Stratigraphy and structure of the Lower Cretaceous Sasayama Group in the Sasayama area, Hyogo Prefecture, southwest Japan

Abstract

The Lower Cretaceous Sasayama Group is divided into the Lower Formation and the Upper Formation based on the lithological characters. In the Sasayama Basin, the Lower Formation is thicker and coarser-grained in the southern limb than in the northern limb, which may be the result of dominant sediment supply from southern hinterland. The folding of the basement may have begun before the sedimentation of the Sasayama Group (older than 138 Ma). It is considered that this movement continued while the Lower Formation of the Sasayama Group was deposited in 138 Ma to 110 Ma, and ceased before the volcanic activity of the Arima Group (about 72 Ma) which overlies the Sasayama Group. -from English summary