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Upper Paleozoic Shales

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Emission Spectroscopy and Geochemistry

Introduction

Geochemistry of sediments is normally determined using X-ray fluorescence (XRF) or occasionally wet chemical methods, although exploration geochemists have in the past sacrificed the accuracy and sensitivity of XRF for the quantity of output obtained using emission spectroscopy. However, Davenport (1970) and Celenk (1972) have studied the problems associated with the emission spectroscopic analysis of rocks, stream sediments, and ore samples and have developed an efficient technique capable of handling many samples and producing results with an acceptable level of accuracy. A number of sedimentary rock analyses have subsequently been performed on the ARL 2900B direct reading spectrometer in the Geology Department at Leicester University, England, and the results have proved most successful (Celenk, 1972; Monteleone, 1973; Turner, 1973; Cubitt, 1975b).

Description of the Spectrometer

Analysis was performed on an ARL 2900B direct reading emission spectrometer with a D.C. arc source unit. The spectral lines for the elements sought are isolated from the remainder of the spectrum by passing the light, produced from the excitation of a sample, over a grating and receiving the resulting lines through a set of secondary slits. The intensities of the lines are measured electronically by photomultiplier tubes and their output is stored in a series of capacitors. A digital voltimeter reads the charge on the capacitors and a peripheral electric typewriter is used to obtain a printed copy of the readout. The optical characteristics of the spectrometer and details of the spectral lines are presented in Celenk (1972) and Cubitt (1975b).

Sample Preparation

As a result of orientation surveys performed by Celenk (1972), the following procedure was adopted for the geochemical analysis of sedimentary rocks. Samples were ground to pass through a 150-mesh sieve and preheated to 600° C, recording the percentage weight loss. One-hundred mg. of each sample was mixed with 150 mg. of buffer (a mixture of one part NaF to three parts "Magicoal" carbon powder), placed in a polystyrene vial containing a lucite ball and homogenized for one minute. The resulting mixture was then packed into a pre-drilled graphite electrode and heated by a Bunsen burner prior to arcing. During the arcing procedure, the filled electrode was used as an anode and a smooth, square-ended, graphite counter electrode was used as a cathode.

Calibration Standards

A set of synthetic bases, U.S. Geological Survey international standard rocks, and British Chemical Standards were analyzed for major and minor elements. The results determined the accuracy of the analytical method.

Mixtures of synthetic bases were prepared from "Specpure" Johnson and Matthey oxides, homogenized, and then fused in a muffle furnace at 950° C for three hours. The fused samples were ground and mixed with carefully weighed amounts of "Spec-Mix" (a mixture of 1.28 percent of each of the 49 element oxides), producing standards with 1000 ppm of all 49 element oxides. Stepwise dilution led to the preparation of further standards with 500, 250, 100, 50, 10, and zero ppm concentrations.

USGS and British Chemical Standards were used for calibration of major element oxides in the rock samples. Precise minor element values have not been recorded for these standards but a range of values is provided by the USGS and other organizations for comparative studies. With minor elements of values greater than 1000 ppm, care must be exercised as the synthetic bases may not be able to match the extremes in concentrations and the analytical results may be erroneous. However, using correction procedures (Celenk, 1972), extrapolation to higher concentrations can produce meaningful results.

Sensitivity, Precision, and Accuracy of the Procedure

Sensitivity of a method is defined as three times the standard deviation obtained by the repeated analysis of a sample containing zero ppm concentrations of the elements under examination (Cameron and Harton, 1967) and practically is the lowest possible concentration at which a particular trace element may be reliably detected. For the minor elements this value is less than 10 ppm except in the case of Zn (11 ppm) where, although two wavelengths were recorded, only one proved sensitive enough for normal analysis.

Precision of the analytical technique is expressed in terms of a coefficient of variation and indicates the reproducibility of the results. It is calculated using the equation: P(%) = (2 x standard deviation x 100)/mean, and is found to be better than 20 percent for all elements.

By comparing the results obtained from this procedure with those calculated by Flanagan (1969), Celenk (1972) evaluated the accuracy of the method and concluded that the method was reasonably consistent, especially when the wide range of values quoted by Flanagan is taken into account.

Details of the precision and sensitivity for the method are presented in Table 6. Accuracies are calculated from data provided by Celenk (1972) and are reported in Table 7 (data were only available for MnO, Ba, Co, Cr, Cu, Ga, Li, Ni, Pb, Sr, V, Zn, Zr).

Table 6--Precision and sensitivity of spectroscopic technique.

  Precision
(%)
Sensitivity
(ppm)
Al2O3 8.8  
CaO 8.6  
Fe 10.9  
K2O 17.7  
MgO 13.5  
SiO2 8.0  
MnO 6.1 8
Ba 12.5 2
Be 6.2 1
Bi 8.6 1
Co 9.8 2
Cr 15.1 8
Cu 9.6 6
Ga 3.8 1
Ge 10.0 1
Li 5.6 2
Mo 15.2 6
Ni 10.9 9
Pb 15.6 8
Sn 17.5 4
Sr 9.0 1
V 11.8 3
Zn 14.1 11
Zr 18.0 8

Table 7--Accuracy of the spectroscopic technique. A comparison of results obtained by Celenk (1972) employing the described equipment and technique to Flanagan's (1969) standardized analysis for rocks GSP-1, AGV-1, and PCC-1.

Standard
Rock
  MnO Ba Co Cr Cu Ga Li Ni Pb Sr V Zn Zr Results
by
GSP-1 RANGE 260-450 855-2000 <3-22 5-18 15-54 12-35 - 3-25 14-80 148-400 38-67 54-340 323-685 Flanagan
1969
MEAN 326 1360 8 13 35 19 36 11 52 247 52 143 544
GSP-1 RANGE 205-297 1029-1576 2-15 B.D.-14 23-45 16-25 9-39 B.D.-8 44-80 168-362 16-114 23-143 256-745 Celenk
1972
MEAN 261 1308 8 5 34 21 20 2 66 263 52 67 436
AGV-1 RANGE 640-870 1047-2700 10-30 8-45 52-83 14-24 - 11-27 18-48 348-1050 70-171 64-304 186-315 Flanagan
1969
MEAN 728 1410 16 13 64 18 12 18 35 657 121 112 227
AGV-1 RANGE 423-759 900-1431 2-20 B.D.-11 48-78 14-22 B.D.-17 B.D.-18 18-53 458-858 46-272 66-141 129-342 Celenk
1972
MEAN 592 1134 0 4 65 19 6 6 37 618 83 101 194
PCC-1 RANGE 610-1430 - 80-330 1840-4780 5-6 - - 1750-3400 - - 21-55 24-100 - Flanagan
1969
MEAN 889 7 112 3090 10 12 0 2430 13 <1 31 53 0
PCC-1 RANGE 623-1126 B.D.-13 88-173 1830-3181 B.D.-7 B.D.-4 B.D.-4 1528-2950 B.D.-21 B.D.-2 8-34 22-128 B.D.-24 Celenk
1972
MEAN 851 2 91 2169 7 1 0 1898 5 0 23 85 9
B.D. = Below detection limit.

Results of the Spectroscopic Analysis

One-hundred-twenty-six samples of Upper Pennsylvanian and Lower Permian shales from Kansas were analyzed using the previously described procedures (sample 170 was unavailable for geochemical analysis). The results are presented in Table 8. However, the following points should be borne in mind when examining Table 8. The results for Cd in the standards (see Cubitt, 1975b for complete tabulation) show anomalously high readings; those for Mo and Zn read slightly higher than normal; and the Fe, SiO2 and Zr lines give low readings. Some care, therefore, must be taken in interpreting the results. It must also be remembered that the extrapolation procedure may overestimate any unusually high readings. Consequently, the value of 114 percent SiO2 in sample 121 must be regarded skeptically. More realistic estimates for the few extreme major oxide values can be obtained from the mineralogical data.

Table 8--Results of emission spectroscopic analysis of Upper Pennsylvanian and Lower Permian shales of Kansas.

  Sample Number
  16 19 20 21 23 24 25 26 27 28 7 31 32 34 36 35 38 40 41 43 46
Major Oxides (Percent)
Al2O3 17.3 17.4 14.8 8.4 11.8 17.8 15.8 15.9 8.8 16.9 12.9 16.4 16.1 16.2 12.9 5.3 17.5 18.3 13.5 14.9 16.9
CaO 0.4 0.4 7.2 21.5 19.5 0.9 2.0 2.9 22.4 0.1 0.1 3.4 2.5 4.2 16.5 29.4 2.0 0.3 14.5 0.4 2.8
Fe Oxides 5.6 4.7 3.0 3.7 3.3 3.7 4.6 3.9 2.1 3.2 5.2 5.0 5.4 4.3 3.7 3.2 5.4 5.1 3.8 4.8 5.1
K2O 2.6 3.3 2.6 1.5 2.9 3.0 3.7 4.0 2.3 2.9 2.2 3.4 3.7 3.6 2.8 1.2 3.8 3.0 2.7 2.7 3.6
MgO 2.0 1.8 3.0 5.2 3.3 1.8 2.1 2.0 1.3 2.0 1.1 2.8 2.3 3.0 2.0 13.8 2.6 2.0 2.5 1.9 2.6
SiO2 71.2 64.6 73.3 39.6 37.7 69.1 62.4- 58.5 35.3 75.4 69.9 62.0 65.3 60.7 50.9 20.6 64.5 68.6 44.5 59.8 69.3
 
Mn/Fe 0.5 0.5 1.6 1.7 2.0 0.3 0.6 0.7 1.3 0.4 0.1 0.6 0.6 0.6 1.0 2.5 0.7 0.5 1.1 0.0 0.4
Minor Elements and Oxides (PPM)
MnO 293.0 242.0 469.0 618.0 656.0 93.0 276.0 273.0 273.0 126.0 67.0 283.0 311.0 247.0 385.0 789.0 350.0 255.0 435.0 181.0 192.0
Ag 0.0 0.0 0.0 1.0 0.0 18.0 1.0 0.0 2.0 0.0 16.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 1.0 6.0 0.0
Ba 392.0 286.0 534.0 152.0 141.0 376.0 278.0 369.0 133.0 231.0 317.0 329.0 353.0 331.0 259.0 92.0 374.0 404.0 283.0 269.0 361.0
Be 3.0 7.0 3.0 5.0 6.0 12.0 6.0 5.0 5.0 3.0 10.0 6.0 4.0 7.0 3.0 8.0 7.0 3.0 5.0 7.0 4.0
Bi 0.0 1.0 0.0 3.0 2.0 2.0 1.0 0.0 4.0 0.0 2.0 1.0 2.0 1.0 1.0 3.0 1.0 0.0 1.0 1.0 0.0
Cd 23.0 31.0 30.0 45.0 49.0 138.0 39.0 15.0 73.0 34.0 58.0 28.0 37.0 19.0 39.0 34.0 19.0 30.0 44.0 52.0 28.0
Co 57.0 35.0 36.0 37.0 42.0 35.0 27.0 33.0 37.0 15.0 21.0 66.0 32.0 27.0 66.0 46.0 28.0 30.0 27.0 73.0 24.0
Cr 109.0 109.0 124.0 76.0 78.0 1428.0 159.0 173.0 77.0 115.0 1064.0 339.0 137.0 197.0 95.0 38.0 110.0 124.0 108.0 482.0 199.0
Minor Elements (PPM)
Cu 23.0 40.0 21.0 9.0 16.0 134.0 41.0 32.0 15.0 22.0 118.0 61.0 57.0 27.0 22.0 8.0 33.0 37.0 23.0 99.0 20.0
Ga 23.0 24.0 16.0 10.0 15.0 24.0 22.0 22.0 12.0 22.0 17.0 23.0 24.0 23.0 16.0 6.0 24.0 26.0 18.0 22.0 23.0
Ge 1.0 1.0 0.0 3.0 3.0 1.0 1.0 1.0 7.0 0.0 1.0 1.0 2.0 1.0 2.0 5.0 1.0 0.0 1.0 1.0 1.0
Li 64.0 35.0 21.0 32.0 30.0 45.0 52.0 42.0 75.0 46.0 43.0 70.0 62.0 63.0 41.0 37.0 63.0 75.0 43.0 47.0 51.0
Mo 6.0 0.0 9.0 34.0 22.0 231.0 0.0 0.0 54.0 0.0 241.0 69.0 2.0 0.0 34.0 47.0 9.0 0.0 13.0 44.0 0.0
Ni 68.0 66.0 61.0 39.0 39.0 363.0 136.0 109.0 45.0 40.0 239.0 321.0 97.0 125.0 140.0 29.0 73.0 76.0 73.0 661.0 122.0
Ph 21.0 63.0 6.0 9.0 28.0 205.0 39.0 43.0 8.0 17.0 77.0 59.0 35.0 27.0 42.0 7.0 38.0 25.0 12.0 356.0 9.0
Sn 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 0.0 0.0 0.0
Sr 149.0 100.0 322.0 923.0 779.0 124.0 90.0 153.0 1471.0 132.0 95.0 211.0 205.0 190.0 925.0 682.0 158.0 111.0 362.0 77.0 154.0
V 198.0 121.0 137.0 78.0 55.0 3607.0 204.0 205.0 85.0 109.0 2358.0 324.0 153.0 205.0 90.0 50.0 234.0 171.0 110.0 808.0 161.0
Zn 286.0 161.0 158.0 38.0 71.0 816.0 515.0 154.0 40.0 153.0 697.0 468.0 209.0 335.0 97.0 0.0 207.0 239.0 156.0 873.0 235.0
Zr 345.0 159.0 354.0 220.0 109.0 140.0 189.0 236.0 194.0 262.0 128.0 236.0 160.0 208.0 165.0 137.0 142.0 131.0 127.0 82.0 206.0
 
Heat Loss 4.1 7.4 6.9 2.5 9.0 29.9 4.4 6.6 7.0 4.9 25.0 8.7 4.5 4.9 8.1. 0.1 4.5 4.0 7.9 15.0 6.1


  Sample Number
  47 48 54 50 53 69 70 71 160 67 61A 63 12 66 15 3 157 161 296 294 290
Major Oxides (Percent)
Al2O3 16.7 16.2 8.9 14.2 12.1 17.7 16.6 17.3 15.0 16.1 17.0 17.7 16.2 6.7 13.5 18.8 15.6 17.0 18.5 9.0 14.4
CaO 4.0 4.1 12.0 8.1 18.2 0.8 6.1 2.6 5.1 0.5 6.2 0.4 3.4 21.4 12.8 0.1 1.1 3.8 5.2 0.1 0.1
Fe Oxides 4.0 4.5 2.8 4.6 3.4 5.4 5.4 4.6 4.3 5.3 5.1 5.9 4.7 5.4 3.8 7.0 5.8 5.0 4.7 2.6 4.4
K2O 3.3 3.4 1.1 3.1 2.8 2.9 2.1 2.6 2.2 3.6 3.6 3.5 2.7 1.1 2.0 4.6 4.9 3.8 2.9 0.5 2.1
MgO 2.6 3.0 0.9 2.1 1.9 2.3 1.8 1.9 1.6 2.0 2.2 2.5 2.4 26.8 1.3 2.0 2.1 2.6 2.1 0.4 0.5
SiO2 58.3 60.9 67.2 49.6 43.9 59.5 66.1 67.6 53.3 59.7 61.3 61.0 65.3 26.9 44.5 59.2 57.6 66.2 67.5 89.0 69.7
 
Mn/Fe 0.5 0.5 2.9 0.6 0.5 0.5 0.9 0.8 0.9 0.5 0.8 0.5 1.2 2.3 1.1 0.6 0.5 0.5 0.6 1.1 0.8
Minor Elements and Oxides (PPM)
MnO 185.0 227.0 821.0 269.0 172.0 255.0 492.0 350.0 382.0 252.0 419.0 279.0 570.0 1251.0 431.0 406.0 269.0 237.0 279.0 295.0 339.0
Ag 3.0 0.0 0.0 11.0 2.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 46.0 0.0
Ba 428.0 417.0 204.0 201.0 310.0 347.0 394.0 446.0 412.0 312.0 416.0 356.0 272.0 123.0 372.0 500.0 353.0 384.0 484.0 180.0 398.0
Be 6.0 3.0 4.0 5.0 8.0 6.0 5.0 5.0 5.0 6.0 6.0 6.0 5.0 6.0 4.0 8.0 6.0 6.0 6.0 2.0 5.0
Bi 0.0 0.0 0.0 1.0 2.0 1.0 0.0 0.0 0.0 1.0 1.0 2.0 0.0 2.0 1.0 2.0 3.0 1.0 1.0 0.0 1.0
Cd 14.0 23.0 20.0 28.0 97.0 30.0 31.0 25.0 19.0 31.0 20.0 34.0 17.0 15.0 14.0 35.0 41.0 22.0 43.0 48.0 35.0
Co 45.0 29.0 77.0 15.0 37.0 32.0 39.0 51.0 31.0 32.0 39.0 36.0 37.0 43.0 23.0 52.0 27.0 32.0 34.0 224.0 40.0
Cr 165.0 149.0 51.0 97.0 566.0 95.0 86.0 109.0 117.0 106.0 119.0 110.0 94.0 35.0 107.0 143.0 169.0 127.0 113.0 40.0 80.0
Minor Elements (PPM)
Cu 9.0 12.0 13.0 25.0 58.0 37.0 28.0 22.0 49.0 23.0 22.0 7.0 37.0 6.0 31.0 35.0 63.0 30.0 26.0 5.0 27.0
Ga 23.0 23.0 9.0 22.0 14.0 24.0 19.0 20.0 20.0 25.0 25.0 27.0 20.0 6.0 18.0 32.0 27.0 24.0 23.0 8.0 19.0
Ge 1.0 1.0 1.0 2.0 2.0 1.0 1.0 1.0 0.0 1.0 1.0 2.0 1.0 2.0 1.0 3.0 3.0 1.0 1.0 0.0 1.0
Li 37.0 37.0 18.0 27.0 32.0 83.0 63.0 61.0 25.0 72.0 66.0 87.0 44.0 15.0 38.0 113.0 68.0 28.0 59.0 6.0 33.0
Mo 0.0 0.0 32.0 6.0 60.0 0.0 10.0 1.0 0.0 0.0 5.0 0.0 15.0 19.0 7.0 0.0 21.0 4.0 0.0 11.0 3.0
Ni 99.0 94.0 44.0 49.0 249.0 50.0 53.0 69.0 83.0 56.0 75.0 53.0 62.0 43.0 61.0 109.0 106.0 59.0 58.0 22.0 27.0
Pb 4.0 7.0 14.0 13.0 177.0 11.0 14.0 19.0 38.0 32.0 28.0 13.0 7.0 4.0 38.0 27.0 44.0 22.0 25.0 6.0 32.0
Sn 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Sr 186.0 307.0 259.0 367.0 731.0 110.0 211.0 169.0 124.0 92.0 324.0 119.0 198.0 301.0 129.0 257.0 136.0 254.0 233.0 68.0 118.0
V 170.0 168.0 74.0 109.0 488.0 130.0 114.0 174.0 83.0 171.0 213.0 161.0 174.0 53.0 102.0 286.0 271.0 166.0 142.0 49.0 89.0
Zn 213.0 255.0 86.0 140.0 909.0 226.0 217.0 266.0 268.0 243.0 250.0 207.0 197.0 0.0 183.0 323.0 430.0 200.0 210.0 108.0 200.0
Zr 205.0 213.0 291.0 141.0 190.0 159.0 229.0 340.0 118.0 152.0 312.0 189.0 339.0 124.0 122.0 240.0 186.0 295.0 217.0 192.0 499.0
 
Heat Loss 4.6 6.4 2.0 8.5 4.8 2.9 4.8 3.4 8.2 3.1 4.5 2.0 3.8 0.9 5.7 6.0 7.0 7.1 3.9 2.0 0.5


  Sample Number
  284 287 281 125 116 110 112 128 130 79 151 82 80 81 85 135 121 138 136 137 149
Major Oxides (Percent)
Al2O3 15.0 16.4 14.2 14.6 15.4 16.6 15.5 17.0 9.0 15.9 17.5 17.4 19.8 17.8 14.0 9.4 4.1 15.5 13.4 9.2 16.2
CaO 1.2 4.7 8.8 0.1 4.1 8.5 0.8 4.2 16.2 14.1 1.1 1.5 1.1 0.3 0.1 17.1 0.1 8.2 7.6 20.8 5.3
Fe Oxides 5.2 4.7 4.7 2.8 4.2 5.1 4.9 5.3 5.8 4.9 4.9 4.9 6.4 5.5 1.9 4.9 2.6 5.2 4.1 4.2 3.9
K2O 3.0 3.1 2.3 1.7 2.9 2.8 2.0 3.4 1.9 3.4 4.2 3.4 3.2 3.4 1.2 2.1 0.1 3.3 2.8 1.5 2.6
MgO 1.6 1.7 3.6 0.7 2.0 2.5 1.1 3.0 7.4 3.6 2.4 1.8 2.0 1.9 0.6 6.0 0.3 2.3 2.8 1.4 2.2
SiO2 57.3 62.0 63.9 83.8 56.4 63.3 79.3 61.6 34.2 52.8 63.4 63.7 65.0 58.0 82.3 27.1 114.0 51.6 52.0 32.3 65.7
 
Mn/Fe 0.4 1.9 1.2 0.2 0.9 0.7 0.6 0.5 1.4 1.2 0.4 0.7 0.4 0.4 0.5 2.0 0.3 0.8 0.8 2.2 0.9
Minor Elements and Oxides (PPM)
MnO 182.0 874.0 549.0 65.0 396.0 341.0 296.0 263.0 789.0 588.0 194.0 330.0 266.0 234.0 96.0 960.0 67.0 400.0 330.0 912.0 368.0
Ag 1.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 2.0 0.0 0.0 0.0 1.0 0.0
Ba 297.0 412.0 807.0 382.0 351.0 251.0 361.0 368.0 203.0 368.0 470.0 376.0 520.0 451.0 284.0 173.0 111.0 315.0 287.0 214.0 379.0
Be 3.0 6.0 6.0 3.0 5.0 6.0 4.0 8.0 5.0 7.0 7.0 5.o 4.0 4.0 4.0 4.0 2.0 5.0 4.0 4.0 6.0
Bi 0.0 1.0 1.0 0.0 1.0 1.0 0.0 2.0 4.0 2.0 1.0 1.0 1.0 1.0 0.0 3.0 0.0 1.0 1.0 4.0 0.0
Cd 22.0 19.0 77.0 56.0 20.0 46.0 41.0 165.0 20.0 23.0 21.0 26.0 29.0 22.0 46.0 10.0 47.0 26.0 28.0 11.0 16.0
Co 15.0 51.0 58.0 70.0 17.0 25.0 33.0 67.0 35.0 39.0 36.0 24.0 31.0 28.0 47.0 48.0 85.0 20.0 34.0 27.0 46.0
Cr 82.0 103.0 91.0 101.0 152.0 99.0 94.0 1097.0 72.0 92.0 146.0 108.0 113.0 125.0 66.0 71.0 66.0 95.0 94.0 61.0 95.0
Minor Elements (PPM)
Cu 8.0 22.0 14.0 5.0 43.0 30.0 5.0 105.0 24.0 23.0 21.0 31.0 34.0 32.0 11.0 14.0 2.0 29.0 24.0 27.0 17.0
Ga 20.0 23.0 16.0 15.0 27.0 22.0 17.0 21.0 12.0 20.0 27.0 26.0 28.0 28.0 12.0 12.0 3.0 22.0 17.0 12.0 19.0
Ge 1.0 1.0 2.0 0.0 1.0 2.0 1.0 1.0 4.0 3.0 1.0 1.0 2.0 1.0 0.0 3.0 0.0 1.0 1.0 4.0 1.0
Li 30.0 60.0 26.0 11.0 29.0 21.0 46.0 35.0 36.0 35.0 48.0 89.0 77.0 94.0 14.0 33.0 7.0 28.0 30.0 40.0 30.0
Mo 0.0 29.0 8.0 11.0 0.0 6.0 0.0 174.0 34.0 27.0 0.0 0.0 0.0 3.0 0.0 26.0 0.0 17.0 2.0 39.0 13.0
Ni 39.0 78.0 41.0 22.0 70.0 61.0 53.0 421.0 61.0 51.0 75.0 52.0 64.0 69.0 19.0 45.0 19.0 43.0 48.0 39.0 50.0
Pb 4.0 14.0 17.0 15.0 15.0 18.0 9.0 184.0 33.0 20.0 22.0 12.0 23.0 18.0 21.0 14.0 7.0 47.0 30.0 37.0 9.0
Sn 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.0 0.0 0.0 0.0 0.0 0.0 0.0 5.0 0.0 0.0 0.0 0.0 0.0
Sr 114.0 198.0 571.0 390.0 181.0 404.0 98.0 136.0 524.0 427.0 195.0 135.0 167.0 175.0 68.0 509.0 21.0 227.0 217.0 438.0 162.0
V 103.0 228.0 103.0 153.0 161.0 139.0 105.0 951.0 70.0 154.0 288.0 166.0 165.0 253.0 73.0 58.0 19.0 94.0 116.0 56.0 138.0
Zn 182.0 198.0 135.0 161.0 247.0 129.0 190.0 903.0 59.0 192.0 220.0 260.0 198.0 317.0 117.0 52.0 44.0 194.0 121.0 51.0 190.0
Zr 105.0 320.0 370.0 507.0 159.0 235.0 289.0 184.0 126.0 195.0 213.0 157.0 155.0 168.0 730.0 79.0 463.0 115.0 153.0 107.0 344.0
 
Heat loss 4.3 1.9 7.4 3.0 6.0 7.9 3.9 11.6 10.5 7.1 3.1 6.9 5.0 6.4 2.4 15.5 0.5 8.3 4.8 10.5 3.9


  Sample Number
  150 152 153 155 105 107 109 94 96 97 144 101 122 97B 148 162 163 171 173 168 192
Major Oxides (Percent)
Al2O3 17.1 18.4 17.1 17.0 10.2 16.2 8.4 7.1 15.6 20.2 17.0 16.3 12.1 14.2 17.7 15.5 13.1 18.3 19.8 15.4 8.3
CaO 0.5 0.5 0.2 0.5 14.6 5.8 25.5 30.8 0.1 2.1 4.2 3.6 13.9 5.0 2.7 0.1 7.6 0.1 0.2 0.1 17.7
Fe Oxides 4.1 5.9 5.7 7.2 2.9 5.3 6.0 3.9 4.3 5.9 5.2 4.8 4.4 3.6 5.2 7.1 10.3 9.6 6.6 6.1 5.4
K2O 3.0 3.4 2.7 2.2 1.4 3.1 1.4 1.8 2.1 3.6 3.4 2.8 3.0 2.4 3.2 2.2 3.4 3.5 2.4 1.7 1.7
MgO 2.0 2.0 1.8 1.5 1.1 2.0 1.1 3.8 1.3 2.4 4.2 1.6 3.0 1.6 2.3 1.0 5.4 1.3 1.6 1.1 8.9
SiO2 70.2 67.4 57.3 72.9 48.8 55.1 21.7 14.6 68.4 65.5 56.7 59.6 51.9 66.6 58.9 71.2 54.5 65.2 67.9 76.5 46.7
 
Mn/Fe 0.5 0.6 0.7 0.5 2.2 0.4 2.6 3.2 0.7 0.8 0.9 0.6 0.9 0.8 0.4 0.3 0.1 0.3 0.7 0.6 4.4
Minor Elements and Oxides (PPM)
MnO 218.0 374.0 417.0 344.0 624.0 185.0 1564.0 1264.0 317.0 469.0 465.0 292.0 374.0 301.0 229.0 179.0 136.0 289.0 449.0 347.0 2385.0
Ag 0.0 0.0 0.0 0.0 0.0 2.0 2.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Ba 400.0 444.0 379.0 452.0 217.0 345.0 256.0 151.0 412.0 684.0 388.0 548.0 284.0 365.0 381.0 380.0 285.0 519.0 529.0 348.0 201.0
Be 3.0 6.0 6.0 3.0 4.0 12.0 6.0 9.0 5.0 7.0 7.0 5.0 2.0 4.0 7.0 4.0 6.0 7.0 5.0 2.0 6.0
Bi 0.0 1.0 0.0 1.0 1.0 3.0 6.0 8.0 0.0 2.0 1.0 1.0 1.0 1.0 1.0 1.0 5.0 3.0 0.0 0.0 3.0
c 23.0 37.0 34.0 27.0 14.0 168.0 5.0 47.0 25.0 19.0 14.0 31.0 22.0 27.0 56.0 38.0 25.0 40.0 26.0 19.0 9.0
Co 16.0 36.0 28.0 55.0 49.0 63.0 52.0 53.0 70.0 73.0 59.0 29.0 32.0 29.0 31.0 41.0 24.0 40.0 31.0 149.0 74.0
Cr 105.0 138.0 83.0 98.0 63.0 376.0 70.0 67.0 81.0 130.0 97.0 95.0 81.0 89.0 490.0 82.0 123.0 106.0 140.0 65.0 53.0
Minor Elements (PPM)
Cu 19.0 42.0 25.0 25.0 15.0 139.0 20.0 25.0 24.0 36.0 26.0 33.0 24.0 22.0 140.0 23.0 55.0 20.0 28.0 22.0 6.0
Ga 24.0 25.0 24.0 22.0 11.0 24.0 12.0 12.0 19.0 28.0 24.0 26.0 15.0 19.0 26.0 20.0 23.0 27.0 26.0 17.0 9.0
Ge 0.0 1.0 1.0 1.0 1.0 2.0 8.0 12.0 0.0 2.0 1.0 2.0 1.0 1.0 1.0 1.0 5.0 4.0 1.0 0.0 3.0
Li 29.0 32.0 84.0 65.0 22.0 49.0 58.0 95.0 49.0 92.0 40.0 57.0 32.0 28.0 48.0 38.0 25.0 118.0 105.0 38.0 24.0
Mo 0.0 6.0 0.0 6.0 18.0 713.0 58.0 93.0 0.0 16.0 19.0 0.0 31.0 0.0 4.0 0.0 39.0 0.0 0.0 10.0 43.0
Ni 36.0 140.0 41.0 73.0 37.0 410.0 48.0 52.0 63.0 97.0 80.0 49.0 55.0 37.0 256.0 42.0 41.0 83.0 50.0 49.0 39.0
Pb 11.0 44.0 12.0 20.0 11.0 164.0 15.0 13.0 16.0 15.0 54.0 7.0 19.0 5.0 53.0 14.0 39.0 15.0 22.0 56.0 5.0
Sn 0.0 0.0 0.0 0.0 0.0 0.0 4.0 20.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Sr 97.0 100.0 85.0 144.0 263.0 198.0 418.0 1375.0 104.0 187.0 158.0 146.0 440.0 133.0 119.0 107.0 220.0 157.0 157.0 96.0 341.0
V 114.0 192.0 106.0 166.0 59.0 1627.0 58.0 76.0 123.0 236.0 148.0 109.0 115.0 93.0 167.0 102.0 181.0 168.0 109.0 112.0 95.0
Zn 156.0 360.0 370.0 350.0 72.0 904.0 35.0 37.0 266.0 282.0 187.0 204.0 99.0 196.0 619.0 219.0 286.0 428.0 273.0 241.0 54.0
Zr 195.0 240.0 196.0 490.0 227.0 234.0 151.0 171.0 378.0 115.0 312.0 144.0 293.0 318.0 113.0 279.0 166.0 206.0 192.0 465.0 402.0
 
Heat Loss 4.0 5.5 5.6 5.9 8.0 17.3 12.0 11.0 1.9 3.3 8.7 8.0 13.0 5.5 7.2 5.0 12.5 6.9 6.2 5.8 2.9


  Sample Number
  194 176 180 181 184 185 186 187 197 200 205 206 208 209 261 262 212 213 264 237 235
Major Oxides (Percent)
Al2O3 17.1 19.6 15.1 16.3 16.4 17.5 18.3 13.6 10.9 17.1 15.4 8.5 8.4 9.1 9.0 12.1 11.6 8.8 13.2 8.3 11.8
CaO 5.7 0.1 0.1 3.4 0.1 3.2 4.4 16.9 16.3 3.7 1.6 29.1 25.8 27.0 23.2 15.3 16.2 25.8 13.8 27.5 14.6
Fe Oxides 4.4 6.1 5.3 4.2 4.8 4.7 5.5 6.9 5.9 4.7 5.7 3.9 4.0 3.9 3.7 3.4 3.7 2.9 4.6 1.8 5.3
K2O 3.0 3.7 3.0 2.2 2.2 2.7 3.1 2.9 2.4 3.0 3.5 1.6 2.3 1.8 2.5 3.0 2.8 2.8 2.6 1.6 3.6
MgO 2.3 2.2 1.1 1.8 1.9 2.6 2.5 3.6 7.9 2.1 2.7 2.1 2.1 4.3 4.3 3.8 2.1 1.6 4.3 2.0 2.7
SiO2 55.2 58.0 60.3 62.6 70.2 63.9 67.0 37.2 46.0 65.2 60.3 31.6 27.6 30.7 35.9 44.0 42.6 26.5 46.5 21.3 40.0
 
Mn/Fe 1.1 0.4 0.4 1.0 0.6 0.6 0.4 4.8 5.6 0.7 0.4 3.8 2.9 2.0 1.2 0.7 0.7 1.5 0.7 1.8 0.6
Minor Elements and Oxides (PPM)
MnO 470.0 237.0 212.0 410.0 276.0 300.0 229.0 3297.0 3297.0 310.0 228.0 1471.0 1172.0 785.0 453.0 224.0 245.0 444.0 320.0 320.0 326.0
Ag 3.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.0 3.0 1.0 2.0 6.0 0.0 3.0 0.0 2.0 0.0
Ba 502.0 475.0 446.0 299.0 405.0 352.0 230.0 457.0 240.0 351.0 350.0 168.0 143.0 180.0 216.0 254.0 261.0 227.0 316.0 174.0 295.0
Be 7.0 7.0 5.0 5.0 2.0 7.0 5.0 7.0 7.0 3.0 5.0 5.0 8.0 7.0 7.0 3.0 4.0 7.0 3.0 3.0 4.0
Bi 1.0 2.0 2.0 0.0 0.0 1.0 1.0 3.0 2.0 0.0 1.0 3.0 6.0 3.0 4.0 1.0 1.0 6.0 0.0 3.0 3.0
Cd 26.0 15.0 31.0 23.0 19.0 21.0 28.0 15. 0 8.0 21.0 29 .0 5.0 18.0 77 .0 7.0 46 .0 7.0 20.0 20.0 6.0 33.0
Co 15.0 45.0 28.0 17.0 45.0 47.0 23.0 32.0 46.0 19.0 29.0 60.0 63.0 34.0 44.0 23.0 27.0 71.0 21.0 62.0 17.0
Cr 86.0 132.0 96.0 84.0 92.0 96.0 109.0 63.0 68.0 84.0 86.0 62.0 74.0 117.0 108.0 572.0 74.0 80.0 75.0 67.0 69.0
Minor Elements (PPM)
Cu 26.0 31.0 17.0 6.0 11.0 19.0 10.0 18.0 29.0 6.0 114.0 15.0 22.0 16.0 22.0 50.0 19.0 31.0 23.0 11.0 13.0
Ga 22.0 30.0 25.0 20.0 20.0 20.0 25.0 17.0 12.0 21.0 22.0 10.0 13.0 10.0 11.0 17.0 14.0 13.0 16.0 10.0 18.0
Ge 1.0 2.0 2.0 0.0 0.0 1.0 1.0 4.0 3.0 0.0 1.0 6.0 9.0 4.0 6.0 1.0 2.0 9.0 1.0 5.0 3.0
Li 21.0 143.0 55.0 22.0 56.0 31.0 18.0 38.0 28.0 36.0 54.0 53.0 93.0 43.0 94.0 86.0 79.0 98.0 75.0 78.0 54.0
Mo 0.0 0.0 0.0 0.0 0.0 2.0 0.0 47.0 44.0 0.0 0.0 58.0 70.0 38.0 54.0 94.0 20.0 71.0 12.0 53.0 15.0
Ni 35.0 95.0 36.0 36.0 52.0 56.0 61.0 53.0 68.0 49.0 50.0 51.0 64.0 72.0 64.0 230.0 43.0 76.0 49.0 38.0 39.0
Pb 11.0 25.0 33.0 10.0 8.0 10.0 12.0 18.0 84.0 7.0 9.0 9.0 8.0 11.0 7.0 23.0 18.0 23.0 19.0 2.0 10.0
Sn 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.0 0.0 4.0 0.0 0.0 7.0 0.0 0.0 0.0
Sr 147.0 143.0 153.0 94.0 112.0 171.0 146.0 729.0 310.0 133.0 197.0 346.0 569.0 1844.0 212.0 267.0 148.0 496.0 469.0 479.0 543.0
V 81.0 284.0 156.0 89.0 140.0 143.0 108.0 115.0 110.0 98.0 94.0 73.0 77.0 76.0 99.0 254.0 76.0 98.0 77.0 88.0 66.0
Zn 155.0 291.0 216.0 172.0 229.0 213.0 132.0 139.0 73.0 213.0 192.0 0.0 46.0 72.0 49.0 229.0 97.0 119.0 102.0 27.0 123.0
Zr 147.0 216.0 276.0 165.0 388.0 359.0 255.0 231.0 320.0 149.0 158.0 212.0 152.0 169.0 151.0 127.0 155.0 173.0 146.0 133.0 97.0
 
Heat Loss 8.1 6.7 3.5 5.9 3.5 4.4 8.8 10.9 8.7 7.4 5.0 1.5 7.0 9.7 10.5 4.3 8.0 8.0 5.0 4.2 14.0


  Sample Number
  238 249 248 234 230 226 227 221 222 243 244 273 253 251 256 265 268 270 272 298 300
Major Oxides (Percent)
Al2O3 15.3 8.5 11.1 10.5 17.1 12.9 15.5 12.1 6.0 14.4 16.9 10.8 11.2 12.8 11.8 9.0 16.1 14.7 12.4 13.0 9.4
CaO 5.9 18.0 14.7 20.9 4.2 10.6 0.2 20.6 38.0 5.5 1.0 10.5 24.3 15.2 10.7 18.5 1.7 4.6 23.3 5.2 13.2
Fe Oxides 4.5 3.6 4.8 4.4 6.3 5.7 4.4 3.8 2.1 5.8 3.0 4.9 3.0 4.4 5.0 3.0 6.6 6.7 4.3 2.8 4.4
K,,O 2.7 1.5 1.8 2.2 4.1 3.8 2.8 1.9 2.4 3.9 4.1 3.1 2.3 3.0 2.4 2.3 4.0 2.9 2.6 2.5 2.4
MgO 3.6 13.1 10.4 5.7 2.6 2.7 2.8 3.5 3.2 3.6 2.9 9.1 3.8 5.2 3.6 2.3 3.3 3.8 4.4 4.0 13.3
SiO2 60.1 33.5 46.0 30.2 58.9 50.6 62.0 42.9 18.7 52.6 58.3 37.9 31.5 40.9 58.0 28.2 61.6 63.1 46.0 58.9 43.1
 
Mn/Fe 0.6 1.3 1.2 1.1 0.9 0.5 0.6 1.7 3.1 0.6 0.3 1.3 1.4 1.2 0.9 1.2 0.5 o.5 1.0 1.1 0.9
Minor Elements and Oxides (PPM)
MnO 270.0 458.0 589.0 465.0 575.0 260.0 272.0 652.0 660.0 361.0 77.0 653.0 406.0 526.0 463.0 349.0 306.0 320.0 416.0 317.0 393.0
Ag 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0
Ba 327.0 189.0 206.0 228.0 1594.0 284.0 287.0 165.0 149.0 468.0 397.0 211.0 224.0 281.0 328.0 234.0 470.0 1194.0 406.0 348.0 253.0
Be 4.0 2.0 3.0 2.0 6.0 4.0 4.0 3.0 10.0 5.0 6.0 4.0 7.0 3.0 4.0 4.0 3.0 3.0 4.0 3.0 5.0
Bi 0.0 0.0 0.0 2.0 1.0 2.0 0.0 1.0 8.0 2.0 0.0 2.0 3.0 1.0 2.0 3.0 0.0 0.0 3.0 0.0 2.0
Cd 23.0 0.0 17.0 1.0 25.0 22.0 18.0 48.0 14.0 18.0 23.0 3.0 0.0 1.0 19.0 0.0 19.0 16.0 8.0 20.0 0.0
Co 19.0 35.0 19.0 29.0 27.0 13.0 19.0 30.0 90.0 21.0 7.0 18.0 42.0 35.0 22.0 38.0 40.0 27.0 44.0 42.0 21.0
Cr 76.0 51.0 55.0 61.0 94.0 66.0 65.0 82.0 59.0 92.0 107.0 68.0 66.0 103.0 66.0 82.0 108.0 90.0 110.0 77.0 87.0
Minor Elements (PPM)
Cu 24.0 10.0 11.0 14.0 40.0 6.0 16.0 13.0 14.0 46.0 34.0 23.0 16.0 13.0 8.0 14.0 17.0 8.0 12.0 14.0 11.0
Ga 17.0 11.0 11.0 14.0 22.0 18.0 17.0 13.0 11.0 23.0 24.0 16.0 13.0 16.0 14.0 13.0 25.0 18.0 15.0 14.0 11.0
Ge 0.0 0.0 0.0 1.0 2.0 3.0 0.0 2.0 14.0 2.0 0.0 2.0 3.0 1.0 2.0 3.0 1.0 1.0 5.0 0.0 2.0
Li 67.0 36.0 51.0 64.0 68.0 37.0 35.0 25.0 124.0 169.0 67.0 73.0 57.0 68.0 47.0 100.0 101.0 59.0 110.0 46.0 106.0
Mo 1.0 35.0 11.0 49.0 4.0 8.0 0.0 25.0 196.0 2.0 0.0 8.0 68.0 39.0 6.0 33.0 0.0 0.0 66.0 0.0 14.0
Ni 49.0 35.0 32.0 54.0 56.0 29.0 34.0 46.0 63.0 77.0 14.0 36.0 49.0 64.0 33.0 38.0 49.0 46.0 65.0 36.0 40.0
Pb 11.0 20.0 3.0 5.0 41.0 7.0 10.0 17.0 7.0 25.0 18.0 8.0 14.0 14.0 10.0 6.0 5.0 5.0 19.0 4.0 19.0
Sn 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.0 0.0 0.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 2.0 0.0 8.0
Sr 261.0 406.0 485.0 493.0 100.0 267.0 53.0 1078.0 836.0 87.0 77.0 199.0 236.0 196.0 156.0 228.0 93.0 90.0 371.0 77.0 101.0
v 60.0 48.0 55.0 89.0 105.0 51.0 54.0 62.0 124.0 104.0 165.0 73.0 120.0 122.0 64.0 68.0 136.0 109.0 158.0 67.0 88.0
Zn 139.0 127.0 55.0 76.0 167.0 135.0 125.0 35.0 0.0 296.0 125.0 87.0 86.0 108.0 133.0 74.0 182.0 161.0 108.0 135.0 72.0
Zr 226.0 105.0 141.0 162.0 175.0 111.0 143.0 159.0 315.0 115.0 108.0 85.0 181.0 143.0 251.0 82.0 235.0 266.0 226.0 412.0 129.0
 
Heat Loss 7.4 11.0 2.4 8.6 7.3 9.5 3.0 6.9 1.8 11.0 8.9 8.0 6.0 7.6 9.0 14.0 4.0 3.5 9.5 8.2 5.0

Table 9--Summary statistics for major oxides and minor elements.

  Statistic
Element Mean Standard
Deviation
Median Min Max
Percent
Al2O3 14.16 3.57 15.40 4.10 20.20
CaO 8.44 8.94 4.60 0.10 38.00
Fe Oxides 4.72 1.34 4.70 1.80 10.30
K2O 2.73 0.82 2.80 0.10 4.90
MgO 3.13 3.14 2.30 0.30 26.80
SiO2 55.29 15.88 58.90 14.60 114.00
 
Mn/Fe 1.04 0.92 0.70 0.10 5.60
P.P.M.
MnO 462.42 477.73 330.00 65.00 3297.00
Ag 1.25 4.76 0.00 0.00 46.00
Ba 345.69 178.86 347.00 92.00 1594.00
Be 5.15 1.94 5.00 2.00 12.00
Bi 1.46 1.58 1.00 0.00 8.00
Cd 29.87 25.74 23.00 0.00 168.00
Co 39.98 25.33 35.00 7.00 224.00
Cr 139.81 188.38 95.00 35.00 1428.00
Cu 28.70 26.04 23.00 2.00 140.00
Ga 18.94 5.97 20.00 3.00 32.00
Ge 1.94 2.25 1.00 0.00 14.00
Li 54.09 29.32 47.00 6.00 169.00
Mo 28.32 73.53 7.00 0.00 713.00
Ni 78.52 86.32 53.00 14.00 661.00
Pb 27.72 43.71 15.00 2.00 356.00
Sn 0.76 2.78 0.00 0.00 20.00
Sr 286.28 283.32 190.00 21.00 1844.00
v 197.91 402.46 114.00 19.00 3607.00
Zn 207.90 179.07 182.00 0.00 909.00
Zr 213.28 107.02 189.00 17.00 730.00
 
Heat loss 6.73 4.18   0.50 29.90%

Summary statistics for all the major and minor elements are presented in Table 9. Two extra parameters are included in the table, the percentage weight loss on ignition (Heat Loss) and the ratio of Mn to Fe.

Ag, Be, Bi, Ge, and Sn are only recorded in minor quantities in samples and therefore appear to have little influence on geochemical variation in the Upper Pennsylvanian and Lower Permian shales. Of the remaining elements and oxides, many show considerable numerical variation with standard deviations of the same order as the means. In terms of the elements, this indicates a lognormal distribution but, as no statistical guidelines are available to determine whether the observed frequencies (Figure 22) are lognormal or not, only raw data are used in further operations. Subsequently, Link and Koch (1975) have applied lognormal theory to pseudolognormal distributions and have shown that positive or negative bias, or a combination of the two, can occur.

Figure 22--Histograms showing the variation and distribution of major oxides and minor elements in Upper Pennsylvanian and Lower Permian shales (total samples = 127). From Al2O3 to SiO2, measurements are in %, and from MnO to Zr in ppm. Scales are 0 to maximum value in 10 divisions (vertical).

Twelve histograms.

Nine histograms.

Stratigraphic Variation in the Geochemistry

The variation of major oxides (Figures 23 and 24) indicates both lithological and stratigraphical control of Upper Pennsylvanian and Lower Permian shales. SiO2 in particular, is distributed in zones that correspond to those established from mineralogical variation in the same shales. The Pleasanton, Kansas City, and Lansing Groups form a zone of highly variable SiO2 values (from 35 to 70 percent) whereas the succeeding Douglas Group shows consistently high values (up to 90 percent). The Shawnee and Wabaunsee Groups show similarities to the Pleasanton-Kansas City-Lansing and Douglas zones respectively although the Shawnee has greater variability of values (20 to 90 percent) and the Wabaunsee does not show such intense SiO2 development. Finally, samples from the Permian Groups all contain relatively small amounts Of SiO2.

Figure 23--Stratigraphic variation of Al2O3, SiO2, and Fe oxides.

No trend to Al2O3 variations; SiO2 has rise from Chase Gp. to Douglas, but highly variable in SHawnee and Douglas Grps; Fe oxides consistent, slight rise in Wabaunsee Gp.

Figure 24--Stratigraphic variation of CaO, MgO, K2O, and heat loss in Upper Pennsylvanian and Lower Permian shales.

CaO and Heat Loss values highly cvariable; MgO values low except for spike near base of Lansing; K2O values low for all groups.

The Al2O3 distribution (Figure 23) shows similarity to the SiO2 graph with corresponding highs and lows. However, zoning the distribution is difficult as sample values only vary from six to 20 percent. The sole indication of stratigraphic control occurs in the Lower Permian where the Al2O3 values are approximately five percent lower than in the Pennsylvanian.

CaO is distributed with high values (zero to 40 percent) in the Pleasanton and Lower Kansas City, in the Lansing, in the Shawnee, and also in the Lower Permian, whereas few samples from the intervening zones have greater than 10 percent CaO. The increase in CaO and MgO in the Permian is comparable with increased carbonate production noted in the shale mineralogy. However, no zones are noted in the MgO distribution as the increase is only gradual throughout the Upper Pennsylvanian and Lower Permian deposits. Only one sample contained more than 15 percent, which is surprising as several dolomite-rich shales were detected by X-ray diffraction. However, an alternative site for MgO may lie within the lattice of chlorite clay minerals (Eckhardt, 1958; Van Moort, 1972).

The iron oxide content varies from 1.8 to 10.3 percent with a mean of 4.7 percent. There is some similarity to both Al2O3 and SiO2 distributions as the iron oxide curve (Figure 23) has high and low values that equate with points on the Al2O3 and SiO2 curves. Highs occur in the Upper Douglas, Lower Wabaunsee, and Lansing Groups, whereas lows are found in the Lower Kansas City, Lower Douglas, Shawnee, Council Grove, and Chase Groups.

The K2O content ranges from 0.5 to 4.9 percent with a mean of 2.7 percent. Apart from a slight decrease in K2O during the Lower Permian, corresponding mineralogically to a decrease in illite content (Weaver, 1967), little information can be gained from the stratigraphic variation in K2O values.

MnO rarely exceeds 1000 ppm in Upper Pennsylvanian and Lower Permian shales. Allowing, therefore, for differences of scale, the MnO (Figure 25) content appears to be closely associated with the carbonate fraction of the shales. For example, the Lansing, Shawnee, Wabaunsee, and Admire Groups contain beds that are rich in MnO, CaO, and calcite. However, the association is not maintained in the Kansas City, Council Grove, and Chase Groups. The concentration of Mn in shales may be related to an increase of Mn2+ ions (substituting for Ca2+ in calcite) in the reducing conditions (Bencini and Turi, 1974) developed at the end of the Pennsylvanian. Alternatively, the low MnO content of some calcareous shales may reflect differences in the original mineralogy of the sediments. Aragonite forms in shallow-water environments (Cloud, 1962) with minor Mn substitution for Ca (Thompson, 1972). Calcite, however, predominates in deep-water carbonate sediments and normally contains abundant Mn (Thompson, 1972). Therefore, the Lansing, Shawnee, Wabaunsee, and Admire Groups contain shales that may represent deposition either at times of deep-water sedimentation or highly reducing conditions. The Council Grove, Chase, and Kansas City Groups, on the other hand, contain shales that were deposited in periods of shallow-water sedimentation or less reducing conditions. Diagenetic processes, particularly dolomitization, do not appear to have seriously modified the original Mn content.

Figure 25--Stratigraphic variation of MnO and Ba in Upper Pennsylvanian and Lower Permian shales.

MnO has spikes in Admite, Wabaunsee, Shawnee, and lower Lansing Grps; Ba has a spike in Chase and Council Grove Grps and a smaller high in Douglas Gp.

Silver (Ag) is found in low concentrations in all samples (a maximum of 46 ppm) and provides negligible information for establishing the geochemical conditions prevailing during the Upper Pennsylvanian and Lower Permian. Beryllium (Be), bismuth (Bi), and germanium (Ge) are also found in minor quantities, probably as sulphides (Bi) or within clay mineral lattices (Be and Ge) (Wedepohl, 1969, 1970).

Barium (Ba) normally occurs as a substitute for Ca2+ in calcareous deposits. However, evidence for any such association is difficult to find in the Upper Pennsylvanian or Lower Permian shales. The distribution of barium (Figure 25) is more akin to the illite and chlorite distributions than to the carbonate fraction. Ba2+ substitution for K+ in illite (Fenner and Hagner, 1967; Krauskopf, 1967) may explain many of the minor peaks in the Ba stratigraphic distribution but two high values in the Lower Permian bear no relation to any other geochemical or mineralogical variable. In this case, the possibility of small amounts of barite occurring in the sediments cannot be ignored.

Taking into account the high Cd values recorded for the standards, cadmium's normal geochemical association with zinc in the ratio of 1:500 (Hawkes and Webb, 1962) is retained in the Kansas shales. High values are recorded in the Kansas City, Shawnee, and Council Grove Groups, whereas low values predominate in the remaining samples (Figure 26). A high Cd value recorded for the Heebner shale (Shawnee Group) indicates a possible association with black shales.

The stratigraphic variation of cobalt (Figure 26) shows only tenuous correlations with other geochemical and mineralogical variables. Two peaks occurring in the Tonganoxie Sandstone (Douglas Group) and Silver Lake Shale (Wabaunsee Group) may represent concentrations of detrital minerals containing cobalt.

Figure 26--Stratigraphic variation of Cd, Co, Cr, Cu, and Li in Upper Pennsylvanian and Lower Permian shales.

Cd has a small spike in Shawnee Gp. and Cobalt has small highs in Douglas and Wabaunsee Grps.; Cr has several spikes in Kansas City, Shawnee, Wabaunsee, and Coucil Grove Grps.; Cu and Li are generally low.

The values of chromium (Cr) recorded in the Upper Pennsylvanian and Lower Permian shales divide the samples into two types. The majority of shales contain around 100 ppm Cr, comparing favorably with the "average shale" quoted in the literature (Vinogradov, 1962). The remaining eight samples (> 400 ppm Cr) are all black shales. This lithology is found in members of the Kansas City, Shawnee, Wabaunsee, and Council Grove Groups and was deposited in a highly reducing, shallow marine environment (Heckel, 1972a), rich in organic matter. Chemical analyses of black shales are characterized not only by a considerable organic carbon content but also by sulphur present as FeS2 (Vine and Tourtelot, 1970). Minor elements such as V, Mo, Cu, Ni, Pb, Zn, and Cr are enriched in black shales by the organic matter which acts either as a biological catalyst (Vine and Tourtelot, 1970) or as a sulphide reducing agent (Mason, 1958). This element association may be of great importance in determining the presence or absence of geochemical periodicity in the Kansas shales, for black shales have been extensively employed as marker horizons in cyclothems.

The overall stratigraphic distribution of copper matches that of Cr although the black shale values are relatively lower than Cr equivalents. Only one high Cu value--in the Hamblin Shale of the Admire Group--cannot be explained in terms of black shale enrichment.

Gallium is present in minor quantities in all shales but is geochemically of great importance. Particular interest is attached to this element as a diagnostic for the salinity of depositional environments, its concentration being generally higher in fresh-water than marine argillaceous deposits (Degens et al., 1958; Tourtelot, 1964). Gallium seems to be depleted in the Upper Pennsylvanian and Lower Permian shales, inferring a marine origin for the shales. For confirmatory evidence, rubidium and boron determinations would be significant.

Lithium may also be used as an indicator of fresh-water or marine depositional environments (Keith and Degens, 1959). The relatively high lithium values generally indicate a marine environment for most of the Upper Pennsylvanian and Lower Permian with some non-marine deposition in the Pleasanton, Douglas, Lower Shawnee, and Wabaunsee.

Molybdenum is another element found concentrated in anoxic environments (Bertine, 1972; Bertine and Turekian, 1973), principally black shales. Within this lithology, Mo concentrations vary between 150 and 750 ppm, whereas the remaining samples have few values over 75 ppm. The Mo distribution has peaks in the Pleasanton, Shawnee (in which the Heebner Shale is prominent), Wabaunsee, and Lower Permian Groups. In the case of the Lower Permian Groups, there seems to have been a general rise in the Mo concentration from negligible amounts in the Upper Wabaunsee to between 30 and 100 ppm for most Permian sediments (Figure 27).

Figure 27--Stratigraphic variation of Mo, Ni, Pb, and Sr in Upper Pennsylvanian and Lower Permian shales.

Mo, Ni, and Pb have a spike in Shawnee Gp, and Ni and Pb have smaller highs in Kansas City Gp.; Sr has highs in Chase, Council Grove, and Kansas City Grps.

Nickel values are also arranged according to the development of black shales and show close correspondence to the Cr, Cu, Mo, Pb, and Zn distributions. The majority of samples have values in the range 0 to 100 ppm (Figure 27), whereas those samples associated with black shales have values ranging from 100 to 700 ppm.

Lead (Pb) shows a similar distribution (Figure 27) to Ni with only minor differences in the Wabaunsee Group samples. Here, two peaks in the Pony Creek Shale and Silver Lake Shale correspond to similar peaks in the Mo distribution (Figure 27) and may be connected with pyrite or organic residues (Wedepohl, 1974). Enriched shales have Pb values that range from 100 to 400 ppm (high for black shales; Wedepohl, 1974), whereas other samples all contain less than 100 ppm Pb.

Strontium, like most other trace elements, has a bimodal distribution (Figure 22), with many shale samples lying in the range 50 to 300 ppm and a few in the range 300 to 1900 ppm. Of the samples from the upper range, most are calcareous shales from the Kansas City, Shawnee, Upper Wabaunsee, and Council Grove Groups. The strontium distribution (Figure 27) appears to be associated with the carbonate fraction and may be controlled by salinity and basinal depth (Veizer and Demovic, 1974). The higher values, coinciding with high carbonate content may, therefore, indicate "hypersaline" or deep-water conditions. This evidence is in agreement with the MnO interpretation of the Shawnee, Upper Wabaunsee, and Admire Groups, but shows discrepancies in the Kansas City and Lower Wabaunsee Groups. The latter case may be explained in terms of low carbonate content but the Kansas City values seem contradictory. Therefore, before the implications of carbonate geochemistry can be extensively applied to calcareous shales, further experimentation and analysis are required. Meanwhile, it can be stated that there appears to be a close correlation among MnO, Sr, and the carbonate fraction and that the MnO and Sr content of the shales may be influenced by depth, original mineralogy, salinity, and basinal conditions.

Both vanadium and zinc distributions (Figure 28) show enrichment in the black shale beds of the Kansas City, Shawnee, and Council Grove Groups. Zirconium (Zr) on the other hand appears to be stratigraphically distributed (Figure 28) according to the quartz content of shales. In sedimentary rocks, Zr occurs primarily as detrital zircons and is, therefore, found concentrated in the coarse detrital beds of the Douglas and Wabaunsee Groups.

Figure 28--Stratigraphic variation of Mo, Ni, Pb, and Sr in Upper Pennsylvanian and Lower Permian shales.

V has spikes in Shawnee and lower Kansas City Grps; Zn has spike in Shawnee and highs in middle and upper Kansas City; Zr is about the same at all groups.

The carbonate and organic contents of shale seem to control the stratigraphic distribution of percentage weight loss on ignition (Heat Loss--Figure 24). This variable has high values recorded in the Kansas City (calcareous and black shales), Shawnee (calcareous and black shales), Council Grove, and Chase Groups (calcareous shales).

Univariate Analysis of Geochemical Data

A number of major oxide and minor element stratigraphic distributions visually examined appeared to contain geochemical oscillations. Statistical clarification and verification of the repetitions were performed by Fourier analysis. First, however, each variable was transformed using linear interpolation (Davis, 1973) from an irregularly spaced data sequence to an equal-spaced sequence having data points at 10-foot intervals. After increasing the data sequence to 218 points, the geochemical variables were analyzed by linear regression to check how equal-spacing the data may have affected the geochemical distribution. No variable, however, assumed a greatly increased goodness-of-fit or correlation coefficient. This enabled the investigator to submit the equal-spaced data points to the Fourier analysis program with the knowledge that any cycles detected would be representative of the original data. To obviate any problems associated with extraneous noise in the data, an 11-term smoothing equation was also applied to the equal-spaced data and the output submitted to the Fourier program.

The first variable studied was SiO2 and, as expected, the raw power spectrum closely matched the quartz spectrum recorded on [Figure 14]. Peaks are recognized at the third, seventh, 14th, 19th, 22nd, 26th, and 33rd harmonics of which the seventh and 14th harmonic peaks are retained in the power spectrum of the smoothed data. The repetitive elements with intervals of 70 and 140 feet probably represent the mineralogical cycles detected on [Figure 14], whereas the small peaks retained in the region of the 30th harmonic possibly indicate a group-by-group cycle in the geochemistry as witnessed by the large-scale stratigraphic zones observed [in the previous section].

The CaO stratigraphic distribution has a raw power spectrum with peaks at the fourth, seventh, ninth, 13th, 15th, 17th, 19th, 21st, 27th, 31st, and 33rd harmonics. After smoothing the equal-spaced data, peaks at the fifth, seventh, ninth, and 13th harmonics are produced. A 70-foot interval cycle is prominent in this data, possibly indicating a cycle in carbonate deposition.

Both the K2O and Fe oxide distribution contain a seventh harmonic peak in their raw power spectra, although in the case of Fe oxides, this shifts to the sixth harmonic after smoothing. Similarly, Al2O3 and MgO have sixth harmonic peaks. Another close agreement between the power spectra of SiO2,, CaO, MgO, and Al2O3 is the occurrence of a peak at the 12th, 13th, or 14th harmonics. However, only SiO2 records a peak around the 30th harmonic.

It seems possible, therefore, to distinguish short-term repetitions in the major oxide geochemistry corresponding to the 70-foot cycles in the mineralogy of the Kansas shales. This is probably a reflection of the lithological cycles distinguished by Moore (1936). A 300-foot cycle distinguished in SiO2, may represent the group-by-group stratigraphic variation noted previously.

A few minor-element distributions were also submitted to these procedures in an attempt to detect periodicity in the shales. MnO, Ba, Co, Cr, Cu, Ga, Li, Mo, and Ni distributions were considered representative of the minor-element variation detected in the Kansas shales and most likely to contain repetitive elements. In MnO, Ba, Cr, Ni, Mo, Cu, and Ga distributions, the 70-foot cycle was again dominant and in Cr, Ni, Mo, and Cu, a 130-foot cycle was also recognized. The only apparent anomaly in this study was Li which had power spectrum peaks at the fifth, ninth, and 12th harmonics. A number of elements also had peaks at harmonics between 25 and 30, but no consistency was noted. Therefore, it appears that the peaks at the seventh and 13th harmonics are the only common features among the minor elements. The heat-loss variable was also analyzed and produced peaks at the seventh and 13th harmonics.

The correspondence of results obtained from the major oxides and minor elements seems to support the hypothesis that there are geochemical cycles of 70-foot and 130-foot intervals. It also appears probable that the minor-element geochemical cycles detected in Cr, Cu, Mo, and Ni are related to the periodic occurrence of black shales. As Moore (1936) has continuously employed black shales as distinctive marker horizons in Upper Pennsylvanian cyclothems and megacyclothems, it may be inferred that the geochemical cycles (and mineralogical as these also indicate 70-foot cycles) are related to Moore's lithological cyclothems.

Geochemical Correlations

Correlations between the geochemical variables are shown in Table 10. All variables have been included in the matrix, as parameters such as Ag, Be, Bi, and Ge that seemed at first glance unimportant [Stratigraphic Variation] may prove to be of significance in a multivariate analysis.

Table 10--Correlation coefficient matrix geochemical variables; r95= ±.15, r99= ±.20, r99.9= ±.27.

Al2O3 1.00                                                      
CaO -.81 1.00                                                    
Fe
Oxides
.47 -.38 1.00                                                  
K2O .67 -.42 .44 1.00                                                
MgO -.42 .38 .03 -.21 1.00                                              
SiO2 .61 -.87 .18 .14 -.45 1.00                                            
Mn/Fe -.59 .68 -.19 -.41 .33 -.55 1.00                                          
MnO -.39 .47 .10 -.26 .33 -.43 .92 1.00                                        
Ag -.18 -.01 -.20 -.25 -.08 .09 .01 -.05 1.00                                      
Ba .54 -.44 .40 .42 -.22 .35 -.29 -.14 -.15 1.00                                    
Be .08 .12 .11 .25 .02 -.21 .16 .16 .13 .02 1.00                                  
Bi -.53 .69 .02 -.09 .14 -.70 .48 .37 .07 -.29 .49 1.00                                
Ca .15 -.16 -.02 .05 -.20 .22 -.24 -.23 .28 .03 .44 .04 1.00                              
Co -.25 .07 -.18 -.42 -.10 .15 .20 .11 .56 -.13 .00 .11 .12 1.00                            
Cr .19 -.18 .00 .16 -.12 .14 -.24 -.20 .37 .04 .47 .01 .67 -.02 1.00                          
Cu .30 -.26 .20 .33 -.17 .12 -.26 -.19 .19 .11 .53 .07 .60 -.05 .74 1.00                        
Ga .92 -.72 .55 .80 -.40 .44 -.57 -.37 -.18 .47 .18 -.30 .12 -.31 .18 .38 1.00                      
Ge -.54 .73 -.07 -.13 .09 -.68 .53 .38 .04 -.25 .41 .93 -.06 .15 -.12 -.08 -.33 1.00                    
Li .12 .08 .24 .37 -.05 -.24 -.09 -.09 -.14 .17 .16 .33 -.17 -.09 -.03 .07 .30 .37 1.00                  
Mo -.16 .22 -.08 -.06 .01 -.19 .10 .04 .23 -.13 .54 .36 .60 .16 .48 .53 -.10 .26 .04 1.00                
Ni .20 -.15 .06 .21 -.11 .08 -.19 -.15 .22 .02 .46 .03 .61 .12 .75 .76 .23 -.07 .03 .53 1.00              
Pb .14 -.14 .06 .13 -.10 .08 -.14 -.08 .21 .02 .44 .04 .59 .13 .68 .68 .15 -.08 -.09 .45 .89 1.00            
Sn -.47 .52 -.18 -.18 .18 -.50 .37 .22 .07 -.25 .29 .71 -.08 .14 -.10 -.09 -.32 .77 .30 .19 -.08 -.08 1.00          
Sr -.51 .71 -.27 -.26 .17 -.59 .46 .32 -.02 -.33 .13 .52 .17 .04 -.12 -.18 -.45 .57 -.01 .14 -.09 -.09 .42 1.00        
V .17 -.19 .03 .12 -.11 .15 -.19 -.16 .39 .04 .54 .05 .62 .01 .87 .69 .18 -.08 -.01 .62 .63 .62 -.08 -.13 1.00      
Zn .48 -.46 .27 .36 -.26 .33 -.43 -.32 .17 .20 .46 -.13 .67 .01 .76 .79 .48 -.26 .05 .44 .83 .77 -.25 -.30 .67 1.00    
Zr .11 -.28 -.09 -.25 -.22 .53 -.02 .00 -.13 .13 -.17 -.29 .04 .33 -.14 -.21 -.07 -.22 -.26 -.07 -.16 -.11 -.18 -.18 -.09 -.04 1.00  
Heat
Loss
-.04 .10 .10 .13 -.06 -.21 -.04 .02 .24 -.05 .36 .28 .34 -.16 .58 .52 .04 .12 .02 .48 .46 .48 .07 .10 .67 .38 -.36 1.00
  Al2O3 CaO Fe
Oxides
K2O MgO SiO2 Mn/Fe MnO Ag Ba Be Bi Cd Co Cr Cu Ga Ge Li Mo Ni Pb Sn Sr V Zn Zr Heat
Loss

Al2O3 has strong positive correlations with SiO2, K2O, Ba, Ga, and Zn, reflecting geochemical associations in feldspar (SiO2) and clay mineral lattices (K2O, Ba, Ga, Zn). Negative correlations with CaO, MgO, Mn/Fe ratio, MnO, Bi, Ge, Sn, and Sr are attributed to the lack of Al2O3 in carbonate environments. CaO shows a positive relationship to Mn/Fe, MnO, Bi, Ge, Sn, and Sr, all of which are commonly associated with carbonates, and negative correlations with SiO2, Al2O3, K2O, Fe oxides, Ba, Ga, and Zn. As noted above, Fe oxides have positive correlations with Al2O3, K,,O, Ba, and Ga and negative with CaO. K2O shows a similar set of correlations to the Fe oxides, indicating a geochemical association in clay minerals or potash feldspar. MgO is positively correlated with CaO, reflecting an association in dolomitic shales, and negatively correlated with SiO2 as quartz contains little MgO.

Considering the minor oxides and elements, a number of variable relationships indicated are clarified by the correlation coefficient matrix. The association of Cd, Cr, Cu, Be, Ni, Mo, Pb, V, and Zn distributions is supported by high positive correlations between all the elements. There is also a strong connection between the minor elements MnO, Bi, Ge, Sn, and Sr of the carbonate fraction. Be, Ga, Li, Cu, and Zn form a tenuous association that probably relates to substitution in clay mineral lattices. Ag, however, has no apparent affinities to any of these groups of minor elements but shows a high correlation with Co, indicating a possible connection with the detrital fraction. The heat-loss variable shows a high correlation with the Cd, Cr, Cu, Be, Ni, Mo, Pb, V, and Zn association, indicating that samples enriched in these elements also contain the most volatile materials.

The associations of geochemical variables elucidated by the correlation coefficient matrix are therefore:

  1. An Al2O3, SiO2, Zr, and possibly Co and Ag combination as a detrital fraction;
  2. A CaO, MgO, MnO, Mn/Fe, Bi, Ge, Sn, and Sr association representing a carbonate fraction;
  3. A Cd, Cr, Cu, Be, Mo, Ni, Pb, V, Zn, and heat-loss geochemical fraction common to black shales;
  4. A K2O, Fe oxides, Ga, Li, and possibly Cu and Zn association forming substitutes in clay mineral lattices.

Multivariate Statistical Analysis of Geochemical Data

In order to further clarify the relationships among major oxides, minor elements, and inter-element associations and to establish the stratigraphic variation in geochemistry, the following standard statistical techniques-principal components analysis, Q-mode cluster analysis, and multiple discriminant analysis-were applied to the geochemical data.

R-mode principal components analysis of the data produced six significant components (eigenvalue > 1.0) which together account for 77 percent of the total variance, each component explaining more than four percent of the data variance (Table 11). Loadings of the variables on the components are shown in Figure 29 and a most complicated picture emerges.

Table 11--Eigenvalues of the principal components extracted.

Component Eigenvalue %
Variance
Cumulative
% Variance
1 7.9 29.2 29.2
2 5.7 21.3 50.5
3 3.1 11.3 61.8
4 1.6 6.0 67.8
5 1.5 5.6 73.4
6 1.1 4.1 77.5

Figure 29--Principal component loadings of geochemical variables. Only loadings greater than ± 0.30 are included.

Key
On all components: Al = Al2O3
Ca = CaO
Fe = Fe oxides
K = K2O
Mg = mgo
Si = SiO2
MF = Mn/Fe
Mn = MnO
On component 1:
1 = Ni
2 = K
3 = V
4 = Bi
5 = Sn
6 = Mn
On component 2:
1 = Ni
2 = Cr and V
3 = Pb
4 = Bi
5 = Cu
6 = Cd
7 = Sr and Ag
On component 3:
1 = Bi and Ge

Component loadings for the geochemical variables.

Since in geochemical investigations the components are not always independent (orthogonal), further insight into the geochemistry of the shales can be gained by performing oblique promax rotations of the six component axes. By this method, the variables influential on each axis are illuminated (Figure 30) and the geochemical controls of sediment evolution outlined. The following explanation for the components can therefore be proposed:

Component 1--The very high loadings of CaO, MgO, MnO, and Sr suggest that this component should be designated the carbonate component. The elements Ge, Bi, Sn, and Sr all show their highest loadings on the component but evidently also play dual or triple roles by showing significant loadings on other factors. The positive loadings of these elements and oxides are opposed by high negative loadings on SiO2 and Al2O3, clearly indicating a detrital phase antipathetically related to a carbonate fraction.

Component 2--The elements Ni, Pb, Cd, Cu, V, Zn, Cr, Mo, and Be dominate this component and have low values in all samples from black shales. In contrast, Zr, Al2O3, and SiO2, have moderate positive loadings on the principal components but are removed by the effect of rotation. Therefore, component 2 is referred to as the black shale component and reflects changes in the conditions under which the shales were deposited. As black shales are normally developed under reducing conditions, the component may also represent an oxidation-reduction contrast or "Eh component."

Component 3--This component shows high negative loadings, in order of magnitude, for K2O, Li, Fe oxides, and Ga against moderate positive loadings for Co, Ag, Zr, and SiO2. On rotation, negative loadings are recorded for Fe oxides, Ga, K2O, and Al2O3 and positive for CaO, Mn/Fe ratio, Mo, and Sr. The close relationship of K2O and Al2O3 is normally associated with potassium feldspar or clay minerals. This is to a great extent substantiated by Ga and Li which often substitute for K+ in clay minerals. The additional high loading of Fe oxides may also be explained in terms of substitution in clay mineral lattices.

Figure 30--Loadings of variables on the first two axes of a principal components analysis, varimax rotation, and promax oblique rotation. In the latter case the axes are not orthogonal (correlation = 0.25) but, for simplicity, are drawn so.

Component loadings for the geochemical variables.

Figure 31--Oblique promax axis loadings. Loadings less than ±0.15 are not illustrated.

Key
On all axes:
Al = Al2O3
Ca = CaO
Fe = Fe oxides
K = K2O
Mg = mgo
Si = SiO2
MF = Mn/Fe
Mn = MnO
On axis 1: 1 = Be and Ca
On axis 3: 1 = Si and Be On axis 2: 1 = Zn and V
2 = Cu
On axis 4: 1 = Ag and K

Component loadings for the geochemical variables.

The positive loadings on the third principal component reflect the inability of detrital elements such as Ag, Co, and Zr to substitute in clay mineral lattices. On rotation this association is replaced by the carbonate component elements, CaO, Sr, and Mn/Fe ratio which again rarely combine in clay mineral lattices.

Figure 32 is a plot of the scores for component 3 against total clay mineral content, as determined by difference: 100 - (quartz + carbonate)%. Correlation is good; the line drawn is believed to represent the most realistic regression with the samples plotting well to the right of it being in error due to the relatively high feldspar content. Since feldspar is not considered in the above calculation, the total clay mineral content in the samples will be exaggerated by the amount of feldspar. It is noticeable from Figure 32 and predictable from the calculation method that the error in samples with a high clay mineral content is small (< 10%), about 10 percent at a 40 percent clay content, and can increase to about 15 percent in low clay samples.

Figure 32--Component 3 scores against percentage total clay.

Curve fit to scatter plot of component 3 scores against percent total clay minerals.

Component 4--High negative loadings for Co, Zr, and, on rotation, SiO2 indicate that this component could represent a detrital component. High positive loadings of MgO (only principal components), Sr, CaO, Ag, and K2O (only promax rotation) provide support for this conclusion. The positive loaded elements and oxides (except possibly Ag) are linked through the process of coprecipitation and rarely form detrital sediments. Scores for this component allow detrital or non-detrital composition for the sample to be differentiated.

Component 5--This component is controlled by the amount of Mn occurring in the shales. MnO and Mn/Fe ratio have high positive loadings whereas Ca, Be (only promax), Zr, and Fe (only principal components) have low positive loadings. These are opposed by low negative loadings for Cd, Li, and SiO2.

As Mn2+ substitutes extensively for Ca in carbonates, the correlation of 0.33 between promax factors 1 and 5 is not unexpected. Although MnO also occurs in sediments as oxides with a general pyrite structure, the negative loading for SiO2, precludes a detrital mineral association. This component is therefore termed the manganese component and is closely related to the carbonate component (component 1).

Component 6--The elements and oxides controlling component 6 show a bipolar distribution with positive loadings recorded for Ag and Co and negative loadings for Zr, K2O, Al2O3, Ga, Sr, and Cd. This component reflects the occasional high values recorded by the Ag and Co variables in sandstones and siltstones and is consequently negatively correlated with promax factor 4. However, as both these variables are generally accorded negligible values in Kansas shales, the majority of scores on component 6 occur between 0.3 and 0.5, with occasional high Co and Ag values producing high scores.

Therefore, the geochemical relationships developed in the Upper Pennsylvanian and Lower Permian shales are found to consist of six associations. First, the geochemical evolution of the shales is influenced by a carbonate component, and then, successively decreasing in significance, a black shale component, a clay mineral component, a detrital component, a manganese component, and finally what can only be termed an Ag/Co component.

Having defined the controls over the geochemical development of Kansas shales, it is possible to examine the stratigraphic effects of these controls by studying the relationships between the samples. The scores of Kansas shale samples on the six significant components were, therefore, submitted to a Q-mode cluster analysis program. The dendrogram produced is shown in Figure 33 and the samples are seen to fall into a number of natural groups. Although most of the samples appear to be closely associated, a maximum of 10 groups or clusters can be distinguished.

Figure 33--Dendrogram of Upper Pennsylvanian and Lower Permian geochemical data. Clusters produced are outlined on the left of the diagram.

Dendogram shoing 6 clusters.

Before examining the stratigraphic distribution of these clusters, it is necessary to confirm that the 10 groups are discrete and not simply a product of the clustering method. The procedure adopted as a test is described [in a previous section] and is based on the multiple discriminant analysis program of Mather (1969a, 1969b). By this method, variation between clusters is maximized to produce two discriminant axes, accounting for 70.9 percent of the sample variance (Figure 34). As the diamonds in Figure 34 represent the means of each cluster ±1 standard deviation on each axis, it can be seen that clusters A, B, C, E, and G are indistinguishable and can be merged. Similarly, group J only consists of two samples and can be merged for convenience with group H. Group 1, on the other hand, is found to be unique and represents black shales with high scores on component 2. A statistically more realistic arrangement of the dendrogram samples is therefore:

  1. Clusters A, B, C, E, and G (referred to henceforth as cluster A),
  2. Clusters H and J (referred to as cluster H in the succeeding discussion),
  3. Cluster D,
  4. Cluster F,
  5. Cluster I.

Figure 34--Plot of cluster groups on first two discriminant axes. Controlling components are superimposed to aid interpretation.

Clusters A, B, C, G, and E are plotted very close together, as are clusters H and J.

When re-examined by discriminant analysis (Figure 35), the revised clusters are found to be discrete units. It can be concluded, therefore, that the geochemical controls outlined previously divide the shale samples into five groups. In Figure 34 the geochemical components are superimposed on the distribution of the groups to show that, although each cluster is unique, it is generally influenced by more than one component. For example, samples in cluster H have high scores on components 1, 4, and 5; cluster I has high scores on component 2; cluster A is characterized by high scores on component 3; and cluster F is controlled by the high scores recorded on the first component. Samples from Group D, on the other hand, are characterized by low scores on components 2 and 5. The controlling components indicate that cluster I consists of black shale samples; clusters H, F, and D are dominated by calcareous and dolomitic shales; and cluster A by quartz, feldspar, and clay-rich shales, although in the latter case some overlap into the calcareous regime does occur. These findings are supported by a comparison between the distribution of shale samples in the X-ray diffraction and geochemical classifications (Table 12).

Figure 35--A plot of revised clusters against first two discriminant axes. Diamonds represent mean of each cluster ±1 standard deviation on each axis.

New revised clusters ploted on first two discriminant axes.

Table 12--Distribution of shale samples in the X-ray diffraction and geochemical classifications, indicating, for example, that of the samples in geochemical cluster F, 4 were classified into X-ray diffraction cluster E, 1 into G, 1 into A, and 2 into H.

  Geochemical Groups
A D F H I
X-Ray
Diffraction
Groups
A 16 1 1   3
B 48 1     3
C 3     2  
D 6        
E 16 8 4   5
G   1 1 5  
H   1 2    

The distribution of the shale samples according to their cluster is shown in Figure 36 and reveals a five-fold division of the stratigraphic column. The lowest division consists of the Pleasanton and Lower Kansas City Group beds and contains samples that fall into all five clusters: the majority of samples belonging to cluster A, four to cluster I, and one from each of the remaining clusters. Samples from cluster I occur at approximately 70-foot intervals and reflect the occurrence of black shale deposits. There is, therefore, a close link between the regularity of black shales (cluster I) and the 70-foot cycles noted in the Cd, Cr, Cu, Mo, Ni, Pb, Zn, and V trace-element distributions. Carbonate-rich shales (clusters D, F, and H) are, in three of the four cases, associated with the cluster I samples, indicating a connection between the occurrence of calcareous and dolomitic shales and the geochemical cycles noted previously.

Figure 36--Stratigraphic distribution of shale samples arranged according to the cluster analysis groups. The horizontal scale is arbitrary.

Samples have been arranged into clusters based on the multivariate analysis; clusters plotted against the stratigraphic chart at same scale as previous charts.

Following the Pleasanton-Lower Kansas City section is an Upper Kansas City, Lansing, and Douglas Groups zone, which consists predominantly of cluster A samples with an occasional calcareous sample. This division reflects the large numbers of siltstones and sandstones occurring in this part of the stratigraphy.

The succeeding Shawnee Group is similar to the Pleasanton-Lower Kansas City section. Samples from all clusters are again recorded although the proportions of cluster I to D, F, and H are slightly different. Two 70-foot cycles are detected. The Wabaunsee Group constitutes the fourth section and bears a close resemblance to the Upper Kansas City-Lansing-Douglas division, i.e., cluster A samples predominate although an occasional calcareous or dolomitic shale is developed. During the Upper Wabaunsee and Lower Permian, calcareous shales dominate a section that alternates among samples of cluster A, D, F, and H.

Summarizing, the stratigraphic distribution of shales can therefore be considered in terms of five sections of which the Pleasanton-Lower Kansas City and Upper Kansas City-Lansing-Douglas sections show geochemical similarities to the Shawnee and Lower Wabaunsee sections respectively. The lower boundary of the Upper Wabaunsee and Permian zone reflects an important change in environmental conditions from the generally clastic deposition of the Upper Pennsylvanian to the carbonate-dominated sedimentation in the Permian. The Pleasanton, Lower Kansas City, and Shawnee Groups also show evidence for geochemical cycle at 70-foot intervals.

Discussion

One-hundred-twenty-six samples of Upper Pennsylvanian and Lower Permian shales were analyzed for major oxides and minor elements using an ARL 2900B direct reading emission spectrometer. From the results, it has been shown that the distributions of SiO2, Al2O3, CaO, MgO, MnO, Co, Cr, Cu, Mo, Ni, Pb, Sr, V, Zn, and Zr are stratigraphically controlled and that the values of Ag, Be, Bi, and Ge are so low that no stratigraphic relationships can be distinguished.

The major oxides present a similar stratigraphic zonation to that displayed by the mineralogical variables, i.e., the Pleasanton, Kansas City, and Lansing beds form one natural division of the stratigraphy and the Douglas, Shawnee, Wabaunsee, and Lower Permian Groups, further divisions. CaO and MgO have high values in the Pleasanton, Kansas City, Lansing, and Shawnee Groups, whereas the Douglas and Wabaunsee Groups are rich in SiO2 and Al2O3. In the Lower Permian Groups, CaO and MgO form the major geochemical components. Fe oxide and K2O distributions are relatively stable throughout the Lower Permian and Upper Pennsylvanian.

The minor elements, on the other hand, reveal a totally different pattern of stratigraphic control. MnO, for example, has a distribution that may reflect differences in the original carbonate mineralogy or the depositional environment of the sediments. High values are recorded in the Lansing, Shawnee, Wabaunsee, and Admire Groups. Similarly, Sr, another geochemical facies indicator, has peaks in the Council Grove, Shawnee, Chase, and Pleasanton Groups that may reflect original mineralogical differences in the carbonate content of the sediments and changes in the depth or salinity of the depositional environment. Ga and Li are enriched in marine sediments relative to fresh water and indicate that parts of the Douglas and Wabaunsee were deposited in a restricted marine or non-marine environment. However, the inference drawn from all four distributions is that a complex interrelationship among salinity, depth, and original mineralogy exists in Kansas shales that cannot be unravelled by simply examining individual geochemical variables. Further information may be gained by a multivariate statistical analysis of the geochemical data (previous section).

Another distinguishing feature of the minor-element geochemical data is the association of Cd, Cr, Cu, Mo, Ni, Pb, V, and Zn with the occurrence of black shales. This has been extensively documented in the literature and arises from the chemical activity of organic residues in a reducing environment.

A third factor influencing the geochemical variation of the Upper Pennsylvanian and Lower Permian shales is elucidated by the distribution of zirconium. As this element is predominantly found in the detrital mineral zircon, the stratigraphic regions rich in Zr probably represent periods of detrital deposition. This conclusion is supported by the distribution of quartz, feldspar, and Co, which have peaks in the Douglas and Wabaunsee Groups.

A comparison of geochemical results obtained in this paper and by Ebens and Connor in a survey of Missouri (1972) has shown that the geochemical variation in the calcareous and black shale deposits, particularly Ca, Cr, Cu, Pb, Ni, Sr, V, and Zn, is regionally controlled. Variables that had equivalent ranges of results in both Kansas and Missouri deposits included Ba, Co, and Zr.

Published reports on the worldwide geochemical evolution of CaO, MgO, K2O, Al2O3, and Fe oxides indicate that the distribution of major oxides in Kansas shales forms a geochemical association that matches worldwide trends during the Upper Pennsylvanian and Lower Permian. However, a negative correlation was noted between the evolutionary trend of Sr in shales (Reimer, 1972) and that reported here.

The factors that may affect the geochemical variation in the Upper Pennsylvanian and Lower Permian shales are, therefore, worldwide geochemical evolution, particularly in the major oxides; regional events such as the distribution of Ca, Cr, Cu, Pb, Ni, Sr, V, and Zn; and a three-fold stratigraphic control of trace elements and major oxides. In the latter case, the associations of variables noted are a carbonate fraction containing CaO, MgO, Sr, MnO, and possibly Ba, Ga, Li, and K2O; a black shale fraction including Cd, Cr, Cu, Mo, Ni, Pb, Zn, and V; and a detrital fraction, SiO2, Al2O3, Zr with possibly Co, and Fe oxides.


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Kansas Geological Survey, Geology
Placed on web May 6, 2009; originally published December 1979.
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