奈良盆地とその周辺の火山灰層序と年代層序

概要

論文の詳細を見る
Nara Basin and its surrounding hilly area are consisted of plutonic basement rocks and overlying Miocene to Pleistocene sediments.　These sediments are called as Miocene Fujiwara, Muro, Nijo Groups, Plio-Pleistocene Osaka Group and Holocene deposits in ascending order. In the present article the author intended to clarify a tephrostratigraphy in the area and to correlate with neighbouring sedimentary basin, especially concerning to Plio-Pleistocene sequences. For the identification and correlation of tephra EDS and VAIS techniques were adopted respectively. Volcanic glass shards were analysed with EDS and 8 major element composition based on 20 glass shards analysis was presented as their average value with standard deviation. Miocene and Pliocene tephra have ill preserved volcanic glass, but in Pleistocene and Holocene volcanic glass shards were in a good state of preservation. Many layers of tephra of the lower Pliocene were found and upper Pliocene tephra were very restricted in the present sequence. In the outskirts area of the Nara basin radiometric age of representative tephra was measured, and in the present area their time planes were extended safely by means of present tephra correlation.
奈良教育大学の論文