Takayanagi, Yukio (1998): Depositional environments of bedded cherts of the Shimanto Terrane, the Kii Peninsula, inferred from normal paraffin and major element compositions. Nippon Chishitsugaku Gakkai, Tokyo, Japan, Chishitsugaku Zasshi = Journal of the Geological Society of Japan, 104 (8), 501-515, georefid:2002-041954

Depositional environments of Cretaceous bedded cherts and their intercalated shales from Ugura, the Kii Peninsula, in the Shimanto Terrane were discussed on the basis of n-paraffins (C (sub 12) -C (sub 38) ) and major elements contained in them. For comparison, n-paraffins in marine sediments from a pelagic environment (DSDP Site 305) and a coastal environment (off-Shikoku) were also analyzed. Inverse correlation of SiO (sub 2) versus TiO (sub 2) and Al (sub 2) O (sub 3) observed in the Shimanto cherts and shales suggests that they resulted from a mixing of biogenic silica and clastic materials. Major element compositions of the Shimanto cherts suggest that they deposited in an environment free from hydrothermal activities. The n-paraffins in pelagic Site 305 sediments are low in concentration and composed mainly of short-chained molecules (C (sub 14) -C (sub 23) ) derived from marine autochthonous organisms. On the contrary, the coastal off-Shikoku sediments contain a large amount of long-chained n-paraffins with a strong odd-carbon number predominance, which probably were derived from terrestrial higher plant waxes. The n-paraffins in most Shimanto shale partings are low in concentration and are short-chained (C (sub 14) -C (sub 23) ). Two possible origins are considered for the n-paraffins in Shimanto shales, namely, marine autochthonous organisms or products of thermal degradation of complex organic matter. Some Shimanto shales, however, contain a small amount of long-chained n-paraffins with a strong odd-carbon number predominance. This suggests that the Shimanto shales have preserved the n-paraffin composition acquired during deposition. The low abundance of long-chained n-paraffins in the Shimanto shales suggests that the bedded cherts deposited in an environment with little contribution of terrigenous organic matter. The MnO/TiO (sub 2) ratio in marine sediments generally increases with increasing distance from the continent. The ratio of the Shimanto bedded cherts are larger than those of sediments from continental margin regions and smaller than those of typical pelagic sediments. It is, therefore, inferred that the Shimanto bedded cherts deposited in a more pelagic environment than continental margin regions. This inference is consistent with that based on their n-paraffin compositions.
West: 157.5059 East: 157.5101 North: 32.0008 South: 32.0007
Expedition: 32
Site: 32-305
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2002-041954 (c.f. for more detailed metadata)
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