白令海北部陆坡全新世以来长链正构烷烃的古环境意义

本文对白令海北部陆坡B2-9站位沉积物岩芯开展了高分辨率的生物标志物分析，获得了研究区近一万年来陆源长链正构烷烃（简写为烷烃）的输入及其源区植被结构的变化等相关记录。结果表明，nC₂₇是烷烃中最高的主碳峰，对烷烃总量的贡献也最大，这可能与源区木本植物的丰度及其分布有关；nC₂₃的含量也较高，可能主要是来源于北半球沿海地区广泛分布的一类沉水植物。全新世期间，烷烃总量分别在7.8 ka B.P.，6.7 ka B.P.和5.4 ka B.P.经历了三次阶梯状的下降过程，呈现出四个相对稳定的阶段，可能主要受控于早全新世海平面上升以及源区气候环境和植被分布的变化。烷烃的分子组合特征各参数（如CPI、ACL以及nC₃₁/nC₂₇等）的变化则表明，烷烃主要来自陆生高等植物，且全新世期间植被结构较为稳定，木本植物占据优势。此外，在几个较短的时期内，烷烃总量及其分子组合特征等参数的变化具有同步性，表明在这些时期特殊的气候条件下，源区木本植物烷烃对烷烃总量的贡献率的增加可能低于草本植物烷烃和化石烷烃。

Paleoenvironmental implications of Holocene long-chain n-alkanes on the northern Bering Sea Slope

The records of high-resolution terrestrial biological markers (biomarkers) from Core B2-9 from the northern Bering Sea Slope over the last 9.6 ka BP were presented in the study. Variations in input of terrestrial long-chain n-alkanes (referred to as n-alkanes) and vegetation structure in their source regions were investigated. The results show that the nC₂₇ is the main carbon peak and has the greatest contribution rate of the total n-alkane content; this might be related to the abundance of woody plants and their spatial distribution in the source region. nC₂₃ is another n-alkane having a relatively high content; this was mainly derived from submerged plants widespread along the coastal areas in the northern hemisphere. Total n-alkane content dropped quickly at ca. 7.8 ka BP, ca. 6.7 ka BP and ca. 5.4 ka BP, and was followed by four relatively stable stages mostly controlled by sea-level rise, climate change and vegetation distribution in the source region. Variation in carbon preference index (CPI) indicates that the n-alkanes primarily originated from higher land plants, and the average chain length (ACL) and nC₃₁/nC₂₇ ratio reveal the relatively stable presence of woody/herbaceous plants during the Holocene, and dominate woody plants in most of the time. Simultaneous variation in total n-alkane content, nC₂₇ content and its contribution, CPI, ACL and nC₃₁/nC₂₇ ratio over several short periods suggest that the growth rate of the woody plant n-alkane contribution was lower than that of herbaceous plants and fossil n-alkanes under the particular climatic conditions of the source region.