Eocene ostracodes from the Iwaya Formation on Awajishima Island, southwestern Japan

Yamaguchi, Tatsuhiko; Matsubara, Takashi; Kamiya, Takehiro

doi:10.2517/prpsj.9.305

Cited by 10 publications

(12 citation statements)

References 24 publications

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“…1 A: localities of Eocene marine ostracodes around the Japanese Islands. 1, Middle-Upper Eocene Iwaya Formation (Yamaguchi et al, 2005). 2, Upper Eocene-lowermost Oligocene sequence (Yamaguchi et al, in press).…”

Section: Introductionmentioning

confidence: 99%

“…Ostracodes potentially record paleoclimatic information related to the shallow-marine realm, although few studies have investigated Eocene ostracodes in the Northwest Pacific region (e.g., Yamaguchi et al, 2005;Yamaguchi, 2006;Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…According to Yamaguchi et al (2005, in press), the Eocene ostracode fauna from Kyushu contains many species also found in the coeval fauna from the East China Sea, but none of the species of the contemporaneous fauna from the Seto Inland Sea (Yamaguchi et al, 2005;Yamaguchi, 2006). The faunas of both Kyushu and the East China Sea contain warm-water taxa that are not found in the fauna of the Seto Inland Sea.…”

Section: Introductionmentioning

confidence: 99%

“…This latitudinal separation between the two areas would have led to faunal differences due to oceanographic variations. On this basis, Yamaguchi et al (2005) concluded that the Eocene faunal difference between Kyushu and the Seto Inland Sea should reflect the difference in paleoclimate that caused the provincialism. This hypothesis requires testing based on evidence obtained from areas north of the Seto Inland Sea; however, there exist insufficient records of Eocene ostracodes from Hokkaido: previous studies undertaken by Hanai (1970) and Hanagata (2002) provided neither illustrations nor taxonomic descriptions.…”

Section: Introductionmentioning

confidence: 99%

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Eocene ostracode assemblages with Robertsonites from Hokkaido and their implications for the paleobiogeography of Northwestern Pacific

Yamaguchi

Kitamura

2009

Bull. Geol. Surv. Japan

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Abstract:We report on Eocene ostracode species from Hokkaido, northern Japan for the first time and discuss their paleobiogeographic implications. Five species were found in the lower part of the Sankebetsu Formation in the Haboro area, and the Akabira and Ashibetsu Formations in the Yubari area, central Hokkaido. The ostracode assemblages are characterized by Robertsonites, a circumpolar Arctic genus of the modern fauna. This finding marks the southernmost occurrence of the Eocene record of the genus, as well as the oldest occurrence. As the characteristics of the Eocene Hokkaido fauna are similar to those of the modern-day fauna in the Seto Inland Sea, a contrast in species composition is observed between the Seto Inland Sea and Kyushu. This contrast is attributable to differences in sea temperature. Five species are described, including Robertsonites ashibetsuensis sp. nov.Keywords: Eocene, Hokkaido, Ostracoda, paleobiogeography, Robertsonites 1 Course of Earth Sciences, School of Natural System, College of Science and Engineering, Kanazawa University, Kakumamachi, Kanazawa City, 920-1192, Japan 2 Department of Geology, Faculty of Science, Niigata University, 8050 Ikarashi-2nocho, Niigata City, 950-2181, Japan Bulletin of the Geological Survey of Japan, vol.59 (7/8), 2008 Fig. 1 A: localities of Eocene marine ostracodes around the Japanese Islands. 1, Middle-Upper Eocene Iwaya Formation (Yamaguchi et al., 2005). 2, Upper Eocene-lowermost Oligocene sequence (Yamaguchi et al., in press). 3, uppermost Eocene-lowermost Oligocene Kishima Formation . 4, Middle Eocene-Lower Oligocene Iojima Group (Yamaguchi, 2006). 5, Lower Eocene Oujiang and Middle Eocene Wenzhou Formations (Yang et al., 1990). 6, Lower Eocene Oujiang Formation (Liu, 1989). B: distribution of Paleogene strata and localities of examined samples in Hokkaido. Geology after Editioral Committee of Hokkaido (1990).Eocene ostracodes from Hokkaido, northern Japan (Yamaguchi and Kurita) 2.1 Ashibetsu and Akabira Formations (Middle Eocene) These formations consist of shale beds and alternating beds of shale and sandstone that represent marine intervals in the coal-bearing deposits of the Ishikari Group in the Sorachi area. These strata yield the Ishikarian molluscan fauna, indicating a Middle Eocene age (Mizuno, 1964). This age assignment is supported by fission track dating of the underlying Yubari and Wakkanabe Formations (ca. 44-42 Ma;Tanai, 1986) and the ages of calcareous nannofossils in the overlying Poronai Formation (late Middle Eocene; Okada and Kaiho, 1992). Poronai Formation (Middle-Upper Eocene)The Poronai Formation, which overlies the Ishikari Group in the Sorachi and Ishikari areas, is dominantly mudstone, and has a thickness of 600 m. It is correlated with the calcareous nannofossil Zone CP14-CP15 of Okada and Bukry (1980) (Okada and Kaiho, 1992) and the dinoflagellate cyst Bellatudinium hokkaidoanum and Trinovantedinium boreale Zones (Kurita, 2004). Fossil planktic foraminifers from the formation indicate a Middle-Late Eocene age (~...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Eocene ostracode assemblages with Robertsonites from Hokkaido and their implications for the paleobiogeography of Northwestern Pacific

Yamaguchi

Kitamura

2009

Bull. Geol. Surv. Japan

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“…The following marine sediments have been revised as the Eocene-Oligocene: the Tainohata Formation of the Kôbe Group in the west Kôbe area (Ozaki et al, 1996;Matsubara et al, 2010;A in Fig. 1); the Iwaya Formation of the Kôbe Group in the north Awajishima area (Yamamoto et al, 2000b;Yamaguchi et al, 2005; Fig. 1); the Maéjima Formation in the Ushimado area (Matsubara, 2002b;C in Fig.…”

Section: Introductionmentioning

confidence: 99%

Molluscan fauna of the “Miocene" Namigata Formation in the Namigata area, Okayama Prefecture, southwest Japan

尚志

2013

Jour. Geol. Soc. Japan

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The molluscan fauna of the Namigata Formation, traditionally accepted to be of Miocene age, are reexamined taxonomically, and the geologic age of the formation and its paleogeographic implications are discussed. The formation is subdivided into the main part and two new members (the Senjuin Shell-Sandstone and Ônishi Conglomerate members). The Namigata Formation yielded species of Gastropoda, species of Bivalvia and species of Scaphopoda. The occurrences of Molopophorus watanabei Otuka, Acila (Truncacila) nagaoi Oyama and Mizuno, Chlamys (Nomurachlamys?) namigataensis (Ozaki), and Isognomon (Hippochaeta) hataii Noda and Furuichi indicate that the molluscan age should be revised to the late Late Eocene-Early Oligocene. Taking account of the latest elasmobranch data and preliminary strontium isotope ratio, the age of the formation is confined to the late Late Eocene. The present and recent results show that the First Seto Inland Sea was actually composed of two sea areas that existed at different times: the Paleogene sea area is estimated to have been an open sea facing south to the Pacific Ocean, whereas that in the Miocene is thought to have been an embayment connected to the northwest to the Sea of Japan. Therefore, the concept of the so-called Miocene First Seto Inland Sea should be reassessed in the Cenozoic geohistory of the Japanese Islands.Selected molluscan species including Felaniella (Felaniella) namigataensis n. sp. are taxonomically described and/or discussed.

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First discovery of Eocene coastal-estuarine ostracods from Japan, with the geological history of the migration of estuarine genera in the Far East

Tanaka

Henmi²,

Komatsu³

et al. 2017

Geol. Mag.

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The genus Neomonoceratina, which dominated the ostracod assemblage in the uppermost part of the Akasaki Formation (Miroku Group) of the Kyushu Island, Japan, is associated with the benthic foraminifer Ammonia cf. beccarii, mollusca Terebralia? sp. and Anomia sp., and the oogonium of Charophyceae, indicating a marine-to-brackish estuarine environment involving inflowing freshwater. This is the first record of Eocene coastal-estuarine ostracods from the eastern margin of the Eurasian continent and demonstrates that different pre-Neogene coastal-estuarine ostracod assemblages flourished in this region. The assemblages comprised five ostracod species (including one novel species) assigned to the genera Neomonoceratina, Paijeiborchella, Propontocypris and Parakrithella. These species exhibited genus-level links with the Eocene borehole cores along the continental shelf of the East China Sea and other areas of Kyushu. Fossil data of characteristic Eocene coastal-estuarine genera collected worldwide indicate that different characteristic genera inhabited each region. For example, Neomonoceratina originated on the Indian subcontinent by the Early Paleocene period at the latest, along with the northern drift of the Indian subcontinent. These species subsequently diversified west and east with the equatorial current and counter-current via the Tethys and reached the eastern margin of the Eurasian continent among the various eastwards-migrating species, where one genus ultimately adapted to the coastal-estuarine environment. Notably, the coastal-estuarine ostracod assemblage of the eastern margin of the Eurasian continent differs completely from that of the Tethys during the Eocene period. Our results suggest that coastal-estuarine ostracod assemblages are a powerful tool for palaeogeographic reconstruction.

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Eocene ostracodes from the Iwaya Formation on Awajishima Island, southwestern Japan

Cited by 10 publications

References 24 publications

Eocene ostracode assemblages with Robertsonites from Hokkaido and their implications for the paleobiogeography of Northwestern Pacific

Eocene ostracode assemblages with Robertsonites from Hokkaido and their implications for the paleobiogeography of Northwestern Pacific

Molluscan fauna of the “Miocene" Namigata Formation in the Namigata area, Okayama Prefecture, southwest Japan

First discovery of Eocene coastal-estuarine ostracods from Japan, with the geological history of the migration of estuarine genera in the Far East

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