摘要
为了明确鄂尔多斯盆地西缘中段开阔台地与潮坪相变带的沉积特征及演化规律,选取同心县酸枣子沟剖面中元古界蓟县系地层为对象,实测了地层剖面,进行了系统的薄片显微观察、微量元素分析、碳氧稳定同位素测定及沉积学综合研究,剖析了该区沉积微相类型及垂向演化特征,并建立了不同沉积微相的组合模式。研究结果表明:①该区蓟县系岩石类型包含叠层石白云岩、颗粒白云岩(砂屑为主)、晶粒白云岩及硅质白云岩,叠层石以水平状、丘状和波状形态为主,缺乏大型柱状叠层石;②该区发育水平状—丘状、波状—丘状、水平状—波状—丘状等垂向叠层石组合序列,明确其为弱水动力且高频海平面波动背景下潮间带至潮上带沉积环境的产物;③基于环境指标与碳氧同位素值,判断该区整体处于弱氧化、炎热干燥的古气候与古海洋环境;④垂向沉积序列分析结果表明,该区沉积微相以潮上带、颗粒滩为主,见少量潮间带,经历了早期弱水动力潮坪夹颗粒滩向中晚期强弱交替水动力的颗粒滩与潮坪互层沉积的转变过程。结论认为,酸枣子沟剖面蓟县系沉积特征反映出该盆地西缘中元古界开阔台地向潮坪过渡带相变快、相带窄的特点,其沉积演化主要受控于高频海平面波动。
To clarify the sedimentary characteristics and evolution patterns of the transition zone from open platforms to tidal flats in the middle segment of the western margin of the Ordos Basin,the Mesoproterozoic Jixian System in the Suanzaozigou section of Tongxin County was selected for detailed study.It involved stratigraphic section measurement,systematic thin section microscopic observations,trace element analysis,stable carbon-oxygen isotopes determination,and comprehensive sedimentological investigation.The types of sedimentary microfacies and their vertical evolution characteristics in the study area were identified,and the combination patterns of different sedimentary microfacies were established.The results show that,(i)the rock types of the Jixian System include stromatolitic dolomite,granular dolomite(predominantly arenitic),crystalline dolomite,and siliceous dolomite;stromatolites exhibit mainly horizontal,mound-shaped and wavy morphologies,lacking large-scale columnar ones;(ii)there develops vertically stromatolite assemblages such as horizontal-mound-shaped,wavy-mound-shaped,and horizontal-wavy-mound-shaped,confirming that they were formed in intertidal to supratidal depositional environments under weak hydrodynamic conditions with high-frequency sea-level fluctuations;(iii)discrimination based on environmental proxies and carbon-oxygen isotopes suggests that the study area was characterized by weakly oxidizing,hot and arid paleoclimatic and paleo-oceanic environments;and(iv)vertical sequence analysis reveals the sedimentary microfacies dominated by supratidal zones,grain banks,and minor intertidal zones,indicating a transition from tidal flats intercalated with grain banks under weak hydrodynamics in the early stage to interlaminated grain banks and tidal flats with alternating strong and weak hydrodynamics during the middle-late stages.It is concluded that the sedimentary characteristics of the Jixian System in the Suanzaozigou section reflect the rapid facies changes and narrow facies belts of the Mesoproterozoic open platform to tidal flat transition zone in the western margin of the basin.The sedimentary evolution is primarily controlled by high-frequency sea-level fluctuations.
作者
刘宏宇
景译萱
刘喜欢
李文昌
杨康
张乾
雷微微
张云峰
LIU Hongyu;JING Yixuan;LIU Xihuan;LI Wenchang;YANG Kang;ZHANG Qian;LEI Weiwei;ZHANG Yunfeng(Exploration and Development Research Institute,Sinopec Jiangsu Oilfield Company,Yangzhou,Jiangsu 225009,China;School of Geosciences and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China)
出处
《天然气勘探与开发》
2025年第5期14-24,共11页
Natural Gas Exploration and Development
基金
国家自然科学基金面上项目“埋藏期去白云石化机制及储集意义”(编号:42272181)。
关键词
叠层石
颗粒滩
白云岩
潮坪
沉积特征
中元古界蓟县系
鄂尔多斯盆地西缘
Stromatolite
Grain bank
Dolomite
Tidal flat
Sedimentary characteristics
Mesoproterozoic Jixian System
Western margin of Ordos Basin
