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Akada Formation Kato and Akahane, 1986

• Type locality: Lake Shikanoiri - Lake Nashirazu, Akada, Nagano city, Nagano prefecture
• Type locality: Sengoku, Shinko town, Nagano city, Nagano prefecture
• Coherent formation
• Pliocene
• Correlation: Sarumaru Formation

• Sedimentary facies: Brackish
• Lithofacies: Conglomerate, Sandstone, Siltstone
• Lithofacies (Lower): Andesitic volcanic conglomerate, Tuff, Tuff breccia, Lapilli tuff

• Thickness: 80 - 100 m
• Upper limit: Unconformity (Haibara Formation, Shinoyama Volcanics)
• Lower limit: Unconformity (Susobana Formation, Ronji Formation, Takafu Formation, Kumeji Pyroclastic Member, Joshita Member, Hijiriyama Andesite)

• Distribution: Lake Shikanoiri - Lake Nashirazu - Inuishi - Lake Oyamada - Matsuyama, Akada, Nagano city, Nagano pref.; Sengoku - Mearaiishi - Mount Kokuzo, Shinko town, Nagano city, Nagano pref.

• Kato and Akahane (1986) Geology of the Nagano District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 120p. (in Japanese with English abstract 5p.)