Earth Science (Chikyu Kagaku)
Online ISSN : 2189-7212
Print ISSN : 0366-6611
Volume 64, Issue 6
Displaying 1-4 of 4 articles from this issue
  • Toshio KOHNO, Masaru TAGA, Nobuhiko YAMASHITA
    Article type: Article
    2010Volume 64Issue 6 Pages 209-210
    Published: November 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL FREE ACCESS
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  • Yoshihiro UJIIE, Mitsunari TAKIYA, Takehiro AIZAWA, Maiko SHIMOFUSA
    Article type: Article
    2010Volume 64Issue 6 Pages 211-218
    Published: November 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL FREE ACCESS
    Algae are regarded as possible excellent progenitors of petroleum hydrocarbons. They have been considered to be transformed into type I kerogen in sediments during diagenesis, which generates a large quantity of petroleum hydrocarbons on catagenesis and metagenesis. Living green algae of Chlorella vulgaris were heated to 72-650℃ for 24 hours under the N_2 in open system in the laboratory to investigate the changes in physical and chemical properties of green algae with regards to the hydrocarbon generation. The atomic H/C vs. O/C ratios indicate that the green algae unheated and heated at the temperature below 233℃ belong to type II kerogen, and shift their position towards the origin of the coordinate axes along an extension of the evolution path for type II kerogen on a van Krevelen diagram. The green algae heated at the temperature from 258 to 331℃ belong to type III kerogen and evolve along the evolution path for this type kerogen. After being heated at 380℃ the green algae become "residual organic matter" described by Tissot and Welte (1984), which is characterized by abnormally low H/C ratios associated with high O/C ratios. The kerogen types of the heated algae samples appear to be transformed from II through III to "residual organic matter" towards the origin on a curve crossing the evolution path of type III kerogen on a van Krevelen diagram. It was shown that heated green algae have decreasing trends in weight, atomic H/C and N/C ratios, and brightness (statistical Thermal Alteration Index) with increasing temperature. The changes in the atomic H/C ratio indicated that hydrocarbon generation from living green algae should take place mainly in the temperature range of about 111 and 405℃, which infers green algae have more potential for petroleum generation than pollen (Pinus and Styrax), spores (Athyrium) and leaves (Pinus) as precursors of type II kerogen, and woods (Pinus) as precursors of type III kerogen.
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  • Fossil Mammal Research Group for Nojiri-ko Excavation
    Article type: Article
    2010Volume 64Issue 6 Pages 219-233
    Published: November 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL FREE ACCESS
    The moose deer, Alces alces, is the largest living deer which the main habitat of the species is the high-latitude coniferous forest of cool temperate to frigid zones of Eurasia and North America continents. The fossils of Alces alces were also known from 5 localities in Japan. Chronological ranges of 3 localities in Japan (Hanaizumi site, Kazaana-dokutsu site and Kumaishi-do cave) are limited from the end of MIS 3 to MIS 2. These Japanese records of Alces alces mark the southern limit of the species including both living and fossils. In 2008, a new fossil specimen of Alces alces, 17N III F18-2 was found from the late Late Pleistocene, T3 unit of Tategahana sand Member, Nojiri-ko Formation, Shinano Town, Nagano Prefecture, Central Japan. This is the first Alces alces record from the formation. The specimen is a fragmentary left dentary with almost complete M3. Two specimens, 16N III F18-36 (almost complete left lower M2) and 10N III E17-88 (lateral part of left dentary fragment), collected in previous excavations, are identified as the same individual as 17N III F18-2, since these three specimens fit precisely together. The age of the specimens is about 44,000y. B.P. (MIS3), based on tephrochronological and AMS^<14>C method dating data. This occurrence indicates sympatric distribution of two large-sized cervids, Sinomegaceros yabei and Alces alces. And these findings provide important knowledge on the environmental transition of Nojiri-ko and its surrounding area through Late Pleistocene. The new fossil Alces alces (17N III F18-2, 16N III F18-36 and 10N III E17-88) from the Nojiri-ko Formation marks the oldest record of the species from Japan and indicates that Alces alces had existed in Japan before MIS3. Based on the paleoclimatological and sea bottom topographical studies, it is supposed that the migration of Alces alces from Eurasia to Honshu, across Hokkaido, was in the cool period of MIS4.
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  • Toshio KOHNO, Masaru TAGA, Nobuhiko YAMASHITA
    Article type: Article
    2010Volume 64Issue 6 Pages 235-240
    Published: November 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL FREE ACCESS
    Luminescence properties of selenite from the Jirantai Saline Lake, Inner Mongolia, China were studied. Almost all of the selenite from this locality fluoresces either cyan white (sample name: MGW) or yellow (sample name: MGY) under both long- and short-wave ultraviolet (UV) light. When the selenite face of section (010) is irradiated with UV light, {111} and {103} sectors emit fluorescence, but {110} sector does not. Photoluminescence (PL) emission and excitation spectra at the room temperature are as follows: The PL emission spectrum of the selenite MGW shows bluish green emission peak at approximately 502nm, and the PL emission spectrum of the selenite MGY red emission peak at approximately 670nm. The colors observed with the naked eye and the spectrometer are not equivalent. The excitation spectrum of MGY shows that MGY fluoresces under not only UV light but visible light, and especially it shows the maximum luminescence efficiency under purple light (398nm). The excitation spectrum of MGW shows that MGW fluoresces under not only UV light but visible light as well as MGY, and it shows the maximum luminescence efficiency under blue light (420nm).
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