U.S. DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 1706 U.S. GEOLOGICAL SURVEY PLATE 1 OF 2

A' 99°30’ 27’30” 40°45’ 25’ 99°22’30” 40°45’ CORRELATION OF MAP UNITS Ql

Qfp Qal Ql Ql Ql Qt1a Qaf Holocene Qd Qt1b Ql QUATERNARY Qt2 Wisconsin Qt3 Qaf Illinoian and Pleistocene Qt4 pre-Illinoian

Qaf

Description of map units spring. The second area is slightly drier, and has sandier soils. In the first area soil types are mainly saline Leshara silt loam, Leshara silt loam, Grigston silt loam, and Wann loam. Soils in Qfp Floodplain deposits (Holocene)—Lowest floodplain and island areas of the Platte River. the second area are Anselmo fine sandy loam, Meadin loamy sand, Meadin silt loam, and Deposits of this unit are mostly poorly sorted and clast supported. They consist of O'Neill fine sandy loam. This terrace stands at an average of 5 ft above the floodplain unconsolidated gravel in a sandy or silty matrix interbedded with or overlain by sandy silt Qt1b Terrace 1b deposits (Holocene)—Deposits of the first terrace above the Platte River floodplain on and silty sand. Clasts are round to subangular and are composed of plutonic, metamorphic, the north side of the river. This terrace is somewhat higher and better drained, and may be and sedimentary rock types. Outside the active channels, many soil types are at the surface slightly older than the Qt1a terrace on the south side of the river. This was the only terrace of this unit, including Gothenburg soils or comparable Loamy alluvial beds, Platte loam or identified between the river and the loess hills on the north side of the river, and thus covers a comparable Platte soils, Gibbon loam, Lex loam, Alda loam, Leshara and Gibbon silt loam, significant portion of the map (about 24 square miles). A large number of soil types occur on Qt1b Platte-Alda complex, and Platte-Wann complex. The Gothenburg soil and corresponding this terrace, including the Cozad series, Gosper series, Hord series, Rusco silt loam, and Wood Loamy alluvial beds are the most abundant soil types recognized where Qfp is mapped River series. This terrace stands at an average of 7.5 ft above the floodplain Qaf Alluvial fan deposits (Holocene)—An apron of alluvium derived from and deposited at the Qt2 Terrace 2 deposits (Holocene? and Pleistocene)—Deposits of the second terrace above the Platte base of the loess hills in the northeastern part of the map. The unit extends southward over River floodplain on the south side of the river. In plan view, this terrace is triangular, wedging the Qt1b terrace. Soil types consist of Uly-Holdrege-Coly silt loams, Hobbs silt loam, out because of erosion by the Platte River just to the west of the map boundary. The terrace Cozad silt loam, and Hord silt loam widens eastward to about the middle of the quadrangle; in the southeast part of the map the Qal Alluvium (Holocene)—Thin veneer of alluvium derived mainly from stream that enters the map terrace is mantled by dune deposits of Qd. The northern edge of the terrace is defined by a from the south in section 34, T. 8 N., R. 19 W. Soil types consist primarily of Wann loam topographic break and by a change to the soil types Kenesaw silt loam and Kenesaw and Coly and lesser amounts of Leshara silt loam and Hord silt loam. Overlies terrace Qt1a and silt loams. Soil types over most of this terrace are Hord silt loam. Kenesaw silt loam occurs Qt1b northern edge of dune field Qd in the southeastern part of the quadrangle mainly along the eastern edge of exposure. This terrace stands at an average of 45 ft above the Qd Dune deposits (Holocene and Pleistocene)—Main dune area in southeast part of the map floodplain consists of wind-deposited dune sand and sheet sand intermixed with alluvial material in Qt3 Terrace 3 deposits (Pleistocene)—Deposits of the third terrace above the Platte River floodplain drainages. Soil types are heterogeneous, and include Valentine loamy sand, the Anselmo on the south side of the river. In plan view this terrace narrows to the west and was removed by series, Kenesaw silt loam, and Kenesaw-Coly silt loam. Small areas of Qd mapped in and Platte River erosion in about the middle of the adjacent Overton quadrangle. The terrace south of the Platte River channel are composed of small dunes and sandy zones intermixed widens to the southeast and is partially mantled by dune deposits in the south-central part of with other soil types. Dunes in the main area of deposition have relief of as much as 40 ft. the map. The southern edge of the terrace trends generally east-west just south of the map Dunes in other areas have relief of 10 ft or less. Eolian deposits in the southeast part of the boundary. Soils on this terrace are the same as those on the Qt2 terrace. A change to Kenesaw 42’ 30” 42’ map overlie and obscure older terrace deposits silt loam and Kenesaw and Coly silt loams mark the northern edge of the terrace. The majority 30” Ql Loess (Pleistocene and Holocene)—Loess that forms hills at the northeast corner of the map. of the terrace surface is composed of Hord silt loam, with some Kenesaw silt loam along the Soil types are mainly Uly silt loam, Coly silt loam, Holdrege silt loam, and Uly and eastern-most exposures. This terrace stands at an average of 50 ft above the floodplain Holdrege silt loams, combined. Loess probably consists of the Pleistocene Peoria Loess and Qt4 Terrace 4 deposits (Pleistocene)—Deposits of the fourth terrace above the Platte River floodplain. the Holocene Bignell Loess Only a small part of this terrace occurs in the Elm Creek West quadrangle, in the southwest Qt1b Qt1a Terrace 1a deposits (Holocene)—Deposits of the first terrace above the Platte River floodplain corner of the map. Soil type is Holdrege silt loam. This terrace stands at an average of 97.5 ft on the south side of the river. Two areas of this terrace were mapped; (1) immediately above the floodplain adjacent to the Platte River floodplain (Qfp), in the western and central parts of the map, Contact and (2) immediately south of the Qal unit, about 0.75 mile south of the river floodplain in the eastern part of the map. In the first area the surface is cut by numerous small abandoned Location of test well stream channels; low areas are boggy and hold standing water in the +

28-B-47 +

Qfp Qd Qd Qfp

Qfp

31-B-47 30-B-47 29-B-47 28-B-47

Soil

Qfp Clay Qd Qd Qd Qfp Qd 29-B-47

+ Qt1a Silt

40’ Qd Qd 40’ Qd Sand & gravel Qt1a Qd

Qd

Qd Qd Ogallala Group

Qd Qd Qal Qd Qal Qd Pierre Shale

30-B-47

Qd + Qt1a FEET 100 Qt1a

80

60

Qt2 40

20

Qt3 0

Qd

31-B-47+ Graphical representations of test wells in the Elm Creek West quadrangle Qd

Qt3 Qt4

40°37’30” 99°30’ 40°37’30” 27’30” 25’ 99°22’30” A Base from U.S. Geological Survey 6° SCALE 1: 24 000 Geology mapped by Steven M. Condon, 1999 Elm Creek West Quadrangle, H T 1 1/2 0 1 MILE Condon, Steven, M., 2005, Geologic R H

Nebraska. T R Studies of the Platte River, South-central 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET NEBRASKA Nebraska, and adjacent areas—geologic TRUE NO

MAGNETIC NO 1 .5 0 1 KILOMETER maps, subsurface study, and geologic history: U.S. Geological Survey Profes- APPROXIMATE MEAN QUADRANGLE LOCATION sional Paper 1706. DECLINATION, 2005 CONTOUR INTERVAL 40 FEET NATIONAL GEODETIC VERTICAL DATUM OF 1929

Southwest to northeast topographic profile across the Elm Creek West quadrangle A' A

FEET Qt4 terrace Qt3 terrace Qt2 terrace Qt1a terrace Floodplain Qt1b terrace Alluvial fan Loess hills FEET 2,390 2,390 2,370 Phelps County canal 2,370 2,350 2,350

2,330 0 Excavation for irrigation ditch y 3 a k

w 2,330 k ee r

2,310 ee r 2,310 falo C .S. High f U 2,290 Elm C Interstate 80 Platte River channels Bu 2,290 2,270 2,270 Vertical exaggeration X 30 Geologic Map and Topographic Profile of the Elm Creek West Quadrangle, Nebraska

By Steven M. Condon

2005