DIVISION S-5—SOIL GENESIS,MORPHOLOGY, AND CLASSIFICATION

Loess Distribution in Central and Eastern Kentucky1

R. I. BARNHISEL, H. H. BAILEY, AND SAHAT MATON0ANG2

ABSTRACT

The loess distribution along a transect from Louisville toeastern Pike County, Kentucky was studied. The parametersused to determine the extent and depth of loess were particlesize analyses, titanium content of—and relative amounts of feld-spar in—the coarse, medium, and fine silt fractions. The bestcriterion was the expression of data on the percent silt on aclay-free basis. It was determined that the loess mantle extendsabout 148 km (92 miles) eastward from the Ohio River.Beyond this distance the loess was either too thin to be recog-nized due to mixing with residuum or loess was not present.The entire soil profile was developed in loess up to 68 km (42miles) from the source and from 84-148 km (52-92 miles)along the transect, the upper part of the solum was in loess,the lower part was developed in residual material. It appeared

that loess of two ages associated with the glaciation periods,was present in the initial part of the transect, up to 84 km (52miles) from the Ohio River.

Additional Key Words for Indexing: X-ray emission.

IT is GENERALLY recognized that loess covers large areasof western Kentucky from the Mississippi and Ohio

Rivers eastward into the commonwealth (11, 15, 16).Loess in Kentucky is assumed to have been deposited bythe eolian process with the silty material being blown east-ward from the river valleys by the prevailing winds duringthe glacial periods (16). The loess deposits are known tobe 10 m or more thick along some bluffs of the MississippiRiver, but rapidly diminishing in thickness to about 0.5 mor less in 125 to 150 km (15, 16). Along the Ohio Riverthe loess deposits are reported to be much thinner andextend only some 25 km eastward from the river (15).

Field observations in the course of recent routine soilsurveys in central and eastern Kentucky have repeatedly

484 SOIL SCI. SOC. AMER. PROC., VOL. 35, 1971

raised the question as to the possibility of a heretoforeunreported loess mantle in the area.

Detection of loess where it makes up only a part of thesoil profile is difficult. Hutcheson and Bailey (11) reportthat loess weathering is influenced by the texture of theunderlying residual as well as significant mixing with theunderlying materials when the loess mantle is thin.

Since no single mineral is absolutely resistant to weather-ing, the detection of loess in a mixture is a difficult prob-lem. Minerals such as zircon, tourmaline, garnet, anatase,rutile, quartz, albite, and microcline are more resistant,and several researchers have used these minerals in variousways to determine the presence or absence of loess (1, 2,3, 4, 6, 8, 9, 10, 12, 13). X-ray emission methods,developed by Beavers and his co-workers, have been usedby several of the researchers listed above to measure theZrO2 and TiO2 contents of soils and silt fractions, andthese data were then related to loess distribution.

The use of Zr/Ti oxide ratios (or some other ratio) todetermine the contact of loess with the underlying materialappears to be valid when the underlying material is glacialtill (1, 2, 3, 12, 13). However, Chapman and Horn (6)reported that in Arkansas Zr and Ti contents and theTiO2/ZrO2 molar ratios did not confirm lithological dis-continuities in soils suspected to be developed in two par-ent materials. Similar problems were encountered by Rut-ledge (14) in Ohio in that Ti/Zr ratios did not changeappreciably across obvious lithological discontinuities.However, Rutledge (14) was able to relate the percentsilt on a clay-free basis to these same lithological discon-tinuities.

The objectives of this study were to: (i) try to find achemical, mineralogical, or physical criterion to identifyloess, and ( i i ) determine the distribution of loess in centraland eastern Kentucky.

MATERIALS AND METHODS

Samples for this study were taken from 22 soil profilesstudied along a northwest to southeast transect through cen-tral Kentucky (Fig. 1). The transect began with the first pro-file near Louisville, adjacent to the Ohio River and designatedas LI, and ended with profile L22 near the town of Majestic inPike County, Kentucky. The profiles were located approxi-mately 16 km (10 miles) apart, on broad ridge tops whereerosion was at a minimum. Samples were taken in approximately15-cm (6-inch) increments; however, if a horizon boundary

occurred within any increment, the sample was split into twosamples for analysis. Classification of the soils with respect totype and series is given in Table 1. Table 1 also gives the dis-tance from the Ohio River and the age of the substrate rockmaterial. Figure 1 also relates the sampling sites to the generalgeology of the area.

The soil samples were air-dried, ground, and particles < 2mm used for further investigation in the laboratory. The or-ganic matter was removed from all samples with H2O2, priorto particle size fractionation. These samples were adjusted topH 10 with Na2CO3 and dispersed with a mechanical mixer.The sand was collected on a 300-mesh sieve. The finer materialwas fractionated into four silt sizes, 50-20, 20-10, 10-5, 5-2,and clay, < 2/j,, by an elutriation method patterned after Bea-vers and Jones (5).

The titanium content of the silt fractions was determinedwith a procedure adapted from methods described by Claisse(7) and Beavers (3) as follows: a 0.5-g sample was mixed with15 g Na-borate and 10 g Li-tetraborate. The mixture was fusedin a graphite crucible and the liquid poured onto a heated Alplate, and the resulting 4-cm glass disc was annealed at about450C, then slowly cooled to room temperature. The glass discwas subjected to X-rays generated by a General Electric XRD-5unit operated at 50 Kvp and 40 ma using a Pt-target tube. TheTi Ka fluorescence was counted at 86.13° 2S for 200 sec, usinga LiF analyzing crystal in conjunction with a PR gas-flow coun-ter tube and pulse-height discriminator.

The relative amounts of feldspars in the silt separates weredetermined in "random" grain amounts prepared by sprinklingthe particles on a glass slide. A 1% glue (Duco cement) inmethanol was used as a binding agent. Peaks at d-spacings be-tween 3.28 and 3.16 A were taken as feldspar. The sum of thepeak-heights of these two values are reported in the tables ascounts per sec (cps) to allow proportional comparisons. Abso-lute quantities of feldspars were not determined.

RESULTS AND DISCUSSION

Results from nine of the 22 locations are given in Table2. Additional data on the nine locations along with datafor the remaining 13 profiles are recorded in a thesis byone of the authors (Sahat Matondang. 1969. UnpublishedM.S. thesis, Univ. of Ky.). All particle size distributiondata, except the column otherwise indicated, has been cal-culated on a clay-free basis. Therefore the percent sandplus total silt equals 100%. The percent sand is given sothat if one desires one could calculate the percent sand, silt,

Table 1—Soil profile designations with respect to distance fromthe Ohio River, Soil Series," and age of substrata rockf

Fig. 1—General geology of Kentucky and locations of samplingsites. A = Alluvial, C = Cretaceous, D = Devonian-Silurian,M — Mississippian, P = Pennsylvanian, Q = Quaternary-Tertiary. Dots represent sampling sites for LI to L22.

Soil profileno.

LIL2L3L4L5L6L7L8L9L10LllL12L13L14L15L16L17LI 8L19L20L21L22

DistanceOhio R

km

31935516884

100116132148164180196212228245261277293309325341

fromvermiles

2122232425262728292

102112122132142152162172182192202212

Soilseries

MemphisCriderCriderMercerShelbyvilleMauryMauryMauryLowellLowellFaywoodWhitleyMuseGilpinGilpinGilpinGilpinWeikertGilpinGilpinWeikertGilpin

Geologicage of rock

DevonianDevon anOrdov cianOrdov cianOrdov cianOrdov cianOrdov cianOrdovicianOrdovicianOrdovicianDevonianMississippianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanianPennsylvanian

Soil profile descriptions are on permanent file at the University of Kentucky, Ag. Exp.Sta. Sites were sampled and soils classified with the aid of personnel from the USDASoil Conservation Service, Kentucky.Information taken from geologic maps published by Kentucky Geological Survey.

BARNHISEL ET AL.: LOESS DISTRIBUTION IN KENTUCKY 485

and clay on a whole soil basis. Note that the percent sandon a whole soil basis for loessial parent materials wassmall, and in almost every case this sand material wasactually Fe-Mn concretions.

Lithologic discontinuities were described in the field inthe first five profiles along the transect, and such bounda-ries were believed to separate loess and residuum. Data ofthese sites are included in Table 2. In only two of thesefive profiles, L3 and L4, was there noted a sharp changein the Ti content at this boundary. In the other three pro-files, LI, L2, and L5, the Ti percentage did not changeat the field determined lithologic boundary. The percentTi as presented in Table 2 are those of the 50-2^ silt frac-tions and, therefore, the Ti values do not include any con-tribution that could be present in the sand or clay fractions.In any case, the amount of Ti in the silt could not be usedas a consistent indicator of a change in parent material.A similar lack of correspondence between lithologic boun-daries and Ti percentages was found in Arkansas byChapman and Horn (6).

In only one case, at location L5, was there agreementin the observed lithologic boundary and change in the

amount of feldspar. The feldspar values should be con-sidered as only relative and represent the height of themajor peaks in the X-ray diffraction patterns. However,the use of feldspar as a means of recognizing changes inparent materials was not a consistent measure.

Rutledge (14) used the amount of silt on a clay-freebasis as an indicator of the boundary between loess andglacial till in Ohio. Expressing the particle size distributionin such a manner minimizes the effect of clay movement,which could occur during soil profile development, onrecognizing boundaries between parent materials. How-ever, agreement between the lithologic boundaries as de-scribed in the field and major changes in percent silt wasno better than the change in percent Ti. A small changein percent silt was noted in locations L3, L4, and L5 atwhat was described as a lithologic boundary.

However, it was apparent that the values of percent silton a clay-free basis fell into three categories. A fairly sharpchange in silt content was observed at approximately 96%and below, and another break was observed at about 86%silt. Dashed lines have been drawn in Table 2 to indicatethese changes in silt percentages. It is believed that these

Table 2—Particle size distribution (data expressed on clay-free basis), percent Ti of the silt fraction, and relative feldspar contentof selected profiles. Dashed lines represent significant parent material changes determined by laboratory procedures

(by fielddesignation)

LOESS IAplAp2BlB21tB22tB23tB24tB3IIB1IIB2IIClIIC 2IIC3

LOESS IIIIC4IIC 5IIC6

LOESS IApBlB21tB23t

LOESS IIB24tIIBbIIClIIC2

RESIDUALIIIC3R

LOESS IApBlB21tB22tB23t

LOESS IIB3tIIClIIC2IIC3

ApDlB21tB22t

LOESS IIBxl

Depth

0-1515-3030-4141-5656-7171-8484-9797-112

112-127127-142142-160160-178178-196

196-203203-216216-234+

0-1818-3348-6464-79

79-9494-109

109-124124-140

140-190190+

0-2020-3636-5151-6666-81

81-9797-109

109-122122-132+

0-1818-2525-4343-58

58-76

Sand*

0.692.372.180.681.972.002.292.352.042.761.981.582.43

5. 276.909.32

2.773.002.392. 46

4.735. 128.508. 84

15.20

2.761.632.082. 842 .42

9.755. 114.403.85

3.903. 162.712. 15

8.36

Sand

LI -0.802.942. 810.922.702.643.022.982.493.312 .421.912. 94

6.488. 49

12.02

L2 -

3.463. 753.493. 20

6.436. 81

12.6613.88

23.86

L3 -3.392. 233.494.093.58

13. 948. 237. 926.54

L4 -4.954.303. 823.03

11. 12

Coarse ft50-20n

Memphis50.4050.0252.4451.9649.6259.9055.9358.0157.4157.0056.0643.6141.47

38.7925.4832.90

Crlder -47.5442.0242.3441.22

35. 1631. 2927.7628.86

23.90

Crider -35. 7436.1738.0434.7833. 91

27.6830. 2431.3629.97

Mercer -38.3336.6242. 2936.00

34. 71

SiltMedium20-5(<

<7

- 3 km40. 8439.6938.6939.1643.0333.2337.1134. 5235.5636.0737.7549.3749.27

46.8156.6743.2019 km45.0947. 9546. 2045.85

48.6048. 2948.0845.23

40.72

35 km48.7849.4753.7749.8350. 26

45.7947.2945.6750.0051 km46.7746.6340.9348.47

39. 88

5-2(.

8. 147.366.388. 224.504. 493.844.744.343.893.725.376.23

7.859.50

12.02

4.186.448.239.32

9.6313.6611.6411. 82

11.38

11.9912.034.37

11. 2011.96

12.6414.0214. 7613. 50

9.6512.7813. 2512.46

14. 22

Total

99.3897.0797.5199.3497. 1597.6296.8097.2797.3196.9697.5398.3596.97

93.4591.6588. 12

96.8196.4196.7796.39

93.3993. 2487.4885.91

76.00

96.5197.6796. 1895.8196. 13

86. 1191. 5591.7993.47

94. 7596. 0396.4796.93

88. 81

Ti

0.590.470.530.590.510.460. 500.490.490.450. 520.450.51

0.480.530.56

0. 580.520.550.68

0.560.620.650.62

0. 59

0.560. 550.610.650.59

0.670.860.710.68

0.680.640.710.70

0.70

Feld-spar

191817

9171522199

14121915

13128

20161717

1316168

6

15201517

9

95

1014

14122220

15

Horizon(by field

designation)

RESIDUALIIBx2IlCcnlIICcn2

LOESS IApBitB21t

LOESS IIB22tB23tB24tB31t

RESIDUALIIB32t

LOESS IIAplAp2B21t

RESIDUALB22tB23tB24tB3t

RESIDUA LAplAp2B21tB22tB23tB24tClC2

RESIDUALAlA3B21tB22tCl

RESIDUALAlA3B21tB22tB3t

Bloom coal

Depth

79-9191-104

104-122+

0-2020-3333-51

51-6666-8181-9797-112

112-127+

0-2425-3838-53

53-6969-8484-9999-114+

0-1010-1818-2525-3636-5151-6161-6969-79

0-22-55-15

15-2525-36

0-55-88-15

15-2323-3333-48

Sand*

SiltCoarse Medium

Sand 50-20(1 20- 5n 5-2n

L4 - Mercer -11.6213.0315.00

4. 173.164.15

7.048.609.328.79

10.68

4.985.628.57

10.279.60

10. 267. 90

22.7120.6517. 2420. 1025.2028.4236.0525. 81

13.1414.2011.6710.397.13

16.4317. 2015.8514.03

9.28

TO

51 km15.34 25.36 41.8819.02 39.17 27.7122.50 29.61 34.60

1,5 - Shelbyville - 68 km5.754.425.93

10.0012.0413. 3312.92

17.30

L7 -6.027.64

13. 11

61.5316.7018.6715.33

Lll -30. 4326. 8423.9629.5538.3040. 9055.0844. 39

L17-18.0019.4515.8716.0011.41

L 2 2 -27. 2725. 2824.2522.4520.69

27.6129.9725. 20

20.5525.0024.1727.87

23.07

Maury -24.1521.5719.03

21. 1923.8226.6824.74

54. 2751.0556.42

56.2149.0748.0244.63

45.66

100km59.5258.7655.37

49.4046. 1340. 5345. 51

Total

( c o n t i n u e d )17. 40 84. fi413. 65 80. 5313.04 77.25

12.64 94.5214.42 95.4412.48 94.10

13.6213.8714.7314.68

13. 51

10.3212.2312.58

12. 5713.5014. 2714.39

90.87.86.87.

82.

93.92.86.

83.83.81.84.

38949218

44

995698

16454864

TI

0.880.760.74

0.660.620.69

0.700.700.710.73

0.75

0.640.610.70

0.800.730.830.92

Feld-spar

1213

7

121519

158

129

1

999

9455

Faywood - 164 km25.7422.8425.3822.9023.8623.4719.7425.06

Gllpln -32. 1428.9829.9325.4123.07Gilpln -12.278.78

17.0110.98

6.91

32.8835. 1336. 3833. 2824. 1722. 1814.3815.84

261 km27.7231.7432. 8937.2144. 16341 km43.2640.8736. 4437. 8438. 13

11.0015.4214.3714.4613. 6813.2510.7114.09

21. 8019.5421.3021.7020.61

17.4524. 8922.2528.9934. 16

69.6273. 3976. 1370.6461.7158.9044. 8354.99

81.80.84.84.88.

72.74.75.77.79.

6626123284

9854708120

0.610.620.640.64

0.680.680.720.730.65

0.680.620.610.590.58

8111210

896

109

1112101211

7Q sand of the whole soil.

486 SOIL SCI. SOC. AMER. PROC., VOL. 35, 1971

changes in silt represent boundaries of parent materials,and the various parent materials are indicated in Table 2.The upper 196 cm (77 inches) of the soil profile LI, 3.2km (two miles) from the Ohio River, was reasonably uni-form in percent silt and sand when the data were expressedon a clay-free basis (see Table 2). However, at 196 cm(77 inches) there was a rather sharp decrease in silt witha corresponding increase in sand. The silt percentagesremained between 96 and 86% as deep as samples takenat this location. It is believed that the change in silt percentat 196 cm (77 inches) represents a possible change inparent material. In this case, this change is believed torepresent loess of two ages of deposition associated withglaciation periods. Thorp et al. (15) reported this samephenomenon and identified the two ages as "Wisconsinloess" and "Wisconsin and older loess." The upper loesswill be referred to as Loess I, and the lower loessial mate-rial will be referred to as Loess II. This boundary betweenLoess I and II at location LI was neither confirmed norrefuted by the Ti or feldspar data, and it did not corre-spond with the visually determined lithologic discontinuitydescribed in the field. At location L2, 19 km (12 miles)from the Ohio River, the soil profile appeared to be devel-oping in three parent materials. The upper 79 cm (31inches) representing Loess I, from 79-140 cm (31-55inches) Loess II, and residuum below 140 cm (55 inches).These boundary lines are also indicated by dashed linesin the data in Table 2.

Evidence of Loess I was not recognized beyond locationL5 or 68 km (42 miles) from the Ohio River. At locationL5, Loess I was recognized to be 51 cm (20 inches) thick,Loess II from the 51-112 cm (20-44 inches) depth, andresiduum below 112 cm (44 inches). At location L6,Loess II was observed in the top 38 cm (15 inches) of theprofile. Data for location L7 are given in Table 2, and thedepth of Loess II was 53 cm (21 inches). Loess II wasnot recognized as a significant part of the parent materialin which the soil developed at location L10 or 148 km(92 miles) from the Ohio River. Data for Lll, given inTable 2, indicate a very large amount of sand as comparedwith analyses from samples just discussed. Relatively highsand percentages existed in samples taken from soils onthe remainder of the transect toward the east. The increasein sand is probably related to changes toward coarser tex-tured rock from which the residuum parent material wasderived, see Table 1. Rocks of Devonian age were thesource of the parent material at location Lll. Mississippianrocks outcrop in the region corresponding to L12, withPennsylvanian rocks serving as parent material source forthe remaining locations. A comparison of data for locationL2 with Lll (Table 2) shows the influence of underlayingrock strata of Devonian age on the sand percentage of the140-163-cm (55-64-inch) increment samples at location L2.

At locations, L2, L3, and L4, the lithologic discontinuitydescribed in the field was approximately 15 cm (6 inches)below the point at which a change in parent material isindicated by the dashed lines in Table 2. At location L5,the field determined lithologic boundary was the same asthat between Loess II and residuum.

It is believed that a recognizable loess mantle extendsinto Kentucky up to approximately 148 km (92 miles)east from the Ohio River. For the initial 68 km (42 miles)two ages of loess are recognizable, Loess I, associated withthe Wisconsin glacial age, and Loess II, associated withan older glacial age. Beyond 68 km the presence of twoseparate ages of loess was not recognizable. However, thesesilty materials were believed to be associated with LoessII rather than the younger Loess I. In general, the depthof loess thins as one travels eastward. No presumed sourcesof local loess were recognized; therefore, the Ohio Riveris considered to be the source of loess for the entire area,since throughout the transect, the drainage ways are deeplyintrenched in the landscape. Because one cannot assumea constant wind direction during deposition of the loessialparent materials, a precise correlation between depth ofloess and distance from the source was not possible asinsufficient locations were sampled. The existence of loesswas based largely on the particle size distribution in thesoil profiles, since Ti and feldspar analyses failed to giveconclusive results. Field identification of lithologic discon-tinuities was generally reliable as to presence or absence,but not as to the exact position in the profile.