Millions of years ago the Yangtze River basin was a sea, study finds
- Research on ancient fish fossils provides new evidence for existence of the Yangtze Sea some 438 million years ago
- Fossils were preserved in sedimentary rock layers known as red beds that formed during the Silurian geological period
But some geologists believe the basin, which is home to about a third of China’s population, was a sea 438 million years ago – and a recent study on fish fossils provides new evidence for this.
“Called the Yangtze Sea, its [existence] has been confirmed by multiple pieces of scientific evidence,” Gai Zhikun, a professor at the Chinese Academy of Sciences’ Institute of Vertebrate Palaeontology and Palaeoanthropology, said on Wednesday.
His team classified and compared fish fossils collected from across China for the study. Their findings on the fossils from the Yangtze region were published in the peer-reviewed Journal of Stratigraphy in June.
The fossils were preserved in sedimentary rock layers known as red beds – coloured red by the mineral haematite – that formed in the Silurian, a geological period that lasted from about 443 to 419 million years ago.
The fossils were all of the same prehistoric species that emerged in the early Silurian period and rapidly evolved: the galeaspid, a jawless armoured fish.
“The galeaspid fish was a weak swimmer, and it lived in shallow seas,” Gai said.
Red beds were formed in shallow waters. As the sea level retreated, fine clasts containing haematite accumulated on the seabed and when rocks formed that haematite was preserved in the sediments.
