Cretaceous Fore-Arc Basin and Its Provenance in Sakhalin, Far East Russia: U-Pb Ages of Detrital Zircons From the Yezo Group

In order to reconstruct the pre-Japan Sea configuration of the Cretaceous arc-trench system, we measured U-Pb ages of detrital zircons in the five sandstone samples from the Yezo Group in Sakhalin using LA-ICP-MS. A sandstone sample from the lowermost horizon (Ai Formation) contains abundant Early Cretaceous (110-100 Ma) zircons with minor amounts of pre-Jurassic ones. Four sandstones from the uppermost (Krasnoyarka Formation) are enriched dominantly in Late Cretaceous (100-66 Ma) grains. The YC1 sigma ages of these samples are generally consistent with the previous fossil ages; nonetheless, a possible age extension of the Ai Fm up possibly into the Cenomanian was newly suggested. The stepwise younging in peak age of zircons according to the stratigraphy suggests the continuous replacement of arc granitoid exposures in the Cretaceous magmatic arc in the provenance likely developed on the continent side. This secular trend in zircon age spectra of the Yezo Group in Sakhalin is properly correlated with that in Hokkaido and also with that of coeval sandstones in southwest Japan, suggesting a monotonous sedimentation in the fore-arc basin of the Late Cretaceous arc-trench system developed along the Pacific margin, from Sakhalin to southwest Japan for ca. 2500 km in length. Its spatial dimension corresponds to that of the modern representative fore-arc basin in the Java-Sumatra region.