Monitoring of modern deep-water channels has revealed how migrating channel-floor features generate and remove stratigraphy, improving understanding of how channel morphologies relate to their deposits. Here, seafloor and subsurface data are reconciled through an integrated study of high-resolution bathymetry and three-dimensional seismic data imaging a ca 150 km stretch of the trench-axial Hikurangi Channel, offshore New Zealand. On the seafloor, terraced channel-walls bound a flat, wide, channel-floor, ornamented with three scales of features that increase then decrease in longitudinal gradient downstream, and widen downstream: cyclic-steps, knickpoints and knickpoint-zones (in increasing size). Mass-transport deposits derived from channel-wall collapse, are bordered by wide and flat reaches of channel-floor upstream and by knickpoint-zones (reaches containing multiple knickpoints) downstream. In the subsurface, recognition of ten seismofacies and five types of surface enables identification of four depositional elements: channel-fill, sheet or terrace, levée, and mass-transport deposits. Integration of subsurface and seafloor interpretations reveals that knickpoint-zones initiate on the downstream margins of channel-damming mass-transport deposits; they migrate and incise through the mass-transport deposits and weakly-confined deposits formed upstream, as the channel tends towards equilibrium. Downstream of a knickpoint-zone, a flat channel-floor is bounded by newly-formed terraces. Knickpoints migrate by eroding upstream and depositing downstream, generating filled concave-up (cross-sectional) surfaces in their wake. Within knickpoint-zones, knickpoint-generated surfaces are re-incised by subsequently-passing knickpoints to produce a composite bounding surface; this surface does not delineate the morphology of any palaeo-conduit. The Hikurangi Channel’s subsurface architecture records the localized erosional response to mass-transport deposit emplacement via knickpoint-zone migration, showcasing how transient seafloor features can build channelized stratigraphy. This model provides an additional mechanism to conventional models of channel deposit formation through ‘cut-and-fill’ over long stretches of channel. These findings may aid subsurface interpretation in systems lacking a contemporary self-analogue or with poor data coverage.

中文翻译：

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将海底地貌与地下结构联系起来：大规模运输沉积物和裂点带如何构建深水 Hikurangi 海峡的地层

对现代深水航道的监测揭示了迁移的航道底特征如何产生和去除地层，提高对航道形态与其沉积物的关系的理解。这里，海底和地下数据通过高分辨率水深，三维地震数据的成像综合研究协调CA新西兰近海 150 公里的海沟轴向 Hikurangi 海峡。在海底，阶梯状通道壁包围着平坦、宽阔的通道底板，装饰有三个尺度的特征，这些特征在下游纵向梯度先增加然后减小，并在下游变宽：循环阶梯、拐点和拐点带（尺寸越来越大） ）。源自河道壁塌陷的传质沉积物与上游宽阔平坦的河道底河段和下游的断点带（包含多个断点的河段）接壤。在地下，识别十种地震相和五种类型的表面可以识别四种沉积元素：河道填充、片状或阶地、堤坝和大量输送沉积物。地下和海底解释的整合表明，拐点带始于河道堤坝质量输送沉积物的下游边缘；随着通道趋于平衡，它们通过上游形成的质量输送沉积物和弱封闭沉积物迁移和切割。在拐点区的下游，平坦的渠道底板以新形成的阶地为界。切口通过侵蚀上游和向下游沉积而迁移，在其尾流中产生填充的上凹（横截面）表面。在切点区域内，切点生成的表面被随后通过的切点重新切割以产生复合边界表面；这个表面没有描绘任何古管道的形态。Hikurangi Channel 的地下结构记录了局部侵蚀响应通过小点带迁移对大规模运输沉积物的侵位，展示了瞬态海底特征如何构建通道化地层。该模型为传统的通道沉积形成模型提供了一种额外的机制，这种模型是通过在长通道上“挖填”形成的。这些发现可能有助于在缺乏现代自模拟或数据覆盖率较差的系统中进行地下解释。