中文摘要：

报道了采自墨西哥湾富含水合物和油气渗漏区6个海底表层沉积物样品中有机质的丰度、组成和分布特征。研究发现，所分析的6个沉积物样品中有机质的丰度和组成变化很大，其中S-1、S．7和S-9样品中饱和烃的组成分布主要反映了现代海洋沉积有机质及其受细菌微生物改造作用的特征，而S-8、S-10和S-11样品中饱和烃组成以特征的石油污染成因的不可分辨的混合物（UCM）为主，相关甾萜类参数也表明沉积物受到原油渗漏或泄露污染；另一方面，S-8和S-11样品中正构烷烃不同程度的缺失表明有机质遭受了较为强烈的的生物降解作用。仅在S-1沉积物中鉴定出了与甲烷古细菌厌氧氧化有关的特征标志物——2，6，10，15，19．五甲基二十烯烃系列化合物（PMI△）并且具有极负的碳同位素组成，这表明S-1样品所在海底可能有天然气水合物的产出。

英文摘要：

The abundance, hydrocarbon composition and distribution of organic matters in six seafloor sediments collected from the Gulf of Mexico associated with oil and gas seepage and gas hydrates are studied. The abundance and hydrocarbon composition vary significantly among these six samples. S-1, S-7 and S-9 samples show the characteristics of modem organic matter and microbiodegradation, while aliphatic hydrocarbon composition and distribution of S-8, S-10 and S-11 are clearly dominated by the typical unresolved complex mixture （UCM） of crude oil and related steranes and hopanes ratios are also an indicator of petroleum contamination through oil seeps. Also, the lack of normal alkanes on the chromatograms of S-8 and S-11 is a clearly signature of severe biodegradation. The typical biomarkers 2, 6, 10, 15, 19-pentamethylicosenes （PMI△）, as the evidence of anaerobic methane oxidation, were solely identified in the S-1 sample and the carbon isotopic compositions of these biomarkers are very negative. The characteristics of organic matter suggest that the sea floor under the S-1 sample is likely to be a site associated with the occurrence of gas hydrates or gas venting system.