CARLILE SHALE Blue Hill Shale Member 1. Silty shale, dark-gray to olive-gray, with many irregular laminae and very thin beds of light-olive-gray quartzose siltstone; unit in sharp contact with unit 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 Thickness of exposed part of Blue Hill Shale Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 Total thickness of measured section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.6 Description of Section Measured at STOP 10 NIOBRARA CHALK Fort Hays Limestone Member Feet 12. Chalky limestone, weathered very pale grayish orange to dark yellowish orange, weathers shaly in lower part, medium-hard, porous, caps hill at road cut, fossil fragments scattered throughout; FOSSILS - Ostrea congesta, on Inoceramus deformis, burrow structures . . . . . . . . . . . . 2.0 11. Chalky limestone, weathered very pale grayish orange, dark-yellowish- orange where limonite stained, medium-hard, porous, fragments of Inoceramus scattered throughout; FOSSILS - Ostrea congesta on Inoceramus deformis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 10. Chalky limestone, like 11, large burrow structures common throughout, minute burrows common near top, with Inoceramus fragments common near top of unit; FOSSILS - Inoceramus deformis, Ostrea congesta, burrow structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.25 9. Bentonite, medium-gray weathering grayish orange, calcareous, shaly, waxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.15 8. Chalky limestone, weathered pale grayish orange with nearly white sur- faces, in part limonite-stained, weathers shaly between two beds, medium- hard, burrow structures throughout; basal bed thickens downward from minimum 1.8 feet to 6.0 feet, contains sparse limonite nodules; FOSSILS - worm? burrows, arthropod burrows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2-7.4 Thickness of exposed part of Fort Hays Limestone Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3-18.5 CARLILE SHALE Codell Sandstone Member 7. Siltstone, yellowish-gray to light-olive-gray, very much limonite stained, soft where wet, hard and brittle where dry, quartzose, poorly bedded, breaks blocky, numerous burrow structures, streaked in part with medium- dark-gray shale, especially near middle of unit; upper 0.3 foot locally olive gray, argillaceous, and shaly; FOSSILS - burrow structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Total thickness of Codell Sandstone Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Blue Hill Shale Member 6. Shale, medium-dark-gray, very silty throughout, with numerous irregular- shaped patches (filled burrows) of limonite-stained quartzose silt, color and texture are Blue Hill lithology . . . . . . . . . . . . . . . . . . . 0.75 5. Siltstone, argillaceous siltstone, and shale; siltstone is light olive gray, in part limonite and jarosite stained, and quartzose; argillaceous siltstone is olive gray, stained by jarosite and limonite, thinly and irregularly interlaminated with streaks of clay and has numerous burrow structures; shale is dark gray, very silty, contains very thin laminae of quartzose silt and many burrow structures; unit breaks blocky except for shale; all lithologic gradations from siltstone to shale; unit transitional between Blue Hill and Codell members, characterized by burrow structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 68