摘要:
多年冻土作为一个特殊的负温沉积环境,其化学和生物化学速度相对缓慢。本文通过对多年冻土湖沼沉积物中有机质特征的研究,来了解这种环境中有机质演化特征。研究结果表明,多年冻土湖沼沉积物中有机质的演化程度低,有机质的特征主要由所产生的环境决定,与沉积演化的关系不明显,这种特征的有机质是用以指示环境变化的理想对象。
Abstract:
The characteristics of organic matter in permafrost bog sediments of Qinghai-Xizang (Tibet) Plateau may provide special in-formation on geochemistry and environment history. In this work, sedimentary facies and organic matter of shallow frozen lacus-trine sediments from a depth of 1 .4m, which is the upper limit of permafrost to 4. 5m have been studied systematically. In thisprofile, clay, silt and fine sand layers occur alternatively. The layers of clay contain the highest content of organic matter and thoseof fine sand contain the least. The important characteristics of organic matter in these frosted bog deposits are shown as follows; 1)the organic matter was of simple source which came from local grasses and subjected to little effect of sedimentation; 2) the compo-nents were relatively stable once after frozen in the sediments. In this profile, the Corg and HI range from 0.11 to 4. 77 and 0 to369 in the section of 20 to 40cm respectively and the contents of extracts vary from 108 to 3630ppm. In soluble extracts, contentof alkane, aromatic, non-hydrocarbon and asphaltene groups are from 0.21 to 15.6296，0 . 79 to 19 . 2 96，3. 8 to 46. 55 96 and 2 .0 to 26.996 respectively. In section from 20 to 40cm, the Corg, HI(hydrogen index), content of extracts by CH222 andmethanol (8:2), groups of extracts have the same variations with the depth and,can imply the paleoenvironmental changes. TheOEP and Pr/Ph high than 2 and 1 respectively, Indicating that the sedimentary environment was in oxidation. The distribution ofditerpane and hopane vary clearly with the depth and may be a good indicator to environment. Especially, the biomarkers such aspigment and diterpane may help reconstruct the paleoenvironment and imply the change of environment
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