北京延庆硅化木公园地质剖面陆相层序地层特征分析

Continental sequence stratigraphy analysis of "Fossil Wood" Geological Park Section in Yanqing County,Beijing

陆相层序地层的研究是由海相层序地层研究演变而来,但陆相层序控制因素的不同造成陆相层序在规模、体系域发育特征等与海相层序都具有很大的区别。陆相层序受构造、事件沉积和气候等多因素影响,往往很难找到发育完整又易于观察的层序剖面。文中以北京北部延庆硅化木公园的中生界侏罗系"花盆"盆地为研究对象,通过露头观察、自然伽马点测和采样分析等地质方法,细致观察和分析了整个地质剖面,根据沉积和层序特征,划分出7个陆相层序,在各个层序内部又细分出各种不同体系域类型并确定了识别标志。根据研究结果,总结了陆相山间盆地层序地层的一些典型特征,初步划分出3种典型的陆相层序。同时将本区广泛出现的硅化木化石成因解释为大规模湖泛和火山作用的综合结果,并将木化石的出现作为大规模湖泛出现的标志。研究成果完整呈现了受构造、气候和事件沉积等多重影响的小型陆相山间盆地的湖泊层序典型特征,具备一定的代表性。

The study of continental sequence stratigraphy inherits achievements from marine sequence strata.While continental sequence stratigraphy which has more complex controlling factors develops different scales,system tracts characteristics compared to the marine sequence.These factors include tectonic movement,climatic change,volcanic events and so on.It is difficult to observe an integral sequence section in a local area obviously.In this paper,three typical continental sequence were found and researched detailedly of＂flowerpot＂ basin located in＂fossil wood＂geological park within four square kilometers by outcrop surveying,sampling and natural gamma ray measurement.The first kind sequence is＂normal sequence＂which is affected by climatic and tectonic factors.The second kind is＂event sequence＂which is mainly affected by volcanic events.The last kind is＂transitional sequence＂which is intensively impacted by both mentioned factors.The type and identifying signature of several system tracts were also discussed.The widespread fossil woods in this area were considered as a result of lake-flooding.Its appearance was also considered as an index of flooding.All research findings interpreted typical sequence stratigraphy characteristics of minitype continental basin which was impacted by tectonic movement,climatic change and volcanic events.