Abstract
The Jinzu Group, distributed in the border area between Toyama and Gifu prefectures, can be divided into nine lithofacies that in turn can be grouped into five lithofacies assemblages reflecting deposition in alluvial fan, distal fan, and flood-plain depositional environments. These assemblages are assigned to three formations in the Jinzu Group, interpreted as follows: (1) the Ioridanitoge Formation was deposited in an alluvial fan environment along the basin margin; (2) the Inotani Formation was deposited in fluvial and flood-plain environments; and (3) the Shiroiwagawa Formation was also deposited in flood-plain environments. Fining-upward and fining-basinward trends are evident throughout the Jinzu Group, reflecting ongoing subsidence in the inland part of the basin. A northwestward shift in the location of the Jinzu basin is easily interpreted through thickness and paleoenvironment analyses of the Jinzu Group. The shift is interpreted to have been related to the juxtaposition of Jurassic to earliest Cretaceous accretionary complexes along the eastern margin of the Asian continent during the Hauterivian (Early Cretaceous).
