新疆阿克苏地区中、上奥陶统碳酸盐岩磁化率与层序地层关系

Discussion on the Relationship between Carbonate Magnetic Susceptibility and Sequence Stratigraphy in Middle-Upper Ordovician in Aksu Area,Xinjiang

通过对新疆阿克苏地区中、上奥陶统185块碳酸盐岩样品的磁化率测量和统计,结合碳酸盐岩微相分析和层序地层研究,探讨了碳酸盐岩磁化率变化与沉积环境、层序界面、准层序(组)等之间的关系。研究结果表明:深水低能环境下沉积的钙质泥岩、瘤状灰岩、泥灰岩等通常对应于磁化率低值,且磁化率曲线较为平直;浅水高能环境下形成的含鲕粒砂屑灰岩、鲕粒灰岩等通常对应于磁化率高值;碳酸盐岩地层中淹没型层序界面对应于磁化率测量值的明显减小;准层序(组)的上部单元碳酸盐岩磁化率值比下部单元明显增大,并且其曲线常呈高频振荡状。

Based on measurement and statistical data of 185 Middle-Upper Ordovician carbonate samples,miciofacies analysis of carbonate and sequence stratigraphy research,relationship between carbonate magnetic susceptibility and sedimentary setting,sequence boundaries,parasequence（sets） have been discussed.Results show that normally rocks such as calcareous mudstone,nodular limestone,argillaceous limestone,which were formed at deep water level where energy was low,have relatively low value of magnetic susceptibility,while rocks such as oolite-containing calcarenite,oolitic limestone have high value of magnetic susceptibility,which were formed at shallow water where energy was high.Magnetic susceptibility decreases greatly across submerged sequence boundary in carbonate rocks.Magnetic susceptibility of upper units of parasequence（sets） are bigger than those of lower ones,with a shape of high-frequency oscillation.