A group of international scientists say they have discovered what the Great Barrier Reef looked like thousands of years ago.

A scientific group took part in a drilling expedition off the Queensland coast earlier this year to take samples of reef fossils from deep below the ocean floor. About 225 metres of deep ocean coral fossils taken from the reef earlier this year will now be housed in laboratories in Germany and Japan.

Co-chief scientist Dr Jody Webster says researchers are still compiling an extensive report about what pressures the reef faced during that period.

"We have potentially a fantastic record of sea level changes, climate changes and also reef response changes; how the reef changed in responded to periods of quite extreme environmental stress," he said. "We can look at how the Great Barrier Reef responded to those changes and that actually has important implications how the modern Great Barrier Reef might respond to future changes".

Dr Webster says the findings will be released within the next 12 months.