GENERAL OUTCROP SECTION OF THE BLACK HILLS AREA FORMATION SECTION TIME IN FEET DESCRIPTION QUATERNARY SANDS AND GRAVELS [illegible] [illegible] TERTIARY PLIOCENE OGALLALA GROUP [illegible] Light colored sands and silts MIOCENE ARIKAREE GROUP 0 - 500 Light colored clays and silts while age bed at base OLIGOCENE WHITE RIVER GROUP Brule Formation 0 - 600 Light colored clays with sandstone channel fillings and local limestone lenses Chetron Formation PALEOCENE FORT UNION FORMATION TONGUE RIVER MEMBER 0 - 485 Light colored clays and sands, with coal beds former marl CANNONBALL MEMBER 1.1 - 22? Green mottled shales and yellow sandstones, "r", letter often as concretions LUDLOW MEMBER 0 - 350 Soft-gray clays and sandstones with i.r. beds of lignite. UPPER HELL CREEK FORMATION [Lance Formation] 425 Sand-colored soft brown shale and gray sandstone, with thin lignite lenses in upper part. Lower half more sandy, hard, brittle concretions and thin masses of iron carbonate. CRETACEOUS FOX HILLS SANDSTONE 25 - 200 Grayish-white to yellow sandstone. Calc. PIERRE SHALE 1200-2000 Principal horizon of limestone lenses giving teppe buttes Sharon Springs Nsm [illegible] Dark-gray shale containing scattered concretions Niobrara Formation [illegible] Widely scattered limestone masses, giving small teppe buttes. Turner Sand Zone 100-225 Black fissile shale with concretions CARLILE FORMATION Light-gray shale with numerous large concretions and sandy layers. Well Creek Sands 400-750 Dark-gray shale GREENHORN FORMATION [25 - 30] Impure sandy limestone Weathers buff Belle Fourche Shale (200-350) Dark gray calcareous shale, with thin Orms Lake limestone of base Mowry Shale 300-390 Gray shale with scattered limestone concretions Newcastle Sandstone Clay tour bastonite at base. Skull Creek Shale 150 - 250 Light-gray siliceous shale, fish scales and the layers of basaltine Fall River [Dakota (?)] S.S. 20-60 Brown to light yellow and white sandstone Fuson Shale 170-270 Dark gray to black shale. Minnewaste Limestone 10 - 200 Massive to stibby sandstones Lakota Sandstone 10 - 188 Gray to purple shale Thin sandstones. Morrison Formation 0 - 25 Massive gray limestone Unkpapa Sandstone 25 - 485 Coarse, hard, crisscrossed sandstone mostly buff to gray Compartmental locality and Coal of base. Sundance Formation 0 - 220 Green to maroon shale Thin sandstones Gypsum Spring Formation 0 - 225 Massive fine grained sandstones NUGGET (?) FORMATION 250-450 Greenish-gray shales, thin limestone lenses. Diatomite sandstone red in lower middle. 0 - 45 Red siltstone, gypsum and limestone LOWER SPEARFISH FORMATION 0 - 60 Massive crisscrossed salmon sandstones CRETACEOUS Triassic ? 300-700 Red sandy shale, soft red sandstone and siltstone with gypsum and thin limestone layers. Permian ? Opeche Formation [illegible] Gypsum locally near the base. Minnelusa Sandstone 50 - 135 Massive gray, laminated limestone Yellow to red cross-banded sandstone, limestone and calcareous facies at top. Interbedded limestone, dolomite, shale, and conglomerate Red shales with interbedded limestone and sandstone at base. MISSISSIPPIAN PAHASAPA (MADISON) LIMESTONE 300-630 Massive light-colored limestone. Dolomitic in part Englewood Limestone 30 - 60 Poor to buff limestone Shale locally at base White Wood (Red River) Formation [illegible] Bull dolomite and limestone Winnipeg Formation Green shale with siltstone at top and black sandstone at base. Dead Wood Formation 0 - 100 Massive to buff limestone. Greenish phaccerous shale. Clay, dolomite and flat-pebbled impure conglomerate. Sandstone with conglomerate locally at the base ORDOVICIAN [illegible] 10-400 Shales, slates, siltstones, and breccia grits GAMBRIAN METAMORPHIC and intruded by diorite, metamorphosed to amphibolite, and to granite and pegmatite. IGNEOUS ROCKS PRE-CAMBRIAN