摘要
已有勘探资料表明,西藏尼玛盆地古新统—始新统牛堡组地层具有良好的油气资源显示,然而目前有关于该套地层的地层格架划分仍然薄弱。化学地层学方法在北美页岩气勘探开发中取得了巨大成功,鉴于此,本文以尼玛盆地东部的协德乡南牛堡组剖面作为研究对象,通过对露头样品的主微量元素测试结果进行沉积地球化学、主成分分析、完备总体经验模态分解、以及自相关函数分析,从化学自—异旋回角度以及元素耦合行为出发,探讨地球化学基准面对化学地层格架的控制作用,从而为牛堡组地层提供化学地层划分方案。主成分分析结果表明,牛堡组地层沉积主要受控于细粒碎屑输入、碳酸盐岩、粗粒碎屑输入、氧化还原—生产力、以及盐度这五个因素;经验模态分解和自相关函数分析结果表明,牛堡组地层受到了明显的异旋回驱动,显示出多尺度基准面震荡特点。通过对异旋回信号分量(本征模函数,IMFs)进行重构,并且结合元素相互耦合特性,建立了牛堡组化学地层格架,该结果与岩石地层单元以及沉积相单元一致,证明了本文所提出的化学地层划分方案的可靠性和实用性。
Objectives:The Paleocene—Eocene Niubao Formation in the Nyima Basin of Xizang(Tibet)was recently proved to be a set of petroliferous succession.However,a systematic stratigraphic division scheme still lacks.Thus,we try to use elemental proxies to do a chemo-stratigraphic analysis on the Niubao Formation from the perspectives of geochemistry and autogenic/allogenic processes.With the expectations of not only establishing a stratigraphic scheme for the Niubao Formation,but also exploring a reliable and practical stratigraphic division method.Methods:Based on the early field work,and the later whole-rock X-ray fluorescence(XRF)measurements,sedimentary geochemistry,principal component analysis(PCA),complementary ensemble empirical mode decomposition(CEEMD),and autocorrelation function(ACF),the base level curves of deposition with specific geochemical meanings were reconstructed.Results:XRF analysis detected 10 kinds of major elements(expressed in metallic oxides%)and 12 kinds of trace elements(inμg/g)with good quality,based on which principal component analysis unveiled that the Niubao Formation was mainly controlled by factors of fine terrigenous inputs,carbonate contents,redox—productivity level,and coarse terrigenous inputs.Complementary ensemble empirical mode decomposition(CEEMD)analysis on PCA results,and the further autocorrelation function(ACF)analysis on intrinsic mode functions(IMFs)revealed that the strata were characterized by prominent and multi-scale allogenic forcing,which enables the reconstruction of geochemical base level of deposition,thus the chemo-stratigraphic scheme of the Niubao Formation can be established.Conclusions:The chemo-stratigraphic scheme of the Niubao Formation based on aforementioned methods and processes can be correlated with traditional lithostratigraphic schemes and sedimentary facies,but with more explicit geological meanings,which at the same time can be utilized to regional stratigraphic correlation,testifying the reliability of our chemo-stratigraphic scheme.
作者
尹世滔
张治锋
黄永建
祝有海
张帅
韩中鹏
李亚林
李祥
赵永辉
刘建伟
YIN Shitao;ZHANG Zhifeng;HUANG Yongjian;ZHU Youhai;ZHANG Shuai;HAN Zhongpeng;LI Yalin;LI Xiang;ZHAO Yonghui;LIU Jianwei(School of the Earth Sciences and Resources,China University of Geosciences,Beijing,100083;Oil&Gas Survey,China Geological Survey,Beijing,100083)
出处
《地质论评》
CAS
CSCD
北大核心
2021年第3期667-681,共15页
Geological Review
基金
中国地质调查局项目(编号:DD20190102)的成果。
关键词
古新统—始新统牛堡组
主成分分析
完备总体经验模态分解
自相关函数
自异旋回
Paleocene—Eocene Niubao Formation
principal component analysis
complementary ensemble empirical mode decomposition
autocorrelation function
autocyclicity/allocyclicity
the Nyima Basin of Xizang(Tibet)
