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首页> 外文期刊>Basin research >Miocene shelf-edge deltas and their impact on deepwater slope progradation and morphology, Northwest Shelf of Australia
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Miocene shelf-edge deltas and their impact on deepwater slope progradation and morphology, Northwest Shelf of Australia

机译：中新世陆架边缘三角洲及其对深水斜坡发育和形态的影响，澳大利亚西北大陆架

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Late-middle Miocene to Pliocene siliciclastics in the Northern Carnarvon Basin, Northwest Shelf of Australia, are interpreted as having been deposited by deltas. Some delta lobes deposited sediments near and at the shelf break (shelf-edge deltas), whereas other lobes did not reach the coeval shelf break before retreating landward or being abandoned. Shelf-margin mapview morphology changes from linear to convex-outward in the northern part of the study area where shelf-edge deltas were focused. Location and character of shelf-edge deltas also had significant impact on along-strike variability of margin progradation and shelf-edge trajectory. Total late-middle and late Miocene margin progradation is ca. 13 km in the south, where there were no shelf-edge deltas, vs. ca. 34 km in the north where shelf-edge deltas were concentrated. In the central area, the deltas were arrested and accumulated a few kilometres landward of the shelf break, resulting in an aggradational shelf-edge trajectory, in contrast to the more progradational trajectory farther north. This illustrates a potential limitation of shelf-edge trajectory analysis: only where shelf-edge deltas occur, there is sufficient sediment available for the shelf-edge trajectory to record relative sea-level fluctuations reliably. Small-scale (ca. 400 m wide) incisions were already conspicuous on the coeval slope even before deltas reached the shelf break. However, slope gullies immediately downdip from active shelf-edge deltas display greater erosion of underlying strata and are wider and deeper (>1 km wide, ca. 100 m deep) than coeval incisions that are laterally offset from the deltaic depocenter (ca. 0.7 km wide, ca. 25 m deep). We interpret this change in slope-gully dimensions as the result of greater erosion by sediment gravity flows sourced from the immediately adjacent shelf-edge deltas. Similarly, gullies also incised further (up to 6 km) into the outer shelf in the region of active shelf-edge deltas.
机译：在澳大利亚西北大陆架的北卡那封盆地中新世晚期至上新世硅质碎屑岩被解释为是由三角洲沉积的。一些三角叶在架子断裂附近和在架子断裂处沉积了沉积物（架子边缘三角洲），而其他的叶在陆上撤退或被抛弃之前没有到达同期的架子断裂。在研究区域的北部，货架边缘三角洲集中的货架边缘mapview形态从线性变为凸向外。货架边缘三角洲的位置和特征也对沿边缘的边缘扩展和货架边缘轨迹的变异性产生重大影响。中新世晚期和中新世晚期的总边缘量约为。在南部13公里处，没有大陆架边缘的三角洲，而大约在北部34公里处，大陆架边缘三角洲集中。在中部地区，三角洲被捕集，并在陆架断裂向内数公里处积聚，形成了一条渐进的陆架边缘轨迹，与更北端的渐进轨迹相反。这说明了架子边缘轨迹分析的潜在局限性：只有在出现架子边缘三角洲的地方，才有足够的沉积物用于架子边缘轨迹，以可靠地记录相对的海平面波动。甚至在三角洲尚未达到陆架断裂之前，小斜坡（约400 m宽）的切口就已经很明显地出现在那个年代。但是，从活动的陆缘三角洲立即下沉的坡口沟壑显示出对下层地层的更大侵蚀，并且比从三角洲沉积中心侧向偏移的同卵切缝更宽，更深（> 1 km宽，约100 m深）。宽约25公里）。我们将这种坡度-沟壑尺寸的变化解释为来自紧邻的陆架边缘三角洲的沉积物重力流造成的更大侵蚀的结果。同样，沟渠也在活动的大陆架边缘三角洲的区域进一步切入（最长6 km）到外部大陆架中。

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