Effects of metals and sediment particle size on the species composition of the epifauna of Pinna bicolor near a lead smelter,Spencer Gulf,South Australia

Pinna bicolor (Mollusca: Pelecypoda) were transplanted between four sites near a lead smelter. The species composition of their epifauna (sessile and mobile) was examined in relation to characteristics of both sediments and seston at the sites. Seventy-two taxa were distinguished in the epifaunal community. Substantial differences were found in the short-term sensitivity of some of the species to concentrations of Cd, Pb and Zn in sediments and to sediment particle size. The short-term sensitivity of many species to metals or sediment particle size explained their long-term distribution pattern. Twenty-three taxa were identified as significantly characterizing the faunal differences. Of these, eleven (four molluscs, four bryozoans, two barnacles and one ascidian) were affected by both sediment metal concentration and particle size, and eight (four molluscs, one bryozoan, one polychaete, one hydroid and one barnacle) were affected by metal contamination but not particle size. Of all fauna examined, the Bryozoa were the most metal-sensitive. Four species, Smittina raigii (Bryozoa), Galeolaria sp. 1 (Polychaeta), Epopella simplex (Cirripedia) and Monia ione (Pelecypoda) were identified by their short- and long-term sensitivity to metal contamination, and absence of sensitivity to sediment particle size, as suitable species for monitoring the effects of metal contamination on the epifauna. The implications of the results for toxicity-testing are discussed.     

On the thermal evolution of the terrestrial planets

Physical and chemical constraints for such different planetary objects as the Earth, the Moon and meteorite parent bodies can best be satisfied by thermal history models having high initial temperatures. On the basis of thermal calculations it is suggested that the evolution of the other terrestrial planets (Mars, Venus and Mercury) was also characterized by high initial temperatures. Under these conditions, melting and, consequently, fractionation would set in at an early stage. Because of the resulting redistribution of the long-lived radioactive heat sources and the concentration of these elements in the surface layers, large-scale differentiation could be achieved by partial melting.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.     

A paleomagnetic study of the Mull lava succession

Summary. A paleomagnetic study has been made of a succession of 139 non-overlapping basaltic lavas, representing 91 per cent of the longest remaining succession of flows associated with the Paleogene Mull volcano. All the lavas have experienced considerable hydrothermal alteration, probably at up to several million years after initial magnetization and frequently with alteration to the opaque minerals and the production of new potentially magnetic phases. The question of whether directional remagnetization has taken place while preserving within-unit directional consistency and discreteness of unit mean direction is discussed. Extensive directional remagnetization is excluded as an explanation for the data. If stable directions obtained by alternating field remanence cleaning coincide with original TRM directions then a mean pole position for all temporally independent lava directions from the British Tertiary igneous province is at 71.9° N, 167.2° E, with k:22 and α₉₅:3.0°. This pole is significantly different from the geographic pole. If the difference in palaeomagnetic and geographic poles is interpreted in terms of absolute plate motion, then 2010 km of northwards motion of the western part of the Eurasian Plate, at 3.7 cm/yr, has taken place over the last 55 Myr. This motion has implications for the geological history of the Arctic and for the complexity of mantle motions.     

Provenances of naturalised plants in Australasia

In both Australia and New Zealand, numbers of naturalised flowering plant species have increased steadily since the start of European settlement, and this process shows no sign of abating. Plants native to Western Europe, the Mediterranean basin and the Middle East predominated during the mid‐nineteenth century, but in recent decades other geographical areas (notably the Western Hemisphere, Asia and Southern Africa) have become important sources of adventive plants. Today, the composition of ensembles of naturalised species more closely conforms to the diversity of physical environments in the host area. Species native to mediterranean‐type climates tend to dominate in Victoria, species from the Asian and American tropics are especially significant in Queensland, and species from cool temperate regions compose the bulk of the naturalised flora of south‐western New Zealand.     

Dryland salinity in a subcatchment at Glenthompson,Victoria

Dryland salinity is a widespread and serious environmental problem in western Victoria. As a result river environs and farmland have been seriously degraded with loss of habitat, reduced farm production and increased erosion. Until recently, the preferred method of salinity investigation was centred around expensive drilling programs to obtain information on groundwater provinces. More recently, electromagnetic surveys have provided the means of rapidly assessing the levels of soil and water salinities present within the landscape. At a site south of Glenthompson, Victoria, the results of an electromagnetic survey together with an investigation of relevant soil properties are being used to plan salinity control options. High recharge areas do not appear to be present in the study district. The effects of agronomic control options, such as the establishment of perennial grasses, can be predicted by the use of a monthly water balance whereby climatic factors and the crop's efficiency in plant water use can be related. The likely reduction in deep infiltration can then be estimated.