7. Lignite grading upward into lignitic shale, and carbonaceous shaly silt- stone, brownish-black to dark-gray. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 6. Siltstone, dark-yellowish-brown to light-olive-gray, quartzose, argill- aceous, in part shaly; FOSSILS - upright reed? molds . . . . . . . . . . . . . . . . . . . . 3.4 5. Sandstone, light-olive-gray, quartzose, carbonaceous, poorly cemented, laminated; upper part dark yellowish orange to moderate yellowish brown, gently cross-bedded; FOSSILS - upright reed? molds, tree trunk mold . . . . . . . . . . . 0.8 4. Lignite and lignitic shale, black to dark-gray. . . . . . . . . . . . . . . . . . . . . . . . . 0.5 3. Shale, dark-olive-gray, silty, carbonaceous, weathers flaky, lignitic at base, thin lignite seam at center; FOSSILS - carbonized plant remains 1.5 2. Siltstone, olive-gray, argillaceous, with contorted bedding; FOSSILS - carbonized plant debris, reed? molds . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 1. Shale, dark-olive-gray, silty, carbonaceous, weathers flaky, limonite- and jarosite-stained; FOSSILS - carbonized plant remains . . . . . . . . . . . . . . . . . . . 4.2 Thickness of exposed part of Dakota Formation 28.2 Total thickness of measured section 70.9 Description of Section Measured at STOP 2 Feet CARLILE SHALE Fairport Chalk Member 52. Chalky limestone, weathered pale yellowish gray, highly fractured . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 51. Shaly chalk and chalky limestone; chalk weathered yellowish gray, soft, laminated, with very thin light-gray bentonite seam near base and deeply weathered bentonite seam at top; limestone in four concretionary layers, weathered grayish orange to very pale orange, hard, resistant, fossil- iferous; FOSSILS - Inoceramus cuvieri, I. labiatus, Collignoniceras woollgari, baculitids? (recrystallized), Ostrea congesta, large pelecypod- bored log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Thickness of exposed part of Fairport Chalk Member 5.6 GREENHORN LIMESTONE Pfeifer Shale Member 50. Chalky limestone (Fencepost limestone bed), weathered grayish orange with limonite stain through center of lower 0.7 foot, resistant, speckled; FOSSILS - Inoceramus labiatus, Collignoniceras woollgari, arthropod burrows 1.0 49. Shaly chalk, and chalky limestone; chalk weathered pale grayish orange, breaks blocky, bedding planes limonite stained; lower bed of limestone dark grayish orange, speckled, very even; nodular limestone layers are concretionary, grayish orange to dark yellowish orange, contain few fossils, upper nodules with central layer of skeletal limestone; FOSSILS - Inoceramus labiatus, arthropod burrow, fish scales. . . . . . . . . . . . . . . . . . . . . 5.1 48. Bentonite and gypsum ("sugar sand"); bentonite nearly white, gypsum granular, dark yellowish orange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.36 47. Shaly chalk and chalky limestone; chalk olive black weathering moderate yellowish brown to grayish orange, tough, laminated, speckled, charac- terized by chalky lenses filled with Inoceramus fragments; limestone olive gray weathering dark grayish orange, mostly in nodular layers - some at least partly concretionary, others with relict bedding, contain abundant whole and fragmentary Inoceramus; FOSSILS - Inoceramus labiatus I. cuvieri, fish remains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 50