Channel Sands and Petroleum Potential of Monterey Deep-Sea Fan, California

Abstract

The possibility of substantial petroleum resources in deep water adjacent to the continents in areas of hemipelagic sedimentation has been suggested by numerous authors. One such area adjacent to the United States is the continental rise off California between 33 and 40° N lat. The rise covers 200,000 sq km and consists of three major submarine fans, the Arguello, Monterey, and Delgada, with sediment thicknesses up to 3 km in water depths of 3,000 to 4,500 m. The fans are composed primarily of continental debris carried down submarine canyons and deposited on the fan through a system of branching and meandering submarine valleys and channels. During the development of the fan, the active channelway shifts periodically in response to locally increased gradients, produ ing abandoned channels. The coarser sediment naturally confined to the channel becomes covered, after abandonment, by finer grained material because of slumping, reworking, and subsequent fan deposition. Such channels, after sufficient burial, would make excellent stratigraphic traps for hydrocarbons, especially if abandonment occurs on the upper fan where the grain size of channel-fill sediments is coarser and the channel width and relief are greater. On the Monterey fan, potential stratigraphic traps would be seaward of the mouths of the Monterey-Carmel, Ascension, and Pioneer Canyons as shown by subbottom profiling. The proximity of such potential reserves to the United States and to existing refineries and markets in coastal areas makes buried channels on large deep-sea fans such as he Monterey fan particularly attractive prospects.