AN ABSTRACT OF THE THESIS OF Richard O. Sleezer for the Master of Science Degree 1n Physical Science presented on May 8, 1990. Title: Drainage Development and Chert Gravels in Butler County, Kansas Abstract Approved: _ '. . ~~l(I- Committee Members: Dr. James Aber, Chairperson Prof. Paul Johnston Prof. Charles Webb "k1P\ )'4'------­ Chert gravel in Butler County, Kansas can be divided into two distinctive types. Residual chert gravels have been weathered out in 'place on the dip slopes of the Flint Hills. These gravels are the source for the other type of chert gravels found in Butler County. The second type of chert gravel deposits found in this area are alluvial in nature. These alluvial chert gravels can be used to trace the past positions of streams in Butler County. Alluvial chert gravels are found almost exclusively to the north of east-to-west flowing tributaries in southern Butler County. Apparently the~e .streams are migrating laterally to the south as they cut downward. The simplest and most probable explanation for this southward migration and the resulting asymmetrical preservation of these alluvial chert gravels is a subtle southward tilting of the underlying bedrock. An apparent disparity exists between the pebble roundness value tests conducted: in Butler County and those done along other streams east of the Plint Hills. Bast of the Plint Hills roundness values tend to show a high degree of angularity at the source and a steady increase in roundness values with downstream distance. In Butler County the opposite trend exists. Chert eas~ of the Plint Hills is weathered out on face slopes and is subject to initial mechanical breakup. West of the Plint Hills the chert weathers out on dip slopes by chemical means and is not subject to initial mechanical breakup. This helps to explain why the highest roundness values found in Butler county are associated with a residual deposit and the apparent trend to slight 1ncreases 1n angul ar i ty due to mechan i cal breakup wi th downs t ream di stance. Some quartzite pebbles have been found within the alluvial chert gravels in Butler County. These quartzite pebbles probably originated from a source to the west namely Ogallala-type arkosic gravels in western Kansas. There are two distinct levels of deposits of alluvial chert gravels in Butler County. The upper level occupies a position at or near the top of hills forming the drainage divides between tributaries to the east of the Walnut River. The second level is located somewhat lower on the slopes and is referred to as a high-terrace gravel. Quartzite pebbles have been found only in the upper hill-top locations and it is assumed that the source for quartzite pebbles was not available at the time the younger high-terrace gravels were deposited. DRAINAGE DEVELOPMENT AND CHERT GRAVEL DEPOSITS IN BUTLER COUNTY, KANSAS A THESIS PRESENTED TO THE PHYSICAL SCIENCES DIVISION EMPORIA STATE UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE MASTER OF SCIENCE BY RICHARD O. SLEEZER MAY 8, 1990 \i~.) ..-_s t1~ft _ Approved for the Major Department roved for the Graduate Council ACKNOWLEDGEMENTS I would like to extend thanks and appreciation to the following persons. I would like to:,exp~ess my gratitude to Dr. James Aber for his time and effort in helping me with my field work, and the writing of this thesis. I wish to also thank him for his support as the chair of my graduate committee. I would like to thank Professor Paul Johnston for serving on my committee and for always being available whenever I needed to ask a question or talk about a new idea. I would like to thank Professor Charles Webb for serving on my graduate committee. I would als~ like to thank him for his encouragement and patience over the past two years. This project was a part of the Kansas Geological Survey mapping project which is being conducted by Dr. James Aber. I would like to recognize that my part in this project was aided by a research assistantship provided by Emporia State University. TABLE OP CONTENTS Statement of Goals . page 1 Chapter 1. Introducti~n .........•.•.......•••••• page 2 Chapter 2. Previous Research & Publications ..... page 7 Chapter 3. Methods & Procedures .........•..•..•. page 10 Chapter 4. Results . page 16 Chapter 5 • Interpretation .•..••...•...........•. page 25 Chapter 6 . Cone 1us ions . page 35 Bi bliography .....................•........•.... page 37 FIGURES Figure 1. Map of Kansas I drainage systems ...••....• page 3 Figure 2. Map of "Old. Osage River " ................. page 8 Figure 3. Portion of Leon Quad •..............••.... page 13 Figure 4. Graph of roundness values ................ page 23 Small scale representative map in pocket TABLES Table 1. Roundness values pages 19 & 20 Table 2. Roundness values '.' pages 21 & 22 STATEMENT OF GOALS The goal of this research is to establish a comprehensive map of ~ncient alluvial chert gravels 1n Butler County. This will include distinction between different types, relative positions, and the sizes of given deposits. Such oddities as the presence of quartzite pebbles within the chert gravels, and the presence of these gravels only to the north of the Walnut River's east-to­ west-flowing tributaries will receive special attention. The significance of these deposits is that they provide information about the past and present ,stream morphology and drainage patterns in southern Butler County. They may also provide clues as to the structure and neotectonics of the underlying bedrock. 1 Chapter 1. INTRODUCTION Butler County is located in south-central Kansas (Pig. 1). Butler County is the largest county in Kansas with a land area of 3750 sq. km (1443 sq. mi.). Butler County is almost entirely within the physiographic region known as the Flint Hills. The Osage Cuestas begin at the eastern edge of Butler County, and to the west are the Wellington-McPherson Lowlands and the Arkansas River Lowlands. The climate of Butler County would be classified by Koeppen as "Cwa". This is winter dry, sub-tropical with a long hot summer. The hot month (July) in El Dorado averages 27 degrees C (80.3 p) (Brown in Penner et al. 1975). The cold month (January) averages 0 degrees C (32.2 F). Average precipitation for the year is 82 cm (32 inches), with 71% of this precipitation falling between April and September. The average number of frost free days is 190 extending from April 16 to October 23. Because of the seasonal and yearly variability these averages do not g1ve a complete picture of the climate. Although on average Butler County would be classified as Cwa, a given year might classify as BSk, Dwa, or Cfa. Por example the basic difference between Cwa and Dwa is that in a Dwa climate at least one winter month must average below 0 degrees C and in Cwa climates all months average above 0 2 Figure 1. A map showing the positions of modern streams in Kansas and the locations of counties. 3 degrees C. Similar variations in precipitation could also change the classification. The soils of Butler County are with one exception classified as Mollisals (Penner et al. 1975) in the 7th Approximation System used by the United States Department of Agriculture. Mollisols, as found in Butler County, are basically grassland soils. They are developed from limestone parent rock material, and characteristically display a thick, organic-rich surface layer. The one exception to this is the Goessel Series which is a Vertisol. Vertisols are soils with a high content of cl~y throughout. They usually show evidence of soil mi~ing caused by shrinking and swelling. Although the Kansas Geological Survey includes most of Butler County in the Flint Hills, the topography varies significantly from the eastern edge of the county to the west. The Department of Agriculture divides the county into two distinct resource areas (Penner et al. 1975). The eastern part of' the county is referred to as the Bluestem Hills. This region is strongly sloping and hilly. The western part of the county is referred to as the Central Loess Plains. In general the topography of this region 1S more subdued, and is said to be gently sloping or undulating. 4 The drainage of Butler County is related for the most part to the Walnut River and its tributaries (Pig. 1). This includes: the Whitewater River, the Little Walnut River, Rock Creek, Muddy Cre,ek ,and m'any other small named and unnamed streams. The headwaters of two other major drainage systems are also found in Butler County. The Cottonwood River and the Verdigris River both have tributaries which begin in the northeastern and eastern parts of Butler County respectively. All three of these river systems share a common destination, as they all drain into the Arkansas River. The surface geology of Butler Cou.nty is composed mainly of well-consolidated sedimentary rocks of Permian age. These rock layers tend to slope gently downward to the west. Several important buried structures are found in Butler County, the most obvious of which is Nemaha Arch. This structure is a buried fault zone. In addition several folded structures are present in the area which have been exploited for petroleum production. The focus of thi~ research, however, is on relatively young (Neogene age) chert gravel deposits. Alluvial chert gravels provide effective markers of the past positions of present-day streams. These gravels are erosion resistant, which allows them to be remarkably well preserved. The chert gravels in Butler County have been quarried extensively to be used as a road surfacing material. These 5 open-pit quarries, some of which are still in use, are in general easily accessible and offer excellent opportunities for collection of samples. 6 Chapter 2. PREVIOUS RESEARCH AND PUBLICATIONS Chert gravels in eastern Kansas have been recognized since the late 18005 :(Parker 1884). The origin of these deposits has been a source of much conjecture over the years. O'Connor (1953) established that these gravels are in fact the remnants of stream terraces. Recently, Aber (1985, 1988) has concluded that the source of most of the chert in these deposits is the Flint Hills. He contends however that certain exotic quartzite, black chert, and granite pebbles, which have been found in the~e gravels, must have come from a source farther to the west. Aber (1985: 1988) has proposed that these exotics could have been transported into the area by a now extinct river system he referred to as the "Old Osage River" (Fig. 2). Aber (1988) listed three possible sources for quartzite exotics: (1) basal Cretaceous conglomerates of central Kansas, (2) Ogallala-type arkosic gravels west of the Flint Hills', and (3) glacial erratics derived from northeastern Kansas. He concluded that Ogallala-type gravels and Cretaceous conglomerates were major and minor sources for quartzite exotics in east-central Kansas, but that no glacial erratics were transported into the region. Law (1986) demonstrated that chert gravels in eastern Kansas could be mapped quite easily by referring to available soil survey maps. The Olpe-Kenoma soil complex 7 _i I J Ir- iii i I iL _ ~- I j ,I I GROVE I I ! I i - -----1 MNi , GARNETT 0 I •i •• _.~~ i \ CS -'- '~=-'--~-'-- ~ B"r-- If • GRAVEL WITH QUARTZITE " i o GRAVEL WITHOUT QUARTZITE .. MAIN STEM OLD OSAGE RIVER o lOLA I> TRIBUTARY ROUTE OLD OSAGE o ~~ PRESUMED QUARTZITE SOURCE YilTES CENTER .:::::::. CAPTURE ZONE km Ii, 2g 40~ ~ Jla. "'7 wo AL Figure 2. A map of the now extinct river system referred to by Aber (1966) as the "Old Osage River." 6 and the Olpe series soils closely correspond with alluvial chert gravel deposits in Chase, Lyon, Coffey, and Anderson Counties. This simplifies the mapping process especially in Butler County, becau~~ its soil survey maps and available topographic quadrangles are at the same scale (1:24,000). Aber (1985, 1988) and Law (1986) have both observed an asymmetrical patte~n of preservation of alluvial chert gravels in eastern Kansas. These gravels tend to be located almost exclusively on the northern valley sides of west-to­ east-flowing streams. They also observed that present-day west-to-east-flowing streams tend to be cutting into their southern valley sides. Three possible explanations have been proposed to explain this phenomenon: 1) unequal sediment input, 2) the Coriolis effect, which in the northern hemisphere tends to deflect movements to the right, and 3) subtle crustal tilting to the south, which would explain the southward migration of these streams and the apparent headward expansion of the Arkansas River's southward flowing tributaries. 9 Chapter 3. METHODS AND PROCEDURES Methods and procedures are best divided into three phases. The first phase involved developing an accurate method for mapping the alluvial chert gravels in Butler County. The second phase entailed collection, field observation, and analysis of the gravel itself. The third phase involved drafting a 1:100,000 scale map of Butler County with an appropriate set of symbols to represent the alluvial chert gravels. Phase I: The Olpe-Norge Soil complex as defined in the Butler County Soil Survey (Penner et al. 1975) is 50% Olpe Series soils, 30% Norge Series soils, and 20% Irwin Series soils. Olpe soils tend to be at or near the crests of hills and Norge soils are between the slopes. A representative profile of an Olpe soil appears as follows (Penner'et al. 1975): A1-- 0 to 10 inches, dark-brown (7.5 YR 3/2) silty clay loam, very dark brown (7.5 YR 2/2) when moist; strong, fine, granular structure; slightly hard when dry; pebbles about one half inch in diameter make up 5 percent of this horizon; medium acid; gradual, smooth boundary. Bl-- 10 to 14 inches, dark reddish-gray (5 YR 4/2) heavy 10 silty clay loam, dark reddish (5 YR 3/2) when moist; strong, fine and very fine, subangular blocky structure; hard when dry; firm when moist; thin and patchy clay films; about 10 percent of this horizon 1S chert pebbles one half inch in diameter; slightly acid; gradual, smooth boundary. B2l-- 14 to 30 inches, dark-red (2.5 YR 3/6) gravelly clay, has the same color when moist; moderate and strong, fine, blocky structure; extremely hard when dry, very firm when moist; continuous clay films that clog some pores and cover the surface of some pebbl~s; about 85 percent of this horizon is rounded chert pebbles; slightly acid; clear, wavy boundary. B22t-- 30 to 42 inches, red (2.5 YR 4/6) clay, dark red (2.5 YR 3/6) when moist; moderate, medium, blocky structure; extremely hard when dry, very firm when moist; distinct, thick and continuous clay films; these impart a dark-brown (7.5 YR 4/2) dry color to ped surfaces; about 10 percent of horizon is rounded chert gravel; few, hard, black iron-manganese concretions; neutral; clear, wavy boundary. The boundaries of alluvial chert gravel deposits in Butler County correspond closely with the boundaries of the Olpe-Norge soil complex as mapped by the Soil Conservation Service (Penner et al. 1975). These Soil Survey maps are 11 published at a scale of 1:24,000, which is the same scale as the 7.S-minute topographic quadrangles provided by the Kansas Geological Survey. This allows the data from the Soil Survey maps to b~ transferred directly to the topographic maps by tracing the boundaries using a light table (Pig. 3). Phase II: After the alluvial chert gravels were located using the soil survey maps, it was necessary to field check the data to make sure that the 01pe-Norge soil complex ,included all of the alluvial chert gravels in Butler County. These chert gravels have been quarried extensively, so it was a rather simple matter to examine one quarry after another while checking the locations on the topographic maps. Samples of chert gravels in Butler County were taken along the Little Walnut River. The first sample (site 1) was taken from the source of the chert. This deposit was residual chert which had weathered out of the Florence Limestone, but had not been transported. At this site and at the others a random sample of pebbles was collected. These samples contained enough material so that about 50 pebbles of the desired size could be extracted from them. In addition any unusually large cobbles, quartzite pebbles, or pieces of the fossilized wood were also collected. The samples were wet sieved to separate the small­ 12 Figure 3. A portion of a representative 7.5 minute quadrangle (Leon) with alluvial chert gravel deposits. Solid circles represent hill-top gravels and open circles represent high-terrace gravels. mile 13 ~ •..{ll ~',. -' lkm pebble size (16-25 mm). About fifty of these pebbles from each site was subjected to a roundness test. Pebble roundness was calculated using the Cailleux method: C = d/1 x 1000, where,,(d) repr~sents the diameter of the sharpest corner, (1) is the length of the pebble at its long axis, and (C) is the roundness. This process is repeated for each pebble in the sample, and an average of 50 pebbles from each sample was recorded and graphed. Phase III: The topographic maps with the chert gravel deposits marked on them are useful in that they.show nearly exact locations and sizes for alluvial chert gravel deposits in Butler County. They are, however, difficult to work with, as a large flat area is required to view all the necessary quadrangles. A smaller scale, representative map which included the entire county was a more desireable solution for analysis of patterns. A 1:100,000 scale topographic map of Butler County was available from the United States Geological Survey, and this was selected as a base map. The map borders, township corners, major streams, water bodies, and the locations of the two largest cities were transferred to the base map. Roads and highways were left off the map since they were not necessary for reference points and might tend to detract from the purpose of the map. 14 Alluvial chert gravel deposits in Butler County are not all of the same nature or size. This map is intended to be a representative tool; thus, a set of symbols was established to deline~te between different sizes and types of deposits. Circles of three different sizes were selected to represent the location and size of given deposits. The smallest circles are used to denote deposits that are smaller than 40 acres. Medium-sized circles are used to show deposits larger than 40 acres but smaller than 160 acres. The largest circles represent deposits greater than 160 acres. Most of these deposits tend to be continuous and parallel to the present streams or upwards from them, so these circles are chained together to give a more realistic appearance on the map (map in pocket on back cover). 15 "··~••i ,.._,._.. Chapter 4. RESULTS Gravel distribution: In viewing the ~~pogtaphic quadrangles, it is apparent that the alluvial chert gravels in Butler County tend to be located at two separate and usually distinct levels (Fig. 3). The first level is 10 to 15 meters above the modern flood plain and these deposits will be referred to as "high­ terrace gravels." The second level is located more than 20 meters above the modern flood plain and these deposits will be referred to as "hill-top gravels." High-terrace gravels tend to form chains of arcuate- shaped deposits. These chains may be continuous or broken intermittently by small streams. These deposits also vary widely in areal extent and lateral continuity. In some locations, the high-terrace gravels and hill-top gravels may form relatively continuous deposits from the top of the hills downward to a level some 10 meters above the modern flood plain. Hill-top gravels'are, as the name implies, located at or near the top of the hills which form the drainage divides between modern streams. The hills on which these deposits rest range in elevation from 20 to 30 meters above the modern flood plains. All of the alluvial chert gravels in Butler County are located on the northern banks of east-to-west-flowing 16 .~~_.y ""'_. streams. These streams display a strong tendency to flow along the southern edge of their valleys. Hill-top gravels are usually 1.5 to 3 km north of modern streams, and h~gh-terrace gravels are typically 0.5 to 1.5 km north of modern streams. It would seem that the distance between modern streams and related chert gravels 1S largely dependent on the direction of flow of the stream. Streams such as Hickory Creek, which flow nearly straight west, tend to be farther from their associated chert gravels. Streams such as Muddy Creek which flow in a more southerly direction are closer to their related chert gravel deposits. Pebble and cobble analysis: Twelve individual pebble samples were collected and analyzed. Sample 1 was collected from a residual deposit, and it displayed the highest average roundness value of 118 and the highest standard deviation of 64. Samples 2, 3, 4, 5, 7, and 8 were collected from high-terrace gravel deposits along the Little Walnut River (Table 1). Samples 6a, 6b, 9a, and 9b were collected from two separate hill-top gravel deposits (Table 2). Sample 10 was collected from an isolated deposit in the southeastern corner of Butler County. The average roundness values of the high-terrace gravel samples along the Little Walnut River vary from 104, (sample 4) to 83, (sample 5). Sample 4 has the highest roundness 17 value of any high-terrace sample (104) and second-highest standard deviation for all samples tested (56). Sample 7 has the lowest standard deviation (32). The average roun4ness values of the hill-top gravels vary from 92 (sample 6a) to 61 (sample 9b). Sample 6a has the highest standard deviation (51), while sample 9a has the lowest standard deviation (27). In general roundness values are highest at or near the source of the chert and become progressively lower with increased distance from the source (Tables 1 & 2). This would seem to be true for both high-terrace gravels and hill-top gravels. The lowest standard~deviation values are not found with the highest roundness values, as one might expect. The lowest standard deviation values are found farther from the source areas, except at the one isolated sample site in the southeast corner of the county. A graph of the pebble roundness values versus downstream distance along the Little Walnut River displays trends for both high­ terrace gravels 'and hill-top gravels (Pig. 4). Maximum cobble size decreases in a downstream direction. In or near residual chert gravels, irregularly shaped cobbles greater than 20 em in length can be found. To the west, however, cobbles are rare and for the most part only large pebbles are present in alluvial chert gravels near the Walnut River. 18 ••~"""'M<',_.. iAMPiii1E1 SlIE2 ~3 snE4 SlTB5 SI1E7 SlIE8 1 91 143 40 57 56 '11 .. 2 133 107 91 88 115 63 58 3 100 111 fYl 150 42 125 73 4 94 33 129 118 23 98 71 S 143 '. 29 71 TI 143 100 83 6 fYl 56 6S 61 115 156 9S 7 129 34 40 119 226 56 22 8 71 200 59 11 61 SO 89 9 fYl 73 56 125 91 67 70 10 11 57 61 6S 37 71 .. 75 6S 167 44 98 125 87 61 12 143 100 75 T1 22 37 83 13 100 83 154 32 63 86 73 14 91 212 150 171 61 91 22 15 67 '11 24 36 56 152 152 16 147 128 115 6S 107 125 fYl 17 184 71 100 148 47 100 30 18 79 194 143 91 1Tl SO 118 19 6S 103 53 129 74 67 69 20 119 34 86 M 37 114 148 21 71 192 91 71 54 78 63 22 167 74 61 28 57 91 1~ 23 143 143 80 125 54 57 61 24 lOS 100 56 22S 160 11 89 2S 167 175 80 44 100 121 59 Table 1. A table of the individual roundness values of pebbles in samples taken from high-terrace locations. 19 ~ SITE 1 SlI'E2 SITE 3 SITE 4 SITE 5 8rIE7 SITE 8 26 38 54 133 6S 94 78 88 27 40 M) 67 118 148 91 94 28 78 156 303 71 114 111 95 29 241 153 trI 40 94 61 103 30 143 212 115 152 32 167 114 31 184 74 26 147 94 67 140 32 T1 T1 140 132 75 111 67 33 171 114 32 219 67 34 69 34 139 160 T1 100 tTl 138 133 3S 6S 129 103 33 61 54 57 36 71 51 115 136 138 69 125 37 111 56 86 63 63 114 trI 38 122 36 1M 172 143 49 79 39 212 (IJ 172 SO 29 100 91 40 23 tTl tTl 91 6S 100 86 41 130 59 74 107 a) 79 69 42 103 1m 30 67 lOS 75 217 43 74 103 100 75 24 83 120 44 143 94 64 114 103 6S 100 4S 222 T1 a) 125 32 71 108 46 103 63 179 100 48 148 32 47 167 115 154 313 9S 111 182 48 400 frI 28 74 93 49 49 40 114 188 57 118 115 SO 57 trI 148 T1 100 67 ,IDAV 118 101 94 lot 83 90 89 STANDARD DEVIATION 64 53 48 56 44 32 37 Table 1 continued. The remainder of the roundness values for high-terrace samples with average values and standard deviations. 20 6A 1SiTE6B [Sfffi9A SlIE9B srml0 1 13394 T1 34 29 2 190 43 6S 56 T1 3 33 83 6S 28 83 4 61 89 88 T1 63 5 :188 91 94 118 100 6 172 6S 111 143 74 7 67107 133 28 • 55 8 23 161 29 9 8370 1.• 63 63 10 49 161 67 89 53 11 45B 78 63 61 12 56D 91 fTl 38 13 9413» 26 111 14 106 238 115• 152 38 (fJ15 143 61 54 6S 16 3471 67 30 74 17 31 28 M T1 6S fYI18 115130 30 71 19 74115 140 94 63 (fJ3» 68 57 130 21 121 29 40 100• 167 22 28 57 70 2S 63 23 67 167 106 61 T1 24 30 162 91 51 24 2S 120 20 119 29 88 Table 2. A table of individual pebble roundness values for samples taken from hill-top sites. Also included 1n this table are roundness values for site 10. 21 .lIliIlillil....,,""A-., ;_~,._. __ mwm [§fiE6A mi'E6B SlIE 9A SITE 9B SITE 10 26 73 57 ffl 15 29 'l1 43 107 57 65 100 28 33 83 86 91 190 129 .29 71 42 26 11S 30 6.l 73 83 37 74 31 29 24 118 34 SO 32 115 47 54 103 49 33 S)88 94 11 61 34 75 161 103 83 83 3S (JJ 32 61 24 29 36 SO 98 63 185 57 37 94 47 100 34 57 38 6767 34 33 63 (JJ (JJ39 ffl9S 54 40 38 98 89 29 74 41 94 9S 74 21 61 42 133 86 67tr1 154 43 143 81 129 68 44 115 115 81 42 45 174 56 88 26 46 37 21 53 47 81 184 75 135 115 48 67 114 154 49 49 148 67 26 SO 20 79 61 ~~.-.J 92 8S 6188 11. STANDARD DEVIA110N . 51 46 'rJ 37 34 Table 2 continued. The remainder of the roundness values for hill-top sites and site 10 with average values and standard deviations. 22 "'l'J.. ~..." PEBBLE ROUNDNESS VALUES CHERT GRAVEL (UTILE WALNUT RIVER) B0160 i1: 1 ~ 1 ~ 1 -Hi 3 ~ m z 40 -20 00 .- w "- SlTEM - 8I1E7 VU" SITE 8SI1E4._ BnE2 .... o SITE 3 SlTEM z SITES erre­::;) SIlE. )20 "'I'TTTT ~ o 5 10 15 20 25 30 35 KlLOMEIERS FROM THE PRESENT SOURCE Figure 4. A graph of the average roundness values for all samples taken from sites along the Little Walnut River. Sites 6a, 6b, 9a, and 9b are hill-top locations, others are high-terrace locations. Average values are represented by short horizontal lines and vertical lines represent one standard deviation up·and down. 23 .........",-,-, ' .... Representative map: The presence of two distinctive positions of alluvial chert gravel has been established, therefore, it was necessary t.o have a different symbol for high-terrace gravels and hill-top gravels. The simplest method to accomplish this is to fill in those circles which represent hill-top gravels and leave those circles which represent high-terrace gravels open. It is necessary therefore to delineate between the two relative positions of deposits in a numerical method. The distinction between the two is a matt~r of relative location with respect to the modern associated streams. The lowest hill tops which are occupied by hill-top gravels have an elevation which is approximately 20 meters above the modern flood plain of the related stream. This figure was adopted as the dividing line between those gravels which are represented as hill-top gravels and those which are considered high-terrace gravels. In other words, any gravel deposit which is located more than 20 meters above the modern flood plain has been considered to be a hill-top gravel. Gravel deposits found lower than 20 meters and more than 10 meters above the modern flood plain are shown as high-terrace gravels. 24 Chapter 5. INTERPRETATION Soils: The Butler Coun~y Soil Survey (Penner et a1. 1975) stated that 01pe soils formed in gravelly clayey sediment. The Olpe soil seems to consist of two components. 1) The uppermost component may include a thin layer of loess at the surface. This layer is usually less than 25 em 1n thickness, and may be missing in some profiles. This corresponds roughly to the top of the Al horizon. 2) The second component consists of alluvial materia~ (clay and chert) which was deposited by streams.· This component 1S stained dark red or red brown in most cases and is approximately 1.5 to 3 m in thickness. This component corresponds to the Bl, B21, B22t, and B3 horizons. The chert content varies from 10% to 85% in these horizons. The B horizons of the Olpe soil are a paleosol that began to develop in chert gravel alluvium prior to the deposition of the loess cover in which the surface soil 1S formed. Hill-top gravels display strong oxidation in the B horizon, but B horizons are less strongly oxidized within high-terrace gravels. This suggests that hill-top gravels were subjected to longer or more intense weathering prior to loess coverage than were high-terrace gravels. The soil survey (Penner et al. 1975) pointed out the similarity between the Olpe soil profile and the Florence 25 soil profile. The Florence soil is a true soil. A true soil is one which has formed directly from the underlying bedrock. Its profile is remarkably similar to the Olpe profile with two notable exceptions. In the Florence soil, chert fragments were described as angular in nature. In the Olpe soils, the chert was referred to as "rounded chert pebbles." The Olpe profile description mentions that these chert pebbles become stratified in the lower part of the B2t horizon. The chert fragments in the Florence soil do not display any stratification. The fact that these pebbles are rounded and stratified within the soil profile, are evidence that the chert pebbles in the Olpe soils are alluvial deposits. The Florence soil is related to the Olpe soil in that the Florence is the source of sediment (especially chert) 1n the Olpe soils and the Olpe-Norge soil complex. The two soils are even found in close proximity to each other and may even be somewhat mixed in some locations. The simplest method two distinguish the two soils from each other is by observation of the color of the chert and clay matrix. The chert and clay matrix in the Florence (residual gravels) tends to be orange or orange red in color. The Olpe and 01pe-Norge complex contains chert and clay matrix which tends to be red-brown, brown, or even gray-brown in color. 26 Chert gravels: Pebble analysis of chert gravels in Butler County shows several trends in pebble roundness: 1) the highest roundness values recorded are in residual deposits, 2) roundness values tend to decrease with downstream distance in both high-terrace and hill-top gravels, 3) roundness values at site 10 seem to contradict roundness values along the Little Walnut River, and 4) there seems to be a wide variance in roundness values of samples taken from the same site (Fig. 4 ) . Higher roundness values than would be exp~cted at site 1 could be explained by the situation in which the chert gravels are weathering out of the Florence Limestone. Previous roundness studies of high-terrace and hill-top gravels on west-to-east-flowing streams east of the Flint Hills (Law 1986) showed the opposite trend in roundness. The source of this chert is cherty limestones exposed on the face slopes of the Flint Hills escarpment. These chert deposits are angular shards of chert nodules which have weathered out of the limestone and broken up as they were transported downslope by gravity and erosion. Residual chert gravels in Butler County tend to be weathered out on fairly flat dip slopes and are not subject to initial mechanical breakup. The chert nodules are therefore weathered chemically and are largely intact with relatively few sharp edges. This would seem to explain the 27 ".,._~-- relatively high roundness values found at site 1. If the residual chert gravels did weather out intact, it would seem logical that initially they would tend to suffer mechanical br~akup while they were being transported downstream, as shown by the decrease in maximum cobble size. This could explain the trend of slightly lower roundness values with downstream distance in both high-terrace and hill-top gravels. The single sample taken at site 10 seems to have an average roundness value contradictory to the above explanation. The chert at site 10 comes from ~ different source. This chert was derived from the Wreford Formation and its source area is on the face slope rather than on the dip slope of the Flint Hills. Instead of being a contradiction, site 10 might in fact provide further evidence in favor of the above theory. These explanations are, however, somewhat speculative because of the variance in roundness values within sample sites and the samples themselves. It would seem that much additional analysis of pebble roundness values in this area would be necessary to achieve conclusive results. Gravel distribution: The pattern of distribution of alluvial chert gravels 1n Butler County can be used to make several interpretations about stream patterns, stream morphology past and present, 28 and possibly the structure of underlying bedrock. The asymmetrical nature of the deposits, the two distinct levels of preservation, and the presence of the gravels along the lower reaches of Mudd.y Creek all give clues as to past and present conditions. It is also interesting to note that these alluvial chert gravels are preserved almost exclusively in the southern half of Butler County, east of the Walnut River. The location of these chert gravels in southern Butler County east of the Walnut River can be explained quite easily. These alluvial chert deposits can only form along streams which flow through source areas. The streams west of the Walnut River do not flow through areas in which chert 1S weathering out of underlying limestone strata, therefore significant deposits of alluvial chert gravels are not found west of the Walnut River. The Walnut River is expanding headward, and this explains the lack of alluvial chert gravels in northern Butler County. 'The streams in northeastern Butler County have reached areas with significant residual deposits of chert in relatively recent times. At the time that the streams in southeastern Butler County were depositing chert in hill-top and high-terrace locations, the streams in northeastern Butler County were not yet flowing through areas with significant residual chert deposits. Muddy Creek in southern Butler County has significant 29 ........"~_. alluvial chert gravel deposits even though its headwaters do not reach into the source areas for chert gravels. This does not, however, contradict the above hypothesis about streams in northern Sutler Cou~ty. It seems likely that the chert gravel along Muddy Creek was transported into the area by either Hickory Creek or the Little Walnut River. In either case Muddy Creek would originally have been a part of another stream. The Little Walnut River could have flowed southward roughly parallel to the Walnut River into what is now Muddy Creek. It would have remained in this position until it was captured upstream by th~ Walnut River at some time after the alluvial chert ~ravels along Muddy Creek were deposited. The other possibility is that Hickory Creek and Muddy Creek were connected at the time of deposition of the chert gravels along Muddy Creek. In this case Hickory Creek would have been captured by the Little Walnut River at some time after the chert gravels along Muddy Creek were deposited. Alluvial chert gravels in Butler County are preserved almost exclusively o~ the northern sides of the modern east­ to-west-flowing stream valleys. The streams occupying these same stream valleys also tend to be at or close to their southern bluffs. The Coriolis effect would, presumably, influence these streams to cut into their northern (right) banks. As this obviously is not the case, it seems unlikely that the asymmetrical pattern of gravel preservation was 30 "';;;,..~..;, caused by the Coriolis effect. Another proposed cause of asymmetrical preservation of alluvial chert gravels is an unequal input of sediment. This would imply that· the source areas for the chert were north of the deposits and that a preponderance of the tributaries drained into the main streams from the north. The source areas for the chert are in fact to the east of their present location in Butler County. In addition, there does not appear to be a significant difference in the number of tributaries entering streams from either side. It is seemingly clear that some force other than the Coriolis effect or uneven input of sediment is causing the asymmetrical pattern of preservation of alluvial chert gravels. The simplest explanation for a southward migration of streams in Butler County would be subtle tilting of the underlying bedrock. The existence of crustal tilting has been inferred from the asymmetrical nature of alluvial chert and the current position of streams in their valleys. Subtle crustal tilting has been proposed as a possible cause for the asymmetrical pattern of preservation of chert gravels in eastern Kansas (Aber and Sleezer 1990). A neotectonic structural arch, which is believed to be uplifting along a west-to-east axis roughly parallel to the Kansas/Nebraska border, has been proposed as a possible cause for the aforementioned subtle tilting of the underlying strata in Kansas. This proposal is further 31 strengthened by similar asymmetrical patterns of valley development in western Nebraska which trend in the opposite direction as those in Kansas. Crustal tilting ;would explain the pattern of southward migration of east- or west-flowing streams in eastern Kansas. In addition, this would also explain the apparent headward expansion of south-flowing streams such as the Walnut and Whitewater Rivers, at the expense of drainage basins with other flow orientations. The problem with this explanation is that no tilting of this sort has ever actually been measured by s~rveying or geodetic techniques. In addition, this tilting is probably so subtle that it would be difficult, if not impossible, to measure in the field. It is possible, however, to measure the effect this subtle tilting has had on the streams in Butler County in terms of lateral distance of migration and amount of downcutting. Based cn the positions of hill-top and high-terrace gravels in relation to the current position of modern streafus, the east-to-west flowing tributaries of the Walnut River have'downcut approximately 10 m per km of southward lateral migration. The positions of alluvial chert gravels on the tops of drainage divides between streams in Butler County suggests a regional inversion of topography. The hill-top gravels represent one past position of present-day streams which now occupy positions in valley floors. It would seem that hill ­ 32 ....-..-... top and high-terrace gravels are the result of times when these streams remained at a given elevation long enough to deposit significant amounts of chert. These deposits were thick enough and erosion resis~ant, so that they were preserved as they are seen today. Quartzite erratic pebbles: Several small quartzite pebbles were found within the alluvial chert gravels in Butler County. These pebbles are yellowish brown in color. These quartzite pebbles were only found in the hill-top gravels. It would seem ~hat at the time the hill-top gravels were deposited quartzite pebbles were fairly common. None of these quartzite pebbles, however, have yet been found in the high-terrace gravels. The quartzite pebbles must have been transported into the area at some time during or before the time that the hill-top gravels were deposited. Quartzite pebbles that are found in the hill-top gravels could have been derived from Ogallala-type deposits, which may have extended into the area at this time (Ab~r 1988). Ogallala-type deposits containing quartzite pebbles may have formed a fairly continuous cover in the area. These deposits were apparently completely stripped away before the high-terrace gravels were deposited. Ogallala-type gravel was probably present in central Kansas during late Tertiary (Miocene-Pliocene) time. 33 "'_., , ..--..----.. However, the presence of quartzite in hill-top gravel of Butler County does not fix the age of Butler County chert gravel. The age of hill-top and high-terrace gravels may span a time range from late Tertiary through early Pleistocene. 34 ______...._..,.' -------.0"'_.. __~".~ .._~_, ..... _._ Chapter 6. CONCLUSIONS Alluvial chert gravel deposits can be used to trace the past positions of certain streams in Butler County. These chert gravels show a distinct trend of stream migration toward the south. The most probable cause for this tendency of stream migration in Butler County is subtle crustal tilting to the south. This subtle tilting of the underlying strata would also explain the apparent headward expansion of the Walnut and Whitewater Rivers at the expense of other drainage basins. The apparent disparity in pebble roundness values between studies done along streams east of the Plint Hills and those conducted in Butler County can be explained by a difference in the method by which the chert is weathered out of the source limestone. Chert nodules in source areas in Butler County are predominately weathered out on dip slopes and are not subjected to initial mechanical breakup. This explains the existence of apparently higher pebble roundness values in residual chert gravels in Butler County as opposed to alluvial chert deposits downstream. Quartzite pebbles have been found only in hill-top deposits in Butler County. The probable source for these quartzite pebbles are Ogallala-type gravels found currently in western Kansas (Aber 1988). As none of these quartzite pebbles have been found in high-terrace deposits in Butler 35 County, it is assumed that these quartzite-bearing gravels had been completely eroded away from the region before the high-terrace gravels were deposited. 36 BIBLIOGRAPHY Aber, J. S. 1985. Quartzite-bearing gravels and drainage development in eastern Kansas: TER-QUA Symposium, Series 1, p. 105-110. Aber, J. S. 1988. Upland chert gravels of east-central Kansas: KGS Guidebook Series 6--Regional geology and paleontology of upper Paleozoic Hamilton quarry area, p. 17-19. Aber, J. S. and Sleezer, R. O. 1990. Drainage Development and Neotectonics in the Midcontinent Region: l22nd Annual Meeting, Kansas Academy of Science, Abstracts 9:1. Law, M. S., 1986, Mapping of Upland Chert Gravel Deposits, East Central Kansas. Unpublished research project, Emporia State University, Department of Earth Science. O'Connor, H.G. 1953. Geology, mineral resources, and ground­ water resources of Lyon County, Kansas. Kansas Geological Survey, vol. 12 (part 1: Rock formations of Lyon County), p. 5-24. Parker, J. D. 1884. The Burlington gravel beds. Kansas Ci ty Review of Science and Industry, 8(7):386-387. Penner, H. L., Ekart, S. C. Ewing, D. A. Schmidt, G. and Smith, J. 1975. Soil Survey of Butler County, Kansas: United States Department of Agriculture, Soil Conservation Service. 37 + + f + \, + -t­ o ++ r( 1I> 'I> l-------:r-----------:;;r;;;------~~I~~----~, £> g§ -- ­~~ ::I!" " ~ V) o 20 "" -+- , -,-+ ( +- f /+ ~ D ~ 0 ... -v0, ~ : 0 o 0 0 -0 .. .. ~ III iIII ." 1 ~ 0 0 0 L'" g- ••• lD ~ "­:= S'! -0 0­ lD '" "­ .. -0 .. '" o o