Alexander Clark R, Venherm Claudia
Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA
Mar Environ Res. 2003 Jul-Aug;56(1-2):177-204. doi: 10.1016/S0141-1136(02)00330-6.
Sediment input to SMB appears to be associated with at least two point sources on the shelf, with Malibu Creek and the Hyperion sewage outfall being the most significant. Sediment contributions are sufficient to support apparent mass accumulation rates near these sources up to approximately 1.8 g/cm(2) year, which with distance decrease to approximately 0.5 g/cm(2) year near the shelf break (approximately 80-100 m water depth). Sequestering of material on the shelf and decreasing sediment supply to the slope is evident as rates decrease between 100 and 200 m water depths to less than 0.2 g/cm(2) year. Below 100-200 m water depth, rates are relatively slow throughout a broad region of the slope (0.07-0.14 g/cm(2) year). These slower rates are in general agreement with rates determined on the flanks of the California Borderland basins. Sediment texture fines from approximately 3.5 phi to approximately 7 phi with distance offshore. Texture does not exhibit significant changes from surficial values with depth in the seabed at any given site or between sites on the slope. This similarity in rates and downcore texture over such a broad extent suggests that hemiplegic sedimentation is the dominant mechanism of sediment delivery in water depths >200 m. Seabed distributions of radionuclides suggest that apparent accumulation rates in SMB may be twice the actual accumulation rates. A sediment budget documents that over the past century at least, SMB has served as a sink for 50-100% of the natural and anthropogenic inputs to the coastal ocean.
向圣莫尼卡盆地（SMB）的沉积物输入似乎与陆架上至少两个点源有关，马里布溪和海波龙污水排放口最为显著。沉积物贡献足以支持这些源附近明显的质量积累速率，高达约1.8克/平方厘米·年，随着距离增加，在陆架边缘（约80 - 100米水深）附近降至约0.5克/平方厘米·年。在100至200米水深之间，速率降至小于0.2克/平方厘米·年，这表明陆架上物质的封存以及向斜坡的沉积物供应减少。在水深100 - 200米以下，整个斜坡的广阔区域速率相对较慢（0.07 - 0.14克/平方厘米·年）。这些较慢的速率总体上与在加利福尼亚边境盆地侧翼确定的速率一致。沉积物质地随着离岸距离从约3.5 phi变细至约7 phi。在任何给定地点或斜坡上的不同地点，质地在海床深度上与表层值相比没有显著变化。在如此广阔范围内速率和岩芯质地的这种相似性表明，偏瘫沉积是水深>200米处沉积物输送的主要机制。放射性核素的海床分布表明，SMB中的表观积累速率可能是实际积累速率的两倍。一份沉积物预算文件显示，至少在过去一个世纪里，SMB一直是沿海海洋自然和人为输入物的50 - 100%的汇。
