短语词组短语marginal sand sheet 边缘席状砂delta front sand sheet 前缘席状砂sheet sand 厚度均匀的砂岩层;平伏沙层;层状砂层sheet sand covered 片沙覆盖loch sheet sand 滨浅湖席状砂coverage with sheet sand 片沙覆盖frontal sheet sand 前缘席状砂 返回 sand sheet