鄂尔多斯盆地南部延安组巨厚煤层内古气候旋回分析

Analysis of paleoclimatic cycles in the ultra thick coal seam of Yan’an Formation in the southern Ordos basin

煤是一种气候敏感型沉积物,为了查明煤层中蕴含的古气候信息及其演化控制因素,选取鄂尔多斯盆地南部延安组一段4号巨厚煤层为研究对象,通过系统密集采样,并测试煤的有机显微组分含量、主量和微量元素及有机质稳定碳同位素含量。利用煤岩显微组分、特征元素和碳同位素等方法,分别在该巨厚煤层内部识别出4个温湿-干热交替的古气候旋回,且识别结果非常一致;该结果与前人在邻区4号煤层中使用古植物含量系数法的识别结果也非常吻合。在此基础上,与前人在该巨厚煤层中识别出的米兰科维奇旋回信息进行比较,综合分析认为该巨厚煤层中古气候旋回的发育与演化主要受到天体轨道参数中偏心率长周期的控制。研究成果证实了方法的可靠性,阐明了古气候旋回的成因机制。

Coal is a climate-sensitive sediment that contains abundant paleoclimate information.In order to find out the paleoclimate information contained in the coal seam and the evolution of its controlling factors,the No.4 thick coal seam in the first member of Yan’an Formation in the south of Ordos basin was studied.Based on the intensive sampling of the thick coal seam,the information of organic macerals,major and trace elements,and stable carbon isotopes of organic matter were systematically tested.By using the macerals,characteristic elements and carbon isotopes of coal and rocks,four cycles of paleoclimate with alternation of warm-wet and dry-heat have been identified in the thick coal seam.The results of this study are similar to those of the previous studies in the same seam in the adjacent area,and the paleoclimatic cycle identified by the method of paleovegetation content coefficient was very consistent.Based on the comparative analysis of the Milankovitch cycle information which controlled the climate evolution in the thick coal seam,it is considered that the development and evolution of the paleoclimate cycle in the thick coal seam were mainly controlled by the long period of eccentricity in the orbit parameters of the celestial body.The results confirm the reliability of the method and elucidate the genetic mechanism of paleoclimate cycloaddition.