The relationship between the Na and Ca content with Cl fits on the mixing line, indicating a single source for the high and low-Cl fluids. 1038I. Except for Hole 1038I, which was drilled away from the hydrothermal field, methane in the recovered cores has a thermogenic origin. The presence of benzene and toluene confirm high temperature cracking of organic matter. The estimated temperature of organic maturation is higher than in Middle Valley. The full range of maturity is observed.
Hydrothermal petroleum occurs in the shallow section of several holes.
The regional maturation of organic matter has been rapid for all holes. In Hole 1038I, methane has a biogenic origin at shallow levels and a thermogenic origin deeper in the section. Hydrocarbon compositions reflect the terrigenous source of organic matter in the sediments deposited in Escanaba Trough.