325. “ONIMARU TYPE” CORALS NEWLY FOUND IN THE NORTHERN KITAKAMI MOUNTAIN REGION, JAPAN

In 1950 ATANABE and M. MINATO pointed out that there are two types of Palaeozoic formation in the Kitakami mountain region, N. E. Honshu. Japan. Of them. one type is represented by the relatively shallow sea facies. ranging from the Gotlandian to the uppermost Permian in age. This type of Palaeozoic formation is very fossiliferous in every horizon. although the successions of the fossiliferous layers are occasionally interrupled by unconformities. This type of Palaeozoic formations is typically developed in the southern part of the Kitakami mountain region. On the contrary, in the northern part of the Kitakami mountain region, there are Palaeozic formations, consisting of heavy bedded sandstone. shale, cited. limestone and schalstein. which are observed to be apparently conformable with each other without any sort of stratigraphical breaks. In the second type, the Palaeozoic formation is almost barren of fossils, except that some Permian foraminiferal remains have been found in a few localities. Accordingly Y. ONUKI and others held the belief that these older formations in the northern Kitakami mountain region may be exclusively Permian in formations. Meanwhile, Dr. M. MINAM once suggested from his tectonic point of view, that the most parts of these complexes should be not only Permian but also Carboniferous in age, if still older deposits are not contained in them. The present senior author unexpectedly found some coral remains from the limestone belonging to such older complex of the second type, developing in the city of Kamaishi, lwate Prefecture. According to MINATO, the corals now in problem are definitely of the Lower Carboniferous type, which are * Read June 20. 1956: received Jan. 10. 1957.