甘南沼泽沉积脂类生物标志化合物的组成特征

Compositional features of lipid compounds in sediments from Gannan Marsh,China

较为系统地分析了寒冷潮湿高原气候条件下形成的沼泽泥炭中脂类化合物,研究了它们的组成、来源和成岩过程。结果表明,正构烷烃、正构烯烃、正构脂肪酸、直链烷基酮和直链烷基醇都由长链组分所构成,这些长链组分来自草本植物,并且得到它们单体碳同位素证据的支持。丰富的奥利烯醇和羽扇烷醇均起源于陆源高等植物。存在很少报道过的一系列藿醇化合物,它们起源于细菌。甾酮和甾醇都以C29组分为主,C28和C29组分主要来自高等植物,而C27组分则具有一个细菌源。无奇偶优势的短链正构烷烃、细菌起源的脂肪酸(C14、C15、异构和不饱和脂肪酸)、直链烷基-2-酮、藿类和一些甾酮的存在,都说明在这种沉积环境中沉积有机质已经历了强烈的细菌改造作用;甾烯酮和甾烯醇分别向它们烷烃的化学和生物化学转化也十分明显。

Peats from Gannan Marsh are studied b y GC-MS in order to understand the com position and diagenetic processes of lipids in this depositional environment.Long chain compon ents(C 21 to C 35 )predominate in the n-alkanes,n-alk-1-enes,n-fatty acids,n-alkanones and n-alkanols.Herbaceous origin for these long chain compounds is suggested and this is su pported by their stable carbon isoto pic compositions.Several triterpenoid al-cohols with oleanane or lupane skele tons are also present,and are assign ed to a higher plant source.A series o f hopanoid alcohols which have previo usly been rarely reported in modern s ediments are also present,and are of bacterial origin.Steroid ketones a nd alkanols are dominated by C 29 homologues.C 28 and C 29 steroids are derived mainly from higher plants,whereas t he C 27 component is assigned to a microbial source.The presence of short-chain n-alkanes with no odd-even carbon pred ominance,bacterially derived fatty acids(C 14 ,C 15 ,iso-and unsaturated acids),n-alkanones,hopanoids and some stero id ketones indicate that intense mic robial reworking of the organic matter has taken place in this depositional environment.The chemical and biochemical conversio ns of stenones and stenols to their alkanes are also evident with depth.