The greater proportion of heavy grains in the Permian to Jurassic sedimentary rocks are either stable detrital minerals which have survived intrastratal solution, or authigenic minerals produced hy diagenetic alteration. Mineralogical elements of detrital origin in the rocks represent a wide variety of provenance areas. There are strong flushes of certain mineral groups of igneous oriRin, but these minerals have been partJly altered by percolating solutions. The combined effects of sedimentary processes during deposition, and post-depositional diagenesis, have produced in these Permian-Jurassic rocks a relatively stahle heavy mineral assemblage containing zircon, tourmaline, apatite, and authigenic granular epidote.