Nagao Formation

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Nagao Formation Mori, 1947

Type locality: Oppa river, Ishinomaki city, Miyagi prefecture
Coherent formation
Middle Jurassic, Bajocian - Late Jurassic, Tithonian
Intruded by: Tatebitoge Mass

Sedimentary facies:
Lithofacies (Main part): Shale
Lithofacies (Lower): Sandstone
Sedimentary structures (Main part): Convolute lamination
Sedimentary structures (Lower): Slump structures

Thickness: ca. 500 - 800 m
Thickness (Main part): 500 m or thicker
Thickness (Lower): ca. 20 - 150 m
Upper limit: Unconformity (Yoshihama Formation)
Lower limit: Conformity (Nakahara Formation)

Hashiura Group (Shizukawa - Tsuya, Miyagi pref.)
[ Upper ]
?--?--?--?--?-
Sodenohama Formation
--------------
Arato Formation
--------------
Aratozaki Formation
~~~~~~~~~~~~~~
[ Lower ]

Hashiura Group (Toyoma, Miyagi pref.)
[ Upper ]
~~~~~~~~~~~~~~
Nagao Formation
--------------
Nakahara Formation
~~~~~~~~~~~~~~
[ Lower ]

Hashiura Group (Ishinomaki, Miyagi pref.)
[ Upper ]
~~~~~~~~~~~~~~
Owada Formation
--------------
Ojima Formation
~~~~~~~~~~~~~~
[ Lower ]

Shizukawa-Hashiura Subbelt
[ Upper ]
?--?--?--?--?-
Hashiura Group
~~~~~~~~~~~~~~
Shizukawa Group
~~~~~~~~~~~~~~
Saragai Group
~~~~~~~~~~~~~~
Inai Group
~~~~~~~~~~~~~~
[ Lower ]

South Kitakami Belt (after Permian)
[ West ]
::::::::::::::
Shizukawa-Hashiura Subbelt
::::::::::::::
Karakuwa-Oshika Subbelt
::::::::::::::
Ofunato Subbelt
::::::::::::::
[ East ]

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

Distribution: Oppa river, Ishinomaki city, Miyagi pref.; Okinagura creek - Nagaohigashi creek - Tsukihama creek - Honji - Izumisawa - Nakahara - Jusanhama, Kitakami town, Ishinomaki city, Miyagi pref.; Mitobe river, Shizukawa, Minamisanriku city, Motoyoshi county, Miyagi pref.
Fossils: Belemnoids, Bivalves
Fossils (Ammonoids): Garantiana sp., Holcophylloceras spp., Kepplerites sp., Kranaosphinctes sp., Leptosphinctes sp., Lytoceras cf. neumayri, Normanites sp., Otoites sp., Stephanoceras sp., Taramelliceras sp., Berriasellidae or Olcostephanidae
Fossils (Radiolarians): Archaeodictyomitra sp., Cinguloturris cf. carpatica, Dictyomiitrella? cf. kamoensis, Dicryomiterella cf. kamoensis, Eucyrtidiellum sp., Hsuum sp., Parvicingula sp., Protunuma sp., Stichocapsa convexa, Tricolocapsa? fusiformis, Tricolocapsa plicarum

Takizawa et al. (1990) Geology of the Toyoma District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 126p. (in Japanese with English abstract 8p.)