Predicting when turbidity currents are erosional or depositional (i.e., leaving no depositional record versus leaving a deposit) remains challenging. Here we combine observations from submarine channel morphology with a new sediment transport model to derive thresholds for net erosional, equilibrium, or net depositional flow to predict how far turbidity currents can transport different grain size classes down the channel. The approach was applied to the modern Madden and Omakere Channels, which traverse the Hikurangi subduction margin of the North Island of New Zealand. A bathymetric data set was used to establish the downstream change of channel geometry. Taking account of centripetal and Coriolis forces, the flow superelevation method was used to estimate variations in flow velocity and concentration along the channels. These parameters were used as model inputs to estimate the potential distribution of sand in the system assuming the separate cases of well-sorted and poorly-sorted sediment in suspension. The predicted sand distribution maps deposited by poorly-sorted flows in the channels show good agreement with root mean square amplitude mapping of the seafloor. These results confirm that thicker flows, and those carrying well-sorted suspensions, can bypass sediment over lower slopes than thinner flows and those carrying more poorly-sorted suspensions. The net erosion and net deposition thresholds derived from this study may help to guide and constrain predictions of potential sediment bypass zones in seafloor and subsurface systems and hence better constrain the predicted loci of deposition.

中文翻译：

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应用于新西兰东海岸盆地的沉积物旁路预测新建模方法

预测浊流何时是侵蚀性或沉积性的（即，没有留下沉积记录与留下沉积物）仍然具有挑战性。在这里，我们将海底河道形态的观察结果与新的沉积物输送模型相结合，以推导出净侵蚀、平衡或净沉积流的阈值，以预测浊流可以将不同粒度级别的水沿河道输送多远。该方法应用于现代马登海峡和奥马克雷海峡，它们穿过新西兰北岛的 Hikurangi 俯冲边缘。测深数据集用于确定下游通道几何形状的变化。考虑到向心力和科里奥利力，流动超高方法用于估计沿通道的流速和浓度的变化。这些参数被用作模型输入来估计系统中沙子的潜在分布，假设悬浮液中分选良好和分选不良的沉积物是分开的。由通道中分选不良的水流沉积的预测砂分布图与海底的均方根振幅图显示出良好的一致性。这些结果证实，较厚的水流和那些携带分选良好的悬浮液的水流比较薄的水流和携带更多分选较差的悬浮液的水流可以绕过较低坡度的沉积物。本研究得出的净侵蚀和净沉积阈值可能有助于指导和约束对海底和地下系统中潜在沉积物旁路带的预测，从而更好地约束预测的沉积位置。