黔西纳雍地区下寒武统牛蹄塘组黑色岩系生物标志物的特征

Characteristics of biomarkers of the black rock series of Lower Cambrian Niutitang Formation in the Nayong area,western Guizhou,China

以贵州纳雍地区下寒武统牛蹄塘组黑色页岩为研究对象,分析其中的生物标志化合物。结果表明:奇偶优势(OEP)均值为1.08,接近平衡值1.00,无明显奇偶优势,姥鲛烷与植烷比(Pr/Ph)均值小于1,具明显的植烷优势;萜烷丰度顺序为五环三萜烷>三环萜烷>四环萜烷,规则甾烷以C27略占优势,ΣC27/ΣC29的均值为1.41,大于1,显示有机质来源以浅海相菌藻类等低等水生生物为主;C32αβ22S/(22S+22R)平均值为0.59,Ts/(Ts+Tm)值为0.43,βα-莫烷/αβ-藿烷平均值为0.124,C29甾烷的20S/(20S+20R)平均值为0.39,C29甾烷αββ/(αββ+ααα)平均值为0.41,均表明纳雍地区黑色岩系中的有机质均接近或达到成熟阶段。根据这些特征可以推断,该区域早寒武世牛蹄塘组黑色岩系形成于浅海还原环境,有机质热演化程度较高,其母质主要来源于细菌、藻类等低等水生物。

With the methods and the measures of GC-MS analysis,authors study the biomarkers of the black shale series of Cambrian Niutitang Formation in the Nayong area of Guizhou Province.The results show that OEP values of the n-alkanes close to 1.00,showing no odd-even carbon dominance.The mean of Pr/ Ph is less than 1,indicating that mineral samples possess phytane dominance.The terpanes distribution patterns of mineral samples are pentacyclic terpanes tricyclic terpanes tetracyclic terpanes.The steranes consist mainly of C27-steranes.The average ratio of ΣC27/ΣC29 is 1.41,greater than 1.00.The ratio indicate that the organic matter sources are mainly shallow marine bacteria and algae and other lower aquatic organisms.The average of C32αβ22S/（22S＋22R） is 0.59,and the value of Ts /（Ts＋Tm） 0.43,the ratio of βα-MO alkyl / αβ-Hopane 0.124,the value of C29 sterane 20S/（20S＋20R） 0.39,the ratio of βαββ /（αββ ααα） 0.41.The ratios show that the evolution of organic matter in black shale series of Nayong region is close to or reach maturity.All these characteristics indicate the black shale series of this region is formed in the restore shallow water environment with higher degree of thermal evolution of organic matter,and the parent material is mainly derived from bacteria,algae and other lower hydrobiont.