| 摘要: |
| 通过对冲绳海槽2000多公里的实测单道地震资料(95和99航次)和沉积物柱状样(92航次)分析,认为滑塌和重力流是冲绳海槽西部陆坡(东海陆坡)碎屑沉积物向海槽搬运的重要方式;分析结果表明,西部陆坡这两种作用是广泛存在的。陆坡沉积物堆积速率、地形坡度和构造活动、地震、海啸等因素造成了陆坡南、北和中段之间的滑塌和重力流发育程度存在差异。海底滑塌和重力流这两种作用可以同时发生,也可以单独发生,但柱状样揭示重力流发生得更频繁。从空间分布上看,海底滑塌主要分布于上陆坡的断裂带附近,平行海槽呈带状延伸;而重力流沉积主要分布于断裂带向下一直到槽底的部位。重力流沉积主要有4种表现形式1)沉积物重力蠕动;2)浊积平原;3)透镜状浊积体;4)沿斜坡的碎屑流沉积。上述研究表明,滑塌和重力流不仅是陆架向海槽输送物质的重要方式,也对陆坡沉积结构的塑造起了重要的作用。 |
| 关键词: 冲绳海槽 地震反射 海底滑塌 重力流 |
| DOI： |
| 分类号: |
| 基金项目:国家青年自然科学基金资助项目,40406013号 |
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| DEBRIS TRANSPORT ON THE WESTERN CONTINENTAL SLOPE OF THE OKINAWA TROUGH:SLUMPING AND GRAVITY FLOWING |
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LIU Bao-Hua1, LI Xi-Shuang1, ZHAO Yue-Xia2, ZHENG Yan-Peng1, WU Jin-Long1
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1.First institute of Oceanography, State Oceanography Administration, Qingdao, 266061;2.China Ocean University, Qingdao, 266003
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| Abstract: |
| Slumping and gravity flowing are the most important ways of transporting sediments from upper slope to basin and their implication to slope structure in passive or active continental margins has been discussed in many papers. Okinawa Trough (OT) is a tectonically active back-arc basin. Turbidity deposits have been revealed by piston core samples. However, few papers discussed acoustic characteristics on the slumping and gravity flowing and their deposition impact on the west slope of the OT. About 2000 km of high-resolution single channel seismic profiles were collected in 1995 and 1999 and 3 gravity cores were collected in 1992 in the area. Analyses of these data have shown characteristics of slumping and gravity flowing and the deposition impact on the slope. The gradient of slope and sediment supply indicates that slumping and gravity flowing deposits are extensive on the west slope. But asymmetric development in the north, south and middle part of the western slope was affected by different factors, such as depositional rates, tectonic movements, earthquakes, tsunami and so on. Lithological analysis on core samples showed that the main lithological components of gravity flowing deposits are sand and mud. The layers of the event deposits are very thin with high frequency of occurrences vertically. Slumps distribute mainly in a belt along the through near the fault zone on the upper slope. Gravity flowing deposits distribute mainly from the lower of the fault zone to the OT bottom Four types of occurrence were recognized in seismic reflection patterns: a) undulation reflection configuration indicating sediments creeping, b) flat sheet reflection demonstrating turbidities plain, c) irregular reflection denoting lentoid turbidities body and d) hummock clinoform reflection showing debris flow deposits. Single channel seismic profiles showed that the upper slope had been eroded heavily. The location of slumps and type of gravity flowing deposits followed certain rules. Slumping often appears the top of slope and downward the slope is the sediments creeping or debris flowing deposits. Lentoid turbidities bodies are often on the foot area of the slope, and turbidity plain appears on the bottom of the trough. In general case, slumping and gravity flowing often happen simultaneously, but in this area, they did not. Gravity flowing took place more frequently. In overall, the structure of the slope was the result of serial erosion-deposition. |
| Key words: Okinawa Through, Seismic reflection, Slump, Gravity flowing |
