Are Subannual Turbidity Currents Observed in the Monterey Canyon Competent to Carve Large Crescent-shaped Bedforms within its Axial Channel?

Kostic, Svetlana
[email protected]

Turbidity currents and other gravity flows are the dominant mechanisms of downslope transport of coarse-grained, terrigenous sediments in submarine canyons. The understanding of turbidity current events and other processes that shape submarine canyons in general, and the Monterey Canyon in particular, has expanded in large part due to significant advances in acoustic imaging of canyons and channels. Recent monitoring activities in the Monterey Canyon have revealed: 1) the occurrence of numerous subannual turbidity current events, and 2) the active present-day seafloor displaying trains of crescent-shaped bedforms within the unconsolidated sediment fill in the incised channel of the canyon down to at least 2,100 m water depth. This study employs a full morphodynamic numerical model of turbidity currents over a canyon reach between moorings at 820 m and 1,450 m water depths to examine: 1) run-out distances of several recent turbidity currents driven by suspended sediment and temperature stratification, and 2) the morphodynamic response of the seafloor to the analyzed events. Numerical experiments are expected to provide new insight into substantial changes in seafloor morphology associated with crescent-shaped bedforms observed during subsequent mapping surveys in the axial channel of Monterey Canyon. Some preliminary results suggest that these bedforms may be antidunes. Consistent supercritical flows along the analyzed canyon reach explain at least in part the episodic down-canyon displacement of instrument frames and monuments that had been deployed within the canyon axis.

AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013