Annals of The Tohoku Geographycal Asocciation
Online ISSN : 1884-1244
Print ISSN : 0387-2777
ISSN-L : 0387-2777
The Terrace Structure of Oma-zaki, Aomori Prefecture
Tatsuo WAKO
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1970 Volume 22 Issue 2 Pages 62-66

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Abstract

The Oma-zaki (cape) facing the Tsugaru Kaikyo (strait) is composed of Oma Surface (10-20 m a. s. l.) and Oma-shimote Surface (3-5 m) (Fig. 1).
The C-14 measurement of coaly clay in the deposits underlying the former surface shows the age 21, 500±2, 500 yrs. B. P. (Gak-2591). The material, however, is the terrestrial deposits lying on the true marine deposits. On the thin marine deposits, muck, clay with limonite pipes as well as coaly clay lie (Fig. 3). The C-14 measurement of coaly clay in the deposits underlying the former surface shows the age 21, 500±2, 500 yrs. B. P. (Gak-2591). The material, however, is the terrestrial deposits lying on the true marine deposits. On the thin marine deposits, muck, clay with limonite pipes as well as coaly clay lie (Fig. 3).
The author thinks that the cause on such a feature of terrace deposits is the persistence of swampy condition. Oma-shimote Surface is now at such a phase, although it is necessary to examine the significance of the scarplets and the gentle slopes between the swampy parts and the dry ones within the surface (Fig. 4) as well as the structure of the scarp between two Surfaces (Fig. 5).
At any rate, terrace deposits underlying the upper surface is a typical example of compound structure consisting of marine and terrestrial sediments: the C-14 datum shows the age younger (the degree is unknown) than that of the emergence from sea.

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