Grain Size Analysis Of Sediment And Evolution Of Sendimentary Environment In Jiaozuo Area Since Mid-pleistocene

The study area of this thesis is located in Jiaozuo area, the northwest of Henan Provincewhich has various geomorphic types. The Quaternary layer in Jiaozuo area is considered asfluvial facies. Quaternary lithostratigraphic units in Jiaozuo area is always divided into3units.From past to present, these3units are named as Middle-Pleistocene Kaifeng Formation, Upper-Pleistocene Taikang Formation and Holocene Puyang Formation.This thesis analyzes the character of grain-size in Jiaozuo area. Grain-size is one of the mostimportant feature of deposit, and it could be regarded as a quantitative indicator about theclassification of deposit. It not only can reflect the hydromechanical properties of deposition, butalso can analyze and contrast environment. The main factors of grain-size distribution arematerial source, hydrodynamic conditions, transportation medium and trends. Grain-size can beused to infer sedimentary environment and determine the sedimentary models, estimatehydrodynamic conditions and speculate grain-size trends. There are two basic diagrams that candescribe the grain-size: probability plot and frequency diagram. And the most basic statistics isnamed grain-size parameters. Grain-size parameters include mean particle size, sortingcoefficient, skewness and kurtosis. According to the analysis, the BK2key-well in Jiaozuo areacan be divided into8sections. And the hydrodynamic conditions are divided into5grades. Theyare low energy, low-middle energy, middle energy, middle-high energy and high energy.On the basis of the above analysis, the deposit, sedimentary environment and hydrodynamicconditions of every period are summarized as follows:①Middle-Pleistocene: low energyflood-plain deposit low-middle energy fluvial deposit low-middle energy flood-plaindeposit;②Upper-Pleistocene: high energy fluvial deposit low-middle energy flood-plaindeposit middle-high energy fluvial deposit middle energy flood-plain deposit middleenergy fluvial deposit middle energy flood-plain deposit;③Holocene: middle energy pluvialdeposit. This conclusion creates a good foundation for analyzing stratigraphical cyclic divisionand correlation about the Quaternary deposit in Jiaozuo area.