奄美諸島喜界島の古砂丘より産出した後期更新世陸産貝類化石群集
スポンサーリンク
概要
- 論文の詳細を見る
The Suitengu sand dune located on Kikaijima Island in the Amami Archipelago, intercalated three layers of eolian dust paleosol. They date back to 38-35kyr, 32kyr, and 27kyr ago, during the lastglacial stage. The eolian dust layers have yielded fossils of 22 species of land molluscs, including four extinct ones on the island. In comparison with the minute fossils abundant in the three layers, the large-sized fossils are small in number but have remained intact. This indicates that these fossil assemblages were autochthonous. In partiticular, among the species are Cochlicopa lubrica and Pupilla (Gibbulinopsis) cryptdon, which have become extinct on Kikaijima Island. Now C. lubrica distributes only from the northern part of the Tohoku district to Hokkaido, and P. (G.) cryptdon distributes discontinuously and its habitat is restricted to the coasts of western Japan. They have been unearthed from each of the paleosol layers, which correlate with Heinrich cooling events H4, H4∿H3, H3. The composition of these minute land molluscan fossils differs from layer to layer Gastrocopta (Sinalubinula) armigerella and Tornatellides boeningi are dominant in the lower paleosol layer, Diplommatina (Sinica) dormitor, Carychium cymatoplax and Nakadaella micron in the middle layer, and G. (S.) armigerella and T. boeningi in the upper layer. Judging from the habitats of their recent species, it is inferred that the fossil assemblages in the upper and lower layers were formed near the coast lines and that those in the middle layer were formed in and around forests. This is inferred to be due to the transgression and regression caused by the tectonic movement in the late Pleistocene.
- 日本貝類学会の論文
- 2000-06-30