Surf not up for Palaeozoic creatures – new model reveals ancient sea was a giant lake

The ancient sea was more like a giant salty lake than a rolling ocean, report scientists from Imperial College London in the May edition of the Journal of the Geological Society. A new computer model that simulates how tides in North West Europe would have behaved 300 million years ago shows a sea with so little movement that it was unlike any on Earth today.

Using information on the ancient land masses and the tidal pull of the Moon, the new computer modelling system reveals a picture of a Palaeozoic ocean in which even basic lifeforms would have struggled to survive. Without tides, shallow coastal water is not mixed up, preventing life-saving oxygen from being circulated.

This shortage of oxygen causes lifeforms such as plankton to die and the decay of these lifeforms uses up further oxygen, contributing to the creation of an environment unable to support life. The Palaeozoic period lasted from 570 to 245 million years ago.

Dr Peter Allison, from the Department of Earth Sciences and Engineering and one of the authors of the study, said: “It is very difficult to understand how these huge ancient seas behaved, since we have no examples of this sort of water body on Earth today.

“We have used a new computer model to deduce the tidal range in ancient seas and show that they were almost tideless. Understanding the behaviour of these vast shallow expanses is critical to our knowledge of the ancient climate and environments and to understand how early marine life evolved and diversified,” says Dr Allison.

According to the researchers’ estimates, the new computer programme can model the behaviour of the sea many times faster than existing modelling systems. The model, developed by Dr Chris Pain, Dr Matthew Piggott and Martin Wells, has great potential for examining other patterns of ocean behaviour.

PhD student Martin Wells adds: “The modelling technology developed here at Imperial is a novel and fascinating means of investigating the ancient Earth. Although this is ‘blue-skies’ research now, we are validating an exciting new modelling technology which will ultimately help us to predict climate change.”