不同波谱分析方法对羌塘盆地雁石坪侏罗系夏里组沉积旋回分析的探讨

Investigation on Sedimentary Cycles Analysis using Different Spectral Analysis Methods for the Jurassic Xiali Formation in Yanshiping,Qiangtang Basin

频谱分析软件对沉积物的旋回性研究是一种客观、准确的方法,但实际操作中发现不同分析软件会造成结果的差异性,而探讨这种差异对于地质研究具有重要意义.藏北羌塘盆地雁石坪地区中侏罗世夏里组发育了一套以砂岩、泥岩为主的高频沉积旋回地层,该地层在沉积物颜色上也表现出良好的韵律性.本文利用文军等羌塘盆地雁石坪区夏里组岩性、颜色进行Redfit波谱分析,发现夏里组存在7个主要的米兰科维奇周期,分别为岁差周期17.6ka、21.3ka、轴斜率周期38ka、50.6ka、短偏心率周期95ka、123ka和长偏心率周期400ka,它们是控制本区夏里组沉积旋回发育的主要因素,特别短偏心率与长偏心率周期协同(400ka-123ka-95ka周期系列)控制该区的高频沉积旋回演化.对比前人研究结果,认为Redfit频谱分析相对Walsh谱分析对地质现象的解释具有较好的准确性、解释也更合理.

Spectrum analysis software is a kind of objective and accurate method for researching of sedimentary cycles.But in the actual operation,the different spectral analysis method may lead to different results,whose discussion has important significance in geological study.There is good rhythmicity of Xiali formation which developing a succession of high-frequency cyclic stratum composing of sandstone and mudstone in Yanshiping,Qiangtang basin,northern Xizang.In this paper,the spectral analysis of redfit software was used to analyze the lithology and color of Xiali formation which comes from the paper of Wen Jun,et al.And the results show Xiali formation exist seven major Milankovitch cycles,which are axial precession(17.6ka and 21.3ka),obliquity cycle(38ka and 50.6ka),eccentricity cycles encompassing short eccentricity cycles(95ka and 123ka)and long eccentricity cycles(400ka).All of them are the main factors controlling the development of sedimentary cycles in Xiali formation.Particularly,the evolution of the high-frequency sedimentary cycles of Xiali formation may be dominated by the 400ka-123ka-95ka eccentricity cycles.Thus comparing with walsh spectrum analysis,we find that redfit spectrum anylysis have better accuracy,rationality on geology explaining.