A time when the Mediterranean became cut off from, then reconnected to, the Atlantic has been securely dated. An approach known as astrochronology lies behind this achievement. Some time between five and six million years ago, the Mediterranean Sea became isolated from the Atlantic Ocean. In consequence some areas dried out — hence the title of Kenneth Hsue's book The Mediterranean was a Desert — and large salty lakes recharged by rivers flowing through deep canyons replaced the previously marine basins. During this time, the remaining bodies of water were either too salty or not salty enough for normal marine fauna to flourish. This was the so-called Messinian salinity crisis. Because Messinian sediments are essentially devoid of marine fossils this dramatic geological event has been difficult to date or place accurately in the global stratigraphic record, meaning in turn that its causes and environmental impact have been unclear.
展开▼
