UNIVERSITY OF OKLAHOMA
GRADUATE COLLEGE
FINE SCALE 3D ARCHITECTURE
OF A DEEPWATER CHANNEL COMPLEX,
CARBON COUNTY, SOUTH-CE...
FINE SCALE 3D ARCHITECTURE
OF A DEEPWATER CHANNEL COMPLEX,
CARBON COUNTY, SOUTH-CENTRAL WYOMING
A THESIS APPROVED FOR THE
...
© Copyright by STAFFAN KRISTIAN VAN DYKE 2003
All Rights Reserved
ACKNOWLEDGEMENTS
I would like to extend an overwhelming appreciation and special thanks to my
advisor, Roger Slatt, for gu...
TABLE OF CONTENTS
Acknowledgements…………………………………………………………….……..iv
Table of Contents…………………………………………………………………......v
List of...
Physical Description…………………………………………27
Hydrodynamic Interpretation………………………………...28
Lithofacies 4 (F4): Parallel to Subpar...
E4: Proximal levee………………………………..……………….................47
Interpretation……………………………………………............……47
Facies Relations...
Channel-Fill Sandstone 7………………………............………………….....87
Vertical and Lateral Geometry…………………............………….....87
Li...
D9. Channel-Fill Sandstone 8……………………………….CFS08
D10. Channel-Fill Sandstone 9……………………………….CFS09
D11. Channel-Fill Sandstone...
LIST OF FIGURES
FIGURE PAGE
Fig. 1.01: Chronostratigraphic chart of Upper Cretaceous strata, southern
Wyoming…………………………………...
Fig. 3.06: Sinuous submarine channel-fill deposit localities………………………...45
Fig. 3.07: Oblique depositional strike view of ...
Fig. 4.23: Location and number of detailed measured sections (black)
with outcrop dimensions (red) on Channel-fill Sandsto...
LIST OF APPENDICES
APPENDIX (LOCATED ON ATTACHED CD) FOLDER
A. Detailed Measured Sections in Digital Format………………………DMS
B....
ABSTRACT
Nine channel-fill sandstones comprise a 255ft thick stratigraphic succession in
the deepwater Dad Sandstone Membe...
This distribution of facies, coupled with GPR data, suggests the sandstones
filled sinuous channels. The shale-clast congl...
Chapter 1
INTRODUCTION
Research Objectives
This thesis research has two main objectives. The first objective is to
documen...
Significance
The study of submarine slope channel deposits is of great importance for
many different reasons: (1) document...
Fig. 1.01: Chronostratigraphic chart of Upper Cretaceous strata, southern Wyoming (Modified
after Schell, 1973).
Location ...
Fig. 1.02: Shaded relief map of Wyoming and Washakie Basin (Modified after Sterner,
1997).
This region nicely exposes all ...
The processes involved with the deposition of channel-fill sandstones are
thought to resemble those of subaerial fluvial s...
Fig. 1.03: Topographic map of Spine 1 and Spine 2 (from Slatt, 2003).
Fig. 1.04: Spine 1 with 9 channel-fill sandstones wi...
This geologic overview has been modified from Pyles (2000) and Witton
(2000). During the Cretaceous, the Western Interior ...
non-marine clastic sediments interfingering with one another, thus representing
marine transgressions and regressions that...
The final transgression and regression of the late Cretaceous was known as the
Bearpaw transgressive-regressive cycle. It ...
Fig. 1.07: Major geologic features surrounding field area (Baars et al., 1988).
As relative sea-level began to rise, the L...
crustal contraction, 3) supracrustal loading, or 4) stress-induced subsidence as a result
of tectonic loading (Cross and P...
Fig. 1.08: Lewis Shale Stratigraphic Column (from Slatt, 2003).
Both the underlying Almond Formation and the overlying Fox...
broader, more extensive third-order cycle existed, there in fact are many fourth-order
cycles of aggradation and progradat...
reserves had been produced, thus leaving much room for new unconventional
development concepts to exceed the production ca...
Her work also involved the recognition of facies in a borehole image log from a
well drilled through the same stratigraphi...
Data Collection
The succession of the nine stacked leveed channel-fill sandstones was
characterized by 121 closely-spaced,...
Outcrop Plane. “Outcrop Face” and “Outcrop Plane” were constructed in GOCAD™
allowing the raw data to portray the nine cha...
Fig. 1.11: Channel-fill boundary nomenclature
.
A handheld gamma-ray scintillometer was used to record the natural gamma
r...
Data Analysis
Channel-fill sandstones 1 through 10 were mapped with the dm-scale Trimble
™ GPS units and detailed measured...
3-Dimensional GOCAD ™ Model
A 3-Dimensional GOCAD ™ model has been designed to capture the
channel-fill sandstone outcrop ...
Chapter 2
LITHOFACIES DESCRIPTION
Introduction
Previous work performed by Witton (2000) and Slatt et al. (2000, 2001, and
...
Lithofacies Types
Eight lithofacies were recognized in the field; they are: F1) sandstone with
water-escape structures (so...
Three of the eight facies constitute classic Bouma Sequence deposits (Fig.
2.01); they are: F4, F5, and F6. F4, parallel t...
Fig. 2.02: “Knobby” texture interpreted as weathered vertical/subvertical dewatering pipes.
Fig. 2.03: Dewatering pipes lo...
Hydrodynamic Interpretation
Sandstones with water-escape structures, such as vertical pipes, are formed by
hindered settli...
Fig. 2.04: Structureless Sandstone with geologically unrelated holes pockmocking surface of
Channel-fill Sandstone 3.
Hydr...
Fig. 2.05: Temporal and Spatial relations in flow environments (Modified from Kneller, 1995)
Fig. 2.06: Walker’s (1978) cl...
Fig. 2.07: Lowe (1982) classification of High Density Turbidity Current (HDTC) and Low
Density Turbidity Current (LDTC).
L...
Fig. 2.08: Low-angle, high amplitude crossbedding from Channel 1 (from Slatt, 2003).
Hydrodynamic Interpretation
Primary c...
personal communication, 2003). The in-channel barforms are interpreted to lie on the
pointbar-equivalent side of the chann...
Fig. 2.09: Planar laminae on outcrop exposure on Channel-fill Sandstone 6.
Fig. 2.10: Planar laminae located in Channel-fi...
Hydrodynamic Interpretation
Planar bedding occurs in both the lower and upper flow regime. It exhibits
parallel bedding. F...
includes those with lee slope deposition, as well as those with lee and stoss slope
deposition (Fig. 2.12).
Fig. 2.11: Cli...
These deposits are diagnostic of a sediment-choked system and are interpreted to
occur at either the inner channel-levee m...
Fig. 2.13: Shale/mudstone facies bounded by structureless sandstone facies.
Hydrodynamic Interpretation
Facies F6, shale a...
deposited as the tail-end of a turbidity current as opposed to pelagic rain (not
quiescent enough in this environment for ...
Fig. 2.14: Stacked shale-clast conglomerates (A) interbedded with turbidites (B) on Channel-fill
Sandstone 1.
Fig. 2.15: F...
Hydrodynamic Interpretation
The shale-clast conglomerates are interpreted to have originated as debris flow
deposits. Thes...
Lithofacies 8 (F8): Slump Beds
Physical Description
Slump beds (Fig. 2.17) are found only in a few of the channel-fill san...
Hydrodynamic Interpretation
Slump beds are interpreted to have formed as a coherent unit of the failed
inner-channel margi...
Chapter 3
ENVIRONMENT OF DEPOSITION AND FACIES RELATIONSHIPS
Introduction
The purpose of this chapter is to categorize the...
Fig. 3.01: Enviroments of Deposition (E) 1-5 contained within a leveed-channel system.
Interpretations
Associated with eac...
Fig. 3.02: Situations leading to different flow behaviors (Modified from Kneller, 1995).
Kneller’s (1995) (Fig. 2.05) diag...
Fig. 3.04: Flow movement within a sinuous channel-bend.
The following text in this chapter hypothesizes on the expected fa...
steady (uniform velocity over time) (Kneller, 1995). Since the flow can do any three
of these when exiting the channel-ben...
E2: Outer-side of sinuous channel bend
Interpretation:
E2 is the outer-side of a sinuous bend in a channel-fill system. Fi...
Fig. 3.05: 3D seismic horizon slice (photo courtesy of H. Posamentier).
Fig. 3.06: Sinuous submarine channel-fill deposit ...
E3: Inner-side of sinuous channel-bend
Interpretation:
This interpretation is based mainly on field observations and perso...
Additionally, Abreau et al (2002) noted that these features dominate the fill of
many submarine channels and exhibit thems...
contorted/convoluted bedding planes, climbing ripples (F5, due to high sediment
input), reverse grading within associated ...
Fig. 3.09: Proximal levee with convoluted bedding and climbing ripples associated with Channel-
fill Sandstone 4
Fig. 3.10: Proximal levee with 2-inch set of climbing ripples associated with Channel-fill
Sandstone 4
Facies Relationship...
Another match is the sand/shale ratio, which is much higher here than in the
interpreted distal levee region.
E5: Distal l...
Facies Relationship:
E5 contains these two diagnostic facies, where they appear on a detailed
measured section of distal-l...
Chapter 4
3D MODEL DESCRIPTION AND INTERPRETATION
Introduction
The 3D model that all outcrop measurements were based upon ...
and appropriate lines that represented channel boundaries (Fig. 1.11) and detailed
measured section localities could be dr...
Structureless sandstone: yellow, (F3) Cross-bedded sandstone: magenta, (F4) Parallel
to sub-parallel laminated sandstone: ...
Viewing the Data
Representing 3D images in 2D space has proven to be a difficult task. The
following guidelines are recomm...
basemap, pointing north, which contains all nine channel-fill sandstones (Fig. 4.02).
Note that the arrow is oriented diff...
Fig. 4.02: Planview basemap of nine stacked channel-fill sandstones. F1 (blue): sandstone with water-escape structures (so...
Channel-Fill Sandstone 1
Fig. 4.03: Channel-fill Sandstone 1 location in Field Area. F1 (blue): sandstone with water-escap...
Fig. 4.04: Locations of detailed measured sections on Channel-fill Sandstone 1 (1.01 – 1.22).
F1 (blue): sandstone with wa...
Vertical and Lateral Geometry:
The detailed measured sections of Channel-fill Sandstone 1 can be located on
Figure 4.03 an...
Lithologic Stacking Patterns and Locations:
In the northern region of Channel-fill Sandstone 1 are numerous shale-clast
co...
Fig. 4.06: “Prong;” located in the eastern region of Channel-fill Sandstone 1. F1 (blue): sandstone with water-escape stru...
Fig. 4.07: Shale-clast conglomerate facies found in northern-most portions of Channel-fill Sandstone 1 model. F1 (blue): s...
Fig. 4.08: Western-most flank of Channel-fill Sandstone 1 ends at MS# 1.0.1. F1 (blue): sandstone with water-escape struct...
Interpretation:
The large number of F7 (shale-clast conglomerate) beds in the northern region
of the channel-fill interbed...
drilled, the lithologic cuttings expelled from the borehole were recorded, measured,
and bagged for later analysis. After ...
Fig. 4.10: Example of gamma-ray log from Borehole 1
These plots were then positioned accordingly to their proper X, Y, Z l...
guided by field notes and cutting samples from each borehole. The field notes were
instrumental in the interpretations bec...
Fig. 4.12: Strike cross-section of Boreholes 1-2-3-4 of Channel-Fill Sandstone 1.
Electro-Magnetic Induction techniques we...
Fig. 4.13: Electro-Magnetic Induction and GPR (3-B to 3-B’) carried out on eastern flank of
Channel-Fill Sandstone 1 (Blue...
Fig 4.14: Ground-Penetrating Radar facies located in the subsurface of Channel-Fill Sandstone 1
(Young et al., in press).
...
Vertical and Lateral Geometry:
There are two major trends to the Outcrop Face of Channel-fill Sandstone 2,
N-S and E-W (Fi...
Fig. 4.16: F7, shale-clast conglomerates and F3, crossbedded sandstone, located on Channel-fill Sandstone 2. F1 (blue): sa...
Interpretation:
The northern region of the channel-fill environment is dominated by facies F7,
shale-clast conglomerates (...
Vertical and Lateral Geometry:
Channel-fill Sandstone 3 shows similar N-S and E-W trends as the previous
channels. The det...
Fig 4.18: Diagnostic facies of Channel-fill Sandstone 3. F1 (blue): sandstone with water-escape structures (some cross-bed...
Interpretation:
The presence of F7 in the northeastern and southeastern regions of the
channel-fill (Fig. 4.18) are interp...
Fig. 4.20: Location and number of detailed measured sections (white) with outcrop dimensions (red) on Channel-fill Sandsto...
Vertical and Lateral Geometry:
The detailed measured sections of Channel-fill Sandstone 4 can be found on
Figure 4.19 and ...
Fig. 4.21: Diagnostic facies located on Channel-fill Sandstone 4. F1 (blue): sandstone with water-escape structures (some ...
Interpretation:
The southernmost flank, in the stratigraphically lower portions, shows the
dominant facies to be crossbedd...
Fig 4.22: Amalgamated channel-fills CFS 4a and CFS 4b, comprising Channel-fill Sandstone 4.
CFS4b is dominated by F8 and F...
Channel-Fill Sandstone 6
Fig. 4.23: Location and number of detailed measured sections (white) with outcrop dimensions
(red...
Lithologic Stacking Patterns and Locations:
The northwestern regions of the channel-fill environment are dominated by
basa...
Fig. 4.24: Diagnostic facies of Channel-fill Sandstone 6. F1 (blue): sandstone with water-escape structures (some cross-be...
Fig 4.25: Amalgamated channel-fills CFS 6a and CFS 6b, comprising Channel-fill Sandstone 6.
CFS6a is interpreted to have i...
Channel-Fill Sandstone 7
Fig. 4.26: Location and number of detailed measured sections (black) with outcrop dimensions
(red...
Lithologic Stacking Patterns and Locations:
Dominated in the western portions of Channel-fill Sandstone 7 (CFS7) is
facies...
Fig. 4.27: Diagnostic facies of Channel-fill Sandstone 7. F1 (blue): sandstone with water-escape structures (some cross-be...
Channel-Fill Sandstone 8
Fig. 4.28: Location and number of detailed measured sections (black) with outcrop dimensions
(red...
Lithologic Stacking Patterns and Locations:
Channel 8 shows some unique lithologic patterns. In the western portion of
the...
Fig. 4.29: Diagnostic facies of Channel-fill Sandstone 8. F1 (blue): sandstone with water-escape structures (some cross-be...
Interpretation:
These unique stacking patterns reveal an interesting interpretation. The
eastern side of CFS8 is interpret...
Channel-Fill Sandstone 9
Fig. 4.30: Location and number of detailed measured sections (white) with outcrop dimensions (red...
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming
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Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming

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Nine channel-fill sandstones comprise a 255ft thick stratigraphic succession in the deepwater Dad Sandstone Member, Lewis Shale, Wyoming. This succession has been characterized by measuring 121 closely-spaced outcrop stratigraphic sections, decimeter-scale GPS-tracing (Global Positioning System) of bed boundaries, drilling and gamma-logging of 8 shallow boreholes, ground-penetrating radar (GPR), and electro-magnetic induction (EMI) behind the outcrops. A 3D facies and architectural model was built using GOCAD TM.

Each channel-fill sandstone is separated by thin-bedded, very fine sandstone/mudstone strata. Channel facies include structureless sandstone with fluid escape structures, structureless sandstone without fluid escape structures, rippled to climbing rippled sandstone, parallel to subparallel laminated sandstone, cross-bedded sandstone, shale-clast conglomerate, thin-bedded sandstone/mudstone, and slumped beds. In separate channel-fill sandstone, these facies can be complexly interbedded, but there is a tendency for shale-clast conglomerates to comprise the base and one side of a channel-fill, whereas cross-bedded sandstones comprise the opposite side. Massive/fluid escape structured sandstones typically occupy the top of these successions. Proximal to distal levee beds occur adjacent to some of the channel sandstones.

This distribution of facies, coupled with GPR data, suggests the sandstones filled sinuous channels. The shale-clast conglomerates are thought to be the product of slumping of adjacent levee walls from the steeper channel margin, and the cross-bedded sandstones are interpreted to be in-channel bar or dune forms. These channels probably fed sand into the deeper basin contemporaneously with levee formation; the channel-fill sandstones represent the product of later backfilling episodes. The slumped and erosive nature of some channel margins support this interpretation.

This 3D outcrop characterization provides an excellent, scaled analog for leveed channel reservoirs. The complex vertical stratigraphy indicates individual channel sandstones can be mutually isolated reservoirs. The complex internal channel sandstone distribution indicates internal reservoir fluid flow will also be complex. A figure illustrating the relation of channel-fill sandstone sinuosity relative to one another in outcrop has also been created.

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Fine Scale 3D Architecture of a Deepwater Channel Complex, Carbon County, South-Central Wyoming

  1. 1. UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE FINE SCALE 3D ARCHITECTURE OF A DEEPWATER CHANNEL COMPLEX, CARBON COUNTY, SOUTH-CENTRAL WYOMING A THESIS SUBMITTED TO THE GRADUATE FACULTY In partial fulfillment of the requirements for the degree of Master of Science (Geology) By Staffan Kristian Van Dyke Norman, Oklahoma 2003
  2. 2. FINE SCALE 3D ARCHITECTURE OF A DEEPWATER CHANNEL COMPLEX, CARBON COUNTY, SOUTH-CENTRAL WYOMING A THESIS APPROVED FOR THE SCHOOL OF GEOLOGY AND GEOPHYSICS BY Chair: Dr. Roger Slatt Member: Dr. Douglas Elmore Member: Dr. Roger Young
  3. 3. © Copyright by STAFFAN KRISTIAN VAN DYKE 2003 All Rights Reserved
  4. 4. ACKNOWLEDGEMENTS I would like to extend an overwhelming appreciation and special thanks to my advisor, Roger Slatt, for guiding me through this project as well as giving me invaluable insight over the course of writing this thesis and during my 3 year stay at the University of Oklahoma. Thanks for believing in me, Roger. I would also like to extend appreciation to my committee members, Douglas Elmore and Roger Young. They have not only provided valuable insight into the project, but have also been very understanding with all the problems encountered at the end of thesis writing. I thank Ozzie Ilaboya for all the help and advice regarding GOCAD™, without whom, none of this would have been possible. All teachers and fellow graduate students at the University of Oklahoma are also thanked, and their memory will forever be burned into my conscious – thanks for everything. A particular thanks goes to my field assistants, Andria Parker and Ash Hall. Lastly, I would like to thank my family, Gene, Astrid, and Tor Van Dyke. This work is dedicated to them, in particular, to my mother for being the best mom in the world and always being there for me when I needed somebody. I love you mom and you will always be number one in my book.
  5. 5. TABLE OF CONTENTS Acknowledgements…………………………………………………………….……..iv Table of Contents…………………………………………………………………......v List of Figures……………………………………...……………………………….....x List of Appendices......................................................................................................xiii Abstract…………………………………………………………………………...…xiv CHAPTERS PAGE 1. INTRODUCTION…………………………………………………………………….1 Research Objectives…………………………………………...………1 Significance……………………………………………………...…….1 Location of Study Area and Description of Outcrop………..……..….3 Geologic Overview……………………………………….….……..…6 Lithostratigraphy and Sequence Stratigraphy………………………..10 Lewis Shale Petroleum System……………………………….……...12 Previous Studies……………………………………………………...13 Data Collection………………………………………………………15 Data Analysis………………………………………………………...18 3-Dimensional GOCAD™ Model…………………………………...19 2. LITHOFACIES DESCRIPTION…………………………………………….…..20 Introduction…………………………………………………………..20 Lithofacies Types………………………………………………….....20 Lithofacies 1 (F1): Structureless to Cross-Bedded Sandstone with Water-Escape Structures……………............22 Physical Description…………………………………….…...22 Hydrodynamic Interpretation…………………………….......23 Lithofacies 2 (F2): Structureless Sandstone without Water-Escape Structures…………………….............24 Physical Description…………………………………………24 Hydrodynamic Interpretation………………………………...25 Lithofacies 3 (F3): Cross-Bedded Sandstones without Water-Escape Structures ……………........................27
  6. 6. Physical Description…………………………………………27 Hydrodynamic Interpretation………………………………...28 Lithofacies 4 (F4): Parallel to Subparallel Laminae……....................28 Physical Description…………………………………………28 Hydrodynamic Interpretation………………………………...30 Lithofacies 5 (F5): Rippled or Climbing-Ripple Sandstone…............30 Physical Description…………………………………….…...30 Hydrodynamic Interpretation…………………………...……31 Lithofacies 6 (F6): Shale or Mudstone……………………................32 Physical Description…………………………………………32 Hydrodynamic Interpretation………………………………...33 Lithofacies 7 (F7): Shale-Clast Conglomerates……………...............34 Physical Description…………………………………………34 Hydrodynamic Interpretation………………………………...36 Lithofacies 8 (F8): Slump Beds……………………………...............37 Physical Description…………………………………………37 Hydrodynamic Interpretation………………………………...38 3. ENVIRONMENT OF DEPOSITION AND FACIES RELATIONSHIPS..……..39 Introduction……………………………………………………………..........39 Interpretations………………………………………………………………..40 E1: Non-sinous (Straight) leveed-channel environment……………………..42 Interpretation…………………………………………………………42 Facies Relationship…………………………………………………..42 E2: Outer-side of sinuous channel bend………….……………….................43 Interpretation…………………………………………………............43 Facies Relationship………………………………………............…..44 E3: Inner-side of sinuous channel bend…………………………............…...45 Interpretation…….……………………………………............……...45 Facies Relationship……………………………………............……..46
  7. 7. E4: Proximal levee………………………………..……………….................47 Interpretation……………………………………………............……47 Facies Relationship………………………………………............…..50 E5: Distal levee…………………………………………………............……51 Interpretation…………………………………………............….…...51 Facies Relationship……………………………………............……..52 4. 3D MODEL DESCRIPTION AND INTERPRETATION…………………..…...53 Introduction…………………………………………………………………..53 Viewing the Data……………………………………………............……….55 Channel-Fill Sandstone 1……………………………………............….........58 Vertical and Lateral Geometry……………………............……..…...60 Lithologic Stacking Patterns and Locations………............……..…..61 Interpretation…………………………………………............…..…..65 Subsurface………………………………………............………..…..65 Channel-Fill Sandstone 2…………………………………............……….....71 Vertical and Lateral Geometry…………………………............….....72 Lithologic Stacking Patterns and Locations……………..............…..72 Interpretation……………………………………………..............…..74 Channel-Fill Sandstone 3……………………………………….....................74 Vertical and Lateral Geometry…………………………............….....75 Lithologic Stacking Patterns and Locations……………..............…..75 Interpretation…………………………………………............…..…..77 Channel-Fill Sandstone 4………………………………………............….....77 Vertical and Lateral Geometry…………………………….................79 Lithologic Stacking Patterns and Locations………………............…79 Interpretation…………………………………………............………81 Channel-Fill Sandstone 6………………………………………............….....83 Vertical and Lateral Geometry…………………………….................83 Lithologic Stacking Patterns and Locations…………............………85 Interpretation……………………………………………............……85
  8. 8. Channel-Fill Sandstone 7………………………............………………….....87 Vertical and Lateral Geometry…………………............………….....87 Lithologic Stacking Patterns and Locations………............…………88 Interpretation……………………………………............……………88 Channel-Fill Sandstone 8……………………………………............…….....90 Vertical and Lateral Geometry………………………............…….....90 Lithologic Stacking Patterns and Locations…………............………91 Interpretation…………………………………………............………93 Channel-Fill Sandstone 9……………………………………............…….....94 Vertical and Lateral Geometry……………………............……….....95 Lithologic Stacking Patterns and Locations…………............………95 Interpretation……………………………………………............……95 Channel-Fill Sandstone 10…………………………………............………...97 Vertical and Lateral Geometry………………............…………….....97 Lithologic Stacking Patterns and Locations………............…………98 Interpretation………………………………………............…………98 5. CONCLUSIONS……….…….……………………………………………….....100 6. REFERENCES CITED…………………………………………………………..105 APPENDICES………………………………………………………………………CD FOLDER Detailed Measured Sections in Digital Format………………………DMS Gamma-Logs of Eight Shallow Boreholes…………………………..BHGL Copy of Thesis Text…………………………………………………THESIS GOCAD™ Data Files……………………………………………….GOCAD SUBFOLDER D1. Raw Data…………………………………………………RD D2. Channel-Fill Sandstone 1……………………………….CFS01 D3. Channel-Fill Sandstone 2……………………………….CFS02 D4. Channel-Fill Sandstone 3……………………………….CFS03 D5. Channel-Fill Sandstone 4……………………………….CFS04 D6. Channel-Fill Sandstone 5……………………………….CFS05 D7. Channel-Fill Sandstone 6……………………………….CFS06 D8. Channel-Fill Sandstone 7……………………………….CFS07
  9. 9. D9. Channel-Fill Sandstone 8……………………………….CFS08 D10. Channel-Fill Sandstone 9……………………………….CFS09 D11. Channel-Fill Sandstone 10..…………………………….CFS10 D12. Digital Elevation Map……………………………………DEM D13. Quickview………………………………………………….QV
  10. 10. LIST OF FIGURES FIGURE PAGE Fig. 1.01: Chronostratigraphic chart of Upper Cretaceous strata, southern Wyoming……………………………………………………….…………… ..2 Fig. 1.02: Shaded relief map of Wyoming and Washakie Basin………………………………….………...……………….…………….3 Fig. 1.03: Topographic map of Spine 1 and Spine 2…….……………………………5 Fig. 1.04: Spine 1 with 9 channel-fill sandstones with detailed measured sections colored black; overlain on topographic contours (Generated in GOCAD™ v.2.0.6, 003)……………….……………………………………...5 Fig. 1.05: Cretaceous Western Interior Seaway .……………………….……………..6 Fig. 1.06: Paleogeographic Map for Lower Maastrichtian time…..….……………….7 Fig. 1.07: Major geologic features surrounding field area..……………..…………….9 Fig. 1.08: Lewis Shale Stratigraphic Column.………………………...….………….11 Fig. 1.09: Initial work characterizing the Dad Sandstone Member..……….………..14 Fig. 1.10: Example of detailed measured section produced for thesis research ……16 Fig. 1.11: Channel-fill boundary nomenclature……..…………………………...…..17 Fig. 2.01: Classic Bouma Sequence deposits………..……………………………….21 Fig. 2.02: “Knobby” texture interpreted as weathered vertical/subvertical dewatering pipes……………………………………………………………..22 Fig. 2.03: Dewatering pipes located at the top of Channel-fill Sandstone 1………...23 Fig. 2.04: Structureless Sandstone with geologically unrelated holes pockmocking surface of Channel-fill Sandstone 3….……..………………...24 Fig. 2.05: Temporal and Spatial relations in flow environments.....…………………25 Fig. 2.06: Walker’s (1978) classification of deepwater deposits….…………………26 Fig. 2.07: Lowe (1982) classification of High Density Turbidity Current (HDTC) and Low Density Turbidity Current (LDTC)………………………26 Fig. 2.08: Low-angle, high amplitude crossbedding from Channel 1……… …..…..27 Fig. 2.09: Planar laminae on outcrop exposure on Channel-fill Sandstone 6….…….29 Fig. 2.10: Planar laminae located in Channel-fill Sandstone 1……………… …...…29 Fig. 2.11: Climbing-Ripple Facies located in Channel-fill Sandstone 6………..…...31 Fig. 2.12: Climbing-ripple facies description……………………………………......32 Fig. 2.13: Shale/mudstone facies bounded by structureless sandstone facies……….33 Fig. 2.14: Stacked shale-clast conglomerates (A) interbedded with turbidites (B) on Channel-fill Sandstone 1……..……………………………35 Fig. 2.15: Faint imbrication of shale clasts occur in Channel-fill Sandstone 1……...35 Fig. 2.16: Debris Flow Rheology……………..………………………..……….……36 Fig. 2.17: Slump beds bounded in yellow from Channel-fill Sandstone 1 “Prong.”...37 Fig. 3.01: Enviroments of Deposition (E) 1-5 contained within a leveed-channel system ………......……………………..………………….39 Fig. 3.02: Situations leading to different flow behaviors…………..………….……..40 Fig. 3.03: Planform view of flow movement within a leveed-channel system……....41 Fig. 3.04: Flow movement within a sinuous channel-bend...…………..……………41 Fig. 3.05: 3D seismic horizon slice……………………..…………………………....44
  11. 11. Fig. 3.06: Sinuous submarine channel-fill deposit localities………………………...45 Fig. 3.07: Oblique depositional strike view of Channel-fill Sandstone 1…………....46 Fig. 3.08: Environments of deposition of Channel-fill Sandstone 4………………....48 Fig. 3.09: Proximal levee with convoluted bedding and climbing ripples associated with Channel-fill Sandstone 4……………………..……………..49 Fig. 3.10: Proximal levee with nice set of climbing ripples associated with Channel-fill Sandstone 4…………………………………….…………50 Fig. 3.11: Distal levee deposits from Channel-fill Sandstone 4…...…..…….………51 Fig. 4.01: 3D GOCAD™ model of Dad Sandstone Member, Lewis Shale; “Prong” region of Channel-fill Sandstone 1 circled in red; brown represents “Outcrop Plane,” while other colors represent “Outcrop Face” of the nine channel-fill sandstones..……..…….…55 Fig. 4.02: Planview basemap of nine stacked channel-fill sandstones...…….....……57 Fig. 4.03: Channel-fill Sandstone 1 location in Field Area...……………...…..…….58 Fig. 4.04: Locations of detailed measured sections on Channel-fill Sandstone 1 (1.01 – 1.22) ……...……………………………...59 Fig. 4.05: Plan view map of surface outcrop dimensions of Channel-fill Sandstone 1 …………………………………………………….60 Fig. 4.06: “Prong;” located in the eastern region of Channel-fill……………………62 Fig. 4.07: Shale-clast conglomerate facies found in northern-most portions of Channel-fill Sandstone 1 model……..…………………………..63 Fig. 4.08: Western-most flank of Channel-fill Sandstone 1 ends at MS# 1.0.1.… …64 Fig. 4.09: Boreholes (1-8) with locations of dip (green; 5-3-6) and strike (white; 1-2-3-4) cross-sections, located on eastern flank of Channel-Fill Sandstone 1 ………………………...………………...66 Fig. 4.10: Example of gamma-ray log from Borehole 1…...……………….………..67 Fig. 4.11: Dip cross-section of Boreholes 5-3-6 of Channel-Fill Sandstone 1…....…68 Fig. 4.12: Strike cross-section of Boreholes 1-2-3-4 of Channel-Fill Sandstone 1.…69 Fig. 4.13: Electro-Magnetic Induction and GPR (3-B to 3-B’) carried out on eastern flank of Channel-Fill Sandstone 1….……………...…70 Fig 4.14: Ground-Penetrating Radar facies located in the subsurface of Channel-Fill Sandstone 1 …………………………………….…….…….71 Fig. 4.15: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 2………..…….…71 Fig. 4.16: F7, shale-clast conglomerates and F3, crossbedded sandstone, located on Channel-fill Sandstone 2…..……………………………..………73 Fig. 4.17: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 3…………..…….74 Fig. 4.18: Diagnostic facies of Channel-fill Sandstone 3...………………….....……76 Fig. 4.19: Location of Channel-fill Sandstone 4 on Spine 1……………..……....…77 Fig. 4.20: Location and number of detailed measured sections(black) with outcrop dimensions (red) on Channel-fill Sandstone 4………….…..…78 Fig. 4.21: Diagnostic facies located on Channel-fill Sandstone 4.………………..…80 Fig. 4.22: Amalgamated channel-fills CFS 4a and CFS 4b, comprising Channel-fill Sandstone 4………...................................................82
  12. 12. Fig. 4.23: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 6……………….83 Fig. 4.24: Diagnostic facies of Channel-fill Sandstone 6.……………………….…85 Fig. 4.25: Amalgamated channel-fills CFS 6a and CFS 6b, comprising Channel-fill Sandstone 6…........................................................86 Fig. 4.26: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 7…………….…87 Fig. 4.27: Diagnostic facies of Channel-fill Sandstone 7…...……………………...89 Fig. 4.28: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 8…………….…90 Fig. 4.29: Diagnostic facies of Channel-fill Sandstone 8…...…………………...…92 Fig. 4.30: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 9…………….…94 Fig. 4.31: Diagnostic facies of Channel-fill Sandstone 9…………………………..96 Fig. 4.32: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 10….………..…97 Fig. 4.33: Diagnostic facies Channel-fill Sandstone 10...………………………….99 Fig. 5.01: First generation conceptual model representing channel-fill sandstones in 3D space (no channel sinuosity recorded)………………….101 Fig. 5.02: Second-generation diagram representing channel-fill sandstone sinuosity………………………………………………………..102
  13. 13. LIST OF APPENDICES APPENDIX (LOCATED ON ATTACHED CD) FOLDER A. Detailed Measured Sections in Digital Format………………………DMS B. Gamma-Logs of Eight Shallow Boreholes………………………….BHGL C. Copy of Thesis Text……………………………………….………THESIS D. GOCAD™ Data Files…………………………………….……....GOCAD SUBFOLDER D1. Raw Data…………………………………………………RD D2. Channel-Fill Sandstone 1……………………………….CFS01 D3. Channel-Fill Sandstone 2……………………………….CFS02 D4. Channel-Fill Sandstone 3……………………………….CFS03 D5. Channel-Fill Sandstone 4……………………………….CFS04 D6. Channel-Fill Sandstone 5……………………………….CFS05 D7. Channel-Fill Sandstone 6……………………………….CFS06 D8. Channel-Fill Sandstone 7……………………………….CFS07 D9. Channel-Fill Sandstone 8……………………………….CFS08 D10. Channel-Fill Sandstone 9……………………………….CFS09 D11. Channel-Fill Sandstone 10..…………………………….CFS10 D12. Digital Elevation Map……………………………………DEM D13. Quickview…………………………………………………QV
  14. 14. ABSTRACT Nine channel-fill sandstones comprise a 255ft thick stratigraphic succession in the deepwater Dad Sandstone Member, Lewis Shale, Wyoming. This succession has been characterized by measuring 121 closely-spaced outcrop stratigraphic sections, decimeter-scale GPS-tracing (Global Positioning System) of bed boundaries, drilling and gamma-logging of 8 shallow boreholes, ground-penetrating radar (GPR), and electro-magnetic induction (EMI) behind the outcrops. A 3D facies and architectural model was built using GOCAD TM . Each channel-fill sandstone is separated by thin-bedded, very fine sandstone/mudstone strata. Channel facies include structureless sandstone with fluid escape structures, structureless sandstone without fluid escape structures, rippled to climbing rippled sandstone, parallel to subparallel laminated sandstone, cross-bedded sandstone, shale-clast conglomerate, thin-bedded sandstone/mudstone, and slumped beds. In separate channel-fill sandstone, these facies can be complexly interbedded, but there is a tendency for shale-clast conglomerates to comprise the base and one side of a channel-fill, whereas cross-bedded sandstones comprise the opposite side. Massive/fluid escape structured sandstones typically occupy the top of these successions. Proximal to distal levee beds occur adjacent to some of the channel sandstones.
  15. 15. This distribution of facies, coupled with GPR data, suggests the sandstones filled sinuous channels. The shale-clast conglomerates are thought to be the product of slumping of adjacent levee walls from the steeper channel margin, and the cross- bedded sandstones are interpreted to be in-channel bar or dune forms. These channels probably fed sand into the deeper basin contemporaneously with levee formation; the channel-fill sandstones represent the product of later backfilling episodes. The slumped and erosive nature of some channel margins support this interpretation. This 3D outcrop characterization provides an excellent, scaled analog for leveed channel reservoirs. The complex vertical stratigraphy indicates individual channel sandstones can be mutually isolated reservoirs. The complex internal channel sandstone distribution indicates internal reservoir fluid flow will also be complex. A figure illustrating the relation of channel-fill sandstone sinuosity relative to one another in outcrop has also been created.
  16. 16. Chapter 1 INTRODUCTION Research Objectives This thesis research has two main objectives. The first objective is to document the 3-dimensional surface geometry of nine submarine slope channel sandstones in outcrops of the Lewis Shale through detailed measured sections and computer modeling via GOCAD™. The second objective is to correlate channel facies in 3-D space in order to better document reservoir-scale features of leveed- channel deposits and their lateral continuity and vertical connectivity. This research study also attempts to better understand the reservoir aspect of the petroleum system, i.e., the Dad Sandstone Member of the Upper Cretaceous Lewis Shale in southern Wyoming (Fig. 1.01).
  17. 17. Significance The study of submarine slope channel deposits is of great importance for many different reasons: (1) documenting the facies scale character of channel-fill sandstones, (2) reservoir characterization for better field development planning, (3) understanding the progressive evolution of sinuous submarine channels, and (4) determining the active mechanisms that force sinuosity. This thesis will not solve all of these problems, but will offer insight into better understanding and documenting these factors. It is also hoped that the resultant 3D model and its correlations will help to shed light on expected lateral continuity and vertical connectivity of reservoir scale facies in analog fields located within other deepwater sinuous channel systems, such as those found in the deepwater Gulf of Mexico and offshore West Africa. With the real-scale, outcrop-based 3-dimensional GOCAD™ model, fluid flow simulation can also be performed and compartmentalization within channel reservoirs can be modeled. The 3-D model will impact future work on reservoir characterization within other submarine slope channel complexes around the world. It is necessary to solve the unknowns in these types of problems by developing better depositional models from outcrop work, which will have direct bearing on new field development solutions in the future.
  18. 18. Fig. 1.01: Chronostratigraphic chart of Upper Cretaceous strata, southern Wyoming (Modified after Schell, 1973). Location of Study Area and Description of Outcrop The study area outcrops along the Sierra Madre Uplift in the eastern portion of the Washakie Basin, south-central Wyoming, Carbon County, within Sections 24 and 25 of T16N R92W (Fig. 1.02). From the town of Baggs, which is located 3 miles north of the Wyoming-Colorado border, the outcrop can be easily accessed by traveling 23.5 miles north on Hwy. 789 and approximately 4 miles east on a dirt road (to the west of the dirt road is a metal quanset hut). The study area is a resistant ridge referred to as Spine 1, which trends ENE-WSW. Spine 1 and another ridge to the southeast, called Spine 2, are separated from one another by a 0.5 mile wide modern floodplain (Fig, 1.03). Spine 2 trends E-W.
  19. 19. Fig. 1.02: Shaded relief map of Wyoming and Washakie Basin (Modified after Sterner, 1997). This region nicely exposes all 3 successive components of a complete Lowstand Systems Tract in one place (Witton, 2000); from the base of the outcrop, there are two sheet sandstones (basin floor fans) overlain by nine leveed channel-fill sandstones (the subject of this thesis) and then an interval of predominantly mudstone (prograding complex). Sinuous leveed-channel systems are formed in the deepwater regions of the ocean basins. Those described in this text are found on the slope. They are aggradational channels, i.e., the channel depression is a result of levee aggradation. Upon sea level rise, these vacant channel depressions become backfilled with sediment. The channel related sediments are referred to as channel-fill sandstones.
  20. 20. The processes involved with the deposition of channel-fill sandstones are thought to resemble those of subaerial fluvial systems. Many of the geological features recognized in subaerial fluvial systems are also recognized in submarine leveed-channel systems. These features include: 1) inner-side, point-bar style deposits, 2) outer-side cut-bank style erosion, 3) proximal levee regions, and 4) distal levee regions. Nine of these channel-fill sandstones have been identified as comprising Spine 1 and are the main focus of the research (Fig. 1.04). Originally, Witton (2000) identified 10 separate channel-fill sandstones, but due to more in-depth work using GPS and GOCAD™ v.2.0.6, sandstone boundaries mapped in 3D space indicate her Channel-fill Sandstone #5 is actually the western part of Channel-fill Sandstones #2 and #4. As the nomenclature was already deeply entrenched in most of her work, I have retained the original 1 – 10 designations. Channel-fill Sandstone #5 is no longer present.
  21. 21. Fig. 1.03: Topographic map of Spine 1 and Spine 2 (from Slatt, 2003). Fig. 1.04: Spine 1 with 9 channel-fill sandstones with detailed measured sections colored black; overlain on topographic contours (Generated in GOCAD™ v.2.0.6, 2003) Geologic Overview
  22. 22. This geologic overview has been modified from Pyles (2000) and Witton (2000). During the Cretaceous, the Western Interior portion of the United States was inundated with an elongate, relatively shallow epeiric seaway known as the Western Interior Seaway (Fig. 1.05). The Western Interior Seaway was bounded on the west by an active Cordilleran highland, through the modern day states of New Mexico, Colorado, Wyoming, and Montana, and to the east by the Canadian Shield (Molenaar and Rice, 1988). It stretched from the Gulf of Mexico to the Northern Boreal Sea (Krystinik, 1995). Fig. 1.05: Cretaceous Western Interior Seaway (Reproduced from Witton, 2000) This Cordilleran Highland system was the main source of terrigenous material to the Western Interior Cretaceous basin. Due to varying rates of sedimentation and crustal loading throughout the basin at the time, varying rates of subsidence occurred. The western portion of the Washakie Basin records thick sequences of marine and
  23. 23. non-marine clastic sediments interfingering with one another, thus representing marine transgressions and regressions that occurred during late Cretaceous time. Weimer (1960) indicated four major transgressions and regressions in the early Upper Cretaceous. This was supported by his work of tracing the main interfingerings of marine and non-marine clastic sediments, which represented the paleo-shorelines. Kauffman (1977) suggested ten major transgressions and regressions. Wiemer’s fourth transgressive-regressive cycle matched Kauffman’s ninth transgressive-regressive cycle. Fig. 1.06: Paleogeographic Map for Lower Maastrichtian time (After McGookey et al., 1972)
  24. 24. The final transgression and regression of the late Cretaceous was known as the Bearpaw transgressive-regressive cycle. It was during this last phase that the Lewis Shale was deposited in south-central Wyoming (Fig. 1.06). Deposition was largely controlled by sediment supply, intrabasin tectonics, and eustacy. Active deltas from the north-northeast and those projecting eastward from the Washakie basin (Hale, 1961) channeled sediments into deeper regions of the basin, particularly those similar to regions as the study area location. At the time of sediment deposition in the location of the study area, the water depth was calculated to be as deep as 1450 ft. based on the decompacted relief of individual clinoforms from Pyles (2000) regional cross section. In the lower Maastrichtian, west of the study area, was the Sevier Orogenic Belt, contained within the Cordilleran Highlands. This was a classic fold-thrust belt resulting when the Farallone oceanic plate subducted under the continental plate. Just east of the fold-thrust belt was the foreland basin, and most of Wyoming was contained within this basin at the time. During the Laramide Orogeny (Campanian to Paleocene) and its associated uplifts, the foreland basin was segmented into many local sub-basins, including the Washakie basin (McMillen and Winn, 1991). The Washakie basin is part of the Greater Green River Basin, which itself is a product of horizontal compression and fragmentation of the craton that occurred during the Laramide orogeny (Baars et al., 1988). Figure 1.07, provided by Baars et al. (1988), shows that the basin is bounded to the north by the Wamsutter Arch, to the east by the Sierra Madre Uplift, to the south by the Cherokee Arch, and to the west by the Rock Springs Uplift.
  25. 25. Fig. 1.07: Major geologic features surrounding field area (Baars et al., 1988). As relative sea-level began to rise, the Lewis Shale was deposited onto a muddy slope; as sea-level deepened considerably in middle to late Lewis time, sedimentation into the basin was mainly sourced from deltaic systems. During most of the early Maastrichtian, basin subsidence rates outlasted rates of sedimentation; this was due to either 1) subcrustal loading and subcrustal cooling caused by the low angle subduction of the oceanic crust of the Farallone plate, 2) thermal decay and
  26. 26. crustal contraction, 3) supracrustal loading, or 4) stress-induced subsidence as a result of tectonic loading (Cross and Pilger, 1978). Lithostratigraphy and Sequence Stratigraphy The Lewis Shale Formation can be broken into three informal members: the Lower Shale Member, the Dad Sandstone Member, and the Upper Shale Member (Fig. 1.08). The Lewis Shale was formally named by Cross and Spencer (1899) for exposed thick marine sequences (Gill et al., 1970). The type locality is found east of Mesa Verde National Park in Fort Lewis, southwestern Colorado. Originally the name was meant to designate rocks deposited during a regression and transgression of Campanian age in the San Juan Basin. Later, the name was mistakenly extended to include rocks of younger regressive- transgressive cycles not even recorded in the San Juan basin. This nomenclature is inherently wrong and is very confusing, but has become entrenched in the literature.
  27. 27. Fig. 1.08: Lewis Shale Stratigraphic Column (from Slatt, 2003). Both the underlying Almond Formation and the overlying Fox Hills Sandstone interfinger with the Lewis Shale on a regional scale (Gill et al., 1970). The Lower Shale Member comprises several hundred feet of black shale, while the Dad Sandstone Member is composed of interbedded shale and sandstone, ranging in thickness from 300 to 700 feet. The upper shale member is generally dark to olive gray, silty to sandy, nonresistant, and locally contains fossiliferous limestone or siltstone concretions (Gill et al., 1970). McMillen and Winn (1991) studied well log and seismic reflection data. They concluded that the Lower Shale Member was deposited as part of a 3rd order transgressive systems tract, while the Dad Sandstone Member and the Upper Shale Member were deposited as part of the ensuing 3rd order highstand systems tract. Pyles’ (2000) work, the most comprehensive to date, detailed the region within a fourth-order sequence stratigraphic framework. Pyles showed that although the
  28. 28. broader, more extensive third-order cycle existed, there in fact are many fourth-order cycles of aggradation and progradation within the 3rd order cycle. This work showed the valuable use and wealth of knowledge gained from a high-order sequence stratigraphic framework approach to an area. Lewis Shale Petroleum System Three major components to any petroleum system are: 1) source, 2) reservoir, and 3) trap/seal. The source is defined as strata of high organic carbon (C) content; a high total-organic-carbon (TOC) percentage is necessary for the generation of kerogen, the precursor to hydrocarbons. If hydrocarbons are generated, there must be a reservoir to house them. The reservoir can be any lithology with porosity and permeability, e.g., limestone, sandstone, and siltstone. In order for these hydrocarbons to be trapped, they must collect under some sort of trap or seal. Stratigraphically this component is usually an impermeable lithology that seals the hydrocarbons, or in structural traps, confines the hydrocarbons by a variety of means, e.g. fault seals. The Lewis Shale within south-central Wyoming is an unconventional gas reservoir with an estimated 24 TCF of gas in place, with 10.7 TCF recoverable (Doelger and Barlow, 1997). The Federal Energy Regulatory Commission designated the formation as a tight gas sand (Winn et al., 1985). As of 1997, only 6% of the total
  29. 29. reserves had been produced, thus leaving much room for new unconventional development concepts to exceed the production capabilities of reservoirs. There is a third-order condensed section near the top of the Lower Lewis Shale comprised of organic-rich shale known as the Asquith Marker; it ranges in thickness from thirty to eighty feet. It is generally believed by most who work this region, that the Asquith Marker is the most likely source-rock of the Lewis Shale Petroleum System (Slatt, Lewis Consortium field notes, 2001). The reservoir-prone lithology of the Lewis Shale petroleum system is the Dad Sandstone Member. The hydrocarbon seals for this petroleum system consist of bentonite clays and shales (Slatt, Lewis Consortium field notes, 2001). Previous Studies In 2000, work was completed in the field area by Elizabeth Witton (Witton, 2000). Her work characterized the field area by delineating the northernmost ridge, Spine 1, into its constituent parts: the lowermost two sheet sandstone bodies, the originally interpreted 10 separate channel sandstone bodies, and fourteen units within the overlying prograding complex (Fig. 1.09). Her work, which included outcrop interpretation and descriptions, was instrumental in setting up the basis for this research. Witton classified four separate lithofacies: A) continuous thick-bedded sandstones, B) discontinuous thick-bedded sandstones with rip-up clasts, C) thin- bedded sandstones, and D) thin-bedded, laminated mudstones and shale.
  30. 30. Her work also involved the recognition of facies in a borehole image log from a well drilled through the same stratigraphic interval about 8 miles away. This work was accomplished by first describing detailed measured sections of the outcrop to recognize and categorize the four different facies. The facies were then correlated to sedimentary features identified on the image log. More recently, Slatt et al. (2002) and Pyles and Slatt (2002) have provided evidence suggesting the channel sandstones are leveed-channel deposits similar to those that produce hydrocarbons in many deepwater settings (Abreau, 2002). Fig. 1.09: Initial work characterizing the Dad Sandstone Member (Witton, 2000)
  31. 31. Data Collection The succession of the nine stacked leveed channel-fill sandstones was characterized by 121 closely-spaced, detailed, measured sections, dm-scale GPS- tracing of bed boundaries, outcrop gamma-logging with a handheld scintillometer, drilling/gamma-logging of 8 shallow boreholes, ground-penetrating radar (GPR) behind outcrop, and Electro-Magnetic Induction (EMI). The GPR and EMI data were not used in this thesis as they form parts of other thesis research at University of Oklahoma. Lateral variations within each channel-fill sandstone were noted in the field and at these points detailed measured sections were emplaced and described. Enough detailed measured sections were completed so that all lateral variations within each channel-fill sandstone outcrop were recorded. The sections were measured using a Brunton Compass and a Jacob Staff. This method was carried out for each channel-fill sandstone, with measured sections ranging from as many as 26 for Channel-fill Sandstone 1 to as few as 6 for smaller channel-fill sandstones, such as Channel-fill Sandstone 9 (Fig. 1.10). These measured sections range in thickness from 2ft to 34ft. All 121 detailed measured sections are cataloged on the CD in Appendix A. Trimble ™ GPS units were used to delineate 3-D geometry of outcrops and to accurately locate detailed measured sections in 3-D space. GPS “Line Measurements” of bed boundaries were recorded in the field to best represent the 3- dimensional nature of the outcrop (Fig. 1.11). Walking the three lines: 1) Base, 2) Outside Top, and 3) Subsurface Top, provided two planes: 1) Outcrop Face and 2)
  32. 32. Outcrop Plane. “Outcrop Face” and “Outcrop Plane” were constructed in GOCAD™ allowing the raw data to portray the nine channel-fill sandstone bodies in their basic morphological structure as seen on Spine 1 (Fig. 1.04). Along with all of the channel- fill sandstone data, a topographic map was digitized and corrected for elevation. This was than input into GOCAD™ as a pseudo-DEM (Digital Elevation Map). Fig. 1.10: Example of detailed measured section produced for thesis research (located in CD as Appendix A).
  33. 33. Fig. 1.11: Channel-fill boundary nomenclature . A handheld gamma-ray scintillometer was used to record the natural gamma radiation of the channel-fill sandstones at all of the measured stratigraphic sections (Slatt et al., 1995). A complete log profile of each measured section within every channel sandstone was input into digital format for comparison with outcrop measured sections (Appendix A). Eight shallow boreholes were also drilled and gamma-logged for the lowermost Channel-fill Sandstone 1.
  34. 34. Data Analysis Channel-fill sandstones 1 through 10 were mapped with the dm-scale Trimble ™ GPS units and detailed measured sections were completed on all nine channel-fill sandstones. Enough of these detailed measured sections were obtained so that a very accurate representation of all channel-fill sandstones on Spine 1 and all of their internal facies characteristics were attained to build a 3D geologic model in GOCAD™. Each of the eight gamma-logged boreholes was input into digital format and was interpreted for its internal lithology based on the merits of its gamma-log pattern as well as cuttings from the borehole. The boreholes were then interpreted with both strike and dip direction cross-sections, thus gaining valuable insight on the character of subsurface facies within Channel 1 in a region where speculation was very high and outcrop exposure very poor. Additional work has been carried out by Dr. Roger Young and Ph.D. student Julie Staggs who use GPR (Ground-Penetrating Radar) techniques to document the shallow subsurface character of Channel Sandstone 1 (Young et al., in press), Dr. Alan Witten and M.S. student Ryan Stepler used Electro-Magnetic Induction (EMI) techniques to document the subsurface character of the sandstone and shale within the eastern-most flank of the lowermost channel-fill sandstone. Most of Dr. Young’s and Julie Stagg’s work on Spine 1 is focused primarily on Channel-fill Sandstone 1. Some of their work will be incorporated within later chapters of the thesis since their techniques have the means of tracking channel geometry in the subsurface.
  35. 35. 3-Dimensional GOCAD ™ Model A 3-Dimensional GOCAD ™ model has been designed to capture the channel-fill sandstone outcrop geometry and internal fill architecture with 3- Dimensional facies correlation through regions within the outcrop. The measured sections were the basis for this correlation. Bed boundaries, recorded by the Trimble ™ GPS units, provide the skeletal structure for the model of the channel-fill sandstones seen in outcrop. The detailed measured sections were input manually into the model, whereby facies correlations were accomplished. As aforementioned, Trimble™ GPS units were used to record X,Y,Z points in 3D space along outcrop boundaries. After daily field work sessions, these data were retrieved and stored in GPS Pathfinder™ on a laptop computer. Upon arrival back at the University of Oklahoma, the files were then transferred as text (*.txt) files to GOCAD™ with proper header format for computer recognition. The data was then capable of being manipulated and viewed in GOCAD™. Each field day’s work was saved as a separate file and each file contained its own cache of points in 3D space. These data had to be meticulously sorted and classified in the GOCAD™ lab to fit points to their proper channel boundary designations. After all points had been designated to their proper locations and all channel boundaries had been defined, channel facies were then input. The channel facies were then correlated to one another in 3D space. Additional description of the model and its correlations are found in additional chapters.
  36. 36. Chapter 2 LITHOFACIES DESCRIPTION Introduction Previous work performed by Witton (2000) and Slatt et al. (2000, 2001, and 2002) interpret Spine 1 to comprise a sinuous leveed-channel system. The steeper side of each channel-fill sandstone was interpreted to have abundant debris flow deposits (represented by facies F7, shale-clast conglomerate facies and the shallower side was interpreted to contain cross-bedded sandstone) (Witton, 2000). The resultant 3D GOCAD™ model was built to test this interpretation and those offered in the text.
  37. 37. Lithofacies Types Eight lithofacies were recognized in the field; they are: F1) sandstone with water-escape structures (some cross-bedded), F2) structureless sandstone (without water-escape structures), F3) cross-bedded sandstones (without water-escape structures), F4) parallel to subparallel laminated sandstone, F5) rippled or climbing- rippled sandstone, F6) shale or mudstone, F7) shale clast conglomerates, and F8) slumped beds. With the exception of the shale-clast conglomerates (F7) and slump beds (F8), the facies are fine-grained and well-sorted. Fig. 2.01: Classic Bouma Sequence deposits (Modified from Jordan et al., 1993)
  38. 38. Three of the eight facies constitute classic Bouma Sequence deposits (Fig. 2.01); they are: F4, F5, and F6. F4, parallel to subparallel laminae is categorized as Bouma division Tb. Rippled or climbing-rippled sandstone, F5, is interpreted as Bouma division Tc and is the product of traction of grains along the sea bed during lower flow regime conditions (Weimer and Slatt, in press). The final facies categorized within the Bouma Sequence is F6, a shale or mudstone, denoted by Te. Lithofacies 1 (F1): Structureless to Cross-Bedded Sandstone with Water-Escape Structures Physical Description The structureless to cross-bedded sandstone with water-escape structures consists of yellowish-tan, fine-grained, well-sorted sandstone. It is the second most abundant facies. This facies exhibits primary low-angle cross-bedding in some exposures, and in all of the exposures, secondary water-escape “knobs” (Fig. 2.02). Water escape structures are common in the upper portions of the outcrop exposures, particularly in Channel-fill Sandstone 1 (Fig. 2.02 and 2.03). This position within the channel-fill facies sequence indicates that these sands may have been deposited as liquefied/fluidized flows.
  39. 39. Fig. 2.02: “Knobby” texture interpreted as weathered vertical/subvertical dewatering pipes. Fig. 2.03: Dewatering pipes located at the top of Channel Sandstone 1.
  40. 40. Hydrodynamic Interpretation Sandstones with water-escape structures, such as vertical pipes, are formed by hindered settling of sediments in a liquefied and/or fluidized flow (Weimer and Slatt, in press). As the sediment in this facies is finally deposited, water migrates toward the top of the flow, leaving a cavity in its pathway into which the surrounding sediments collapse (Fig. 2.06). Because grain size varies within the deposit, differential cementation occurs, giving rise to surficial differential weathering and the development of the more resistant “knobs” (Slatt, personal communication, 2003). Lithofacies 2 (F2): Structureless Sandstones without Water-Escape Structures Physical Description Structureless sandstone without water-escape structures are the most abundant facies within the outcrops (Fig. 2.04). It is a yellowish-tan sandstone. This sandstone does not exhibit any visible primary or secondary sedimentary structures. Thickness of this facies can reach significant heights (up to 80% of the channel-fill stratigraphic column, in some cases up to 24ft) and may represent many separate flow events.
  41. 41. Fig. 2.04: Structureless Sandstone with geologically unrelated holes pockmocking surface of Channel-fill Sandstone 3. Hydrodynamic Interpretation Structureless sandstones are deposited in only one spatial and temporal flow condition, steady depletive (Kneller, 1995; Fig. 2.05). Both Walker (Fig. 2.06; 1978) and Lowe (Fig. 2.07; 1982) differentiated structureless sandstone from Bouma division Ta. This was based on the interpretation that these sandstones tended to exhibit: 1) water-escape structures, 2) fewer associated shale interbeds, 3) an increase in erosionally-based and irregularly bedded sandstone, and 4) sandstone beds that are thicker than associated beds (Weimer and Slatt, in press).
  42. 42. Fig. 2.05: Temporal and Spatial relations in flow environments (Modified from Kneller, 1995) Fig. 2.06: Walker’s (1978) classification of deepwater deposits.
  43. 43. Fig. 2.07: Lowe (1982) classification of High Density Turbidity Current (HDTC) and Low Density Turbidity Current (LDTC). Lithofacies 3 (F3): Cross-Bedded Sandstones without Water-Escape Structures Physical Description This yellowish-tan sandstone is the third most abundant facies. These deposits tend to manifest low-angle, high amplitude cross-bedding features (Fig 2.08). Many times it is difficult to reveal the low-angle cross-bedding in the field because of the position of the sun.
  44. 44. Fig. 2.08: Low-angle, high amplitude crossbedding from Channel 1 (from Slatt, 2003). Hydrodynamic Interpretation Primary cross-bedding is formed by sediments that move along the seafloor as tractive bedload. Traction can be defined as “a mode of sediment transport in which the particles are swept along (on, near, or immediately above) and parallel to a bottom surface by rolling, sliding, dragging, pushing, or saltation” (Jackson, 1997). Cross- bedding is a lower flow regime feature. The low-angle nature of the cross-bedding indicates that these features were most likely in-channel bar or dune forms (Slatt,
  45. 45. personal communication, 2003). The in-channel barforms are interpreted to lie on the pointbar-equivalent side of the channel-fill system or upon the channel floor. Lithofacies 4 (F4): Parallel to Subparallel Laminae Physical Description Parallel to subparallel laminae, L4, are found in yellowish-tan, fine-grained, well-sorted sandstone (Fig. 2.09 and 2.10). The deposit was not found in abundance in the field. This facies is characterized by parallel to subparallel bedding planes, or laminations. It occurs within many of the stratigraphically higher channel-fill sandstone bodies, i.e., Channels 6 – 10.
  46. 46. Fig. 2.09: Planar laminae on outcrop exposure on Channel-fill Sandstone 6. Fig. 2.10: Planar laminae located in Channel-fill Sandstone 1.
  47. 47. Hydrodynamic Interpretation Planar bedding occurs in both the lower and upper flow regime. It exhibits parallel bedding. For lower flow regime deposits, the flow velocity is very low. This is a very simple deposit, exhibiting only planar bedding in plan view and horizontal laminae in side view. Planar bedding, deposited in upper flow regime conditions, exhibits current lineations due to the high flow velocity. Current lineations form as concentrations of heavy minerals align themselves in the direction of flow. In plan view, the current lineations are visisble, but only the laminae can be seen from the side view. Figure 2.10 exhibits Bouma division Tb-Tc, categorizing Tb within the lower flow regime; all F4 deposits in the field are interpreted to be lower flow regime planar bedding. Lithofacies 5 (F5): Rippled or Climbing-Ripple Sandstone Physical Description Facies F5, exhibits ripples or climbing-ripples in a yellowish-tan sandstone. This deposit is not abundant within the outcrop exposures, however, nearly all nine channel-fill sandstone bodies contain this facies. Channel-fill Sandstone 6 contains a 2’2” thick set of climbing-ripples (Fig. 2.11). The climbing-rippled sandstone
  48. 48. includes those with lee slope deposition, as well as those with lee and stoss slope deposition (Fig. 2.12). Fig. 2.11: Climbing-Ripple Facies located in Channel-fill Sandstone 6. Hydrodynamic Interpretation Rippled sandstone and climbing-rippled sandstone are categorized in the uppermost division of lower flow regime deposits. Standard ripples are formed by particles as they move by traction along the seafloor. Slowly they stack upon one another until the angle of repose is met (28º - 30º), and at this point the sedimentary particle is transported along the face of the lee slope, where either it remains or continues to move. The climbing-rippled sandstone has a sedimentary input that exceeds its sedimentary output, particularly those with lee and stoss slope deposition.
  49. 49. These deposits are diagnostic of a sediment-choked system and are interpreted to occur at either the inner channel-levee margin of the channel-fill environment or in proximal levee environments (Browne and Slatt, 2002). Fig. 2.12: Climbing-ripple facies description. Lithofacies 6 (F6): Shale or Mudstone Physical Description The shale and/or mudstone located within the channel-fill sandstones tend to exhibit erosive tops (Fig. 2.13). This facies is colored light to dark gray and is composed of clay-sized particles. F6 is mostly absent from many of the channel-fill sandstone bodies, but is quite abundant within Channel-fill Sandstone 1.
  50. 50. Fig. 2.13: Shale/mudstone facies bounded by structureless sandstone facies. Hydrodynamic Interpretation Facies F6, shale and/or mudstone, is interpreted to be deposited from either the tail-end of a turbidity current flow or as pelagic rain. The major process by which this facies is deposited in the channel-fill environment is interpreted to be the tail-end of a turbidity current flow. Channel-fill lithologies are comprised mainly of sandstone facies. Since very few F6 facies are exhibited in the field, it is interpreted that any shale and/or mudstone located in the channel-fill environment must be
  51. 51. deposited as the tail-end of a turbidity current as opposed to pelagic rain (not quiescent enough in this environment for this type of deposition to occur). Lithofacies 7 (F7): Shale-Clast Conglomerates Physical Description The shale-clast conglomerates of the channel-fill sandstones in Spine 1, F7 (Fig. 2.14 and 2.15), are light to dark gray in color. The shale clasts are light gray and the matrix is dark gray or yellowish-tan. The internal architecture exhibited within the shale clasts themselves show a thinly laminated facies. Additionally, the shale clasts exhibit imbrication within this faices. L7 is quite abundant and is located in almost all of the channel-fill sandstones. F7 tends to occur mainly as small, thin deposits (usually 2-4in thick).
  52. 52. Fig. 2.14: Stacked shale-clast conglomerates (A) interbedded with turbidites (B) on Channel-fill Sandstone 1. Fig. 2.15: Faint imbrication of shale clasts occur in Channel-fill Sandstone 1.
  53. 53. Hydrodynamic Interpretation The shale-clast conglomerates are interpreted to have originated as debris flow deposits. These flows contain a high matrix strength and therefore move in a plastic, laminar, cohesive state (Weimer and Slatt, in press). As the debris flow is transported, the flow region is delineated into two components, the Shear Flow Region and the Plug Flow Region (Fig. 2.16). The Shear Flow Region, located at the basal part of the flow, generates shear stresses that overcome the matrix shear within the flow (Weimer and Slatt, in press). It is possible that shale clasts found in the lower regions of debris flows (i.e., in the Shear Flow Region) could have been imbricated by these shear stresses (Fig 2.15). The Plug Flow Region contains the major bulk-volume of sediments in transport. It tends to remain in the same position during its entire transit, except at the flow/seawater contact where the sediments may exhibit a decrease in velocity due to frictional forces (Weimer and Slatt, in press). In Spine 1 deposits, shale clast conglomerates are interpreted to comprise the failed, slumped margins of levees. Fig. 2.16: Debris Flow Rheology (from Weimer and Slatt, in press)
  54. 54. Lithofacies 8 (F8): Slump Beds Physical Description Slump beds (Fig. 2.17) are found only in a few of the channel-fill sandstones, but are a very diagnostic feature, helping to orient the channel-fill sandstone into its environment within the channel system. They tend to range in thickness from 2ft to 7ft. F8 exhibits many different characteristics within their deposits, including the parallel interbedding of sandstone and siltstone and a lower sand/shale ratio than other lithofacies. They range in color from yellowish-tan to light and dark grey. Fig. 2.17: Slump beds bounded in yellow from Channel-fill Sandstone 1 “Prong.”
  55. 55. Hydrodynamic Interpretation Slump beds are interpreted to have formed as a coherent unit of the failed inner-channel margin wall within a leveed-channel system. They represent the initial flow event of any sedimentary gravity flow and exhibit high matrix strength. Due to their high sediment concentration they move in a plastic flow state (Weimer and Slatt, in press). This facies is closely related to the hydrodynamic interpretation of F7, but it differs from it mainly by the fact that the deposit exhibits a coherent unit of different beds while F7 is one bed. The interpreted slump beds contain what was once the channel margin, comprised largely of proximal-levee facies deposits. All of this evidence points to slump beds having been formed on the steep side of the channel margin, or the cutbank-equivalent side of a channel-fill system.
  56. 56. Chapter 3 ENVIRONMENT OF DEPOSITION AND FACIES RELATIONSHIPS Introduction The purpose of this chapter is to categorize the facies into their environment of deposition within a leveed-channel system. Descriptions of lithologic stacking patterns found to occur in the field will also be included. There are five major environments of deposition related to the leveed-channel system (Fig. 3.01): E1) non-sinuous leveed-channel system, E2) outer-side of sinuous channel bend, E3) inner-side of sinuous channel bend, E4) proximal levee, and E5) distal levee.
  57. 57. Fig. 3.01: Enviroments of Deposition (E) 1-5 contained within a leveed-channel system. Interpretations Associated with each environment of deposition is a particular lithologic stacking pattern which is diagnostic in determining its associated environment within the channel-fill system. Kneller’s 1995 (Fig 2.05 and 3.02) diagrams were used to develop the guidelines in interpreting these environments. Figure 3.03 and 3.04 were also drawn to help support and guide the interpretations.
  58. 58. Fig. 3.02: Situations leading to different flow behaviors (Modified from Kneller, 1995). Kneller’s (1995) (Fig. 2.05) diagrams relate the deposited facies to Bouma divisions Ta-Te. Although these are noted in the chapter, Bouma division Ta is classified as a separate deposit. This interpretation rests primarily on the fact that both Walker (Fig. 2.06; 1978) and Lowe (Fig. 2.07; 1982) recognize the presence of water-escape structures within their normally-graded to massive deposits (other than the water-escape structures, most sandstones in F1 are structureless). Witton (2000) interpreted the outer-side of a channel margin (E2) to contain numerous debris flow deposits (F7). This concept was also very instrumental in helping to guide the interpretations introduced in this chapter. Fig. 3.03: Planform view of flow movement within a leveed-channel system.
  59. 59. Fig. 3.04: Flow movement within a sinuous channel-bend. The following text in this chapter hypothesizes on the expected facies to be found at these five environments of deposition (E1 – E5). E1: Non-sinuous (Straight) leveed-channel environment Interpretation: E1 is interpreted as the straight, U-shaped portion of a sinuous channel system. Figures 3.03 and 3.04 show that the flow out of a channel-bend, into the straight portions of the system is interpreted to be spatially depletive (downcurrent decrease in velocity; Fig. 3.02). Figure 2.05 shows there are three temporal considerations to factor in with the spatial descriptions of the flows, they are: waxing (increasing in velocity over time), waning (decreasing in velocity over time), and
  60. 60. steady (uniform velocity over time) (Kneller, 1995). Since the flow can do any three of these when exiting the channel-bend, all deposits related to these three spatial- temporal flows could be expected to be found in this non-sinuous environment. Facies Relationship: If the flow was to increase in velocity while exiting the channel-bend, the expected spatial-temporal relation would be “waxing depletive.” A waxing depletive deposit yields an inverted classic Bouma Sequence (Kneller, 1995). The expected deposit contains Bouma divisions Te/Td, which underlie Tc, Tb, and Ta, respectively. Relating these Bouma divisions to aforementioned facies would yield the expected lithologic stacking pattern of (base to top): F6, F5, and F4. If there is a range in grain size, this stacking pattern will exhibit reverse grading. If the flow out of the channel-bend was to remain steady, the expected lithologic stacking pattern would yield a continuous deposit of Bouma division Ta or Tb (F4), and further downstream, Tc (F5). The last scenario is the least diagnostic of all, waning depletive. In fact, all “waning” flows show more or less the same deposit: a classic, normally graded Bouma Sequence (top to bottom): Ta, Tb (F4), Tc (F5), Td, and Te (F6).
  61. 61. E2: Outer-side of sinuous channel bend Interpretation: E2 is the outer-side of a sinuous bend in a channel-fill system. Figures 3.03 and 3.04 show that the expected spatial flow in this environment is accumulative (downcurrent increase in flow velocity), because the movement of the flow is similar to that of water traveling down a waterslide. Since “waxing-accumulative” and “steady-accumulative” both yield erosion within the system, the only setting that deposition can occur is “waning-accumulative.” Facies Relationship: In a “waning accumulative” flow, the classic Bouma Sequence is expected to be deoposited. Thus the lithologic stacking pattern to be recognized in the field contains the facies (from base to top): F4, F5, and F6. Ideally, this deposit would also be normally graded, helping to define the boundary between flow events. Frequently bounding the facies in the lithologic stacking pattern of E2, are shale-clast conglomerates, or F7. The process by which this facies is deposited is the slumping of adjacent levee walls into the channel-fill axis (Fig. 3.05 and 3.06). This is the most diagnostic facies in the set.
  62. 62. Fig. 3.05: 3D seismic horizon slice (photo courtesy of H. Posamentier). Fig. 3.06: Sinuous submarine channel-fill deposit localities (modified from Peakall et al., 2000).
  63. 63. E3: Inner-side of sinuous channel-bend Interpretation: This interpretation is based mainly on field observations and personal communication with Slatt (2003). Witton (2000) initially interpreted the outer-side of a sinuous channel-bend to contain debris-flow deposits (shale-clast conglomerates) concentrated at one end (Fig. 2.14 and 2.15). Field observations show that directly opposite these deposits are large sandstones exhibiting cross-bedding features (Fig. 3.07). These large structures of low-angle, high-amplitude, cross-bedding (Fig. 2.08) are interpreted to occur as in-channel bar or dune forms (Slatt, 2003). Fig. 3.07: Oblique depositional strike view of Channel-fill Sandstone 1 (from Pyles and Slatt, 2002).
  64. 64. Additionally, Abreau et al (2002) noted that these features dominate the fill of many submarine channels and exhibit themselves as shingled seismic reflections that dip toward the channel axis. These features are interpreted to form as a result of the lateral and downdip migration of the channel, with deposition of lateral accretion beds in the inner side of the channel and erosion at the outer side of the channel (Abreau et al, 2002; Beaubouef, 2002). Facies Relationship: The expected lithologic stacking pattern for E3 is simply a continuous deposit of lateral accretion surfaces with contained cross-bedded sandstone (F3). E4: Proximal levee Interpretation: E4, interpreted as the proximal levee region within the leveed-channel system, is based on two extensive detailed measured sections taken on Channel-fill Sandstone 4 and 8 (Figs. 3. 08 - 3.10). Proximal levees are known to contain silt to very fine grained sand because the sediments deposited in this environment originate from overflows from the channel. These overflows tend to be finer grained than the rest of the flow confined within the channel because larger grains are located near the base of these flows. Significantly, dip magnitudes and orientations also vary because the flows trend in different directions as they flow over the levee margin (Browne and Slatt, 2002). Other facies exhibited in E4 are parallel/subparallel (F4) to
  65. 65. contorted/convoluted bedding planes, climbing ripples (F5, due to high sediment input), reverse grading within associated splay deposits, and generally a higher sand/shale ratio than distal levee facies. Fig. 3.08: Environments of deposition of Channel-fill Sandstone 4 (from Slatt, 2003).
  66. 66. Fig. 3.09: Proximal levee with convoluted bedding and climbing ripples associated with Channel- fill Sandstone 4
  67. 67. Fig. 3.10: Proximal levee with 2-inch set of climbing ripples associated with Channel-fill Sandstone 4 Facies Relationship: All of the facies described above (convoluted bedding, climbing ripples, etc.) are contained within the two detailed measured sections recorded. Along with matching these facies, inversely-graded deposits also occur in the measured sections.
  68. 68. Another match is the sand/shale ratio, which is much higher here than in the interpreted distal levee region. E5: Distal levee Interpretation: Distal levee deposits contain a lower sand/shale ratio than proximal levee deposits (Brown and Slatt, 2002). This is expected as the overbank flows typically are depleted of energy as they reach the distal, lower gradient portions of the levee region, depositing the finest material in the flow. The dominant facies within E5 is continuous parallel bedding, making them more laterally extensive than the proximal levee facies (Fig 3.11). Fig. 3.11: Distal levee deposits from Channel-fill Sandstone 4.
  69. 69. Facies Relationship: E5 contains these two diagnostic facies, where they appear on a detailed measured section of distal-levee deposits belonging to Channel-fill Sandstone 4 (Appendix A). Comparison of the above interpretation with this measured section shows that the grain-size of the deposits are silt and clay sized particles, typically interbedded. Immediately apparent is the low sand/shale ratio. Parallel bedding is the dominant facies exhibited on the measured section (Appendix A).
  70. 70. Chapter 4 3D MODEL DESCRIPTION AND INTERPRETATION Introduction The 3D model that all outcrop measurements were based upon was built in GOCAD™ v.2.0.6 (4th Quarter, 2002). This is a robust package of software that allowed the raw data collected from the Trimble™ GPS units to be viewed and manipulated in 3D space. The software was instrumental in developing the resultant 3D model (see CD) and helped guide many new interpretations of the channel-fill sandstone boundaries. Data was first recorded in the field with Trimble™ GPS units which recorded the position of the interpreter as he walked actual outcrop boundaries. These data were then transferred to a PC-based laptop with Trimble™ Pathfinder GPS Software. This software stored the data as *.ssf files which were then exported as *.dbf files into Microsoft™ Excel. After the X,Y,Z points were isolated into their separate columns, an appropriately designed header format was input so the file could be recognized in GOCAD™ v.2.0.6. At this point, the files were viewed in 3D space
  71. 71. and appropriate lines that represented channel boundaries (Fig. 1.11) and detailed measured section localities could be drawn. After all channel-fill sandstone boundaries and detailed measured section localities were drawn, facies boundaries were delineated from the measured sections and emplaced on the measured section lines within GOCAD™. After this task had been carried out for all nine channel-fill sandstone bodies, correlations then commenced along the Outcrop Face (Fig. 1.11) of each. The resultant correlations resemble fence diagrams that float in 3D space relative to one another. Another benefit of GOCAD™ is the ability to measure the distance between two points and also to find the precise X,Y,Z locality of any point, whether it be a channel boundary, facies boundary, or any other point of interest. Additionally, the data may be rotated, tilted, slid, or zoomed-in and out. After the model was completed, the locations of particular lithologic stacking patterns were recognized while examining the model. Some of these stacking patterns are diagnostic in interpreting the environment within a leveed-channel system as stated in Chapter 3. When these stacking patterns were recognized in the model, the related environment (E1 – E5) was assigned to that locality of the Channel-Fill Sandstone. These observations have led to a general interpretation of each Channel-Fill Sandstone body and its classification within the environments of deposition of a leveed-channel system. The above-ground vertical and lateral geometry of each Channel-Fill Sandstone was also recorded. Each facies within the model was represented by a unique color. The classification is as follows: (F1) Sandstone with water-escape structures: blue, (F2)
  72. 72. Structureless sandstone: yellow, (F3) Cross-bedded sandstone: magenta, (F4) Parallel to sub-parallel laminated sandstone: dark-gray, (F5) Rippled or climbing-rippled sandstone: dark-green, (F6) Shale: blue-violet, (F7) Shale-clast conglomerate: red, and (F8) Slumped bed: white. Fig. 4.01: 3D GOCAD™ model of Dad Sandstone Member, Lewis Shale; “Prong” region of Channel-fill Sandstone 1 circled in red; brown represents “Outcrop Plane,” while other colors represent “Outcrop Face” of the nine channel-fill sandstones.
  73. 73. Viewing the Data Representing 3D images in 2D space has proven to be a difficult task. The following guidelines are recommended to the reader to help view the pictures offered in this chapter. Each picture has a figure in the lower left corner (Fig. 4.01) denoting three axes: X (east), Y (north), and Z (altitude). Each axis has both magnitude and direction, i.e. it not only points in these designated directions, but the inverse of the length of the arrow also represents the amount of tilt in that direction. This figure is essential to orient oneself in the 3D space, as viewed in the GOCAD™ model. Referring back to Figure 1.11, two planes are defined here: 1) the Outcrop Face and 2) the Outcrop Plane. The “Outcrop Plane” is colored brown in all figures (Fig. 4.01). The “Outcrop Plane” does not designate any facies described, it is simply the top plane of each individual channel-fill sandstone. It is handy to keep a list of the color designations for the facies, as they appear in every figure and are denoted by their classification (F1 – F8) and are seldom re- described. Topographic contour intervals are also labeled on every figure where they appear; these also help to orient the reader. In some of the figures (Fig. 4.16 and 4.17) there is a black region seen; this region is simply the extent of the Digital Elevation Map (DEM) where there is no elevation data; i.e. a no-data zone. Many of the figures are encapsulated within others to help orient the reader when viewing certain pictures. Most pictures can be related back to the planview
  74. 74. basemap, pointing north, which contains all nine channel-fill sandstones (Fig. 4.02). Note that the arrow is oriented differently in different figures due to the 3 dimensional character of the outcrop faces.
  75. 75. Fig. 4.02: Planview basemap of nine stacked channel-fill sandstones. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  76. 76. Channel-Fill Sandstone 1 Fig. 4.03: Channel-fill Sandstone 1 location in Field Area. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  77. 77. Fig. 4.04: Locations of detailed measured sections on Channel-fill Sandstone 1 (1.01 – 1.22). F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  78. 78. Vertical and Lateral Geometry: The detailed measured sections of Channel-fill Sandstone 1 can be located on Figure 4.03 and 4.04. The lateral geometry of Channel-fill Sandstone 1 can be characterized by measuring the distance along the Outcrop Face in its two major trends: N-S and E-W. All detailed measured sections located on Channel-fill Sandstone 1 are located on Figure 4.03. A N-S trending face outcrops along the narrow side of Spine 1, on its eastern side. This measurement is 62ft (Fig. 4.05). Any E-W trending face outcrops along the wider edge of the spine in its northern region. This associated measurement for Channel-fill Sandstone 1 is over 600ft. (Fig 4.05) for this trend. The thickness of this channel-fill ranges from 8ft to 34ft. Fig. 4.05: Plan view map of surface outcrop dimensions of Channel-fill Sandstone 1. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  79. 79. Lithologic Stacking Patterns and Locations: In the northern region of Channel-fill Sandstone 1 are numerous shale-clast conglomerates dipping southward (Fig. 4.06 and 4.07). Also located in the northern region, contained within the “prong” area is a large slumped bed (Fig. 4.06). Channel-fill Sandstone 1 is capped primarily by F1 sandstone with water-escape structures. The crossbedded sandstone facies (F3; magenta) is shown to occur in the southern portions of the channel-fill region. Volumetrically, in most portions of the channel, structureless sandstone (F2) dominates the channel-fill. In the westernmost flank of the channel-fill, sandstones show tapering out to the last measured section, 1.0.1 (Fig. 4.08). At this location, stacking patterns involve significant amounts of shale and/or mudstone (F6).
  80. 80. Fig. 4.06: “Prong;” located in the eastern region of Channel-fill Sandstone 1. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  81. 81. Fig. 4.07: Shale-clast conglomerate facies found in northern-most portions of Channel-fill Sandstone 1 model. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue- violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  82. 82. Fig. 4.08: Western-most flank of Channel-fill Sandstone 1 ends at MS# 1.0.1. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  83. 83. Interpretation: The large number of F7 (shale-clast conglomerate) beds in the northern region of the channel-fill interbedded with slumped beds (F8) indicate deposition on the outer side of a sinuous channel bend (E2; Fig. 3.06). The beds have slumped from the channel margin/levee walls into the channel. F3, lateral accretion surfaces (crossbedded sandstone), are located on the southern portion of the channel-fill environment. This facies is once again very diagnostic of its environment of deposition, in this case, it is interpreted to be located on the inner-side of a sinuous channel bend, E3 (Fig. 3.08). Coupled together, these two interpretations suggest the northern portion was the steeper, cut-bank equivalent side to the channel-fill, while the southern portion represented the tapering, feathered edge of the point-bar equivalent side of the channel-fill. Subsurface: Channel-Fill Sandstone 1 was uniquely separated from the other eight channel-fill sandstone bodies because it was the only one to include the drilling and gamma-logging of eight shallow boreholes. The boreholes were drilled along the eastern flank of the channel-fill sandstone (Figs. 4.09 – 4.12), Electro-magnetic induction (EMI; Fig. 4.13) and ground-penetrating radar (GPR; Fig. 4.14) images of the area are also shown. The first major process carried out was the drilling of the eight shallow boreholes (Borehole 1 – Borehole 8). While these shallow boreholes were being
  84. 84. drilled, the lithologic cuttings expelled from the borehole were recorded, measured, and bagged for later analysis. After each borehole was drilled, a gamma-ray sonde was lowered into the borehole and retrieved at a steady rate, recording the natural gamma-radiation emitting from the lithologies in the subsurface. These measurements were stored onto a PC-based field laptop computer. The data was then manipulated in Microsoft™ Excel in order to create gamma-ray (cps) vs. depth (ft) plots (Fig. 4.10). . Fig 4.09: Boreholes (1-8) with locations of dip (green; 5-3-6) and strike (white; 1-2-3-4) cross- sections, located on eastern flank of Channel-Fill Sandstone 1.
  85. 85. Fig. 4.10: Example of gamma-ray log from Borehole 1 These plots were then positioned accordingly to their proper X, Y, Z location and cross sections were drawn in both the dip (Fig 4.11) and strike (Fig. 4.12) sections of the channel-fill sandstone body. Three main facies were recognized in the subsurface, they are: 1) sandstone (interpreted as channel-fill sandstone), 2) shale- clast conglomerates (debris-flow deposits), and 3) shale (interpreted to be deposited outside of the channel-fill environment). The cross section interpretations were
  86. 86. guided by field notes and cutting samples from each borehole. The field notes were instrumental in the interpretations because depth regions were recorded as “well” to “poorly lithified.” These descriptions helped to guide the interpretation because the sandstone in the subsurface showed it to be “poorly lithified,” while the shale was found to be “well lithified” (shale-clast conglomerates fall between these two since they comprise both lithologies). Fig. 4.11: Dip cross-section of Boreholes 5-3-6 of Channel-Fill Sandstone 1.
  87. 87. Fig. 4.12: Strike cross-section of Boreholes 1-2-3-4 of Channel-Fill Sandstone 1. Electro-Magnetic Induction techniques were carried out by Ryan Stepler and Dr. Alan Witten (2003; Fig. 4.13). It involved a twenty-frequency (1 kHz to 20 kHz) EMI dataset collected over a 54m by 70 m area grid and inverted for resistivity and depth. Through Stepler’s geophysical work, EMI data correlates nicely with the cross-section interpretations from the eight shallow boreholes (Fig 4.11 and Fig. 4.12).
  88. 88. Fig. 4.13: Electro-Magnetic Induction and GPR (3-B to 3-B’) carried out on eastern flank of Channel-Fill Sandstone 1 (Blue arrow represents interpreted base of Channel-fill Sandstone 1;Stepler, 2003). Ground-Penetrating Radar techniques were carried out by Dr. Roger Young and Julie Staggs (2003). GPR involves high frequency radar waves penetrating the subsurface. At bed boundaries these waves are reflected back upward where they are recorded at a receiver on the surface. Their work identified different radar facies, each denoting a portion of a radar profile characterizing a particular stratigraphic facies and associated depositional features (Fig. 4.14; Young et al., 2003).
  89. 89. Fig 4.14: Ground-Penetrating Radar facies located in the subsurface of Channel-Fill Sandstone 1 (Young et al., in press). Channel-Fill Sandstone 2 Fig. 4.15: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 2.
  90. 90. Vertical and Lateral Geometry: There are two major trends to the Outcrop Face of Channel-fill Sandstone 2, N-S and E-W (Fig. 4.15). The N-S trend is recorded as 415ft. in length, while the E- W trend is recorded as 360ft. in length. The detailed measured sections on Channel- fill Sandstone 2 are found in Figure 4.15. The thickness of this channel-fill varies from 2ft. to 10ft. Lithologic Stacking Patterns and Locations: In the northern regions of the interpreted channel-fill environment are numerous shale-clast conglomerates (F7; Fig. 4.16). To the base of these deposits lies a shale/mudstone facies (F6). Capping these two units in the northern region and continuing south to the crossbedded facies, F3, is F2, structureless sandstone. The southern region is dominated by lateral accretion surfaces represented by low-angle crossbeds (Fig. 4.16).
  91. 91. Fig. 4.16: F7, shale-clast conglomerates and F3, crossbedded sandstone, located on Channel-fill Sandstone 2. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue- violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  92. 92. Interpretation: The northern region of the channel-fill environment is dominated by facies F7, shale-clast conglomerates (Fig. 4.16). This is a diagnostic facies of the outer-side of a sinuous channel bend. The southernmost region within the model shows a laterally continuous deposit of crossbedded sandstone. Once again, this is a diagnostic facies representing the inner-side of a sinuous channel bend. The two previous interpretations hold that the northern region of Channel-fill Sandstone 2 is the cut-bank equivalent side of the channel-fill system, while the southern region is interpreted as the point-bar equivalent side of the channel. Channel-Fill Sandstone 3 Fig. 4.17: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 3.
  93. 93. Vertical and Lateral Geometry: Channel-fill Sandstone 3 shows similar N-S and E-W trends as the previous channels. The detailed measured sections on Channel-fill Sandstone 3 can be found on Figure 4.17. The E-W trend, usually the longer of the two, is only 80ft. The N-S trend has a length of 335ft (Fig. 4.17). Thicknesses of this channel-fill range from 4ft. to 8ft. Lithologic Stacking Patterns and Locations: Within Channel-fill Sandstone 3, the following facies are present (Fig. 4.19): F6 (shale/mudstone), F1 (sandstone with water-escape structures), F2 (structureless sandstone), and F7 (shale clast conglomerate). F7 is located on the northeastern and southeastern portions of the channel-fill. F6 (shale/mudstone) is located at the base of the channel and is found in the northeastern region. The northern region of the channel-fill environment is otherwise dominated by F2 (structureless sandstone without water escape structures), while the medial and southern regions of the channel are otherwise dominated by F1 (sandstone with water-escape structures).
  94. 94. Fig 4.18: Diagnostic facies of Channel-fill Sandstone 3. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  95. 95. Interpretation: The presence of F7 in the northeastern and southeastern regions of the channel-fill (Fig. 4.18) are interpreted to represent the outer-side of a sinuous channel bend (E2), or the cut-bank equivalent side. Field observations and those made in GOCAD™ lead to the additional interpretation that Channel-fill Sandstone 3 (CFS 3) and the overlying channel-fill sandstone, CFS 4, are amalgamated. Channel-Fill Sandstone 4 Fig. 4.19: Location of Channel-fill Sandstone 4 on Spine 1
  96. 96. Fig. 4.20: Location and number of detailed measured sections (white) with outcrop dimensions (red) on Channel-fill Sandstone 4.
  97. 97. Vertical and Lateral Geometry: The detailed measured sections of Channel-fill Sandstone 4 can be found on Figure 4.19 and 4.20. There are three major trends to the Outcrop Face of Channel- fill Sandstone 4. This indicates that this channel-fill outcrop wraps around Spine 1 from its southern slope to its northern slope. The main trend, SE-NW is 430ft. in length. The second main trend is located in a region known as the “Eagle’s Nest.” This face is 88ft. in length and is located on the southern slope of Spine 1 (Fig. 4.20). The northern-slope of Channel-fill Sandstone 4 is 70ft. in length. The thickness of this channel-fill ranges from 4ft. to 16ft. Lithologic Stacking Patterns and Locations: Channel-fill Sandstone 4 shows many interesting lithologic patterns located in its southern-most flank (Fig. 4.21). Some of the facies included are F1 (sandstone with water-escape structures), F2 (structureless sandstone), F3 (crossbedded sandstone), F7 (shale-clast conglomerates), and F8 (slumped beds). While F1 and F2 dominate the rest of the channel-fill, they are represented equally with all other facies at this portion of the channel-fill environment. The northernmost flank and the eastern region of the channel-fill environment is dominated by facies F1 and F2 with a rogue F7 facies lying near the base of the channel in the northeastern-most region (Fig. 4.21).
  98. 98. Fig. 4.21: Diagnostic facies located on Channel-fill Sandstone 4. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  99. 99. Interpretation: The southernmost flank, in the stratigraphically lower portions, shows the dominant facies to be crossbedded sandstone (F3) and in the northern portion of the channel-fill there resides a lone F7 facies near the base of the deposits. This stratigraphically lower region of the channel-fill environment is interpreted to have been a separate channel-fill system within the entire Channel-fill 4 “Complex” (Fig. 4.22). The overlying facies F8 and F7 are interpreted to be amalgamated onto the channel-fill system of the lower region. This interpretation holds that the stratigraphically lowest portion of the channel-fill sandstone, denoted by CFS4a is overlain by CFS4b (Fig. 4.22). CFS4a shows that the southern portion of the channel-fill environment was dominated by the diagnostic facies, F3, crossbedded sandstone. This facies is interpreted to represent the locality within the inner-side of a sinuous channel bend. The northernmost portion of CFS4a shows F7 to be the only diagnostic facies. This facies is interpreted to be the cut-bank equivalent side of the channel. Once again, two diagnostic facies were used in conjunction to interpret the environments represented by the channel- fill.
  100. 100. Fig 4.22: Amalgamated channel-fills CFS 4a and CFS 4b, comprising Channel-fill Sandstone 4. CFS4b is dominated by F8 and F7 facies in the southern region of the channel-fill. This interpretation holds that the southern region is the cut-bank equivalent side of the channel and it eroded into the underlying crossbedded sandstone of CFS4a to create amalgamated channel-fill deposits.
  101. 101. Channel-Fill Sandstone 6 Fig. 4.23: Location and number of detailed measured sections (white) with outcrop dimensions (red) on Channel-fill Sandstone 6. Vertical and Lateral Geometry: The detailed measured sections of Channel-fill Sandstone 6 can be located on Figure 4.23. Channel-fill Sandstone 6 is another channel-fill body that extends across both slopes of Spine 1 (Fig. 4.23). It also has three major trending faces (Fig. 4.23). The major SE-NW trend is 355ft. The secondary southern-slope trend is 105ft. in length, while the northern-slope trend is 95ft. in length. The thickness of this channel-fill ranges from 2ft. to 8ft.
  102. 102. Lithologic Stacking Patterns and Locations: The northwestern regions of the channel-fill environment are dominated by basal F7 units capped by F3 facies (Fig. 4.24). The western part of the medial portion of the channel, trending NW-SE, is dominated by facies F1 and F2 with a small portion of F5 (climbing rippled sandstone) cropping out near the top of the channel- fill. The eastern segment of the medial portion of the channel-fill is underlain by facies F3 and is capped by facies F1. In the southeastern-most region of the channel- fill, F5 (rippled or climbing-rippled sandstone) is encapsulated within F1 deposits, capped by facies F3. Interpretation: Two diagnostic facies occur in this channel-fill, F3 (crossbedded sandstone) and F7 (shale-clast conglomerate). Once again, two diagnostic facies of different channel environments are located in the same geographical region. This channel-fill system is thus interpreted to contain two amalgamated channel-fills. The lower region of CFS6 is interpreted as CFS6a, the lower fill, and CFS6b, the upper fill (Fig. 4.25).
  103. 103. Fig. 4.24: Diagnostic facies of Channel-fill Sandstone 6. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  104. 104. Fig 4.25: Amalgamated channel-fills CFS 6a and CFS 6b, comprising Channel-fill Sandstone 6. CFS6a is interpreted to have its steep side on the northwestern-most side of the channel-fill system with a feathered, tapering edge on the southeast. CFS6b lacks two diagnostic facies as CFS6a, but contain plentiful F3 deposits throughout the entire stretch of its channel-fill. The resultant interpretation holds that CFS6b was dominated in this region by the inner-side of a sinuous channel bend (E3).
  105. 105. Channel-Fill Sandstone 7 Fig. 4.26: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 7. Vertical and Lateral Geometry: The detailed measured section of Channel-fill Sandstone 7 can be located on Figure 4.26. Channel-fill Sandstone 7 is primarily found on the northern slope of Spine 1 and thus has only two major trends, NE-SW and E-W (Fig. 4.26). The major E-W trending face is 430ft. in length, while the minor NE-SW trend is only 105ft. The thickness of this channel-fill ranges from 2ft. to 10ft.
  106. 106. Lithologic Stacking Patterns and Locations: Dominated in the western portions of Channel-fill Sandstone 7 (CFS7) is facies F2, structureless sandstone and F3, crossbedded sandstone (Fig. 4.27). In the eastern region of CFS7 is facies F8, slumped beds (Fig. 4.27). Otherwise, CFS7 is dominated by facies F2. Interpretation: Since the western portion of CFS7 includes the diagnostic facies F3, this region of the channel-fill is interpreted to be the point-bar equivalent, inner-side of a sinuous channel bend (E3). The eastern section of CFS7 shows a slight, but prominent facies, F8. F8 is diagnostic of cut-bank equivalent, outer-side sinuous channel bends, E2. This interpretation yields that the eastern portion of CFS7 is the cut-bank equivalent side of the channel-fill, while the western portion is interpreted to be the point-bar equivalent of the fill. Field observations and those made in GOCAD™ lead to the additional interpretation that Channel-fill Sandstone 7 (CFS 7) and the overlying channel-fill sandstone, CFS 8, are amalgamated (Fig. 4.01)..
  107. 107. Fig. 4.27: Diagnostic facies of Channel-fill Sandstone 7. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds.
  108. 108. Channel-Fill Sandstone 8 Fig. 4.28: Location and number of detailed measured sections (black) with outcrop dimensions (red) on Channel-fill Sandstone 8. Vertical and Lateral Geometry: The detailed measured sections on Channel-fill Sandstone 8 can be found on Figure 4.28. There are two major trends associated with the Outcrop Face of Channel-fill Sandstone 8, they are N-S and E-W trends (Fig. 4.28). The major E-W trend is 475ft. in length, while the N-S trend is 180ft. in length. The thickness of this channel-fill ranges from 4ft. to 12ft.
  109. 109. Lithologic Stacking Patterns and Locations: Channel 8 shows some unique lithologic patterns. In the western portion of the channel-fill system, the basal portion is dominated by facies F7, shale clast conglomerates (Fig. 4.29). Capping these units and laterally extending to the east and stratigraphically downward to the same plane as the F7 deposits are facies F3, crossbedded sandstone. In the eastern regions of the channel-fill this same type (mirror-image) of lithologic stacking pattern exists, i.e., the shale-clast conglomerate (F7) facies resides on the east and facies F3, crossbedded sandstone, resides on the west (Fig. 4.29).
  110. 110. Fig. 4.29: Diagnostic facies of Channel-fill Sandstone 8. F1 (blue): sandstone with water-escape structures (some cross-bedded), F2 (yellow): structureless sandstone (without water-escape structures), F3 (magenta): cross-bedded sandstones (without water-escape structures), F4 (dark gray): parallel to subparallel laminated sandstone, F5 (dark green): rippled or climbing-rippled sandstone, F6 (blue-violet): shale or mudstone, F7: (red) shale clast conglomerates, and F8: slumped beds
  111. 111. Interpretation: These unique stacking patterns reveal an interesting interpretation. The eastern side of CFS8 is interpreted to have a steep, cut-bank side (E2) on its eastern flank by the diagnostic F7 facies and a shallower, point-bar side (E3) on its western flank by the diagnostic F3 facies. The western side of CFS8 is interpreted as the mirror image of the above interpretation. The western flank of the western portion of CFS8 is interpreted to be the steep, cut-bank side (E2) of the channel-fill, while the eastern flank of the western portion is interpreted to be the shallower, point-bar (E3) side of the channel-fill.
  112. 112. Channel-Fill Sandstone 9 Fig. 4.30: Location and number of detailed measured sections (white) with outcrop dimensions (red) on Channel-fill Sandstone 9.

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