Tracing end-member fluid sources in sub-surface iron mineralization and dolomitization along a proximal fault to the dead sea transform

Shear faults in Upper Cretaceous limestones of the central Negev desert adjacent to the Dead Sea Transform (DST) feature extensive ferruginous mineralization and dolomitization. This has been related to topographically driven flow of metalliferous groundwaters through an underlying clastic (Nubian Sandstone) aquifer and rise of the fluids up the fault zones. The present study combines Pb and Sr isotope measurements with detailed sampling and petrography at the eastern end of the Paran fault (Menuha Ridge) in order to identify the types of groundwater and the sources of enriched elements in this regional-scale sedimentary mineralization. Ferroan and non-ferroan dolomitization along the Paran fault caused significant enrichment of several elements (Mg, Cu, Mn, Ni, V, Zn, Pb, and U) and ⁸⁷Sr/⁸⁶Sr values that are significantly higher than the Upper Cretaceous limestone country rock. The non-ferroan dolomite and the ferroan dolomite sampled at three sites along the Menuha Ridge have similar ⁸⁷Sr/⁸⁶Sr values 0.7076-0.7089, and 0.7077-0.7086, respectively. Additionally, there is a positive correlation between Mg-content of the dolomites and their ⁸⁷Sr/⁸⁶Sr values. The isotopic composition of Sr and Pb of dolomite corresponds to the mineralogical type identified in the mineralized rock (non-ferroan dolomite, simple-zoned ferroan dolomite, and complex-zoned ferroan dolomite). The ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb ratios of Fe oxides and dolomites from the three sites plot on a straight line, where the simple-zoned ferroan dolomite values are at the non-radiogenic end of the line and the complex-zoned ferroan dolomites at the radiogenic end. Both ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁷Pb/²⁰⁴Pb ratios in dolomites and to a lesser degree in Fe-oxides suggest that a mixing between two end-members controls the behavior of Pb in the mineralization products along the Paran fault. Rather than a single fluid source, the study indicates that two types of metalliferous groundwaters were involved in the dolomitization and mineralization along the Paran fault. The first, and hitherto undocumented, fluid source is the Mg-rich Dead Sea Rift brine, migrating in the sub-surface before dolomitizing the carbonate bedrock. Migration of the brines took a deep path to the site of mineralization, with temperatures reaching 75 °C. Based on the geological history of the region, this probably took place in the Late Miocene-Early Pliocene interval. The second type of groundwater acquired its high solute concentrations from leaching igneous rocks and clastic sediments in the sub-surface, and infiltrated along the Paran fault, precipitating Fe-rich minerals and caused the first stage of dolomitization. This groundwater flowed at shallower depth than the DSR brines, and at lower temperatures (T ? 50 °C). The study shows that sedimentary mineralization in faults adjacent to active transform fault zones may arise from the combination of several different fluid flow regimes.     

Trade unions and climate change: The jobs versus environment dilemma

Trade unions are actively engaging with the climate change agenda and formulating climate change policies. Although governments are placing considerable effort on changing consumer behaviour, arguably the most significant impacts on climate change will be through changes in production. Even changes in consumption will have consequences for production. Changes in production will affect workers through the loss of jobs, the changing of jobs, and the creation of new jobs. The jobs versus environment dilemma is a significant issue affecting workers worldwide. In this paper we focus on the ways in which international trade unions are conceptualising the relationship between jobs and the environment, which provide the point of departure from which climate change policies can be formulated. Extended interviews were conducted with senior policy makers in national and international trade unions. On the basis of their responses, four discourses of trade union engagement with climate change are discussed: ‘technological fix’, ‘social transformation’, ‘mutual interests’ and ‘social movement’, which are theorised in the context of the different international histories and models of trade unionism. All discourses imply a re-invention of unions as social movements but do not see nature as a partner in human development.     

Assessment of soil losses and siltation of the K’sob hydrological system (semiarid area—East Algeria)

Soil losses and siltation of the hydrological system (watershed–dam) of K’sob were obtained using direct and indirect methods. The Wadi K’sob watershed of 1,484 km², average slope of 0.14, and average elevation of 1,060 m is located in a semiarid climate. The average annual rainfall is 341 mm and the mean annual water discharge is 0.89 m³/s. Data from the Medjez gauging station located 6 km upstream of the dam, are the daily liquid flow and instantaneous concentrations of suspended sediments. Over a time period from 1973 to 2010, the relationship between water and sediment discharges is quantified by the equation: Q _s?=?5.6 Q ^1.31. Thus, in view of the availability data on a daily scale, the assessment of soil erodibility of the K’sob watershed was used to estimate specific soil losses of 203 t?km^?2?year^?1or 301,000 t eroded annually from the K’sob basin. The bathymetric measurements of the sediment volumes deposited in the K’sob dam, has quantified the annual siltation of 0.8 hm³, corresponding to an average erodibility of the K’sob watershed of 809 t?km^?2?year^?1. However, when adding the volume of sediment removed by the dredging operation and de-silting by the valves during heavy floods, the value of soil losses is 2,780 t?km^?2?year^?1. The indirect assessment of soil erodibility of the basin was obtained by applying two models: the quantitative geomorphological analysis (QGA) and PISA model (prediction of silting in the artificial reservoirs, in Italian: Previsioni dell’Interimento nei Serbatoi Artificiali) using physical and climatic factors in the watershed. The obtained results by QGA method underestimate specific soil losses of 524 t?km^?2?year^?1. The PISA model gives a value of 2,915 t?km^?2?year^?1, which is close to the value obtained by bathymetric measurements. This study concludes that PISA model is most suitable to estimate soil loss and siltation of the K’sob hydrological system.     

Diatom assemblage changes in lacustrine sediments from Isla de los Estados, southernmost South America, in response to shifts in the southwesterly wind belt during the last deglaciation

Isla de los Estados (54° 45′S, 63° 10′–64° 46′W) lies east of the main island of Tierra del Fuego and is the southeastern-most point in Argentina. Because of its geographic position near the latitudes of the Southern Hemisphere Westerlies and the strong influence of the Antarctic Circumpolar Current (ACC), the area is suitable for paleoecological and paleoclimate research. The island is not far north of the Subantarctic Front, which limits the northern boundary of the ACC. Paleoenvironmental study in this geographic location can shed light on past changes in atmospheric and marine circulation patterns. Diatom analysis of the lower part of a sediment sequence from Laguna Cascada (54° 45′ 51.3′′S, 64° 20′ 20.07′′W) enabled inference of changing lake conditions between 16 and 11.1 cal ka BP. Between 16 and 14.4 cal ka BP fragilarioid diatom species, often a pioneer group, dominated the record. Their presence shows seasonally open-water conditions from the onset of sedimentation. In zone II (14.4–12.8 cal ka BP), the dominance of planktonic/tychoplanktonic Aulacoseira spp. might represent longer ice-free periods and windier conditions, which would have kept this heavy species suspended in the water column. This period corresponds to the Antarctic Cold Reversal, when the Southern Hemisphere Westerlies were possibly centered on the latitudes of Tierra del Fuego, resulting in windy and wet conditions. Zone III (12.8–11.1 cal ka BP) is dominated by benthic diatom taxa that are mainly associated with peat and wetland vegetation. This suggests that climate conditions had become milder and less windy, favoring aquatic productivity and terrestrial vegetation development. This change in environmental conditions may have been a consequence of the southward movement of the Southern Hemisphere Westerlies at the start of the Antarctic Holocene thermal optimum.     

Tsunami Wave Analysis and Possibility of Splay Fault Rupture During the 2004 Indian Ocean Earthquake

The 2004 Indian Ocean tsunami was observed by two satellites, close in space and time, that traversed the Indian Ocean 2?h after the Sumatra–Andaman earthquake, but which observed different tsunami lead wave morphologies. The earlier satellite, Jason-1, recorded a lead wave with two peaks of similar amplitude and wavelength, while the later satellite, TOPEX/Poseidon, recorded a lead wave with only one longer wavelength uplift. To resolve this disparity, we examine the travel paths of long wavelength waves over the seafloor bathymetry. Waves traveling from the margin will traverse significantly different paths to arrive at the two satellite transects. The result is that the satellites are sensitive to different parts of the margin; Jason-1 is highly sensitive to the margin in the area of the epicenter, while TOPEX is sensitive to a more northerly section. By developing solutions of the ocean gravity wave equations, accounting for dispersion, we show that the double peak of the Jason-1 satellite observations are consistent with coseismic rupture of a splay fault of limited along-strike extent, located north of Simeulue Island. The doubly peaked morphology can be reproduced with co-activation of the subduction zone interface and the splay fault, which creates a seafloor uplift pattern with two distinct areas of uplift. The Jason-1 satellite is sensitive to a splay fault in this portion of the margin, whereas the TOPEX satellite would not be significantly affected by this uplift pattern. By back-projecting satellite observation points to the margin, we constrain the location of the proposed splay fault and find that it correlates with a bathymetric high. The aftershock locations, uplift of corals on Simeulue Island and a fault scarp on Pulau Salaut Besar are also consistent with the activation of a splay fault in the area delimited by the back-projection. Our work also shows that it is critical to fully capture gravity wave dispersion in order to represent features of the lead wave profile that may not be as well characterized by the shallow water (long-wavelength) model. It is also necessary to account for dispersion so as to precisely assess wavefront travel times; this leads us to conclude that the rupture must have reached very near to the trench and propagated with an updip rupture velocity of order 2.0?km/s or more.     

Creating a greater partnership: analysing partnership in the Catholic Church development chain

This paper presents results from a project designed to explore the meaning and function of partnership within the Catholic Church development chain. The geography literature has had little to say about such aid chains, especially those founded on faith-based groups. The relationships between three Catholic Church-based donors – referred to as A, B and C – with development personnel of the diocese of the Abuja Ecclesiastical Province (AEP) as well as other Catholic Church structures in Nigeria were analysed. The aim was to explore the forces behind the relationships and how 'patchy' these relationships were in AEP. Respondents were asked to give each of the donors a score in relation to four questions covering their relationship with the donors. Results suggest that the modus operandi of donor 'A' allows it to be perceived as the 'best' partner, while 'B' was scored less favourably because of a perception that it attempts to act independently of existing structures in Nigeria rather than work through them. There was significant variation between diocese in this regard, as well as between the diocese and other structures of the Church (Provinces, Inter-Provinces and National Secretariat). Thus 'partnership' in the Catholic Church aid chain is a highly complex, contested and 'visioned' term and the development of an analytical framework has to take account of these fundamentals.     

Biological risk and pollution history of polycyclic aromatic hydrocarbons (PAHs) in Nansha mangrove,South China

Chinese government has taken various measures to alleviate pollution caused by polycyclic aromatic hydrocarbons (PAHs) in the region of Pearl River Delta since the economic reform in 1978, but the effectiveness of these measures remains largely unknown. This study aimed to elucidate the biological risk and pollution history of PAHs by measuring the concentrations of 28 PAHs in the surface and core sediments, respectively, in Nansha mangrove. Results found that the biological risk of PAHs was low without obvious spatial variation. The PAH concentration along the depth gradient indicated that PAH pollution was stabilized since the early 1990s while the source of PAHs has gradually changed from combustion of coal to petroleum products. This implied that the mitigation measures taken by the Chinese government were effective. Compared to marine bottom sediment, we propose that using mangrove sediment can provide a more accurate and precise estimate of pollution history of PAHs.     

The criteria for the biogeneicity of microbially induced sedimentary structures (MISS) in Archean and younger, sandy deposits

The identification of fossils or biogenic sedimentary structures in rocks of Archean age is difficult, because similar lithological features could rise from purely physical or chemical processes alone. Therefore it is important to define criteria that serve the secure definition of a fossil or structure in question as of biological origin. Such criteria have been established for stromatolites and microfossils.This contribution discusses the 6 criteria of biogeneicity of ‘microbially induced sedimentary structures’ (MISS). Those structures are found in sandy deposits of early Archean age to the present, and rise from the interaction of benthic microbiota with physical sediment dynamics. The six criteria for their biogeneicity are: (i) MISS occur in rocks of not more than lower greenschist facies; (ii) in stratigraphic sections, MISS correlate with turning points of regression–trangressions; (iii), MISS correlate with a characteristic depositional facies that enhances the development and the preservation of microbial mats; (iv), the distribution of MISS correlates with the ancient average hydraulic pattern; (v), the geometries and dimensions of fossil MISS correspond to that of the modern ones; (vi), the MISS include at least one of 9 specific microtextures.