Unidirectionally Migrating Submarine Channels and Lobes of Hybrid Turbidite‐Contourite Fans: Variations in Morphologies and Architectures With Exploration Significance

The current study utilizes a global submarine channel‐lobe database to document morphologies and architectures of submarine channels and lobes that are characterized by unilateral stacking patterns and are uniquely related to the persistent action of along‐slope processes. The studied channel examples migrated sideways both parallel to and opposite to contour‐current directions, resulting in unidirectionally downstream‐ and upstream‐migrating channels, respectively. Unidirectionally downstream‐migrating channels differ from unidirectionally upstream‐migrating channels in that they are confined totally by incisions rather than flanked by overbank levees developed downstream of contour currents, and have steep channel walls with truncations developed downstream rather than upstream of contour currents. They all display an asymmetrical channel cross‐section and record a global (latitudinal) variation in channel cross‐sectional asymmetries. The strength of the power‐law relationship of channel cross‐sectional asymmetries to latitudes suggests that the Ekman spiral systematically varied with latitude is the most plausible causal mechanism for latitudinal variations in channel cross‐sectional asymmetries. The documented depositional lobes show sideways migration in the same and opposite directions of contour currents, resulting in unidirectionally downstream‐ and upstream‐migrating lobes. They are distinguished from turbidite lobes by their along‐slope elongated morphologies, isobath‐parallel distribution patterns, and unilateral stacking patterns. Their close association with unidirectionally migrating channels constitutes hybrid turbidite‐contourite fans that have reservoir properties distinct from those of regular turbidite fans by positive permeability‐porosity but negative petrophysical property‐grain size relationships. From this study, we suggest that there can be two significantly different patterns of unidirectional channel/lobe migration. Our results, therefore, contourite to diminish the debate on unilateral channel migration and to cast light on the exploration significance of hybrid turbidite‐contourite fans.