Instituto de Ciencias de la Tierra Jaume Almera, CSIC, Solé i Sabarís s/n, 08028 Barcelona, Spain.
Nature. 2011 Dec 14;480(7377):359-63. doi: 10.1038/nature10651.
The Messinian salinity crisis (5.96 to 5.33 million years ago) was caused by reduced water inflow from the Atlantic Ocean to the Mediterranean Sea resulting in widespread salt precipitation and a decrease in Mediterranean sea level of about 1.5 kilometres due to evaporation. The reduced connectivity between the Atlantic and the Mediterranean at the time of the salinity crisis is thought to have resulted from tectonic uplift of the Gibraltar arc seaway and global sea-level changes, both of which control the inflow of water required to compensate for the hydrological deficit of the Mediterranean. However, the different timescales on which tectonic uplift and changes in sea level occur are difficult to reconcile with the long duration of the shallow connection between the Mediterranean and the Atlantic needed to explain the large amount of salt precipitated. Here we use numerical modelling to show that seaway erosion caused by the Atlantic inflow could sustain such a shallow connection between the Atlantic and the Mediterranean by counteracting tectonic uplift. The erosion and uplift rates required are consistent with previous mountain erosion studies, with the present altitude of marine sediments in the Gibraltar arc and with geodynamic models suggesting a lithospheric slab tear underneath the region. The moderate Mediterranean sea-level drawdown during the early stages of the Messinian salinity crisis can be explained by an uplift of a few millimetres per year counteracted by similar rates of erosion due to Atlantic inflow. Our findings suggest that the competition between uplift and erosion can result in harmonic coupling between erosion and the Mediterranean sea level, providing an alternative mechanism for the cyclicity observed in early salt precipitation deposits and calling into question previous ideas regarding the timing of the events that occurred during the Messinian salinity crisis.
墨西拿盐度危机（596 万至 533 万年前）是由于大西洋流入地中海的水量减少，导致广泛的盐沉淀和地中海海平面下降约 1.5 公里，这是由于蒸发造成的。在盐度危机时期，大西洋和地中海之间的连通性降低被认为是由于直布罗陀弧形海峡的构造抬升和全球海平面变化造成的，这两者都控制着补偿地中海水文赤字所需的水量流入。然而，构造抬升和海平面变化的不同时间尺度与解释大量盐沉淀所需的地中海和大西洋之间浅连接的长持续时间难以协调。在这里，我们使用数值模拟表明，大西洋流入引起的海峡侵蚀可以通过抵消构造抬升来维持地中海和大西洋之间的这种浅连接。所需的侵蚀和抬升速率与之前的山地侵蚀研究一致，与直布罗陀弧形海峡的海洋沉积物的当前海拔一致，并与地球动力学模型表明该地区下方存在岩石圈板块撕裂一致。在墨西拿盐度危机早期，地中海海平面适度下降，可以通过每年几毫米的抬升来解释，而由于大西洋流入，侵蚀速率也相似。我们的研究结果表明，抬升和侵蚀之间的竞争可以导致侵蚀和地中海海平面之间的谐波耦合，为早期盐沉淀沉积物中观察到的周期性提供了另一种机制，并对发生在墨西拿盐度危机期间的事件的时间提出了质疑。
