Age Estimation of the Japan Sea on the Basis of Stratigraphy, Basement Depth, and Heat Flow Data

抄録

Ages of the Japan and the Yamato Basins in the Japan Sea were examined on the basis of three independent methods; stratigraphic consideration of the basin sediments, age-depth correlation, and age-heat flow correlation. Basement depths of the Japan and the Yamato Basins after sediment loading correction were compared with those of other marginal seas in the Western Pacific whose ages are well constrained. The age estimations by age-depth correlation and age-heat flow correlation show good coincidence in the Japan Basin. The age estimation of the Yamato Basin, however, shows a discrepancy among the three methods; the basement depth shows an age range from 6Ma to 0Ma, sediment stratigraphy shows that of about 10Ma, and heat flow data show the age from 30Ma to just over 10Ma. This discrepancy can be explained by the thick accumulation of Neogene volcaniclastics which are represented as acoustic basements on seismic reflection records with a refraction velocity of 3.5km/sec. The final estimated age of the Japan and the Yamato Basins is identical with a range of 30Ma or older to 15Ma or slightly younger.