[ Top ] [ Japanese ]

Nechi Formation (Suzuki et al, 1985) Nagamori et al., 2010

• Type locality: Nechigawa river - Kitanosawa, Itoigawa city, Niigata prefecture
• Coherent formation
• middle Miocene - early Pliocene (ca. 6.4 - 3.5 Ma, FT, Diatoms)
• Contemporaneous heterotopic facies (Upper): Umikawa Formation
• Correlation: Nakanomata Mudstone Member, Shiiya Formation, Upper Teradomari Formation
• Intruded by: Dykes of Eboshiyama Formation

• Sedimentary facies: Marine
• Depth of water: Upper bathyal - Lower Sublittoral (Shellfishes)
• Lithofacies: Sandy mudstone, Muddy sandstone, Sandstone
• Lithofacies (Minor): Tuffaceous sandstone, Andesite pyroclastic rocks, Glendonite
• Sedimentary structures: Trough cross-stratification, Parallel stratification

• Thickness: ca. 800 - 1,500 m or thicker
• Thickness (Pyroclastic rocks): 1 - 550 m
• Upper limit: Bottom of sandstone and tuffaceous sandstone-bearing horizon
• Upper limit: Conformity (Nadachi Formation), Unconformity (Umikawa Formation, Sarukura Formation, Eboshiyama Formation, Kajiyashiki Formation, Takanomine Formation)
• Lower limit: Conformity (Sennozawa Formation, Imai Formation)

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

• Distribution: Nechigawa river - Kitanosawa - Mount Eboshidake - Umikawa river, Itoigawa city, Niigata pref.
• Fossils: Fishes (Bones), Sponges (Makiyama chitanii), Diatoms, Trace fossils, Plant fragments
• Fossils (Omma-Manganji fauna): Acila nakazimai, Conchocele bicecta, Glycymeirs yessoensis, Nuculana onoyamai, Turritella saishuensis motidukii, Turritella saishuensis saishuensis, Yabepecten tokunagai

• Nagamori et al. (2018) Geology of the Itoigawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 75p. (in Japanese with English abstract 3p.)
• Nagamori et al. (2010) Geology of the Kotaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 130p. (in Japanese with English abstract 4p.)
• Takeuchi et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.123-142 DOI