The lacustrine organic-rich fine-grained sedimentary rocks of the Early Cretaceous Bayingebi Formation are widely distributed in the Yin'e Basin and they have become important source rocks for oil and gas exploration. To reveal the influence of paleoclimate warming event on sedimentary environment evolution and organic matter sources, the petrological and molecular geochemical analyses of the upper member of the Bayingebi Formation (K₁b²) were carried out using optical microscopy, X-ray diffraction, scanning electron microscopy, Rock-Eval pyrolysis and gas chromatography–mass spectrometry, in order to establish the paleoecological models of the Early Cretaceous freshwater and saline lakes. The oil shale and dark mudstone of K₁b² are both in the immature-early mature stage and have good potential for hydrocarbon generation, with a dominance of type I and type II₁ kerogen. Two types of primary dolomite were found in this formation: microcrystalline dolomite with uniform structure, and the microbially originated spherical dolomite aggregates. The K₁b² can be divided into four units based on its lithology and logging curve characteristics. Unit II was deposited in the peak of lake development, under the warm-humid paleoclimate with abundant annual precipitation. There was greater influx of freshwater than other units, which resulted in the unstable stratification of the water column and less reducing condition of the lake bottom water body. Lower aquatic organisms and vascular plants were unprecedentedly prosperous, which were indicated by short-term thriving phenomena of telalginite, and the large input of terrestrial OM and highest abundance of the OM compared to other units. A lake water salinization event occurred during the sedimentation period of Unit III under the cooling climate, causing a transition from a freshwater lake to a high-salinity lake with reducing condition and stable stratification of the water column. Salinity of lake water increased the competitiveness of salt-tolerant algae and bacteria. The salty environment is beneficial for the thriving of single to halophilic genus of microorganism and lead to significantly lower abundance of telalginite. The biological sources of OM were mainly bacteria, algae and emergent plants, with limited contribution of terrestrial higher plants. The anoxic alkaline environment and high salinity condition at the lake bottom were beneficial for the formation of carbonate minerals and the preservation of OM. This were characterised by medium abundance of OM and high hydrocarbon generation potential. The study on the petrological and molecular geochemical characteristics of these organic-rich fine-grained sedimentary rocks is of great significance for investigating the genetic mechanisms and resource potential of oil and gas.

早白垩世巴音格壁组湖相富有机质细粒沉积岩在银鄂盆地广泛分布，已成为油气勘探的重要烃源岩。为揭示古气候变暖事件对沉积环境演化和有机质来源的影响，采用光学显微镜、X射线衍射、扫描等手段对巴音格壁组上段（K ₁ b ²）进行了岩石学和分子地球化学分析。电子显微镜、Rock-Eval 热解和气相色谱-质谱法，以建立早白垩世淡水和盐湖的古生态模型。_{K 1} b ²油页岩和深色泥岩均处于未成熟-早成熟阶段，具有良好的生烃潜力，以Ⅰ型和Ⅱ型₁型干酪根为主。在该地层中发现了两种类型的原生白云石：结构均匀的微晶白云石和微生物来源的球形白云石聚集体。K ₁ b ²根据其岩性和测井曲线特征可分为四个单元。Ⅱ单元沉积于湖泊发育的高峰期，处于暖湿古气候，年降水量充沛。淡水流入量大于其他单元，造成水体分层不稳定，湖底水体还原条件较差。低等水生生物和维管植物空前繁盛，表现为藻藻的短期繁荣现象，以及陆生有机质输入量大，有机质丰度高于其他单位。三号机组在降温气候下沉积期发生湖水盐渍化事件，导致淡水湖向高盐度湖过渡，水体呈还原状态，分层稳定。湖水盐度增加了耐盐藻类和细菌的竞争力。盐分环境有利于单菌至嗜盐微生物的繁衍，导致燧石丰度显着降低。OM的生物来源主要是细菌、藻类和挺水植物，陆生高等植物贡献有限。湖底缺氧碱性环境和高盐度条件有利于碳酸盐矿物的形成和有机质的保存。其特点是中等丰度的 OM 和高生烃潜力。