Reconstruction of phosphate formation environments (from data on distribution of lanthanides)

The criteria for the evaluation of the REE composition of phosphorites and sedimentary rocks have been determined. These data are required to reconstruct depositional environments. Literature data on the geochemistry of some phosphorite deposits of Eurasia are considered. The REE patterns of Mesozoic phosphorites of the East European Platform are studied. On the basis of REE contents, the ratios of lanthanides and fields on the La–(Nd + Sm)–(Y + Dy), La–(Ce + Nd + Sm)–(Y + Dy), and LREE–MREE–(HREE×10) diagrams have been determined as indicators of climate and the depth and facies conditions of sedimentation.     

Evaluation of short-term fallowing as a strategy for the management of recurring organic enrichment under salmon cages

Rotation of cages within fish farm leases and the subsequent fallowing of areas of seabed is commonly used to allow recovery of infaunal communities following periods of organic enrichment. To investigate the effect of different background environmental conditions on recovery response, two Atlantic salmon (Salmo salar) fish farm sites in southeast Tasmania were sampled over two commercial fallowing cycles. Despite similar stocking levels and feed input there were significant differences in the way in which sediment at each farm responded to the cessation of fish stocking. Sediments at both farms showed some improvement in the community structure over a three month fallow period, but the community structure only recovered to that present before stocking not to that at the reference sites. The similarity of the impact sites to the reference sites increased from ca. 25% to 31% at one site and 11% to 27% at the other after fallowing. Rate and extent of recovery were affected by farm location, initial impact of the sediments, and length of fallow period. Initial recovery was faster at the more sheltered site than at the more exposed site, possibly reflecting differences in environmental resilience with the more sheltered location better able to assimilate organic inputs. Accordingly general fallowing management protocols may need to be adapted to reflect differences between sites. The findings of this study suggest that the recovery response of benthic communities can be predicted once baseline conditions are understood.     

Forest fragmentation in Massachusetts,USA: a town-level assessment using Morphological spatial pattern analysis and affinity propagation

Forest fragmentation has been studied extensively with respect to biodiversity loss, disruption of ecosystem services, and edge effects although the relationship between forest fragmentation and human activities is still not well understood. We classified the pattern of forests in Massachusetts using fragmentation indicators to address these objectives: 1) characterize the spatial pattern of forest fragmentation in Massachusetts towns using Morphological Spatial Pattern Analysis (MSPA); and (2) identify regional trends using archetypal towns in relation to town history, geography and socioeconomic characteristics. Six fragmentation indicators were calculated using MSPA for each town to represent patterns and processes of fragmentation. We then used these indicators and the proportion of forested land to group towns across Massachusetts with similar patterns of fragmentation. Six representative towns typify different types of forest fragmentation, and illustrate the commonalities and differences between different fragmentation types. The objective selection of representative towns suggests that they might be used as the target of future studies, both in retrospective studies that seek to explain current patterns and in analyses that predict future fragmentation trends.     

The effects of a spillage of diesel fuel on a rocky shore in the sub-Antarctic region (Macquarie Island)

On 3 December 1987, the supply ship Nella Dan ran aground at Macquarie Island (54°29′S, 158°58′E) releasing about 270 000 I of oil, mostly light marine diesel, into the sea. At the time of the incident, many marine invertebrates were washed up dead along 2 km of shoreline. Twelve months later, the shore community was investigated using 1. algal and invertebrate populations of the littoral and sublittoral rocky shore, and 2. the invertebrate communities living in the holdfasts of the giant kelp Durvillaea antarctica, which were collected for later examination. Investigations were undertaken at both affected and control locations. Analyses of differences in community structure involved nested ANOVA and multidimensional scaling techniques. On the rocky substrate, the effect of the spill was restricted to some biota of the lower littoral and sublittoral zones—particularly echinoderms and the patellid limpet Nacella macquariensis. There were differences in cover for some algal species between locations. Within the kelp holdfasts, communities were dominated by peracarid crustaceans at control locations and by polychaetes (particularly the opportunistic groups—capitellids, cirratulids and spionids) at oil-affected locations.

The communities have recently been re-surveyed (in the summer of 1994–1995) to assist in the interpretation of the results and to gauge the extent of recovery of the affected biota.     

A statistical model of the geomagnetic field

Summary A statistical model of the geomagnetic field is derived, based on the assumption of an axial geocentric dipole field of strengthH _e at the equator perturbed by randomly directed components of constant magnitudeh. The model fits the dispersions found from an analysis of the 1945 field, and the ratioh/H _e obtained for this field and from the palaeomagnetic data both average to about 0.4. The model predicts that during reversal of the dipole field, the field intensity falls to between 0.2 and 0.4 of the steady field intensity, and this agrees with estimates made from the palaeomagnetic observations.     

An application of three-dimensional electrical resistivity imaging for the detection of an underground waste-water system

A 3D electrical resistivity imaging survey is presented in this paper. The objective was to investigate an underground wastewater system at the University of Malaya, Malaysia. Apparent resistivity data were collected along ten parallel lines using a Wenner-Schlumberger configuration; electrode cables were oriented in the x-direction with 3 m spacing. Roll-along measurements using a line spacing of 3 m were carried out covering a grid of 20 × 10 electrodes. All data sets were merged into a single data file in order to perform a 3D inversion. Two different 3D least squares algorithms, based on the robust inversion method and the smoothness-constrained technique, were used for the inversion of the apparent resistivity data. Both the horizontal and vertical extents of the anomalous zones found by inversion are displayed. The results indicate the superiority of the robust inversion method over the smoothness-constrained technique at this site. The results are in sufficient accordance with previously known information about the investigation area. The results show that 3D electrical resistivity imaging surveys, in combination with an appropriate 3D inversion method, can be highly useful for engineering and archaeological investigations as well as for environmental applications.     

Evolution of an advancing gravel front: observations from Vedder Canal,British Columbia

Channelization of the lowermost part of Vedder River in 1922 initiated a natural experiment relevant to the unresolved question of how abrupt gravel–sand transitions develop along rivers. The new channel (Vedder Canal) had a fine bed and a much lower slope than the gravel‐bed river immediately upstream. Changes in morphology and sedimentology as gravel advanced into and along the Canal are documented using air photos, historical surveys, and fieldwork. The channel aggraded and steepened until stabilized by occasional gravel extraction in recent decades. The deposited material fines progressively along the Canal but the gravel front has retained an abrupt appearance because it has advanced by the sequential development of discrete gravel tops on initially sandy alternate bars. Near the gravel front the bed is highly bimodal and there is a sharper drop in the extent of gravel‐framework surface facies than in bulk gravel content. Ahead of the front, gravel is restricted to thin ribbons which often become buried by migrating sand. Calculations show that even though the gravel bed at the head of the Canal is almost unimodal, size‐selective transport during floods can account for the strong bimodality farther downstream. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of landscape restoration and degradation on storm surge and waves in southern Louisiana

The purpose of this investigation was to examine storm surge and wave reduction benefits of different environmental restoration features (marsh restoration and barrier island changes), as well as the impact of future wetland degradation on local surge and wave conditions. Storm surge simulations of two representative hurricanes were performed using the ADCIRC storm surge model with the inclusion of radiation stress gradients from the STWAVE nearshore wave model. Coupled model simulations were made for a number of landscape configurations that involved both restored and degraded wetland features. The impact of barrier island condition on hurricane surge and waves was also evaluated. Effects of landscape features were represented by changes in elevation and frictional resistance. Restoration and degradation of marsh resulted in decreases (for restoration cases) and increases (for degradation cases) in both surge and waves. The magnitude of change was correlated with the magnitude of the horizontal extent and elevation changes in the marsh. In general, the wave change patterns are consistent with the water level changes. Deflation of the Chandeleur Islands (barrier island chain) resulted in slightly increased surge. Results suggest that coastal marsh does have surge and wave reduction potential. Results also indicate that the impact of the landscape features is amplified in areas where there are levee “pockets.” Barrier islands and coastal ridges reduce wave heights, even if in a degraded condition and thus can reduce wave energy in wetland areas, protecting them from erosion.     

Status of sedimentation in King Talal Dam,case study from Jordan

This paper focuses on characterizing the current status of physical and chemical characteristics of King Talal Dam (KTD) sediments. The quality of sediments was investigated based on several international sediment quality guidelines. The volume of sediment and sedimentation rate in (KTD) was also estimated. Five types of granulometric textural facies were observed for the sediments of KTD reservoir bed, with an average grain size distribution of gravel (1.38%), sand (32.38%), silt (32.35%) and clay (32.38%). The fraction of <63 micron showed that the total mean size was 8.0 micron. Other sediment parameters in KTD were 7.0% for total organic matter (TOM), 7.3 for pH, 35.9% for CaCO₃ and 100.5 meq/100 g for cation exchange capacity, with dominant mineralogical constituents of quartz, calcite, dolomite, clay minerals and minor feldspar. The total concentrations of F, Cl, NO₂, NO₃, PO₄ and SO₄ in sediment samples were lower inward for KTD. The vast majority of trace metals in sediments were generally within the standard limits recommended for soils. TOM and grain size of sediment are major factors governing the trace metal concentrations. The calculated geoaccumulation index (I _geo) and enrichment factor of metals in bottom sediments showed that the metals were in the following order: Cd > Pb > Zn > Co > Cr > Ni > Fe > Cu > Sr > Mn and Cd > Zn > Pb > Co > Cr > Ni > Cu > Sr > Mn, respectively. Based on the sonic survey of KTD reservoir, the annual sedimentation rate was about 0.4061 MCM/year, in which about 18.66% of the reservoir initial storage capacity was lost to sediments and a projected lifespan of about 198 years.     

Fluid inclusion and cathodoluminescence studies on fluorite from the Kerio valley, Kenya

The Kerio valley lies between the Elgeyo escarpment and the Tugen hills which mark the western margin of the Kenya rift valley. The main fluorite deposits are located in the southern part of the valley at Kimwarer, Choff and Kamnaon.Three types of inclusion fillings were identified: Liquid+Vapour, Liquid+Daughter Minerals and Liquid. The L+V type is dominant. Inclusions occur as clusters, trails along the crystal growth zones and as isolated ones. Low salinities, apparently lower than the 5% wt. NaCl equivalent, were established. Homogenization temperatures suggest that fluorite mineralization took place at different stages and at temperatures between 120 and 180 °C. Isolated readings above 180°C may be referring to the original inclusions in limestone. These measurements and the absence of CO₂ in the inclusions, as well as the occurrence of vugs and crustifications with fluorite, suggest that mineralization took place at relatively shallow depths.Emission spectrum lines representing Eu²⁺, Dy³⁺, Tb³⁺ and Sm³⁺ in fluorite were identified. Sm³⁺ was detected only in the pinkish luminescence of veined fluorite, whereas the pinkish zone in banded fluorite contains Tb³⁺. Eu²⁺ which gives the strongest emission lines in the blue part of the visible spectrum, apparently is responsible for the strong blue cathodoluminescence (CL) in fluorite. The dominance of Eu²⁺ peaks further points to the fact that fluorite mineralization in the Kerio valley took place in an environment that was enriched in Lanthanide Rare Earth Elements (LREE). The presence of rare earths and radioactive elements in fluorite points towards their enrichment in the environment of fluorite mineralization. A juvenile origin of mineral forming solutions is proposed.Two generations of fluorite were established: allotriomorphic fluorite, forming the matrix, and the idiomorphic variety, occurring either in barite or in druzes in early fluorite. Barite in turn forms idiomorphic crystals in allotriomorphic fluorite. Relics of calcite occur in both K-feldspars and in early fluorite. Oxides and hydroxides of Fe, Mn, Ti and Al commonly occur in open spaces in fluorite. Of significance is the presence of gold in fluorite. Fluorite mineralization is of hydrothermal origin in the post-Miocene era and was formed as a result of metasomatic replacement of marble and open space fillings.