秩父堆積盆地北縁における新第三系下部層のFT年代

概要

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Fission track dating was carried out on tuffaceous samples collected probably from the lower part of Miocene sequence in the northern part of the Chichibu sedimentary basin, northeast Kanto Mountains. The aim of the dating was to determine the age of the beginning of the Miocene transgression which caused the deposition of voluminous clastic sediments in the Chichibu basin. Zircon FT ages were obtained from the Nenokami Formation and the Shirasu Sandatone Member of the Ushikubi Formation. The ages were 16.0±0.7Ma and 16.7±1.1Ma, respectively. These ages were determined using a standard statistical approach to eliminate old detrital zircon crystals from the age population. The FT results are consistent with stratigraphic order, and suggest that the depositional system probably was developed at the end of the lower Miocene at least.
地学団体研究会の論文
2006-07-25