Sedimentary features associated with channel overbank flow: examples from the Monterey Fan

Abstract

Abstract Overbank flow of turbidity currents sweeping through the entrenched Monterey Fan Channel has generated erosional and depositional features along the channel walls and across the adjacent levees. These features, investigated with side-scan sonar, SeaBeam bathymetry, submersibles, and a towed camera sled include fields of sediment waves, overbank channels, gullied walls and terraces, and slump scars. Overbank flow occurs where the channel path is straight, but is accentuated along sharp outside bends. Along straight channel segments sediment waves trend oblique to the channel and are commonly present on the right-hand (when looking downstream) levee adjacent to the channel. Along curved segments of the channel path, large sediment waves, with crests sub-parallel to the channel and with wavelengths reaching 3 km, are present on the outside levee as far as 15 km from the channel. Commonly, a gully is present on the lee side of the sediment wave, near the mid-point of the wave crest. Gullies are the heads of a tributary system of overbank channels, which feed a larger trunk channel on the fan surface.