ABSTRACT: The results of the time-series analysis for the several late Cenozoic turbidite successions in the forearc and backarc basins, central Japan, and its application to the sedimentary process analysis
Tokuhashi, Shuichi1, Yoshiroy Ishihara2,
Yuichiro Miyata1, and Isao Mita3
(1) Geological Survey of Japan, Ibaraki, Japan
(2) Yamaguchi Univ, Yamaguchi, Japan
(3) Nihon Tennen Gas Ltd, Shirako-machi, Japan
It is very important to estimate the effects of orbital forcing cycles such as Milankovitch cycles in the turbidite successions in order to predict the chronological development of turbidite sandstones. The time-series analysis for several late Cenozoic turbidite successions both in backarc and forearc basins, central Japan, have been carried out. Main results are as follows: 1) Two kinds of patterns, i.e. a sawtooth-type pattern and a pulse-type pattern, have been recognized in the vertical variation pattern both of total number and total thickness of turbidite sandstone beds intercalated in the definite thickness of hemipelagic mudstone. 2) The detailed sedimentological analyses have led to the conclusion that the sawtooth-type pattern does not reflect the sedimentological effect within the basin such as the shifts of depocenters, but reflects the exterior cause outside the basin, while the pulse-type pattern is derived from the turbidite succession which reflects the shifts of depocenters in the basin. 3) Most of the analysed Tertially turbidite successions both in backarc and forearc basins show the sawtooth-type pattern and strongly indicate the existence of periodic cycles of a few tens of to one hundred of thousand years, probablly reflecting Milankovitch cycles. The pulse-type pattern, recognized only in one turbidite succession, does not show the periodic change with a definite term. 4) It is stressed that the patterns recognized in the vertical variation of turbidite successions are useful to estimate not only the cyclicity in the turbidite succession but also the depositional process of the successions.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia