某地下第三系T层粒度分布特征及沉积环境

碎屑沉积的粒度研究,已有七十余年历史。近二十年来,无论分析方法及资料解释,都有长足进步,因而已经成为岩石定量研究和环境(相)推断方面的重要手段。

GRAIN-SIZE DISTRIBUTION CHARACTERISTICS AND THE SEDIMENTARY ENVIRONMENT OF LOWER TERTIARY "T"|BEDS FROM A CERTAIN AREA

The author suggestes that in analyzing the grain size of clastical deposits by thin section method, the primary matrix must be taken into account and diagenetic matrix and authigenic clay should be removed. In terms of the probability cumulative frequency curves, the Lower Tertiary "T" beds of Northeast China may be divided into ten types with different grain-sizes reflecting such sedimentary environments as distributary channel, mouth bar, distributary mouth bar in wave zone, distant bar, offshore beach in wave zone. Moreover the turbidites are also distinguished. In the author’s opinion, only by combining the vertical grouping of probability cumulative curves with the sedimentary sequences and their primary structures one can effectively determine the sedimentary environment and subdivide sand bodies. Basing on a certain model conceived, we can reasonably interprete the individual grain-size distribution. It is suggested that the "T" beds resulted chiefly from the products of the delta front to the wave zone of shallow sea. In the area studied there exist three mouth bars extending northward to the wave zone beach. The south part of the same area is marked by deep water turbidites which have developed as result of a syngenetic faulting.