ABSTRACT

Radium activity and salinity have been determined in pore fluids from sediment cores taken during submersible dives in Garden Banks block ^#382 and Mississippi Canyon block ^#929 on the Gulf of Mexico slope. The ²²⁶Ra activity and salinity of these pore fluids range from 0.43x10⁴ to 28.3x10⁴ dpm/100 L and 45 to 139 , respectively. The radium activities of these saline pore fluids are highly anomalous as they exceed by factors of 320 to 21,430 the values reported from the Gulf of Mexico ambient deep water (13.2 dpm/100 L) but are consistent with the range of ²²⁶Ra values and salinities measured in produced waters from oil and gas rigs in the Gulf Coast region. The strong positive correlation observed between the pore fluid salinity and their ²²⁶Ra activity suggests that the dominant component of the pore fluids is derived from deep-seated formation waters advecting to the sea floor through fault conduits. This new source of radium internal to the Gulf of Mexico offers an alternative explanation for the previously reported higher levels of ²²⁶Ra in the water column of the Gulf compared to the inflowing Caribbean Sea waters. The impact of the natural discharge of these highly radioactive fluids on the offshore marine habitats is presently unknown and requires further investigation.