Provenance Change in Cretaceous-Paleogene Fore-arc in Western Hokkaido: U-Pb Dating of Detrital Zircons from the Yezo Group

To reconstruct the tectono-sedimentary history of the Cretaceous-Paleogene arc-trench system in western Hokkaido, U-Pb ages were measured of detrital zircons in 11 Cretaceous and Paleogene fore-arc sandstones of the Yezo Group in the Oyubari and Mikasa areas. Age spectra of dated zircons demonstrate that Aptian sandstones of the basal Yezo Group are characterized by the dominant occurrence of Early Cretaceous grains with small amounts of Jurassic, Triassic, Permian, and Precambrian grains (Type 1). In contrast, those of Cenomanian to Paleocene sandstones of the middle to upper Yezo Group are dominated almost totally by mid- to Late Cretaceous grains (Type 2). This remarkable change from Type 1 to Type 2 occurred irreversibly during the Albian, indicating that the surface crust in the provenance in western Hokkaido was significantly renewed then. Among nine sandstones of Type 2, a positive correlation exists between zircon peak age and stratigraphic age, suggesting the unidirectional/gradual replacement of exposed magmatic rocks in the provenance, in particular, new volcanics/intrusives (Rebun-Kabato belt to the west). The pre-Cretaceous zircons in Type 1 sandstones were probably recycled from sandstones in the Jurassic accretionary complexes of the Oshima belt to the west. The coeval and identical turnover in zircon age spectra of the Cretaceous fore-arc sandstones recognized in Southwest Japan, from Kyushu to Kanto district, suggests that the fore-arc basin and its provenance with monotonous arc crustal rocks have ubiquitously developed along the Cretaceous East Asian margin over more than 1,500 km before the Miocene opening of the Japan Sea.

Automated summary

By measuring the U-Pb ages of detrital zircons in Cretaceous and Paleogene fore-arc sandstones of the Yezo Group in western Hokkaido, it was found that there was a significant transition in tectono-sedimentary history from Early Cretaceous dominance to mid- to Late Cretaceous dominance. This transition suggests a significant renewal of the surface crust in the provenance during the Albian. The coeval turnover in zircon age spectra of fore-arc sandstones along the Cretaceous East Asian margin implies a ubiquitous development of fore-arc basins and their provenances over more than 1,500 km before the Miocene opening of the Japan Sea.