Geomorphology of Upper Indus Fan and Its Channel‐Levee System: Unveiling the Submarine Fan Complexity With High‐Resolution Multibeam Bathymetric Data

Abstract

The Indus Fan, located in the Arabian Sea, is the second‐largest submarine fan on Earth. Understanding its fan morphology and Channel‐Levee System (CLS) is crucial because of its role in transporting sediment, organic carbon, nutrients, and contaminants to the deep‐sea. However, accurate mapping of upper Indus Fan channels remains incomplete due to inadequate seabed bathymetric data. This study presents high‐resolution multibeam bathymetry of the upper Indus Fan to unveil its complex morphology and CLS. The data reveal a truly vast, highly meandered, and deeply incised active CLS with an extensive network of abandoned CLS. The fan exhibits highly diverse geomorphology, characterized by channel‐wall failures, sediment waves, and mass transport deposits. Only one channel is active, with others abandoned through avulsion processes. Outer levees of abandoned CLSs locally exhibit collapse, erosion, and interaction with adjacent CLSs, altering CLS morphology and reducing its preservation potential. Channel sinuosity is mostly achieved through preferential preservation of inner bend deposition and outer bend erosion, possibly favored by the muddy nature of the deposits. Meander bend cutoffs are widespread in the channel–levee belts, with neck cutoffs being more common along the channel path. The presence of multiple knickpoints, plunge pools, and neck cutoffs, along with compound asymmetrical meandering bends, highlights the role of autogenic processes in governing flow dynamics, terrace formation, and channel evolution. This study improves the understanding of the Indus Fan channel network through the mapping of one of the largest CLSs on Earth and showcases its morphological complexities.