Around 11 million years ago, the territory of nowadays Slovakia looked entirely different. The plains of western and south-eastern Slovakia were covered by the Pannonian Sea. Small islands were jutting out from the sea, now known as mountains like the Small Carpathians. The Tribeč Mountains near the town of Nitra were a peninsula.
In the north, the Turiec basin near the town of Martin was filled with an isolated and shallow lake. Now an international team of scientists led by geologist Michal Šujan, from the Faculty of Natural Sciences at Comenius University, have determined the timescale when the lake existed and disappeared.
The span was determined with a new method never used for this purpose.
The Slovak Spectator talked to Šujan about their research, the method and what eventually happened to the lake.
They knew about the lake, but not its age
Even though a given terrain can undergo significant transformation over millions of years, a scientist can glean a lot of information from various elements such as the depositional record, which can relate the dynamics of the environment or fossils.
"For decades, it has been known that in the past the Turiec Basin was covered by a lake, with the lower time limit dating back approximately 12 million years, determined by the age of volcanic rocks found beneath the lake sediments," explains Šujan. He adds that the fossils of molluscs and ostracods point to the origin of the sediments. The fossils are in muddy layers that can reach a thickness of up to one kilometre.