Irisawa Formation

Irisawa Formation Agency for Natural Resources and Energy, Ministry of International Trade and Industry, 1976

Invalid synonym: Naruko Lacustrine Deposit

Type locality: Irisawa - Uenohara, Narukoonsen, Osaki city, Miyagi prefecture
Coherent formation
Naruko caldera fill deposit
Pleistocene (11.8 yBP, ¹⁴C)

Sedimentary facies: Lacustrine
Lithofacies: Tuffaceous silt, Tuffaceous sands, Conglomerate

Thickness: 230 m or thicker
Upper limit: Unconformity (Lava domes)
Lower limit: Abut unconformity (Granitoids, Tertiary volcanic rocks)

Naruko volcano
[ Upper ]
~~~~~~~~~~~~~~
Lava domes
~~~~~~~~~~~~~~
Irisawa Formation
~~~~~~~~~~~~~~
Yanagisawa Tuff
~~~~~~~~~~~~~~
Nizaka Tuff
~~~~~~~~~~~~~~
Ichihasama Pumice
~~~~~~~~~~~~~~
Iwadeyama Pumice
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Irisawa - Uenohara, Narukoonsen, Osaki city, Miyagi pref.

Tsuchiya et al. (1997) Geology of the Iwagasaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 96p. (in Japanese with English abstract 4p.)