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.     

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.     

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.     

Upper mantle heterogeneities in Africa deduced from Rayleigh wave dispersion

Rayleigh-wave group velocities have been measured along 11 paths on the African continent, north of the equator. The results lead to a division of this part of the continent into three regions: cratonic areas, non-cratonic areas (“mobile zones”), and a region located to the east of the meridian 31°E (Red Sea neighbourhood, Ethiopia, Djibouti). The highest velocities are found beneath the cratonic areas, at ～ 200 km depth (～ 5%). At greater depths, the “mobile zones” exhibit higher velocities than the cratonic regions, but the difference is not as marked (～ 2%) and the resolution is poor. Velocities in the eastern region are similar to those found under young oceanic regions.     

A late quaternary pollen record from the Transvaal bushveld, South Africa

Pollen spectra from cores of organic spring deposits from the Transvaal provide evidence for the climatic evolution of the province during the last 35,000 yr B.P. or more. The past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities. Evidence is provided for an early moist, cool phase with relatively mesic bushveld and expanded montane forest in the central Transvaal, followed by a drier period with drier bushveld which probably lasted until approximately 25,000 yr B.P. During the next phase, which at the latest ended about 11,000 yr B.P., the temperatures were probably 5°–6°C cooler than at present. At that time bushveld vegetation in the central Transvaal was replaced by open grassland with macchia elements. Climatic amelioration came and semiarid savanna returned to the plains, at first gradually and then developing into a warm Kalahari thornveld-type vegetation. After 6000 yr B.P. it apparently became slightly wetter and a more broad-leafed bushveld developed. About 4000 yr B.P. it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types. After 2000 yr B.P. conditions gradually became warner until about 1000 yr B.P., when the modern climate of the central Transvaal bushveld originated.     

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.     

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.