The origin and isotopic composition of dissolved sulfide in groundwater from carbonate aquifers in Florida and Texas     

R.O. Rye  William Back  B.B. Hanshaw  C.T. Rightmire  F.J. Pearson 《Geochimica et cosmochimica acta》1981,45(10):1941-1950

The δ³⁴S values of dissolved sulfide and the sulfur isotope fractionations between dissolved sulfide and sulfate species in Floridan ground water generally correlate with dissolved sulfate concentrations which are related to flow patterns and residence time within the aquifer. The dissolved sulfide derives from the slow in situ biogenic reduction of sulfate dissolved from sedimentary gypsum in the aquifer. In areas where the water is oldest, the dissolved sulfide has apparently attained isotopic equilibrium with the dissolved sulfate (Δ³⁴S = 65 per mil) at the temperature (28°C) of the system. This approach to equilibrium reflects an extremely slow reduction rate of the dissolved sulfate by bacteria; this slow rate probably results from very low concentrations of organic matter in the aquifer.In the reducing part of the Edwards aquifer, Texas, there is a general down-gradient increase in both dissolved sulfide and sulfate concentrations, but neither the δ³⁴S values of sulfide nor the sulfide-sulfate isotope fractionation correlates with the ground-water flow pattern. The dissolved sulfide species appear to be derived primarily from biogenic reduction of sulfate ions whose source is gypsum dissolution although upgradient diffusion of H₂S gas from deeper oil field brines may be important in places. The sulfur isotope fractionation for sulfide-sulfate (about 38 per mil) is similar to that observed for modern oceanic sediments and probably reflects moderate sulfate reduction in the reducing part of the aquifer owing to the higher temperature and significant amount of organic matter present; contributions of isotopically heavy H₂S from oil field brines are also possible.  相似文献   

The acquistion and application of basic land use data in urban growth analysis: A case study of Metropolitan Lagos     

Adeniyi  P. O. 《GeoJournal》1981,5(3):209-223

Basic to the study of urban growth is information on population and land use changes. These basic data are generally lacking in Nigeria. This paper examines and assesses the growth of urban land use of Lagos (the Federal Capital of Nigeria) through a systematic utilization of sequential serial photographs (taken in 1962 at a scale of 1:40,000, and in 1974, at a scale of 1:20,000) and computer techniques. The land use data resulting are then used in evaluating the population growth of Lagos. The resulting population estimate is then compared with the available population data. The study concludes by recommending the use of remote sensing, especially aerial photography for the acquisition of basic urban data not only in Nigeria but also in other developing countries lacking in such data.  相似文献   

Axially symmetric flow round a non-conducting obstacle in the shape of a hemisphere by a homogeneous electrical current field     

Klement Rosa  Reviewer O. Praus 《Studia Geophysica et Geodaetica》1981,25(4):376-392

m amamu n¶rt;ma au ¶rt; nmuaa mu n ma a, ¶rt;a ¶rt;¶rt; maua mu n ¶rt; nmam ¶rt;um n¶rt; nnmmu n. u m umau n aa mau a, m m nmmu ma nu ¶rt;¶rt; n naa u umuu n. maa a¶rt;aa a u um ¶rt;uam. a u nu¶rt;m um ua u au, nu u n a auu mam, n¶rt;ma [5, 6]. m um nu num m amamu au ¶rt; nmuaa mu n, n¶rt;mau u¶rt; ¶rt;a nu a¶rt;a.  相似文献   

The interaction of positive streamers with charged and uncharged water drops in vertical electric fields     

E. O. Oladiran 《Pure and Applied Geophysics》1981,119(5):966-977

Investigation was carried out to study the interaction of positive streamers with charged and uncharged drops in a vertical electric field configuration. Results obtained for vertical and horizontal positions of the photographic films show that streamer interactions with neutral and negative drops are similar and further confirmed earlier results byPhelps (1972). It showed that indirect streamer interaction with droplets is effected by branches being sent to the drops from the main channel. The visibility of the branches on the Lichtenberg figures and the degree of interaction of streamers with drops depend on the drop size, its initial charge and shape, and/or the separation of the drops from the main channel. Suppression of streamer propagation among the positively charged drops was observed.  相似文献   

Volcanism and vertical tectonics in the Pacific Basin related to global Cretaceous transgressions     

Seymour O. Schlanger  Hugh C. Jenkyns  Isabella Premoli-Silva 《Earth and Planetary Science Letters》1981,52(2):435-449

The dominance of volcanic processes and the importance of vertical tectonics in the geological evolution of the Pacific Basin has been recognised since the time of Charles Darwin. Data gathered on several legs of the Deep Sea Drilling Project (DSDP) and numerous marine expeditions in the past decade have confirmed Menard's postulate that the Pacific Basin was the scene of volcanism on an enormous scale in Mesozoic time. Widespread mid-plate volcanism between ～110 and 70 m.y. B.P. characterised the area bounded by the Line Islands, the Mid-Pacific Mountains and the Nauru Basin-Marshall Islands. Heating of the Pacific lithospheric plate during this period of volcanism resulted in regional uplift and the bathymetric evolution of the area diverged significantly from a “normal” Parsons-Sclater subsidence curve. The Farallon plate, now almost entirely subducted, was also the scene of mid-plate volcanism that produced such features as the Nicoya Plateau now found as an allochthonous ophiolitic terrain landward of the middle America trench. Large, benthonic, reef-associated foraminifera comprising a pseudorbitoid fauna, hitherto considered to be largely restricted to Central America, have now been additionally recorded from DSDP Sites 165, 315 and 316 in the Line Islands, Site 462 in the Nauru Basin, and in New Guinea. The distribution of this fauna, of Campanian/Maastrichtian age, is interpreted as indicating “stepping stone” connections (aseismic ridges, plateaus and seamounts) between the Caribbean, Farallon, and Pacific plates 70–80 m.y. B.P. Similarities between the geology of the Nauru Basin and the Caribbean Ocean crust reinforce the interpretation of the latter as a former part of the Farallon plate. Estimates of the sea-level and continental freeboard change caused by the thermally induced uplift of the Pacific and Farallon plates, as well as substantial areas in the Atlantic and Indian Ocean Basins, indicate that such shallowing of the sea floor could have been the major factor in causing global Cretaceous transgressions.  相似文献   

Deformation properties of the lithosphere derived from data on recent crustal movements of the earth     

T. L. Tolkunova  Reviewer O. Novotný 《Studia Geophysica et Geodaetica》1978,22(3):295-298

aamuam a¶rt;aa ¶rt;uu ¶rt; m u¶rt;mu, uau n¶rt; uu mua ¶rt;uu a uau u . a auu au mmuu mam ¶rt;au mua ¶rt;uu ¶rt;am m am ¶rt; ¶rt;au ma um.  相似文献   

О ВЗАИМОДЕЙСТВИИ МЕЖДУ ВЫСОТНЫМИ АТМОСФЕРНЫМИ ВИХРЯМИ И НАЗЕМНЫМ ТЕЧЕНИЕМ     

Vojtěch Vítek  Рецнзенm O. Zikmunda 《Studia Geophysica et Geodaetica》1978,22(4):415-416

Summary It is shown that non-divergent vortices may induce, as a result of the resonance effect, a rapid surface development.  相似文献   

Ore dust pollution,hatching and egg temperatures in birds     

T. Erasmus  W. Strydom  O. Tipshraeny  R.J. Watling 《Marine pollution bulletin》1978,9(2):48-52

Dry ore dust pollution decreased the hatching success of fowl eggs from 76% in the control to 57% when manganese ore dust and 54% when iron ore dust were used. Daily wetting of eggs aggravated the ore dust effect. When eggs were covered with ore dust, the heat exchange properties of eggs exposed to direct sunlight were significantly changed. Manganese and iron ore dust covered eggs heated and cooled at a significantly faster rates than the controls. The interior uppermost area may reach a temperature of 54°C after 60 minutes in the sun. Manganese ore dust covered brown eggs were the most affected and white eggs the least. Ore dust pollution therefore poses a threat to the hatching success of bird eggs.  相似文献   

Noble gases in the earth's mantle     

D.P. Thompson  A.R. Basu  E.W. Hennecke  O.K. Manuel 《Physics of the Earth and Planetary Interiors》1978,17(2):98-107

The abundances and isotopic compositions of noble gases in two samples from ultramafic xenoliths in alkali basalt, a young kaersutitic amphibole separated from a peridotite xenolith from Dish Hill, California and an ancient whole-rock lherzolite xenolith from Baja California, are reported and compared with the results of analyses on other mantle samples. In addition to previously recognized excesses of ³He and ¹²⁹Xe, our results indicate that ambient gases in the mantle show a general enrichment of the lighter-mass nonradiogenic isotopes of Ar, Kr and Xe, and Ar with ⁴⁰Ar/³⁶Ar = 3 · 10².  相似文献   

Detrital barytes in the Karoo Supergroup of Southern Africa     

T. O. Reimer 《Mineralium Deposita》1978,13(2):235-244

Beds of sedimentary barytes are found in late Paleozoic sediments in the northeasternmost part of South Africa and adjoining parts of Rhodesia. The baryte horizon consists of 2 beds of composite thickness of up to 50 cm within a sequence of partly porcellaneous shales. It is dark gray to redbrown in colour, in places also black, and then contains traces of H₂S. It usually consists of fine-grained subrounded tabular grains of detrital origin. This horizon frequently contains aggregates of upward diverging acicular baryte which formed diagenetically within the detrital baryte. The deposit was formed through reworking of semiconsolidated clays containing baryte concretions. Such shales are known to occur to the west of the baryte deposit in contemporaneous sediments.

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Zusammenfassung In spätpaläozoischen Sedimenten im Nordosten Südafrikas und dem angrenzenden Bereich Rhodesiens treten sedimentäre Barytlagen auf. Die Barytzone besteht aus zwei Lagen mit einer gemeinsamen größten Mächtigkeit von 50 cm, innerhalb einer Abfolge teilweise verkieselter Tonschiefer. Der Baryt ist dunkelgrau bis rotbraun, stellenweise auch schwarz, und enthält dann Spuren von H₂S. Er besteht meist aus feinkörnigen kantengerundeten schwach plattigen Kristallen detritischer Herkunft. Die Zone enthält häufig Aggregate aus nach oben divergierenden nadeligen Barytkristallen, die sich frühdiagenetisch im detritischen Baryt bildeten. Das Vorkommen entstand durch Aufarbeitung von Barytkonkretionen in schwach verfestigten Tonen. Entsprechende Tonschiefer treten in gleichaltrigen Sedimenten westlich des Barytvorkommens auf.

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