Geochemical Characters And Environmental Significance Of The Mid-Pleistocene Sediments On Southern Margin Of The Songliao Basin

The northeast plain is the largest alluvial plain in China with a concentration of people and developed productive forces. It is an important base of agriculture and livestock husbandry and habitat of oil. Today, our country pays more much attention to rejuvenate the old industrial bases in northeast China. This paper does the research of environmental changes of northern quaternary. It is not only meaningful for our theories of basic subject, but also for the construction of national economy. Songliao Basin is a vital part in the northeast China. Therefore, the Medio-Pleistocene sedimentary on the south margin of Songliao Basin is researched as an object. This paper tries to discuss on the sources, depositional environment of the sedimentary and the response of sedimentary sequence to climate changes.The research area is in the upwelling area on the southern margin of the Songliao River Basin. It is between the periods of glacial period and interglacial period. Under strong and weak cold wave as well as advance and retreat of monsoon, the natural environment changes obviously. Studying on the formation and evolvement of quarternary natural environment on the southern margin of Songliao Basin is of great significance to the exploration of climatope variation in Northeast China. Meanwhile, the research can provides foundation to scientific exploit of natural resources in the northeast plain and environmental protection. Moreover, it has a great meaning to predict the variation tendency of natural environment. Therefore, This paper analyzes the key profiles, OSL dating and geochemical characters in the research area. This paper discourses the variation disciple of paleoclimate on the southern margin of Songliao Basin in the mid-pleistocene relying on the topic of 1/250000 geological and geomorphic interpretation in the quarternary period in the project《the remote sensing investigation and monitor of basic geologic environment in the Yellow River Valley》. It can provide a proof of the factors that affect the climate and environmental variation laws and tendency in the quarternary. Moreover, it can provide data for basic investigation of climateope change.During the course of study, the methods of field conversation and records, GPS positioning, digital photography, OSL dating, profile research and geochemical analysis are adopt. Besides these methods, the inductive coupling plasma analyzer is used to analyze the contents of geochemical element of typical profile. Meanwhile, this paper uses X ray fluorescence spectrometer to analyze the contents of macroelements and trace elements of the four profiles.Through the research of the four Brickyards of San Jiazi, Yi Laxi, A Cheng ya gou town and Lian Hua in Lian Hua village of Fang Zhen county, the results show a certain regularity. The Changes of precipitation facies are as follows: fluvial facies, limnetic facies, aeolian facies. The sedimentary layers from the bottom up are as follows: sand layer, black clay, gray clay, yellow clay, loess layer.Through OSL dating, the lower limit age of the study area is 149.6±10.4ka that is between the age of Medio-Pleistocene 0.20×106 aB. P.and late Pleistocene epoch 0.073×106 a B. P .. The glacial epoch is between Mindel-Riss interglacial and Riss glaciation. Compared with the four profiles, the profiles have similar sedimentary environment and the contact relation is plano conformable contact. It is considered that the time difference is small. Therefore, this paper thinks the age of study area is Medio-Pleistocene.This paper chooses five geochemical indicators to distingue the environmental changes in the research of the brickyards of San Jiazi, Yi Laxi, A Cheng ya gou town and Lian Hua in Lian Hua village of Fang Zhen county. The indicators are as follows: Sr/Ba,Al2O3/(Al2O3+CaO+Na2 O),Sr / Cu,(K2 O+Na2O+CaO) /Al2O3,Rb/Sr.This verdict is the Songliao Basin is in the warm and humid climate for this period by analyzing the five indicators. Moreover, there is a possibility of the existence of ancient Songliao Lake. On the later stage, the temperature increases, the environment turns to drought gradually.