深水复合水道体系沉积特征及时空演化规律——以东非鲁武马盆地中中新统为例

鲁武马盆地中中新统复合水道体系表现出复杂的充填特征及时空演化规律。以地震资料为基础,借助三维可视化、沿层相干切片、层间振幅属性提取等多种地震解释技术,总结地震分辨率下复合水道体系内各个级别水道的平面分布规律,建立纵、横向演化模式。鲁武马盆地中中新统复合水道体系可以细分成4个可识别的级别:复合水道体系,水道复合体,复合水道及水道。沿水流方向,复合水道体系由强限制型向局部限制型演化,在较远端分化为三期独立水道复合体;水道复合体表现出4种沉积方式,2种方式与复合水道体系一致且同步发育,另外2种为较弱限制型和非限制型。复合水道体系内深水沉积主要受海平面变化、地形坡度以及底流作用的影响,沉积规模、搬运距离、沉积位置、延伸方向及外部形态随时空发生改变。复合水道体系呈现出复杂的多级别充填特征,垂向叠置样式随沉积位置的差异而不同,早期水道复合体末期的分布影响后期水道复合体发育的位置。

Depositional characteristics and temporal and spatial evolution of deep water channel complex systems: A case study of Middle Miocene in the Rovuma Basin, East Africa

The channel complex systems of the Middle Miocene in the Rovuma Basin, East Africa exhibits complex filling characteristics and space-time evolution. The distribution of various hierarchies in channel complex system is analyzed under seismic resolution by several seismic techniques, such as 3D visualization, horizontal coherence slice, interval slice of root mean square amplitude, and the vertical and lateral evolution models are established. The channel complex system in Middle Miocene in the Rovuma Basin is composed with four identified hierarchies including channel complex system, channel complex set, channel complex and channel. The channel complex system evolves from strongly restricted to locally restricted along the direction of turbidity currents. The channel complex system is differentiated into three independent channel complex sets in the distal. The channel complex set shows four depositional patterns, two patterns are consistent and synchronous with the channel complex system, the other two patterns are weak confined and unconfined channel complex sets. Deep water deposition in channel complex systems is mainly affected by the sea level change, slope gradient and bottom current, the sedimentary scale, transport distance, deposition position, extension direction and external morphology change with time and space. The channel complex system presents a complex multi-level filling feature. The vertical overlap patterns vary with the location of the deposits. The late distribution of early channel complex set affect the development of the later channel complex set.