Outcrop Based Facies and Architecture Analysis of the Regional Intertonguing of Early Jurassic Kayenta Formation with the Navajo Sandstone, Kanab Canyon, Utah

Muhammad Sadeed Hassan

A thesis submitted in conformity with the requirements for the degree of Master of Applied Science Department of Earth Sciences University of Toronto

Muhammad Sadeed Hassan

Master of Applied Science

Department of Earth Sciences University of Toronto

2015 Abstract

The establishment of the extensive Navajo erg can be identified in the Lower Jurassic rocks of the Kanab Canyon area by three distinct and successively thicker advances over the marginal fluvial Kayenta. A total of 15 fluvial and eolian facies were identified based on several vertical sedimentological logs. The facies were summarized in four main facies associations, representing multistorey braided fluvial channels, unconfined ephemeral fluvial sandsheets, erg margin and eolian dune depositional settings. The eolian units have a consistent paleoflow towards the east, which opposed the fluvial paleoflow towards the west. Fluvial architectural element analysis was completed in four lateral outcrop profiles. Additionally, two lateral architectural profiles were completed within the eolian units. Based on systematic vertical facies association transition and overall decrease in fluvial energy upsection, three drying-up trends were identified. These trends are proposed to be correlative across the basin and likely represent climatic cycles.

Acknowledgments

First and foremost, I would like to thank my supervisor Dr. Andrew Miall for introducing me to this area of research and providing me with much needed guidance, editorial assistance and financial support. I would also like to thank my committee members, Dr. Ulrich Wortmann and Dr. Nick Eyles for their editorial support and guidance.

Introduction to the geology of the southwest USA, field logistics and the progress of this project would have been impossible without the help of Dr. Gerald Bryant. Gerald and his wife Deb have made every trip to Utah very memorable and enjoyable. Gerald has also been a genuine mentor and a true source of inspiration.

I would also like to thank Tassos Venetikidis for his support through every phase of this project. I truly cherish the times we have spent together in Kanab during the two field seasons. I am grateful for your immense field knowledge and also providing the motivation on days when things were not the clearest. Thanks for all the great laughs and for being a true friend.

Thanks to all the other graduate students in the department for providing a great social and academic environment. I feel lucky to have met so many people during my time at the University of Toronto. Special thanks to Stefan Markovic for the great discussions and always lending an ear.

Last but definitely not the least, the support from my family and friends comes in countless ways. Thanks for keeping me sane and providing me with much needed distractions and of course, always believing in me. I would not have completed this without the constant love and support.

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Table of Contents

Acknowledgments ...... iii

Table of Contents ...... iv

List of Tables ...... viii

List of Figures ...... ix

List of Appendices ...... xii

Chapter 1 ...... 1

Introduction and Background ...... 1

1.1 Introduction and Research Objectives ...... 1

1.2 Study Area ...... 2

1.3 Methods ...... 3

1.4 Tectonics and Basin Setting ...... 5

1.4.1 Kayenta-Navajo Depositional Basin ...... 5

1.4.2 Basin Subsidence ...... 7

1.4.3 Jurassic Paleogeography and Climate ...... 8

1.5 Previous Work ...... 9

Chapter 2 ...... 14

Sedimentology, Facies Description and Associations ...... 14

2.1 Introduction ...... 14

2.2 Facies Description ...... 19

2.2.1 Massive to crudely stratified intraformational conglomerate (Gm)...... 19

2.2.2 Trough cross bedded intraformational conglomerate (Gt) ...... 20

2.2.3 Erosional scours with muddy intraclasts sandstone (Sc) ...... 21

2.2.4 Horizontal to low angle laminated sandstone (Sh) ...... 23

2.2.5 Rippled sandstone (Sr) ...... 24

2.2.6 Planar cross bedded sandstone (Sp) ...... 25

2.2.7 Interbedded laminated siltstone and mudstone (Fl) ...... 26

2.2.8 Massive mudstone (Fm) ...... 27

2.2.9 Flaser bedded mudstone (Ff) ...... 28

2.2.10 Structureless to mottled siltstone and mudstone (Fr) ...... 29

2.2.11 Wavy Laminated Sandstone (Sw) ...... 31

2.2.12 Structureless sandstone (Eolian) (Sse) ...... 33

2.2.13 Planar-tabular cross bedded sandstone (Eolian) (Spe) ...... 34

2.2.14 Large scale cross bedded sandstone (Eolian) (Sle) ...... 35

2.2.15 Interdune carbonate (Fc) ...... 35

2.3 Paleocurrent Analysis ...... 37

2.4 Facies Associations ...... 39

2.4.1 Facies Association 1 (FA1): Multistorey braided fluvial channels ...... 39

2.4.2 Facies Association 2 (FA2): Unconfined fluvial sandsheets and overbank deposits ...... 41

2.4.3 Facies Association 3 (FA3): Sandsheet and erg margin ...... 44

2.4.4 Facies Association 4 (FA4): Eolian dune and draa ...... 46

2.5 Petrography ...... 48

2.5.1 Springdale Member ...... 50

2.5.2 Lower Kayenta ...... 50

2.5.3 Kayenta Eolian ...... 51

2.5.4 Upper Kayenta ...... 51

2.5.5 Lamb Point Tongue ...... 52

2.5.6 Tenney Canyon Tongue ...... 52

2.5.7 Navajo ...... 52

2.6 Cement ...... 53

2.6.1 Dolomite Cement and Source ...... 54

2.6.2 Authigenic Clays ...... 54

2.7 Point Count Analysis ...... 55

Chapter 3 ...... 58

Fluvial and Eolian Outcrop Architectural Studies ...... 58

3.1 Introduction ...... 58

3.1.1 Fluvial architectural scheme and element analysis ...... 59

3.1.2 Eolian architectural and elements analysis ...... 64

3.2 Fluvial Architectural Analysis ...... 65

3.2.1 Springdale Dry Canyon Panel 1 ...... 66

3.2.1.1 Interpretation ...... 67

3.2.2 Springdale Dry Canyon Panel 2 ...... 70

3.2.2.1 Interpretation ...... 71

3.2.3 Upper Kayenta Panel ...... 74

3.2.3.1 Interpretation ...... 75

3.2.4 Tenney Canyon Tongue Panel ...... 77

3.2.4.1 Interpretation ...... 78

3.3 Eolian Architectural Analysis ...... 81

3.3.1 Lamb Point Tongue ...... 81

3.3.1.1 Interpretation ...... 81

3.3.2 Navajo ...... 84

3.3.2.1 Interpretation ...... 86

Chapter 4 ...... 87

Fluvial and Eolian Vertical Transitions ...... 87

4.1 Introduction ...... 87

4.2 First fluvial to eolian transition ...... 87 vi

4.2.1 Interpretation ...... 89

4.3 Second Fluvial to Eolian Transition ...... 91

4.3.1 Interpretation ...... 92

4.4 Third Fluvial to Eolian Transition ...... 94

4.4.1 Interpretation ...... 95

4.5 Eolian to Fluvial Transition ...... 97

4.5.1 Eolian Soft Sediment Deformation ...... 98

Chapter 5 ...... 102

Discussion and Conclusion ...... 102

5.1 Summary and Discussion ...... 102

5.2 Conclusion ...... 107

References ...... 108

Appendix I ...... 115

Appendix II ...... 125

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List of Tables

Table 2- 1 Facies Summary ...... 15

Table 2- 2 Rock samples categorized by facies and point count analysis...... 48

Table 2- 3 Normalized QFR values from point count analysis for each unit ...... 55

Table 2- 4 Normalized point counted QFR values for each facies ...... 57

Table 3-1 Summary of fluvial bounding surfaces hierarchy ...... 59

Table 3-2 Summary of fluvial and eolian architectural elements ...... 61

Table 3-3 Summary of eolian bounding surfaces ...... 64

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List of Figures

Figure 1-1 Kanab study area...... 3

Figure 1-2 Early to Mid-Jurassic tectonic and depositional features...... 6

Figure 1-3 Decompacted basin subsidence curves ...... 8

Figure 1-4 A) Stratigraphic panel Glen Canyon Group...... 10

Figure 1-5 Relevant Kayenta, Navajo and Kayenta-Navajo studies in the region...... 11

Figure 2- 1 Gm facies...... 20

Figure 2- 2 Gt facies...... 21

Figure 2- 3 Sc facies ...... 22

Figure 2- 4 Sh facies...... 24

Figure 2- 5 Sr facies...... 25

Figure 2- 6 Sp facies ...... 26

Figure 2- 7 Fl facies...... 27

Figure 2- 8 Fm facies ...... 28

Figure 2- 9 Ff Flaser ...... 29

Figure 2- 10 Fr Facies ...... 30

Figure 2- 11 Sw facies...... 32

Figure 2- 12 Sse facies ...... 33

Figure 2- 13 Spe facies...... 34

Figure 2- 14 Sle facies...... 35

Figure 2- 15 Fc facies...... 36

Figure 2- 16 Summary of paleocurrent measurements from each unit ...... 38

Figure 2- 17 Springdale Channel ...... 40

Figure 2- 18 Upper Kayenta fluvial examples...... 43

Figure 2- 19 Facies association 3...... 45

Figure 2- 20 Facies association 4...... 47

Figure 2- 21 Photomicrographs of various types of cements ...... 54

Figure 2- 22 QFR ternary plot for all point counted samples ...... 56

Figure 3-1 Map showing the lateral profile studies...……………………………………………65

Figure 3-2 Lower Springdale Member Dry Canyon exposure architecture panel ...... 68

Figure 3-3-3 Springdale sandy braided river model...... 70

Figure 3-4 Upper Springdale Member Dry Canyon exposure architecture panel ...... 73

Figure 3-5 Upper Kayenta architectural element analysis outcrop panel...... 76

Figure 3-6 Sheetflood fluvial plain depositional model ...... 78

Figure 3-7 Tenney Canyon Tongue architectural element analysis outcrop panel ...... 80

Figure 3-8 Lamb Point Tongue architectural outcrop panel ...... 83

Figure 3-9 Navajo architectural outcrop panel ...... 85

Figure 4-1 First fluvial to eolian transition...... 88

Figure 4-2 Relationship of sedimentation rate and pedogenesis rate ...... 90

Figure 4-3 Second fluvial to eolian transition ...... 93

Figure 4-4 Third fluvial to eolian transition...... 95

Figure 4-5 Terminal fan model...... 96

Figure 4-6 Eolian to fluvial transitions...... 100

Figure 5-1 Kayenta-Navajo transition synthesis...... 103

Figure 5-2 Basin correlation of Kayenta-Navajo drying upward cycles...... 106

List of Appendices

Appendix I Sedimentological Logs……………………………………………………………115

Appendix II Thin Section Descriptions……………………………………………………….125

xii 1

Chapter 1

1 Introduction and Background 1.1 Introduction and Research Objectives

The main objective of this research is twofold, firstly is to gain a more comprehensive understanding of the temporal framework of fluvial-eolian facies successions present in the Early Jurassic deposits of the Kayenta Formation (Kayenta) and the Navajo Sandstone (Navajo). Secondly, the aim is to provide an explanation for the cyclic nature of the fluvial and eolian units which is consistent with the existing studies in the depositional basin. The chosen study area of Kanab canyon, Utah covers an approximately 36 km2 and contains some of the thickest and most accessible exposures of the Kayenta-Navajo intertonguing units (Fig. 1-1). These contrasting depositional systems are governed by major allogenic and autogenic controls which are deciphered through outcrop based vertical logs as well as lateral architectural studies. The chosen study site of Kanab Canyon, Utah provides the needed resolution at which to analyze this erg margin interaction. Previous studies have examined this fluvial-eolian interaction at various scales and localities (Middleton and Blakey, 1983; Sargent, 1984; Tuesink, 1989; Luttrel, 1987; Herries, 1993; Long, 2008); however, the combined use of detailed vertical sections, petrographical analysis, and facies architectural studies applied within this study will provide the much needed summation to the Kayenta-Navajo transition in the western region of this Jurassic retro-arc foreland basin.

This study applies a chronological approach to facies assemblages within the fluvial and eolian depositional systems of an ancient erg margin. In addition, major surfaces at unit boundaries help to mark hiatuses in deposition which are used to isolate possible autogenic and allogenic controls. The outcrop quality in the area allow for continuous lateral exposures which are the basis for photo-mosaic interpretations. Without major dating controls in these non-marine continental rocks, detailed mapping and study of major unconformities can provide a relative chronological scheme to understand the cyclic nature of this interaction. Modern dating techniques of continental siliciclastic rocks are not within the unit scale resolution needed. Therefore, other methods of subdividing these units become important for a temporal scheme.

Based on vertebrate fauna assemblage the Kayenta has been dated between 190 Ma to 200 Ma, with the deposition taking place over a minimum of 5 Ma (Peterson and Pipiringos, 1979). An early Jurassic age is now well accepted for the Kayenta-Navajo.

1.2 Study Area

The study area (Fig. 1-1) was chosen for its exceptional outcrop exposures and accessibility. The cliff faces in Kanab canyon offer continuous lateral exposures and are ideal for architecture studies. The three-dimensional exposures also help with understanding paleo-geomorphic features and analysis of paleoflow directions. These outcrops are the key to the analysis of fluvial channels in their entirety. The Kanab canyon area located in the western-central area of the paleo-basin and has preserved some of the thickest sequences of both fluvial Kayenta and eolian Navajo units.

The present day Kanab creek flows from a north to south orientation and therefore the rocks of Kayenta-Navajo are exposed in the east and west facing cliffs. The cliffs in many cases reach almost 100 meters in height. Stratigraphically, the southern region of the Kanab canyon study area exposes the oldest rocks of the Glen Canyon Group, with the Moenave Formation at the base and the Navajo Sandstone towards the north creating a plateau. For the purpose of this study all major contacts are exposed within the units of interest, except the upper boundary of the Navajo. Most of the land accessed during the field excursions was public or private land, and permission for access was arranged accordingly.

Figure 1-1 Kanab Canyon study area marked in red star, located just north of the town of Kanab and 90 km east of St. George. The field study area is approximately 36 km2 (Google Earth, 2013).

1.3 Methods

The main techniques applied in this study include: detailed vertical sedimentological logs (Appendix I), petrographic analysis (Appendix II) and lateral architectural panels. Majority of the field data was collected during the summer of 2013, and a follow up field visit was completed during April 2014. Architectural analysis was undertaken using outcrop panoramas as well as vertical logging sections. Lateral profiles were only taken where outcrop quality was good and the cliff face was clearly exposed. Due to the nature of the rocks, the finer grained facies produce less resistant and poor cliff faces therefore the sandier facies were preferably chosen for lateral profiles. The lateral profiles were mainly completed in cliff faces exposing the stacking patterns of paleo-fluvial channels as well as where paleocurrent measurements could be obtained. Within eolian units, lateral architectural analysis was completed in areas that showed

4 several hierarchical eolian bounding surfaces or a variety of paleo-geomorphic features. The lateral panels were used to display the facies and develop a more detailed facies association scheme.

Individual photos were stitched to form a photo-mosaic using Adobe Photoshop® which provided the base field maps for architectural analysis, paleocurrent measurements and major bounding surfaces. These photomosaic show the variability in fluvial and eolian elements in orientations parallel and perpendicular to paleoflow. Inaccessible cliff faces were studied using a TruPulse® laser rangefinder monocular, which allowed remote measurements of vertical and horizontal distances. Further addition to stitched and interpreted photo-mosaics was completed using the drawing software, CorelDraw®.

Detailed vertical sections were completed in each fluvial to eolian and eolian-fluvial transition zone, totaling to 7 sections. These logs document the variation in grain size, sedimentary structures, unit thickness, nature of contacts, paleocurrent measurements and relative unit relationships. Furthermore, 61 rock samples were collected, of which 45 were used to produce thin sections and used in petrographic analysis. A sample was taken from each facies, but only the silt to sand sized rocks were prepared into thin sections. The petrographic work was essential in defining the major facies and facies assemblages.

Paleoflow measurements in fluvial and eolian rocks were obtained within the most reliable features and bedforms. The paleoflow data were compiled and displayed using Rose.Net. Simple statistical values were also obtained from the software application.

The basic fluvial lithofacies terminology was adapted from Miall [1978] with some additions. The bounding surface hierarchy and architectural element analysis was applied using Miall [1985; 1996] classification scheme. No major modifications were made to the existing terminology and schemes.

The eolian lithofacies are less defined in the literature; however some eolian facies nomenclature was modified from Tuesink [1989]. The hierarchy of bounding surfaces in eolian photomosaics utilize Brookfiled [1977] naming and classification scheme. Further discussion on the modification of the eolian architecture scheme and the proposed element scheme is discussed in Chapter 3.

1.4 Tectonics and Basin Setting

1.4.1 Kayenta-Navajo Depositional Basin

The extensive outcrops of Mesozoic eolian deposits represent some of the largest and best preserved eolian accumulations in the geologic record. These erg deposits are widely spread throughout the Permian to Jurassic successions of the southwest USA. The preservation of these continental rocks requires large scale consistent accommodation generation. After the breakup of Pangea in the Late Triassic to Early Jurassic, the south and western margin of North America transitioned from an island arc setting to an Andean type convergent margin (Dickinson, 1976) (Fig. 1-2). This resulted in the formation of a northwest to southeast aligned retro-arc basin known as the Utah-Wyoming-Idaho trough in the southwestern USA. Coeval deformed strata present in Nevada supports a flexural subsidence model associated with a compressional foreland basin setting (Bjerrum and Dorsey, 1995; Allen et al., 2000). Furthermore, evidence of a coeval continental volcanic arc is present through central Arizona and has been named the Mogollon Highlands (Dickinson, 1981).

Loading of the continental crust from the Cordilleran belt dates back to Early Jurassic, with eolian and non-eolian sediments preserved at maximum accommodation generation. Originally, the Early Jurassic was marked by extension followed by contraction during the Middle to Late Jurassic (Allmendinger, 1992). Recently however, the plutons in northwest Nevada have given an age of a shortening event between 200 and 185 Ma in the Early Jurassic (Wyld, 1996). This supports a retro-arc foreland basin model, where the loading and contraction provided the necessary flexural subsidence for basin formation. The basin fill is the thickest in the west, as expected and these wedge shaped fills are present throughout the Mesozoic, separated by regional unconformities coeval with loading in the western Cordillera (Riggs and Blakey, 1993; Peterson, 1994; Allen et al., 2000). Since the Glen Canyon Group is truncated by the J2 unconformity everywhere (the boundary between Absaroka and Zuni Sequences of Sloss, 1963), it is difficult to say that the increase in thickness towards the west is solely a result of increased subsidence, uplift and truncation towards the east or a combination (Blakey, 1994).

Figure 1-2 Early to Mid-Jurassic tectonic and depositional features. The preserved intertonguing zone of the Kayenta and the Navajo is shown in brown. The paleocurrent data from the Kayenta and Navajo is summarized from Luttrell (1987) and show opposing paleoflow. Figure modified from Dickinson and Gehrels, 2003; Blakey, 2008; Blakey et al., 1988.

Provenance studies based on petrographic work (Luttrell, 1987) and zircon dating (Dickinson and Gehrels, 2003) has helped to establish the major source areas for the Kayenta and the Navajo. The overall Kayenta basin is roughly oriented northeast to southwest, with sandier

7 deposits in the north, sourced from the Uncompahgre uplift, and siltier deposits in the south, sourced from the Cordilleran arc and the Mogollon highlands towards the south and southeast (Luttrell, 1993). The zircon studies from the Navajo erg show inheritance from the Appalachian (475-525Ma) and Grenville (1125-1225 Ma)) orogens located in the east coast of North America (Dickinson and Gehrels, 2003). Large trans-continental fluvial systems are suggested as the main transport system for these zircons which were further incorporated by eolian processes into the Navajo and Kayenta deposits (Marzolf, 1988).

1.4.2 Basin Subsidence

Based on the decompacted subsidence curves (Fig. 1-3) for the Jurassic basin, a slow background subsidence is superimposed on two distinct events at 205-185 Ma and 180-160 Ma (Allen et al., 2000). The 205-185 Ma, Early Jurassic event is coeval with the deposition of the Navajo erg, whereas the later event is associated with the deposition of the younger Entrada Sandstone (Mid Jurassic). The deformed strata in Nevada have been used to explain the orogenic load for these basin subsidence events (Allen et al., 2000). The shape of the curves suggests flexural control on foreland basin subsidence thereby allowing preservation of the massive erg deposits. Conversely, the main driving mechanism for the slow basin subsidence does not fit a thermal contraction curve and is attributed to dynamic subsidence caused by subduction of oceanic crust under the North American plate (Burgess et al., 1997).

Figure 1-3 Decompacted basin subsidence curves for Zion, Capitol Reef and Moab area of Utah. Navajo and Entrada erg deposits correspond to the highest subsidence rate with a convex up signature typical of flexural loading (Allen et al., 2000)

1.4.3 Jurassic Paleogeography and Climate

Paleogeographic reconstruction studies of the early Jurassic, place the Kayenta-Navajo system between 5-25° paleo-latitude, which is consistent with modern day arid to semi-arid areas of the world (Kocurek and Dott, 1983). After the breakup of Pangea during the Late Triassic, sea levels were beginning to rise due to high rates of sea floor spreading forming mid oceanic ridges. The early Jurassic was a greenhouse world, during which the temperatures were warm and humid with arid continental interiors (Golonka and Ford, 2000).

Based on general circulation models for the Jurassic, evaporation is higher than precipitation between 30°N and the equator (Sellwood and Valdes, 2006). However, in the southwest of USA, the western cordillera produced an orographic effect, which amplified the latitudinal effect (Kocurek and Dott, 1983). The wind patterns deduced from paleocurrent measurements of Early Jurassic windblown strata are generally consistent with climate models. The wind blew from the northeast-northwest, as a result of the clockwise rotation of the high pressure cell off the west coast of Pangaea (Loope et al., 2001). A strong monsoonal weather pattern however persisted

9 throughout the deposition of the Navajo, as evident from the intervals of slumping and slope failures in the Navajo eolian dunes (Loope et al., 2001; Bryant, 2011).

Loope et al. [2004] presented a review for the Early Jurassic wind patterns and concluded that the dominant wind direction recorded by the cross bedding of the Navajo is related to the north- south monsoonal wind flow over Pangea during northern hemisphere winter. Furthermore, magnetic properties of the Triassic and Jurassic rocks of the Colorado Plateau places the four corner region at about 10-17° during the early Jurassic, which is consistent with the aforementioned wind patterns (Steiner, 1983; Loope et al., 2004).

1.5 Previous Work

The Kayenta and Navajo were formally recognized as formations within the Glen Canyon Group by Averitt et al. [1955]. Averitt and his coworkers defined the stratigraphy of the Glen Canyon Group and recognized the main tongues of the Kayenta and Navajo in Utah and Arizona. A series of US Geological Survey professional papers further defined the overall stratigraphy and sedimentology of the Jurassic rocks in Utah and Arizona (Harshbarger et al 1957; Pipiringos and O’Sullivan, 1978; Peterson and Pipiringos, 1979). Based on paleontological and stratigraphical criteria the Kayenta and Navajo has been assigned to the late Sinemurian and early Toarcian, representing an accumulation time span of minimum 8 million years to a maximum of 15 million years (Allen et al., 2000 and references therein). Radiometric dates from within the Kayenta or Navajo have never been published, so it is only from age dating the overlying Temple Cap Formation [Kowallis, 2001] and the palynomorph study from the underlying Moenave [Litwin, 1986] that the Kayenta-Navajo are age bracketed. Unlike the overlying eolian Entrada Sandstone, the Kayenta and Navajo do not have coeval marine rocks preserved towards the west.

The intertonguing of the Kayenta with the Navajo was noted by early workers in the area, but it wasn’t until Wilson [1958] that separate fluvial and eolian tongues were allocated to the Kayenta and Navajo. The regional extent and facies relations of the intertonguing were first described in detail by Middleton and Blakey [1983]. Further major study locations relevant to this work are summarized in Figure 1-5.

In ascending order the Glen Canyon Group includes the fluvial/lacustrine Moenave Formation and its eolian eastern equivalent, Wingate Formation. Overlying conformably is the Springdale

10 member, which is now assigned to the Kayenta Formation (Lucas and Tanner, 2006). In the Kanab study area, the main eolian tongue of the Navajo overlies the Kayenta and is named the Lamb Point Tongue (LPT), which is overlain by the fluvial Kayenta tongue, named Tenney Canyon Tongue (TCT). The Glen Canyon Group is underlain by the J0 unconformity and capped by the J1/J2 unconformity. Figure 1-4A outlines the overall stratigraphy of the Early Jurassic in a general east to west cross section. The stratigraphic units of interest in the Kanab study area are shown in Figure (1-4B), which outlines the nomenclature for the main units and tongues used in this study.

Figure 1-4 A) Stratigraphic panel oriented east to west for the Glen Canyon Group. Overlying and underlying units are included for reference. B) Stratigraphic nomenclature for the units and tongues in the Kanab canyon study area. Modified from Long, 2008 after Allen et al., 2000.

The intertonguing of the Kayenta and Navajo suggests that deposition was relatively continuous and concentrated in the southern edge of the erg advance (Fig. 1-2); however significant surfaces are recognized within these deposits and are discussed in Chapter 4. The two main recognized tongues of the Navajo and the Kayenta are the LPT and TCT, respectively. These tongues are most prominent in the western part of the basin, and reach the maximum thickness around the Kanab to Zion area. Middleton and Blakey [1983] were the first to describe the intertonguing in the central part of the basin, from Moenkopi Arizona to west of Kanab. Several allogenic

11 controls were suggested for the intertonguing, none of which have been entirely confirmed by later work.

The fluvial Kayenta Formation has been well studied throughout its exposures in the Colorado Plateau (Fig. 1-5). The sandier ledge forming units of the Kayenta are prominent in outcrop and contrast the upper muddier slope forming units. The Kayenta has been traditionally separated into ‘sandy’ facies present in the northeastern parts of the basin and ‘silty’ facies concentrated in the southwestern part of the basin (Harshbarger et al., 1957). The transition between the two broad facies is gradational and the Kanab study area falls within the ‘silty facies’. This terminology is misleading at a finer resolution but suffice for an overall general view. The lower Kayenta, including the Springdale Member, is coarser grained than the remaining Kayenta deposits upsection. Coarser grained facies also occur upsection in the silty facies, but are not common. Therefore, this author and others [Long, 2008] recommend applying this terminology with caution.

Figure 1-5 Relevant Kayenta, Navajo and Kayenta-Navajo studies in the region.

The architectural element analysis and bounding surface scheme was initially developed and applied to the Kayenta Formation in west central Colorado (Miall, 1985; Miall, 1988). Further sedimentological and architectural studies within the Kayenta basin provided the initial understanding of low sinuosity braided fluvial systems in the geologic record (Bromley, 1991; Luttrell, 1993; Sanabria, 2001). Bromley [1991] presented detailed fluvial paleocurrent and

12 lithofacies data on architectural panels and related the fluvial architecture to underlying salt movement. First detailed basin wide study of Kayenta was completed by Luttrell [1987]. This study provided a clearer understanding of the sedimentology and provenance of the fluvial drainage. Luttrell [1993] also documented the changes in lithofacies within the basin and related it to the migration of facies belts.

Sargent [1984] provided a detailed sedimentological and petrological study of the Kayenta Formation in south central Utah, near Capital Reef National Park area. Friz [1985] expanded the study area of Sargent [1984] and identified an eastward thinning tongue of the Navajo within the Kayenta in the Capital Reef Area. The aforementioned studies are not included in Figure 1-5 because studies that followed in the next few decades are much more detailed and regional.

Taylor [1994] made use of the Kayenta outcrops as an ephemeral-fluvial analogue for similar subsurface oil and gas reservoirs. The identified facies were regarded in terms of important features for a hydrocarbon reservoir such as in situ permeability. Fluid flow models were also constructed to analyze the role of main facies in reservoir performance.

Sanabria [2001] focused on the sedimentary structures found within the Kayenta and associated them with ideal ephemeral fluvial flows. This in turn was used to formalize a sequence stratigraphic model for arid to semi-arid ephemeral fluvial deposits. The sedimentary features were analyzed at various scales along the Vermillion cliffs, Echo cliffs of northern Arizona and the Moab area in southeastern Utah (Fig. 1-5). A total of 13 high frequency cycles were proposed as an explanation for the Kayenta and Navajo rocks exposed in the area (Sanabria, 2001).

The overall transition from dominantly fluvial to the establishment of a full erg is no doubt attributed to allogenic controls. The transition is marked by two major tongues in the Kanab study area which have been included in previous research (Tuesink, 1989; Long, 2008). Tuesink [1989] described the Kayenta-Navajo transition in southwest Utah and provided a facies assemblage for the intertonguing. Based on twelve vertical logs, Tuesink [1989] proposed an overall depositional model for the study area. The variations in sedimentary structures regionally were used as evidence to support the changes in depositional environments, but only preliminary conclusions were drawn from the data.

Herries [1993] proposed three fluvial to eolian drying up cycles for the transition units of Kayenta-Navajo in and around Moenkopi wash, northeastern Arizona. Each cycle represents greater fore erg advancement over the alluvial plain capped by a stabilization surface. These three fluvial-eolian cycles are attributed to climatic, tectonic or eustatic effects.

Long [2008] proposed 12 high frequency and 3-4 low frequency Milankovitch related cycles for the Kayenta in northeastern Arizona based on lithofacies association and lateral architectural profiles. Furthermore, the fluvial channel fills are described to have a range of high to low energy lithofacies which grade vertically into eolian associated facies. An overall change in fluvial style from sandy braided perennial streams to flashy ephemeral streams is proposed. A long term increase in aridity is recognized within the Kayenta based on the aforementioned evidence.

Although there have been innumerable studies on various components of the Navajo, only a few have been regional in nature with a strong focus on sedimentology, lithofacies and importance of non-eolian units. These include the work by Marzolf [1983] and Sansom [1992]. Marzolf [1983] provided a regional paleocurrent analysis and the association with non-eolian units such as interdunes, erg margin and fluvial deposits. Marzolf [1983] also concluded that the LPT in the western part of the basin is coeval with the lower 50 m of the main body of the Navajo in south- central Utah. Furthermore, there are several recognized deposition hiatuses within the Navajo and the entire formation is not coeval. Sansom [1992] completed a detailed sedimentological study of the Navajo in two different parts of the basin with a focus on genetically related non- eolian units. The two contrasting study sites presented by Sansom [1992] allowed an eolian genetic stratigraphy to be compiled, based on recognition of major eolian supersurfaces.

This current study provides the local scale focus on the Kayenta-Navajo transition on the western end of the basin. The Kanab study area has been previously examined by several workers, however have only been included in large scale studies at a very coarse resolution. This study will allow a focus on the exceptional outcrop exposures at Kanab Canyon in a regional context with some new techniques and depositional models.

Chapter 2

2 Sedimentology, Facies Description and Associations 2.1 Introduction

The Kayenta-Navajo transition in the Kanab study area is categorized into 15 facies, each of which are described in terms of its sedimentology, structures, occurrence and outcrop characteristics. The facies are then summarized into facies associations based on the depositional environment interpreted. The following list summarizes the details discussed for each facies:  Sedimentary texture (grain size, shape, sorting);  Colour, thickness and outcrop appearance  Sedimentary structures  Distribution  Petrography, diagenetic history, temporal relationships  Porosity, cement

Furthermore, a short summary of the petrography and paleocurrent measurements is also discussed. The facies description and associations discussed herein would be applied in Chapter 3 and 4 to characterize the large scale fluvial and eolian architecture within each transition. The facies discussed herein are summarized in Table 2-1.

1 Table 2- 1 Facies Summary

Facies Thickness and Sedimentary Interpretation/Facies Name Sedimentology Occurrence Code Lateral Extent Structures Association

Gm Massive to crudely Maximum 1 m; Sub-rounded; Dipping Springdale Member and Lag deposits; stratified discontinuous poorly sorted accretion Lower Kayenta; Rarely in longitudinal bar intraformational ledges elements; minor Upper Kayenta migration conglomerate imbrication

Gt Trough cross Maximum 2 m; Sub-rounded; Trough cross Springdale Member and Lag deposits, basal bedded Follows channel poorly sorted bedding Lower Kayenta channel scours intraformational base conglomerate

Sc Erosional scours Few cm to Sub-angular to Imbrication; Springdale Member; Channel scour fills with muddy interbedded ~ 1 rounded; poorly dipping ~5-10° Lower Kayenta and Upper intraclasts m sorted (bimodal Kayenta, Tenney Canyon sandstone distribution); clasts Tongue range in size ~cm to > 50 cm

Sh Horizontal to low Max 1.5 m thick, Sub-rounded to Horizontal Springdale Member; Upper flow regime; low

angle laminated interbedded with sub-angular; well lamination; Lower Kayenta; Upper angle bar accretion sandstone Sr, laterally sorted parting lineation; Kayenta; Tenney Canyon continuous horizontal Tongue ledges (10’s of contacts meters)

Sr Rippled sandstone Maximum 1.5 m Sub-rounded to Critically to sub- Springdale Member; Lower flow regime; thick, laterally sub-angular; well critically Lower Kayenta; Upper commonly associated continuous sorted climbing ripples, Kayenta; Tenney Canyon with Sh ledges (10’s of crossbedding, Tongue meters) asymmetrical ripples

Sp Planar cross Individual Sub-rounded- sub- Normal grading Springdale Member; Dunes; linguoid and bedded sandstone foresets up to 2.5 angular; well sorted in each lamina, Lower Kayenta transverse bars; m thick; larger foresets, Associated with Sc continuous dip of 10-25° ledges

Fl Laminated Maximum 1.5 m Angular; well Laminated beds, Lower Kayenta; Upper Overbank fines and siltstone and thick, sorted faint ripples, Kayenta; Tenney Canyon waning flood stages; mudstone Continuous undulatory Tongue associated with flood recessive slopes contacts plain deposition

Fm Massive mudstone mm to 10’s of - Laminated beds, Lower Kayenta; Upper Overbank and drape cm; laterally desiccated upper Kayenta; Tenney Canyon deposits, Overlies sandy discontinuous contacts, blocky Tongue Sr/Sh ledges to nodular structure

Ff Flaser bedded Upto 1 m; - Laminated flaser Lower Kayenta; Upper Floodplain and channel mudstone laterally bedding Kayenta; Tenney Canyon flood waning stage discontinuous Tongue

Fr Structureless to Few cm to max 2 - Massive, nodular Springdale Member, Paleosol development, mottled siltstone- m; Laterally calcite horizons, Lower Kayenta; Upper overbank deposits or mudstone discontinuous desiccation, Kayenta; Tenney Canyon pedogenically altered (10’s of meters) Tongue channel infills

Sse Structureless ~3 meters thick, Sub-rounded, well Reminiscent Eolian Kayenta Eolian sandsheet sandstone (Eolian) laterally sorted (bimodal eolian dunes (< continuous (10’s distribution) 0.5 m), of meters) recumbent folds,

Sw Wavy laminated Few cm to max 2 Rounded, Laminated wavy Eolian Kayenta, Lamb Damp eolian sandsheet, sandstone (Eolian) m; Laterally moderately sorted beds, Point Tongue, Base of sabkha, possible presence continuous ( 10’s (bimodal Navajo of evaporates to 100’s of distribution) meters)

Spe Planar tabular 0.5 m to 3 m; Sub-rounded to Cross beds, wind Eolian Kayenta, Lamb Crescentic dunes, small cross bedded Laterally sub-angular, ripples and Point Tongue, Navajo transverse dunes sandstone (Eolian) continuous moderately sorted avalanching deposits (grainflow), inverse grading

Sle Large scale trough 3 m up to 10 m; Sub-rounded to Cross beds, wind Eolian Kayenta, Lamb Transverse dunes, or planar cross Laterally sub-angular, ripples and Point Tongue, Navajo crescentic dunes; full erg bedded sandstone continuous moderately sorted avalanching development (Eolian) deposits, inverse grading

Fc Interdune 0.1 m to 0.5m, Sub-rounded to Wavy laminated Lamb Point Tongue, Interdune ephemeral carbonate laterally sub-angular; calcite, Tenney Canyon Tongue, ponds (limestone to continuous desiccation, Navajo dolostone)

2.2 Facies Description

2.2.1 Massive to crudely stratified intraformational conglomerate (Gm)

The Gm facies is composed of massive to crudely bedded gravel which is predominantly matrix supported. The gravel to boulder sized clasts are mainly composed of siltstone, mudstone and carbonate lithology in decreasing abundance. In the upper sections of the Springdale member, Gm facies shows calcite cementation with some prominent oxidation halos around clasts that are visible in hand sample. The base of the facies is commonly clast supported and grades into matrix supported conglomerate. The clasts are generally sub-angular to sub-rounded. Mudstone clasts show lamination and some minor deformation when present in this facies.

This Gm facies is typically seen in the Springdale Member, Lower Kayenta (LK) and rarely in Upper Kayenta (UK) and Tenney Canyon Tongue (TCT). The maximum thickness of this facies is 1 m and forms discontinuous ledges in outcrop. The light to dark gray colour of the facies is primarily from calcite cementation. The matrix is primarily yellow-reddish orange in colour and is silt to mud sized, with concentrated oxidation. The average size of the clasts is pebble sized, but large (~50cm) clasts are also seen at one locality (Fig. 2-1C). Early calcite cementation leached from this unit is present at one locality within the Springdale (Fig. 2-1B). This unit also shows erosional lower contact, which may display loading structures in addition to preferential cementation. The Gm units sometimes show < 10° dipping accretion elements (Fig. 2-1B). The overall facies colour is strongly influenced by the clasts present as well as the iron oxidation.

Figure 2- 1 Gm facies; all examples from Springdale Member (A) Large scale dipping Gm facies overlain by sandy infill (B) Dipping surfaces at approximately 12°, lower contact shows early cementation and loading (C) Large boulder within the Gm facies.

2.2.2 Trough cross bedded intraformational conglomerate (Gt)

This facies is only seen in the Springdale and occur as lensoidal features marked by a distinct erosive lower contact (Fig. 2-2A). The colour is red-orange with a range of gray-red shades from the various clasts. The clast grain size ranges from coarse sand to pebble sized and are generally sub-rounded. The conglomerate is mostly clast supported, stratified and show imbrication of the clast a-axis. The clast lithology includes mudstone, cemented carbonate and sandstones, similar to the Gm facies discussed above. The Gt facies occur in association with the sandy beds into which it truncates and is sometimes overlain by. The bedding surface of this facies shows abundant mud clasts that are flat and in many cases erode out due to preferential weathering in outcrop (Fig. 2-2B). Overall this facies is very similar to the Gm in terms of colour, thickness and outcrop appearance; however the largest grain size encountered in this facies is pebble sized. Unlike the Gm, no preferential cementation and loading structures in the lower surfaces are seen in this facies.

Figure 2- 2 Gt facies, examples from Springdale, Dry Canyon (A) Lower erosive surface of Gt, yellow lines highlight the troughs (B) Bedding surface of Gt showing preferential weathering and abundant muddy pebble sized clasts (C) Lensoidal nature of the Gt facies in its entirety, yellow lines mark the troughs.

2.2.3 Erosional scours with muddy intraclasts sandstone (Sc)

The Sc facies is composed of muddy intraclasts within a sand matrix. This facies is present in the Springdale, LK, UK as well as the TCT; it commonly grades into sandstone ledges composed of a mix of Sr, Sh or Sp facies (Fig. 2-3A&B). The mud clasts range in size from coarse sand to boulder sized, whereas the matrix is silt to fine sand. The major lithologies of the intraclasts are mud and carbonate, with some occasional organic material. The intraclasts are angular to subrounded, flattened and show imbrication. The clast boundaries show oxidation halos and sometimes have less defined boundaries as a result of calcite cement growth, as seen in the photomicrographs (Fig. 2-3C&D). The facies sometimes has a primary dip of up to 10° and

22 occurs with interbedded fine sand and imbricated mudclasts in fine sand matrix. In outcrop, the facies does not always form resistant ledges, and is laterally discontinuous. In petrographic analysis, the mud is heavily oxidized and preserves some primary lamination. Carbonate clasts are also common with micritic calcite which is distinct from the euhedral calcite and dolomite cement.

Figure 2- 3 Sc facies: A) Boulder sized mud intraclasts marking the channel base. Image from Springdale Member (B) Small scale imbrication of mud intraclasts in the Sc (C & D) Plain polarized and cross polarized photomicrographs of Sc with abundant carbonate clasts and heavily oxidized mud intraclasts.

2.2.4 Horizontal to low angle laminated sandstone (Sh)

The Sh facies is composed of horizontal laminated sandstone which forms lamina of a few mm. The lamina sets can reach up to 1.5 m in thickness and from laterally continuous and competent ledges in outcrop. The Sh facies is commonly interbedded with ripple sandstone (Sr) facies. This facies is prominent in both LK and UK units but are also present in the Springdale and TCT. The siltstone-sandstone is moderately to well sorted and form high porosity beds. The high porosity nature of these deposits has allowed abundant fluid movement through these rocks which is why these rocks have less iron oxide and exhibit patchy calcite cementation. As a result, the overall colour of this facies is lighter red to tan (Fig. 2-4A). The Sh commonly grades vertically into climbing ripple deposits marking a change in fluid velocity. Thin mud drapes or erosional surfaces sometimes demarcate the boundaries following these Sh/Sr sets. Typically each lamina is 1-5 mm in thickness and is normally graded. The bedding planes of this facies often display parting lineation and were used for paleocurrent measurements. In thin sections, the quartz and feldspar grains often exhibit overgrowths (Fig. 2-4D). This facies along with Sr form the majority of the sandy ledge forming deposits of the LK and UK.

Figure 2- 4 Sh facies (A & B) Horizontally laminated beds with transition to climbing ripples up section, examples from Upper Kayenta and Springdale, respectively (C) Sh photomicrograph showing well sorted sub-angular sand with minor to no cement (D) Same photomicrograph at higher magnification displaying quartz overgrowths on most grain contacts (back arrows).

2.2.5 Rippled sandstone (Sr)

Evidence of straight crested, sinuous, linguoid and climbing ripples are present in all the fluvial rocks of the Kayenta and collectively form the Sr facies. This pale to reddish-brown facies forms competent ledges and range in thickness from a few centimeters to approximately 1.5 meters. The sandstone is mainly fine sand-coarse silt, sub-angular and moderately sorted. Based on point counts within this facies the sandstone is subfeldspathic to sublithic arenite. Bioturbation is also sometimes present on the upper surfaces of the ledge forming facies. Rib and furrow structures are commonly seen on the bedding plane surfaces of this facies and used for paleocurrent

25 indicator (Fig. 2-5 F&G). The ripple indices average around 15 for many linguoid and climbing ripples within the Upper Kayenta. The critically to sub-critically climbing ripples are always associated with horizontally laminated facies and usually occur in co-sets (Fig. 2-5A&B). These couplets of facies are present throughout Springdale, LK and UK.

Figure 2- 5 Sr facies. (A) Interbeds of Sh and Sr; the outlines depict the ripples and cross laminations with Sh, example from Springdale (B) Similar interbeds of Sh and Sr, development of climbing ripples ; example from Upper Kayenta C) Linguoid current ripples on bedding plane; arrow indicates paleoflow, example from Springdale (D & E) Photomicrographs of Sr facies from Upper Kayenta shown in ppl and cpl, respectively, field of view shows the higher mud content and cement from this facies (F & G) Rib and furrow and parting lineation on bedding surface within the Lower Kayenta.

2.2.6 Planar cross bedded sandstone (Sp)

This facies comprises of planar tabular crossbedded sandstone which is present mainly in LK and UK but is predominate in the Springdale (Fig. 2-6). The planar cross beds are commonly underlain by the facies Sc and are overlain by erosive surfaces followed by muddy facies. The thickness of individual foresets can reach up to 2 meters. The pale to light red-orange sandstone is mainly fine to medium sand and the lamina display normal grading. The dip angles of the cross beds range from 10°-25° and are either straight or sigmoidal in shape. The lateral

26 continuity of this facies is higher than some other sandstone facies described herein. The facies can be laterally traced for tens of meters in outcrop and is associated with facies Sh ans Sr.

Figure 2- 6 Sp facies at various scales, examples from Upper Kayenta (A) and Springdale (B,C) Evidence for 2D dune migration (D) Large scale fluvial epsilon cross beds from the Springdale.

2.2.7 Interbedded laminated siltstone and mudstone (Fl)

This heterolithic facies consists of interbedded siltstone and mudstones (Fig. 2-7). The individual beds range in thickness from a few centimeters each to more than 10 cm and in many cases the sandy beds are thicker than the muddy beds. Darker red and purple colour of the fine laminated beds indicates highly oxidized units. Evidence of bioturbation and pedoturbation is generally low in these deposits. The combined siltstone and mudstone thickness ranges from a few centimeters up to 1.5 m. The laminated mudstone from this facies is similar in composition to the intraclasts of the Sc facies. This facies shows scouring on upper and lower surfaces, but the example in Figure 2-7A shows the scours infilled by fissile laminated mud. The lower contacts of the siltier facies can be slightly undulatory, straight or gradational. This facies is found commonly

27 underlying eolian units and are in direct contact with eolian sandstones in the LPT transition. The facies also occur within the LK, UK and TCT, forming recessive slopes in outcrop. Desiccation cracks are also sometimes present on the upper contacts of the muddier beds of this facies and the Fm facies. Within the TCT this facies also exhibit discontinuous bleached lamina, probably representing poorly developed paleosol horizons.

Figure 2- 7 Fl facies with heterolithic sandstone and mudstone (A) Scoured bases of Fl facies with laminated sandstone and mudstone (B) Smaller intervals of fissile mudstone with minor evidence of bioturbation or pedoturbation.

2.2.8 Massive mudstone (Fm)

The massive mudstone commonly occur as few mm drapes to 10’s of centimeters beds overlying sandstone facies. The facies is dark red to shades of purple and maroon and very discontinuous laterally. These form the recessive slopes in outcrops and are difficult to find in good condition. Evidence of desiccation is present on the upper surfaces of these facies and generally displays an overall blocky to nodular structure (Fig. 2-8B). Mottling of this facies is sometimes seen within the TCT, but is generally unaltered in the Lower and Upper Kayenta. The upper and lower contact of this facies is planar to slightly erosive. In the Navajo transition, the Fm is seen directly in contact with the eolian Spe facies.

Figure 2- 8 Fm facies of massive mudstone (A) Massive mudstone with distinct sand filled desiccation cracks present at relatively equal intervals of ~ 1m apart, example from TCT to Navajo transition (B) Thicker Fm deposit with mud cracks at upper surface, from first eolian transition.

2.2.9 Flaser bedded mudstone (Ff)

Flaser bedding is typically associated with tidally influenced marine environments (Reineck and Wunderlich, 1968), but the Kayenta displays similar facies especially within the LK, UK and TCT. The facies is primarily composed of silt to fine sand sized grains with isolated to continuous muddy layers (Fig. 2-9A). This facies forms non-competent ledges and normally occurs in discontinuous recessive slopes where exposure is of poor quality. Therefore, only a few rock samples were collected from such recessive facies. Martin [2000] described similar facies from the Kayenta in the Moab area.

The facies can range from true flaser bedding to a lenticular structure depending on the mud content preserved. Relict ripple lamination can be observed in the sandy parts of this facies, with muddy components mainly occupying the ripple troughs, which give an appearance of flaser bedding in cross-section. The facies also displays evidence of bioturbation and pedoturbation which in many cases adds to the mottled appearance of this facies in cross-section. The photomicrograph from a sandier section of this facies highlights the isolated muddy intervals within the predominantly rippled sand (Fig. 2-9B).

Figure 2- 9 Ff Flaser bedded siltstone (A) Flaser bedded recessive interval of Upper Kayenta (B) Photomicrograph in cpl showing predominantly sandy interval with mainly isolated to layered muddy intervals (C) Ff facies from the Lower Kayenta.

2.2.10 Structureless to mottled siltstone and mudstone (Fr)

The Fr facies encompasses fluvial structureless and mottled silt to fine grained sand of the LK and TCT and is a major component of the pedogenically altered intervals. This fluvial silty- sandy facies forms laterally continuous ledges. Complete paleosol horizons (Fig. 2-10A) are rarely preserved in its entirety and the Fr is commonly associated with immature paleosol development or lower horizons of a developed paleosol Figure 2-10B. The grains are mostly subangular to sub-rounded and typically show micritic calcite cement with oxidation that is primary in origin (photomicrographs in Fig. 2-10). The grain to grain contact within this facies is generally low, especially when the micritic calcite concentration is high. The siliciclastic grains appear to be ‘floating’ in calcite cement in thin section (Fig. 2-10B&F). Grains of fine grained

30 carbonate material are also common and are generally well rounded. Bleached horizons, laterally continuous on 10’s of meters, are also present within this massive facies. Relict cross bedding or lamination is sometimes also evident, especially in rocks from TCT (Fig. 2-10C). Nodular calcite horizons are also present in this facies. Overall, this facies shows strong oxidation due to the higher mud content, thus appears darker shades of red-purple in outcrop.

Figure 2- 10 Fr Facies (A) Complete preserved paleosol horizon just below first eolian transition, Fr facies occurs towards lower parts of the complete horizon (B) Local continuation of Fr beds and thicknesses; white beds are nodular horizons (C) Fr example from TCT with some preserved

31 primary bedding (D) Fr at local scale in TCT (E) Photomicrograph in cpl of a carbonate grain (F) Photomicrograph in cpl with micrite supported clasts (G) Photomicrograph in cpl of a tubular structure from TCT.

2.2.11 Wavy Laminated Sandstone (Sw)

The Sw is a wavy laminated siltstone and sandstone facies that form low angle to horizontal wind ripple strata. These broad sheets have crinkly to wavy laminations of few centimeters in scale and sometimes have regular intervals of upheaved laminae forming teepee structures (Fig. 2-11C). Overall the grain size has a bimodal distribution of coarse silt-fine sand and rounded medium-coarse sand. The coarser grains are generally more rounded and form a lag on the finer grained wind ripple lamina (Fig. 2-11E). These coarser grains also exhibit a frosted appearance. Petrographic examination of this facies shows calcite cementation and moderate iron oxidation. The facies range in thickness from 10 cm up to 1.5 m. The thicker facies is found within the fluvial to eolian transitions, whereas thinner sections are present below the Fc facies. The contacts are always flat to gradational and the facies are laterally continuous at a scale of tens of meters.

Figure 2- 11 Sw facies (A) TCT to Navajo transition, interbeds of coarse silt and medium sand (B) UK to LPT transition, Sw is 2 m in thickness directly underlying Spe facies (C) TCT-Navajo transition with tipi structures (D) Calcite cement with abundant oxidation, samples below Fc facies (cpl), E) Laminae of coarser and finer grains with large variance in roundness (ppl).

2.2.12 Structureless sandstone (Eolian) (Sse)

This eolian facies is recognized by its distinct lack of stratification or presence of sedimentary structures. The grain size ranges from very fine sand to medium sand, with sub-rounded grains. Overall, the grains are moderately sorted and have very low cement. The facies is most prominent at the transition to the first eolian incursion in the LK and is almost 2.5 meters thick. The pale to red siltstone has very low calcite cement content. Soft sediment deformation is present in the form of recumbent folded strata that has an overall very ‘lumpy’ appearance (Fig. 2-12B). Presence of sandstone ledges with preserved cross bedding is also present as isolated features. These can range in size from 10 cm to 50 cm and are relict eolian dune of Spe facies (Fig. 2-12D).

Figure 2- 12 Sse facies (A) Vertical extent of the Sse facies with isolated horizontal and low angle lamination preserved (B) Recumbent fold with lumpy appearance (C) Photomicrograph in cross

34 polarized light showing moderate sorting with well-rounded medium sand (D) Isolated eolian dune in Sse with preserved low angle dipping laminae.

2.2.13 Planar-tabular cross bedded sandstone (Eolian) (Spe)

This facies comprises of sets and co-sets of planar to trough cross bedded sandstone at a scale of less than 3 m. The foresets maximum foreset dip encountered is 25° in sections parallel to paleo- transport. Foresets range from straight planar to slightly curved with asymptotic lower contacts. Alternating laminae of grainfall, grainflow and wind ripples are present; with predominately grainfall lamina near foreset toes. Overall, the sandstone is well sorted, sub-rounded to well rounded and range in size from very fine to coarse sand, with inversely graded avalanching deposits generally coarser grained than wind ripple laminae. Quartz overgrowth is commonly seen at grain contacts and fractures are common on coarser grains (Fig. 2-13B). The facies forms thick ledges and steep cliff faces, which are easily recognizable in outcrop. The overall colour is light orange to a bleached pale colour. The contacts between individual sets are sharp. Although it is difficult to map the extent of the dune architecture in three dimensional, some trough cross beds are better preserved in the Sle facies. Inclined to flat lying surfaces between sets are common in the LPT and the Navajo, discussed further in Chapter 3.

Figure 2- 13 Spe facies (A) LPT photomicrograph sampled from lower toe sets showing a bimodal grain distribution with higher degree of roundness in coarser grains (B) LPT photomicrograph of medium well rounded sand with fractures (C) Spe at an outcrop scale with multiple sets.

2.2.14 Large scale cross bedded sandstone (Eolian) (Sle)

This facies consists of eolian large scale planar and trough cross bedding, typically found in upper part of the LPT and in the Navajo (Fig. 2-14). These form gently sloping pink to tan coloured cliff faces. The grains are well sorted and roundness is generally high within the bottomsets of the cross beds. The grain size ranges from fine to coarse sand. Planar cross stratification range in thickness from 3 to 10 m. The cross strata pinch out and vary in thickness, as result of the orientation of the dune morphology. The apparent cross strata dip is 15-25° with bottom of foresets normally having a lower apparent dip angle.

Large scale convoluted bedding is common near the upper sections of the LPT (Fig. 2-14), lower contact of Navajo and underlying major Fc interdune deposits. Some small scale convoluted bedding also occurs underneath first and second order eolian surfaces. The soft sediment deformation features are isolated in space and time based on the outcrop exposure in Kanab (Discussed further in Chapter 4).

Figure 2- 14 Sle facies outlining the large scale nature of the eolian dune facies. Soft sediment deformation present as convoluted bedding in the upper parts of LPT is highlighted in green in the image above. Major bounding surfaces between sets are outlined in black.

2.2.15 Interdune carbonate (Fc)

This facies is limited to the LPT and the Navajo sandstone consisting of carbonate beds which are associated with eolian facies Spe and Sle, except for one ~30 cm carbonate bed identified in TCT, just overlying the contact with LPT. The facies range in thickness from 0.1 m to about 0.5 m and have a pale bleached to gray colour in outcrop. The lower contact commonly preserves Fl

36 and Fm facies and have gradational contacts, as shown in Figure 2-15. In most occurrences the majority of the calcite is replaced by dolomite. The dolostone is structureless to cryptalgal laminated and generally becomes more calcareous upsection and has a planar desiccated upper surface. Figure 2-15A-C outlines the transition into complete carbonate Fc facies. The upper contacts of the Fc are always abrupt and are overlain by Spe or Sle facies. The carbonate is micritic but contains scattered fine to coarse well rounded frosted siliciclastic sand sized grains. The bedding planes in the limestone commonly show desiccation cracks with minor amounts of bioturbation and eolian dissolution features. No preserved fossils were seen in this facies.

Figure 2- 15 Fc facies (A) Lower eolian Spe facies with no carbonate material and abundant quartz overgrowth on grains (B) Initiation of Fc facies with minor silliciclastic material, marked by yellow arrows (C) Fc with complete dolostone (D) Cryptalgal lamination (E) Complete transition from Spe to Fc (F) Upper planar surface with desiccation evidence, marked in white dotted line.

2.3 Paleocurrent Analysis

The paleocurrent measurements from each unit are summarized on rose diagrams in Figure 2-16. The fluvial units consistently show a west to northwest paleoflow, whereas the eolian units show an east to southeast paleo-wind direction. Measurements were only taken at bedforms or surfaces which were significant, since major surfaces give a more reliable paleoflow direction (Allen, 1966). Measurements from all range of eolian and fluvial hierarchical structures show remarkable consistency.

The fluvial units show a higher variance in UK and TCT, which maybe a result of measurements obtained from smaller fluvial bedforms which have a higher variability in direction or represent actual variation in flow direction. The general fluvial paleocurrent is in agreement with established northwest-southwest trends obtained by Averitt et al. [1955], Sargent [1984], Luttrell [1987], Tuesink [1989], and Long [2008]. Minor variations are present and likely reflect local effects. In eastern regions of the Kayenta basin, particularly in the Moenkopi area, some fluvial channels were noted to be oriented towards the northeast-southwest (Herries, 1993), which has been postulated to be a result of the tectonic Zuni lineament. Further to the northeast in western Colorado, the paleocurrents in the Kayenta were reported to span southwest to northwest (Miall, 1988; Bromley, 1991).

The eolian units are generally much more consistent than the fluvial units and show a lower variance. The paleo-wind direction is towards the east; however the mean is slightly shifted towards the southeast in the upper units of the Navajo. The remarkable consistency of the paleo- wind direction of the eolian tongue units with the main body of the Navajo attest to their genetic relation. Most dunes in the eolian system are interpreted to be transverse dunes, which is why little variability is present in the foreset dip orientations.

Figure 2- 16 Summary of paleocurrent measurements from each unit

2.4 Facies Associations

In order to understand the Kayenta-Navajo depositional systems, the genetically related facies described above have been grouped together to form facies associations. This aids in reconstructing the depositional environments for the overall Kayenta-Navajo transition. Associations of individual facies were determined based on lateral and vertical relationships in the field, petrographic analysis and paleocurrent measurements. Since the scale of the study is localized with respect to the overall Kayenta-Navajo system, lateral relationships can only be applied locally but vertical relationships are more significant in determining the progressive change in depositional environment. Four facies associations were developed representing four different depositional settings.

2.4.1 Facies Association 1 (FA1): Multistorey braided fluvial channels

This association is represented by coarser grained facies, namely Gm, Gt, Sc, Sp, Sr, Sh and minor amounts of Fm and Fl. Laterally discontinuous channel lags marking basal channel sections are represented by Gm and Gt which are common in the Springdale. The basal sections of channels are also marked by muddy intraclasts conglomerate, facies Sc which vertically grade into sandier facies of Sp, Sh and/or Sr. Erosional bases of channels can be traced along the outcrop and form concave up surfaces. These channel bodies are infilled with facies of Sc, Sp, Sh and Sr in decreasing abundance.

Large preserved channels, width of up to 50 m, within the Springdale have basal facies of Gt, Gm and Sc, marking the initial channel scours. The concave up scour channel surfaces are easily recognized in outcrop (Fig. 2-17). The dips of channel margins range from 15 to 50°. Fine grained facies are rare in this association and occur as clasts in the basal channel lags. Multistorey channels truncate previously deposited facies associated with channel bars and channel infills.

The gravel facies commonly show clasts of fine grained carbonate, which are interpreted to be originating from calcretes in the associated floodplain deposits. Although no direct preserved overbank fines are preserved in this facies association, their presence is inferred from the clast fragments. Calcium carbonate has been diagenetically reorganized into dolomite by magnesium rich pore water although there may be some dolomite of primary origin. The presence of primary

40 dolocretes is also evident in arid to semi-arid environments and has been explained as the product of precipitation by evaporation (Wright and Tucker, 1991).

Although this facies association collectively recognizes multistory fluvial channels, isolated channels in cross section are also rarely present in the Springdale, LK and TCT. Internal scour surface normally marked by Sc truncates the tabular facies of Sp, Sh as shown in Figure 2-16 from the Springdale. In this case both margins of the channel are preserved and show a steep bank cut on the right margin. The horizontally laminated to planar cross stratified units of previous bar deposits have been truncated at an angle of 50° by a channel with width: thickness ratio of 1:5. Minor calcite cementation is present on the surrounding Sh and Sp facies of the Springdale in Figure 2-17. The channel fill deposit appears massive and has low angle bar accretion. Surfaces within the channel fill sand continue from one side of the channel to the other in cross section with only minor muddy intraclast surfaces associated as channel fill. The steep channel cut could suggest evidence for early cementation in the adjacent bar deposits and also points to a single depositional event from high sediment load discharge. A depositional continuity is present in this channel fill and is typical of a cut and fill feature. These channels are similar to channels recognized by Taylor [1994] in the Springdale in the eastern parts of the basin.

Figure 2- 17 Single Springdale Channel, perpendicular /oblique to the direction of flow. Sandstone channel cutting into existing Sh,Sp facies (sandy bedforms); at its steepest the channel cut is 50°.

Fluvial systems that have a constant discharge rework their overbank deposits continuously and thus these adjacent deposits have very low preservation potential. In semi-arid systems, the flashy nature of the flow allows preservation of adjacent bar deposits in a braided type fluvial

41 system. Paleocurrent measurements from this facies association record a consistent drainage towards west and southwest. This consistent paleoflow is further evidence for low sinuosity of the channels. Furthermore, the lack of floodplain preservation, reworking of barform deposits and large muddy intraclasts basal channel scours points to a likely ephemeral fluvial discharge.

Overall, this facies association represents deposits of a multistory low sinuosity braided and likely ephemeral channels. The presence of coarser grained facies with broad aggrading channel forms is evidence to this. The lack of overbank fines and high energy deposits are also indicative of this interpretation. Massive sandy channel fills with little preserved sedimentary structures indicate deposition by rapid debris flows. The braided nature of these channels is inferred from the large epsilon type cross bedding indicating migrating barforms. Low sinuosity of the channels is consistent with unidirectional paleoflow directions.

The architectural element analysis of the Kayenta fluvial system is discussed in Chapter 3 which further demonstrates this facies association in the Springdale and LK. It is evident from the examples provided in this study as well as earlier studies by Luttrell [1987], Miall [1988] and Bromley [1991], that the Kayenta system represents a multistory braided fluvial channel.

2.4.2 Facies Association 2 (FA2): Unconfined fluvial sandsheets and overbank deposits

This facies association consists of laterally continuous unconfined fluvial sandsheets that have less pronounced lower contacts than FA1. Generally the fine grained content increase in this facies association as compared to FA1 and basal channel scours are less prominent or absent. These extensive tabular sandstones-siltstones mainly consist of rippled to horizontally laminated sandstone (Sh and Sr) and commonly vertically grade into each other. The siltstones to sandstone bodies show coarsening upward trends and are capped by facies Fl, Fm or Fr facies. Bioturbation is moderate to extensive in this association and pedogenesis is also present. This facies association is common in the UK and TCT and form laterally resistant-recessive ledges in outcrop.

The typical vertical succession consists of non-channelized sandstone which has a sharp to erosional contact with underlying mudstones and/or interbedded mudstones-siltstones. Muddy rip up clasts are sometimes present at the base of the sandstone (Fig. 2-18). The sandstone is

42 usually massive to ripple laminated at the base and grades into horizontally laminated and or climbing ripples deposits. The siltstones-sandstones are poorly to moderately sorted with abundant calcite cementation. The sandstones bodies also show slight channelization features at < 3 m scale. The sandstones are overlain by mottled mudstones and or interbedded mudstone- siltstone deposits (facies Fm and Fr). The upper surfaces of the sand bodies show some early cementation and sometimes have an undulatory contact. Overall one succession is approximately 1-2 m in thickness.

This facies association represents fluvial distal to proximal sheetflood deposits of a large distributary system that signify longer hiatuses between flooding events which allowed extensive bioturbation and pedogenesis to take place. Small eolian dunes are present within the TCT as encapsulated bedforms, however their presence is rare. Channelization is also rare in this facies association, however laterally continuous sandsheets predominate. Fluctuating and waning flow conditions are responsible for variation in Sr, Sh, Fl and Fm facies. Commonly, Sr grades into Sh without any recognizable deposition hiatus, indicating an increase in flow velocity or shallowing of the water upsection. This is seen throughout the deposits of LK, UK and TCT. The range of sedimentary structures and grain size within this facies association indicate the flow strength and likely the flood duration. The clean uncemented Sh beds have been deposited under shallow upper flow regime conditions. In a continuous terminal fan/ distributary fluvial system, this facies association is marked by the river morphology of channelized to non-channelized flows (Nicholas and Fisher, 2007). Fluctuating ephemeral flow conditions are responsible for the deposition of laterally unconfined fluvial sandsheets. The lack of well-preserved facies such as Sp, St and intermediate flow regime facies further indicates that deposition was rapid which did not allow other bedforms to develop. Massive appearance is also common in the sandsheets which may be a result of rapid deposition or extensive bioturbation (Glennie, 1970). The ledges also show lower surfaces with loading structures, common in saturated sediments. An example of this facies association is studied in detail using the fluvial architectural element analysis in Chapter 3.

Figure 2- 18 Upper Kayenta fluvial sandsheet unit, with minor channel scouring. Channel cutting into muddy floodplain facies. Sh- horizontal laminated sandstone; Sr- ripple laminated sandstone; Fm- massive mudstone; Fl- interbedded sandstone mudstone; Fr-structureless mudstone.

On a basin scale, a decrease in grain size and the scale of sedimentary structures in the downstream direction system are indicative of deposition on a broad fluvial distributary system terminating in an erg. This is typical of semi-arid climate belts where large rainfall events produce sporadic flash floods filling the topographic lows. When enough water is released the flood waters extend beyond the channelized areas as erosional unconfined flows (Tunbridge, 1981). Distal facies of a terminal fan system is indicated by high proportion of floodplain facies and sheet deposits with minor channelization (Kelly and Olsen, 1993; Nicholas and Fisher, 2007). In the proximal channelized sections, a high width to depth ratio for channels is present, which are typical of dryland regions where sparse vegetation cover and sand sized material form easily erodible banks (Taylor, 1994). During a flooding episode in the distal region of the fluvial system, water is lost to evaporation and infiltration which produce hyperconcentrated flows. During the initial phases of a flood, the flow is spread out laterally, eroding previously established highs and flattening the topography. In the case of the Kayenta-Navajo, the floods

44 die out due to water loss from evaporation and infiltration. The Bijou creek model outlines an ephemeral stream which is composed mainly of horizontally laminated sandstones which are accumulated under upper flow regime conditions (Miall, 1996). This facies association is similar to the Bijou Creek model, operating in a widely spread distal reaches of a fluvial distributary system. Furthermore, the flood deposits of Bijou Creek were recorded to accumulate 1m to 4m of sediment in less than 12 hours (McKee et al., 1962). Therefore, only large flooding events are preserved in the thick accumulation of FA2 and most of the time is preserved in 5th order pedogenically altered fluvial surfaces.

2.4.3 Facies Association 3 (FA3): Sandsheet and erg margin

This facies is present in the transitional fluvial to eolian units. The facies consist of Sw, Sse, Spe and minor amounts of Fm and Fl (Fig. 2-19D&E). The fine grained muddy facies laterally grade into other dominant facies of this association. The contacts between the facies are usually flat and sharp. Fluvially reworked eolian beds are present where eolian facies are directly underlain or overlain by fluvial facies and vice versa. Deflation lags with coarse grained frosted sand grains are common in this facies and at bed contacts indicating eolian textural maturity. Desiccation features and adhesion structures are also common at the facies contacts.

This facies association is typified by clean moderately sorted eolian sands with little to no cement. Quartz overgrowths are common on grain contacts. A bimodal distribution of roundness exists, whereby the fine to medium sand is more rounded and has high sphericity than the silt. This distribution is indicative of saltation and suspension processes, respectively. The Sw facies are vertically and laterally associated with Spe which are less than 1.0 m in thickness. These planar cross beds are deposited mainly from 2D transverse or barchans dunes that advance by avalanching. The paleocurrent measurements from these deposits show a consistent unimodal pattern towards the east to southeast. The wavy laminated sandstones show abundant coarse grained deflation lag deposits and the undulatory nature of the laminations are a result of adhesion structures or evaporate dissolution. Small scale teepee structures are also found within the Sw facies.

The primary depositional environment for this facies association is eolian dune to eolian sandsheet possibly at erg margin setting with occasional fluvial input indicated by the presence of mud and fluvially reworked grains. The surfaces separating eolian dune deposits and the

45 fluvial or eolian sandsheet deposits are marked by major surfaces, since they record a change in external controls. (Stokes, 1968; Kocurek, 1988). Small <0.5 m eolian dunes are also preserved within the Sw facies and further indicate a sand starved system (Fig. 2-19A).

Figure 2- 19 Feature of facies association 3. (A) Wavy laminated sandstone with preserved dune topography, UK-LPT transition (B) Extensive bioturbation with vertical tubular structure extending from upper surface, UK-LPT transition (C) Mud curls, TCT-Navajo transition (D+E) UK-LPT transition, Spe-planar cross bedded eolian sandstone, Sw- wavy laminated sandstone, Sse- structureless sandstone, Fm-massive mudstone.

The base of this facies association is commonly marked by mudcurls within the toesets of the eolian crossbeds (Fig. 2-19C). This vertically grades into facies Sse which may be marked by discontinuous mud drapes at bed surfaces. Isolated eolian dunes on the scale of <2m are also present within the Sse as marked by the distinct steep cross beds dipping in the regional wind direction. Bioturbation and desiccation may be present on planar deflation surfaces within these units (Fig. 2-18B). This extensive exposure and bioturbation development on surfaces occurred post deflation, suggesting a hiatus before which the following dune advance occurred. Similar erg margin facies association descriptions were provided by Langford and Chan [1989] for the older Permian Cutler Formation and Cedar Mesa Sandstone. Clemmensen et al. [1989] also

46 recognized similar sandsheet eolian facies and categorized them as erg margin association within the underlying Moenave-Wingate system.

Further west of this study area, around St. George, the tongues of the Kayenta and Navajo are not recognizable as discrete units but are recognized as ‘transitional Navajo’. This transitional unit is mostly composed of facies association similar to what is described here with association of Sw, Spe and Sse. The transitional Navajo and FA3 is interpreted as deposits of an eolian sand sheet environment during which evaporitic material may have precipitated and produced several unique disturbed bedding. Wavy bedding in this eolian environment has been explained by adhesion silt and sand on to a moist sabkha surface (Glennie, 1970). Overall the FA3 represents an eolian sand starved system associated with an early stage of erg development. Many of the adhesion structures present within this facies association indicate a groundwater table close to the surface, in a generally arid setting.

2.4.4 Facies Association 4 (FA4): Eolian dune and draa

This association consists of facies Spe, Sle, Fc and Fl. The eolian crossbedded sandstones contribute to the majority of this facies. These steep to low angled eolian crossbedded units are composed of grainflow, grainfall, wind ripples and coarse grained deflation lags (Hunter, 1977). The eolian dune deposits are categorized into Spe and Sle, based on the size of the cross bedding present (Fig. 2-20). The Spe and Sle, although similar in nature, vary in size and occurrence. Sle is the product of draa-scale migration of bedforms over which smaller Spe dunes migrate (Kocurek, 1991). This facies association composes more than 90% of LPT and Navajo. The total thickness in the LPT of this facies association is almost 60 m and the within the Navajo exposed in Kanab canyon it is more than 100 m. Architectural analysis of this facies association is discussed further in Chapter 3.

Soft sediment deformation (SSD) horizons within this facies association are important indicators for large scale wetting of the dunes. In the examples studied in the Kanab area, the SSD’s show a strong near surface effect of dune failures. Although, the occurrence of these SSD seems to be spatially unclear, an interpretation is presented in Chapter 4 based on the architectural photo- mosaic of one such example from Kanab canyon. These SSD’s occur in areas of the Navajo erg that are thought to be well beyond the influence of fluvial incursion. One unequivocal

47 interpretation from such SSD is that the Navajo erg must be wet at the time of such large scale failures.

This facies association represents a full erg system with occasional interdune deposits. Minor amounts Fm and Fl facies are associated with the interdunes. The unidirectional paleo-wind direction is collected from available cross bedding and other indicative sedimentary structures. The Fc represents a wet to damp interdune system occurring during a stable phase of dune migration. The carbonate interdunes are only present within the LPT, TCT and Navajo units. These formed in response to regional water table rise since these interdunes lack evidence of fluvial channels. The transition to the carbonate interdune is marked by a wetting upward succession, an example of which is shown in Figure 2-15.

Figure 2- 20 Facies association 4. LPT: Large scale cross bedding with prominent 2 meter ledge of carbonate interdune in lateral extent with peripheral edges preserved. White arrows mark the extent of interdune development, Sle-large scale eolian cross bedding, Spe- eolian planar cross bedding, Fc-inerdune.

Carbonate interdunes with algal laminated structures and crinkly lamination (facies Fc) suggest that abundant biologic activity was taking place within the associated ephemeral interdune ponds. The ponds were present within the topographic lows between large dunes and were fairly extensive in a local scale. Based on petrographic analysis, loose eolian grains blew into the ponds, although the abundance of siliciclastic grains decrease in the central/deeper sections of these ponds. This suggests that in the deeper reaches of the ponds, the influence of nearby dunes was minimal. The absence of siliciclastic fines in the Fc facies also indicates minimal to no settling from suspension. Thick Fc facies were present only in the LPT and in the Navajo, which developed during times of stable dune migration. However, given their nature, location and

48 lensoidal shape in cross section, these were present at geologically short periods. Nonetheless, these ponds represent geomorphic and groundwater stability within the ergs.

Precipitation and preservation of carbonate in a lacustrine environment is a function of internal lake processes. Two main types of structures are present within the Fc facies: wavy laminae and structureless tabular carbonate. These are attributed to microbialite growths forming stromatolitic and cryptic structures, respectively. These algae can survive water depths up to 30 m in a range of climates (Kocurek, 1996). Furthermore, these algae communities typically develop on lithified ground as observed in the modern Namib Desert (Lancaster and Teller, 1988). This may further support the case that these interdunes are formed on eolian supersurfaces.

2.5 Petrography

A total of 61 rock samples were collected out of which 56 samples were prepared into standard petrographic thin sections. Out of the 56 samples, only 40 samples were point counted for lithology. The results of which are discussed in this section. Table 2-2 summarizes the thin sections by facies.

Table 2- 2 Rock samples categorized by facies and point count analysis. SM- Springdale, LK-Lower Kayenta, KE- Kayenta Eolian, UK- Upper Kayenta, LPT- Lamb Point Tongue, TCT- Tenney Canyon Tongue, NV-Navajo

Facies Facies Name Rock Sample ID Point Count Analysis Code

Gm Massive to crudely SM03 SM03 stratified intraformational conglomerate

Gt Trough cross bedded Not Sampled Not Sampled intraformational conglomerate

Sc Erosional scours with SM01, SM05 SM01

muddy intraclasts sandstone

Sh Horizontal to low SM06, LK03, UK05, SM06, UK05, angle laminated UK09, UK10, UK12, UK09, UK10, sandstone UK13, TCT02, TCT05, UK12, UK13, TCT02, TCT05,

Sr Rippled sandstone SM04, LK01, LK02, SM04, LK02, UK01, UK02, UK03, UK01, UK03, UK07, TCT03, TCT07 UK07, TCT07

Sp Planar cross bedded SM02 SM02 sandstone

Fl Laminated siltstone UK06, UK08, UK11, UK11 and mudstone TCT01, TCT06

Fm Massive mudstone N/A N/A

Ff Flaser bedded LK07, UK04, TCT04 - mudstone

Fr Structureless to LK04, LK05, LK06, - mottled siltstone and TCT08 sandstone

Sse Structureless KE01, KE02, NV01 KE01, KE02, sandstone (Eolian) NV01

Sw Wavy laminated LPT02, NV03, NV05 LPT02, NV03, sandstone (Eolian) NV05

Spe Planar tabular cross KE03, KE04, LPT01, KE03, KE04, bedded sandstone LPT03, LPT07, NV02, LPT01, LPT03,

(Eolian) NV04, NV06, NV07 LPT07, NV02, NV04, NV06, NV07

Sle Large scale cross LPT04, LPT10 LPT04, LPT10 bedded sandstone (Eolian)

Fc Interdune carbonate LPT05, LPT06, LPT08, LPT05, LPT06, LPT09, LPT11, NV08, LPT08, LPT11, NV09, NV10 NV10

2.5.1 Springdale Member

The Springdale Member of the Kayenta has fine to coarse sandstone with moderate sorting and mainly sub-angular to sub-rounded grains. There are patchy clay zones in the coarser fluvial rocks whereas the finer grained facies have higher clay and cement content. Overgrowth on both quartz and feldspar grains is present generally where calcite cement is absent. Two channel lags were sampled and show calcite mud chips with early oxidation rims around the grains. Preferential oxidation of lithic clasts is also present in the channel lag samples. Generally higher lithics are present in the Springdale member sandstones than the fluvial rocks of the remaining Kayenta Formation. This is also evident in the point count analysis (Table 2-3). Channel lags have higher calcite cement percentages present versus the remaining fluvial facies. Dolomite cement is not exclusive to one facies, however is common in the conglomerate facies of Gm and Gt. The dolomite forms rhombohedral crystals and is replacive in most occurrences. Within the conglomeratic facies of the Springdale the dolomite cement concentration is likely a function of clast lithology.

2.5.2 Lower Kayenta

The mean grain size in the LK is around 0.08 mm, finer than the underlying Springdale Member. The grains are angular to subangular and the overall sorting in the LK is moderate. Clay matrix is common in the rocks and composes of almost 5% of the rocks. Abundant cement is present,

51 ranging from 10-40% and overall rock samples are highly oxidized. The pores are commonly lined with platy clay minerals. Overall calcite cementation consists of large euhedral calcite to dolomite crystals. The overall grain to grain contact is low in the rocks, which may indicate early calcite cementation and some reworking through bioturbation and soil development processes. Distinct paleosol units were sampled (LK04 and LK06) that show micritic calcite matrix with floating sand to silt sized grains. These are sampled from the upper portions of massive fluvial sandsheet deposits. Poikilotopic gypsum cement is also present in some samples, enclosing the various siliciclastic grains. The intensity of mottling in thin section increases as sections approach eolian units in a vertical section. Many of the fluvial units display feldspar grains with a range of alteration. This can be used to suggest that minimal clay authigenesis has occurred and most clay minerals present in the fluvial rocks may have formed during or shortly after deposition.

2.5.3 Kayenta Eolian

The Kayenta eolian unit begins with a massive eolian sandsheet that shows crude bedding and very few sedimentary structures. The massive sheet contains isolated <1m steeply dipping eolian cross beds from small dunes. Samples for thin sections were collected from the massive sheet as well as the isolated dunes. The unit overall displays moderate to well sorting. The grains are subrounded to sub-angular, with a bimodal distribution of coarse well-rounded and high sphericity grains and fine sand of low roundness and low sphericity. Overall there is minor amount of matrix and clay present. The unit also shows minor to no oxidation; the upper section of the unit shows a bleached appearance in outcrop and has no carbonate cement, however the grains show abundant quartz overgrowths. Generally, the overall percentage of matrix increases towards the top of the unit, which may be a result of sieving of fines from the overlying fluvial units.

2.5.4 Upper Kayenta

The UK is similar to LK in petrographical features. Grain roundness ranges from sub-rounded to subangular, and are moderately sorted. The grains display an overall low to medium sphericity. Higher percentages of matrix and cement are generally present. Most of the rocks have moderate oxidation. Grain overgrowths are present and are normally manifested on the grain edges not directly in contact with the dolomite cement. The dolomite cementation is likely one phase due to large grain size and the abundance. Influence of eolian grains is generally low, only a few

52 possible ones identified near the upper transition zone. Patchy calcite and gypsum cement is present in some facies. Pore alignment of fine clays in some samples is also present.

2.5.5 Lamb Point Tongue

The eolian facies of the LPT display similar characteristics to the previous eolian unit. The grains are sub-rounded to rounded and sphericity is generally higher than the fluvial units. Matrix/clay content is minimal in eolian units but increases towards the proximity of the interdune deposits. The grain size in many cases shows a bimodal distribution, of 0.2 mm and around 0.8 mm. Overall iron oxidation of the units is very minor to none. There is abundant overgrowth on the grain, and the feldspars generally show low alteration with preserved twinning. In the erg marginal facies the wavy lamination have micritic calcite cement as a result of some bioturbation or paleosol development. The grains are generally well rounded and show high sphericity but overgrowths make it appear angular and odd shaped. The interdune related facies show increased calcite cement and fine grained material as well as high sphericity grains from grainfall on dune slip faces. Clastic filled mudcracks are also present in carbonate interdune deposits.

2.5.6 Tenney Canyon Tongue

The TCT has similar characteristics as the LK. The overall sorting is poor-moderate with generally angular to subangular grains. The average grain size is in the silt to fine sand range. The framework grains are generally 70% of the overall rock with the remaining taken up by calcite and matrix. All of the samples are highly oxidized and well cemented with calcite or dolomite. Intervals of ‘pods’ with higher amounts of clay occur in the thin sections. Most of the clay matrix and cement is obliterated with oxidation. There is no real evidence of major overgrowth on the grains. The sandier ledges in the TCT show flasers of oxidized and clay lenses. Some grains that have overgrowths show iron staining on earlier grain boundary, possibly indicating another early phase of oxidation. Kaolinite and chert-like filling in pores is common.

2.5.7 Navajo

The Navajo generally displays fine to medium sand grains with a bimodal distribution. The larger grains are well rounded with high sphericity whereas the finer grains are subangular to angular with low sphericity, which is why the sorting is moderate-poor in thin section. The framework grains commonly make up 90% of the overall thin section, with remaining attributed

53 to minor quartz overgrowths and porosity. The massive eolian sandsheet facies has distinct lamina of finer grained and eolian grains. Larger calcite cement is present in coarser grained lamina whereas finer grained has smaller patchy cement. The thin section displays high porosity, up to 20% in some examples. Grain coating of clays and oxide is also present on the eolian grains. The wavy laminated facies has small troughs with coarse sand eolian grains deposited in otherwise fine cemented sand. Damp conditions likely held fine sand grains in place while coarser well rounded sphere eolian grains are blown into be deposited in the troughs at the surface. The Fc have large well developed calcite grains, which are dolomitized. There is minor amount of opaque minerals and oxide staining in the Fc. There are also lenses of micritic calcite within the Fc, likely a biomediated precipitate.

2.6 Cement

The cements present in the Kayenta include calcite, dolomite, clay, iron oxides, silica, and gypsum (Fig. 2-21). These cements are present mainly within the fluvial rocks and maybe facies specific. Clay and iron oxide however are not ubiquitous across all facies. Quartz and feldspar overgrowths are present within facies with higher porosity and where other cement is not present. In cases where other types of cement exists within the same rock as the overgrowths, the grain boundaries directly in contact with other cements do not show overgrowths. Cement chronology may be extracted from these physical relationships. Gypsum cement is present as patchy poikilotopic crystals and is likely not pervasive. Primary carbonate, mainly calcite, is common within the Sc, Fm and Fr. In cases where early interstitial clay or oxidation is present, later diagenetic cements are absent.

Figure 2- 21 Photomicrographs of various types of cements in cross polarized light. (A) UK02 calcite/dolomite cement (B) UK11 Cherty or amorphous silica cement (C) LK02 Unknown cement, maybe kaolinite (D) UK05 Quartz overgrowth I KE01 Gypsum cement (F) LK04 Primary micritic carbonate.

2.6.1 Dolomite Cement and Source

The source of dolomite cement in this environment is nonmarine, likely from Mg rich groundwater which precipitates out as a result of evaporation (Wright and Tucker, 1991). Other sources of carbonate in this environment are pedogenetic processes, as evidenced by the calcrete nodules. In the conglomeratic facies, the source of carbonate is directly related to the lithic fragments. Presence of gypsum, as evidenced from the thin section and outcrop, could also be a source for the Mg in dolomite. Another possible source is windblown dust into the Kayenta streams which are further disseminated into lenses. There may be a small component of primary dolomite formed as dolocretes on overbanks and fluvial floodplains as well.

2.6.2 Authigenic Clays

The clay content is identified in thin section by the high birefringence and high relief. The clay content is higher in the fluvial rocks than eolian, and the highest concentrations are found in the TCT. Clay XRD analysis conducted by Taylor [1994] from the Springdale identified presence of

55 illite, smectite and chlorite and these clays were interpreted to be authigenic in origin. However, within the overall Kayenta, the major clay mineral is kaolinite which based on SEM also shows authigenic origin. Samples that contain dolomite cement show less clay content suggesting the clay formed after cementation (Taylor, 1994). Dutta and Suttner [1984] deciphered paleoclimate from oxygen isotope present in authigenic clay found in alluvial sands. A similar approach could be applied to the sandstones of the Kayenta to determine a related climate signal.

2.7 Point Count Analysis

The Gazzi-Dickinson method was applied to point count sand and coarse silt sized grains from thin sections (Ingersoll et al., 1984). Only the fine to coarse sand sized grains were accurately point counted, therefore the final QFR diagram is biased towards the coarse grained facies. Based on the analysis of 41 samples, the average composition of the quartz, feldspar and lithics in each unit are summarized in Table 2-3.

Table 2- 3 Normalized QFR values from point count analysis for each unit Tenney Normalized Lower Kayenta Upper Lamb Point Springdale Canyon Navajo Percentage Kayenta Eolian Kayenta Tongue Tongue Quartz 84.03 92.45 88.33 86.47 86.58 86.33 85.40 Feldspar 7.03 6.48 10.90 11.13 10.99 8.79 12.67 Rock 8.94 1.07 0.77 2.40 2.43 4.88 1.93 Fragments

Overall, the quartz content is very similar throughout the transition, with higher amounts in LK and KE. The feldspar content generally shows no certain trend, but has higher percentages in the Navajo. The rock fragments are significantly higher in the Springdale than any other unit in the transition, similar to the trend observed by Taylor (1991). The QFR normalized values for all the samples are plotted on a QFR diagram (Fig. 2-22) and classify the sandstones as subfeldspathic arenites to sublitharenite. A few fluvial and eolian samples are also plotted as quartz arenites.

Figure 2- 22 QFR ternary plot for all point counted samples

The QFR values are summarized by facies in Table 2-4. It should be noted that the number of samples for each facies varies; therefore commonly occurring facies such as Sh and Sr have a much more representative facies average than the Gm which only has one sample. The silt to clay sized facies of Fl shows a higher amount of quartz which is likely a result of maturation and resistance to weathering. The eolian facies of Sse, Sw, Spe and Sle all have very similar QFR values, whereas the Fc has higher quartz content as a normalization effect. The Sc has low quartz content and a higher proportion of rock fragments as expected.

The Uncompahgre Uplift towards the east in Colorado may have been a major source of immature lithics in the eastern Kayenta system (Luttrell, 1987). The source of the major lithics and plutonic feldspars analyzed herein are sourced from the volcanic-plutonic rocks towards the southeast. The volcanic-plutonic terrain sourced the feldspars and abundant quartz in the system. Similar aged rocks from southern Arizona Santa Rita Mountains are likely the ideal source for the immature grains, whereas the Mogollan highlands further to the south sourced the distal source of the lithic and feldspathic supply (Luttrell, 1993).

Table 2- 4 Normalized point counted QFR values for each facies

Facies Gm Gt Sc Sh Sr Sp Fl Fm Ff Fr Sse Sw Spe Sle Fc Average

Quartz 85 - 78 87 87 83 92 - - - 88 88 85 84 89

Feldspar 2 - 8 10 10 8 7 - - - 11 10 13 13 9

Rock 13 - 14 4 3 9 1 - - - 1 2 2 3 2 Fragments

Chapter 3 3 Fluvial and Eolian Outcrop Architectural Studies 3.1 Introduction

The previous chapter defined the main facies and facies associations present in the Kayenta- Navajo transition in Kanab Canyon. The focus of this chapter is to apply the identified facies to the lateral outcrop profiles within the fluvial and eolian units. This aids in determining the overall lateral facies changes as well as the interpretation of the overall depositional system.

The deposits of the fluvial Kayenta show a relatively high degree of lateral variability, which is why vertical profiles and petrographic studies are not sufficient. Lateral profiles and architectural studies were conducted where possible within each unit and are used as base maps to present and interpret data. Six lateral architectural profiles were completed, four within the fluvial units and two within the eolian units. Two fluvial profiles are completed within the Springdale member, one in the Upper Kayenta (UK) and one in the Tenney Canyon Tongue (TCT). The eolian profiles are completed within the Lamb Point Tongue (LPT) and the main Navajo unit. These profiles were limited to outcrop quality and exposure. Careful analysis of the major fluvial surfaces, elements, facies and paleocurrents are marked using the defined architectural analysis scheme of Miall (1985; 1996). Given the lack of complexity and a defined architectural scheme for eolian rocks, stitched photopanels are marked with major bounding surfaces, facies and paleocurrent measurements.

It is important to properly identify surfaces in terrestrial rocks which allows time markers to be established where no other chronological bounds exist. The intrinsic nature of fluvial and eolian processes does not allow samples to be dated at the resolution of major bounding surfaces. The architectural elements inherently provide an interpretation of genetically related packages of strata but further implications of this method are discussed in the associated interpretation section.

3.1.1 Fluvial architectural scheme and element analysis

The original fluvial hierarchal scheme for bounding surfaces was simplistic, with 3 types of bounding surfaces (Allen, 1983). This was further refined to include 6 main fluvial surfaces (Miall, 1988). The major bounding surfaces separating minor and major fluvial elements are developed on a hierarchical basis and range from 0th order to 6th order, small scale to large scale fluvial features, respectively. The fluvial bounding surfaces have been summarized in Table 3-1. The original eight fluvial architectural elements [Miall, 1985] have also been updated since to include several sub-elements and several new ones. The architectural elements have been summarized in Table 3-2 and now include more than 20 elements. This list is not an exhaustive literature review of all the elements, but presents a workable element list needed for the scale of this study. Many of the elements summarized in the table are mentioned for the sake of table completion and are not applied in this study.

Table 3-1 Summary of fluvial bounding surfaces hierarchy (summarized form Miall, 1985)

Bounding Scale Description Surface (m)

0th order 100-101 Individual foreset or horizontal laminae.

1st order 101-102 A set boundary; usually erosional to some degree, but not cross cutting the previous set, separating similar lithofacies. Interpreted as the result of orderly migration of bedforms under conditions of steady flow

2nd order 101-103 A co-set bounding surface; usually erosional, separating co-sets of dissimilar lithofacies. Interpreted as resulting from a change in flow conditions, e.g. from seasonal discharge variations

3rd order 102-103 Minor erosional scours, which cross cut sets and co-sets; interpreted as reactivation surfaces, such as those created by the formation of chute channels or levee crevasses

4th order 102 The only non-erosional bounding surface; therefore rare in outcrop. Interpreted

as preservation through very rapid burial of an upper surface of a major sedimentary feature such as in a channel sand bar.

5th order 102-104 The basal erosional surface of any major channel system, often immediately overlain by substantial lag gravels. Geometry often mirrored 3rd order surfaces, separating progressively smaller channel fills. Identified by sharp changes in paleocurrent trend across the surface. Interpreted as the deepest extent of erosion to occur during the formation of a major assemblage of related architectural elements

6th order 102-105 Laterally extensive erosional surfaces which may merely be coalesced 5th order surfaces, but traceable over large distances. Interpreted as separating major member-scale units within a sedimentary system, such as eolian and fluvial members within a single formation

Table 3-2 Summary of fluvial and eolian architectural elements

Element Associated Element Main facies Geometry, surfaces and relationships Symbol References

Single, multistory, finger, lens or sheet with an erosional Miall, 1985; Miall, CH Channel Elements base. Bounded below by 5th surface 1996

Solitary ribbon sandstones. Channels with w/d ratios of Friend 1983; Eberth CHR Ribbon channels <15:1, further divided into narrow (<5:1) and broad (5- and Miall 1991; Miall 15:1) 1996; Gibling, 2006

Any Friend 1983; Eberth CHS Sheet channels combination Channels with w/d ratios >15:1, “sheet like” and Miall 1991; Miall 1996; Gibling, 2006

Small channels, concave up erosional base, bounded by 4th CV Crevasse channels order surface. CRS and CRM for minor and deep stable Miall, 1996 crevasse channels, respectively.

ChCH Chute channels Small bar top channels, some upstream accretion Long, 2006

Lens or blanket shaped units, tabular in nature, bounded by Gravel bars and Miall, 1985; Miall, GB Gm, Gt, Gp 3rd or 4th order surfaces, may occur as eolian dry sheets bedforms 1996 with SB

Lens, sheet, blanket, or wedge shaped sand bodies. Maybe St, Sp, Sh, Sl, Miall, 1985; Miall, SB Sandy bedforms present as minor bars or component of DA, LA elements, Sr, Se, Ss 1996 Constrained by 1st or 2nd order surfaces.

Sediment gravity Narrow or elongate lobes or eolian dry sheets, maybe Miall, 1985; Miall, SG Gm, Gms flow deposits interbedded with GB or SB. Irregular, non-erosional bases, 1996

0.5-3 m thick, width upto 20 m and downstream length of several km

Sandy sheet St, Sp, Sh, Sl, SE Compound sheet like units of SB with w/d ratio of >20:1 Cotter, 1987 elements Sr

Lens of related sandy bedforms with flat or channeled base Downstream St, Sp, Sh, Sl, with convex up 3rd order internal erosional surface and Miall, 1985; Miall, DA accretionary Sr, Se, Ss, Gm, upper 4th order bounding surface. Built from downstream 1999 macroforms Gp, Gt migration of simple or compound macroforms and bars.

Wedge, sheet or lobe of SB or GB elements, internal lateral Lateral accretion accretion surfaces. Includes heterolithic strata (HIS) and LA Miall, 1985 macroforms epsilon cross stratification. Typically bounded by 2nd roder surfaces.

Transitional between DA and LA elements where Downstream St, Sp, Sh, Sl, orientation of 0th order foresets is between 30-60 degrees Long, 2006; Ghazi DLA lateral-accretion Sr, Se, Ss, Gm, down slope of the modal strike associated with 1st and 2nd and Mountney, 2009 surfaces Gp, Gt order surfaces

Upstream lateral- LA sets in which foresets of SB indicate bedforms migrated ULA Long, 2006 accretion surfaces up the surface of the macroform Upstream Opposite of DA, paleoflow up the back slope of bar UA Long, 2006 accretion elements complex Laminated sand Represent deposition from non-channelized flows, as bar LS Sh, Sl Miall, 1985 sheet top, bar-flank sands or deposits of overbank sheet floods

Thicker channelized sheets, lens and scour fills of LS units Upper flow with convex up geometry. May include humpback and URF Sh, St, Se, Ss Fielding, 2006 regime elements sinusoidal dunes and up-flow and down-flow dipping low angle cross beds

Scoop-shaped elements typically with an asymmetric fill, Sh, Sl; any HO Hollow elements deep points in channel bases, develop at confluence points Miall, 1996 combination where stream channel meet

St, Sp, Sh, Sl, LA sets located at sharp inner bends in high sinuosity river, Counter-point bar CPB Sr, Se, Ss, Fm, down river from point bars, usually associated with higher Smith et al., 2009 deposits Fl fines content

Originally defined as OF (Miall, 1985). Thin to thick tabular units of overbank material, include pedogenic Miall, 1996; Eberth FF/OF Floodplain fines Fm, Fl horizons, FFP and FFD used for proximal and distal and Miall, 1991 floodplain facies respectively, also can be a fill of abandoned channels

Crevasse-splay Lobate or lenticular sheets found in channel-proximal CS St, Sr, Fl Miall, 1996 elements settings, may occur as wings of CHS

Sheet to wedge shaped units, thinning away from channel Miall, 1996; Ghazi LV Levee elements FL, Sh, Sr margins into adjacent floodplains, equivalent of FFP and Mountney, 2009

Eolian Dune Eolian dune within an erg or erg margin. Occur as tabular Long, 2008 and this ED Spe, Sle Element sheets and occasionally with preserved upper surface study

Occur as tabular sheets or minor lenses with some low Eolian Sandsheet Long, 2008 and this ES Sw, Sse inclined beds, upper surface shows desiccation, some minor Element study lenses or beds with massive eolian sandsheets

Mostly occur as lenses or carbonate or interbedded fluvial fine or chert facies. Include pedogenic and or desiccation EF Interdune Fc, Fm, Fl This study surfaces. Distal and proximal elements further defined as EFD and EFP.

3.1.2 Eolian architectural and elements analysis

A complete eolian element scheme, equivalent to the one developed for fluvial rocks, does not exist. In fluvial-eolian systems, such as the Kayenta-Navajo system, two eolian elements of ES and ED, representing eolian sand sheets and eolian dunes were added by Long [2008]. This scheme has been applied to the eolian architecture studies at hand. One additional element of ‘EF’ is also added for the carbonate interdune facies of (Fc, Fl, Fm). The existing Brookfield [1977] hierarchical scheme for eolian bounding surfaces has been applied herein with no further modifications. The ‘supersurface’ of Kocurek, [1988] has also been identified and applied to the architectural analysis. The eolian architectural element additions and bounding surface hierarchy are presented in Table 3-3 and Table 3-2, respectively.

Table 3-3 Summary of eolian bounding surfaces

Eolian Scale (m) Description Reference

Bounding Surface

3rd order 10-100 Bundles of lamina within co-sets of cross laminae, Brookfield, reactivation surfaces along the slip face of individual 1977 dunes

2nd order 10-1000 Gentle to moderately dipping surfaces bounding sets Brookfield, of cross strata, may truncate 3rd order surfaces 1977

1st order 1000-10000 Flat lying or convex up, cuts across cross bedding Brookfield, and other dune structures, truncate 2nd order surfaces. 1977 Deflation surfaces separating individual dunes

Supersurface/ ~100000 Horizontal surfaces, removal of sand by deflation Stokes, 1968; down to the water table surface or dune denudation Loope, 1985; Stokes surface and stabilization in response to autogenic controls Kocurek, 1988

3.2 Fluvial Architectural Analysis

Four fluvial architectural analyses were completed: two within the Springdale, one in UK and one in TCT. Figure 3-1 summarizes all the architectural studies completed within Kanab canyon. Specific facies, architectural elements, bounding surfaces and paleoflow measurements are marked on the interpreted panel directly below the photomosaic. Further close-up images of specific features are also shown on the photopanels. Features and symbols used in the architectural panels are summarized within the legend of each figure.

Figure 3-1 Map showing the lateral profile studies completed with the Kanab study area. The profiles included in this chapter are outlined in red.

3.2.1 Springdale Dry Canyon Panel 1

The architectural panel presented in Figure 3-2 is from the lower Springdale Member of the Kayenta Formation. The orientation of the photographed outcrop is 40° and 220°, which is nearly parallel to the regional fluvial paleoflow direction of west to southwest. The photo-mosaic covers a lateral distance of approximately 60 meters and a maximum height of 7 m.

Based on the architectural element scheme, 4 major elements were identified. The element GB marks the basal section of the architectural panel. The minimum exposed thickness of this element is 0.5-2 m and is laterally continuous across the whole photomosaic. The overlying elements of SB and DA are separated by a 4th order surface. Vertically and laterally, this transitions into various orientations of migrating macroforms of DA and LA, separated by 3rd and 4th order surfaces.

Determining between DA and LA can be challenging in a 2D outcrop exposure. When the orientation of the accretion surface is within 60° of the cross-bedding of the same element, than the element is roughly parallel or oblique to the local flow and can be classified as a DA. Similarly, if the orientation of the accretions surface and the encompassing cross bedding is greater than 60°, the flow is perpendicular and the element is LA (Miall, 1994). The evidence from cross bedding and accretion surfaces indicates that the Springdale Dry Canyon 1 panel shows an oblique orientation of mainly DA elements, however the upper parts of the panel show migration of mainly LA elements.

This architectural panel exhibits a unique orientation of fluvial bar macroform migration. The main lithofacies present include Gm, Gt, and Sc near the basal contact, whereas the remaining section is dominated by Sh, and Sp, with minor amounts of Fm. These lithofacies are separated by low angle sigmoidal 3rd order bounding surfaces. The dip of these 3rd order surfaces range from 0° to maximum of 20°. Four main recumbent folds have also been identified and these features are pronounced by 1st the 2nd order bounding surfaces within the DA/LA elements. Individual lithofacies have a varying dip and paleo-orientation, but the average paleoflow is oriented towards 248°. A minor finning upward trend can be observed in individual growth bedforms. Some growth bedforms are overlain by a mud drapes only a few mm in thickness. The presence of the Sh,Sp and Fm couplets likely represent changes in flow stages, marked by hiatuses and reactivation surfaces.

Large sigmoidal cross beds are typical of this panel and indicate migrating downstream and laterally accreting channel bars. These foresets were used for measuring paleocurrent direction. The consistent grain size and paleoflow orientation likely represent consistent channel processes with abrupt flow conditions, marked by recumbent folding. The amplitude or height of the macroform systematically varies within this panel. Just above the main basal Gm lithofacies the macroforms are flat lying with <10° slopes. Presumably, changes in flow depth and orientation of the bedforms likely caused the changes in the thickness of the cross bedded strata.

3.2.1.1 Interpretation

The sigmoidal cross-bedding present in the DA/LA of this panel are typical of ephemeral stream deposits as shown by North and Taylor (1996) and Sanabria (2001). The sets of sigmoidal cross beds have been shown to develop on humpback dunes in flume experiments under transitional conditions from subcritical to supercritical flow (Saunderson and Lockett, 1983). In this panel the sigmoidal cross beds occur in very fine to fine sand and are on the order of 1-2 m in scale, consistent with the aforementioned flume experiment.

Recumbent overturned folds are prominent in this architectural panel and are present in the steeper foresets. The main deforming force for the recumbent folds is current drag resulting in gravitationally induced downslope slip (Allen and Banks, 1972; McCormick and Picard, 1969). However, shear forces alone, based on the flow law, are relatively small. Therefore, drag force solely could not cause the deformation of a substantial unit of sand. A correct model needs to account for the attitude, shape and lateral extent of these features. However, if the sand loses its cohesion and behaves like a viscous liquid even small shear stress could cause overturning of the beds in a small amount of time (Allen and Banks, 1972). Studies on modern environments show that the slumping of loosely to unconsolidated sand can occur on subaqueous slopes as low as 0.5 (Walker and Massinghill, 1970). Most workers accept that sediment in deformed crossbedding is water saturated at the time of deformation, but need not to be fully submerged (Selley et al., 1963; Allen and Banks, 1972). Therefore, the Kayenta bed streams must have been partially saturated periodically in order to produce recumbent folded strata.

Figure 3-2 Lower Springdale Member (Dry Canyon exposure) architectural element analysis outcrop panel

Paleo-channel characteristics have largely been developed by Schumm (1968) based on the data collected on stable alluvial stream channels in semi-arid to semi-humid regions of the Great Plains of the USA. Data from modern channels such as bank full width, depth and percent of silt- clay in channel bed are used to develop empirical relationships. These relationships are used for determining the nature of the sediment load moved by the paleo-channel, which is important in determining the width-depth ratio of paleo-channels. In a system such as this, the channel perimeter is constantly cannibalized and do not normally get preserved in the geological record. Therefore, producing paleo-morphological channel characteristics based solely on quantitative measurements from grain size variations is inaccurate. Furthermore, typical point bar models from meandering river systems have been largely used as paelohydraulic indicators which cannot be directly applied to a system such as the Kayenta.

The architectural element analysis, paleocurrent measurements and vertical profiles give a strong indication for certain established fluvial facies models. Previous studies of the Kayenta (Miall, 1978; Bromley, 1991; Luttrel, 1993; Sanabria, 2001; Long, 2008) have pointed to a low sinuosity braided fluvial system that is perennial or ephemeral. There is enough evidence to suggest that a low sinuosity braided river system was dominant during the early Springdale time, and the architectural panel in Figure 3-2 shows migrating fluvial dune forms (Fig. 3-3), however it is difficult to establish the ephemerality of this system. The evidence supporting an ephemeral model includes bedload dominated, multi-lateral sand sheet bodies, lack of overbank fines and channel plugs, presence of midchannel bars without major desiccation surfaces, low paleocurrent variance, convex up erosional scours, and recumbent folds. The lack of overbank fine facies present in this section of the Kayenta is proof to the cannibalistic and recycling nature of the laterally migrating channel bars in a braided fluvial system. The muddy intraclasts as well as pedocarbonate grains present in the fluvial channel lags attest to the presence of corresponding overbank facies. Furthermore, the presence of recumbent folds occurring at third order bounding surfaces attest to shear in saturated sand causing downslope or lateral gravitational failure in the form of overturned folds. Therefore, the evidence largely points to an ephemeral braided channel system operating during Lower Springdale time.

Figure 3-3-3 A) Plan view of the Springdale sandy braided river with abundant mid channel migrating bars B) Diagram outlining the 3D nature of the midchannel bar migration in an arbitrary instant in time during the foreset deposition. The black arrows mark the paleoflow direction. The scale of the DA/LA interpreted from the foreset heights.

3.2.2 Springdale Dry Canyon Panel 2

The architectural and element analysis presented in Figure 3-4 is from the upper Springdale Member and is a photograph of the southern cliff face in the Dry Canyon. Due to the steep vertical cliffs present in this panel, it was difficult to ground truth certain surfaces, therefore a handheld monocular survey tool was used to map the lateral extent of major surfaces. Many major surfaces and facies were checked on the north side of the canyon, where slopes were more accessible. Paleoflow measurements are minimal from this panel due to the inaccessibility of many of the outcrop; however the main channel scours are oriented towards 295°, roughly perpendicular to the cliff face. The photo-mosaic is approximately 200 meters in its lateral extent and at maximum of 30 meters in height.

The architectural panel presented in Figure 3-4 shows complex lateral interaction and stacking of multistorey channel elements. Seven main elements are recognized in this panel, five of which are channel elements. The fill complexes include elements of channels (CH), sandy bedform (SB), lateral accretion deposits (LA), downstream accreting deposits (DA) and minor gravel bars/bedforms (GB).

The basal section of the architectural panel is similar to the Dry Canyon panel 1 and shows identical DA and LA elements. Channels are defined by fifth order concave-up scour surfaces. The migrations of sandy channel bars comprise the SB elements within the channels. Minor amounts of Fl and Fm facies make up the OF/FF elements which are lensoidal in shape. Some preserved concave down 4th order surfaces are also identified on the channel scour surfaces, in filled with GB, DA, and LA elements. A large set of LA are truncated by the 4th channel element on the right side of the panel. These elements are dipping in the same orientation as the Dry canyon Panel 1 elements.

Some large channel elements are approximately 70 meters across, with a minimum depth of roughly 3 meters but could be deeper where not truncated by overlying elements. The right channel margins are better defined than left margins. The channel margins are also marked by Sc facies with some mud clasts that are upto 0.5 m in length. These muddy intraclast beds mark channel fill episodes and where visible in its entirety they are mapped as 5th order surfaces. However, in most channel fill complexes present in this panel, the muddy intraclast units are not identifiable in the deeper central sections of the channels.

3.2.2.1 Interpretation

This profile is interpreted as a succession of thick sandstone sheets infilling large channels (~100m ), with presence of laterally and downstream accreted fluvial bars. The lower part of the succession is dominated by mainly DA, LA and SB with Sh, Sr, Sp, St and Gm facies. These represent migrating channel bars and subaqueous dune complexes. The lateral extent of the channels is not visible in the lower section of this panel, which is similar to the Dry Canyon Panel 1. Further up, channels become more defined and channel fill complexes are typical of modern day braided ephemeral rivers with basal scour fill trough cross bedding overlain by planar to horizontal stratified sand (Abdullatif, 1989). However, the uppermost laminated mud and silt with bioturbation are commonly absent within the channel fill complexes due to erosive

72 nature of subsequent flow events. Nevertheless, the large mud intraclasts within the channel fills attest to the presence of mud lined channels and associated muddy floodplain deposits. This panel shows a complex of large multistory braided channels which are likely ephemeral in nature.

The preserved channels give a good estimate of channel paleo-morphological characteristics during the Springdale deposition. Channel dimensions are a factor of both allogenic and autogenic controls. In a semi-arid environment such as during the Kayenta deposition, the allogenic controls largely govern the hydrodynamic regime as well as the local bed and bank material. Paleohydraulic relationships have been developed based on modern channel width and depth ratio for high sinuosity rivers (>1.7) (Leeder, 1973; Schumm, 1968). Unfortunately, the same statistical relationships are not well developed for low sinuosity or braided rivers (Miall, 1996). What is expected is the width/depth ratio for low sinuosity rivers is much greater than high sinuosity meandering rivers. In Figure 3-4, the preservation of channel margins are seen at an oblique orientation to paleoflow and thus show large and small channel parameters.

Figure 3-4 Upper Springdale Member (Dry Canyon exposure) architectural element analysis outcrop panel

3.2.3 Upper Kayenta Panel

The UK panel chosen for this architectural study is near the middle of the Kayenta-Navajo stratigraphic section and displays the typical architecture present within this unit. The lateral outcrop profile (Fig. 3-5) is approximately parallel to regional paleoflow as shown by the scour surfaces, trough cross stratification and bed lineation. The higher silt content in this unit is evident by the poorer quality of outcrop and recessive slopes. A total of 6 paleoflow measurements were obtained from this panel, all of which are concentrated near the lower sections of the panel. A total of 11 architectural elements were identified. On average, the sand bodies range in thickness from 0.5m to 2.0 m and show a gradational fining upward trend. Sedimentary structures within the sandier units are limited to horizontal-low angle laminations, climbing ripples, planar-trough cross bedding and some massive units. Vertically, scour to planar contacts grade into trough to planar cross bedding which quickly grade into horizontally laminated beds to massive beds, capped by massive to silt interbedded mudstone. Bleached horizons are common at mudstone and sandstone contacts and obliterate any primary structures.

In Figure 3-5 the laterally extensive amalgamated sand units are separated by fluvial 5th order surfaces, demarking separate fluvial sandsheets. Internally, these sand units show 2nd and 3rd order surfaces representing facies changes and minor reactivation surfaces. The main surfaces are flat lying however, a few small scale concave up surfaces are also identified. In the lower left section of this panel, within the 4th architectural element, a large concave up scour surface is present within the sandstone which is infilled with interbeds of silt-mudstone units. Laterally, the infilled mudstone-siltstone interbeds pinch out to less than 0.1 m and merge with the a 5th order surface capping the upper surface of the sand unit.

The architectural elements of SB and SE contain the laterally extensive fluvial sand sheets. SB elements define channel fill of Sp, Sh and St lithofacies, whereas the SE elements define compounded sand sheets of SB. These elements generally lack the organization present in DA and LA elements and generally show the amalgamation of various bedforms. Lithofacies St was identified in some SB and SE elements and where present, was used for paleocurrent measurements. The upper most elements in the panel is interpreted to be UFR and LS based on persistence of lithofacies Sh, Sl, and St which likely represent transitional upper flow regime conditions.

Channelization similar to the ones seen in the Springdale is not present in the Upper Kayenta. However, small scale scours and large fluvial sand sheets (width: height ratio > 20:1) are typical of this unit. Three-dimensional dunes typified by trough cross bedding are also present in some sections of the tabular sand sheets. Element 5 composed of SE shows well-developed St facies which is bounded by a 5th order surface. The element laterally however is dominated by Sh facies.

3.2.3.1 Interpretation

The Lower Kayenta is separated from the Upper Kayenta by a 10 m thick persistent eolian unit. The fluvial to eolian transitions are discussed in more detail in Chapter 4; however the fluvial units present within this study are parts of the same fluvial system. The UK represents an overall broad distal fluvial plain, with shallow unconfined to channelized ephemeral streams based on the overall architecture of lateral sand sheets, and presence of facies associations 2.

The planar to slightly scoured 5th order surfaces attest to the low erosive powers of the Kayenta streams in this section. The overall structures in this unit represent flow conditions transitional between upper and lower flow regime conditions. Concave up fluvial scour surfaces are also present but at a scale much smaller than channel scours present within the Springdale.

Flat lying 5th order contacts between subsequent flooding events and laterally extensive sheets suggest little new accommodation space creation. The overall ephemeral nature of the streams is supported by the grain size, sorting, extensive lateral sheets, and major planar 5th order fluvial surfaces. The architecture further supports the distal relation of this unit to the underlying LK and Springdale. Furthermore, vertical aggradation of these fluvial unconfined sand sheets is characteristic of ephemeral streams (Deluca and Eriksson, 1989). An overall decrease in channel size, depth and strong presence of facies association 2, supports an ephemeral unconfined fluvial system, which is a more distal part of a terminal fan distributary system.

Figure 3-5 Upper Kayenta architectural element analysis outcrop panel.

3.2.4 Tenney Canyon Tongue Panel

The TCT is the last of the fluvial units in the overall Kayenta-Navajo transition and generally has poor exposures due to the high percentage of fine material. The panel chosen for architectural study is in direct contact with the overlying Navajo (Fig. 3-7). The outcrop is oriented roughly north to south and the fluvial paleoflow is perpendicular to the orientation of the outcrop; whereas the eolian paleoflow is at an oblique angle to the outcrop. Due to the overall quality of the outcrop, it is difficult to trace all major fluvial and eolian surfaces,

The lithofacies present within the lower fluvial unit primarily includes Sh, Sp, Sr, and Sl; and fine grained facies dominated by Fl, Fm and Ff. The units are present as couplets of sandy facies which fine upwards and capped by fine grained facies. These couplets are bounded above and below by 5th order fluvial surfaces marking the deposition of likely single flooding event. The sandstone bodies are slightly scoured to planar at the base and gradually increase in fine grained material. At the outcrop scale, the surfaces can be traced laterally without any major hiatuses. The corresponding muddier units are not well exposed and form recessive slopes. However, in places where the fine grained facies are exposed, they show extensive bioturbation. Minor facies changes and laterally continuous surfaces of bedforms are marked by 2nd and 3rd order fluvial surfaces. Confirmative paleoflow measurements were rare in this panel due to the high abundance of Sh and Sl facies.

A total of 6 fluvial architectural elements and 2 eolian elements are identified in this panel. The fluvial architectural elements include SB and LS. The extensive fine grained facies are included within these elements since they likely represent continuous deposition and are capped by 5th order surface. The LS and SB elements represent periods of unconfined fluvial discharge mainly in upper flow regime conditions.

An eolian supersurface and similarly 6th order fluvial surface separates the TCT fluvial and overlying Navajo eolian units. This surface is planar to slightly erosive and shows evidence of pedogensis. There is also an overall decrease in thickness of the fluvial sandstone units approaching the supersurface. The architectural elements present above the supersurface are eolian ES and ED elements. These represent sandsheet elements and eolian dune elements,

78 respectively. Discontinuous dunes are present within both elements with paleo-wind flow towards 100°. First and second order eolian surfaces were recognized in these elements and are marked on the panel.

3.2.4.1 Interpretation

The architectural elements identified in this panel are typical of unconfined ephemeral fluvial flooding events, separated by periods of non-deposition. The couplets of sandy and muddy facies are identified as one major flooding event. Most Fl, Fm and Fr facies show extensive bioturbation, representing times of exposure. Abdullatif [1989] showed that modern ephemeral flows in the Gash River contain Sh fill at different positions within ephemeral channel fills. In the TCT, the Sh facies entirely compose the sandy fills with minor amounts of Sr and Sp within most of the LS and SB elements. Parallel laminated sand represent deposits of high energy unconfined sheet floods as outlined by the ‘Bijou Creek’ model (Miall, 1996) (Fig. 3-6). Muddier units and lower flow regime structures may be deposited at final stage of unconfined sheet floods with interfingering sand and silt deposits (Scott et al., 1969), as evident in the deposits of TCT (Fig. 3-7). Presence of multistory parallel laminated sandstones is associated with ephemeral flow deposits (Tunbridge, 1981). In this system, the evidence of high discharge events alternating with deposits of quiescent period when the channel is dry establishes the ephemerality of this fluvial system (Picard and High, 1973).

Figure 3-6 Sheetflood fluvial plain depositional model (Miall, 1985)

Distal plains of broad fluvial distributary systems typically have entire deposits composed of SB element. However, the lateral continuity of the sand sheets, association of SB and LS and the thickness of the sand sheets indicate a likely ‘Bijou Creek’ type model for the fluvial unit. Overall aggradation of channels and progressive abandonment is slow based on vertical stacking. The characteristic architecture of these elements has been best described by Tunbridge [1981] and Sneh [1983]. Furthermore, in a typical terminal fan model [Kelly and Olsen, 1993] the TCT represents the most distal or basinal zone which is characterized by higher proportion of unconfined flow deposits and preservation of non-channelized facies in association with eolian facies. The large variance of paleocurrent data from this unit further supports a typical radial pattern of a terminal fan or several amalgamated distal fan systems.

The eolian units are in direct contact with the fluvial units in this panel. The contact between the TCT and the Navajo is interpreted as an eolian `supersurface’, with abundant evidence of exposure and likely deflation down to a planar watertable surface. The unit directly underlying the contact is facies Fm and Fl. The surface represents peneplanation of the existing fluvial sand sheets primarily by deflation. The overlying eolian unit has horizontally laminated eolian sand and is interpreted as an eolian sandsheet with minor developed dunes. No carbonate interdune was identified in this transition. The development of a thick (~2m) eolian sandsheet is indicative of a sand starved system, during which the erg is still establishing.

Figure 3-7 Tenney Canyon Tongue architectural element analysis outcrop panel

3.3 Eolian Architectural Analysis

3.3.1 Lamb Point Tongue

The LPT panel is photographed near the upper most part of the unit, where it is in direct contact with the overlying TCT. This simplistic eolian panel is representative of the overall architecture of LPT (Fig. 3-8). The panel is oriented in a north to south orientation. The first, second and third order hierarchical surfaces have been identified, with the supersurface marked between the eolian and fluvial unit. The large scale high angle crossbeds (Sle) are typical of the eolian units in LPT and the Navajo and show a consistent paleoflow direction. Only two paleoflow measurements were taken from the most accessible parts of the outcrop, where the slipface can be identified more confidently. Soft sediment deformation (SSD) is also identified in upper parts of the units, near the contact with the TCT.

3.3.1.1 Interpretation

The study of modern eolian dunes and erg systems has revealed much about the dune morphology, size, and the representation of surfaces within these units. This information is useful in understanding the ancient eolian systems. Based on the architectural panel, an overall decrease in eolian foresets is present from the base of the panel to the upper contact. The second major set of cross strata from the bottom, bounded by 1st order surface above and below, shows a decrease in set thickness from right to left. This is likely a result of crescentic dune morphology.

On large dunes (facies Sle) such as the one present in LPT, grainflow is mostly tabular at the dune slip-face and wedge out sharply at the toe. Empirical relationships relate grain flow measurements to the dune height but complexities in wind variation, supply of sand and other controls are not accounted for, therefore the values obtained from such relationships are not reliable (Sweet and Kocurek, 1990). However, general relationships show that less than 10% of a dune is to be preserved and based on crossbed thickness in the LPT this would suggest that the dunes are in excess of 150 m in height (Rubin and Hunter, 1982). Furthermore interbedded grain flow, and wind-ripple strata at the toe of the dunes is present at a cyclic manner in the cross beds. These are attributed to annual summer and winter changes in wind direction and termed ‘fluctuating-flow cycles’ (Hunter and Rubin, 1983). This cyclicity is most prominent in the

82 second crossbed set from the LPT panel, but at closer inspection it is found in most large scale cross bedded strata within the Navajo.

The Sle facies is interpreted to be deposited by large eolian dunes and together with Spe, form the ED eolian elements. The simple cross-beds represent dunes with a single slip face with basal tangential wind ripple strata. The decrease in crossbed sets upsection is likely related to a decrease in sand supply and the diminishment of the erg. This may be a result of rising groundwater conditions locally.

The upper parts of the unit, shows large scale SSD concentrated in more than one crossbed set. This type of deformation is found throughout the exposures of LPT and the Navajo and is normally associated with wet to damp interdune deposits. However, the SSD displayed in Figure 3-8 is present near the upper contact of the LPT and sometimes truncated by the overlying super surface. The SSD in eolinites has been explained by failure of the lee face of an advancing dune into an interdune area with a shallow watertable (Horowitz, 1982). Variation and updates to this model based on outcrop event analysis [Gerald, 2011] has shed new light in the steps involved. The local extent of the SSD, its association with the overlying TCT and overall implication is discussed further in Chapter 4.

Figure 3-8 Lamb Point Tongue architectural outcrop panel

3.3.2 Navajo

This panel is taken at the last major set of outcrops near the Kanab Canyon highway 89 and represents the last unit in the Kayenta-Navajo transition (Fig. 3-9). The Navajo panel is oriented north to south and exhibits trough to scalloped cross bedding within the eolian Navajo Sandstone. This unique orientation of the Navajo cross strata is not common in most Navajo outcrops. A first order surface separates the majority of the trough-scalloped cross bedded lower unit from the overlying planar tabular cross bedded unit. The eolian units, as seen in this architectural panel, are simplistic when no SSD or interdune deposits are present.

Scalloped cross bedding is the migration of small scour pits along the toe of a main dune or the lee face (Rubin, 1987). The scalloping of the underlying deposits is directly related to the position of the scours along the dune. Although normally encountered in fluctuating flow conditions, scalloped cross-bedding in the Navajo could be a result of superimposed bedforms (Rubin, 1987). Determining the role of cyclic flow in the formation of scalloped crosssbeds is difficult due to the three dimensionality of the dunes.

A north-easterly wind direction for the Kayenta-Navajo is well established based on extensive studies (Blakey et al., 1988; Marzolf, 1988, Tuesink, 1989). The wind direction is consistent throughout the Navajo basin with slight local variations. The crossbedded units in the Navajo panel show a slight change in orientation from the base to the top. The planar cross stratified units in the upper parts of the panel show a consistent dip direction, although only one measurement was taken at this panel, the style of crossbedding in the lower part of the panel is distinctly different. The lower part of the panel shows complex trough sets to scalloping cross beds. The main central trough in the lower section is 20 m wide and more than 6m in height. More complex sets of scalloped crossbeds are developed on the right of side of the main trough, truncating into a planar corssbedded unit. The set of scalloped cross beds thin out towards the right into trough crossbeds that are 6 m wide and less than 2 m in height.

Figure 3-9 Navajo architectural outcrop panel

3.3.2.1 Interpretation

The Navajo panel exposures represent deposits of very large crescentic dunes with slipfaces that preserve mainly grainfall processes. The lower section of the panel represents an oblique view of crossbedding that are infilling a large scour at the base of the dune toe. The paleoflow measurement is obtained from the central large trough, assuming flow perpendicular to the plane of the outcrop. The scalloped cross beds present on the left side of the panel are truncated on the left side by the next scallop, suggesting that the main bedform likely had irregular scour pits on the lee face which migrated to the left and away from the orientation of the outcrop (Rubin and Hunter, 1983).

The scalloped cross bedding at the base of the panel is truncated by a planar fist order surface. This surface is persistent in the panel and marks a change in orientation of the bedforms, based on the difference in the style of overlying cross bedding. The main paleoflow is towards the south-west. Some small troughs, less than 2 m thick, are present on the right side of this crossbed set. The smaller troughs on the right of the large central trough can be interpreted as reactivation surfaces. Overall, the variation above and below the 1st order surface occurred as a result of migration of large transverse brachanoid ridge dunes. This represents deposition in full erg conditions, where sediment supply is high and various scale of eolian bedforms are able to develop.

Chapter 4

4 Fluvial and Eolian Vertical Transitions 4.1 Introduction

The Kayenta vertically transitions into the Navajo in the Kanab study area in two separate but equally significant fluvial ‘events’. These are marked by the genetically related fluvial and eolian tongues. The cyclic nature of this transition is recognized in other parts of the depositional basin; however the thickness of the intertonguing interval in the Kanab study area is the thickest in the basin. Each transition was logged and studied in detail, the findings of which are summarized in this chapter. The detailed sedimentological logs are provided in Appendix I. This chapter separates each of the three main fluvial to eolian vertical transitions and presents them under individual headings. The overall eolian to fluvial transitions for each unit are all summarized in one section.

4.2 First fluvial to eolian transition

The ‘first fluvial to eolian transition’ covers the vertical facies transition of the Lower Kayenta (LK) into the first major eolian unit. This eolian unit separates the lower from the upper Kayenta and is not formally recognized due to its < 5 m thickness. For the purpose of this study, this eolian unit will be referred to as the ‘Kayenta Eolian’ (KE). The underlying LK and Springdale are cumulatively 75-80 meters thick.

The LK is mainly composed of facies association 1 (FA1) and facies association 2 (FA2) with generally channelized to non-channelized fluvial deposits. This 12 meter unit represents multistory fluvial sandstones which commonly show low angle channel scouring into existing channel infill and minor overbank deposits. The overall finer grained overbank fluvial facies are more abundant in the LK than the Springdale. The transition from Springdale to LK is unclear in outcrop, and is likely gradual. The Springdale is different from the immediately overlying LK based on grain size, petrology, architecture and overall exposure quality, as shown in Chapter 2 and 3.

The LK shows tabular sandstone bodies with minor preserved accretion elements and low angle dipping surfaces. The LK exhibits a gradual decrease in large fluvial channels from the underlying Springdale and an increase in non-channelized overbank deposits of fine to very fine sand. The logged section (Appendix I) shows an increased preservation and lateral continuity of paleosol horizons. Some of the best examples of the complete calcisol and aridisol vertical profiles are preserved in the LK (Fig. 4-1A), a few meters below the contact with the overlying KE. The paleosol horizons are up to 1.2 m in thickness and are truncated by a sharp upper contact. The paleosol horizon observed in this section (Fig. 4-1A) is similar to Retallack’s [1988] field description of aridisol. However, the various soil horizons recognized by Retalack occur at different depths in the LK. The rhizoliths and the vertical burrows occur lower in the section, whereas the blocky peds are marked near the upper surface of the soil horizon. Furthermore, the oxidation of the overall unit does not allow for any formal master horizons to be recognized in outcrop.

Figure 4-1 First fluvial to eolian transition A) Complete aridisol horizon preserved underlying KE; Ideal aridisol section with major horizons is shown on the left (Retallack, 1988) B) Fluvial scours underlying KE C) Recumbent folds in eolian Sse facies D) Upper KE surface with dinosaur footprint.

The sandy channel infills are thinly bedded and show minor scouring into existing channel infills or paleosol horizons (Fig. 4-1B). The interbedded sandy and silty units are in direct contact with the overlying massive eolian unit. This massive unit is approximately 3.5 meters in thickness and shows evidence of fluvial mud in a unit dominated by eolian structure and grains. The petrographic samples from this facies shows predominately eolian well rounded, moderate sphericity fine to medium sand grains. Small isolated eolian dunes are present in the overall massive unit and show bioturbation on upper surfaces. Overturned eolian cross beds and soft sediment deformation is also evident in this unit (Fig. 4-1C). Presence of wind ripple deposits within medium sand further supports the eolian influence in this unit. A muddy lag surface is present near the upper contact, which shows evidence of early paleosol development with micro topography. The unit directly overlying is composed of facies Sw which altogether form the facies association 3 (FA3). The unit directly overlain is composed of facies Spe which terminates in a planar supersurface, showing evidence of exposure through pedogenic development and dinosaur tracks (Fig. 4-1D).

4.2.1 Interpretation

The first fluvial to eolian transition represents the initial encroachment and establishment of the Navajo erg over the widespread fluvial system. The Springdale shows evidence of large channels with abundant mid channel bars and coarse basal channel lags truncating into pre-existing channel infill deposits. The overall grain size is coarser and the concentration of lithics in the sandstone is higher than the overlying fluvial units. The Springdale, as established earlier in Chapter 3, represents wide (> 70 m) low sinuosity braided channels. These channels gradually transition into the overlying LK deposits, which show smaller channel size with minor architectural elements of LA, DA, and SB. The LK overall has more fine grained facies than the Springdale and better preserves pedogenic horizons in existing channel sands and muddier overbank deposits. The LK transitions into the KE, as summarized by FA3.

Well-developed paleosol horizons are normally formed in well drained soils (Kraus, 2002). Furthermore, paleosols can be classified based on the equilibrium between sediment accumulation rate and the rate of pedogeneiss development, which can result in compound versus composite paleosols (Morrison, 1978). Figure 4.2 outlines the relation of pedogensis and sedimentation rate in such a subsiding basin. The evidence of single complete well preserved

90 horizons of paleosols in the LK is an indication of slow accumulation rate and low channel avulsion (Kraus, 2002). Conversely, in the underlying Springdale paleosol horizons are not preserved and are only inferred indirectly through presence of carbonate rich nodules in channel lags. The high sedimentation rate is inferred for the Springdale as evidenced from large multistory channel aggradation, which likely slows down during the deposition of the LK.

Figure 4-2 Relationship of sedimentation rate and pedogenesis rate in developing a compound versus composite paleosol horizon. A- paleosol surface, has roots and mix of organics; Bw- B horizon showing colour or structure development; Bt- B horizon showing accumulation of clay; C- subsurface horizon, more weathered than fresh bedrock, mild mineral oxidation and accumulation of silica and carbonates; Ab- A horizon with buried soil horizons; Cb- C horizon with buried soil horizons (Kraus, 1999).

The eolian massive unit overlies a well-developed paleosol in fluvial overbank sand which is indicative of the temporary shut-down of fluvial channels as the eolian sand sheet gradually established. The early development of wet sandsheets marks the beginning of FA3 and indicates conditions of low eolian sediment supply and higher watertable conditions. The developed cross bed sets in KE are small (<2m) and represent small poorly developed eolian dunes, further indicative of low eolian sediment supply. Large well developed cross bed sets of transverse dunes are not present in this transition. FA3, representing a sandsheet erg margin facies, is only a few meters thick in this transition. The eolian environment represented by FA3 persists for a short period in this transition, as indicated by the overall thickness and lack of major eolian

91 bounding surfaces. The unit is capped by a supersurface, which represents deflation down to the water table and likely widespread erosion. This eolian unit has not been traced back into the main Navajo erg, but field reconnaissance identified this unit further east of the Kanab area in the Echo Cliffs, and is likely genetically related to the main Navajo erg.

4.3 Second Fluvial to Eolian Transition

The second fluvial to eolian transition is recorded by the vertical transition of the UK to the Lam Point Tongue (LPT), which is the main recognized eolian tongue of the Navajo. The UK is approximately 30 meters thick and the transition zone underlying the full developed erg facies of LPT is between 10-12 meters. Vertical logs at this transition were completed at two separate locations (Appendix I), both of which showed very similar order of transitional facies and bed thicknesses.

The UK is similar to the LK in outcrop appearance but is mainly composed of FA2. Very few channelized bodies with channel infill and fluvial dipping surfaces are encountered. However, the majority of the fluvial deposits show transitional units between Sr and Sh facies with abundant climbing ripple deposits (Fig. 4-3A). Individual unconfined fluvial sandsheets are approximately 1.5 m thick and fine upward into muddier facies of Fl and Fm that are less than 1 m. Mudcracks and bioturbation are sometimes present on these upper fluvial surfaces (Fig. 4- 3B).

The FA3 is initiated by facies Sse which shows preserved isolated eolian dunes, with some fluvial and eolian lags. The FA3 is approximately 10 meters in thickness and shows strong evidence of fluidization and soft sediment deformation. Eolian dunes preserved within this unit show faint grain fall strata, and in some cases preserve evidence of weak pedogenesis on the upper surfaces (Fig. 4-3D&E). The upper surfaces of the eolian sandsheet deposits indicate wet to damp conditions as evidenced by desiccation features and adhesion warts, but do not show extensive development of paleosols. Small eolian dune topography is normally present in FA3 (Fig. 4-3C). In Figure 4-3C facies Spe of FA3 forms cross strata less than 1 m in thickness which alternates with facies Sw. Large eolian crossbed sets develop quickly in this transition with set thicknesses in excess of 2 m. The cross strata dip at 22-25° with tabular to tangential lower contacts. Grainfall laminae alternate with grainflow laminae in the cross beds which are difficult

92 to distinguish, however wind ripple laminae are present near the toes of large tangential cross beds.

4.3.1 Interpretation

The lack of strongly erosive channel base for the UK fluvial deposits suggests a decrease in fluvial energy relative to the underlying Springdale and LK. There is an overall lack of coarser bedload and abundance in sandy bedforms. The dominance of Sh and Sr facies suggests fluctuating flow conditions in an ephemeral setting (Picard and High, 1973). In many cases, the channel fills show multiple couplets of Sh and Sr facies without major hiatuses, suggesting fluctuating flow within multiple short lived or a single continuous flooding event. Based on channel architecture, the channels do not exceed 1 m in thickness. Texturally massive channel fills are also present which likely represent turbulent deposits that do not form any sedimentary structures, further indicating the ephemerality of the fluvial events. Paleocurrent data from this unit is rare due to the lack of structures that show paleoflow; however the ones that were collected show an average paleoflow towards 265.8°, which is consistent with the underlying fluvial units. Additionally, no major change in sand grain provenance is observed from the underlying fluvial units suggesting their genetic relation.

The LPT is a thick and regionally recognized eolian tongue of the Navajo. The LPT pinches out to less than a few meters towards the east and merges with a more transitional Navajo unit towards the west. The presence of similar, but condensed transition in the Moenkopi area, near the eastern edge of the basin, points to the basinal presence of this tongue or the presence of similar processes across the basin. This is discussed later in the context of the basin and points to an overall allogenic control to these units, assuming a temporal relation can be established.

The transition to LPT is marked by approximately 15 m of FA3 which develops into more than 30 meters of FA4. The initial units of FA3 overly pedogenically altered fluvial units, similar to the first transition and represents gradual establishment of more arid conditions. Carbonate interdunes were not identified in the transitional units/FA3, however thick algal laminated carbonate interdunes are present throughout the LPT. These interdunes are randomly oriented in space at first approximation and usually overly first order eolian surfaces (Tuesink, 1989). The carbonate rich interdune deposits are fairly persistent and are more than a 100 m in lateral extent, pinching out to sandier lateral margins higher up on the dune slope (Fig. 4-3G).

Figure 4-3 Second fluvial to eolian transition A) Sr and Sh alternating facies from UK. B) Desiccated upper surfaces of fluvial sand sheets. C) LPT with preserved eolian dune topography. D) Eolian dune surface with tubular structures. E) Eolian dune in Sse

94 preserving upper bioturbated surface. F) Poorly developed paleosol horizon. G) LPT with carbonate interdune thinning towards the left.

4.4 Third Fluvial to Eolian Transition

The final and third transition marks the ultimate encroachment of the main Navajo erg over the fluvial TCT, after which eolian units persist for few 100 meters regionally. The TCT is unlike the other fluvial units in terms of its architecture, sedimentology and paleoflow direction. The TCT commonly contains 1 to 2 meter thick fluvial sandstone sheets interbedded with siltier heterolithic facies. The TCT is entirely composed of FA2 with only occasional channelized sandstone bodies. Minor lateral accretion elements are also present within channel fills and are mainly composed of Sh, Sp and St facies. The contacts between major fluvial sand sheets are planar to slightly erosional. The unit displays abundant pedogenesis of varying intensity, with higher amounts present in facies Fm and Fl (Fig. 4-4A). Bioturbation and pedogenic horizons are not limited to finer grained facies but are also present in sandier fluvial sandsheets of unconfined flow deposits. Complete paleosol horizons are rare, but composite horizons with indistinguishable pedogenic boundaries are common. Massive to mottled fluvial sandstone units are also common, with most sedimentary texture obliterated as a result of bioturbation and pedoturbation (Fig. 4-4C).

The preservation of small eolian dunes is observed within the TCT unit, just below the transitional eolian units of FA3. The eolian dunes are no more than a few meters high and less than 1 m in lateral extent. The intensity of bioturbation increases vertically upsection near the transitional units. Facies Sse marks the initiation of FA3, similar to the transitions before, however in this transition it is less than 2 meters in thickness. Minor soft sediment deformation and fluid escape features are also observed within the Sse. Muddy intraclasts and scoured surfaces infilled with mud suggest fluvial influence. This unit truncates in a planar surface and is overlain by FA4 (Fig. 4-4D). The occurrence of a localized bioturbated and desiccated mudstone separates two major eolian cross bed sets and laterally transitions into mudcurls at the adjacent toe sets of eolian cross beds (Fig. 4-4B). The eolian sand sheets deposits of FA3 commonly show disrupted bedding. The transition units are cumulatively 10-15 meters thick before the FA4 typical of the Navajo begin to dominate. The eolian crossbed sets quickly develop into facies Sle representing large transverse dune bedforms.

Figure 4-4 Third fluvial to eolian transition A) Composite paleosol in TCT. B) Fluvial to lacustrine mud with sand infilled mudcrack. C) Pedogenic carbonate nodules developed in fluvial sandsheets. D) Alternating facies association 3 and 4 at transition.

4.4.1 Interpretation

The third and final fluvial to eolian transition records the ultimate establishment of the eolian Navajo erg over the largely ephemeral alluvial plain of the Kayenta, represented by the TCT. This final fluvial to eolian transition is thicker than the previous two transitions. The TCT represents an ephemeral alluvial plain of a distal terminal fan distributary system (Fig. 4-5). This is supported by abundant unconfined fluvial sheetfloods with minor scouring and erosive base. Furthermore, the abundant compound paleosols as well as bioturbation attest to long periods of sub aerial exposures during low flood stage. Lastly, the dominance of eolian sandsheet deposits in FA3 up section indicates the complete shutdown of the fluvial system and the gradual encroachment of the Navajo erg. The TCT and the overall Kayenta fluvial system record the

96 progression of several terminal fans migrating into a large established erg. Similar facies associations are recognized in the terminal fan model.

Figure 4-5 Terminal fan model representing systematic facies association changes (Kelly and Olsen, 1993).

The Navajo is a wet eolian system and evidence of wet to damp conditions, SSD and freshwater carbonate interdunes all attest to this. The Sw facies, typical of all previous transitions, are explained by adhesion of windblown sand into a damp to wet surface (Glennie, 1970). The repeated establishment of the sandsheet erg marginal FA3 alternating with FA4 is separated by planar deflation surfaces. Early cementation in this environment is also common and may also be

97 responsible for the irregular but planar nature of the bedding. The vertical changes in this transition can be related to the gradual drop in regional water table and increasing eolian sediment supply. The overall vertical transition records a slow trend towards an arid environment.

4.5 Eolian to Fluvial Transition

The fluvial to eolian transitions are very systematic and gradual as discussed above, however the eolian to fluvial transitions form very abrupt contacts (Fig. 4-6C&D). Both the KE and the LPT show similar upper surfaces, with overlying establishment of the fluvial UK and the TCT, respectively. The planar deflation or supersurface present at the top of these units are likely formed by deflation down to the water table.

The upper unit of KE shows evidence of pedogenesis and also dinoturbation. Small SSD features were identified on fallen blocks near the transition (Fig. 4.5A); however the deformation has not been identified directly in outcrop. Direct evidence of dinosaur footprints is present on this surface which likely formed when conditions were damp to moist, during the phase of non- deposition. Evidence of pedogenic development in the form of carbonate nodules and bioturbation is also present. This surface is immediately overlain by fluvial muddy facies of the UK which quickly develops into sandier channelized to non-channelized fluvial facies. These supersurfaces are significant in the basin since similar surfaces are present in the eastern areas of the basin, including Sand Springs and Moenkopi Wash locations. This hiatus in deposition represents the formation of a stable surface as suggested by silicified tree trunks, evidence of carbonate producing organisms, and steep fluvial incision into the surface suggesting prior cementation in the Sand Springs area (Long, 2008). Fluvial incisions into these supersurfaces were not identified in the Kanab study area. Furthermore, the supersurfaces have been shown to be regional timelines across the basin by conceptual models (Blakey, 1994). The temporal correlation of these surfaces across the basin remains uncertain.

The second major eolian to fluvial transition marked by LPT to TCT, show similar characteristics as the transition from KE to UK. The planar surface present at the upper boundary of the LPT is interpreted to be a supersurface. This surface shows significant carbonate and iron rich nodular development with minor undulation and scouring, similar to surfaces described in the Permian Cedar Mesa Sandstone (Mountney, 2006). The supersurface is overlain by muddy

98 fluvial facies which quickly develop into a thick carbonate unit (Fig. 4.5B) and is fairly extensive in the Kanab study area. Tuesink [1989] identified this lacustrine carbonate further east of Kanab Canyon, roughly spanning an area 10 km by 15 km. The thickness of the carbonate unit is fairly consistent at 25-30 cm, and shows abundant desiccation features on the upper surface. The unit is not an ideal ‘interdune’ since no corresponding eolian dunes are identified laterally with this unit. This highly dolomitized carbonate unit lacks eolian grains, and lacks algal laminations, commonly seen in the interdunes of the LPT and Navajo. Where the carbonate unit is absent, the supersurface is directly overlain by muddy fluvial facies of the TCT. This fresh water carbonate interval represents initial raising of the groundwater table infilling a regional topographic depression which formed after a period of non-deposition and formation of the eolian supersurface. This lacustrine carbonate unit may be fed by fluvial channels, but the lack of siliciclastic material within the carbonate supports a strong groundwater control.

In the onset of the development of a supersurface, the under saturated winds, with respect to their potential sand-transporting capacity, would have produced eolian sand sheets. However, there is no evidence of such facies at these transitions. The rising watertable deduced from the preservation of SSD near these contacts ‘foreshadows’ the oncoming fluvial system. The dune complex deflationary phase is recorded in the supersurface. The extensive supersurfaces recorded in the Permian Cedar Mesa Sandstone, record an erg deflationary phase in the form of eolian sandsheets and extensive rhizolith bearing units, however this is largely absent from the Kayenta-Navajo intertonguing zones (Mountney, 2006). Deflation is triggered by rising groundwater and likely a wetter climate which would lower the eolian accumulation, and favour the fluvial deposits to quickly occupy the available accommodation space.

4.5.1 Eolian Soft Sediment Deformation

The underlying eolian crossbed set of the LPT directly in contact with the supersurface displays extensive eolian SSD (Fig. 4-6C). This intense large scale deformation is locally correlatable in the study area and in most cases it is truncated by the supersurface. The large fluid escape feature present in the Cave Lakes Canyon display a strong west to east directionality to the fluid flow with evidence of fluid escape in a form of a large pipe structure occurring at the most eastern end of the entire SSD (Fig. 4-6C). The SSD features, where present elsewhere, in the upper section of the LPT display a similar directionality to fluid flow, with abundant planar shear surfaces. The

SSD features are strongly associated with interdune deposits in the Navajo system and have a strong groundwater control (Bryant et al., 2013; Bryant, 2011). Whereas carbonate interdunes are direct evidence of groundwater table intersecting with the surface topography, large SSD can also be used as indirect evidence for saturated to partially saturated conditions in the subsurface. Furthermore, eolian SSD in ancient eolinites have been interpreted to be both a subsurface and surface phenomena. In the LPT SSD case, the deformation occurred in the subsurface and expanded more than one cross bed set.

Large scale SSD horizons were also identified in the Navajo just overlying the TCT (Fig. 4-6E). This SSD feature likely expanded more than a few hundred meters in lateral extent based on minimal outcrop exposures, and is likely at similar scale as the SSD present in upper LPT. The SSD within the Navajo is bounded by a 1st order eolian surface and does not continue into the overlying cross bed sets. Similar in scale to the LPT SSD horizon, the SSD in Navajo shows comparable features; however unlike the LPT feature no fluid escape direction can be established.

100

Figure 4-6 Eolian to fluvial transitions A) SSD in KE. B) Nodular pedogenically altered upper contact of LPT. C) Large scale SSD in upper LPT at Cave Lakes Canyon, truncated

101 by overlying TCT. General fluid escape direction towards the right (east). D) LPT and TCT contact marking the 40cm carbonate pond deposit in TCT overlying the eolian supersurface E) Large scale SSD in Navajo overlying the TCT contact.

The dune collapse model developed by Horowitz [1982] to explain the SSD is largely valid and can provide the explanation as a first approximation. Earthquake induced deformation seems to be the most plausible and attractive causation of the large scale deformation. The liquefaction depth from modern earthquake data is less than a few tens of meters (Obermeier, 1996; Obermeier et al., 2002) which is a magnitude smaller than the depths of liquefaction recorded through these ancient eolinites SSD, considering only the lowest tenth of the dune bedform is preserved as a crossbed set. Recent SSD outcrop studies have shown the influence of liquefaction within the Navajo to reach more than 40 m below the surface (Bryant et al, 2013; Bryant and Miall, 2010). Additionally, large basement structures and unconsolidated saturated sand can amplify seismic shaking which can cause liquefaction at much greater depths. Analysis of similar scale sand pipe structures in the Entrada Sandstone as well as large scale SSD in Navajo sandstone are best explained by such seismic triggers (Huuse et al., 2005; Bryant, 2011). Even if the exact model of SSD causation in eolinites is disputed, it is largely agreed that saturated conditions need to be present in order to produce such large penecontemporaneous liquefaction features (McKee et al., 1962). The SSD can be used as a proxy for high water table conditions in the Navajo at certain instances. Furthermore, the presence of SSD horizons near the contacts with fluvial units can be largely attributed to persistent wet conditions and high water table control as the gradual transition from an arid to humid system is occurring.

102

Chapter 5

5 Discussion and Conclusion 5.1 Summary and Discussion

The overall transition from fluvial deposits of the Kayenta to the eolian deposits of the Navajo occurs in three distinct events. Two main types of fluvial systems of the Kayenta are summarized as follows: low sinuosity multistory braided fluvial channels (FA1) and ephemeral unconfined fluvial sandsheets (FA2). A gradual transition from FA1 to FA2 is recorded in the deposits of the Springdale, LK, UK and TCT (Fig. 5-1). Abundant sedimentological and architecture data supports that there is a decrease in channel depth as well as occurrence of channelization upsection. Furthermore, the overall intensity of pedogeneic development upsection associated with FA2 strongly indicates a lower frequency of fluvial flooding events and long periods of non-deposition. The eolian sandsheet to erg marginal environment with occasional influence of fluvial channels is summarized by FA3. Large eolian dune and draa facies are summarized by FA4, which represent the final encroachment of full eolian dune complex. Three identical and systematic transitions from FA1 to FA4 followed by an extensive development of a supersurface suggest a strong climatically induced signal (Fig. 5-1A&B). Similar cyclicity is widely recognized in the depositional basin and although the supersurfaces have not been traced laterally everywhere, isolated local recognition of these surfaces suggest regional presence of similar processes.

Relative thicknesses of units are highly dependent on sedimentation rates, and many depositional environments, such as non-marine fluvial and eolian systems, have an intrinsic or autogenic control on deposition. Highly variable and episodic sedimentation, especially in fluvial and eolian environments, record ‘more gap than record’ in a stratigraphic section (Ager, 1973; Miall, 2014). This concept is illustrated in Figure 5-1C which employs a qualitative version of a ‘Cantor function’ to sedimentation (Plotnick, 1986). Vertical sections on the graph represent assumed periods of sedimentation, whereas horizontal sections represent periods of non- deposition, as marked by the development of widely recognized surfaces. Two large hiatuses represent supersurfaces and record the transition back to a humid phase (Fig. 5-1C). This plot

103 qualitatively summarizes the approximate time represented by the various units and where major hiatuses maybe present. Although no quantitative measurements are used, this speculative graph illustrates that supersurfaces may represent significant non-deposition time in a generic vertical section.

Figure 5-1 Kayenta-Navajo transition synthesis A) Summarized Kanab ideal vertical section with representative paleoflow rose diagram for each unit; B) Corresponding facies association; C) Stratigraphic thickness accumulation versus time; D) Relative climatic cyclicity and drying up cycles.

In the Kayenta-Navajo system, changes in climate are manifested as facies changes and are largely controlled by moisture availability (Bullard and Livingstone, 2002). As the Navajo erg was establishing, interaction with marginal fluvial channels is expected and best explained through climatic controlled changes in surface water and groundwater. Surface runoff from the Mogollon highlands towards the southeast fed the Kayenta channels. Regional rainfall patterns largely controlled the availability of surface water and groundwater. During early Kayenta time, more frequent runoff constantly supplied the Kayenta channels and the terminal distributary

104 system was fed by large proximal channels carrying abundant bedload, whereas during times of TCT a gradual decrease in surface flow and presence of distal facies is manifested by ephemeral unconfined fluvial floods separated by longer periods of exposure. Each successive flooding event eroded and scoured the upper most layer of pre-existing deposits. As the climate got drier, previously high water table would begin to fall and the fluvial plain sediments become available for eolian recycling. The surface expression of regional groundwater table is seen in the form of freshwater carbonate interdunes in the eolian sediments. Indirect evidence of wet eolian sediments near the transition contacts is inferred from large SSD horizons within the LPT and Navajo. This large climatically controlled cyclicity is expressed as a qualitative sinusoidal function in Figure 5-1D. The time represented by each cycle varies and is speculated to be on the scale of 0.5 to 2 million years. This timescale is associated with global cycles of orbital forcing (Miall, 2010). Early Jurassic marine equivalent rocks are not preserved in the depositional basin to confirm any direct influence of eustatsic sea level changes. However, an approximate sinusoidal curve representing fluctuating climate is proposed and can track the phases of humidity and aridity, corresponding to various units in this transition (Fig. 5-1D). A time lag likely exists between the peak of each climatic cycle and the corresponding deposits. Subsequently, the transitional wetting phase of each cycle is represented in the eolian supersurface.

The Kayenta fluvial system represents an overall westward migration of several laterally amalgamated distributary fluvial systems terminating in an erg. This is very similar to the terminal fan model which is characterized by distributary channels and has a systematic downstream decrease in grain size, channel scale and an increase in the ratio of overbank to channelized deposits (Kelly and Olsen, 1993). Furthermore, distal or basinal zone of the terminal fan model is associated with eolian dunes and eolian sandsheets. Individual fans are interpreted to not exceed 100 km in radius and show a radial pattern in paleoflow direction. The early Kayenta system records a relatively continuous paleoflow direction towards the west and represents a more proximal distributary zone; however greater paleoflow variance upsection is related to the distal or basinal zone of the terminal fan systems. The presence of the associated eolian tongues, suggest that the amalgamated terminal fan system is terminating in an erg under climatically driven changes. A similar style of fluvial terminal fans is recognized in the east to central area near Echo Cliffs (Sanabria, 2001). North and Warwick [2007] argue that a terminal

105 fan model does not support a generic facies model and no evidence of such fan systems occur in modern environments. However, in the case of the Kayenta the model fits the observed rock record with minor inconsistencies. Additionally, there is an overall abundance of distributary fluvial systems, such as the Kayenta, in the geological record and modern examples (Weissmann et al., 2010).

The three fluvial to eolian transitions represented by the Kayenta-Navajo tongues in the Kanab area represent drying upward cycles (Fig. 5-1D) overprinting the generic receding terminal fan systems. The tectonic setting indicates a background of flexural subsidence and likely does not contribute to the cyclicity seen at the intertonguing scale. The overall aridity in this system is supported by the gradual change in the fluvial style as well as increasingly thick incursions of eolian tongues. The first Kayenta eolian unit represents a short lived arid period which is followed by wetter conditions favourable for the development of the fluvial UK. The transition from UK to LPT is thicker than the first transition, and marks the encroachment of full erg conditions that likely persisted longer than the first eolian incursion. The transition from LPT to TCT is marked by regional flooding and then gradual drying within the TCT followed by the final advance of the Navajo erg system which persisted for a few million years.

In the Tuba City and Sand Springs area, the drying up cycles varies from what is seen towards the West (Fig. 5-2). The complete stratigraphic section is thinner and the drying up cycles are represented by ephemeral fluvial units mixed with floodplain and interdune facies which abruptly transition into eolian dunes (Herries, 1993; Long, 2008). However, each identified drying upward cycle ends in a similar eolian supersurface (Long, 2008). Three major drying up cycles were interpreted in the Tuba City and Echo Cliffs area (Sargent, 1984; Herries, 1993 and Sanabria, 2001). A total of 12 ‘medium scale’ cycles were identified within the 112 m of section in the Kayenta at Sand Springs and West Sand Springs area (Long, 2008). The cycles were shown to have a time span of about 400, 000 years, in response to the Milankovitch eccentricity cycle. A total of 13 sequences within the Kayenta were recognized in the Echo Cliffs and each sequence boundary is placed at coarse grained fluvial units or base of eolian units (Sanabria, 2001). These sequences collectively form 3-4 lower frequency drying up cycles; similar to what is recognized towards in the Kanab study area. In the St. George area, the drying-up cycles are not distinct and collectively form the transitional Navajo. Figure 5-2 summarizes the regional presence and possible correlation of the recognized drying up cycles in the basin. This regional

106 recognition of similar facies transition strongly suggests an allogenic control to the cyclicity; however the supersurfaces separating these cycles maybe time transgressive.

Figure 5-2 Basin correlation of Kayenta-Navajo drying upward cycles; cross section oriented West to East. The eastern section shows higher frequency cycles which are interpreted to correlate with western lower frequency cycles (modified from Long, 2008).

The underlying Moenave Formation-Wingate Sandstone exhibits a similar cyclicity as seen in the Kayenta-Navajo. Furthermore, similar fluvial to erg drying up cycles are observed in the Permian Cedar Mesa Sandstone, which displayed 12 separate eolian erg accumulation deflation sequences with a recurring interval of 413,000 years for each cycle, attributed to the Milankovitch long eccentricity cycle (Mountney, 2006). Loope [1985] suggested that a complete cycle of erg construction and destruction based on sediment rates occur in a 30,000 year span, but when non-deposition time spans are included a cycle is approximately 400,000 years (Heckel, 1980). In the case of the intertonguing present in the Kayenta-Navajo, the units may represent similar time spans, which give a complete cycle duration in the 105 to 106 year range. However, due to the lack of dating controls and temporal correlation across the basin, the duration of cyclicity is uncertain. As demonstrated by this study, the larger trend towards aridity encompasses smaller scale cyclicity in the form of the intertonguing of depositional systems. A hierarchy of cyclicity is presented in these deposits, which if analyzed at the appropriate scale may show local to sub-regional correlation. The cyclicity observed as the intertonguing units of Kayenta with Navajo is attributed to climatic cycles that are likely controlled by fluctuating groundwater conditions.

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5.2 Conclusion

In conclusion, the lower Jurassic fluvial Kayenta Formation transitions into the overlying eolian Navajo Sandstone in three discrete and similar ‘drying upward’ cycles. These cycles show increasingly greater influence of the encroaching eolian erg system over the Kayenta alluvial plain. The transitions are marked by a systematic and predictable facies association scheme, separated by non-deposition hiatuses represented by the development of supersurfaces. The vertical change in fluvial style from coarse grained channelized deposits of the Springdale and Lower Kayenta to the finer grained unconfined fluvial units of the Upper Kayenta and the Tenney Canyon Tongue, further attest to the overall recession of several large terminal fans. Similar sets of three major drying-upward cycles have been documented from several sites regionally within the basin. These may provide temporal correlation between widely separated deposits that record an allogenic climatic control.

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Appendix I

Sedimentological Logs

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Appendix II Thin Section Descriptions

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Framework Grains Matrix Cement Sample Unit/ Lithic Facies Overall Size Quartz Feldspar Overall Overall Iron Oxide ID Formation Sorting Roundness Sphericity Fragments Size Roundness Lithology Lithology Size Notes % (mm) (%)1 (%)1 % % (%)1

Quartz Patches of Springdale 0.1- Subangular Mainly overgrowth SM01 Sc 93 moderately Low 78 8 14 <5 <0.1 Angular 1 to 2 - minor clay Minor Mmbr 0.6 to rounded quartz and minor zones clays

Patches of Springdale 0.1- Clay and minor clay SM02 Sp 95 moderately Subangular Low 83 8 9 3 - - - 3 - Minor grain coating Mmbr 0.5 calcite zones with calcite

Patchy, pore filling Springdale a few moderately Inter- SM03 Gm 75 Subrounded Medium 85 2 13 - - - - Calcite 25 and lining some Mmbr mm to well granular fill mudclast

Patches, Springdale 0.1- Platy to Clay- Qaurtz and SM04 Sh, Sr 95 moderately Subangular Low - - - 5 <0.1 1 to 2 some inter- Minor Mmbr 0.7 angular quartz clay granular fill Minor; concentrated in Springdale a few Inter- SM05 Sc 75 moderately Subrounded Medium 89 8 3 - - - - Calcite 25 clasts and some outer Mmbr mm granular fill rims of grains Mainly Sh --> Calcite, Patchy, Springdale max moderately Platy to clay Patchy intergranular, SM06 massiv 90 Subrounded Medium 85 9 6 5 <0.1 quartz 4 - around Mmbr 0.4 to well angular around lining the grains e overgrowth grains grains

Notes Values obtained from the point 1 count analysis

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Framework Grains Matrix Cement Sample Lithic Unit/Formation Facies Quartz Feldspars Overall ID Overall % Size (mm) Sorting Roundness Sphericity Fragments Overall % Size Roundness Lithology Size Lithology (%)1 (%)1 % (%)1 Iron Oxides Half of thin Moderately Calcite and section oxidized LK01 Lower Kayenta Sr 75 0.08 Angular Low ------25 Sorted clay coating clays calcite

Low, Half of thin section Sr --> Moderately Calcite and LK02 Lower Kayenta 80 0.1 Angular Low 91 6 3 minor - Clay 20 oxidized coating massive Sorted clay clays clays calcite

Clay and Abundant LK03 Lower Kayenta Sh, Fr 80 0.07 Moderate Angular Low - - - 5 - - Clay 15 calcite oxidation.

Clay and Abundant LK04 Lower Kayenta Fr 60 0.1 Moderate Angular Low - - - 40 calcite oxidation.

LK05 Lower Kayenta Fr 85 0.08 Poorly Angular Low 93 7 0 5 Clays - Clay 10 Calcite Moderate

Poorly to Clay and LK06 Lower Kayenta Fr; Ff 65 0.08 Angular Low - - - 35 Abundant moderate calcite

Clay and Abundant occurs in LK07 Lower Kayenta Ff 75 0.08 Poorly Angular Low - - - 5 Clays - Clay 20 calcite bands

Notes 1 Values obtained from the poin t count analysis

128

Framework Grains Matrix Cement Sample Unit/ Lithic Facies Feldspars Overall Overall ID Formation Overall % Size (mm) Sorting Roundness Sphericity Quartz (%)1 Fragments Size Roundness Lithology Size Lithology (%)1 % % (%)1 Iron Oxides

Bimodal Kayenta None- very KE01 Sse 90 (0.3mm) and Moderate Subrounded Low-Medium 87 10 3 5 - - Mainly Clay 2 - Clay/ calcite Eolian patchy (1mm)

Bimodal Kayenta Moderate to None- KE02 Sse 100 (0.4mm) and Subrounded Medium 88 11 1 - - - - - Quartz None Eolian well minor (1mm)

Kayenta KE03 Spe 80 0.2 Moderate Subangular Low 91 9 0 5 - Mainly Clay 15 Clay/ calcite Moderate Eolian

Kayenta Minor KE04 Spe; 90 0.2mm Poor Subangular Low 87 12 1 10 Angular Quartz Clay/ calcite None Eolian (<2%)

Notes Values obtained from the point count 1 analysis

129

Framework Grains Matrix Cement Sample Unit/ Lithic Facies Overall Size Quartz Feldspar Overall ID Formation Sorting Roundness Sphericity Fragment Size Roundness Lithology Overall % Size Lithology % (mm) (%)1 (%)1 % (%)1 Iron Oxides Upper Angular- Mainly Max UK01 Sr 87 0.2 Moderately Subangular Low 80 7 13 5 0.05mm 8 Calcite Minor coatings Kayenta Subangular Qtz 0.4mm Mainly Upper Subangular- Max Abundant; present as coatings UK02 Sr 80 0.2 Moderate Low 85 5 10 5 0.05 Angular Lithics 15 Calcite Kayenta subrounded 1.0mm around quartz as well as flasers and Qtz Mainly Max Upper Moderately Subrounded UK03 Sr 85 0.3 Medium 85 5 10 <5 0.05 Angular Lithics 15-20 0.3 Calcite Low Kayenta Well to rounded and Qtz mm Upper UK04 Ff 30 0.15 Poorly Angular Low 95 <5 <5 70 Clay - - - - Clays High Kayenta Upper Subrounded Max UK05 Sh 95 0.2 Well Medium 94 2 4 0 - - - ~2 Calcite None to very low Kayenta to rounded 0.6 Half of slide oxidized with Upper Low- UK06 Fl 75 0.2 Moderately Subangular 5 Clay 20 Calcite mudchips pronounced by the Kayenta Medium oxidation. Half is bleached. Upper Sr --> 0.4 mm UK07 70 Moderately Subrounded Medium 93 5 2 - - - 30 Calcite None Kayenta massive max Upper Moderate Low- Mostly concentrated in smaller UK08 Fl 80 0.2 Subangular 5 Clay 15 Calcite Kayenta to poorly Medium fine grained stringers Upper Subrounded None-minor; a few mud clasts UK09 Sh 93 0.4 max Moderately Medium 78 17 6 5 Clay 2 (Minor) Calcite Kayenta to rounded oxidized Upper 0. 15 Subangular- Some rounded oval opaques, UK10 Sh 90 Moderate Medium 89 9 2 <3 Clay 7 Calcite Kayenta avg subrounded overall none-minor oxidation Upper Subangular- Low- Clay/ UK11 Fl, Fr 75 0.15 Moderate 92 7 1 10 15 Calcite Moderate Kayenta subrounded Medium Clastics Upper Moderate- UK12 Sr, Sh 80 0.2 Subangular Medium 90 7 3 <3 Clay 20 Calcite Minor; reminiscent oxides present Kayenta well Upper Subangular- Low- Moderate oxidation and grain UK13 Sr 80 0.2 Moderate 90 8 2 20 Clay Clay <2 Calcite Kayenta subrounded Medium coatings

Notes 1 Values obtained from the point cou nt analysis

130

Framework Grains Matrix Cement Sample Unit/ Facies Overall Size Quartz Lithic Overall Overall Iron Oxides ID Formation Sorting Roundness Sphericity Feldspars(%)1 Size Lithology Size Lithology % (mm) (%)1 Fragments(%)1 % % Lamb Point 0.3 and Moderatley Subrounded Moderate- LPT01 Spe 98 82 14 4 2 Clastics/Clay 0 - - None Tongue 1.0 - well to Rounded High Subangular Lamb Point LPT02 Sw 83 0.2 Moderately to Moderate 90 8 2 10 Clay 7 Calcite Minor Tongue subrounded Lamb Point Subrounded LPT03 Spe 98 0.2 Moderately Moderate 83 15 2 2 Clastics/Clay 0 None Tongue to Rounded

Lamb Point Subrounded LPT04 Sle 98 0.25 Moderately Moderate 81 16 3 2 Clastics/Clay 0 None, very minor Tongue to Rounded

Lamb Point 0.2 and LPT05 Fc 80 Poorly Rounded High 87 9 3 0 20 Calcite Some Tongue 0.8

Lamb Point Poor- Subrounded Moderate- LPT06 Fc 70 0.25 94 5 1 0 30 Calcite Some Tongue Moderately to Rounded High

Lamb Point 0.1- Poor- Subrounded LPT07 Spe 100 Moderate 83 14 3 0 0 None Tongue 1mm Moderately to Rounded

Lamb Point 0.1- Subrounded LPT08 Fc 80 Poor Moderate 90 7 3 0 20 Clacite None, minor Tongue 1mm to Rounded

Lamb Point 0.1- Subrounded LPT09 Fc 35 Poor Moderate ------65 Calcite None, very minor Tongue 1mm to Rounded

Lamb Point 0.1- Subrounded Moderate- LPT10 Sle 100 Moderate 86 11 3 0 None Tongue 1mm to Rounded High

Lamb Point 0.1mm- Poor- Subrounded Moderate- Minor to moderate LPT11 Fc, Fr 75 87 11 2 5 Clay 20 Calcite Tongue 1mm moderate to Rounded High oxidation

Lamb Point 0.15 LPT12 Fc, Fl 60 Poor Subangular Low - - - 10 Clay/Clastics 30 Calcite Moderate Tongue avg

Lamb Point LPT13 Fc N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A None Tongue

Notes 1 Values obtained from the point count analysis

131

Tenney Poor- Angular- TCT01 Canyon Fl 65 0.15 Low - - - 15 Clay Clay 20 Calcite Highly oxidized Moderate Subangular Tongue

Tenney TCT02 Canyon Sh 70 0.15 Moderate Subangular Low 86 7 7 10 Clay 20 Calcite Highly oxidized

Tongue

Tenney TCT03 Canyon Sr, Fr 65 0.2 Moderate Subangular Low - - - 10 Clay 25 Calcite Highly oxidized

Tongue Tenney Poor- TCT04 Canyon Ff 70 0.05 Angular Low - - - 20 Clay 10 Calcite Highly oxidized Moderate Tongue

Tenney Poor- TCT05 Canyon Sh, 77 0.2 Angular Low 83 13 4 8 Clay 15 Calcite Highly oxidized Moderate Tongue

Tenney TCT06 Canyon Fl 70 0.15 Moderate Angular Low - - - 10 Clay 20 Clacite Highly oxidized

Tongue

Tenney Poor- TCT07 Canyon Sh, Sr 80 0.2 Subangular Low 80 16 4 7 Clay 13 Calcite Highly oxidized Moderate Tongue Tenney Poor- TCT08 Canyon Sh, Fr 75 0.05 Subangular Low - - - 20 Clay 5 Calcite Highly oxidized Moderate Tongue

Notes 1 Values obtained from the point count analysis

132

Framework Grains Matrix Cement Unit/ Sample ID Facies Overall Size Quartz Lithic Overall Overall Iron Oxides Formation Sorting Roundness Sphericity Feldspars(%)1 Size Lithology Size Lithology % (mm) (%)1 Fragments(%)1 % % Large: Large grains 2 types: High well 0.8 avg Sphericity NV01 Navajo Sse 85 Poor rounded; 89 9 2 3 - Clay 12 Calcite None, very minor and 0.08 Finer: finer avg Low- subangular Medium Bimodal: Bimodal: Bimodal: Well High Very Quartz NV02 Navajo Spe 98 0.7 and Poor rounded 86 12 2 3 2 Very minor sphericity minor Overgrowths 0.1 and and low subangular Bimodal: Bimodal: Well High NV03 Navajo Sw 75 0.05-0.8 Poor rounded 90 7 3 10 Clay 15 Calcite Minor-moderate sphericity and and low subangular Moderate- Minor- present as grain NV04 Navajo Spe 95 0.15 Subrounded Medium 86 12 2 5 Clay 0 - - well coating

Subangular- Low- NV05 Navajo Sw 75 0.15 Moderate 83 15 2 5 Clay 20 Calcite Moderate subrounded Medium

Moderate- NV06 Navajo Spe 98 0.2 Subrounded Medium 80 17 3 2 Clay 0 - None well

Moderate- NV07 Navajo Spe 98 0.2 Subrounded Medium 83 14 2 2 Clay 0 None well

Minor amounts lining NV08 Navajo Fc N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A textural lineation.

Minor amounts lining NV09 Navajo Fc N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A vugs.

Moderate- NV10 Navajo Fc 88 0.2 Subrounded Medium 84 13 3 2 Clay 10 Calcite well

Notes 1 Values obtained from the point count analysis