630.7 I6b no. 701 cop. 8 UNIVERSITY OF | .INOIS LIBRARY AT URBANA-CHAMPAIGN AGRICULTURE some mineralogid properties of Seaton, Fayette, 701 Sri Illinois University of Illinois Agricultural Experiment Station Bulletin 7O1 by ROBERT L. JONES and A. M. BEAVERS CONTENTS Analytical Procedure 5 Results and Discussion 7 Summary 21 Literature Cited 22 Appendix A: Profile Descriptions 24 Appendix B: Analytical Data 27 The authors wish to thank H. L. Wascher, Department of Agronomy, and P. R. Shaffer, Department of Geology, University of Illinois, for reading and commenting on the manuscript. We are also grateful to W. W. Hay, Depart- ment of Geology, for preparation of electronmicrographs. COVER E/ecfronmicrogrcrph of clay fraction from Clinton silt loam (Sample 16419). Magnification = 15,660 X. SOME MINERALOGICAL PROPERTIES OF SEATON FAYETTE, AND CLINTON SOILS IN ILLINOIS By ROBERT L. JONES and A. H. BEAVERS 1 SEATON, FAYETTE, AND CLINTON SOILS constitute a developmental sequence of relatively youthful Gray-Brown Podzolic soils de- veloped in Wisconsin-age loess in the upper Mississippi valley. In Illinois these soils occur northward along the Mississippi River from its confluence with the Illinois River. Seaton and Fayette soils are developed in loess from 15 to 25 feet thick on Illinoian till in extreme northwest Illinois. Fayette may be developed in loess as thin as 5 feet on till or bedrock. Clinton soils are developed in loess from 8 to 15 feet thick on Illinoian till. In general, these soils occur in the sequence Seaton, Fayette, and Clinton, with increasing distance from loess source. As might be ex- pected, the median diameter of the loess decreases through this sequence. Structural development is most prominent in Clinton soils. Better internal drainage occurs in Seaton and Fayette soils than in Clinton. Some physical and chemical characteristics of these soils are summarized in Table 1. The Seaton and Fayette profiles used in this study are described in Illinois Station Bulletin 587 (North Central Regional Publication 46), Loess-Derived Gray-Brown Podzolic Soils in the Upper Mississippi River Valley (Muckenhirn et al., 1955). This publication gives profile descriptions, mechanical analyses, exchangeable cations, and pH data. The Clinton profile was sampled in Warren County (T9N, R1W, NW, NW, NW), and is about nine miles south of the Clinton profile from Warren County (Profile No. 15) described in Bulletin 587. Mechan- ical analyses, pH, and organic carbon data from the Clinton profile used in this study are given in Appendix B. These data differ only in minor aspects from the Clinton profile described in Bulletin 587. Profile descriptions for the three soils are given in Appendix A. The locations of these profiles and loess depth in the area in which these soils are developed are given in Fig. 1. The Seaton profile is 0.9 mile, the Fayette 8.2 miles, and the Clinton 24.9 miles from the Mississippi River bluff. It is apparent from the map that sediment blown by northwesterly winds from valley trains of the Iowa River would particularly influence the character of loess in this area. This part of Illinois has a mean annual rainfall of about 35 inches and a mean annual temperature of about 50 F. 1 ROBERT L. JONES, Research Associate in Soil Mineralogy, A. H. BEAVERS, Professor of Soil Mineralogy. BULLETIN NO. 701 [June, Table 1 . General Profile Characteristics of Seaton, Fayette, and Clinton Soils Seaton Fayette Clinton Loess Median diameter decreases through the sequence Thickness (feet) 25+ 12-15 5-15 Soil Profile Structural development weak moderate Internal drainage good good Maximal B clay content 20-27 27-36 Coarse-silt fine-silt ratio 1 . 5-2 .5 .9-1.5 Exchange Ca exchange Mg ratio 1 . 8-3 .0 1 . 6-2 . 8 moderate to strong moderately good 36-43 .7-. 9 1.4-1.8 X SAMPLING SITE BLUFF (WHERE NO ISOPACH) QO'' ISOPACH APPROXIMATE ISOPACH Sampling site locations and Peorian loess thickness in the sampling area. Isopachs drawn from data in the Agronomy Department files. (Fig. 1) J964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 5 Loess distribution, thickness, carbonate content, and relationship to soil development in Illinois have been discussed by Smith (1942). In the area between Lomax and Dallas City, Krumbein (1937) found loess thickness followed the relationship y = 26e~- 17x , where x is the distance from the bluff in miles. This loess-thinning relationship is different from that of Smith, who gives y = 434 200 log x for Peoria loess along a traverse southeast from the Illinois River. Using Smith's data, Waggoner and Bingham (1961) arrived at a log-log relation- ship between thickness and distance. All investigators agree that this thinning is much more rapid than a simple arithmetic regression. Two studies have been made at the University of Illinois on the soils described here. In a study of ped surfaces and interiors, R. B. Grossman (1959) used samples from the Seaton and Fayette sites and from a Clinton site near the one reported here. From microscopic study of thin sections made from the zone of maximum clay accumu- lation, Grossman concluded that size of oriented clay coatings does not change significantly. However, movement and accumulation of iron to form concretions and formations of gray void peripheries and inter- connections between voids by veins increase through the sequence of Seaton to Clinton. The latter venation is related to progressively stronger structural development occurring through the sequence. In the second study, W. D. Nettleton (1958) analyzed the distri- bution of nitrogen in other soils and in the Seaton, Fayette, and Clinton soils used in this report. Of particular interest to the present mineralog- ical investigation is the fact that Nettleton found marked fluctuations in fixed ammonium above 20 inches in each of the soils. He also dis- covered that the ratio of B-humus nitrogen to humic acid nitrogen de- creases through the Seaton to Clinton sequence. Among horizons, the ratio is highest in the A 2 or B 2 . The purpose of the study reported here is to characterize and dif- ferentiate Seaton, Fayette, and Clinton soils in west-central Illinois on the basis of certain mineralogical and chemical properties. The study also considers the effect of loess stratigraphy and transport of loess over moderate distances on mineralogical characteristics. ANALYTICAL PROCEDURE Mechanical Fracf/onaf/on After wet sieving to SOyu., silt fractions were obtained with the fractionator described by Beavers and Jones (1962). These fractions corresponded to 5 to 20/i (or fine silt) and 20 to 50ju (or coarse silt). 6 BULLETIN NO. 701 [June, Elemental Analysis A GE XRD-5 X-ray unit was used for spectrographic analysis. Pertinent machine-operating data are given in Table 2. Samples were prepared by mixing 6 grams of silt with 0.2 gram dried Permount, wetting the mixture with 0.6 ml of toluene, and pressing at 10,000 p.s.i. for several seconds into duplicate pellets. Table 2. X-Ray Machine Operating and Analytical Data K Ca Ti Fe Zr Tube target W W W W W Tube voltage (kv) 50 50 50 50 50 Tube current (ma) 45 45 45 45 45 Spectral line Ka Ka Ka Ka Ka Seller slit (inches) .020 .020 .020 .010 .010 Optical path He He He air air Analyzing crystal LiF LiF LiF LiF LiF Counter tube FP a FP a P b FP a P b Counts Peak 100 seconds 100 seconds 100 seconds 100 seconds 100,000 Background .... .... .... 100,000 Standards addition addition NBS 76, NBS 76,81, NBS 76,77, 81,102 102, 78,102 addition a FP = flow proportional. b P = proportional. X-Ray Diffraction Analysis A GE XRD-5 X-ray unit was used for diffraction analysis. This unit utilized a copper tube operated at 50 kv and 15 ma. Semi-quanti- tative estimations of the principal feldspar components of several hori- zons were made from peak intensity measurements obtained by irra- diation of ground total sample. Clay mineral analyses were made on parallel-oriented specimens prepared on ceramic slides. The method of Kinter and Diamond (1956) was followed in sample preparation, ex- cept that suction was used instead of centrifugation. Clay mineral species were identified on the basis of interpretation of glycolated samples and magnesium-saturated samples heated at 550 C. for 30 minutes. To determine the occurrence of acid labile chlorite, clay samples were heated at 70 to 90 C. in 0.2 N HC1 for four hours. Selected magnesium- and potassium-saturated samples were parallel- oriented on glass slides and analyzed in glycolated condition. For purposes of semi-quantitative clay mineral interpretation and profile evaluation, adjustments to solvated montmorillonite were made 1964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 7 by multiplying the 7 A net count signal by 2 and the 10A net count signal by 3. The evaluation of chlorite to kaolinite was made on the basis of the twofold greater reflecting power of kaolinite in the 25 two-theta region. Cation exchange capacity was determined on the total clay sample with calcium as the exchangeable ion (Jackson, 1958). Calcium was estimated by flame photometer. Calcium Carbonate Equivalent Content of calcium carbonate or calcite was calculated from data obtained by gravimetrically determining CO 2 adsorbed on Micobite. This method is a modification of the one described by Jackson (1958). Heavy and Light Mineral Determination For coarse silt, the amounts of minerals occurring in the fractions greater than 2.89 sp. gr. and less than 2.30 sp. gr. were determined in duplicate by decanting from bromoform (2.89 sp. gr.) and bromoform- nitrobenzene mixtures (2.30 sp. gr.). The floating fraction was de- canted after freezing the lower portion of the centrifuge tube. Three centrifugations with mixing were performed in the case of the 2.89 or heavy mineral separation. Decantation was carried out until nearly complete separation of the light mineral fraction was accomplished with 2.30 sp. gr. liquid. Large disparities for the 2.89 separation were not uncommon. Salient mineralogic characteristics of these fractions were determined by microscopic examination. Magnetic Susceptibility The pellet technique of Jones and Beavers (1963) was used in de- termining the magnetic susceptibility of the total air-dry sample. A Faraday balance was used to determine the susceptibility of the coarse- silt fraction. Mercury tetrathiocyanatocobaltate (16.44 X 10~ 6 cgs) served as the standard. RESULTS AND DISCUSSION Elemental Analysis Elemental data are given in Figs. 2 and 3 and in Table 3. In gen- eral, the data are remarkable because of the few differences occurring vertically within each profile and between the three profiles. In addi- tion to the report of concentration, peak to background ratios are given for zirconium because the ratios tend to emphasize differences in zir- conium content that are not apparent in the elemental report. BULLETIN NO. 701 [June, Zr(P/8) % Ti 2 KEY TO FIGS. 2 AND 3 Seafon: box Fayeffe: triangle Clinton: circle 5-20," fraction: dashed line 20-50.il fraction: solid line %ca 1.8 Z2 2S 3.0 %K 2 Distribution of titanium, zirconium, and potas- sium in the fine- and coarse-silt fractions. (Fig. 2) Distribution of calcium and iror in the fine- and coarse-sill fractions. (Fig. 31 7964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 9 Among the five elements analyzed, two or three groups of similarly behaving elements are present. Calcium and iron, particularly in the fine-silt fraction, are similar because they have undergone removal from the upper 20 to, 25 inches of the profile. In contrast, titanium, potassium, and zirconium do not appear to be either concentrated or removed. Zirconium and titanium differ from potassium in the marked fluctuations occurring vertically in the profile, especially in the coarse- silt fraction and in the surficial 20 to 25 inches. Zirconium content in the fine silt and potassium content in both silt-size fractions is re- markably constant vertically. Assuming a mobility or weathering sequence of Fe > Ca > K > Ti = Zr, some weathering trends can be found among the elemental profiles. These trends, occurring mostly below 40 to 50 inches, are most apparent in the lower B horizons. The iron profiles of both frac- tions are most striking in this respect. The fact that elemental analyses for Fayette tend to approach those of Seaton more than Clinton prob- ably reflects the effect of bluff distance on weathering. In addition to the greater potential weathering occurring with dis- tance from loess source, the silt becomes increasingly impoverished in heavy minerals because of differential settling. The net result of differ- ential corrasion, weathering, and sedimentation is a fine-textured sedi- ment in which few mineralogical changes occurred at distances greater than 20 miles to windward of the bluff. However, in the zone formed by the bluff and 8 to 12 miles to leeward, great changes occur because of differential settling. The variations within the profile of zirconium and titanium in the coarse silt are interpreted as the result of differ- ential settling of heavy minerals. Better grading of loess is apparent in the fine-silt analyses for these elements. Data obtained by Johnson (1961) for titanium and zirconium in loess at the bluff along the Illinois and Mississippi rivers also indicate variability with depth. The latest loess, represented by the upper 20 to 30 inches, is most representative of the differential settling phenomenon, although zirconium data for coarse silt of the Seaton profile undergo changes to the depth that this profile was sampled. These data suggest that the uppermost loess was deposited during a recent period characterized by winds of fluctuating carrying capacity. Discussions of the influence of differential settling on mineralogical characteristics of sediments formed under aqueous circumstances can be found in Rubey (1933) and Brajnikov (1944). Alternatively, it is possible that pedologic processes might give rise to these elemental differences. For example, mixing by soil fauna peculiar to the Seaton site may be invoked. However, elemental data for the other soils do not support such a pedogenic origin. o o u O o: _D O C o VI d> 1/1 _>. O E J?? LLJ -Q O ' w"* O^OOOOiO O ~* O O O*O*OOO* O ?s fs O 00 00 & O f*5 ^** f*5 (N O rs ^- (N H -H O^ O^ * O 00 O -^ CQ lO'^fS'O ^nOO-- ^^-^-s^ lS t ~~ t f- IT) \T) \f)lT) 6 a o^ ^o . C 1 ( ^.......*1. CSCSCNCN CNCSfNCS CNCSfSCS CSrSCNCN CSCNfSCS CN tstscses cscsestv cscstNM tstNfses O ^ (J G^ oooo oo'oo poop pppp pppp ~ <<<< CQ'BQBOM PQCIOOQBQ caojcno uuou *pii/s oo t-.. O cs*ooOO ^t 06 O O (S O -* < OO>O>O ~HI fe^ NO ^ g cs c C ON (S O W) ON IO 00 W5 B? MfOOO(N -HO>OO 00 CM O ON Nfl Nfl _! Tjl ON NO CS (S O *f 00 t^l^t^ON OOOiOiO IONOONO OOOiO 't'* C 3^< r5ONONO t- 00 1^ TUCSON rOON^NO ^JrO'Cro OO OO O 00 NO Tf O 00 O ^j ^j ON ON T!< t^ rj> w> TJI \r> cs fl O r<5 OOfSOO O ON _J tS < O rO O CN f*5 O O ~H O -^ CS -H CN CS 00 o * -to _:ow)-H ots-^'t NO oo pNKsrt -oooo OOO O> ON ON O ON O O ^ TJ O O O> OOOO OOOO rt (NCSCSCS ONOOOOOO OOOOONOO ONONOOOO oooo oooo oooo oo^o -ooo oooo ooo ooo"^ "^ooo oooo oooo C'C ...flC ? >. OO*N^H CM CS S? L v Z o r^OfS *~ O^lc^ O'O^Ov 1 OOCN\O CN^t> f*5 CS *H 2 COl>."oO COOOO^O O-H- CM(*)nOr5 " es e5 6? PNICSO) (N (S fS (N CStSCSCS (N CS O4 'I'OO.^O _^NOONO lOONfOOO ONOO " ^oto -a^SK NO; c' ; ts. tS CS CS tN CS _;NO _:r^ r^ 00 O ^^ CS Tf NO 00 O CS TP NO OOOCS CSCSPO*O fO'O'OfO ^t^f^t'^l' ^fl/il/5 OOOO OOOO OOOO OOO 00 ON O - cs ro ^ 10 *O t^ OO -. - i CSfNrsr*! CSCSCSCS '!"}">"* Tf * Tf ^ 03 o o X N <<<( fflgQcooQ paaaoau ouo <<<< cacacpa CQCOPQ uuuu o o *i- ^1^ OMO iO ONOiDO O - 7 ? ?-:-? -r^r"? tT"?^ ^o 1/500 c r- r 11 12 BULLETIN NO. 701 [June, The striking accumulation of calcium in the upper C 2 of Clinton probably reflects differences in dolomite content. The upper C 2 has 9.10 percent calcium carbonate equivalent (8.38 percent dolomite) as compared with 5.32 percent (4.90 percent dolomite) in the lower C 2 . The absence of calcite X-ray reflections in the upper C 2 suggests that the calcium content difference is not due to authigenic secondary carbonate. Compared with strongly developed soils in loess thinner than 75 inches (Beavers et al., 1963) in south-central Illinois, weathering as expressed by CaO-ZrO 2 and Fe 2 O 3 -ZrO 2 ratios in all three of these soils has not progressed very far. Therefore, on the basis of elemental data, it appears warranted to classify these soils as youthful. Clay Mineralogy The clay mineralogy of these soils is similar. The distributions of montmorillonite, illite, and kaolinite plus chlorite are given in Table 4. Representative diffractograms of potassium- and magnesium-saturated samples are reproduced in Fig. 4. Much greater changes occur verti- cally within the profiles than between the profiles. In general, the clay contents are comparable to those reported by Glenn et al. (1960) for Tama silt loam in southwestern Wisconsin and Frye et al. (1962) for Peorian loess along the Mississippi River north of Alton, although the minerals are not defined consistently among the reports. Caldwell et al. (1955) reported predominance of montmorillonite and accessory illite, kaolinite, and quartz in the less than 0.5/A fraction of two Fayette soils developed in Peorian loess in Minnesota. Montmorillonite, probably approaching nontronite in composition, undergoes marked destruction from C horizons upward to surficial horizons of these soils. The course of montmorillonite transformation is best observed in the potassium-saturated and glycol-solvated samples. Throughout the profiles, and especially in the Clinton profile, where there may be influence of underlying Illinoian till, vermiculite forma- tion is indicated by the collapse of expandable minerals to 10A on K saturation. The precursor of this vermiculite is not certain but may be illite and larger (>2/t) mica particles. There is evidence of aluminum interlayer formation of the mont- morillonite-type minerals in the B horizons of the Seaton and Clinton profiles. This interlayer assemblage gives a 14A component on both potassium and magnesium saturation. In the lower B horizon, "de- graded" montmorillonite expands to 17A when magnesium-saturated and glycolated. This behavior is similar to that reported by Pawluk (1963) for interlayer minerals in podzols of Alberta. Upon heating, all diffractograms with interlayer minerals showed marked "shoulders" 1964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 13 on the low angle side of 10A. This interlayered mineral assemblage also occurs in the upper B of Fayette (not shown in Fig. 4). The absence of a rational reflection for montmorillonite and the occurrence of a complex interlayered species (10A + 14A + 17A) is particularly apparent in the magnesium-glycolated samples of surface horizons. Because the A horizons undoubtedly have clay minerals con- tributed as loess and dust over a long period of recent time, the inter- pretation of the diffractograms relative to underlying materials is difficult. The following weathering scheme is suggested for clay minerals in these soils (cf. Jackson, 1963) : Kaolinite Illite I-. ^ Aluminous Mica (Minor in these soils interlayered with ex- pandable vermiculite in A horizons.) Chlorite 14A Interlayer Assemblage Montmorillonite ^-14A Interlayer Phase (Expandable to 17A with Mg saturation incipient weathering.) Formation of the 14A intergrade seems to be closely associated with unimpeded or good internal drainage of these soils. This intergrade mineral occurs to over 30 inches' depth in Seaton, and is confined to the upper 10 inches of the other two soils. Electronoscopic examination of clay from the B 2 of Clinton (Sam- ple 16419) indicates that a planar habit is the most common shape present. Cation exchange capacity (Table 4) of the clay fraction does not appear to vary consistently with weathering within the profiles. On the average, the clay fraction within the sola has approximately 55 to 65 me./lOO grams exchange capacity. Higher exchange capacities in the A horizons may be due to resistant organic matter. The trend of weathering of clay minerals should lower the capacity of the total clay fraction. Heavy and Light Mineral Determination The content of heavy minerals in selected horizons is given in Table 5. Even allowing for the imprecision of the heavy-mineral separation technique, several trends are apparent from the data. As expected, heavy-mineral content decreases below 20 inches in the profile from Seaton to Clinton, or with distance from the bluff. This is con- 14 BULLETIN NO. 701 [June, sistent with the elemental data for iron. The similar TiO 2 -ZrO 2 ratios (coarse silt) indicate that the same ratios of heavy minerals, in this case rutile and zircon, seem to be deposited at all three sites. Table 4. Diffraction Analysis of Crystalline Clay Minerals' 1 in the Less than 2/x Fraction and Cation Exchange Capacity (C.E.C.) of Selected Samples Depth Horizon Lab. No. Clay Minerals Kaolinite Chlorite Illite Mont- morillonite b C.E.C. (inches) 4-9 17054 SEATON % % me./lOOg. clay 70 12-15 A2 C 17056 ( d ) 21-24 B2 17059 18 42 40 64 27-30 B2 17061 20 27 53 32-34 B3 17063 14 30 56 75 34-36 B3 17064 19 29 52 36-38 B3 17065 12 31 57 40-44 B4 17067 13 23 68 48-52 B4 17069 9 27 64 56-60 Cl 17071 9 31 60 70-80 Cl 17073 7 23 70 76 FAYETTE 2-5 A2 17027 22 63 15 55 5-8 A2 17028 31 52 17 14-17 Bl 17031 24 40 36 22-25 B2 17034 15 35 50 60 28-31 B2 17036 12 31 57 31-33 B2 17037 13 35 52 33-35 B2 17038 13 29 58 57 35-37 B2 17039 11 32 57 37-40 B2 17040 15 30 55 43-46 B2 17042 11 26 63 50-55 B2 17044 13 31 56 60-70 Cl 17046 12 22 66 80-90 Cl 17048 13 26 61 55 CLINTON 1-5 Al c 16414 23 55 22 82 5-8 A2 C 16415 23 56 21 8-11 A-B 16416 17 41 42 45 16-19 B2 16419 16 35 49 22-25 B2 16421 14 29 57 57 30-37 B2 16423 12 24 64 48-60 Cl 16425 12 34 54 75-80 C2 16427 11 31 58 85 a Calculated for the purpose of comparing profiles. Results are to be interpreted in only a semiquantitative manner. b Includes 14 A intergrade and "degraded" montmorillonite. c Treated with HjOz prior to dispersion. All samples oxidized before cation exchange determination. d Characteristics of diffractograms prevented quantitative determination (see Fig. 4). 7964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 15 M d(A) d(A) CLINTON SEATON d(A) FAYETTE X-ray diffraction patterns of clay-size separates from selected horizons. K = potassium-saturated and glycolated M = magnesium-saturated and glycolated Recording is linear. (Fig. 4) 16 BULLETIN NO. 701 [June, Seaton and Fayette are generally lower in heavy mineral content above 20 inches (Table 5 and Fig. 5). This fact is indicative of weath- ering and surficial Recent loess. Throughout the Clinton profile there appears to be little variation in heavy-mineral content. Although sam- ples from closer intervals were used for the Seaton and Fayette profiles, more vertical variation of heavy minerals appears to occur in these soils. This variation is also consistent with the elemental analyses and magnetic susceptibility data for Seaton and Fayette. Contrast between vertical variation in these soils is undoubtedly indicative of grading. The best graded material occurs at the Clinton site. The most salient mineralogical characteristics of the heavy-mineral fraction as determined microscopically are as follows: (1) There is no significant difference in mineralogy within or between profiles. (2) Opaque minerals constitute approximately half of this fraction. (3) Opaque minerals are principally leucoxene and surficially oxidized (or hematitic) magnetite, and less than one-third of the opaque min- erals are black metallics. (4) Amphibole constitutes about half of the non-opaque or translucent suite. (5) Other prominent translucent minerals in the order of their occurrence are tourmaline > pyroxene > biotite-muscovite > chlorite = zircon = garnet > staurolite = actino- lite = rutile. (6) Micas have marginal birefringence even in the calcar- eous horizons. Among the many mineralogical features, it is interesting to note that Glenn et al. (1960) found that amphibole is abundant in the heavy- mineral fraction of the C horizon of a Tama profile in southwestern Wisconsin. The alteration of ilmenite to leucoxene, the oxidation of magnetite, and the weathering of the micas under acid and alkaline conditions are striking. Frye, Glass, and Willman (1962) report much less opaque minerals in the fine- and very fine-sand fractions of Peoria loess along the Mississippi River north of Alton than is found in the coarse silt of the Seaton, Fayette, and Clinton soils. However, they report as much as 60 percent amphibole in the sand fraction (62-250^). This percent is comparable to that found in the coarse-silt fraction. X-ray diffraction analyses of the total sample indicate that minerals approaching albite and microcline in composition are the principal feldspar components of the C horizons of these soils. The amount of albite is particularly striking (Table 6). Frye et al. (1962) found more potassic feldspar (16 percent) than plagioclase feldspar (9 percent) in the sand fraction of Peoria loess along the Mississippi River north of Alton, Illinois. Diffraction data also indicate that calcareous hori- zons are composed predominantly of dolomite. 1964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 17 Table 5. Heavy-Mineral Content of 20 to 50/x Fraction and Magnetic Susceptibility of Total Soil and 20 to 50/j. Fraction Depth Horizon Lab. No. Xg total Xg 20-50 M Heavy minerals 20-50 M total* (inches) X 10- 6 cgs X10- 6 cgs % % SEATON 4-9 A, 17054 22.6 n.d. 2.41 1.18 9-12 A-, 17055 23.0 19.4 1.94 1.01 12-15 A 2 17056 n.d. 22.6 1.52 .89 15-18 A 2 17057 21.9 n.d. n.d. n.d. 18-21 B, 17058 n.d. 24.6 n.d. n.d. 21-24 B 2 17059 22.8 21.6 2.96 1.60 27-30 B 2 17061 22.4 29.2 n.d. n.d. 32-34 B 3 17063 26.1 n.d. 3.66 1.96 36-38 B 3 17065 22.1 29.2 3.37 1.92 40-44 B 4 17067 22.4 31.5 3.78 2.25 48-52 B 4 17069 23.9 31.8 3.35 1.84 56-60 G! 17071 21.9 32.7 4.02 2.23 70-80 G! 17073 25.7 29.6 4.10 2.39 95-105 Co 17075 17.2 26.5 n.d. n.d. FAYETTE 2-5 A 17027 19.8 20.1 .60 .30 5-8 A 17028 n.d. n.d. 1.21 .64 12-14 A, 17030 20.2 22.4 1.88 .92 17-19 B! 17032 18.4 30.1 1.70 .73 22-25 B 2 17034 15.0 26.7 3.71 1.51 28-31 B 2 17036 18.1 31.8 3.04 1.24 33-35 B 2 17038 n.d. n.d. 3.52 1.50 37-40 B 2 17040 16.7 22.1 2.81 1.14 43-46 B 2 17042 13.8 27.6 n.d. n.d. 50-55 B 2 17044 17.5 26.7 4.02 1.55 60-70 G! 17046 16.9 27.1 4.06 1.62 80-90 G! 17048 15.6 22.1 2.69 1.22 100-110 C t 17050 12.8 19.2 n.d. n.d. 125-140 G! 17052 5.3 5.0 n.d. n.d. CLINTON 1-5 A, 16414 11.2 9.2 1.35 .60 8-11 A-B 16416 12.3 10.0 1.32 .54 13-16 B 2 16418 10.1 10.1 n.d. n.d. 16-19 B, 16419 n.d. 9.9 1.04 .29 19-22 B 2 16420 9.6 n.d. n.d. n.d. 25-30 B 2 16422 11.9 16.5 n.d. n.d. 30-37 B 2 16423 11.8 18.5 1.67 .55 48-60 G! 16425 9.8 11.0 2.40 .89 60-75 G! 16426 8.3 8.8 n.d. n.d. 75-80 C 2 16427 4.0 5.8 2.08 .72 80-90 C 2 16428 3.9 5.8 n.d. n.d. Percent heavy minerals in 20-50/i X percent 20-50/t in soil. 18 BULLETIN NO. 701 [June, 10 20 30- 40 a. bJ 50 60 70- 80- 90 D SEATON A FAYETTE O CLINTON Heavy-mineral content (>2.89 sp. gr.) of the coarse-silt fraction. (Fig. 5) Table 6. Relative Contents of Feldspar and Carbonate Minerals in Deep Horizons Depth Horizon Lab. No. Feldspar content Carbonate (inches) 80-90 Ci SEATON 17074 Microcline > Albite None 90-105 C 2 17075 Albite > Microcline Dolomite 100-110 Ci FAYETTE 17050 Albite > Microcline None 125-140 Ci 17052 Albite > Microcline None 75-80 . C 2 CLINTON 16427 Albite = Microcline Dolomite 80-90.. a 16428 Albite = Microcline Dolomite 7964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 19 The light-mineral distribution of these soils (Table 7) indicates an almost linear decrease of plant opal from the surface to 20 inches, where opal makes up 0.10 percent by weight or less. Seaton and Fayette appear to have higher opal contents at depth, and Seaton has the highest opal content throughout. This distribution is consistent with an interpretation involving slow deposition of Recent loess on a sparsely grassed landscape. Higher opal content at depth would be expected near the bluff for example, at the Seaton site than at a distance because of the loess thickness-distance relationship. Other evidence for such a Recent loess has been cited by Beavers et al. (1962) and by Jones and Beavers (1963). Table 7. Plant Opal Content of Selected Horizons Depth Horizon Lab. No. Opal content (inches) 4-9 SEATON Ai 17054 % 51" 12-15 Ao 17056 .31 18-21 B! 17058 .10 2-5. . FAYETTE A 2 17027 .32 5-8 A 2 17028 .18 12-14 A 3 17030 .21 17-19 Bi 17032 .06 0-1 CLINTON Ai 16413 .44 1-5 . Ai 16414 .33 13-16 Bi 16418 .05 Percent light minerals in 20-50/i X percent 20-50/1 in soil. In addition to graminous opal represented principally by infillings of fundamental, bulliform, and trichome cells, occasional fragmented opaline monactine sponge spicules occur in the light-mineral concen- trate (Fig. 6). These spicules are probably of Recent age, and were derived from sponge fauna inhabiting the upper Mississippi drainage. The opaline tests of the radiolarian Dictyomitra was found in the Ci of Seaton. Jones, Hay, and Beavers (1963) reported this and other microfossils in loess of Illinois, and indicated that the fossils were derived from Cretaceous rocks in the northern Great Plains. Dicty- omitra in Seaton probably had such an origin being blown from a valley train after reworking and transport from the west. SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 21 Magnetic Susceptibility Magnetic susceptibility data for total sample and for the coarse-silt fraction are given in Table 5. In general, the susceptibility data are consistent with heavy mineral and elemental data, indicating marked fluctuations in mineralogy of the upper solum in both Seaton and Fayette. Better grading of the loess is suggested by a rather uniform susceptibility content throughout the Clinton profile. Decrease of susceptibility of the total sample from Seaton to Clinton is partly attributable to decrease in mean particle size of the ferrimag- netics. This decrease in mean particle size reduces the overall suscep- tibility of the total sample. However, this effect is thought to be sub- ordinate to the other processes described above. The slightly poorer drainage of Clinton also causes lower susceptibility values. SUMMARY Because of the differences in loess depth between Seaton, Fayette, and Clinton soils, the age of the loess in which these soils are devel- oped probably varies markedly. Using the 22,000 year B.P. date of Frye et al. (1962) for the base of Peoria loess, the Clinton solum has developed in Peoria loess deposited principally from 22,000 to about 11,000 years B.P. Evidence has also been presented that a veneer of Recent loess deposited since 11,000 years B.P. is present in the surface. At the Seaton and Fayette sites the sola are developed in much thicker Recent loess and much younger Peoria loess. The titanium and zir- conium analyses and the TiO 2 -ZrO 2 ratio indicate that the Peoria loess is fairly uniform in composition below 20 inches to the depth sample for the three soils. Elemental analyses, heavy-mineral analyses, and magnetic suscep- tibility data indicate that upper portions of the sola of Seaton, Fayette, and Clinton soils of northwestern Illinois are developed in Recent loess. Vertical variability of the parameters measured in Seaton and Fayette soils and relatively uniform analyses for the Clinton soil suggest that grading is important in interpretation of mineralogical characteristics of these loessial soils. The upper portions of the sola are low in calcium and iron content in the 5 to 20ju, and 20 to 50/A fractions. This is probably indicative of leaching loss, and possibly a reflection of deposition of a Recent loess blanket poor in these elements. Calcium and iron are also among the first elements to weather in these relatively youthful soils, particularly in the fine-silt fraction. Iron-zirconium and calcium-zirconium ratios suggest similar weathering of these elements. Titanium-zirconium ra- tios indicate similar proportions of minerals bearing these elements. 22 BULLETIN NO. 701 [June, Heavy-mineral and magnetic susceptibility data indicate a decrease in the heavy-mineral fraction with distance from the bluff or loess source. The forces of grading are invoked to explain this decrease, although progressive weathering through the soil sequence is not en- tirely discounted. Distribution of plant opal with depth substantiates the depth-distribution pattern; that is, opal is distributed deepest in soils at the bluff. Clay mineral weathering is closely related to internal drainage, and is expressed by progressive formation of a 14A aluminous intergrade mineral derived from montmorillonite upward in the profile. Mica and illite weather to vermiculite throughout the profile. Deposition of Recent loess that is somewhat weathered before depo- sition complicates interpretation of the mineralogy and weathering of the surficial horizons of these soils. Recognition of this relationship is important, and some of the hypotheses for weathering based on studies in the upper Mississippi Valley and elsewhere may need to be reevalu- ated in light of it. Contrary to physical appearance, loess need not be uniform in mineralogy either vertically within the section or with distance from source. LITERATURE CITED 1. BEAVERS, A. H., and JONES, R. L. A fractionator for silt. Soil Sci. Soc. Am. Proc. 26:303-304. 1962. 2. BEAVERS, A. H., FERHRENBACHER, J. B., JOHNSON, P. R., and JONES, R. L. The CaO 2 -ZrO 2 ratio as an index of soil weathering. Soil Sci. Soc. Am. Proc. 27:408-412. 1963. 3. BRANNIKOV, B. Sur I'importance de la granulometrie pour 1'etude quantitative des mineraux lourds dans un sediment. Bui. Soc. Geol. France 14:381-390. 1944. 4. CALDWELL, A. C, FAINHAM, R. S., and HAMMERS, F. L. A chemical and mineralogical study of clay minerals from several Gray-Brown Podzolic soils in Minnesota. Soil Sci. Soc. Am. Proc. 19:351-354. 1955. 5. FRYE, J. C, GLASS, H. D., and WILLMAN, H. B. Stratigraphy and min- eralogy of the Wisconsinan loesses of Illinois. 111. State Geol. Surv. Cir. 334. 55p. 1962. 6. GLENN, R. C., JACKSON, M. L., HOLE, F. D., and LEE, G. B. Chemical weathering of layer silicate clays in loess-derived Tama silt loam of southwestern Wisconsin. Proc. 8th Nat. Conf. on Clays and Clay Minerals, pp. 63-83. 1960. J964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 23 7. GROSSMAN, R. B. Characterization of ped surfaces in contrast to ped interiors from B horizons of some major great soil groups in Illinois. Unpublished Ph.D. dissertation, University of Illinois. 188p. 1959. 8. JACKSON, M. L. Soil chemical analysis. Prentice-Hall, Inc., Englewood Cliffs, N. J. 498p. 1958. 9. JACKSON, M. L. Interlaying of expansible layer silicates in soils by chemical weathering. Proc. llth Nat. Conf. on Clays and Clay Min. pp. 29-46. 1963. 10. JOHNSON, P. R. X-ray spectrographic analysis of loess deposits in Illi- nois. Unpublished Ph.D. dissertation, University of Illinois. 130p. 1961. 11. JONES, R. L., and BEAVERS, A. H. Sponge spicules in Illinois soils. Soil Sci. Soc. Am. Proc. 27:438-440. 1963. 12. JONES, R. L., and BEAVERS, A. H. A technique for magnetic suscepti- bility determination of soil materials. Soil Sci. Soc. Am. Proc. 28: 47-49. 1964. 13. JONES, R. L., HAY, W. W., and BEAVERS, A. H. Microfossils in Wis- consinan loess and till from western Illinois and eastern Iowa. Sci- ence 140:1222-1224. 1963. 14. KINTER, E. B., and DIAMOND, SIDNEY. A new method for preparation and treatment of oriented aggregate specimens of soil clays for x-ray diffraction analysis. Soil Sci. 81:111-120. 1956. 15. KRUMBEIN, W. C. Sediments and exponential curves. Jour. Geol. 45: 577-601. 1937. 16. MUCKENHIRN, R. J., ALEXANDER, L. T., SMITH, R. S., SlIRADER, W. D., RIECKEN, F. F., McMiLLER, P. R., and KRUSEKOPF, H. H. Field descriptions and analytical data of certain loess-derived Gray-Brown Podzolic soils in the upper Mississippi River valley. 111. Agr. Exp. Sta. Bui. 587 (N. C. Reg. Pub. 46). 80p. 1955. 17. NETTLETON, W. D. Distribution of some forms of nitrogen in selected loess-derived soils in Illinois. Unpublished M.S. thesis, University of Illinois. 35p. 1958. 18. PAWLUK, S. Characteristics of 14A clay minerals in the B horizons of podzolized soils of Alberta. Proc. llth Nat. Conf. on Clays and Clay Minerals, pp. 74-82. 1963. 19. RUBEY, W. W. The size-distribution of heavy minerals within a water- laid sandstone. Jour. Sed. Pet. 3:3-29. 1933. 20. SMITH, G. D. Illinois loess. 111. Agr. Exp. Sta. Bui. 490. pp. 139-184. 1942. 21. WAGGONER, P. E., and BINGHAM, CHRISTOPHER. Depth of loess and distance from source. Soil Sci. 92:396-401. 1961. BULLETIN NO. 701 [June, APPENDIX A: PROFILE DESCRIPTIONS C//nfon Silt Loam Warren County, T9N, R1W, Sec. 2, NWJ4, NW i/ 4 , NW ]/ 4 . Sampled on east side of gravelled road at first cut south of section line by R. T. Odell and G. D. Smith (November 19, 1940). Colors determined on air- dry crushed samples by R. L. Jones, May, 1963. This description follows the style and format of the descriptions in Illinois Agricultural Experiment Station Bulletin 587 (North Central Regional Publication 46). Description Brown leaf mould. Platy friable silt loam. Gray-coated, weakly nut-like. Subangular nut-like structure coated with yellow and gray specks. Aggregates Yt to % inch in up- per part, increasing to 1 ; in lower part. Blocky. Nearly massive. Horizon Depth (inches) Sample No. Munsell Color Notation Ao 0-1 16413 10YR 5/2 A, 1-5 16414 10YR 6/2 A 2 5-8 16415 10YR 6/3 8-11 16416 10YR 6.5/3 Bi 11-13 16417 10YR 6.5/4 B 2 13-16 16418 10YR 6.5/4 16-19 16419 19-22 16420 10YR 6.5/4 22-25 16421 25-30 16422 30-37 16423 10YR 6.5/4 37-48 16424 10YR 7/4 c, 48-60 16425 10YR 6/4 60-75 16426 10YR 6/4 C 2 75-80 16427 10YR 7/4 82-90 16428 10YR 7/4 D 94+ Dark Illinoian till soil. Secrfon Silt Loam Henderson County, TUN, R4W, Sec. 8, NW y 4 , NW 1/4, NE y 4 . Sampled on east side of road 24 rods north of intersection. Six-percent slope to south. The following description is somewhat modified from that written by R. B. Grossman, July 30, 1957. Colors are for moist conditions and, unless otherwise noted, refer to the ped surface. Sampled within several rods of the site sampled for Illinois Bulletin 587 (Profile No. T40). This description follows a more modern format than those in Bulletin 587. Horizon A 3 Depth (inches) 0-5 5-10 10-15 Description Dark brown (10YR 3/3) friable silt loam; weak fine- crumb structure ; clear boundary. Brown ( 10YR 4.5/3) soft to slightly hard silt loam; weak to moderate fine-platy structure ; clear boundary. Light yellowish-brown (10YR 6/4) and dark brown (7.5YR 4/3) hard silt loam, breaking to yellowish-brown (10YR 5/4) ped interior; moderate to strong, fine to medium subangular blocky structure; clear boundary. 7964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 25 B! 15-20 Yellowish-brown (10YR 6/4) with some dark brown (7.5YR 4/3) hard silt loam, breaking to yellowish-brown (10YR 5/4) ped interior; moderate to strong, fine to medium subangular blocky structure; clear boundary. B 21 20-26 Dark brown (7.5YR 4/3) and yellowish-brown (10YR 6/4) hard to very firm silt loam, breaking to brown (7.5YR 5/5) ped interior; moderate to strong, medium to fine, blocky to subangular blocky structure ; clear boundary. B 22 26-33 Brown (7.5YR 4/3) firm to very firm silt loam, breaking to yellowish-brown (10YR 5/4) ped interior; strong medium blocky structure ; gradual boundary. B 3 33-43 Brown (7.5YR 4/3) firm to very firm silt loam with few light yellowish-brown (10YR 6/4) mottles on vertical faces, breaking to brown (10YR 5/3) ped interior; weak to moderate, medium to coarse prismatic structure ; grad- ual boundary. C l 43-66 Dark brown (7.5YR 4/2) firm to friable silt loam, break- ing to brown (10YR 4/3) ped interior; weak, very coarse prismatic structure. Fayette Silt Loam Warren County, TUN, R3W, Sec. 9, NE 14 NE i/ 4 , SE 14. Sampled 27 rods west of bridge and 9 rods west of top of slope. Six-percent slope to southwest. Colors are for moist conditions and, unless otherwise noted, refer to the ped surface. Sampled within several feet of the site sampled for Bulletin 587 (Profile No. T39). This description is somewhat modified from that written by R. B. Grossman, August 29, 1957. Depth Horizon (inches) Description AH 0-4 Very dark grayish-brown ( 10YR 3/2) very friable silt loam ; weak fine-crumb structure ; clear boundary. A 12 4-7 Brown (10YR 5/3) very friable silt loam; weak fine- platy structure ; clear boundary. A 21 7-13 Brown (10YR 5/3) very friable to soft silt loam; mod- erate fine-platy structure ; clear boundary. A 3 13-15 Light yellowish-brown (10YR 6/4) mottled dark brown (7.5YR 4/2) firm silt loam, breaking to yellowish-brown (10YR 5/4) ped interior; moderate fine subangular- blocky-to-platy structure ; clear boundary. B x 15-20 Light yellowish-brown ( 10YR 6/4) mottled brown (7.5YR 4/2) firm silt loam, breaking to yellowish-brown (10YR 5/4) ped interior; fine subangular blocky to blocky structure ; clear boundary. B 21 20-30 Dark brown (7.5YR 4/2) with some gray (10YR 7/2, dry) firm to very firm silt loam, breaking to yellowish- brown (10YR 4.5/4) ped interiors; strong medium to fine blocky structure ; gradual boundary. 26 BULLETIN NO. 701 [June, B,, 30-39 Dark brown (7.5YR 4.5/2) with some light gray (10YR 7/1, dry) very firm silt loam, breaking to brown ( 10YR 5.5/3) ped interior; prismatic structure, breaking to strong medium to coarse blocky structure ; gradual boundary. B ; , 39-53 Brown (7. SYR 5/2) very firm silty clay loam, breaking to brown (10YR 5.5/3.5) ped interiors with common fine, faint yellowish-brown mottles; strong medium prismatic structure, breaking to moderate to strong, coarse blocky structure ; diffuse boundary. G! 53-72 Brown (7. SYR 5/3) fine silt loam, breaking to light yellowish-brown (10YR 6/4) ped interior with common, medium, faint brownish-yellow and very pale brown mottles ; moderate to strong coarse prismatic structure. Clinton Silt Loam Warren County, TUN, R1W, Sec. 21, NW y 4 , NW y 4 , 35 rods south of fence and 11 rods east of road center. Five-percent slope to southwest. Colors are for moist condition and, unless otherwise noted, refer to the ped surface. The following description is somewhat modified from that written by R. B. Grossman, August 31, 1957. Note that this profile is 9 miles north of the Clinton used in the mineralogic study. The profile is thought to be from the same pit as the soil described in Illinois Bulletin 587 (Profile No. 15). Depfh Horizon (inches) Description A l 0-4 Dark gray (10YR 4/1) friable silt loam; weak fine-crumb to platy structure ; clear boundary. A 2 4-10 Pale brown (10YR 6/3) friable silt loam; weak fine to very fine platy structure ; clear boundary. A 3 10-13 Pale brown (10YR 6/3) firm silt loam, breaking to yellow- ish-brown (10YR 5/4) and dark yellowish-brown (10YR 4/4) ped interior; moderate fine subangular to coarse platy structure; very vesicular; clear boundary. B! 13-18 Pale brown ( 10YR 6/3) and brown (10YR 4/3) firm to very firm silt loam, breaking to yellowish-brown ( 10YR 5/4) ped interior; strong fine-subangular-blocky structure; clear boundary. B 21 18-26 Dark grayish-brown (8.75 YR 4/2) and pale brown (10YR 6/3) very firm silty clay loam, breaking to yellowish- brown (10YR 5/4) and dark grayish-brown (8.75YR 4/2) ped interior; strong fine to medium blocky structure; weakly vesicular; clear boundary. 1964] SEATON, FAYETTE, AND CLINTON SOILS IN ILLINOIS 27 B 22 26-38 Dark brown (7.5YR 4/2) and pale brown (10YR 6/3) very firm silty clay loam, breaking to yellowish-brown (10YR 5/4) ped interior with dark brown (7.5YR 4/2) coatings; strong medium blocky structure with tendency to prismatic; clear boundary. B 3 38-48 Dark brown (7.5YR 4/2) and pale brown (10YR 6/3) extremely firm silty clay loam, breaking to yellowish- brown (10YR 5/4) ped interior with many medium dis- tinct yellowish-brown and very pale brown mottles ; strong medium-to-coarse prismatic structure; moderately vesicu- lar ; gradual to diffuse boundary. Cj. 48-68 Dark brown (7.5YR 4/2) very hard silt loam, breaking to brown (10YR 5/3) ped interior with many medium dis- tinct yellowish-brown and light brownish-gray mottles and a few Fe-Mn concretion-like mottles; weak, very coarse prismatic structure ; very vesicular. APPENDIX B: ANALYTICAL DATA Mechanical Analysis, Organic Carbon, and pH Data for Clinton Silt Loam" Sample No. Depth Sand 50 M Silt 2-20 M Fine silt 2-20 M Clay 2M Organic carbon pH 16413. . inches 0-1 % 1.0 % 78.2 % 38.0 % 16.2 % 3.38 5.4 16414 1-5 .9 85.1 40.4 12.8 1.01 4.2 16415 5-8 1.0 83 6 40.2 15 4 .50 4.2 16416 8-11 .6 78 2 37.6 21.2 .38 4.1 16417.. 11-13 .6 72.8 36 7 26.1 .31 4.2 16418... . . 13-16 .5 65 1 35 4 34.4 .31 4.2 16419 .. . 16-19 4 63 1 35 2 36 4 .27 4.1 16420 .. 19-22 4 62 8 35 6 36 3 .26 4.2 16421 .. 22-25 5 64 4 36 9 35 1 .24 4.3 16422 25-30 4 66 8 38 8 32 5 .23 4.3 16423 30-37 3 69 7 36 8 30 .19 4.4 16424 37-48 6 71 2 36 7 28 1 .20 4.6 16425 . 48-60 7 72 7 35 5 26.3 .19 4.9 16426 . 60-75 1 2 74 4 35 7 23.3 .18 5.7 16427 75-80 .8 81.3 46.5 14.4 ( b ) 7 3 16428 80-90 6 76.9 50.7 16.2 ( b ) 7 4 * Presentation of these data follows that of Illinois Agricultural Experiment Station Bulletin 587 (X. C. Regional Publication No. 46). b Calcareous. 4M 6-64 83201 UNIVERSITY OF ILLINOIS-URBANA Q 630.7IL6B "08 BULLETIN. URBANA 701 1964 30112019530549