The extractable organic matter of 10 immature samples from a marl bed of one evaporitic cycle of the Vena del Gesso sediments (Gessoso-solfifera Fm., Messinian, Italy) was analyzed quantitatively for free hydrocarbons and organic sulphur compounds. Nickel boride was used as a desulphurizing agent to recover sulphur-bound lipids from the polar and asphaltene fractions. Carbon isotopic compositions (delta vs PDB) of free hydrocarbons and of S-bound hydrocarbons were also measured. Relationships between these carbon skeletons, precursor biolipids, and the organisms producing them could then be examined. Concentrations of S-bound lipids and free hydrocarbons and their delta values were plotted vs depth in the marl bed and the profiles were interpreted in terms of variations in source organisms, 13 C contents of the carbon source, and environmentally induced changes in isotopic fractionation. The overall range of delta values measured was 24.7%, from -11.6% for a component derived from green sulphur bacteria (Chlorobiaceae) to -36.3% for a lipid derived from purple sulphur bacteria (Chromatiaceae). Deconvolution of mixtures of components deriving from multiple sources (green and purple sulphur bacteria, coccolithophorids, microalgae and higher plants) was sometimes possible because both quantitative and isotopic data were available and because either the free or S-bound pool sometimes appeared to contain material from a single source. Several free n-alkanes and S-bound lipids appeared to be specific products of upper-water-column primary producers (i.e. algae and cyanobacteria). Others derived from anaerobic photoautotrophs and from heterotrophic protozoa (ciliates), which apparently fed partly on Chlorobiaceae. Four groups of n-alkanes produced by algae or cyanobacteria were also recognized based on systematic variations of abundance and isotopic composition with depth. For hydrocarbons probably derived from microalgae, isotopic variations are well correlated with those of total organic carbon. A resistant aliphatic biomacromolecule produced by microalgae is, therefore, probably an important component of the kerogen. These variations reflect changes in the depositional environment and early diagenetic transformations. Changes in the concentrations of S-bound lipids induced by variations in conditions favourable for sulphurization were discriminated from those related to variations in primary producer assemblages. The water column of the lagoonal basin was stratified and photic zone anoxia occurred during the early and middle stages of marl deposition. During the last stage of the marl deposition the stratification collapsed due to a significant shallowing of the water column. Contributions from anaerobic photoautotrophs were apparently associated with variations in depth of the chemocline.

中文翻译：

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墨西拿蒸发序列中古环境变化的分子指标（Vena del Gesso，意大利）。II：单个泥灰岩层中游离和硫结合碳骨架的丰度和 13C 含量的高分辨率变化

对来自 Vena del Gesso 沉积物（Gessoso-solfifera Fm.，Messinian，Italy）的一个蒸发循环的泥灰岩床中的 10 个未成熟样品的可提取有机物进行了定量分析，以确定游离碳氢化合物和有机硫化合物。硼化镍用作脱硫剂，从极性和沥青质馏分中回收与硫结合的脂质。还测量了游离碳氢化合物和硫键碳氢化合物的碳同位素组成（delta 与 PDB）。然后可以检查这些碳骨架、前体生物脂质和产生它们的生物之间的关系。S 结合脂质和游离碳氢化合物的浓度及其 delta 值与泥灰岩床中的深度作图，并根据源生物的变化、碳源的 13 C 含量、和环境引起的同位素分馏变化。测量的 delta 值的总体范围为 24.7%，从源自绿色硫细菌（绿藻科）的成分的 -11.6% 到源自紫色硫细菌（色球藻科）的脂质的 -36.3%。来自多种来源（绿色和紫色硫细菌、球石藻、微藻和高等植物）的成分混合物的解卷积有时是可能的，因为定量和同位素数据都是可用的，并且因为游离或 S 结合池有时似乎包含来自单一来源。几种游离的正构烷烃和 S 结合脂质似乎是上水柱初级生产者（即藻类和蓝藻）的特定产物。其他来源于厌氧光合自养生物和异养原生动物（纤毛虫），显然部分以绿藻科为食。根据丰度和同位素组成随深度的系统变化，还识别出四组由藻类或蓝藻产生的正构烷烃。对于可能源自微藻的碳氢化合物，同位素变化与总有机碳的变化密切相关。因此，由微藻产生的抗性脂肪族生物大分子可能是干酪根的重要组成部分。这些变化反映了沉积环境和早期成岩转变的变化。由有利于硫化的条件变化引起的 S 结合脂质浓度的变化与初级生产者组合的变化相关。泥灰岩沉积早期和中期，泻湖盆地水体分层，透光带缺氧。在泥灰岩沉积的最后阶段，由于水体显着变浅，分层坍塌。厌氧光能自养生物的贡献显然与趋化层深度的变化有关。