Carbon chemistry of ODP Holes 108-658A and 108-659B (Table 1)

Preliminary results of lipid analyses of six samples from Site 658, underlying a present-day active upwelling cell, and of one sample from Site 659 are reported in this paper. Long-chain unsaturated ketones of prymnesiophyceae algae origin are the most abundant compounds in extracts from Site 658, followed by marine-derived steroids. n-Alkanes are of minor importance in these samples, but they predominate in the sample from Site 659. Our interpretation of the results indicates that organic-matter preservation was good to excellent at Site 658 and poor at Site 659, and that an analysis of only aliphatic hydrocarbons leads to an overestimation of the contribution of terrigenous organic matter at Site 658. Increased primary productivity, high sedimentation rates, and oxygen-depleted water masses associated with upwelling are thought to be the key factors for preservation. At the present stage of research, no specific biomarkers have been found that indicate upwelling.

本文报道了取自现今活跃上升流区下方658站位（Site 658）的6个样品，以及659站位（Site 659）的1个样品的脂质分析初步结果。源自定鞭藻纲（Prymnesiophyceae）藻类的长链不饱和酮类物质是658站位提取物中丰度最高的化合物，其次为海源甾类化合物。正构烷烃（n-Alkanes）在上述658站位的样品中占比相对较低，但在659站位的样品中占据主导地位。本研究对结果的解译表明，658站位的有机质保存状况整体良好至极佳，而659站位则较差；仅通过脂肪烃（aliphatic hydrocarbons）分析会高估658站位的陆源有机质（terrigenous organic matter）贡献占比。研究认为，与上升流相关的初级生产力提升、高沉积速率以及缺氧水团是有机质良好保存的关键因素。在当前研究阶段，尚未发现能够指示上升流活动的特异性生物标志物（biomarkers）。