It is characterized not only by typical flysch features such as rhythmic sedimentation of turbidites and cast molds, but particularly by cyclic sedimentation forming a cyclic sequence.

• 留凤关群,早有人认为属复理石沉积,不过都未提出具体资料。1954年,靳予贵在其所绘地质图中标出“复理石式沉积”。