[ Top ] [ Japanese ]

Koura Formation Tomita and Sakai, 1938

• Type locality: Koura, Kashima town, Matsue city, Shimane prefecture
• Coherent formation
• early Miocene (20 - 18 Ma; 24 - 22 Ma, FT)
• Correlation: Mita Formation, Hata Formation
• Intruded by: Dolerite sills

• Sedimentary facies (Upper): Brackish
• Sedimentary facies (Middle): Fluvial, Lacustrine
• Sedimentary facies (Lower): Fluvial, Lacustrine
• Sedimentary facies: Storm-dominant shelf
• Sedimentary facies: Submarine fan
• Sedimentary facies: Gravity flow deposits, Turbidite, Channel-fill deposits
• Sedimentary facies (Minor): Aqueous pyroclastic flow deposits
• Depth of water: Storm wave base or deeper
• Lithofacies: Conglomerate, Sandstone
• Lithofacies (Minor): Shale, Andesite lava, Volcanic breccia, Volcanic conglomerate, Tuff, Pyroclastic surge deposit, Rhyolite pyroclastic flow deposit, Dacite pumice tuff
• Sedimentary structures: Cross stratification, Parallel stratification, Wave ripples, Current ripples, Climbing ripples, Graded bedding, Slump structure
• Paleocurrent: from West-northwest to East-southeast

• Thickness: 200 - 800 m or thicker
• Upper limit: Bottom of the black shale dominated horizon
• Upper limit: Conformity (Josoji Formation)
• Lower limit: Unc onformity (Plutonic rocks)

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

• Distribution: Koura - Minamikobu, Kashima town, Matsue city, Shimane pref.; Hoda - Tasumi - Kitaura - Ui - Cape Jizozaki, Mihonoseki town, Matsue city, Shimane pref.; Hishine - Yokan - Yabi town, Izumo city, Shimane pref.
• Fossils: Anodonta etomoensis, Corbicula sp., Cristaria muraii etomaensis, Cuneopsis nagahamai, Cuneopsis nipponensis kourensis, Cuneopsis praeambiguus, Hyriopsis oyamai, Lamprotula sakaii, Lamprotula shimanensis, Ostrea sp., Parreysis nipponensis, Portlandia sp., Semisulcopira sakamotoi, Viviparus (Sinataia) uryuensis kosasanus
• Fossils (Daijima-type flora): Tree truncks, Acer sp., Alangium aequalifolium, Alnus sp., Berchemia racemosa, Cinnamomum schuchzeri, Comptonia naumanni, Glyptostrobus europaeus, Laurus promigenius, Lindera miyataensis, Metasequoia japonica, Metasequoia occidentalis, Parabenzoin cf. trilobum, Parrotia fagifolia, Planera ungeri, Potomogeton sp., Quercus glauca, Quercus mandraliscae, Salix sp., Tilia sp., Ulmus longifolia, Vitis sp., Zelkova ungeri

• Kano (2018) Jour. Geol. Soc. Japan, vol.124, no.10, pp.781-803 DOI
• Nomura et al. (2018) Jour. Geol. Soc. Japan, vol.124, no.2, pp.95-109 DOI
• Sakai et al. (2013) Jour. Geol. Soc. Japan, vol.119, no.4, pp.285-299 DOI
• Sato et al. (2011) Jour. Geol. Soc. Japan, vol.117, no.8, pp.439-450 DOI
• Utada (2007) Jour. Geol. Soc. Japan, vol.113, no.8, pp.438-453 DOI
• Kano et al. (1998) Geology of the Taisha District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 58p. (in Japanese with English abstract 3p.)
• Kano et al. (1994) Geology of the Matsue District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 126p. (in Japanese with English abstract 5p.)
• Kano et al. (1991) Geology of the Imaichi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 79p. (in Japanese with English abstract 5p.)
• Kano and Nakano (1986) Geology of the Etomo District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 30p. (in Japanese with English abstract 3p.)
• Kano and Nakano (1985) Geology of the Mihonoseki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 28p. (in Japanese with English abstract 3p.)
• Kano and Yoshida (1985) Geology of the Sakaiminato District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 57p. (in Japanese with English abstract 5p.)