岡山大学 地球科学研究報告
Published by Okayama University Earth Science Reports Editorial Committee

吉備高原周辺の古第三系に関する最近の知見とその古地理学的意義

Tanaka, Hajime
Hotani, Shu
Yamamoto, Yasuo
Danhara, Tohru
Abstract
The "Kibi Plateau" forms a unique geomorphic province with the gently-sloping and stable continental feature. Gravel deposites called the "Mountain Gravels", are distributed sporadically in the Kibi Plateau, and have been considered Pliocene deposits. However, recent fission-track ages of the tuff beds intercalated in the deposits have indicated that the ago of deposits are Paleogen in the age. So far, fission-track ages (using zircon) of 61 to 65, 55, 37, 34 to 35 and 27 Ma are obtained. Remaining the belt-like distributions of the Paleogene gravelly valley-full deposits suggest that the Kibe Plateau has been keeping as a stable block, and repeated periods of incision followed by sedimentation of valley-fill deposits are occurred in the area during Paleogene period.
Keywords
Kibi Plateau
gravelly valley-fill deposites
fission-track ages
Paleogene palaeogeography
ISSN
1340-7414
NCID
AN10506284
NAID