EDIMENT WAVES ON THE TURBIDITE FAN AND CHANNEL IN MONTEREY BAY, CALIFORNIA, USA
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摘要: 蒙特利峡谷穿过陆架和陆坡，于谷口外(水深约2 900 m)发育了95 600 km2的浊积扇。峡谷底滩地和扇面上均发育大面积的深水沉积物波底形。扇上沉积物波的特征有：波高为30~100 m，波长1~2 km；在笔直流道段，波峰垂直或斜交于流道延伸，而在弯曲流道段，波峰平行于流道延伸；波两侧不对称，迎流侧长而背流侧短，有向上游迁移的趋势；由夹细砂层的粉砂质黏土组成，顶部均为30~50 cm的黏土薄层披覆。推断为晚更新世—早全新世的低海平面时期发育的残留沉积物波。峡谷底主流道两侧也发育沉积物波，其形态类似于扇面上的波，但尺度较小，波峰呈波状或新月形延伸，由夹粗砂、小砾石层的砂质粉砂层组成，推断为晚全新世海平面上升时期的沉积。现代高海平面时期，陆源物质较多沉积于近岸和陆架，浊流下泄时，大部分碎屑物质沉积于峡谷底滩地上，只有少部分极细粒物质沉积于浊积扇和扇上沉积物波之上。Abstract: 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.
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Key words:
- continental slope /
- turbidite fan /
- canyon /
- channel /
- sediment wave
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