Lateral spread and submarine creep are processes that occur near the headwalls of both terrestrial landslides and submarine mass-transport complexes (MTCs). Both submarine creep and spread deposits may contain giant (km-scale) coherent blocks, but their transport processes remain poorly constrained. Here we use seismic reflection data to determine the geometry, scale, and origin of a Late Miocene mass-transport complex (MTC) located in the Kangaroo Syncline, offshore NW Australia. We show that this large remobilised mass of carbonate ooze is ca. 170–300 m thick and covers an area of at least 1,050 km². The deposit is defined internally by two distinct seismic facies: (a) large, upward-tapering blocks (210–300 m thick, 170–210 m wide and 800–1,200 m long) with negligible internal deformation, which decrease in height and spacing along the transport direction (identical, but in situ, seismic facies forms undeformed slope material immediately updip of the deposit headwall); and (b) troughs (160–260 m thick, 190–230 m wide and 800–1,200 m long) comprising moderately deformed strata, which contain ‘v’-shaped, pipe-like structures that extend upwards from the inferred basal shear surface to the top surface. The lack of deformation within the blocks, and their correlation to adjacent in situ deposits, suggests they underwent limited transport (ca. 50 m–70 m). The relatively high degree of deformation within the intervening troughs is attributed to the vertical expulsion of fluids and sediment during hydraulic failure of the sediment mass. We present a hydraulic failure model that invokes evacuation of the lower slope by a precursor MTC and which formed the space to trigger the lateral spread. Our study also provides new insights into the genesis and rheology of subaqueous lateral spreads. The genetic links identified between mass wasting and spatially focused fluid flow, as well as disturbing the deep seafloor, indicate that submarine landslides may also create important deep-sea biodiversity hotspots.

中文翻译：

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海底侧向展布中巨大块体和流体逸出结构的形成及其意义

横向扩展和海底蠕变是在地面滑坡和海底大规模运输群（MTC）的顶壁附近发生的过程。海底蠕变沉积物和散布沉积物都可能包含巨大的（千米规模）连贯块体，但其运输过程受到的约束仍然很有限。在这里，我们使用地震反射数据来确定位于澳大利亚西北部袋鼠Syncline的中新世晚期运输复合体（MTC）的几何形状，尺度和成因。我们表明，这种较大的碳酸盐渗出物质量约为。170–300 m厚，至少覆盖1,050 km ²。该矿床内部由两个不同的地震相定义：（a）向上倾斜的大块体（210-300 m厚，170-210 m宽，800-1,200 m长），内部变形可忽略不计，其高度和间距减小沿传输方向（相同但原位，地震相形成未变形的斜坡材料，立即沿沉积顶壁上升）；（b）槽（厚160–260 m，宽190–230 m，长800–1,200 m），包括适度变形的地层，其中包含“ v”形的管状结构，从推断的基础剪切面向上延伸到顶部表面。区块内部缺乏变形，并且与邻近的原位沉积物相关，这表明它们进行了有限的运输（约50 m–70 m）。插入槽内较高程度的变形归因于在沉积物团的水力破坏期间流体和沉积物的垂直排出。我们提出了一种液压破坏模型，该模型调用了前驱MTC撤离下坡并形成了触发横向扩展的空间。我们的研究还为水下亚侧向扩散的成因和流变学提供了新的见识。大量浪费与空间集中的流体流动之间的遗传联系以及对深海底的扰动表明，海底滑坡也可能造成重要的深海生物多样性热点。我们提出了一个液压破坏模型，该模型调用了前驱MTC撤离下坡并形成了触发横向扩展的空间。我们的研究还为水下亚侧向扩散的成因和流变学提供了新的见识。大量浪费与空间集中的流体流动之间的遗传联系以及对深海底的扰动表明，海底滑坡也可能造成重要的深海生物多样性热点。我们提出了一个液压破坏模型，该模型调用了前驱MTC撤离下坡并形成了触发横向扩展的空间。我们的研究还为水下亚侧向扩散的成因和流变学提供了新的见识。大量浪费与空间集中的流体流动之间的遗传联系以及对深海底的扰动表明，海底滑坡也可能造成重要的深海生物多样性热点。