川西前陆盆地下侏罗统白田坝组沉积特征

摘要

依据钻井、露头及岩心资料,结合区域地质特征,详细研究了川西前陆盆地下侏罗统白田坝组沉积相和岩相古地理特征.结果表明,川西前陆盆地下侏罗统白田坝组主要发育冲积扇相、曲流河相、湖泊三角洲相和湖泊相4种沉积相类型.冲积扇相主要发育扇中和扇端两个亚相,扇根不发育;曲流河相发育河道和洪泛平原两个亚相;湖泊三角洲相发育三角洲平原、三角洲前缘两个亚相,前三角洲亚相不发育;湖泊相主要发育滨浅湖亚相和半深湖亚相,深湖亚相不发育.龙门山前缘的邛崃、安县、江油、旺苍、南江等地冲积扇广泛发育,大小、形状不同的冲积扇连接叠覆构成冲积扇群.在安县地区发育的冲积扇往东砾石由粗变细,逐渐过渡到河流的砂岩相.在金堂、三台等地河流入湖形成三角洲相沉积,并由三角洲进入湖泊沉积区,构成冲积扇-河流-三角洲-湖泊的沉积模式.%The sedimentary facies and palaeogeography of the Lower Jurassic Baitianba Formation in western Sichuan foreland basin is explored on the basis of weU logs, outcrops and cores in integration with regional geological data. The Lower Jurassic Baitianba Formation consists of four sedimentary facies, including the alluvial fan, meandering river, lacustrine delta and lacustrine facies. The alluvial fan facies may be subdivided into two 8ubfacies : mid-fan and fan fringe subfacies. The meandering river facies may also be subdivided into two subfacies :channel and floodplain subfacies. The lacustrine delta facies include the delta plain and delta front subfacies. The lacustrine facies include the littoral-shallow lake and bathyal lake subfacies. The alluvial fans are widely developed in Qionglai, Anxian, Jiangyou, Wangcang and Nanjiang. The alluvial fans in Anxian extends eastwards, and graded into fluvial sandstone facies and delta facies in Jintang and Santai, and finally developed into lake facies,displaying the alluvial fan-river-delta-lake sedimentary model.