Organic carbon and biomarker record from the Laptev Sea continental margin

In order to understand the processes controlling organic carbon deposition (i.e., primary productivity vs. terrigenous supply) and their paleoceanographic significance, three sediment cores (PS2471, PS2474. and PS2476) from the Laptev Sea continental margin were investigated for their content and composition of organic carbon. The characterization of organic matter indudes the determination of buk parameters (hydrogen index values and C/N ratios) and the analysis of specific biomarkers (n-alaknes, fatty acids, alkenones, and pigments).
Total organic carbon (TOC) values vary between 0.3 and 2%. In general, the organic matter from the Laptev Sea continental margin is dominated by terrigenous matter throughout. However. significant amounts of marine organic carbon occur. The turbidites, according to a still preliminary stratigraphy probably deposited during glacial Oxygen Isotope Stages 2 and 4, are characterized by maximum amounts of organic carbon of terrigenous origin. Marine organic carbon appears to show enhanced relative abundances in the Termination I (?) and early Holocene time intervals, as indicated by maximum amounts of short chain n-alkanes, short-chain fatty acids, and alkenones. The increased amounts of faity acids, however, may also have a freshwater origin due to increased river discharge at that time. The occurrence of alkenones is suggested to indicate an intensification of Atlantic water inflow along the Eurasian continental margin starting at that time.
Oxygen Isotope Stage l accumutation rates of total organic carhon are 0.3, 0.17, and 0.02 C/cm**2/ky in cores PS2476, PS2474, and PS2471, respectively.

为厘清控制有机碳沉积的过程（即初级生产力与陆源输入的相对贡献）及其古海洋学意义，本研究对拉普捷夫海大陆边缘的3个沉积物岩芯（PS2471、PS2474与PS2476）开展了有机碳含量与组成的分析。有机质表征工作包括块体参数（氢指数值与碳氮比）的测定，以及特定生物标志物（正构烷烃(n-alkanes)、脂肪酸(fatty acids)、烯酮类化合物(alkenones)与色素）的分析。
总有机碳（Total Organic Carbon, TOC）含量介于0.3%至2%之间。总体而言，拉普捷夫海大陆边缘的有机质整体以陆源物质为主，但也存在一定体量的海源有机质。根据尚处于初步阶段的地层学研究，可能形成于冰期氧同位素2期与4期的浊积岩，以陆源来源有机碳含量达到峰值为特征。末次冰消期I（？）与全新世早期时段的海源有机质相对丰度似乎有所升高，短链正构烷烃、短链脂肪酸与烯酮类化合物的含量峰值可印证这一结论。不过该时段脂肪酸含量的升高也可能源自淡水输入，与当时河流径流量增加有关。烯酮类化合物的出现表明，自该时段起，沿欧亚大陆边缘流入的大西洋水团强度有所增强。
氧同位素1期的总有机碳堆积速率在岩芯PS2476、PS2474与PS2471中分别为0.3、0.17与0.02 C/(cm²·ky)。