Compartmentalization of submarine channel splays controlled by growth faults and mud diapir

Abstract

Submarine channels and their associated overbank deposits can demonstrate vast array of geomorphological expressions and extremely complex depositional architectures. Defining their distribution around seabed deformation is crucial to better understand the dynamics of sediment routing, networking, and deep-sea fan compartmentalization. Here, we investigate the interactions between the geomorphological evolution of submarine channel splays and the structural deformation induced by growth faults. The well-imaged seismic records of the Amaku Channel Levee System (ACLS), from the offshore Niger Delta Agbada Formation, offers a key location to delineate the responses of splays to structures. An integrated interpretation of seismic reflection and well log data allowed us to define a new type of composite splay – named here the “Fork Splay Complex” (FSC). The FSC were introduced by a fault-diverted channel segment, distributing a set of branched individual splays (Sp1-Sp4). They develop particular zones of connectivity across low fault throws and compartmentalized elements between high fault throws. Downstream, two fan-shaped splays (Splay A and B) emerged from deflected channel segments, the Splay B is particularly rotated and elongated distally where a fault interfered its spatial distribution. Based on this study, we provide evidence that the digitated splays, while less expanded than the lobate splays, potentially maintain a stable distribution of coarse-sediment thicknesses, which is implied to be the major control on channel to lobe transition (CLTZ) –i.e., in the confluence zone between FSC and Channel J. The resolved patterns of the investigated splays serve as prototypes for understanding how structural deformation controls slope sedimentary system architectures, with the aim of assisting subsurface interpretation and characterizing sand connectivity or compartmentalization.