Frio Formation  search
BTChronostratigraphic Units
 .Phanerozoic
 ..Cenozoic
 ...Paleogene
 ....Oligocene
 .....Frio Formation
RTLouisiana
 Texas
SNConsists of dark to very dark, varicolored shales and silty shales and massive to thin-bedded strata of sand and silty sand. Subsurface.