Interpretation of the magnetic field from a sphere in the wavenumber domain

A Fourier transformation of the magnetic field from a magnetized sphere allows a particularly simple interpretation of the parameters of the sphere. The depth to the centre and total magnetic moments of the sphere are related to the intercept and slope of the power spectrum. The horizontal centre and direction of magnetization are related to slope and intercept of the phase spectra in two perpendicular, horizontal directions. Examples with artificial data contaminated by various noise components are presented.     

Nd isotopic variations of Phanerozoic paleoceans

The size of various Phanerozoic paleoceans, determined from paleogeographic maps, provides a framework for assigningε_Nd measurements of primary authigenic marine minerals to individual paleoceans and for establishing theirε_Nd versus age curves. We report newε_Nd data (in the range from 80 to 750 Ma) for the largest Phanerozoic and Late Precambrian paleocean, the Pacific/Panthalassa Ocean (PPO), and limited data on some small Paleozoic paleoceans. These new data and all other published data on paleoceanε_Nd values are used to determine the trends through time ofε_Nd in seven Phanerozoic paleoceans. The variations in paleoceanε_Nd curves are due to changes in the rate of crustal additions and in paleoceanic geometry. From these data we can calculate a meanε_Nd curve and a mean Nd model age curve for Phanerozoic seawater. These curves show large variations with age and reflect the variations ofε_Nd in erosion products from the continents as a function of age. The high erosion rates of young, uplifted areas enhanceε_Nd and Nd model age variations of Phanerozoic seawater. This makes it difficult to quantitatively recover crustal addition rates from these curves; however, it makes the episodic nature of continental additions more evident.     

Resolving the Holocene alluvial record in southeastern Australia using luminescence and radiocarbon techniques

A previous assessment of radiocarbon (¹⁴C) dates from alluvial units in southeastern Australia revealed a gap in the geochronological record that coincides with the Holocene climatic optimum. This gap in the alluvial record can be further refined using optically stimulated luminescence (OSL). The chronology of Holocene river terraces on Widden Brook, a sandy alluvial stream in southeastern Australia, was established using ¹⁴C and OSL techniques. Combined use of these independent techniques allows for a more rigorous assessment of the alluvial record. The robust chronology, consisting of 38 ¹⁴C and 11 OSL samples, permitted identification of significant depositional variation within the catchment, resulting from localised geomorphic processes. The three terrace sequences identified yielded distinct chronologies, suggesting alluvial deposition at different times. The sequences exhibited a continuous chronology, which indicated continuous deposition throughout the Holocene. The chronology of terrace sequences within this catchment suggests that terrace formation can be attributed to localised geomorphic processes rather than climatic forcing. Copyright © 2010 John Wiley & Sons, Ltd.     

Pedotransfer functions estimating soil hydraulic properties using different soil parameters

Estimates of soil hydraulic properties using pedotransfer functions (PTF) are useful in many studies such as hydrochemical modelling and soil mapping. The objective of this study was to calibrate and test parametric PTFs that predict soil water retention and unsaturated hydraulic conductivity parameters. The PTFs are based on neural networks and the Bootstrap method using different sets of predictors and predict the van Genuchten/Mualem parameters. A Danish soil data set (152 horizons) dominated by sandy and sandy loamy soils was used in the development of PTFs to predict the Mualem hydraulic conductivity parameters. A larger data set (1618 horizons) with a broader textural range was used in the development of PTFs to predict the van Genuchten parameters. The PTFs using either three or seven textural classes combined with soil organic mater and bulk density gave the most reliable predictions of the hydraulic properties of the studied soils. We found that introducing measured water content as a predictor generally gave lower errors for water retention predictions and higher errors for conductivity predictions. The best of the developed PTFs for predicting hydraulic conductivity was tested against PTFs from the literature using a subdata set of the data used in the calibration. The test showed that the developed PTFs gave better predictions (lower errors) than the PTFs from the literature. This is not surprising since the developed PTFs are based mainly on hydraulic conductivity data near saturation and sandier soils than the PTFs from the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

Fatal ingestion of floating net debris by two sperm whales (Physeter macrocephalus)

In 2008 two male sperm whales (Physeter macrocephalus) stranded along the northern California coast with large amounts of fishing net scraps, rope, and other plastic debris in their stomachs. One animal had a ruptured stomach, the other was emaciated, and gastric impaction was suspected as the cause of both deaths. There were 134 different types of nets in these two animals, all made of floating material, varying in size from 10 cm² to about 16 m². The variability in size and age of the pieces suggests the material was ingested from the surface as debris rather than bitten off from active gear. These strandings demonstrate that ingestion of marine debris can be fatal to large whales, in addition to the well documented entanglements known to impact these species.