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June 1984

COMMENTS ON THE GEOLOGIC HISTORY OF THE OGALLALA FORMATION IN THE SOUTHERN PANHANDLE OF NEBRASKA

Robert F. Diffendal University of Nebraska - Lincoln, [email protected]

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Diffendal, Robert F., "COMMENTS ON THE GEOLOGIC HISTORY OF THE OGALLALA FORMATION IN THE SOUTHERN PANHANDLE OF NEBRASKA" (1984). Papers in Natural Resources. 116. https://digitalcommons.unl.edu/natrespapers/116

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Proceedings of the

Ogallala Aquifer Symposium II

Lubbock, Texas June 1984

Edited by:

George A. Whetstone Texas Tech University Water Resources Center CO~~S ON THE GEOLOGIC HISTORY OF THE OGALLALA FORMATION IN THE SOUTHERN PANHANDLE OF NEBRASKA R.F. Diffendal, Jr.

Abstract The southern Panhandle of Nebraska and the adjoining parts of southeastern Wyoming and northeastern Colorado are unusual places to examine the geologic history of the Ogallala Formation because they are much closer to the source areas of much of the sediment which makes up the unit than are other sites along the Ogallala outcrop belt. This study in Nebraska combined with results of earlier work there, in southeastern Wyoming, and ; northeastern Colorado, outlines the complex cut and fill history of the Ogallala close to Rocky Mountain source areas. Parts of the Ogallala consist of fills of sand and gravel, including very large, locally derived clasts, deposited in anastomosing channels carved into bedrock. These channels may be several kilometers wide, up to 50+ m deep, and may cut across other older Ogallala channels with similar geometries. Local tributary fills also occur in the Ogallala. These fills usually are composed of sediments eroded by streams from Miocene and Oligocene sandstone and siltstone formerly exposed along paleovalley sides near the sites of sediment deposition. Up to six volcanic ash deposits have been found in super­ posed sequences of the Ogallala in the study area. These deposits have blanket, lens, shoestring and irregular geometries. Ash colors are shades of yellow and gray. Shards vary from silt to coarse sand size. Ash deposits are up to 6-7 m thick. Caliche (calcrete and silcrete) occurs throughout the Ogallala but seems to be better developed toward the present top of the formation. The overall geologic history of the Ogallala in the southern Panhandle of Nebraska is one of multiple cycles of erosion and deposition. It is not the history of a single major episode of erosion followed by gradual valley filling that has been reported previously from elsewhere along the Ogallala out­ crop belt.

Conservation and Survey Division, IANR, University of Nebraska­ Lincoln, Lincoln, NE 68588-0517.

194 195 Introduction There is a certain mirage-like quality to the Ogallala Formation both in the field and in the literature. Depending upon the time of day and the lighting conditions the same out­ crop can look quite different. These differences can cause important features, such as unconformities, either to be seen readily or to be missed completely. This transforming quality may have more to do with the nature of the western United States than with that of the geologic unit. Whatever the cause, the problem has been observed by other workers. Loren Eiseley's encounter with a rattlesnake on the High Plains (1957, p. 183­ 184) is a case in point. Eiseley sat for several hours before noticing a coiled rattlesnake by his boot. The snake may have been there all the time, and then again it may not have been. The same problem can be found in a review of the literatuce.. Two or more workers have looked at the same sequence of rocks and have described it and interpreted its origin differently. Subtle, and not so subtle, differences have crept into the writing of individual authors over time, often transforming their original ideas fundamentally.

The remainder of this paper will exa~ine some of the variations in perceptions about the Ogallala Formation in general and also what is known about the Ogallala specifically in the southern Nebraska Panhandle and adjacent areas where N.H. Darton did most of his early work on the ~,it. Darton (1899a, b) named and (1899b) described the Ogallala Formation in western Nebraska and subsequently changed the spel­ ling of Ogallala to Ogalalla (Darton, 1903c). Most recent reports by other workers accept 1899 as the date when Darton named this unit.· The change in spelling and the date of first publication of the formation name, however, have been reported previously in several ways in some of the more widely read and cited literature. Table r is an attempt to clear up the confu­ sion in this literature. A chronological account of the spelling and other changes to which the Ogallala has been subjected over the years, it begin~ with the establishment of the first U.S. Post Office at the tow~ bearing the name. If the table were extended farther back in ti~e,· other spelling variations could be noted.

Deposition of the Ogallala Smith'(1940, p. 77-94) discussed the origin of the Ogallala and dismissed the ideas of earlier workers that the Ogallala was either a lacustrine deposit or a composite alluvial fan. He argued, instead, that the formation was a warped and dissected piedmont alluvial plain deposit. The mode of deposition in Kansas, stated clearly by Smith (1940, p. 85-87), follows. 196 TABLE I CHANGES IN SPELLING OF OGALLALA AND DATE OF FORMATION DESIGNATION ATTRIBUTED TO DARTON

Date Source Spelling 11 July 1873 u.s. Post Office. Records in N.S.H.S* Ogalalla 1879 Brewster's Map of Nebraska. Ogalalla 1879 Johnson's Late Map of Nebraska. Ogalalla 10 November 1882 U.S. Post Office. Records in N.S.H.S.* Ogallala 1885 Official State Atlas of Nebraska. OgaJ.lala 1890 Department of Interior, General' Land Office Map. Ogallala 1896 Darton works in western Nebraska. 1897 Renshawe et al. map 30' series Ogalalla Quad:'" 1898 Morsell reports on talk given by Darton at Geol. Soc. Washington on 23 Febr. 1898. Darton says two formations overlie White River Series but Morsell does not report names. 1898 Darton submits text of Prelim. Report on the Geology and GroundWater Resources of Nebraska Wes~ of the 103rd Meridian. 1898' Darton gives talk at Geol. Soc. Amer. Mtg. in New York, ,28-30 Dec., and names formation. 1899a Abstract of 28-30 Dec. 1898 talk by Darton published in Febr. 1899. Oga.!.lala Fm. 189gb Darton's Prelim. Report ••• published p. 734-735. Ogallala Fm. 1900 Renshawe's 30' series Ogala.!.la Quad. pub 1ished. June 1901 Darton completes work on Camp Clarke and Scotts Bluff folios. 1903a,b Darton's Camp Clarke and Scotts Bluff folios published. Ogallala Fm. 1903c Darton's Professional Paper 17 Ogalalla Fm. published. 1905 Darton's Professional Paper 32 Ogalalla Fm. pub 1ished. 1913 Darton prepares geologic map for Syracuse-Lakin, Kansas, folio. 197 (TABLE I, continued) Apri I 1917 Darton completes work on Syracuse­ Lakin, Kansas, folio. 1920 Darton's Syracuse-Lakin folio Ogalalla Fm (In text) published. Ogallala Fm (Geol. Map) 1928 Darton recognized format ianin New Mexico. Ogallala Fm. 1931 Elias publishes Wallace County, Kansas, report. In a footnote says he will use Ogallala (not Ogalalla). Ogallala Fm. 1938 Wilmarth in.U.S.G.S. Bulletin 896 shows differences in Darton's spellings of Oga 11 ala. 1938, 1939 Lugn raises Ogallala to group status. Ogallala Gr. 1941 Schultz and Stout, p. 13, claim Darton first used term Ogallala as formation name 1n 1898. Also quote from Darton (1920) and change Darton's spelling of Ogalalla to Ogallala. Ogallala Gr. 1943 Condra and Reed publish Bulletin 14. Ogallala Gr. 1945 Frye publishes Thomas County Report. Ogallala Fm. 1956 Frye, Leonard and Swineford in work on Ogallala of northern Kansas point out that Darton. named Ogallala in 1899 but claim he spelled it Ogalalla. Misquote from 1899 ,work using OgalaTla spelling. Ogallala Fm. 1959 Reed, in Condra and Reed, Bulletin 14A. Ogallala Fm. 1959 Frye and Leonard on correlation of Ogallala between west Texas and Nebraska point out (p. 10) that Darton named formation in 1899 but claim original spelling was Ogalalla Ogallala Fm. 1971 Frye (p. 5) says Darton named Ogallala in 1905. 1975 Leonard and Frye (p. 8) say Darton named formation in 1899 but spelled i t II 0gal allaII at t hat time. 1977 Schultz (p. 17) misquotes spelling of Ogalalla in Darton (1920). Ogallala Fm. 1978 Walkp.r (p. 13) says Darton named Ogallala in 1898.

NOTE: Underlined dates indicates year of publication. * Nebraska State Historical Society. 198

"Deposition probably began ~ith the filling of stream channels, leading to more frequent overflow and thus to the upbuilding of the floodplains. This soon led to shifting of the channels themselves, and probably to the development of anastomosing patterns. As filling progressed, the valley flat overlapped farther and farther east and ~est. Relief ~as lowered, the valley plains grew broader, and finally the divides were overtopped, and there follo~ed overlapping and coalescing of the depositional zones of individual streams. As depositional areas gre~ broader the rate 'of upbuilding must have declined, allowing greater time for the work of soil processes on the successive accretions of sediment. Undoubtedly the trunk streams deployed into branching distributaries, and these shifted sluggishly across broad and overlapping triangular areas. The bedrock divides ~ere buried' deeper and deeper, and one vast, continuous alluvial plain came to extend from the slopes of the Rockies perhaps as far as the Flint Hills in Kansas. Probably the waters of the depositing streams were gradually dissipated as they neared the border of this plain, so that none escaped beyond. Eastward and westward the margins of the alluvial mantle thinned out against the older rocks, and at the south the Sierra Grande highland probably rose gradually above the depositional surface." This theme of the gradual deposition of the Ogallala through time was adopted in later publications. Of particular importance are the works of Frye and his co-workers because they are cited and quoted often when the origin of the forma­ tion is discussed. Frye, Leonard, and Swineford (1956, p. 49), in an extensive work on Ogallala stratigraphy in Kansas, argued against the idea that the unit was a " .•.series of alluvial fans of vast extent, sweeping outward from the Rocky Mountains." Their Figure 2 (ibid, p. 19) and summary (p. 64-67) clearly illustrate their thoughts on the depositional history of the Ogallala Formation. They recognized three largely intergrada­ tional, but formally named members of the formation which formed a single package of sediments deposited during a single cycle of alluviation. Initially, sediments were deposited on the floors of valleys carved into bedrock during an episode of erosion (Fig. lA). Deposition continued to fill in the valleys (in the fashion outlined earlier by Smith, 1940) until the interstream divides were covered and a single aggradational plain was developed. Frye and Leonard (1957) extended this aggradational concept to the entire Ogallala sequence across the Great Plains. They still recognized a three-member Ogallala and claimed that the base of the middle member was completely conformable and gradational with the underlying member. The base of the upper member was primarily conformable and gradational with the middle member. The same general depositional scheme was outlined once 199

A B s N s N

LOWER OGALLALA LOWER OGALLALA

MIDDLE OGALLALA MIDDLE OGALLALA

UPPE ROGALLA LA UPPER OGALLALA

Figure 1. A. Frye and Leonard's concept of Ogallala deposition, modified after F&l, 1957, Fig. 2. B. Concept of Ogallala ~uts and fills, used in this paper. 200 again by Frye and Leonard (1959) but, while the 'three-fold rock unit subdivision was retained in their Figure 1 for Kansas and Nebraska, three floral zones and no ·members were shown in Okla­ homa and Texas. They introduced (ibid, p. 16) an apparent con­ tradiction by calling the uppermost unit, the Kimball, in the northern plains a zone and not a member. With respect to the depositional history of the formation, Frye and Leonard (ibid, p. 17) said: "Deposition of the formation started during late Miocene time along major valleys that extended through Crosby and Floyd counties and parts of the Panhandle in Texas, northern Kansas, and several positions in Nebraska, including Cherry County. Initial alluviation was localized in the lowest parts of independent valley systems, and as these erosional valleys were filled there was progres-' sive obliteration of the erosional topography, accompanied by shifting of channels across former minor diVides, with ultimate burial of most major divides. The surface of the alluviating plain was not without character as natural levees, aban­ doned channel segments, and interfluve depressions must have imparted significant relief and locally produced shallow water-table lakes. The fact that some areas of the flood plains were stable for significant periods of time during late stages of Ogallala deposition is attested by the presence of buried soil profiles." Frye (1971) reviewed the history of the Ogallala, but moved away from rock unit subdivision of the formation. Instead·, he subdivided the Ogallala into three informal zones based on fossil seeds and vertebrates. Later, Leonard and Frye (1975, p. 8-9 and measured sections) outlined the depositional history of the Ogal­ lala once again and applied the zone nomenclature developed in Texas to the Ogallala of New Mexico, but based their zonal sub­ divisions on " .•.lithologic similarities, rather than on a firm paleontologic basis." From the foregoing review it should be obvious that the idea of a generally continuous alluv!ation of the Ogallala was firmly entrenched for nearly four decades follOWing the work of Smith (1940). However, Sen! (1980, p. 1) claimed that the Ogal­ lala in Texas " ..•was deposited by coalescent, low-gradient, wet alluvial fans that headed in mountains to the west," and offered sound evidence that the Ogallala consisted of three overlapping fan lobes of ~ifferent ages. In 1981, Shepherd and Owens said that the Ogallala in southeastern Wyoming was also an alluvial fan deposit. They supported this idea in part by claiming that Moore (1963) also had proposed the idea (he did not) and by using a cross section taken from Denson and Bergendahl (1961) that 201 shows a wedge-shaped mass of Ogallala thinning away from an up­ lift. Denson and Be~gendahl (1961) called their figure, repro­ duced here in modified form (Fig. 2), a schematic diagram and not a cross section. Anyone familiar with the country and the geo­ logy along the line of the diagram knows that the diagram should not be mistaken for a cross section. Accurate cross sections, transverse to the long axes of paleovalleys in Nebraska, were prepared by Smith and Souders (1971) for Kimball County, by Smith and Souders (1975) for Banner County, and by Swinehart (1980, p. 126) for the Nebraska Panhandle and the area just to the east. Swinehart's cross sections are reproduced here (Fig. 3). If these cross sections show an Ogallala alluvial fan, then it is a very large one with a rather unusual geometry. (Souders, Swinehart and DeGraw (in press) have prepared a major revision of the Mebraska Tertiary including a cross section that should be published in 1984 or 1985.]

Naming an Aquifer "Ogallala" Another idea that comes from the nomenclature used in the recent literature on the Ogallala is that there is a High Plains­ Ogallala aquifer. In Nebraska, the application of the rock unit name, Ogallala, to a complex geohydrologic unit has clouded the facts that there may be more than one aquifer in the Cenozoic deposits in one area and that an aquifer in another area may include the Oqallala Formation as well as younger and/or older deposits. Perhaps. geohydrologic units should not be given the names of rock formations when the two cannot be proven to be identical. Following these notes on some of the High Plains "mirages," several aspects of the geology of the Ogallala Formation in the southern Nebraska Panhandle will be examined.

Major Paleovalley Fills At least in the southern Nebraska Panhandle neither the gradual alluviation model of Smith (1940) and later workers nor the alluvial fan model fits the depositional style of the Ogal­ lala. In this area the Ogallala is typified by multiple cuts and fills with complex geometries and by the presence of remnants of sediments which fill high-gradient tributaries to main paleo­ valleys. The Ogallala here is depicted best by the model illus­ trated in Figure lB. Time lines in this model need not be nearly horizontal. Ogallala beds of markedly different age may be found laterally adjacent to one another and Ogallala beds of equivalent age may ~lso be deposited at higher positions along paleovalley sides rather than in the axes of the paleovalleys. The multiple Ogallala cutting and filling episodes of this model are generally similar to those show~ to be the case in Texas bv Seni (1980) and in Sioux County, Nebraska, by Skinner, Skinner, and Gooris (1977) . 202

A To

p£

SOUTH Older Cretaceous , DAKOTA WYOMING ~ -A~ --

__~B.RASKA A I COLORADO'

Figure 2. Schematic diagram, southeast Wyoming to Nebraska Panhandle. Modified after Denson and Bergendahl, 1961, Fig. 209.2. Ogallala Formation is stippled. I 203

A

Tw ___:------12~OOI

CrelaceOUI 2000'

D ~ooo'

4~00'

4000'

3~OO' . 1 3000'

Figure 3. South-North cross-sections across western Nebraska. Modified after Swinehart, 1980, p. 126. Ogallala is stip­ pl.ed. Reproduced wtth permission of He'ldref Publications. 204 The Ogallala beds south of the North Platte River are more similar in color and grain size variations to the Ogallala of southwest and south-central Nebraska than they are to units in the Ogallala north of the North Platte River, with the possible exception of areas in the extreme western part of the outcrop belt (Fig. 4). The sediments of the formation north of the North Platte River and east of Box Butte and northern Sheridan counties generally are olive in color and contain fewer distantly derived clasts larger than pebble size than do the rocks south of the North Platte. This seems to be true not only in surface expo­ sures but also in samples from test holes drilled in the Sand Hills region. Brown and pinkish brown colors are more common in the sequence south of the North Platte River. In the southern Nebraska Panhandle remnants of coarse clastic fills are exposed on the surface and in canyon walls at many sites, particularly along and just south of the northern margin of the Cheyenne Tablelands (Fig. 5). The cuts in which the fills were deposited have nearly vertical sides at some sites and have floors with irregular transverse profiles with up to 20-m of relief. Some of these cuts, which are up to 2-3 km wide and up to 50+ m deep, are in older Ogallala rocks, and others in Ogallala and pre-Ogallala rocks. Older Ogallala and pre-Ogallala boulders and blocks up to 66 cu m or more in volume are included in the fills at many sites (Diffendal, in press a). One of these coarse qrained fills has cut across an older fill of similar type at a·site southwest of Harrisburg in Banner County (Fig. 5).

Local Tributary Fills This author has previously reported on the occurrence of high gradient, steep-sided Ogallala tributaries to main pa1eo­ valleys (Diffendal, 1982). These tributaries are filled with locally derived sediments, reworked distant source sediments. or combinations of both types. Beds in these tributary fills have primary dips of up to 4 degrees or more in a downva11ey direction. Such variable sediment types and relatively high primary dips also occur in sediments founj along Holocene tribu­ tary gullies in the area. PreViously unreported Ogallala tribu­ tary fills have recently been found along the edge of the Cheyenne Tablelands southeast of Coumbe Bluff in Garden County, and south of Harrisburg in Banner County (Diffendal, in press b).

Volcanic Ash Deposits Frye, Leonard, and Swineford (1956. p. 18. 25-28") reviewed briefly their earlier work on the petrologic characteristics of volc~~ic ash beds in the Ogallala and recognized ten ash falls during deposition of the formation in northern Kansas. Accord:ng to their findings, the ash deposits in each fall have unique 205

Figure 4. Map showing distribution of Ogallala Formation in Nebraska. Wide stipple pattern is belt north of North Platte and Platte rivers. Close stipple pattern is gen­ erally south of these rivers. N a m

~ 1 :~~ ; ~ "

Figure 5. landsat image 6f part of Nebraska Panhandle. Channels filled with coarse clastic sediments shown by dashed lines. Arrows show general flow directions. 207 features which allow any single ash to be separated from the others. In the southern Panhandle of !'Tebraska more than three ash falls in an Ogallala sequence have been reported previously by Diffendal, Pabian, and Thomasson (1982, p. 11) at Ash Hollow in southeastern Garden County, and by Diffendal (1982, p. 972-973) at Greenwood Canyon in south-central Morrill County. The loca­ tions of known ash deposits in these two areas are shown on Figures 6 and 7. Multiple ash deposits also occur in th~ Ogal­ lala sequence south of Broadwater in southeastern Morrill County on the Fairchild and the Gillespie ranches. The locations of these ash bodies are shown in Figure 8. All but one of the ash deposits shown on the three maps (Figs. 6-8) are gray in color. The single remaining ash found in the vicinity of Ash Hollow in the ~n~-1/4 SW-l/4 sec 12, T. 15 N., R. 42 W. is yellowish gray. The only other yellowish gray ash found by the author in the Ogallala Formation is located southwest of Keystone in Keith County, Nebraska. Work is currently being done by S. White of the University of Nebraska-Omaha, in association with J.B. Swinehart, W. Ear­ rash, and this author, on the multiple ash deposits at Ash Hollow and Greenwood Canyon. Samples from each of the ashes have been collected and-are being studied to see if they have characteristics distinct enough to allow separation of ashes on other than stratigraphic grounds and to see whether the ash sequences at the two sites have similar chemical compositions.

M~re than one hundred separate ash localities have been found by the author in the Ogallala sequences along the North and South Platte rivers. Samples have been collected, prepared, and irradiated for fission track dating. These dates and the results of the chemical studies just noted may allow more precise corre­ lations of these Ogallala rock sequences than have been possible previously. The ash deposits found so far have the following other characteristics. Their geometries vary from "shoestring" channel fills that can be traced for up to 1 km, through lens- and irreg­ ular shapes, to broad blankets covering up to several sections. The maximum thickness of all deposits 1s between 6 and 7 m, with most being less than 2 m. Most of the ash beds are uncemented. ~~ere they are cemented, calcium carbonate is the principal cement, although some silica cement occurs at some sites. Either the whole mass may be cemented or only the upper part may be. Black lichen often covers the surface of indurated ashes giving them the look of the so-called mortar beds in the sequence. Only a few scraps of bone and some fossil grass husks, nutlets, and endocarps have been found in the ashes. The number of ash bodies seems to increase with increasing thickness of the formation 208

Figure 6. Map of volcanic ash localities (bolder black lines) in the Ash Hollow vicinity, Garden County, Nebraska. Base after U.S.G.S. 7.5' maps. 209

l lines) in the Figure 7. Mapd ofCanyonvo canicviCini..ashty t1Morracalities,'11. CountYt(bolderNebraska,black Base after GreenwooU.S.G.S. 7.5' map. 210

ii i STUD~~. I. r---i ! AREA , . I .,-...... , Wy;!iii---J +-:7" . I :~I '-- ~ )I . ! -~'-----' l I r !i,.-.....,-----< '1-'--~'__': I ' 32 T. 18 N.

5

T. f.- -+-~"__I_~::....::__~~?_~~~r__---:l~..;:o.L.;.....;;.-.-----_j17 N.

R. 48 W.

Figure 8. Map of volcanic ash localities (bolder black lines) on the Fairchild and the Gillespie ranches! Morrill County! Nebraska. Base after U.S.G.S. 7.5' map. 211 combined with increasing quantities of channel deposits of coarser character in the sequence.

Floral and Faunal Information The fossil plant materials of the Ogallala in Nebraska include diatom frustules, and charophyte stem and gyrogonite fragments (Diffendal, Pabian, and Thomasson, 1982). Angiosperm anthoecia, achenes, nutlets, endocarps, spores, pollen, and leaf and stem fragments have also been found in abundance at some sites. The first four types of vascular plant materials just mentioned are perhaps the best known because of the work by M.K. Elias (1942). The floral zones later defined by Frye and his co-workers in the papers cited earlier are based on the work of Elias and their own collections. Recent studies by Thomasson (1979) in Kansas and in Nebraska (1977) have brought tne earlier work into question and make problematic the acceptance of the floral zones of Elias, Frye and others. The last four vascular plant fossil types have been reported by MacGinitie (1962) from sites in north-central Nebraska yielding a diverse tree flora not as yet found in the Ogallala to the west. Andrews (1970) also described diatoms from this area. No important work has been done on the invertebrate fossils from the Ogallala in the southern Panhandle of Nebraska. Exter­ nal mo'ds of gastropods and ostracods have been found in dia­ tomites at several sites, but these fossils remain unidentified. From all of the reports on fossil vertebrates from the Ogallala the casual reader may conclude that the vertebrate fauna from the Nebraska Panhandle and the area around the town of Ogal­ lala is well known and forms a key element of biostratigraphic correlation with Ogallala sequences 1n other states. Unfor­ tunately, only a few summary papers exist on vertebrates from the area: these include those of Hesse (1935) on the type Ogal­ lala site, Schultz and Stout (1948) on five "Kimball-Sidnev" sites, Breyer (1981) on the so-called Kimballian faunas from several sites, Voorhies (1984) on aspects of the Uptegrove fauna in northern Cheyenne County, and Bown (1980) on the Lemoyne fauna. References to other papers on fossil vertebrates from the study area may be found in the works just cited, but the fact is that not much published information on the faunas from this key area exists. I know of no work comparable in scope to that of Schultz (1977) on the biostratigraphy of the Texas Pan­ handle and adjacent Oklahoma. The author has found many new vertebrate localities in the study area since 1975. Some of these sites are potential quar­ ries which could yield valuable additional faunas to those already reported and described.. Inquiries en site locations by 212 ve~teb~ate paleontologists inte~ested in the Ogallala a~e wel­ comed. Whileve~teb~ate fossils do occu~ in almost eve~y Ogal­ lala lithology, they occur only sporadically in most. Diatomites and olive sands and sandstones are the only beds that have yielded fossils at almost eve~y site whe~e these sediments occur.

Ca1iches

Caliches a~e common th~oughout the Ogallala sequence in the study area (Diffendal, 1982; in p~ess b). They do seem to increase in numbe~ and amount of individual development upward th~ough the st~atigraphic sequence at many sites, but the question of thei~ o~igin ~emains an open one. Is their p~esence due to a high wate~ table, inc~easing aridity, decreased deposi­ tion, a combination of these facto~s, or some other cause? Ca1iches in the study area need to be examined more carefully than has been done previously.

Conclusions

At least in the southern Neb~aska Panhandle and the Keith County area, the Ogallala is a complex alluvial sequence of extreme heterogeneity. Many features of the unit remain poo~ly known in this, the type region of the Ogallala and its membe~s. A multidisciplinary study of the area by interested geologists, paleontologists and hydrologists could yield much information to clear up the doubts that this author has about some claims made by others on the geologic and paleontolgic histo~y of the Ogallala, and on the hydrologic characte~istics of the unit.

Acknowledgements M.R. Voorhies and A.P. Diffendal offered helpfUl sugges­ tions for imp~ovement of the manuscript.

References Cited

Andrews, G.W., 1970. tate Miocene nonmarine diatoms f~om the Kilgore area, Cherry County, Nebraska; O~S. Geological Survey Professional Paper 683A, 24 p.

Anon. 1879. Johnson's late map of Neb~aska; Rand McNally and Co., Chicago, It. Anon. 1885. Official state atlas of Nebraska; Everts and Kirk Co., Philadelphia, PA., 207 p. 213

Bown, T.M. 1980. The fossil Insectivora of Lemoyne Quarry (Ash Hollow Formation, Hemphillian), Keith County, Nebraska; Transactions of Nebraska Academy of Sciences, VIII:99-122. Brewster, C. 1879. Map of Nebraska; H.R. Page and Co., Chicago, IL. Breyer, J.A. 1981. The Kirnballian Land-Mammal Age: Mene, mene, tekel, upharsin (Dan. 5:25); Journal of Paleontology, 55(6}:1207-1216. Condra, G.E. and Reed, E.C. 1943. The geological section of Nebraska; Nebraska Geological Survey Bulletin 14:1-82. Condra, G.E. and Reed, E.C. 1959. The geological section of Nebraska with current revisions; Nebraska Geological Survey Bulletin 14A:1-82+4 unnumbered pages. Darton, N.H. 1899a. Relations of Tertiary Formations in the western Nebraska region; American Geologist, 23(2}:94. Darton, N.H. 1899b. Preliminary report on the geology and water resources of Nebraska west of the one hundred and third meridian; U.S. Geological Survey 19th Annual Report, Part 4, Hydrography:719-814. Darton, N.H. 1903a. Camp Clarke folio Nebraska; U.S. Geological Survey Geologic Atlas of the United States, Folio 87, 4 p. Darton, N.H. 1903b. Scotts Bluff folio Nebraska; U.S. Geological Survey Geologic Atlas of the United States, Folio 88, 5 p. Darton, N.H. 1903c. Preliminary report on the geology and water resources of Nebraska west of the one hundred and third meridian; U.S. Geolo~ical Survey Professional Paper 17, 69 p. - Darton, N.H. 1905. Preliminary report on the geology and under­ ground water resources of the central Great Plains; U.S. Geological Survey professional Paper 32, 433 p. Darton, N.H. 1920. Syracuse-Lakin folio Kansas; U.S. Geological Survey Geologic Atlas of the United States, Folio 212, 10 p. Darton, N.H. 1928. "Red beds" and associated formations in New Mexico; U.S. Geological Survey Bulletin 794, 356 p. Denson, N.M. and Bergendahl, M.H. 1961. Middle and Upper Terti­ ary rocks of southeastern Wyoming and adjoining areas; U.S. Geological Survey Professional Paper 424C:Clb8-r17? 214

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