混合沉积和混积岩的讨论

DISCUSSION ON MIXING DEPOSIT AND HUNJI ROCK

混合沉积物是指陆源碎屑与碳酸盐 (包括异化粒等 )在沉积上的混合。混合沉积可分为狭义的和广义的 ,狭义的是指陆源碎屑与碳酸盐组份的混合 (在同一岩层内 ) ,而广义的混合则包括了狭义的和陆源碎屑与碳酸盐层构成交替互层或夹层的混合。混合沉积很早就引起了人们的注意 ,尽管碎屑岩和碳酸盐岩的研究与应用已很成熟 ,但对混积岩的研究多被忽视了。对狭义的混合沉积物有必要起一成因名称———混积岩。当人们接触到混合沉积时 ,除了分析研究它们的组分和结构特征外 ,还必须去思考 ,它们为什么能经常频繁地交互出观 ,或是直接混合在一起 ?倒底是 :①陆源碎屑跑到碳酸盐的沉积背景里 ?②碳酸盐跑到陆源碎屑的沉积背景里 ?③二者分别从各自的源地跑到第三种沉积背景里 ?还是④二者本来就在同一沉积背景里 ?接下来就要思考是什么动力条件使它 (们 )能从这个沉积背景 (环境 )“跑”到另一个沉积背景 (环境 )里去 ?是水 ?是风 ?是自身 ?还是别的什么力量 ?那么 ,又是怎样的水动力或风动力条件呢 ?是正常条件 ,还是突发事件 ?很明显 ,要分析研究混合沉积和混积岩 ,这些问题就不得不细细加以考虑 。

The mixing deposits mean the mixing of terrigenous clastics (siliciclastics) and carbonates (including allochem grains). The mixing deposits can be understood in narrow sense or in broad sense. In narrow sense, the mixing deposits mean that terrigenous clastics and carbonates are mixed within the same bed. In broad sense, in addition to those in narrow sense, the mixing deposits also include the interbedding of terrigenous clastics and carbonates which constitute a series of alternated clastic beds and carbonate beds. Although the study and application of the siliciclastic rocks and the carbonate rocks are very successful, the researches on the mixing deposit are often ignored. It is necessary to propose a new genetic term 'hunji rock' to represent the mixing sediments in narrow sense. When we study the mixing deposit, we need to think about why the terrigenous clastics and carbonates are mixed and whether they are directly mixed together in the same bed or they are mixed as a series of alternated beds? There are several mixing mechanisms for the direct mixing: 1) terrigenous clastics are transported into carbonate sedimentary environments; 2) carbonates are transported into terrigenous clastic environments; 3) both terrigenous clastics and carbonates are transported into another environment; and 4) both terrigenous clastics and carbonates are originally formed in the same environments. After recognizing mixing mechanisms, we need to analyze transporting dynamic conditions,such as water, wind, particle itself, or other forces. Furthermore, we need to think what water energy and wind energy take action,and to think whether they are gradual mixing or catastrophic mixing. Obviously, these questions must be considered carefully and researched thoroughly when we want to recognize and study the mixing deposits and hunji rock.