Clathrates are ice-like, crystalline solids composed of water and low molecular weight gas molecules. Because of the unique pressure and temperature fields in which they are stable, clathrates tend to be abundant in continental slope and rise sediments in the deep sea. The resulting precipitation of solid clathrates within marine sediments is detectable from the occurrence of bottom-parallel reflectors which are visible in seismic reflection records, are generally parallel to the ocean bottom, and cut across other sediment reflections. The bottom parallel reflector apparently represents the base of the clathrate stability field. Below this reflector the clathrate decomposes into fresh water and dissolved gas. Few pristine samples of clathrates from the deep-sea have ever been fully analyzed, since the clathrates tends to decompose rapidly when brought to the sea surface. Recently the Ocean Drilling Program has developed a pressure core barrel which is capable of retrieving a one meter long sample of marine sediment and returning the material to the drillship under in situ pressure. During a recent engineering test of this system, an undisturbed sample was recovered from the Nankai Trench. the present award will support preliminary development of the necessary analytical techniques to examine this unexpected sample important in fully documenting chemical reactions and conditions and in evaluating the release of clathrates gasses to the atmosphere during sea-level changes.
