Authigenesis in West Virginia Sandstones

Abstract

The authigenic minerals in the Oriskany, Berea, and Big Injun sandstones are quartz, calcite, dolomite, orthoclase, microcline, albite, chlorite, kaolinite, and pyrite. Most of the quartz grew in open spaces, but some replaced clastic calcite. Two stages of silicification occurred in parts of the Berea sandstone. Authigenic chlorite appears as fringes around the detrital grains or around the early quartz growths. Calcite occurs as secondary rims on clastic calcite and as a cementing material in the voids. Rhombs of dolomite occur in the interstices and as replacements of feldspar and the clayey matrix. Authigenic feldspar is present in the form of overlays around detrital grains. Secondary kaolinite occurs as an alteration product of feldspar and as a filling in many of the voids which remained after the crystallization of the other minerals. Most of the authigenic minerals formed after burial, because the secondary growths are generally free of strain and fill the cracks in fractured grains of mica and feldspar. The secondary calcite and chlorite probably formed from primary constituents in the sediments. Most of the silica was apparently derived from outside sources because little solution of quartz occurred at the points of contact between the detrita! grains.