Six holes were drilled in water 600-3,000 feet deep and penetrated up to 1,000 feet of Pliocene-Recent clayey sediments. Samples from near diapiric structures showed systematic increases of pore-water salinity with depth. Anomalous concentrations of K and Br indicate that at least one plug contains late-stage evaporite minerals. Salinities approaching halite saturation were observed. Samples from holes away from diapiric structures showed little change in pore-water chemistry, except for loss of SO (sub 4) and other variations attributable to early-stage diagenetic reactions with enclosing sediments. Thus, increased salt concentrations in even shallow sediments from this part of the Gulf appear to provide an indicator of salt masses at depth.