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以砂泥岩样品的常量/微量元素地球化学特征分析为主要手段,探讨广东肇庆地区奥陶纪沉积环境,为尚显薄弱的云开古陆北缘下古生界沉积学研究提供佐证。以“相当B含量”、Ga、K、Rb、V、Sc等元素组分及其比值为判别指标,分析研究区奥陶系碎屑岩沉积的古水体性质和古环境变化。结果表明,奥陶纪早-中期(缩尾岭群沉积期)海水明显淡化、富氧;奥陶纪晚期(三尖群沉积期)以半咸水-正常咸水为主,水体还原性增强。结合地层岩相特征,认为研究区在奥陶纪期间整体为云开古陆东北缘的滨-浅海,早期可能存在受淡水影响的海陆过渡环境,例如三角洲或河口湾,晚期由于海平面上升逐渐成为浅海陆棚。研究结果有助于进一步了解云开古陆周缘奥陶纪沉积演化,并为开展更为详细的沉积学研究提供参考。
Taking the analysis of constant / trace element geochemical characteristics of sandstone and shale samples as the main measure, the author discusses the sedimentary environment of Ordovician in Zhaoqing area, Guangdong Province, and provides evidence for the study of Paleozoic sedimentology in the northern margin of the Yunkai ancient land. The paleohydrological properties and paleoenvironmental changes of Ordovician clastic sediments in the study area were analyzed with elemental components of Ga, K, Rb, V, Sc and their ratios as discrimination index. The results show that seawater in the early-mid-Ordovician (sedimentary period of the Moutilingling Group) is obviously desalinated and enriched in oxygen. In the Late Ordovician (sedimentary period of the Triangle Group), the saltwater is mainly in half-saltwater-normal saltwater and the water reducibility is enhanced . Based on the lithofacies characteristics of the strata, it is considered that the study area is generally foreland-shallow sea in the northeastern margin of the Yunkai ancient land during the Ordovician period. In the early stage, there may be a land-sea transitional environment affected by freshwater such as delta or estuary. Become a shallow sea shelter. The results will help to further understand the Ordovician sedimentary evolution in the margins of the Yunkai, Yunnan Province, and provide a reference for more detailed study of sedimentology.