Uraninite and Thorianite
WASSERSTEIN1 suggested that the generation by radioactive decay of Pb4+ of smaller ionic radii within the crystal lattice of uraninite caused a shrinkage in the unit cell proportionate to the geological age and the shrinkage was of the order of 0.0025–0.0041 Å. per hundred million years. The anomaly in the relation of cell dimensions of Bisundni and Gaya uraninites with the age, reported by Holmes2, was explained by Wasserstein3 by classifying uraninites into two different types—α-type for Bisundni uraninite and γ-type for Gaya uraninite, the latter being apparently anomalous and requiring heat treatment under oxidizing conditions in order to reduce the cell size to correspond to that of an α-type analogue. Wasserstein did not, however, state the temperature and period of heating and the conditions under which the cell size of γ-uraninite was reduced to correspond to age values consistent with those of the α-type.
The Age of Uraninite and Monazite from the Post-Delhi Pegmatites of Rajputana
Abstract Uraninite and monazite collected by Dr. H. Crookshank from pegmatites occurring respectively at Bisundni and Soniana (Rajputana) have been analysed for U, Th, and Pb by Mr. A. A. Srnales, and the isotopic constitution of the lead separated from each mineral has been determined by Dr. W. T. Leland and Prof. A. O. Nier. The three ages calculated from the uraninite ratios AcD/RaG, RaG/U and AcD/U are 740, 733, and 733 m.y. The monazite is considerably altered but the corresponding ratios indicate that its age lies between 700 and 865 m.y., which is consistent with the more reliable estimate determined from the uraninite. It is shown from tectonic evidence that the Delhi erogenic belt is younger than the Satpura belt (previously dated at about 900 m.y.) and that both are younger than the Aravalli and Dharwar belts.
Archaeological Survey of Dangoyama Kofun by 3DGPR
We presented a three-dimensional ground penetrating radar (3DGPR) system for the archeological investigation in a harsh site, where we have to deal with many trees and/or great topographic variations. This system consists of a commercial GPR system with a laser positioning system. With this system, we can move the GPR antenna freely, on which a positioning detector can record accurate position for each GPR data trace. We applied our 3DGPR system at Dangoyama Kofun, a burial mound, in Fukushima prefecture, Japan. A lot of trees and bushes covered the survey area and cannot be cut. We acquired six datasets in two days in this area. We successfully imaged the boundary between the original surface of the burial mound and the covering soil clearly at about 0.3 m depth around the mound. Furthermore, we found some strong reflections appeared at 0.8 m depth in the top area of the mound, which can be from the artificial parts of the burial mound. The results would greatly aid the following archaeological excavation. In addition, we compared the non-interpolated depth slice with interpolated depth slice at same position and demonstrated that the interpolation process on threedimensional GPR data may introduce some artifacts which might mislead our interpretation.