CAJ | 학술논문

本研究对松科一井嫩江组一和二段(K2n1和 K2n2)岩芯样品进行了有机碳稳定同位素和单体烃分子碳同位素分析,结合其他地球化学参数探讨了沉积环境与母质生物之间的关系。正构烷烃碳同位素在–35.7‰~–28.7‰之间变化,显示了各链长正构烷烃具有不同的母质生源。其中,中链正构烷烃(MCA)碳同位素明显贫13C,偏轻达5‰,可能与其先体母质部分地利用了有机质降解的贫13C的CO2有关。嫩江组藿烷碳同位素(δ13Chopane)处于–32.00‰~–68.65‰之间,在嫩一段下部的δ13Chopane偏轻达到–68.65‰,表明该时期存在甲烷营养菌。在嫩一段δ13CGa较重、δ13Chopane显著偏轻的层段与水体分层、间歇性透光带缺氧相对应,反映了该时期的化跃层界面较浅,缺氧层上升到了透光带,这种极端的水体环境有利于沉积有机质的保存,造成了该层段高 TOC、高 HI的富有机质烃源岩的形成；而在嫩二段伽马蜡烷缺失、δ13Chopane较重时,则反映了水体的化跃层界面较深,环境相对较为氧化,有机质保存条件变差,导致了该段TOC和HI相对较低。由此可见,水体化跃层界面的深浅不仅控制了湖泊沉积有机质的丰度,还影响了水体中微生物的发育,在化跃层较浅的层段,嗜甲烷菌、化学自养菌发育,而在化跃层较深的层段,水体中以化学自养菌为主。另外,δ13CGa和δ13C4-甲基甾烷与水体盐度呈正相关关系,水体盐度越高,其碳同位素值越重。
본연구대송과일정눈강조일화이단(K2n1화 K2n2)암심양품진행료유궤탄은정동위소화단체경분자탄동위소분석,결합기타지구화학삼수탐토료침적배경여모질생물지간적관계。정구완경탄동위소재–35.7‰~–28.7‰지간변화,현시료각련장정구완경구유불동적모질생원。기중,중련정구완경(MCA)탄동위소명현빈13C,편경체5‰,가능여기선체모질부분지이용료유궤질강해적빈13C적CO2유관。눈강조곽완탄동위소(δ13Chopane)처우–32.00‰~–68.65‰지간,재눈일단하부적δ13Chopane편경체도–68.65‰,표명해시기존재갑완영양균。재눈일단δ13CGa교중、δ13Chopane현저편경적층단여수체분층、간헐성투광대결양상대응,반영료해시기적화약층계면교천,결양층상승도료투광대,저충겁단적수체배경유리우침적유궤질적보존,조성료해층단고 TOC、고 HI적부유궤질경원암적형성；이재눈이단가마사완결실、δ13Chopane교중시,칙반영료수체적화약층계면교심,배경상대교위양화,유궤질보존조건변차,도치료해단TOC화HI상대교저。유차가견,수체화약층계면적심천불부공제료호박침적유궤질적봉도,환영향료수체중미생물적발육,재화약층교천적층단,기갑완균、화학자양균발육,이재화약층교심적층단,수체중이화학자양균위주。령외,δ13CGa화δ13C4-갑기치완여수체염도정정상관관계,수체염도월고,기탄동위소치월중。
Stable carbon isotopic compositions (δ13C) of organic matter and molecular hydrocarbon biomarkers in the first and second members of Nenjiang Formation (K2n1 and K2n2) from the SK-1 drilling well are studies, and combined with other geochemical parameters, aimed to investigate the relationship between depositional paleoenvironment and initial organisms of organic matter. Then-alkanes show a wide range of carbon isotopic values, varying from–35.7‰ to–28.7‰, indicating that then-alkanes with different carbon chain lengths may have different sources. For example, the medium-chainn-alkanesare significantly depleted in13C and more negative (ca. 5‰) than short-chain and long-chainn-alkanes, whichareprobably due to its original organism partly utilized the13C-depleted CO2 from degradation of organic matter. Theδ13C values of hopanes varyfrom–32.00‰ to–68.65‰, with the lightest value (ca.–68.65‰) in the lower part of K2n1, suggesting a predominant origin of methanotrophic bacteria. Isotopically heaviergammacerance and significantly lighterhopanes inK2n1, coincide with water stratification and intermittently anoxicphotic zone, whichrepresentashallow chemocline. The extreme water environment,anoxiaspreading upward toeuphotic zone,isconducive to the preservation of organic matter, resulting in high values of TOC and HI in this section.By contrast, absence of gammacerane and isotopicallyheavierhopanes inK2n1reflect the deeper chemocline, corresponding toarelatively oxicenvironment and low values of TOC and HI. Thus, the depth of water chemocline can not only control the abundance of organic matter in lacustrine sediments,butalso affect the growth of microbial community.Chemoautotrophic bacteriaare dominantinthe water body with a deeper chemocline whilechemoautotrophic bacteria and methanetrophic bacteriadevelopintheshallower chemocline.Moreover,δ13C values of gammacerance and 4-methylsteranesare related to water salinity, i.e., the higher the water salinity is, the isotopically heavier gammacerance and 4-methylsterane would be produced.