The Triassic of the southern margin of the Tethys in the Levant and its correlation across the Jordan Rift Valley

The Triassic of the Levantine region consists of four sedimentary cycles: I. Scythian — Lower Anisian; II. Early Upper Anisian; III. Late Upper Anisian — Carnian; IV. Late Carnian — Norian.Regional biofacial affinities point to the existance of a western Tethyan Werfen facies (cycle I), a sephardic biofacies (cycles II and III) and a rather alpinotype platform facies (cycle IV). A correlation across the Jordan Rift Valley is suggested, primarily based on bio- and lithostratigraphic evidence of the Permo-Triassic rocks. The stratigraphic implications of this correlation support the existance of a left lateral strike slip along the Jordan Rift Valley.

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Zusammenfassung Die Trias im Levant ist in vier Sedimentationszyklen gegliedert: I. Skythian — Unteres Anisian; II. Oberes Anisian; III. Oberes Anisian — Karnian; IV. Oberes Karman — Norian.Die regionalen Faziesbeziehungen deuten auf das Vorhandensein einer Westtethyalen Werfener Fazies (Zyklus I), einer West- und Südtethyalen Sephardischen Fazies (Zyklen II und III) und einer eher alpinotypischen Plattformfazies (Zyklus IV).Eine Korrelation der permisehen und untertriadischen Gesteine auf beiden Seiten des Jordantales wird vorgeschlagen. Die stratigraphischen Folgerungen dieser Korrelation unterstützen die Existenz einer linken Transversalverschiebung entlang des Jordantal Rifts.

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Résumé Le Trias du Levant comprend quatre cycles sédimentaires: I. Scythien-Anisien inférieur; II. Anisien supérieur; III. Anisien supérieur — Carnien; IV. Carnien supérieur — Norien.La succession des biofaciès débute par le faciès Werfénien, qui englobait pratiquement la Téthys occidentale éotriasique toute entière (cycle I). Dans le courant du Mésotrias, le faciès Sépharade s'étend aux marges méridionales et occidentales de la Téthys (cycles II et III), tandis qu'un faciès de plateforme d'affinité plutôt alpine représente le Trias terminal (cycle IV).Une corrélation des séries Permo-Eotriasiques du Néguev et de Transjordanie est proposée. Les implications stratigraphiques de cette corrélation appuient l'existence d'un coulissage sénestre tout au long du Rift de la vallée du Jourdain.

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Stable abundance,but changing size structure in grenadier fishes (Macrouridae) over a decade (1998–2008) in which deepwater fisheries became regulated

A ten-year time series (1998–2008) from a trawl survey of the continental slope of the NE Atlantic was analyzed to assess temporal variation in the abundance and length frequency of seven species of deepwater grenadier fish. This period coincided (in 2003) with the regulation of deepwater fisheries in this area. None of the species declined in numbers or biomass over the period, and 2 species significantly increased. This suggests that the declines in abundance of these deepwater species following the onset of fishing in the 1970s may now have stabilized, albeit at much lower levels than the virgin biomass. Although two metrics of body size (mean length and maximum length) did not show any evidence for consistent decrease over time, there were significant changes in the overall length–frequency distributions. The species found in shallower depths (500 m) had a greater number of larger individuals in 2008 whereas those found deeper (1500 m) tended to have a greater number of smaller individuals. This suggests the presence of a lagged indirect effect of fishing on species that live beyond the actual depths that fishing takes place.     

Impact of redox-stratification on the diversity and distribution of bacterial communities in sandy reef sediments in a microcosm

Relationships between microbial communities and geochemical environments are important in marine microbial ecology and biogeochemistry. Although biogeochemical redox stratification has been well documented in marine sediments, its impact on microbial communities remains largely unknown. In this study, we applied denaturing gradient gel electrophoresis (DGGE) and clone library construction to investigate the diversity and stratification of bacterial communities in redox-stratified sandy reef sediments in a microcosm. A total of 88 Operational Taxonomic Units (OTU) were identified from 16S rRNA clone libraries constructed from sandy reef sediments in a laboratory microcosm. They were members of nine phyla and three candidate divisions, including Proteobacteria (Alpha-, Beta-, Gamma-, Delta-, and Epsilonproteobacteria), Actinobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Verrucomicrobia, Spirochaetes, and the candidate divisions WS3, SO31 and AO19. The vast majority of these phylotypes are related to clone sequences from other marine sediments, but OTUs of Epsilonproteobacteria and WS3 are reported for the first time from permeable marine sediments. Several other OTUs are potential new bacterial phylotypes because of their low similarity with reference sequences. Results from the 16S rRNA, gene clone sequence analyses suggested that bacterial communities exhibit clear stratification across large redox gradients in these sediments, with the highest diversity found in the anoxic layer (15–25 mm) and the least diversity in the suboxic layer (3–5 mm). Analysis of the nosZ, and amoA gene libraries also indicated the stratification of denitrifiers and nitrifiers, with their highest diversity being in the anoxic and oxic sediment layers, respectively. These results indicated that redox-stratification can affect the distribution of bacterial communities in sandy reef sediments.     

The massive stibnite veins of the French Palaeozoic basement: a metallogenic marker of Late Variscan brittle extension

The stibnite ore deposits of the French Palaeozoic basement are spatially related to major Late Variscan strike-slip faults. They occur as small discontinuous veins mostly hosted in epizonal or catazonal siliciclastics. Stibnite crystallizes in the final stage of a polymetallic paragenesis from an antimony-bearing solution, which deposits a first discrete Fe-As assemblage at 300–400°C and 0.5–0.8 Kbar. Experimental data have shown that antimony solubility drastically decreases on cooling. Characterization of the Late Variscan antimony-bearing fluids enables us to predict the temperature range - 270/150°C - under which stibnite was precipitated. Since the latter coincides with the fluid inclusion homogenization temperature range, the pressure at which stibnite crystallized can be estimated from vapour pressure data to have been around 0.1 Kbar. Extensional brittle shear zones, developed at the end of the Late Variscan orogeny (probably at the Westphalian/Stephanian boundary), drained the hydrothermal fluids near to the surface (c. 1000 m ?) reaching the critical P-T conditions for stibnite crystallization.     

Identification of the last glacial maximum in the Upper Paleolithic of Portugal using magnetic susceptibility measurements of Caldeirão Cave sediments

We have sampled Upper and Middle Paleolithic sediments in Caldeirão Cave, Portugal, for paleoclimatic analysis. This work involved measuring magnetic susceptibility (MS) on continuous vertical profiles of a series of ∼8 cc sediment samples, and using the MS data as a paleoclimate proxy. Previous work has shown that caves can be ideal recorders of paleoclimatic variations because they are protected environments. Pedogenesis outside the cave during time of cool climate produces sediments with low MS magnitudes, while warmer climates yield higher MS magnitudes. Eroded soils collect in caves in sediment sequences where futher pedogenesis and biological disturbance is minimal. Continuously sampled profiles of those sediments found in an archaeological context then allow paleoclimatic estimates for all archaeological levels. Results of our work here include identification of the last glacial maximum, at ca. 24,000–22,000 B.P. (calibrated), defined by very low MS values found in basal Solutrean levels in the cave. Distinctive ca. 2500 year Neo-glacial cycles, defined by the MS data within the Early Upper Paleolithic and Solutrean, are consistent with published ¹⁴C duration estimates for the Upper Paleolithic in Caldeirão Cave. © 1998 John Wiley & Sons, Inc.     

The nature of rainfall in the main drainage sub-basins of Uganda

Abstract

A study of rainfall trends and temporal variations within seven sub-basins of Uganda spanning from 1940 to 2009 has been made. Rainfall climatologies are constructed from observational data, using 36 station records which reflect hydroclimatic conditions. Long-term changes in rainfall characteristics were determined by non-parametric tests (Mann-Kendall and Sen’s T tests), coefficient of variation (CV), precipitation concentration index and drought severity index. Magnitude of change was estimated by applying Sen’s estimator of slope. Decadal variability of rainfall with marked seasonal cycles is evident. Temporal variability of drought patterns is detected. Variations in annual rainfall are low with no significant trends observed in the main drainage sub-basins. Significant trends occur in October, November, December and January. A noticeable decrease in the annual total rainfall was observed mostly in northwestern and southwestern sub-basins. Rainfall trend in the second normal of June–July–August (JJA) was decreasing in all the main drainage sub-basins.

Editor Z.W. Kundzewicz; Associate editor S. Yue

Citation Nsubuga, F.W.N., Botai, O.J., Olwoch, J.M., Rautenbach, C.J.deW., Bevis, Y., and Adetunji, A.O., 2014. The nature of rainfall in the main drainage sub-basins of Uganda. Hydrological Sciences Journal, 59 (2), 278–299.     

Lens eddies in rotating two-fluid systems

Abstract

Laboratory experiments are conducted on the instantaneous release of a constant volume of intermediate density fluid along the interface of a two-layer fluid system in rigid body rotation about a vertical axis. Such a system leads to the development of a thin lens of fluid with anticyclonic motion which grows in radial extent to reach an equilibrium radius as the radial motion is captured by Coriolis effects, becomes unstable to non-symmetric dusturbances, and finally decays due to the action of fluid viscosity. Scaling and dimensional analysis arguments are advanced for the growth, equilibrium and decay phases of the motion. The scaling analysis for the initial growth and equilibrium phases are shown to be in good agreement with the experimental observations. The lens decay data do not collapse under the assumption of a simple Ekman spindown model assuming immiscible fluids. An empirical fit of the data for the decay phase is presented.     

An Evaluation of Soil-Gas Surveying for H2S for Locating Subsurface Hydrocarbon Contamination

A soil-gas survey was conducted at a gasoline service station and a former fire training facility to determine if surveying for hydrogen sulfide could be useful in locating nonaqueous phase hydrocarbon fuel in the subsurface. Relative; to total organic vapor, oxygen, and carbon dioxide distributions, detectable hydrogen sulfide concentrations were much more restricted to the suspected source vicinity at both sites. Appreciable levels of soil-gas hydrogen sulfide. up to 600 Vppb. were observed in areas characterized by anaerobic or microaerophilic conditions having bulk oxygen levels below 4 percent. Based on the hydrogen sulfide distribution, nonaqueous phase hydrocarbon fuel was located at each site. These results suggest that soil-gas surveying for hydrogen sulfide may help locale mobile or residual gasoline and other nonaqueous phase hydrocarbons in the subsurface.     

Interactions of uranium with bacteria and kaolinite clay

We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10^− 6 M- and 4 × 10^− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH₃COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10^− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH₃COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium.