Douglas Creek Member of the Green River Formation contains large volumes of oil and gas trapped in a complex of fractured low-permeability sandstone reservoirs. Pariette Bench Field. The sandstones were derived from source terranes south of the Uinta Basin. Secondary silica and several generations of authigenic calcite, dolomite and ankerite form a replacive cement in the sandstones. Syntaxial overgrowths. Authigenic illite, authigenic carbonate. Enrichment of carbon and oxygen in early diagenetic calcite and fossiliferous rock relative to late diagenetic ankerite indicates a trend toward lighter isotopic carbonate compositions with increasing diagenesis.--Modified journal abstract.