SUMMARY OF THE RESEARCHES ON THE SUBMARINE 



CONFIGURATION x\ND BOTTOM DEPOSITS OF THE 



NEIGHBOURING SEAS OF JAPAN 



DURING 1939-1948 



By HiROSHi NiiNO, Suisan, Koshusho, Japan 



A SUMMARY of the investigations on the submarine configuration and 

 bottom deposits of the neighbouring seas of Japan during the period 

 covering 1938-1940 is given here. Researches having been carried out 

 extensively along various lines, only tlie outstanding results are 

 presented. 



(1) Submarine Configuration of the Neighbouring Seas of Japan 



1. General Configuration 



A. Pacific Ocean 



The increase in number of the sounding stations by the echo-sounding 

 method has resulted in the necessity for revision of previous marine 

 charts, and, consequently, a new chart is in the process of publication. 

 Bathymetric charts (No. 6080 and others) of the neighbouring seas of 

 Japan are being published by the Hydrographic Section of the Bureau 

 of Transportation, and at present a new one for the Japanese coasts 

 is now in press. According to this chart, the Japan Trench is narrower 

 than indicated on previous charts, and a depth of 10,600 metres was 

 sounded in it. The Mariana Trench comprises three parts, and the 

 Caroline Oceanic Basin can be divided into two parts in east-to-west 

 direction. The Yap ridge is a prolongation of the Mariana ridge, and 

 the submarine ridge north of Palau continues to the Okino-tori-shima. 

 The bottom configuration of the South Japan Sea (south-east of Shikoku) 

 is complicated, there being many depressions, steep slopes, and, 

 according to the Fisheries Experiment Station, there has been discovered 

 a shallow area measuring 480 metres at 29° 51' N. lat., 133° 21' E. long. 



Concerning the coral reefs of the former Japanese mandated 

 territory there are numerous reports, and it is now known tliat the 

 foundations of them consist of the Tertiary or pre-Tertiary formations, 

 whose ages have been determined by paleontological evidence. Among 

 the coral-reefs there exists a peculiar type known as the Table reef. 



B. . 



South China Sea. — Sounding investigations have revealed the exist- 

 ence of a peculiar depression, measuring more than 70 metres in width, 

 between Kainan-to and French Indo-China. 



Philippine Seas. — The submarine configuration of the Philippine 

 seas more resembles that of the East India Islands than the neigh- 

 bouring seas of Japan. Submarine valleys are well developed along 

 the south-eastern coast. 



Japan Sea. — According to the results of investigation of the 

 Fisheries Experiment Station of the Hydrographic Section and of 

 Korea, the submarine configuration of the Japan Sea is quite complicated 

 in the southern half and in the central part there is the Yamato Bank 

 (285 m.), North Yamato Bank (418 m.), and north-west of the Oki 

 Islands is the Oki Bank (275 m.). Also, along the Japanese Islands, 

 there exist many ridges. 



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