论文部分内容阅读
1∶5万区域地质调查表明,四合屯—上园地区的珍稀化石沉积层为同一时期的陆相湖泊沉积物,相当于义县组的中部层位。该湖泊早期发育在李八郎沟—四合屯—黄半吉沟一带,中晚期沉积中心向东北部迁移,水体面积逐渐扩大,最终到达上园一带。在湖泊的扩展及演化过程中,常伴随有火山活动,在四合屯一带就发现了湖相枕状熔岩。珍稀化石沉积层之下发育四套旋回性非常明显的爆发—沉积相、爆发相和溢流相的基性—中基性火山岩石组合。在沉积层的上部,出现一套酸性的火山爆发物。该沉积层形成之后,区内出现一期广泛的基性火山岩活动。在不同地域,火山—沉积岩石组合有较大的变化,这种变化可能受制于古地貌背景的差异。
1: 50000 regional geological survey shows that the rare fossil sediments in Sihetun-Shangyuan area are continental lake sediments in the same period, equivalent to the middle layer of the Yixian Formation. The lake was developed in the early Li Ba Lang ditch - Sihetun - Huang Banjigou area, the middle and late sedimentary centers migrate to the northeast, the water area gradually expanded and finally reached the park area. During the expansion and evolution of the lake, volcanic activity is often accompanied by lacustrine pillow-shaped lava in the area of Sihetun. Under the rare fossil sedimentary layer, there are four sets of very obvious swirling eruptions - sedimentary facies, eruptive facies and basic-volcanic rock assemblages of the overflow phase. At the top of the sediment, an acidic volcanic eruption occurred. After the sedimentary layer was formed, a wide range of basic volcanic activity occurred in the area. In different regions, volcanic-sedimentary rock assemblages have a greater change, this change may be subject to the differences in paleogeomorphic backgrounds.