Evolution of sedimentation rate and its main controlling factors in the deep-lacustrine area of the Chang 7 member, Yanchang formation, Ordos Basin

• Establishes the first high-resolution floating astronomical time scale for the Chang 7 Member and quantitatively reveals a significant negative correlation between sedimentation rate and lake-level fluctuations. • Quantitatively reconstructs the lake-level change curve, overcoming the challenge of quantitative paleo-water-level recovery in continental lacustrine basins. • Elucidates that the dynamic equilibrium among paleoclimate, lake level, and sediment supply is the fundamental mechanism controlling sedimentation rate evolution, providing a new theoretical basis for shale oil exploration. Variations in sedimentation rate within the deep-lacustrine settings recorded abundant information about the paleoclimate and paleo-lake-level fluctuations. During the Late Triassic, the Ordos Basin was a large intracratonic depression lacustrine basin. Moreover, the Chang 7 Member preserves a complete deep-lacustrine record. Analyzing the variations in sedimentation rate of the Chang 7 Member not only could enhances understanding of the coupling relationship with controlling factors like lake-level changes, but also holds implications for hydrocarbon exploration. Focusing on Well Zhang 22 located in the center of the deep lake, a high-resolution chronological framework was established (237.51–241.56Ma) for the Chang 7 Member. And then, sedimentation rates were calculated, and a depositional noise model was used to reconstruct the lake-level curve of the Chang 7 Member. Integrated with geochemical indicators, the main controlling factors of the variations in sedimentation rate of the Chang 7 Member were revealed. Paleoclimate, by regulating sediment supply and lake-level changes, jointly control the variations in sedimentation rate. Warm climates promote lake-level rise and reduce sedimentation rates during the depositional period of the Chang 7 Member, but arid climates have the opposite effect. Sedimentation rate variations reflect the dynamic equilibrium among paleoclimate, lake-level, and sediment supply, providing insights for shale oil exploration in future.