Trail of sand in upper Monterey Canyon: Offshore California

Detailed sampling of the axis and flanks of upper Monterey Canyon (water depths of < 1500 m) was undertaken using a remotely operated vehicle (ROV)-deployed vibracoring system. The objective was to document the characteristics and distribution of sediment within the canyon and to elucidate the sources and processes by which materials move into and through the canyon. Detailed multibeam bathymetric surveys guided the sampling. The combination of core data, multi-beam bathymetry, and multi-beam reflectivity reveals for the first time the facies and facies distribution patterns associated with the axial channel of an active submarine canyon. Coarse-grained deposits form a narrow trail of material that is tightly restricted to the axial channel floor, indicating that upper Monterey Canyon is an active submarine system closely coupled to sand transport along the shoreline. Sand from the modern beach and nearshore environment captured by the canyon head is moving down the axial channel of the canyon, while fine-grained sediments are accumulating on the flanks of the canyon. Our observations suggest that other submarine canyons in close proximity to the shoreline are presently active and that a modern supply of sand-sized material is moving down these canyon systems.