碳酸盐与硅质碎屑的混合沉积机理和控制因素探讨

Mechanism of Mixied Siliciclastic—Carbonate Sediments and Its Controlling Factors

混合沉积作用是一类特殊而又有重要研究价值的沉积现象,混合沉积作用的研究虽已经取得了一定的进展,但目前国内对其沉积机理、控制因素等方面的认识仍不够深入,经典的范例较少。本文在国内外研究进展的基础上,结合笔者等近期的研究成果,阐述和总结了混积岩产出的沉积环境,混合沉积的4种类型、4种剖面结构以及与之相对应的沉积机理与控制因素等混合沉积研究的重点和难点问题。并以下刚果盆地Albian阶Sendji组混积岩的研究为例,利用频谱分析的方法求得混积地层较好地保存了米兰科维奇旋回,证实了受米兰科维奇旋回影响的气候因素对混合沉积作用的发生、发展具有极为重要影响,同时混合沉积作用强弱及其旋回性变化也是区域构造活动的响应,构造活动的强弱与混积作用范围、规模密切相关。

Mixed sedimentation of terrigenous clastic and carbonate is a sedimentary phenomena has special sedimentational mechanism and significance. Although many progresses have been achieved in the research of mixed sedimentation of terrigenous clastic and carbonate, much divergence still exists in the geological concepts, classification, mechanism of hybrid processes and the controlling factors. Based on research advances and some concrete examples home and aboard, combinated with writers’s recent geological investigation, this paper illustrated four categories of mixed sedimentary type and profile structure. The profile structure is characterized by 4 types, including： ① alternating deposits of terrigenous debris and carbonate, ② alternating deposits of terrigenous debris and diamicton, ③ alternating deposits of carbonate and diamicton, and ④ alternating deposits of diamicton themselves. The cause of the mixed sedimentation, depositional mechanism were also discussed. Climate changes caused by orbital are widely recorded in mixed sedimentary record. The cycles of mixing procession could be responses of pulse regional tectonic activities.