Temperature evolution between 50 K and 320 K of the thermal expansion tensor of gypsum derived from neutron powder diffraction data

The unit cell parameters, extracted from Rietveld analysis of neutron powder diffraction data collected between 4.2 K and 320 K, have been used to calculate the temperature evolution of the thermal expansion tensor for gypsum for 50 ≤ T ≤ 320 K. At 300 K the magnitudes of the principal axes are α ₁₁  = 1.2(6) × 10⁻⁶ K⁻¹, α ₂₂  = 36.82(1) × 10⁻⁶ K⁻¹ and α ₃₃  = 25.1(5) × 10⁻⁶ K⁻¹. The maximum axis, α ₂₂ , is parallel to b, and using Institution of Radio Engineers (IRE) convention for the tensor orthonormal basis, the axes α ₁₁ and α ₃₃ have directions equal to (−0.979, 0, 0.201) and (0.201, 0, 0.979) respectively. The orientation and temperature dependent behaviour of the thermal expansion tensor is related to the crystal structure in the I2/a setting. Received 12 February 1998 / Revised, accepted 19 October 1998     

Geological evidence for neotectonic activity during deglaciation of the southern Sperrin Mountains,Northern Ireland

In the southern Sperrin Mountains, Northern Ireland, stacked glacigenic sequences that accumulated during deglaciation (ca. 17000–13000 yr BP) overlie a basement of jointed and mascerated bedrock. The glacigenic sequences comprise interbedded glaciotectonic shears, diamictic breccias and rock rafts. At one site a normal fault with a metre‐scale vertical displacement cuts through part of the sequence and is overlain by a glacial diamict. Sediments at an adjacent site show that faulting and associated hydrothermal activity was related to neotectonic reactivation of pre‐existing Caledonian lineaments caused by ice unloading. From stratigraphical and directional evidence, fault reactivation occurred early in the deglaciation after north central Ireland ice had retreated southwards into lowland areas, but before Sperrin Mountain ice readvanced from the north. This relationship provides evidence for the relative timing of neotectonic activity in Northern Ireland, and demonstrates the effects of glacio‐isostatic unloading near ice‐sheet centres. Copyright © 1999 John Wiley & Sons, Ltd.     

NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers

Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger‐Doll Research (SDR) equation, which is based on the Kozeny–Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. The SDR equation includes empirically determined constants. Decades of research for petroleum applications have resulted in standard values for these constants that can provide accurate estimates of permeability in consolidated formations. The question we asked: Can standard values for the constants be defined for hydrogeologic applications that would yield accurate estimates of K in unconsolidated aquifers? Working at 10 locations at three field sites in Kansas and Washington, USA, we acquired NMR and K data using direct‐push methods over a 10‐ to 20‐m depth interval in the shallow subsurface. Analysis of pairs of NMR and K data revealed that we could dramatically improve K estimates by replacing the standard petroleum constants with new constants, optimal for estimating K in the unconsolidated materials at the field sites. Most significant was the finding that there was little change in the SDR constants between sites. This suggests that we can define a new set of constants that can be used to obtain high resolution, cost‐effective estimates of K from NMR logging in unconsolidated aquifers. This significant result has the potential to change dramatically the approach to determining K for hydrogeologic applications.     

The genus Pseudo-nitzschia (Bacillariophyceae) in New Zealand: analysis of the last decade's monitoring data

The diatom genus Pseudo-nitzschia blooms throughout New Zealand's coastal waters. More than a decade of monitoring data were analysed in this study and seasonality was a significant factor in the appearance of Pseudo-nitzschia blooms. Austral spring and summer were the main bloom periods, although there were regional differences. Between January 2000 and August 2011, 8.4% of 29,000 seawater samples analysed for Pseudo-nitzschia exceeded the voluntary trigger level for biotoxin testing (10×10⁴ cells l^?1), and these were analysed by fluorescent in situ hybridisation (FISH) assays. Pseudo-nitzschia fraudulenta and P. pseudodelicatissima (low domoic acid [DA] producers) were the dominant bloom formers throughout New Zealand (each contributing 25%) followed by the highly toxic P. australis (10%). Shellfish flesh testing for DA was triggered on 8477 occasions between 2000 and 2011, but no samples exceeded the regulatory limit (20 mg/kg); the maximum concentration was 13 mg/kg (Marlborough Sounds, mid-winter 2010).     

Subglacial processes from drumlins in Clew Bay,western Ireland

Interpretation of subglacial processes and environments can be usefully informed by the stratigraphy and structures of sediments preserved within drumlins, and the down‐ice variability of these sediments. Drumlins in Clew Bay, western Ireland, were formed by westward late Pleistocene ice flow onto the Atlantic shelf, but the depositional processes and environments of these sediments remain uncertain. This study describes and interprets the drumlin stratigraphy and sediment properties and structures from two drumlins on the south side of Clew Bay. Drumlin sediments are dominated by massive to stratified diamicton deposited subglacially by deformation of flows of varying rheology. Folds, shears and clastic dikes within the sediments suggest active subglacial water flow related to variations in ice flow and ice‐bed coupling. The distal ends of the drumlins are dominated by stratified diamicton and gravel units with sandy interbeds. These sediments reflect deposition in a leeside subglacial cavity formed coevally with bedform development. A model is proposed that can account for sediment stratigraphic patterns and drumlin formation. Copyright © 2015 John Wiley & Sons, Ltd.     

Outlier separability analysis with a multiple alternative hypotheses test

Outlier separability analysis is a fundamental component of modern geodetic measurement analysis, positioning, navigation, and many other applications. The current theory of outlier separability is based on using two alternative hypotheses—an assumption that may not necessarily be valid. In this paper, the current theory of outlier separability is statistically analysed and then extended to the general case, where there are multiple alternative hypotheses. Taking into consideration the complexity of the critical region and the probability density function of the outlier test, the bounds of the associated statistical decision probabilities are then developed. With this theory, the probabilities of committing type I, II, and III errors can be controlled so that the probability of successful identification of an outlier can be guaranteed when performing data snooping. The theoretical findings are then demonstrated using a simulated GPS point positioning example. Detailed analysis shows that the larger the correlation coefficient, between the outlier statistics, the smaller the probability of committing a type II error and the greater the probability of committing a type III error. When the correlation coefficient is greater than 0.8, there is a far greater chance of committing a type III error than committing a type II error. In addition, to guarantee successful identification of an outlier with a set probability, the minimal detectable size of the outlier (often called the Minimal Detectable Bias or MDB) should dramatically increase with the correlation coefficient.     

Evaluating geological heritage: correspondence on Ruban, D.A. ‘Quantification of geodiversity and its loss’ (PGA, 2010, 121(3): 326-333)

This article comments on the recent paper in this journal by Ruban (2010) which presented a simple quantitative scheme for the calculation of landscape geodiversity and its application to evaluating geodiversity between different locations. This comment article highlights some conceptual and methodological issues in the set-up and application of Ruban's scheme, and suggests that geodiversity as a measure can only be meaningful if it is set within a wider context of landscape and geological conservation and management. Some examples of conservation strategies in Great Britain are described in order to illustrate this wider context.     

Adsorption of copper (II) on mesoporous silica: the effect of nano-scale confinement

Nano-scale spatial confinement can alter chemistry at mineral–water interfaces. These nano-scale confinement effects can lead to anomalous fate and transport behavior of aqueous metal species. When a fluid resides in a nanoporous environments (pore size under 100 nm), the observed density, surface tension, and dielectric constant diverge from those measured in the bulk. To evaluate the impact of nano-scale confinement on the adsorption of copper (Cu²⁺), we performed batch adsorption studies using mesoporous silica. Mesoporous silica with the narrow distribution of pore diameters (SBA-15; 8, 6, and 4 nm pore diameters) was chosen since the silanol functional groups are typical to surface environments. Batch adsorption isotherms were fit with adsorption models (Langmuir, Freundlich, and Dubinin–Radushkevich) and adsorption kinetic data were fit to a pseudo-first-order reaction model. We found that with decreasing pore size, the maximum surface area-normalized uptake of Cu²⁺ increased. The pseudo-first-order kinetic model demonstrates that the adsorption is faster as the pore size decreases from 8 to 4 nm. We attribute these effects to the deviations in fundamental water properties as pore diameter decreases. In particular, these effects are most notable in SBA-15 with a 4-nm pore where the changes in water properties may be responsible for the enhanced Cu mobility, and therefore, faster Cu adsorption kinetics.