It was long thought that the late Yanshannian epoch is the transition period from trench-arc system (Andes-type active continental margin) to trench-arc-marginal sea system (Western Pacific-type).

• 经长期考虑；认为燕山晚期中国东部是沟一弧体系(安第斯型)向沟一弧一边缘海体系(西太平洋式)转化的过渡时期.