Oyama Formation

Oyama Formation (Kojima, 1954) Eto et al., 1998

Invalid Synonym: Oyama Tuffaceous Sandstone Formation, Osawa Formation, Yamanaka Formation

Type locality: Moritogawa river, Oyama, Hayama city, Miura county - Sakurayama, Zushi city, Kanagawa prefecture
Accretionary complex
Miocene

Sedimentary facies: Marine
Lithofacies: Tuffaceous sandstone
Lithofacies (Minor): Mudstone, Mudstone-dominant interbedded sandstone and mudstone, Lignite
Sedimentary structures: Slump structures

Thickness: 1,900 m
Upper limit: Thrust fault (Kinugasa Formation), Tagoegawa Unconformity (Tagoegawa Sandstone and Conglomerate Member, Shimoyamaguchi Sandstone and Conglomerate Member)
Lower limit: Transitional (Abuzuru Formation)

Hayama Group
[ Upper ]
~~~~~~~~~~~~~~
Yabe Formation
::::::::::::::
Kinugasa Formation
/--/--/--/--/-
Oyama Formation
--------------
Abuzuru Formation
--------------
Morito Formation
?--?--?--?--?-
[ Lower ]

Mineoka Belt (Miura peninsula)
[ Upper ]
~~~~~~~~~~~~~~
Miura Group
~~~~~~~~~~~~~~
Hayama Group
?--?--?--?--?-
[ Lower ]

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

Distribution: Shimokoji - Oyama, Hayama city, Miura county, Kanagawa pref.; Sakurayama, Zushi city, Kanagawa pref.; Ikegami , Yokosuka city, Kanagawa pref.
Fossils: Shellfishes (Thracidora gigantea), Radiolarians, Mastigophora

Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.375-395, DOI
Eto et al. (1998) Geology of the Yokosuka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 128p. (in Japanese with English abstract 3p.)