ABSTRACT

Continental shelves generally supply large-scale mass-wasting events. Yet, the origin and significance of shelf-derived mass-transport deposits (MTDs) for the tectonostratigraphic evolution of subduction complexes and their trench-slope basins have not been extensively studied. Here, we present high-resolution, outcrop-scale insights on both the nature of the reworked sediments, and their mechanisms of development and emplacement along tectonically active margins, by examining the Middle Miocene shelf-derived MTDs outcropping in the exhumed southern portion of the Hikurangi subduction margin. Results show that periods of repeated tectonic activity (thrust propagation, uplift) in such compressional settings not only affect and control the development of shelfal environments but also drive the recurrent generation and destruction of oversteepened slopes, which in turn, favour the destabilisation and collapses of the shelves and their substratum. Here, these events produced both large-scale, shelf-derived sediment mass-failures and local debris flows, which eventually broke down into a series of coalescing, erosive, genetically linked surging flows downslope. The associated MTDs have a regional footprint, being deposited across several trench-slope basins. Recognition of tectonic activity as another causal mechanism for large-scale shelf failure (in addition to sea-level changes, high-sedimentation fluxes) has implications for both stratigraphic predictions and understanding the tectonostratigraphic evolution of deep-marine fold-and-thrust belts.

摘要

大陆架通常供应大规模的大规模浪费活动。然而，对于俯冲杂岩及其沟坡盆地的构造地层演化而言，陆架衍生的物质输送沉积物（MTD）的起源和意义尚未得到广泛研究。在这里，我们通过检查中中新世陆架衍生的 MTD 在挖掘出的南部部分露头，就重新加工的沉积物的性质及其沿构造活动边缘的发育和就位机制提出了高分辨率、露头尺度的见解。 Hikurangi 俯冲边缘。结果表明，重复构造活动的时期（推力传播，隆起）在这种压缩环境中不仅影响和控制陆架环境的发展，而且还推动过度陡峭斜坡的反复产生和破坏，这反过来又有利于陆架及其底层的不稳定和坍塌。在这里，这些事件产生了大规模的、陆架衍生的沉积物质量破坏和局部泥石流，最终分解成一系列聚结的、侵蚀性的、与基因相关的下坡涌流。相关的 MTD 具有区域足迹，沉积在几个沟槽斜坡盆地中。认识到构造活动是大规模陆架破坏的另一个因果机制（除了海平面变化，