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首页> 外文期刊>Marine Geology >Shelf sedimentation on a tectonically active margin: A modern sediment budget for Poverty continental shelf, New Zealand
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Shelf sedimentation on a tectonically active margin: A modern sediment budget for Poverty continental shelf, New Zealand

机译：构造活动边缘上的陆架沉积：新西兰贫困大陆架的现代沉积物预算

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The combination of high sediment yields and the prevalence of tectonically controlled accommodation on collision margins such as that adjacent to the Waipaoa River, NZ, create the potential for these areas to contain high-resolution records of natural and anthropogenic signals. This study describes modern (100-yr) sedimentation patterns off the Waipaoa and quantifies a sediment budget for the continental shelf, which is compared to long-term Holocene trends. ~(210)Pb and ~(239,240)pu geochronologies reveal three main shelf depocenters. Two of these depocenters are located in subsiding synclinal basins on the mid-shelf, landward of the actively deforming Ariel and Lachlan anticlines. The depocenters exhibit accumulation rates ranging from 0.75 to 1.5 cmyr~(-1) and display both steady-state and non-steady-state ~(210)Pb activity profiles. Textural characteristics of the non-steady-state cores indicate the possible preservation of flood event layers. The third depocenter is located near the shelf break and has accumulation rates as high as 1.0cm yr~(-1) The inner shelf and central mid-shelf are characterized by low, uniform ~(210)Pb activity profiles and low accumulation rates, indicating that sediment is bypassing the inner shelf region and being deposited on the mid- to outer shelf. The modern sedimentation patterns seen in this study are similar to those for the Holocene, suggesting that regional tectonics are the major influence on Poverty shelf sedimentation. A modern, bulk sediment budget estimates that 3.6 + - 0.9 × 10~6tyr~(-1) of sediments remains on the shelf, amounting to only approx 25% of the 15 Mt of sediments discharged from the river per year. This indicates massive export of sediments from the study area to the adjacent slope or along the shelf. In contrast, studies of the Mid-Late Holocene sediment budget in the same area indicate that the sediment input and shelf trapping have been roughly in balance. When compared with the modern budget, this suggests an extraordinarily rapid shift from shelf trapping to shelf bypassing, most likely driven by increasing sediment discharge in response to deforestation.
机译：较高的沉积物产量和碰撞边缘（如新西兰怀波阿河附近的碰撞边缘）的构造控制性住宿的普遍存在，为这些地区包含高分辨率的自然和人为信号记录创造了潜力。这项研究描述了怀波阿附近的现代（100年）沉积模式，并量化了大陆架的沉积物预算，并将其与全新世的长期趋势进行了比较。 〜（210）Pb和〜（239,240）pu年代学揭示了三个主要的陆架沉积中心。这些沉积中心中的两个位于活跃变形的Ariel和Lachlan背斜的陆架中部下沉向斜盆地中。沉积中心的沉积速率范围为0.75至1.5 cmyr〜（-1），并显示稳态和非稳态〜（210）Pb活性曲线。非稳态岩心的纹理特征表明可能保留洪水事件层。第三个沉积中心位于陆架断裂附近，堆积速率高达1.0cm yr〜（-1）。内陆架和中部中层架子的特征是低，均匀的〜（210）Pb活性曲线和低堆积速率，表明沉积物绕过内层架区域并沉积在中层到外层架上。在这项研究中看到的现代沉积模式与全新世相似，这表明区域构造是对贫困大陆架沉积的主要影响。现代的大量沉积物预算估计，架子上仍保留有3.6 +-0.9×10〜6tyr〜（-1）的沉积物，仅占河流每年排放的15 Mt沉积物的约25％。这表明沉积物从研究区域大量出口到相邻的斜坡或沿架子。相比之下，对同一地区中晚期全新世沉积物预算的研究表明，沉积物输入和架子圈闭大致平衡。与现代预算相比，这表明从架子诱集到架子绕行异常迅速，这很可能是由于森林砍伐导致沉积物排放量增加所致。

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