Stratigraphic sequence and age of the Upper Cretaceous Daxingzhuang Formation in western Liaoning province

The Upper Cretaceous Daxingzhuang Formation in western Liaoning is mainly distributed in Jinzahou and Yixian and also outcrops sporadically in the Boluochi ,Chaoyang,and Jianguo,Fuxin.Ex-cept in the Fuxin area where it is composed of intermediate-basic lavas and pyroclastic rocks,in other ar-eas it consists of intermediate-acid and acid lavas,lava-clastic rocks,pyroclastic rocks,pyroclastic-sedi-mentary rocks and subvolcanic rocks.It lies unconformably on the Lower Cretaceous Yixian,Jiufutang and Sahai Formations and disconformably on the Cretaceous Sunjiawan Formation.Its K-Ar age is80.83Ma ,indicating a Late Cretaceous age.This phase of volcanism is characterized by alternating explosion and out-pouring.In the late phase subvolcanic rocks were in truded.The activity was weak and the distribution of the subvolcanic rocks is limited.