| Research Abstract |
In the 11-International Congress of the International Union for Quaternary Research held in Moscow in 1983, and establishment of a boundary between Pleistocene and Holocene epoches was discussed, and it was dicided to be established at Maltemys and Solderga near Goeteborg in Scandinavia. However, any research concerning this boundary in Japan is not yet start by the Japanese stratigraphers and palaeontologists. Th present investigator, therefore, has made the researches of sedimentology, stratigraphy and palaeontolog during the late Pleistocene and Holocene in the Hokuriku district, especially Toyama, Nanao, Hakui, Kanazawa, Komatsu, Fukui, Mikata and Obama lowland areas from the view poin of five principal categories such as lithostratigraphy, biostratigraphy, chronostratigaraphy,morphostratigraphy, and climatostratigraphy etc., for a establishment of the Pleistocene/Holocene boundary in Japan.
1) Stratigraphy and sedimentary environment of the Postglacial deposits The Postglacial depo
… More
sits of the alluvial lowland areas in coasts usually indicate a simular stratigraphic succession. The stratigraphic succession in these areas can be summarized in ascending order as Lowest member (gravels), Lower member (alternation of clay and sand with peats), Middle member (marine sand), and Upper member (sand and clay).
2) Palaeontology, especially pollen and diatom analyses, and molluscan fossils Judging from the palynological analysis of the Postglacial deposits from the coastal lowland areas in the Hokuriku district, the palaeoclimatic change during the last 20,000 years may be inferred as follows: 165,000 - 20,900 years ago:cold or slightly cold, dry, nonmarine facies; 140,000 - 16,500 years ago:cold and slightly dry, nonmarine; 120,000 - 14,000 years ago: slightly cold and dry, nonmarine; 10,500 - 12,000 years ago: cool, slightly wet, nonmarine of brackish; 9,000 - 10,500 years ago: slightly cold and we brackish to nonmarine; 5,000 - 9,000 years ago: warm and wet, marine; 1,500 - 5,000 years ago: cool and slightly dry, brackish to nonmarine; the last 1,500 years ago: mild and wet brackish.
On the basis of the stratigraphy, palaeontology,especially pollen and diatom analyses, palaeovegetation and palaeoclimatology, the boundary between Pleistocene and Holocene is established stratigraphically between Lower and Middle members. Less
|
