Organic geochemistry and pore water chemistry of sediments from Mangrove Lake,Bermuda     

Patrick G. Hatcher  Bernd R.T. Simoneit  Fred T. Mackenzie  A.Conrad Neumann  Donald C. Thorstenson  Sol M. Gerchakov 《Organic Geochemistry》1982,4(2):93-112

Mangrove Lake, Bermuda, is a small coastal, brackish-water lake that has accumulated 14 m of banded, gelatinous, sapropelic sediments in less than 10⁴ yr. Stratigraphic evidence indicates that Mangrove Lake's sedimentary environment has undergone three major depositional changes (peat, freshwater gel, brackish-water gel) as a result of sea level changes. The deposits were examined geochemically in an effort to delineate sedimentological and diagenetic changes. Gas and pore water studies include measurements of sulfides, ammonia, methane, nitrogen gas, calcium, magnesium, chloride, alkalinity, and pH. Results indicate that sulfate reduction is complete, and some evidence is presented for bacterial denitrification and metal sulfide precipitation. The organic-rich sapropel is predominantly algal in origin, composed mostly of carbohydrates and insoluble macromolecular organic matter called humin with minor amounts of proteins, lipids, and humic acids. Carbohydrates and proteins undergo hydrolysis with depth in the marine sapropel but tend to be preserved in the freshwater sapropel. The humin, which has a predominantly aliphatic structure, increases linearly with depth and composes the greatest fraction of the organic matter. Humic acids are minor components and are more like polysaccharides than typical marine humic acids. Fatty acid distributions reveal that the lipids are of an algal and/or terrestrial plant source. Normal alkanes with a total concentration of 75 ppm exhibit two distribution maxima. One is centered about n-C₂₂ with no odd/even predominance, suggestive of a degraded algal source. The other is centered at n-C₃₁ with a distinct odd/even predominance indicative of a vascular plant origin. Stratigraphic changes in the sediment correlate to observed changes in the gas and pore water chemistry and the organic geochemistry.  相似文献   

FIELD APPLICATIONS OF CHEMICAL TIME-SERIES SAMPLING     

Joseph F. Keely  Fred Wolf 《Ground Water Monitoring & Remediation》1983,3(4):26-33

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Geology of the Northwest African continental margin : U. von Rad, K. Hinz, M. Sarnthein and E. Seibold (Editors), Springer-Verlag, Berlin, 1982, xi + 703 pp., 325 figures, DM 110.00, approx. US $51.20 (hardcover)     

K. H. Wolf 《Dynamics of Atmospheres and Oceans》1983,7(3):185-187

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Etudes minéralogique et gėochimique des dépȯts sulfurés sous-marins actuels de la ride est-pacifique (21°N) | E. Oudin,with the participation of C. Fouillac and L. Le Bel,and the collaboration of seven other researchers, 1982. Documents du BRGM,No. 25, BRGM,Paris, xvii + 241 pp., FF100.00 (paperback)     

K.H. Wolf 《Earth》1983,19(4):341-342

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The sea floor,an introduction to marine geology | E. Seibold and W.H. Berger, 1982. Springer-Verlag,Berlin, vii + 288 pp., 206 figs., DM46.00, approx. US$21.50 (paperback)     

K.H. Wolf 《Earth》1983,19(4):354-355

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Geologie und Lagerstättenerkendung im Rheinischen Braunkohlenrevier: Fortschritte in der Geologie von Rheinland und Westfalen,vol. 29. E. Reiche and H.-J. Leuschner (Editors), Geologisches Landesamt Nordrhein-Westfalen,Krefeld, 1981, 575 pp., DM 104.00 (hardcover)     

D. Juch  R. Wolf 《International Journal of Coal Geology》1983,2(3):297-298

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Astronomical Engineering: A Strategy For Modifying Planetary Orbits     

D.G. Korycansky  Gregory Laughlin  Fred C. Adams 《Astrophysics and Space Science》2001,275(4):349-366

The Sun's gradual brightening will seriously compromise the Earth'sbiosphere within 10⁹ years. If Earth's orbit migrates outward,however, the biosphere could remain intact over the entiremain-sequence lifetime of the Sun. In this paper, we explore thefeasibility of engineering such a migration over a long timeperiod. The basic mechanism uses gravitational assists to (in effect)transfer orbital energy from Jupiter to the Earth, and therebyenlarges the orbital radius of Earth. This transfer is accomplishedby a suitable intermediate body, either a Kuiper Belt object or a mainbelt asteroid. The object first encounters Earth during an inward passon its initial highly elliptical orbit of large ( 300 AU)semimajor axis. The encounter transfers energy from the object to theEarth in standard gravity-assist fashion by passing close to theleading limb of the planet. The resulting outbound trajectory of theobject must cross the orbit of Jupiter; with proper timing, theoutbound object encounters Jupiter and picks up the energy it lost toEarth. With small corrections to the trajectory, or additionalplanetary encounters (e.g., with Saturn), the object can repeat thisprocess over many encounters. To maintain its present flux of solarenergy, the Earth must experience roughly one encounter every 6000years (for an object mass of 10²² g). We develop the details ofthis scheme and discuss its ramifications.  相似文献   

Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity   总被引：2，自引：0，他引：2  

Isabelle Panet  Valentin Mikhailov  Michel Diament  Fred Pollitz  Geoffrey King  Olivier de Viron  Matthias Holschneider  Richard Biancale  Jean-Michel Lemoine 《Geophysical Journal International》2007,171(1):177-190

The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December ( M _w= 9.2) and 2005 March ( M _w= 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin.  相似文献   

An Estimate of Global Mean Sea-level Rise Inferred from Tide-gauge Measurements Using Glacial-isostatic Models Consistent with the Relative Sea-level Record   总被引：1，自引：0，他引：1  

J. M. Hagedoorn  D. Wolf  Z. Martinec 《Pure and Applied Geophysics》2007,164(4):791-818

This study is concerned with the influence of the glacial-isostatic adjustment caused by the last Pleistocene deglaciation on the present-day sea level. The viscoelastic deformation caused by the time-variable ice and ocean loads is simulated by computing the resulting perturbations for a spherical, self-gravitating, incompressible, Maxwell-viscoelastic earth model. The associated variation of the earth rotation is described in terms of the Liouville equation, which is solved by means of the MacCullagh formulae. This allows the determination of the vertical displacement and geoid height and, thus, the solution of the sea-level equation. We test several viscosity and ice models and evaluate them by comparison of the computed response with the Holocene relative sea-level record. Using the optimum combination of viscosity and ice models, we then estimate the influence of the last Pleistocene deglaciation on the tide-gauge measurements. A comparison between the observational and residual linear trends for the tide-gauge measurements shows a significant reduction of the variance and geographical variability for the latter, in particular for the formerly ice-covered regions of North America and Scandinavia. The favoured value determined for the global mean sea-level rise is (1.46±0.2) mm a⁻¹.  相似文献   

Robust H∞ control for aseismic structures with uncertainties in model parameters     

宋刚  林家浩  赵岩 《地震工程与工程振动(英文版)》2007,6(4):409-416

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LMI toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 El Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.  相似文献