A high-temperature hydrothermal deposit on the seabed at a gulf of California spreading center     

P.F. Lonsdale  J.L. Bischoff  V.M. Burns  M. Kastner  R.E. Sweeney 《Earth and Planetary Science Letters》1980,49(1):8-20

A submersible dive on a turbidite-covered spreading axis in Guaymas Basin photographed and sampled extensive terraces and ledges of talc. The rock contains siliceous microfossils, smectite, and euhedral pyrrhotite as well as rather pure iron-rich talc. Sulfur and oxygen isotopes indicate precipitation around a hydrothermal vent, at about 280°C.  相似文献   

Rival private governance networks: Competing to define the rules of sustainability performance     

Timothy M. Smith  Miriam Fischlein 《Global Environmental Change》2010,20(3):511-522

Private governance of environmental and social performance of organizations, processes and products is gaining prominence in market and policy arenas, and thus, increasingly influencing sustainability outcomes. This study presents a concept of rival private governance where multiple initiatives compete for rule-setting authority. Specifically, we argue that heterogeneous actors organize in network form to establish legitimacy of new sustainability governance fields. In an effort to preempt threats from these new fields of governance, nonparticipating actors create rival private governance networks and compete based on each network's ability to access unique relational assets from participants. Based on the cases of carbon off-set standards, green building rating systems and sustainable forestry certifications, we suggest that this competitive market vetting results in pressures toward the convergence of governance rules over time, but not a single winning set of rules. Our findings illustrate that multiple and competing networks can provide innovative, legitimate and dynamically evolving governance of sustainability, while presenting new challenges for public and private sector actors.  相似文献   

Three monthly coral Sr/Ca records from the Chagos Archipelago covering the period of 1950–1995 A.D.: reproducibility and implications for quantitative reconstructions of sea surface temperature variations     

Miriam Pfeiffer  Wolf-Christian Dullo  Jens Zinke  Dieter Garbe-Schönberg 《International Journal of Earth Sciences》2009,98(1):53-66

In order to assess the fidelity of coral Sr/Ca for quantitative reconstructions of sea surface temperature variations, we have generated three monthly Sr/Ca time series from Porites corals from the lagoon of Peros Banhos (71°E, 5°S, Chagos Archipelago). We find that all three coral Sr/Ca time series are well correlated with instrumental records of sea surface temperature (SST) and air temperature. However, the intrinsic variance of the single-core Sr/Ca time series differs from core to core, limiting their use for quantitative estimates of past temperature variations. Averaging the single-core data improves the correlation with instrumental temperature (r > 0.7) and allows accurate estimates of interannual temperature variations (~0.35°C or better). All Sr/Ca time series indicate a shift towards warmer temperatures in the mid-1970s, which coincides with the most recent regime shift in the Pacific Ocean. However, the magnitude of the warming inferred from coral Sr/Ca differs from core to core and ranges from 0.26 to 0.75°C. The composite Sr/Ca record from Peros Banhos clearly captures the major climatic signals in the Indo-Pacific Ocean, i.e. the El Niño–southern oscillation and the Pacific decadal oscillation. Moreover, composite Sr/Ca is highly correlated with tropical mean temperatures (r = 0.7), suggesting that coral Sr/Ca time series from the tropical Indian Ocean will contribute to multi-proxy reconstructions of tropical mean temperatures.  相似文献   

Landscape and climatic changes during the end of the Late Prehistory in the Amblés Valley (Ávila, central Spain), from 1200 to 400 cal BC     

Jos A. Lpez-Sez  Antonio Blanco-Gonzlez  Lourdes Lpez-Merino  M. Blanca Ruiz-Zapata  Miriam Dorado-Valio  Sebastin Prez-Díaz  Ana Valdeolmillos  Francesc Burjachs 《Quaternary International》2009,200(1-2):90

Correlations between ecological and cultural changes occurred during a short period between the end of Subboreal and the beginning of Subatlantic in the Amblés Valley (Ávila, central Spain) are analyzed, taking into account palaeopalynological and archaeological data. Plant dynamics from pollen analyses, both from archaeological sites and peat bogs, have been interpreted in relation to human settlements and the transformation of economic practices. These provided a comprehensive hypothesis on human/climate interactions at the beginning of the 1st millennium cal BC. There was an ecological crisis in the region that lasted for a century (ca. 850–760 cal BC). This was especially sharp due to both the geographical constraints of the area and its previous agrarian history. This event implied a sudden and abrupt climatic change from xeric and warm conditions (Subboreal) to more humid and cooler ones (Subatlantic). Environmental stress derived from climatic crisis could be an important factor in the explanation of the historical process, whose main consequences were both the origin of the Iron Age peasant villages and the end of the ‘dehesa’ type landscape.  相似文献   

HHSMT observations of the Venusian mesospheric temperature, winds, and CO abundance around the MESSENGER flyby     

Miriam Rengel  Paul Hartogh  Christopher Jarchow 《Planetary and Space Science》2008,56(13):1688-1695

We present submillimeter observations of ¹²CO J=3-2 and 2-1, and ¹³CO J=2-1 lines of the Venusian mesosphere and lower thermosphere with the Heinrich Hertz Submillimeter Telescope (HHSMT) taken around the second MESSENGER flyby of Venus on 5 June 2007. The observations cover a range of Venus solar elongations with different fractional disk illuminations. Preliminary results like temperature and CO abundance profiles are presented.These data are part of a coordinated observational campaign in support of the ESA Venus Express mission. Furthermore, this study attempts to contribute to cross-calibrate space- and ground-based observations, to constrain radiative transfer and retrieval algorithms for planetary atmospheres, and to a more thorough understanding of the global patters of circulation of the Venusian atmosphere.  相似文献   

Quantifying capability of a local seismic network in terms of locations and focal mechanism solutions of weak earthquakes     

Lucia Fojtíková  Miriam Kristeková  Jiří Málek  Efthimios Sokos  Kristián Csicsay  Jiří Zahradník 《Journal of Seismology》2016,20(1):93-106

  相似文献   

Closing and continentalization of the South Pyrenean foreland basin (NE Spain): magnetochronological constraints     

Elisenda Costa  Miguel Garcés  Miguel López‐Blanco  Elisabet Beamud  Miriam Gómez‐Paccard  Juan Cruz Larrasoaña 《Basin Research》2010,22(6):904-917

This paper presents new magnetostratigraphic results from a 1100‐m‐thick composite section across the marine to continental sediments of the central part of the SE margin of the Ebro basin (NE Spain). Integration with existing marine and continental biochronological data allows a robust correlation with the geomagnetic polarity time scale. The resulting absolute chronology ranges from 36.3 to 31.1 Ma (Priabonian to Rupelian), and yields an interpolated age of ～36.0 Ma (within chron C16n.2n) for the youngest marine sediments of the eastern Ebro basin. This age is in concordance with a reinterpretation of earlier magnetostratigraphic data from the western South Pyrenean foreland basin, and indicates that continentalization of the basin occurred as a rapid and isochronous event. The basin continentalization, determined by the seaway closure that resulted from the uplift of the western Pyrenees, was probably coincident with a mid‐amplitude eustatic sea level low with a maximum at 36.2 Ma. The base level drop that followed the basin closure and desiccation does not appear associated to a significant sedimentary hiatus along the margins, suggesting a late Eocene shallow marine basin that rapidly refilled and raised its base level after the seaway closing. Rapid basin filling following continentalization predates the phase of rapid exhumation of the Central Pyrenean Axial Zone from 35.0 to 32.0 Ma, determined from the thermochronology data. It is possible then that sediment aggradation at the front of the fold‐and‐thrust belt could have contributed to a decrease in the taper angle, triggering growth of the inner orogenic wedge through break‐back thrusting and underplating. Contrasting sedimentation trends between the western and eastern sectors of the South Pyrenean foreland indicate that basin closing preferentially affected those areas subjected to sediment bypass towards the ocean domain. As a result, sediment ponding after basin closure is responsible for a two‐fold increase of sedimentation rates in the western sector, while changes of sedimentation rates are undetected in the more restricted scenario of the eastern Ebro basin.  相似文献   

The symbiotic stellar lines at 6830 Å, 7088 Å; An origin in optically thick fluorescence     

S. O. Kastner 《Astrophysics and Space Science》1991,185(2):265-275

The question of the origin of the symbiotic stellar lines at 6830 Å and 7088 Å, recently proposed to arise from Raman scattering of ultraviolet Ovi lines by hydrogen, is examined quantitatively by comparing line intensities expected from this process with the intensity of an Feii line photoexcited by one of the same Ovi lines. It appears that Raman scattering does not yield sufficient intensity to account for the symbiotic lines. An alternative mechanism for producing the lines exists, however, in off-line-center photoexcitation of optically thick hydrogen by the Ovi lines. This gives intensities which are higher than Raman intensities, and which are more consistent with the Feii fluorescent line intensity. Observed further redward shifts are also explained by the mechanism. It is therefore suggested that the proposed hypothesis of Ovi–Hi interaction may be valid, but that the process involved is probably not second-order Raman scattering but first-order fluorescent scattering.  相似文献   

Transboundary flow modeling: the Zohor depression of Austria and the Slovak Republic     

Fendek M  Fendekova M 《Ground water》2005,43(5):717-721

Estimation of available ground water is a basic aspect of ground water management. Mathematical modeling is one of the methods that can be effectively used to obtain such estimates. A numerical model was used to calculate available ground water in the Zohor depression-an aquifer transcending national boundaries between the Slovak Republic and Austria. The aquifer, formed by Quaternary sediments overlying Neogene sequences, is composed of various clays interbedded with layers of sand, gravel, sandstones, and conglomerates. The AQUA computer model package was used to simulate flow in the aquifer. For model compilation, the following data were used: (1) effective precipitation; (2) surface water levels in surface water gauging profiles; and (3) withdrawal amounts. Hydraulic parameters of the aquifer were estimated based on information from 86 wells located in the area. The model was verified using data on ground water levels from a monitoring network. The simulation of the aquifer system permitted the estimation of the available ground water in the study area, showing that an additional 587 L/s can be abstracted. Ground water inflows to the Morava River, which flows through the region, range from 745 to 3100 L/s.  相似文献   

Albian high-resolution biostratigraphy and isotope stratigraphy: The Coppa della Nuvola pelagic succession of the Gargano Promontory (Southern Italy)   总被引：1，自引：0，他引：1  

Valeria Luciani  Miriam Cobianchi  Hugh C. Jenkyns 《Eclogae Geologicae Helvetiae》2004,97(1):77-92

  相似文献