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西北太平洋盆地高频(3.5和12千赫)音响测深剖面上所记录到的海底回波可划分为五种基本类型;其中四种与沉积作用有关。最广泛记录到的两种回波类型大致与最上部海底沉积物类型有关:Ⅰ型(A和B)回波(清晰而连续的平行浅层反射)通常是在沉积物由具火山灰夹层的硅质软泥构成的盆地西北部记录到的。而Ⅱ型回波(顶部10至20米清晰而连续的浅层反射和其下半透射的不连续浅层反射)则是夹燧石层的褐(红)色粘土为主的盆地东南部的特征。Ⅲ型回波的特点是不整合的,迁移的或截切的浅层反射,偶尔是规则的重复双曲线回波带;它们代表估计可能即太平洋底层水(下面简称PBW)的温盐合成底流(即等深流)的流动所造成的侵蚀—沉积床底形态。产生Ⅲ型回波的地区大都面积较局限并分布于海山,海脊以及能提高局部洋流流速的其它地形隆起的麓部。少数Ⅲ型回波反射带亦呈区域性展布。例如,有一片宽阔的Ⅲ型回波区沿北太平洋盆地的南部边界分布,PBW从南面流经很宽的地形间隙在该处进入北太平洋,另一宽广的Ⅲ型回波区则在皇帝海山链以西。Ⅲ型回波所指示的沉积物改造幕的地质时代和延续时间还不清楚。水文测量和海底照相结果表明目前在整个盆地中仅有微弱的或停滞的PBW水流。可能大部分沉积物改造发生在大洋水团循环比现在快的更新世和较老冰期期间。Ⅳ型回波是局部的小型(<5至25公里)滑塌—碎屑流沉积物所产生的延时波,不相干波,或模糊回波。这些沉积物常见于极平缓的海丘(幅度小于100米)的底部。这类沉积物大都出现在硅质沉积物分布区(Ⅰ型回波)。显然,这些沉积的物性反映了它们是比较不稳定的,因此,比褐色粘土更易遭到破坏。
The submarine echoes recorded on the deep-sea (3.5 and 12 kHz) acoustic sounding profiles of the Northwest Pacific Basin can be divided into five basic types; four of them are related to sedimentation. The most widely recorded types of echoes are roughly related to the type of seafloor sediment at the very top: Type I (A and B) echoes (clear and continuous parallel shallow reflections) are typically found in sediments consisting of volcanic-intercalated silicon Silty mud formed in the northwestern part of the basin was recorded. While Type II echoes (clear and continuous shallow reflections from the top 10 to 20 meters and discontinuous shallow reflections from the lower translucence) are characteristic of southeastern parts of the brown (red) colored clay dominated by chert . Type III echoes are characterized by unconformity, migrated or truncated shallow reflections and, occasionally, regular hyperbolic echo bands; they represent the temperature-salt synthetic underflow that may be estimated as the Pacific Ocean Bottom Water (PBW) (Ie isobath flow) caused by the flow of erosion - sediment bed morphology. Most of the areas that produce type III echoes are more limited and are located in seamounts, ridges and other uplifted ridges of other terrains that can increase the velocity of local ocean currents. A small number of type Ⅲ echo reflection zone also showed a regional distribution. For example, there is a broad Type III echoes along the southern boundary of the North Pacific basin. The PBW flows into the North Pacific from the south through a wide topographic gap. West of the chain. The geologic age and duration of sediment remodeling curtains indicated by Type Ⅲ echoes are not clear. Hydrographic measurements and sea bottom photography results show that there is currently only weak or stagnant PBW water flow throughout the basin. Most sediment alterations may have occurred during the Pleistocene and older glacial cycles where the oceanic water mass cycles faster than it is now. Type IV echoes are delayed waves, incoherent waves, or fuzzy echoes generated by localized small (<5-25 km) slump-debris flow deposits. These deposits are common at the bottom of extremely flat sea mounds (less than 100 meters). Most of these sediments occur in the siliceous sediment distribution (type Ⅰ echo). Obviously, the physical properties of these deposits reflect that they are relatively unstable and therefore more susceptible to damage than brown clay.