松辽盆地上白垩统嫩江组三四段沉积有机质及多环芳烃化合物组成分布与古气候意义

The distribution of polycyclic aromatic hydrocarbons(PAHs) in sediments from Upper Cretaceous Nenjiang Formation of Songliao Basin and its paleoclimate significance

对松辽盆地上白垩统嫩江组嫩三段(K_2n^3)和嫩四段(K_2n^4)岩芯样品有机质组成丰度、多环芳烃化合物组成分布等进行了分析。结果显示,嫩三段和嫩四段沉积岩有机碳含量(TOC)分别在1.37%~2.52%和0.12%~0.82%之间,可溶有机质族组成含量为沥青质>非烃>饱和烃>芳烃,沥青质、非烃、饱和烃和芳烃占可溶有机质的比例分别为21.1%~54.9%,15.4%~27.8%,12.7%~19.2%和1.7%~11.0%。在嫩三段和嫩四段沉积有机质中检出了多种高丰度的多环芳烃化合物,主要为萤蒽(Fla)、芘(Py)、苯并萤蒽(Bflas)、苯并a蒽(Ba An)、苯并e芘(Be Py)、晕苯(Cor)、茚并芘(Inpy)、菲(P)、苯并[g,h,i]苝(Bghi P)、■(Chry)、甲基菲(MP)、惹烯(Ret)和苝(Pery)等;其中,菲、甲基菲、惹烯和?等化合物主要是来自原始有机质输入和成熟转化的产物。多环芳烃化合物的相关比值及其在垂向上的变化表明,嫩三段中的萤蒽、芘、苯并萤蒽、苯并a蒽、苯并e芘等多环芳烃化合物主要是生物质燃烧的产物;茚并芘和苯并[g,h,i]苝等则主要形成于原始有机质的成熟转化。嫩四段中的萤蒽、芘、苯并萤蒽、苯并a蒽和苯并e芘等多环芳烃化合物主要是生物质燃烧的产物,茚并芘和苯并[g,h,i]苝为生物质燃烧成因和成岩演化混合来源,而嫩四段底部检测到的较高丰度的苝可能主要与陆源有机质的输入及转化有关。最后,嫩江组中的多环芳烃化合物,特别是生物质燃烧来源的多环芳烃环合物的相对丰度在垂向上的变化可能表明嫩三段和嫩四段沉积时期古气候发生了由温湿气候向干旱气候的转变。

The core samples from the members 3 and 4 of Nenjiang Formation （K2n3 and K2n4） in the Songliao Basin have been analysed for organic matter abundance and the composition and distribution of polycyclic aromatic hydrocarbons （PAHs）. The results show that the TOC content of sediments in K2n3 （member 3） and K2n4 （member 4） is in the range of 1.37% to 2.52% and 0.12% to 0.82%, respectively. The relative abundance of soluble organic matter fractions is in an order of aromatic hydrocarbons 〈 aliphatic hydrocarbons 〈 polar compounds 〈 asphaltene, their relative percentage being in the range of 21.1% to 54.9% （asphaltene）, 15.4% to 27.8% （polar compounds）, 12.7% to 19.2% （aliphatic hydrocarbons） and 1.7% to 11.0% （aromatic hydrocarbons）, respectively.A large number of PAH compounds are detected in the sediments, including fluoranthene （Fla）, pyrene （Py）, benzofluoranthene （Bflas）, benzo[a]anthraeene （BaAn）, benzo[e]pyrene （BePy）, coronene （Cor）, indeno[1, 2, 3-cd]pyrene （Inpy）, phenanthrene （P）, benzo[ghi]perylene （BghiP）, methylPhenanthrene （MP）, chrysene （Chry）, retene （Ret） and perylene （Pery）. Among these PAH compounds, the P, MP, Chry and Ret are mainly derived from the original organic matter input and its diagenetic transformation. The ratios of PAH compounds suggest that the Fla, Py, Bflas, BaAn, and BePy in the sediments of K2n3 were largely originated from the combustion of biomass, and the Inpy and BghiP perhaps generated from the diagenetic transformation of original organic matter. While the Fla, Py, Bflas, BaAn and BePy in the K2n4 were mainly derived from the combustion of biomass, and the Inpy and BghiP in the K2n4 were originated from the mix sources （the combustion of biomass and the diagenesis process）. The high abundance of Pery in the K2n4 was likely related to the specific terrigenous organic matter input. Finally, vertical variations in the relative abundance of these PAH compotmds in the sediments of K2n3 and K2n4 suggest that the Songliao Basin may experience a climatic shift from relative warm-humid to arid during the sedimentation period of K2n3 and K2n4.