贵州普定碳酸盐岩上覆松散堆积物的沉积环境初探

通过对贵州省普定县马官地区不同地貌部位的4个剖面进行详细的粒度分析,把粒度参数以及频率曲线与各种沉积环境的特征进行对比,排除了河流沉积、风成沉积的可能性。研究区域各剖面的粒度分布特征表明其沉积环境属于碳酸盐岩溶蚀残余风化,同时还有坡面流水和地下水作用的参与。

DEPOSITIONAL ENVIRONMENTS OF THE INCOMPACT SEDIMENT OVERLYING CARBONATE ROCK IN PUDING OF GUIZHOU

In this paper we make a grain size analysis of the samples from 4 different profiles to study the depositional environments of the incompact sediment overlying carbonate rock.These profiles come form karst basin,karst wadi,nek and hillside of karst peak in Puding Town of Guizhou Province.The origin of the incompact sediment overlying carbonate rock is a hot issue.Although many researchers have worked in this field in China,it is still weak on the whole.In this paper we choose a small research area to distinguish the depositional environments and the origin of the incompact sediment overlying carbonate rock through making a grain size analysis of the samples from 4 profiles belonging to different topography positions.Grain size distribution of the incompact sediment overlying carbonate rock in Puding Town of Guizhou Province is as follows.The mean grain-size value ranges from 5.02 to 7.34,which belonging to fine silt and sandy silt.The incompact sediment is poorly sorted to very poorly sorted,mainly symmetrical with a few fine skewed,mainly mesokurtic with a few platykurtic,mainly unimodal with a few bimodal.The grain size becomes coarser along the depth in profiles.We compare the parameter and the curve of grain size distribution of the measured samples with the characteristics of several kinds of depositional environments,and the results exclude the possibility of alluvium,aeolian,and lacustrine sediments.At the same time the depositional environments in research area is different from brown-yellow unit,typical red clay unit,and vermiculated red earth unit which are widespread in mid-subtropics.Based on grain size analysis within and between every profile,the incompact sediment overlying carbonate rock was shown to be mainly the production of corrosion of carbonate rock.It was mainly deposited under a weathering condition with fine-grained deposits being carried from higher topography positions to lower topography positions in karst peak by overland flow.In addition,the deep sediment in karst basin may be affected by groundwater and some incompact sediment may relate to the characterastics of the protolith horizons.