CLAY MINERALOGY AND SEDIMENTARY PETROGRAPHY
OF LOWER TO MIDDLE PALEOZOIC ROCKS FROM A
SINGLE CORE FORM NORTHWEST GEORGIA
A THESIS
Presented to
The Faculty of the Division of Graduate Studies
by
Ali Ihsan Gevrek
In Partial Fulfillment
of the Requirements for the Degree
Master of Science
in the School of Geophysical Science
Georgia Institute of Technology
August, 1978 MINERALOGY AND SEDIMENTARY PETROGRAPHY
LOWER TO MIDDLE PALEOZOIC ROCKS FROM A
SINGLE CORE FROM NORTHWEST GEORGIA
Approved:
CharlefE. Weaver, Chairman
Kevin C. Beck
Charles 0. Poiiara, Jr.
Date approved by Chairman: ii
ACKNOWLEDGMENTS
I would like to sincerely thank Dr. Charles E. Weaver,
my major director, for his guidance, advice, and for pro
viding me with the thesis subject.
I greatly appreciate Drs. Charles 0. Pollard, Jr.,
and Kevin C. Beck for being on the reading committee and for
their fruitful criticisms. Thanks are also extended to Drs.
John E. Husted and Howard R. Cramer for their suggestions
on the Lower Paleozoic Appalachian problems.
The Georgia Geological Survey is to be thanked for
providing me the core. A number of people helped me in this
work. Dianne Clark encouraged me and Annette Plunkett typed
this thesis; special thanks go to them. Brad Broekstra,
Robert J. Bullwinkel, and Rick Griffin helped by carrying
the core boxes and correcting English grammar; special thanks
to them.
Finally, thanks to my father, Ismail Gevrek, and my mother, Meryem Gevrek, for their moral support.
This research was supported by Government of the
Turkish Republic. iii
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS . ii
LIST OF TABLES iv
LIST OF PLATES vi
LIST OF ILLUSTRATIONS vii
SUMMARY viii
Chapter
I. INTRODUCTION . . 1
Geologic Setting Depositional Environments of Formations in the Core
II. METHODS AND PROCEDURES 10
III. RESULTS AND DISCUSSION 11
Sedimentary Structures Distribution of Sedimentary Structures in the Formations Mottled Matter in Formations Sedimentary Petrography Distribution of Clay Minerals in the Core IV. CONCLUSION 6 6 APPENDIX I. PREPARATION OF ORIENTED, FLAT-LAYERED SPECI MENS 6 8
II. PREPARATION OF RANDOM POWDER PACKS SPECIMENS . 7 0
III. IDENTIFICATION OF CLAY MINERALS WITH ORIENTED,
FLAT-LAYER SPECIMEN 71
IV. CALCULATION OF CLAY PERCENTAGE 73
BIBLIOGRAPHY 74 iv
LIST OF TABLES
Table Page
1. Observed Stratigraphic Units in the Core .... 4
2. Stratigraphy of the Core 5
3. Sedimentary Structures in the Core 12
4. Distribution of Clay Mineral Percentages According to the Lithology and Depth 30
5. Illite Sharpness Ratio According to the Formations 32
6. Illite Crystallinity Index Distributions According to the Formations 3 2
7. Distribution of 2M Percentage 35
8. Observed Thin Section Samples in the Core ... 39
9. Grain Size and Degree of Roundness of Quartz Grains in the Observed Thin Sections 40
10. Data Sheet for the Thin Section Description of a Sample From the Floyd Shale Formation .... 41
11. Data Sheet for the Thin Section Description of a Sample From the Chattanooga Shale Formation . 4 2
12. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation .... 43
13. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation .... 48
14. Data Sheet for the Thin Section Description of a Sample From the Sequatchie Formation ..... 50
15. Data Sheet for the Thin Section Description of a Sample From Sequatchie Formation 51
16. Data Sheet for the Thin Section Description of a Sample From the Carters Formation 53
17. Data Sheet for the Thin Section Description of a Sample From the Lebanon Limestone Formation . 55 V
Table Page
18. Data Sheet for the Thin Section Description of a Sample From the Ridley Formation 59
19. Data Sheet for the Thin Section Description of a Sample From the Pond Spring Formation .... 62
20. Data Sheet for the Thin Section Description of a Sample From the Knox Group 6 3
21. Data Sheet for the Thin Section Description of a Sample From the Knox Group 65 LIST OF PLATES
Plate Page
1. Lenticular Bedding with Connected Thick Lenses and Lenticular Bedding with Isolated Lenses in the Floyd Shale Formation ...... 13
2. Wavy Bedding in the Floyd Shale Formation ... 14
3. Load Cast in the Chattanooga Shale Formation . 16
4. Interlayered Shale and Fine-Grained Sandstone
Beds in the Chattanooga Shale Formation .... 17
5. Graded Bedding in the Red Mountain Formation . 18
6. Graded Bedding in the Red Mountain Formation . 19
7. Graded Bedding in the Red Mountain Formation ,. 21 8. Ptygmatopic Sandstone Dikes in the Red Mountain Formation 22 9. Trace Fossils in the Red Mountain Formation . . 24
10. Interlayered Shale and Fine-Grained Sandstone Bedding in the Sequatchie Formation 25
11. Stylolites in the Limestone Bed of Knox Group . 26
12. Interlayered Calcareous Mudstone Bedding and Calcisiltite Bedding in the Ridley Formation . 27
13. Sedimentary Boudinage in the Pond Spring Forma tion 28 vii
LIST OF ILLUSTRATIONS
Figure Page
1. Index Map of Georgia Showing Location of Floyd County and of the Studied Core 2
2. Lithologic Log of the Core 6
3. Distribution of Clay Minerals in the Sedimen tary Environment 34
4. Curve for Determination of Percent 2M Dioctahedral Mica 3 6
5. Siderite Inclusions in Quartz From Sample No. 19 44
6. Microcrystalline Quartz Grains in Limonite Cement From Sample 19 4 5
7. Secondary Quartz Overgrowths From Sample No. 23 49
8. Angular and Subangular Quartz Grains in the Silt-Shale Bed of the Sequatchie Formation . . 52
9. Quartzitic Calcarenite From Sample No. 45 . . 54
10. Bryozoon Fossil in the Lebanon Limestone From Sample No. 47 56
11. Trilobite Fossil in the Lebanon Limestone From Sample No. 47 57
12. Brachioped Fragments in the Lebanon Limestone From Sample No. 4 7 5 8
13. Dolomite Rhombs in Hemetitic Cement From Sample No. 4 8 6 0
14. Dolomite Rhombs in Hematitic Cement From Sample No. 48 61
15. Stylolite in Microcrystalline Calcite Ooze From Sample No. 51 64 viii
SUMMARY
A single core from Floyd County, Georgia, 2000 feet
long and four inches in diameter, was analyzed for its clay
minerals and sedimentary petrography. The column of rocks
represented ranges from the Knox Group through the Floyd
shale. The following results were found.
1. Illite and iron-rich chlorite were the most abundant
clay minerals, and a major amount of kaolinite was pre
sent only in a portion of the Red Mountain formation.
Illite and iron-rich chlorite were allogenetic, but
kaolinite was authigenic. 2M illite type of mica poly
morph was present throughout the core but the lMd type
was dominant.
2. Illite percentages showed little relation to depositional
environment. Iron-rich chlorite percentages remained
fairly constant throughout the core. The illite sharp
ness ratio diminished with increasing depth and was lower
in rocks from nonmarine environments than in those from
marine environments. The illite crystallinity index
remained fairly constant throughout the core.
3. Megascopic sedimentary structures from the core were
described. Lenticular bedding with connected thick lenses,
lenticular bedding with isolated lenses, wavy bedding,
graded bedding, trace fossils, sedimentary boudinage ix
sandstone dikes, and load casts were found.
Petrographic studies of the core indicated that the Floyd shale was deposited as a fine-grained arqillaceous mud. hematite in the Red Mountain formation was postdeposi- tional. A high degree of pressure solution was observed in the Red Mountain formation. Siderite cement was pre sent in the Red Mountain formation, and dolomite cement was present in the Sequatchie formation. These carbonate cements occurred as secondary pore-filling without any replacement of grains. The Lebanon Limestone formation was fossiliferous. The Ridley formation was dolomitic.
The Pond Spring formation was intraclastic. The lime stone bed of the Knox Group was nonfossiliferous. 1
CHAPTER I
INTRODUCTION
The purpose of this study was to determine the distri bution of the various clay minerals and the sedimentary petrography of a single core, 2000 feet long and four inches in diameter, taken from Floyd County, Georgia. The Lower
Paleozoic section and sedimentary environments of Northwest
Georgia had been investigated by field observations (Butts and Gildersleeve, 1948; Milici and Smith, 1969; Chcwns, 1972).
Weaver (1958) had given the X-ray diffraction analyses of clay minerals for the solution of geological problems concerning
Upper Mississippian-Lower Pennslyvanian sediments of Central
United States. In his work, the distribution of the clay mineral suites are discussed in terms of the sedimentary environments. The method of his research was considered to be effective and therefore applied to study the sample core taken from Floyd County, Georgia (Figure 1). In addition to the X-ray analyses, seventeen thin sections of the core were observed under a petrographic microscope to obtain petro- graphic information.
Geologic Setting
The area in which the well was drilled was mapped and described by Butts and Gildersleeve (1948). Detailed investi- Miles £ Drilled Area
Figure 1. Index Map of Georgia Showing Location of Floyd County and of the Studied Core (Map is from Cressler, 1970). 3
tion have been reported by Milici and Smith (1969), Cressler
(1970), Nunan (1970), and Chowns (1972). The author used the interpretation of Milici and Smith (1969) for stratigraphy and Chowns (1972) for sedimentary environments.
With this writer's knowledge, it is impossible to determine true stratigraphic thicknesses, and relationships for the following reasons:
1. The sedimentary rocks in the core was heavily deformed.
2. One would need several more cores to make three-dimensional
correlations.
3. Some parts of the core were not available.
Description of Formations in the Core
The comparison of the lithologic well log data of the researched core with field observations of Milici and Smith
(1969), and Chowns (1972) was used to identify the stratigraphic units of the investigated core. These descriptions are seen to be in agreement with Weaver (personal communication), and are listed in Table 1 and Table 2. A lithologic log of the core is given in Figure 2.
Depositional Environments of Formations in the Core
Floyd Shale Formation
Pettijohn (1970) and Colton (1970) state that the formations of Mississippian age were formed in a deltaic environment in the Appalachian Basin, and Ferm and Ehrlich
(1967), and McLemore (1972) indicate that the Floyd shale 4
Table 1. Observed Stratigraphic Units in the Core.
Depth Formation or (feet) Group Description
38 0 to Floyd Shale Light gray, fissile (less fissile 387 than Chattanooga shale) (Cressler, 1970).
388 to Chattanooga Black, highly fissile clay or silt 400 Shale shale (Cressler, 1970).
400.9 to Red Mountain Red stained shale with interbeds of 511 siltstone and fine-grained sand stone (Chowns, 19 72) .
652 to Sequatchie Greenish gray shale (no hematite 780 staining) with interbeds of medium gray siltstone (Chowns, 1972).
1710 to Carters Mottled, medium-gray calcisiltite 1715 (Milici and Smith, 1969) .
2000 to Lebanon Lime Gray, massive, and fossiliferous 2014.1 stone limestone with mattled dark gray calcisiltite (Milici and Smith, 1969).
2014.2 to Ridley Medium-dark gray calcisiltite and 2033 dolomitic "fucoidal" limestone limestone (Milici and Smith, 1969).
2124 to Pond Spring Red caleisiltites are interbedded 2131 with mattled red calcareous mud- stone (Milici and Smith, 1969) .
2157 to Knox Group Thick-bedded, fine-grained, gray 2167 and limestone, and light gray dolomite 3270 to (Milici and Smith, 1969) . 3271 5
Table 2. Stratigraphy of the Core (After Milici and Smith, (1969) and Chowns, (1972)).
Depth* Stratigraphic Age (ft) Units Sedimentary Environment
Missis Floyd Shale sippian 380 Formation Deltaic
Devonian 400 Chattanooga Shale Terrgenous, shallow Formation euxinic sea
Silurian 500 Red Mountain Littoral to open marine Formation
Upper 600 Sequatchie Supratidal flat Ordovician Formation
Middle 1710 Carters Formation Intertidal Ordovician
Middle 2000 Lebanon Limestone Shallow marine carbonate Ordovician Formation
Middle 2014 Ridley Formation Terrigenous alluvial Ordovician
Middle 2130 Pond Spring Shallow marine carbonate Ordovician Formation
Lower 327 0 Knox Group Shallow marine and tidal Ordovician flat carbonate
*Depth is not scaled. 6
Depth Formation Lithology (ft) 380' Flovd Shale
Chattanooga Shale 400.
No Sample 484-1
Red Mountain
Sequatchie
750-E
Figure 2. Lithologic Log of the Core. 7
Depth Formation (ft) Lithology
Sequatchie
78
Wo Sample 171CB Carters Lebanon I , .L Limestone 201$
Ridley 203
Ho Sample*
Pond Spring 2129'
.i" i Knox Group 216 2
No Sample
327H 49O0f Fo Sample
*No sample was collected over these inter vals; the depth scale is therefore tele scoped to conserve space.
Scale - 1 mm = 1 ft
LEGEND
'Shale JUU{ Dolomite
S iltstone Calcisiltite
Sandstone Calcareous ^ Mudstone Limestone Dolomitic Limestone Figure 2. Continued 8
formations were formed in a deltaic environment in the
northern Alabama and in Northwest Georgia. The lenticular
bedding (see page 13) is found in the Floyd shale formation.
These lenticular beds are characteristic of deltaic environ
ment Kukal (197L), and Reineck and Singh (1975).
Chattanooga Shale Formation
Chowns (19 72) believes that the Chattanooga shale was
formed in a terrigenous, shallow, and euxinic sea environment.
Red Mountain Formation
The Red Mountain formation was believed to be deposited
in littoral to open-marine environments (Chowns, 1972).
Sequatchie Formation
The core section was equivalent to Chowns' Gray
Sequatchie Facies of the Sequatchie formation. He explained
that the Gray Sequatchie Facies was deposited in a supratidal environment.
Carters Formation
Milici and Smith (1969) concluded that the Carters
formation occurred in the intertidal environment.
Lebanon Limestone Formation
The Lebanon Limestone is equivalent to Allen and
Lester's off shore environment (Allen and Lester, 1957,
Zone-2). Bryozoan fossils (see page 56), and alternation of limestone and calcisiltite suggest that the Lebanon limestone was formed in the subtidal part of a shallow marine carbonate environment (Kukal, 1971). 9
Ridley Formation
Allen and Lester (1957), and Milici and Smith (1969)
concluded that the Ridley formation was deposited in the near-
shore environment. Chowns (19 72) concluded that the Ridley
formation was formed in a terrigenous alluvial environment.
Pond Spring Formation
There was no previous suggestion as the depositional
environment of the Pond Spring formation. However, petro-
graphic studies (see page 62) suggest that the investigated
part of the Pond Spring formation was deposited in a shallow-
marine carbonate environment or winnowed carbonate sand
environment (Willis and Tyrrell, 1969).
Knox Group
Pettijohn (1970) states that the Knox carbonate sedi ments were formed in a tidal flat and supratidal environments
in the central and western part of Appalachian Basin during
Early Paleozoic time. The portion of the Knox Group that was present in the core suggests the rocks were probably formed
in a shallow-marine and tidal flat carbonate environments as
Chowns (19 72) claimed. 10
CHAPTER II
METHODS AND PROCEDURE
Types of Analyses
X-ray powder diffractometry was the principal tool for
the clay mineralogic studies. Oriented samples (see Appendix
I) used were for clay analyses of the less than 2 micron grain
size, and the following measurements were made: a) the types of clay minerals, b) volume percentages of clay minerals, and c) sharpness ratios and crystallinity indices of clay minerals.
The polymarphs of illite were identified using random powder packs (see Appendix II). Laboratory equipment was provided by the School of Geophysical Sciences.
The oriented samples were run on a Philips-Norelco
X-ray diffractometer, using CuKaNi filtered radiation at 2 settings of 10 cps., multiplier 5, and ratemeter 4, with kV45 and mA20. The scanning speeds used were 1° 20 per minute with a chart speed of 15 inches per hour. Methods, assump tions, and conventions for the identification of the clay minerals with oriented specimens and calculation of clay percentages are given in Appendix III and in Appendix IV. 11
CHAPTER III
RESULTS AND DISCUSSION
Sedimentary Structures
A sedimentary structure is a structure in a sedimen
tary rock and is formed either contemparaneously with deposi
tion or shortly after, but before consolidation at deposits.
The sedimentary structures are indicators of the: a) type
of depositional environment (Bouma, 1962), b) bathymetric
zonation of the depositional environment (Seilacher, 1964),
c) the direction of current movement (Pettijohn, 1964), d)
the velocity of fluids in the depositional environment (Allen,
1963), and e) the bottoms and tops of sedimentary layers
(Shrock, 1948).
The sedimentary structures are identified and described
using the terminologies of Pettijohn and Potter (1964),
Conybeare and Crook (1968), and Reineck and Singh (1975).
Identified sedimentary structures are listed in Table 3.
Distribution of Sedimentary Structures in the Formations
Floyd Shale Formation
The Floyd Shale formation contains lenticular bedding with conn-cted thick lenses (Plate 1), lenticular bedding with
isolated lenses (Plate 1), and wavy bedding (Plate 2). These .12
Table 3. Sedimentary Structures in the Core.
Sample Depth No. (ft) Formation or Group Sedimentary Structures
Tl 384 Floyd Shale Wavy bedding T2 386 Floyd Shale Lenticular bedding with connected thick lenses and lenticular bedding with connected isolated lenses. T4 397 Chattanooga Shale Interlayered bedding with fine-grained sand stone and shale T5 398 Chattanooga Shale Load casts T6 407 Red Mountain Graded bedding T7 411 Red Mountain Sandstone dikes T8 421 Red Mountain Graded bedding T9 422 Red Mountain Graded Bedding T10 491 Red Mountain Trace fossils Til 713 Sequatchie Interlayered bedding with fine-grained sand stone and shale T12 2019 Ridley Interlayered bedding with calcisiltite and calcareous mudstone T13 2130 Pond Spring Sedimentary boudinage T14 2167 Knox Group Stylolites 13
Plate 1. Lenticular Bedding with Connected Thick Lenses and Lenticular Bedding with Isolated Lenses in the Floyd Shale Formation. 14
Plate 2. Wavy Bedding in the Floyd Shale Formation. 15
beddings are composed of light-colored fine-grained sand
stone lenses and dark-colored shale layers with concordant
contacts.
Chattanooga Shale Formation
The Chattanooga Shale formation contains load casts and interlayered shale and fine-grained sandstone beds. The
load casts are composed of shale and fine-grained sandstone with a discordant botryoidal contact (Plate 3). The inter
layered shale and fine-grained sandstone beds have concordant planar contacts (Plate 4).
Red Mountain Formation
Graded Beddings. Sample T6 is 2 cm thick and at the base contains well-sorted and well-rounded quartz grains that are 0.4 to 0.5 mm in diameter. Well-sorted and well-rounded quartz grains that are 0.1 to 0.2 mm in diameter occur in the upper portion of the bed. However, quartz grains that are 0.1 to 0.2 mm in diameter as matrix and shale pellets are present in the bottom section (Plate 5). Sample T8 is composed of
4 thin units; a) 0.5 cm thick and contains well-sorted and well-rounded quartz grains which are 0.1 to 0.2 mm in diameter, b) 1 cm thick and contains well-sorted and well-rounded quartz grains which are 0.5 to 0.7 mm in diameter. Quartz grains which are 0.1 to 0.2 mm in diameter are present as matrix, c) 1 cm thick and includes well-sorted and well-rounded quartz grains that are 0.4 to 0.5 mm in diameter, d) 0.5 cm thick, the same as the unit a (Plate 6). Sample T9 is composed of Plate 3. Load Cast in the Chattanooga Shale Formation. 17
Plate 4. Interlayered Shale and Fine-Grained Sandstone Beds in the Chattanooga Shale Formation. Plate 5. Graded Bedding in the Red Mountain Formation. 19
Plate 6. Graded Bedding in the Red Mountain Formation. 20
six thin units; a) 2 cm thick and contains well-sorted and
well-rounded quartz grains which are 0.1 to 0.2 mm in diameter,
b) 2.5 cm thick and includes well-rounded and well-sorted
quartz grains that are 0.3 to 0.5 mm in diameter, c) 2 cm
thick and contains well-sorted and well-rounded quartz grains
that are 0.5 to 0.6 mm in diameter, d) 4 cm thick and contains
well-sorted and well-rounded quartz grains that are 0.7 to
0.8 mm in diameter, e) 1 cm thick and the same as the unit
d (Plate 7). Both sample T6, sample T8, and sample T9 are
well-induroted and silica cement. The origin of the graded
bedding is turbidity currents (Bouma, 1962 and Middleton,
1967).
Ptygmatopic Sandstone Dikes. Sandstone dikes have the
irregular ptygmatic shape described by Dzulynski and Walton
(1965). The word ptygma is a metamorphic and igeneous term.
The "tope" suffixe is preferred in the sedimentary terminology.
"Tope" is from Greek (topos) which means "place, region, or position" (Friedman, 1965). Thus ptygmatic type sandstone dikes are called ptygmatopic type sandstone dikes. The ptygmatopic sandstone dikes are injected downward into the shale.
The dikes contain well-sorted and well-rounded quartz grains
(0.1 to 0.4 mm in diameter). The dikes are 0.5 to 4 cm long, contain silica cement and are well-induroted (Plate 8).
Biogenic Structures. Sturctures produced by trace fossils are 3 to 0.5 cm long and 0.5 to 1 cm in width. The width increases from top to bottom. The trace fossils are Plate 7. Graded Bedding in the Red Mountain Formation. 22
Plate 3. Ptygmatopic Sandstone Dikes in the Red Mountain Formation. 23
similar to vertical tubes and identified as the skolithos
type of Selley (1976) (Plate 9).
Sequatchie Formation
The Sequatchie formation contains interlayered shale
and fine-grained sandstone layers (Plate 10).
Knox Group
The limestone beds of the Knox Group contains stylolites.
Sutured and sharp peak type stylolites (Park and Schot, 1968) are observed (Plate 11). The stylolite seams contain
pyrrhotite (Fe^ 7S), a mineral which was identified by X-ray diffraction.
Other Formations
The Carters, Lebanon Limestone, Ridley, and Pond Spring formations contain interlayered calcareous mudstone and calcisiltite beds range from 2 to 4.5 cm in thickness. Plate
12 shows interlayered calcareous mudstone and calcisiltite bedding of the Ridley formation. Also, the Pond Spring for mation includes sedimentary boudinage (Plate 13) .
Mottled Matter in Formations
The Carters, Lebanon Limestone, and Pond Spring forma tions contain mottled matter which is composed of calcite, dolomite, ankerite, and cristobalite, as determined by X-ray diffraction analyses. The calcite (100) peak ranges from
3.01 A° to 3.03 A° and dolomite (100) peak ranges from 2.88 A0 to 2.90 A°. These -d-spacing valves indicate a variation in composition of the calcite and dolomite. The data suggests 24
Plate 9. Trace Fossils in the Red Mountain Formation. 25
Plate 10. Interlayered Shale and Fine-Grained Sandstone Bed ding in the Sequatchie Formation. 26
Plate 11. Stylolites in the Limestone Bed of Knox Group. Plate 12. Interlayered Calcareous Mudstone Bedding and Calcisiltite Bedding in the Ridley Formation. 28
Plate 13. Sedimentary Boudinage in the Pond Spring Formation. 29
that the calcite has excess Mg and that the dolomite has
excess ca.
Distribution of Clay Minerals in the Core
The results of the X-ray diffraction analyses of clay
minerals are given in Table 4. The illite content shows a
general decrease with depth and no constant relation to environ
ment. The chlorite is inversely related to the illite con
tent (Figure 3). Kaolinite appears only in a portion (74
feet) of the Red Mountain formation. No clay minerals were
recovered from the Knox Group carbonate rocks. It is likely
that not enough carbonate was dissolved.
Crystallinity Indices and Sharpness Ratio
Weaver (1960) defined the sharpness ratio as the ratio of the intensity of the (001) illite peak at 10 A° to the intensity of the (001) illite peak at 10.5 A°. This sharp ness ratio shows the relative degree of metamorphism to which
illite was exposed. Kubler (1964) defined the crystallinity index as the (001) illite peak width at mid-height. This term of crystallinity is in current usage in clay mineralogy.
Lydka (197 3) described a crystallinity index which consisted of measuring the (001) illite peak height at 10 A° which is divided by the width of mid-height of the peak.
The sharpness ratio and the crystallinity index of
Kubler are calculated for illite in this study (Tables 5 and
6). The illite sharpness ratio decreases with increasing depth and the illite sharpness ratio is lower in rocks from Table 4. Distribution of Clay Mineral Percentages According to the Lithology and Depth.
Sample Depth Clay Mineral Percentages Number (ft) Lithology Stratigraphic Unit Illite Chlorite Kaolinite
SI 380 Shale Floyd Shale 84 16 — S5 385 Shale Floyd Shale 84 16 — S7 387 Shale Floyd Shale 84 16 S8 389 Siltsonte Floyd Shale 88 12 — S9 395 Shale Chattanooga Shale 82 18 — Sll 396 Shale Chattanooga Shale 81 19 -—- S13 397 Shale Chattanooga Shale 86 14 — S15 407 Fine grained ss. Red Mountain 86 14 — S16 409 Fine grained ss. Red Mountain 89 11 — S21 412 Fine grained ss. Red Mountain 86 14 — S22 416 Sandstone Red Mountain 90 10 S23 421 Sandstone Red Mountain 92 C O S24 484 Sandstone Red Mountain 80 20 S25 489 Sandstone Red Mountain 85 15 S26 494 Sandstone Red Mountain 87 13 S27 510 Sandstone Red Mountain 83 17 — S28 512 Sandstone Red Mountain 81 19 — S29 652 Shale Sequatchie 77 23 S30 662 Fine grained ss. Sequatchie 77 23 — S31 665 Fine grained ss. Sequatchie 76 24 — S32 666 Siltsone Sequatchie 8 0 20 S33 675 Shale Sequatchie 79 21 — S34 680 Shale Sequatchie 75 25 — S35 688 Shale Sequatchie 75 25 — S36 689 Shale Sequatchie 75 25 — S37 710 Fine grained ss. Sequatchie 73 27 —--
Continued Table 4. Continued
Sample Depth Clay Mineral Percentages Number (ft) Lithology Stratigraphic Unit Illite Chlorite Kaolinite
S38 714 Shale Sequatchie 76 24 — S39 724 Shale Sequatchie 77 23 -- S40 730 Fine grained ss. Sequatchie 76 24 -- S41 735 Shale Sequatchie 77 23 -- S42 742 Fine grained ss. Sequatchie 73 27 -- S43 753 Fine grained ss. Sequatchie 79 21 -- S44 765 Shale Sequatchie 73 27 -- S45 770 Shale Sequatchie 79 21 -- S46 776 Shale Sequatchie 76 24 S47 780 Shale Sequatchie 76 24 S48 1710 Cal mudstone Carters 94 6 — S49 2008 Limestone Lebanon 75 25 — S50 2014 Limestone Lebanon 75 25 — S51 2021 Cal mudstone Ridley 80 20 S52 2033 Cal mudstone Ridley 79 21 — S53 2123 Cal mudstone Pond Spring 79 21 —-- S54 2162 Limestone Knox — — — Table 5. Illite Sharpness Ratio Distributions According to the Formations.
Formation Variation Mean S. Deviation N
Floyd Shale 0.. 04 3,.0 7 0,.2 3 4 Chattanooga Shale 0.,1 6 3., 10 0,.4 9 3 Red Mountain 0.,2 2 3..1 1 0.. 50 10 Sequatchie 0.,1 1 3..5 2 0..8 2 19 Carters 0 3 ,1. 8 -- 1 Lebanon Limestone 0., 06 2. .25 0.,3 5 2 Ridley 0.,2 2 2 ..1 8 0., 67 2 Pond Spring 0 1., 6 -- 1
Table 6. Illite Crystallinity Index Distributions According to the Formations.
Formation Variation Mean S. Deviation N
Floyd Shale 0., 68 3,.7 5 0,. 9 4 Chattanooga Shale 0.,8 8 3..6 0 1,.1 5 3 Red Mountain 0..1 2 3,,4 3 0 .3, 6 10 Sequatchie 0., 28 3., 53 0 ., 54 19 Carters 0 4 -- 1 Lebanon Limestone 0.,2 0 3.,4 5 0.,6 3 2 Ridley 0., 01 3 ,4, 0 0.,1 4 2 Pond Spring 0 4 - — 1 3 3
a nonmarine environment than in those from a marine environ
ment. This lower sharpness ratio in a nonmarine environment
can be explained by assuming that there are some authigenic
illites in the marine environment, especially in the carbonate
rich rocks. The illite crystallity index (Kubler, 1964)
remains fairly constant throughout the core (Figure 3), but
is inversely related to the sharpness ratio. Both sharpness
ratio and crystallinity index (Kubler, 1964) indicate that
the illite is relatively well-crystallized.
Polymorphs of Mica
Yoder and Eugster (1955) established the relationships
between mica polymorphs and their stabilities using synthetic
and natural material. They concluded "lMd transforms to 1M
at lower temperature (<200C°-350C°) , 1M transforms to 2M at
higher temperature (>200C°-350C°) ." There is another mica
polymorph, 3T, but 3T mica is relatively rare (Weaver and
Pollard, 1973). Dunayer De Segonzac (1968) noted that for
illite polymorphs, "lMd is not stable and shifts to stable
form either as 1M or 2M. 1M is less stable than 2M which is
the most stable illite polymorph."
The 2M percentage of illite for my samples was calcu
lated (see Table 7) by the method described by Maxwell and
Howell (1967). Figure 4 shows the nomogram used in this technique; it corresponds to their Figure 2. The 2.80 A0 intensity corresponds to the 2M (116) illite reflection.
The 2.58 A° intensity corresponds to the 2M (13D, (202) (116) 34
0) u
wCu 0) > •••• 1H • 0> +J to c & 4-). c 0 » as ra crt u 0 0 M03
to 1 rd >u
•p W Ph 1) 0) -C -p H > 0
-p 0 0) rH 4J rH 0 0 Figure 3. Distribution of Clay Minerals in the Sedimentary Environment. Table 7. Distribution of 2M Percentage. Sample 12.80 % 2M in Number Formation 12.58 Total Illite SI Floyd Shale 0.08 40 S7 Floyd Shale 0.06 2 5 S10 Floyd Shale 0.06 25 Sll Chattanooga Shale 0 0 S15 Red Mountain 0.05 20 S24 Red Mountain 0.07 30 S36 Sequatchie 0.14 57. 5 S44 Sequatchie 0.09 37. 5 S48 Carters 0.10 40 S50 Lebanon 0.09 37. 5 S52 Ridley 0.07 30 S53 Pond Spring 0.06 25 0.30 I 2.80 A PEAK / I 2.58 A PEAK Figure 4. Curve for Determination of Percent 2M Dioctahedral Mica. (Maxwell and Hower, 1967) 37 1M (131), and (130) illite reflections (Maxwell and Howell, 19 67). The investigated formations generally have less than 40 percent 2M illite and the remaining illite is the lMd variety, assuming these are the only polymorph present. Origin of Illite, Chlorite, and Kaolinite Some of illite is a fine-grained muscouite derived by physical weathering of metamorphic rock (Weaver, 1959), but much is formed by the diagenetic alteration of montmarillonite or mixed-layer illite-montmorillonite. Velde and Howell (1963) noted that many authors assumed that structurally different micas were of different origins. In any event, in the literature many recent sediment studies show illite is of detrital origin. Illite is stable in the alkaline environment and is unstable in the acidic environment (Millot, 1970 and Blat, et. al., 1972). Weaver (1958) pointed out that illite is stable in a marine environment and weathered illite is able to absorb several percentages of ^0 from seawater and contract to 10 A°. In the researhced core sample, illite is probably derived by erosion of the illite-rich greenschist facies and other low-grade rocks of the "Piedmont." Weaver and Pollard (1973) concluded that most chlorite in shales is of detrital origin, and is directly derived from low-grade metamorphic rocks. The chlorite was probably derived from low-grade metamorphic rocks, as was the illite. Duonyer De Segonzac (1968) indicated that kaolinite is 38 stable in the acidic environment. Weaver and Pollard (1973), explained that kaolinite starts to decompose at about 150 C° during progressive diagenesis. A small portion (74 feet) of the Red Mountain formation contains kaolinite (13%). Petro- graphic observations of pressure-solution between quartz grains (see Table 13) indicated that kaolinite probably formed during the diagenetic alteration of the rock. Sedimentary Petrography Thin Sections Seventeen representative thin sections from selected depths (Table 8) in the core were observed; twelve were described and classified using the terminology of Folk (1962, 1974). Grains, matrix, and cement were identified using the definition of Krynine (1943). Thin sections were cut perpen dicular to the bedding. Composition of twelve of the thin sections were determined by point counting at least 4 00 points per slide. The data sheets for twelve of the thin sections are given in Table 10 through 21. The other five thin sec tions were observed, but not fully described. Grain size and degree of roundness of quartz grains are listed in Table 9. 39 Table 8. Observed Thin Section Samples in the Core. Slide Depth No. (ft) Formation 5 384 Floyd Shale 14 389 Chattanooga Shale 19 413 Red Mountain 22 416 Red Mountain 23 471 Red Mountain 24 484 Red Mountain 30 662 Sequatchie 33 665 Sequatchie VI 688 Sequatchie 45 1710 Carters 47 2008 Lebanon Limestone 48 2014 Ridley 49 2124 Pond Spring 50 2126 Pond Spring 51 2157 Knox Group 55 3271 Knox Group 5 6 3271 Knox Group Table 9. Grain Size and Degree of Roundness of Quartz Grains in the Observed Thin Sections. Slide No. Formation Grain Size, mm Roundness 5 Floyd Shale 0. 02 to 0. 05 Subangular to subrounded 14 Chattanooga Shale 0. 04 to 0. 06 Subangular to subrounded 19 Red Mountain 0. 09 to 0. 2 Subrounded to rounded 22 Red Mountain 0. 03 to 0. 05 Rounded to well-rounded 23 Red Mountain 0. 25 to 0. 30 Well-rounded 24 Red Mountain 0. 07 to 0, ^8 Rounded to well-rounded 30 Sequatchie 0. 02 to 0. 03 Subangular to subrounded 33 Sequatchie 0. 02 to 0. 04 Subangular to subrounded 37 Sequatchie 0. 02 to 0 .0 4 Subangular to subrounded 45 Earters 0. 07 to 0. 13 Subangular to subrounded 49 Pond Spring 0. 07 to 0. 09 Subrounded to rounded 50 Pond Spring 0. 05 to 0. 09 Subrounded to rounded 41 Table 10. Data Sheet for the Thin Section Description of a Sample From the Floyd Shale Formation. Slide No. 5 Depth 384 (feet) Rock Name - Clay-shale Comments - Most quartz grains include rutile needles and a few vacvoles. All quartz grains have slightly undulatory extinc tion clay minerals"'" (Illite and chlorite are present as flakes.) The flakes of clay minerals are tightly packed and lie parallel to the bedding. Composition Percent A. Grains Quartz 11 B. Matrix Clay Minerals 87 C. Accessary minerals Ferruginous Minerals 2 D. Cement3 Total 100 Clay minerals which are illite (84%) and chlorite (16%) are ^identified by X-ray diffraction. ^Hematite is common, but magnetite is also rarely present. Cement is made up of clay minerals, which cannot be dif ferentiated . 42 Table 11. Data Sheet for the Thin Section Description of a Sample From the Chattanooga Shale Formation. Slide No. 14 Depth 389 (feet) Rock Name - Quartzitic medium-crystalline dolomite. Comments - Most quartz grains are embayed by dolomite. The matrix is medium-crystalline intergranular dolomite which is chemically precipitated as interstitial cement in pore spaces Euhedral, medium-to coarsely-crystalline dolomite occurs in the dolomite cement. There is no evidence that the dolomite in the rock is detrital. Composition Percent A. Grains Quartz 40 B. Matrix"1" C. Cement Dolomite 57 D. Accessory Minerals Ferruginous Minerals 3 Total 100 "^"Matrix is dolomite, which is chemically precipitated, so the matrix composition is included in the cement composition. 43 Table 12. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation. Slide No. 19 Depth 413 (feet) Rock Name - Siderite-cemented quartzarenite Comments - Most quartz grains are free of inclusion, but some of them have inclusions that are microlites, vacuoles, or side- rite (see Figure 5). In general, all quartz grains are characterized by strongly to slightly undulose extinction. Seventy percent of the quartz grains have concave-convex con tact, but thirty percent of the quartz grains are "luster- mottled" in siderite cement. Fine to very fine silt-sized quartz grains are concentrated in a small area (1 mm length and 0.5 mm in width) , each of which is cemented by limonite, probably derived from oxidation of siderite cement (see Figure 6). The rock, therefore, is characterized by limonite spots; it corresponds to the "spotted" sandstone of Pettijohn, 1975. The matrix is an assemblage of clay minerals. Hematite is common opaque minerals which coat and penetrate only a few quartz grains as interstitial cement. The absence of hematite coating at many quartz grains and concave-convex quartz contact indicate that the hematite is postdepositional rather than predepositional and syndepositional. The distinction between primary and secondary siderite is difficult to make. However, "luster-mottled" quartz grains and siderite inclusions in quartz grains indicate that an original calcite cement was precipitated as interstitial cement in pore spaces. Calcite was then replaced by siderite probably by reaction with iron- 4 4 Figure 5. Siderite Inclusions in Quartz from Sample No. 19 Crossed Nicols. 0.1 cm Figure 6. Microcrystalline Quartz Grains in Limonite Cement from Sample 19 Crossed Nicols. 46 Table 12. Continued rich solutions during late diagenesis (Carozzi, 1972). Composition Percent A. Grains Quartz 33 Rock Fragments T1 Feldspar 2 B. Matrix Clay Minerals T1 C. Cement Siderite 10 D. Accessory Minerals Ferruginous Minerals 5 Total 100 T = trace amount Includes hematite and limonite Slide Wo. 22 Depth 416 (feet) Rock Name - Siderite-cemented quartzarenite Comments - The slide is similar to Slide No. 19 (see page 43 ). Siderite cement percentages are increased, and limonite spots are not present. Composition - Quartz (65%) , siderite (33%) , and accessory minerals (2%). 47 Table 12. Continued Slide No. 24 Depth 434 (feet) Rock Name - Siderite-cemented quartzarenite Comments - The slide is similar to Slide No. 19 (see page 43) Siderite cement percentages are increased, and limonite spots are not present. 48 Table 13. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation. Slide No. 23 Depth 471 (feet) Rock Name - Highly siliceous quartzarenite Comments - This sample is almost 100 percent quartz. Both sutured and concave-convex contacts are present. Quartz grains are cemented by secondary quartz overgrowths (see Figure 7) which were formed by pressure-solution as indicated by concave-convex and sutured contacts (Taylor, 1950 and Pettijohn, et. al., 1972). A trace of siderite cement is present. Some of the siderite cement replaced quartz at the edge of overgrowths; this replacement apparently happened later than the overgrowths. 49 Figure 7. Secondary Quartz Overgrowths from Sample No. 23 Crossed Nicols. 50 Table 14. Data Sheet for the Thin Section Description of a Sample from the Sequatchie Formation. Slide No. 30 Depth 662 (feet) Rock Name - Clay-shale Comments - Quartz grains are embayed by dolomite cement. Clay minerals"1" (illite and chlorite) are tightly packed and lie parallel to the bedding. Composition Percent A. Grains Quartz 7 B. Matrix Clay minerals 90 C. Cement Dolomite 3 Total 100 "'"Clay minerals which are illite (77%) and chlorite (23%) are identified by X-ray diffraction. 51 Table 15. Data Sheet for the Thin Section Description of a Sample from Sequatchie Formation. Slide No. 3 3 Depth 665 (feet) Rock Name - Silt-shale Comments - Clay minerals^ (illite and chlorite) are loosely packed and randomly oriented. Composition Percent A. Grains Quartz 60 B. Matrix Clay minerals 35 C. Cement Dolomite 5 Total 100 ^Clay minerals which are illite (76%) and chlorite (24%) are identified by X-ray diffraction. Slide No. 37 Depth 688 (feet) Rock Name - Silt-shale (see Figure 8) Comments - Similar to Slide No. 33, but clay mineral percen tages are smaller. Composition - Quartz (64%), clay minerals (25%), and dolomite (11%) . 52 Figure 8. Angular and Subangular Quartz Grains in the Silt- Shale Bed of the Sequatchie Formation from Sample No. 37 Crossed Nicols. 53 Table 16. Data Sheet for the Thin Section Description of a Sample from the Carters Formation. Slide No. 45 Depth 1710 (feet) Rock Name - Quartzitic calcarenite {see Figure 9). Comments - Some of the quartz grains are coated by hematite. Very fine to fine calcite is moderately sorted and subrounded. Very fine to fine calcite grains suggest that they are pro bably penecontemporaneous carbonate sediment grains which were deposited as pore-filling cement. Composition Percent A. Grains Quartz 57 Calcite1 40 B. Accessory minerals 2 Ferruginous minerals 3 Total 100 1 Calcite is as pore-filling cement. 2 Hematite 54 55 Table 17. Data Sheet for the Thin Section Description of a Sample From the Lebanon Limestone Formation. Slide No. 47 Depth 2008 (feet) Rock Name - Biopelmicruditic limestone Comments - This sample contains pellets, fossils, and fossil fragments. The pellets are aggregates of microcrystalline calcite, rounded, well-sorted, and loosely packed. The pellet grain sizes range from 0.06 to 0.09 mm. The pellets are embedded in a microcrystalline calcite ooze (micrite) matrix. pryozoans and trilobites are common fossils in this formation. Stictoporella Ulrich1 type bryozoans (see Figure 10) and 2 Proetus steminger (see Figure 11) type trilobite fossil are observed. Bryozoan and brachiopod fragments are the most common fossil fragments (see Figure 12). Composition Percent A. Grain Pellet 16 Fossils 4 Fossil fragments 11 B. Matrix Micrite 69 Total 100 Identified from Moore, R. C, et. al. , (1952). Identified from Moore, R. C., et. al., (1952). 56 Figure 10. Bryozoan Fossil in the Lebanon Limestone from Sample No. 47 Crossed Nicols. 57 Figure 11. Trilobite Fossil in the Lebanon Limestone from Sample No. 47 Crossed Nicols. 0.1 cm Figure 12. Brachiopod Fragments in the Lebanon Limestone from Sample No. 47 Crossed Nicols. 59 Table 18. Data Sheet for the Thin Section Description of a Sample from the Ridley Formation. Slide No. 48 Depth 2014 (feet) 1 2 Rock Name - Dolomitic limestone ' Comments - Microcrystalline calcite ooze (micrite) is coated by hematitic cement. Very fine crystalline euhedral dolomite rhombs are concentrated in hematitic cement (idiotopic dolomite of Friedman, 1965). Composition Percent A. Grains Dolomite 27 B. Matrix Micrite 50 3 23 C. Cement 100 Total ^See Figure 13 ^See Figure 14 Hematite 60 Figure 13. Dolomite Rhombs in Hematitic Cement from Sample No. 48 Crossed Nicols. 61 62 Table 19. Data Sheet for the Thin Section Description of a Sample From the Pond Spring Formation Slide No. 49 Depth 2124 (feet) Rock Name - Intrasparruditic limestone Comments - This sample is composed of intraclats, sparry cal cite, and quartz. The intraclasts are angular and poorly sorted. Their grain size ranges from 1.5 mm to 2.5 mm. Most of them have a contorted internal structure, but some of.them are featureless aggregates. All intraclasts are embedded in sparry calcite cement. The intraclasts are fragments of penecontemporaneous carbonate origin. Quartz grains are cemented by sparry calcite cement. Composition - Intraclast (72%) , sparry calcite (18%) , and quartz (10%) Slide No. 50 Depth 2126 (feet) Rock Name - Intrasparruditic limestone Comments - This sample is similar to Slide No. 49. 63 Table 20. Data Sheet for the Thin Section Description of a Sample From the Knox Group. Slide No. 51 Depth 2157 (feet) Rock Name - Dismicritic limestone Comments - This sample is composed totally of microcrystalline calcite ooze (micrite). Some of the micrite (10%) has been replaced by dismicrite. There are microscopic stylolites (see Figure 15) which are filled by dismicrite. 64 0.1 cm Figure 15. Stylolite in Microcrystalline Calcite Ooze from Sample No. 51 Crossed Nicols. Table 21. Data Sheet for the Thin Section Description of a Sample From the Knox Group. Slide No. 55 Depth 3271 (feet) Rock Name - Finecrystalline dolomite Comments - This sample is a pure dolomite composed of very finecrystalline subhedral and anhedral dolomite crystals which are strongly interlocked in dolomite cement. The texture (of the very finecrystalline subhedral and anhedral dolomite crystals indicate that dolomites are probably accumulated directly on the sea floor as a dolomite ooze (dolomicrites), and were concentrated as authigenic dolomite (Carozzi, 1972 and Folk, 1974). Slide No. 56 Depth 3271 (feet) Rock Name - Finecrystalline dolomite Comments - This sample came from near Slide No. 55, but was cut parallel to bedding. The sample composition is the same as Slide No. 55. 6 6 CHAPTER IV CONCLUSIONS The clay minerals in the core, primary illite and chlorite are direct indicators of source rock and to a lesser extent indicates of sedimentary environment. The illite and chlorite are allogenetic and probably derived by erosion of the illite-rich greenschist facies and other low-grade rocks of the "Piedmont." The clay suite shows no constant relation to sedimentary environment. The illite sharpness ratio decreased with increasing depth. The 2M illite polymorph is present throughout the core, but the lMd type is predominant, suggesting that the sediments were never deeply buried. Kaolinite is present only in a portion of the Red Mountain formation. The petrographic evidence suggested that the kaolinite is authigenic. The core contains a number of megascopic sedimentary structures; sandstone dikes, trace fossils, sedimentary boudinage, gradded bedding, wavy bedding, lenticular bedding with connected thick lenses, lenticular bedding with isolated lenses, and load casts. These sturcutres are characteristic of the various depositional environments assigned by other authors. Petrographic studies of the core indicated that the Floyd shale was deposited as a fine-grained argillaceous mud. 67 Hematite in the Red Mountain was postdepositional. Pressure solution occurred in the sandstones of the Red Mountain formation, and dolomite cement is present in the Sequatchie formation. These carbonate cements are secondary and occur as pore-filling without any replacement of grains. The Lebanon Limestone is fossiliferous. The Ridley formation is a dolomitic limestone. The Pond Spring formation is introclastic. The limestone bed of the knox Group is a non- fossiliferous micrite. 6 8 APPENDIX I PREPARATION OF ORIENTED, FLAT-LAYER SPECIMENS (From Junhavat, 1977) 1. Grind the sediment (do not crush) into very fine parti cles (powder). 2. Weigh out 4 grams of sample, then load into a 50 ml beaker. 3. Pour in 15 ml of 0.4 percent calgon. 4. Fill with distilled water to 50 ml beaker level, then stir. 5. Pour the liquid into the blender and blend it for 3 minutes, then poor it back into the 50 ml beaker. 6. Draw the liquid off the surface of the sample with an eye dropper and then drop onto a glass slide and leave it for 24 hours to dry. After 24 hours the sample is ready to be X-rayed. Notice: The above preparation is for sediment which has no calcium carbonate in it. If it has carbonates for example limestone or calcreous shale, etc., it has to be treated for carbonate first. Carbonate Treatment a. After step 2 mentioned above, pour 45 ml of 0.1 N Hcl into the 50 ml beaker. The bubbles of carbon dioxide should appear. b. Stir sample 4 or 5 times per day for 2 days. c. Place all liquid and residual sample in a centrifuge tube. d. Centrifuge it for 15 or 20 minutes until all residue settles. e. Pour out supernate, then pour distilled water into the beaker to wash out the Hcl. Transfer to the centri fuge tube. f. Shake the centrifuge tube, and centrifuge it again. g. Repeat step e. and f. 2 or 3 times. After this treatment, the sample should not have any more carbonate, so start from step 3 and finish through step 6. 7 0 APPENDIX II PREPARATION OF RANDOM POWDER PACK SPECIMENS (From Rloss, F. D., 1971) Grind the sediment into very fine particles (powder). Sieve the sample with a 2 00-mesh sieve. Transfer it into powder pack holder. The holder should not be tightly packed and its surface should be smoothed. 1 APPENDIX III IDENTIFICATION OF CLAY MINERALS WITH ORIENTED, FLAT-LAYER SPECIMEN (after Weaver, C. E., 1958 and Junhavat, S., 1977) After drying minerals on a glass slide (see Appendix I, step 6), they will have preferred orientation because of the particle shape of the clay minerals. Each clay mineral group has a specific and characteristic layer thickness. Clay minerals are identified from the basal 00& reflections which are assumed to lie parallel to the surface of the glass slide. The oriented, flat-layer specimen is run on a Philips-Norelco X-ray diffractometer, using CuKa filtered 2 radiation in Norelco unit at a setting of 10 cps., multi plier 5, and ratemeter 4 with kV45 and mA20. The scanning speeds used were 1°29 per minute with a chart speed of 15 inches per hour. When X-rays strike the clay powder, the X-ray will strike the (001) crystal face and yield the (00Z) reflections and produce on X-ray pattern on the strip chart recording. Differing incident angle (0) on differing types of clay minerals produce different (00JL) reflections. The first reflection is (001) , the second is (002) , the third is (003), and the fourth is (004) and so on. From the angle of incidence (0) for each reflection, a "d" value can be calculated by the Bragg equation: 7 2 2Sin8hk£ The (001) reflection gives the "d" value for the unit cell. The 11 d" value for (001) , so the "d" values are related as follows: (002) - 1/2 (001), (003) = 1/3 (001), (004) = 1/4 (001), and so on. Grim (1968) lists the "d" values for the following clay minerals: Kaolinite: (001) = 7.16A°, (002) = 3.57A°, (003) = 2.37A° Chlorite: (001) = 14.20A0, (002) = 7.12A°, (003) = 4.75A°, 004 = 3.56A° 73 APPENDIX IV CALCULATION OF CLAY PERCENTAGE (from Junhavat, S., 1977) After getting the X-ray pattern: 1. Identify all clay mineral peaks. 2. Draw a background curve under the clay mineral peaks. 3. Measure the area under (001) clay mineral peaks. 4. Divide the area by a correction factor. 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