Abstract
Coral-dominated reef assemblage occurs in several limestone beds of the Toyonishi Group (upper Jurassic-lower Cretaceous) in Murotsu area, Yamaguchi Prefecture. The corals mostly show upright growth positions and form reef frameworks. They occur throughout in the limestone facies and are expanded even in the intercalated mudstone facies. The corals are divided into two types by their growth forms; the massive type indicating a relatively high-energy condition, and the branching type implying a low-energy condition. The latter is accompanied by dasycladacean algae, which are indicative of calm water. The limestone differs from the other Japanese Upper Jurassic to Lower Cretaceous limestone (e.g. the Torinosu Group) in showing abrupt lithologic change from the underlying calcareous sandstone to the reefal limestone, and lacking stromatoporoids, calcareous sponges, hydrozoans, microencrusters, and ooids.
