ANCIENT trees have been unearthed as engineers dig up the ground to prepare for Halton’s new Mersey Gateway bridge.

Workmen discovered tree trunks that are more than 6,500 years old as they were excavating material underneath the saltmarsh in Widnes.

The timbers were sent for carbon dating and tests reveal that one of the timbers was 4,500 years old while another was from the Stone Age, estimated to be 6,500 years old.

Victoria Pollard, environment manager for Merseylink, which is building the bridge, said the tree rings of the timbers show when the water in the estuary became saline.

“The tree rings are fascinating because they tell us the period when the Mersey estuary in this area changed from a freshwater to a saline environment, which we can now date as taking place around 5,000 years ago,” she said.

“This data will be important in comparison with other dated sequences for the estuary to provide greater understanding of the pre-estuary environment and the date when the estuary changed.”

Mark Leah from Cheshire Archaeology Planning Advisory Service, said: “This is very useful information which simply wasn’t available from this part of the Mersey estuary prior to the project.

“The targeted investigation has, therefore, generated some information of real value to understanding the changing environment of the area in the past."

A sample of the tree trunks will be put on display at the Mersey Gateway visitor centres at Catalyst Science Discovery Centre in Widnes and at Runcorn Shopping Centre.

Cllr Rob Polhill, leader of Halton Council, said: “It’s amazing how such an iconic project which will shape Halton’s future has shed so much light on its past.

“The borough has a rich and diverse history and I would encourage people to go to our visitor centres to find out more.”

Both visitor centres are free to visit.

The centre at the Catalyst Museum in Widnes is open from 10am to 4pm, Tuesday to Sunday and the Runcorn centre is open from 10am to 4pm Monday to Friday.