Off-shore seismological experiments south of Provence in relation to “Glomar Challenger” deep sea drillings (JOIDES-DSDP,Leg 13)

The evaporitic layer located at 35 km south of Toulon, according to compressional-wave velocity measured in samples from JOIDES-DSDP Leg 13 drillings in the Mediterranean Sea, could be constituted by gypsum or anhydrite, halite having been deposited in the most central parts of the basin. These deductions are in favour of the supposed “bull's eye” structure for evaporitic layers in the Mediterranean Sea.     

Sediment community oxygen consumption in the deep Gulf of Mexico

Sediment community oxygen consumption (SCOC) has been measured from the continental shelf out to the Sigsbee Abyssal Plain in the NE Gulf of Mexico (GoM). SCOC rates on the continental shelf were an order of magnitude higher than those on the adjacent continental slope (450–2750 m depth) and two orders of magnitude higher than those on the abyssal plain at depths of 3.4–3.65 km. Oxygen penetration depth into the sediment was inversely correlated with SCOC measured within incubation chambers, but rates of SCOC calculated from either the gradient of the [O₂] profiles or the total oxygen penetration depth were generally lower than those derived from chamber incubations. SCOC rates seaward of the continental shelf were lower than at equivalent depths on most continental margins where similar studies have been conducted, and this is presumed to be related to the relatively low rates of pelagic production in the GoM. The SCOC, however, was considerably higher than the input of organic detritus from the surface-water plankton estimated from surface-water pigment concentrations, suggesting that a significant fraction of the organic matter nourishing the deep GoM biota is imported laterally down slope from the continental margin.     

Multivariate Analysis of an LA-ICP-MS Trace Element Dataset for Pyrite

Application of multivariate statistics to trace element datasets is reviewed using 164 multi-element LA-ICP-MS spot analyses of pyrite from the Moonlight epithermal gold prospect, Queensland, Australia. Multivariate analysis of variance (MANOVA) is used to demonstrate that classification of pyrite on morphological and other non-numeric factors is geochemically valid. Parallel coordinate plots and correlation cluster analysis using Spearman??s coefficients are used to discover unexpected elemental relationships without making assumptions a priori. Finally, principal component analysis and factor analysis are used to demonstrate the presence of sub-classes of pyrite. Corroborated with geological data, statistical analysis provides evidence for successive generations of hydrothermal fluids, each introducing specific metals, and for partial or complete replacement of different minerals. The data permit reinterpretation of Moonlight as a telescoped system where epithermal-Au (± base metals) is superposed onto early porphyry-Mo mineralization.     

Terrace reconstruction and long profile projection: a case study from the Solent river system near Southampton,England

River terrace sequences are important frameworks for archaeological evidence and as such it is important to produce robust correlations between what are often fragmentary remnants of ancient terraces. This paper examines both conceptual and practical issues related to such correlations, using a case study from the eastern part of the former Solent River system near Southampton, England. In this region two recent terrace schemes have been constructed using different data to describe the terrace deposits: one based mainly on terrace surfaces; the other on gravel thicknesses, often not recording the terrace surface itself. The utility of each of these types of data in terrace correlation is discussed in relation to the complexity of the record, the probability of post-depositional alteration of surface sediments and comparison of straight-line projections with modern river long profiles. Correlation using age estimates is also discussed, in relation to optically stimulated luminescence dating of sand lenses within terrace gravels in this region during the PASHCC project. It is concluded that the need for replication at single sites means that this approach has limited use for correlative purposes, although dating of sediments is important for understanding wider landscape evolution and patterns of human occupation.     

Dissipative structures in a nonlinear dynamo

This article considers magnetic field generation by a fluid flow in a system referred to as the Archontis dynamo: a steady nonlinear MHD state is driven by a prescribed body force. The field and flow become almost equal and dissipation is concentrated in cigar-like structures centred on straight-line separatrices. Numerical scaling laws for energy and dissipation are given that extend previous calculations to smaller diffusivities. The symmetries of the dynamo are set out, together with their implications for the structure of field and flow along the separatrices. The scaling of the cigar-like dissipative regions, as the square root of the diffusivities, is explained by approximations near the separatrices. Rigorous results on the existence and smoothness of solutions to the steady, forced MHD equations are given.     

Role of landscape parameters in riverine run-off,and sediment and organic matter yield on Disko Island,West Greenland

Measurements of discharge and suspended sediment and organic matter yield from nine different drainage basins on the island Disko in central West Greenland were carried out in the period 19–30 July 1997. A series of landscape properties (glacier cover, altitude, slope, aspect and vegetation cover) were measured for each drainage basin from a digital elevation model and a satellite image. Principal Component Analysis and regression statistics have been used to examine which landscape parameters dominate the measured discharges and yields. It is concluded that differences in suspended sediment and organic matter yield between the drainage basins can be explained by the measured morphometric properties while differences in water run-off can not. Glacier cover percentage and percent area above 800 m a.s.l. were the most important parameters influencing suspended sediment and organic matter yield in the drainage basins on Disko during the study period.     

Two‐dimensional lower bound analysis of offshore pile foundation systems

The objective of this paper is to present a simplified method to determine the pile foundation system capacity based on the lower bound theorem of plasticity. The motivations for determining the lower bound capacity are the following: (1) to evaluate the accuracy of solutions based on the upper bound method; (2) to provide a conservative and efficient solution to the system capacity; and (3) to provide information about load distribution among individual piles at the verge of failure for the pile system. The failure mechanisms for a single pile and for the pile system are assumed to be two‐dimensional. For a typical long offshore pile, the upper and lower bound analyses produce identical lateral capacities. A simplified failure surface for loads at the single pile head is proposed and verified through analysis of 16 case study piles. With this proposed failure surface for a single pile, the lower bound failure load of the pile foundation system is obtained using the elastic compensation method enhanced with the linear matching method. Comparing with the existing upper bound and finite element solutions, the proposed lower bound method is capable of accurately and efficiently predicting the ultimate capacity of a pile foundation system. Copyright © 2015 John Wiley & Sons, Ltd.     

Ceres lightcurve analysis—Period determination

The sidereal period of Ceres is refined from 9.075 h to 9.074170±0.000002, making use of recent and historical lightcurves spanning almost 50 years. An observed increase in the amplitude of the lightcurve with solar phase angle is consistent with bright, discrete albedo features contributing a greater fraction of light as the defect of illumination increases. Observations near the same phase angle over this time span show no evidence of changes that would indicate active surface processes.     

Modelling two‐dimensional steady‐state groundwater flow and flow sensitivity to boundary conditions in blanket peat complexes

This study used a two‐dimensional steady‐state finite‐element groundwater flow model to simulate groundwater flow in two Newfoundland blanket peat complexes and to examine flow system sensitivity to changes in water table recharge and aquifer properties. The modelling results were examined within the context of peat‐forming processes in the two complexes. Modelled flow compared favourably with observed flow. The sensitivity analyses suggested that more highly decomposed bog peat along bog margins probably has/had a positive impact on net peat accumulation within bog interiors. Peat with lower hydraulic conductivity along bog margins effectively impedes lateral drainage, localizes water table drawdown to extreme bog margins, and elevates water tables along bog interiors. Peat formation and elevated water tables in adjacent poor fens/laggs currently rely on placic and ortstein horizons impeding vertical drainage and water flow inputs from adjacent bogs. Modest reductions in atmospheric recharge were found to govern bog‐flow‐system geometries in a way that would adversely affect paludification processes in adjacent fens/laggs. Copyright © 2004 John Wiley & Sons, Ltd.