Japan's sediment flux to the Pacific Ocean revisited
Japan's sediment flux to the Pacific Ocean revisited
复制标题
DOI：
10.1016/j.earscirev.2014.03.004
复制
发表时间：
2014-08
影响因子：
12.1
通讯作者：
O. Korup;Y. Hayakawa;A. Codilean;Y. Matsushi;H. Saito;T. Oguchi;H. Matsuzaki
中科院分区：
文献类型：
--
作者：
O. Korup;Y. Hayakawa;A. Codilean;Y. Matsushi;H. Saito;T. Oguchi;H. Matsuzaki
量化从岛弧向俯冲带输送陆地沉积物的数量和速度，对于精确估计海沟填充物的厚度是必不可少的，而海沟填充物的厚度最终可能控制海底滑坡和引发海啸的特大地震的位置和时间。尽管有这些令人鼓舞的见解，知识的侵蚀和沉积物出口的速度从日本岛屿太平洋俯冲带仍然是不完整的，尽管越来越多的高分辨率数据的表面变形，气候，地质和地形。传统上，整个岛弧的自然侵蚀速率是通过几年到几十年记录的地形集水指标和水库沉积速率的回归来估计的。我们回顾目前的研究在这种情况下，纠正系统的偏见，在一个最广泛使用的预测，并提出了新的估计十年到千年尺度的侵蚀率日本的陆地内前弧。我们借鉴了几个独立的和前所未有的库存质量浪费，水库沉积，和浓度的cosmogenic 10 Be河砂。我们发现，在日本阿尔卑斯山，几毫米/年的天然10 Be剥蚀率已经持续了几个世纪到几千年，并且在误差范围内，与人工水库沉积推断的沉积物产量大致一致。局部例外情况可能是由于沉积物储存的释放或区域滑坡事件触发瞬时沉积物脉冲。我们的概要进一步揭示，排水日本东海岸流域明显不同的构造，岩性，地形和气候特征之间的东北，日本阿尔卑斯山，和南海内弧段，这是强调了一个显着的不对称模式侵蚀率沿着岛弧。日本阿尔卑斯山的侵蚀速率最高（至少达到3毫米/年），这标志着两个俯冲带的碰撞，高地形起伏，山坡和陡峭的博克海峡通过质量浪费促进快速剥蚀。类似的，如果稍微低一点，侵蚀率在日本西南部的南海内前弧，最有可能是由于较高的台风驱动的降雨总量和变化，而不是其高地形起伏。相比之下，我们估计的侵蚀和通量率是最低的东北内弧前集水区，饲料沉积物进入日本海沟。我们的结论是，日本阿尔卑斯山的碰撞造山驱动一些岛弧的最高侵蚀率，尽管在日本西南部类似的隆起和降水控制。我们推断，在广泛的河流筑坝，水库建设和沿海工程，日本的总沉积物出口到太平洋的总进入南海海槽的增生边缘，而不是相对缺乏沉积物的日本海沟。与太平洋其他地区山区集水区的沉积物通量的记录相比，尽管地势高，坡度陡，地震活动性很高，暴雨频繁，但日本内弧的河流排水处于中间位置。然而，日本阿尔卑斯山的千年级剥蚀平均速率是世界上最高的。这些晚全新世速率与现代速率之间的局部不匹配强调了沉积物保留的人为指纹，这可能显着减少了岛弧向其俯冲带的质量通量，就像东亚和东南亚其他地方的情况一样。
Quantifying volumes and rates of delivery of terrestrial sediment from island arcs to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami-generating mega-earthquakes. Despite these motivating insights, knowledge about the rates of erosion and sediment export from the Japanese islands to their Pacific subduction zones remains patchy regardless of the increasing availability of highly resolved data on surface deformation, climate, geology, and topography. Traditionally, natural erosion rates across the island arc have been estimated from regression of topographic catchment metrics and reservoir sedimentation rates that were recorded over several years to decades. We review current research in this context, correct for a systematic bias in one of the most widely used predictions, and present new estimates of decadal to millennial-scale erosion rates of Japan's terrestrial inner forearc. We draw on several independent and unprecedented inventories of mass wasting, reservoir sedimentation, and concentrations of cosmogenic10Be in river sands. We find that natural10Be-derived denudation rates of several mm yr− 1in the Japanese Alps have been sustained over several centuries to millennia, and are, within error, roughly consistent with sediment yields inferred from artificial reservoir sedimentation. Local exceptions may likely result from release of sediment storage or regional landsliding episodes that trigger transient sediment pulses. Our synopsis further reveals that catchments draining Japan's eastern seaboard differ distinctly in their tectonic, lithological, topographic, and climatic characteristics between the Tohoku, Japanese Alps, and Nankai inner forearc segments, which is underscored by a marked asymmetric pattern of erosion rates along the island arc. Erosion rates are highest (up to at least 3 mm yr− 1) in the Japanese Alps that mark the collision of two subduction zones, where high topographic relief, hillslope and bedrock-channel steepness foster rapid denudation by mass wasting. Comparable, if slightly lower, erosion rates characterise the Nankai inner forearc in southwest Japan, most likely due to higher typhoon-driven rainfall totals and variability rather than its high topographic relief. In contrast, our estimated erosion and flux rates are lowest in the Tohoku inner forearc catchments that feed sediment into the Japan Trench. We conclude that collisional mountain building of the Japanese Alps drives some of the highest erosion rates in the island arc despite similar uplift and precipitation controls in southwest Japan. We infer that, prior to extensive river damming, reservoir construction, and coastal works, the gross of Japan's total sediment export to the Pacific Ocean entered the accretionary margin of the Nankai Trough as opposed to the comparatively sediment-starved Japan Trench. Compared to documented contemporary rates of sediment flux from mountainous catchments elsewhere in the Pacific, the rivers draining Japan's inner forearc take an intermediate position despite high relief, steep slopes, very high seismicity, and frequent rainstorms. However, the average rates of millennial-scale denudation in the Japanese Alps particularly are amongst the highest reported worldwide. Local mismatches between these late Holocene and modern rates emphasise the anthropogenic fingerprint on sediment retention that may have significantly reduced the island arc's mass flux to its subduction zones, as is the case elsewhere in east and southeast Asia.