EDIMENT WAVES ON THE TURBIDITE FAN AND CHANNEL IN MONTEREY BAY, CALIFORNIA, USA

The Monterey canyon, which is a well known canyon system in California, USA about 90 km long, cuts through the shelf and the continental slope and forms a turbidite fan of 95600 km ² at the canyon mouth of about 2 900 m in depth. The bottom of the canyon and the fan is decorated with large areas of deep-water sediment waves. The sediment wave on the fan is about 30~100 m in height, with a wavelength of 1~2 km. In the straight channel, the wave crests are perpendicular or oblique to the channel axis, while in the curved channel, the crests are parallel to the channel axis. Waves are asymmetrical with longer stoss side and shorter lee side, indicating a moving up slope. The sand wave consists of silty clay with fine sand intercalations, and the top is covered by a thin layer of clay with a thickness of 30~50 cm. It is supposed to be a residual sediment wave developed during the Late Pleistocene to the Early Holocene at low sea level. Sediment waves are also developed on both sides of the main channel. They are similar to those on the fan, but small in scale. Wave crests are wavy or crescent-shaped. They are composed of sandy silt deposits with coarse sand and small gravel intercalations. It is supposed to be deposited during late Holocene when sea level was rising. For the meantime, sea level is high, most of the terrigenous sediments deposited in nearshore water and on continental shelf. Turbidity flow was discharged on the bottom of the canyon. Only few extremely fine grained materials were deposited on turbidite fan to form sediment waves.