Thomas K. Kelty
Excellent exposures of the nonmarine, Pliocene to Pleistocene Palm Spring Formation allow the investigation of the spatial permeability variations. By sampling with a field permeameter, the permeability variations between and within sedimentary lithofacies, as well as effects of a major intraformational, angular unconformity on the permeability structure of the lower Palm Spring Formation are characterized.
A systematic permeability distribution of the major lithofacies within the lower Palm Spring Formation is revealed by this work. The highest mean permeability is found in the coarse-grained matrix of conglomerates and the horizontally laminated and cross-bedded sandstones. The massive and rippled sandstones exhibit the lowest mean permeability. The three lithofacies that show the greatest variability about the mean are the conglomerates, horizontally laminated sandstones and massive sandstones. This study indicates that field observations of sedimentary features can be correlated with permeability variations in the Palm Spring Formation. Permeability data are utilized to estimate the correlation ranges over a horizontal distance of 500 meters within a sandstone bed. This analysis and field observations indicate that the correlation distance of permeability corresponds with the width of channels in the sandstone bed. Sampling of the Palm Spring Formation adjacent to an intraformational unconformity demonstrates that there is a decrease in permeability directly beneath the unconformity. This permeability reduction is due to secondary mineralization loca ized along the unconformity that possibly occurred during subaerial exposure.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California