Processes of late Quaternary turbidity current flow and deposition on the Var deep‐sea fan, north‐west Mediterranean Sea
Processes of late Quaternary turbidity current flow and deposition on the Var deep‐sea fan, north‐west Mediterranean Sea
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DOI：
10.1111/j.1365-3091.1993.tb01350.x
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发表时间：
1993-06
期刊：
影响因子：
3.5
通讯作者：
D. Piper;B. Savoye
中科院分区：
文献类型：
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作者：
D. Piper;B. Savoye
高分辨率地震boomer剖面，垂直分辨率小于1米，连同活塞芯和以前的侧扫声纳数据，被用来描述晚第四纪沉积的瓦尔深海扇。年代学控制由有孔虫生物地层学和岩心放射性碳测年提供，并通过地震相关性扩展到整个扇。区域侵蚀事件对应于氧同位素阶段2和6冰川最大。岩心和地震数据确定了一个广泛的表面砂层，这与1979年的前三角洲破坏和随后的海底电缆断裂有关。数值模拟限制了1979年浊流的特征。它起源于前三角洲上部的一个相对较小的滑坡，该滑坡使足够的物质处于悬浮状态，形成一个加速的浊流，该浊流侵蚀了瓦尔峡谷的沙子。浊流在上谷只有30米厚，但在中谷经历了显著的流动扩张，厚度超过120米，并以约2.5 m s−1的速度溢出瓦尔沉积脊东部。其他全新世浊流（重现间隔为1000年）有些泥泞和厚，但也沉积砂的堤坝中谷，并推断有一个类似的滑动相关的起源。晚更新世浊流在瓦尔沉积脊上沉积了厚的泥层。沉积物波的存在和从堤坝不对称性推断的平均横流斜率表明，其中一些水流的厚度达数百米，流速约为0.35 m s−1。这种与全新世浊积岩的对比表明，滑坡的起源是不可能的。厚泥床沉积在堤坝上的估计时间是几天到几周。因此，晚更新世的流动可能是瓦尔河冰川水的超密度流动的结果。晚更新世至全新世浊积岩沉积的变化更多地受沉积物供给变化的控制，而不是受海平面变化的控制。
High-resolution seismic boomer profiles, with a vertical resolution of less than 1 m, together with piston cores and previous side-scan sonar data, are used to describe late Quaternary sedimentation on the Var deep-sea fan. Chronological control is provided by foram biostratigraphy and radiocarbon dating in cores, and is extended over the fan by seismic correlation. Regional erosional events correspond to the oxygen isotopic stage 2 and 6 glacial maxima. Cores and seismic data define a widespread surface sand layer that is correlated with prodelta failure in 1979 and subsequent submarine cable breaks. Numerical modelling constrains the character of this 1979 turbidity current. It originated from a relatively small slide on the upper prodelta that put sufficient material in suspension to form an accelerating turbidity current which eroded sand from the Var Canyon. The turbidity current was only 30 m thick on the Upper Valley, but experienced significant flow expansion in the Middle Valley to thicknesses of more than 120 m, where it spilled over the eastern Var Sedimentary Ridge at a velocity of about 2·5 m s−1. Other Holocene turbidity currents (with a recurrence interval of 1000 years) were somewhat muddier and thicker, but also deposited sand on the levees of the Middle Valley, and are inferred to have had a similar slide-related origin. Late Pleistocene turbidity currents deposited thick mud beds on the Var Sedimentary Ridge. The presence of sediment waves and the mean cross-flow slope inferred from levee asymmetry indicates that some of these flows were many hundreds of metres thick and flowed at velocities of about 0·35 m s−1. This contrast with Holocene turbidites suggests that a slide origin is unlikely. Estimated times for deposition of thick mud beds on the levees are many days to weeks. The Late Pleistocene flows may therefore result from hyperpycnal flow of glacial outwash in the Var River. The variation in the Late Pleistocene to Holocene turbidite sedimentation is controlled more by variations in sediment supply than by sea-level change.