Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments
Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments
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DOI：
10.1016/s0146-6380(99)00164-3
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发表时间：
2000-01-01
影响因子：
3
通讯作者：
Naraoka, H
中科院分区：
文献类型：
--
作者：
Brincat, D;Yamada, K;Naraoka, H
研究了从贝加尔湖岩芯中提取的正构烷烃的分子分布和碳同位素组成(Delta(13)C)。根据观察到的高CPI27-33值(范围8.7-10.8)，从高等植物的叶蜡中提取的正构烷烃具有典型的高CPI27-33值，推测了奇数碳数长链(>；C-27)正构烷烃的陆地来源。在晚更新世冰期-全新世间冰期气候变化中，n-C-27烷烃的丰度相对于n-C-31同系物的丰度发生了变化，这可能表明了之前从孢粉学分析得出的气候诱导的植被变化。化合物同位素分析表明，在整个岩心序列中，叶蜡C-27-C-33正构烷烃的增量(13)C值在-31.0-33.5‰的范围内非常均匀。这种同位素组成范围是植物利用C-3光合作用途径生物合成正构烷烃的特征。我们的数据表明，相对于全新世剖面总有机碳的增量(13)C值而言，冰期沉积物中大量有机质中的C-13-富集不太可能归因于晚更新世冰期期间贝加尔河流域C-4型植被的扩张。(C)2000爱思唯尔科学有限公司。保留所有权利。
The molecular distribution and the carbon-isotopic composition (delta(13)C) of n-alkanes extracted from a Lake Baikal core spanning the last 20 kyr of sediment accumulation have been investigated. A terrestrial origin has been inferred for the odd carbon-numbered long-chain (> C-27) n-alkanes, on the basis of the observed high CPI27-33 values (range: 8.7-10.8) typical of n-alkanes derived from leaf waxes of higher plants. A shift in the abundance of n-C-27 alkane relative to n-C-31 homologue is observed across the late Pleistocene glacial-Holocene interglacial climate change, perhaps indicative of the climate-induced vegetational change previously deduced from palynological analyses. Compound-specific isotope analyses indicate remarkably uniform delta(13)C values in the range of -31.0 to -33.5 parts per thousand for the leaf-wax C-27-C-33 n-alkanes in the entire cored sequence. Such an isotopic compositional range is characteristic for n-alkanes biosynthesized by plants utilizing the C-3 photosynthetic pathway. Our data suggest that the observed C-13-enrichment in the bulk organic matter in the glacial age sediments, relative to delta(13)C values of total organic carbon in the Holocene section, is therefore unlikely to be attributed to an expansion of C-4-type vegetation in the Baikal watershed during the late Pleistocene glacial interval. (C) 2000 Elsevier Science Ltd. All rights reserved.