| Co-Investigator(Kenkyū-buntansha) |
HASEGAWA Yoshiyuki Niigata Univ., General Educat, Professor., 教養部, 教授 (80018572)
YANAGIDA Juichi Kyushu Univ., Faculty of Science, Professor., 理学部, 教授 (70037183)
IGO Hisayoshi Tsukuba Univ., Eath Science, Professor., 地球科学系, 教授 (20015572)
OZAWA Tomowo Nagoya Univ., Faculty of Science, Associate Professor., 理学部, 助教授 (80037233)
OKIMURA Yuji Hiroshima Univ., Faculty of Scien, Professor., 理学部, 教授 (60033825)
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| Research Abstract |
When we are to accept the base of fusulinid Sphaeroschwagerina vulgaris-fusiformis Zone in Urals as the beginning of the Permian, it is now possible to trace the zone in Japan within carbonate facies. As exemplified in the Akiyoshi limestone plateau, however, it is difficult to pin-point the C/P boundary in field, owing to the nature of outcrop being scattered pinnacles of massive, partially brecciated limestone.
It provides a very good example of faunal sequence though, especially of foraminifers starting from Lower Carboniferous to Upper Permian. Occurrence of other taxa (conodonts, smaller foraminifers, corals, brachiopods, cephalopods, bryozoans, etc.) is rather meager in Akiyoshi to supplement in recognizing the C/P boundary.
Significant environmental change may be sought within the Triticites Limestone of Upper Carboniferous in Akiyoshi, where bands and patches of black sparry calcite are intercalated in the high-energy limestones. This peculiar lithology contains "Microcodium" like structure and shows relatively low C value, both indicating the influence of fresh-water to the formation of carbonate in the marine Akiyoshi limestone.
The effect of global sea-level change may be more precisely detected in future within the sequence of Akiyoshi limestone formed upon a volcanic sea mount.
C/P boundary has been sought also within chert sequence of basinal facies in Japan, where radiolarians and conodonts have proved to be useful for zonation. Environmental change may also be detected in this type of lithologic sequence, which accounts for the global change in sea water composition. Problem is that it has been difficult to correlate zonation thus established within basinal facies with that of epicontinental or near shore facies in classical areas.
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