辽西南部中生代地层序列及特征

MESOZOIC STRATIGRAPHIC SEQUENCE AND ITS CHARACTERISTICS IN SOUTHERN WESTERN LIAONING PROVINCE, NORTHEAST CHINA

辽西南部兴城、葫芦岛等地中生代地层由老到新可划分为下三叠统红砬组、中侏罗统海房沟组、中—上侏罗统髫髻山组、上侏罗统土城子组以及下白垩统义县组。红砬组分布在杨家杖子和喜鹊沟向斜内,海房沟组主要分布于兴城龙回头盆地,髫髻山组和土城子组分布于金岭寺—羊山盆地南端的娘娘庙、杨树湾一带,义县组主要分布在小德营子、新台门和兴城—老滩等地。南票虹螺蚬地区原定"红砬组"的叶肢介化石组合所在层位有可能属于乐平统蛤蟆山组,白马石中华史麦斯果植物群化石层的归属和时代尚需进一步研究,新台门和高桥地区产热河生物群化石的湖相沉积夹层属于义县组。本区中生代地层缺失较多,海房沟组和义县组均存在不整合于新太古代花岗岩之上的情况,是本区独特的燕山运动地质记录,并且表明山海关古陆/隆起在中生代仍然影响着辽西地区的沉积古地理格局。

The Mesozoic strata in southern Western Liaoning Province,Northeast China can be divided into the Lower Triassic Hongla Formation,the Middle Jurassic Haifanggou Formation,the Middle-Upper Jurassic Tiaojishan Formation,the Upper Jurassic Tuchengzi Formation,and the Lower Cretaceous Yixian Formation.The Hongla Formation is distributed in the Yangjiazhangzi and Xiquegou Synclines,the Haifanggou Formation mainly in the Longhuitou Basin of Xingcheng,the Tiaojishan and Tuchengzi formations in the Niangniangmiao and Yangshuwan areas of the southern Jinlingsi-Yangshan Basin,and the Yixian Formation in the Xiaodeyingzi,Xintaimen and Xingcheng-Laotan areas.The conchostracan-bearing horizon previously assigned to the Hongla Formation in the Hongluoxian area,Nanpiao may belong to the Lopingian Hamashan Formation,the stratigraphic assignment and geological age of the bed yielding Schmeissneria sinensis in Baimashi need a further study,and the lacustrine layers bearing the Jehol Biota in Xintaimen and Gaoqiao belong to the Yixian Formation.In general,stratigraphic lacunae are common among the Mesozoic strata in southern Western Liaoning,with the Haifanggou and Yixian formations uncomfortably overlying the Neoarchean granites in some areas,recording the Yanshanian Movement in this region and also indicating that the Shanhaiguan Paleoland/Paleouplift still exerted an influence on the sedimentary paleogeographic pattern in western Liaoning in the Mesozoic.