24. ELECTRON PARAMAGNETIC RESONANCE STUDY OF THERMAL ALTERATION OF KEROGEN IN DEEP-SEA SEDIMENTS BY BASALTIC SILL INTRUSION

Site 368 on the Cape Verde Rise was noteworthy for the finding of a basaltic sill of Miocene age intruded into an organic-rich Cretaceous black shale. The sill extended from 957.0 to 970.5 meters and drilling terminated at 984.5 meters in the black shale. Methane was present above the sill but little or no ethane was present. Approaching the sill, ethane increased but propane and higher hydrocarbons were not detected. The sill was encountered in Core 368-60; Core 368-61 was entirely basalt, and Core 368-62 broke through the sill. Neither gas in large amounts nor liquid hydrocarbons were detected in Core 368-62 or Core 368-63. EPR analysis in conjunction with other more conventional measures of maturity of organic materials was performed. We report, here, preliminary results and some modest speculations on the implications of these findings.