Geology of the Ogallala/High Plains Regional Aquifer System in Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Papers in Natural Resources Natural Resources, School of April 1995 Geology of the Ogallala/High Plains Regional Aquifer System in Nebraska Robert F. Diffendal University of Nebraska - Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/natrespapers Part of the Natural Resources and Conservation Commons Diffendal, Robert F., "Geology of the Ogallala/High Plains Regional Aquifer System in Nebraska" (1995). Papers in Natural Resources. 75. https://digitalcommons.unl.edu/natrespapers/75 This Article is brought to you for free and open access by the Natural Resources, School of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in Natural Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Geologic Field Trips in Nebraska and Adjacent Parts of Kansas and South Dakota: Parts of the 29th Annual Meetings of the North-Central and South-Central Sections, Geological Society of America Lincoln, Nebraska Robert F. Diffendal, Jr., Chair Charles A. Flowerday, Editor Guidebook No. 10 Published by the Conservation and Survey Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, in conjunction with the GSA regional sections meeting, April 27–28,1995. Geology of the OgallalaIHigh Plains Regional Aquifer System in Nebraska Field Trip No. 6 R. F. (Bob) Diffendal, Jr. Conservation and Survey Division University of Nebraska-Lincoln, Lincoln, NE 68588 This guide is mostly figures with a reference River valley, we have traveled across land underlain section containing some of the pertinent literature on by glacial tills, loesses, and fluvial deposits of Qua- the Cenozoic geology we will see over the next four ternary age. A great deal about the early views on days. Copies of some of the cited works will be Pleistocene geology in eastern Nebraska is in Lug11 assembled in a packet and handed out on the morn- (1935). More recently, Reed and Dreeszen (1965) ing of April 29th. We will make all 17 stops (fig. I) attempted to classify and show the relationships if the weather is reasonably good and the roads are between Pleistocene units in Nebraska (fig. 2). This passable. On the first day, April 29, we will try to classification was widely accepted until the work of get to stops 1-5, the more distal parts of the Ogallala Boellstorff (1978) began to show that the stratigra- and younger deposits in Nebraska. 011 April 30, we phy was even more complex in places than previ- will try to visit stops 69. Stops 10-15, in areas closer ously depicted. At present, I believe that this classifi- to the sediment sources of the Ogallala and some of cation is still in a state of flux; several workers are the younger units, will be examined on May I. Stops trying to clarify the relationships between units and 16-17 will be made 011 our return trip to Lincoln. to better define the ages of those units. Between the work of Lugn and that of Reed and Dreeszen, Luen- April 29, 1995 inghoener (1947) tried to work out the post-Kansas Stop 1. Todd Valley. Our first stop will be geologic history of the lower Platte River valley (fig. north of North Bend, Nebraska, on the surface of the 3). We are standing on the Todd Valley terrace, Todd Valley fill to see some of the Quaternary geo- noted in figure 2 as medial Pleistocene, and are morphology of eastern Nebraska and to review lookii~gsoutl~ at the Platte Valley. The valley fill some aspects of Quaternary stratigraphy in the east- beneath the terrace surface and the Holocene alluvi- ern part of the state. From Lincoln to the Platte um beneath the Platte Valley are good aquifers and 0 20 40 M6k 0- 20 10 X4b-e." VALLEY GRttLtY 14. 'DEUEL 15. @17 I PERKINS HAYES FRONTIER Fig. I. May of Nebraska showing locations of stops on field trip no. 6. 61 CLASSlFlCATlON TERRACE SURFACES TIME ROCK STRATIGRAPHIC STRATI- GRAPHIC EOLIAN FLUVIATI L E GLACIAL - -- - k A - 7 Biqnell Loess 2 0 s Lore Absent 2 2 0 C 0 __I- N S Mediol 3 3 --?-? - Absent Unnomed Absent Unnamed 4 4 Probobtr Absent 5 6 K Pearlette Volconic Ash ...... Minor Er~sxon- Major Erosion : lnterrtodiol Soil - Interglociol Soil *rim Currently Identified Fig. 2. Classification of the Pleistocene deposits of Nebraska (modified after Reed and Dreeszen, 1965, fig. 3). Fig. 3. Map of lower Platte Valley area. Approxitnate dimensions of block are 50 x 80 miles (after Lueninghoener, 1947, fig. 1). have been developed for irrigation and municipal relationships of Pliocene and older Cenozoic units in water supplies. As we go north, we will drive off of northcentral Nebraska and south-central South the fairly flat lands of the Todd Valley fill and up Dakota and those in western Nebraska are illus- onto the better dissected lands underlain by eolian trated in figure 6. Swinehart and Diffendal (1990) deposits and glacial tills that generally have more have shown the general Pliocene and older strati- limited water resources. We will be traveling over graphic units beneath the Nebraska Sand Hills area these deposits for the most part until we reach the between north-central and western Nebraska. valley of the Elkhorn River near Norfolk, Nebraska, Stop 2. Ashfall Fossil Beds State Historical where we will once again be driving over Holocene Park. This is one of the truly extraordinary mamma- alluvium. lian vertebrate fossil localities in North America. From near Norfolk we will drive west across Mammal fossils have been known from this area at the glacial till border and begin to cross lands un- least as far back as the 1920s, but the site was first derlain by eolian sands, loesses and alluvium. The studied in 1971 by M. R. Voorhies, who found the alluvium we will see from this point on ranges in first skull and later the rest of the skeleton of a baby age from late Pliocene to Holocene. For the most rhino here. A test excavation, opened in 1977, re- part, these deposits were laid down by the develop- vealed the intact skeletons of rhinos and three-toed ing Platte River and its tributaries from late Pliocene horses. Much more faunal and some floral remains to late Wisconsinan time (fig. 4). Most of the Ogal- have been found here subsequently and described lala/High Plains Aquifer System in Nebraska and by Voorhies in a number of papers, particularly most of the sites of greatest abundance of ground- Voorhies (1985, 1990a). The fossils occur in a volcan- water in Nebraska (fig. 5) occur in the areas where ic ash in the Caprock Member of the Ash Hollow the Platte system or its ancestral drainages devel- Formation (fig. 7). oped. Land for the park was acquired in 1986, and As we travel from U.S. Highway 20 north to the park was dedicated in 1991. Since then tens of Ashfall Fossil Beds State Historical Park (stop 2), we thousands of visitors have come to see the fossils will encounter some of the stratigraphic units noted and the continuing excavation and study of these by Diffendal and Voorhies (1994) and shown in fossils by Voorhies and other paleontologists. figure 6. Of the four Pliocene stratigraphic units The formations exposed in the area (fig. 7) are recognized in parts of northcentral Nebraska, only part of the Ogallala/High Plains Aquifer System, the Long Pine Formation is present in this area. The which the U.S. Geological Survey has defined in a 1. Late Pliocene (-2,500,000 yrs ago) 3. lllinoian (-200,000 yrs ago) ... ........ Terminal moraines of last ice advances 2. Early Pleistocene (-1,500,000 yrs ago) 4. Late Wisconsin (-30,000 yrs ago) Terminal moraines of last ice advances Fig. 4. Postulated evolution of PlaffeRiver and related drainages (modified after Souders, Swinehart, and Dreeszen, 1990). 0 100 Miles 0 100 Kilometers Fig. 5. Saturated fhickrless of the High Plair~sRegiorlal - Aqlrifer in Nebraska (modified after Weeks and others, 1988). number of publications as including almost all of the of the area along and adjacent to the river has been Cenozoic units named in figure 6. For an overview, described in detail most recently by Skinner and see Gutentag and Weeks (1980), Weeks and Guten- Johnson (1984) and by Voorhies (1990b). tag (1981), and Weeks and others (1988). The various Stop 5. Valentine and Ash Hollow formations. tributaries of Verdigre Creek in the area are perenni- Skinner and Johnson (1984) subdivided these forma- al streams fed by springs coming from the Long tions into a number of members, some of which can Pine Formation and the Ogallala Group. be seen exposed in roadcuts and natural exposures Stop 3. Long Pine Formation. Skinner and Hib- northeast of the city of Valentine, Nebraska (fig. 9). bard (1972) described the units in this area and We will get a good view of these at this stop and originally placed them in the early Pleistocene. The also see the late-Pleistocene fluvial high terrace Keim, Long Pine, Duffy, and Pettijohn formations along the Niobrara River. have subsequently been placed in the Pliocene and are equivalent in age to the Broadwater Formation April 30, 1995 of western Nebraska (fig. 6). The physical connec- Stop 6. Snake River Falls. The geologic section tion of these two named units was implied by Stan- exposed here (fig. 10) was illustrated and described ley in Stout and others (1971). The Keim, Duffy, and by Skinner and Johnson. Part of the Caprock Forma- Pettijohn are local units, while the Long Pine is tion of the Ash Hollow forms the resistant ledge widespread (fig.

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