GEOLOGICAL SURVEY CIRCULAR 106
June 1951
GEOLOGIC CONSTRUCTION-MATERIAL RESOURCES IN MITCHELL ^COUNTY, KANSAS
Frank E. Byrne, Wendell B. Johnson, and Denzil W. Bergman
PREPARED IN COOPERATION WITH THE STATE HIGHWAY COMMISSION OF KANSAS R. C. Keeling, State Highway Engineer S. E. Horner, Chie* Geologist R. D. Finney, Chief Engineer
Prepared as Part of a Program of the Department of the Interior for Development of the Missouri River Basin UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director
Washington, D. C.
Free on application to the Geological Survey, Washington 25, D. C. CONTENTS
Page Page
Introduction...... l Sanborn formation ...... 15 Purpose of the investigation ..... 1 Areal distribution ...... 15 Geography ...... /1 General description ...... 16 Area covered by the investigation. 1 Representative measured section 16 Topography ...... 1 Thickness ...... 16 Drainage...... 1 Construction materials ..... 16 Climate ...... 1 Terrace deposits...... 16 Transportation routes ...... 3 Areal distribution ...... 16 Investigation procedure ...... 3 General description ...... 16 Acknowledgments ...... 3 Representative measured section 17 Characteristics of the outcropping Thickness ...... 17 stratigraphic units ...... 4 Construction materials ..... 17 General ...... 4 Alluvium ...... 17 Dakota sandstone ...... 4 Areal distribution ...... 17 Areal distribution...... 4 General description ...... 17 General description...... 4 Representative measured section 17 Representative measured section. @ Thickness...... 17 Thickness ...... 6 Construction materials ..... 17 Construction materials ..... 6 Inventory of construction materials ... 17 Graneros shale ...... 6 General...... 17 Areal distribution...... 6 Aggregate for concrete ...... 18 General description...... 6 Engineering and geologic Representative measured section. 7 characteristics ...... 18 Thickness ...... 7 Stratigraphic sources and per Construction materials ..... 7 formance characteristics ... 18 Greenhorn limestone ...... 7 Sanborn formation ..... 18 Areal distribution...... 7 Alluvium ...... 18 General description ...... 7 Road metal ...... 18 Lincoln limestone member. . 7 Engineering and geologic Hartland shale member ... 8 characteristics ...... 18 Jetmore chalk member ... 8 Aggregate for concrete ... 18 Pfeifer shale member .... 8 Indurated rocks ...... 18 Representative measured sections 9 Limestone gravel ..... 19 Thickness ...... 13 Stratigraphic sources and per Construction materials ..... 13 formance characteristics ... 19 Carlile shale ...... 13 Sources of aggregate for Areal distribution...... 13 concrete ...... 19 General description ...... 13 ' Indurated rocks ...... 19 Fairport chalky shale Dakota sandstone. ... 19 member ...... 13 Greenhorn limestone . . 19 Blue Hill shale member ... 13 Carlile shale ..... 19 Codell sandstone member . . 14 Niobrara formation. . . 19 Representative measured Sanborn formation ..... 19 sections ...... 14 Mineral filler ...... 19 Thickness ...... 14 Engineering and geologic Construction materials ..... 14 characteristics ...... 19 Niobrara formation ...... 14 Stratigraphic sources and per Areal distribution...... 14 formance characteristics ... 19 General description...... 15 Sanborn formation ..... 19 Representative measured Terrace deposits...... 20 section ...... 15 Riprap ...... 20 Thickness ...... 15 Engineering and geologic Construction materials ..... 15 characteristics ...... 20 CONTENTS (Continued) Page Page Inventory of construction mate rials -- Stratigraphic sources and per Continued formance characteristics . . 20 R ip r ap - - C ontinue d Greenhorn limestone . . . 20 Stratigraphic sources and per Niobrara formation .... 20 formance characteristics . , 20 Subgrade and'embankment Dakota sandstone ..... 20 material...... 21 Greenhorn limestone . . . 20 Engineering and geologic Niobrara formation .... 20 characteristics ...... 21 Structural stone ...... 20 Stratigraphic sources and per Engineering and geologic formance characteristics . . 21 characteristics...... 20 Fine-granular sediments . 21 Stratigraphic sources and per Coarse-granular sediments 21 formance characteristics . , 20 Broken or crushed rock . . 21 Greenhorn limestone . . , 20 Dakota sandstone . . . 21 Niobrara formation. . . , 20 Graneros shale . . . . 21 Calcareous binder ...... 20 Greenhorn limestone . 21 Engineering and geologic Carlile shale . . . . . 1 characteristics...... 20 Niobrara formation . . ILLUSTRATIONS Page Plate 1. Map showing construction materials and geology of Mitchell County, Kans. ... In pocket Figure 1. Index map of Kansas showing area covered by this report and by other construction materials investigations reports ...... 1 2. Chart showing temperature ranges at C'oncordia, Kans...... 1 3. Chart showing precipitation ranges at Beloit, Kans...... 1 4. Outcropping Stratigraphic units in Mitchell County, Kans., and their construction materials ...... 5 TABLE Page Table 1. Summary of materials tests In pocket GEOLOGIC CONSTRUCTION MATERIAL RESOURCES IN MITCHELL COUNTY, KANSAS
INTRODUCTION Purpose of the Investigation short distance southeast of Tipton in the area known as the Blue Hills. The State Highway Commission of Kansas and the United States Geological Survey are co The two most conspicuous typographic fea operating in the compilation of a State-wide in tures in the county are the valley of the Solomon ventory construction materials. A field party River and the Blue Hills. The valleys of the composed of personnel from the two cooperat North and South Forks of the Solomon River, ing agencies was sent into Mitchell County, which join in the vicinity of Cawker City to form Kans. , in the summer of 1948 to investigate the Solomon River, are incised about 50 Teet be .sources of engineering construction materials. low the general level; in the eastern part of the This report of the Mitchell County investigation county, the valley of the Solomon River has been is a part of the general inventory and a contri incised to a depth of about 150 feet. In the valley bution to the geologic mapping and investigation is an extensive terrace which, in the vicinity of of mineral resources being made in connection Glen Elder, is only slightly more than a mile with studies of the Missouri River basin. \J wide but increases in width to almost 4 miles at the eastern boundary of the county. The primary objective of the investigation The Blue Hills in the southwestern part of was to accumulate all field and laboratory data Mitchell County stand conspicuously above the pertaining to the geologic materials in Mitchell general level. The hills are buttes and mesas County that would be of use in the construction capped by the Fort Hays limestone member of of dams, highways, airports, and other engi the Niobrara formation. (See pi. 1 and fig. 4.) neering structures. Additional geologic data Their steep slopes have been cut into the Carlile are included in this report but only to the extent shale. The highest of the hills project almost of providing information useful in the develop 300 feet above the surrounding upland plain. ment of the prospects reported in the inventory, or for the location of other materials required Most of the area of Mitchell County is oc for future engineering needs. cupied by a rolling upland plain only moderately dissected by the tributaries of the Solomon River Geography in the central and northern parts of the county and by those of Salt Creek in the southern part. Area Covered by the Investigation The walls of the valleys through which the smaller streams flow are gently sloping for the Mitchell County is in the second tier of most part- a shoulder formed by the Greenhorn Kansas counties south of the Nebraska border limestone (see pi. 1 and fig. 4) marks the top of and in the seventh tier west of the Missouri man- of the valley walls. I.iterstream areas are border. (See fig. 1.) It comprises 20 townships flat to rounded. and covers an area of about 720 square miles. The county is bounded on the north by Jewell Drainage and Cloud Counties, on the east by Cloud and Surface drainage in Mitchell County is con Ottawa Counties, on the south by Lincoln Coun trolled by the Solomon River ami its tributaries. ty, and on the west by Osborne County. (See pi. 1.) The longest tributaries, Walnut and Clay Creeks, head in the Blue Hills and flow Topography northward. Salt Creek is the largest stream in the southern part of the county. It is another The average altitude of Mitchell County is tributary of the Solomon River, which it joins in 1, 500 feet. The lowest point, about 1,310 feet, the northern part of Saline County. is on the Solomon River at the east boundary and the highest point, about 1, 885 feet, is a Climate
1 Missouri River Basin, conservation, control, and use Mitchell County is in an area of continen of water resources: 78th Cong.. 2d sess., S. doc. 191, tal-type climate in which the summers are rel 1944. atively long and hot and the winters short and Report in Report prepo ration published
Figure I. Index map of Kansas showing areas covered by this report and by other construction materials investigations
EXPLANATION EXPLANATION - Days in which precipitation 'n *h' ch maximum temperature was more than 90° f. Data far bath charts (no concrete construction) compiled from I was more than I inch in which maximum temperature was between 6I*~9O° F. Climatological Data (no construction activity) (no interference with any type of construction) Kansas Section , Days in which precipitation far years 1937 to 9 was between 0.11 and I inch in which maximum temperature was between 4I°-60° F. 1946, inclusive. (no Interference n/ira concrete construction; (no bituminous surfoc/nffs laid} Issued by no bituminous surfacing* laid) Weather Bureau I Days in which precipitation I was between a trace and O.I inch in which maximum temperature was between 32*-40*F. United States (no interference ir/rn construction} (concrete construction requires protection} Department of Commerce in which maximum temperature was less than 32* F I Days in which there was the concrete construction) I no precipitation ' (no interference with construction)
Figure 2.-Chart showing temperature ranges at Concordia, Kansas. Figure 3._Chart showing precipitation ranges at Beloit, Kansas fairly cold. The mean annual temperature is branch line of the .Union Pacific that starts in about 54 ° F. and ranges from a low of about Beloit and extends southeastward. It is traversed 280 F . in January to a high of about 80° F. in by U. S. Highway No. 24 and Kansas highway 14. July. (These figures were interpolated from A second Kansas Highway (No. 128) extends north data from nearby stations inasmuch as the from a point a short distance northwest of Glen weather station at fieloit does not maintain rec Elder. East of Beloit, U. S. Highway No. 24 is ords on temperature.) On the average, there constructed of concrete; west of Beloit it is of are 75 cloudy days a year, 110 partly cloudy the black-top type of construction, as is Kansas days, and 180 clear days. The ground is Highway 14. Kansas Highway 9, entering the covered with snow on the average of 28 days of county from the east, is a metaled all-weather the year. The average annual precipitation is road as far as its junction with U. S. 24 a mile 24. 17 inches. The average date of the first north of Beloit. That part of Kansas Highway 128 killing frost in the fall is October 14 and that which is included in this county is a metaled all- of the last killing frost in the spring is April weather road. 27. 2/ County and township roads, for the most Figure 2, a chart showing temperature part, follow section lines. Some of them are ranges at Concordia, Kans. (about 30 miles metaled with materials available locally, where northeast of Beloit), was compiled from Cli- as others are maintained as earth roads. matological Data 3/ for the years 1937 to 1946, inclusive, to provide basic data on temper The locations of railroads and roads are ature in relation to engineering construction. shown on plate 1. The chart indicates, for the 10-year period, the number of days each month in which the Investigation Procedure maximum daily temperature fell within certain designated ranges based arbitrarily on tem This report is based on field work of the peratures important to various phases of engi reconnaissance type. The base map was pro neering construction. vided by the State Highway Commission of Kansas (scale: 1 mile to 1 inch). Drainage Days in which the maximum temperature lines were taken from aerial photographs does not exceed 32° F. occur only from No (scale: 1 mile to 4 inches) made available by vember to March, inclusive, with the maxi the Mitchell County office of the Soil Conserva mum incidence of 9. 9 days in January. August tion Service of the United States Department of is the warmest month in the year and on the Agriculture. The areal distribution of the strati-- average of 15. 3 days maximum temperatures graphic units that crop out in Mitchell County exceeds 90° F. The chart also shows the was then mapped in the field. The mapped strat- average difference between the daily maximum igraphic units are those recognized by the and minimum temperatures for each month. United States Geological Survey 5/and the The greatest difference in daily temperatures, Kansas Geological Survey. 6/ The principal 24° F. , is in July; and the least difference, emphasis of this report is on construction ma 18° F. , is in January and February. terials. Geologic problems not critically re lated to construction materials, therefore, are Inasmuch as precipitation also conditions considered to be of secondary importance. the number of working days in engineering construction, figure 3, a chart showing precip An effort was made to accumulate all ex itation ranges at Beloit, Kans. , is presented isting data pertaining to construction materials to show the effect of this climatic factor. The in the county; these are presented in table 1, a ranges in precipitation were selected arbi summary of materials tests. trarily. Acknowledgments As based on a 10-year average 4/ there were 19. 7 days in June, for example, in Appreciation is expressed to the following which no measurable precipitation fell; 4. 4 for contributing information found useful in the days in which, the precipitation ranged from a compilation of the geologic map and construction- trace to 0. 1 inch; 4 days in which 0. 11 to 1 materials data included in this report: the State inch of rain fell; and 1. 9 days in which the Highway Commission of Kansas at Topeka and precipitation was more than an inch. Continuing Manhattan, Kans. , S. E. Horner, chief geolo rains fall, for the most part, in the late spring gist, R. D. Finney, engineer of materials; and and early fall and other rainfall is generally in W.E. Gibson, engineer of tests; the Mitchell the form of showers of .short duration. County office of the Soil Conservation Service, United States Department of Agriculture; and Transportation Routes the county engineer and residents of Mitchell County. Mitchell County is served by two railways, the Missouri Pacific which extends westward This report, in manuscript form, was re- across the northern part of the county, and a viewed by various members of the State High- 9 Wilmarth, M. G., Lexicon of geologic nanes of the 2 Flora, 8. D., The climate of Kansas: Kansas State United States: U. S. Geol. Survey Bull. 896, pts. 1 and Board Agr. Bept., vol. 67, no. 285, 320 PP., 1948. 2, (2,396 pp.), 1938. 3 U. 8. Dept. Commerce, Weather Bur.: Cliraatological 8Moore, R. C., Prye, J. C., and Jewett, J. M., Tabu Data, Kansas section, 1937-46. lar description of outcropping rocks in Kansas: Kansas 4 (ft), cit., Weather Bur., 1937-46. Geol. Survey Bull. 52, pt. 4, 212 pp., 1944. way Commission of Kansas and the United though its outcrop is masked in many places by States Geological Survey. the younger Sanborn formation. (See fig. 4.) The Dakota sandstone makes a bold outcrop at the CHARACTERISTICS OF THE OUTCROPPING base of the south wall of the valley of Salt STRATIGRAPHIC UNITS Creek in T. 9 S. , R. 7 W. Only isolated out crops of it are mapped on the north side of Salt General Creek, as in the eastern part of T. 9 S., R. 7 W. and the southwestern part of T. 9 S. , R. This discussion of the stratigraphic units 6 W. The westernmost exposure of the forma cropping out in Mitchell County emphasizes the tion is in the valley of a small stream in the areal distribution, general characteristics, SW^SEAsec. 35, T. 9 S., R. 8 W. Outcrops of thickness, and the construction materials in this and other formations of Cretaceous age are each geologic formation or member. This part shown in more extensive areas on a geologic of the report presents the geological informa map constructed by Landes 7/ which shows, for tion required for the location and effective de the most part, only the bedrock in the area and velopment of the construction materials. does not depict the unconsolidated geologic formations that mask it in many places. A summary of the data for each geologic formation or member is presented in figure 4. General Description The areal distribution oi the local stratigraphic units is shown on plate 1, a map showing con The Dakota sandstone, unlike other for struction materials and geology of Mitchell mations of Cretaceous age cropping out in this County, Kans. Each unit is indicated by an county, was deposited under nonmarine condi identifying symbol, and its outcrop areas are tions. As exposed in Mitchell County, this for shown by a distinctive pattern. Plate 1 is mation consists of about 14 feet of sandstone printed in four parts for more convenient use underlain by about 7 feet of shale. (For a typi in the field; there is an area of overlap 2 cal exposure, see the representative measured miles wide along the contacts between the parts. section,) The sandstone occurs in massive beds which show cross-bedding indicative of its non- The locations of pits and quarries also marine origin, and is fine-grained and soft. are shown on plate 1. The Symbols indicate Most of the beds are gray orange or red brown whether the pit or quarry is or has been oper and weather gray brown or tan gray. Lenses ated or is a prospect, the type of construction and concretionary masses of brown iron oxide material available at each site, and the quanti (iron-stones) are numerous in it. ty of the material (in units of 10, 000 cubic yards) that can be removed under no more than The beds of shale which are exposed be moderate overburden (unconsolidated sedi neath the sandstone in some outcrops are ments less than 6 feet thick). Most of these usually silty and none ale areous, although thin sources are listed in table 1. Materials repre clay zones do occur. The shale is varicolored - sented on the map by inclined letters have not that is, it exhibits interbedded zones of gray, been tested and are not listed in table 1. All tan, red brown, gray orange, and blue black. materials sources listed in table 1 are num When weathered, these zones develop lighter bered within each materials classification ac shades of the same colors. Some layers of cording to the following plan: The numbering shale are thin-bedded, others are blocky, and starts in the northeastern-most township and still others are platy. Iron-oxide stains occur continues along the same tier to the west on many of the fracture planes. boundary of the county; it is continued in the next tier south starting again with the town Plant fossils are abundant in the Dakota ship in the eastern-most range and proceeding sandstone in outcrops in other parts of Kansas to the west boundary of the county, and so on. but were not found in the exposures of the for Within a township the sources are numbered in mation in this county. In some places the plant the same sequence as are the sections of the remains are so concentrated that they form township. lenses of low-grade coal (lignite), a fact which confirms the nonmarine origin of this unit. Dakota Sandstone The beds of sandstone in the Dakota form Areal Distribution a conspicuous rounded bench which, in this county, is usually near the base of a valley The Dakota sandstone of Cretaceous age wall. The average surface slope of an outcrop is the oldest stratigraphic unit that outcrops of this formation is more than 12 percent. IB/ in Mitchell County. (See pi. 1 and fig. 4.) It The more firmly the sandstone is cemented by underlies the entire county but is concealed by pore-space deposits of calcium carbonate or younger, overlying formations except along the iron oxide, the more conspicuous the bench it Solomon River in the eastern part of the county forms. All of the beds examined in Mitchell and Salt Creek in the southeastern part. Its most extensive area of outcrop is that along the 7 Landes, K. K., The geology of Mitchell and Osborne Counties, Kans.: Kansas Geol. Survey Bull. 16, pi. 2, north wall of the valley of the Solomon River in 1930. sees. 22, 23, 26, and 27, T. 7 S. , R. 6 W. 8 Slope data for the outcropping stratigraphic units Several small isolated outcrops occur just east are interpretations of.a reconnaissance soil-conservation of this large one. The formation is well ex survey map published by the Soil Conservation Service, posed at the base of the south wall of the valley U. S. Department of Agriculture, in cooperation with the of the Solomon River in T. 8 S., R. 6 W. , al Kansas State Agriculture Experiment Station. ^1^s Stratigraphic units
EHE-EIE-E ~
Dark blue-gray, very thin/bedded, noncalcareous clay shale; Blue Hill silty zones near top; interbedded zones of septarlan concre | 200 shaie tions and selenite crystals; marine; few fossils; erodes to =~E=^-^^ member form badland-type topography. 4> O
Fairport As usually exposed, is similar to underlying Pfeifer shale-, marine; ') 100 chalky shale _ member fossiiiferous; weak outcrop expression.
r^==i r- Pfeifer shaie "Fencepost" bed at top; alternating layers of dark gray to orange- gray chalky shales ond thin layers of ton-gray chalky lime Road metal y . . 18 member Structural stone <^_i^' i _____ 1_ stones; marine; fossiiiferous; forms hillside bench. Riprap Greenhornlimestone 18 Jetmore chalk "Sheil-rock" bed at top; alternating layers of blue-gray and tan- Calcareous binder >F^^^IE^E member gray chalky shales and limestones; marine-, fossiiiferous; hillside bench. Fill material / i i i Hartland sh. Alternating thick beds of calcareous, gray and gray-orange siity shales, : 27 thin beds of tan-gray chalky limestones, and thin seams of benton- HP""<^ ~ l- member ite; marine i fossiiiferous; weak outcrop. Road metal ^ OJL-: '-U-= Lincoln Is. Alternating thick layers of thin-bedded, gray to brown shale, thin beds : 22 of hard crystalline limestone and thin beds of bentonite-, F ~ member marine; fossiiiferous; weak outcrop. F ^ _- Graneros Interbedded thick layers of noncalcareous, thin-bedded, blue-gray clay ^£S_Z25E 21 shale, thin seams of bentonite, and lenses of red-brown sand None jt- shale stone; marine; nonfossitiferous; weak outcrop. Dakota Massive, cross-bedded, soft, orange to brown sandstone under Road metal 25 lain by noncalcareous, varicolored silt shale; non- marine; sandstone form* rnn.«niriinn Figure 4.-.Outcropping Stratigraphic units in Mitchell County, Kans. and their construction materials. County are soft and easily pulverized (friable), is about 25 feet, and most of the outcrops are but, in other parts of the State, local beds in from 10 to 15 feet thick. Only the uppermost the formation are so firmly cemented by pore- part of the formation is exposed locally and its space deposits of silica that they are quart- total thickness is probably in excess of 200 zitic. feet. Representative Measured Section Construction materials. --Materials from the Dakota sandstone in Mitchell County are This outcrop of the Dakota sandstone was used as road metal and fill material. measured in a cut along U. S. Highway 24 in the NE^NWi sec. 27, T. 7 S. , R. 6 W. : Graneros Shale Feet Areal Distribution Soil: Silt, sandy; reddish-brown . . . . 1.0- The Graneros shale and the overlying formations of Cretaceous age (see fig. 4) Dakota sandstone cropping out in Mitchell County are of marine origin. The Graneros shale crops out only in Sandstone, massive, soft; red-brown; the east-central and south-central parts of the weathers gray brown ...... 9 county. (See pi. 1.) Individual outcrops are Sandstone, powdery, very fine-grained; generally concealed beneath the younger San- gray-orange; weathers light gray born formation and are thus of limited areal orange; intersected by thin veins extent. The most extensive exposure is that of calcium carbonate and brown iron along the south wall of the valley of Salt Creek oil ide ...... 1.2 in the southern part of T. 9 S. , R. 7 W. and Sandstone, massive, soft, cross - the eastern part of the next township west. The bedded; red-brown; weathers gray formation is here exposed immediately above brown; thin parting of silt about a an extensive outcrop of the Dakota sandstone. foot below top; ironstone con Very small isolated outcrops occur in some of cretionary zone near middle; weath the valleys of streams tributary to Salt Creek ered surface pitted ...... 2. 8 and, in the eastern part of the county, in valleys Sandstone, soft, cross-bedded; gray- of streams tributary to the Solomon River. orange becoming tan in basal part; weathers tan gray; numerous inter- General Description bedded thin partings of silt. . . . . 1. 1 Siltstone, very soft except for inter - The Graneros is predominantly a non- bedded lenses of harder material, calca^-eous clay shale but includes some thin cross-bedded; gray, red-brown, silty zones and other slightly calcareous zones. gray-orange, and tan; weathers The shale is soft and thin-bedded. The beds tan; small ironstone concretions are usually gray or blue gray and weather scattered throughout ...... 8. 2 light gray or tan. Some of the fractures in the Shale, silty, noncalcareous; thin- shale are filled with thin veins of calcium car bedded; mottled dark-gray, tan, bonate (calcite). Numerous small crystals and and gray-orange; weathers tan . . .0. 2 occasional veins of a variety of gypsum Ironstone lens, very hard; red-brown .0. 2 (selenite) are scattered throughout the shale. Shale, silty, noncalcareous; thin- Many of the fracture planes are stained with bedded; mottled tan and gray- brown iron oxide. This shale is generally non- orange; weathers tan ...... 0.3 fossiliferous. Shale, silty, noncalcareous; cross- bedded; dark-gray; weathers gray; Included in the formation are interbedded interbedded thin lenses of yellow layers and thin seams of white to cream- silty shale ...... 1. 1 colored bentonite. The weathered surface of Shale, clayey, noncalcareous; the bentonite is orange-colored or reddish platy; blue-black; weathers light brown. Although most of the bentonitic layers blue black; soft, red-brown iron are no more than 0. 2 foot thick, a bed a foot stone concretions scattered thick is remarkably persistent in the upper throughout ...... 8 most part of the formation. Bentonite is altered Shale, clayey but contains some volcanic ash, and its volume is greatly in silt-size particles, noncalcareous; creased when it becomes saturated with water. blue-black; weathers light blue black; ironstone concretions scat The Graneros shale also includes inter tered throughout ...... 1.0 bedded thin layers and lenses of sandstone. The Shale, silty, noncalcareous; platy; sandstone is thinbedded and is usually slightly blue-black; weathers light blue calcareous. Its color is red brown because of black; iron stains on fracture the presence of iron oxide which, together with planes ...... 2.0 calcium carbonate, was deposited in the pore- Total thickness exposed (base covered)20. 9 spaces between the sand grains and serves as the cementing substance. Thickness This formation, because of its softness, The greatest thickness of the Dakota makes only a very weak outcrop. It is largely sandstone exposed at the surface in this county masked by the slopewash and gravity-moved sediments (colluvium) mapped on plate 1 as crops out extensively in the eastern part of part of the Sanborn formation. The surface Mitchell County but, for the most part, is slope developed in an outcrop of the Graneros buried beneath younger formations farther shale is usually more than 12 percent. west. (See pi. 1. and fig. 4.) This formation forms the greater part of the walls of the val Representative Measured Section leys of the Solomon River and its tributaries in the vicinity of Beloit. It is conspicuously The entire thickness of the Graneros displayed, also, throughout much of the shale is exposed in a road cut in the watershed of Salt Creek. The Greenhorn sec. 24, T. 8S., R. 6 W. as follows: limestone caps most of the interstream Feet areas in eastern Mitchell County but is con Overlain by the Lincoln limestone member cealed beneath the Sanborn formation except of the Greenhorn limestone along the edges of the deeper valleys. Although thin and usually discontinuous outcrops are Graneros shale: mapped on plate 1 along the Solomon River as Shale, clayey, somewhat calcareous; far west as Cawker City, the Greenhorn lime brown and gray; weathers light stone is concealed beneath a younger Cre gray; numerous crystals of taceous formation, the Carlile shale, in the selenite ...... 0. 9 western part of the county. Bentonite; cream-colored; weathers orange and red ...... 1. 0 General Description Shale, clayey, noncalcareous; soft; very thin-bedded; dark blue-gray; The Greenhorn limestone is shown on weathers light gray; numerous small plate 1 as a single map unit (Kg) but the crystals of selenite throughout and description of this formation will be based fractures filled with thin veins of up'on the members of which it is composed. the same material; thin lenses of These are, in upward order: the Lincoln iron-stained sandstone in upper part; limestone member, Hartlant shale member, interbedded thin seams of bentonite Jetmore chalk member, and Pfeifer shale throughout ...... 10. 1 member. Sandstone, slightly calcareous; thin- bedded; red-brown; weathers brown, 1. Lincoln limestone member of the occasional thin veins of calcite . . . 0.5 Greenhorn limestone. --The Lincoln member Shale, clayey, noncalcareous; soft; is composed of alternating thick beds of shale, thin-bedded; blue-gray; weathers thin layers of limestone, and thin seams of light blue gray; small crystals of bentonite. The greater part of its thickness, selenite scattered throughout; therefore, is shale. The shale is silty for the fractures filled with thin veins of most part and heavily impregnated with cal brown iron oxide; several thin cium carbonate. It is soft and thin to very lenses of iron-stained sandstone in thin-bedded, although a few thin layers of upper part ...... 6.1 platy shale appear in the upper part of the Shale, silty, noncalcareous; soft; member. The unweathered shale shows zones thin-bedded; red-brown; weathers of tan gray, gray orange, gray brown, brown, tan ...... 0.6 and dark gray; the weathered rock is light Shale, clayey but with some silt- gray or tan gray. Thin fracture fillings of size particles, noncalcareous; soft; calcite and selenite occur in some of the beds. thin-bedded; gray; weathers Iron-oxide stains are common along fracture light gray ...... '... 2. 25 planes and concretions of the same material Total thickness (underlain by the are present in limited numbers. Dakota sandstone)...... 21.45 Whereas most of the limestones of the Thickness Greenhorn limestone are soft and chalky, those in the Lincoln member are hard and crystalline. The outcrop of the Graneros shale cited The beds of limestone range from 0. 1 to 0. 6 as the representative measured section is the foot in thickness with one 0. 6-foot-thick bed thickest exposure of this formation found in near the base and one 0. 6-foot-thick bed near Mitchell County. In most outcrops, a thickness the top of the member. The beds are generally of 10 feet or less of the formation is exposed at massive but some near the top have platy the surface. structure. The rock is usually some shade of brown and weathers tan gray. A strong odor of Construction Materials oil can be detected in freshly broken blocks. The seams of bentonite interbedded with So far as is known, materials of the the shales and limestones range from 0.05 to Graneros shale have not been used in engi 0. 3 foot in thickness. This material shows a neering construction. blocky structure and is white or light gray when fresh but weathers gray orange or red Greenhorn Limestone brown. Areal Distribution Unlike the underlying Graneros shale, the Lincoln limestone member of the Green The second Cretaceous formation of horn limestone is generally fossiliferous. marine origin, the Greenhorn limestone, Clams, fish scales, and shark teeth are most abundant, and coiled shellfish (cephalopods) 3. Jetmore chalk member of the Green are present in limited numbers. Although horn limestone. --The Jetmore chalk member most of the beds of limestone contain fossils, is composed of -alternating beds of shale and only the shales in the upper part of the member . limestone; most of the limestones range from are fossiliferous. 0. 2 to 0. 4 foot in thickness and the shales from 0. 8 to 1 foot in thickness. The propor Landes jj/states that the Lincoln limestone tionate thickness of the limestones, therefore, is at least 22 to 24 feet thick; this is confirmed is greater in the Jetmore than it is in the un by a complete section of the member (see derlying Hartland shale and Lincoln limestone representative measured section) which shows members. a total thickness of 22 feet. Outcrops of the Lincoln limestone member are few. The bed The beds of shale are silty and highly of limestone 0. 6-foot thick near the top of calcareous. They tend to be thin-bedded in the the member forms an identifiable bench on lower part of the member and platy in the up some hillsides. per part. The lower beds are generally blue gray and weather light blue gray; whereas the 2. Hartland shale member of the Green upper beds are generally gray orange and horn limestone. --The Hartland shale member, weather tan gray. Thin seams of calcite are as the Lincoln limestone member below it, is scattered throughout the shale zones, and composed of thick beds of shale, thin layers of iron-oxide stains are common. limestone, and thin seams of bentonite. How ever, the shales of the Hartland are more The top of the Jetmore chalk member is chalky than those of the Lincoln. Limestones of defined as the top of the "shell-rock" bed. the Hartland are generally chalky rather than The name "shell-rock" refers to the great crystalline. The beds of shale in this member abundance of clam shells that the bed contains. are composed predominantly of chalky silt but This is a massive bed of limestone and is some thin zones of clay are also present. The usually slightly more than a foot thick. The shale is generally soft and is platy to thin- beds of limestone lower in the member are bedded. Alternating zones of light gray, gray less thick and chalky. They are tan gray in the orange, and, less commonly, red brown are upper part and blue gray in the lower part. conspicuous on unweathered surfaces; weathered Iron-oxide stains and ferruginous concretions exposures are usually tan gray but may show are typical of the limestones. zones of light gray and gray orange. Very thin partings of calcium carbonate occur in Fossils, especially clams, are numerous some parts of the member, and iron-stained to abundant in the beds of limestone but are zones are found at various levels. less numerous in the beds of shale. The coiled shells of cephalopods are occasional fossils in The beds of limestone in the Hartland the Jetmore chalk member. shale member range from 0. 1 foot to 2. 2 feet in thickness. Although most of the limestone The greatest thickness of the Jetmore is soft and chalky, some of it is hard and chalk member measured in Mitchell County is crystalline and has much the same appearance 18 feet and many of its exposures are from 12 as the limestone of the Lincoln member. The to 15 feet thick. Outcrops of the Jetmore are beds are generally thin-bedded to blocky but easily identified by the close-spaced beds of are somewhat massive in the upper part. The chalk it contains and by the shell-rock bed limestones are generally gray or tan gray, which makes a prominent shoulder on many of occasionally red brown, and almost all of them the valley walls. One or more of the lower weather tan gray. The beds of limestone char limestones may form a less well developed acteristically are broken by very thin partings bench below the shell-rock shoulder. The Jet- of chalky shale. Iron-stained zones occur in more outcrops at many places in the general some of the thicker limestones. area of outcrop of the Greenhorn limestone. The interbedded seams of bentonite range 4. Pfeifer shale member of the Green from 0. 05 to 0. 65 foot in thickness. This ma horn limestone. --The Pfeifer shale member terial, white or light-gray where unweathered, is composed of alternating beds of chalky is present as orange or red-brown streaks on shale, which average 0. 5 foot in thickness; weathered outcrops. It is generally blocky but chalky limestones, which average 0. 2 foot in some seams are finely granular. thickness; and occasional thin seams of bentonite about 0. 1 foot in thickness. The beds Clam shells, fish scales, and shark of shale are platy and tan gray or orange gray teeth are numerous or abundant in some zones in the upper part of the member, and are of this member. The Hartland shale member thin-bedded and dark gray in the lower part. develops a poor outcrop expression. Most of Most of the upper beds weather gray orange its exposures are low on the walls of the deeper and the lower ones weather light gray. valleys in the eastern part of the county. The top of the member is defined as the The maximum thickness exposed in top of the "Fencepost" bed. This is a mas Mitchell County is 27 feet but a typical out sive layer of tan-gray limestone character crop shows only 10 or 12 feet of the total ized by a red-brown band of iron oxide ex thickness. tending through the middle part of the lime stone. The bed is 0. 6 foot thick. Its name in 90p. cit., p. 29. dicates the use that was made of this lime- stone in earlier years; at the present time it Feet is used as building stone. Limestone, chalky; soft; tan- gray; weathers light gray. ... 1.5 The other beds of limestone in the Shale, silty, calcareous; thin- Pfeifer shale member are chalky soft massive bedded; mottled tan-gray and and light gray or tan gray. Many of them are gray-orange; weathers tan marked by thin red-brown streaks of iron ox gray ...... 85 ide. Bentonite, red-brown and gray- orange ...... 65 Several thin seams of bentonite are in- Limestone, chalky; soft; light- terbedded with the shales of this member. gray; weathers tan gray; iron Despite their thinness, each one of them can stains on fracture surfaces ... .3 be traced over a wide area. The weathered Shale, silty, calcareous; thin- bentonite is white, but, as exposed in the face bedded; mottled gray-orange of an outcrop, it is a streak of gray orange or and red-brown; weathers red brown. light gray; iron stains on bedding planes. Clarn-shell Another persistent bed included in this fragments, fish scales, and member is the one known as the "sugar sand. " shark teeth ...... 2. 1 It is 0. 2 foot thick and occurs about 5feet be Limestone, chalky; tan-gray; low the base of the "Fencepost" bed. It is weathers light tan gray; composed of small grains of calcite and is occasional thin calcite gray orange. seams and iron stains. Clam-shell fragments, fish Fossilized clam shells are abundant in scales, and shark teeth .... 0. 3 the beds of limestone but are not so numerous Shale, silty, calcareous; thin- in the beds of shale. bedded; red-brown; weathers gray orange; iron-stained. The total thickness of the Pfeifer shale Clam-shell fragments and member in Mite hell County is 18 feet. Most fish scales ...... 45 of that thickness is exposed in many of the Shale, clayey, calcareous; blocky; outcrops of the member. This shale has a gray-orange; weathers gray . . .35 strong outcrop expression and is readily iden Shale, very silty, calcareous; tified by the "Fencepost" bed, which forms a massive; mottled tan and red- conspicuous angular shoulder at the top of the brown; weathers light gray; walls of many valleys; the shoulder is marked iron stains on fracture sur by crescent-shaped quarries which were faces. Clam-shell fragments opened wherever the over-burden was thin. and fish scales ...... 1.3 Bentonite; orange ...... 2 Representative Measured Sections Limestone; thin-bedded with shale partings; gray-orange; 1. The section of the lower part of the weathers gray. Clams Pfeifer shale member exhibits the full thick and fish scales ...... 2. 2 nesses of the Hartland shale and Lincoln Limestone, thin-bedded; light- limestone members. It was measuredin a road gray; weathers tan gray; cut in the SE^SE^ sec. 24, T. 8 S. , R. 6 W. , occasional small con as follows: cretions of iron oxide ..... 0.2 Feet Shale, silty, calcareous; platy; mottled light-gray and red- Soil: brown; weathers tan gray; occasional seams of calcite. Greenhorn limestone: Clam shells, fish scales, and Jetmore chalk member (0. 4 foot present) shark teeth ...... 1.4 Limestone, chalky; red-brown to Bentonite; orange ...... 03 tan-gray; weathers light red Shale, silty, calcareous; platy; brown; concretions of iron oxide in mottled light-gray and reddish- middle part; thin seams of brown; weathers tan gray; oc calcite. Clam shells, fish casional thin seams of calcite. scales, shark teeth, and oc Clam shells, fish scales and casional shellfish ...... 4 teeth .. t ...... 8 Hartland shale member (27. 18 feet thick) Bentonite; orange ...... 1 Bentonite; tan-gray ...... 2 Shale, silty, calcareous; platy; Shale, silty, calcareous; thin- mottled light-gray and bedded; tan-gray; weathers red-brown; weathers tan light gray; iron-oxide stains gray; occasional seams of on fracture surfaces. Clams, calcite. Clam shells, fish fish scales, and shark teeth ... 2.4 scales and teeth ...... 3.3 Shale, silty, calcareous; thin- Bentonite; orange ...... 0.2 bedded; red-brown; weathers Shale, silty, calcareous; platy; tan gray; iron-oxide stains mottled gray-orange and gray; on bedding planes. Fish scales weathers.tan gray. Clam and some clam-shell fragments . 2.65 shells, fish scales and teeth . . .3 Feet Feet Bentonite; mottled gray-orange Shale, silty, calcareous; thin- and brown...... 2 bedded; gray-brown; weathers Shale, silty, calcareous; platy; light gray. Fish scales...... 08 brown; weathers tan gray. Clam Limestone, crystalline; platy; shells, fish scales and teeth . . 1.0 hard; red-brown; weathers Bentonite; orange; thin lenses of tan gray. Fish scales and iron oxide ...... 15 shark teeth ...... 1 Shale, silty, calcareous; brown; Shale, silty, calcareous;.thin- weathers tan gray. Clam shells, bedded; reddish-brown; fish scales and teeth ...... 6 weathers tan gray; iron-oxide Limestone; thin-bedded; crystalline; concretions in middle part . . .4 beds separated by very thin Shale, clayey, calcareous; very shale partings; gray; weathers thin-bedded; gray-brown to tan gray. Clam shells, fish black; weathers tan gray; scales and teeth ...... 5 irregular thin lenses of hard, Shale, silty, calcareous; platy; crystalline gray-brown lime mottled gray-orange and light- stone. Fish scales...... 4.0 gray; weathers tan gray; oc Bentonite; mottled cream and casional very thin beds of gray red-brown ...... 3 crystalline limestone. Clam Shale, clayey, calcareous; thin- shells, fish scales and teeth. . . 1.3 bedded; dark-gray; weathers Bentonite; orange ...... 05 light gray; iron-oxide streaks Limestone, chalky; blocky; gray- throughout; small crystals of orange; weathers gray. Clam selenite along bedding planes . 4.9 shells, fish scales and teeth . . .1 Shale, very silty, calcareous; Bentonite; orange ...... 1 thin-bedded; red-brown; Shale, silty, calcareous; platy; weathers tan gray; thin seams occasional very thin partings of bentonite; crystals of of lime stone,v brown to reddish- selenite along fractures . . . 5.1 brown; weathers tan gray. Clam Shale, silty, calcareous; thin- shells, fish scales and teeth . . 1. 4 bedded; tan-gray; thin cal Lincoln limestone member (22.03 careous partings ...... 1.4 feet thick) Limestone, crystalline; Limestone, crystalline; gray- thin-bedded; thin partings of orange; weathers light gray. silty shale; red-brown; weathers Clam shells...... 6 tan gray. Clam shells, fish Shale, silty, calcareous; thin- scales and teeth ...... 1.0 bedded; gray-orange; weathers Limestone, crystalline; tan-gray; light gray; thin calcareous weathers gray. Clam shells, layers ...... 8 fish scales and teeth ...... 3 Limestone, crystalline; dark- Shale, silty, calcareous; platy; gray; weathers light gray. brown; weathers gray. Clam Abundant shark teeth...... 2 shells and fish scales ...... 2 Shale, silty, calcareous; thin- Bentonite; orange ...... 0. 05 bedded; gray-brown; weathers Limestone, chalky; thin-bedded; gray; interbedded very thin light-gray; weathers tan gray. layers of crystalline lime Fish scales ...... 15 stone ...... 0.7 Shale, silty, calcareous; platy; brown to black; weathers gray; occasional thin limestone Underlain by the Graneros shale. 2 seams ...... 3 Complete sections of the upper two members Shale, silty, calcareous; platy; of the Greenhorn limestone, the Pfeifer shale brown to dark-brown; weathers member and Jetmore chalk member, were tan gray; occasional thin measured in a road cut in the NW^NEj^sec. seams of calcite ...... 2 10, T. 7 S. , R. 8 W. : Bentonite; gray-orange ...... 2 Limestone, chalky; platy; very Feet soft; dark-gray and red-brown; weathers tan gray; occasional Greenhorn limestone: irregular carbonaceous seams. Pfeifer shale member (18. 18 feet thick) Clam shells, fish scales, and "Fencepost" limestone bed; shark teeth ...... 4 massive; light-gray with Shale, silty, ^calcareous; thin- red-brown streak through bedded; dark-gray and gray- middle; weathers tan gray. brown; weathers gray. Fish Occasional clam shells scales and shark teeth ...... 3 and rare shells of Bentonite; red-brown ...... 0.3 cephalopods ...... 0.6 Limestone, chalky; gray-brown; Shale, silty, calcareous; weathers tan gray. Fish platy; tan; weathers scales abundant ...... 05 dark gray. Clam shells .... .3 10 Feet Feet Shale, silty, calcareous; platy; Limestone, hard; light-gray; mottled light-gray and gray- weathers tan gray; lenticular; orange; weathers gray. A few thin seams of calcite throughout. clam shells ...... 0.2 Clam shells ...... 0.3 Shale, silty, calcareous; platy; Shale, silty,. calcareous; platy; gray-orange; weathers gray-orange; weathers light light gray orange. A few clam gray orange; thin seams of shells ...... 2 calcite throughout. Clam Bentonite; mottled-gray and gray- shells ...... 5 orange ...... 1 Limestone, hard; light-gray; Shale, silty, calcareous; platy; thin seams of calcite mottled gray-orange and scattered throughout. Clam light-gray; weathers light shells ...... 2 gray. Occasional clam shells . .6 Shale, silty, calcareous; platy; Limestone, soft; light-gray gray-orange; abundant seams of streaked with gray-orange; calcite. A few clam shells . . . .5 weathers gray; lenticular. Limestone, hard; gray; weathers Occasional clam shells .... .2 light gray; calcite seams; Shale, silty, calcareous; platy; lenticular. Clam shells . . . . .2 mottled gray-orange and light- Shale, silty, calcareous; platy; gray; weathers light gray gray-orange; abundant seams of orange. Occasional clam calcite. Clam shells ...... 6 shells ...... 1.4 Limestone, hard; light-gray. Limestone, hard; tan-gray; Clam shells ...... 02 weathers tan. A few clam Bentonite; mottled-gray and shells ...... 0.2 orange ...... 0.02 Shale, silty, calcareous; platy; Shale, silty, calcareous; platy; gray-orange with streaks of dark-gray; weathers gray. A light-gray; weathers light few clam shells ...... 2 gray orange ...... 9 Limestone; lenticular;, light-gray. Bentonite; gray-flecked with Abundant clam shells ...... 2 gray-orange ...... 01 Shale, silty, calcareous; platy; Shale, silty, calcareous; some dark-gray with streaks of gray- what blocky; light-gray with orange; weathers dark gray; streaks of gray-orange; seams of calcite. Abundant weathers light gray orange. clam shells ...... 4 Fish scales ...... 6 Limestone; lenticular; gray; Granular calcite; "sugar sand" weathers light gray; seams bed; mottled-cream and of calcite. Abundant clam yellow ...... 25 shells ...... 2 Shale, silty, calcareous; platy; Shale, silty, calcareous; platy; light-gray; weathers light dark-gray mottled with gray- orange. Fish scales and a orange; weathers gray. A few few clam shells ...... 2 clam shells ...... 3 Limestone, hard; red-brown with Limestone; irregular; light-gray. light-gray band at top and Abundant clam shells ...... 1 base. Clam shells ...... 3 Shale, silty, calcareous; soft; Shale, silty, calcareous; platy; thin-bedded; dark-gray mottled gray-orange; weathers gray. with gray-orange becoming blue A few clam shells ...... 0.1 black near base; weathers dark Bentonite; mottled-white and gray. A few clam shells .... 0.3 red-brown ...... 1 Limestone; irregular; tan; Shale, silty, calcareous; platy; weathers light gray. A few gray-orange; weathers light clam shells ...... 1 gray orange. Fish scales and Shale, silty, calcareous; soft; a few clam shells ...... 6 thin-bedded; blue-black; Limestone, hard; gray-orange; weathers light blue black. weathers light gray; lenticular. A few clam* shells ...... 2 Some clam shells ...... 3 Limestone; irregular; tan; Shale, silty, calcareous; platy; weathers light gray. A few , gray-orange; weathers light clam shells ...... '.. . 1 gray orange. Clam shells . . . 1.4 Shale, silty, calcareous; thin- Limestone, hard; light-gray; bedded; blue-black; weathers weathers tan gray; thin calcite light blue black. A few clam streaks throughout. shells ...... 7 Clam shells ...... 3 Limestone, hard; tan-gray; Shale, silty, calcareous; platy; weathers light gray; a few gray-orange. Clam seams of calcite. Abundant shells...... 5 clam shells ...... 2 11 Feet Feet Shale, silty, calcareous; platy; Limestone, hard; massive; gray; gray-brown. A few clam weathers light gray; ironstone shells ...... 0.6 concretions in middle part. Limestone; irregular; gray-orange Clam shells ...... 9 with irregular red-brown Shale, silty, calcareous; thin- streaks in middle part; bedded; blue-black; weathers weathers light gray orange. light blue black. A few clam A few clam shells ...... 1 shells ...... 8 Shale, silty, calcareous; platy; Limestone, hard; gray; weathers gray-brown. A few clam shells . . 5 light gray; ironstone concretions Limestone, hard; irregular; tan; in middle part. Clam shells . . 0.2 weathers tan gray; some seams Shale; silty, calcareous; thin- of calcite. Abundant clam bedded; blue-black; weathers shells ...... 1 light blue black. A few clam Shale, silty, calcareous; platy; shells ...... 8 gray-brown. A few clam Limestone, hard; dark-gray; shells ...... 7 weathers gray; somewhat Shale, silty, calcareous; thin- crystalline ...... 2 bedded; blue-black; weathers Shale, silty, calcareous; thin- light blue black. A few clam bedded; blue-black; weathers shells ...... 4 light blue black. A few clam Shale, silty, calcareous; platy; shells ...... 8 mottled tan-gray and gray- Limestone, hard; dark-gray; orange; weathers light gray weathers gray; irregular thin orange; calcite seams. Clam seams of calcite; iron-oxide shells, fish vertebrae ...... 9 stains on weathered surface. Jetmore chalk member (18. 20 feet thick) Clam shells ...... 3 "Shell-rock" limestone bed; Shale, silty, calcareous; thin- massive; hard; tan-gray. bedded; blue-black; weathers Great abundance of clam light blue black. A few clam shells ...... 1.1 shells ...... 1.9 Shale, silty, calcareous; platy; Limestone, soft; light gray; iron- light-gray mottled with some oxide concretions in middle gray-orange; weathers light part; hard crystals inside con gray orange. A few clam cretions; tendency to shatter shells ...... 1.2 and split. A few clam shells . . 0.4 Limestone, hard; irregular; Shale, silty, calcareous; thin- light-gray; weathers tan. A bedded; blue-black; weathers few clam shells ...... 1 light blue black; somewhat Shale, silty, calcareous; platy; jointed. A few clam shells ... .7 light-gray mottled with gray- Limestone, hard; gray; weathers orange; weathers light gray tan gray. A few clam shells . . .3 orange. A few clam shells ... .3 Shale, silty, calcareous; thin- Limestone, hard; irregular; tan- bedded; blue-black; weathers gray; numerous seams of light blue black. A few clam calcite. Clam shells ...... 2 shells ...... 7 Shale, silty, calcareous; platy; Limestone; irregular; blue-gray; mottled light-gray and gray- weathers light blue gray. A orange; weathers light gray few clam shells ...... 2 orange; numerous seams of cal Shale, silty, calcareous; thin- cite. Abundant clam shells . . .9 bedded; blue-black; weathers Limestone, hard; gray; weathers light blue black; somewhat tan gray; irregular thin seams jointed. A few clam shells ... 1.0 of calcite. Abundant clam Limestone, hard, light-gray; shells ...... 0.3 iron-oxide concretions in Shale, silty, calcareous; platy; middle part. A few clam gray-orange with blue-black shells ...... 0. 3 layer near top; weathers Shale, silty, calcareous; thin- light gray orange; abundant bedded, blue-black; weathers irregular seams of calcite. light blue black. A few clam' Clam shells ...... 9 shells ...... 1.0 Limestone, hard; light-gray. Limestone, hard; mottled gray Abundant clam shells ...... 3 and gray-orange; weathers Shale, silty, calcareous; platy; tan gray. A few clam shells . . .2 gray-orange with blue-black Shale, silty, calcareous; thin- zone in middle part; weathers bedded; blue-black; weathers light gray orange; thin seams light blue black. A few clam of calcite. Clamshells .... .9 shells ...... 9 12 Feet chalky shale member is very similar to the Pfeifer shale member of the Greenhorn lime Limestone, hard; mottled-gray and stone from which it is arbitrarily separated by gray-orange; weathers light the "Fencepost" limestone bed. This basal gray; iron-oxide conretions and member of the Carlile shale consists of inter- stains in middle part; tends to bedded shales, limestones, and occasional thin split near middle. A few clam seams of bentonite. The shales are chalky and shells ...... 4 thin-bedded for the most part but are very Underlain by Hartland shale member. thin-bedded in some zones and blocky in others. They are tan gray and weather cream. Many of Thickness the fracture and bedding planes are stained red brown by iron oxide. The beds of shale are The total thickness of the Greenhorn usually slightly more than a foot thick. limestone in Mitchell County is about 81 feet The limestones in the Fairport member are and is distributed among the four members as chalky and soft. They occur in massive beds, follows: Lincoln limestone member 22 feet; some of which weather platy. Their color is Hartland shale member 27 feet; Jetmore cream in fresh exposures, and buff in weathered chalk member, 18 feet; and Pfeifer shale mem exposures. Many of the beds, as those in the ber 18 feet. The entire formation does not Pfeifer shale member of the Greenhorn lime crop out at any one place in the county but a stone, are marked by reddish-brown streaks of number of exposures of about half of the for iron oxide. The limestones in the lower part of mation were noted. Surface slopes developed the member tend to be nodular and average in outcrops of the Greenhorn limestone range from 2 to 12 percent or more, and are usually 0. 3 foot in thickness. from 7 to 12 percent. Only occasional thin seams of bentonite are included in the Fairport chalky shale member. Construction Materials They are usually from 0. 05 to 0. 02 foot thick, and appear as red-brown or gray-orange streaks Materials from the Greenhorn lime in (the face of) a weathered outcrop. stone in Mitchell County are used as: road metal, structural stone, riprap, calcareous Clam shells are numerous in both shale binder, and fill material. and limestone. A section of the Fairport chalky shale member measured by Landes 10/ in the Car 111 e Shale eastern part of Osborne County indicates that Areal Distribution it is about 100 feet thick. The only conspicuous outcrops of this member are those of its basal The Carlile shale, the third Cretaceous part which are frequently associated with outcrops formation of marine origin, is exposed in of the underlying Pfeifer shale member. The only a few places in the eastern part of the upper part of the Fairport chalky shale member county, but crops out widely in the western is largely masked by the younger Sanborn part. (See pi. 1 and fig. 4.) The easternmost formation. Surface slopes developed in the exposures are those at the top of the valley basal part of this member are generally from walls of some of the streams tributary to the 7 to 12 percent or more; those of the upper Solomon River near Beloit. The outcrops become part generally range from 2 to 5 percent. more numerous and more extensive in the west ern part of the watershed of the Solomon River. 2. Blue Hill shale member of the Carlile The Carlile is well exposed in the watershed of shale. --The Blue Hill is a noncalcareous clay Salt Creek in the south-central part of the coun shale (although some silty zones are included ty. However, its outcrops are most extensive in its upper part) and is black or dark blue and most numerous in the area of the Blue Hills gray. The silty zones contain numerous lime- southeast of Tipton. The Carlile shale underlies cemented concretions some of which are as many of the interstream areas in the western much as 8 feet in diameter. The clay shales, two-thirds of the county but is concealed beneath which predominate in the member, are very the younger Sanborn formation and, in the Blue thin bedded; the silt shales, however, tend to Hills area, beneath the Fort Hays limestone be platy. Iron-oxide stains are found along member of the Niobrara formation. The forma many of the fracture surfaces. tion dips at a low angle toward the northwest, as do all of the formations of Cretaceous age. Several zones of spheroidal concretions (septaria), averaging from 1 to 3 feet in di General Description ameter, are included in the clayey middle and lower parts of the Blue Hill shale member. The Carlile shale is shown on plate 1 as a They are formed by the intersection of single map unit (Kc) but the description of this radiating veins and concretric shells of cal formation will be based on the members of cium carbonate. Frequently they develop which it is composed. These are, in upward around the coiled shell of a cephalopod. order, the Fairport chalky shale member, Blue Hills shale member, and Codell sandstone Numerous zones of selenite crystals are member. included in the Blue Hill member and, upon weathering and erosion of their shale matrix, 1. Fairport chalky shale member of the Carlile shale. --The lower part of the Fairport . clt., pp. 21-23. 13 reflect sunlight in a manner that gives a hill Feet side a sparkling appearance. The crystals average about 2 inches long but may be as Shale, silty, calcareous; thin- much as 5 or 6 inches long. bedded to blocky in middle part; tan-gray; weathers The total thickness of the Blue Hill cream; iron-oxide stains shale member is about 200 feet and the along fracture planes. Clam greater part of that thickness is exposed on shells fairly abundant . . . . . 1.4 the sides of the Blue Hills. This member Limestone, chalky, soft; massive; has a bold outcrop expression and, in some cream, weathers buff; nodular. of the more extensive outcrop areas, small Fragments of clam shells . . . .2 streams have eroded the soft clay shale to Shale, silty, calcareous; thin- produce a badland-type of topography. The bedded; tan-gray; weathers surface slopes of outcrops are steepest cream. Fragments of clam (more than 12 percent) in the area of the Blue shells ...... 0.6 Hills and usually range from 7 to 12 percent elsewhere in the county. Total thickness present (underlain by Pfeifer shale member of the Green 3. Codell sandstone member of the horn limestone) ...... 4. 5 Carlile shale. --The Codell sandstone mem ber, although generally very thin, can almost 2. The following section is representative always be identified at the contact of the of the Codell sandstone and Blue Hill shale mem Carlile shale and the overlying Fort Hays bers of the Carlile shale. It was measured in a limestone member of the Niobrara formation. cut bank along a tributary of Carr Creek in the The thickness of the Codell varies (greatly) sec. 34, T. 8 S. , R. 10 W. : within short distances. Landes ll/ reports that it is 42 inches thick at the north end of Feet the Blue Hills; in other places in the county, however, it is less than a foot and its average Fort Hays limestone member of the is probably about 2 feet. The Codell is a fine Niobrara formation: ...... 35- grained sandstone or siltstone and contains a moderately high percentage of clay. It is Carlile shale: usually yellow brown, but some exposures more heavily stained with iron oxide are red Codell sandstone member (0. 5 foot thick) brown. Sandstone, fine-grained; gray and reddish-brown; weathers reddish Representative Measured Sections brown ...... 5 Blue Hill shale member (23- feet exposed) 1. The outcrop of the basal part of the Shale, clayey but some interbedded Fairport chalky shale member was meas silty zones; noncalcareous; ured in a road cut in the NW^SW^sec. 21, T. 7 thin-bedded to very thin-bedded; S. , R. 7 W. as follows: dark blue-gray; weathers light blue gray; numerous cal Feet careous concretions; veins of calcium carbonate in some Sanborn formation: Gray-brown silt; abun fractures; fracture surfaces dant lime nodules in lower part .... 7* commonly iron-stained .... 23t Fairport chalky shale member of the Base covered. Carlile shale: Thickness Limestone, chalky, soft; massive; weathers platy; tan-gray with The total thickness of the Carlile shale light-brown streak near middle; is about 302 feet. The average thicknesses of weathers buff; case-hardened. its members are: Fairport chalky shale Clam shells ...... 3 member, 100 feet; Blue Hill shale member, Bentonite; flaky; mottled orange 200 feet; and Codell sandstone member, 2 tan and buff ...... 0.3 feet. The thickest and most conspicuous Shale, clayey silt, highly cal outcrops are those of thr Blue Hill. careous; thin- to very thin- bedded; tan; weathers Construction Materials cream; iron-oxide stains along bedding and fracture Construction materials from'the Car planes. Fragments of clam lile shale in Mitchell County are road metal shells ...... 1.5 and fill material. Limestone, semicrystalline; soft; massive; light tan-gray with Niobrara Formation light-brown streak through middle part; weathers buff; Areal Distribution nodular. Clam shells . ( . . . 2 The uppermost formation of Cretaceous Hop. cit.. p. 19. age exposed in Mitchell County, the Niobrara, 14 , j .mCjrnbers, the Fqs^t Hays , Feet "lime stone '"member (the lower member) and,. -.1-.' .'-, the Smoky Hill chalk member (the ui per mem- " Limestpn^:r~T >~'^"T^j~ ~ "~' ^^" "i * * "'~ I"* 7Y~r * ^""vT", """^"^i 1-^- ^r - ' "- b.e.r^.^See |ig^ 4. }, However, pnljf. the Fort Hays ." ,Iying beds' pf jUimestpne tar,e.. s.,cpu|ity,,.and only, in the area ' / simUa^to;^® lj^i>--- tl>Jl ''rm3^e cap 1.2 ^ pi, 1,) IShale; tins a.iyi.tjhe. under-',!,1" ...._ the', higher "', tying fee^s'o| atwU'er are...r , r, - ; ... e.- w^sternm.0st1pajrt qf the county, -yjj-r.l -i ' x- -j.t - L - J-Q]{ sW^B ;' ? i bu, *if so, is concealed beneath the younger. .1 Sanborn formation. 2,4 Shale .1 ^ Limestone ,, ,., . .*..*. ., ,r .. .-, 2.3 'Shale . . .' '...... 1 of Jhe Limestone ...... 1.8 ^ ; .ijif thick layers of, Shale ....-.;;;..,*, ... ..--,?. ..,.-: .v . 1 chalky limestone separated by thin parting^ , s Ljimeatonpr L. ^ r. -*,-*.,« ,.j,, ;j V.,'£, ; i 1.4 of chalky shale. The beds of limestone are .'. t$^ale.;'! ,, i; ^^,.-;,,_.',, «, : .t,,r,«';,. ,3 massive althou^h.sopne of thein* b,ecoiji?.platy , .3 when weathered. -The Tock-is usually crream- colpr^d jii|4,;^ea^ie^s. to.spi?ie shade. of .gray. he,il,»j oJT^^^,\ftn^Cjoy ster s a r e f pund rin ,it , _ . fut'not,iji t^e,ltfeundaia,c,e.thgit.liiey pccur. in ttie unde.rly.pg jf.gr J^tions, .of Cretaceous age .- The i aver age 2. 5 feet in thickr : The partings of shale are only about 0. 1 foot thick. The shale has a tendency to b« platy, is always chalky, and its color is'usu- qr, Hays limestone member typiAajly. wjeatheaj me chanically to produce a "shattered" zone. The th« shattered fragments of liinestoae are 5 or 6 o^-t H%ysilim«s tone j estimated to be inches long, angular, and irregularly disc about 50 feet. ' mate.?ials-. '^- t s . Out4rjops,of tiMr FiajstHay* limestone mem f f orn Itm^ stone1 *aem- ber form bold escarpments generally -from- 35; ' to 40 feet high. The total thickness of the mem ber is estimated,KOB.th«--t>asiB of a topographic and. fill tnaterialJ i map published by i^e United States Geological Survey, to be about 50 feet. . ." , f ttf- .= : ! v-.;> -- -J.i; .. -.--.r. /I.'.'-!' .. SagbprAdFpr-ynajtiOjia. > Representative Measured Sectijon ' i !;: :i >>-E,-t^ ^,'i i.. -v - ' i ; - -: - : .Tike .foliowi*g sefction.; of tftes Fort-Hays limestone member; of-the NiobPara formation i£ v -- i'ln MUchell Couirty, 6h" plate* 15, General Description some deposited by the wind, and colluvium moved down the valley wall through the action of The Sanborn formation is composed of mantle creep. materials deposited by wind (loess), streams, slopewash, and through the action of gravity A phenomenon known as "catstep" erosion is (colluvium). Although the formation is sub displayed on the steeper slopes of the Sanborn divided into members in Nebraska and in some formation. The catsteps are slump blocks that parts of Kansas, this practice was not followed moved down the slope by gravity when saturated in Mitchell County inasmuch as the materials with water. The blocks are formed by scarps characteristics of the two or more members from 1 foot to 3 feet high, and the blocks are recognized in the county are essentially simi usually from 15 to 20 feet wide. lar. The treatment of the Sanborn formation as arK undivided unit seems adequate to serve Surface slopes in the valley phase of the the purpose of this inventory of construction formation range from 2 to 5 percent for the materials. most part. Those in the upland phases are as great as 2 percent in broad interstream areas Although brown in some places, gray is and range from 2 to 5 percent in narrow inter- the prevailing color in th« Sanborn formation. stream areas. The "A" horizon of the soil profile is darker than the underlying horizons and is brown, Representative Measured Section dark brown, or black. Buried ap.il zones occur in a few places in the county. The Sanborn formation, as usually ex posed in this county, is so homogeneous that no The Sanborn formation is composed pre section of it was measured. In almost all dominantly of silt-size particles. The weather places it is a gray or gray-brown silt, clayey ing of the silt in the upper part of the formation and noncalcareous in its upper part, and heavily has broken the particles down to clay size; impregnated with secondary calcium carbonate thus the upper part of the formation is a in its tower part. clayey silt and the lower part is largely com posed of silt. Leaching of calcium carbonate Thickness from the upper horizons of the soil profile, through the action of downward-percolating The thickness of the Sanborn formation subsurface water, causes this part of the for ranges from a feather edge to a maximum of mation to be noncalcareous. The calcium car approximately 30 feet on the crests of some of bonate has been re-deposited in the lower the interstream areas. horizons of the profile either in a disseminated stain or as calcareous pipes, concretions, and Construction Materials nodules. Construction materials from the Sanborn A granitic gravelly sand composed pre formation in Mitchell County are: Aggregate dominantly of sand-size particles of quartz and for concrete, road metal, mineral filler, and feldspar occurs in the basal part of the forma fill material. tion just above the wall of the valley of the Solomon River. Exposures of the sand are in Terrace Deposits frequent and of small extent. They are best along the south side of the valley because most Areal Distribution of the recent erosive activity of the Solomon River has been directed against the south valley- Terrace deposits of Quaternary age are wall and has removed the valley phase of the conspicuous in the valleys of the principal Sanborn formation which masks the deposits of streams in Mitchell County. (See pi. 1 and gravelly sand along the north side of the valley. fig. 4.) Narrow extensions of the terraces ex The largest deposit is cited in table 1 as sample tend into the valleys of the larger tributary fa 1. streams. The most extensive terrace is that of the Solomon River which ranges in width Where the Sanborn formation rests on the from about a mile, in the western part of the Carlile shale at the base of the escarpment county, to almost 4 miles in the eastern part. formed by the Fort Hays limestone member of The terrace in the valley of Salt Creek is the Niobrara formation, its lower part is a also prominant but its average width is limestone gravel. The gravel-size particles are only 0. 75 mile. The terraces along smaller fragments of the Fort Hays. That they show streams average less than 0. 5 mile wide. The little rounding indicates that they have not been surface slope of a terrace deposit is less transported very far from the bed of limestone than 2 percent. from which they were derived. The deposits of limestone gravel contain a heavy intermixture General Description of silt-size particles. The terrace sediments are composed The upland phase of the Sanborn formation predominantly of tan to light-brown silt-size was deposited by wind, for the most part, and particles intermixed with clay in the upper is therefore classified as loess. The valley part of a deposit and interbedded with lenses phase may represent the dissected remnant of of gravel in the lower part. Most of the clay- an old high-level stream terrace, but it also in size fraction is probably derived through the cludes some material deposited by slopewash, weathering of silt in the process of soil 16 development. A dark brown or black "A" hori- the most recent geologic formation in the coun velopment. A dark brown or black "A" hori ty and are being laid down by present-day zon is always present at the top of a deposit streams. Alluvium is defined in this report as and one or more buried "A" horizons may the material which underlies the present flood- occur within the deposit. The particles of plain of a stream. The floodplain is the area ad gravel usually wellrounded, are interbedded jacent to the stream channel that is covered by as lenses in the lower part of a deposit and water during normal flood stage; its surface are fragments of the Dakota sandstone, slope is less than 2 percent. The terrace de Greenhorn limestone, and Fort Hays lime posits are composed of alluvium laid down by stone member of the Niobrara formation. these same streams flowing at higher levels in earlier geologic time. Crude columnar structure is exhibited in most of the cut banks eroded into this Alluvium is mapped only along the Solomon formation. The faces of the cuts stand nearly River. Deposits of it are also present in the val vertically. Whereas the upper part of a de leys of Salt Creek and some of the larger tribu posit is noncalcarcous, the lime leached from tary streams but could not be shown because it has been redeposited in the lower part in the map is on too small a scale. The alluvium in the form of nodules and pipe-like concretions, the valley of the Solomon River averages 0. 3 and as a disseminated impregnation. mile in width. Representative Measured Section General Description This section of a terrace deposit was The alluvium of the Solomon River is com measured in a road cut on the south side of posed of clay and silt and interbedded lenses of the Solomon River in the SE&SWj- sec. 32, T. local gravel and gravelly sand. Gravel bars are 7 S., R. 6 W. : quite numerous in the channel of the Solomon River, as in the channels of other -streams in the Feet county. The particles of gravel are fragments of the Cretaceous formations which crop out in the Soil: Silty clay; black 1.7 watershed of the stream. They include water- Terrace deposit: worn fragments of the Fort Hays limestone member of the Niobrara formation, concre Silt, somewhat clayey, noncal- tions and clay balls eroded from the Carlile careous; dark-brown ...... 1.3 shale r the limestones in the Greenhorn lime Silt; blocky; light-brown; abundant stone, and the Dakota sandstone that is along thin streaks of calcium carbonate the Solomon River in the eastern part of the and some small pipe-like con county and along Salt Creek in the south-cen cretions of the same material; tral part. stands in vertical bank and ex hibits crude columnar structure . . 4. 3 Representative Measured Section Silt; somewhat blocky; tan; small lens of local gravel in middle The alluvium shows so little relief that part; numerous small nodules a representative section could not be meas of calcium carbonate; stands ured. in vertical bank and exhibits crude columnar structure .... 4* Thickness Total thickness exposed (base covered) 9. 6- The alluvial deposits are undoubtedly thickest along the Solomon River and are es Thickness timated to be about 30 feet thick. Similar deposits along other streams are thought to The terrace along the Solomon River be no more than 20 feet thick. stands from 25 to 30 feet above the level of the river. The heights of other terraces in the Construction Materials county are 20 feet or less above stream level. In the absence of test-hole data, it was impos Construction materials from alluvium in sible to determine the full thickness of the ter Mitchell County are: Aggregate for concrete, race deposits. road metal, and fill material. Construction Materials INVENTORY OF CONSTRUCTION MATERIALS Construction materials from terrace de General posits in Mitchell County are mineral filler and fill material. The objectives of this inventory of con struction materials in Mi'tchell County are to Alluvium define the construction materials as they are classified in this report and to relate the ma Areal Distribution terials to the map units in which they occur. The deposits formed by streams in their Whenever available, laboratory-test present gradational cycles are mapped as al data have been introduced into the report to luvium. (See pi. 1 and fig. 4.) They constitute aid the reader in his evaluation of the materi- 17 als. The information given in table 1 is based 1. Sanborn formation. One sample of on standard testing procedures of the Ameri fine aggregate (fa 1) was obtained from the can Association of State Highway Officials 12/ Sanborn formation. (See table 1.) The material and the State Highway Commission of Kan is a fine-grained sand composed largely of sas. 13/ It is expected that prospects listed quartz, subordinately of particles of feldspar, in this report will be proved by subsequent and occasional particles of opal and chalcedony. augering, drilling, or test pitting and that the Opal and chalcedony are not present in injurious materials themselves will be subjected to amounts. The material contains only a moderate laboratory testing prior to production for spe amount of wash, it is clear in the colorimeter cific uses. test, but its compressive strength ratio after 3 days is 0. 83. The deposit from which this ma Although numerous prospect pits and terial was sampled is in the basal part of the quarries were located in the field, no attempt Sanborn formation just above the south wall of was made to complete an exhaustive survey of the valley of the Solomon River. Other similar all possible sources. If the construction materi deposits are undoubtedly along the south side of als that are available in Mitchell County can be the river. related to the geologic formations mapped on plate 1, then the use of that map will aid the 2t Alluvium. Five samples (ma 1, ma 2, field man in his search for the materials needed ma 3, ma 4, and ma 5) were collected from the in a construction project. It will eliminate the alluvium of the Solomon River by the State non-productive areas from the search and, at Highway Commission in a State-wide .sampling the same time, will indicate the areas in which program carried out in 1932. The samples were the needed materials are most likely to occur. obtained from gravel bars in the stream bed. The gravel-size particles are fragments of Aggregate For Concrete limestones cropping out in the watershed of the Solomon River; the band-size particles are Engineering and GeoloRJc Characteristics predominantly fragments of quartz and feld Aggregate for concrete is classified as spar. The gradation factor of the samples fine aggregate and mixed aggregate in table 1 ranges from a minimum of 3. 08 to a maximum and on plate 1. In this report the distinction is of 3. 84; the amount of wash ranges from 1 to an arbitrary one based on the percentage of 3 percent. The colorimeter test shows that material retained on a standard No. 4 sieve. there is a small to moderate amount of or The portion of a sample retained on that sieve ganic material intermixed with the alluvium. is designated as the coarse fraction. The ma Compressive-strength ratios are all above terial is classified as a mixed aggregate if the unity, and the loss through wear is uniformly coarse fraction is 5 percent or more by weight 3 percent. of the whole sample, and as a fine aggregate if the coarse fraction is less than 5 percent. Fine The alluvium of the Solomon River is the and mixed aggregate will be considered to most important source of aggregate for con gether because of the standard practice of crete in the county. The alluvial deposits of bringing the grading to specifications by sweet other streams are composed predominantly of ening or screening. silt-size particles. Lenses of gravel and sandy gravel are included in the terrace de The materials reported in this and other posits but lie at such depths below the surface classifications are exposed at the surface or are that they cannot be developed economically. under unconsolidated overburden sufficiently thin that they may be economically developed. Road Metal Because of the added expense in the removal of the overburden, deposits of sand and gravel Engineering and Geologic Characteristics overlain by thick or consolidated beds usually are not included, nor are relatively inacces Road metal, known also as surfacing sible deposits. material, crushed stone, and aggregate is defined in this report as any material that Stratigraphic Sources and Performance Char may be applied to a road to improve the per acteristics formance characteristics of that road. The following materials are available in Mitchell Two of the geologic formations mapped on County for use as road metal. plate 1 are actual or potential sources of aggre gate for concrete. They are the Sanborn forma 1. Aggregate for concrete. (Table 1). tion and alluvium. 12 The American Association of State Highway Officials, 2. Indurated rocks. Indurated rocks Standard specifications for highway materials and methods available in Mitchell County for use as road of sampling and testing, pt. 2, 5th ed., 1947. Absorption, metal are (a) chalky limestone, a compact, PP. 251-252, Compressive strength, pp. 257-258, Deval massive layer of calcareous material ranging abrasion, pp. 235-236. Liquid limit, pp. 198-201. Los from soft to moderately hard; (b) shale, a Angeles abrasion, pp. 237-239, Plasticity index, pp. 202- very thin-bedded to massive layer composed 204. Specific gravity, pp. 249-250, Toughness, pp. 240- 241. Weight per cubic foot, pp. 253-254. of clay- or silt-size particles, or both; (c) 13 State Highway Connission of Kansas, Standard speci sandstone, a layered rock composed of sand- fications for State road and bridge construction, 1945. size particles of quartz cemented by pore- Gradation factor, p. 16, Sieve analysis, pp. 333-334, space deposits of calcium carbonate, silica, Soundness, pp. 335-336. iron oxide, clay, or varying combinations of these. The materials included here under in the interbedded shales and limestones below the durated rocks are listed in table 1 and mapped "Fencepost11 bed were submitted for laboratory on plate 1 under the more specific designation testing. The test data shown in table 1 indicate of limestone, shale, and sandstone, because that the "Fencepost11 limestone bed is acceptable in addition to their use as road metal two of for use in the construction of roads of the traffic - them, limestone and sandstone, may be used bound macadam type; however, because the bed as structural stone and riprap. is so thin, a sufficient quantity of rock for this use probably could not be produced. The inter- 3. Limestone gravel. A deposit com bedded shales and limestones below the "Fence- posed of subangular to rounded gravel-size post" bed are used in north-central Kansas in the fragments of limestone in a matrix of silt-size construction of stabilized roads. This member of particles is here classified as limestone grav the Greenhorn limestone crops out extensively in el. the areas mapped as Kg on plate 1. Stratigraphic Sources and Performance Char (c) Carlile shale. --One sample (sh 3) of acteristics the Fair port chalky shale member was submitted to the Road Materials Laboratory but no tests 1. Sources of aggregate for concrete. The were performed on it because it slakes quickly materials listed in the section on aggregate when immersed in water. The basal part of this for concrete have been used in Mitchell County member is similar lithologically to the Pfeifer as road metal on light-traffic roads or as shale member of the Greenhorn limestone, and base-course material in roads of the concrete is probably acceptable for the same use in or black-top type of construction. Their sources road stabilization. and performance characteristics have been dis cussed under Aggregate for concrete. (d) Niobrara formation. -- The Fort Hays limestone member (see Is 3 in table 1) is 2. Indurated rocks. utilized throughout north-central Kansas as a source-of rock'for the construction of traffic- (a) Dakota sandstone. -- Three samples of bound macadam. The "shattered" zone in this the Dakota sandstone (ss 1, ss 2, and ss 3) were member can be removed with a blade but the collected and submitted to the Road Materials massive ledges must be quarried. Roads con Laboratory of the State Highway Commission structed of this material give good perfor for testing. However, two of them (ss 1 and ss 2) mance in wet weather but have a tendency to slaked so quickly under water that no tests were "dust" seriously in prolonged dry weather. performed. The one sample on which tests were completed (ss 3) shows an abrasion loss of 96. 2 3. Sanborn formation. --Numerous percent and a soundness ratio of 0. 77. So far as samples (see table 1) of limestone gravel were is known, all of the sandstone ledges in the collected from the Sanborn formation. Where Dakota exposed in this county are composed of used as a road metal, the particles of silt poorly cemented sand grains and are therefore size serve as a binder for the gravel-size easily pulverized. Similar rock has been quar particles of local limestone. This material is ried in other counties in Kansas and, because it used extensively as metal on light-traffic usually pulverizes during the quarrying opera roads in north-central Kansas. tion, it has been used as loose road metal on light-traffic roads and as base-course material. Mineral Filler Large quantities of this material are present in the areas mapped on plate 1. Engineering and Geologic Characteristics (b) Greenhorn limestone. -- A combined Material composed predominantly of sample (sh 2) of the Lincoln limestone and silt-size mineral particles (50 percent or Hartland shale members of the Greenhorn lime more of the material passing the No. 200 stone was submitted to the testing laboratory as sieve) is classified in this report as mineral material potentially useful in road stabilization. filler. It has no more than a trace of sticks Although the results of the test shown in table 1 or organic debris,- but may contain minor do not include the plasticity index of the materi amounts of fine sand or clay. W. E. Gib son al, that index is probably moderately high be of the Road Materials Laboratory of the State cause of the content of clay in these two members Highway Commission of Kansas states (oral of the Greenhorn limestone. communication) that material will qualify for mineral filler only if laboratory tests in Three samples of the Jetmore chalk mem dicate a low coefficient of cementation. ber were submitted for testing. -- Two (Is 4 and Is 5) were collected from the "shell-rock" bed Stratigraphic Sources and Performance and the third (Is 1) was collected from the in Characteristics ter bedded limestones and shales below the "shell-rock11 bedr. Successful use of this and Two Stratigraphic units were sampled as similar material in the construction of a light possible sources of material to be used as type of traffic-bound macadam has been observed mineral filler; these are: the Sanborn forma on many roads in north-central Kansas. tion and terrace deposits. From the Pfeifer shale member of the 1. Sanborn formation. --One sample Greenhorn limestone one sample (Is 2) of the (mf 4) of the Sanborn formation was tested for "Fencepost11 limestone bed and another (sh 1) of use as mineral filler. The test data show that its cementation factor is excessive, undoubt Kansas. Inspection reveals that this rock is not edly because of a too-heavy intermixture of acceptable for this use inasmuch as it disinte clay. The deeper zones in the formation con grates within a short time. Its low specific tain much less clay and would be productive of gravity and soundness ratio and its high absorp acceptable mineral filler in those places tion percentage (see Is 3 in table 1) are ade where erosion has removed the surficial zone quate reasons to explain the failure of the rock. of clayey silt. Structural Stone 2. Terrace deposits. --Of the three samples of potential mineral filler obtained Engineering and geologic characteris from terrace deposits (see table 1), only one tics. Structural stone, as defined in this re (mf 3) had a coefficient of cementation within port, is any hard, dense, rock material that acceptable limits. This sample was obtained can be qurraied and produced to desired size and by augering and does not include the upper, shape. Materials fulfilling these requirements weathered part of a deposit in which the per occur in the Greenhorn limestone and the Nio centage of clay is highest. Presumably, if brara formation in Mitchell County. the upper horizons of the soil profile were stripped away from the Sanborn formation and Stratigraphic sources and performance terrace deposits, the material exposed would characteristics. 1. Greenhorn limestone. Two contain only a negligible percent of clay-size limestone beds in the Greenhorn limestone are particles and thus would have a coefficient of used in this and adjacent areas as structural cementation within acceptable limits. stone. The shell-rock limestone bed at the top of the Jetmore chalk member has been Riprap used to a limited extent as structural stone. Although acceptable for this use, its ap Engineering and Geologic characteris pearance is not altogether pleasing. The tics. Riprap, as defined in this report, is any "Fencepost" limestone bed, which marks the material suitable for protecting- earthen fills top of the Pfeifer shale member, is the source from erosion. To be acceptable for this use the of most of the structural stone used in Mit material must be relatively sound and free from chell County. The stone has adequate bearing cracks and other structural defects or impuri strength, withstands weathering well, and has ties that would cause it to disintegrate through a very pleasing appearance. Many farm abrasion, slaking, or freeze-and-thaw. It is homes and other farm buildings, city resi desirable that the material be in blocks having dences, business houses, and municipal build approximately rectangular faces 7 inches or ings have been constructed of it. more in width and that the specific gravity be 2 or higher. 2. Niobrara formation. Limited use of stone from the Fort Hays limestone member Stratigraphic sources and performance in the construction of farm buildings was ob characteristics. Three of the geologic forma served in this county. Although the rock is tions cropping out in Mitchell County are actual easily produced to desired size and shape, it or potential sources of rock for use as riprap: weathers fairly rapidly and, where used close (1) Dakota sandstone, (2) Greenhorn limestone, to the ground and thus subject to excessive and (3) the Niobrara formation (Fort Hays moisture, it disintegrates rapidly through limestone member). slaking and the process of freeze-and-thaw. 1. Dakota sandstone. The sandstone of the Calcareous Binder Dakota firmly cemented by pore-space deposits of silica (quartzite) or calcium carbonate Engineering and geologic characteris (quartzose sandstone) is acceptable, on the tics. To be classified as calcareous binder basis of field observation in other counties, for the material must be composed essentially of use as riprap. However, no ledges so cemented calcium carbonate and must be soft and easily were found in Mitchell County. An intensive pulverized. Two of the geologic formations search of the area of outcrop of the Dakota mapped on plate 1 are sources or potential sandstone mapped on plate 1 would possibly re sources of calcareous binder: (1) Greenhorn veal one or more such ledges not discovered in limestone and (2) the Niobrara formation. this investigation. Stratigraphic sources and performance 2. Greenhorn limestone. Use of the characteristics. 1. Greenhorn limestone. "shell-rock" limestone bed of the Jetmore chalk The inter bedded chalky limestones and chalky member and the "Fencepost" limestone bed of shales of the Jetmore chalk and Pfeifer shale the Pfeifer shale member as riprap has been members of the Greenhorn limestone appear observed on a number of small dams in north- to be acceptable for use as calcareous binder. central Kansas. Although the test data shown in The rock is highly calcareous and, for the table 1 indicate that neither of these is highly most part, is soft and relatively easy to pul desirable in this use, field observation reveals verize. that they perform acceptably when used to pro tect small structures. 2. Niobrara formation. The Fort Hays limestone member has been accepted by the 3. Niobrara formation. Blocks of the Fort State Highway Commission of Kansas as a Hays limestone member have been used as potential source of material suitable for use riprap on several small dams in north-central as calcareous binder. The beds of chalky limestone are soft, easily pulverized, and 2. Coarse-granular sediments. A very free from deleterious substances. However, small quantity of sand and gravel is available this source of calcareous binder is available for use in the construction of subgrades and em only in the Blue Hills area in the southwest bankments. The two sources are the basal part part of the county, whereas far greater of the Sanborn formation and the alluvium of the quantities of binder may be obtained from the Solomon River. It is possible that the more ex much more extensive outcrops of the Jetmore tensive deposits of limestone gravel which occur chalk and Pfeifer shale members of the in the basal part of the Sanborn formation might Greenhorn limestone. (See pi. 1.) also prove acceptable for this use. Subgrade and Embankment Material 3. Broken or crushed rock. The forma tions of Cretaceous age are the only potential or Engineering and geologic characteris actual sources of broken or crushed rock in tics. --This definition of subgrade and em- Mitchell County. bankment material is adapted from the speci fications compiled for the American Dakota sandstone. The beds of sandstone Association of State Highway Officials. 14/ in this formation are easily pulverized and Suitable geologic materials shown as "fill mate might produce material acceptable for some rial" in fig. 4 and in sections on outcropping types of subgrades or embankments. stratigraphic units) for this kind of construction are (1) Fine-granular unconsolidated sediments, Graneros shale. The bentonitic clay shales including soil, of which 50 percent or more pass of the Graneros exhibit such low bearing strength through a No. ZOO sieve; (2) coarse-granular that it is doubtful that they would be acceptable unconsolidated sediments and broken or crushed for use in the construction of a subgrade or em consolidated rocks, of which at least 65 percent bankment. by weight is retained on a No. 200 sieve; (3) broken or crushed rock. Greenhorn limestone. The bearing strength of material obtained from the Lincoln Stratigraphic sources and performance limestone and Hartland shale members of characteristics. All of the materials listed this formation probably is low; the strength of above are available in Mitchell County for the the material obtained from the Jetmore chalk and construction of subgrades and embankments and Pfeifer shale members is undoubtedly appreciably may be the product of excavation along the align higher. ment of the structure, or they can be obtained from adjacent areas. The geologic formations in Carlile shale. Except for the Codell sand which these materials occur are: stone member and the lower part of the Fairport chalky shale member, the Carlile shale is com 1. Fine-granular sediments. The Sanborn posed predominantly of clay. formation and terrace deposits contain almost unlimited quantities of silt or clayey silt. The Niobrara formation. Lroken or crushed extensive outcrops of these formations are rock from the Fort Hays limestone member mapped on plate 1 and indicate the almost uni apparently is acceptable for use in the con versal availability of the material over the struction of subgrades or embankments but if county.___ the environment in which it is used is one of 14 Am. Assoc. State Highway Officials, Highway mate a high moisture content, its acceptability will rials, pt. 1, Specifications, pp. 37 and 38, 1937. be doubtful. 21 INT.-CUP. SEC., WASH., D.C.MSdM Southeastern Mitchell County EXPLANATION Alluvium (Clay and silt Interbedded with lenses of local gravel and granitic gravelly sand. Source or potential source c of- aggregate, road metal, mineral filler.) Sanborn formation (Gray or brown silt, clayey near surface and lenses oi limestone gravel and granitic gravelly sand in basal I part. Source or potential source of: aggregate, road metal, mineral filler, fill material.) Fort Hays limestone member of the Niobrara formation (ThicH beds of massive, cream-colored chalky limestone separated by thin partings of chalky shale-, shatter ed zone below fop; forms escarpment. Source or potential source of: road metal, structural stone, fill material, calcareous binder.) Carlile shale (Thin zone of red-brown sandstone at top; upper part blue-gray noncalcareous clay shale with zones of septarian concretions and selenlte crystals', lower part orange-gray chalky shale interbedded with chalky lime stone near base} forms local areas of badland topog raphy. Source or potential source of: road metal, fill material.) Greenhorn limestone (Gray, orange-gray, and dark gray shales interbedded with Graneros shale (Thin-bedded blue-gray noncalcareous clay shale with interbedded seams of bentonite and lenses of red- brown sandstone* Not a source of material.) Dakota sandstone (Thick layer of massive cross-bedded soft gray-orange to red-brown sandstone underlain by varl-colored non- calcareous sitty shale} forms hillside bench. Source or potential source of: road metal, fill material.) ^^ Geologic boundary fa Fine aggregate ma Mixed aggregate ls L'mestone Ig Limestone gravel . sh 5halje rnf Mineral filler ss Sandstone /s Inclined letters indicate materials not listed in Table I. Is 2 Vertical letters indicate materials listed in Table I and their sample number. 1.0 Quantity of material available (in units of IO,OOO cubic yards). Operated pit or quarry Prospect pit or quarry Township corner ioe R7 W 98° 00' R 6 W City Federal (US) highway Slate highway Drafted by R. M. Soelter, C. E. Grieshaber CIRCULAR 106 PLATE I Geology by W B. Johnson and D. W Bergman and V. L. Stallbaurner. Other roads, all classes MAP OF MITCHELL COUNTY, KANSAS United States Department of the Interior H I I I I- Railway Base adapted from map prepared by Showing Construction Material Sources and Geology Geological Survey Section line State Highway Commission of Kansas. 1950 and Stream, permanent Approximote mean State Highway Commission of Kansas Stream, intermittent Drainage from aerial photographs provided Scale declination, 195 Geological Department by U. S. 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