中国石油大学学报（自然科学版）2025，Vol.49Issue(2)：28-41,14.DOI:10.3969/j.issn.1673-5005.2025.02.003
东营凹陷南部古近系沙四下亚段米兰科维奇旋回驱动的湖盆环境演化与沉积响应
Environmental evolution and sedimentary response of lake basins driven by Milankovitch cycles in the lower sub-member of Member 4 of Paleogene Shahejie Formation,Southern Dongying Sag
摘要
Abstract
The evolution of sedimentary environments driven by astronomical cycle in shallow lakes,along with the deposition-al processes of fine-grained sediments,remains unclear.In this study,comprehensive analyses of petrology,palynology and geochemistry,as well as spectral and wavelet analyses,have been conducted on shallow-lacustrine sediments from the lower fourth Member of Shahejie Formation in the southern Dongying Sag.The influences of eccentricity and obliquity on the evolu-tion of sedimentary environment and the deposition of fine-grained sediments were elucidated.During arid periods driven by the negative-phase superposition of long and short eccentricity,lake levels fell,and seasonality was weak,leading to the widespread development of shallow-water deltas.On this basis,a temporary lake-level rise caused by increased obliquity fur-ther induced the periodic retrogradation of the shallow-water delta toward the southern edge of the basin.These processes ulti-mately resulted in the alternating deposition of thin-bedded silty fine sandstones(from underwater distributary channels)and thick-bedded mudstones(from beach mats).When shallow water deltas were poorly developed,the supply of silt-grained sediments was insufficient,leading to deposition of thick-bedded mudstones(from mud flats)in the shallow-lacustrine envi-ronment.Subsequently,transient humid climates driven by increased obliquity triggerred flood events that transported silt-grained sediments into the shallow-lake environment.Lake waves further reworked these sediments,forming siltstones(from sand flats).During humid periods driven by the positive-phase superposition of long and short eccentricity,lake levels rose,and seasonality was strong.Coastal currents,influenced by monsoons,reshaped the shallow-water delta,leading to formation of beach bars in the shallow-lake environment.Additionally,high-frequent lake-level fluctuations driven by obliquity resulted in the alternating deposition of thin-bedded siltstones(from beach bars)and thickly-bedded mudstones(from beach mats).During the antiphase superposition of long and short eccentricity,lake levels were higher than that in humid periods but lower than that in arid periods.High-frequent lake-level fluctuations driven by obliquity primarily resulted in the alternating deposi-tion of thin-bedded siltstones(from mouth bars)and thickly-bedded mudstones(from beach mats).关键词
米兰科维奇旋回/东营凹陷/滨浅湖/细粒沉积岩/沉积环境Key words
Milankovitch cycle/Dongying Sag/shallow lake/fine-grained sedimentary rock/sedimentary environment分类
石油、天然气工程引用本文复制引用
李荣堃,操应长,林敉若,王艳忠,焦红岩..东营凹陷南部古近系沙四下亚段米兰科维奇旋回驱动的湖盆环境演化与沉积响应[J].中国石油大学学报（自然科学版）,2025,49(2):28-41,14.基金项目
国家自然科学基金项目(42488101,42072161) （42488101,42072161）
