Diatom
Online ISSN : 2186-8565
Print ISSN : 0911-9310
ISSN-L : 0911-9310
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Volume 28
Displaying 1-4 of 4 articles from this issue
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Article
  • Tertiariopsis costatus, a new diatom species from the Mio-Pliocene freshwater sediment of Masuzawa Formation, Iwate Prefecture, Japan
    Hiroyuki TANAKA, Tamotsu NAGUMO
    2012 Volume 28 Pages 1-6
    Published: December 31, 2012
    Released on J-STAGE: August 30, 2013
    DOIhttps://doi.org/10.11464/diatom.28.1
    JOURNAL FREE ACCESS
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    A new Tertiariopsis species, T. costatus sp. nov., is described from a Mio-Pliocene freshwater sediment of the Masuzawa Formation, Iwate Prefecture, Japan. The taxon displays most of the characteristics associated with the genus Tertiariopsis such as a single rimoportula on the mantle, mantle fultoportulae with three satellite pores and mantle fultoportulae and rimoportula covered by a marginal lamina, but has a unique characteristic of thin costae located on the inner mantle between the valve rim and mantle fultoportulae. Moreover, the single rimoportula is usually found on the end of one of these thin costae.
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  • Hyalogramma M.Garcia (Fragilariales, Bacillariophyceae): a new hyaline araphid genus from Brazilian marine sandy beaches
    Marinês GARCIA
    2012 Volume 28 Pages 7-13
    Published: December 31, 2012
    Released on J-STAGE: August 30, 2013
    DOIhttps://doi.org/10.11464/diatom.28.7
    JOURNAL FREE ACCESS
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    Observation of sand samples collected from dissipative marine sandy beaches in Southern Brazil revealed the presence of a new hyaline araphid diatom, characterized by the presence of two rimoportulae per frustule (located in a diagonal position at each apex), two simple apical pore fields on the mantle at each valve pole, striae that are not visible in LM, a very narrow sternum visible only in SEM, and open and similar bands ornamented by 3–5 rows of poroids. The new species, Hyalogramma brasiliensis M.Garcia, belongs to a new araphid genus, Hyalogramma M.Garcia, and is placed within the family Fragilariaceae.
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  • Freshwater fossil diatoms from the Ningyo-toge Formation of Onbara and Tatsumi-toge areas at the Okayama-Tottori prefectural boundary, Japan
    Hiroyuki TANAKA
    2012 Volume 28 Pages 14-18
    Published: December 31, 2012
    Released on J-STAGE: August 30, 2013
    DOIhttps://doi.org/10.11464/diatom.28.14
    JOURNAL FREE ACCESS
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    Fossil diatom assemblages were investigated from the Onbara and Tatsumi-toge areas in the Ningyo-toge Formation, which is distributed around the border of Okayama and Tottori Prefectures and is estimated to be Late Miocene to Pliocene in age. Plant fossils have also been reported from these areas. In total five samples, three from Onbara and two from Tatsumi-toge, were observed in order to examine the relationship between the diatoms at the two sites. The diatom assemblages were all dominated by freshwater centric diatoms with a relative frequency of 97–100%. Two samples from the Onbara area, original materials of fossil plants, and one sample from the Tatsumi-toge area, near the horizon of plant fossil sampling site, were dominated by Cyclotella kohsakaensis H.Tanaka & H.Kobayasi and Aulacoseira sp., while one sample taken near the plant fossil horizon in Onbara area and one from Tatsumi-toge, the horizon of the plant fossil sample site, were dominated by Cyclotella iris Brun & Hérib. s.l. and Aulacoseira ambigua （Grunow） Simonsen, indicating each area consists of at least two horizons. These species compositions do not correspond to that of Naru, a vicinal site whose diatom species composition was previously reported, suggesting it also belongs to a different horizon.
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  • Diatom assemblages in tsunami deposits in a paddy field and on paved roads from Ibaraki and Chiba Prefectures, Japan, generated by the 2011 Tohoku tsunami
    Yuki SAWAI, Masanobu SHISHIKURA, Yuichi NAMEGAYA, Yushiro FUJII, Yukar ...
    2012 Volume 28 Pages 19-26
    Published: December 31, 2012
    Released on J-STAGE: August 30, 2013
    DOIhttps://doi.org/10.11464/diatom.28.19
    JOURNAL FREE ACCESS
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    We visited Juo and Kashima (Ibaraki) and Hasunuma (Chiba) a few days after the 2011 earthquake off the Pacific coast of Tohoku. The tsunami left sandy deposits in paddy fields and on paved roads in the study sites, and the deposits comprise graded and laminated sandy sediments. Diatoms are abundant in the deposits and consist of mixed assemblages, including species with different environmental preferences. Diatom valves are better preserved than in modern tsunami deposits associated with the 1998 Papua New Guinea and the 1994 Java tsunamis, although some selective preservation is recognized due to the damage of species with fragile valves.
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