四川盆地中三叠统雷口坡组有利沉积相带及岩相古地理特征

Favorable Sedimentary Facies Zones and Lithofacies Palaeogeography of Middle Triassic Leikoupo Formation in Sichuan Basin

依据四川盆地古地理背景和古气候条件,结合中三叠统雷口坡组野外剖面、岩心和薄片的观察以及单井和连井沉积相等的分析认为,盆地周边水下隆起的障壁作用和干旱炎热气候条件共同影响雷口坡组的沉积相特征,海平面升降变化是控制沉积相发育和空间分布的重要因素。雷口坡组总体为一套障壁蒸发潟湖沉积,可分潟湖边缘坪、潟湖、潮坪和台缘障壁四种沉积亚相类型,并可进一步划分出多种微相。台缘障壁亚相潟湖边缘白云岩坪和颗粒浅滩是有利的沉积相带。雷口坡组可划分出SQ1—SQ4四个层序。绘制了雷口坡期各时段体系域的岩相古地理图,并分析了它们的岩相古地理特征。

Triassic Leikoupo reservoirs are widely developed in whole Sichuan Basin. It is shown that the sedimentary facies of Leikoupo reservoirs are influenced by depositional environments including barriering of surrounding underwa- ter uplifts and dry climate and sea level fluctuations are the important factors that control the development and spatial distribution of sedimentary facies. Leikoupo Formation is overall a set of barrier to evaporating lagoon facies sediments, which can be divided into four subfacies including the lagoon-edge flats, lagoons, tidal fiats and plateform-edge barri- ers. Some microfacies can be further divided. The dolomite flats and grain shoals axe the favorable sedimentary facies belts. Sequences SQ~ to SQ4 can be identified in Leikoupo Formation. Lithofacies paleographic maps are drawn to each system tracts during Triassic Leikoupo sedimentation and corresponding paleogeography characteristics are analyzied.