Abstract: Importance of Textural and Diagenetic Properties of Berea Sandstone (Mississippian) in Central West Virginia

R. E. Larese, M. T. Heald

Petrologic evidence strongly supports the hypothesis that the Berea Sandstone (Mississippian) in central West Virginia was deposited in a predominantly nonmarine channel environment. Two subsurface channels (Cabin Creek, Gay Fink) intersect the shoreline of the regressive marine facies (at 70°) and parallel regional slope. Sedimentary and textural characteristics of these sublitharenite deposits differ significantly from those of the marine facies and include sharp basal and semitransitional to transitional upper contacts and upward fining of grain size. Several sedimentary and textural parameters are related indirectly to gamma-radiation logs which characteristically have "Christmas tree" signatures. These logs have proved useful for extrapolation of textural trends and constitute a powerful tool for environmental interpretation, although they are not commonly used for such purposes in previous studies of the Appalachian basin.

A combination of diagenetic processes influenced by original sedimentologic conditions has significantly affected porosity and permeability. Porosity reduction by cementation and compaction is common; however, authigenic chlorite coatings on detrital grains inhibited quartz cementation. Restricted to the channel-facies, these coatings were developed best in the basal parts (17% porosity). Prismatic overgrowths on quartz grains with breaks in the chlorite coatings indicate that silica was available and that conditions were favorable for authigenesis. Some secondary porosity (2.4%) was generated by the selective solution of orthoclase and plagioclase feldspar. Illite-sericite coatings were dominant in the upper parts of the channel facies, possibly originating as a result of reworking d ring subsequent marine transgressions. The clays promoted pressure-solution effects which were largely responsible for development of an impermeable caprock (< 2.0% porosity).

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC