Acoustical characterization of sediments by Parasound and 3.5 kHz systems: Related sedimentary processes on the southeastern Weddell Sea continental slope, Antarctica
Acoustical characterization of sediments by Parasound and 3.5 kHz systems: Related sedimentary processes on the southeastern Weddell Sea continental slope, Antarctica
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Parasound 和 3.5 kHz 系统对沉积物的声学表征：南极洲威德尔海东南部大陆坡的相关沉积过程
DOI：
10.1016/0025-3227(93)90018-q
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
M. Weber
中科院分区：
文献类型：
--
作者：
G. Kuhn;M. Weber
在南极洲Lyddan冰隆西北部威德尔海大陆斜坡东南部的四次极地考察中进行了海底剖面测量。利用高分辨率地震反射系统（3.5kHz和Parasound）的地震记录对沉积物回波类型进行分类。通过对两种系统的比较，说明了Parasound系统的优越性。较小的光束角产生较高的空间分辨率，这大大减少了衍射双曲线。利用4种基本的回波类型（P =延长型，L =层状型，D =衍射双曲线型，W=楔形型），可区分出10种离散的沉积物回波模式。绘制了它们的区域分布图和声波信号进入沉积物的深度图，在研究区东部追踪到了西南-东北向的沉积脊，脊的东南侧有平行的通道。长时间和高反射率的回声类型的通道底部表明沉积的主要是粗粒沉积物受侵蚀过程的影响。这些渠道被解释为来自大陆架和陡峭的上斜坡的底层水流的排水系统。流向为东北方向，与威德尔环流相反。与此相反，沉积物脊显示高达80米的海底穿透力和回声类型的不同，多层反射平行运行的表面反射。脊部沉积物为“堤”式沉积物，在科氏力的作用下，由河道溢出，优先沉积在西北翼，在大陆坡中部缓倾斜阶地上广泛分布着楔形反射体分隔的沉积单元。这些沉积物被认为是由同沉积滑塌和具有东北方向运动的近源泥石流产生的。
Subbottom profiling was performed during fourPolarsternexpeditions to the southeastern Weddell Sea continental slope, northwest of Lyddan Ice Rise, Antarctica. Analogue records from high resolution, seismic reflection systems (3.5 kHz andParasound) were used to classify sediment echo types. A comparison between the two systems shows the advantage of theParasoundsystem. The smaller beam angle produces a higher spatial resolution, which reduces the diffraction hyperbolae considerably. The higher vertical resolution and deeper penetration provide more detailed information concerning seismic stratification.Using four basic echo categories (P = Prolonged, L = Layered D = Diffraction hyperbolae,W=Wedgingsubbottoms), ten discrete sediment echo patterns were distinguished. Their regional distribution and the depth of acoustic signal penetration into the sediment were mapped.SW-NE trending sediment ridges with channels running parallel on the southeastern side of the ridges were traced in the eastern part of the study area. The prolonged and highly reflective echo types of the channel bottoms indicate deposition of predominantly coarse-grained sediments affected by erosional processes. These channels are interpreted as drainage systems for bottom water currents derived from the shelf and steep upper slope. The flow direction is towards the northeast, counter to the Weddell Gyre. In contrast, the sediment ridges show up to 80 m subbottom penetration and an echo type of distinct, multi-layered reflectors running parallel to subparallel with the surface reflector. The sediments of the ridges are interpreted to be “levee”-sediments, overspilled from the channels and preferentially deposited on the northwestern flank due to the Coriolis force.Sedimentary units separated by wedge shaped reflectors are widespread on the gently inclined terrace in the middle part of the continental slope. These sediments are presumed to be produced by syn-sedimentary slumping and proximal debris flows having a northeastern direction of movement.