駿河舟状海盆底コア資料の<14>^C年代

Abstract

The roles of various event deposition in the environmental changes of sea floor should be noticed and the method of study should be more fully developed than up to now. From this point of view, we tried to adopt the analysis of variation in the radiocarbon ages of various organic fractions in a turbidite sediment core from the Suruga Trough off Shizuoka, Central Japan. That is, different organic fractions of the plant residues and clastic sediment materials of the same horizon in a core showed relevant ^<14>C ages. From these results, it was assumed that the plant residues in the core originated in river flood and were mixed with older sediments of shallow sea when the sediment layer was overloaded and collapsed forming the turbidity current to the depth of over 2000 meters. Such evnts must have occurred with considerble frequency, that is, several times in one thousand years. For reference, the age of a wood fragment in another pebbly core from the Suruga Trough was measured also. The result reveals that the pebble layer distributed in the Suruga Bay and the Suruga Trough is very recent sediments transported by some kind of gravity flow.