兰州九洲台黄土剖面重矿物研究

A Study on Heavy Mineral Compositions of Jiuzhoutai Loess Profile,Lanzhou

本文着重研究了兰州九洲台黄土剖面重矿物组成的基本特征.不同时代黄土地层重矿物组成具有复杂性、一致性和差异性,反映出九洲台黄土是风成的,沉积物主要来源于我国西部广泛分布古老岩石山岭和其有联系的大戈壁沙漠的风化产物,由于搬运营力的变化,使重矿物组分具有不均匀的特征.重矿物及 R 值表明,九洲台黄土沉积环境比东部西峰剖面和洛川剖面更邻近于来源区;黄土和古土壤层沉积时,主要反映相当干冷为主的气候条件,二者气候环境演变过程的差别很小,黄土层时常表现为冷湿相结合,古土壤时常表现为干暖相结合水热条件.马兰黄土沉积阶段,末次冰期有突出的表现.

This paper lays stress on studying the fundamental features of heavy miner-al compositins of Jiuzhoutai loess profile(Lanzhou).The heavy mineral compositions inloess strata of different times have their complxitins compatibilities and disparities.It isindicated that Jiuzhoutai loess is aeolian,and the sediments originate from westermwidely-distributed ancient lithical mountains and their relevant sedimentary products inthe Gobi desert.As a result of the varietly of transportation agents,the content varietlyof heavy mineral compositions is heterogeneous.The R value of heavy mineral indicatesthat the depositional climatic environment of Jiuzhourai loess is nearer to the source re-gion than eastern Xifengzhen profile and Lechuan profile,the climatic cinditions informing deposits of loess and fossil soil are dryness and coldness,and the difference inclimatic environment between deposits of loess and ancient soil is very small;the loess isofen marked by a combination of cold and humidity while the depicted fossil soil comp-bintion of dryness and warmth.The last ice age shows a very prominent effect upon thedepositting of Malan loess.