Alpine olivine- and titanian clinohumite-bearing assemblages in the Erro-Tobbio peridotite (Voltri Massif, NW Italy)

The microstructures in the Erro-Tobbio peridotite indicate several stages of recrystallization of olivine + titanian clinohumite-bearing assemblages. The development of these assemblages is closely associated with serpentinite mylonites, in which they occur in shear bands and foliations and are inferred to have grown synkinematically, in veins, and as post-kinematic radial aggregates. In the peridotite wall-rock adjacent to these mylonites, the same assemblages have recrystallized statically at the expense of original olivine and pyroxenes, mesh-textured chrysolite and antigorite veins. In addition, the olivine-bearing assemblage occurs in widespread vein systems. The brittle deformation of the peridotite resulting in the development of these vein systems is closely related to ductile deformation of metagabbroic dykes in the peridotite. Although early metasomatism resulted in extensive rodingitization of the gabbros, some dykes show an eclogitic assemblage of Na-clinopyroxene + garnet + chloritoid + chlorite ± talc. These observations, the microstructures and the mineral chemistry all suggest that the assemblages in the ultramafic rocks and metagabbros developed during a prograde evolution towards high pressures (>13–16 kbar, 450–550° C), and during subsequent decompression. This metamorphic evolution is considered to be related to Late Cretaceous intraoceanic subduction in the Alps-Apennine system and closure of the Piedmont-Ligurian basin.     

Conservation as disturbance: Upheaval and livelihood diversification near Tarangire National Park,northern Tanzania

Recent studies have identified poverty reduction near parks and protected areas, findings that challenge an extensive literature on the social burdens associated with protected areas. These studies move the discussion on the social dynamics of conservation forward, however, they do not offer insight into the underlying mechanisms that shape household-level outcomes such as income and wealth. By focusing on protected areas as centers of uncertainty, upheaval, and disturbance, this study examines the character and incidence of livelihood diversification within communities near Tarangire National Park in northern Tanzania compared to communities far from the park. Livelihood diversification is well understood as a coping and/or risk mitigation strategy pursued in response to various types of shocks, and uncertainty more generally. This study draws on mixed methodologies to construct multivariate statistical models to estimate the effect of proximity to the park on measures of livelihood diversification. The results indicate that proximity to park is strongly correlated with livelihood diversification, suggesting that households near the park are adapting to opportunities and constraints and may be seeking to reduce variance in income and wealth in response to disturbances and uncertainty associated with the park.     

Methods of fitting the Fisher-Tippett type 1 extreme value distribution

Methods are described for estimating the parameters of the Fisher-Tippet Type 1 extreme value distribution and associated return values from measured extremes, such as maximum wave height. A comparison of these methods, with simulated data, shows that those using Gumbel's plotting position are least satifactory. Maximum likelihood methods give the smallest mean square errors, but the very much simpler method of moments is nearly as good.     

The effect of low level supplementary heating on diving duration

The exothermic reaction which proceeds when small sachets containing particulate mixtures of iron and magnesium are flooded with sea water, has been used for thermal support of free divers. Initial application of such generators to heating of the hands (Burton and Chan, 1981), and later extension to heating of the torso, have been described previously (Chan and Burton, 1981, 1982). Of considerable interest during field trials of the torso heating system was a strong subjective impression among those taking part, that significant increases of dive duration and decreases of perceived discomfort could be obtained with relatively low levels of power generation, for example less than 50% of that required for thermal balance. In this paper, a simple mathematical model of human stored heat loss is used to rationalize this observation. Also it successfully predicts voluntary exposure times of unheated divers who become cold. When used to estimate body heat debt, the model enables documented dives by this laboratory and by others, including recent exposures in Antarctica using low level supplementary heating, to be analysed.     

A sonic well log of the basement complex of the Walvis Ridge

A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ～-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval.     

The composition and origin of metal in howardites

Howardites can be divided into two main groups, Ni-rich (>350ppm Ni) and Ni-poor (<150ppm Ni). In the Ni-rich group Ni occurs principally in metal grains associated with melt rocks and is largely derived from projectiles which caused the melting. The metal in Bununu, Kapoeta and Malvern melt rocks plots in the meteoritic Ni-Co range and in Bununu and Kapoeta is enriched in P. By contrast, most metal grains in primary lithic and crystal clasts in howardites are Ni-poor and plot mainly in the composition field of pristine lunar anorthosite metal. However, there are variations in the abundance and exact composition of primary metal from howardite to howardite and each therefore represents a discrete source region. The matrix metal in Bholgati, Bununu, and Kapoeta shows the diversity of compositions expected in a polymict breccia, with compositions plotting in and between the anorthositic and meteoritic Ni-Co fields. Other howardites show a more limited range of matrix metal compositions, because of limited metal-bearing clasts.Petersburg differs from other howardites in several ways. The metal in primary clasts has a unique $\text{Ni}\text{Co}$ ratio of about 40, which indicates derivation from a different reservoir from other howardite primary clasts. The metal in the matrix consists of large grains intergrown with silicates with compositions clustering tightly at 3.3% Ni, 0.2% Co. This is interpreted as equilibration, possibly as the result of deeper burial for Petersburg than for other howardites.     

Diatoms and aquatic palynomorphs in surface sediments of the White Sea bays as indicators of sedimentation in marginal filters of rivers

Diatom algae, aquatic palynomorphs, and the grain-size of surface sediments from bays of the White Sea were investigated in a program dedicated to the study of marginal filters (MF) in the Severnaya Dvina, Onega, and Kem rivers. Three microalgal assemblages are established in surface sediments, which replace each other successively with distance from river mouths and are characterized by a gradual decrease in a share of freshwater species of diatoms and Chlorophyceae algae, significantly varying concentrations of marine diatoms and dinocysts due to changes in water salinity, grain-size composition of sediments, quantitative distribution of suspended particulate matter (SPM), and water productivity at different marginal filter stages.