基于有机-无机地球化学约束的胶莱盆地下白垩统莱阳群沉积环境重建

Reconstruction of Sedimentary Environment of Lower Cretaceous Laiyang Group in Jiaolai Basin Constrained by Organic-Inorganic Geochemistry

为了解决胶莱盆地下白垩统莱阳群沉积环境归属问题,深化对油气地质条件的认识,通过生物标志物、主量元素、微量元素等相关比值,结合有机与无机理论,对胶莱盆地莱阳群沉积时期(瓦屋夼组和水南组)的古环境进行重建。结果表明,在莱阳群泥岩中正构烷烃具有低碳优势,Pr/Ph>1.0,C_(27)-C_(28)-C_(29)规则甾烷呈上升型分布,气候“C”值与CIA值均较高,且喜氧元素Ni等大量富集。反映莱阳群沉积时期,有机质为水生藻类与高等植物混合输入,古气候干热,沉积水体处于偏氧化淡水湖相沉积。

In order to solve the controversy on the sedimentary environment of Laiyang Group and deepen the understanding of the oil and gas forming conditions,taking the mudstone samples of Wawukuang Formation and Shuinan Formation in Jiaolai Basin as an example,the paleoenvironment during the period of Laiyang Group deposition in Jiaolai Basin is reconstructed by analysis of biomarkers,major elements and trace elements and combining organic geochemistry with elemental geochemistry.The research result shows that n-alkanes have the advantage of low carbon number,Pr/Ph ratio is greater than 1.0,C_(27)-C_(28)-C_(29)regular steranes show an ascending distribution,climate indicators"C"value and CIA value are high,and Ni and other oxygen elements are largely enriched.This reflects that the organic matter input in Cretaceous Laiyang Group was the mixture of aquatic algae and high plants,the paleoclimate condition is dry and hot under the oxidized lacustrine depositional environment.