A final solution of this problem will be possible only after careful paleomagnetic studies in which the sections are very accurately pinpointed to regions in which continental movements definitely did not take place. Such sections may be found on the Russian, Siberian, and Chinese Platforms. The Paleomagnetism Commission was accordingly assigned the task of organizing studies designed to solve this problem.
The reports in the second group dealt with the geophysical conditions accompanying the formation of specific types of rocks. A. G. Komarov considered the changes which take place in extrusive rocks after their formation. For platform formations, magnetic and structural aging takes place, without any variation of the chemical composition of the rock. For mobile belts, the initial stages of metasomatic metamorphism are observed. These are accompanied by the addition of considerable quantities of magnesium and ferrous iron, by the loss of alkalis, ferric iron, and silicon, and by a change in the magnetization of the rocks as a function of the chemical effects.
A. N. Shmeleva studied the magnetization of sedimentary rocks, both in a natural state and after reprecipitation, and she showed that secondary magnetization can be distinguished by this means. The precipitation was carried out during the course of a year, with deposit formation at a pressure of 1.5 kg/ .
The effect of consolidation of the remanent magnetization of artificially precipitated sediments was investigated by A. Ya. Vlasov and his coworkers. It was found that the consolidation brought about by a vertical pressure of 1666 reduced the inclination by almost 10'; lateral pressures resulted in an increase of the inclination. The artificial sediments possessed high magnetization stability, with respect to constant and variable magnetic fields and also with respect to temperature variations.
T. A. Martynova studied changes in the magnetic properties of ferruginous quartzites of the Kursk magnetic anomaly. It was found that the magnetic susceptibility and the remanent magnetization decreased at the boundary of the oxidation zone (in the weathering crust). The relation between the amount of remanent magnetization of a rock and the degree of its meta morphism was established. This same subject was treated by V. I. Zavoiskii
and Z. A. Krutikhovskaya, who made a study of iron quartzites from Krivoi Rog. These investigators reported that the magnetization direction depends both on the rock structure and on the orientation of the eutaxitic structure of the rock.
The magnetization of rocks in the alkali massif of the part of the Ukrainian Shield in the vicinity of the Sea of Azov was studied by N. P. Mikhailova. The remanent magnetization was found to depend on the susceptibility, Q being a quantity which characterizes the structure of the rock and its position in the massif. However, it is doubtful whether this Q factor can be used for age correlation.
During the discussion of the foregoing reports, it was suggested that further studies of artificially precipitated rocks be made, and that particular attention be given to the reprecipitation conditions (flow, salinity of water, and particle dimensions).
The third group of reports dealt with the physical fundamentals of paleomagnetism. G. N. Petrova justified her suggestion that the magnitude of the so-called disruptive field be taken as a stability parameter. In addition, she described the properties and limits of the temporary magnetization of ferromagnetic rocks.
The viscous magnetization of rocks was investigated by L. E. Sholpo, who suggested that the viscous magnetization during any time period be computed by extrapolation. Laboratory studies showed that magnetic viscosity is more evident in rigid materials and that it depends on the ferromagnetite concentration. The author did not elaborate upon the latter factor.
S. Yu. Brodskaya and M. A. Grabovskii presented the results of a study of the magnetic parameters of artificial rocks. The dependence of these parameters on the concentration of ferromagnetic components in one component and two-component media was investigated. Formulas for calculating the magnetization of one-component and two-component samples were derived for all concentrations. There was good agreement between the experimental and calculational data.
The report of A. G. Zvegintsev and A. Ya. Vlasov contained the findings of a study of thermal magnetic hysteresis in various fields, over a temperature range from 20 to 700°C.