Anomalous isotopic concentrations in the sea off Southern California

Measurements are reported of the ¹⁰Be concentrations in 15 sediments from the sea off southern California. The sedimentation patterns are modelled with a two component system, one component having the high ¹⁰Be concentration of pelagic sediment and the other the low concentration of continental runoff. The pelagic component, brought to the region by the California Current with the Pacific Ocean as reservoir, is very likely the source not only of anomalously high ¹⁰Be deposition but also of similar effects with ²¹⁰¹Pb, ^239,240pu and ²⁴¹Pu.     

Weather modification in arid regions: The Israeli experience

One of the suggestions for modifying weather in semi-arid zones is to alter the albedo over large geographical areas. Work on exploration of this suggestion has been going on for a number of years. Most of the effort along these lines has been to use numerical models, in which it is possible to alter the albedo. One of the questions asked is: What is the minimum size area over which the albedo should be altered to create a noticeable effect in the desert atmospheric flow? In this review, we show, by means of numerical experimentation, using Negev data, that the minimum size desert area which should be affected is 250 km. Experiments to enhance rainfall by cloud seeding in Israel have been carried out for about 26 years. Most of the experimentation has been taking place in the northern part of the country. There are two methods for seeding—“static”, in which seeding causes changes in the cloud's microphysics, and “dynamic”, in which seeding causes changes in the cloud's dynamics. Results of both types of experiments in Israel are discussed. Experiments are now under way to apply these techniques to desert clouds.     

Glacier variations in the Sierra Nevada, California, as related to a 1200-year tree-ring chronology

A time-series of tree-ringwidth indices for alpine timberline foxtail pine (Pinus balfouriana) from the Sierra Nevada of California shows a growth response to summer, late fall, and early winter temperatures that is the inverse of that resulting in the expansion of alpine glaciers. These are correlated with lichen-dated moraines and avalanche deposits that accumulated during subsequent decades. Minima in the ringwidth record, reflecting marked temperature declines occurred at 810, 1470, 1610, 1700 and 1810. Cold periods of lesser extent are also indicated between 1190 to 1400 and suggest that the initial pulses of the Sierran Matthes advances may have begun as early as 1190, or 150 yr earlier than previously dated. The Matthes advances were preceded by a period of pronounced warmth from 900 to 1190 during which timberline rose 10 m to its present elevation. A warm period is also indicated between 1500 and 1580. Recent work extending the tree-ring chronology to 3031 yr B.P. and radiocarbon dating of weathered samples to 6300 yr B.P. suggests that the chronology may ultimately be applicable to the dating of earlier Sierran glacier advances.     

RbSr systematics and crustal contamination models for calc-alkaline igneous rocks

New strontium isotopic data of calc-alkaline Pliocene-to-Quaternary lavas (southern Peru) confirm their anomalous isotopic composition compared to those of calc-alkaline rocks from active margins where continental crust is not involved. Gradual enrichment of radiogenic Sr occurs during fractional crystallization of calc-alkaline magma. The variation of the isotopic composition of these lavas as well as⁸⁷Sr/⁸⁶Sr versus 1/(⁸⁶Sr) diagrams form the basis for a model involving processes of fractional crystallization combined with mixing and addition of radiogenic Sr that originated in continental crust and was transported by a fluid phase.     

87Rb87Sr age of soils and rock from Mare Crisium Luna 24

The soil and one gabbroic fragment from Mare Crisium, brought back by the Luna-24 mission, have been measured through the ⁸⁷Rb/⁸⁷Sr method. The soil is one of the least radiogenic from the moon, comparable with Luna-16 soils. The gabbroic rock, which has a very low Rb/Sr ratio, gives an internal isochron age of 3.74 ± 0.58 Ga and an initial Sr ratio of 0.699085 ± 0.000070.     

Avian cholera and organochlorine residues in an American oystercatcher

Pasteurella multocida, the causative bacterium of avian cholera, was isolated from cultures of the liver and heart blood of a female, adult American oystercatcher (Haematopus palliatus) found dead on the Cape Romain National Wildlife Refuge, South Carolina, in May 1973. This is apparently the first record of avian cholera in the oystercatcher. Low levels of DDE were identified in tissues of the oystercatcher.     

Calcium-aluminum-rich inclusions in the Allende meteorite: evidence for a liquid origin

We have made a detailed examination of the mineralogy, textures and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite. They can be classified into four types—hibonite-bearing, fassaite- and olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are hibonite and olivine free. Examples of each type appear to have crystallized from a liquid rather than by agglomeration of solid nebular condensates. Some lines of evidence for a liquid origin are (1) the presence of spherical and ovoid shapes, (2) rims containing minerals (e.g. hibonite, perovskite) that are more refractory than minerals inside the inclusion, (3) eutectic and poikilitic textures, (4) minerals that are completely enclosed by more refractory minerals and (5) glass and fine-grained grossular stringers.Thermodynamic calculations and comparisons with liquidus phase diagrams indicate that the CAI could have been produced by direct condensation to metastable subcooled liquids that subsequently crystallized (blander and Katz, 1967) or by remelting of an equilibrium high-temperature condensate by impact. The diopside rims in some hibonite-bearing CAI and the paucity of metal in fassaite-olivinebearing CAI are more consistent with direct condensation of a liquid. The sluggishness of solid-solid reactions at the relatively high temperatures at which the CAI formed argues against assuming equilibrium in calculations at lower temperatures.     

Rayleigh waves in a medium with an undulated surface

A numerical method is developed which can be used to determine the characteristics of Rayleigh wave propagation in a homogeneous medium where, at each surface point, the radius of curvature is large compared to the wavelength of Rayleigh waves. This method is deduced from experimental results on seismic modeling of some simple cases.In the general case we compute two effects of surface topography on the Rayleigh waves: a dispersion and attenuation of the waves due to the whole path and a local modulation of the displacement components depending on the local curvature. Therefore, both effects are not to be neglected in the case of precise measurement of the velocities and of the amplitudes from which the attenuation factor is carried out.     

Louis Jones (1914–1975)

Sans résumé Les numéros entre parenthèses renvoient à la bibliographie qui figure à la fin de la notice.     

Laboratory simulation of diffusion in contaminated marine sediments

Wastes from offshore oil drilling activities are often discharged to the marine environment. Solid wastes that settle onto the bottom sediment may pose a health threat to marine organisms and eventually to man through the food chain. We need to understand their fate in order to predict the chemical concentration levels and life-times in the sediment and adjoining aquatic boundary layer. A laboratory simulation of selected in-bed processes that addresses contaminant leaching from the sediment is proposed. The process chosen for simulation in this study is the coupled desorption-diffusion of contaminants from the bed to the water column. A simple mathematical model of the process is also proposed. Preliminary results using organic chemicals for both the simulation and the model are presented. The results suggest that the experimental procedure represents a good way of estimating the diffusive leaching rates of hydrophobic compounds from contaminated sediments.