近岸水下扇坡积朵叶体沉积模式与成因机制

通过水槽沉积模拟实验，发现近岸水下扇体系内存在一种特定沉积背景下与扇主体伴生的新沉积类型——坡积朵叶体。这种朵叶体发育于陡坡带砂砾岩体与滑塌浊积岩之间，是向扇根方向尖灭且缺失其所对应的扇根连接的独立砂体。区别于常规的近岸水下扇退积式正韵律的粒序，坡积朵叶体具有独特的前积反韵律的旋回特征，自然电位曲线多为漏斗状的反旋回，地震表现为向上下两侧尖灭的中强反射。研究结果认为坡积朵叶体主要有直接沉积和后期垮塌滑动两种成因机制，所需沉积背景条件为水体较浅，物源供应充足，休止角大于5°。该类型的沉积体与早期扇体与晚期扇体中间均发育泥岩隔层，自成圈闭，具有重要的油气勘探价值。

Sedimentary Model and Genetic Mechanism for the Alluvial Lobes of the Offshore Underwater Fan Slope

Based on the flume deposition simulation, there exists a new sedimentary type in the near-shore underwater fan system, which is associated with the fan body under a specific sedimentary background-slope accumulation lobes. It is an independent sand body developed between the sandy gravel rock body and the fluxoturbidite in the steep slope belt, which is pointed out by the fan root direction and lacks the corresponding fan root connection. Different from the normal grain sequence of the normal positive rhythm for the offshore subsurface fan recession, the porphyritic lobes have a unique characteristic of a reverse cycle of proplanar reverse rhythm, the spontaneous potential curve is mostly a funnel-shaped reverse cycle, and the earthquake is a medium strong reflection to the top and bottom of both sides. According to the study, there are mainly two genetic mechanisms of direct deposition and late-stage collapse and sliding, and the required sedimentary background conditions are shallow water and an abundant material supply, with a resting Angle of greater than 50. The mudstone interlayer is developed in the middle of the early and late fan body and the sedimentary body.