Heavy mineral analyses of the surface Neogene sediments and the cuttings from Higashi Ishinazaka Oil Well.

Abstract

studies were made on the heavy mineral assemblages of the coarse clastic sediments, - tuffs, tuffaceous sediments and sand-stones, - obtained from the Dewa hilly land in the east of Sakata city, Yamagata prefecture.
The same studies were carried out on the cuttings from Higashi Ishinazaka R-1 Oil Well.
The results showed a fairly close correlation between the surface and the subsurface data, and also showed the usefulness of the heavy mineral analyses to the subdivision of the formation.
Studies on the refractive indices of the plagioclases in the tuffs of this area revealed a dacitic composition.