Dodo weblog 2007

Working in wet conditions has its own specific difficulties. Yesterday a local contractor, Sotramon, started to drill holes with a diamond-headed borer (to get through the layer of dumped basalt) and installed the pumps. It took us several hours to drill six holes around the 2 x 2 meter sized excavation pit. In each hole we lowered a rubber tube down to groundwater level. We then connected the tubes to two powerpul pumps and started to drain the pit. But the meshes of the filters we used to prevent sand from being sucked up soon turned out to be too small. The pumps simply didn't extract enough water. Fortunately a local tailor was quickly able to produce better permeable filters.

Kenneth Rijsdijk and I started to investigate the general groundwater system of the surrounding swamp area. To get a good view of the water flow, we intend to drill water extraction holes on several spots. Fresh water quality and quantity is a determining factor of a good functioning ecosystem, and, in the case ouf Mare aux Songes, also favours the preservation of animal bones. We hypothesize that ground water permeates calcium rich sediments that were laid down by the sea thousands or even millions of years ago. As the water flows through the sediments it picks up calcium from shells and corals. When the water surfaces, the calcium impregnates the bones of animals that died in the swamp. Calcium forms a fine layer on the inner walls of bone cells, thus making them immune for deterioration by aggressive swamp acids.

Tamara Vernimmen had a meeting with Dr Claudia Baider, head of the Mauritius Herbarium at the Sugarcane Research Institute (MSIRI), based in Reduit. With Dr. Baider she discussed the possibilities of conducting reseaching into the endemic Mauritian trees. We expect this research to be very useful for the interpretation of wood samples that emerge from the Mare aux Songes swamp, which inevitably emerge during the excavation.