The evolution of the Tugela canyon and submarine fan: A complex interaction between margin erosion and bottom current sweeping, southwest Indian Ocean, South Africa
The evolution of the Tugela canyon and submarine fan: A complex interaction between margin erosion and bottom current sweeping, southwest Indian Ocean, South Africa
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DOI：
10.1016/j.marpetgeo.2013.03.012
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发表时间：
2013-06
影响因子：
4.2
通讯作者：
E. Wiles;A. Green;M. Watkeys;W. Jokat;R. Krocker
中科院分区：
文献类型：
--
作者：
E. Wiles;A. Green;M. Watkeys;W. Jokat;R. Krocker
沿着东南非洲被动大陆边，沉积物从上大陆坡转移到海隆的情况记录甚少。在印度洋西南部的纳塔尔山谷收集的新的条带测深和海底下数据，使人们能够深入了解图格拉峡谷和扇形系统的演变。注意到峡谷形态的几个明显的下坡变化。峡谷地势起伏增大，深度越深越宽。基底露头仅限于峡谷的顶部，随着深度的增加而变得不那么突出。峡谷壁和底部的阶梯状阶地在峡谷的中坡部分变得突出，并且与峡谷剖面的横截面不对称性显著增加有关。当代图格拉峡谷位于最后一个充填阶段的洼地内。该峡谷是渐新世中期、中新世中期和上新世晚期几个阶段的内陆隆起所造成的下坡侵蚀和下切的产物。每一阶段之后是古峡谷形式的远洋填充。下坡时，隆起阶段保存在主峡谷深泓线内的切阶和轴向切口中。当代峡谷是一个垂死的功能，沉积物饥饿的货架区目前席卷的Agulhas电流减少了材料可用于峡谷切口和风扇的发展。北大西洋深水洋流带来的额外洋流阻碍了相关扇体的发展。
The transfer of sediment from the upper continental slope to rise is poorly documented along the southeast African passive margin. New swath bathymetric and sub-bottom data collected in the Natal Valley, southwest Indian Ocean, provide insight into the evolution of the Tugela canyon and fan system. Several distinct downslope changes in canyon morphology are noted. The canyon increases in relief and widens with depth. Basement outcrop is restricted to the head of the canyon becoming less prominent with depth. Step-like terracing of the canyon walls and floor becomes prominent in the mid-slope portions of the canyon and is related to a marked increase in the cross sectional asymmetry of the canyon profile. The contemporary Tugela canyon rests within a depression of the last phase of infilling. The canyon is the product of downslope erosion, and incision, caused by several phases of hinterland uplift in the mid Oligocene, mid Miocene and late Pliocene. Each phase was followed by pelagic infilling of the palaeo-canyon form. Downslope, the uplift phases are preserved in the cut-terraces and axial incisions within the main canyon thalweg. The contemporary canyon is a moribund feature, sediment starvation of the shelf area by current sweeping of the Agulhas current has decreased the material available for canyon incision and fan development. Additional current sweeping by the North Atlantic Deep Water current has stunted the development of the associated fan complex.