The Quaternary Strata And Environmental Research In The Yuanmou Basin

Yuanmou basin is one of the standard locations of Quaternary stratigraphy inSouthwest China,predecessors have done a lot of research.But there still exist manydifferences in strata research of the Yuanmou basin. This paper aims to establish astandard stratigraphic column of Quaternary in this area, to provide comparativestandards for future regional geological survey and Quaternary geology study.Based on sections measurements, comprehensive analysis of climate proxies asgranularity and magnetic susceptibility, this paper sorted out and determined theQuaternary stratigraphic units of the Yuanmou Basin, and eventually established astandard stratigraphic column in the study area.1.Yuanmou Formation is divided into four stages, the first stage isfluvio-lacustrine deposits,the lithology include multiple sedimentary cycles from claylayers,brown coal layers to medium-grained sand layers;the second stage is thetransitional deposits stage between the first stage and the third stage,it belongs tofluvio-lacustrine deposits; the third stage is fluvio deposits,the lithology is mainly forsand layers, clay layers, fine gravel layers,almost no brown coal layers;the fourthstage is pluvial deposits,the lithology is mainly for sand layers, sandy clay layers,gravel layers etc.2.The lithology of Longjie Formation is uniform, mainly for a suit of gray-green,gray clayey silt layers,Longjie Formation and Yuanmou Formation are angularunconformity,the deposit cause is dammed lake deposits.3.The climate characteristics of Yuanmou Formation: the first stage alternatesfrom cold to warm, and have a larger range; the second stage still alternates from coldto warm, but the wave frequency and amplitude are small; the third stage is overallrelatively dry, appeares two warm periods; the fourth stage is the coldest stage in thefour stages. The climate of Longjie Formation is warmer and wetter than YuanmouFormation’s climate.