通过对辽南瓦房店市岳山地区详细的野外地质调查, 在桥头组中首次发现两处冰筏坠石冰碛沉积现象.坠石大小不等, 均呈椭球倒锥状, 磨圆较好, 岩性分别为灰褐色细粒石英砂岩和黄褐色铁质胶结细粒石英砂岩, 寄主围岩岩性为黄绿色粉砂质页岩且环绕坠石沉积, 两者岩性差别较大, 界线清晰.另外在桥头组中采集的碎屑锆石最小206Pb/238U年龄为662±16 Ma (～ (207)Pb/206Pb年龄为884±28 Ma), 可以推断桥头组形成晚于800 Ma, 应为新元古代中晚期沉积产物.根据以上证据及层序学资料, 笔者把辽宁地区出露的桥头组、长岭子组 (康家组)厘定为辽宁地区第二次冰碛事件, 形成时代确定为新元古代中北方世 (南华世).%Based on the detailed field geological investigation in Yueshan City of Wafangdian in southern Liaoning, two sets of moraine deposits comprising ice raft falling rocks were firstly found in Qiaotou Formation.The falling rocks are ellipsoidal and inverted conical in shape with various sizes and good rounding.The lithology is grayish brown fine quartz sandstone and yellowish brown iron cemented fine quartz sandstone.The host rocks of ice rafts are yellowish green silty shale, which is quite different from the falling rocks with distinct boundary.In addition, the minimum206Pb/238U age of detrital zircon collected from Qiaotou Formation is 662±16 Ma (～ (207)Pb/206Pb age is 884±28 Ma), therefore it can be inferred that Qiaotou Formation was deposited later than 800 Ma, which should be the Middle—Late Neoproterozoic sedimentary product.Based on the above evidence and sequence data, Qiaotou Formation and Changlingzi Formation (Kangjia Formation)were determined as products of the second moraine event in Liaoning, and their formation time were defined as Neoproterozoic Middle Beifang epoch (Nanhua epoch).
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