[SGL36-P09] Stratigraphy, sandstone composition, and detrital zircon U-Pb ages of Permian strata in the Hongo-Moribu area of the Hida-gaien belt, central Japan
Keywords:Permian, Hida-gaien belt, sandstone composition, detrital zircon, U-Pb age
In the present study, the "Moribu Formation" in the Hongo area is subdivided into units I to IV based on their lithology. Unit I consists of dark gray fine- to medium-grained sandstone with interbedded limestone. Units II to IV are characterized by dark gray fine- to medium-grained sandstone and alternating sandstone and shale. These characteristics are similar to the lower to upper parts of the Moribu Formation in the type locality. This correlation indicates that the stratigraphy of the "Moribu Formation" in the Hongo area lacks the basal part consisting of conglomerate of the type locality. We collected 10 sandstone samples from units I to IV in the Hongo area. Based on the result of modal analysis, the sandstones can be classified as feldspathic to lithic wacke. Qm–F–Lt ternary diagram shows that the examined sandstones plot in the dissected arc to basement uplift fields proposed by Dickinson et al. (1983). According to Yoshida and Tazawa (2000), the sandstones of the basal to middle parts of the Moribu Formation are characterized by the composition of undissected arc to basement uplift. Therefore, our result indicates that a more extensive distribution of a granitic basement was present in the provenance of the Permian strata.
The U-Pb ages of detrital zircons were examined for medium-grained sandstone of the middle part of the Moribu Formation. A clear youngest age peak of 272.4 ± 2.6 Ma was recognized, which corresponds to late Kungurian to early Roadian. This result is in good agreement with biostratigraphic age constraints by fusulinids and brachiopods for the formation.