Norphlet Formation (Upper Jurassic) - Berg - Hughes Center

Ernest A. Mancini et al 883EXPLANATIONGas DiscoveryNorphlet Updip LimitMISS.20 miles10 0 10 20 kilometers^'Lowei Mobile Bay-Mary Ann Field (gasiMobile Block 823-Well NoMobile Block 867-Well NoFigure 2—Major structural features and Norphlet petroleum fields in southwestern and offshore Alabama (modified from Wilson,1975; Minii, 1984).predominately quartz-rich sandstone, which is referred toas the Denkman Sandstone Member (Murray, 1961; Tyrrell,1972), consistschiefly of agray to brown, moderatelywell-sorted to well-sorted, very fine to medium-grainedsubarkose, according to the classification scheme of Folk(1974), containing subrounded to rounded quartz grains(Figure 4A, B, C, D). The average composition of theDenkman is 72.5% quartz, 15.0% feldspar (plagioclase,microcUne, and orthoclase), 4.4% rock fragments (chert,shale, phyllite, schist, and quartzite), 3.8% cement (carbonate,quartz, and anhydrite), 3.2% authigenic clay(illite), and 1.1% accessory minerals (Wilkerson, 1981).The Denkman typically consists of an upper massive toindistinctly horizontal, wavy, laminated sandstone (Figure5A, D) and a lower cross-bedded sandstone having highangle(up to 30°) foreset laminae (Figures 5B, C, and 6A).The lower cross-bedded sandstone that comprises most ofthe Denkman Sandstone Member also is characterized byhorizontal to low-angle laminae (Figure 5E) and by ripplelaminae (Figure 5F). Figure 7 illustrates a typical verticalsequence of paleoenvironments in the Denkman SandstoneMember as observed in the Getty Peter Klein 3-14