Particle saturation of the outer zone: A nonlinear model

Properties of the steady state and transient behavior of geomagnetically trapped radiation are analyzed by means of phenomenological equations that concisely summarize the operative dynamical processes. The equations provide for a realistic coupling between electromagnetic wave energy, particle intensity, and pitch-angle anisotropy in the context of the outer zone. Applications include magnetospheric enforcement of a limit on stably trapped particle flux. the smooth transition between weak pitch-angle diffusion and strong diffusion, parasitic particle precipitation by natural and man-made radio signals, natural and artificial injections of trapped radiation, and the consequences of magnetospheric cold-plasma injection.     

Interactive Knowledge Generation in Urban Green Building Transitions

Knowledge coproduction between practitioners and scientists offers promising opportunities for the emerging research field of the geography of sustainability transitions. Drawing on experiences from an international research project on urban green building transitions, this article explores the potentials and challenges of interactive and collaborative knowledge generation methods in understanding sustainability transitions. Our results show that ongoing engagement with local experts and practitioners through interactive World Café workshops and follow-up exchanges allows for a better understanding of the research context and knowledge exchange to all participants involved in the research process.     

Tourism impacts on benthic communities of sandy beaches

This study evaluated the effect of human trampling on the benthic macrofauna of two beaches in Southeast Brazil with different levels of intensity of tourism, Grussaí (more impacted) and Manguinhos (less impacted), during periods of high and low tourism activity. The macrofauna of urbanized (U) and non‐urbanized (NU) sectors of the inter‐tidal zone was sampled and the number of visitors was recorded. General linear models revealed a decreasing in abundance of macrofauna species in the urbanized sectors of analyzed beaches, which are exposed to higher trampling impact than in non‐urbanized areas. At Manguinhos Beach, trampling did not affect the macrofauna (<1 visitors ? m^?²), except for the polychaete Scolelepis sp., which was less abundant in the U sector. Considering the benthic community, Atlantorchestoidea brasiliensis, Hemipodia californiensis and Scolelepis sp. were more sensitive to human trampling pressure and may be used as potential bioindicators of tourism impact. Management plans should consider mitigation of the effects of tourism, such as the control of the visitor number and their decentralization.     

Ermittlung der Nachweis-, Erfassungs- und Bestimmungsgrenze nach DIN 32645 mit Hilfe eines Programms Calculation of Detection Limit,Identification Limit and Determination Limit according to DIN 32645 with the Aid of a Computer Programs

The new German standard specification DIN 32645 defines detection, identification and determination limit of analytical experiments and contains formulas for their calculation. The detection limit is a qualitative value, only at the determination limit a quantitative statement is possible. The identification limit is no limit of decision for analyses. The expenditure for calculating these parameters is considerable. Therefore, a computer program was developed and tested at the analysis of herbicides with GC-MS after enrichment with solid phase extraction (SPE). It proved that the program is also very useful at the development of analytical methods, because it allows a quick examination of changes of the analytical method. After optimization detection limits for the herbicides were achieved which amount 10–20% of the limit of the German drinking water regulation.     

Early Cretaceous magmatism of Mount Hermon, Northern Israel

 Early Cretaceous (146–115 Ma) magmatism in the region of Mt. Hermon, Northern Israel, is part of an extensive Mesozoic igneous province within the Levant associated with the evolution of the Neotethyan passive margin of Gondwana. The initial stages of activity were characterised by the emplacement of tholeiitic dykes (146–140 Ma) which were uplifted and eroded prior to the eruption of a sequence of alkali basalts, basanites and more differentiated alkaline lavas and pyroclastics from 127 to 120 Ma. The latest stages of activity (120–115 Ma) were highly explosive, resulting in the emplacement of diatreme breccias. Trace element and Sr-Nd-Pb isotope data for the most primitive Early Cretaceous mafic igneous rocks sampled suggest that they were derived by mixing of melts derived by variable degrees of partial melting of both garnet- and spinel-peridotite-facies mantle sources. Though isotopically heterogeneous, the source of the magmas has many similarities to that of HIMU oceanic island basalts. Earlier Liassic (200 Ma) transitional basalts and Neogene–Quaternary (15–0 Ma) alkali basalts erupted within northern Israel also have HIMU affinities. The petrogenesis of the Early Cretaceous and Cenozoic basalts is explained by partial melting of a lithospheric mantle protolith metasomatically enriched during the Liassic volcanic phase, which may be plume-related. Received: 23 July 1998 / Accepted: 6 December 1999     

Sedimentology and geochemistry of an exceptionally preserved last interglacial sapropel S5 in the Levantine Basin (Mediterranean Sea)

A combined study of lithological, geochemical and physical sediment properties is reported from a completely laminated S5 sapropel, recovered in three gravity cores (M40-4 SL67, M51-3 SL103, M51-3 SL104) from the Pliny Trench region of the eastern Mediterranean. The thickness of the studied sapropel S5 varies between 85 and 91 cm and tops most S5-sapropels in the Mediterranean. Based on optical features like color and thickness of laminae, the sapropels were subdivided into thirteen distinct lithostratigraphic zones. These zones, as well as the finer layering pattern within them, could be followed exactly among the three cores, indicating that the processes responsible for this variation acted at least on a regional scale. The sapropel sediment is characterized by exceptionally high porosity, which is strongly correlated with Si/Ca. This relationship implies that the sapropel is in essence an organic-matter rich diatomite and its exceptional thickness can be explained by preservation of diatoms forming a loosely packed sediment fabric. Compared to other S5 sapropels, the preservation of diatoms has apparently led to a twofold increase in the thickness of the sapropel layer. Relative abundances of 10 elements were determined at ultra-high resolution (0.2 mm) by XRF-scanner over the complete length of each sapropel including several cm of enclosing marl. An analysis of the chemical data indicates that the lowermost 13 cm of the sapropel is chemically more similar to the underlying marl and that the sediment chemistry shows different signals at different scales. The strongest pattern is the contrast between the sapropel and the surrounding marl, which is accentuated in elements indicative for redox conditions as well as terrigenous sediment input and productivity. Within the sapropel, a mm- to cm-scale layering is observed. The abundances of many elements are systematically linked to the pattern of these layers, indicating a common origin, related to productivity and/or terrigenous sediment and/or redox conditions. This pattern indicates a link to a regional climatic process, making the S5 sapropel horizon in M40-4 SL67, M51-3 SL103 and M51-3 SL104 a potential high-resolution archive of climatic variability during the last interglacial in the Mediterranean Sea and its adjacent landmasses.     

Stable and clumped isotopes in desert carbonate spring and lake deposits reveal palaeohydrology: A case study of the Lower Jurassic Navajo Sandstone,south‐western USA

Carbon, oxygen and clumped isotope (Δ₄₇) values were measured from lacustrine and tufa (spring)‐mound carbonate deposits in the Lower Jurassic Navajo Sandstone of southern Utah and northern Arizona in order to understand the palaeohydrology. These carbonate deposits are enriched in both ¹⁸O and ¹³C across the basin from east to west; neither isotope is strongly sensitive to the carbonate facies. However, ¹⁸O is enriched in lake carbonate deposits compared to the associated spring mounds. This is consistent with evaporation of the spring waters as they exited the mounds and were retained in interdune lakes. Clumped isotopes (Δ₄₇) exhibit minor systematic differences between lake and tufa‐mound temperatures, suggesting that the rate of carbonate formation under ambient conditions was moderate. These clumped isotope values imply palaeotemperature elevated beyond reasonable surface temperatures (54 to 86°C), which indicates limited bond reordering at estimated burial depths of ca 4 to 5 km, consistent with independent estimates of sediment thickness and burial depth gradients across the basin. Although clumped isotopes do not provide surface temperature information in this case, they still provide useful burial information and support interpretations of the evolution of groundwater locally. The findings of this study significantly extend the utility of combining stable isotope and clumped isotope methods into aeolian environments.     

Unterdevonische Baryt-Fahlerz-Mineralisation und ihre steilachsige Verformung im Gro\kogel bei Brixlegg (Tirol)

Zusammenfassung Für die Baryt-Fahlerz-Lagerstätten im Schwazer Dolomit (Unterdevon) bei Brixlegg (Tirol, Österreich) liegen sehr differierende Altersangaben zwischen Tertiär und Oberkarbon vor. Hier werden am Beispiel des Bergbaues Großkogel Befunde dargelegt, welche hydrothermale Stoffzufuhren bereits im Unterdevon wahrscheinlich machen. Es wird submarine Entstehung mit der Anlage synsedimentärer schichtkonkordanter und-diskordanter Erzkörper angenommen. Der erzführende Sedimentkomplex liegt heute als steilachsige Großfalte vor. Die primäre Paragenese, hauptsächlich bestehend aus Quarz, Pyrit, Fahlerz und Baryt, wurde samt dem Nebengestein durch die Diagenese sowie durch die Auswirkungen der variszischen und alpidischen Orogenese und epizonalen Metamorphose im Gefüge verändert.

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Early Devonian barite-tetrahedrite mineralization and its steep axial deformation in the Grosskogel near Brixlegg (Tyrol)

Summary Very different ages are attributed to the barite-tetrahedrite deposits in the Schwazer Dolomite (Early Devonian) near Brixlegg (Tyrol, Austria), varying between Tertiary and Upper Carboniferous. In this paper observations on the ore deposit of Grosskogel indicate an introduction of hydrothermal material probably in the Early Devonian. The deposit is believed to be of submarine origin with formation of synsedimentary conformable and inconformable ore bodies. The ore-bearing sedimentary complex now forms a large, steep axial fold. The primary paragenesis (consisting mainly of quartz, pyrite, tetrahedrite and barite) together with the wallrock, was altered by diagenesis, the effect of Variscian and Alpidian orogenesis, and by epizonal metamorphism.

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Mit 4 Abbildungen     

Eh ph Diagrams for mn, fe, co, ni, cu and as Under Seawater Conditions: Application of two new Types of eh ph Diagrams to the Study of Specific Problems in Marine Geochemistry

E_H pH diagrams have been calculated using the PHREEQC programme in order to establish the predominance fields of Mn, Fe, Co, Ni, Cu and As in bottom waters from the Angola Basin. Predominance fields are presented separately for both aquatic species and solid mineral phases in order to simplify interpretation of the data. The diagrams show significant differences from standard E_H pH diagrams for these elements calculated for freshwater at 25 °C and 1 bar which assume an element concentration of 10^-6 M. In particular, our diagrams show that Mn²⁺ and NiCO ₃ ⁰ are the predominant aquatic species for Mn and Ni in bottom seawater and FeOOH, Fe₂O₃, Fe₃O₄, CoFe₂O₄, CuFe₂O₄, CuFeO₂, and Ba₃ (AsO₄)₂ the predominant solid phases for Fe, Co, Cu and As, respectively. Mn and Ni are therefore undersaturated and Fe, Co, Cu and As supersaturated in bottom seawater from the Angola Basin. Neither rhodochrosite (MnCO₃) nor siderite (FeCO₃) can form in this marine environment in equilibrium with seawater. A mixed Mn-Ca carbonate is therefore formed within the pore waters of reducing sediments. The high Ni/Cu ratios in cobalt-rich manganese crusts formed adjacent to the oxygen minimum zone may be explained by the change from Cu²⁺ to CuCl ₃ ^2- as the dominant aquatic species of Cu in seawater at an E_H of +0.48 V.