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1 Diatom 27: December 2011 Diatom biostratigraphy of the lower Miocene Yunagaya Group Diatom biostratigraphy of the lower Miocene Yunagaya Group, Joban area, Japan Yukio Yanagisawa Institute of Geology and Geoinformation, Geological Survey of Japan, Advanced Industrial Science and Technology, AIST Tsukuba Center 7, Higashi, Tsukuba, Ibaraki , Japan Abstract The lower Miocene marine diatom biostratigraphy has been established for the Yunagaya Group distributed in the Joban area, Fukushima and Ibaraki Prefectures, eastern Japan. The Yunagaya Group is composed of the Kunugidaira, Goyasu, Mizunoya, Kamenoo, Honya and Misawa Formations in ascending order. Diatoms are contained in the mudstone of the Mizunoya, Kamenoo, Honya and Misawa Formations. The Mizunoya, Kamenoo, Honya and lower Misawa Formations correlate with the Crucidenticula sawamurae Zone NPD 2B and the upper Misawa Formation is assigned to the Crucidenticula kanayae Zone NPD 3A. The first occurrence of Mediaria splendida s.l., a useful biohorizon dated at 17.6 Ma, is found near the base of the Honya Formation. On the basis of diatom biochronology, the ages of the base and top of the Yunagaya Group are estimated at 18.2 Ma and 16.9 Ma, respectively. The late early Miocene marine and terrestrial climate changes reconstructed by well-preserved plant, molluscan and various microfossil assemblages are synchronous with changes in oxygen isotope records, suggesting that the late early Miocene climate fluctuations in the Joban area were controlled by global climatic change. Key index words: biostratigraphy, diatom, fossil, Japan, Joban, Miocene Fig. 1 Received 1 July 2010 Accepted 25 October

34 Yukio Yanagisawa 2005 Fig. 2 Fig. 1. Geologic map of the Joban area after Suto et al. 2005. A. Hisanohama district, B. Hirunotaira district. Formation Group Fig.

2 34 Yukio Yanagisawa 2005 Fig. 2 Fig. 1. Geologic map of the Joban area after Suto et al A. Hisanohama district, B. Hirunotaira district. Formation Group Fig. 2 Paleogene Neogene Miocene Pliocene 1957 Fig. 3A Fig. 3B 3 Fig. 3A 1999 Akiba 1986 biohorizon 12 biozone NPD code= North Pacific Diatom zone Yanagisawa & Akiba 1998 D

Diatom biostratigraphy of the lower Miocene Yunagaya Group 35 Fig. 2. Stratigraphy of the Miocene sequence in the Joban area after Suto et al. 2005. A. Hisanohama section, B. Hirunotaira section.

3 Diatom biostratigraphy of the lower Miocene Yunagaya Group 35 Fig. 2. Stratigraphy of the Miocene sequence in the Joban area after Suto et al A. Hisanohama section, B. Hirunotaira section. Watanabe & Yanagisawa 2005 Gradstein et al Sanfilippo & Nigrini 1998 Okada & Bukry 1980 Blow 1969 Miller et al Fig. 27 Ma mega annum= Tables 1, 2 Figs Fig. 25 Stephanopyxis Kisseleviella carina Stephanopyxis 90% 10% Thalassionema Trochosira spinosa Delphineis kamenooensis Chaetoceros Fig. 26 Stephanopyxis 90% Kisseleviella carina Thalassionema

36 Yukio Yanagisawa Fig. 3. Sample location maps. A. Hisanohama district, B. Hirunotaira district. Topographic maps Yotsukura and Otsu at 1 : 25,000 in scale Geographical Institute of Japan.

4 36 Yukio Yanagisawa Fig. 3. Sample location maps. A. Hisanohama district, B. Hirunotaira district. Topographic maps Yotsukura and Otsu at 1 : 25,000 in scale Geographical Institute of Japan. Crucidenticula sawamurae C. kanayae var. pacifica Mediaria splendida s.l. C. sawamurae D25, 18.1 Ma NPD2B Crucidenticula sawamurae C. kanayae D30, 17.1 Ma NPD3A Crucidenticula kanayae Fig. 27 Mediaria splendida s.l. NPD2B 17.6 Ma Fig. 25 C. sawamurae C. kanayae var. pacifica M. splendida s.l. NPD2B NPD3A C. sawamurae NPD2A Thalassiosira fraga T. fraga C. sawamurae NPD2B C. sawamurae NPD2B Fig. 26 C. sawamurae C. sawamurae NPD2B Fig NPD2B NPD2B D Ma 2. NPD3A D Ma 3. Mediaria splendida s.l Ma 17.6 Ma M. splendida s.l. NPD2B Stichocorys delmontensis S. wolffii N Fig. 27

5 Diatom biostratigraphy of the lower Miocene Yunagaya Group 37 Table 1. Occurrence chart of diatoms in the Hisanohama section. Section section 1 section 2 section 3 Diatom zones NPD 2B Crucidenticula sawamurae Zone NPD 3A C. kanayae Zone Formations Mizunoya Kamenoo Honya Misawa Sample number Original sample number JOB- Preservation P P P P P P P P P M M P P P P M P M P P P M M P M P P P P P P Abundance C R R R R C C C C C R R R R R C R R C R R A A R R R R R R R R Actinocyclus octonarius Ehrenb Actinocyclus cf. normanii W.Greg. Hust A. cf. ingens f. planus M.C.Whiting et H.-J.Schrad A. cf. tenerus Bréb. G.W.Andrews Actinoptychus senarius Ehrenb. Ehrenb A. splendens Shadbolt Ralfs A. vulgaris Schmann 1 Aulacoseira spp Cavitatus exiguus Yanagisawa et Akiba C. jouseanus Shesh.-Por. D.M.Williams C. linearis Shesh.-Por. Akiba et Yanagisawa 3 C. miocenicus H.-J.Schrad. Akiba et Yanagisawa Cocconeis californica Grunow 1 + Coscinodiscus lewisianus Grev. 1 C. marginatus Ehrenb C. perforatus Ehrenb C. radiatus Ehrenb C. spp Craspedodiscus coscinodiscus Ehrenb. 1 + Crucidenticula ikebei Akiba et Yanagisawa C. kanayae var. pacifica Akiba et Yanagisawa C. sawamurae Yanagisawa et Akiba Delphineis kamenooensis Yanagisawa D. miocenica H.-J.Schrad. G.W.Andrews + D. ovata G.W.Andrews D. cf. surirella Ehrenb. G.W.Andrews Diploneis smithii Bréb. Cleve Diploneis spp Eucampia sp. A 1 1 Goniothecium rogersii Ehrenb. 1 Grammatophora spp. 1 Hyalodiscus obsoletus Shesh.-Por Ikebea tenuis Brun Akiba Kisseleviella carina Shesh.-Por Koizumia adaroi Azpeitia Yanagisawa Mediaria splendida Shesh.-Por. s.l Melosira scopos A.Mann 1 Nitzschia sp. A small Odontella aurita Lyngb. C.Agardh + Paralia sulcata Ehrenb. Cleve Plagiogramma staurophorum W.Greg. Heib. 1 1 Proboscia alata Brightw. Sundstöm 1 P. interposita Hajós R.W.Jord. et Priddle Pseudodimerogramma elliptica H.-J.Schrad Rhaphoneis amphiceros Ehrenb Rhizosolenia miocenica H.-J.Schrad R. styliformis Brightw R. cf. styliformis Brightw. robust 3 Stellarima spp Stephanopyxis schenckii Kanaya + 5 S. spp Stictodiscus kittonianus Grev. + Tetracyclus spp Thalassionema obtusa Grunow G.W.Andrews T. nitzschioides Grunow H.Perag. et Perag Thalassiosira mizunamiensis Yanagisawa T. spp Thalassiothrix longissima Cleve et Grunow Triceratium condecorum Brightw. 1 1 Trochosira spinosa Kitton Total number of valves counted Resting spore of Chaetoceros Preservation; M: moderate, P: poor. Abundance; C: common, R: rare

6 38 Yukio Yanagisawa Table 2. Occurrence chart of diatoms in the Hirunotaira section. Section section 4 Diatom zones NPD 2B Formation Mizunoya Sample number Original sample number JOB- Preservation P P P P P Abundance C C R R R Actinocyclus cf. normanii W.Greg. Hust. 1 A. cf. ingens f. planus M.C.Whiting et H.-J.Schard A. cf. tenerus Bréb. G.W.Andrews 1 1 Actinoptychus senarius Ehrenb. Ehrenb Aulacoseira spp C. marginatus Ehrenb C. spp. 2 Crucidenticula sawamurae Yanagisawa et Akiba - + Delphineis miocenica H.-J.Schard. G.W.Andrews 1 Ikebea tenuis Brun Akiba 2 17 Kisseleviella carina Shesh.-Por Odontella aurita Lyngb. C.Agardh 3 Paralia sulcata Ehrenb. Cleve Rhizosolenia styliformis Brightw. 2 Stellarima spp Stephanopyxis schenckii Kanaya + 1 S. spp Tetracyclus spp. + Thalassionema nitzschioides Grunow H.Perag. et Perag Triceratium condecorum Brightw. 4 Trochosira spinosa Kitton Total number of valves counted Resting spore of Chaetoceros Preservation; P: poor. Abundance; C: common, R: rare CN1 CN D Ma M. splendida s.l Ma 2 sediment accumulation rate curve Fig. 25 D Ma M. splendida s.l Ma m 16.9 Ma Fig Ma 18.0 Ma 18.2 Ma Fig Ma Ma 20.9 Ma Ma Ma Ma Ma Fig Ma Ma NPD2B 18.1 Ma m m 300 Figs 4 6. Crucidenticula kanayae var. pacifica Yanagisawa et Akiba [Sample 26]. Figs. 7, 8. Crucidenticula sawamurae Yanagisawa et Akiba [Sample 12]. Fig. 9. Crucidenticula ikebei Akiba et Yanagisawa [Sample 23]. Fig. 10. Delphineis kamenooensis Yanagisawa [Sample 18]. Fig. 11. Delphineis miocenica H.-J.Schrad. G.W.Andrews [Sample 26]. Fig. 12. Delphineis cf. surirella Ehrenb. G.W. Andrews [Sample 21]. Fig. 13. Kisseleviella carina Shesh.-Por. [Sample 07]. Fig. 14. Ikebea tenuis Brun Akiba [Sample 09]. Fig. 15. Thalassionema obtusa Grunow G.W.Andrews [Sample 10]. Fig. 16. Thalassionema nitzschioides H.Perag. et Perag. [Sample 10]. Fig. 17. Koizumia adaroi Azpeitia Yanagisawa [Sample 22]. Fig. 18. Trochosira spinosa Kitton [Sample 21].

7 Diatom biostratigraphy of the lower Miocene Yunagaya Group 39

40 Yukio Yanagisawa Fig. 19. Thalassisira mizunamiensis Yanagisawa [Sample 18]. Fig. 20. Proboscia interposita Hajós R.W.Jord. et Priddle [Sample 05]. Figs 21, 22.

8 40 Yukio Yanagisawa Fig. 19. Thalassisira mizunamiensis Yanagisawa [Sample 18]. Fig. 20. Proboscia interposita Hajós R.W.Jord. et Priddle [Sample 05]. Figs 21, 22. Rhizosolenia styliformis Brightw. robust form [Sample 05]. Fig. 23. Rhizosolenia miocenica H.-J.Schrad. [Sample 30]. Fig. 24. Actinocyclus cf. ingens f. planus M.C.Whiting et H.-J.Schrad. [Sample 05]. 300

Diatom biostratigraphy of the lower Miocene Yunagaya Group 41 Fig. 25. Stratigraphic distribution of selected diatom species and sediment accumulation rate curve in the Hisanohama section.

9 Diatom biostratigraphy of the lower Miocene Yunagaya Group 41 Fig. 25. Stratigraphic distribution of selected diatom species and sediment accumulation rate curve in the Hisanohama section. Geomagnetic polarity time scale: Gradstein et al ; Diatom zonation and biohorizons: Akiba 1986 and Yanagisawa & Akiba 1998 partly revised by Watanabe & Yanagisawa Yabe 2008 Ogasawara et al Yabe 2008 Fig. 27

10 42 Yukio Yanagisawa Fig. 26. Stratigraphic distribution of selected diatom species in the Hirunotaira section. Diatom zonation: Akiba 1986 and Yanagisawa & Akiba 1998 partly revised by Watanabe & Yanagisawa Yabe 2008 Ogasawara et al Yabe A D A 1995a 2001 Yabe 2008 Yabe C 1995b 2000 A B Mytilus tichanovitchi O Hara & Nemoto Crucidenticula sawamurae Kisseleviella carina C Yabe C D Cibicides subdepressus Nodogenerina lepidula 1990 Denticulopsis C A 18 Ma B Ma C Ma D 16.6 Ma Ma Ma

11 Diatom biostratigraphy of the lower Miocene Yunagaya Group 43 Fig. 27. Early to middle Miocene chronostratigraphy in the Joban area. Geomagnetic polarity time scale: Gradstein et al ; R: radiolarian zonation of Sanfilippo & Nigrini 1998, N: nannofossil zonation of Okada & Bukry 1980, P: planktonic foraminiferal zonation of Blow 1969 ; D: diatom zonation of Akiba 1986 and Yanagisawa & Akiba 1998 partly revised by Watanabe & Yanagisawa 2005.

12 44 Yukio Yanagisawa / 34 Ma Zachos et al Ma 4 Mi 1 Mi 1a Mi 1b Mi 2 Miller et al Billups & Schrag 2002, Billups et al Mi 1b 17.7 Ma Mi Ma Fig. 27 Mi 1b 17.9 Ma Mi 1b Mi Ma 16.7 Ma Fig. 27 A Mi 1b 17.9 Ma Mi 1b B C Ma Mi 1b Mi Ma D 18.2 Ma 16.9 Ma Kisseleviella carina Zone Thalassiosira fraga Zone 6 18 Akiba, F Middle Miocene to Quaternary diatom biostratigraphy in the Nankai Trough and Japan Trench, and modified Lower Miocene through Quaternary diatom zones for middle-to-high latitudes of the North Pacific. In: Kagami, H., Karig, D.E., Coulbourn, W.T., et al. eds Initial Reports of the Deep Sea Drilling Project 87: U.S. Government. Printing Office, Washington D.C. Billups, K. & Schrag, D.P Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18 O/ 16 O mesurements on benthic foraminifera. Paleoceanography 17: DOI: / 2000PA Billups, K., Channel, J.E.T. & Zachos, J Late Oligocene to early Miocene geochronology and paleoceanography from subantarctic South Atlantic. Paleoceanography 17: DOI: /2000PA Blow, W.H Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: Brönnimann, P. & Renz, H.H. eds Proceedings of the First International Conference on Planktonic Microfossils. pp Leiden, Netherlands. Gradstein, F., Ogg, J. & Smith, A A Geologic Time Scale. 589 pp. Cambridge University Press In pp

13 Diatom biostratigraphy of the lower Miocene Yunagaya Group pp pp pp Miller, K.G., Wright, J.D. & Fairbanks, R.G Unlocking the ice house: Oligocene-Miocene oxygen isotopes, eustasy, and margin erosion. Journal of Geophysical Research 96: : Ogasawara, K., Ugai, H. & Kurihara, Y Short-term early Miocene climatic fluctuations in the Japanese Islands. In: Ratanasthien, B., Rieb, S.L. & Chantraprasert, S. eds Proceedings of the 8th International Congress on Pacific Neogene Stratigraphy, Chiang Mai. pp Chiang Mai University, Chiang Mai, Thailand. O Hara, S. & Nemoto, N Molluscan fossils from the Goyasu Formation in the Futaba distinct of the Joban Coalfield. Journal of the College of Arts and Sciences, Chiba University, Series B 15: O Hara, S. & Nemoto, N Molluscan fossils from the type Goyasu Formation of the Joban Coalfield. Journal of the College of Arts and Sciences, Chiba University, Series B 17: Okada, H. & Bukry, D Supplementary modification and introduction of code numbers to the low-latitude cocolith biostratigraphic zonation Bukry, 1973, Marine Micropaleontology 5: Sanfilippo, A. & Nigrini, C Code numbers for Cenozoic low latitude radiolarian biostratigraphic zones and GPTS conversion tables. Marine Micropaleontology 33: I 143 pp : : : : : Watanabe, M. & Yanagisawa, Y Refined Early to Middle Miocene diatom biostratigraphy for the middle- to high-latitude North Pacific. The Island Arc 14: Yabe, A Early Miocene terrestrial climate inferred from plant megafossil assemblages of the Joban and Soma areas, Northeast Honshu, Japan. Bulletin of the Geological Survey of Japan 59: a 101: b 28: : Yanagisawa, Y. & Akiba, F Refined Neogene diatom biostratigraphy for the northwest Pacific around Japan, with an introduction of code numbers for selected diatom biohorizons. Journal of the Geological Society of Japan 104: : Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292:

Diatom27_17-32.pdf

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