五峰阶(Wufengian Stage)位于石口阶之上,曾用于中国上奥陶统顶部的一个阶,大致与欧洲的阿什极尔阶相当。五峰阶自下而上含有六个笔石带:①Pleurograptus lui带;②Dicellograptus szechuanensis带;③Tangyagraptus typicus带;④Diceratograptus mirus带;⑤Paraorthograptus typicus带和⑥Diplograptus bohemicus带。后人厘定为五个化石带,自下而上为:①Dicellograptus complexus带,②Tangyagraptus typicus带,③Paraort...