Koma Group

Koma Group Kosaka and Tsunoda, 1969

Invalid synonym: Dotaira Formation, Niimiyagawa Formation

Coherent formation
early - middle Miocene (17 - 13 Ma, Radiometric age)
Intruded in: Tsuburai Body, Kaikoma Granite, Yakejizo Granite, Quartz diorite dyke, Andesite dyke

Lithofacies: Island arc tholeiite
Lithofacies: Volcanic rocks, Sedimentary rocks

Thickness: 6,000 - 6,300 m or thicker

Koma Group
[ Upper ]
~~~~~~~~~~~~~~
Momonoki Subgroup
-------~~~~~~~
Kushigatayama Subgroup
~~~~~~~~~~~~~~
[ Lower ]

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

Distribution: Koma mountains, Yamanashi pref.

Ozaki and Sugiyama (2018) Geology of the Minobu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 169p. (in Japanese with English abstract 7p.)