Abstract The termination of a deep-sea turbiditic channel represents the ultimate sink of terrigenous sediment in the oceans or lakes. Such environment is characterized by rapid slope decrease and by loss of confinement of turbidity currents. It results in the deposition of Channel-Mouth-Lobes that can be separated from the channel mouth by an erosional (scoured) or by-pass dominated Channel-Lobe Transition Zone. Several factors can control the occurrence, extent and morphologic expression of the area such as the slope break angle, the upslope and downslope angle and the mud/sand ratio in flows. Disentangling these factors remains challenging due to the scarcity of outcrops and to the usual faint morphologies and low thickness of deposits. With bathymetric and seismic data we calculated the morphometric parameters of 8 channel-levees and their Channel-Mouth Lobes from the deepest area of the Rhone fan, a mud-sand rich system, and among which the youngest one (called neofan) was deposited at the end of the Last Glacial Maximum between 21.5 and 18.3 ka cal. BP. Emplacement and shape (finger-shaped or pear-shaped bulges) of Channel-Mouth Lobes is controlled by the seabed morphology (adjacent channel-levees and salt diapirs). A less prominent morphology of the neofan is attributed to premature quiescence related to the post sea-level rise sediment starvation. We show that the occurrence and expression of a Channel-Lobe Transition Zone is controlled by the gradient upstream of the channel mouth slope break. The extended Channel-Lobe Transition Zone and detached lobe of the neofan are attributed to the high upslope gradient (0.26°) while the less detached or attached lobes of other channel-levees is attributed to lower upslope gradient (0.13°). We show that scouring and scours concatenation into flutes at the Channel-Lobe Transition Zone is a major driver for the inception of channels and further confinement of turbidity current. For the first time we show that concatenation of scours in shingled disposition developed an incipient channel sinuosity at this very early stage of channel development. The channel-levee can extend downslope nearly instantaneously by tens of kilometers when isolated nascent channels connect to the channel mouth.

中文翻译：

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关于深海扇通道的终止：来自罗纳扇的例子（狮子湾，西地中海）

摘要 深海浊流通道的终点代表了海洋或湖泊中陆源沉积物的最终汇。这种环境的特点是坡度迅速下降和浊流的约束丧失。它导致沟口叶瓣的沉积，可以通过侵蚀（冲刷）或旁路主导的河道叶瓣过渡带将其与河道口分开。有几个因素可以控制该区域的发生、范围和形态表现，例如坡折角、上坡和下坡角度以及流中的泥砂比。由于露头的稀缺以及通常微弱的形态和沉积物的低厚度，解开这些因素仍然具有挑战性。利用测深和地震数据，我们计算了罗纳扇最深区域的 8 条河道堤及其河口叶瓣的形态参数，其中最年轻的一条（称为新扇）沉积于末次盛冰期结束，温度介于 21.5 和 18.3 ka 之间。BP。航道口叶的位置和形状（指状或梨形凸起）受海床形态（相邻的航道堤和盐底辟）控制。Neofan 不太突出的形态归因于与海平面上升后沉积物饥饿相关的过早静止。我们表明，航道-波瓣过渡带的发生和表达受航道口坡折断上游梯度的控制。Neofan 延伸的河道-波瓣过渡带和分离的波瓣归因于高上坡梯度（0.26°），而其他河道堤的分离或附着较少的波瓣归因于较低的上坡梯度（0.13°）。我们表明，冲刷和冲刷在通道-叶过渡区连接成槽是通道开始和进一步限制浊流的主要驱动力。我们第一次表明，在通道发展的这个非常早期的阶段，叠瓦配置中的冲刷串联形成了初期的通道弯曲。当孤立的新生河道与河道口连接时，河道堤几乎可以瞬间向下延伸数十公里。26°），而其他渠道堤坝的较少分离或附着的瓣归因于较低的上坡梯度（0.13°）。我们表明，冲刷和冲刷在通道-叶过渡区连接成槽是通道开始和进一步限制浊流的主要驱动力。我们第一次表明，在通道发展的这个非常早期的阶段，叠瓦配置中的冲刷串联形成了初期的通道弯曲。当孤立的新生河道与河道口连接时，河道堤几乎可以瞬间向下延伸数十公里。26°），而其他渠道堤坝的较少分离或附着的瓣归因于较低的上坡梯度（0.13°）。我们表明，冲刷和冲刷在通道-叶过渡区连接成槽是通道开始和进一步限制浊流的主要驱动力。我们第一次表明，在通道发展的这个非常早期的阶段，叠瓦配置中的冲刷串联形成了初期的通道弯曲。当孤立的新生河道与河道口连接时，河道堤几乎可以瞬间向下延伸数十公里。我们第一次表明，在通道发展的这个非常早期的阶段，叠瓦配置中的冲刷串联形成了初期的通道弯曲。当孤立的新生河道与河道口连接时，河道堤几乎可以瞬间向下延伸数十公里。我们第一次表明，在通道发展的这个非常早期的阶段，叠瓦配置中的冲刷串联形成了初期的通道弯曲。当孤立的新生河道与河道口连接时，河道堤几乎可以瞬间向下延伸数十公里。