Approach to the Quaternary Sedimentary Environment of West Chifeng Plateau

Influenced by bath the coustal movement and the climatie fluctuation, the sedimentary environment has occured alternately as fluvial and lake within the area of West chifeng Plateau since Quaternary.With the uplift of crust, it can be divided into five sedimentary stages under cold climate, in which fluvial deposits formed dominantly (not include the 5th stage) .The so and δi of the sediments in the first stage are higher than other stages. It shows strong hydrodynamic and the bad sorting. Because of the inrich of unstable mineral in eaeh cold stage, the associate section of unstable nrineral is easly seen (K K) except a part of K K, which causeel by climatie fluetuation.Most of the traee elemeuts are dispersed and a few are concentrated in every stage.This phenomenon is related to source of materials besides the influence of climate in our opinion.The temperature in the third stage is higher than the fourth. Similarily, it can be divided 5 sedimentary stages under Warm climate, when the crust descents or. stable relatively.The lacustrine seelimentation played a leading role in evey warm stage with the exception in the first one.Because of the inrich of stable minerals in each warm stage, the association seetions of stable minerals exist in the mineral content curve (K K) except a part of K K which coused by climatie fluctuation. The most of the trace elements are concentrateed and only a few are scattered as a result of the warm-humid climate and rapid deposition. Aceording to the materials on hand, the fourth and fifth warm stages helong to fresh-water or light salt-water environment.