Clipperton Science Expedition Log
March 7th, 2008
After 6 days at sea, and a few more unloading the boat and setting up camp, the science component of the Clipperton Expedition is finally established on the island and collecting samples. Yesterday we ventured onto the lagoon for the first time to do a basic survey of the bathymetry. Under blazing sun, and a light breeze, we collected our first sediment core from the large basin known as Fosse Occidentale. The recovered section measured 101 cm and consisted of approximately 35 cm of fine grained white material overlain by 65 cm of layered organic matter.
Our working hypothesis is that the white material is authigenic carbonate, but we do not yet have a satisfying explanation as to exactly why or how the material was deposited. Acid tests of the white material confirm the composition, but the source remains unknown. The obvious assumption is that the transition from carbonate rich to organic rich sedimentation marks the surficial closure of the lagoon to the sea, but this alone may not fully explain all of the observations. If the lagoon were open to the sea, it seems unlikely that such fine grain authigenic material could be deposited in an open ocean near-shore setting. The next step is to attempt to ascertain whether the sedimentation pattern is widespread across the entire lagoon, or whether it is limited to the basin that we collected sediment from. This will help us to determine whether the change was entirely geochemical, or whether a major change in surface hydrology and exposure to wave action is partially responsible.
We plan to spend the rest of the day finishing with our equipmentsetup so that we can move forward with a comprehensive sediment survey. By collecting additional surface cores from each of the basins we hope to determine the spatial extent of the changes we observed in the initial sediment core, and to help us formulate a plan about where to focus our subsequent efforts.
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