白彦砾岩的形成时代及砾石组构特征分析

通过对白彦砾岩中孢粉取样鉴定及其砾石组构的统计研究,孢粉组合特征显示其形成时代为中侏罗世,并非通常认为的古近纪。砾石组构特征显示为湖滨相或海滨相成因,砾岩中金刚石特征显示出与蒙阴常马金刚石原生矿的相似性。综合分析认为,白彦砾岩形成于中侏罗世鲁西地区单断拉分盆地诞生之前,应为三台组沉积之前的沉积物。白彦砾岩沉积时代的确定,对恢复该区岩相古地理、确定金刚石原生矿的剥蚀与搬运等都具有重要意义。

Analysis on the Forming Times and Gravel Fabric of Baiyan Conglomerate

Through statistical studies on identification of pollen samples and conglomerate fabric,as showed by pollen assemblages,the formation time of Baiyan conglomerate was in middle Jurassic,not the Paleogene which was generally considered.As showed by gravel fabric,its origin was littoral or coastal features.Characteristic of diamond in conglomerate showed that it had similar charcterstics with Changma diamond in Mengyin county.Through comprehensive analysis,it is regarded that Baiyan conglomerate was formed in western Shandong in Jurassic before the birth of pull-apart basin.It should be the production before the deposition of Santai formation.Determination of deposition times of Baiyan conglomerate will play an important role in restoring lithofacies paleogeography and determining erosion and transportation of the primary diamond mine.