| OCR Text |
Show 85 stratigraphic units the difficulty composition overlap of in the grain study area. Only sandstone samples separation. selected because of identification in siltstones and mudstones. The overall of these Middle to Upper Jurassic sandstones is very similar, with suggest that analysis of more samples would to were The full data are given in Appendix result in further not Knoll) samples are nearly pure quartz petrologic C and summarized in Table 5. The upper Entrada Sandstone and upper Wanakah Formation Steer enough arenites (Pettijohn et (bed at Black aI., 1987), with a high percentage of monocrystalline quartz (80-86%). The average quartz-feldspar-lithic (QtFL) composition (Table 6; Figure 29) of these sandstones is 89, 8, Sandstone) and 88, 4, 8 (Wanakah Formation). The Summerville Formation average monocrystalline quartz (78%, increasing total lithic content a Member et samples (12%, Summerville Formation is also subarkosic arenite composition Salt Wash Member sandstones range in sublitharenites to lithic arkosic arenites. (Pettijohn Member) and 22%, Salt Wash to are decreasing all subarkosic arenites Morrison Formation sediments, texturally more immature et aI., 1987); however, Tidwell from quartz arenites to arkosic arenites and composition from subarkosic arenites and Clay matrix (kaolinite minor component (0-7%) of all of the sandstones and trend of general (81, aI., 1987). The average sandstone composition for Tidwell and Salt Wash Member sandstones range in grained Salt Wash Member Summerville Formation to 68%, Salt Wash Member) is observed. Summerville Formation sandstones (Pettijohn (Entrada QtFL composition of the (86, 10, 5) and Tidwell (84, 10, 5) and 11, 9) sandstones is similar (Table 6; Figure 29), although 4 especially and sericite) forms a analyzed. the Salt Wash Member, (more poorly sorted and more are coarser angular grains) |
