The growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass : a case study from Spireslack Surface Coal Mine, Scotland

Fault architecture and fracture network evolution (and resulting bulk hydraulic properties) are highly dependent on the mechanical properties of the rocks at the time the structures developed. This paper investigates the role of mechanical layering and pre-existing structures on the evolution of strike–slip faults and fracture networks. Detailed mapping of exceptionally well exposed fluvial–deltaic lithologies at Spireslack Surface Coal Mine, Scotland, reveals two phases of faulting with an initial sinistral and later dextral sense of shear with ongoing pre-faulting, syn-faulting, and post-faulting joint sets. We find fault zone internal structure depends on whether the fault is self-juxtaposing or cuts multiple lithologies, the presence of shale layers that promote bed-rotation and fault-core lens formation, and the orientation of joints and coal cleats at the time of faulting. During ongoing deformation, cementation of fractures is concentrated where the fracture network is most connected. This leads to the counter-intuitive result that the highest-fracture-density part of the network often has the lowest open fracture connectivity. To evaluate the final bulk hydraulic properties of a deformed rock mass, it is crucial to appreciate the relative timing of deformation events, concurrent or subsequent cementation, and the interlinked effects on overall network connectivity

Core surprise : Characterising the internal structure of an ancient plate boundary fault in Scotland

Knowledge of the structure and rheology of large, earthquake-hosting plate boundary faults is lacking as they are normally poorly exposed or difficult to find on the surface. Recently, several drilling projects have been undertaken to explore the internal structure of active plate boundary fault zones at depth to understand how this constrains seismic slip behaviour. All of these projects highlight the presence and importance of clay-rich rocks within the fault core in controlling slip behaviour along these large faults. The Highland Boundary fault (HBF) in Scotland, provides a rare opportunity to study the internal fault architecture of a well-exposed along-strike section of an ancient plate boundary fault. The HBF extends for over 240 km, however, is only well-exposed along a 560 m section at Stonehaven. Here, serpentinite juxtaposes quartzofeldspathic crustal rocks, a common feature at many plate boundaries (e.g., sections of the San Andreas fault and Alpine fault, New Zealand). We collected six across-fault transects aiming to capture the internal structure of the HBF and its along-strike variability. Within the fault core we discover four mechanically and chemically distinct clay-rich units, which have sharp contacts. Despite evidence of internal strain within the clay-rich fault rocks, relatively intact clasts of wall rock and microfossils are preserved. From mineralogical observations it can be interpreted that the clay-rich rocks along this section of the HBF, formed through fluid-assisted, shear-enhanced chemical reactions between wall rocks of contrasting chemistry. Our field evidence also demonstrates that plate boundary faults can be structurally variable along strike at various scales. The total thickness of the fault core varies from 3 to 10.7 m over an along strike distance of 560 m. Not every unit is laterally continuous along strike, and each unit varies in thickness. We compare our observations with studies on other plate boundary systems. For example, the HBF has analogous thickness and mineralogy to drill core recovered from the San Andreas fault. Highly variable fault core structures and related properties such as mineralogy, may exert significant control on earthquake rupture and slip behaviour at large plate boundaries

Amplified Concern for Social Risk in Adolescence: Development and Validation of a New Measure.

In adolescence, there is a heightened propensity to take health risks such as smoking, drinking or driving too fast. Another facet of risk taking, social risk, has largely been neglected. A social risk can be defined as any decision or action that could lead to an individual being excluded by their peers, such as appearing different to one's friends. In the current study, we developed and validated a measure of concern for health and social risk for use in individuals of 11 years and over (N = 1399). Concerns for both health and social risk declined with age, challenging the commonly held stereotype that adolescents are less worried about engaging in risk behaviours, compared with adults. The rate of decline was steeper for social versus health risk behaviours, suggesting that adolescence is a period of heightened concern for social risk. We validated our measure against measures of rejection sensitivity, depression and risk-taking behaviour. Greater concern for social risk was associated with increased sensitivity to rejection and greater depressed mood, and this association was stronger for adolescents compared with adults. We conclude that social risks should be incorporated into future models of risk-taking behaviour, especially when they are pitted against health risks

A nocturnal atmospheric loss of CH2I2 in the remote marine boundary layer

This is the final version of the article. It was first available from Springer via http://dx.doi.org/10.1007/s10874-015-9320-6Ocean emissions of inorganic and organic iodine compounds drive the biogeochemical cycle of iodine and produce reactive ozone-destroying iodine radicals that influence the oxidizing capacity of the atmosphere. Di-iodomethane (CH?I?) and chloro-iodomethane (CH?ICl) are the two most important organic iodine precursors in the marine boundary layer. Ship-borne measurements made during the TORERO (Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOC) field campaign in the east tropical Pacific Ocean in January/February 2012 revealed strong diurnal cycles of CH?I? and CH?ICl in air and of CH?I? in seawater. Both compounds are known to undergo rapid photolysis during the day, but models assume no night-time atmospheric losses. Surprisingly, the diurnal cycle of CH?I? was lower in amplitude than that of CH?ICl, despite its faster photolysis rate. We speculate that night-time loss of CH?I? occurs due to reaction with NO? radicals. Indirect results from a laboratory study under ambient atmospheric boundary layer conditions indicate a k_(CH?I?+NO?) of ?4 ? 10??? cm? molecule?? s??; a previous kinetic study carried out at ?100 Torr found k_(CH?I?+NO?) of 4 ? 10??? cm? molecule?? s??. Using the 1-dimensional atmospheric THAMO model driven by sea-air fluxes calculated from the seawater and air measurements (averaging 1.8 +/? 0.8 nmol m?? d?? for CH?I? and 3.7 +/? 0.8 nmol m?? d?? for CH?ICl), we show that the model overestimates night-time CH?I? by >60 % but reaches good agreement with the measurements when the CH?I?+ NO? reaction is included at 2?4 ? 10??? cm? molecule?? s??. We conclude that the reaction has a significant effect on CH?I? and helps reconcile observed and modeled concentrations. We recommend further direct measurements of this reaction under atmospheric conditions, including of product branching ratios.LJC acknowledges NERC (NE/J00619X/1) and the National Centre for Atmospheric Science (NCAS) for funding. The laboratory work was supported by the NERC React-SCI (NE/K005448/1) and RONOCO (NE/F005466/1) grants

Saltmarsh blue carbon accumulation rates and their relationship with sea-level rise on a multi-decadal timescale in northern England

Feldwork and elemental and thermogravimetric analyses were conducted as a part of the NERC funded (NE/R010846/1) Carbon Storage in Intertidal Environments (C-SIDE) project (https://www.c-side.org/).Saltmarshes are widely thought to sequester carbon at rates significantly exceeding those found in terrestrial environments. This ability arises from the in-situ production of plant biomass and the effective trapping and storage of both autochthonous and allochthonous organic carbon. The role saltmarshes play in climate change mitigation, through accumulating ‘blue’ carbon, depends on both the rate at which carbon accumulates within sediments and the rapidity with which carbon is remineralised. It has been hypothesized that carbon accumulation rates, in turn, depend on the local rate of relative sea-level rise, with faster sea-level rise providing more accommodation space for carbon storage. This relationship has been investigated over long (millennial) and short (decadal) timescales but without accounting for the impact of higher quantities of labile carbon in more recently deposited sediment. This study addresses these three key aspects in a saltmarsh sediment study from Lindisfarne National Nature Reserve (NNR), northern England, where there is a comparatively pristine marsh. We quantify rates of carbon accumulation by combining a Bayesian age-depth model based on 210Pb and 137Cs activities with centimetre-resolution organic carbon density measurements. We also use thermogravimetric analyses to determine the relative proportions of labile and recalcitrant organic matter and calculate the net recalcitrant organic matter accumulation rate. Results indicate that during the 20th century more carbon accumulated at the Lindisfarne NNR saltmarsh during decades with relatively high rates of sea-level rise. The post-depositional loss of labile carbon down the core results in a weaker though still significant relationship between recalcitrant organic matter accumulation and sea-level change. Thus, increasing saltmarsh carbon accumulation driven by higher rates of sea-level rise is demonstrated over recent multi-decadal timescales.Peer reviewe