Discussion on the Geologic Survey Method used on the Mobara Gas Field in 1949

Abstract

The methods used in 1949 by geologists of the Oil Section of the Geological Survey of Japan for the survey of the Mobara Gas Field, Chiba Prefecture, are discussed. The writer believes that the primary objective in the stratigraphic study of sedimentary deposits should be the determination of the true relation between the strata and the time planes. The writer recommends that the distribution of the following four elements should be shown on geologic maps of sedimentary basins : (a) Lithologic types ; (b) time planes (indicated by such markers as tuff beds); (c) macrofossil facies; (d) microfossil facies. The combination of elements (a) and (b) indicates the relation of the mappable lithologic units to the time of deposition, and elements (c) and (d) indicate the environment of deposition.