わが国における珪質鞭毛虫類およびヱブリア類の層位学的研究の現状
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The silicoflagellates and ebridians, minute silica-secreting planktonic flagellates, have been known both in the fossil state and from the present seas for more than one century. For many years engaged in the study of fossil diatom deposits, I have been able to collect specimens of silicoflagellates and ebridians found in association and mount them on slide glasses for microscopic examination.<BR>Since the siliceous tests of these fossils, though minute, are preserved quite safely, and since they are found over wide areas especially in the Tertiary and later formations, they seem to be highly estimated as being valuable stratigraphical indices.<BR>Little has been known of them in our country, however. The present paper aims at elucidating important features, stratigraphical as well as paleontological, of these minute fossils.<BR>The silicoflagellates and ebridians date back as fossil to the Upper Cretaceous. Together with diatoms, radiolarians, pollens and spores, they are excellent indicators of fossil marine deposits. A few of them are found living near the surface of the sea, and play a part of an excellent indicator of the water-mass of the Recent sea. Our Research Group has been examined silicoflagellate and ebridian remains in many cores taken by “Seifu-Maru” from the Sea of Japan 1966 to 1967. Each sample were taken from within the upper one centimeter of core.<BR>The number of silicoflagellates increases along the Tsushima Warm Current and the other cold one which flows down from northern seas. The state of silicoflagellate distribution in these two recent currents was also recognized in the cases of core locations at the bottom of the Sea of Japan. If the geographical relationship between the core locations and two currents in the Sea of Japan were nearly the same in Past time as it is now, the ratio method (<I>Dictyocha /Distephanus</I>) is naturally applicable to the above cases. Fig. 3 shows the relationship between the ratio of <I>Dictyocha/Distephanus</I> and latitude of core locations.<BR>Fossil silicoflagellates and ebridians found from the diatmites and diatomaceous mudstones of Note Peninsula, Central Japan, are highly estimated as being valuable indices of the Neogene Tertiary, viz. Middle Miocene and later.<BR>G. Dallas Hanna pointed out that these organisms are paleontologists almost ideal marker-fossils. The Tertiary formations taken into consideration in this paper would turn out to be very useful as a key in the stratigraphical research in Japan, if the details of the facies characteristics of the rock and of the faunal assemblages of the contained silicoflagellates could be more closely investigated.
- 社団法人 東京地学協会の論文
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