Tube-like schlieren structures in the Fürstenstein Intrusive Complex (Bavarian Forest,Germany): Evidence for melt segregation and magma flow at intraplutonic contacts

Tube-like schlieren structures occur at the boundary between two units of the Fürstenstein Intrusive Complex, the Tittling and the Saldenburg granites. We have analysed the magnetic fabrics, petrographic variation and geochemistry of key examples of these structures in order to test the hypothesis that they originated as granitic microdiapirs. The rims of the schlieren structures have high magnetic susceptibility compared to their interiors and surrounding granite due to the enrichment of biotite ± opaques. The low anisotropy that characterizes the AMS fabric is probably caused by magmatic flow. Hypersolidus microfabrics support this interpretation. Magnetic fabric orientation within the schlieren structures differs significantly from the NE–SW-trending magnetic foliation generally observed within the hosting Tittling granite. A steeply plunging magnetic lineation and a NNE–SSW girdle distribution of the magnetic foliation poles within the schlieren structures are consistent with the conical geometry of the schlieren structures evolved during the rise of the magma. Based on geochemistry, granite in the schlieren structures is interpreted to be differentiated melt expelled from the Tittling granite mush that formed after early crystallization of plagioclase. We suggest that the schlieren structures are pockets of residual melt of the Tittling granite that were mobilized buoyantly due to a thermal input from the neighbouring Saldenburg granite. The mafic rims of the schlieren structures formed as a result of early crystallization and subsequent accumulation due of the Bagnold effect. The results of the magnetic and geochemical investigations allow us to interpret the schlieren structures as diapiric in nature and consequently as “within-chamber diapirs” (sensu Weinberg et al., 2001).     

From contesting to conversing about resilience: kickstarting measurement in complex research environments

Natural Hazards - Landslides are one of the most damaging disastrous phenomena that frequently lead to serious problems in hilly areas. The Namchi region of South Sikkim district as a part of...     

Changes in atmospheric circulation and the Arctic Oscillation preserved within a millennial length reconstruction of summer cloud cover from northern Fennoscandia

Cloud cover currently represents the single greatest source of uncertainty in General Circulation Models. Stable carbon isotope ratios (δ¹³C) from tree-rings, in areas of low moisture stress, are likely to be primarily controlled by photosynthetically active radiation (PAR), and therefore should provide a proxy record for cloud cover or sunshine; indeed this association has previously been demonstrated experimentally for Scots pine in Fennoscandia, with sunlight explaining ca 90% of the variance in photosynthesis and temperature only ca 4%. We present a statistically verifiable 1011-year reconstruction of cloud cover from a well replicated, annually-resolved δ¹³C record from Forfjord in coastal northwestern Norway. This reconstruction exhibits considerable variability in cloud cover over the past millennium, including extended sunny periods during the cool seventeenth and eighteenth centuries and warm cloudy periods during the eleventh, early fifteenth and twentieth centuries. We find that while a generally positive relationship persists between sunshine and temperature at high-frequency, at lower (multi-decadal) frequencies the relationship is more often a negative one, with cool periods being sunny (most notably the Little Ice Age period from 1600 to 1750 CE) and warm periods more cloudy (e.g. the mediaeval and the twentieth century). We conclude that these long-term changes may be caused by changes in the dominant circulation mode, likely to be associated with the Arctic Oscillation. There is also strong circumstantial evidence that prolonged periods of high summer cloud cover, with low PAR and probably high precipitation, may be in part responsible for major European famines caused by crop failures.     

The radio–optical correlation in steep-spectrum quasars

Using complete samples of steep-spectrum quasars, we present evidence for a correlation between radio and optical luminosity which is not caused by selection effects, nor caused by an orientation dependence (such as relativistic beaming), nor a by-product of cosmic evolution. We argue that this rules out models of jet formation in which there are no parameters in common with the production of the optical continuum. This is arguably the most direct evidence to date for a close link between accretion on to a black hole and the fuelling of relativistic jets. The correlation also provides a natural explanation for the presence of aligned optical/radio structures in only the most radio-luminous high-redshift galaxies.     

Patterns of unsuccessful shell-crushing predation along a tidal gradient in two geographically separated salt marshes

Gradients in salt marsh ecosystems that result from reduced tidal inundation time in the high marsh offer an opportunity to assess the importance of predation as a selective agent (indexed by the time-averaged record of unsuccessful predation, which integrates potentially confounding short-term – inter-seasonal and inter-annual – fluctuations in predation pressure). Spatial patterns in selection pressure are expected to decrease landward from the seaward edge of the marsh. Interaction between shell-breaking predators and their snail prey, Littoraria irrorata, however, generated a pattern in the frequency of sublethal injury (shell repair), standardized for snail size, that did not follow this simple, single-variable prediction of decreasing repair frequencies with distance from the seaward edge of the marsh, based on inundation time alone. Patterns of repair frequency increased landward from the seaward edge of the marsh, only declining as predicted after a zone of dense stands of salt marsh grass. The interaction of tidal inundation time and primary habitat structure ( e.g. physical vegetative barriers to dispersion of predators into the marsh) is hypothesized to shape selection gradients in salt marshes, as inferred from the record of unsuccessful predation.     

The Canada-Newfoundland Atlantic Accord Implementation Act: Transparency of the environmental management of the offshore oil and gas industry

This paper considers the overall outcome of a “public environmental audit” of the government management of the oil and gas offshore industry in eastern Canada. Five requests for data sets were placed using the Access to Information Act; all five requests were denied by the Canada-Newfoundland Labrador Offshore Petroleum Board. This lack of access to environmental monitoring data significantly hinders the ability of independent scientific inquiry and/or public involvement in the environmental assessment process.     

Towards a critical analysis of fictive geographies

Summary The recent 'culture turn' in geography has generated a good deal of interest in the structure of scientific knowledge and modes of writing, but there has less attention to the construction of other forms of knowledge and writing. While humanistic and regional geographers have referred to literature on the whole without comment on genre, mode of production or range of consumption, more recent critical geographers have regarded literature as a material artefact which fulfils a role designated by its position in various social and economic processes. This paper critiques both positions as offering a limited vision of the relationship between geography and literature and attempts to offer an engagement with literary fiction which analyses the content and form of the text, but also leaves room for its distinctive voice.     

Erosion-driven drawdown of atmospheric carbon dioxide: The organic pathway

Rapidly eroding, coastal mountain belts, where steep rivers and submarine channels connect upland sources to nearby marine sinks are hotspots of organic carbon transfer from life biomass, soil and exhumed bedrock into geological storage. Using observations from the Southern Alps of New Zealand, and Taiwan, we have mapped this organic pathway to geological carbon sequestration, and can evaluate the magnitude and efficiency of transfers between sources and sinks. We demonstrate that POC is harvested by landsliding, but importantly also by common and widespread surface runoff on steep hillslopes. Although terrestrially sourced POC is found in many sedimentary environments associated with mountain belts and frontier basins, it appears to be most abundantly trapped and preserved in marine turbidites. The loss of all forms of POC in onward transport through short, steep routing systems to this repository is limited. This is in marked contrast to larger routing systems, in which only the most resilient forms of POC survive into long-term deposition.     

Heavy metals in surface sediments of Waiwhetu Stream,Lower Hutt,New Zealand

Abstract

Surface sediment samples (60 μm‐2 mm, and < 60 μm fractions) from the Waiwhetu Stream, Lower Hutt City, New Zealand, were leached with dilute HCl to remove the mobile heavy‐metal fraction. Cd, Cr, Cu, Pb, Zn, Al, Fe, and Mn analyses of the leachates show that sediments of the upper reaches area of the stream are generally uncontaminated. In contrast, sediments in the lower reaches area are highly contaminated, despite clean‐up measures in the late 1970s. Lead and Zn are the most significantly enriched metals with concentrations over 1000 mg kg^?1 adjacent to some drains. In the polluted zone, metals originate from either upward remobilisation from underlying sediment (contaminated in the early 1960s and 70s) or more recent industrial spillages. Similar trends exhibited by Cd, Cu, Cr, Zn, Pb, and Al indicate that a proportion of the metal enrichment downstream probably results from a naturally higher clay content of sediments near the mouth of the stream. Fe and Mn show reverse trends to the other metals, indicating that a high proportion of these two metals occurs in substrate different to that of the other metals. The orange brick‐coloured sediments of the upper reaches of the stream indicate oxides upstream; the black sediments in the lower reaches indicate sulphides downstream.