al . Generalized stratigraphic columnofPrecambrian and Paleozoic Table 1. Paleozoic Era Precambrian Precambrian Ordovician Cambrian Cambrian Devonian Paleozoic Paleozoic Lower(?) Lower(?) Middle Period Rock Rock Period Description units Upper units inLincoln and Union Counties,SouthDakota Wise Lake Fm.(?) Davis Formation Formation Davis Undifferentiated Kaskaskia 0- >35 Gray, vuggy dolostone Undifferentiated Undifferentiated Sioux QuartziteSioux basement rocks rocks basement Galena Group Group Galena Dunleith Fm. Decorah Fm.

Bonneterre Bonneterre Crystalline Crystalline sandstones sandstones Mt. Simon Mt. Simon Formation Formation Glenwood Formation Formation Formation Formation Sandstone Sandstone Sandstone Sandstone Sandstone Sandstone Wonewoc Platteville St. Peter St. Peter

Period of nondeposition erosionPeriod (unconformity) or nondeposition of erosion or period Possible dolostone beds Gray-green shale with thin Gray, cherty dolostone Gray, vuggy dolostone medium-grained, relatively sandstone, typically poorly Pink to white, fine-grained fine-grained white, to Pink medium-grained, with thin fine-grained gravel layers local sandy and silty beds orthoquartzite withorthoquartzite minor Shalewith dolostone and other metamorphic rocks mature, withmature, base shaley metagabbro, and various coarse-grained sand to Brown dolostonewith Dolostone withDolostone minor beds of redto purple Possibly granite- or shale, and siltstone, Sandstone, fine- to to fine- Sandstone, Sandstone, fine- to to fine- Sandstone, Sandstone, fine- to to fine- Sandstone, rygensae 0- > Gray-greenshale quartzite-derived Variably colored medium-grained to conglomeritic to glauconitic sand Gabbro, granite, worm burrows cemented catlinite Thickness 0 - >1000 0 - >1000 0 - > 0 - > 0 - > in feet feet in 0 - 95 ? 0 - >27 0 - > 0 - > 0 - 80 0 - 55 0 - 40 0 - ?

150 135 57 12 14 19

Sequence Tippecanoe Sauk

Thickness Cretaceous Period Rock units Description

Era Era in feet Cyclothem Medium- to dark-gray limestone, chalk,  and calcareous shale; locally Niobrara Formation 0 – 95 pyritic, Niobrara burrowed, containing some bentonite; fossiliferous Cross-bedded Codell sandstone Sandstone 0 - ? containing Member sharks teeth Greasy, concretionary, Blue Hill Carlile organic-rich 0 – 230 Member Shale shale; contains bentonite Dark gray,

Upper Fairport fissile, greasy, Chalk calcareous shale; 0 – 190 Member locally silty and

Cretaceous burrowed Gray, silty, Greenhorn Mesozoic calcareous shale, Greenhorn Limestone calcarenite, and 0 - 50 fossiliferous limestone Gray-brown, waxy to gritty, 0 – 70 Graneros Shale slightly calcareous shale

Interbedded shale, siltstone, Dakota Formation and sandstone 0 – 415 with minor coal Time equivalent Upper mostIncludes the to of the Cretaceous. Split Rock Creek Formation. seams

Kiowa-Skull None encountered ------rocks undifferentiated ? ------Cretaceous Lower
Creek Jurassic None encountered Triassic None encountered

Period of erosion or nondeposition (unconformity)

Table 2. Generalized stratigraphic column of Mesozoic units in Lincoln and Union Counties, South Dakota Drill hole and location Depth interval (in feet): Generalized description Rock unit Age Wagner-Larson. 330-581: Brown, white or pink sand, fine to coarse, subangular to subrounded, locally quartz-rich, some igneous grains, pyrite, calcite; Unknown Lower(?) MLN-280. chips of quartzite, dolostone, shale. Shaley intervals; intervals with black phosphate pellets; intervals containing coal and Paleozoic NE SW SW NW sec. 22, shells. T. 93 N., R. 50 W. 581-585: Sand, white with pink grains, medium to coarse, angular to rounded, some pink feldspar and quartz. Granite-derived sand(?) Cambrian(?) Cross section M-M’ in 585: Pink granite. Basement rock Precambrian app. B. 360-495: Sand, very fine to coarse, angular to rounded, locally quartz-rich, some pyrite, siderite, calcite; chips of chert, dolostone, Unknown Lower(?) shale. Intervals with phosphate pellets. Paleozoic 495-640: Shale, greenish-gray, locally calcareous. Silty or sandy intervals containing minor chert or dolostone chips. Trace anhydrite. Galena Group, Decorah Ordovician Wagner No.1-Blanchard. Formation MLN-317. 640-675: Sand, white, fine to medium, upper part with frosted and etched quartz grains, lower part is shaley. St. Peter Sandstone Ordovician NE NW NW NW sec. 29, 675-700: Shale, gray to grayish-green with interbedded limestone. Locally sandy areas. Davis Formation Cambrian T. 92 N., R. 49 W. 700-755: Sand, white, medium, well-sorted. Upper part is calcite cemented; the lower part is shaley. Wonewoc Sandstone Cambrian Cross sections O-O’ and 755-814: Light gray limestone, locally dolomitic or cherty. Bonneterre Formation Cambrian DD-DD’ in app. B. 814-815: Black, carbonaceous fissile shale, slight oil show. Mt. Simon Sandstone(?) Cambrian(?) 815-839: Sand, white to pink, fine to coarse, angular to rounded, some fine feldspar; lower part of heavily weathered granite. Granite-derived sand and regolith Cambrian(?) 839: Granite. Basement rock Precambrian 390-523: Gray dolostone with local, thin sand or limestone interbeds. Unknown Devonian(?) 523-615: White to gray dolostone, locally cherty. Local thin sand or shale interbeds. Galena Group Ordovician 615-765: Sandstone (uppermost part) and gray shale. Sandstone is cherty with gray dolostone and shell fragments. Shale is locally Galena Group, Decorah Ordovician calcareous. Lowermost shale contains limestone chips. Formation; lowermost shale – Sioux Valley Platteville and Glenwood No.1-Lafleur. Formations? MLN-345. 765-805: Sand, gray. Uppermost sand contains round, frosted quartz grains. St. Peter Sandstone Ordovician SW NE NW SW sec. 18, 805-900: Interbedded limestone, sandstone, shale, and dolostone. Davis Formation Cambrian T. 90 N., R. 48 W. 900-964: White sand, fine to medium. Local quartz rich zones. Intervals containing chips of dolostone, shale, and limestone. Under Wonewoc Sandstone Cambrian Cross sections Q-Q’ and artesian conditions. DD-DD’ in app. B. 964-1007: Gray to white dolomitic limestone. Bonneterre Formation Cambrian 1007-1015: Pink to red-brown sand, rounded, mostly quartz. Mt. Simon Sandstone Cambrian 1015-1029: Sand, white, fine, angular to subangular, mostly quartz. Granite-derived sand(?) Cambrian(?) 1029: Granite. Basement rock Precambrian 409-444: Gray, vuggy dolostone and limestone, locally sandy or shaley. Some layers of inches-thick greenish silica mud. Rare fossil Unknown Devonian(?) molds. 444-520: Gray, dolostone, locally fossiliferous. Vuggy from 444-472. Cherty from 472-520. Sandy and shaley lenses also present. Galena Group Ordovician 520-530: Sandstone, brown to pink, and sandy dolostone. Galena Group Ordovician 530-646: Gray-green shale with local sandy zones and dolostone layers. Shell fragments concentrated in thin zones. Galena Group, Decorah Ordovician Formation South Dakota Geological 646-660: Brown dolostone with worm burrows; apparently organic-rich. Platteville Formation Ordovician Survey hole 660-672: Gray-green shale. Glenwood Formation Ordovician R20-2002-1. 672-697: Gray, mature, fine-grained quartzose sandstone with thin, pink sandstone lenses and one black organic-rich layer. St. Peter Sandstone Ordovician NW NW NW NE sec. 13, T. 90 N., R. 50 W. 697-752: Green-gray shale with dolostone and glauconite sand interbeds. Davis Formation Cambrian 752-794: Brown, gray, and white, well-sorted, fine- to medium-grained quartzose sandstone with minor dolostone lenses. Under Wonewoc Sandstone Cambrian artesian conditions. 794-878: Dolostone and shale with some sandy zones and glauconite sand lenses. Bonneterre Formation Cambrian 878-897: White, pink, and brownish-gray, fine- to coarse-grained quartzose sandstone. Locally dolomite or pyrite cemented. Mt. Simon Sandstone Cambrian 897-908: Reddish-brown, sticky mud with crumbly, reddish-brown sand-sized fragments and mica flakes. Saprolite Cambrian(?) 908: Metagabbro. Basement rock Precambrian

Table 3. Selected drill holes that intersect Paleozoic strata in Union County with abbreviated logs

Time Divisions Time (yrs) Iowa Hartford Hartford Clay County Minnehaha Section section section (Christensen County This study (Hallberg, (Boellstorff, (Steece, and Stephens, (Tomhave, (Richmond and Fullerton, 1986) 1986) 1978) 1965) 1967) 1994)

Nonglacial Nonglacial Nonglacial Holocene sediment sediment sediment 10,000 Dows Fm. Loess Loess Late Late 14,000 loess Late Wisconsin Late Wisconsin Wisconsin till Wisconsin till till 35,000 Middle Wisconsin

65,000

Early  Late Pleistocene Wisconsin Loess 79,000 Yarmouth- 132,000 Illinoian(?) Sangamon till Paleosol

Illinoian Pleistocene Late Middle Middle Late ?---?---?--?-—Loess----

302,000
Yarmouth(?) sol(?) Pale Yarmouth-Sangamon Paleosol

A1 tills

Pre-Illinoian No ash stratigraphic found for marker Classic A till Illinoian till Illinoian till Pre-Illinoian 1 3 till “Kansan” 3 till Pleistocene Middle Middle Middle Middle Pearlette Pearlette Hartford Sappa Fm. Pearlette “O” Pre-Illinoian 610,000 “O” Ash “O” Ash Ash silts and clays Ash 2 till

Grand Island Pre-Illinoian sand and Pre-Illinoian 1 till A tills A till Kansan till 2 2 gravel 2 till Pre-Illinoian Nebraskan Pre-Illinoian 0(?) till Pleistocene

Early Middle Middle Early A till A till 3 3 till 1 till Pre- Bishop Illinoian 738,000 Ash 788,000 Western-derived, A4 tills Newton Hills, Alcester quartz B tills sand. May range in age to Early Middle Pleistocene Pearlette Early Pleistocene 1,270,000 “S” Ash 1,650,000

Pearlette 2,010,000 “B” Ash

Pliocene 2,140,000 C tills 2,480,000

Table 4. Generalized stratigraphy of Pliocene(?) and Pleistocene sediments in Lincoln and Union Counties and comparison with regional stratigraphy