Abstract ........................................................ 1
Introduction .................................................... 1
Objectives of Study ............................................. 3
Historical Coal Geology and Stratigraphy ........................ 3
Early Mapping and Coal-Bed Nomenclature Problems ................ 4
State-to-State Mapping Problems .............................. 4
Coal-Bed Splitting and Merging Problems ...................... 4
Derivative-Name Problems ..................................... 5
Availability of Data and Data Control-Point Spacing ............. 5
Depositional Environments and Facies of Coal-Bearing Strata ..... 5
Computerized Modeling ........................................... 6
New Sources of CBM Data ......................................... 7
Revised Basinwide Coal Stratigraphy and Nomenclature ............ 7
Depositional Concept of Coal Splitting in the Powder River
Basin ........................................................... 7
Regional Cross-Section Lines .................................... 8
Wyodak Coal of Mapel (1973) .................................... 27
Cross Section H-H' .......................................... 27
Cross Section N-N' .......................................... 28
Basinwide Lateral Variation of the Wyodak Coal ................. 28
Basin South of Gillette, Wyoming ............................ 28
Revised Nomenclature of Wyodak Coal South of Gillette,
Wyoming ........................................................ 29
Basin North of Gillette, Wyoming ............................ 29
Revised Nomenclature of Wyodak Coal North of Gillette,
Wyoming ........................................................ 30
North-South Cross Sections ..................................... 31
Effects of Stratigraphic Overlap of Coal Zones ................. 31
Paleodepositional Interpretations .............................. 34
Paleodeposition of the Wyodak Coal Zone and Related Rocks ... 34
Paleotectonically Controlled Alluvial Drainage ................. 37
Interplay of Alluvial Accommodation Space, Tectonics, and
Coal Zone Overlap .............................................. 37
Regional Paleogeographic and Paleotectonic Patterns of Merged
Coal Bodies .................................................... 39
Summary ........................................................ 41
Acknowledgments ................................................ 42
References ..................................................... 42
Appendix ....................................................... 47
ures
1. Map of the Powder River Basin showing the data points and
active mining areas in Wyoming and Montana .................. 2
2. Diagram of hierarchical order of coal splitting that is
typical of Fort Union and Wasatch coal beds ................. 8
3. Map of the Powder River Basin in Wyoming and Montana
showing locations of 17 regional lines of cross sections;
the coalbed methane, oil and gas, and coal drillhole wells
used to construct cross sections; areas where beds are not
split or overlapped; locations of major channel sandstones;
and coal mine areas ......................................... 9
4. Cross section A-A'showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southernmost part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 10
5. Cross section B-B'showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 11
6. Cross section C-C' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 12
7. Cross section D-D' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 13
8. Cross section D"-D"" showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 14
9. Cross section E-E'showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the southern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 15
10. Cross section F-F' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 16
11. Cross section G-G' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 17
12. Cross section H-H' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 18
13. Cross section I-I' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 19
14. Cross section J-J' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 20
15. Cross section K-K' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northern part of the Wyodak
extent, Powder River Basin, Wyoming ........................ 21
16. Cross section L-L' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northernmost part of the Wyodak
extent, Powder River Basin, Wyoming and Montana ............ 22
17. Cross section M-M' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the northernmost part of the Wyodak
extent, Powder River Basin, Montana ........................ 23
18. Cross section N-N' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the eastern part of the Wyodak
extent, Powder River Basin, Wyoming and Montana 24
19. Cross section O-O' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the central part of the Wyodak
extent, Powder River Basin, Wyoming and Montana ............ 25
20. Cross section P-P' showing lateral and vertical
lithostratigraphic variations of the Fort Union and
Wasatch Formations in the western part of the Wyodak
extent, Powder River Basin, Wyoming and Montana ............ 26
21. Map of the Powder River Basin showing areal distribution
of pollen and spore zonations (P5 and P6) for the late
Paleocene Wyodak and Dietz coal zones (modified from
Nichols, 1999) ............................................. 32
22. Map of the Powder River Basin showing elevations (with
respect to sea level) at the base of the Wyodak coal zone
and equivalent coal beds ................................... 35
23. Map of the Powder River Basin showing the thickness of
the Wyodak coal zone and equivalent coal beds .............. 36
24. Composite structure map of the Powder River Basin (PRB),
Bighorn Mountains, and Black Hills showing locations of
thrust and normal faults, lineaments, and folds. Inset is
a northwest-southeast (NW-SE) cross section across the
eastern PRB showing structural relief of the Belle
Fourche arch and zones of weakness in the Precambrian
crystalline basement. Compiled from Wilson (1936),
Hoppin and Jennings (1971), Slack (1981), Marrs and
Raines (1984), and Jenkins (1986) .......................... 38
25. Thickness isopach map of the merged Wyodak coal bodies
west of the "Middle and South Groups" of coal mine areas
in the southern part of the Powder River Basin.
Superimposed on these coal bodies are the northeast- and
northwest-trending lineament zones, and coals mines ........ 40
Table
1. Coal-bed names of the Upper Fort Union Formation from
original, previous, and this study .......................... 33
Appendix
1. Appendix includes the Well Number (tie well indicated
by <>); Cross Section where the well is represented;
American Petroleum Institute (API)/Well ID number;
Operator of the well; Well Name; County; State; Log Type
(gamma ray, resistivity, lithologic log (lith-log), and
spontaneous potential) used from the well; Well Type
(coalbed methane (CBM), oil, natural gas, and coal).
A more extensive Appendix in Microsoft Access format is
on the CD-ROM that accompanies this report .................. 48
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