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Deepwater Channel Evolution in the Pleistocene-Holocene Lucia Chica Channel System, Offshore Central California

Maier, Katherine L.*1; McHargue, Tim 1; Paull, Charles K.2; Graham, Stephan 1; Caress, David 2
(1) Geological and Environmental Sciences, Stanford University, Stanford, CA.
(2) Monterey Bay Aquarium Research Institute, Moss Landing, CA.

New technologies have provided exceptionally high-resolution imaging of the Lucia Chica channel system, offshore central California, and these data enable the evolution of Deepwater channels to be documented at an unprecedented level of detail. Imaging of the Lucia Chica channel system using Autonomous Underwater Vehicle technology developed by the Monterey Bay Aquarium Research Institute resulted in nearly continuous imaging of over 70 km2 of the seafloor with a lateral resolution of 1 m and a vertical resolution of 0.3 m. The survey also resulted in >560 km of chirp profiles with 150 m line spacing and 11 cm vertical resolution, providing subsurface imaging at a scale similar to outcrop geometries. This high-resolution imaging allows detailed investigation of channel evolution and a review of avulsions stages, from scours to incipient channels to channels with continuous thalwegs. Specifically, detailed imaging leads to these interpretations: 1) Repeated avulsions preserved a series of adjacent channels on the seafloor; 2) Channel inception phases are erosional; 3) Splay deposits occur at the sites of at least some avulsions; 4) Channels both bifurcate and avulse; 5) Trains of scours occur in areas of least confinement; 6) Point bars and inter-channel bars are not present; 7) Disconnected channels can be reactivated instead of abandoned; 8) Channel morphology is significantly influenced by channel maturity, but possibly not by gradient. Differences in relief, sinuosity, and levee development between adjacent channels correspond with relative channel age and avulsion sequence and demonstrate the influence of channel maturity on morphology. The interpreted sequence of channel development involves erosional channel inception through scouring and incipient channels (defined by linear train of scours) prior to development of a continuous thalweg. Channel narrowing, deposition of levees, increasing channel relief, and development of sinuosity occur as channels evolve. This evolutionary sequence may occur in other Deepwater channel systems, making the Lucia Chica channel system a potential analog for reservoir-scale channel deposits.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California