K loss, as well as Mg loss, occurs at shallower depths. Nearby geophysical profiles and 3D stress models have been interpreted as showing that seismic velocities decrease at 40 m depth due to opening of fractures as rock is exhumed toward the surface. Given our interpretations of both the geochemical and geophysical data, we infer that the onset of chemical weathering of feldspar coincides with the opening of these fractures. The data highlight the ability of geochemistry and geophysics to complement each other and enrich our understanding of Earth's Critical Zone.

  8. Terminal weather information management

    NASA Technical Reports Server (NTRS)

    Lee, Alfred T.

    1990-01-01

    Since the mid-1960's, microburst/windshear events have caused at least 30 aircraft accidents and incidents and have killed more than 600 people in the United States alone. This study evaluated alternative means of alerting an airline crew to the presence of microburst/windshear events in the terminal area. Of particular interest was the relative effectiveness of conventional and data link ground-to-air transmissions of ground-based radar and low-level windshear sensing information on microburst/windshear avoidance. The Advanced Concepts Flight Simulator located at Ames Research Center was employed in a line oriented simulation of a scheduled round-trip airline flight from Salt Lake City to Denver Stapleton Airport. Actual weather en route and in the terminal area was simulated using recorded data. The microburst/windshear incident of July 11, 1988 was re-created for the Denver area operations. Six experienced airline crews currently flying scheduled routes were employed as test subjects for each of three groups: (1) A baseline group which received alerts via conventional air traffic control (ATC) tower transmissions; (2) An experimental group which received alerts/events displayed visually and aurally in the cockpit six miles (approx. 2 min.) from the microburst event; and (3) An additional experimental group received displayed alerts/events 23 linear miles (approx. 7 min.) from the microburst event. Analyses of crew communications and decision times showed a marked improvement in both situation awareness and decision-making with visually displayed ground-based radar information. Substantial reductions in the variability of decision times among crews in the visual display groups were also found. These findings suggest that crew performance will be enhanced and individual differences among crews due to differences in training and prior experience are significantly reduced by providing real-time, graphic display of terminal weather hazards.

  9. Heat production in an Archean crustal profile and implications for heat flow and mobilization of heat-producing elements

    NASA Technical Reports Server (NTRS)

    Ashwal, L. D.; Morgan, P.; Kelley, S. A.; Percival, J. A.

    1987-01-01

    Concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100-km transect of the Superior Province of the Canadian Shield have been obtained. The relatively large variation in heat production found among the silicic plutonic rocks is shown to correlate with modal abundances of accessory minerals, and these variations are interpreted as premetamorphic. The present data suggest fundamental differences in crustal radioactivity distributions between granitic and more mafic terrains, and indicate that a previously determined apparently linear heat flow-heat production relationship for the Kapuskasing area does not relate to the distribution of heat production with depth.

  10. Pb, Sr, and Nd isotopic compositions of a suite of Late Archean, igneous rocks, eastern Beartooth Mountains: implications for crust-mantle evolution

    USGS Publications Warehouse

    Wooden, J.L.; Mueller, P.A.

    1988-01-01

    A series of compositionally diverse, Late Archean rocks (2.74-2.79 Ga old) from the eastern Beartooth Mountains, Montana and Wyoming, U.S.A., have the same initial Pb, Sr, and Nd isotopic ratios. Lead and Sr initial ratios are higher and Nd initial ratios lower than would be expected for rocks derived from model mantle sources and strongly indicate the involvement of an older crustal reservoir in the genesis of these rocks. Crustal contamination during emplacement can be ruled out for a variety of reasons. Instead a model involving subduction of continental detritus and contamination of the overlying mantle as is often proposed for modern subduction environments is preferred. This contaminated mantle would have all the isotopic characteristics of mantle enriched by internal mantle metasomatism but would require no long-term growth or changes in parent to daughter element ratios. This contaminated mantle would make a good source for some of the Cenozoic mafic volcanics of the Columbia River, Snake River Plain, and Yellowstone volcanic fields that are proposed to come from ancient, enriched lithospheric mantle. The isotopic characteristics of the 2.70 Ga old Stillwater Complex are a perfect match for the proposed contaminated mantle which provides an alternative to crustal contamination during emplacement. The Pb isotopic characteristics of the Late Archean rocks of the eastern Beartooth Mountains are similar to those of other Late Archean rocks of the Wyoming Province and suggest that Early Archean, upper crustal rocks were common in this terrane. The isotopic signatures of Late Archean rocks in the Wyoming Province are distinctive from those of other Archean cratons in North America which are dominated by a MORB-like, Archean mantle source (Superior Province) and/or a long-term depleted crustal source (Greenland). ?? 1988.

  11. Using Forecasting to Teach Weather Science

    NASA Astrophysics Data System (ADS)

    Tsubota, Y.; Takahashi, T.

    2009-09-01

    Weather affects our lives and hence, is a popular topic in daily conversations and in the media. Therefore, it is not only important to teach weather, but is also a good idea to use 'weather' as a topic in science teaching. Science education has two main objectives: to acquire scientific concepts and methods. Weather forecasting is an adequate theme to teach scientific methods because it is dependent on observation. However, it is not easy to forecast weather using only temporal observation. We need to know the tendency of 'weather change' via consecutive and/or continuous weather observation. Students will acquire scientific-observation skills through weather observation. Data-processing skills would be enhanced through a weather-forecasting contest. A contest should be announced within 5 days of school events, such as a school excursion and field day. Students submit their own weather forecast by gathering weather information through the internet, news paper and so on. A weather-forecasting contest compels the student to observe the weather more often. We currently have some different weather forecasts. For example, American weather-related companies such as ACCU weather and Weather Channel provide weather forecast for the many locations all over the world. Comparing these weather forecasting with actual weather, participants such as students could evaluate the differences between forecasted and actual temperatures. Participants will judge the best weather forecast based on the magnitude of the difference. Also, participants evaluate the 'hitting ratio' of each weather forecast. Students can learn elementary statistics by comparing various weather forecasts. We have developed our weather web-site that provides our own weather forecasting and observation. Students acquire science skills using our weather web-site. We will report our lessen plans and explain our weather web-site.

  12. Weather Fundamentals: Hurricanes & Tornadoes. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series, for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes) features information on the deadliest and most destructive storms on Earth. Through satellite…

  13. Now, Here's the Weather Forecast...

    ERIC Educational Resources Information Center

    Richardson, Mathew

    2013-01-01

    The Met Office has a long history of weather forecasting, creating tailored weather forecasts for customers across the world. Based in Exeter, the Met Office is also home to the Met Office Hadley Centre, a world-leading centre for the study of climate change and its potential impacts. Climate information from the Met Office Hadley Centre is used…

  14. FREEZING WEATHER IN PENINSULAR FLORIDA,

    DTIC Science & Technology

    The synoptic situations which bring serious freezing weather to the Florida Peninsula are discussed generally by presenting various weather charts...scheme is presented which might permanently eliminate serious freezing in the Florida Peninsula. Before any solution can be reached, it t necessary to be

  15. Weather to Make a Decision

    ERIC Educational Resources Information Center

    Hoyle, Julie E.; Mjelde, James W.; Litzenberg, Kerry K.

    2006-01-01

    DECIDE is a teacher-friendly, integrated approach designed to stimulate learning by allowing students to make decisions about situations they face in their lives while using scientific weather principles. This learning unit integrates weather science, decision theory, mathematics, statistics, geography, and reading in a context of decision…

  16. Weather Fundamentals: Rain & Snow. [Videotape].

    ERIC Educational Resources Information Center

    1998

    The videos in this educational series, for grades 4-7, help students understand the science behind weather phenomena through dramatic live-action footage, vivid animated graphics, detailed weather maps, and hands-on experiments. This episode (23 minutes) gives concise explanations of the various types of precipitation and describes how the water…

  17. The pioneers of weather forecasting

    NASA Astrophysics Data System (ADS)

    Ballard, Susan

    2016-01-01

    In The Weather Experiment author Peter Moore takes us on a compelling journey through the early history of weather forecasting, bringing to life the personalities, lives and achievements of the men who put in place the building blocks required for forecasts to be possible.

  18. Aviation Weather Information Requirements Study

    NASA Technical Reports Server (NTRS)

    Keel, Byron M.; Stancil, Charles E.; Eckert, Clifford A.; Brown, Susan M.; Gimmestad, Gary G.; Richards, Mark A.; Schaffner, Philip R. (Technical Monitor)

    2000-01-01

    The Aviation Safety Program (AvSP) has as its goal an improvement in aviation safety by a factor of 5 over the next 10 years and a factor of 10 over the next 20 years. Since weather has a big impact on aviation safety and is associated with 30% of all aviation accidents, Weather Accident Prevention (WxAP) is a major element under this program. The Aviation Weather Information (AWIN) Distribution and Presentation project is one of three projects under this element. This report contains the findings of a study conducted by the Georgia Tech Research Institute (GTRI) under the Enhanced Weather Products effort, which is a task under AWIN. The study examines current aviation weather products and there application. The study goes on to identify deficiencies in the current system and to define requirements for aviation weather products that would lead to an increase in safety. The study also provides an overview the current set of sensors applied to the collection of aviation weather information. New, modified, or fused sensor systems are identified which could be applied in improving the current set of weather products and in addressing the deficiencies defined in the report. In addition, the study addresses and recommends possible sensors for inclusion in an electronic pilot reporting (EPIREP) system.

  19. Regional-seasonal weather forecasting

    SciTech Connect

    Abarbanel, H.; Foley, H.; MacDonald, G.; Rothaus, O.; Rudermann, M.; Vesecky, J.

    1980-08-01

    In the interest of allocating heating fuels optimally, the state-of-the-art for seasonal weather forecasting is reviewed. A model using an enormous data base of past weather data is contemplated to improve seasonal forecasts, but present skills do not make that practicable. 90 references. (PSB)

  20. Widespread Surface Weathering on Early Mars

    NASA Astrophysics Data System (ADS)

    Loizeau, Damien; Carter, John; Mangold, Nicolas; Poulet, François; Rossi, Angelo; Allemand, Pascal; Quantin, Cathy; Bibring, Jean-Pierre

    2014-05-01

    The recent discovery of widespread hydrous clays on Mars indicates that diverse and widespread aqueous environments existed on Mars, from the surface to kilometric depths [1,2]. The study of the past habitability and past climates of the planet requires assessing the importance of sustained surface water vs. subsurface water in its aqueous history. Using remote sensing data, we propose that surface weathering existed on Mars, suggesting that Mars experienced durable episodes of sustained liquid water on its surface. Weathering profiles are identified as vertical sequences of Al-rich clays and Fe/Mg-rich clays in the top tens of meters of the surface, similar to cases of pedogenesis on Earth (e.g. [3,4]). Such localized clay sequences have been reported by other works in 3 regions of Mars [5-8] and a similar origin was also proposed. Their frequency is however likely underestimated due to limitations of orbital investigations and re-surfacing processes. A large survey of the CRISM dataset leaded to a down-selection of ~100 deposits with clear vertical sequences, widely distributed over the southern highlands and grouped in regional clusters [9]. These putative weathering sequences are found either on inter-crater plateaus, on the floor of craters and large basins, or on crater ejectas. We investigated the thickness of the altered sequences, the age of the altered units and the different geological contexts to further understand the weathering process(es). Using few HiRISE DEMs where possible, and CTX DEMs, we find that the thickness of the exposed Al clays is on average of the order of several meters to few tens of meters. The clay sequences reported here are consistent with terrestrial weathering sequences which form under wet climates over geological timescales (>105-107 years). The combined age assessment of the altered unit and the unaltered capping (where present) provides constraints on the age of the weathering itself. All investigated cases point to an

  1. Widespread Surface Weathering on Early Mars

    NASA Astrophysics Data System (ADS)

    Loizeau, D.; Carter, J.; Mangold, N.; Poulet, F.; Rossi, A.; Allemand, P.; Quantin, C.; Bibring, J.

    2013-12-01

    The recent discovery of widespread hydrous clays on Mars indicates that diverse and widespread aqueous environments existed on Mars, from the surface to kilometric depths [1,2]. The study of the past habitability of the planet requires assessing the importance of sustained surface water vs. subsurface water in its aqueous history. Using remote sensing data, we propose that surface weathering existed on Mars, suggesting that Mars experienced durable episodes of sustained liquid water on its surface. Weathering profiles are identified as vertical sequences of Al-rich clays and Fe/Mg-rich clays in the top tens of meters of the surface, similar to cases of pedogenesis on Earth (e.g. [3,4]). Such localized clay sequences have been reported by other works in 3 regions of Mars [5-8] and a similar origin was also proposed. Their frequency is however likely underestimated due to limitations of orbital investigations and re-surfacing processes. A large survey of the CRISM dataset leaded to a down-selection of 104 deposits with clear vertical sequences, widely distributed over the southern highlands and grouped in regional clusters [9]. These putative weathering sequences are found either on inter-crater plateaus, on the floor of craters and large basins, or on crater ejectas. We investigated the thickness of the altered sequences, the age of the altered units and the different geological contexts to further understand the weathering process(es). Using few HiRISE DEMs where possible, and CTX DEMs, we find that the thickness of the exposed Al clays is on average of the order of several meters to few tens of meters. The clay sequences reported here are consistent with terrestrial weathering sequences which form under wet climates over geological timescales (> 105-107 years). The combined age assessment of the altered unit and the unaltered capping (where present) provides constraints on the age of the weathering itself. All investigated cases point to an active weathering

  2. Kinetically limited weathering at low denudation rates in semiarid climatic conditions

    NASA Astrophysics Data System (ADS)

    Schoonejans, Jérôme; Vanacker, Veerle; Opfergelt, Sophie; Ameijeiras-Mariño, Yolanda; Christl, Marcus

    2016-02-01

    Biogeochemical cycling within the Critical Zone depends on the interactions between minerals and fluids controlling chemical weathering and physical erosion rates. In this study, we explore the role of water availability in controlling soil chemical weathering in semiarid climatic conditions. Weathering rates and intensities were evaluated for nine soil profiles located on convex ridge crests of three mountain ranges in the Spanish Betic Cordillera. We combine a geochemical mass balance with 10Be cosmogenic nuclides to constrain chemical weathering intensities and long-term denudation rates. As such, this study presents new data on chemical weathering and 10Be-derived denudation for understudied semiarid climate systems. In the Betic Cordillera, chemical weathering intensities are relatively low (~5 to 30% of the total denudation of the soil) and negatively correlated with the magnitude of the water deficit in soils. Chemical mass losses are inversely related to denudation rates (14-109 mm/kyr) and positively to soil thickness (14-58 cm); these results are consistent with kinetic limitation of chemical weathering rates. A worldwide compilation of chemical weathering data suggests that soil water balance may regulate the coupling between chemical weathering and physical erosion by modulating soil solute fluxes. Therefore, future landscape evolution models that seek to link chemical weathering and physical erosion should include soil water flux as an essential driver of weathering.

  3. Weathering instability and landscape evolution

    NASA Astrophysics Data System (ADS)

    Phillips, Jonathan D.

    2005-04-01

    The argument in this paper is that the fundamental control on landscape evolution in erosional landscapes is weathering. The possibility of and evidence for instability in weathering at four scales is examined. The four scales are concerned with weathering processes, allocation of weathered products, the interrelations of weathering and denudation, and the topographic and isostatic responses to weathering-limited denudation (the regolith, hillslope, landscape unit, and landscape scales, respectively). The stability conditions for each model, and the circumstances under which the models themselves are relevant, are used to identify scale-related domains of stability and instability. At the regolith scale, the interactions among weathering rates, resistance, and moisture are unstable, bu