EXPLANATORY TEXT OF THE

GEOLOGICAL MAP OF ,TAPAN

Scale 1 : 75,000

MUROZOMI

Zoue 31 Col. X:X:r

Sheet 266

By

Touyoshi Akagi

Geology

Mica Schut develops nor thward of Murozumi and in Iwai­

shima, where it forms the b•se of the island and trends N. 20'-

30' E. dipping 60' E.S.E. [t is intruded by granite and ie

extremely disturbed in the nor&bcast of Murozumi.

Phyllite dovelops in Mukojimo. and 'raiklvamura, a nd runs

N. 70'-SO' E. dipping 70' N.N.\V. H is about 4,000 m. in thick­ness.

The Upper P'1la>ozoic geoerally strikes N. 70'-SO' E. dipping 60'-76'N.N.W. It is about 7,000 m. in thickness.

The Tertiary sandstone and couglomerale develop along the

cliff on the uor th side of Iwaishima and mea.su.re about 25 m. in thickness.

Diluvium and Alluvium. consisting of sand and gravel, develop near the ,·ivers and along the coast.

Biotite ~nite and hornblende biotite granite ooou.r in a wide area, intruding the Upper Palm-0ioio rocks.

Granite Porphyry, pegmotite and quartz porphyry occur in phyllite and grani te as dvkcs.

2

Quartz prophy,.ite and diorite porphyrite intrude the phyl!ite as dykes .

Pyroxene andesite extrndfog tho mica schist, occupies t.he lops of Iwaishima and Koiwwawma.

EconOlnic Geology_

~nese or. : The Kurumaki mine is s;tualed t~ the southwest of Eboshldakb and yielded about 259 tons of ore in

1917, but it has now boon wrecked. The deposit is intercalated in hornstone w;tb a thickness of from one lo two feet and runs

N, 80'-906W. with tho inclination N. 70'-&5'. The ore is psilo­melane.

Limestone: Limestone is quarried ,nd bnrnt out at several places in Kasado-jima.

BnildinA stone : Biotite granite is q~arriod at Shimbata in Mitsuimura; but it is only used loca.lly f~ foundation and wall materials.