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Masters Theses Student Theses and Dissertations
1978
Sedimentology of the Hannibal formation in Northeastern Missouri and Western Illinois
Michael Harry Deming
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Recommended Citation Deming, Michael Harry, "Sedimentology of the Hannibal formation in Northeastern Missouri and Western Illinois" (1978). Masters Theses. 3334. https://scholarsmine.mst.edu/masters_theses/3334
This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. SEDIMENTOLOGY OF THE HANNIBAL FORMATION IN NORTHEASTERN MISSOURI AND WESTERN ILLINOIS
BY
MICHAEL HARRY DEMING, 1952-
A THESIS
Presented to the Faculty of the Graduate School of the
UNIVERSITY OF MISSOURI-ROLLA
In Partial Fulfillment of the Requirements for the Degree
MASTER OF SCIENCE IN GEOLOGY
1978 T4 438 C . .l 172 pages Approved by
(Advisor)
. ' , I .
/ ii
ABSTRACT
The Hannibal Formation (Kinderhookian) occurring in northeastern Missouri and western Illinois is a fine grained, terrigenous, sedimentary unit which can be di vided into an upper and a lower portion, based on li thology. The upper portion consists of alternating coarse and argillaceous, fine siltstone units, while the lower portion consists of a silty mudstone with an occasional thin siltstone unit. At the extreme western margin of the formation, near where the Hannibal almost pinches out, the formation consists entirely of a silty claystone. Extending southward along the study area, the coarse siltstone units of the upper Hannibal become thinner, and eventually pinch out completely. Results obtained from petrographic study, grain-size analysis, and sedimentary properties indicate an upward-coarsening sequence in most coarse siltstone units. These units consist of predom inantly poorly sorted, angular, coarse and medium silt size particles. Sand-size particles also occur in the Hannibal, but in very minor quantities. The Hannibal contains associated trace fossils which represent Seilacher's Cruziana and Zoophycus facies, indicating tranquil, shallow water, marine conditions. x-ray analysis indicates four clay mineral assem blages. Dioctahedral illite is the most prominant clay mineral, with disordered kaolinite occurring in iii substantial quantities. Iron and magnesium-rich chlorite and vermiculite also occur in the formation, but in rel atively minor amounts. The Hannibal sediments were deposited in a restrict ed, shallow, tranquil sea from a northern source area. A low-lying drainage area, restricted marine circulation, and the possible existence of barrier islands explain the occurrence of predominantly silt and clay deposits, with only traces of sand-size particles. The study area is located in the distal portion of the formation, where the lower Hannibal mudstones represent pro-delta deposits, and the upper Hannibal siltstones represent delta front deposits. iv
ACKNOWLEDGEHENTS
I am grateful to my advisor, Dr. A. C. Spreng, Department of Geology, University of Missouri-Rolla, for his guidance, encouragement and valuable sugges tions throughout the course of this study. I would like to extend a special thanks to the other members of my committee, Dr. A. H. Harvey and Dr. S. K. Grant. Dr. Grant was very helpful in his supervision and guid ance on the use of the X-ray diffractometer. Special thanks are also extended to Dr. H. A.
Tourtelot, United States Geological Survey, and Dr. E. A. Bolter, Department of Geology, University of Missouri-Rolla, for discussing various aspects of this study; to R. G. Wagner, Missouri State Highway Commis sion, for informing the author of possible sampling locations in the study area; to D. L. Binz for develop ing the best method for preparing samples for viewing in the scanning electron microscope; and to S. D. Sea- wright, Amoco Pipeline Company, for drafting the fig- ures and illustrations in this study. The author is also greatly indebted to his mother, Kathleen L. Deming, for doing the typing of his manu- script. v TABLE OF CONTENTS
Page
AB!;~C:~...... jt]L ACKNOWLEDGE}.f!NTS ...... i v LIST OF ILLUSTRATIONS ...... ix LIST OF TABLES. • • • • • • • • • • • • • • • • • • . • • • • • • • • • • . • . • • • . xii I. INTRODUCTION...... 1 A. PURPOSE OF INVESTIGATION...... 1 B. PREVIOUS WO'RK.. • • • • • • • • • • • • • • • • . • • • • • . 2 C. LOCATION OF TYPE SECTION...... 3 D. TERMINOLOGY AND DEFINITIONS...... 3 II. STRATIGRA.PHY. • • • • • • • • • • • • • • • • • • • • • • • • • • • • 6 A. ORIGIN OF NAMES ...... 6 B. GEOLOGIC SETTING...... 7 C. DISTRIBUTION AND THICKNESS...... 10 D. STRATIGRAPHY OF AREA...... 10 E. STRATIGRAPHY OF HANNIBAL FORMATION. . . 14 F. AGE AND CORRELATION WITH OTHER FORMA.TIONS. • • • • • • • • • • • • • • • • • • • • • • • • • 19 G. PALEONTOLOGY ...... 21 III. FIELD AND LABORATORY PROCEDURES...... 26 A. INTRODUCTION...... 2 6 l' . FIELD SAMPLING ...... 2 9 C. SAMPLE PREPARATION...... 31 1. Grain Size Analysis...... 31 a. Sieve Analysis...... 33 b. Pipette Method...... 33 vi
Page c. Technique of Analysis...... 37 2. Thin-Section Analysis...... 40 3. X-ray Diffraction...... 40 4. Scanning Electron Microscope...... 41 IV. RESULTS OF ANALYSIS ...... 44 A. GRAIN SIZE ANALYSIS...... 44 1. Sieve Analysis...... 44 2. Pipette Analysis...... 45 a. His togram...... 45 b. Graphic Mean...... 47 c. Inclusive Graphic Standard Deviation ...... 47 d. Inclusive Graphic Skewness.... 53 e. Graphic Kurtosis...... 53 3. Results of Size Analysis...... 55 a. Conclusions from Size anal- ysis...... 57 B. THIN SECTION ANALYSIS AND CEt1ENTING AGENTS...... 61 C. X-RAY DIFFRACTION...... 62 1. Mineral Identification...... 62 2. Semi-Quantitative Analysis of Clay Minerals...... 65 a. Procedure...... 65 b. Results...... 67 D. ELECTRON MICROSCOPE STUDY...... 71 1. Introduction...... 71 2. Particle Morphology...... 71 vii
Page a. Form ...... 71 b. Sphericity ...... 73 c. Roundness ...... 77 d. Surface Texture ...... 77 3. Conclusions from Grain Morphology. 77
E. ]?~~()~<=()~()(;~ ••••••••••••••••••.•.••.•• 80 F. TRANSPORT DYNAMICS ...... 83
v. ENVIRO~mNT OF DEPOSITION ...... 86 A. INTRODUCTION ...... 86 B. PALEOENVIRONMENT ...... 86
c. DEPOSITION OF THE HANNIB~ SEDIMENTS .. 90
VI. S~Y ...... 94 BIBLIOGRA.PHY...... 99 VITA...... 112
APPENDICES...... 113 A. DESCRIPTION OF MEASURED STRATIGRAPHIC SECTIONS...... 113 1. Hannibal Section (A) ...... 115 2. Hannibal South Section (B) ...... 121 3. Atlas South Section (C) ...... 125 4. Hannibal North Section (D) ...... 128 5. Pleasant Hill South Section (E) ...... 132 6. Hamburg Section (F) ...... 137 7. Hannibal Core East (G) ...... 141 8. Hannibal Core West (H) ...... 143 viii
Page B. PERCENT OF SILT, CLAY, AND CARBONATE MATERIALS .... , ...... 145 C. GRAIN SIZE PARAMETER DATA ...... 152 D. QUANTITATIVE INTERPRETATION OF CLAY MINERALS • • • • • • • • • • • • • • • • . • . . • • • . • . • • . . • . • 15 7 ix
LIST OF ILLUSTRATIONS
Figures Page 1. Photograph of the Hannibal Formation at its type locality. At this location the Hannibal is over lain by the Burlington Formation and underlain by the Louisiana Limestone...... 4 2. Distribution of the Hannibal Formation modified from Laudon (1929), Workman and Gillette (1956), and Binz (1978)...... 8 3. Isopach map of the Hannibal Formation in north eastern Missouri and western Illinois, modified from Binz (1978)...... 9 4. Generalized stratigraphic column for northeastern Missouri...... 12 5. Photograph of section B showing the alternating characteristics of the coarse (more resistive beds) and argillaceous, fine siltstone units of the upper Hannibal...... 16 6. Photograph of the silty mudstones comprising the lower Hannibal Formation, exposed on the west side of "lover's leap"...... • ...... • . . . 16
7. Photograph of sample C-3b showing spec~ens of Taonurus caudagalli (whorl structure) and Scalarituba missouriensis (tubes) ....•...... 23 8. Photograph of the lower portion of a coarse silt stone unit at section B, showing hollow Scalari- tuba missouriensis tubes and low angle cross- bedding...... 24 9. Photograph of Hannibal float (sample B-200) showing several spectmens of Taonurus caudagalli. 24 10. Index map showing locations of sections, exclud- ing G and H...... 2 8 11. Frequency distribution of mean grain size for all samples analyzed. The mean values are grouped in .5MZ units. The bottom of each symbol equals the percent frequency of that rock type •...... 48 X
Figures Page 12. Frequency distribution of inclusive graphic standard deviation for all samples analyzed. The standard deviation values are grouped into Folk and Ward's (1957) verbal sorting classi fication. The bottom of each symbol equals the percent frequency of that rock type ...... 50
13. Standard de~iat~on (sorting) as a function of mean gra1.n s1.ze...... 52 14. Frequency distribution of inclusive graphic skewness for all samples analyzed. The skew ness values are grouped into Folk and Ward's (1957) verbal skewness classification. The bottom of each symbol equals the percent fre- quency of that rock type ...... 54 15. Frequency distribution of graphic kurtosis for all samples analyzed. The kurtosis values are grouped into Folk and Ward's (1957) verbal kurtosis classification. The bottom of each symbol equals the percent frequency of that rock type...... 56 16. Histograms of a typical coarse-grained silt stone unit showing the change of grain size distribution from the upper sample (B-lla) to the lower sample (B-llc) ...... 58 17. Histogram of a typical argillaceous fine- grained siltstone unit ...... 59 18. Histogram of a typical silty mudstone unit ...... 59 19. Histogram of a silty claystone from section H ... 60 20. Diagram illustrating the decrease of the average mean grain size for all coarse siltstones inter- polated across measured sections ...... 60 21. Clay mineral ratios of upper and lower Hannibal interpolated across measured sections ...... 69 22. Histograms of sphericity and roundness of 122 individual silt-size particles observed in the Hannibal Formation...... 74
23. Sphericity a~ a f~nction ?f grain-size for 119 individual s1.lt-s1.ze part1.cles ...... 76 xi
Figures Page 24. Electron micrograph (500 X) of sample C-8a showing typical silt-size particles compris- ing the Hannibal Formation ...... 78 25. High magnification (10,000 X) electron mi crograph showing lobate surface texture of an individual grain in sample C-8a ...... 79 26. Bathymetric zonation of common trace fossils modified from Seilacher (1967) ...... 82 27. Location of the Hannibal sediments on Passega's (1964) C/M diagram...... • ...... 84 28. Boundaries of the Hannibal sediments on Visher's (1969) sediment transport dynamics diagram...... 84 29. Cross sections showing the postulated Kinder hook deposition of the Hannibal Formation, Chouteau Group, and Northview Formation in Missouri...... 93
30. Expl~nation of symbols used on stratigraphic sect1.ons...... 114 31. Hannibal section (A) ...... 119 32. Hannibal section (A) continued ...... 120 33. Hannibal South section (B) ...... 124 34. Atlas South section (C)...... 127 35. Hannibal North section (D) •.•••.•.....•..••••.•. 131 36. Pleasant Hill South section (E) ...... 135 37. Pleasant Hill South section (E) continued ...... 136 38. Hamburg section (F) ...... 139 39. Hamburg section (F) continued ...... 140 40. Hannibal Core East (G) ...... 142 41. Hannibal Core \"est (H) ...... 144 xii
LIST OF TABLES
Table Page I Location of Stratigraphic Sections Described and Sampled...... 27 II Grain Size Scale for Terrigenous Sediments, Modified from Folk (1968)...... 34 III Verbal Scale for Sorting, Skewness, and Kurtosis (Modified from Folk and Ward, (1957).. 51 IV Form and Surface Texture Classifications...... 72 V Verbal Scale for Sphericity and Roundness...... 75 1
I. INTRODUCTION
The Hannibal Formation is a fine-grained terrigenous sedimentary unit containing a lower bluish-green fissile mudst.one which grades vertically into a series of coarse and argillaceous fine siltstone units. The southwesternmost extent of the Hannibal Formation is exposed in northeastern Missouri in Marion, Pike, Ralls, Lincoln, Lewis, Knox and Monroe counties, and along the bluffs of the Mississippi River in both Missouri and west ern Illinois. Where the Hannibal crops out, it forms gentle slopes and is covered with vegetation. The most visible exposures are along the Mississippi River where river erosion has formed steep bluffs along the flood plain. Several Hanni bal sections studied are well exposed along these bluffs, but rarely is one section complete. A. PURPOSE OF INVESTIGATION The purpose of this study is to ascertain the envi ronment of deposition that developed the sediments of the Hannibal Formation which marks the beginning of the Nis sissippian record in northeastern Missouri. This objective is carried out by presenting stratigraphic details of the Hannibal at the type area and vicinity in northeastern Missouri. Grain size parameters and grain morphology are used in order to establish depositional modes of various siltstone units within the Hannibal. In addition, a 2
semi-quantitative study of the clay minerals occurring in the formation and their distribution are utilized to es tablish the origin of the less silty units of this forma tion. Paleoecology is determined by fossil assemblages occurring in the Hannibal. B. PREVIOUS WORK Since the Hannibal Formation has no significant eco nomic value, very little research has been focused on it. Most studies have been of a paleontologic or stratigraphic type. In Missouri, Branson and Mehl (1933) did an intensive study of conodont assemblies in the Hannibal Formation. Several Missouri geologists, Laswell (1957), Rowley (1908), and Williams (1955) have made detailed geologic maps of the Hannibal along with other Mississippian formations which crop out in northeastern Missouri. The Hannibal Formation was used by Collinson, Scott and Rexroad (1962) as one of many formations used in producing several biostratigraphic ranges and correlation charts based on conodonts from De vonian and Mississippian rocks of the Upper Mississippi Valley. Conkin and Pike (1965) identified various forami nifera occurring in the Hannibal. Moore (1928) probably has the best published stratigraphic description of the Hannibal along with other described early Mississippian
formations. In Illinois, Workman and Gillette (1956) described the Hannibal stratigraphically in the surface and subsurface, 3 and through well hole data made several north-south and east-west cross sections of the whole Kinderhook series throughout Illinois.
In Iowa, Van Tuyl (1925) described and identified sev eral types of invertebrate fossils he observed in the En glish River Formation, the Iowa equivalent to the Hannibal. C. LOCATION OF TYPE SECTION The type section of the Hannibal Formation is along the western b l uffs of the Mississippi River south of the town of Hannibal, Missouri, SE 1/4, SE l/4, Sec. 28, T. 57 N., R. 4 W., Hannibal Quadrangle (Figure 1). The bluff at this locality is extremely steep, and is regarded by the citizens of Hannibal as "lover's leap". The bluff is com posed of three formations. At the base, 18 feet of upper Louisiana limestone is exposed. Above this is 68 feet of Hannibal overlain by approximately 100 feet of Burlington. When Keyes (1892) named the Hannibal, he did not state the type locality, but it is reasonably certain this is the section he considered as the type. D. TEID1INOLOGY AND DEFINITIONS In 1:his study, the word terrigenous describes those substances derived from erosion of a land area outside the basin of deposition, and carried into the basin as solids (Folk, 1968). Terrigenous is a superior choice over "detrital" or "clastic" which some geologists regard as applicable to both terrigenous and allochemical materials .
Clay minerals should not be confused with clay-size, 4
Figure 1. Photograph of the Hannibal Formation at its type locality. At this location the Hannibal is overlain by the Burlington Formation and underlain by the Louisi ana Limestone . 5 as the latter refers to any particle less than 3.9 microns in diameter, whether it is clay, quartz, feldspar, or other minerals. The term "siltstone" is used for any indurated sedi mentary rock composed of at least two-thirds silt-sized particles. Claystone is an indurated sedimentary rock con sisting of two-thirds or greater clay-size particles. Mud stone is the intermediate rock name given to the indurated sedimentary rock containing less than two-thirds silt and/or less than two-thirds clay-sized particles. Shale is defined as a terrigenous rock whose parti cles have a diameter less than 62.5 microns (Clark, 1954). Thus, siltstone, mudstone and claystone can all be re garded as types of shales. 6
II. STRATIGRAPHY
A. ORIGIN OF NAMES The Hannibal Formation was first formally mentioned by S'tvallow (1855) as the "Vermicular shale and siltstone". He used the descriptive "Vermicular" because of the abun dance of worm burrows seen in the upper siltstone of the formation. Swallow included all the strata between the upper Chouteau (Mississippian) and the lower Louisiana Limestone (Devonian-Mississippian) as the "Vermicular shale and siltstone". The name Hannibal was first introduced by Keyes (1892) for the shales overlying the Louisiana Limestone (Devonian Mississippian), and underlying the Chouteau Limestone (Mississippian) along the bluffs of the Mississippi River in the town of Hannibal. Keyes made the mistake of calling the formation above the Hannibal the Chouteau when it is actually the Burlington Limestone. Moore (1928) defined the Hannibal to be the shales and siltstone overlying the Glen Park and underlying Chouteau. Later Moore (1935) indicated that the Glen Park Limestone should also be included in the Hannibal Formation. In this study, the Hannibal Formation is defined as the terrigenous sedimentary unit above the Louisiana Lime stone and below the Chouteau Formation. 1~ere Louisiana is absent, Saverton is used. For the upper boundary, where Chouteau is absent, the Burlington Limestone forms the 7 boundary. B. GEOLOGIC SETTING The Hannibal Formation occurs northeast of the Ozark uplift area in Missouri, northwest of the Vandalia Arch and west of the La Salle Anticlinal Belt in Illinois (Figure 2). It crops out along the axis of the Lincoln fold in both Missouri and Illinois. Isopach maps suggest that the Lincoln arch had no influence upon the deposition of the Hannibal sediments (Figure 3). The Hannibal Formation lies on the Louisiana Lime stone (Devonian-Mississippian) at the type locality. In other places it rests on Saverton (Devonian) or Grass Creek (Devonian). The irregularity in thickness and distri.bution of all three units seems to indicate some type of discon formity between the Hannibal and pre-Hannibal strata. Branson (1944) believes the unconformity marks the encroach ment of a Mississippian sea which advanced over an eroded surface of Devonian formations. Williams (1943) believes that the existence of this unconformity can best be seen at the type section in Hannibal, Missouri at the Hannibal Louisiana contact. He observed several channel cuts in the upper Louisiana that were filled with Hannibal shale, Some of the large channels are as much as five feet deep and from eight to ten feet across the top. The Hannibal is overlain by one of two Mississippian age carbonates, either the Chouteau or Burlington Formation. In Illinois, the Hannibal is overlain by the Chouteau, but 8
0 25 50 IOWA ·\. ILLINOIS I I I I SCALE IN MILES .) I ./· ,_/" ( (. ). .I .f HANNIBAL ./ DISTRIBUTION "7 ~ \
' \ 4-~~'V MISSOURI Figure 2. Distribution of the Hannibal Formation modified from Laudon (1929), ~Jorkman and Gillette (1956), and Binz (1978). ILLINOIS MISSOURI ® 0 12 24 I I I SCALE IN MILES CONTOUR INTERVAL 20 FEET Figure 3. Isopach map of the Hannibal Formation in northeastern Missouri and western Illinois} modified from Binz (1978). 10 further west where the Chouteau has been eroded, the Bur lington Formation overlies the Hannibal. C. DISTRIBUTION AND THICKNESS The Hannibal Formation occurs mainly in central and west-central Illinois, and extends into southeastern Iowa and northeastern Missouri (Figure 2). In the outcrop area, the average thickness of the Hannibal is 60 to 100 feet. The thickness is rarely uni form from one exposure to another, and can be seen to change several tens of feet in thickness within just a few miles (Figure 3). The Hannibal thins rapidly west and south of the type section to a thickness of approximately 15 feet in Andrew County to the west, and Lincoln County to the south. The Hannibal does not occur in central Missouri, and reports of its occurrence in the subsurface by earlier writers are probably mis-identified Saverton or Grassy Creek Forma tions. Southeast from the type section, along the Missis sippi River, the Hannibal generally increases in thickness from 68 feet at Hannibal, Missouri to 130 feet at Hamburg, Illinois. This is an increase of 62 feet in 42 miles. From Hamburg, Illinois southwest to Troy, Missouri, the Hannibal thins to 15 feet, which is a decrease in thick ness of 115 feet in 23 miles. D. STRATIGRAPHY OF AREA Paleozoic strata ranging in age from Middle Ordovician to Lower Mississippian are well exposed in northeastern 11 Missouri. The Ordovician and Silurian formation in this area hold little significant interest as far as the genesis of the Hannibal sed~ents is concerned. Therefore, readers more interested in these units should refer to Howe (1961), Branson (1944) and Koenig, Martin and Collinson (1961). Due to the unconformity between the Hannibal and pre Hannibal strata, this unit is underlain by several Devonian and unassigned Devonian-Mississippian formations. The en suing paragraphs will contain a brief description of each of these formations, plus descriptions of the Chouteau and Burlington formations which overlie the Hannibal in north eastern Missouri. Figure 4 contains a generalized strati graphic column of these formations as they appear in the study area. The Grassy Creek Formation (Devonian) is a dark col ored, fissile to thin-bedded, carbonaceous shale averaging only a few feet in thickness. At its type section in Louisiana, Missouri, the lower few inches consist of a greenish brown mudstone containing coarse, well-rounded, frosted sand grains. This is overlain by a few inches of blue-green mudstone, succeeded by one inch of medium grained sandstone. This formation extends west into cen tral Illinois where it is considered to be equivalent to the New Albany Formation. It is also equivalent to the Chattanooga Formation in Tennessee and southwestern Mis souri, and the Maple Mill Formation in Iowa, and is re ferred to as the "Kinderhook Shale" by subsurface workers 12 LIMESTONE, LIGHT BUFF, MASSIVE, COARSELY CRINOIDAL WITH CHERT LAYERS. ?O'-IOO' DOLOMITE, BUFF, FINELY CRYSTALLINE CRINOIDAL. LIMESTONE t....LIGHT BUFFLDOLOMITIC IN UPPER POKTIONS, CRINOIDAL. LIMESTONE 1 GRAY, FINELY CRYSTALLINE CRINOIDAL. o'-12 1 LIMESTONE, BROWNISH GRAY, FINELY CRYSTALLINE 1 ARGILLACEOU~ NODULAR APPEARING SURFACE, CALC II E GEODES. ·:.·::-:,.:-:: :.::::·1 SILTSTONE, ALTERNATING LAYERS OF --·-·-· COARSE SILTSTONES AND ARGILLACEOUS, FINE SILTSTONE, GREEN TO BUFF GRAY, THIN TO MASSIVE BEDDING L:.SCALARITUBA ...... ·. MISSOURIENSIS AND TAONUtiUS ...J ·::·-::: .. ·: ..... : •.: cAODAGALU COMMON . MUDSTONE 1 SILTY, OLIVE GREEN, FISSILE --·-'"'-·-· PYRITIC, LOWER PORTION POORLY EXPOSED. -·-·-·-·- ·--·-·- =-~~-~·-·--· ·---·--·-· z I I I~ <( LIMESTONE MEDIUM TAN TO GRAY :zD.. Z I I I I I <(~ 0 ~_ 40 ~ LITHOGRAPHIC, MEDIUM TO SLABBY -CI) ~ I I I I II ZCI) C/) BEDDED DOLOMITIC BEDS, CALCITE OCI) GEODES. ~C/) § 2 '-14 I MUDSTONE I GRAYISH -GREEN I SOFT I WITH SILTSTONE BEDS. 3 '-IO' MUDSTONE, DARK BROWN TO BLACK, DISTINCTLY FISSILE. Figure 4. Generalized stratigraphic column for northeastern Missouri. 13 in the Forest City Basin area. The Saverton Formation (Devonian) is an easily weath ered, grayish-green mudstone ~ith thin lenses of frosted, sand-size grains which grade upward into an argillaceous siltstone (VanDuyn, 1954). Since the Grassy Creek and Saverton formations are virtually identical in fossil assemblages and mineralogy, the two formations are consid ered as one stratigraphic unit (Grassy Creek) by many geol ogists. The Louisiana Limestone (Devonian-Mississippian) is composed of dense lithographic gray limestone beds sepa rated by brown, thin beds of dolomite. Many of the lime stone beds contain calcite-filled geodes. This formation ranges from a few inches to 70 feet in thickness, but has an average thickness of about 40 feet. In Missouri, the Chouteau (Mississippian) is con sidered a group, composed of three formations. In ascend ing order, they are the Compton, Sedalia, and Northview. In northeastern Missouri, the Northview is not present and the Compton and Sedalia Formations cannot be distinguished from one another. Thus, in northeastern Missouri, this unit will be called undifferentiated Chouteau. It is a carbonate unit with a lower massive, brown, soft, fine grained limestone and dolomite containing calcite spar, weathered to a hacky surface. The upper portion consists of thin-bedded, fine-grained, gray ltmestone. The Burlington Formation (Mississippian) is a thick 14 (70 to 100 feet) carbonate unit with a lower brown coarsely crystalline, highly crinoidal limestone, and a middle and upper portion consisting of bedded, light gray, coarsely crystalline limestone, with layers of cream-colored chert nodules. This formation lies unconformably on undifferen tiated Chouteau; and where the Chouteau is absent, it lies unconformably on the Hannibal Formation. E. STRATIGRAPHY OF HANNIBAL FORMATION In Missouri, the Hannibal is composed of four lithol ogies, a lower silty mudstone that grades upward into al ternating coarse siltstone and fine argillaceous siltstone units. Silty claystones also comprise the Hannibal in the subsurface near the formation's western extremity. The lower Hannibal is generally a green to bluish green, fissile mudstone with an occasional thin (less than one foot) resistive bed of siltstone- or calcite-cemented mudstone (Figure 6). These mudstones consist of approxi mately equal amounts of fine- to medium-silt and clay-sized particles. For the most part the percent of silt increases upward in the unit. Well rounded, very fine sand-sized quartz grains occur throughout this lower unit. The color of this unit can mainly be attri buted to moisture and il lite clay content. Illite is the dominant clay mineral in the upper and lower Hannibal, and is what g ives this f orma tion its greenish hue. Chlorite, kaolinite and vermi c u l i te also occur in this formation, but in lesser amounts . 11ois ture seems to be the main cause of the bluish tint seen in 15 several units. When several differently colored samples are placed in an oven and heated until dry, all samples attain the same color. The siltstone portion of the upper Hannibal actually consists of alternating units of coarse and argillaceous fine siltstones. These units range in color from light gray, olive-gray, yellow-green, dusty yellow, to olive brown. The coarse siltstone units average from only a few inches to three or four feet thick. They are more resis tive than the finer silt.stone units, and in many places form terraces (Figure 5). These coarse siltstone units consist of predominantly moderate to poorly sorted, coarse and medium size silt particles with lesser amounts of fine silt and clay. Most of these units decrease in grain size down the individual unit. This decrease in grain size is attributed to the loss of coarse silts and/or the addition of finer silts and clays. A few of these units contain minor amounts of medium- and fine-grained sand-sized par ticles. About half the units contain traces of very fine sand. Color of these units is due to moisture and illite, as in the lower Hannibal, and also disseminated pyrite and oxidized pyrite. Several siltstone units contain dissemi nated granular pyrite which gives the rocks a peppery appearance. Where the pyrite has been oxidized, the unit is generally yellowish to brown in appearance. With an increase in illite clays, the siltstones become greener. 16 Figure 5. Photograph of section B showing the alternating characteristics of the coarse (more resistive beds) and argillaceous, fine siltstone units of the upper Hannibal. Figure 6. Photograph of the silty m~dstones comprising the lower Hannibal Format~on, exposed on the west side of "lover's leap". 17 Moisture gives a rock a darker hue than its true dry color. Most of these coarse siltstone units are cemented with cal cium carbonate and/or ferruginous materials. The calcium carbonate amount ranges from 0 to 37 percent, but most siltstones average approximately 2 to 6 percent. Other, more weathered, siltstones are cemented with ferruginous materials derived from the oxidation of pyrite. The hard est, most durable siltstones are those cemented with both calcium carbonate and ferruginous cements. Massive appearance is characteristic of these coarse siltstones, but in some places these beds contain several bedding planes. Throughout the entire Hannibal Formation, it appears that bedding is dependent upon clay content. The higher percentage of clay, the thinner the bedding. However, bedding characteristics occurring in the coarse units cannot be related to clay content, grain-size, sort ing, cement, or extent of weathering. Since lithology apparently has no relationship to the bedding of these coarse siltstones, the bedding planes may be termed dia stems since the bedding is marked by an abrupt rather than a gradual change. Occasionally low angle cross-bedding can be seen in these siltstone units. Another striking feature of these coarse siltstones is the abundance of worm burrows identified as Scalarituba missouriensis. This trace fossil occurs in most of the coarse siltstone units, and occasion ally within the finer, more argillaceous siltstones. Also occurring in several of these units is a rooster tail 18 appearing trace fossil called Taonurus caudagalli. Tao nurus caudagalli is observed only in the coarser siltstones and never in the finer siltstones or mudstones. The finer siltstone units of the upper Hannibal con tain predominantly poorly sorted, medium to very fine, silt-sized particles with a 20 to 40 percent clay-size fraction. They are less indurated than the coarse silt stones, and are usually platy or thin-bedded. These units are less cemented than the coarser units, and are easily weathered. West and south of the type section, the Hannibal For mation thins rapidly. On the western extremities of the formation near Kirksville, Missouri, the Hannibal is only 15 feet thick. In this area it is composed only of a green, fissile, calcareous, silty claystone. Southeast of the type section, along the Mississippi River, the Hannibal increases in thickness due to an increase in the mudstones of the lower portion of the formation, while the coarse siltstone units of the upper Hannibal become thinner and several units completely disappear. Besides the thinning and pinching out of these siltstone units, the mean grain size also decreases southeast of the type section. At Hannibal, Missouri, the formation contains 11 prominent coarse siltstone units. At Hamburg, Illinois, 42 miles southeast of the Hannibal, the formation has only two thin siltstone units. 19 F. AGE AND CO~LATION WITH OTHER FORMATIONS The 1948 Mississippian Subcommittee of the Committee on Stratigraphy of the National Research Council considered the Hannibal Formation as part of the Kinderhookian Series. This was primarily based on the occurrence of the conodont genera Siphonodellat found in the upper and middle portions of-the Hannibal. Siphonodella is an excellent index fossil of the Kinderhookian Series because this genus is distinctt short-ranging, and has a world wide occurrence (Collinsont Scott, and Rexroadt 1962). Several investigators have attempted to establish a Devonian-Mississippian contact through the use of fossil assemblages. Branson and Mehl (1933) described conodonts from the Grassy Creek Formation and pointed out that these conodonts were typical of Upper Devonian formations. Later Branson (1938) stated that not only does the Grassy Creek Formation contain Devonian conodonts genera and no Missis sippian genera, but that the same is also true for the over lying Louisiana Limestone. The Grassy Creek and Louisiana even contain the same species of conodonts, but the number of species is less in the Louisiana than in the Grassy Creek. With this evidence it would seem logical to place the Grassy Creek and Louisiana Limestone in Upper Devonian and to draw the Devonian-Mississippian boundary immediately below the Hannibal. On the other hand, Williams (1943) assigned the Louisiana to lower ~1ississippian on the basis of what he identified as Mississippian brachiopods and 20 pelecypods occurring in the Louisiana. Mehl (1961) be lieves these megafossils are neither typically Mississip pian nor Devonian, but that the conodonts in the Louisiana are clearly indicative of Devonian age. With the debate still at hand, this study will recognize the Grassy Creek as being Upper Devonian, while the Louisiana Limestone will be unassigned Devonian-Mississippian, and the Hannibal will be exclusively Lower Mississippian (Kinderhookian). The conodonts found in the upper Hannibal are similar to those of the lower Chouteau Formation. This suggests that the Hannibal and Chouteau are time-equivalent. Some geologists believe the Hannibal is an early phase of the Chouteau and should be placed as the lowermost formation in the Chouteau Group. The Hannibal Formation is not present in central Missouri and cannot be correlated to the Northview Forma tion occurring in southwestern Missouri. The Hannibal and Northview are very similar in both lithologic character istics and fossil assemblages, but they were deposited in two separate basins under similar processes, but at dif ferent times. The Hannibal sediments were deposited dur- ~·ing early Kinderhookian times, while the Northview was de posited in· late Kinderhookian time. The two formations are divided stratigraphically by the Chouteau Group. In Missouri, the Hannibal is considered a formation with no members. In Illinois, the Hannibal is considered a group containing three formations. In ascending order, 21 they are the Glen Park, Maple Mill Shale, and English River Siltstone. A dark shale unit within the Maple Mill Forma tion is called the Nutwood member. In Iowa, the name Han nibal is not used, but Van Tuyl (1925) correlated the Han nibal of Missouri with the English River Formation near Burlington, Iowa. The terrigenous Maple Mill Formation in Iowa is not equivalent to the lower ·Hannibal but is Devo nian in age and can be correlated to the Grassy Creek For mation in Missouri (Thomas, 1949). G, PALEONTOLOGY Some geologists regard the Hannibal as a relatively non-fossiliferous unit, when in fact large quantities of conodonts and trace fossils can be found. Lesser amounts of macrofossils also occur in the formation. The conodonts and macrofossils are usually pyritized, and the latter are generally not well preserved. Branson and Mehl (1933) identified 76 species of cono donts in the Hannibal Formation. Van Tuyl (1925) and Bran son (1938) both identified brachiopods, pelecypods, gastro pods, and indicated the presence of trilobites in the Han nibal. Miller and Furnish (1938) identified several differ ent species of Hannibal cephalopods. The Hannibal contains two major genera of conodonts, Siphonodella and Gnathodus. Siphonodella occurs in the middle. and upper portions of the Hannibal, as previously stated, while Gnathodus is restricted to the lower Hannibal only (Collinson, Scott, and Rexroad, 1962). 22 The coarse siltstone units of the upper Hannibal con tain an abundance of trace fossils. These trace fossils include Taonurus caudagalli, sometimes referred to as "rooster-tail" markings, and Scalarituba missouriensis, postulated as worm burrows or feeding trails (Figure 7). It was Scalarituba missouriens·is Swallow (1855) was re ferring to when he used the descriptive name "Vermicular shale and siltstone" for the Hannibal. Chondrites were also observed in the Hannibal, but only at a few locations. Almost every coarse siltstone unit of the Hannibal contains Scalarituba missouriensis (Figure 8). They are most likely worm burrows filled with less indurated mate rial, usually finer silts and clay. In ferruginous beds, the burrows are usually more oxidized than the surrounding rock. In unoxidized siltstones, the burrows are a darker green or gray color than the surrounding rock. The darker green color is probably due to the concentration of illite clays in the burrows. Occasionally these burrows are filled with pure white kaolinite clay. Scalarituba missouriensis can be described as sub-cylindrical tubes, 1 to 2 mm in diameter and approximately 5 to 10 mm long. In some cases, burrows are observed to be 5 mm in diameter and as long as 20 mm, but these are rare. These trails curve in all di rections. It is generally found that the thinner the bur row, the higher the angle of curvature. Several quarter mm diameter worm burrows obtained an angle of curvature of approximately 20° while 2 mm diameter burrows ranged from 23 Figure 7. Photograph of sample C-3b showing speci mens of Taonurus caudagalli (whorl structure) and Scalarituba missouriensis (tubes). 24 Figure 8. Photograph of the lower portion of a coarse siltstone unit at section B, showing hollow Scalarituba missouriensis tubes and low angle cross-bedding. Figure 9. Photograph of Hannibal float (sample B-200) showing several specimens of Taonurus caudagalli. 25 0 to 4°. The paths of the burrows are usually parallel to the bedding, while in a few cases they are seen to deviate vertically at about 5°. Another common trace fossil found within the upper coarse siltstone units of the Hannibal is Taonurus cauda galli (Figure 9). As mentioned before, this is sometimes referred to as "rooster-tail" markings because of the re semblance to a curved sweep of a rooster's tail. They are believed to be feeding trails of a worm-like organism and not fucoids as previously described by Shepard (1898). When observed in cross-section, the consecutive burrows making up Taonurus caudagalli are sub-cylindrical, ranging from 1/2 mm to 1 1/2 mm in diameter. Most are horizontal, parallel to the bedding, but occasionally specimens are slightly inclined to the bedding plane. Chondrites are observed in only three separate coarse siltstone units in the entire study area. These trace fossils are plantlike structures having a tunnel system which branches in all directions but never crosses one an other. The width of the tunnel remains constant, usually about one mm in those specimens found in the Hannibal. Because of their general appearance, they were once be lieved to be plant fossils, and later as digitate stromat olites. Through research conducted by Simpson (1957), it is now confirmed that these structures are the result of creatures excavating into sea floor sediments, and should be regarded as dwelling or feeding burrows. 26 III. FIELD AND LABORATORY PROCEDURES A. INTRODUCTION Field work was first initiated during the summer of 1977 and completed in the spring of 1978. The Hannibal Formation crops out extensively in north eastern Missouri and western Illinois, but well exposed sections suitable for measuring were difficult to locate. The criteria used in selecting units to be measured were: (1) well exposed unit having little or no vegetation al cover; (2) complete or nearly complete section adequate enough so that results from laboratory analysis would be representative of the formation at this locality; and (3) a section some lateral distance from previously measured sections so that laboratory results will be conducted over a large areal extent. Using these criteria, most sections measured were confined to exposed bluffs along the Missis sippi River, road cuts, and cores that were made available (Table 1 and Figure 10). On this basis, a total of six sections and two cores were measured and sampled. Before sampling, each lithologic unit was described on the outcrop. Color description was based on the Rock Color Chart prepared by the Geological Society of America . The nature of the bedding was noted by using Payne's (1942) classification. Fossils, cements, textures, sedimentary structures, concretionary zones, gradational contacts, and all other peculiarities of each unit were also noted. 27 TABLE I LOCATION OF STRATIGRAPHIC SECTIONS DESCRIBED AND SAMPLED Section Section Label Name Location A Hannibal SE 1/4, SE 1/4, Sec. 28, T. 57 N. , R. 4 W. , Hanni bal Quad., Marion County, Missouri. B Hannibal South SE 1/4, SW 1/4, Sec. 26, T. 55 N. , R. 3 W. , Hanni bal Quad., Ralls County, Missouri. c Atlas South NE 1/4, SE 1/4, Sec. 35, T. 54 N. , R. 1 W. , Nebo Quad., Pike County, Illi nois. D Hannibal North SW 1/4, NE 1/4, Sec. 27, T. 58 N. , R. 5 W. , Quincy Quad., Marion County, Missouri. E Pleasant Hill NE 1/4, SW 1/4, NE 1/4, South Sec. 12, T. 53· N., R. 2 E., Nebo Quad., Calhoun County, Illinois. F Hamburg NW 1/4, NE 1/4, Sec. 35, T. 51 N. , R. 2 E. , Hardin Quad., Calhoun County, Illinois. G Hannibal Core SW 1/4, SE 1/4, SE 1/4, East NW 1/4, Sec. 33, T. 64 N., R. 17 W., Pure Air Quad., Adair County, Missouri. H Hannibal Core NW 1/4, NE 1/4, NE 1/4, West NE 1/4, Sec. 32, T. 64 N., R. 17 W., Pure Air Quad., Adair County, Missouri. 28 ILLINOIS MISSOURI MISSOURI 10 MILES Figure 10. Index map showing location of sections, excluding G and H. 29 Stratigraphic sections and descriptions of individual units are located in Appendix A. B. FIELD SAMPLING One to three samples were collected from each distinct lithologic unit of the Hannibal. In thin units, one foot or less, only one sample was taken to represent that unit. In units greater than two feet thick, three samples were usually taken, one at the top, one in the middle, and one at the base of the unit. In less indurated mudstones and fine siltstones, the trench method was used to obtain a statistical representation of that whole unit. Every sample was labeled and numbered at the time of sampling. A simple method was used to assign each sample its own serial number in order that sample locations could be quickly identified on a columnar section, or even the outcrop itself. Each measured section is referred to by a capital letter. Distinct lithologic units within a sec tion are designated by a number. Lower case letters are used to indicate where on the unit the sample was taken; for example, "a" indicates that a sample was taken from the top of a unit, "b" indicates the middle of the unit, and "c" indicates the base of the unit. A lower case "n" ' "s" , "e" or "w" is used to indicate a second sample collected at the same horizon but at a different location on the out crop, either north, south, east or west of the standard line of sampling. Using this system, the specimen labeled "B-3a", for example, would indicate that this sample came 30 from the top portion of the third lithologic unit in Sec tion B. If it were marked "B-3an", it would indicate that another sample was taken at the horizon but further north on the outcrop. Each massive siltstone sample was also marked with a true north arrow on top so that each sample could be reoriented in the laboratory for the making of thin-sections. Most samples collected were large, weigh ing several pounds, so that the specimen would contain a weathered surface and an unweathered portion, allowing both weathered and unweathered characteristics to be ex amined. The samples were placed in a waterproof plastic bag and sealed in order to reduce escape of the formation water. Later, several samples were allowed to dry so that color changes could be noted. The trench method was used for less indurated mud stones and fine siltstones. A trench was dug with a shovel until fresh, unweathered rocks were exposed. The unit was described and samples were collected throughout the entire trough, then placed in a plastic bag and labeled, using the method previously described. A few samples were also collected in talus at the bottom of outcrops and in washes. These rocks are extreme ly weathered and contain better exposed fossils than do the less weathered rocks on the outcrop. These samples were designated by a capital letter identifying the section, followed by a three digit number. 31 C. SAMPLE PREPARATION 1. Grain Size Analysis. Grain size parameters of the various units of the Hannibal Formation were determined by sieving for sand particles, and by the pipette method for silt- and clay-size particles. Grain size studies are conducted on all of the various types of lithologies occur ring in the Hannibal, with special emphasis on the coarse siltstone units. Before any grain size laboratory method could be initiated on a sample, it first had to be disag gregated completely to its individual grains. This takes great care considering that all the samples are very fine grained and cemented with calcium carbonate and/or ferru ginous materials. Several different methods of disaggre gation were tested in an attempt to find the best proce dure for these types of samples. Samples were crushed, acidized, shaken, boiled, placed in solutions of sodium carbonate, sodium hydroxide, hydrogen peroxide and various hydrocarbons. Most of these procedures failed for one reason or another. The best method found was acidification with a mild acid at near boiling temperatures for several days. This procedure is described in more detail in the ensuing paragraphs. Samples from the coarse siltstone units are first cut, using a diamond saw. An unweathered, equidimentional block weighing approximately 30 grams is cut from each sample to be processed for grain size analysis. For those less in durated, fissile, friable mudstones, and fine siltstones 32 which could not be sawed, 30 grams of unweathered samples are hand chosen from the total samples. Samples are then broken into smaller aggregates, approximately 4 mm in diam eter, using a large mortar and pestle. The sample is then weighed. Weighing the samples at this time and then again after acidification will give a percentage of carbonate material present in each sample. The sample is treated with 5 percent hydrochloric acid to remove all carbonate cement. Additional acid is added to the sample until all effervescing has ceased. To make sure the acid is still present when effervescence ceases, a few drops of the solu tion are placed on a piece of limestone. If it reacts, no additional acid is required. The sample is placed in a sand bath and kept at near boiling temperatures for 48 to 72 hours. Those samples cemented with ferruginous material usually require stronger acid (15%HC1) and longer heating time for disaggregation. As the solution vaporizes from the beaker, distilled water is added. This process con stantly dilutes the acid until no acid can be detected. At this time most of the liquid in the beaker is allowed to vaporize, and each sample is washed into a large evap oration dish. Here it is allowed to dry completely. Sam ples containing minor amounts of clay are placed in an oven and kept at a temperature of 50°C until dry. Argil laceous samples are dried at room temperature. Each sample is again weighed when dry to calculate percent of carbon ate. Each sample is now ready for sieving. 33 a. Sieve Analysis. Three U. S. Standard Sieve Mesh screens are used. They are chosen to separate the sand size fraction of these siltstones and mudstones into Went worth size classes (Table 2), developed by Wentworth (1922). The three screens used are 60 mesh, 120 mesh and 230 mesh. These represent the boundaries of medium sand, fine sand, and very fine sand, respectively. Besides catching the sand-sized fraction of the sample, the screens also catch aggregates of silt not yet completely disag gregated. These aggregates are placed on a hard board and crushed with a rubber hammer until they are completely dis ~ggregated. The rubber hammer is used so that the individ ual sand and silt grains are not broken. Sand caught on each screen is observed under a binocular microscope, and the mineralogy, shape and other characteristics of the grains are noted. Silt and clay passing through the 230 mesh sieve screen is placed in an envelope and stored. b. Pipette Method. Determining size parameters for grains less than 4 0 (62.5 microns) in diameter has long been a problem. Early workers used several different methods for determining the grain sizes of fine materials. Among the most widely used methods were the centrifuge, air analyzer, rising current elutriator, manometric tubes, continuous sedimentation cylinder, decantation, hydrometer method, and the pipette method. For a more detailed description and history of these methods, the reader is referred to Krumbein (1932). 34 TABLE II GRAIN SIZE SCALE FOR TERRIGENOUS SEDIMENTS, MODIFIED FROM FOLK (1968) u. s. Standard Sieve Mesh if Millimeters Phi (0) Wentworth size Class 10 2.00 -1 Very coarse sand 18 1.00 0 Coarse sand 35 0.50 1 Medium sand 60 0.25 2 Fine sand 120 0.125 3 Very fine sand 230 0.0625 4 Coarse silt 0.0312 5 Medium silt 0.0156 6 Fine silt 0.0078 7 Very fine silt 0.0039 8 0.0020 9 Clay-size 0.00098 10 35 The most accurate methods used are those based upon Sir George Stokes' formula which expresses the rates of settling of spherical particles in a fluid. The formula is written as V = cr2, where V is velocity, r is the particle radius, and C is a constant relating relative densities of fluid and particles, acceleration due to gravity, and the viscosity of the fluid. In this study, the pipette method will be utilized because of its simplicity and high degree of accuracy. This method has been described by several workers, such as Robinson (1922), Jennings, Thomas and Gardner (1922), Olmstead, Alexander and Middleton (1930), but prob ably the best published procedure for pipette analysis is by Folk (1968). This method operates on the assumption that particles will settle in the suspension as individual particles, according to Stokes' formula. If the suspension is thor oughly stirred so that particles are uniformly distributed and then allowed to settle, particles having a particular diameter will have passed a certain depth in the suspension at a specific time. If a sample is taken above this depth at this specific time, it would represent all the materials in the suspension having a slower settling velocity, or in this case smaller particle diameter. In order that Stokes' formula could have a practical application, Folk (1968) re wrote the formula by substituting actual working variables (time, depth, specific gravity, fluid temperature) for the 36 original variables in the formula. Stokes' formula is thus rewritten as: T = ------~D~------1500 • ~ . Where T is the time in minutes, D is the depth in centi meters, d is the particle diameter in millimeters, and~ is a constant which depends on fluid temperature (viscosi ty), gravitational force and specific gravity of particles in suspension. Since ~ is a variable, its value was deter mined from a chart contrived by Folk (1968, p. 40). Using this formula, a preselected depth, D, usually 10 em, and particle diameter, d, can be entered into the formula, and then time, T, can be determined. ~t this moment, particles of the selected diameter and greater will have passed this point. Twenty ml of the suspension is then pipetted at this depth to represent the fraction of parti cles with a diameter less than the one calculated. These samples are dried, weighed, and tabulated so that cumulative curves and histograms can be plotted. These procedures are described in more detail in the following section. Stokes' formula was derived for spherical particles and thus does not pertain to particles deviating from a true sphere. However, Krumbein (1932) suggested that an "equiv alent radius" of particles be used. He maintained that the settling velocity of any shaped particle is equivalent to a theoretical sphere with the same long axis radius. Theoretically, Stokes' law applies to particles of any 37 size, but it has been found by experimentation that parti cles greater than 0.07 mm actually have a slower settling velocity than what would be calculated in Stokes' formula. This is due to drag forces produced by the large particles as they fall in a fluid medium. Thus, particle size greater than 0.07 mm {4 0) cannot be determined in any type of experiment involving Stokes' Law. The lower limit of Stokes' law is restricted to those particles with a diam eter of 0.2 micron since particles smaller than this diam eter are kept in suspension by Brownian movement. Another aspect to contend with in the pipette method is the zone of intake by the pipette when sampling at depth D, at critical time T. Kohn (1928) photographed the pro cess of pipette sampling and observed that pipette suction takes in suspension in a spherical zone around the sampling depth D. He contends that since part of this sphere is above D and part below D, the error is essentially compen- satory. c. Technique of Analysis. Disaggregated samples in the minus 230 mesh size are run through a sample splitter until 10 to 15 grams of sample are obtained. According to Folk {1968), this is the optimum amount of sample to use. If a suspension contains more than 15 grams of sample, the particles would interfere with one another and individual settling rates could not be maintained. After weighing the sample, it is placed into a 200 ml beaker and distilled water is added. The beaker is placed 38 in a sonic vibration tank for approximately 15 minutes to disaggregate any sediment still present in the sample. After this, the suspension is poured into a liter cylinder. The beaker is continuously washed until all particles have been transferred into the cylinder. Two to two and one-half grams of sodium phosphate are added to the suspension as a dispersant to keep the quartz and clay minerals from floc culating. The cylinder is then filled to the one liter marker with distilled water. Tap water should never be used since it contains ions that would tend to cause some floc culation in the suspension. The suspension is stirred and allowed to stand for a 24 hour flocculating test. If no flocculation is observed during this time period, the anal ysis is ready to proceed. If flocculation does occur, more dispersant is needed. Temperature of the suspension is measured and sampling times are calculated for 5 0 to 10 0, using Stokes' formula. The cylinder is again vigorously stirred until starting time. Twenty seconds after starting time, the first twenty ml sample is pipetted out of the cylinder at the depth of 20 em. This represents the total amount of sample in the cylinder. Since 20 ml is 1/50 of one liter, multiplying the weight of the first sample by 50 gives the weight of the total sample in the cylinder. Most of the samples are taken at 10 em below the surface. The 9 0 and 10 0 measurements are taken at the 5 em depth since this shallower depth cuts the settling time in half. All 39 pertinent information is recorded on a prepared form. After the sample is withdrawn by a 20 ml pipette and ex pelled into a previously weighed 50 ml beaker, the pipette is washed out with distilled water which is also expelled into the same 50 ml beaker. The beaker is then placed on a heater and kept at 50°C to 60°C until all water is vapor ized from the beaker. Each beaker is weighed and the weight is recorded. The weight of the beaker is subtracted from the weight of the beaker plus the sample to obtain the weight of the sample alone. The weight of the dispersant divided by 50 is then subtracted from each value to obtain the actual weight taken with each pipette sample. Each value is multiplied by 50 to get the actual amount of the "coarser than a certain Wentworth size fraction" in the total sample. Cumulative percent coarser calculations are determined by using the following formula: Cumulative Percent Coarser (CPC) = 100 S+F-P S+F ~fuere F is the total weight of fine material passing through the 230 mesh screen, P is the value obtained by multiplying each pipette sample by 50, and S is the sand fraction not passing through the 230 mesh sieve. Since the amount of sand is negligible and too small to be mea sured, for all practicality, S is a constant "0" in all calculations in this study. To determine the true percent of a "coarser than" value, its "CPC" value need only be subtracted from the "CPC" value of the preceding 0 unit. 40 With these values, a histogram can be plotted. 2. Thin-Section Analysis. Thin-sections are made of several siltstone units for packing and fabric analysis, and also to examine the possible occurrence of imbrications and cross-bedding. Rocks which are chosen to be studied in thin-sections are marked in the field with a true north arrow so they can be re-oriented in the laboratory. All thin-sections are oriented perpendicular to the bedding at several different compass directions. Those siltstones cemented with carbonate material are stained with Alizarin Red S for calcite and/or dolomite identifi cations. 3. X-ray Diffraction. X-ray diffraction is used for identification of various minerals occurring in the Hanni bal. It is also used to conduct a semi-quantitative inter pretation of the amounts of clay minerals present. For those samples chosen to be X-rayed, a 1/2 gram chip (one representing the mineralogy of the whole specimen) is selected and crushed in a mortar. The crushed powder is transferred into a test tube and distilled water is added. The test tube is shaken and placed in a sonic vibrator for further dispersal of clay aggregates. After complete disaggregation, the suspension is poured onto a labeled glass slide and allowed to dry at room bemperature. The dry sample is then placed under a high intensity lamp where all remaining water is vaporized. This method of 41 sample preparation works very well for mineral identifica tion in argillaceous siltstones and mudstones, but fails in clay mineral identification in most of the coarse siltstone samples. These siltstones contain such small amounts of clay that clay mineral X-ray peaks are very weak or totally obscured on the X-ray trace. To obtain a greater concen tration of these clay minerals for identification, unused samples processed for pipette analysis are put into a water filled cylinder, stirred and allowed to settle. The 0.2 micron portion is siphoned off at the appropriate time and depth calculated from Stokes' formula. Water is vaporized until a concentration of clay particles is obtained. The concentration is poured onto a slide and allowed to dry at room temperature. Using this process, the clay mineral peaks are more intense and easily identifiable, but since a size separated sample is used, no quantitative analysis is performed on these samples. For quantitative work, four X-ray traces are run on each sample in the following order: (1) dry at room temperature, (2) glycol treat, (3) heat at 300°C for half an hour, and (4) heat at 550°C for half an hour. All traces are run on a Phillips diffraction X-ray unit, using copper Ka radiation generated at 50 kilovolts and 20 milli amps, 1o beam slit, and scanning at 2° per minute. 4. Scanning Electron Microscope. Several san~les from the massive siltstone units are prepared for viewing in a Coates and Welter field emission scanning electron 42 microscope. For calculating sphericity and roundness of these silt-size particles, it is found that the electron microscope is superior to a regular petrographic micro scope. The electron microscope has good resolution at power (400X) for photographs of representative silt grains. Size parameters of individual silt grains are measured on each photograph for calculating sphericity and roundness. Form and surface features of silt grains are also noted. Several methods are attempted for the preparation of siltstones for viewing. All methods that use an indurated, whole rock sample fail. either because the silt grains are covered with cement, or because the working pressure of the machine (2xlo-7 torr) cannot be reached because of the high porosity and low permeability of the siltstone samples. Since indurated samples cannot be used, disaggregated silt is taken from stored samples used for pipette grain size analysis. These samples are heated in an oven for 30 minutes at a temperature of 80°C to drive off most hydro scopic water. Conductive specimen cement is applied to a stage mount and spread evenly across the mount. Silt is sprinkled across the cement and allowed to dry. Excess silt is blown off. After the cement is dry, the sample is placed in Denton Vacuum DV-515 diffusion pump until a pres sure of 2xl0-6 torr is reached. This process is used to drive off remaining hydroscopic water and any other resi due on the sample or mount. Each specimen is then sputter coated with palladium-gold for 30 seconds at 7 amps. The 43 palladium-gold is used to coat the grains so electrons can be reflected off the grain surfaces to the detector. With out this coating, the specimen would absorb the electrons and emit an iridescent glow. 44 IV. RESULTS OF ANALYSIS A. GRAIN SIZE ANALYSIS 1. Sieve Analysis. Sieving is performed on all samples to remove and observe the sand-size fraction pres ent in each sample. Most samples analyzed contain at least traces of very fine sand-size particles (+230 mesh). An appreciable amount of the samples contains fine sand (+120 mesh), while only 31 percent contains medium size sand grains (+60 mesh). The sand-size fraction of these samples is predomi nantly quartz with lesser amounts of black, tarnished, granular, globular pyrite. Also observed in minor amounts are euhedral cubic and octahedral pyrite, biotite, and orthoclase feldspar. Euhedral pyrite predominantly occurs within the mudstones of the formation, while octahedral pyrite is observed only within the claystones of Section H. The quartz sand grains vary in appearance from a brown in color (due to ferruginous coating) to frosted, dull, and occasionally clear. The quartz sands are pre dominantly dull with the frosted grains occurring mainly in medium and, to a lesser extent, fine-grained sands. These sands range from angular to rounded, with in creased angularity occurring in the fine and very fine sands. The very fine sands are mainly angular and sub angular, while the fine and medium sands are subangular and subrounded. The frosted, medium and fine sand grains 45 are predominantly rounded to subrounded, and probably indi cate a wind-blown origin. 2. Pipette Analysis. Grain size parameters of silt size particles can be obtained by using graphic measures or computational methods. In this study, graphic measures are used because of their superiority to computational methods in this type of investigation. Computational methods can not be used since data received from pipette analysis is open ended (unmeasured clay-size particles beyond 10 0) and these methods work on the assumption that the entire distri bution (0 to 100%) of a sample is included. By using graphic measures, this problem is alleviated, in addition to the fact that graphics yield to a more readily scruti nizing visual inspection. Percentages for each silt size and the cumulative per cent of each sample are calculated from data obtained from the pipette analysis. Individual silt and clay percentages are used to make a histogram, while the cumulative percent is plotted on probability ordinate paper. From this, the mean, standard deviation, skewness, and kurtosis are all graphically calculated. Percent of the various size silt particles, clay-size particles, and carbonate material for individual samples, are listed in Appendix B. Grain size parameter data are tabulated in Appendix C. a. Histogram. For each sample analyzed, individual percentages for each Wentworth size category are calculated and a histogram is prepared~ The abscissa of the histogram 46 is divided into phi units, ranging from 4 to 10 phi. These histograms have little significant statistical value except for observing modes and for examining the general features of the sediments. Samples analyzed from the coarse siltstone units of the upper Hannibal are 69 percent unimodal (having only one mode), and 31 percent bimodal. The modal size for 19 per cent of these samples occur at 5 0 to 6 0 (medium-grained silt). Bimodal samples occur with the increase of clay size materials. Thirty-one percent of the samples are bi modal, with the primary mode occurring at 6 0 to 7 0, and the secondary mode occurring at 8 0 to 10 0 (clay-size par ticles). Samples from the argillaceous, fine-grained siltstone units of the Hannibal are 25 percent unimodal and 75 per cent bimodal. The mode of 12 percent of the samples is lo cated at 6 0 to 7 0, and 13 percent at 7 0 to 8 0 (fine grained silt). The bimodal samples are again caused by in creases of clay-size materials. Twelve percent of these samples have a primary mode at 5 0 to 6 0, and a secondary mode at 8 0 to 10 0, while 63 percent have a primary mode at 6 0 to 7 0, and a secondary mode at 8 0 to 10 0. The silty mudstones of the lower Hannibal are all bi modal. With the primary mode stated first, they proceed as follows: 10 percent are coarse silt and clay, 70 percent are medium silt and clay, 10 percent are fine silt and clay, and 10 percent are clay and medium silt. 47 Several samples from Section H are silty claystones which are all unimodal, with the mode occurring at 8 0 to 10 0 (clay-size particles). b. Graphic Mean. In this study'· the mean value is determined by using Folk and Ward's (1957) graphic mean formula (Mz): 016 + 05o + 084 Mz = 3 In all graphic formulas, 0percent is the phi value occurring on the abscissa, corresponding to that percent value on the cumulative frequency graph. This formula is the best graphic measurement for de termining overall mean size. Because this formula is based on three points, it is superior to Inman's (1952) graphic mean formula ((016 + 084)/2), which is only based on two points. Errors occur in using Inman values when curves be- come skewed. The mean grain size ranges from 4.77 0 to 11.1 0. Figure 11 illustrates the average mean grain size for the various types of lithologies. The mode for the coarse siltstones is around 5.5 0 to 6 0 (medium silt), while the mode for the finer siltstones is from 6.25 0 to 6.75 0 (fine silt). The primary mode for the silty mud stones is at 8.5 0 to 9.0 0 (clay-size). c. Inclusive Graphic Standard Deviation. Standard deviation of a sample is the value currently used to ascer tain the sorting of that sample. Inman (1952) suggested that the graphic standard deviation be calculated by: 48 -Q- COARSE SILTSTONE -D- ARGILLACEOUS, FINE SILTSTONE >- -l:r SILTY MUDSTONE 0z lJJ ::::> ~ 0:: LL OL-~~~--~--~~--~~~~---L--~--L-~ 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.0 MEAN GRAIN SIZE Figure 11. Frequency distribution of mean grain size for all samples analyzed. The mean values are grouped in .5 Mz units. The bottom of each symbol equals the percent frequency of that rock type. 49 0= This formula embraces only the central 68 percent of the distribution, and thus the sorting coefficient obtained is for only this 68 percent. This type of formula is adequate for normal distribution, but fails for bimodal and skewed distributions. Folk and Ward (1957) suggest using a formu la that embraces 90 percent of the distribution. They call this the Inclusive Graphic Standard Deviation (crr): This will be the formula used for calculating standard de- viation in this study. The standard deviation for all samples studied range from 0.44 to 8.73, and can best be scrutinized by examining Figure 12. This frequency diagram indicates that the finer grained the rock, the higher standard deviation it will possess. Using Folk and Ward's (1957) classification of sorting (Table 3), the Hannibal sediments range from extremely poorly sorted to well-sorted. Examining Figure 13, it can be seen that the samples studied are predominantly moder ately sorted and poorly sorted. This figure also indicates a general trend in sorting. As mean size (phi units) in creases, the sorting decreases (higher standard devia tion). Both Figure 12 and Figure 13 indicate that the finer grained the rock, the poorer the sorting. so 0 COARSE SILTSTONE C ARGILLACEOUS, FINE SILTSTONE A SILTY MUDSTONE (.)> z LLI ::::> @ 0::: LJ... 1- z ~ 0::: ~ .35 .50 .71 1.0 2.0 4.0 INCLUSIVE GRAPHIC STANDARD DEVIATION Figure 12. Frequency distribution of inclusive graphic standard deviation for all samples analyzed. The standard deviation values are grouped into Folk and Ward's (1957) verbal sorting classification. The bottom of each symbol equals the percent frequency of that rock type. Numbers on the abscissa are not to scale but indicate numeric boundaries between verbal classes. TABLE III VERBAL SCALE FOR SORTING, SKEWNESS, AND KURTOSIS (MODIFIED FROM FOLK AND WARD, 1957) Sorting crr Skewness SKI Kurtosis Ka terms terms terms Very well 0135 Very negative -1.00 . -0130 Very 0167 sorted skewed platykurtic l~ell sorted 0135. 0.50 Negative skewed -0130 . ·0110 Platykurtic 0167 . 0190 Moderately 0.50 . 0171 Nearly ·0110 . +0110 Mesokurtic 0I 90 • 1.11 well sorted symmetrical Moderately 0171 . 1. 00 Positive +0110 . +0130 Leptokurtic 1.11 • 1. 50 sorted skewed Poorly 1. 00 • 2I 00 Very positive +0130- +1.00 Very 1. 50 • 3I 00 sorted skewed leptokurtic Very poorly 2100 . 4100 Extremely 3100 sorted leptokurtic Extremely 4100 poorly sorted 52 2.5 • VERY POORLY • SORTED z • • 0 • • 2.0 • • • • ~ • • • > • • • • L&J 0 • •• • • 0 • • • • •• POORLY a:: • •• • • <( SORTED 1.5 • • 0z • • ~ • • en • • • u • •• • • • • • % • ••• a.. • • • • <( ••• • a:: • :· • (!) • • • • • • • L&J ~ en :::>_, u z 0.5 • VERY WELL SORTED 0 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 MEAN SIZE (PHI) Figure 13. Standard deviation (sorting) as a function of mean grain size. 53 d. Inclusive Graphic Skewness. Inman (1952) sug gested that graphic skewness (SKG) be measured using: 016 + 0·84 - (2 · 05o) SK = G 084 - 016 Again this formula only embraces the central 68 percent of the curve, while most skewness occurs in the extremities of the curve. Thus, Folk and Ward (1957) developed a better skewness formula entailing 90 percent of the curve. This formula is called the Inclusive Graphic Skewness (SKI): 016 + 084 - <2 ·05o) 05 + 095 - <2 ·05o) SKI = + 2 <084 - 016) 2 <095 - 05) This formula averages together the skewness of the central portion and the skewness of the tails to obtain an overall skewness for the entire curve. The skewness values for the Hannibal sediments range from very negative (-1.74) to very positive (+0.95), but as shown in Figure 14, the skewness values are predomi nantly very positively skewed. The coarse siltstone units studied show that 84 per cent are very positive skewed, 10 percent are positive, 5 percent are nearly symmetrical, and 1 percent are negative skewed. The argillaceous, fine-grained siltstones are 100 percent very positive skewed. The silty mudstones of the Hannibal are 71 percent very positive, 15 percent positive, 7 percent nearly symmetrical, and 7 percent negative skewed. e. Graphic Kurtosis. A curve with normal 54 0 COARSE SILTSTONE 0 D ARGILLACEOUS, FINE SILTSTONE ~ SILTY , MUDSTONE ~ (.)z w :::> @ 0:: LL ....z w (.) 0:: ~ 0------~--~--~------L------~------~ -1.00 -0.30 -0.10 0.10 0.30 1.00 INCLUSIVE GRAPHIC SKEWNESS Figure 14. Frequency distribution of inclusive graphic skewness for all samples analyzed. The skewness values are grouped into Folk and Ward's (1957) verbal skewness classification. The bottom of each symbol equals the percent frequency of that rock type. Numbers on the abscissa are not to scale but indicate numeric boundaries between verbal classes. 55 distribution will have a straight line plot on probability paper and have a kurtosis of 1.00. Kurtosis is the measure used to describe the departure of a curve from a normal curve. If the central portion of a curve is better sorted than the tails, it is peaked (leptokurtic); if the central portion is not well-sorted, the curve is flat (platykurtic). In this study, graphic kurtosis (Kc) used by Folk and Ward (1957) is used: 095 - 05 Using the verbal scale for kurtosis (Table 3), the coarse siltstone units are 3 percent platykurtic, 4 percent mesokurtic, 3 percent leptokurtic, 54 percent very lepto kurtic, and 36 percent extremely leptokurtic. This indi cates that the coarse-grained particles within these sam ples are better sorted than the finer particles (Figure 15). The argillaceous, fine-grained siltstones are 10 per cent platykurtic, 10 percent mesokurtic, 40 percent lepto kurtic, and 40 percent very leptokurtic. The kurtoses for both types of siltstones are similar and may indicate that both have relatively the same degree of sorting. The silty mudstone units are 14 percent platykurtic, 29 percent mesokurtic, 36 percent leptokurtic, 14 percent very leptokurtic, and 7 percent extremely leptokurtic. 3. Results of Size Analysis. The Hannibal Formation is comprised of four lithologies: coarse-grained siltstone, 56 IOOr-----~r----~------,------.------~-----4 0 COARSE SILTSTONE C ARGILLACEOUS , FINE SILTSTONE A SILTY MUDSTONE o~----~~--~~----~------~------L______j 0.67 0.90 1.11 1.50 3.00 GRAPHIC KURTOSIS Figure 15. Frequency distribution of graphic kurtosis for all samples analyzed. The kurtosis values are grouped into Folk and Ward's (1957) verbal kurtosis classification. The bottom of each symbol equals the percent frequency of that rock type. Numbers on the abscissa are not to scale but indicate numeric boundaries between verbal classes. 57 argillaceous fine-grained siltstone, silty mudstone, and silty claystone. The coarse-grained siltstones are located in the upper Hannibal and are composed of mainly coarse and medium silt. Fine silt, very fine silt, and clay-size par ticles usually make up less than 30 percent of the rock. Most of these units decrease in mean grain size strati graphically downward. This change is mainly due to the de crease in coarse grained silt, and in the increase in medi um grained silt (Figure 16). The fine-grained siltstones are very similar in silt content to the lower portion of the coarse siltstone, but with an appreciable increase in clay-size materials (Figure 17). The silty mudstones of the lower Hannibal are composed of about one-third clay size material and two-thirds silt, predominantly medium size silt (Figure 18). Silty claystones are only observed in Section H (Hannibal core east). These claystones are composed of approximately two-thirds clay and one-third silt, predominantly very fine silt (Figure 19). a. Conclusions from Size Analysis. Grain size analysis indicates a decrease in grain size downward most of the coarse siltstone units . When dealing with sand stones, this type of situation is indicative of either re gressive seas or progressive sediments. One or both of these conditions may be the cause of this grain size de crease. The upper Hannibal is characterized by alternating units of coarse and fine-grained siltstone units. Through SAMPLE B-II a SAMPLE B-Ile I I T I I I I I I ...- I 50 ,.... - 50 ,_ - 40 - - 40 - - ~ r- 2 2 w 30 ~ - f- (.) ~ 30 - 0:: 0: w w !l. !l. 20 - - 20 - - 10 I- - 10 - - 4 5 6 7 8 4 5 6 7 8 ~ ~ Figure 16. Histograms of a typical coarse grained siltstone unit showing the change of grain size distribution from the upper sample (B-lla) to the lower sample (B-llc). lJ1 co SAMPLE D-17 SAMPLE A-17 I I I I I I I l I I 50 1- - 50 ~ - 40 - - 40 1- - 1-z 1- w z 30 - (.) 30 1- - w - a: u w Ct: a. ~ 20 - - 20 - - 10 - - 10 - - - 4 5 6 7 8 4 5 6 7 8 0 0 Figure 17. Histogram of a typical Figure 18. Histogram of a typical argillaceous fine-grained silty mudstone unit. siltstone unit. lJ1 1.0 60 SAMPLE H-2 I I I 1 60 r- - 50 ~ - J wz 40 I- - (.) 30 w0:: ~ - CL 20 ~ - 10 1- - I I 4 5 6 7 8 0 Figure 19. Histogram of a silty clay stone from section H. SECTIONS D A 8 c E F CJ) 5.0 w z 5.1 0 5.2 J- CJ) J- -...... J -:e CJ) w \S{W CJ) (!) <( 0:: Q: g w (.) ~ ...J ...J <( a:: 0 LL 6.5 Figure 20. Diagram illustrating the decrease of the average mean grain size for all coarse siltstones interpolated across measured sections. 61 size analysis, it appears that the argillaceous, fine grained siltstones are more related (texturally) to the coarse siltstones overlying each, and probably are basal phases of that unit. When averaging together all the mean grain sizes for each coarse siltstone sample analyzed, it becomes apparent that the average silt grain size decreases south along the Mississippi River (Figure 20). B. THIN SECTION ANALYSIS AND CEMENTING AGENTS The examination of 36 thin sections from the coarse siltstone units indicates that all samples studied are grain supported, with most samples cemented with ferrugi nous and/or carbonate cement. The ferruginous material is disseminated throughout those samples cemented with this agent. These iron oxides are most likely the result of ox idation of pyrite, which is plentiful within these silt stones. The carbonate cement is predominantly calcium car bonate with minor amounts of dolomite. Calcite is mainly disseminated, but occasionally it is observed in sub parallel bands. It is within these bands that dolomite rhombohedra are observed. The carbonate cement is measured in each sample by weighing the sample, acidizing it in diluted hydrochloric acid, and then re-weighing it. The difference in weight of the sample before and after leaching is taken as the car bonate content. Carbonate cement ranges from 0 to 39.6 percent. The carbonate percent for individual samples is 62 given in Appendix B. There is a definite increase in carbonate material within the argillaceous, fine-grained siltstones and silty mudstones of the Hannibal. The coarse siltstones average from 0 to 10 percent carbonate, while the finer grained units average from 15 to 25 percent carbonate. This may indicate that carbonate material in the Hannibal Formation has a syngenetic origin. If the carbonate originated sec ondarily from migrating groundwaters, it would be expected that carbonate amounts would increase in the more permeable units such as the coarse siltstones. This is not the case; therefore, carbonate cement is probably primary. C. X-RAY DIFFRACTION 1. Mineral Identification. With the use of X-ray diffraction, mineralogy is obtained in the siltstone, mudstone, and claystone units comprising the Hannibal For mation. Quartz is by far the most prominent mineral in the siltstones, while quartz and clay minerals are most abun dant in the mudstones and claystones. Also occurring in lesser amounts are calcite, dolomite, pyrite, biotite and orthoclase feldspar. Clay minerals occurring in the Hannibal Formation are classified as illite, kaolinite, chlorite, and vermiculite. Illite is identified by a series of basal reflections 0 • • at lOA (002), 5A (004), 3.3A (006), and so forth. Illit e is a general name for a group of three-layered mica-like clay minerals which exhibit broad peaks, when compared with 63 a true mica, and will show no significant changes when glycolated or heat treated. The illites occurring in the Hannibal are of the dioctahedral variety. This can be seen by the strong (002) basal reflection and the position of 0 the (060) reflection near 1.50A (Grim, Bradley, and Brown, 1951). The (060) reflection for trioctahedral forms occurs 0 near 1.53A and the (002) basal reflection is weak or absent. Kaolinite is characterized by prominent basal reflec- 0 0 0 tions at 7.18A (001), 4.4A (030), 3.58A (002), and so forth. Comparing X-ray traces to tables originated by Brindley (1961), it appears that the kaolinite occurring in the Hannibal Formation is a disordered crystallized variety. Chlorite is identified by the basal reflections occur ring at 14.sA 2. Semi-Quantitative Analysis of Clay Minerals. a. Procedure. Quantitative analysis of clay miner als using X-ray diffraction has been described by several investigators, namely Talvenheimo, Gerhardt and White (1952), Johns, Grim and Bradley (1954), Jarvis (1958), Schultz (1960), and others. Probably one of the best pub lished procedures for quantitative analysis is by Schultz (1964). This study will use the same basic procedures de vised by Schultz (1964) with some modification when needed. This will be considered a "semi" quantitative study because of all the possible errors and assumptions arising from this type of investigation. Since this study uses X-ray peak heights (intensity) and peak areas of basal reflec tions of various clay minerals, the assumption is that all clay minerals occurring in the Hannibal Formation have nearly the same absorption coefficient. A problem also occurring is that minerals present in a sample may contrib ute to the intensity of various clay mineral X-ray peaks; for example, mica minerals will add intensity to illite peaks, vermiculite may be interpreted as chlorite, and computations for chlorite present cannot be adjusted for iron-rich chlorites because of the weak or absent (001) basal reflection. Some of these errors are sure to exist, so the percent calculated for each type of clay is prob ably not exact. Even so, relative amounts of each clay can be noticed and changes from one location to another can be observed. Calculations for quantitative analysis are 66 based on X-ray peak heights and peak areas from basal re flections of clay minerals in the 7A to 17A range. The peak height is the intensity of a peak at a specific 28 angle while peak area is a sum of five intensity measure ments. One measurement is the peak heights, and the other four measurements are peak intensities l/2o and 1° incre ments on both sides from the peak height. Background radi ation must be subtracted from all peaks before calculating these values. The first quantitative calculation involves finding the amount of both kaolinite and chlorite together. Both 0 of these clay minerals have basal reflections at about 7A. The peak area is obtained at this angle to represent the combined amount of kaolinite and chlorite. The illite peak 0 area at about lOA is obtained from the X-ray trace run on the sample heated at 300°C for half an hour. This value represents the amount of illite present in the sample. Heating the sample to 3000C will destroy most of the materials that might add to the X-ray reflection at this angle, but illite, being basically unaffected by heat, will remain stable. Thus, the quantitative formula used for kaolinite and chlorite is: 0 ______7_A~p_e_a_k __ a_r_e_a ______~------X 100 Kaolinite + Chlorite = 0 0 (percent) 7A + lOA peak area 300°C peak area To determine how much chlorite is present in this combined percent value for chlorite and kaolinite, several samples 67 are heated at 550°C for half an hour, and X-rayed. An other portion of the same sample is acid-treated in 50 per cent hydrochloric acid for 24 hours, heated to ssooc and X-rayed. Kaolinite is relatively unaffected by acid, while chlorite is easily removed. Comparing the two X-ray traces shows that 141 peak is absent and the 71 peak is decreased. These changes are due to the absence of chlo rite in the acid-treated sample. Examining all samples run in this manner shows that the 71 peak in the unaci dized samples range from one to 2.4 times as intense as the acidized sample. Therefore, the average value (1.52) will be multiplied by the value of the 71 peak to repre sent that amount of the peak caused by kaolinite reflec tion. The 141 peak is obtained from an X-ray trace run on a sample heated at ssooc for half an hour. Heating at this temperature increases the intensity of the chlorite reflection, and also destroys other materials that may contribute to the reflection at this angle. Thus, the percent of chlorite is: 141 550°C peak height Chlorite = (kaolinite + chlorite) X 9 (percent) 1.52 X 7A peak height The percent of kaolinite and illite are calculated by the following formulas: Kaolinite (percent) = (kaolinite + chlorite) - chlorite Illite (percent) = 100 - (kaolinite + chlorite) b. Results. No quantitative analysis is conducted on the coarse siltstone units of the upper Hannibal 68 because of the minor amounts of clay minerals present. However, two micron portions of several of these units are X-rayed for a qualitative study of the clay minerals pres ent. Illite is by far the most prominent clay mineral. Kaolinite is identified in most samples, and chlorite is never observed. This does not necessarily mean chlorite is absent. It may exist in such minor quantities that its X-ray peaks cannot be detected. Quantitative analysis is conducted on the argilla ceous, fine siltstone units of the upper Hannibal, the lower Hannibal mudstones, and the silty claystones at Section H. In these units illite predominates, forming 53 to 96 percent of the clay minerals, but averaging from 75 to 85 percent . Kaolinite is also present in all samples ranging from 3 to 45 percent, and averaging 15 to 25 per cent. Chlorite is present in all samples in the lower Hannibal, and in most of the samples from the upper Hanni bal. Chlorite ranges from 0 to 10 percent, averaging about 3 percent. Vermiculite is also observed in several samples but no quantitative study is conducted on this mineral. Samples X-rayed for this quantitative study and the results found can be observed in Appendix D. No major clay mineral trend can be recognized when comparing clays from one section to clays of another sec tion. However, a distinct increase of kaolinite is observed in the lower Hannibal (Figure 21). There are two possible reasons for this increase: (1) the lower Hannibal 69 SECTIONS H D A B C E F 100...------r----T - T------ ILLITE r z w I (.) a:: w a.. UPPER HANNIBAL H D A 8 c E F 100~------~------~------~-- ILLITE r z w (.) a:: w a.. KAOLINITE CHLORITE LOWER HANNIBAL Figure 21. Clay mineral ratios of upper and lower Han nibal interpolated across measured sections. 70 was deposited closer to the source area than was the upper Hannibal; and (2) the lower Hannibal accumulated more rapidly than did the upper sediments of the formation. Several investigators, Hayes (1962), Parham (1962), and Hathaway and Sachs (1965), observed increases in kaolinite in near shore facies throughout the world. With this evi dence, the exact condition existing during Hannibal time cannot yet be determined. Grim (1951) and Carroll (1970) believe that an in crease of kaolinite found in stratigraphic units indicates periods of more rapid sedimentation. This may be the case of the lower Hannibal. As previously discussed, the more rapid the sedimentation, the less time is available for the chemical change of kaolinite to other clay minerals. Figure 21 indicates that there is a general decrease of kaolinite in the lower Hannibal, south along the study area. This may indicate a source area to the north. The clay minerals which occur in the Hannibal may indicate deposition in an outer neritic environment. Pryor and Glass (1961) studied clay mineral assemblages in Cenozoic sediments, and found that fluvial environments are dominantly kaolinite, inner neritic environments are composed of nearly equal amounts of kaolinite, illite, and smectite, and the outer neritic environments are domi nantly smectite. As previously discussed, smectite changes to mica-like minerals (illite) during diagenetic processes. If this is the case, the illite clay occurring in the 71 Hannibal Formation today may be altered smectite, formed during the period which followed its original deposition. D. ELECTRON MICROSCOPE STUDY 1. Introduction. Because of the fine-grained nature of the Hannibal sediments, it is established that the scan ning electron microscope is the most useful tool to utilize in obtaining particle morphology. Many investigators, for instance Krumbein (1941), Curray and Griffiths (1955), Beal and Shepard (1956), Porter (1962), Folk (1968), and others maintain that the particle morphology of sand-size parti cles can be used as environmental indicators. This study examines the particle morphology of silt-size particles of the Hannibal to ascertain their effectiveness as environ mental indicators. Because of the high operating cost of the· microscope, only eight samples are scanned and photo graphed. One sample is examined from each exposed section to observe any changes · occurring from one section to an other. In two cases, two samples from one siltstone unit (upper and lower) are examined for particle morphology changes within a single unit. 2. Particle Morphology. a. Form. The form of a particle is obtained by visual inspection and classified as one of three main categories: compact, elongate or platy (Table 4). The Hannibal sediments are represented by particles of all three form types. However, compact and compact elongate particles predominate. All other forms are TABLE IV FORM AND SURFACE TEXTURE CLASSIFICATIONS Form Description Surface Texture Description (Folk, 1968) (Porter, 1962) Compact Particle is Abraded Asurface with a equidimensional chipped or ground appearance. Elongate Particle is Lobate Asurface with a rod like distinct cobbled appearance Platy Particle is Corroded Asurface which disc-like appears to result from the removal of material by solution in contact with the sand or silt. Smooth Smoothness of sur- face is evident. Faceted Evidence of planes or facets associ· ated with crystal· linity. '-1 N 73 present, but in minor amounts. It is observed that platy particles are generally restricted to larger (4 0 to 6 0) particles, while elongate particles are observed mostly in finer (6 0 to 7 0) silt grains. The compact and compact elongate particles occur in all sizes. These observations remain nearly constant with all samples examined. b. Sphericity. There are numerous formulas for calculating the sphericity of a particle. This study will use Riley's (1941) two dimensional formula stated as: Di l/2 SPHERICITY = De where Di is the diameter of the largest inscribed circle and De is the diameter of the smallest circumscribing circle. Di and De are measured directly from photographs, but since this sphericity formula is a two dimensional calculation, a particle being measured must have its two longer axes parallel to the surface upon which it is rest ing. No calculation is conducted on those particles not satisfying this condition. The sphericity of the Hannibal silts range from 0.4 to 0.9, with 86 percent of the particles occurring between 0.6 to 0.8 (Figure 22). 'l'herefore, using Folk's (1968) sphericity classification (Table 5), these silts pre dominantly range from elongate to very equant particles. Only slight variation is observed between samples. Figure 23 shows a scatter diagram of particle size vs. sphericity. This diagram indicates that as particle size increases, 74 0.1 0.2 0.3 0.4 Q5 0.6 0.7 0.8 0.9 1.0 SPHERICITY 40 I- ~ 30 (.) ~2 a.. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 ROUNDNESS Figure 22. Histograms of sphericity and round ness of 122 individual silt-size particles observed in the Hannibal Formation. TABLE V VERBAL SCALE FOR SPHERICITY AND ROUNDNESS Sphericity Scale Folk (1968) Roundness Scale Powers (1953) Very elongate Under 0. 60 Very angular 0.0. 1.0 Elongate 0.60. 0.63 Angular 1.0. 2.0 Subelongate 0.63 . 0.66 Subangular 2.0 - 3.0 Intermediate 0.66 . 0.69 Subround 3.0 . 4.0 Sub equant 0.69. 0.72 Round 4.0 . 5.0 Equant 0.72. 0.75 Very round 5.0 . 6.0 Very equant Over 0.75 76 1.0 -I 1 I • I I • • • • • •• • • • • 0.9 I- • • • - • .. _ •• • ••• • • • • • ... • • • •• • • • • • • • 0.8 1- • :. • • •• • - • • • • • • • • •• • • • • • • • • • • • • • • • • • >- 0.7 I- • • •• • - 1- • • • (.)- \ • • • • • • • • • • -ct: • • • • w • • • 0.6I- • • - a:en • • • • • 0.5 1- - • 0.41- - I I I 1 I 0 10 20 30 40 50 60 MICRONS Figure 23, Sphericity as a function of grain size for 119 individual silt-size particles. 77 the sphericity also generally increases. c. Roundness. Roundness is defined by Wadell (1932) as the average radius of curvature of all the corners of a particle divided by the radius of the largest inscribed circle. This type of calculation is difficult to obtain and compile for a large number of grains. Most investi gators use comparison charts to obtain visual estimates of roundness. In this study, the roundness of all parti cles are visually estimated by using Power's (1953) com parison chart. The Hannibal silts range from 0.2 to 0.8, with the mode occurring at 0.3 (Figure 22, p. 76). Powers (1953) contrived a roundness classification using a log- arithmic scale (Table 5). Since 70 percent of the Hanni bal silt ranges from 1.58 to 2.52 on Power's scale, it should be classified as angular to subangular. d. Surface Texture. Porter (1962) applied the electron microscope to study the surface textures of sand grains, and developed a surface texture classification (Table 4, p. 74). Applying this classification, it appears the Hannibal silts are predominantly lobate (having a cobbled appearance), with some particles appearing to be smooth (no pronounced markings). Figure 25 is an electron micrograph, showing the lobate texture of an individual silt particle. 3. Conclusions from Grain Morphology. The grain morphology of the Hannibal silts shows little significant variation from one section to another, and unlike most 78 Figure 24. Electron micropgraph (500 X) of sample C-8a showing typical silt-size particles comprising the Hannibal Formation. 79 Figure 25. High magnification (10,000 X) electron micrograph showing lobate surface tex ture of an individual grain in sample C-8a . 80 sands, these silts cannot be used as environmental indica tors. It may be concluded that silt-size particles, being fine-grained and light weight, do not receive the physical abrasion that large, heavy sand grains acquire. Folk (1968) developed a roundness sorting classifica tion based on the graphic standard deviation from the roundness cumulative curve. Determining this value, the Hannibal silts fall into the "very poor roundness sorting" category. Sand-size particles, which fall into this category, usually indicate a multiple source area. This may also be the case of the Hannibal silts. On the other hand, the Hannibal silts may have acquired their basic grain morphologies before being eroded and deposited at their present location. Folk suggests that in this type of situation, the most useful method of obtaining the pres ent rate of rounding is to determine the 16 percentile of a roundness cumulative curve. So determined, the value indicates that the Hannibal silts are in the angular cate gory. If this value is to be believed, it is assumed that very little abrasion (rounding) on the silt particles occurred during the transportation and deposition of the Hannibal silts. E. PALEOECOLOGY Trace fossil communities are excellent bathymetric indicators in sedimentary rocks. The behavior of trace fossils is mainly a response to food supply which is con trolled by bathymetric gradient (Seilacher, 1967). Thus, 81 different types of trace fossils occur at different depths. There are two main types of trace fossils: suspension feeders and sediment feeders (Figure 26). Nutrients on which these organisms feed remain in suspension in the near shore, high energy environments, thus allowing only those organisms equipped to feed in this type of environment to thrive. Because of the high energy and rapid sedimenta tion in this environment, these organisms make vertical, or near vertical, burrows produced from suspension feeding. The other type of trace fossils are the sediment feeders. These organisms live in deeper, more tranquil water which, because of the prevailing low energy, allows nutrients to settle to the bottom. These organisms mine through these sediments to feed, thus creating hear horizontal trails. Because of the near horizontal nature of the trails des cribed as Scalarituba missouriensis and Taonurus cau dagalli, and the branch structures described as Chondrites, it appears that all three are sediment feeders. Figure 26 illustrates the four major facies formed by different assemblages of trace fossils (Seilacher, 1967). The Glossifungite facies is the high energy, rough water, shore environment. The Cruziana facies occupies the shallow, shelf environment, while the Zoophycus facies is shallow \vith tranquil water. The deepest environment is the Nereites facies, characteristic of flysch deposits. Using Seilacher's (1967) bathymetric classification, Scalarituba missouriensis and Chondrites occur in the -z I 1- Q. w c CHONDRffES TAONURUS GLOSSIFUMiiTE CRUZIANA FACIES FACIES FACIES NEREITES FACIES SUSPENSION FEEDERS SEDIMENT FEEDERS Figure 26. Bathymetric zonation of common trace fossils, modified from Seilacher (1967). 00 N 83 Cruziana facies, while Taonurus caudagalli is character istic of the Zoophycus facies (Figure 26). Thus, the silt stone units of the upper Hannibal which contain these trace fossils represent sediments that were deposited relatively slowly, in moderately shallow, tranquil waters. F. TRANSPORT DYNAMICS There are several lines of evidence to suggest that the Hannibal sediments were deposited in a low energy environment. The lack of sedimentary structures, poor sorting, and paleoecology all indicate tranquil conditions during Hannibal time. Passega (1964) studied the textural relationship of ten thousand samples ranging in age from Paleozoic to Recent, and determined that the mode of transportation of a specific sample can be determined by using what he called C/M patterns. In this type of study, "C" (the one percentile) is plotted against "M" (the median diameter). The intersection of the two will fall within one of several transportation modes (suspension, traction, rolling, etc.). Using this procedure on 33 samples, it became apparent that all silt - and clay-size particles in the Hannibal were transported by suspension only (Figure 27). On the same lines, Visher (1969) developed a sediment transport dynamics diagram where cumulative percent is p lot ted against grain siz e. Using t h is proce dure, t h e s ame resul t occurred (Figure 28). The Hannibal sediments were evi dently transported in suspension. 84 LLI ....J ....z LLI <..>(1) ~~ w-(.) ~~ II (.) 20 30 100 M =MEDIAN (MICRONS) Figure 27. Location of the Hannibal sediments on Passega's (1964) C/M diagram. HANNIBAL c..::::.:·-- .... , SEDIMENTS -~c::J 99.9 .... ~- z 99 LLJ ~ 90 I ~ LaJ 50 Jt > ti # .....1 10 v "-.."'~" :;::) "./ 2: J 1.0 I a ~ 0.1 b¢\o~ ~~~ I 1.0 0.5 0.25 0.125 0.067 GRAIN SIZE (mm) Figure 28. Boundaries of the Hannibal sediments on Visher's (1969) sediment trans port dynamics diagram. 85 Visher (1960), through laboratory investigation, was able to derive specific water velocities necessary for the transportation of different size particles. He concluded that silt-size particles could be transported in water velocities as low as 0.5 em/sec. He maintained that if the percent silt of a sample was multiplied by 0.5 em/sec., the value obtained would be the water velocity above the sea floor at time of deposition. Following this procedure, the water velocity at the time of deposition for the coarse siltstones ranged from 0.44 em/sec. to 0.46 em/sec., the argillaceous siltstones ranged from 0.37 em/sec. to 0.42 em/sec., and the mudstones ranged from 0.17 em/sec. to 0.37 em/sec. Values generally decrease southward along the Mississippi River. With all this evidence, it seems peculiar that the silty mudstones of the lower Hannibal contain noticeable amounts of predominantly well rounded, dull, very fine quartz sand grains, while the siltstone units of the upper Hannibal have very few well rounded sand grains. This sit uation can best be explained by Morris (1957) who observed experimentally that at relatively low fluid velocities, well rounded grains appear to travel faster than angular grains because the rounded grains show a better ability to roll. The well rounded quartz grains occurring in the coarse siltstones of the upper Hannibal are predominantly frosted, indicating most likely a wind-blown origin. 86 V. ENVIRONMENT OF DEPOSITION A. INTRODUCTION Knowledge of the environment of deposition of sedi mentary units is very important in the field of geology, not only for scientific interests, but also for the ex ploration, exploitation, and evaluation of various economic resources. For the past century, geologists have employed various methods and approaches (stratigraphy, paleontology, grain size parameters, grain morphology, etc.), to ascertain the depositional environment of different sandstone units all over the world, predominantly for hydrocarbon exploration. Very little investigation has been conducted on siltstone units since they are not very common. Recently, however, new hydrocarbon exploration has been conducted on fine grained terrigenous units within the Appalachian Basin (Pepper, De Witt and Demarest, 1954; Dennison, 1971; and Walls, 1975), and the Illinois Basin (Lineback, 1966). Continued study of fine-grained sediments may eventually lead to new exploration frontiers. B, PALEOENVIRONMENT During Kinderhookian times (Early Mississippian), northeastern Missouri and western Illinois were covered with a shallow marine sea which, because of the existing tranquil conditions, was depositing fine-grained sedi ments onto a pre-Mississippian eroded surface. The eroded 87 surface accounts for the variable thickness of the Hannibal Formation seen in both exposed sections and isopach maps (Workman and Gillette, 1956; Binz, 1978). Several investigators have offered theories regarding the source area of the Hannibal sediments. Branson (1938, 1944) believed that the Hannibal sediments were derived from the south from the Ozark dome area; Weller and Sutton (1940) believed that eroded Paleozoic formations in north ern Illinois and adjacent areas provided these sediments; and Workman and Gillette (1956) concluded that the Hannibal sediments were deposited from the west. Evidence compiled by the author tends to agree basically with Weller and Sutton (1940) that the Hannibal sediments were derived from the north. This can be justified by stratigraphic examin ation which indicates that proceeding southward through the study area (away from the source), the coarse siltstone units of the upper Hannibal became thinner and more argillaceous. Most of these units pinch out at Hamburg, Illinois; a mean grain size decrease is also observed. A review of the literature indicates that the Hannibal Forma tion in Iowa (called the English River Formation by Iowa geologists) consists entirely of siltstone with no reported lower shale member (VanTuyl, 1925), while only mudstone units are believed to comprise the Hannibal in central Illinois (Workman and Gillette, 1956). This seems to indi cate that this northern source area is probably in the vicinity of southeastern Iowa and northwestern Illinois. 88 Several investigators, Folk and Ward (1957), Mason and Folk (1958), Harrison (1959), Friedman (1961, 1967), Fuller (1961), Passega (1964), and Visher (1969) have applied statistical coefficients (mean, standard deviation, skewness, kurtosis) to separate what appears to be homo geneous sediments into units which differ in deposit·ional origin. Procedures developed by these authors and con ducted on Hannibal samples indicate that the upper part of the formation consists of several siltstone units, most of which exhibit graded bedding with an increase in grain size upward within each individual unit. This suggests deposition from prograding sediments and/or regressive marine conditions. Sediments deposited in a regressive marine environ ment are characterized by a basal unit composed of poorly sorted silt and clay, overlain by alternating thin beds of fine and coarse detritus (Visher, 1965). Grain size within a regressive marine unit will increase upward (Berg and Davies, 1971), and the entire sequence from the basal shale up to the littoral units can be developed in a sixty foot section (Visher, 1965). These observations are re markably similar to observations made on ·the Hannibal Formation. There are still factors concerning the Hanni bal that do not completely fit into the idealized re gressive marine model. For instance, some siltstone units of the upper Hannibal are not thin, several reaching from three to five feet thick. Also, the topmost unit of the 89 Hannibal does not contain appreciable amounts of coarse sand which is observed in most regressive marine deposits. Regressive seas appear to have influenced the deposition of the Hannibal sediments, but there also seem to be other contributing factors. Deltaic deposits are a mixture of regressive marine and fluvial processes. The distal pro-delta and delta front deposits are equivalent to the low energy environ ment observed in regressive marine deposits (Visher, 1965). In recent deltaic complexes, large quantities of silt and clay have been observed being transported in suspension (Gould, 1970). Known ancient deltas contain large volumes of silt and clay, especially in their distal portions (Pepper, De Witt, and Demarest, 1954; Pryor, 1960; Carrigy, 1971; Dennison, 1971; Hobday and Mathew, 1975; McBride, Weidie and Walleben, 1975; and Walls, 1975). Several of the graded clastic units range up to several feet thick in a deltaic deposit rather than the one foot or less typical of a regressive marine sequence . This explains why s everal of the coarse siltstone units of the upper Hannibal are thicker than those units deposited by exclusively regres sive seas. The occurrence of predominantly fine-grained deposits indicates that the source of the terrigenous sediments was probably a low lying drainage area, eroded by streams or rivers, t hat carried predominan t ly f ine grained materials. Such streams have been observed today in southern California. These streams drain into the 90 Pacific Ocean, carrying predominantly silt and clay, with only minor amounts of coarse material (Revelle and Shepard, 1939). Another possibility for the predominance of fine grained materials and the absence of substantial amounts of sand is that since ancient deltas were smaller than present-day deltas, the seas were more protected by land barriers hampering wave and current action needed to dis- perse coarse-size particles (Allen, 1964) . Comparing evidence obtained from this study to characteristics ·of known depositional environments, it is concluded that the Hannibal Formation was deposited in a combined regressive marine-deltaic complex with the study area occurring in the distal portions of the complex. The regressive marine condition dominated the deposition with new sediments constantly being added to the complex from perhaps a small lobate delta. For a better understanding of just how much this delta actually influenced deposition, further study must be conducted on the proximal nortion of the formation, closer to the source area. C. DEPOSITION ---OF THE HANNIBAL SEDIMENTS The boundary between the Devonian and Mississippian System was marked by periods of local warping and uplifting in Missouri and Illinois. Workman and Gillette (1956) postulated that during Kinderhookian times, the Shuyler arch, Vandalia arch, and Ozark dome (Figure 2, p . 8) were all uplifted, forming an embayment in central Illinois, 91 opening out to the west through northeastern Missouri. The siltstones, mudstones, and claystones of the Hannibal For mation were deposited into this embayment from a northern source area. The study area is located in the distal por tion of the complex where the silty mudstones comprising the lower Hannibal represent a pro-delta facies, while the siltstone and argillaceous siltstone units of the upper Hannibal represent the delta front deposits. The combina tion of regressive marine and deltaic process produced the sheet-like coarse siltstone units of the upper Hannibal. The source province was probably a low relief area eroded by streams or rivers, which drained southward into the Kinderhook seas. Because of the limited source area, lower ener.gy fluvial systems, and/ or barrier is lands, little sand was deposited in the depositional basin. The bulk of the Hannibal sediments was deposited through sus- pension, with the finer grained silts and clays traveling greater distances from the source area. The alternating characteristics of the delta-front : coarse siltstone units and fine, argillaceous siltstone units may be caused by variation in sediment supply and/or differential subsidence of the basin, causing local re- i gression and transgression. The coarse siltstones would .! : have been deposited during regression, while the fine ., argillaceous siltstones were deposited during local trans- gression. This type of situation has been observed in the Niger River delta by Short and Stauble (1967). 92 The deepest portion of the depositional basin was in the southern section where subsidence was probably the greatest. Before Hannibal time, the conditions in this part of the basin were suitable for the accumulation of marine carbonates called the Glen Park Formation. The Hannibal sediments continued to be deposited over this formation until transgressive seas stopped Hannibal-type sedimentation, and accumulations of carbonate occurred extensively in both Missouri (excluding the Ozark dome area) and Illinois. These carbonates now comprise what is called the Chouteau Group. The entire Kinderhook series was brought to an end in northeastern Missouri and Illinois by the uplift of the Shuyler arch, Vandalia arch, La Salle anticlinal belt, and the Ozark uplift (Workman and Gillette, 1956). The uplift of these structures caused extensive pre-Osagean erosion in this area before the depo sition of the Burlington Limestone. Because of these uplifts, the Hannibal source area may have been reactivated, once again depositing terrige nous sediments into a newly formed basin in southwestern Missouri. These sediments are called the Northview Forma tion, and this may explain why the Northview and Hannibal sediments are so similar. Figure 29 contains a southwest northeast cross-section across Missouri during various time intervals of the Kinderhookian, illustrating the deposition and accumulation of Kinderhookian formations occurring in Missouri. 93 0 100 200 SCALE IN MILES MISSOURI A A' DEPOSITION OF EARLY HANNIBAL SEDIMENTS I KINDERHOOKIAN DEVONIAN STRATA A A' ACCUMULATION MIDDLE CHOUTEAU CARBONATES KINDERHOOKIAN DEVONIAN STRATA DEPOSITION OF A NORTHVIEW SEDIMENTS A' LATE CHOUTEAU GROUP KINDERHOOKIAN DEVONIAN STRATA Figure 29. Cross sections showing the postulated Kinderhook deposition of the Hannibal Formation, Chouteau Group, and North view Formation in Missouri. 94 VI. SUMMARY The Hannibal Formation occurs primarily in western and central Illinois, extending into southeastern Iowa and northeastern Missouri. In the study area (northeastern Missouri and western Illinois), ~the Hannibal contains three main rock types: siltstones, mudstones, and clay stones. The siltstones comprise predominantly the upper portion of the formation which consists of alternating units of massive, grayish-green, coarse siltstones and fine argillaceous siltstones. To the south in the study area, these coarse siltstone units become more argilla ceous and thinner until they almost pinch-out. Sand-size grains (predominantly very fine sand) occur throughout the siltstone in minor amounts and are mainly sub-angular to sub-rounded. Most of the siltstone units are cemented with calcite and/or ferruginous materials. The lower por tion of the Hannibal consists of greenish, fissile, silty, mudstones. This portion of the formation becomes thicker southward along the study area. The silty claystones of the formation are only observed from cores taken west of the type section (Hannibal, Missouri) near where the Hannibal nearly pinches out. Grain size studies conducted on the different lithol ogies of the Hannibal indicate that the coarse siltstone units are comprised primarily of coarse (4 0 to 5 0) and medium (5 0 to 6 0) size silt grains. Most of these 95 exhibit graded bedding where mean grain size increases stratigraphically upward in the individual unit. The more argillaceous siltstone units contain approxi mately 20 to 25 percent clay-size particles, with primarily coarse and medium silt, the medium-size silt predominating. The silty mudstones of the lower Hannibal are approximately two-thirds silt, predominantly medium-size, and one-third clay. The silty claystones, observed near the extreme western margins of the formation, consist of approximately two-thirds clay and one-third silt, predominantly very fine silt. Statistical coefficients calculated from grain size data indicate that the Hannibal sediments are poorly to moderately sorted, resulting from the deposition of these sediments from suspension in a low energy environment (velocity less than 0.5 em/sec.). Also observed is a de crease in average mean grain size of the coarse siltstone units, southward along the study area. This signifies that silt being deposited from suspension acts similarly to sand being deposited from higher energy media (traction, saltation), in which a systematic decrease in grain size occurs further from the source area. Paleoecology is determined from trace fossil assem blages occurring in the Hannibal Formation. The most con spicuous trace fossil is Scalarituba missouriensis with Taonurus caudagalli also occurring in many of the coarse siltstone units. Also observed at several localities is what appears to be Chondrites. All three organisms are 96 sediment feeders with Scalarituba and Chondrites occurring in Seilcher's (1967) Cruziana facies, and Taonurus occur ring in the Zoophycus facies. Both facies are indicative of a tranquil, shallow marine environment. ~~sed on X-ray diffraction analysis, the Hannibal is obsefy~d, t:o contain several different clay minerals. Dioctahedral illite is the most prevalent clay mineral, comprising approximately 60 to 70 percent of the total clay. Ten to 30 percent of the clay matrix is composed of disordered kaolinite, with iron- and magnesium-rich : ~hlorites and vermiculite occurring in minor quantities. i 1The occurrence and relative ratios of these clay minerals give strong evidence that the Hannibal_was deposited in a ( /! , ••• ~.• ' (' ~ • .. ,. ' ,.. :. • •-. ~ \ neritic marine environment. !.. Inasmuch as kaolinite chem- ically changes to other clay minerals upon entrance into a marine environment, it is suggested that since the Hanni- hal contains an appreciable amount of kaolinite, the source area providing the sediments for the Hannibal is probably kaolinite-rich. Had kaolinite not been present in sub- stantial quantities when first introduced into the marine environment, very little would have survived the altera tion to other clay minerals. If the alteration of kaolinite to other clay minerals is a function of the time exposed to marine conditions, it would be expected that kaolinite abundance would decrease farther from the source area. The amount of kaolinite occurring in the upper Hannibal siltstones is erratic, while a general decrease 97 of kaolinite quantities is observed southward along the study area in the lower Hannibal mudstones. This indi cates that the source area is north of the study area. Grain morphology remains fairly constant throughout the coarse siltstone units of the Hannibal with no signi ficant variation occurring from one locality to another. The silt-size particles are predominantly angular to sub angular and probably acquired their basic forms, spheri city, roundness, and surface texture before being eroded and transported to their present location. Little or no abrasion occurred during the transportation and deposition of these silts, indicating that suspension was the main medium of transportation. The Hannibal sediments were deposited from a northern source into a restricted, marine, embayment located in north-central Illinois, northeastern Missouri, and south eastern Iowa. The source area was probably eroded by one of several fluvial systems which may have carried predomi nantly fine-grained materials. (fine sand, silt and clay) to the embayment. 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L., Editor, Houston Geol. Society, p. 359-367. Weller, M. J., and Sutton, A. H., 1940, Mississippian border of Eastern Interior Basin: Am. Assoc. Petroleum Geologists Bull., V. 24, p. 765-858. 111 Wentworth, C. K., 1922, A scale of grade and class terms for clastic sed~ents: Jour. Geology, V. 30, p. 377- 392. Williams, J. H., 1955, The geology of the Hannibal Quad rangle: Unpub. manuscript, Missouri Geol. Survey and Water Resources, p. 76. Williams, J. S., 1943, Stratigraphy and fauna of the Louisiana Limestone of Missouri: U. S. Geol. Survey, Professional Paper 203, p. 13-133. Workman, L. E., and Gillette, T., 1956, Subsurface stra tigraphy of the Kinderhook Series in Illinois: Illinois Geol. Survey, Rept. Investigation 189, p. 7-46. 112 VITA Michael Harry Deming was born on December 12, 1952, in Smithville, Missouri. He received his primary and secondary education in Raytown, Missouri. He received a Bachelor of Science degree in Geology from Northwest Missouri State University in Maryville, Missouri. In August 1976, he enrolled in the Graduate School of the University of Missouri-Rolla, in Rolla, Missouri, where he held a teaching assistantship in the Geology Department for a period of two years. Mr. Deming is currently employed by Amoco Production Company in Houston, Texas. 113 AP~ENDIX A DESCRIPTION OF MEASURED STRATIGRAPHIC SECTIONS The following are sections of the Hannibal Formation measured from exposures in northeastern Missouri and west ern Illinois. Each description includes: (1) a graphic representation of each section as it more or less appears on the exposure, (2) sample locations, (3) plot of the mean grain size for each sample analyzed, and (4) a written description of each unit within an individual section. All sections were measured with a rule and hand level. Bedding of each unit was described by using Payne's classi fication. Color of each unit described was determined by using the Rock Color Chart available from the Geological Society of America. Color of the individual units of the Hannibal varies with moisture content. All sections were relatively wet when measured, and probably have been re corded having a darker hue than they would appear to have in their dry state. Explanation of the unit and sample numbers, plus lithologic symbols, are given on the following page (Figure 30). 114 ~LIMESTONE SILTY MUDSTONE CARBONACEOUS 1:_1.~.(:_1_:, SILTY LIMESTONE MUDSTONE II I I I DOLOMITIC LIMESTONE LOESS LIMESTONE WITH rr-Tl CALCAREOUS ~ CHERT NODULES ~ rJ®T1 LIMESTONE WITH CROSS -BEDDING ~ CALCITE FILLED GEODES lzar~l ITZIJ LIMESTONE WITH CARBONATE ~CRINOIDS IES;:!)I STRINERS ~ LIMESTONE WITH TAONURUS ~ SILICEOUS NODULES ~ CAUDAGALLI VERMICULAR, SCALARITUBA I I ARGILLACEOUS LIMESTONE I' I 1~ r-11 MISSOURIENSIS 8 DOLOMITE IP<=> I HOLLOW WORM BURROWS HOLLOW WORM BURROWS [] SILTSTONE ~ SHOWING SEGMENTATION [8 ARGILLACEOUS SILTSTONE ~ CHONDRITES FEET BELOW SEA ,,------LEVEL IN CORES " " ~------.., " " I " " -' I 8 00 -~r.-~-:---:---...... -- -- UNIT NUMBER 7 :~ : \ ...... ---( ...... _--SPOT SAMPLING ..... · .... 8 07--+-'--~=-:::--:_-::::-r__--- ._ .. .._ - -TRENCH SAMPLING Figure 30. Explanation of symbols used on stratigraphic sections. 115 1. HANNIBAL SECTION (A) Section is exposed along the river bluffs southeast of Hannibal, Missouri, Sec. 28, T. 57 N., R. 4 W., Marion County, Missouri. Unit Thickness No. Description in Feet Burlington Formation 1. Limestone, light brown, finely crystalline Appox. 90-100 becoming more coarsely crystalline higher (not meas ured) up, very crinoidal, layers of chert nodules in upper part. Hannibal Formation 2. Claystone, silty, grayish yellow green, 1.0 fissile, slightly calcareous. 3. Siltstone, coarse-grained, grayish yellow 1.8 green, massive, vermicular; Taonurus present; disseminated pyrite; slightly ferruginous; small {1/2 mm) ferruginous concretions. 4. Siltstone, fine-grained, argillaceous, gray- 1.0 ish yellow green, very thin-bedded with thin (5 mm) calcareous stringers. 5. Siltstone, coarse-grained, grayish, yellow 2.4 green, massive vermicular; slightly ferru- ginous at bottom; disseminated pyrite. 6. Siltstone, fine-grained, argillaceous, grayish 2.1 yellow green, fissile; small (0.1 mm) 116 Unit Thickness No. Description in Feet ferruginous concretions. 7. Siltstone, coarse-grained, pale greenish 2.2 yellow to moderate yellow, ferruginous, thick-bedded; disseminated pyrite; calcare- ous, vermicular; Chondrite present. 8. Siltstone, fine-grained, argillaceous, gray- 0 . 9 ish yellow green, fissile, slightly ferrugi- nous; low angle cross-bedding. 9. Siltstone, coarse-grained, grayish yellow, 3.1 massive; disseminated pyrite; calcareous at bottom; vermicular; Taonurus present. 10. Siltstone, fine-grained, argillaceous, pale 0.8 greenish yellow, fissile, pyritic. 11. Siltstone, coarse-grained, yellowish gray, 1.5 massive, slightly ferruginous; disseminated pyrite; slightly calcareous; vermicular. 12. Siltstone, fine-grained, very argillaceous, 3.1 pale greenish yellow, fissile, slightly calcareous. 13. Siltstone, fine-grained, argillaceous, 2.3 greenish yellow, platy, calcareous, vermicu lar, slightly ferruginous; fractures filled with carbonate material , 14. Siltstone, fine-grained, argillaceous, 2.3 117 Unit Thickness No. Description in Feet yellowish gray, very thin-bedded, slightly calcareous. 15. Siltstone, fine-grained, argillaceous, 1.7 yellowish gray, thin-bedded, vermicular, calcareous. 16. Siltstone, fine-grained, argillaceous, 1.7 yellowish gray, thin-bedded. 17. Siltstone, coarse-grained, yellowish gray, 2.8 thin-bedded calcareous, with hollow worm burrows, vermicular; Taonurus present; dis- seminated pyrite. 18. Siltstone, fine-grained, very argillaceous, 2.5 pale olive to grayish olive, fissile, slightly ferruginous, slightly carbonaceous. 19. Siltstone, coarse-grained, grayish olive, 1.4 thin-bedded, vermicular. 20. Mudstone, silty, greenish gray, fissile; 1.5 dark gray laminations in lower portion. 21. Siltstone, coarse-grained, grayish yellow 1.6 green, massive, vermicular. 22. Mudstone, silty, olive green, fissile. 2.7 23. Unexposed. 2.9 24. Siltstone, coarse-grained, grayish yellow 1.5 green, medium-bedded, slightly ferruginous with disseminated pyrite; vermicular; 118 Unit Thickness No. Description Taonurus present; calcareous at top. 25. Mudstone, silty, greenish gray, fissile; gray 18.3 laminations at bottom. 26. Siltstone, fine-grained, argillaceous, gray- 1.1 ish yellow green, thin-bedded, slightly calcareous with disseminated pyrite, highly fracture. 27. Mudstone, silty, greenish gray, fissile . 2.2 Louisiana Formation 28. Limestone, brown, dolomitic, medium-bedded. About 30 119 MEAN GRAIN SIZE IN PHI UNITS 5 10 0 -- ' ' '- '- ' / ' / / / \ Figure 31. Hannibal section (A). 120 MEAN GRAIN SIZE IN PHI UNITS 5 6 7 8 9 10 .-.-·· 20·~-~·:_.,------~ ·-:·-·-.:.. ._!-.··- 0 -- •• - .. .--A- 0 - ·.:;·:f· .. ·:· .'···----® <( 21 .:~:.:..::.J·:·:...... · ... 21 . ' . ' .--. -·- " 22.:..·.····~:'·----@ ..... " -.-·_.___; 5~ " ·-·.-·-· u.. ' /' / 2.9 FEET / / 23 COVERED / 24 ;:,-~::·._-<·.-:_·:~:.: :·. :: ----'19\ 10 -·.. ·-.. :.:.... ·.~.· .< ~ -·--· - --:-_:_-:-_-:- ~8 -.-·-·-·-.-·- ~ -·-·---·-.-· -·-·-·- .-.~.-· -·-·-·--.-.-· ·-·-·- ---·-·- --·-·- -.--.-·- -.-.-· --·-·- --·-·-· -.-.-·- 26 -~: :..;.t;.·:: -:·:::-: <:-~: :.<::::.. :__ :.. :· ~ ,____. - . -.-··-----lr:;.;]27 27 -·-·-··-·-·-· ~ ~~-~-~-~-~~·~-~~~---~ Figure 32. Hannibal section (A) continued. 121 2. HANNIBAL SOUTH SECTION (B) Section located on road cut seven miles south of Hannibal, Missouri on Highway 79, Sec. 26, T. 55 N., R. 3 W., Ralls County, Missouri. Unit Thickness No. Description in Feet Burlington Formation 1. Limestone, light brown, medium-bedded, 43.0 crinoidal, stylolitic with cream-colored chert nodues, ferruginous. Hannibal Formation 2. Siltstone, argillaceous, dusty yellow at 1.7 top, light olive brown at bottom, more ferruginous at top; thinly bedded, with dis- seminated pyrite; calcareous; lower part friable. 3. Siltstone, coarse-grained; moderate yellow 1.7 on weathered portions, light gray on un- weathered portions; vermicular, massive. 4. Siltstone, fine-grained, very argillaceous, 1.6 dark greenish gray, friable. 5. Siltstone, coarse-grained, greenish gray, 3.9 massive; platy at top; vermicular; Taonurus present containing hollow worm burrows; dis seminated pyrite; ferruginous concretions. 122 Unit Thickness No. Description in Feet 6. Siltstone, fine-grained, very argillaceous, 0.5 olive gray, friable. 7. Siltstone, coarse-grained, light gray, 2.2 massive; very thinly bedded at top; ver micular; Taonurus present; containing hollow worm burrows, some worm burrows filled with kaolinite. 8. Siltstone, fine-grained, argillaceous, green- 1.1 ish gray, platy, calcareous. 9. Siltstone, coarse-grained, light gray, 3.8 massive; thinly bedded at top; vermicular; Taonurus present, containing hollow worm burrows; burrows concentrated in lenses; low angle cross-bedding. 10. Siltstone, fine-grained, argillaceous, medi- 1.3 urn dark gray, platy. 11. Siltstone, coarse-grained, greenish gray, 2.0 massive, vermicular; containing hollow worm burrows which are more numerous at top; Taonurus present at top; Chondrite present. 12. Siltstone, fine-grained, argillaceous, 0.8 greenish gray, very thin-bedded, vermicular; Taonurus present; slightly calcareous . 13. Siltstone, coarse-grained, light gray, 1.8 massive, thin-bedded at top, vermicular; 123 Unit Thickness No. Description in Feet Taonurus present; containing hollow worm burrows, some burrows· filled with kaolinite. 14. Siltstone, fine-grained, argillaceous, 1.5 greenish gray, platy calcareous. 15. Siltstone, coars·e-grained, light olive gray, 4.1 massive, thin-bedded at top, vermicular; Taonurus present; containing hollow worm burrows. 16. Siltstone, fine-grained, argillaceous, dark 2.7 greenish gray, platy, vermicular; calcareous along fractures. 17. Siltstone, coarse-grained, medium light gray, 1.1 massive, very vermicular; Taonurus present, also some hollow worm burrows. 18. Siltstone, fine-grained, very argillaceous, 1.6 olive gray, platy. 19. Siltstone, coarse-grained, greenish gray, 1.7 thin-bedded, very vermicular; Taonurus present. 20. Mudstone, silty, greenish gray, fissile, 7.0 slightly ferruginous. 124 MEAN GRAIN SIZE IN PHI UNITS 5 6 7 0 10 _-:;-_ a;-- 'o-~ / / / / < -- -- ..._ -- ·--·-,_, 9.02 2 -·- -·- - _,--- __ , __ - _,------. - ~-._ Figure 33. Hannibal South-- section (B) 125 3. ATLAS SOUTH SECTION (C) Section is exposed three miles south of Atlas, Illi nois on Highway 96, Sec. 35, T. 54 N., R. 1 W., Pike County, Illinois. Unit Thickness No. Description in Feet 1 . Loess Variable Burlington Formation 2. Limestone, buff, medium-bedded, very cri- 2.5 noidal, containing layers of cream-colored chert nodules. Hannibal Formation 3. Siltstone, alternating units of coarse- 3 . 3 grained siltstone and fine-grained argil laceous siltstone. Unit is grayish yellow, massive, very calcareous, ferruginous; dissentinated pyrite; very fractured, vermicular; Taonurus present. 4. Siltstone, fine~grained, argillaceous, gray- 7,0 ish yellow, ferruginous, friable; more silty at top, more calcareous at bottom. 5. Siltstone, coarse-grained, dusty yellow, 1.8 massive, vermicular; Taonurus present; dis- seminated pyrite; slightly fractured. 6. Siltstone, fine-grained, very argillaceous, 9 . 1 grayish olive, platy , slightly ferruginous; 126 Unit Thickness No ..______D_e_s_c_r __ i~p_t_i_o~n ______~i~n~F~e==e~t~ lower portion more ferruginous than upper . 7 . Siltstone, coarse-grained, light olive brown, 1.5 massive, vermicular; Taonurus present; very calcareous; disseminated pyrite; fractured, slightly ferruginous; some ferruginous con- cretions. 8. Mudstone, silty, pale olive, slightly vermi- 20.8 cular, slightly ferruginous, friable. 127 MEAN GRAIN SIZE IN PHI UNITS 4 5 6 7 8 0 5 w~ 5 w lL 12 10 7 @ -.------·- --·------·------·-----~14 - -·--- ~ ---.--. 8 -·-_--_··~ -- \-----~ ---·-- Figure 34. Atlas South section (C) 128 4. HANNIBAL NORTH SECTION (D) Section is exposed on Highway 168, eight miles north of Hannibal, Missouri; Sec. 27, T. 58 N., R. 5 W., Marion County, Missouri. Unit Thickness No. Description in Feet Burlington Formation 1. Limestone, buff, thin-bedded, chert lenses. 70-90 Hannibal Formation 2. Siltstone, coarse-grained, yellowish gray on 2.6 top, light gray on bottom; slightly ferrug- inous on top; vermicular; calcareous in lower portion, slightly laminated in upper portion. 3. Siltstone, fine-grained, very argillaceous, 0.7 greenish gray, fissile, slightly ferrug- inous, calcareous. 4. Siltstone, coarse-grained, greenish gray, 2.4 massive, slightly ferruginous; vermicular; slightly calcareous; disseminated pyrite; fractures filled with ferruginous material. 5. Siltstone, fine- and course-grained alter- 3 . 1 nating, greenish gray, thin-bedded, slightly ferruginous, slightly calcareous. Unaccessible and unmeasurable section About 6. 5.0 129 Unit Thickness No. Description in Feet 7. Siltstone, fine-grained, argillaceous, very 1.0 friable, slightly calcareous. 8. Siltstone, coarse, light greenish gray, 1.9 massive, vermicular, slightly calcareous. 9. Siltstone, fine-grained, argillaceous, 1.1 greenish gray, friable. 10. Siltstone, coarse-grained, grayish yellow 1.4 green, medium-bedded, vermicular, slightly calcareous. 11. Siltstone, fine-grained, argillaceous, green- 1.0 ish gray, friable. 12. Siltstone, coarse-grained, light olive gray, 2.5 massive, vermicular; slightly calcareous; several kaolinite filled worm burrows in lower portion. 13. Siltstone, fine-grained, argillaceous, green- 1.1 ish gray, friable, slightly calcareous. 14. Siltstone, coarse-grained, greenish gray, 1 . 5 thin-bedded, vermicular . 15. Siltstone, fine-grained, argillaceous, green- 0.9 ish gray, friable. 16. Siltstone, coarse-grained, greenish gray, 1 .5 massive, slightly ferruginous, slightly calcareous, vermicular. 130 Unit Thickness No. Description in Feet 17. Siltstone, fine-grained, argillaceous, green- 1.1 ish gray, vermicular. 18. Siltstone, coarse-grained, grayish olive 3.4 green, massive, slightly ferruginous, slightly calcareous, vermicular. Lower Hannibal not exposed. 131 MEAN GRAIN SIZE IN PH I UNITS 6 7 0 ------~-- 10 ------~ ------ Figure 35. Hannibal North section (D). 132 5. PLEASANT HILL SOUTH SECTION (E) Section exposed on Highway 96, two miles south of Pleasant Hill, Illinois; Sec. 12, T. 53 N., R. 2 E., Cal houn County, Illinois. Unit Thickness No. Description in Feet Chouteau Formation 1. Limestone, pale yellowish organge, fine 7.2 grained, dolomitic, containing calcite geodes. Hannibal Formation 2. Siltstone, fine-grained, argillaceous, gray- 6.5 ish yellow green, very friable, thin-bedded, slightly ferruginous. 3. Siltstone, coarse-grained, argillaceous, 1.7 yellowish gray, thin-bedded, slightly ferrug- incus, vermicular; Taonurus abundant. 4. Siltstone, coarse-grained, grayish yellow, 1.0 massive, ferruginous, slightly calcareous; with disseminated pyrite; vermicular, hori- zontal zones of highly ferruginous-stained silt. 5. Siltstone, fine-grained, argillaceous, pale 0.9 greenish yellow, very thin-bedded, friable. 6. Siltstone, coarse-grained, grayish yellow 0.8 green, massive, ferruginous, vermicular; 133 Unit Thickness No , Description in Feet Taonurus present. 7. Siltstone, fine-grained, argillaceous, 6.5 siltier toward bottom, greenish gray, slightly ferruginous, vermicular. 8. Siltstone, coarse-grained, yellow green, 0.7 massive, slightly ferruginous, vermicular. 9. Mudstone, very silty, grayish yellow green, 3.7 very thin-bedded, ferruginous, friable. 10. Siltstone, coarse-grained, argillaceous, 0.5 grayish yellow green, thin-bedded, highly fractured. 11. Mudstone, silty, moderate yellow green, 5.1 siltier at top, slightly ferruginous, thin- bedded. 12. Siltstone, coarse-grained, argillaceous, 0.4 yellowish gray, very thin-bedded, ferrug- incus, containing disseminated pyrite. 13. Mudstone, silty, dusty yellow green, very 12.1 thin-bedded, slightly ferruginous, more ferruginous at bottom, calcareous in lower portion. 14. Siltstone, coarse-grained, massive, ferrug- 1 . 3 incus, containing disseminated pyrite, vermicular; Taonurus present. 134 Unit Thickness No. Description in Feet 15. Mudstone, silty, dusty yellow green, very 7.9 thin-bedded, friable, slightly ferruginous. 16. Siltstone, coarse-grained, argillaceous, 0.9 grayish yellow green, thin-bedded, very calcareous, vermicular; containing dissemi- nated pyrite. 17. Mudstone, silty, grayish green, very thin- 2.4 bedded, slightly ferruginous. 18. Siltstone, coarse-grained, argillaceous, 0.3 pale greenish yellow, massive, calcareous, ferruginous, vermicular. 19. MudsLone, silty, pale olive, pyritic, cal- 2.1 careous. 20. Siltstone, coarse-grained, argillaceous, 0.8 grayish olive, thin-bedded, vermicular; slightly ferruginous; slightly calcareous. 21. Mudstone, silty, grayish olive green, very 3.0 thin-bedded, slightly ferruginous. 22. Unexposed. 23.1 Glen Park Formation 23. Limestone, fine-grained, silty, dusty yellow, 2.6 blocky, slightly ferruginous. 135 MEAN GRAIN SIZE IN PHI UNITS 5 6 7 ...... ,_._. ·~· 0 ---=-·------r.-· --•--;- a._: .... ~-·--- 2 _._...._._----:-::...:-:-.:=-'.: 10 - ..-- . -.----·----. . .. - II c9 -.-- ·-.--...---.. -· ...._ ·-,.- -:--:"' ~ .--;- . ==-·.. 13 -:__-.:_-_...... ,. --·-·- -• -L-_._.___._...:...._ .___._ ...... -·--=-·--·- - --. -·--:... · -·--·-,...... _-· .. Figure 36. Pleasant Hill South section (E). 136 MEAN GRAIN SIZE IN PHI UNITS 5 6 7 -·-- -· :-. ~-=---B -·-·- ·------~· 13 _._-_1.=-:-_---- ~ .------·- . ~· -=- ~ ___fj5\ . -·--. ~ - .--.- 0 ·--·- -· .___ ~---=--. :::::. ___:__-_-_-_ ~ 1- ·-·--- ~ 5~ -= -=------:-- ~ u.. 15 ~----=-=--- -. . --:__---:=_:-=!_-@a -·---. - .. 23.1 FEET COVERED 22 Figure 37. Pleasant Hill South section (E) continued. 137 6. HAMBURG SECTION (f) Section is exposed on the north part of Hamburg, Illi nois; Sec. 35., T. 51 N., R. 2 E., Calhoun County, Illi- nois. Unit Thickness No. Description in Feet Chouteau Formation 1. Limestone, brownish buff, argillaceous, 15.0 dolomitic, 1/4 inch calcite geodes, fine grained; medium-bedded on bottom, thinner bedding toward top; knobby surface. Hannibal Formation 2. Unexposed. 53.0 3. Siltstone, yellowish gray, massive, ver- 2.0 micular, very calcareous, ferruginous; containing disseminated pyrite. 4. Unexposed. 15.0 5. Mudstone, silty, dark yellowish brown, 14.0 carbonaceous, very calcareous, friable. 6. Siltstone, grayish yellow green, massive, 1.0 slightly vermicular, very ferruginous, very calcareous; containing disseminated pyrite. 7. Mudstone, silty, greenish gray, friable, 35.0 slightly ferruginous. 8. Unexposed. 8.0 138 Unit Thickness No. Description in Feet Glen Park Formation 9. Limestone, silty, buff gray, oolitic. 2.0 139 MEAN GRAIN SIZE IN PHI UNITS 5 6 7 8 53 FEET 2 COVERED 0 15 FEET 4 COVERED --___,--- . --. - :--:J..: -.-~---- 10 5 6 7 . --:- ....::__ - ----.fll - ---.-'. ~ ------·--. . .. Figure 38. Hamburg section (F). 140 MEAN GRAIN SIZE IN PH I UNITS 5 6 7 8 9 T 1 -----·- -· ------.-.-- -.--·--- -- ~o ------·------.... . - w ---.------~5w -, ___ _ LL. ------.-- -.------·- ----·----- '-10 7 --__:_-=------. ------· ------1fl 0 -----___. ___ _ ~ ------.------~--- _....------.------.__..- -·------·--·------·------.------·-----.--- --.------.---·---. -----\----· 8 FEET 8 COVERED l 9 I l. I . I T ~~--J'L----L-.' ----~----~ r . · 1 . 1 · l · 1 · . 1· , Figure 39. Hamburg section (F) continued. 141 7. HANNIBAL CORE EAST (G) Core taken eleven miles northwest of Kirksville, Mis souri; Sec. 33, T. 64 N., R. 17 W., Adair County, Missouri. No samples taken. Unit Thickness No. Description Depth in Feet Chouteau Formation 1. Limestone, fine-grained, cri 800-819 19.0 noidal, with siliceous nodules, containing shale partings. Hannibal Formation 2. Mudstone, silty, greenish gray, 819-835 16.0 fissile; very silty on bottom; vermicular; calcareous stringers; pyritic. Louisiana Formation 3. Limestone, lithographic, cal 835-840 5.0 cite-filled geodes. Grassy Creek Formation 4. Mudstone, silty, dark gray 840-850 10.0 ish olive, carbonaceous. 142 800 - 2 ., "'- ~~ * :;) Figure 40. Hannibal Core East (G). 143 8. HANNIBAL CORE WEST (H) Core taken twelve miles northwest of Kirksville, Missouri; Sec. 32, T. 64 N., R. 17 W., Adair County, Mis- souri. Unit Thickness No. Description Depth in Feet Chouteau Formation 1. Limestone, fine-grained, cri- 850-856 6.0 noidal, siliceous nodules. Hannibal Formation 2. Claystone, silty, bluish gray 856-871 15.0 pyritic, vermicular, calcare- ous stringers, crumbly. Grassy Creek Formation 3. Claystone, dark gray to black, 871-881 10.0 carbonaceous. 144 MEAN GRAIN SIZE IN PHI UNITS 8 9 10 850--r-~~--~----~ . 2 u.. 856 --.--- -..:------.--0I -- --!..-- --. - .._ ----- NO RECOVERY 2 - . - - ·-----0 "- 2 ·--- --. ...__....._ ..J ----. Cl --- CD ------::-.., sci.- -z ·--- I - z ----- Cl -----·- X .- ·--·------· ------r-- ·-- ~ -.._.--- __ .__. - -·. - - ;---. ----G) ---.--·-.__, 3 NO RECOVERY 871 Figure 41. Hannibal Core West (H). APPENDIX B PERCENT OF SILT, CLAY, AND CARBONATE MATERIAL Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent percent percent percent percent percent A·l 0 37 22 6 35 6.7 A·2a 42 46 2 2 8 5.0 A·2c 22 60 5 1 12 5.0 A-4a 29 53 2 2 14 7.8 A-4b 25 55 6 1 13 3.0 A·6a 34 49 3 1 13 4.0 A·6b 22 64 8 4 2 A-7 20 44 22 4 10 A-Sa 49 35 3 0 13 22.0 A·Bb 49 34 2 2 13 23.8 32 1 2 9 A-10 56 12."7 5 1 16 A-12a 32 46 17.3 29 45 7 1 18 28.8 1-' A-12b +' lJ1 Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent percent percent percent percent percent A·15a 41 46 5 4 4 19.0 A·15b 49 34 10 3 4 23.5 A-16 31 1 43 12 13 • A-17 21 38 8 1 32 37.0 A-18 18 50 7 7 18 • A·19a 31 46 11 4 8 0.0 A·19b 20 55 8 4 13 3.1 A·21a 47 39 4 1 9 8.8 A·21b 43 44 4 0 9 0.0 A-23 48 33 5 1 13 7.7 A-24 18 33 17 12 20 • A-26 39 41 9 3 8 4.8 A-27 22 35 15 7 21 • A-28 40 32 2 1 25 39.0 B·l 47 30 4 4 15 1.0 Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent percent percent percent percent percent B-3a 25 55 8 4 8 0.0 B·3c 38 39 9 2 12 1.0 B·4a 18 36 21 4 21 8.0 B·5a 29 48 5 2 16 1.0 B-Sc 18 54 11 5 12 1.0 B-7a 36 45 7 1 11 1.0 B-7c 25 51 13 2 9 1.0 B-9a 39 43 4 4 10 0.0 B-9c 41 42 5 3 9 0.0 B-lla 47 37 5 3 8 0.0 B-llc 27 56 8 3 6 0.0 B-13 25 52 6 1 16 0.0 B·l5a 33 45 5 0 17 0.0 B-15c 22 65 1 0 12 0.0 B-16 19 l~9 12 4 16 15.0 ~ 45 7 0 17 +' BR18 31 0.0 '-J Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent percent percent percent . percent percent B·20a 26 52 7 5 10 B·20c 25 53 6 4 12 B-21 12 33 20 7 28 9.0 C·la 41 50 3 2 4 36.0 C-lb 15 57 13 4 11 1.0 C·3a 28 47 8 7 10 1.0 C-3b 28 50 5 1 16 35.0 C·Sa 15 47 9 2 27 C·Sb 30 45 9 2 14 C-7 17 54 10 7 12 C·Ba 37 41 6 6 10 4.0 e-Bb 25 57 4 1 13 4.6 e-lla 20 56 9 3 12 C-llb 25 52 8 3 12 54 12 3 C-13a 18 13 t-1 +' (X) Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent _ percent percent percent percent percent C·l3b 17 57 10 3 13 C-14 15 40 8 3 34 C·15 15 40 8 3 34 D·2a 45 50 1 3 1 D-2c 20 61 9 1 9 D·Sa 22 63 3 1 11 5.0 D-Sc 26 57 4 4 9 6.0 D-7 15 40 15 0 30 11.0 D-8a 33 48 6 2 11 4.6 D-8c 11 56 3 3 27 8.9 D-10a 72 15 5 1 7 4!6 D-lOc 26 56 4 6 8 6.1 D-12a 50 34 6 2 8 7.2 D-12c 38 44 6 1 11 38 24 6 q. 28 9.0 1-1 D-13 +' \0 Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate .No. percent percent percent percent percent percent D·14a 57 29 7 1 6 2.3 D·14b 48 39 1 3 9 3.1 D·16a 45 35 7 1 12 0.0 D·16c 47 38 4 5 6 2,9 D·17 15 53 5 4 23 14.0 D·18a 36 45 7 3 9 5.9 D·18b 32 55 8 2 3 6.1 E·2a 8 48 25 3 16 3.2 E·2b 16 50 14 5 16 1.9 E·5a 6 50 25 6 13 1.4 E·Sc 12 46 27 0 15 1.2 E·Ba 14 52 23 0 11 2.3 E-Bb 12 '•6 31 4 7 1.1 E·12a 26 57 9 3 5 1.5 55 6 2 E·12b 31 6 2.3 1-1 VI 0 Sample Coarse silt Medium silt Fine silt Very fine silt Clay Carbonate No. percent percent percent percent percent percent E-16a 55 25 11 2 7 1.0 E-16c 4 78 8 4 6 2.4 E-17 3 48 15 5 29 E-19a 4 61 16 5 14 37.77 E-19c 12 56 15 4 13 34.22 E-24 20 35 10 2 33 F-1 2 20 44 0 34 F-2 3 24 50 11 12 F-3 9 40 16 3 32 F-4 18 49 9 5 13 H·l 2 14 14 13 57 10.8 H-2 1 9 8 16 66 27.7 H-3 4 2 5 13 76 28.7 152 APPENDIX C GRAIN SIZE PARAMETER DATA Sample Mean Size Standard Deviation Skewness Kurtosis No. Mz (0) or SKI KG A-1 7.47 1.82 0.53 0.73 A-2a 5.33 0.90 0.42 2.21 A-2c 5.68 1.12 0.36 2.14 A-4a 5.68 1.64 0.56 3.42 A-4b 5.73 1.75 0.52 1.03 A-6a 5.33 1.20 0.38 2.62 A-6b 5.47 0.71 0.06 1.87 A-7 5.88 0.74 0.45 0.76 A-Sa 5.23 1.17 0.67 2.70 A-8b 5.14 1.18 0.82 2.77 A-10 5.18 0.95 0.60 2.23 A-12a 5.75 1.69 0.58 2.95 A-12b 6.17 4.00 0.69 1.25 A-15a 5.27 0.78 0.35 1.55 A-15b 5.23 0.76 0.59 1.45 A-16 6.12 1.82 0.47 1.30 A-17 9.88 3.53 0.86 1.24 A-18 6.22 1.54 0.50 1.19 A-19a 5.60 1.60 0.57 3.34 A-19b 5.82 1.52 0.51 3.21 A-21a 5.20 1.05 0.47 2.31 A-21b 5.28 0.95 0.44 2.00 153 Sample Mean Size Standard Deviation Skewness Kurtosis No. Mz (0) or SKI KG A-23 5.43 1.25 0 . 68 2.35 A-24 6.50 1.90 0.54 1.07 A-26 5.62 1.62 0.59 3 . 09 A-27 6.42 2.53 0.65 1.99 A-28 8.66 2.81 0.90 3.38 B-1 5.75 1.79 0. 70 2.91 B-3a 5.62 1.59 0.48 3.89 B-3c 5 . 60 1.52 0.52 2 . 52 B-4a 6.66 1.10 0.52 2.51 B-5a 5.88 1 . 83 0.62 3.20 B-5c 5.98 1.66 0.58 2.41 B-7a 5.48 1.57 0.54 3.21 B-7c 5.68 1.70 0.50 3.56 B-9a 5.53 1.07 0.39 2 . 53 B-9c 5.38 2.20 0.41 5.60 B-11a 5.25 1.03 0.33 2.09 B-11c 5.51 0.93 0.12 1.82 B-13 5.98 1.75 0.48 3.06 B-15a 6.60 4.10 0. 73 7.78 B-15c 5 . 03 1.23 -0.09 4.00 B-16 6.18 0.78 0.52 2.14 B-18 6.43 4.00 0 . 64 7.57 B-20a 5.71 2.04 0.42 4 . 24 B-20c 5.76 1.84 0.36 3.89 154 Sample Mean Size Standard Deviation Skewness Kurtosis No. Mz (0) o I SKI KG B-21 9.02 2.58 0.77 1.44 e-la 4.77 0.56 0.11 0.98 e-lb 6.56 1.74 0.32 2.19 e-3a 5.76 1.37 0.40 1.85 e-3b 6.43 3.97 0.71 7.95 e-5a 7.45 3.34 0.78 0.86 e-5b 5.71 1.29 0.38 3.83 e-7 5.98 1.43 0.47 1.84 e-Sa 5.71 1.31 0.42 2.01 e-Bb 5.63 1.44 0.31 3.18 e-lla 5.80 1.28 0.32 2.92 e-llb 5.80 1.52 0.30 2 . 80 e-13a 5.88 2.92 0.33 6.17 e-13b 5.90 3.37 0.30 7.79 e-14 8.93 2.50 0.64 1.30 e-15 8.58 2.41 0.83 1.32 D-2a 5.15 0.50 0 . 15 0 . 98 D-2c 5.60 1.57 0.48 3.81 D-5a 5.22 1.30 0.47 3.61 D-5c 5.52 1.10 0.43 2.43 D-7 6.72 0.87 0.71 1.20 D-8a 5.55 1.15 0.46 1.99 D-8c 6.63 1.83 0 . 70 0 . 84 155 Sample Mean Size Standard Deviation Skewness Kurtosis No. Mz (0) or SKI Kc D-lOa 5.12 8.73 0.62 2.53 D-lOc 5.70 1.72 0.55 3.80 D-12a 5.33 1.03 0.55 1.96 D-12c 5.55 1.50 0.54 3.24 D-13 7.35 1.72 0.78 1.24 D-14a 5.18 1.04 0.68 2.34 D-14b 5.30 0.98 0.39 2.33 D-16a 5.57 1.22 0.68 2.07 D-16c 5.32 1.14 0.58 2.08 D-17 7.52 1.68 0.79 2.81 D-18a 5.53 1.10 0.48 2.07 D-18b 5.40 0.61 0.11 1.13 E-2a 6.40 2.37 0.49 3.82 E-2b 6.21 1.98 0.48 2.50 E-5a 6.27 1.24 0.46 1.79 E-Sc 5.98 1.85 0.31 2.93 E-8a 5.91 1.10 0.20 1.72 E-8b 5.98 1.31 0.15 2.12 E-12a 5.47 0.78 0.17 1.52 E-12b 5.38 0.91 -0.01 1.88 E-16a 5.80 0.78 0.47 3.69 E-16c 5.40 1.20 0.63 1.87 E-17 7.10 1.18 0. 70 0.98 E-19a 6.37 2.05 0.64 3.86 156 Sample Mean Size Standard Deviation Skewness Kurtosis No. Mz (0) a I SKI KG E-19c 6.00 2.57 0.33 2.57 E-24 11.10 4.28 -1.74 1.07 F-1 6.61 0.44 0.30 0.90 F-2 5.80 1.95 0.36 3.38 F-3 8.82 2.45 0.79 1.62 F-4 6.65 2.51 0.61 6.35 H-1 9.10 3.11 0.22 0.84 H-2 9.21 2.35 -0.02 0.92 H-3 8.45 1.53 1.17 1.02 157 APPENDIX D QUANTITATIVE INTERPRETATION OF CLAY MINERALS Sample No. Illite Kaolinite Chlorite Vermiculite percent percent percent present A-1 71.0 29.0 0.0 A-7 56.0 44.0 0.0 A-16 55.0 45.0 0.0 A-27 83.0 15.0 2.0 A-18 76.0 24.0 0.0 A-20 53.0 47.0 0.0 B-2 71.1 27.6 1.3 B-4a 80.8 16.9 2.3 B-6 63.2 35.3 1.5 X B-10 62.7 36.5 0.8 B-16 66.0 33.0 1.0 B-19 65.4 32.0 2.6 B-21 64.6 34.6 0.8 C-9 96.2 3.8 0.0 C-12 89.6 5.2 5.2 X C-14 77.0 13.0 10.0 C-15 74.3 21.0 4.7 X D-7 89.5 3.5 7.0 D-13 84.6 14.0 1.4 158 Sample No. Illite Kaolinite Chlorite Vermiculite percent percent percent present D-17 54.5 43.0 2.5 E-1 81.3 17.6 1.1 X E-6 78.2 20.3 1.5 X E-ll 82.3 15.8 1.9 X E-13 86.3 12.5 1.2 X E-17 89.3 2.5 8.2 X E-18 65.5 30.2 4.3 E-24 67.9 30.6 1.5 F-3 80.4 14.9 4.7 X F-2 80.0 15.5 4.5 X F-1 80.9 15.9 3.2 X H-1 88.0 12.0 0.0 H-2 67.0 31.0 2.0 H-3 70.0 30.0 0.0