JIMBo : GEOLOGY OF JAPANESE SAKHALIN. 5 



Japanese explorer Matsuura contains a great many names well transliterated into 

 the Japanese kana (syllabic signs) ; the outlines, however are naturally wrong. 

 Just the reverse is found in our charts, published by the Hydrographie Office. 

 The coast-line to the north of Cape Patience is very wrong in almost all maps. . 

 In order to trace the principal geotectonic lines of Sakhalin, one must first look at 

 the Geological Map of Hokkaido, prepared by my joint work princijjally with 

 Messrs. T. ISHIKAWA and S. YOKOVAMA. One will very easily find the 

 striking similarity of rocks and fossils collected in these two islands. The 

 north-south line is very important in the Island of Sakhalin, which is meridionally 

 elongated, with its narrowest portion on about 48°, and a big depression on the 

 east, forming Patience bay (called after the war " Shichiro-wan ") or the 

 broken part of the outer zone of sedimentary rocks. 



But the principal difficulty in the geological structure is to trace the southern 

 prolongation of the Median Depression. The Cretaceous terrains on the west side 

 of the axis of old rocks in Hokkaido are similar to those on the west side of the 

 Depression in Sakhalin. Therefore the ^Median Depression of the former has no 

 equivalent in the latter. 



The occurrence of Cretaceous fossils on the east coast, towards the north of 

 Cape Patience, is of special interest, since Hokkaido also has the same on its far 

 eastern part. 



The island of Kaibato, lying on the northern continuation of a line joining 

 Rishiri and other volcanoes in Hokkaido, must form with them a single zone 

 of volcanic eruption, though there is no regular volcanic cone on the 

 Kaibato. 



The Kaihyötö, whose name is always heard when speaking about the fisheries 

 in Sakhalin, is geologically a little piece of land, detached from the region of Cape 

 Patience, just like smaller rocks in its vicinity. 



The strike of many coal-seams and generally of various sedimentär}' strata is 

 very often either exactly or nearly north to south. Also man}- large rivers show 

 the greater part of their watercourse meridional. Striking examples are found in 

 Pilevo. Agnevo, Khoi, Shitka, Xitui, Makunkotan, Chikaporonai, Naibuchi, Riitaka 

 and others, not to mention particularly the main rivers on the Median Depression. 



The oldest geological formation in Sakhalin consists of Crystalline Schists, 

 which compose the whole northern part of the Susuya ^Mountains and a little 

 portion of the Northeastern Mountain-land. They are an alternation of gray and 

 black sericite-schists. with various green schists ; among the essential components 

 of the latter we find pyroxene, hornblende, and chlorite. A gray, dirt}--looking 



