Abstract
Based on facies analysis, the depositional environments of the lower Cretaceous transgressive Arida Formation are divided into four depositional facies : upper-middle shoreface, lower shoreface, inner shelf, and outer shelf facies. In addition, abundant bivalve fossils are divided into three fossil assemblages : Pterotrigonia pocilliformis (lower shoreface), Nanonavis yokoyamai (inner shelf) and Periploma (?) monobensis (outer shelf). The paleo-ecology of these fossils was previously unknown, but their habitats are inferred from the mode of occurrence, especially autochthonous fossils and articulated valves, and depositional environments.
