GEOLOGY OF JAPAN 67 



They are generally considered to be Pleistocene in age. 



The Eecent deposits consist of fluviatile sand, gravel and clay, 

 besides beach-sand and snbaerial secondary deposits of dune-sand and 

 loam. 



3. Igneous Rocks. 



It has already been recognized that the igneous rocks of the 

 regions surrounding the Pacific are mostly of the calc-alkaline series. 

 So are those of Japan, although very rarely several alkaline recks are 

 also found to occur in small isolated areas. 



The schistose granite occurs near the Ryoke Metamorphics and 

 lienetrates the latter in various forms, changing sandstones and clay- 

 slates into such metamorphics. It embraces the three varieties of 

 schistose hornblende-granite, hornblende-biotite-granite and biotite- 

 granitn. 



The granite is the most widely spread of all plutonic eruptives. 

 There is little evidence of granite having intruded in the Palaeozoic 

 Era, whereas in the Mesozoic it seems to have come out in great 

 quantities. In several places, granite exerted contact action on the 

 Cretaceous rocks, suggesting the later ags of its intrusion. There are 

 many varieties, such as biotite-gTanite, two-mica-granite, hornblende- 

 granite and pyroxene-granite, although the last-mentioned is of rare 

 occurrence. 



The diorite and gabbro are of common occurrence in small areas, 

 usually as the marginal facies of granite or as stocks genetically 

 related to granite. The age of iri'uption was probably Mesozoic in 

 most cases, but the c[uartz-diorite intruding the Misaka Series seems 

 to belong to the Tertiary age. 



The peridotite and serpentine occur together with gabbro and 

 diorite, intruding into the Palaeozoic and Mesozoic Formations. Nor- 

 thern Hitachi and middle Higo are localities noted for peridotite. 

 Serpentine seems to have been derived from peridotite and gabbro. 



The diabase is found intercalated in the Palaeozoic Formation, 

 and the great' development of variegated schalsteins wiiich accompany 

 it bears witness to the mighty eruptions of this rock in the Palaeozoic 

 Era. The rock occurs also in the Mesozoic. 



The quartz-porphyry occurs as large masses together with granite 

 in Chugoku, Hida, Mino, Shinano, etc. Other occurrences are mostly 



