Preliminary mesozoic palaeomagnetic results from Israel and inferences for a microplate structure in the Lebanon

Preliminary results from a few Triassic, Jurassic and Cretaceous rocks indicate that Israel has behaved as part of the African plate during this period. Earlier palaeomagnetic results from the Lebanon, previously explained in terms of a separate Levantine plate, can be better explained in terms of differential motion between fault blocks in response to motions along the Dead Sea Fault. The available evidence allows determination of the net motions of specific fault blocks and is consistent with independent palaeogeographic indicators of the pretectonic relationship between these blocks.     

How special are brightest group and cluster galaxies?

We use the Sloan Digital Sky Survey (SDSS) to construct a sample of 625 brightest group and cluster galaxies (BCGs) together with control samples of non-BCGs matched in stellar mass, redshift and colour. We investigate how the systematic properties of BCGs depend on stellar mass and on their privileged location near the cluster centre. The groups and clusters that we study are drawn from the C4 catalogue of Miller et al. but we have developed improved algorithms for identifying the BCG and for measuring the cluster velocity dispersion. Since the SDSS photometric pipeline tends to underestimate the luminosities of large galaxies in dense environments, we have developed a correction for this effect which can be readily applied to the published catalogue data. We find that BCGs are larger and have higher velocity dispersions than non-BCGs of the same stellar mass, which implies that BCGs contain a larger fraction of dark matter. In contrast to non-BCGs, the dynamical mass-to-light ratio of BCGs does not vary as a function of galaxy luminosity. Hence BCGs lie on a different Fundamental Plane than ordinary elliptical galaxies. BCGs also follow a steeper Faber–Jackson relation than non-BCGs, as suggested by models in which BCGs assemble via dissipationless mergers along preferentially radial orbits. We find tentative evidence that this steepening is stronger in more massive clusters. BCGs have similar mean stellar ages and metallicities to non-BCGs of the same mass, but they have somewhat higher α/Fe ratios, indicating that star formation may have occurred over a shorter time-scale in the BCGs. Finally, we find that BCGs are more likely to host radio-loud active galactic nuclei than other galaxies of the same mass, but are less likely to host an optical active galactic nucleus (AGN). The differences we find are more pronounced for the less massive BCGs, i.e. they are stronger at the galaxy group level.     

Fate of bacterial biomass derived fatty acids in soil and their contribution to soil organic matter

Soil organic matter (SOM) is a major pool of the global C cycle and determines soil fertility. The stability of SOM strongly depends on the molecular precursors and structures. Plant residues have been regarded as the dominant precursors, but recent results showed a major contribution of microbial biomass. The fate of microbial biomass constituents has not yet been explored; therefore, we investigated the fate of fatty acids (FA) from ¹³C labeled Gram-negative bacteria (Escherichia coli) in a model soil study [Kindler, R., Miltner, A., Richnow, H.H., Kästner, M., 2006. Fate of gram negative bacterial biomass in soil—mineralization and contribution to SOM. Soil Biology & Biochemistry 38, 2860–2870]. After 224 days of incubation, the label in the total fatty acids (t-FA) in the soil decreased to 24% and in the phospholipid fatty acids (PLFA) of living microbes to 11% of the initially added amount. Since the bulk C decreased only to 44% in this period, the turnover of FA is clearly higher indicating that other compounds must have a lower turnover. The ¹³C label in the t-FA reached a stable level after 50 days but the label of the PLFA of the living microbial biomass declined until the end of the experiment. The isotopic enrichment of individual PLFA shows that the biomass derived C was spread across the microbial food web. Modelling of the C fluxes in this experiment indicated that microbial biomass is continuously mineralized after cell death and recycled by other organisms down to the 10% level, whereas the majority of biomass derived residual bulk C (～33%) was stabilized in the non-living SOM pool.     

Geochemistry of salt marsh sediments deposited during simulated sea-level rise and consequences for recent and Holocene coastal development of NW Germany

De-embankment in the salt marshes of the island of Langeoog was carried out in 2004, thereby inducing an artificial transgression within an area of 2.2 km². Material from three suspended matter traps (SMTs) located along a N–S transect was collected monthly between January 2006 and February 2007. Besides geochemical (major and trace elements) and grain-size analyses, the duration and height of water cover were continuously measured by pressure gauges during the sampling period at two sites, thus revealing inundation frequency (max. 280 year⁻¹) and level (max. 2.4 m). Generally, the silt-dominated SMT material exhibits a geochemical composition similar to that of suspended particulate matter from the adjacent Wadden Sea. However, distinctly increasing enrichments of TOC, P, Mn and Mo from the shoreline towards the higher salt marsh clearly indicate fractionation processes during material transport. Geochemical comparison with older Holocene coastal deposits reveals a mixture of brackish and tidal flat sediments, thus reflecting an early stage of sea-level rise and the development from a terrestrial towards a marine-dominated system. Sedimentation rates are higher than the local sea-level rise, as revealed by vertical salt marsh growth. Storm surges deliver the highest amounts of sediment and play an important role in salt marsh accumulation within the study area. Average accumulation rates of TOC (780 t year⁻¹), P (54 t year⁻¹) and Mn (5.2 t year⁻¹) in the de-embanked area suggest that the former sand-dominated sediments currently receive significant amounts of reactive organic-rich material, thus fostering biogeochemical cycling.     

Carbon in olivine single crystals analyzed by the 12C(d,p)13C method and by photoelectron spectroscopy

Carbon subsurface concentration profiles in olivine single crystals from San Carlos, Arizona, and the Sergebet Island. Red Sea, containing total carbon between 60–180 wt.-ppm, were analyzed by means of the ¹²C(d. p)¹³C nuclear reaction and by x-ray induced photoelectron spectroscopy (XPS) in combination with acid etching and with Ar⁺ ion sputtering respectively, between 200–930 K. The (d, p) analysis reveals equilibrium subsurface C profiles extending 1–2 μm or more into the bulk. Their steepness is a function of temperature. Typical mean C concentrations at 300 K in the resolvable layers, 0–0.6, 0.6–1.2, and 1.2–1.8 μm. are 1.8, and 0.6 wt.-%, corresponding to enrichment factors over the mean bulk C concentration of the order of 100, 40 and 30 respectively. In the topmost atomic layers analyzed by XPS the carbon is enriched by a factor of the order of 1000, decreasing with increasing temperature. The results suggest that the carbon is in a truly dissolved state and highly mobile, subject to a reversible subsurface segregation. Most probably local lattice strain associated with the solute C species provide the driving force for this diffusional process. The C diffusion coefficient was determined from the (d, p) data below 300 K: D= 10^?13 exp(?7.8/RT) [m²· sec^?1; KJ · mole^?1] and from XPS data between 450–925 K: D = 10^?14 exp(-6/RT) [m² · sec^?1; KJ · mole^?1] The estimated error of the preexponential factors is ± one order of magnitude, that of the activation energies ±3.5 and ±2 KJ mole^?1 respectively.     

Organic compounds in the early atmosphere formed abiotically from atomic carbon

The recent discovery that atomic carbon occurs plentiful in olivines from mantle-derived rocks opens new aspects for the chemical evolution of the early atmosphere and the origin of life. It has been shown conclusively that atomic carbon which is dissolved in the model oxide MgO is capable of reacting in an O₂-free atmosphere with the lattice oxygen to give CO₂ and with the lattice hydrogen, derived from OH^–, to give a profuse variety of hydrocarbons.The diffusional processes and low temperature gas/solid interface reactions involved in these processes are expected to introduce, purely abiotically, isotope fractionation resulting in a¹³C enrichment of the CO₂ fraction and in a¹³C depletion of the hydrocarbon fraction which may be confused with the¹²C/¹³C isotope fractionation along biological pathways.Atomic carbon dissolved in olivines and in basalts shows a similar behaviour and yields similar quantities as C in MgO: 1–2 mg/g CO₂ and 25–100g/g hydrocarbons degassing between 400 and 1000 °C. On a geological scale this means that each cubic kilometer of basaltic magma degassing in an O₂-free atmosphere has the capacity of sending off about 3–6·10⁹ kg (2·10⁹ m³) of CO₂ and about 1–3·10⁸ kg (2·10⁸ m³) of hydrocarbons. The presence of water modifies the composition to give, among others, alcohols and organic acids.On the basis of these results we are led to the conclusion that the early atmosphere of the earth may have contained a very high concentration of abiotically formed organic compounds of great chemical complexity.

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Zusammenfassung Die Entdeckung des atomar gelösten Kohlenstoffs in Olivinen aus Mantelgesteinen führt zu neuen Vorstellungen über die Zusammensetzung der Uratmosphäre und Entwicklungsbedingungen des Lebens. Atomarer Kohlenstoff im MgO ist in der Lage, in einer O₂-freien Atmosphäre mit dem Gittersauerstoff zu CO₂ zu reagieren und mit dem aus OH^– stammenden Gitterwasserstoff eine große Vielfalt von organischen Verbindungen zu bilden.Diffusionsprozesse und Gas-Festkörper-Austauschreaktionen, die an diesen Reaktionen beteiligt sind, führen nach ersten Untersuchungen zu einer¹³C-Anreicherung im CO₂ und einer¹³C-Abreicherung bei den Kohlenwasserstoffen. Diese¹²C/¹³C-Fraktionierung ist gleichsinnig mit der biologischen¹²C/¹³C-Fraktionierung.Atomarer Kohlenstoff in Olivinen und Basalten zeigt ein sehr ähnliches Reaktionsverhalten wie im MgO und führt zu ähnlichen Reaktionsprodukten: 1–2 mg/g CO₂ und 25–100g/g Kohlenwasserstoffe zwischen 400–1000 °C. Übertragen auf geologische Verhältnisse bedeutet dies, daß jeder km³ eines entgasenden basaltischen Magmas 3–6·10⁹ kg (2·10⁹ m³) CO₂ und 1–3·10⁸ kg (2·10⁸ m³) abwüschen Kohlenwasserstoff abgeben kann. Die Anwesenheit von Wasser führt zur Bildung von Alkoholen und organischen Säuren. Diese Ergebnisse deuten darauf hin, daß die Uratmosphäre und die Ursuppe viel reicher waren als bisher angenommen an komplexen organischen Verbindungen, die rein thermisch entstanden sind.

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Résumé La découverte du carbone atomique dans les olivines du manteau entraîne de nouvelles idées sur la composition de l'atmosphère originelle et sur les conditions du développement de la vie. Comme l'est le cas pour le MgO, le carbone atomique dans les olivines est capable de réagir, dans une atmosphère exempte de O₂, avec l'oxygène du réseau cristallin en formant du CO₂, et avec l'hydrogène provenant des groupements OH^– du réseau, pour former une grande variété de composés organiques.Les processus de diffusion et d'échange gas-solide liés à ces réactions provoquent, d'après les premiers résultats, un enrichissement en¹³C dans le CO₂ et un appauvrissement en¹³C dans les hydrocarbures formés. Ceci ressemble au fractionnement dû à des réactions biologiques.Le comportement du carbone atomique et sa réactivité se retrouvent dans les basaltes et les olivines. La gamme des produits de réaction et leur quantité ressemble à celle du MgO: 1–2 mg/g CO₂ et 25–100g/g composés organiques. A l'échelle géologique ceci implique que chaque km³ de magma basaltique dégazé en contact avec une atmosphère exempte d'oxygène pouvait émettre 3–6·10⁹ kg, soit 2·10⁹ m³ de CO₂ et 1–3·10⁸ kg, soit 2·10⁸ m³ d'hydrocarbures abiotiques. La présence d'eau entraîne la formation d'alcools et d'acides organiques.La conclusion tirée de ce travail indique que l'atmosphère originelle et la»soupe primordiale» étaient plus riches qu'on ne l'a admis jusqu'à présent en composés organiques dûs à des processus purement thermiques, et donc abiotiques.

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. MgO , COg, -, , . , , — — ¹³ ₂ . ¹²/¹³ , . , , - : 1–2 / O₂ 25–100 / , 400–1000 . , 3–6·109 (2·10^{9 3}) ₂ 1– 3·10⁸ (2·10^{8 3}) . . , , , , .

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Presented in part at the meeting Precambrian Problems, Copenhagen, March 1981.