���������˳Dz�ׯ�������� “����������—����—����—���»�ɽ�緢��” �����������ش�����—������ص����϶ˡ�ͨ��ʵ������ʹ�����ߵ��飬ȷ�ϲ�ׯ�����������Ի�ɽ��Ϊ���ĵز�ɻ��������飬����һ�����仮��Ϊ 3 �����Զ�: �¶� (K ₁ y ¹ ) ��ɰ���Һ�����- -�л��Ի�ɽ����ɣ��ж� (K ₁ y ² ) �ɺ�������Һ����Ի�ɽ����ɣ��϶� (K ₁ y ³ ) �����ԡ�ƫ���Ի�ɽ����ɡ��Լ�ɽ�����ɽ�Һͻ�ɽ��м���е��ʯ���� LA - ICP - MS �������е� U - Pb ����������������������¶κ��жε�����ֱ�Ϊ 131. 5 ±1. 4 Ma �� 129. 2 ±1. 0 Ma���λ�ɽ״��λ���¶εĴ��氲ɽ�Ҽ�Ȩƽ������Ϊ 126. 0 ±1. 2 Ma���ý���뱱������—��������������׼��������һ�¡����ݻ�ɽ- -�������жԱȹ�ϵ����ׯ������������������׼������С��²��Աȣ���ȱʧ�����׼�����������ϲ��ԱȵIJ�λ����ʾ��ʱ�ڻ�ɽ�緢���ĸ���������—������ء�

The Caozhuang area of Xingcheng in southwestern Mesozoic Fuxin- -Yixian basin��western Liaon- ing��belongs to“the Mesozoic Jinxi- - Jinzhou- - Fuxin- - Yixian volcanic eruptive belt”�� The strata mainly volcanic in composition in the Caozhuang area should be grouped into Yixian Formation through the section measuring and large scaled investigation in this area��and can be further divided into three members from in ascending order�� The lower member (K ₁ y ¹ ) consists of glutenite and intermediate��intermediate- basic volcanic rocks�� The middle member (K ₁ y ² ) consists of lacustrine sediments and intermediate volcanic rocks��and the upper member (K ₁ y ³ ) consists of intermediate and meta- alkaline volcanic rocks�� LA -ICP - -MS zircon U -Pb dating of the volcanic and pyroclastic rocks of the Jianshan section reveals that the K ₁ y ¹ and K ₁ y ² were formed in 131. 5 ±1. 4 Ma and 129. 2 ±1. 0 Ma�� respectively�� The weighted mean age of the intrusive trachyandesite in K ₁ y ¹ is 126. 0 ±1. 2 Ma��consistent with the age obtained from the type section of Yixian Fomation in Fuxin - Yixian basin�� Taking the correlation with the volcanic- sedimentary sequences��we propose that the Yixian Formation in Caozhuang area can be regarded as the lower and middle Yixian Formation in the type section��with missing its upper part in the Caozhuang area��indicating that the center of volcanic eruption was closer to the Fuxin - - Yixian basin at that time��