Detrital zircon U-Pb ages of the accretionary complex in the Chichibu Belt in the central part of the Akaishi Mountains, central Japan

Abstract

U-Pb dating of detrital zircons was undertaken for three sandstone samples of the accretionary complex in the Chichibu Belt, central Akaishi Mountains, central Japan. The youngest single-grain ages are 170.1±2.3 Ma (1σ), 158.2±1.5 Ma, and 159.9±4.2 Ma. The weighted-mean ages of the youngest clusters are 176.7±1.2 Ma, 166.2±1.3 Ma, and 163.7±0.9 Ma. These youngest single-grain and cluster ages lie in the Toarcian to Kimmeridgian during the Jurassic. Therefore, the terrigenous clastic sediments of the accretionary complex in the Chichibu Belt in this area were deposited in the Toarcian or later.