华北地台北缘辽北地区南华系沉积初步研究

A prelimianry study on Nanhua System in northern Liaoning Province,north margin of the North China Platform

中国南华系冰成地层的分布及沉积特点一直为新元古界研究的热点,北方地区是否存在南华系沉积地层仍存在很大的争议,本文通过近3年对辽宁地区新元古代岩石地层单位的野外地质调查、对比与研究,确定了辽宁北部地区在新元古代时期存在冰碛堆积物,并划分出两期冰碛作用阶段,即:新元古代南华纪第一次殷屯冰期,南华纪第二次汎河冰期;其中第一次冰期为一套陆相冰碛堆积,主要岩性为灰紫色块状厚层杂砾岩夹含砾粗砂岩透镜体,分布于辽北铁岭;第二次冰期堆积主要涉及辽北陆相冰水堆积的汎河组。同时确认出永宁组为第一次殷屯冰期前的陆源河流相沉积;陈千户组(陆相)为第一次殷屯冰期和第二次汎河冰期之间的间冰期沉积产物。

The distribution and sedimentary characteristics of the Nanhua glacial strata in China have always been the focus of the Neoproterozoic study,and whether there is glacial strata of Nanhua System(Cryogenian System)in northern China has always been controversial.In this paper,the field geological survey,comparison and study of Neoproterozoic lithostratigraphic units in Liaoning region are conducted in the past three years,it is determined that moraine deposits existed in the Neoproterozoic period in the northern Liaoning area,and two stages of moraine action have been divided,namely,the Neoproterozoic Nanhua Yintun Ice Period and the Neoproterozoic Nanhua Fanhe Ice Period.The first glacial period is a set of continental moraine accumulation,whose main lithology is grayish-purple thick massive conglomerate intercalated with gravelly coarse sandstone lens,distributed near Tieling in the northern Liaoning.The second glacial deposition consists of the northern Liaoning,mainly involving the Fanhe Formation of continental ice water accumulation.At the same time,it is confirmed that the Yongning Formation(terrigenous river facies)was formed before the first Yintun glacial period;the Chenqianhu Formation(continental facies)were formed in the interglacial period between the first Yintun glacial period and the second Fanhe glacial period.