Paleomagnetism of the Cu�CZn�CPb-bearing Kupferschiefer black shale (Upper Permian) at Sangerhausen, Germany

Syngenetic, diagenetic and epigenetic models have been proposed for the Cu?CZn?CPb Kupferschiefer mineralization at Sangerhausen, Germany. Paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the Sangerhausen Syncline. The mineralization is richest in the ??0.5-m-thick Upper Permian (258?±?2?Ma) Kupferschiefer black marly shale (nine sites) and dies out over ??0.2?m in the underlying Weisliegend sandstones (three sites) and overlying Zechstein carbonates (two sites). Except for one site of fault zone gypsum, characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization. These directions provide a negative fold test, indicating that the remanence postdates Jurassic fault block tilting. Rock magnetic measurements show that the Kupferschiefer shale marks a redox front between the oxidized Weissliegend sandstones and non-oxidized Zechstein carbonates. The 14 site directions give a Late Jurassic paleopole at 149?±?3?Ma. It is significantly different from the paleopole reported by E.C. Jowett and others for primary or early diagenetic Rote F?ule alteration that gives an age of 254?±?6?Ma on the current apparent polar wander path and is associated with Kupferschiefer mineralization. We suggest that the Late Jurassic extensional tectonic event that formed the nearby North German Basin also reactivated Variscan basement faults and extended them up through the overlying strata, thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the Kupferschiefer shale. The possibility of a 53?±?3?Ma mineralization age is also considered.     

Petroleum source rocks of the Tarfaya Basin and adjacent areas, Morocco

This work characterizes the source rock potential of the Tarfaya Basin and enabled us to reconstruct its geochemical history. Outcrop samples covering different stratigraphic intervals, plus the northwestern part of the Zag/Tindouf Basin (Bas Draa area), were analyzed for total organic carbon (C_org) and total inorganic carbon contents and total sulfur content. Rock-Eval analysis and vitrinite reflectance measurements were performed on 56 samples chosen on the basis C_org content. A set of 45 samples were extracted and non-aromatic hydrocarbons were analyzed by way of gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (GC-MS). Non-isothermal open system pyrolysis at different heating rates was applied to obtain kinetic parameters for modelling petroleum generation from four different source rocks.High quality petroleum source rocks with high C_org content and hydrogen index (HI) values were found for samples of Eocene, Coniacian, Turonian and Cenomanian age. Most samples were carbonate rich and organic/sulfur values were high to moderate. Various maturity parameters indicated immature or possibly early mature organic matter. Based on organic geochemical and petrological data, the organic matter is of marine/aquatic origin (Cenomanian) or a mixture of aquatic and terrigenous material (Eocene). The Early Cretaceous interval did not contain high quality source rocks, but indications of petroleum impregnation were found.     

Phyllosilicates synthesis: a way of accessing edges contributions in NMR and FTIR spectroscopies. Example of synthetic talc

A series of new-generation synthetic talcs were prepared by varying the hydrothermal synthesis duration from a few hours up to 2 months. Crystallinity and particle size analysis of the synthetic products were evaluated by photon correlation spectroscopy, transmission electron microscopy, differential thermal analysis and unoriented X-ray diffraction, and then analyzed by various spectroscopic methods such as Fourier transformed infrared spectroscopy and solid-state ¹H and ²⁹Si magic angle spinning nuclear magnetic resonance. The new process for preparing synthetic talcs allows to obtain single-phased particles which after few hours grow heterogeneously and simultaneously in both the c* direction and the (ab) plan. Fine particles, observed for whatever the synthesis duration, lead to the presence of numerous sheet edges surfaces due to particle size which represents the main difference with natural talc. Spectroscopy data show the influence of the fine particles on signals and highlight that synthetic talc characterization is a potential tool for better understanding crystal chemistry of natural talc.     

Persistence of Artemisia steppe in the Tangra Yumco Basin,west-central Tibet,China: despite or in consequence of Holocene lake-level changes?

The closed Tangra Yumco Basin underwent the strongest Quaternary lake-level changes so far recorded on the Tibetan Plateau. It was hitherto unknown what effect this had on local Holocene vegetation development. A 3.6-m sediment core from a recessional lake terrace at 4,700 m a.s.l., 160 m above the present lake level of Tangra Yumco, was studied to reconstruct Holocene flooding phases (sedimentology and ostracod analyses), vegetation dynamics and human influence (palynology, charcoal and coprophilous fungi analyses). Peat at the base of the profile proves lake level was below 4,700 m a.s.l. during the Pleistocene/Holocene transition. A deep-lake phase started after 11 cal ka BP, but the ostracod record indicates the level was not higher than ~4,720 m a.s.l. (180 m above present) and decreased gradually after the early Holocene maximum. Additional sediment ages from the basin suggest recession of Tangra Yumco from the coring site after 2.6 cal ka BP, with a shallow local lake persisting at the site until ~1 cal ka BP. The final peat formation indicates drier conditions thereafter. Persistence of Artemisia steppe during the Holocene lake high-stand resembles palynological records from west Tibet that indicate early Holocene aridity, in spite of high lake levels that may have resulted from meltwater input. Yet pollen assemblages indicate humidity closer to that of present potential forest areas near Lhasa, with 500–600 mm annual precipitation. Thus, the early mid-Holocene humidity was sufficient to sustain at least juniper forest, but Artemisia dominance persisted as a consequence of a combination of environmental disturbances such as (1) strong early Holocene climate fluctuations, (2) inundation of habitats suitable for forest, (3) extensive water surfaces that served as barriers to terrestrial diaspore transport from refuge areas, (4) strong erosion that denuded the non-flooded upper slopes and (5) increasing human influence since the late glacial.     

Simultaneous measurements of tidal straining and advection at two parallel transects far downstream in the Rhine ROFI

This study identifies and unravels the processes that lead to stratification and destratification in the far field of a Region of Freshwater Influence (ROFI). We present measurements that are novel for two reasons: (1) measurements were carried out with two vessels that sailed simultaneously over two cross-shore transects; (2) the measurements were carried out in the far field of the Rhine ROFI, 80 km downstream from the river mouth. This unique four dimensional dataset allows the application of the 3D potential energy anomaly equation for one of the first times on field data. With this equation, the relative importance of the depth mean advection, straining and nonlinear processes over one tidal cycle is assessed. The data shows that the Rhine ROFI extends 80 km downstream and periodic stratification is observed. The analysis not only shows the important role of cross-shore tidal straining but also the significance of along-shore straining and depth mean advection. In addition, the nonlinear terms seem to be small. The presence of all the terms influences the timing of maximum stratification. The analysis also shows that the importance of each term varies in the cross-shore direction. One of the most interesting findings is that the data are not inline with several hypotheses on the functioning of straining and advection in ROFIs. This highlights the dynamic behaviour of the Rhine ROFI, which is valuable for understanding the distribution of fine sediments, contaminants and the protection of coasts.     

Enhancing the Sustainability of Household Fe0/Sand Filters by Using Bimetallics and MnO2

Filtration systems containing metallic iron as reactive medium (Fe⁰ beds) have been intensively used for water treatment during the last two decades. The sustainability of Fe⁰ beds is severely confined by two major factors: (i) reactivity loss as result of the formation of an oxide scale on Fe⁰ and (ii) permeability loss due to pore filling by generated iron corrosion products. Both factors are inherent to iron corrosion at pH > 4.5 and are common during the lifespan of a Fe⁰ bed. It is of great practical significance to improve the performance of Fe⁰ beds by properly addressing these key factors. Recent studies have shown that both reactivity loss and permeability loss could be addressed by mixing Fe⁰ and inert materials. For a non‐porous additive like quartz, the threshold value for the Fe⁰ volumetric proportion is 51%. Using the Fe⁰/quartz system as reference, this study theoretically discusses the possibility of (i) replacing Fe⁰ by bimetallic systems (e.g., Fe⁰/Cu⁰), or (ii) partially replacing quartz by a reactive metal oxide (MnO₂ or TiO₂) to improve the efficiency of Fe⁰ beds. Results confirmed the suitability of both tools for sustaining Fe⁰ bed performance. It is shown that using a Fe⁰:MnO₂ system with the volumetric proportion 51:49 will yield a filter with 40% residual porosity at Fe⁰ depletion (MnO₂ porosity 62%). This study improves Fe⁰ bed design and can be considered as a basis for further refinement and detailed research for efficient Fe⁰ filters.     

Long-term correlations in earth sciences

In this article we review the occurrence and consequences of long-term memory in geophysical records like climate and seismic records, and describe similarities with financial data sets. We review several methods to detect linear and nonlinear long-term correlations, also in the presence of external trends, and show how external trends can be detected in data with long-term memory. We show as well that long-term correlations lead to a natural clustering of extreme events and discuss the implications for several geophysical data sets.     

Simulating Martian regolith in the laboratory

Regolith and dust cover the surfaces of the Solar Systems solid bodies, and thus constitute the visible surface of these objects. The topmost layers also interact with space or the atmosphere in the case of Mars, Venus and Titan. Surface probes have been proposed, studied and flown to some of these worlds. Landers and some of the mechanisms they carry, e.g. sampling devices, drills and subsurface probes (“moles”) will interact with the porous surface layer. The absence of true extraterrestrial test materials in ample quantities restricts experiments to the use of soil or regolith analogue materials. Several standardized soil simulants have been developed and produced and are commonly used for a variety of laboratory experiments. In this paper we intend to give an overview of some of the most important soil simulants, and describe experiments (penetrometry, thermal conductivity, aeolian transport, goniometry, spectroscopy and exobiology) made in various European laboratory facilities.     

Dynamical mass estimates of young massive clusters in NGC1140 and M83

We present virial mass estimates of young massive clusters (YMCs) in the starburst galaxies NGC1140 and M83, determined from high spectral resolution VLT echelle spectroscopy and high spatial resolution Hubble Space Telescope imaging. The survivability of such clusters is important in testing the scenario that YMCs are potentially proto-globular clusters. As young clusters, they lie in the domain in which dynamical masses appear to overestimate true cluster masses, most likely due to the clusters not being virialised. We find that the dynamical mass of NGC1140-1 is approximately ten times greater than its photometric mass. We propose that the most likely explanation for this disparity is the crowded environment of NGC1140-1, rather than this being solely due to a lack of virial equilibrium.