Influence of the ventilation of a karst show cave on the surrounding vadose CO2 reservoir (Nerja,South Spain)     

J. Benavente  I. Vadillo  C. Liñán  Y. del Rosal  F. Carrasco 《Environmental Earth Sciences》2015,74(12):7731-7740

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Modeling of Landslides in Valles Marineris,Mars, and Implications for Initiation Mechanism     

Meaza Tsige  Javier Ruiz  Ian A. del Río  Alberto Jiménez-Díaz 《Earth, Moon, and Planets》2016,118(1):15-26

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Occurrence and turnover of DMSP and DMS in deep waters of the Ross Sea,Antarctica     

Alison N. Rellinger  Ronald P. Kiene  Daniela A. del Valle  David J. Kieber  Doris Slezak  Hyakubun Harada  John Bisgrove  Jordan Brinkley 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(5):686-702

High concentrations of the phytoplankton metabolite dimethylsulfoniopropionate (DMSP) and its degradation product dimethylsulfide (DMS) are associated with blooms of Phaeocystis antarctica in the Ross Sea, Antarctica. Episodic and rapid vertical export of Phaeocystis biomass to deep water has been reported for the Ross Sea, therefore we examined the distribution and microbial consumption rates of DMSP and DMS throughout the sub-euphotic water column. Total DMSP (dissolved+particulate; DMSPt) was present at 0.5–22 nM at depths between 70 and 690 m during both the early bloom (November) and the late bloom (January). Sub-euphotic peaks of DMSP were sometimes associated with mid-water temperature maxima, and elevated DMSP below 70 m was found mainly in water masses characterized as Modified Circumpolar Deep Water or Antarctic Shelf Water. Overall, 50–94% of the integrated water-column DMSPt was found below the euphotic zone. At one station during the early bloom, local maxima of DMSPt (14 nM) and DMS (20 nM) were observed between 113 and 240 m and these maxima corresponded with high chlorophyll a concentrations, P. antarctica cell numbers, and Fv/Fm (the quantum yield of photosystem II). During the late bloom, a sub-euphotic maximum of DMSPt (15.8 nM) at 250 m cooccurred with peaks of chlorophyll a concentration, DMSP lyase activity, bacterial production and dissolved DMSP consumption rates. DMSP turnover contributed ～12% of the bacterial carbon demand between 200 and 400 m. DMS concentrations peaked at 286 m but the maximum concentration (0.42 nM) was far lower than observed during the early bloom, probably because of relatively rapid biological consumption of DMS (1–3 turnovers per day) which, in turn, contributed to elevated dissolved dimethylsulfoxide (DMSO) concentrations. Relatively stable DMSPt distributions at some sites suggest that rapid sinking of Phaeocystis biomass is probably not the major mechanism responsible for mesopelagic DMSP accumulations. Rather, subduction of near-surface water masses, lateral advective transport or trapping of slowly sinking P. antarctica biomass in intermediate water masses are more likely mechanisms. We found that a culture of P. antarctica maintained cellular integrity during 34 days of darkness, therefore the presence of intact cells (and DMSP) at depth can be explained even under a slow sinking/advection scenario. Whatever the mechanism, the large pools of DMSP and DMS below the euphotic zone suggest that export exerts a control on potential DMS emission from the surface waters of the Ross Sea.  相似文献   

An integrated magnetic,geochemical and archeointensity investigation of casting debris from ancient metallurgical sites of Michoacán,Western Mesoamerica     

Juan Morales  María del Sol Hernández-Bernal  Avto Goguitchaichvili  José Luis Punzo-Díaz 《Studia Geophysica et Geodaetica》2017,61(2):290-309

The ability of baked clay-elaborated objects to record the temporal variations of both direction and intensity of the geomagnetic field at the time of their elaboration or last use has been widely used during the last decades to fill the gaps left by available time-discrete volcanic-rock logs for a better knowledge of the evolution of the geomagnetic field. Further refinement of the secular variation curves has motivated the search for alternative non-conventional materials as attractive targets for archeomagnetic studies. Both clay and copper have been used since pre-Hispanic times for the elaboration of a wide variety of ornamental and utilitarian objects in Mesoamerica. Previous studies carried out in Europe and Israel have shown the usefulness of copper slags as one of these non-conventional materials. We present the results of an integrated study carried out on ten copper slags from seven ancient metallurgical sites of Michoacán. The analysis included a series of rock magnetism experiments, scanning electron microscope analysis, archeointensity determinations following the Thellier-Coe method and their corresponding dating. Based on the results obtained the slag-set analyzed can be divided in two main groups: low Fe concentrations (associated with high Cu concentrations) for slags comprising the first group, and high Fe concentrations (associated with low Cu concentrations) for slags from second group. Slags from the first group are characterized by almost reversible thermomagnetic curves, while those corresponding to the second group show a quite irreversible behavior. A crystalline (vitreous) structure within the massive surface of the slags is observed for those coming from the second (first) group. These striking features could reflect significant differences in the metallurgical process followed at these sites, which according to archeological and historical evidences correspond to Colonial and pre-Hispanic usage metallurgical sites; first and second group, respectively. The good experimental behavior exhibited by these materials demonstrates the suitability of copper slag to obtaining absolute archeointensity data which can be used to improve the existing Mesoamerican archeomagnetic record. This in turn, can be used both for geomagnetic field modelling purposes and archeomagnetic dating.  相似文献   

Origin and evolution of the atmospheres of early Venus,Earth and Mars     

Helmut Lammer  Aubrey L. Zerkle  Stefanie Gebauer  Nicola Tosi  Lena Noack  Manuel Scherf  Elke Pilat-Lohinger  Manuel Güdel  John Lee Grenfell  Mareike Godolt  Athanasia Nikolaou 《Astronomy and Astrophysics Review》2018,26(1):2

We review the origin and evolution of the atmospheres of Earth, Venus and Mars from the time when their accreting bodies were released from the protoplanetary disk a few million years after the origin of the Sun. If the accreting planetary cores reached masses \(\ge 0.5 M_\mathrm{Earth}\) before the gas in the disk disappeared, primordial atmospheres consisting mainly of H\(_2\) form around the young planetary body, contrary to late-stage planet formation, where terrestrial planets accrete material after the nebula phase of the disk. The differences between these two scenarios are explored by investigating non-radiogenic atmospheric noble gas isotope anomalies observed on the three terrestrial planets. The role of the young Sun’s more efficient EUV radiation and of the plasma environment into the escape of early atmospheres is also addressed. We discuss the catastrophic outgassing of volatiles and the formation and cooling of steam atmospheres after the solidification of magma oceans and we describe the geochemical evidence for additional delivery of volatile-rich chondritic materials during the main stages of terrestrial planet formation. The evolution scenario of early Earth is then compared with the atmospheric evolution of planets where no active plate tectonics emerged like on Venus and Mars. We look at the diversity between early Earth, Venus and Mars, which is found to be related to their differing geochemical, geodynamical and geophysical conditions, including plate tectonics, crust and mantle oxidation processes and their involvement in degassing processes of secondary \(\hbox {N}_2\) atmospheres. The buildup of atmospheric \(\hbox {N}_2\), \(\hbox {O}_2\), and the role of greenhouse gases such as \(\hbox {CO}_2\) and \(\hbox {CH}_4\) to counter the Faint Young Sun Paradox (FYSP), when the earliest life forms on Earth originated until the Great Oxidation Event \(\approx \) 2.3 Gyr ago, are addressed. This review concludes with a discussion on the implications of understanding Earth’s geophysical and related atmospheric evolution in relation to the discovery of potential habitable terrestrial exoplanets.  相似文献   

Interpretation of observations by inversion     

J.C. del Toro Iniesta 《Astronomische Nachrichten》2003,324(4):383-387

The most recent developments in inversion techniques of the radiative transfer equation are critically reviewed and some of their findings are summarized to illustrating their achievements. Two significantly different approaches are currently being used that deserve consideration, each characterized by whether or not the model solar atmospheres are changed iteratively by the algorithm. The comparison between the two may help in finding future inversion techniques that can solve many challenging problems of solar physics that still need to be properly settled. These problems themselves suggest strategies that look more suitable than others.  相似文献   

Molecular characterisation of vitrinite in relation to natural hydrogen enrichment and depositional environment     

M. J. Iglesias  A. Jimnez  J. C. del Río  I. Surez-Ruiz 《Organic Geochemistry》2000,31(12)

The Py-GC/MS results of the study carried out on two groups of vitrinites (perhydrous and non-perhydrous) of different age and properties and on a trimaceralic coal associated with one of the perhydrous group are discussed. Such a study provides information about the effect of natural hydrogen enrichment on vitrinite structure at the molecular level. Moreover, the influence of the different conditions in the sedimentary environment on the chemical structure of the vitrinite is also discussed. This influence is inferred through differences in the distribution and relative amount of phenolic compounds found in the pyrolysates from two samples of two different coal-beds in the same basin but formed under different paleoenvironmental conditions. For vitrinites with a high H/C atomic ratio, despite having a strong perhydrous character, their pyrolysates exhibit the highly phenolic signature typical of lignin-derived material with only minor aliphatic compounds. Thus, the major chemical structural elements in these vitrinites are simple phenols with a high contribution of para alkyl-substituted derivatives. However, there is no parallel relationship between the evolution of the oxygenated functionalities and the reflectance values. From the results obtained a coalification pathway where hydrogenation processes predominate over thermal ones is proposed. The presence of resin-like substances and/or oils (which are two of the causes of natural hydrogen enrichment) in the molecular structure of vitrinites have, therefore, affected the normal evolution of the lignin and contributed to the special properties of this type of materials.  相似文献   

Monogenetic vulcanism in sierra Chichinautzin,Mexico     

A. L. Martin del Pozzo 《Bulletin of Volcanology》1982,45(1):9-24

The variation in the activity patterns of the Chichinautzin volcanic rocks is discussed. This sequence of lavas and pyroclastic deposits is located in the central part of the Mexican Volcanic Belt, directly south of Mexico City, and is typical of its Quaternary monogenetic vulcanism. One-hundred and fourty-six volcanoes and their deposits covering 952 km² were mapped. Cone density is 0.15 km² with heights ranging from to 315 m and crater diameters from 50 to 750 m. Ratios of cone height/diameter decreased from 0.20 to 0.12 with age. Basal diameters varied from 0.1 km to 2 km. Lavas are mainly blocky andesites but some dacites and basalts were found. Lengths of flows range from 1.0 to 21.5 km with heights of 0.5 to 300 m and aspect rations of 21.4 to 350. Three types of volcanic structures are found in the area: scoria cones, lavas cones and thick flows lacking a cone. Pyroclastic deposits are basically Strombolian although some deposits were produced by more violent activity and lava cones seem to have formed by activity transitional to Hawaiian-type vulcanism. Therre is a dominant E-W trend shown mainly by the orientation of cone clusters. The Chichinautzin volcanic centers are compared to the monogenetic volcanoes of the Toluca and Paricutin areas which are similar.  相似文献   

Carbon and oxygen isotopes of Maastrichtian–Danian shallow marine carbonates: Yacoraite Formation, northwestern Argentina     

Rosa Marquillas  Ignacio Sabino  Alcides Nobrega Sial  Cecilia del Papa  Valderez Ferreira  Stephen Matthews 《Journal of South American Earth Sciences》2007,23(4):304-320

The Maastrichtian–Danian limestones of the Yacoraite Formation (northwestern Argentina) show carbon and oxygen isotopic values consistent with shallow marine conditions. The members of the formation respond to different sedimentary environments and are characterised by distinctive stable isotopes and geochemistry. The basal Amblayo Member is composed of high-energy dolomitic limestones and limestones with positive isotopic values (+2‰ δ¹³C, +2‰ δ¹⁸O). The top of the member reveals an isotopic shift of δ¹³C (−5‰) and δ¹⁸O (−10‰), probably related to a descent in the sea level. The sandy Güemes Member has isotopically negative (−2‰ δ¹³C, −1‰ δ¹⁸O) limestones, principally controlled by water mixing, decreased organic productivity, and compositional changes in the carbonates. The isotopically lighter limestones are calcitic, with a greater terrigenous contribution and different geochemical composition (high Si–Mn–Fe–Na, low Ca–Mg–Sr). These isotopic and lithological changes relate to the Cretaceous–Palaeogene transition. The Alemanía Member, composed of dolomitic limestones and pelites, represents a return to marine conditions and shows a gradual increase in isotopic values, reaching values similar to those of the Amblayo Member. The Juramento Member, composed of stromatolite limestones, shows isotopic variations that can be correlated with the two well-defined, shallowing-upward sequences of the member.  相似文献   

The Bullas (Murcia, SE Spain) earthquake, 29 January 2005     

E. Buforn  S. Cesca  T. Goded  C. del Fresno  D. Muñoz 《Journal of Seismology》2006,10(1):65-72

The intensity and focal mechanism of the Bullas earthquake of 29 January 2005 have been determined. The intensity assessment has been carried out using the EMS-98 scale and plotted on an intensity map. The focal mechanisms for the main shock and largest aftershock have been estimated from moment tensor inversion of body waves. The mechanisms obtained show left-lateral strike-slip faulting and foci at shallow depths, 3–4 km. These results are compared with those of the Bullas 2002 and Mula 1999 earthquakes in the same region.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Journal of Seismology.  相似文献