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

Overbank flow of turbidity currents sweeping through the entrenched Montere y Fan Channel has generated erosional and depositional features along the c hannel walls and across the adjacent levees. These features, investigated w ith side-scan sonar, SeaBeam bathymetry, submersibles, and a towed camera s led include fields of sediment waves, overbank channels, gullied walls and terraces, and slump scars. Overbank flow occurs where the channel path is s traight, but is accentuated along sharp outside bends. Along straight chann el segments sediment waves trend oblique to the channel and are commonly pr esent on the right-hand (when looking downstream) levee adjacent to the cha nnel. 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. (C) 2000 El sevier Science B.V. All rights reserved.