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| 近十万年来渭南黄土波谱-地球化学环境信息探讨 | |
| 引用本文： | 张言,文启忠,杨凤筠,刘东生.近十万年来渭南黄土波谱-地球化学环境信息探讨[J].第四纪研究,1994,14(3):214-244. |
| 作者姓名： | 张言 文启忠 杨凤筠 刘东生 |
| 作者单位： | 冶金工业部天津地质研究院 |
| 摘 要： | 本文对我国陕西渭南剖面的黄土、化学组成、元素地球化学、稀土元素配分模式和矿物波谱特性等进行了一些实验研究，并在此基础上分析提取环境信息，试图建立黄土中高分辨演化序列及其所表征的环境变迁标志之间的关系，编制了干旱化黄土波谱－地球化学综合特征曲线图。最后，对近十万年来环境变迁的规律和发展趋势进行了初步探讨。 |
| 关 键 词： | 黄土波谱 地球化学 环境信息 干旱化 |
DISCUSSION ON GEOCHEMICAL ENVIRONMENT INFORMATION-SPECTRUM OF LOESS FOR THE LAST 0.1Ma IN WEINAN AREA |
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| Institution: | Tianjin Geological Academy, MMI; 2. Guangzhou New Technical Institute of Geology, Chinese Academy of Scienced; 3. Tianjin Grological Academy, MMI,Institute of Geology, Chinese Academy of Sciences |
| Abstract: | Abstract:The climate and environment evolution is a multi-varaible and multi-level systemwith linear or non-linear relationship. The problems concerned are under researchand exploration. This paper discusses climate and environment evolution for the last0.1 Ma and sums up regularities and the evolutionary trend by tests of establishinghigh resolution horizons within the strata and evolutionary marks of the palaeoclimateas well as their relationship.Weinan profile, Weinan county of Shanxi province is one of the typical loessprofiles in China. Stratigraphical division from top to bottom is follows: So Holocence loess and soil, L(1-1) Malan loess, L(1-2) paleosol, L(1-3) Malan loess, L(1-4) paleosol,L(1-5) Malan loess and S1 paleosol. Main chemical composition, micro-elements are similar for the loess and paleosol within the profile. However, some of their elementgeochemical data are varied with samples collected from different intervals (table5). Compared to L(1-2),L(1-4). and S1 paleosols, L(1-1), L(1-3),L(1-5) three loess horizons arehigher in ratios of S/S + A, C/NK + C and lower in H/DC + H,Fe(Ⅲ)/ΣFe, reflecting that the former and latter are different in contents of Si-Al, alkline-alklineearth elements, carbonate-structural water and their redox state under supergence environment geochemical action. REE contents are similar for loess and paleosol, andthe uniformity of REE patterns indicates same source of their raw materials.In order to explore mineral spectrum-geochemical integrated characteristicsof loess and paleosol and their enviroment recorded inforpsation, quantity tests ofreflect spectrum were carried out with U.S. IRIS spectroradiometer. The measurement range was 500-2 500nm, the band width 2-4nm. Tests show that the shapesof spectrum curves for different samples from profile are stable and similar to eachother. They are formed as bands, and the bands is closely spaced at.short Wave rangeand more widely spaced at long wave range. The reflectances of all samples increase sharply at the 500-1 350urn range and the slope of their curves is about k= 1.4.The largest volume of reflectance is corresponding to about 2 150nm band. The strong'absorptions for every spectrum curves are appeared at about 1 410urn, 1 920nm,2 210nm bands and, partly, weak absorptions at 2 350nm, 940nm. All above showcharacteristics of structural water, hydroxyl, carbonate, ferrous and ferric minerals inloess and paleosol. Some differences in reflectance of spectral background lines canbe seen between loess and paleosol. The former is higher in reflectance than latter,that, maybe, is meaningful for distinguishing paleoenvironment of loess and paleosolin the loess plateau.Samples were systematically collected in 10cm and 20cm space interval from theprofile. Results of determination show that in near infrared region the backgroundlines of samples for different ages form spectral bands and the spectrum vibrationare emerged (Fig. 2), which are characterized by irregular ordering during the last0.1Ma. Climate and environment evolved with time, and the ununiformed cyclic vibration of spectrum appeared (Fig. 3).Based on the spectrum-recorded information and element geochemical data wascompiled the loess spectum-geochemical integral characteristics and palaeo-environmentevolution map (Fig. 4), from which 3 cyclic evolution and development processof climate environment during the last 0.1Ma can be recognized, i. e. 5' stage→4'stage, 3c'→3b' stages, and 3a'→2'→1' stages three cycles. Compared with curve ofdeep sea oxygen isotope data, the 1',2',3'(3a', 3b',3c') 4' and 5' stages of loess spectrum-geochemical integral curves are, generally respectively, corresponding to the1,2,3,4,5a and 5b stages of curve, measured δ(18)O in Caribbean core, in which 3b'stage is maybe equal to hollow section of the 3th stage for δ(18)O curve. The above results are preliminary and further check is needed. Time limits ofloess and paleosol are yet to be defined by chronologist |
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