Christchurch biologist Bryan Molloy says matai and totara logs discovered in the Avon-Heathcote estuary near McCormack's Bay date from pre-European settlement of the Canterbury plains.
The former department of agriculture scientist says it's hard to determine the age of the logs because the plains are like a "huge club sandwich" with layer upon layer of forest sediment and river gravel.
But Dr Molloy told Waatea News they may have come from the period when Captain Cook sailed past and observed activity on the land from a distance.
Dr Molloy says the logs are all that remains of the forests that once cloaked the area known as the Riccarton Bush or Putaringamotu.
