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A PEDOGENIC APPROACH TO THE CLASSIFICATION OF PALEOHISTOSOLS

Mary E. Faw

A Thesis

Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

May 2012

Committee:

James E. Evans, Advisor

Margaret Yacobucci

Jeff Snyder

© 2012

Mary Faw

All Rights Reserved

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ABSTRACT

James E. Evans, Advisor

This study assessed the transition between and the underlying siliciclastic sedimentary rocks, such as , , and mudstones. These underlying siliciclastic deposits are often referred to as underclays. These underclays often contain pedogenic features such as roots and . This study found that the underlying sedimentary deposits are cumulate profiles while the combination of the underlying and the overlying forms a polygenetic profile. The use of the terms cumulate and polygenic soil profiles, a form of presented by

Marriot and Wright (1993), is to emphasize the continuity of the soil transition from a soil (typically a protosol or ) to an organic soil () with intermediate phases and/or with partial overprinting of the underlying mineral soil.

This study develops a field-based classification scheme for paleosols, by recognizing that there was an alteration in the hydrogeologic regime changing the soil from one that received clastic to one that received little to no clastic sediment.

In this study, application of the soil profile models presented by Marriott and Wright

(1993), were modified to create four terms to describe : paleo-histosol, paleo- histogleysol, argillaceous paleo-histogleysol, and argilllaceous paleo-gleysol.

This classification system was tested by describing three coal seams, from the

Cretaceous and the of the San Juan

Basin, and the Pittsburgh Formation of the Appalachian Basin. It was

iv possible to evaluate the success of this system by being able to reclassify the deposits as paleosols, by finding no evidence of between successive paleosols or diagenetic changes, and by finding the environmental implications consistent with other data and studies of the same units.

In summary, this study determined that what has classically been described as

“coal-underclay” sequences are better understood as polygenetic histosol-histogleysol sequences. The advantages in this method are: (1) a recognition that the similarities represent the continuity of soil-forming processes at a given locality, and (2) a recognition that the primary environmental change is the reduction in siliciclastic sediment input at this locality, due to hydrologic change. It also appears that the development of were hydrologically necessary for the to establish themselves, develop and become preserved as a coal, unless the histosol formed from () that had been transported from its place of development.

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For Charles, who believed in me.

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ACKNOWLEDGMENTS

I would like to thank my committee members at Bowling Green State University,

Dr. J. Evans, Dr. J. Snyder, and Dr. P. Yacobucci, in their advisement and suggestions regarding this research. I would also like to thank Ohio’s Department of Natural

Resources for access to Brown’s Bog and allowing me to collect samples. And thanks to Carol Heckman at BGSU for allowing me use of the SEM laboratory.

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TABLE OF CONTENTS

Page

INTRODUCTION ...... 1

Soils and Paleosols…………………………………………………………………. 1

Coals Versus Paleohistosols………………………………………………………… 3

Potential Importance of Paleohistosols…………………………………………….. 3

Purpose of This Thesis……………………………………………………………… 4

GENERAL BACKGROUND ABOUT SOILS AND PALEOSOLS ...... 6

Soil Properties ...... 6

. Soil Composition ...... 6

Soil Textures ...... 6

Soil Structures ...... 6

Soil Horizons ...... 9

Soil Classification ...... 11

. Formation and Development of a Soil ...... 12

Paleosols ...... 14

Recognition of Paleosols...... 14

Paleosol Classification ...... 15

HISTOSOLS, PALEOHISTOSOLS, AND COALS ...... 16

Histosols ...... 16

Formation of Histosols ...... 16

Classification of Histosols ...... 19

Paleohistosols ...... 20 vii

Recognition of Paleohistosols …………………………………………….. 20

Formation of Peat …………………………………………………………. 20

Classification of Peat ……………………………………………………… 21

Coal ……………………………………………………………………………….. 21

Formation of Coals ……………………………………………………….. 21

Classification of Coal …………………………………………………….. 22

UNDERCLAYS ...... 24

Description and Recognition of Underclays ...... 24

Origin of Underclays...... 25

Classification of Underclays ...... 27

Underclays as Parts of Soil Sequences…………………………………… 28

GEOLOGIC BACKGROUND ...... 30

San Juan Basin of ...... 30

Menefee Formation, Mesaverde ………………………………… 31

Fruitland Formation ………………………………………………………. 32

Appalachian Basin of ...... 33

Pittsburgh Formation, Monongahela Group ...... 35

METHODS ...... 36

Outcrop Studies …………………………………………………………………… 36

Lithofacies Analysis...... 36

Pedofacies Analysis ...... 36

SEM Analysis …………………………………………………………………… 37

FIELD RECOGNITION OF PALEOSOLS ...... 39 viii

Brown’s Lake Bog ...... 38

Description of Cores ...... 38

Menefee Formation ...... 38

Descriptions of Coal and Underclays ...... 38

SEM and Petrographic Analysis ...... 41

Fruitland Formation ...... 43

Descriptions of Coals and Underclays ...... 43

SEM and Petrographic Analysis ...... 46

Pittsburgh Formation ...... 47

Descriptions of Coal and Underclays ...... 47

SEM and Petrographic Analysis ...... 48

DISCUSSION ...... 50

Paleosol Evaluation ...... 50

Environment of ...... 51

Menefee Formation ...... 51

Fruitland Formation ...... 52

Pittsburgh Formation ...... 52

Summary of Field Relationships ...... 53

Evidence for Pedogenic Origins of Underclays ...... 53

Underclay-Coal Sequences as Soil Sequences ...... 54

Proposed Field Classification of Underclay-Coal Sequences ...... 55

SUMMARY AND CONCLUSION ...... 56

Summary ...... 56 ix

Conclusion ...... 56

REFERENCES ...... 57

APPENDICES ...... 104

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LIST OF FIGURES/TABLES

Tables Page

1 Master Soil Horizons ...... 63

2 Subordinate Horizons of Significances to Science ...... 64

3 Coal Macerals and their Origin ...... 65

4 Coal Rank ...... 65

5 classification ...... 66

6 Pedo-facies classification as proposed by this study ...... 67

Figures Page

1 Triangle ...... 68

2 Soil Ped Classification ...... 69

3 Soil Orders ...... 70

4 Complex Soil Profiles ...... 71

5 Flow Chart for Paleohistosols ...... 72

6 Flow Chart for Paleogleysols ...... 72

7 Regional in Durango, Colorado ...... 73

8 Stratigraphic Correlation of the ...... 74

9 Stratigrapic Section of Monongahela Group ...... 75

10 Brown’s Lake Bog ...... 76

11 Sample Locations of Menefee Formation Stratigraphic Section ...... 77

12 Sample 06MF01 ...... 78

13 Sample 06MF02 ...... 79

14 Thin Section of 06MF02 from the Menefee Formation ...... 80 xi

15 Sample 06MF03 ...... 82

16 Sample 06MF04 ...... 83

17 Sample 06MF05 ...... 84

18 Sample 06MF06 ...... 85

19 Sample 06MF07 ...... 86

20 Sample Locations of Fruitland Formation Stratigraphic Section ...... 87

21 Sample 06MF08 ...... 88

22 Sample 06MF09 ...... 91

23 Sample Locations of Pittsburgh Formation Stratigraphic Section ...... 92

24 Thin Section of I7900306 from the Pittsburgh Formation ...... 93

25 Sample I7900406 ...... 94

26 Sample I7900506 ...... 95

27 Sample I7900602 ...... 96

28 Sample I7900706 ...... 97

29 Proposed Soil Profiles of Menefee Formation ...... 98

30 Pedogenic Results for the Menefee Formation ...... 99

31 Proposed Soil Profiles of Fruitland Formation ...... 100

32 Pedogenic Results for the Fruitland Formation ...... 101

33 Proposed Soil Profiles of Pittsburgh Formation ...... 102

34 Pedogenic Results for the Pittsburgh Formation ...... 103

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CHAPTER 1: INTRODUCTION

Soils and Paleosols

Fossil soils are called paleosols (Mack et al., 1993; Marriott & Wright, 1993;

Retallack, 1988, 1993), and have been widely studied (Gardner et al., 1988; Hughes et al., 1992; Mack et al., 1993; Marriott & Wright, 1993; Retallack, 1988, 1993). Despite the value of paleosol deposits in providing information on paleoclimate, , tectonic rates, , and , there is still a major disconnect between the classification of modern and ancient soils. The classification system used for modern soils in the U.S. ( Staff, 2010) recognizes 13 major soil orders (e.g. , spodosols, , etc.). The classification system is based on a variety of criteria that simply can not be obtained from the ancient record, such as annual precipitation, soil pH, mean annual temperature, or characteristics of the . As a consequence, Mack et al. (1993) proposed a classification system for paleosols that used some of the modern soil orders, combined others, and created several new ones, to establish nine paleosol orders. However, Mack et al. (1993) did not attempt to reclassify histosols (modern histic soils and ancient examples of histosols, which include peat, lignite, and coal). The criteria used to subdivide modern histosols are based on modern vegetation types and , and would be difficult to apply to the ancient record. In addition, the commonly used classification of coals is based on coal rank, which is based on , and has no relationship to depositional environment or paleoclimate. 2

In addition, the definitions used for suborders of organic soils (e.g., histosols) are difficult to apply to paleosols, depending on factors such as annual precipitation and annual temperature, and climate data not generally available from the ancient record.

Finally, as noted by Mack et al. (1993), classifications based on the thickness of organic soils horizons cannot be readily be used in paleosols because of the difficulty in accurately and consistently calculating the precompaction thickness of coals, though it may be possible to do corrections based on the in the surrounding clastic rocks. This paper will term ancient histosols, which have been traditionally termed as peat, lignite, or coals, as paleohistosols. In other words, paleohistosols are the protoliths of what turned into , lignites, or coals as a consequence of burial diagenesis. In addition the organic-rich mineral soils that underlie paleohistosols, that have previously been called underclays, will be described in this paper, as other types of paleosols, such as paleogleysols, to emphasize their pedogenic origin.

The goal with this study is to show how various depositional systems affect the formation of paleohistosols and their associated deposits (e.g., underclays), and how this information can be used to classify paleohistosols into a system suitable for field work applications. This approach is based on the understanding that underclays are mineral soils that formed in a dynamic environment that mixed clastic sediment and organic matter accumulation. Over time, the organic matter component increased relative to the clastic sediment input, leading to the formation of histosols. This indicates that the transition from underclays to histosols (and possibly to peats) is hydrological in character, representing increasing isolation from clastic sediment sources.

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Coals Versus Paleohistosols

The term coal has primarily an economic use and does little to describe the type of depositional environment, or the development of the soil. The term paleohistosols is used in this context to help bridge that conceptual gap. In other words, the term paleohistosols is used to describe the protolith of macerals that later became peat, lignite, or coals. This use is consistent with recognizing the role of underlying parent materials or related materials in a soil sequence.

This concept is not universally applicable, because there are also some cases where peats and coals are clastic accumulations, unrelated to the underlying sediments.

These instances may indicate a period of ; for example in 2005 Hurricane Katrina ripped up coastal peats and redeposited them elsewhere. However, very few peats, lignites, or coals in the have accumulated from rafted debris

(Wagner & Pfefferkorn, 1997; Retallack, 2001), and these organic deposits are best understood as allochthonous organic matter accumulations.

Potential Importance of Paleohistosols

Underclays are sediments or sedimentary rocks found at the of many coal seams, typically coal seams associated with cyclic (Rahmani & Flores,

1984). Because underclays are found at the base of many coal seams, they are economically important and can often be followed laterally to find the adjacent coal seam. This could result in finding deposits of coal where surface exposures are 4 unavailable. So they are important to (1) understand the environmental association of different deposits (peat, lignite, coal and underclays), (2) understand the mode of origin of deposits, and (3) extract information about environmental change (hydrologic conditions). For these reasons paleohistosols, peats, lignites, coals, and their related materials, such as underclays, are important as environmental indicators. For example, the presence of peat, lignites or coal might indicate conditions about, or changes, in and . This information could be very useful in comparing modern day depositional environments to past depositional environments, for example, in characterizing the pedogenic role of climate. In addition, this could potentially contribute to studies of climate change.

Purpose of This Thesis

This study focuses on reclassifying peats, lignites, or coals as types of paleosols

(e.g. paleohistosols), applying pedogenic concepts to evaluating field occurrences of these organic deposits and related deposits, and extracting environmental information from paleohistosol sequences. Specifically, this study explored three alternative hypotheses for the origin of underclay. The first hypothesis is that underclays are not related to the formation of certain coals. The second hypothesis is that underclays are not primary features, but have been formed by diagenesis related to coalification (i.e., the process of coal formation). The third hypothesis is that underclays and coals formed as a pedogenic sequence, in other words, underclays represent genetically-related precursors to coal development. 5

This study used field evidence to show that in many instances the third hypothesis, which states that underclays and coals are pedogenic sequences, is correct. In this study, three separate coal seams that formed under different depositional systems were evaluated for evidence indicating soil-forming processes on the macro-scale and micro-scale. If indications of soil-forming processes were found, then the sequences were re-classified using a modified classification system to be one of the 10 complex soil types proposed by Marriott and Wright (1993), as discussed in the following section. The study then evaluated the usefulness of the pedogenic concept in environmental analysis.

The deposits are reclassified as paleosols by identifying the soil features in the deposits, and because there is no evidence for unconformities between successive paleosols or diagenic changes, they most likely represent a paleosols sequence. Also, other data and studies of the same units supported that the environmental implications were consistent with the studies findings.

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CHAPTER 2: GENERAL BACKGROUND ABOUT SOILS AND PALEOSOLS

Soil Properties

Modern soils are classified according to properties such as composition, color, texture, horizon thickness, and soil structures (Mack et al., 1993). These will be considered in turn.

Soil Composition.

Soils are composed of mineral matter, organic matter (in various stages of decay), organisms, water, and gases (within pores). The common in a soil can include , feldspar, and mica, and minerals such as kaolinite, chlorite, smectite, and vermiculite (Schaetzl & Anderson, 2005). Important accessory minerals include hematite, goethite, , and . Typically soils are ~45% mineral constituents and ~5% organic matter, with ~50% bulk porosity (filled by fluids or air).

Soil Textures.

Soil texture is defined by the percentage of , , and clay found in each soil.

The percentage of each determines the soil textural classification. For example, a soil can be considered as a sandy , sandy clay, silty clay, or silty clay loam (Fig. 1). Soil texture is important, because it can determine the porosity and permeability of the soil, and determine hydrological properties such as field capacity and wilting point, which determines what kind of may grow in certain soils.

Soil Structures.

Soil structures are features that develop from grain aggregates (peds). All soils have structures that develop to varying degrees. From a geological standpoint, these 7 structures can range from massive to laminated, can include vugs, voids, fractures, joints, and slickensides, and can be laterally and vertically discontinuous, with veins, mottling, or nodules. Soil structures can be modified or destroyed in the depositional environments

(such as loss of nodules by wetting and drying cycles) or can be lost due to compaction or diagenesis (Retallack, 2001).

Modern soils are typically highly porous and may contain systems of open cracks and vugs or voids. Porosity features can include an interconnected network of pores

(packing voids), small irregularly shaped pockets (vugs), or near-spherical holes

(vesicles). These are often absent from paleosols because they were destroyed through compaction, but sometimes indications of the former pores are preserved due to infilling by translocated clays or iron-oxide minerals (sesquioxides) or crystals of later cements.

In addition, paleosols can contain original or modified soil structures such as peds, , glaebules, and pedotubules. (Retallack, 2001)

Crystals sometimes form in certain kinds of soils or paleosols, particularly alkaline and salty soils. The crystals can be found filling in cracks and cavities of the soil, such as root channels, but the presence of crystals are not diagnostic features of a soil (Retallack, 2001).

Peds (Fig. 2) are soil aggregates that can be found between cracks and other soil openings, are reflective of the type of soil present and the type of environment they form in, and form according to the arrangement of the primary soil particles (Retallack, 2001;

Schaetzl & Anderson, 2005). They are a modern soil feature that can be preserved in a paleosol. They are classified based on their size, angularity, and shape. Peds can be classified as platy, prismatic, columnar, angular blocky, subangular blocky, granular, or 8 crumb (Fig. 2). Compaction and alteration can make peds hard to identify in paleosols, however certain peds are more likely to be preserved, such as platy and columnar peds

(Retallack, 2001).

Cutans are features that form on the surface of peds, clasts, or crystals, and these can be useful in interpreting and classifying paleosols. The various terms used for cutans describe their composition and end with ‘-an’, such as argillan (clay composition), ferran

(iron composition), and silan (silica composition). There are also subcutanic features, such as neocutans (which are thick cutans that lose intensity with distance from the surface) and quasicutans (which are related to the surface, but do not form at the surface, such as halo clod skins). Cutans originate in one of three ways: there are illuviation cutans which form from materials being translocated downward in a soil profile, diffusion cutans which are formed by a progressive alteration of the soil downwards from the surface, and stress cutans which are formed by differential forces in the soil

(Retallack, 2001).

Glaebules are formed from the same materials as cutans, and are distinguished from cutans as being naturally segregated lumps of the soil material. Common examples are nodules and . Nodules are massive internally due to continuous growth, while concretions have concentric layers, due to discontinuous or perhaps seasonal growth. Glaebules can be found in soils and paleosols, but they also can be found in other environments such as in cooling volcanic tuffs, on floors, in shallow , and around springs (Retallack, 2001).

Pedotubules are a term to classify all tubular features found in soils and paleosols.

Burrows can be valuable indicators of the paleoenvironment, but care needs to be taken 9 when interpreting them because the burrows found in marine or lacustrine environments can often look similar (Retallack, 2001).

Soil Horizons.

Soil horizons are horizontal layers that represent the locus of physical, chemical, and biological processes. Soil horizons are distinguished from each other by changes to the from additions, losses, transfers and transformations of the material

(Soil Survey Staff, 2010). Commonly, soil horizons are divided into subordinate sub- horizons (Sprecher, 2001). The complete set of soil horizons includes the O-horizon, A- horizon, E-horizon, B-horizon, K-horizon, C-horizon, and R-Horizon. (Mack et al.,

1993; Retallack, 1988; Richardson & Vepraskas, 2001; Richardson et al., 2001; Singer &

Munns, 1999; Sprecher, 2001; Winegardner, 1995). These horizons are explained below and in Table 1.

The O-horizon is a surface layer dominated by undecomposed or partly decomposed organic material. The O-horizon can also contain mineral matter, such as alluvial sediment or dust input. The O-horizon can be saturated with water for extended periods of time (Soil Survery Staff, 2010).

The A-horizon is an organic-rich mineral layer that forms at or near the surface of the soil, or below the O-horizon. The mineral composition of the A-horizon shows a breakdown of the original parent material and an accumulation of and decomposed organic material mixed with the minerals. The A-horizon is not dominated by the organic matter. The A-horizon may show some transitional characteristics of the

E-horizon, but is not dominated by those characteristics (Soil Survey Staff, 2010). The

A-horizon is typically darker than the other layers, may contain roots, and is typically 10 more friable or crumbly then the lower horizons (Sprecher, 2001). The A-horizon commonly contains granular or crumb peds.

The E-horizon is found beneath the A-horizon and shows eluviation (or ) of one or more of the following: dissolved , clay minerals, iron sesquioxides, and aluminum oxides (Soil Survey Staff, 2010). The loss of these materials typically results in the modification to obliteration of much of the original structure (Soil Survey

Staff, 2010). The E-horizon may contain reddish mottles due to variations in conditions (Sprecher, 2001). The E-horizon will commonly have granular and crumb peds.

The B-horizon forms below the O, A, or E-horizons and shows illuviation, a concentration of the translocated clay minerals or iron sesquioxides leached from the overlying horizons. Thus the B-horizon can show a concentration of clay minerals, iron sesquioxides, or aluminum oxides. It may feature platy, blocky, or prismatic ped- structures, or it may show brittleness or strong gleying (Soil Survey Staff, 2010). This horizon is usually red, orange, or brown due to the concentration of sequisoxides; however under waterlogged conditions the B-horizon will be grey due to reduction and removal of the iron pigmenting minerals. The accumulation of clay can allow for water to perch in and above the clay horizon, which can be important in the formation of hydric soils, but does not always lead to their formation (Sprecher, 2001).

The K-horizon can form in the subsurface, in arid regions, where dissolved salts precipitate. The K-horizon can be dominated by an accumulation of precipitated carbonate (calcrete or ), silica (silcrete), or (gypcrete). (Soil Survey Staff,

2010) 11

The C-horizon is the parent material and has a gradational upper contact into the soil, lacks the properties of the O, A, E, or B horizons, and is thought to be the parent material from which the soil originally formed (Reallack, 1988; Soil Survey Staff, 2010).

The R-horizon is a special case of C-horizon when the parent material is consolidated and unweathered (Retallack, 1988). Many soil scientists do not distinguish between the C-horizon and the R-horizon.

Soil Classification.

The USDA Soil classification system (Soil Survey Staff, 2010) is a hierarchical of six levels which include (in descending order): order, suborder, great group, subgroup, family, and series. The classification of soil orders describe the major soil forming processes. The suborders contain information on the hydrologic regime, soil composition, and precipitation. The Great Groups evaluate diagnostic layers, or the base status of layers, or horizon expression, and characteristics of ground water ponding. The subgroups evaluate local regime. The families evaluate local variability in mineralogy, texture, soil temperature, and soil pH. Each is based on local features such as the slope, surface water flooding, and surface texture and series are named for local geographic features (Sprecher, 2001).

The most important criteria used in soil classification are the superposition, composition, and thickness of diagnostic soil horizons (Fig. 3). For example, histosols typically have thick O-horizons, and are underlain by minor to non-existent A, E and B horizons overlying the C-horizons. In contrast spodosols typically have a bleached layer with an accumulation of iron and/or aluminum minerals in the spodic layer (O-horizon), 12 quartz and feldspar clays enrich the A and B-horizons, and clay silicates are found in the

C-horizon. (Retallack, 2001; Soil Survey Staff, 2010).

Formation and Development of a Soil.

Ultimately, the formation of any soil is determined by the five soil forming factors, which are organisms, topography, climate, parent material, and time (Jenny,

1941; Richardson et al., 2001). These factors operate in any given soil through four soil- forming processes which are additions, deletions, transformations, and translocations of materials, such as organic matter, dissolved ions, and minerals (Richardson et al., 2001).

Soil development refers to progressive changes in a soil over time. Assuming there are not major changes in the five soil forming factors (above), a soil should show stronger horizon development over time. The best developed soils form when the accumulation rate of organic matter, dissolved ions, and minerals is positive but not too high. A soil has a lower chance of developing if the sediment accumulation rate is greater than the rate of soil formation (Leeder, 1975; Marriot & Wright, 1993).

Significant, short-term can disrupt the soil-forming process, after which the soil may or may not continue to form if the increment of deposition is significant.

Marriott and Wright (1993) presented profiles for paleosols that formed under these complex conditions (Fig. 4). These profiles have been divided into 10 types of soil complexes: cumulate soils, composite sets, compound sets, composite truncated sets, compound truncated sets, cumulate truncated sets, reformed profiles, polygenetic soils, truncated polygenetic soils, or increased maturity sets.

For example, environments with slow but continuous soil development, such as many , might produce cumulate soil profiles. In wetlands, these types of soils 13 would represent conditions where vegetation would be quickly reestablished on top of any incremental deposit of mineral sediment (such as clastic sediments from a layer). In the geologic record, after burial, compaction, and diagenesis, such a soil would be represented as a peat, lignite, or coal with features such as interbedded organic-rich clays (carbonaceous ), and non-organic-rich clays (shales), in addition to preserved primary structures and features such as root structures. In other words, in this example, mineral sediment deposition would not significantly inhibit continued organic (wetland) soil formation. Organic matter derived from vegetation should accumulate and form an organic horizon during these periods of slower sedimentation.

Continuing this example, if environmental conditions were to change, possibly as a significant hydrologic change such as a change in the groundwater table position, but no erosion or clastic deposition occurred, and then a polygenetic soil would develop.

Schaetzl and Anderson (2005) state that any major environmental change, whether internal or external, can result in a polygenetic soil. However, if the change is not easily detectable, that the soil might be misclassified as monogenetic. An example of a polygenetic soil in the geologic record might be the transition from organic claystones

(underclays) to coals, representing a decrease in mineral sedimentation on the soil surface and an increase in the organic matter accumulation.

Continuing this example further, suppose in some areas infrequent but major flooding events deposit a thick clastic sediment layer on a surface which interrupts soil development. If a new soil forms above this sediment layer, the resulting set of soils would be classified as either a composite set or a compound set. A composite set forms when the two different soil profiles overlap vertically (the soil profile from the upper soil 14 is superimposed on at least part of the soil profile of the lower soil), and a compound set forms when the two soil profiles do not overlap, or are completely separated (Marriott &

Wright, 1993). Both of these situations can create identification problems. In the one case, because typical soil-forming processes might result in features such as easily identifiable soil horizons, but earlier soil profiles can be modified in composite soils. In the other case, compound sets might be interpreted as two unrelated sorts. Finally, water- logged environments have soil horizons that are more difficult to recognize because leaching has little time to develop before more sediments accumulate.

Paleosols

Recognition of Paleosols.

Paleosols are ancient soils. Typically, these older soils are found beneath the modern zone of and soil formation, but in some cases paleosols can be exhumed by modern erosion. A paleosol can be lithified or unlithified (e.g., a buried soil). Buried soils are soils that have been covered by sediment such as alluvial material, and are no longer part of the active soil forming process, but any part of the soil that is exhumed will be affected by the modern soil forming processes. Paleosols can also be superimposed (i.e., composite, compound, or polygenetic soils), meaning that one soil profile might have established itself on top of another soil profile. If soils have been superimposed, it might be possible to interpret which portions of the soil profile can be separated, in order to distinguish their features from one another. In general, paleosols can be recognized by changes in composition or texture, presence of soil horizons, and presence of soil structures (Boggs, 2001; Schaetzl & Anderson, 2005; Retallack, 1988). 15

Paleosol Classification

There are numerous difficulties in recognizing and classifying paleosols. First, one complication for paleosol classification is that typically the upper part of a paleosol has been eroded. Second, there might be poor development of soil horizons due to incremental sediment accumulation, , or relict features from the parent material (Retallack, 1988). For example, some lowland soils may have experienced high rates of sediment accumulation during soil development, which interrupted the gradation of soil horizons that are seen in mature soils. Other soils contain relict beds from the parent sedimentary material, such as sand with , that haven’t been fully incorporated into the soil or destroyed by bioturbation. Third, there are many situations where paleosols are hard to recognize because of erosion of the top of one soil and subsequent deposition of sediment and formation of a new soil on top (Fig. 4) (Retallack,

1988).

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CHAPTER 3: HISTOSOLS, PALEOHISTOSOLS, AND COALS

Histosols

Formation of Histosols.

Histosols are organic-rich soils, typically having a thick O-horizon. The O- horizon develops in many soils, however in most cases other types of soils do not accumulate a significant amount of humus material, and the O-horizons are typically relatively thin in comparison. The development of a thick O-horizon is due to humification, which are the processes involved in the breakdown of the organic litter that accumulates on the soil surface. In most soils, the accumulation and breakdown of the litter is typically in equilibrium or close to it, resulting in minimal organic matter accumulation. If the humification is rapid, such as in a warm moist climate, then the O- horizon will be thin, in other words either humic materials are broken down, and lost at the soil surface, or else they are translocated into the sediments below. In contrast, if the rate of organic material accumulation is larger then the rate of humification, thicker O- horizons will form. Thus the factors that favor the formation of histosols include lower rates of , cooler temperatures, wetter environments, and/or a lack of in the soil itself, which is usually due to water-logged conditions (Schaetzl &

Anderson, 2005).

The criteria used for the recognition of modern histosols are still not fully agreed upon by researchers. There is general agreement that histosols contain significant amounts of organic matter, but consensus is lacking about the necessary average organic matter content, O-horizon layer thickness, or duration of water saturation for the resulting soil to be classified as a histosol. For example, Singer & Munns (1999) state that 17 histosols are understood to be a type of soil that is composed of at least 20 percent organic if it isn’t saturated for more than a few days, or at least 20 percent organic carbon in over half of their soil profile thicknesses. However, according to Richardson &

Vepraskas (2001) histosols must contain more than 12-18% organic carbon in at least two-thirds of the thickness above bedrock or mineral soil layers, be less than 10 cm thick, or be saturated for most of the , and that over half of the upper 80 cm of soil needs to be organic material. If a soil has a layer of organic material less than the required average amounts or O-horizon layer thickness, it called a histic epipedon in a non-histosol

(Richardson & Vepraskas, 2001).

In addition, histosols can be described as a type of that forms in environments that are saturated with water during most of the vegetative growing season

(Richardson & Vepraskas, 2001). According to this comment, histosol formation can only occur in aqueous environments where the water is of a certain depth, there is isolation from mineral sediment sources, and/or water body salinity is not too high

(Wanless et al., 1969). In terms of climate, suitable environments can range from subarctic marshes to wetlands in tropical . Geologically, the most significant peat or coal-accumulating environments include , alluvial , delta plains, and other coastal areas (Donaldson, 1974; Warwick, 2005). Overall, the greatest thickness of peat or coal accumulation would be in actively subsiding deltas or in environments experiencing a slow rise in (Donaldson, 1974).

Coastal environments of interest might include five types of tidal wetlands that are major organic-accumulating environments: estuarine marsh, submerging coastal marsh, submerged upland marsh, emerging coastal marsh, and the floating marsh 18

(Richardson & Vepraskas, 2001). In this study, all of these are potential locations for histosol formation. These tidal wetland settings are important because understanding these depositional environments will produce some of the most important paleo-histosol deposits, and produce the maximum thicknesses of coals. Estuarine marshes, which form in river-influenced tidal areas, may form lenses of organic matter if there are extended periods of time where mineral deposition is low. Submerging coastal marshes form behind barrier islands within a protected lagoonal setting. Plants growing in this area provide the organic material and will trap tidal sediments. Sandy lenses are possible, and finer-grained and sand lenses may occur on the landward side. Submerged upland marshes are due to a slow and continuous rise in sea level in a setting where the soils were once -drained off of a gentle slope. This allows for the accumulation of organic matter at a rate similar or equal to . The O horizon in this setting is thinnest towards the coast and thickens towards the sea. Emerging coastal marshes are less common and can be found in tectonically active regions in which case the organic soils formed at sea level are lifted above sea level. Floating marshes do not commonly occur in tidal setting, but when they do, the organic material floats on top of the water due to trapped air and its low density. (Richardson & Vepraskas, 2001; Tucker, 2001)

Three general types of organic matter are known to accumulate as histosols, which are humus, peat and sapropel (Tucker, 2001). Humus is uniform organic matter, with no shape or structure. Peat, which is the organic deposit that is known to produce coal, consists of a dense mass of plant debris that is not particular to any latitude that is prevented from full decomposition due to acidic and anaerobic conditions. At higher latitudes, lower temperatures decrease the effect of decomposition by bacteria, which will 19 increase the preservation potential of organic matter, creating the most favorable conditions for peat formation (Tucker, 2001). In addition to lower temperatures, organic matter preservation is enhanced in because most of the bacteria that degrades organic matter is found in oxygen-rich subaerial and many subaqueous environments (Tucker, 2001). Anoxic environments can also be produced under such conditions as stratified lakes and marine basins, leading to the production of sapropel

(Tucker, 2001). While sapropels are associated with anoxic conditions, they do not lead to the formation of histosols, for obvious reasons. In summary, accumulations of organic matter known to form histosols and peats (and after burial and alteration, forming lignites and coals) include high rates of organic matter productions, cooler temperatures, and anoxic conditions produced by water saturated soil conditions. (Tucker, 2001)

Classification of Histosols.

Organic soils are classified as the order Histosol. Histosols are subdivided into five suborders, based on the degree of the decomposition of the organic matter and the degree of water saturation. The five orders are folists, fibrists, hemists, saprists, and wassists (Collins & Kuehl, 2001; Singer & Munns, 1999; Soil Survey Staff, 2010). The fibrists, hemists and saprists are categorized by the degree of organic decomposition, the fibrists having the least and the saprists having the most (Singer & Munns, 1999, Soil

Survey Staff, 2010). The folists represent the organic soils that are saturated with water for only a few days at a time after a heavy rain (Singer & Munns, 1999, Soil Survey

Staff, 2010). Wassists have positive (saturated) for more than 21 hours of each day of the year (Soil Survey Staff, 2010). Paton (1978) revised this classification, by stating that fibrists are composed of more than 2/3 of fibers, hemists contain 1/3 – 2/3 20 fibers, and saprists contain less than 1/3 fibers. Paton (1977) also pointed out that folists occur only in cold or very humid environments.

Paleohistosols

Recognition of Paleohistosols.

A paleosol created from a histsol is called a paleohistosol. In the geological record, the preservation of a paleohistosol can create an economic organic-rich deposit, such as peat, lignite or coal. Problems with preservation and recognition of paleohistosols in the geologic record can include erosion, compaction, weathering

(especially oxidation), or diagenesis. This paper will refer to deposits as paleohistosols

(rather than as peat, lignites or coal) to emphasize their pedogenic origin.

Often found underlying paleohistosols are organic-rich mineral soils called

“underclays.” This will be discussed in more detail later. Considered as soils, it would be more correct to call these deposits as mineral soils such as , , or gleysols (Gardner et al., 1988; Retallack, 2001)

Formation of Peat

Peats are one type of economically valuable deposits developed from paleohistosols. For peat to be preserved in the geologic record, it would need to form under conditions that would allow it to be buried and to not be eroded significantly.

Some conditions would be an area with subsidence, or sea level rise, for instance, would favor peat preservation. The formation of peat is favored by vegetated sites that are isolated from clastic deposition. Climate influences the distribution of vegetation, which in turn influences the composition and distribution of peat (Pashin, 1998). While peats 21 have been found in virtually any climate zone, it is not always clear whether those peats formed in that climate zone or whether they have been merely become exhumed and exposed there.

Classification of Peat

Historically, peats have been classified based on composition. There are two general types of peats that area produced in anoxic environments that are understood to form coals. The first are moorland peats, which are generally composed of remnants of , sedges, rushes and sphagnum (Tucker, 2001). The second are fen peats, which are composed of remnants of branches and leaves. Of the two types, fen peats are recognized as one of the major precursors of coal deposits (Tucker, 2001). Warwick

(2005) proposed an alternate means of categorizing the peat-forming environments, by categorizing them as Type-A and Type-B paleo-peat deposits. Type-A paleo-peats formed in ever-wet tropical environments that were fed by -poor precipitation, and tend to be topographically domed. Their deposits are also low in clastic content.

Type-B paleo-peats formed in more seasonal tropical environments where they obtained most of their moisture from ground and surface waters that were relatively enriched in nutrient content, and tended to be planar in their topographic expression. These deposits tend to be higher in clastic content.

Coals

Formation of Coals

Bates & Jackson (1984) state that coals are organic rocks that consist of carbonaceous material that is greater than 50% by weight and greater than 70% by 22 volume. For this paper, coals are the diagenetic result of lithified buried soils (paleosols), or, in other words, the protolith of a coal was a paleohistosol (Fig. 5).

The constituents of coals are macerals (Table 3), which represent both different original materials and show the effect of differential preservational modes of plant fragments. The major families of macerals are vitrinites (macerals that originated from wood tissue), inertinites (consist of altered woody tissues such as charcoal), and liptinites

(composed of variable amounts of algae, spores, cutins, and resins). Any individual coal is a combination of different types of maceral families. These combinations are classified as lithotypes or microlithotypes.

One complication in interpreting paleohistosols from coals is the effects of about

90% compaction on the original soil textures and fabrics (Scott, 2002). For example,

Cohen & Stack (1996) conducted a study of in Panama, and found that a peat bed 840 cm thick, which contained up to 16 vegetation assemblages, would form a coal seam less than a meter thick. The amount of compaction and the diagenesis of coals make it difficult to interpret their origin; however classification of macerals and maceral groups provide insights into the original organic materials (Tucker, 2001).

Classification of Coal

In the field, coal deposits are classified according to the reflectivity (brightness) of the coal, such that a shiny coal is rich in vitrain and a dull coal is rich in durain

(Galloway & Hobday, 1996; McCabe, 1984). The vitrain and durain contents are unrelated to peat accumulation (the original materials) but are related to subsequent compaction and diagenesis. A common economic classification of coals is based on coal rank (Table 4), creating definitions for peat, lignite, , and anthracite coal, 23 based on the percentage of vitrinite reflectance (Scott, 2002). Coals become more reflective as burial temperatures increase. The diagenetic effects of increased temperature and increased pressure are relative increases in carbon content due to decreases in water, nitrogen and other volatile materials (Retallack, 2001).

This study uses the term paleohistosols instead of the peat, lignite, and coal, because these economic terms aren’t adequate for classifying the deposits from the perspective of a soil sequence (Fig. 6). Many of the difficulties in classifying paleohistosols accurately are due to pre-burial erosion and weathering, compaction, and diagenesis, in contrast peat, lignite, and coal are the products of these processes.

24

CHAPTER 4: UNDERCLAYS

Description and Recognition of Underclays

Underclays (also called seatearths or seatrocks) are the clays or shales that are found at the base of many coal deposits, and are noted to be a part of the cyclic sedimentation known as cyclothems (Rahmani & Flores, 1984). One interpretation of underclays is the sediments that form the underclays change upwards into an organic-rich mineral paleosol (that episodically receives increments of inorganic sedimentation), as a consequence of the underclay sediments becoming colonized by vegetation.

Many coal have noted the presence of underclays at the base of most, if not all, coal beds. While some argue that underclays are not related to the superposed coal seams (next section), others suggest that underclays indicate a pedogenic transition from a mineral soil to an organic soil (coal deposit), because underclays are so closely linked with coals that they can be relied on to predict where coal seams are located

(Anderson, 1964; Davies-Vollum, 1999; Logan, 1842; Rimmer & Eberl, 1982; Wilson,

1965). By this reasoning, underclays formed as autochthonous features that were precursors to the formation of coal, and thus the underclay-coal sequence may be viewed as a pedogenic sequence. However, McCabe (1984) believes that although underclays form prior to the formation of a coal, they should not be used as part of the environmental interpretation of the coal essentially because the transition from underclay to coal indicates an environmental change. One insight to resolve this controversy is that underclays may also contain pedogenic slickenslides, which are formed in clay-rich soils due to wetting and drying (Driese et al., 2003). This would imply that the underclays 25 originally formed as . Vertisols are high shrink/swell soils that form when water pools long enough for anaerobic bacteria to deplete the waters of oxygen (Richardson &

Vepraskas, 2001; Driese, et al., 2003). As stated earlier, anoxic environments are also conducive to organic accumulation due to slower rates of decomposition. This implies that the underclay and the overlying coal represent similar environmental setting.

An example of an underclay is the Pennsylvanian Nodaway Underclay in

Kansas, which was described by McMillan (1956) as a plastic, typically ash-gray clay containing plant fragments, rare slickenslides and iron-rich concretions. The Nodaway

Underclay forms a series of thin discontinuous beds under the coal seam. The contact between the underclay and the coal is typically sharp but occasionally can be gradational, especially where the coal consists of carbonized impressions of plant fragments, or resembles more of a carbonaceous mudstone.

In this study underclays show features of buried soils, or lithified buried soils or paleosols. Viewed as buried soils, they can be compared to modern soils found in wetland environments, such as entisols, inceptisols, or gleysols. Viewed as paleosols, they can be classified as paleoentisols, paleoinceptisols, or paleogleysols (Fig 6).

Origin of Underclays

There has been much debate over whether underclays are allochthonous or autochthonous. Allochthonous models consider that the mineral content of the underclay is inherited from outside the depositional environment (Grimm & Allen, 1938;

Schultz, 1958), while the autochthonous models consider that both the minerals and the coal formed in place by pedogenesis (Gardner et al., 1988). 26

As previously discussed, histosols typically form in , marshes, and other such environments characterized by waterlogged conditions. Lack of evidence of mineral alteration or uniformity in mineral orientation in the underclays supports the argument that the underclays were also waterlogged (Grim & Allen, 1938) and thus saturated surface conditions existed prior to histosol formation as well as during histosol formation

(Gardner et al., 1988). Sprecher (2001) noted that -rich layers have an important role in the formation of hydric soils because they are impermeable and allow for saturated sediment conditions or surface water ponding, leading to reducing conditions that favor the preservation of organic matter. Reducing conditions and leached organic would be expected to cause mineral alteration in underclays.

Many authors (Gardner et al., 1988; Huddle and Patterson, 1961; Hughes et al.,

1992; Patterson and Hosterman, 1960; Rimmer and Eberl, 1982; Wnuk and Pfefferkorn,

1987) have noted that many underclays do not show the kind of progressive mineralogical zonation that might be expected in a soil profile. This has spurred many theories, such as Huddle and Patterson (1961) and Patterson and Hostermann (1960), that state that the lack of profile development in underclays is due to the water-logged environment and that mineralogical modification was primarily due to acid leaching from waters, and plant roots. As an alternative, Hughes et al. (1992) believes that the lack of consistent zonation is due to a continuous series of depositional and soil-forming events that lead to the formation of a single underclay rather than a single soil forming event. Another theory is that the underclay formed from alternating flood deposits and pedogenic events such that organic matter and/or minerals from previous events were destroyed or altered by overlying soils (Wnuk and Pfefferkorn, 1987). Wilson (1965) 27 studied the underclays of the South Wales Coalfield and interpreted the underclay-coal relationship to represent a transition from an oxidizing non-swamp environment to a reducing swamp environment. This interpretation is similar to Stout (1923), who believed that oxygen-rich water initially destroyed the plant debris, but then as the water became more stagnant (anoxic), the plant debris were preserved.

These examples can be restated according to Marriott and Wright’s (1993) model

(Fig. 4) for soils forming under complex conditions. Some of the above examples which require continuous or episodic sedimentation would be better understood as polygenic soils, compound soils, or cumulate soils. As stated earlier, case where the pedogenic transition from underclays to the coals was continuous would be examples of polygenetic soils. Cases where two or more soils are separated from each other by, for example, a flooding event would be examples of compound soils. Finally cases where vegetation quickly re-establishes itself after incremental sedimentation (such as a flood layer), would be examples of cumulate soils.

Classification of Underclays

Hughes et al. (1992) has described four distinct types of underclays as found present in the Illinois Basin that are believed to have different depositional origins or alterations. These are -type, gley-type, fireclay-type and -type. Shale-type underclays are thought to be (allochthonous) detrital deposits derived from unaltered source material. Gley-type underclays are believed to have been (autochthonous) pedogenically altered clays under relatively saturated conditions. Fire-type underclays are likely to have formed by intense weathering from silica extracting plants

(autochthonous), but it is possible that they formed in near-shore environments due to the 28 differential and deposition. The sandstone-type found in the Illinois Basin resulted from pedogenic weathering (autochthonous) or postburial of fresh water that altered the feldspar into authigenic kaolinite.

This classification scheme is useful for identifying the type of clay present, and can be used in identifying clays not associated with coals. These terms are largely based on composition and not pedogenic origin.

Underclays as Parts of Soil Sequences

The common appearance of underclays being overlain by coal can be interpreted as the natural evolution of the depositional environment. Recognition of underclays as paleosols (e.g. paleogleysols, paleoinceptisols) means that these soils formed under certain conditions of: (1) continued pedogenesis of the parent material, augmented by (2) inputs of organic matter from in situ plant growth or from detrital organic matter (transported by ) and further augmented by (3) detrital sediment input by physical processes such as floods or storms. Because these paleosols (the underclays) are mineral-rich, they can be interpreted as initially cumulate soils. Many of these underclay paleosols show poorly developed horizonation (paleoentisols or paleoinceptisols) indicating high rates of clastic sediment input. In addition, many of these underclay paleosols show evidence for saturation (gleying, mottling, sesquioxides) indicating high or fluctuating water tables. In summary, underclay paleosols consistently indicate or near-wetland depositional settings. In such scenarios, when increments of clastic sedimentation decrease, but the vegetation input continues to accumulate, then the soil would be expected to transition from a mineral soil (with minor organic matter present as a histic epipedon) into an organic soil (histosol), or eventually a 29 paleohistosol (Rahmani & Flores, 1984). The resulting compound or polygenic soils enter the geologic record as underclays capped by coals.

30

CHAPTER 5: GEOLOGIC BACKGROUND

San Juan Basin of Colorado

During the Colorado (Pennsylvanian-) as part of the Ancestral

Rocky Mountains, two mountain ranges called Frontrangia and Uncompahgria, were formed in central and western Colorado. The sediment eroded from these mountains and deposited around them, formed the to the east of the Front Range

Uplift, the between the two mountain ranges, the Sangre de Cristo

Formation to the southeast, and the Hermosa Group and the to the west of the Uncompahgre uplift. During Permian time, these mountain ranges were eroded away, so that by the end of the Permian, Colorado was essentially flat, with smooth plains and low . These plains gave way to a series of ergs, ephemeral river deposits, and playas during the period and early . Rifting began to widen the area during the Jurassic, and volcanic activity intermittently covered the area with ash. In a more humid paleoclimate, a series of fluvial and lacustrine deposits formed the Morrison

Formation (Chronic and Williams, 2002). Eustatic sea level rise during the Cretaceous formed the , an epicontinental sea that extended between Alaska and the (Buillit et al., 2002; Olsen et al., 1999). This seaway covered most of the state of Colorado (Chronic and Williams, 2002). A series of transgressions and regressions in the region led to deposition of the , ,

Mesa Verde Group, , Picture Cliff Sandstone, and Fruitland Formation (Fig

7). 31

The Laramide Orogeny at the end and the beginning of the Cenozoic, resulted in block uplifts and relative sea level fall. The intermittent sandstone and coal layers found here are known as the . The Laramide Orogeny continued for approximately 32 million , and during this time the zone of deformation migrated from the west to the south. These changes caused the uplift of the Colorado

Plateau and the opening of the in southern Colorado and

(Chronic & Williams, 2002).

The San Juan Basin was the southern extension of the Western Interior Seaway in

Colorado and New Mexico. During the Cretaceous, the San Juan Basin experienced multiple transgressions and regressions, and environments varied from non-marine to marginal marine to marine environments (Baars, 2000; Chronic & Williams, 2002). It was within the San Juan Basin that the Gallup Sandstone, Mesa Verde Group, and

Pictured Cliff Sandstone were deposited as three separate progradational-retrogradational events (Fig. 8) (Buillit et al., 2002; Olsen et al., 1999). The Cretaceous coal deposits associated with these progradational-retrogradational cycles are found in the San Juan

Basin Durango-Pagosa Springs coal fields, and are interpreted as coastal in origin

(Kirschbaum & Biewick, 2008). Donaldson et al. (1979) noted that there are depositional units interbedded with the coal deposits that are indicative of deltaic environments. This observation has aided in exploration for subsurface coal-deposits.

Menefee Formation, Mesaverde Group.

The Menefee Formation (Fig. 8), which is deposited above the Point Lookout

Sandstone and is overlain by the , consists of shale interbedded locally with lenticular sandstone and tabular coal beds. The unit is interpreted to have 32 been deposited in lower coastal , marsh, and lagoonal environments (Baars, 2000;

Buillit et al., 2002; Chronic & Williams, 2002; Kirkham et al., 1999; Olsen et al., 1999).

The shales vary in color from grey-brown to black, the black shale being .

Sandstone beds are well cemented, contain ripple marks and some organic debris

(Kirkham et al., 1999). The Menefee Formation is divided into two parts, the lower

Menefee Formation and the upper Menefee Formation. The lower Menefee Formation is interpreted as a sand-rich system that feed the deltas of the Point Lookout

Formation, while the upper Menefee Formation is a nonmarine-paludal to alluvial-plain system (Olsen et al., 1999).

Fruitland Formation.

The Fruitland Formation (Fig 8) was deposited during the , and was deposited above the Picture Cliffs Sandstone (Fassett & Hinds, 1971; Pashin, 1998).

It is interpreted as a marginal marine deposit (Snyder et al., 2003). The lower portion of the Fruitland Formation formed in a non-marine, brackish-water, lagoonal, or swampy coastal-plain environments. The coals of the Fruitland Formation are interpreted to have formed in backshore swamp environments, and contain lenses of mudstones, siltstones, sandstones and carbonaceous shales which were deposited within channels

(Carroll et al., 1999; Snyder et al., 2003). Coals in the Fruitland Formation are interpreted as swamp deposits in back- environments, which now make up the underlying Picture Cliff Sandstone. The coals formed between 76 and 73 Ma (Fassett,

2000; Riese et al, 2005). The coals can be as much as 18 m to 36 m thick, although many coal seams are thin. The thin coals are interpreted to have formed at the edges of and between margin settings (Huffman and Taylor, 1991; Riese et al., 33

2000; Riese et al., 2005). Thus, the lateral migration of distributary channels and the onshore-offshore shoreline migration have caused individual coal beds to be patchy or to have variable thicknesses (Snyder et al., 2003). The upper part of the Fruitland

Formation is composed of fluvial sandstones and shale (Carroll et al., 1999).

Appalachian Basin of West Virginia

The Appalachian Basin has a complex history of sedimentation including the

Salinic (), Taconic (), Acadian (-Mississipian), and

Allegheny (Pennsylvanian-Permian) (Ettensohn, 2004). This study focuses on the cyclical sedimentation in the Appalachian Basin during the Alleghenian Orogeny within the Pennsylvanian Pittsburgh Formation.

With the onset of the Alleghenian orogeny (Pennsylvanian-Permian), the sediment input into the basin initially decreased, while subsidence continued. This allowed for marine depositional environments to invade the area, so that above older deltaic deposits can be found the crossbedded sandstones of the Loyalhanna

Formation, and overlying fluvial-deltaic reds beds of the Mauch Chunk Formation (Faill,

1999). The Mauch Chunk Formation red beds are locally intertongued with marine and shales. Continued uplift to the southeast caused extensive erosion and increased the sediment supply, and the alluvial plain deposits of the Pottsville Group formed on top of the delta deposits of the Mauch Chunk Formation. Following the

Pottsville Group, there were two major sequences of cyclic coal deposition, interspersed with marine shales and freshwater limestones (Faill, 1999). The lowermost one is called 34 the Allegheny Group, which accumulated on a lower delta plain during the Desmoinesian

(Faill, 1999). The Allegheny Group is comprised of a repeating successions (or cyclothems) of coal, , and clastics which range from claystones to coarse- grained sandstones (Edmunds et al., 1999). The overlying is called the

Conemaugh Group (Fig 9), which consists of repeating successions (or cyclothems) of claystones, siltstones, and sandstones that were deposited due to the westward of a delta plain during the Missourian. The Conemaugh Group also contains some red beds that have red colors due to their parent material, and some coal beds. The Conemaugh Group is divided into two formations: the Glenshaw Formation, and the Casselman Formation. The Glenshaw Formation is dominated by marine facies while the Casselman Formation has marine and freshwater deposits. A second cycle of major coal deposition is found in the overlying Monongahela Group, which is divided into the Pittsburgh and Uniontown Formations (Edmunds et al., 1999; Faill, 1999). The sediments deposited in the Monongahela Group are interpreted to form in low-energy environments such as marginal upper delta plain, lacustrine, or paludal environments

(Edmunds, 1999). The Monongahela Group contains limestones, dolostones, calcareous mudstones, shales, and thin-bedded siltstones and laminites, and coal beds (Edmunds et al., 1999). These coals are interpreted to have formed in isolated, relatively low-energy alluvial plains. One of these, the Pittsburgh Coal Bed, seems to have formed across the entire southern Pennsylvanian area, but the other coals were more isolated from each other and limited in their extent (Edmunds et al., 1999). The Sewickly Coal Bed, which is included in this study, is one of the coals found within the Monongahela Group.

35

Pittsburgh Formation, Monongahela Group.

The Sewickly Coal Bed is part of the Pittsburgh Formation, of the Monongahela

Group in the Appalachian Basin. The coal is Late Pennsylvanian in age. Eble et al.

(2003) used spore counts from the Sewickly Coal Bed and found a dominance of tree fern and Calamites spores. They inferred that the Sewickly Coal Bed formed as a topogenous, planar with consistent water cover. They also concluded that the high ash content and the carbonate shales were probably due to clastic sediment input from flooding events in the mire. No brackish-water or marine have been identified in the

Monongahela Group or in the underlying Conemaugh Group (Ettensohn and Denver,

1979; Sturgeon & Hoare, 1968). The related sediments change from marine to marine with river influence during Pottsville-Conemaugh-time due to multiple transgressions and regressions (Fig 9). The lithologies of the sediments indicate deltaic-bay to lacustrine environments that were eventually filled in with sediments of alluvial plain environments of the Dunkard Group during Conemaugh-Monongahela-time (Cross and Schemel, 1956;

Donaldson, 1974; Ettensohn and Denver, 1979; Kovach, 1979).

36

CHAPTER 6: METHODS

Outcrop Studies

Stratigraphic sections from the outcrops used in this study were measured using a tape measure, and rocks were described according to composition, color, organic content, textures (), and . Paleosol features were observed in order to interpret the origins of peats and coals. Study areas included the Pittsburgh

Formation of the Monongahela Group in the Appalachian Basin, the Menefee Formation of the Mesa Verde Group of the San Juan Basin, and the Fruitland Formation of the San

Juan Basin.

This study also looked at the sediment cores taken from, a modern wetland,

Brown’s Lake Bog, Ohio. The cores were collected using push cores to minimize impact on the bog environment. These cores were analyzed according to organic content and clastic content, and then digitally arranged to create a transect across the bog and study early stages in paleohistosol development.

Lithofacies Analysis

Lithofacies are described using facies classification, as can be seen in Table 5.

For instance a trough crossbedded sandstone would be denoted as St. A massive sandstone would be designated as Sm. A finely laminated sand, silt or mud would be designated as Fl. Coals or carbonaceous are designated as C, and a lithofacie with pedogenic features are called a paleosols (P).

Pedofacies Analysis

This study proposes four terms to aid in describing the coals and their underclays from the perspective of a complex soil sequence. The first, to describe types of 37 underclays that showed complex soil features, such as roots, gleying and organic matter interspersed with layers of sedimentation, is termed as argillaceous paleo-gleysol (ApG) .

These complex soils have had a high rate of sedimentation during their development, and would have 0-20% organic matter. Argillaceous paleo-histogleysol (ApHg), would describe underclays with soil features (roots, organic matter, gleying) that have approximately 20-50% organic matter. The increase in organic matter accumulation indicates a change in the hydrologic regime causing the influx of sediment to begin to decrease and thereby allowing the plants to accumulate. These paleosols are still being interrupted with sediment input, just not at as great of a rate. The third pedofacies to describe soils that have about 50-95% organic matter, indicate that the sediment input has decreased even further, allowing plants to establish themselves for even longer periods of time before a period of sediment input, or the sediment input is slowly being deposited along with the organics preventing an absolute disruption of the soil formation. These pedo-facies, called paleo-histogleysols (pHg), may appear as an organic shale with many thin layers of coal interspersed throughout. The final pedo-facies, paleo-histosol (pH), would be a compressed histosol that shows a genetic relation to underlying clays and sandstones.

SEM Analysis

Samples from the outcrop studies were prepared and analyzed at Bowling Green

State University with a high resolution Hitachi S-2700 scanning electron microscope

(SEM) to verify the macro-scale analysis of the outcrops. These samples were compared to sediment petrography studies completed by Welton (1984). Sample preparation for 38 geologic samples varied according to the known composition of sample. All samples underwent an ultrasonic cleaning, and were handled carefully to avoid contamination.

Clay and sandstone samples were mounted and then coated using a Hummer, while coal and organic clays were each mounted with graphite and fishing putty respectively. The voltage for rock samples was set at 15V to avoid charging the material.

X-ray diffraction point analysis was performed on one sample to confirm what was identified in the image. X-ray diffraction analysis is useful in that it identifies the elements present in the sample, and their location in the sample with a high amount of accuracy, and it also will not destroy the sample.

39

CHAPTER 7: FIELD RECOGNITION OF PALEOSOLS

Brown’s Lake Bog

Description of Cores

The push-cores shown in Figure 10, were dominated by roots and other organic content. The clastic content increased with the distance from the center of the bog, though there was not a great amount of clastics in the cores. Likewise, the organic content was greater towards the center of the bog, and decreased with distance from the center. The organic debris was accumulated towards the surface, and decomposition increased with depth.

Menefee Formation

Descriptions of Coals and Underclays

A 412-cm section was measured from The Menefee Formation (Table 7). At the base was a 26 cm thick layer of a black, sandy mudstone (Fsm) that was fissle with vertical roots and twigs. This was probably a marsh or lagoonal deposit. As a pedofacies, it would be viewed as an argillaceous paleo-histogleysol (ApHg), due to the organic matter interspersed throughout the mudstone, and the roots that tapered down through the layers.

Above this lay a 20 cm layer of a rooted underclay, whose roots taper and bifurcate downward. A pedofacies interpretation of this layer would be as a argillaceous paleo-gleysol (ApG), due to the presence of roots, combined with the lack of organic matter accumulation.

An 11 cm layer of a flat topped coal that filled the topography lay above the underclay, and it had vertical joints. This may have been a much vegetated marsh 40 deposited, evidenced by the accumulation of the plant matter. Since this is a layer that shows connection to the layers beneath, by the evidence of rooting in the layers underneath, this layer as a pedofacies would be seen as a paleo-histosol (pH).

A fissle, gray silty mudstone that was 54 cm thick lay above this. It contained roots, coal fragments, and small vertical burrows. Because this layer showed evidence of soil formation, as a pedofacies, it would be classified as an argillaceous paleo-gleysol

(ApG).

Above this was a 25 cm, laminated, very fine-grained, rooted sandstone. This may have formed due to a flood event or a channel scour. Because of the greater amount of clastic content versus the organic content, this layer would be seen as an argillaceous paleo-gleysol (ApG).

Next is a 13 cm, rooted, laminated very-fine grained sandstone with alternating layers of mud drapes that are ~6 mm thick each. These muds draps also contained coal and other organic debris. As a pedofacies this layer would be seen as an argillaceous paleo-histogleysol (ApHg).

Above this was deposited a 6 cm fissle, rooted, gray mudstone that contained coal fragments and small blebs. Some of the coal formed thin layers in the mudstone. This layer, as a pedofacies, would be seen as a paleo-histogleysol (pHg).

A coal (12 cm) with thin vitrinite blebs and thin organic layers lay above the laminated sandstone. As a pedofacies, this would be seen as a paleo-histosol (pH), due to the organic content.

The following eight layers were not determined to be part of a soil forming sequence. Above this lies a 14 cm thick, interbedded, fine-grained sandstone and 41 mudstone that is rippled, with some flaser bedding. Next is a 20 cm thick medium- grained sandstone that is lenticular with flaser bedding. At its base is wavy bedding. A

21 cm thick layer of gray silty mudstone lays above this. Next was a 7 cm fine-grained sandstone with coal fragments, that are thought to have been organic matter rafted in.

Preserved above this is a 27 cm grey- mudstone. Above this lies a layer of nodular that measured 9 cm thick. The layer above the chert is a planar laminated, heterolithic sandstone and shale (37 cm), with the sandstone laminae typically measuring

4 cm thick. Above this is a 110 cm sandstone layer.

SEM and Petrographic Analysis

In the Menefee Formation, five samples from the underclays were studied using

SEM, and the locations of these samples are shown in Figure 11. Sample 06MF01 (Fig.

12) was taken from a black, sandy mudstone (underclay) that contained vertical roots, and twigs. In both images (A & B) the clay particles that compose the mudstone are arranged in a vertical, semi-linear fashion through the center of the image, while the distinctive conchoidal fracturing that is typical of coals, runs parallel on either side.

These thin seams of coal and the presence of roots, led to the conclusion that this underclay was part of a cumulate soil sequence, since the development of a coal with soil features, indicates that the sediment input slowed down or ceased for a period of time.

This was also determined to be an argillaceous paleo-histogleysol (ApHg).

Sample 06MF02 (Fig. 13) was also taken from the Menefee Formation in a rooted underclay that contained some coal fragments, and was located in the unit above

06MF01. In Figure 13 a coal seam or root is located in the center of the image with clay on either side. The clay has also attached itself to the coal, as it can be seen along the 42 edge of the coal. In the upper right corner there is a sand grain (~70 μm) with clayskins

(argillans). This sample was also analyzed under this section. These images (Fig 14 A -

C) show that the clastics form layers with some root structures that taper downward through the layers, and image D shows some twigs and other organic matter preserved within the layers. This sample was determined to be part of a cumulate soil, and as a pedofacies, it was determined to be a argillaceous paleo-gleysol (ApG).

In the Menefee Formation, two samples of coal were also analyzed using SEM

(Samples 06MF03 and 06MF07). The locations of these two samples can be seen in

Figure 11. Sample 06MF03 was taken from a coal that filled the underlying topography, had a flat surface, and had vertical joints. Under the SEM (Fig. 15) the coal is smooth with some conchoidal fracturing, which is best viewed in Figure 15A. Figure 15B showed what appeared to be very fine-grained sand particles is distributed in the coal without any evident orientation or layering. This is interpreted to be a paleo-histosol

(pH).

Sample 06MF04 (Fig. 16) was taken from a sample of silty mudstone that contained roots and some coal fragments. In Figure 16A the clay wraps around the coal fragments, and silt-sized particles are scattered throughout the images taken of this sample. In the center of this image are coal fragments found in this sample. In Figure

16B, there is an unusual structure in the center that appears to be a clay structure. This was found to be a cumulate soil, and as a pedofacies, it would be called an argillaceous paleo-gleysol (ApG).

Sample 06MF05 (Fig. 17) is of a rooted, laminated, very fine-grained sandstone that contained some wood fragments, within the Menefee Formation. In the center of 43

Figure 17A is an example of a void created by plucking of a sand grain approximately

100 μm in diameter. The clasts surrounding this vug are approximately silt sized. In the center of Figure 17B is a clump of silt sized particles. This layer is interpreted to be a argillaceous paleo-gleysol (ApG).

Sample 06MF06 (Fig. 18) was a very laminated, fine-grained sandstone with mud drapes (argillans), that was rooted and contained coal fragments. The left half of Figure

18A shows the distinctive conchoidal fracturing of a coal. The right half of this image shows the mud drapes found in this deposit. Figure 18B is from the same sample, and shows a layer of sand grains with clay draped on the grains. As a pedofacies, this was determined to be an argillaceous paleo-histogleysol (ApHg).

Sample 06MF07 (Fig. 19) was taken from a coal with thin vitrinite blebs, thin layers of organics, and oxidation (orange weathering) along fractures. Under the SEM, there were clastics interbedded or embedded in the coal throughout this sample and they appeared to have been deposited as layers, which can be seen in both images. This was determined to be a paleo-histosol (pH).

Fruitland Formation

Descriptions of Coals and Underclays

The Fruitland Formation measured a total of 639 cm thick (Figure 20). At the base of the formation is a 12 cm thick coal (Table 8). As a lithofacies this would be a coal (C), but as a pedofacies it is interpreted as a paleo-histosol (pH). 44

Above this lies an interbedded black shale and thin coal seams. The coal is 1-2 mm thick and is discontinuous. As a lithofacies, this would be a carbonaceous mud/coal

(C). As a pedofacies, it is interpreted as a paleo-histogleysol (pHg).

Above this lies a 30 cm thick coal seam that consists of interbedded vitrinite layers (~1-2 mm thick) and there were plant fragments. As a lithofacies this would be a coal (C), but as a pedofacies it is interpreted as a paleo-histosol (pH).

A wavy bedded, fine-grained sandstone (Sr) (4 cm thick) with coal fragments was deposited on top of this coal seam. As this has interrupted the soil forming process, and does not seem to have roots, it would not be a pedofacies.

A 16 cm thick bed of organic shale with discontinuous coal blebs that each measured 2 mm thick was deposited on top of the sandstone. As a lithofacies, this would be a carbonaceous mud/coal (C). As a pedofacies, it is interpreted as a paleo-histogleysol

(pHg).

This bed transitioned upward into a 43 cm thick bed of highly compacted coal with discontinuous bedding. As a lithofacies this would be a coal (C), but as a pedofacies it is interpreted as a paleo-histosol (pH).

Above this lies a fissle organic shale (37 cm thick) with organic fragments. As a lithofacies, this would be a carbonaceous mud/coal (C). As a pedofacies, it is interpreted as a paleo-histogleysol (pHg).

Next lay an amalgamated coal layer (75 cm thick) with vitrinite lenses. As a lithofacies this would be a coal (C), but as a pedofacies it is interpreted as a paleo- histosol (pH). 45

Deposited above this was a 22 cm thick organic shale, which transitioned into a

28 cm thick coal with vitrinite layers. This first would be a carbonaceous mud/coal (C) as a lithofacies. As a pedofacies, it would be a paleo-histogleysol (pHg). The second would be a coal (C) as a lithofacies, but as a pedofacies it is interpreted as a paleo- histosol (pH).

This cyclic deposition was interrupted with a 3 cm thick medium grained sandstone (Ss), which was followed by a 48 cm thick fissle gray mudstone-

(Fsm), that transitions into a wavy bedded fine-grained sandstone (Sr) (63 cm thick).

Above this is a covered section 105 cm thick slope. None of these were found to be a pedofacies.

The next exposed section is a highly compacted coal (38 cm thick) that had thin layers of vitrinite. As a lithofacies this would be a coal (C), but as a pedofacies it is interpreted as a paleo-histosol (pH).

Deposited above the coal is an organic shale with siltstone lenses (13 cm thick), which is followed by a 15 cm thick coal with partings and compressions. This first would be a carbonaceous mud/coal (C) as a lithofacies. As a pedofacies, it would be a paleo-histogleysol (pHg). The second would be a coal (C) as a lithofacies, but as a pedofacies it is interpreted as a paleo-histosol (pH).

Above this is a 18 cm thick fissle organic shale. As a lithofacies, this would be a carbonaceous mud/coal (C). As a pedofacies, it is interpreted as a paleo-histogleysol

(pHg).

Next was a coal (40 cm thick) interbedded with thin shales. Finally, topping the section is a 9 cm organic shale. The first would be a coal (C) as a lithofacies, but as a 46 pedofacies it would be a paleo-histosol (pH). The second would be a carbonaceous mud/coal (C) as a lithofacies. As a pedofacies, it is interpreted as a paleo-histogleysol

(pHg).

SEM and Petrographic Analysis

There are 8 coal seams in this stratigraphic transect of the Fruitland Formation.

Two samples were taken for SEM analysis the locations of which can be seen in Figure

20. Sample 06MF08 is a coal with thin vitrinite layers, and sample 06MF09 is a highly compacted coal with thin layers of vitrinite.

Sample 06MF08 (Fig. 21 A-E) was tested using X-ray diffraction point dot mapping, to verify the elemental composition of the sample. There is distinctive zoning particularly with aluminum, carbon, and silica. The aluminum and silica are detected in higher concentrations to the left of image where the clastics are seen in heavier concentrations. Carbon is detected throughout the entire image, however it is mapped in heavier concentrations to the right of the image where there are fewer clastics. This

SEM analysis is interpreted to show that the matrix is composed primarily of carbon

(coal) and that the clastics are predominately silica, however because these samples could not be and polished into a smooth surface, this type of elemental detection is subject to error in that the textural differences can make the elements appear in higher concentrations.

Sample 06MF09 is a coal that is highly compacted and contains thin layers of vitrinite (Fig. 22). Conchoidal fractures of the coal can be observed in both of these images. In addition, in Figure 22A there are some very fine-grained sand interspersed 47 with the coal. These represent some of the clasts are incorporated into the coal.

However, they do not seem to be in layers, which could be due to the which side the coal sample is observed at. Finally, conchoidal fracturing in the coal can be observed in

Figure 22B.

Pittsburgh Formation

Descriptions of Coals and Underclays

The stratigraphic section of the Sewickly Coal Bed stratigraphic section (Figure

23) of the Pittsburgh Formation consisted of a total of 230.6 cm (Table 9). At the base of the section was a 19.1 cm thick quartz, mica sandstone lithofacies (Ss). This transitions upward into a planar, discontinuous, very fine-grained silty shale lithofacies (Fr), that is interbedded with clay and organics (20.3 cm thick). The shale contains occasional sand lenses and the organic content increased towards the top of the seam. Above this lay a clay that grades into sand with interbedded organics (16.5 cm thick). Next is a silty shale lithofacies (Fr) interbedded with organic shale, that measured 3.2 cm. Deposited above this is a 19.7 cm thick planar bedded silty sandstone. The combination of these lithofacies is interpreted as an argillaceous paleo-histogleysol (ApHg), as a pedofacies.

The silty sandstone transitioned upward into an interbedded, yellow-grey shale and organic shale (26.7 cm thick). At the base is a thin discontinuous coal seam. This seam is interpreted as a paleo-histogleysol (pHg). 48

At the top of the section was a 125.1 cm thick blocky vitrinite-rich coal, that had two layers of a dull coal that are 18.4 cm and 3.2 cm thick respectively. As a pedofacies this is interpreted as a paleo-histosol (pH).

SEM and Petrographic Analysis

Three samples of the underclays from the Sewickly Coal Bed (Pittsburgh

Formation) were analyzed using SEM, and one sample, I7900306, was analyzed as a thin section. The locations of these samples are shown in Figure 23.

Sample I7900306 was taken from a clay that graded into a sandstone with interbedded organics (Fig. 24). These organic layers are visible in the thin sections, forming thin layers alongside the layers of clastics.

Sample I7900406 (Fig. 25) was obtained from the Pittsburgh Formation in a layer composed of silty shale interbedded with organics and also containing mica and clay.

The layered elements in image A is may be mica flakes due to their platy shape. Figure

25B shows flaky clay minerals and very fine-grained . Neither roots nor coal fragments are seen in this sample, however organic matter was identified at the outcrop.

Sample I7900506 (Fig. 26) was obtained from a planar bedded silty sandstone. In both images it appears to also contain some coal blebs that were not identified at the macro-scale, surrounded by clay and sand particles.

Sample I7900602 (Fig. 27) was obtained from an organic shale that contained mica flakes and contained discontinuous coal seams at the base. Through the center of

Figure 27A is a curving feature that was typical of this sample. This feature is part of a small coal seam that ran through the sample. There were many other such seams in this 49 sample. Another small coal seam can be seen in Figure 27B extending through the sample.

There was one layer of coal in the Pittsburgh Formation, the Sewickly Coal Bed.

This coal is a blocky vitrinite coal that has two layers of a dull coal. Sample I7900706 is a vitrinite-rich coal, and the location of this sample may be seen in Figure 28. Under

SEM (Fig. 28) distinct layering of clastics can be observed throughout the coal. While the layers weren’t throughout the entire sample, there were clastics distributed throughout the sample, in discontinuous layers.

50

CHAPTER 8: DISCUSSION

Paleosol Evaluation

In each field area the coals were interpreted as humified organic matter of ancient wetlands. Many individual coals were observed under a Scanning Electron Microscope

(SEM). Often, these coal samples showed evidence of finely interbedded clastic sediments, either finely disseminated or as layers in the coal sample.

These paleogleysols underlaid the paleohistosols described above. Many of these had roots and organic content that was observed on the macro scale, but some that did not have organic content observed on the macro scale, did in fact have coal blebs observed on the micro-scale (SEM).

This study proposes four terms for describing these paleohistosols as pedogenic sequences (Table 6). These terms are as follows: (1) argillaceous paleo-gleysols (ApG),

(2) argillaceous paleo-histogleysols (ApHg), (3) paleo-histogleysols (pHg), and (4) paleo- histosols (pH).

Layers that don’t show a great amount of organic matter, but still contain root structures, would be termed argillaceous paleo-gleysols (ApG). These layers are dominantly clastic in composition, but they also have some thin layers that have roots tapering down from them, or even thin organic layers.

Argillaceous paleo-histogleysols (ApHg) would be used to describe the varieties of underclays that have soil features, and distinct organic layering, and may underlie a coal. The organic layers here have roots bifurcating down from them, and these organic 51 layers are found to be in a higher concentration then as is seen with the argillaceous paleo-gleysols.

The dominantly organic shales that may lie above an underclay, or under a coal would be termed as paleo-histogleysols (pHg). These pedo-facies may have multiple layers of thin coals, and many roots bifurcating down. The organic content is high, but the thin coals have been interrupted with increments of sediment.

The term, paleo-histosol (pH), would be used to describe the coals, which are compressed histosols, and often contain as we saw in our SEM images, thin layers of clastics. These coals must first be determined to be autochthonous before classifying them as a paleo-histosol.

Environment of Pedogenesis

Menefee Formation.

The Menefee Formation (Figure 29), which formed in lower coastal plain, marsh and lagoonal environments, is interpreted as having two polygenetic profiles which probably indicate a change in the hydrogeologic regime by a migration in the water flow or a flood event causing a need for the region to re-establish its soils. The unit also contains multiple cumulate soil profiles which contain clays interbedded with organic clays. These are interpreted as gleysols, because they are soils that established themselves under a predominantly waterlogged setting. In instances where the section is truncated and then the paleosol reestablished, there would be considered evidence for cumulate truncated profiles. A portion of the Menefee Formation, as seen in Fig 30, is interpreted as having a paleo-histosol, a paleo-histogleysol, a argillaceous paleo-histogleysol, and a argillaceous paleo-gleysol. The argillaceous paleo-gleysol is a sandstone that has root 52 features. Above this, argillaceous paleo-histogley, is a laminated sandstone-mudstone that is also rooted. Overlying this is a paleo-histogleysol, which is a mudstone with coal fragments, and coal blebs, and is also rooted. And above this layer is a paleo-histosol, which is a coal with vitrinite layers. Under SEM magnification, this coal showed very thin microscopic layers of clastics, which indicates that sediment input continued, just at a lesser rate.

Fruitland Formation.

The coals of the Fruitland Formation formed in a backshore swamp environment.

The studied section within the Fruitland Formation (Figure 31) has what are interpreted as a series of polygenetic profiles that were initiated by cumulate soils. These cumulate soils showed a continuation of sediment accumulation and organic matter accumulation, supported by the presence of roots. Within one of the coal seams are variations in the coal maceral in the form of continuous layers, between vitrinite and dull coals. A portion of the Fruitland Formation (Fig. 32) is interpreted as having paleo-histosols and paleo- histogleysols. The deposition of these paleohistosols and paleo-histogleysols are cyclic in , shown by the repetition of the paleo-histogleysols establishing themselves, followed by the paleo-histosols establishing themselves on top of the paleo-histogleysols.

Pittsburgh Formation.

The studied section within the Pittsburgh Formation (Figure 33) contained a series of cumulate soils with occasional increases in sedimentation which didn’t truncate the profile forming a composite set which was overlain by cumulate soils. The entire section is interpreted as a polygenetic soil profile, due to the change in the sediment input in the soil forming process. The coal seam (seen in Fig. 34) is interpreted as having a base of 53 argillaceous paleo-histogleysol, which was overlain by a paleo-histogleysol. The paleo- histosol then tops off the section. So in summary, the Pittsburgh Formation shows a steady decrease in the sediment input, along with an increase in the establishment of organic matter and roots, leading to the accumulation of organic matter forming a paleo- histosol.

Summary of Field Relationships

All of these profiles show that while even sedimentation may continue in an area, with the continued establishment of plants over the sediment deposits, these profiles can still be considered as soils, even though there are not distinct horizons. Both the Menefee

Formation and the Pittsburgh Formation show evidence for a decrease in the clastic sediment input, upward resulting in histosol formation. The Fruitland Formation section shows alternating formation of histosols episodically interrupted by clastic sediment that were part of distributary channels in the backshore environment. So, while these coals develop under complex conditions that prevent the formation of distinct soil horizons, it is clear that the presence of roots, carbonaceous sediments, calcareous nodules, and the presence of organic matter indicate soil profiles.

Evidence for Pedogenic Origins of Underclays

While there is value in classifying these deposits as coals, primarily for economic reasons, it is also clear they represent soils and depositional units. For example, SEM images show that these paleohistosols contain interspersed clastic materials, which may at times form distinct layering. This indicates that while the paleohistosol is primarily the result of organic accumulation, the paleohistosols also received increments of sediment input. In addition, many of the samples observed in the Fruitland Formation, Menefee 54

Formation, and Pittsburgh Formation, show that the underclays have root structures in them. Not only is the presence of roots an example of the presence of a soil, but there are also organic materials, sometimes found in layers, or even forming small discontinuous coal seams. Another important feature is evidence of gleying, which is a feature of a water-logged soil. Even in some of the paleogleysols that did not have evidence of organic content observable on the macro-scale, coal blebs were observed on the micro scale. This support that even underclays were included in the soil-forming process leading to the formation of coal.

Underclay-Coal Sequences as Soil Sequences

Because these underclay soils developed under watersaturated soil-forming processes, they did not develop typical soil horizons, and must be viewed under a different lens for classification purposes. Underclays with obvious soil features, such as roots, organic matter, or gleying, can be interpreted as cumulate soils. These soils would have developed with vegetation established on soil surface, episodically buried by increments of sedimentation from, for example, a flooding event or a heavy rain.

Alternatively, when the underclays experience a period of time with little to no sedimentation, they may have developed thick organic horizons that were preserved as paleo-histosols (coals). Thus, the transition from paleo-gleysols to paleo-histosols can be considered polygenetic soils. In some cases, the paleo-gleysols and paleo-histosols were superimposed, which disrupted the soil formation process, for example in instances of paleohistosols overlying paleo-histogleysols.

55

Proposed Field Classification of Underclay-Coal Sequences

This paper has proposed four terms that could be used to classify these unique soils, and that describe them from the perspective of a soil (Table 6). First, argillaceous paleo-gleysol (ApG), describe underclays that are dominantly clastic in their composition, lack soil horizons, but show soil features such as gleying, rooting and organic matter, just not in a large quantity. Second, is argillaceous paleo-histogleysols

(ApHg) describe underclays that show a significant amount of rooting, organic matter, and have gleying features. These may also contain coal blebs and may underlay a coal.

Third, paleo-histogleysol (pHg), describes dominantly organic shales with thin layers of coal, root features, and gleying. Fourth, is paleo-histosol (pH) to describe the compressed histosols that overlay paleo-histogleysols, argillaceous paleo-histogleysols, and/or argillaceous paleo-gleysols.

This classification system would be useful for those wishing to describe these soil forming environments from an historical point of view. This could also be useful in understanding the processes required to develop paleo-histosols and modern day histosols.

56

CHAPTER 9: SUMMARY AND CONCLUSION

Summary

This study examined three coal seams (the Meneffe Formation, the Fruitland

Formation, and the Pittsburgh Formation) and a modern day bog (Brown’s Lake Bog).

These were examined for evidence of soil forming features and a classification system was created to describe these coals from the perspective of a soil. We found that the underclays underlying the coals all showed soil features, and we were able to describe them as argillaceous paleo-gleysols, argillaceous paleo-histogleysols, paleo-histogleysols, and paleo-histosols.

Conclusion

Describing these underclays and coals from the perspective of paleosols is useful in understanding the processes necessary for coal formation, and expands our understanding of what is a soil. It would be interesting to see if this classification system is applicable to other coal seams and their underclays, and perhaps this classification system could be expanded to include other soils formed under complex soil conditions.

57

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Table 1: Descriptions of the Master soil horizons.

Master Horizons Characteristics O Layers dominated by organic material (litter and humus) in various stages of decomposition. A Mineral horizons that formed at the surface or below an O horizon and (1) are characterized by an accumulation of humified organic matter intimately mixed with the mineral fraction, or (2) have properties resulting from cultivation, pasturing or similar kinds of . E Light colored mineral horizons in which the main feature is loss of weatherable minerals, silicate clay, iron, aluminum, humus, or some combination, leaving a concentration of mostly uncoated quartz grains or other resistant materials. B Subsurface mineral horizons dominated by (1) illuvial accumulations of clay, iron, aluminum, humus, ect., (2) removal of primary carbonates, (3) residual concentrations or sequioxides, (4) distinctive, non-geologic structure and/or (5) brittleness. C Mineral horizons, excluding hard bedrock, that have been little affected by pedogenic processes and lack properties of O, A, E, or B horizons. Most C horizons are mineral soil layers and retain some rock structure (if developed in residuum) or sedimentary structure (if developed in transported ). Included as C horizons are deeply weathered, soft (see Chapter 8). D Deep horizons that show virtually no evidence of pedogenic ateration, such as leaching of carbonates or oxidation. D horizons are formed in unconsolidated sediments. R Hard, continuous bedrock that is sufficiently coherent to make by hand impractical.

Source: Schaetzl & Anderson (2005)

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Table 2: Subordinate Horizons of Greatest Significance to Wetland Science.

Horizon Significance Oi Fibric organic matter (little decomposition) Hemic organic matter (intermediate Oe decomposition) Oa organic matter (high decomposition) Ap Plowed A horizon Bw Weathering, weakly developed B horizon Bt Increase in illuvial clay in B horizon Bg Gleying significant Btg Increase in illuvial clay and significant gleying Bh Humus rich , spodic horizon

Source: Richardson & Vepraskas (2001)

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Table 3: Coal Macerals and their Origin. Coal Macerals Origin Vitrinites Wood, roots, and bark Liptinites Algae, spores, cutins, and resins Inertinites Altered woody tissues (e.g. Charcol) Ash Sediment, and minerals

Source: adapted from Retallack, 2001

Table 4: Coal Rank Classification Vitrinite Reflectance Burial Coal Rank (%) Temperature (°C) Peat 0.2 Lignite 0.3 30- 65 Sub-bituminous coal 0.4 - 0.5 80 Bituminous coal 0.6 - 2.0 120-170 Anthracite 3 ±200

Source: adapted from Retallack, 2001

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Table 5: Facies classification. Facies code Facies Sedimentary Structures Interpretation Gmm Matrix-supported, massive Weak Plastic (high-strength, viscous) Gmg Matrix-supported gravel Inverse to normal grading Pseudoplastic debris flow (low strength, viscous) Gci Clast-supported gravel Inverse grading Clast-rich debris flow (high stregth), or pseudoplastic debris flow (low strength)

Gcm Clast-supported, massive gravel - Pseudoplastic debris flow (inertial bedload, turbulant flow) Gh Clast-supported, crudely Horizontal bedding, Longitudinal , lag deposits, bedded gravel imbrication sieve deposits Gt Gravel, stratified Trough crossbeds Minor channel fills Gp Gravel, stratified Planar crossbeds Transverse bedforms, deltaic growths from older remnants St Sand, fine to v. coarse, may be Solitary or grouped trough Sinuously crested and linguoid (3-D) pebbly crossbeds Sp Sand, fine to v. coarse, may be Solitary or grouped planar Transverse and linguoid bedforms (2-D pebbly crossbeds dunes) Sr Sand, very fine to coarse Ripple crosslamination Ripples (lower flow regime) Sh Sand, v. fine to coarse, may be Horizontal lamination, part- Plane-bed flow (critical flow) pebbly ing or streaming lineation Sl Sand, v. fine to coarse, may be Low-angle (<15°) crossbeds Scour fills, humpback or washed-out pebbly dunes, Ss Sand, fine to v. coarse, may be Broad, shallow scours Scour fill pebbly Sm Sand, fine to coarse Massive, or faint lamination Sediment-gravity flow deposits

Fl Sand, silt, mud Fine lamination, v. small , abandoned channel, or ripples waning flood deposits Fsm Silt, mud Massive Back swamp or abandoned channel deposits Fm Mud, silt Massive, desiccation cracks Overbank, abandoned channel, or drape deposits Fr Mud, silt Massive, roots, bioturbation Root bed, incipient soil

C Coal, carbonaceous mud Plants, mud films Vegetated swamp deposits P Paleosol carbonate (calcite, Pedogenic features Soil with chemical precipitation ) * v., very; D, dimensional. Source: Miall, 1996

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Table 6: Pedo-facies classification as proposed by this study.

Pedo-Facies Description of structures Composition Textures Structures Argillaceous Paleo- Underclays that are dominatly tan, yellow, 0-20% organic n/a Roots and plant Gleysol (ApG) clastic in composition. May orange matter fragments. May be show rooting, gleying, and massive or have organic matter. faint lamination. Argillaceous Paleo- Underclays with a significant grey, tan, 20-50% organic may be platy, or fine Histogleysol amount of rooting and organic yellow, matter platy lamination. Plant (ApHg) matter. May have gleying and orange fragments, roots. may underly a coal. Paleo-Histogleysol Underclays or shales Black-blue, 50-95% organic may be platy, or fine (pHg) dominated by organic matter. grey, tan, matter platy lamination. Plant Contains thin layers of coals, yellow- fragments, roots. root features, and gleying. orange Paleo-Histosol (pH) Compressed Histosols (Coal) Black-blue Organic matter n/a concoidal rich fracturing

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Figure 1: Soil Texture Triangle from the United States Department of Agriculture Natural Resources Conservation Service (Soil Survey Staff, 2010).

69

Figure 2: A classification of soil peds from Retallack (2001).

70

Figure 3: A representation of various soil orders including their typical climate, vegetation, and soil profiles. (Retallack, 2001)

71

Figure 4: The development of composite, compound and cumulate soil profiles, with the effects of truncation and continuous sedimentation. During the stacking of many soils more complex scenarios develop. Vertical lines indicate upper horizon (e.g. A or B) whereas diagonal lines indicate a lower horizon (e.g. B or C horizon). The first vertical column indicates simplest result of next phase of pedogenesis. The second vertical column indicates either alternative result, or likely subsequent event (where columns are connected by arrows). The diagram illustrates the picture after one or two events but, with later events, the permutations become huge in number. (Marriott & Wright, 1993)

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Figure 5: Flow chart representing the stages of histosols altering to coals, and what this paper views as a paleohistosols.

Figure 6: Flow chart representing the stages of soils, such as gleysols altering into underclays, and what this paper views as paleogleysols.

73

Figure 7: A stratigraphic correlation of the San Juan Basin (Baars, 2000) 74

Figure 8: Regional stratigraphy in the Durango, Colorado Region (Evans et al, 2010). 75

Figure 9: A stratigraphic section containing the Sewickley coal bed of the Monongahela Group. From USGS (http://pubs.usgs.gov/circ/2004/1264/html/trip3/fig11.html)

76

Figure 10: Push-cores from Brown’s Lake bog were taken with 06BLT-01 near the center of the bog, and 06BLT-08 was furthest away from the bog’s center.

77

Figure 11: Stratigraphic section of a portion of the Menefee Formation, in the San Juan Basin, outside Durango, Colorado. The location of samples used for petrography and SEM analysis are shown. The grain sizes are indicated at the bottom of the section and are Clay (C, on the far left), Silt (S), Very Fine sand grains (Vf), Fine sand grains (F), Medium sand grain (M), and Coarse sand grains (C, on the far right).

78

A.

B.

Figure 12: Sample 06MF01 from the Menefee Formation. (A) thin layers of humified organic matter in a fissile mudstone (scale bar = 20 µm), (B) Possible humified roots in a fissle mudstone (scale bar = 20 µm).

79

50µm

Figure 13: Sample 06MF02 from the Menefee Formation, a rooted underclay, with a sand grain coated with argillans and a thin coal bleb or root (scale bar = 50 µm). 80

A.

B.

Figure 14: Sample 06MF02 from the Menefee Formation shown in thin section. (A) Root structure, (B) Root structure. 81

C.

D.

Figure 14 cont.: Sample 06MF02 from the Meneffee Formation shown in thin section. (C) Possible root structure, and (D) Twigs or organic material. 82

A.

B.

2µm

Figure 15: Sample 06MF03 from the Menefee Formation, showing conchoidal fracturing (A) and embedded sand grains (B). 83

A.

10µm

B.

5µm

Figure 16: Sample 06MF04 from the Menefee Formation. (A) Clay wraps (argillans) around some coal fragments (scale bar = 10 µm). (B) Clay structure (scale bar = 5µm). 84

A.

B.

Figure 17: Sample 06MF05 from the Menefee Formation. (A) Void from a clast (scale bar = 100µm). (B) Clay skins (argillans) (scale bar = 10µm). 85

A.

B.

Figure 18: Sample 06MF06 from the Menefee Formation. (A) Coal and mud drapes (scale bar = 10µm). (B) Sand grains with argillans (clay drapes) (scale bar = 10µm).

86

A.

B.

Figure 19: Sample 06MF07 from the Menefee Formation. (A) Clastics forming layers within a paleohistosols (scale bar = 5µm). (B) Clastics within a paleohistosols (scale bar = 5µm). 87

Figure 20: Stratigraphic section of the Fruitland Formation, in the San Juan Basin, outside Durango, Colorado. The locations of samples used for petrography and SEM analysis are shown. Symbols and abbreviations are defined in Fig. 11.

88

A.

10µm

B.

10µm

Figure 21: Sample 06MF08 from the Fruitland Formation with X-ray diffraction point analysis. (A) Original image; (B) Aluminum concentrated primarily to the left of the image (scale bar = 10 µm).

89

C.

10µm

D.

10µm

Figure 21 cont.: Sample 06MF08 from the Fruitland Formation with X-ray diffraction point analysis. (C) Carbon concentrated to the right and left of the image, in areas where there are fewer clastics; (D) Oxygen distributed throughout the image, with a small increase in concentration to the left of the image. 90

E.

10µm

F.

10µm

Figure 21 cont.: Sample 06MF08 from the Fruitland Formation with X-ray diffraction point analysis. (E) Sulfur in minor amounts throughout the whole image; (F) Silica concentrated where more clastics are visible in the original image.

91

A.

10µm

B.

10µm

Figure 22: Sample 06MF09 from the Fruitland Formation. (A) A coal with some clastic materials interspersed (scale bar = 10 µm). (B) Conchoidal fracturing in a coal (scale bar =10 µm).

92

Figure 23: Stratigraphic section of the Sewickly Coal in the Pittsburgh Formation, in West Virginia. The location of samples used for petrography and SEM analysis are shown. Symbols and abbreviations are defined in Fig. 11.

93

A.

B.

Figure 24: Sample I7900306 from the Pittsburgh Formation in thin section. (A) Clasts have oriented themselves in layers, and the arrow points at some organic material. (B) Organic material forming a thin layer (see arrow). 94

A.

20µm

B.

5µm

Figure 25: Sample I7900406 from the Pittsburgh Formation. (A) Clay with what appears to be wood or roots (scale bar = 20 µm). (B) Clay (scale bar 5 µm).

95

A.

B.

Figure 26: Sample 17900506 from the Pittsburgh Formation. (A) possible coal bleb (scale bar = 10 µm). (B) Coal bleb in a silty shale (scale bar = 10 µm).

96

A.

10µm

B.

5µm

Figure 27: Sample I7900602 from the Pittsburgh Formation. (A) Coal seam (scale bar = 10 µm). (B) A small coal seam (scale bar = 5 µm).

97

A.

B.

Figure 28: Sample I7900706 from the Pittsburgh Formation. (A) Layering of clastics in a vitrinite coal (scale bar = 20 µm). (B) A layer of clastics in a vitrinite coal (scale bar = 20 µm).

98

Figure 30

Figure 29: Proposed soil profiles and environments within the Menefee Formation.

99

Figure 30: A portion of the Menefee Formation described with the terms proposed by this study: paleo-histosol (pH), paleo-histogleysol (pHg), argillaceous paleo-histogleysol (ApHg), and argillaceous paleo-gleysol (ApG).

100

Figure 32

Figure 31: Proposed soil profiles of the Fruitland Formation.

101

Figure 32: A portion of the Fruitland Formation described with the terms proposed by this study: paleo-histosol (pH), and paleo-histogleysol (pHg).

102

Figure 33: Proposed soil profiles of the Pittsburgh Formation.

103

Figure 34: A portion of the Pittsburgh Formation described with the terms proposed by this study: paleo-histosol (pH), paleo-histogleysol (pHg) and argillaceous paleo- histogleysol (ApHg).

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APPENDICES

Table A1: Summary of the Stratigraphy at the Menefee Formation in the San Juan Basin.

Layer Thickness (cm) Description

16 110 Sandstone.

Interbedded sandstone and shale. Sandstone typically 15 37 4cm thick, planar laminated.

14 9 Nodular chert.

A grey-olive mudstone. Unweathered (10YR5/6), 13 27 weathered (2.5Y4/2).

12 7 A fine-grained sandstone with coal fragments.

11 21 A gray, silty mudstone. (2.5Y3/0)

A lenticualr, flaser bedded, medium grained sandstone, 10 20 wavy bedding at base. (5Y8/1)

Interbedded finegrained sandstone and mudstone,rippled, 9 14 flaser bedded in part. (2.5Y7/0, 2.5Y5/0)

A coal with thin vitrinite blebs, thin layering with organics, 8 12 orange weathering along fractures.

A fissle, rooted, gray mudstone, contains coal fragments 7 6 and small blebs. Unweathered (2.5Y2/0), weathered (10YR5/8).

Laminated, alternating very fine grained sandstone and 6 13 mud drapes, rooted. Mud drapes are ~6mm thick.

Laminated, very fine grained sandstone, rooted. 5 25 (Unweathered (2.5Y4/0), weathered (10YR6/8). A fissle, gray silty mudstone, yellow-orange along fractures, roots, coal fragments, small vertical burrows 4 54 (2cmx0.3cm). Unweathered (7.5YR3/0), weathered (5YR5/8). Coal. Fills topography, flat top, vertical joints. 3 11 Unweathered (2.5Y2/0), weathered (10YR5/8). Rooted underclay layer, orange weathering, roots taper 2 20 and biofurcates downward. Unweathered (2.5Y6/3), weathered (2.5Y5/2, 2.5Y6/0). Black, sandy mudstone, fissle, vertical roots, twigs, unit 1 26 is more broken near upper contact.

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Table A2 : Summary of the Stratigraphy at the Fruitland Formation in the San Juan Basin.

Layer Thickness (cm) Description Organic shale. Unweathered (2.5Y2/0), weathered 20 9 (2.5Y5/0)

19 40 Coal interbedded with thin shales. (2.5Y3/0)

18 18 Fissle organic shale. (2.5Y2/0)

17 15 Coal with partings and compressions.

Organic shale, with siltstone lense. Unweathered 16 13 (2.5Y3/0) Coal, highly compacted, thin layers of vitrinite. 15 38 Unweathered (2.5Y3/0).

14 105 Covered section.

13 63 Wavy bedded, fine grained sandstone.

12 48 Fissle, gray mudstone-siltstone.

11 3 Medium grained sandstone.

10 28 Coal with thin vitrinite layers. (2.5Y2/0)

9 22 Organic shale. (2.5Y2/0)

Amalgamated coal layer with vitrinite lenses. Vitrinite 8 75 (2.5Y2/0), thinly bedded coal (2.5Y3/0). Fissle, organic shale, with organic fragments. 7 37 Unweathered (2.5Y3/0). Coal, discontinous bedding, highly compacted. 6 43 (2.5Y2/0). Organic shale with discontinuous coal blebs 2 mm 5 16 thick. Unweathered (7.5YR3/0). Wavy bedded, fine grained sandstone with coal 4 4 fragments. Unweathered (2.5Y4/0). Interbedded coal and vitrinite layers, with plant 3 30 fragments (1-2cm thick and 1-2mm thick respectively). Interbedded black shale and thin coal blebs. Coal 1-2 2 20 mm thick, discontinuous. (2.5Y3/0).

1 12 Coal (2.5Y2/0).

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Table A3: Summary of the Stratigraphy of the Sewickley Coal bed, at the Pittsburgh Formation in the Appalachian Basin. Layer Thickness (cm) Description A blocky vitrinite coal with two layers of a dull coal that were 18.4 and 3.2cm 7 125.1 thick. An interbedded yellow grey shale that contained mica flakes, and organic 6 26.7 shale (5Y7/2-5Y5/2, N3). Thin, discontinuous coal seams at base. Grain size <0.1.

5 19.7 A planar bedded, silty sandstone. (5Y5/2, N5)

A silty shale interbedded with organic shale, contains mica and clay. 4 3.2 (5Y7/2, N3)

3 16.5 A clay that grades into sand with interbedded organics. (N5)

A planar, discontinuous, very fine silty shale, interbedded with clay and 2 20.3 organics. Contains occasional sand lenses and there is an increase in organics towards the top.

1 19.1 A quartz, mica sandstone. (5Y7/2, 5YR4/4)