Catastrophic flood of the Mediterranean after the Messinian salinity crisis

摘要

The Mediterranean Sea became disconnected from the world's oceans and mostly desiccated by evaporation about 5.6 million years ago during the Messinian salinity crisis. The Atlantic waters found a way through the present Gibraltar Strait and rapidly refilled the Mediterranean 5.33 million years ago in an event known as the Zandean flood. The nature, abruptness and evolution of this flood remain poorly constrained. Borehole and seismic data show incisions over 250 m deep on both sides of the Gibraltar Strait that have previously been attributed to fluvial erosion during the desiccation. Here we show the continuity of this 200-km-long channel across the strait and explain its morphology as the result of erosion by the flooding waters, adopting an incision model validated in mountain rivers. This model in turn allows us to estimate the duration of the flood. Although the available data are limited, our findings suggest that the feedback between water flow and incision in the early stages of flooding imply discharges of about 10~8m~3s~(-1) (three orders of magnitude larger than the present Amazon River) and incision rates above 0.4 m per day. Although the flood started at low water discharges that may have lasted for up to several thousand years, our results suggest that 90 per cent of the water was transferred in a short period ranging from a few months to two years. This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than ten metres per day.%距今大约560万年前，地中海与世界其他海洋rn分开，而且在这之后被称为“Messinian salinityrncrisis"的时期，随着海水蒸发，海平面急剧下rn降。海水在距今大约530万年前恢复了，但关rn于这一事件(地球历史上已知最大的洪灾)的细rn节仍然很不完整。利用钻孔、地震数据和数值rn模拟所进行的一项研究表明，这是一次灾难性rn的事件：虽然它是从一个可能持续了数千年的rn涓涓溪流开始的，但入注的水中多达90％是在rn不到两年时间里输送到地中海里的。这样一个rn突发的洪灾可能曾使海平面以超过每天10米的rn峰值速度上升。