Testing Sr/Sr as a paleosalinity indicator on mixed marine, brackish-water and terrestrial vertebrate skeletal apatite in late Paleocene-early Eocene near-coastal sediments, Mississippi     

Birger Schmitz  Stephen L. Ingram  David T. Dockery  III  Gran berg 《Chemical Geology》1997,140(3-4):275-287

Mixed marine, brackish-water and terrestrial vertebrate skeletal apatite is found in the late Paleocene-early Eocene Tuscahoma and Bashi Formations of Mississippi. The co-Occurrence in these near-coastal marine deposits of skeletal apatite with different provenances offers a unique opportunity for unraveling the effects of diagenesis on apatite ⁸⁷Sr/⁸⁶Sr composition, with bearings on the use of this isotope pair as paleosalinity indicator. The results show that the Sr isotopes of all originally poorly ordered phases of skeletal apatite have extensively re-equilibrated with pore water with significantly lower ⁸⁷Sr/⁸⁶Sr ratios than late Paleocene-early Eocene seawater. For example, marine shark and ray teeth from the Bashi Formation all have clearly nonmarine ⁸⁷Sr/⁸⁶Sr ratios, 0.7073-0.7075, compared with a coeval seawater ratio in the range 0.7077-0.7078. However, separated shark tooth enamel, with a high original crystallinity, appears to have retained all or most of its in vivo Sr isotopic signature until the present. Here we also show that ⁸⁷Sr/⁸⁶Sr results on recent vertebrate skeletal material from different environments are in good agreement with expected values for respective habitat.

Earlier analyses of calcite material from the Bashi Formation indicated the existence of a shift in seawater ⁸⁷Sr/⁸⁶Sr to a lower value at the Paleocene-Eocene boundary. The strong influence of pore water with low, nonmarine ⁸⁷Sr/⁸⁶Sr on the apatite in the Bashi Formation suggests that the proposed isotopic shift may be an artifact related to diagenetic processes.  相似文献   

Rheology of the Earth and a thermoconvective mechanism for sedimentary basin formation   总被引：1，自引：0，他引：1  

Boris I. Birger 《Geophysical Journal International》1998,134(1):1-12

A power-law non-Newtonian fluid is usually assumed to model slow flows in the mantle and, in particular, convective flows. However, the power-law fluid has no memory, in contrast to a real material. A new non-linear integral (having a memory) model is proposed to describe the rheology of rocks. The model is consistent with the theory of simple fluids with fading memory and with laboratory studies of rock creep. The proposed model reduces to the power-law fluid model for stationary flows and to the Andrade model for flows associated with small strains. Stationary convection beneath continents has been studied by Fleitout & Yuen (1984 ), who used the power-law fluid model and obtained the cold immobile boundary layer (continental lithosphere). In a stability analysis of this layer, the Andrade model must be used. The analysis shows that the lithosphere is overstable (the period of oscillation is about 200  Ma). In the present study, it is suggested that these thermoconvective oscillations of the lithosphere are a mechanism for sedimentary basin formation. The vertical crustal movement in sedimentary basins can be considered as a slow subsidence on which small-amplitude oscillations are superimposed. The longest period of oscillatory crustal movement is of the same order of magnitude as the period of convective oscillation of the lithosphere found in the stability analysis. Taking into account the difference between depositional and erosional transport rates we can explain the permanent subsidence as well as the oscillations.  相似文献   

Coupled oceanic and atmospheric Ekman layers in the tropics adapted to the central pacific ocean     

Prof. Dr. Hans Peter Schmitz 《Ocean Dynamics》1987,40(4):157-179

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Sediments and micronodules in the northern and central Peru Basin     

P. Stoffers  A. Sioulas  G. P. Glasby  W. Schmitz  A. Mangini 《International Journal of Earth Sciences》1984,73(3):1055-1080

The mineralogy and composition of sediments and manganese micronodules from the northern and central sectors of the Peru Basin are discussed. Because of the proximity of the basin to the Carbonate Compensation Depth (C.C.D.), surface sediments vary between calcareous oozes and siliceous muds. Besides biogenic components clay minerals are important. By far the most abundant clay mineral is smectite which is thought to be of diagenetic origin. On a carbonate-free basis, the surface sediments are rather uniform in composition throughout the basin and are similar in composition to those of the equatorial Pacific. Sedimentation rates for the uppermost core sections are in the range of 3 to 5 mm/ 1000 yr.Micronodule compositions show significant variations related to the size class of the micronodules and the depth of occurrence within the sediment column. In general, the chemistry of the micronodules can be explained by the reductive mobilization of Mn within the sediment column and by oxic diagenetic reactions between ferromanganese hydroxides and biogenic opal. The dominant mineral phase is todorokite.

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Zusammenfassung Mineralogie und chemische Zusammensetzung von Sedimenten und Manganmikroknollen aus dem nördlichen und zentralen Teil des Peru-Beckens werden beschrieben. Die Oberflächensedimente bestehen je nach der Lage zur Karbonatkompensationstiefe (C.C.D.) aus karbonatischen bzw. kieseligen Ablagerungen. Neben den biogenen Komponenten sind Tonmineralien (Smektit, Illit) von Bedeutung. Das häufigste Tonmineral ist diagenetisch gebildeter Smektit. Auf karbonatfreier Basis ist die chemische Zusammensetzung der Sedimente sehr einheitlich, vergleichbar mit dem Chemismus zentralpazifischer Sedimente.²³⁰Th-Datierungen ergeben eine Sedimentationsrate von 3–5 mm/1000 a für die obersten Sedimentschichten.In Abhängigkeit von der Korngrößenklasse und der Tiefe in der Sedimentsäule zeigen die Manganmikroknollen große Schwankungen im Chemismus. Remobilisationsprozesse unter reduzierenden Bedingungen in der Sedimentsäule sowie die diagenetischen Reaktionen zwischen Fe-Mn-Hydroxiden und biogenem Opal bestimmen die chemische Zusammensetzung der Manganmikroknollen. Die vorherrschende Mineralphase ist Todorokit.

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Résumé Cette note décrit la minéralogie et la composition des sédiments et des nodules polymétalliques de la partie septentrionale et centrale du bassin de Perou. Les sédiments de surface consistent en dépôts calcaires ou siliceux selon leur situation par rapport à la profondeur de compensation des carbonates (C. C. D.). A côté des composants biogènes, des minéraux argileux (smectites, illites) sont présents en quantité importante. Le minéral argileux le plus fréquent est une smectite diagenétique. La composition chimique de la fraction non carbonatée des sédiments est uniforme, comparable au chimisme de ceux du Pacifique central. Dans les couches les plus élevées, la vitesse de sédimentation, basée sur des datations par²³⁰Th, est de 3 à 5 mm/1000 ans.Le chimisme des micronodules polymétalliques est très variable et dépend de leur profondeur dans le sédiment et de leur dimension. Le chimisme est déterminé par des processus de remobilisation en conditions réductrices dans la colonne sêdimentaire, ainsi que par des réactions diagénétiques entre les hydroxydes de Fe-Mn et l'opale biogène. Le minéral dominant est la todorokite.

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. , (C. C. D.) , . ( , ). . , , . 230 , 3–5 /1000 . . , . .

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Metal precipitation in the Cretaceous-Tertiary boundary clay at Stevns Klint,Denmark     

Birger Schmitz 《Geochimica et cosmochimica acta》1985,49(11):2361-2370

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Biogene und nichtbiogene organische Schmutzstoffe     

Dr. Wolfgang Schmitz  Dr. Walter Kölle 《Aquatic Sciences - Research Across Boundaries》1975,37(1):85-98

Analytical methods and their application on the river Rhine for the identification and determination of refractory organic compounds are reported. 18 hydrocarbons, 32 chlorinated hydrocarbons, 13 organic nitro compounds, 14 ethers, 4 alcohols, 9 phenols, 6 esters and 21 other organic compounds have been identified. In view of the tedious methods which have to be applied, a technique for determining the ratio of persistent to biodegradable organic compounds has to be found. Requirements and perspectives of microbiological assays are discussed and rules for the survey of waste discharges are proposed.  相似文献   

Über Vertikalbewegung in der Unteren Troposphäre     

Dr. H. P. Schmitz 《Pure and Applied Geophysics》1949,15(3-4):215-219

Zusammenfassung Mittels der Differentialgleichungen für den Rotor und die Divergenz horizontaler turbulenter Luftbewegung und der Kontinuitätsgleichung wird näherungsweise die Vertikalbewegung in Abhängigkeit von den Druckänderungen bestimmt, deren zeitliche Variation als vertikal abnehmende periodische Schwankung (unter Berücksichtigung verschiedener Frequenzen ) angenommen wird. In allen durchgerechneten Fällen hängt die Vertikalgeschwindigkeit der Troposphäre in hohem (mit variierendem) Masse von der Reibung ab. Bei vielen, insbesondere den kleineren Frequenzen vorkommender Grösse besteht die Vertikalbewegung der unteren Troposphäre überwiegend aus dem Teil, der ohne Turbulenzreibung nicht entstehen würde. Auf diesem Wege kann die Bodenreibung die Vertikalbewegung und mittels dieser die Luftströmungen und Druckänderungen in allen Höhen massgeblich beeinflussen.

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Summary By means of the differential equations of curl and divergence of horizontal turbulent motion of air and the equation of continuity an approaching vertical motion is determined in dependance of pressure changes the temporal variation of which is supposed as a vertically decreasing oscillation (with regard to different frequencies ). In all calculated cases the vertical motion of the troposphere is modified by friction in a high degree (varying with ). With many, especially the smaller frequencies of realized magnitude vertical velocity of the lower troposphere consists prevailingly of that part which would not arise without additional stress components of turbulent motion. In this way friction at the earth's surface is able to influence essentially the vertical motion and by it the air currents and pressure changes in all levels.

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Monazite begets monazite: evidence for dissolution of detrital monazite and reprecipitation of syntectonic monazite during low-grade regional metamorphism   总被引：2，自引：0，他引：2  

Birger Rasmussen  Janet R. Muhling 《Contributions to Mineralogy and Petrology》2007,154(6):675-689

Back-scattered electron (BSE) imaging and X-ray element mapping of monazite in low-grade metasedimentary rocks from the Paleoproterozoic Stirling Range Formation, southwestern Australia, reveal the presence of distinct, high-Th cores surrounded by low-Th, inclusion-rich rims. Previous geochronology has shown that the monazite cores are older than 1.9 Ga and overlap with the ages of detrital zircon grains (∼3.5–2.0 Ga), consistent with a detrital origin. Many cores have scalloped and embayed surfaces indicating partial dissolution of former detrital grains. Textural evidence links the growth of the monazite rims (∼1.2 Ga) to deformation and regional metamorphism during the Mesoproterozoic Albany-Fraser orogeny. These results indicate that high-Th detrital monazite is unstable under low-grade metamorphic conditions (<400°C) and was partially or completely dissolved. Dissolution was followed by near-instantaneous reprecipitation and the formation of low-Th monazite and ThSiO₄. This reaction is likely to operate in other low-grade metasedimentary rocks, resulting in the progressive replacement of detrital monazite by metamorphic monazite during regional prograde metamorphism.  相似文献   

Attenuation of seismic waves and the universal rheological model of the Earth’s mantle     

B. I. Birger 《Izvestiya Physics of the Solid Earth》2007,43(8):635-641

Analysis of results of laboratory studies on creep of mantle rocks, data on seismic wave attenuation in the mantle, and rheological micromechanisms shows that the universal, i.e., relevant to all time scales, rheological model of the mantle can be represented as four rheological elements connected in series. These elements account for elasticity, diffusion rheology, high temperature dislocation rheology, and low temperature dislocation rheology. The diffusion rheology element is described in terms of a Newtonian viscous fluid. The high temperature dislocation rheology element is described by the rheological model previously proposed by the author. This model is a combination of a power-law non-Newtonian fluid model for stationary flows and the linear hereditary Andrade model for flows associated with small strains. The low temperature dislocation rheology element is described by the linear hereditary Lomnitz model.  相似文献   

Subduction and terrane collision stabilize the western Kaapvaal craton tectosphere 2.9 billion years ago     

Mark D Schmitz  Samuel A Bowring  Volker Gartz 《Earth and Planetary Science Letters》2004,222(2):363-376

Integrative models of crust and mantle structure, age, and growth of the oldest continental nuclei—the Archean cratons—are critical to understanding the processes that stabilize continental lithosphere. For the Kaapvaal craton of southern Africa, conflicting ages of stabilization have been derived from studies of its crust and underlying mantle. New U-Pb zircon geochronological data from the western Kaapvaal craton reveal that two older (3.7 to 3.1 billion year old) continental masses, the Kimberley and Witwatersrand blocks, were juxtaposed by a significantly younger, previously unresolved episode of subduction and terrane collision between 2.93 and 2.88 billion years ago. Geological evidence indicates that convergence was accommodated by subduction beneath the Kimberley block, culminating in collisional suturing in the vicinity of the present-day Colesberg magnetic lineament. The timing of these convergent margin processes is further shown to correlate with the strong peak in Re-Os age distributions of Kimberley block mantle peridotites, eclogites, and eclogite-hosted diamonds. These data thus support the petrogenetic coupling of continental crust and lithospheric mantle through a model of continental arc magmatism, subduction zone mantle wedge processing and terminal collisional advective thickening to form Archean continental tectosphere.  相似文献