Magnetic properties of mafics and ultramafics from Eastern Ghats

Magnetic properties, namely intensity of natural remanent magnetisation (NRM) and magnetic susceptibility, of mafic and ultramafic formations of Eastern Ghats belt in the Godavari Districts, Andhra Pradesh are studied. The formations sampled for the study are, iron-ore, chromite-ore, amphibolite, gabbro, charnockite and khondalite gneiss. Mineralogical differences in iron-ore and the degree of martitisation are reflected in magnetic susceptibility. NRM and susceptibility of chromite-ore are feeble. The gabbro exhibits strong magnetic properties because of its contiguity with iron formation. The Koenigsberger ratio is found to indicate relative palaeomagnetic stability.     

The structure of the natural stratosphere and the impact of chlorofluoromethanes on the ozone layer investigated in a 2-D time dependent model

two-dimensional time dependent model of the stratosphere incorporating the major interactions between radiative-photochemical and dynamical processes is described. The main prognostic equations considered are the thermodynamic equation and the general conservation equation for the minor chemical constituents representing the odd oxygen (O _x =O+('D)+O₃), odd hydrogen (HO _x =HO+HO₂), N₂O, odd nitrogen (NO _x =NO+NO₂+HNO₃), CF₂Cl₂, CFCl₃ and odd chlorine (Cl _x =Cl+ClO+HCl). The zonal wind and mean meridional circulations are determined diagnostically by the integration of the thermal wind equation and the stream function equation in the meridional plane espectively. The large scale eddy processes are parameterized in terms of zonal mean quantities using the generalized diffusion formulation on a sloping surface. The radiative heating and cooling and the hotochemical sources and sinks are incorporated in a form which allows for the major interactions among the minor trace constituents, temperature and mean circulation.Two integrations consisting of natural stratosphere and a stratosphere contaminated by the chlorofluoromethanes through lower boundary fluxes are carried out for 23 model years by changing the declination of the sun every day and using 6-hour time step. The model simulations of temperature, mean circulation, ozone, HO _x , N₂O and NO _x in the meridional plane for the normal stratosphere, show satisfactory agreement with the available observations. Based on the results of second integration it is found that the injection of chlorofluoromethanes in the atmosphere at the estimated current production rates can lead to significant changes in the meridional distribution of ozone, temperature and NO _x in the middle and upper stratosphere. The results also indicate that the percentage total ozone depletion increases from tropics to high latitudes and from summer to winter high latitudes. Also discussed are the results of additional experiments incorporating the reaction of HO₂ with NO and the reactions involving ClNO₃.     

Exploitation of the Gauribidanur array for seismic monitoring

The medium-aperture array at Gauribidanur is in continous operation since 1966. With the recent addition of a 12-bit 16-K computer its potential for the monitoring of underground explosions has improved considerably. The salient aspects of the monitoring system, the present and projected procedures for generation and dissemination of detection data and the long-term storage of data relevant to discrimination research are discussed. An attempt is also made to assess its detection efficiency in the light of the major features of site noise.     

Correlation of water quality parameters and products of exotech radiometer bands

In the analysis of water quality by remote sensing, it is widely reported, that, several parameters of water quality are correlated with the reflectances and the ratios of reflectances of the water body in different spectral bands. In this paper, it is shown empirically, that, the pairwise product of the reflectances in different bands is better correlated than the bands and their ratios. A possible explanation for this pnenomenon is also suggested.     

A study of the serpentinisation in the Vempalle dolomitic limestones near Pulivendala,Cuddapah District

The calcite-dolomite ratio of the Vempalle dolomitic limestones, serpentinised dolomitic limestones, and serpentines from the mineralised zone of the asbestos is determined by infrared spectroscopy. The ratio varies between 2 and 5·4 in the dolomitic limestones, between 1 and 1·5 in the serpentinised dolomitic limestones and it is taken as zero in the serpentines as both calcite and dolomite bands are absent in their infrared absorption spectra. The release of calcite during the serpentinisation is identified, which confirms the formation of serpentine.     

Air-sea interaction studies at the station occupied by R/V Sirius

The transfer formulas are used to compute hourly values of sensible and latent heat exchanges for the period July 29 to July 31, 1974. Also, values of eddy shearing stress at the sea surface, Bowen's ratio and dissipation of kinetic energy are computed. The data used cover part of the GATE period for station 20 occupied by the Brazilian Naval Ship R/V Sirius in the Equatorial Atlantic (0730 N 4000 W). The variations in the computed values are studied in relation to rainfall and the synoptic situation.     

Paleomagnetism of a Paleozoic anorthosite from the Appalachian Piedmont,northern Delaware: possible tectonic implications

Two components of magnetization have been observed in fourty-four samples (five sites) of the anorthosites in the Arden Pluton. One component, withD = 325°,I = ?75°,k = 32, α₉₅ = 13.6°, was isolated in many samples by progressive alternating field demagnetization and in the remainder of the collection by the use of intersecting great circles of remagnetization. The corresponding pole is located at 16°N, 303°E,dp = 22.7°,dm = 24.9°. Assuming the age of the last metamorphism (Taconic, ca. 440 Ma) of the Cambrian Arden Pluton to be the age of the magnetization, this pole deviates significantly from coeval poles thus far obtained from the North American craton. The preferred explanation for this deviation is that the Arden Pluton and the surrounding Piedmont rocks belonged to a different Early Paleozoic plate on the south or east side of the Iapetus Ocean, most likely the African (Gondwana) plate, and that it was transferred to the North American plate during a subsequent continental collision.